The S-90 Go-Kart Final Report

Transcription

1 The S-90 Go-Kart Final Report By James Paolino, Alexander Jadczak, Eric Leknes, and Tarek Tantawy Sean Stenglein. NSF Projects. Ashford, CT

2 Table of Contents 1 Introduction Background Purpose of the project Previous Work Done by Others Products Patent Search Results Map for the rest of the report 4 2 Project Design Optimal Design Objective Subunits Prototype 37 3 Realistic Constraints 47 4 Safety Issues 49 5 Impact of Engineering Solutions 50 6 Life-Long Learning 51 7 Budget and Timeline Budget Timeline 54 8 Team Members Contributions to the Project 56 9 Conclusion References Acknowledgements Appendix Updated Specifications Purchase Requisitions Stress Analysis 67 A Gear Stress Analysis 67 B Roll Bar Stress Analysis 76 C Rear Suspension Bar Stress Analysis 85 D Front Bumper Stress Analysis 94 E Front Suspension Arm Top Stress Analysis 103 F Front Spindle Stress Analysis 112 1

3 1. Introduction This project is to design and build a go-kart for a client with severe cerebral palsy. The client has almost no reliable motor control of his body or limbs, ruling out the possibility of him driving traditionally designed go-karts. The idea behind this project is to take the control that he does have and give him the experience of a real go-kart. To do this a go-kart will be built from the ground up to meet his specifications. It will have three different modes of control: remote control, joystick control, and steering wheel with pedals control. This will allow the client to use the vehicle on day one, and progress to having more and more control of the go-kart with practice. The go-kart will be extremely safe, with software and hardware systems that shut down and stop the vehicle, at the push of a head switch, or if something goes wrong. The vehicle is designed with the client s condition in mind and will ensure that his body is positioned correctly for maximum motor control. Since this would be an awkward position for a normal driver the vehicle will also be adjustable to allow for a wide range of people to be able to drive it. This go-kart will be built from the ground up to meet the client s needs, and it will be safer, more versatile and more fun than anything else on the 1.1 Background This project is intended to design and create a go-kart for a child with severe cerebral palsy. The client is a ten year old male who is very smart and enjoys all things related to motor vehicles and driving. His condition makes it nearly impossible for him to operate a typical go-kart, however. The client has no reliable use of his arms or legs at this time. He has been working to develop enough motor control in his arms to allow him to use a power wheelchair with joystick control. The client can use a head switch with great reliability and this is an important factor in the design of this go-kart. In addition to a lack of reliable motor control the client also needs to be positioned correctly both for comfort, and to optimize the motor control he does possess. He needs to be secured tightly in his seat at the waist. This is to ensure that his waist is constantly at a 90⁰ angle, which helps his movement. The controls must also be setup in such a way that the client s thumbs are pointing upwards. This is both to help train his muscles to maintain that position and for comfort. 1.2 Purpose of the Project The overall purpose of this project is to provide the client with a go-kart that will allow him to experience the thrill of driving just like a person without cerebral palsy can. This go-kart is intended to be a much needed outlet for fun and stress relief in the life of the client. The client s condition does not allow him to control a go-kart in the tradition sense, so other methods of control must be developed. To allow for the client s continued development of motor functionality three progressive methods of control will be implemented. The go-kart will also meet all of the positioning and restraint requirements to allow the client the most safe and comfortable ride possible. The most important part of this go-kart is to maximize the client s safety and fun while using it. 2

4 1.3 Previous Work Done by Others Products There are examples of other projects and products that have attempted to accomplish similar goals to this project. There have been two teams at the University of Connecticut who have developed go-karts for clients with cerebral palsy. In both cases, 2001 and 2008, the project was designated the title E- Racer. In both cases the client had limited mobility, but the relatively efficient use of one hand. The 2001 team modified a go-kart to allow it to be driven with a joystick control. The 2008 team designed their go-kart so it could still be driven with a joystick as well. Both projects created a product costing roughly $2500. An NSF project in 1994 called the Recreational Electra-Scooter was completed at the State University of New York-Buffalo. This device essentially consisted of a platform on wheels that a wheelchair could be secured to. The platform could be programmed to move in either a straight line of in a preset circle. This left the driver with very little responsibility for actual driving, and allowed them to just enjoy the ride. The wheelchair was secured to the platform of the Electa-Scooter in a similar manner to how wheelchairs are secured on public buses. The cost of materials for the Electra-Scooter was $870. A number of other colleges and universities have attempted projects similar to the E-Racer projects done by University of Connecticut senior design teams. In most cases the go-karts were controlled using a joystick system, and most were electric. These products rely on embedded software to interpret input from electrical control systems to drive and steer the go-karts. These projects typically range in price from $1000-$3000. A number of commercially available go-karts are manufactured by Mobility4Kids, which are designed to allow people with disabilities to drive. The controls for these go-karts allow people with loss of lower extremity control and other severe disabilities to control them by the use of a joystick or switch controls. The go-karts are electric powered with electric brakes and are mostly intended for on road or light off road use. The maximum speed of these products is 7 mph. The go-karts are also available equipped with a steering wheel. Mobility4Kids markets go-karts for a variety of different applications, and they range in price from $5300-$ Patent Research Results One patent applies to the control systems of a go-kart for people with disabilities. A device called the Handi-Driver was designed by Keith Alan Roberts in It incorporates the three essential controls of driving; throttle, brake, and steering, into a single steering column. The purpose of this design is to allow people with the use of only one hand to drive a vehicle. The Handi-Driver uses a motorcycle-style grip throttle along with steering and braking levers for control on the steering column. It also incorporates a kill switch so the user can shut down the vehicle if control is lost for any reason. 3

5 1.4 Map for the rest of the report The remainder of this report will consist of a detailed look at the design of the go-kart, including three preliminary designs as well as the finalized optimal design. The optimal design will provide a detailed look at each of the subunits required for the assembly of the go-kart. The components of the optimal design will be analyzed to provide proof that the designed subunits will function properly. The realistic constraints of the designed go-kart will be discussed briefly. How the optimal design addresses various safety issues will be discussed and based upon the optimal design the impact of the engineering solutions will be touched upon. Any new material learned or techniques acquired in the design of the prototype will be listed as well. Next a budget and timeline for the completion of the prototype will be outlined. Tasks will be assigned to team members, and their contributions to the project will be listed. The appendix of this report will include information on the purchase requisitions and the stress analysis of the components of the go-kart. 2. Project Design The project design consists of the three alternative designs as well as a detailed look at the optimal design. The reasons for choosing the optimal design over the alternative designs based upon the design specifications and realistic constraints will be explained. The optimal design will include information on the objective of the project and a detailed description of each subunit will also be included. Figures created in Solidworks as well as pictures of subunits will be included to give a more detailed report of the optimal design. Analysis of the subunits will be included in the description of the subunits and stress analysis will be included in the appendix of the report. Alternative Design One Design 1 is based around an elongated front chassis with a fully enclosed roll cage. Electrical systems are used to control steering, braking, throttle, and forward/reverse selection. The control software is LabView based, and commercial electric motor switching systems will be purchased. A racing seat will be modified to accommodate the client s needs. 4

6 Figure 1: Design 1 This design implements a complete roll cage into the chassis of the vehicle. It has an extended overall length to allow for parts to be placed on the rear chassis. This extended design also allows for and a lot of adjustment for the seat in the front chassis. Overall this design is very rigid and very safe, but is also more top-heavy as a consequence and perhaps too difficult to get our client in and out of. This design implements independent front suspension and semi-independent rear suspension, using the roll cage as a pivot point for the rear suspension. This design uses its stiff roll cage as a front bumper. The electrical systems for the go-kart include: the remote control system, the joystick, and the steering wheel and pedals. Also included are the controlled components. This encompasses the steering motor and its non-software controls, the motor for controlling the throttle, the motor for switching between forward and reverse, and the motor for applying the brake. In addition the power supplies and various buttons are also electrical components for this vehicle. The main software control will be based on the National Instruments LabView platform. LabView will run off of a laptop computer on the go-kart. Input signals from the selected method of control and other sensors will be processed by the LabView program, and the proper outputs will be modified. This approach requires a National Instruments data acquisition system to be on board as well. The LabView program would be designed with two main loops, one for normal operation routines and another to send the go-kart into emergency shutdown. Both the steering motor and the braking motor require control systems that can turn them both forward and reverse directions. To effectively accomplish this, the go-kart will make use of a motor speed controller for the steering motor, and a commercially available h-bridge for the braking motor. The speed controller takes a PWM input from the microcontroller, which, for the purposes of this design, 5

7 designates forward or reverse directions. It is capable of switching up to 160A continuous current, and should not be taxed to that extent in this application. The commercially available h-bridge is a simpler version of the speed controller for the steering motor. It takes a PWM signal from the microcontroller to switch the braking motor between forward and reverse. This application does not require as robust a circuit due to lower current draws, and this h-bridge is only rated at 25A continuous current. Five switches shall be used in order to perform the following operations: Igniting the engine, selecting forward and reverse on the gearbox, engaging the speed limiter, selecting the method of control, and finally a kill switch to halt the engine and stop the go-kart. The kill switch will be a head switch, mounted on the seat of the vehicle. The remaining switches will be mounted on a frame along with the gauges. The steering wheel will be mounted on a telescoping shaft protruding through the dashboard, allowing for adjusting the distance. Turning the steering wheel will adjust a variable resistor and will be read by software to determine the position of the steering wheel. The joystick will be mounted on the dashboard of the go-kart. Magnets will be placed on the rear axle and read by software for determination of the go-kart s speed. A gauge on the dashboard will indicate to the speed of the go-kart. A high-quality racing seat is available for free by donation. This seat can be altered in order to accommodate for the needs of Sean. Ideally, Sean s hip would be at an angle slightly greater than 90 degrees. This gives him extra control over his extremities. The racing seat can be modified in order to put Sean at this desired angle. Also, the seat can be altered in order to keep his back straight. The seat has a five-point safety harness. This allows for maximum safety. The seat needs to be attached to the seat plate. The disadvantage to this would be the need to buy materials for the seat. This design meets all specifications from the project proposal, and should provide the client with the safe enjoyment he desires. Alternative Design Two Design 2 is based around a shortened front chassis that has an open roll cage with side supports. Electrical systems are used to control steering, braking, throttle, and forward/reverse selection. The control software is embedded C based, and electric motor switching systems will be designed. A specially designed seat will be modified to accommodate the client s needs. 6

8 Figure 2: Design 2 This design implements a single roll bar into the chassis design. This will make it easier for our client to get in and out of the vehicle. The overall length of this design is short, with an extended rear chassis for parts storage and a dramatically shortened front chassis. While this front chassis is much shorter than design 1, it should still be long enough for our client to comfortably sit with legs extended. This design implements independent front suspension and semi-independent rear suspension, using the roll bar as a pivot point for the rear suspension. This design uses an independent front bumper to protect the vehicle s delicate steering system and linkage. The electrical systems for the go-kart include: the remote control system, the joystick, and the steering wheel and pedals. Also included are the controlled components. This encompasses the steering motor and its non-software controls, the motor for controlling the throttle, the motor for switching between forward and reverse, and the motor for applying the brake. In addition the power supplies and various buttons are also electrical components for this vehicle. The main software control will come from a Microchip PIC microcontroller that is programmed using embedded C code. The software is responsible for taking the various input signals from the selected method of control, processing the data, and outputting the proper signals based on those inputs. Two main loops will be present in the software code at all times. The first main loop is the primary main loop which controls inputs and outputs during normal circumstances. The other main loop is the emergency main loop which is engaged by the activation of a kill switch. Each main loop will contain other loops and functions required to carry out all of the necessary tasks for operation of the go-kart. 7

9 Both the steering motor and the braking motor require control systems that can turn them both forward and reverse directions. To accomplish this, custom h-bridges are going to be designed and built. The basic concept of an h-bridge is to provide a way to switch current flow between the positive and negative leads of the motor, based on a relatively small electrical signal from the microcontroller. The h- bridge design would use solid-state switching elements to route current between the two legs of the bridge as selected. A challenge for a custom h-bridge is to ensure that all of the components can stand up to the levels of current that they are required to switch. Five switches shall be used in order to perform the following operations: Igniting the engine, selecting forward and reverse on the gearbox, engaging the speed limiter, selecting the method of control, and finally a kill switch to halt the engine and stop the go-kart. The kill switch will be a head switch, mounted on the seat of the vehicle. The remaining switches will be mounted on a dashboard along with the gauges for both speed and fuel. Magnets will be placed on the rear axle and read by software for determination of the go-kart s speed. The steering wheel will be mounted on a ball joint attached to a telescoping shaft protruding through the dashboard allowing for adjusting the distance and angle of the steering wheel much like that seen in a car. Turning the steering wheel will adjust a variable resistor and will be read by software to determine the position of the steering wheel. The joystick will be mounted on the dashboard of the gokart. A possible seating option would be to buy a new seat for Sean. There are seats available for sale that would allow Sean to be positioned in a manner that comforts him and allows for extra control of his extremities. If a seat is purchased, it can be permanently mounted onto the seat plate. Seats can be found with safety harnesses already attached. This would safely strap-in Sean. The disadvantage with this would be the heavy cost of a new seat. This design meets all specifications from the project proposal, and should provide the client with the safe enjoyment he desires. Alternative Design Three Design 3 is based around a longer front chassis and shorter rear chassis with an open roll cage and no side supports. Electrical systems are used to control steering, braking, throttle, and forward/reverse selection. The control software is embedded C based, and electric motor switching systems will be designed. A specially designed seat will be modified to accommodate the client s needs. 8

10 Figure 3: Design 3 (full) This design implements a single roll bar mounted to the chassis so the client can get in and out easily. This design has a shortened rear chassis that is just big enough for the engine, drive train, brake, and battery. The front chassis is extended 8 inches longer than design 2 s. The supports for the roll bar are mounted off to the side, allowing plenty of room for seat clearance on the sides and providing room for electrical components. This design has the lowest center of gravity of the three designs. This design implements independent front suspension and semi-independent rear suspension, using the roll bar as a pivot point for the rear suspension. Due to the shortened rear chassis, this design will have a slightly stiffer rear suspension. This design uses an independent front bumper to protect the vehicle s delicate steering system and linkage. This next picture better shows the front suspension system that will be common to all three designs. 9

11 Figure 4: Design 1-3 (front suspension linkage) The electrical systems for the go-kart include: the remote control system, the joystick, and the steering wheel and pedals. Also included are the controlled components. This encompasses the steering motor and its non-software controls, the motor for controlling the throttle, the motor for switching between forward and reverse, and the motor for applying the brake. In addition the power supplies and various buttons are also electrical components for this vehicle. The main software control will come from a Microchip PIC microcontroller that is programmed using embedded C code. The software is responsible for taking the various input signals from the selected method of control, processing the data, and outputting the proper signals based on those inputs. Two main loops will be present in the software code at all times. The first main loop is the primary main loop which controls inputs and outputs during normal circumstances. The other main loop is the emergency main loop which is engaged by the activation of a kill switch. Each main loop will contain other loops and functions required to carry out all of the necessary tasks for operation of the go-kart. Both the steering motor and the braking motor require control systems that can turn them both forward and reverse directions. To effectively accomplish this, the go-kart will make use of a motor speed controller for the steering motor, and a commercially available h-bridge for the braking motor. The speed controller takes a PWM input from the microcontroller, which, for the purposes of this design, designates forward or reverse directions. It is capable of switching up to 160A continuous current, and should not be taxed to that extent in this application. The commercially available h-bridge is a simpler version of the speed controller for the steering motor. It takes a PWM signal from the microcontroller to 10

12 switch the braking motor between forward and reverse. This application does not require as robust a circuit due to lower current draws, and this h-bridge is only rated at 25A continuous current. Five switches shall be used in order to perform the following operations: Igniting the engine, selecting forward and reverse on the gearbox, engaging the speed limiter, selecting the method of control, and finally a kill switch to halt the engine and stop the go-kart. The kill switch will be a head switch, mounted on the seat of the vehicle. The remaining switches will be mounted on the dashboard of the vehicle. No gauges will be implemented in this design. The steering wheel will be mounted on the chassis of the go-kart on a telescoping allowing for adjusting the distance. Turning the steering wheel will adjust a variable resistor and will be read by software to determine the position of the steering wheel. Springs will be used to return the steering wheel to a centered position when no other forces are applied to it. The joystick will be attached to a telescoping pole attached to seat of the go-kart. Magnets will be placed on a front wheel hub and read by a transducer mounted on the steering linkage that is tangent to the hub. Software will be used for determination of the go-kart s speed. Sean has a seat that the family uses when he is in the car. He is very comfortable with this seat. The seat makes him sit at the angle that he prefers. This angle gives him extra control over his extremities. The seat also has a mounting bracket attached to its bottom. A possible seating solution would be to design and build a coupling mounting bracket on the go-kart s seat plate. The chair also has seat belts built onto it, so Sean will be safely strapped-in while driving the go-kart. This would allow Sean s family to utilize their own seat for the go-kart and whatever uses they may use it for. Also, the cost of making a coupling seat bracket would be small and insignificant. This design meets all specifications from the project proposal, and should provide the client with the safe enjoyment he desires. 2.1 Optimal Design Objective This project is intended to design and create a go-kart for a child with severe cerebral palsy. The client is a ten year old male who is very smart and enjoys all things related to motor vehicles and driving. His condition makes it nearly impossible for him to operate a typical go-kart, however. The client has no reliable use of his arms or legs at this time. He has been working to develop enough motor control in his arms to allow him to use a power wheelchair with joystick control. The client can use a head switch with great reliability and this is an important factor in the design of this go-kart. In addition to a lack of reliable motor control the client also needs to be positioned correctly both for comfort, and to optimize the motor control he does possess. He needs to be secured tightly in his seat at the waist. This is to ensure that his waist is constantly at a 90⁰ angle, which helps his movement. The controls must also be setup in such a way that the client s thumbs are pointing upwards. This is both to 11

13 help train his muscles to maintain that position and for comfort. The most important part of this go-kart is to maximize the client s safety and fun while using it. The go-kart for this project will be built from the ground up to maximize the efficient use of space, and to ensure that the needs of the client are met. The frame will consist of a steel open roll cage design with independent front suspension and semi-independent rear suspension. A 10 horsepower gas motor will provide power for the drive, and also run a 7 amp alternator. A gas motor will be used both to provide adequate power, and for the sounds and attitude it brings to the vehicle. To accommodate the client s lack of physical ability all of the systems on the go-kart will be actuated using electric motors. The electric motors will interface to the mechanical systems to control them without the operator having to apply force directly. This will allow the client to control the go-kart with minimal physical input. The power for all of the electrical components essential to the go-kart will come from a deep cycle car battery. This battery will in turn be charged by the alternator to ensure that there is always electrical power being supplied to the system. The battery will supply the electric motors and the electronic control components. These control components are necessary to take small make use of the user s inputs to the system and translate them into something that can actually drive the go-kart. Three possible methods of control will be available on a user-selectable basis. The main method of control will be a joystick that controls steering, throttle, and braking using a two axis system. This method is similar to the way the client s power wheelchair is controlled, and with practice the hope is that the client will be able to learn this system of control. To allow the client to use the go-kart immediately the second control system is based on remote control. A radio controller designed for model aircraft will be controlled by a guardian with similar controls to the joystick. A radio receiver on the go-kart will take the transmitted signal and feed it to the microprocessor. The final method of control will be a steering wheel and pedals that will allow the vehicle to be operated like a normal car or go-kart. These inputs will be connected to the microprocessor instead of mechanically attached. By running all of the control systems through the same microprocessor system switching between the methods of control is simplified. This method also isolates each system from the motors, ensuring that only one control method can be in use at any given time. In addition to the custom control methods this go-kart will have a number of other features tailored directly to meet the client s needs. The seat is the most important of these features. The Tumble Forms 2 Carrie seating system is designed to keep the client bent 90⁰ at the waist at all times. This is essential for allowing the client to maximize his limited movement while driving the go-kart. The Carrie seat is expensive, so a mount will be made to allow the client s current Carrie seat to easily attached and removed from the go-kart. This will allow the client to have the proper seating arrangements without breaking the budget of the project. The client s most reliable form of physical control is his use of a head switch. For safety reasons, a head switch will be used as a kill switch for the go-kart. This safety feature will allow the client to stop the gokart at any time he feels unsafe or out of control. It is also important for the client s thumbs to be 12

14 pointed upwards while he is performing most activities. The meet this specification Velcro on the steering wheel and the joystick will be coupled with special gloves for the client to wear. The Velcro will hold the client s hands in the correct position regardless of the selected control method Subunits The complete go-kart described above is made up of a number of smaller systems that come together to make everything work. Each of these subunits has to be carefully designed so that it not only accomplishes its task, but also integrates into the larger system. The following section details the design of each of these subunits, and describes where they fit in the complete design. Software Control Architecture The go-kart will rely heavily on software control to allow it to function with minimal physical inputs from the operator. Embedded software takes away the need for complex analog circuits that would otherwise make up a control system like this. The software for the go-kart has two main purposes: to provide control over all of the systems necessary to operate the go-kart, and to recognize when the go-kart is not functioning properly and to shut it down safely. To accomplish these two tasks the software will be comprised of two infinite loops. The primary loop will service all of the normal routines that must be controlled, and check to make sure everything is operating properly. The emergency loop will be activated by the primary loop and will function to safely shut down the go-kart and keep it shut down. The basics of the overall software design are discussed in this section, each major component is discussed in detail in its corresponding section. Microcontroller Hardware The hardware that will be responsible for running the software routines is the Microchip PIC16F877. This is a 40-pin version of Microchip s mid-level 8-bit microcontroller. This microcontroller is ideal because it combines versatility with simplicity. The PIC16F877 has a number of peripherals and modules embedded in its design that can be easily accessed and put to use through relatively simple coding. The PIC includes an on-board analog to digital (A/D) converter, two pulse width modulation modules, and a number of other useful features. The 40 pins combine to have 35 input/output ports, 8 of which can take an analog input and route it through the A/D converter. Due to the constraints of only two PWM modules, however, the go-kart will make use of two PICs running in parallel to one another. Programming Language The PIC16 series microcontrollers are designed to operate based on a 35 function instruction set. Each instruction corresponds to one or two machine cycles of the microcontroller. Programming language that makes use of only instruction set commands called assembly language. Assembly is efficient to run, but tedious to write. For this application embedded C code will be used for writing microcontroller 13

15 software. Embedded C essentially takes the C code programming language and converts it into the equivalent assembly instruction set. This set is then loaded onto the chip and run continuously. C code is more intuitive to use than assembly and there are fewer chances of major software errors that could otherwise prove to be dangerous. Steering Steering Mechanics The steering system of the vehicle is designed to be able to withstand the large forces generated from the steering gearmotor. The gearmotor itself will be mounted to a plate that is attached to the front suspension supports. The gearmotor will have a 2:1 increase in gear ratio so that it will drive the rack and pinion at 180rpm. The gear on the gearmotor output will be a 48tooth spur gear, part number 6325K21 from mcmastercarr.com and the gear on the rack and pinion will be a 24 tooth spur gear, part number 6325K16 from mcmastercarr.com. The assembly will go together as shown in Fig. 5. The ends of the rack and pinion are equipped with 3/8 tie-rod ends with grease fittings and ball joints. To connect to these, more 3/8 tie rod ends (High-Strength Ball Joint Rod End 3/8-24 Rh Female Shank, 5100 Pound Load Capacity with part number 4444T211 from mcmastercarr.com will be attached on either end of long 3/8 diameter tie rods. The configuration can be seen in Fig. 6. Figure 5: Steering Assembly 14

16 Figure 6: Tie Rods The tie rod ends will then connect to the front wheel spindles via the extended lever arms with 3/8 holes as shown above. The steering wheel assembly will be made to be adjustable in terms of height and depth. The depth adjustment will be set by a knob put into a tapped hole in a 7/8 OD, 5/8 ID sheath. A 5/8 rod going through two sets of bearings will be inserted into the sheath on one end and left loose so that the knob pressure can lock it in position while another 5/8 piece of rod that is attached to the steering wheel mount will be inserted into the other end of the sheath. The piece of rod going through the bearings will have its end lathed down to ¼ for a length of about 1.5 so that a timing pulley can be placed on the end of it. Another timing pulley will be fixed to a shaft of a potentiometer and will be mounted to the extended plate that the bearings are mounted to. The area between the bearings will house an assembly consisting of two springs on either side of the steering column, a section of metal cable that has been wrapped around the steering column, and a tack of weld holding the center of the metal cable to the column. The purpose of this apparatus is to center the wheel automatically to give the driver a sense of natural wheel return as well as automatically calibrating the steering wheel to the forward position on startup. The general setup is shown in Fig. 7. The steering assembly will be able to tilt up and down based on the pivot/mounting point at the base of the assembly, and a pin that will slide through the metal tube mounted under the plate shown. The pin will go through two support arms not shown that will be mounted to the front suspension support bar at simple pivot points. The adjustment will be incremental, as there will be set holes drilled in the support arms that the pin can go through to lock the height of the steering assembly. 15

17 Figure 7: Steering Wheel Assembly Steering Control The steering control is one of the most important subsystems on the entire vehicle, and it is also one of the most novel. In order for the steering on this go-kart to be useful to the client it has to be able to move the wheels in a way comparable to how a fully capable person with a steering wheel can. A number of components go into this system which allows it to accomplish this task. The components of the steering control are: the rack and pinion with linkage, a Dayton 1L469 gearmotor, an LWG position transducer, an IFI Thor 883 speed controller, software controls, and the input control. Each of these components will be described in detail below. Dayton 1L469 Gearmotor The Dayton model number 1L469 gear motor will be used as the steering motor in the go-kart. The motor is geared in such a way to produce 50 inch pounds of torque and rotate at 90 RPM. The operating voltage of the motor is 12 volts with a full load current of 9.0amps. The 12 volt input for the motor is ideal for this particular situation as it is the same voltage as the battery. An IFI Thor 883 speed controller will be supplying the gearmotor with the forward and reverse currents allowing the motor to turn clockwise or counterclockwise as needed. The gear motor will only be drawing power when the wheels need to be turned and not when the go-kart is maintaining a particular wheel position, thus the 7 amp alternator will be able to recharge the battery. A gear on the shaft of the motor will interface with the gear on the rack and pinion for the steering of the go-kart. A linear position encoder will give feed back to the logic unit, determining the position of the wheels, and in turn determining whether or not the gearmotor needs to be activated and rotated. Rotating at 90 RPM will move the rack and pinion back and forth from one extreme to the other in a short period of time, allowing for good control over 16

18 Figure 8: Dayton Gearmotor the direction of the go-kart. For the gear ratios selected, it will take one second for the gearmotor to cause the rack and pinion to travel from one extreme to the other. The gear motor will be bolted to a mounting plate which will in turn be welded to the chassis of the go-kart. Position Transducer The rack and pinion is not mechanically connected to any of the user interfaces for the steering control system. For this reason it is important that there is another way of tracking the position of the rack and pinion, and ultimately the wheels themselves. This is done using a NovoTechnik LWG Series position transducer as shown in Fig. 9. This transducer has potentiometric properties based on the position of the shaft in its sleeve. The theory behind this mode of operation is that as the shaft moves it changes the internal resistance of the device. By applying a reference voltage to the device a voltage divider is created. The output voltage of the device then becomes dependent on the position of the shaft, and the corresponding resistance. The LWG position transducer will be attached parallel to the rack and pinion. As the gearmotor moves the rack and pinion the linear motion will also be transferred to the position transducer. With this setup the output voltage of the position transducer becomes a measure of absolute positionof the rack and Figure 9: NovoTechnik Linear Position Transducer 17

19 pinion and ultimately a measure of exactly which way the wheels are turned. This output voltage is connected directly to one of the input ports of the microcontroller for processing. Control Methods The three selectable methods of control are the main user interfaces for the go-kart. Each of them is designed to carry out the same function, but the reason for each method is unique. The joystick is intended to be the primary mode of control for the go-kart. It will likely take a lot of practice for the client to learn how to use, but it provides him with total control of the vehicle for himself. The radio control method is designed to allow the client to use the go-kart right away. His parents will be able to grasp the controls quickly, and this method requires little to no input from the client himself. The steering wheel with pedals method of control is there for two reasons. There is a hope the someday the client will be able to master his condition well enough to drive normally. It is also there to allow other operators a chance to drive the go-kart normally. Joystick The joystick control is considered the primary control because it is the most direct form. Many of the elements of this control system are used in the other two systems also. The joystick is a P-Q Controls Inc., M215-28, which has two axes of motion and a rocker switch at the top. The rocker switch will not be used on the go-kart. When the rocker switch goes unused the joystick has four useful leads. Two correspond to the positive and negative supply voltages, and the other two correspond to the x and y axes of control. The M works like two potentiometers. Each axis outputs a voltage based on the position of the joystick handle. These values are taken separately on the two distinct output leads. Full positive deflection causes an output of 80% of the supply voltage and full negative deflection outputs 20% of the supply voltage. When the handle is resting in the middle both outputs present 50% of the supply voltage. These output voltages are connected directly to an input port of the microcontroller for processing. The M joystick will be used to control the steering, throttle, and braking when the go-kart is in joystick control mode. The x-axis will control the steering, and the y-axis will control both the throttle and the brakes. The direction of the wheels will follow the position of the joystick on the x-axis, and the entire axis will be used for this mode of control. The y-axis will control throttle and braking by splitting the axis down the middle. As the joystick handle is pushed forward up the y-axis the throttle will be progressively opened. Likewise, as the handle is pulled back down the y-axis the brake will be incrementally engaged. When the handle rests in the middle of the y-axis the engine will idle with the brake disengaged. 18

20 Figure 10: M Joystick Radio Control The radio control is the most complex method of control from an electronics standpoint. The radio control will be implemented using a Futaba Skysport 4YF controlled coupled with a Futaba FP-R127DF receiver. This controller-receiver combination is designed for use with model airplanes and offers a 650 foot range. The controller makes use of two twin axis joysticks for control. Each axis on the controller outputs to a different channel on the receiver, giving four possible outputs that can be used for controlling the go-kart. The signal that is output from the receiver is in the form of pulse width modulation (PWM); because it is designed to directly drive the small l servo motors in model airplanes. The pulse width is changed based on the position of the joystick axis on the controller. While PWM is a convenient signal form to drive a servo motor directly, it is difficult to make use of as a microcontroller input. To make use of the signal coming from the receiver the PWM must be converted into an analog voltage before being routed to the microcontroller. The easiest way to make this digital to analog conversion is to use a simple RC circuit to smooth the pulses and give an average DC value. The smoothing effect of the capacitor in the RC circuit creates an averaging effect on the pulses, and creates an analog output proportional to the duty cycle of the PWM. As the duty cycle increases the DC voltage increases giving a controllable analog signal that can be taken by the microcontroller. Once the analog signal arrives at the microcontroller it can be processed in the same manner as the joystick voltage signal. Fig. 7 above shows the effectiveness of this method. The 19

21 circuit in the diagram was run using a 2.5% duty cycle and a 7.5% duty cycle. There is clear change in the output voltage that can be used for A/D conversion. Steering Wheel and Pedals The steering wheel with pedals is the third mode of control for the go-kart. It works off of nearly identical principles as the joystick. The steering wheel will be mechanically attached to a potentiometer via a belt. The turning of the wheel will subsequently turn the potentiometer and change the output voltage with respect to the supply. This voltage will then be sent directly to the microcontroller. A spring mechanism will center the steering wheel when no force is being applied to it. This is intended to give the operator the feel of a normal vehicle where the wheels work to right themselves automatically. The pedals will work in the same way as the steering wheel, except they will be directly linked to potentiometers. There will be separate potentiometers to control the throttle and braking, as they will take inputs from two separate pedals. Both signals from the potentiometers will be connected directly to inputs on the microcontroller. Each of the pedals will also be attached to a spring to bring them back Figure 11: RC Smoothing Circuit Diagram and Results 20

22 to their original position. This is important to ensure that neither pedal remains in the active position when the operator does not intend for them to be there. Steering Software Control The software control for steering is responsible for taking information from two main inputs and using the gathered information to update a single output. The inputs for the steering control come from the LGW position transducer and the steering output from the selected control method. Both of these inputs are of the same form when they arrive as signals at the microcontroller. They are both analog DC voltages, and their magnitude is based on the mechanical positions at their respective origins. Each signal must go through an analog to digital conversion (ADC) process in within the microcontroller to be useful for digital analysis. The ADC process is carried out by a routine in the software that utilizes a 10- bit converter that is on board the PIC16F877 microcontroller. The conversion process compares the input voltage level to a known reference voltage level and assigned a number based on the relationship between the two levels. This number is stored to a location on the chip and can be used for comparisons. The ADC routine written in embedded C code is shown below. void ReadADC(){ unsigned char wheel1, posit1; ADCON1 = 0x49; //set for left justified if(contmode == 0) { ADCON0 = 0x09; // Enable ADC, Fosc/2, for AN1 //ADCON0 = 0x29; // Enable ADC, Fosc/2, for AN5 } else if(contmode == 1) { ADCON0 = 0x01; // Enable ADC, Fosc/2, for AN0 //ADCON0 = 0x29; // Enable ADC, Fosc/2, for AN5 } else if(contmode ==2) { PORTD = 0xFF; return; } ADIE = 0; // Masking the interrupt ADIF = 0; // Resetting the ADC interrupt bit ADRESL = 0; // Resetting the ADRES value registers ADRESH = 0; ADGO = 1; // Staring the ADC process } while(!adif) continue; wheel1 = ADRESH; // Wait for conversion complete //Store position of joystick/rc/wheel Both input signals undergo ADC and are stored as finite, 10-bit, values. The software takes the 8 most significant bits from these values and stores them as designated variables. One input represents the wheel position and the other represents the desired wheel position. When both inputs are close in value the wheels are essentially in the correct position. If the control value is much different than the wheel 21

23 values then the software must configure the output so the gearmotor can move the wheels to the correct position. The code shown below demonstrates this comparison method using embedded C code. The variable posit holds the position value of the wheels, and the variable wheel holds the position value of the steering input. The variable toler is defined at the beginning of the program and is a value that represents the maximum error or tolerance allowed between the two position values before the motor is made to update the position of the wheels. The final value for toler will be decided after the performance of the steering is tested. The example code here is configured to update PORTD, a digital output port on the microcontroller. This is to demonstrate the feasibility of the code. When the code is finalized the output will be a PWM signal that is sent to a speed controller connected to the gearmotor. void SUpdate(unsigned char posit, unsigned char wheel) { if(posit>=wheel-toler && posit<=wheel+toler) { PORTD = 0; //No change if encoder is within tolerance of input } else if(posit>wheel+toler) { PORTD = 0x0F; //Move to left to compensate } else PORTD = 0xF0; //Move to right to compensate } return; Speed Controller The gearmotor that powers the steering for the go-kart will be directly regulated by an IFI Thor 883 speed controller. Speed controllers take an input signal and modulate the direction and level of current that a motor receives. This in turn controls the direction and speed of the motor. The Thor 883 takes a PWM signal, which will come from the output of the microcontroller, and uses the encoded information to drive the motor. For the purposes of the go-kart the speed controller will be used only to control the forward and reverse motion of the motor. The 120A continuous current rating for the Thor 883 makes it ideal for the application with the Dayton 1L469 gearmotor, because there is little to no chance of the motor drawing enough current to blow the speed controller. Drive Train 22

24 The drive train system of the go-kart is designed to be both robust and adjustable. It consists of an engine mounting plate, a gearbox mounting plate, and the rear axle. The engine mounting plate will be welded to the chassis at a pre-determined position so that the exhaust from the muffler does not expel directly onto any components and so that the engine has enough clearance from the rear suspension. The horizontal positioning of the gearbox mounting plate will be determined by the position of the Comet 500 series torque convertor setup. The end of the gearbox will have an extra support bearing that will be mounted to the rear chassis on a slotted piece of metal. The gearbox mounting plate itself will be adjustable so that the tension in both the torque convertor belt and the drive chain can be adjusted by turning a 5/8 lead screw. This assembly can be seen in Fig. 12 and Fig. 13. The rear area where the engine mounting plate will be welded to is shown in Fig. 14. Figure #12: Gearbox Mount Assembly Figure #13: Gearbox Mount Assembly (Under) 23

25 Figure #14: Rear Chassis (Full) The driven large sprocket on the rear axle has been tested under a high simulated load, as well as the axle itself. The included stress analysis shows that they can withstand the forces generated by the 10HP Tecumseh engine under maximum loading conditions with an 800lb assumed vehicle/passenger weight. Full stress analysis can be found in Appendix A. Both the gearbox and torque convertor are rated to handle up to 16hp 4-stroke engines. The torque convertor clutch is designed to engage at 2100rpm, meaning that the engine should never stall upon engagement due to the fact that at 2100rpm it is high up in its power curve. This will provide good initial acceleration of the vehicle, allowing for a thrilling ride and powerful cornering in off-road conditions. Engine The engine selected for this vehicle is the Tecumseh Formula Horizontal Engine with Electric Start 10 HP, 1in. x 2 7/8in. Shaft, Model# HM T. The reason for this engine s selection is that it comes with a muffler, a gas tank, a kill switch, a 7 amp alternator, an electric starter and emergency pull-start option, as well as having 10hp and a 1 diameter drive shaft with ¼ keyway which fits the donated torque convertor clutch. This motor is also designed for off-roading, so the oil sensor automatic shutoff is set up so that it won t automatically shut off the engine if it gets jostled in off-road conditions. The 10hp fits with the hp ranges for the transmissions (8hp-16hp) without being too powerful since the client does not need to go very fast. Also, the price of the motor compared to similar motors with similar features is competitive at $ This motor should allow for an exciting ride with lots of torque to provide good initial acceleration for the client with a max rpm of about

26 Figure 15: Tecumseh Formula Horizontal Engine Torque Convertor The automatic part of the transmission is a Comet 500 series torque convertor with a low range of 3.34:1 and a high range of.81:1. This will ensure that at low engine rpm the transmission will still have enough power to accelerate the go kart by providing a reduction of 3.34 which will be augmented to the roughly 6:1 gear ratio provided by the fixed axle and gearbox sprockets. The torque convertor is belt driven and the clutch is centrifugal, so the passenger will be able to easily maneuver the vehicle at low speeds due to a combination of belt slipping and engine loading decreasing the shaft rpm. This dynamic transmission is commonly found in snowmobiles, and allows the engine to reach its full power curve. Gearbox The gearbox is made by Comet, and is for go-karts, utility vehicles and other applications up to 16 hp. Lightweight, rugged gearbox that allows operator the selection of three positions: forward, neutral and reverse. Forward ratio is 1:1 and the reverse ratio is 2.7:1. This is to be used with other comet torque Figure #12: Gearbox and Torque Converter 25

27 convertors, like the 500 Series mentioned. The gearbox will have a drive sprocket mounted to its output shaft, which will engage the drive sprocket on the axle. The input shaft will have the driven clutch of the torque convertor as well as an extra support bearing on the end of the input shaft. The gearbox s mounting plate will be adjustable so that the proper belt and chain tensions can be achieved. Throttle A servo motor controlled by the microcontroller will operate the rotary valve controlling the throttle on engine. Rotation in one direction gives the engine more gas, and rotation in the opposite direction limits the gas entering the motor. This throttle motion will be controlled by a closed loop system that will verify the expected position of the servo motor and ensure that the throttle is always in the correct place. Input Control The input for the throttle control system comes from the selected method of overall control. These methods of control are described above in the Steering Control section of this report. Regardless of the method of control, the signal that ends up as an input to the microcontroller is an analog voltage corresponding to the position of the input controller. This analog signal is converted to digital as it enters the microcontroller and from there the software uses this signal for comparison. Feedback Potentiometer The shaft of the servo motor that is attached to the throttle control will also be attached directly to a potentiometer. This potentiometer will serve to provide feedback data for the position of the servo motor and ultimately the throttle. As the servo motor turns it will also turn the potentiometer, which will modify the output voltage going to the microcontroller. This step is not necessary for the function of the servo motor, but it is useful to confirm that the servo motor is operating correctly. In an important application like throttle control it is important to be sure that all components are responding properly to the control system. If the signal from the potentiometer does not correctly correspond to the PWM signal being sent to the servo motor the software will automatically send the go-kart into the emergency shutdown routine. Throttle Servo Motor PWM The servo motor on the throttle takes a pulse width modulation signal to determine the position in its rotation that it should jump to. The various positions of the throttle control valve will correspond to different points in the servo rotation, and the PWM signals corresponding to those points. The software will take the digitally converted signal from the selected control method and compare the desired position of the throttle to the actual position of the throttle servo. If the two positions do not match within a relative tolerance the software will modify the output port to the PWM signal corresponding to the desired position. 26

28 Braking System The system for braking control is very similar to the system for steering control. It uses a smaller gearmotor to move the lever to open and close the caliper. The action of the gearmotor is controlled using a microcontroller and a commercial H-bridge. Mechanical Braking System The brake system has been over-built as a safety concern. The 10 disk brake is much larger than a typical 6 disk brake used on most go-karts. This combined with a high end twist-type caliper system allows for tremendous forces to be generated on the brake with moderate forces applied to the caliper lever arm. The lever arm will be actuated by using a high-torque gearmotor that will have a further improved mechanical advantage before being linked to the caliper lever arm. The increase in mechanical advantage is possible due to the fact that the brake caliper lever only needs to move ½ for a fully open to fully closed position, so the gearmotor being used can convert all of its speed in its rotating parts to a very high pulling force. The general position of the brake and the general location of where the caliper will be located can be seen in Fig. 17. AME 218-series gearmotor The AME 218-series gearmotor will be used to apply a force to the braking mechanism. This gear motor operates at 12 volts, the same voltage supplied by the batter, rotating at 116 RPM when no load is applied. With no load on the gearmotor 1.4 amps are drawn and at stall the gearmotor draws 21.3 amps. This gearmotor is able to supply 98 inch pounds of torque. The Simple-H H-bridge will be supplying the power to this gear motor in the forward and reverse directions. When current is flowing Figure 17: Rear Base Composite Assembly 27

29 in the forward direction, this gearmotor will rotate applying a force to the brake lever on the disc brake assembly. The lever will then in turn press the ceramic pads against the disc brake, slowing the go-kart. A linear position encoder will be used to determine the position of the brake lever, and in turn will determine whether or not the gearmotor needs to be turned on and the position of the lever adjusted. This feedback will keep the motor from applying excessive force to the braking assembly and will keep the motor from burning out due to extended periods of activation. Sending current through the gearmotor in the reverse direction will release the brake. The position of the gearmotor will be constantly monitored whether it is applying a force to the braking mechanism or released. Braking Control System Braking H-Bridge The commercial H-bridge that will be used to drive the braking gearmotor is the SyRen Regenerative Motor Driver. This driver takes a PWM signal from the microcontroller and uses it to switch the direction of the current flowing into the gearmotor. The SyRen is rated for use with 25A continuous current and can handle current spikes up to 45A. This is much more current than the braking gearmotor would ever actually draw, which means that the chances of this component failing are small. The SyRen will control switching between full forward, full reverse and idle. This will correspond to the opening and closing of the brake calipers, as well as allowing them to hold position. Braking Position Transducer The braking motor has no way of tracking its own position, so position will be measured using a NovoTechnik LWG Linear Position Transducer. The equipment and method for control using this position transducer is nearly identical to the method used for tracking the steering position. It is important to have data about the position of the brake calipers to allow for smooth braking. If the braking were to be done using only limit switches the only braking options would be full brakes or no brakes. The position transducer allows enough feedback from the brake mechanism to the microcontroller to incrementally increase braking power using the software. Braking Control Software The software controlling the braking system takes two inputs and compares them to modify a single PWM output. The two inputs are the signal from the selected control method, and the signal from the linear position transducer attached to the braking gearmotor. The input from the user controls will only utilize the bottom half of the y-axis (except for the pedal control method) and the software will default to no brakes when the go-kart is accelerating. The braking will be setup to run to a specified number of positions based on the intensity of the stopping needed. Each position of the brake will be a case and have constraints. If the position transducer is not in the correct position based on the current selected case the software will send the appropriate PWM to the H-bridge to correct the position of the brakes. 28

30 Gearbox Control The go-kart will have a transmission that can switch the drive from the engine between forward and reverse. This will be accomplished by attaching a linear actuator to the selector arm of the transmission. The linear actuator will be controlled by the software and a custom designed H-bridge. Gearbox H-Bridge The transmission H-bridge will be designed using a very simple h-bridge concept. It uses two mechanical relays and two limit switches to route current between the two poles of the linear actuator. The diagram below shows the design of the h-bridge. When the first relay is activated by a signal from the microcontroller it opens and allows current to flow into the positive terminal from the high side of the bridge. When the linear actuator reaches the limit switch it cuts off the current flow from the negative terminal of the actuator. The linear actuator will stay in place until the microcontroller activates the other relay at which point the actuator will move off of the first limit switch and move until it hits the other limit switch. Gearbox Control The software control for the transmission will be a very simple design. A switch on the side of the gokart will be able to be set for either forward or reverse. This switch will send a digital signal to the correct input pin on the microcontroller. The software will compare the digital signal to the last one it received and if they are different it will activate the output to switch which relay is active at that point. This method is a simple, yet effective way to switch gears without heeding to physically move the handle. Motion System 9234c120 linear actuator The Motion System Corp model 9234C120-R10 linear actuator will be used to move the gear lever on the gearbox of the go-kart. This actuator is able to provide enough force and has a long enough stroke to push the gear lever from the forward to reverse positions. This actuator operates at 12 volts, consequently the same voltage as the battery for the go-kart. The speed at which the actuator moves is suitable for the task of changing gears in the gearbox. External limit switches will be placed such that the current flowing to the actuator will be halted once the gear lever is in its proper position. This will 29

31 Figure #14: Motion System Linear Actuator keep the actuator from exerting unnecessary forces on the gear lever and will also protect the actuator from becoming burnt out due to it perpetually being on. A bolt trough the ball joint on the actuator will connect to the gear lever and the actuator will be mounted to the chassis of the go-kart. Other Mechanical Systems Roll Cage System The roll cage system is an extremely robust, over-engineered design that will keep the passenger safe in the case of a rollover at speed (approx 30mph). The roll cage will be made of a single piece of bent 1.5 OD ¼ wall thickness pipe that is reinforced by two extra pieces of pipe as shown in Fig

32 There will be extra pieces mounted to the chassis that support these side bars. The roll bar needs to be able to withstand significant lateral forces, and a stress simulation has been included to prove that the design is more than strong enough. Full stress analysis can be found in Appendix B. Also the roll cage will feature a dual role: both a safety role and a suspension role. The rear suspension will mount to a crossmember on the roll cage. The forces generated by the rear suspension will be mostly absorbed by the two side supports that are angled forward. The remaining forward forces will be taken up by the gussets welded to the bottom of the main roll bar and the side assemblies that are welded to the chassis to support the side support tubes. The roll cage system will also include a rigid steel pipe welded to the main roll bar that the joystick can mount to. In the same way that the steering wheel depth is adjustable, the joystick will have a knob that can be tightened built into it that can fix it in position at any depth along the steel pipe. Seat System Figure 19: Full Go-Kart Assembly The seat system is designed to be adjustable and strong. The seat mounting plate has to be strong enough to control the passenger s inertia, as it is the only real structural interface between the passenger and the vehicle. In order to accomplish both strength and adjustability, a heavy duty linear actuator has been chosen to move the seat mounting plate forward and backward on two strong, 31

33 Figure 20: Seat Actuator Assembly reinforced steel rails. The seat mounting plate is fixed laterally by the geometry of the rails and the up/down movement is restricted by tabs and angle iron welded to the seat mounting plate. The linear actuator is rated for 750lbs, which is more than any passenger that can fit in the vehicle can possibly weigh. The linear actuator setup can be seen in Fig. 20. The seat coupler for the seat mounting plate will be made out of steel, and there will be two separate couplers, one for the normal seat for test driving, and one for the special seat for the client. The bracket for the normal seat has been designed and looks Fig. 21. The seat coupler for the client s special car seat will be the reciprocating piece to the bracket currently mounted to the bottom of their seat, which looks like Fig. 22. The seat area will be protected from tree-branches, and other off-road Figure 21: Alternate seat Mounting Coupler 32

34 debris by side panels made out of fiberglass. Also, the seat area will have the roll bar support arms running along the edges, which will completely encase the passenger with structural supports in the case of a rollover, making them much safer. Duff-Norton LSPD Figure 22: Seat Bracket The Duff-Norton LSPD linear actuator will be used to adjust the seat position on the gokart. This motor has a 750 pound capacity and a 12 inch stroke arm. The operating voltage of this particular actuator is 12 volts, corresponding to the voltage of the battery used in this project. The maximum current draw for this actuator is about 14 amps when the actuator is applying 750 pounds of force. Current will only be drawn when the seat is being adjusted so the 14 amp draw is acceptable even through the alternator is only supplying 7 amps of current to the battery. The speed at which the seat will be adjusted will be comparable to that of adjusting a standard electric car seat. The actuator will extend or contract based upon the direction of current flow through the actuator. Two internal limit switches which will stop current from flowing when the actuator has reached the extremes of its stroke. These limit switches will help to keep the actuator from being damage during usage. One side of the actuator will be bolted to the seat mounting bracket, pushing it along rails which the mounting bracket rests on. The other side of the actuator will be attached to the frame of the go-kart. Front Suspension System The front suspension system is designed to allow for independent front wheel suspension while impacting the steering system minimally. The front suspension will use Adjustable Shock Absorbers from northerntool.com that have 520lb load rating and 2 of max compression. The shocks will be mounted in parallelogram suspension arm assemblies at the bottom and in the front suspension support bar that 33

35 Figure 23: Front suspension Arm Assembly runs along the front of the chassis. The parallelogram suspension arms ensure that the front wheels are always vertical with respect to the ground, and causes less of a toe in effect on the front wheels when the suspension is compressed. The suspension arms can be seen in Fig. 23. The design of the suspension arm allows for the front wheel spindles to have maximum turning radius based on the rack and pinion s maximum stroke length. Also, the suspension arms are extremely rugged, so that if for some reason the front bumper does not hit an obstruction that is too low to the ground, the suspension arms should not bend or break upon normal impacts at reasonable speeds (<20mph). The front suspension assembly can be seen in Fig. 24. This shows the numerous Figure 24: Front Suspension 34

36 reinforcements to the front area where the suspension arms connect to the front chassis. It also shows the relative positioning of the front bumper to the suspension arms, showing that most objects that would endanger the suspension arms would be blocked by the bumper, except for low-lying obstacles. Rear Suspension System Figure 25: Rear Suspension The rear suspension system is a three pivot point system that uses heavy duty pins to hold the front and rear chassis together. The upper portion of the rear suspension coincides with the roll cage, as mentioned above. The rear bar of the rear suspension has been tested under simulated loads, and as the weakest of the three pivot points, still shows that it can withstand more than the expected loads. Full stress analysis can be found in Appendix C. The main components to the rear suspension are the upper segment with parallel steel sheaths, the lower segment with parallel solid steel rods, and the two Figure 26: Isometric Wire View 35

37 Figure 27: Seat Actuator Assembly 14 coil-over off road springs that interface the upper and lower segments. The idea is that the springs will provide much of the support for the rear suspension, but the space between the steel sheath and solid steel rod will be greased, trapping air in the hollow segment above the solid steel rods. This air will act as a further dampener for the suspension when experiencing jarring impacts, and will improve the quality of the rear suspension by increasing the force required to bottom out the suspension. This suspension assembly can be seen in Fig. 25. The actual mounting points for the rear suspension assembly can be seen in the following image showing an isometric wire frame view of the vehicle in Fig. 26. Chassis (Front and Rear) The chassis for the vehicle is broken up into two subunits: the front chassis and the rear chassis. These two units are joined by a solid ¾ steel rod at a pivot point used by the rear suspension. The front chassis can be seen in Fig. 28. These chassis are made to be extremely rigid and strong. They are reinforced with 2 side length right, isosceles triangle gussets at every corner to increase their rigidity. They are however designed to have a moderate amount of flex in the case of twisting. This is to accommodate the numerous high energy impacts that the vehicle will probably encounter while driving off road. The risk of making the chassis resistant to twist is that it could cause a weld joint to snap, since the forces from random off-roading impacts can be very large. By keeping the chassis rigid in the x-y plane by flexible in the x-z plane, the front and rear chassis are more suitable to handle the rigors of off roading without sustaining any structural damage, no matter how rough the terrain. 36

38 Figure 28: Front View Front Bumper The front bumper will be made out of a single solid piece of 1 x1 steel. This should be able to withstand any impact and transfer the impact to the reinforced front section of the front chassis. The front bumper can be seen in Fig. 30. Since the front piece will be solid steel, the forces that will hit the bumper will travel through that piece and into the 4 front bumper support bars. To test if these bas were up to a severe impact, a stress analysis has been performed on them. Full stress analysis can be found in Appendix D. The front bumper should be strong enough to withstand any impact from the vehicle at speeds under 10mph without any significant deformation, and at speeds above 30mph the front bumper will crumple appropriately, absorbing the energy of the impact like the nose cone of a race car, making the collision more plastic, and therefore helping to protect the passenger from excessive g forces. 2.2 Prototype The final prototype is derived from the optimal design created in BME Some aspects of the design were changed based on realistic physical constraints and tests, but by in large the finished product remains consistent with the design. The final product consists of a number of smaller subsystems and each of them will be reviewed in the following sections. This review will consist of in depth descriptions and pictures along with mention of deviation from the original optimal design (Figure 29). 37

39 Figure 29: S-90 Go-kart final prototype For the software control, the go-kart is operated using embedded C code on PIC16 microcontrollers. Three microcontrollers ended up being used in the final design (Figure 30). This is an increase from the two that were proposed in the original optimal design report. The extra microcontroller allowed for additional interrupt and input/output pins to be used that would have otherwise not been available. The microcontrollers take input information from peripheral sensors such as user inputs and system feedback and interpret the data to create output signals. These signals are then routed to the proper speed controllers or electric motors to drive and control the go-kart. The software control operates on a two loop system. The first main loop constantly runs and is tasked with converting input information to output information for normal operation of the go-kart. The secondary loop is an emergency shutdown loop that can be triggered by either a head switch or by the remote kill switch. The emergency loop is tasked with executing a pre-programmed routine to modify all important outputs to stop the go-kart, cut the engine and allow for safe steering. The software control selection software was implemented perfectly from the optimal design, allowing the user to cycle through all three modes of control. Additionally, all three modes of control can be used to safely operate the vehicle. 38

40 Figure 30: S-90 electronics enclosure The steering system did not stray far from the optimal design with only minor changes to the way the steering wheel raised/lowered and minor changes to the way the rack and pinion output shaft was reinforced. The steering wheel is connected to a potentiometer used as a voltage divider transducer by a notched belt. The transducer raises and lowers with the actual steering wheel. The steering gear motor is attached to the chassis by welded bolts and additional screws for fine tuning (Figure 31). The rack and pinion is bolted to tabs welded to the chassis and a stabilizer bar has been welded to the tie rod ends at the ends of the rack and pinion. The stabilizer bar is necessary for keeping the steering linkage rigid. The tie rods were fabricated from bolts welded to steel pipes and go from the rack and pinion to the from wheel hubs. The suspension is designed to be minimally effected by changes in the suspension, but a small amount of deflection in the wheel angle can be noted when the suspension is fully engaged. Under normal load the front wheels are calibrated to be about 1-2 degrees toe-in. This is useful for making aggressive turns in off-road conditions. 39

41 Figure 31: Steering assembly The steering control did not change at all from the original optimal design. The steering control consists of a steering motor and its speed controller. The controller gets its signals from a PIC16 PWM output. The software for the steering control system takes an input from one of the control mode transducers and compares the desired location of the wheels based on the transducer to the actual location of the wheels based on a string-pot feedback transducer. The feedback transducer is anchored to the front plate and has a string that moves with the rack and pinion. If the software determines that the feedback position is different from the desired position of the wheels, the PWM output is changed to trigger the gear motor to move the rack and pinion in the correct direction. When the position of the feedback transducer matches the desired position of the wheels, the gear motor is stopped. This method allows the direction of the wheels to be set on a user defined basis. The system works very well, and the response time of the wheels is comparable to normal analog steering systems. All three control methods described in the original optimal design report were created and are working. Each control method carries out the functions of steering, throttle control, and braking, based on user input. The easiest mode of control to use is the joystick (Figure 32). The joystick works on a two axis system where the horizontal axis controls steering and the vertical axis is split between controlling the throttle and controlling the brake. Each axis is a separate potentiometer and the signals from these potentiometers are input into the steering microcontroller for analysis. The second mode of control is by wireless remote control. This system also operates on a similar two axis joystick where the horizontal axis is for steering and the vertical axis is for throttle and brake. The technical implementation of the remote control system is different from the normal joystick however. The remote control system communicates with an onboard receiver which sends PWM signals from the remote control to the microcontroller inputs. The processing of the PWM input has changed since the original optimal design report was written. Originally this input was going to be low pass filtered in order to average the PWM into a readable analog voltage. After testing this, method was determined to be too imprecise to give the driver reasonable control over the vehicle. A new system was devised to interpret PWM signals in the microcontroller based on the use of interrupts and an on chip timer. The method uses the interrupt 40

42 Figure 32: Joystick with connection point port s ability to detect the rising and falling edge of the PWM signal to time the length of the pulse width itself. Once the length of the pulse width is known by the microcontroller, this length can easily be processed into the appropriate output form by the software. The third and final mode of control is a steering wheel with pedals. This mode of control is intended to allow any user to drive the go-kart as they would a normal vehicle. The steering wheel, the gas pedal, and the brake pedal are each connected to their own potentiometer, which are in turn connected to microcontroller inputs. Each of these control methods can be selected by pressing a button on the left front dashboard. The control modes are cycled through and lights on the dashboard indicate which control method is activated at any point. The drive train deviated from the optimal design because the gear box turned out to be defective. As a replacement a jack shaft was constructed, which allows for direct forward transmission (Figure 33). Also, a chain tensioner was added as it was determined that chain slippage was a problem for the optimal design transmission. This realization occurred during prototype testing. The new modification has been tested and eliminates chain slip. The transmission was used to tension the chain and the engine is able to start with a key and has a high oil level shutoff which triggers upon extreme accelerations. Testing has confirmed that the alternator provides ample current to charge the battery during extended use. Furthermore, the engine provides enough torque to move the go-kart up thirty percent grades with 200 pound passengers. 41

43 Figure 33: Transmission drive system Engine power output is controlled by a throttle linkage which is connected to a servo motor. The servo currently installed replaced the original servo motor which after testing was determined to not provide sufficient torque. Control of the throttle servo changed very little from the original optimal design. The only change to the software controls for the new throttle involved changing the direction of the pulse width modulation signal as it correlated to the user input. In general the throttle servo takes a PWM input from the microcontroller, which is modified based on user inputs from the control modes. The throttle servo is the only device on the go-kart that is connected to a 6V regulator. In order to provide the throttle servo with consistent power at 6V, a heat sink system was developed for the 6V regulator (Figure 34). This development was in response to the testing which confirmed that under heavy use the voltage regulator experienced thermal shutdown. The addition a four cubic inch, square, aluminum heatsink dissipates more than enough heat and allows optimal performance from the servo under all conditions. 42

44 Figure 34: 6V regulator with heatsink The mechanical braking system had minimal changes from the original optimal design. The braking system consists of a braking gear motor, a lever arm, a tie rod, a piston, a piston housing, a hydraulic pump, a hydraulic hose, a hydraulic caliper system, and a disc brake rotor (Figure 35). This differs from the old system in that it implements a hydraulic caliper instead of a twist type caliper system. This allows for higher closing forces to be generated on the disc brake rotor, allowing for greater braking power. The transducer feedback system from the optimal design did not change. The brake motor is allowed to stall for full braking power to be achieved and it has been determined that this does not Figure 35: Brake linkage system 43

45 overheat the braking speed controller system. In field testing the prototype brake system was shown to not lock up the wheels, but bring the vehicle to a fast, controlled stop. The design also changed from the original optimal design because it was determined that the original lever arm coming off the brake gear motor was too long, reducing the total force seen at the hydraulic piston. This was fixed by shortening the lever arm to less than half the original distance, causing an increase in braking power. The control system for the brake changed very little from the optimal design. Control of the braking motor comes from a small speed controller which takes a PWM signal from the throttle and braking microcontroller. The microcontroller takes user input signals from the control modes and compares the desired braking position to the position given by the braking feedback transducer. The PWM signal is then modified to drive the braking motor to adjust the mechanical position of the brake until it satisfies the position designated by the user input. The roll cage was implemented from optimal design and consists of quarter inch reinforced round steel tubing. While the roll cage has never been tested in a roll over it has withstood g-forces incurred from a front collision and from extreme pressure on the rear suspension, which it supports. The seat actuator assembly worked perfectly off the optimal design using a track on delrin spacers which allow for high weight capacities to move with minimal friction on the two support rails (Figure 36). The seat actuator assembly has been able to withstand over two hundred pounds of force under driving conditions without bending or braking and over four hundred pounds of static load. The seat bracket for the bucket seat followed the optimal design perfectly, however the seat bracket for the client s Carrie Seat needed to be modified since a new Carrie Seat had been purchased after the optimal design was finalized. The new design uses the existing bolt-hole pattern to mount a permanent steel fixture with welded nuts. A modular seat bracket fixture contains two bolts that fit into the prewelded nuts and can be removed so the Carrie Seat can be used as a car seat. When the unit is bolted together it allows for the universal bracket to fit into the six-hole bolt pattern for mounting purposes. Figure 36: Seat actuator with switch 44

46 Figure 37: Remote killswitch receiver module The front and rear suspension systems were fabricated based on the optimal design specifications. All components went together as planned and have held up to rigorous field testing. The only modification of the rear suspension was to clamp the rear suspension together to avoid failure of the suspension in the event that the rear wheels leave the ground. The front bumper and chassis followed exactly from the optimal design. The chassis was cut, welded, and ground as well as primed and painted for outdoor use. During field testing, the front bumper as well as the rigid chassis held up to substantial impacts without any bending or denting. No welds showed any signs of cracking after close inspection and upon further test driving the vehicle showed no signs of defect from the impromptu crash test. The original killswitch was created based on the optimal design and operates as it was intended to. After testing the need was seen for a killswitch that does not require software and a killswitch that directly grounds the engine spark plug was added. Additionally, testing revealed the original remote killswitch module to be unreliable and it was replaced with a system capable of both directly grounding the engine spark plug and triggering the emergency loop in the software. All electrical circuits for this project were created originally on a bread board. After testing systems using the bread board the design was transferred into the SPICE program Multisim. From there, the design was imported into National Instruments Ultiboard for the design of the final print circuit board (PCB) (Figure X). The PCB incorporates all the central electronics into a single area and allows for the connection of all peripheral devices to the control electronics. The PCB features a number of different sections that are integrated to control the vehicle. These include the three microcontrollers, the timing circuit, the voltage regulators, and the output pins. The PCB uses mostly through hole components for 45

47 Figure 38: The PCB their robustness under the relatively extreme conditions of go-kart driving. By using a PCB for the main body of circuitry, the electronics are condensed and are able to fit into the electronics housing of the gokart. It creates a permanent system that will not shake loose or become disconnected during normal driving conditions. The prototype operated well under all three modes of control, however there are specific issues associated with each method of control that should be noted. In steering wheel and pedals mode, the vehicle responds very naturally to the throttle pedal, but there is a slight delay upon activation of the brake pedal. This is just due to the linkage system of the brake, and does not pose any problem for the operation of the vehicle, but is something that needs some getting used to. The steering wheel in this mode does not act naturally at all. The main issue is that there is no tactile feedback from the wheel since it is not connected to the steering linkage. It makes for an unnatural ride, and coupled with the discrete nature of the steering control system in this mode it requires some time to get comfortable driving in this mode. Joystick mode seems to be by far the most natural system for user interface, and the high sensitivity in the joystick transducers allows for much smoother steering than in steering wheel and pedals mode. The main problem with joystick mode is that in order to make the joystick useable for the client, the stiff springs in the joystick were removed and replaced with weak springs. This has led to the joystick being easy to move, but unfortunately relatively unable to center itself fully without input from a user. The consequence of this in the test driving phase was that the vehicle was fine for making turns, but was very difficult to keep in a straight line. The sensitivity of the joystick coupled with the loose spring causes the vehicle to swerve rapidly from right to left in an oscillatory manner while maintaining a relatively straight trajectory overall. If the user stabilizes the joystick very firmly, this can be avoided, however if the driver loses focus, the vehicle will begin to oscillate and shake the rider violently at high speeds due to the rapid changes in centripetal acceleration. 46

48 In wireless mode, the vehicle is easy to drive, but there have been some issues observed when the transmitter is too close to the vehicle. The consequence of this is that the acceleration cuts off and the brake is applied. This should not be a concern, but can make for a jerky ride for the passenger. For this reason it is recommended that the transmitter be kept at least 20 ft from the vehicle. The range of the transmitter has been tested over 1000ft, and when the vehicle gets out of range, the system is designed to cut acceleration and apply the brakes. The wireless remote control can be hard to operate when the vehicle is pointed at the transmitter since the steering directions are reversed, but the operator can compensate for this by turning his/her body in the direction the vehicle is pointed for a more natural control. Overall, the vehicle is able to accelerate quite rapidly under full throttle, and for this reason it is not recommended that the vehicle ever reaches top speed unless the operator is extremely comfortable with the steering. Due to the fact that the steering changes rapidly and with no feedback to the driver, the operator can experience a surprising amount of g-forces that can cause the steering to get even worse. The vehicle stops when using the brakes, but the stop is gradual and controlled. No matter how hard the operator slams on the brake pedal or pulls the joystick, they must keep in mind that the vehicle will never decelerate at a higher rate than usual, and it is impossible to lock up the wheels with the braking system. This is yet another case for not driving the vehicle at max speed. The vehicle meets all expectations, and at low speeds is incredibly easy and enjoyable to drive. 3. Realistic Constraints Economic This engineering project, as with all other design projects, has a set budget which cannot be adjusted. A larger budget would allow for the purchasing of better components and result in a better final product. The projected cost of all parts for this go-kart far exceeds the budgetary constraints given, but will ultimately result in a better design. Luckily, donated and salvaged parts required for this go-kart are available for free, allowing for the design of better go-kart, while staying under the allocated funding. It is important to note that if this go-kart were to be manufactured, the free parts would no longer be available and the cost of the go-kart would increase from $2300 for a prototype to $7000 for a production model. Environmental The 10 HP engine for this go-kart will be gas powered and operation of the go-kart will result in the release of carbon dioxide and other emissions from the combustion engine. Other components of the go-kart are also known to be potential hazards to the environment. The Die Hard battery used to supply power to the electrical components of the go-kart contains materials that are corrosive and dangerous. Electronic components can also be hazardous to the environment and in the event of a malfunction, the proper disposal of any circuit boards is required. Since this go-kart is going to be operated in the outdoors, it must be driven carefully so the terrain is not excessively damaged. 47

49 Outdoor operation also requires that the go-kart be built in such a way so that environmental factors do not hinder its operation. Water can cause electrical components to short, so all electrical components must be protected from any type of moisture. This includes waterproofing the circuit board with the logic units, speed controller, and h-bridge. Mechanical components must be protected from dirt, dust, water, or any other environmental factors which could hinder their operation. Gearmotors, linear actuators, and servos need to be encased in a way such that the environment does not limit the function of the component. The gas engine for this project was chosen because it was specifically made to endure off road and outdoor conditions. Some of the components of this go-kart are rated for certain temperature ranges and parts that are suitable for outdoor temperatures must be found to ensure proper operation. All components must be shock resistant and able to absorb impacts if necessary. Sustainability As mentioned before, the go-kart will be gas powered and therefore it should be refueled before operation to obtain the maximum driving time. Depending on the speed at which the go-kart is operated the operation time will vary greatly. The go-kart will run much longer at a slow to moderate operating speed as opposed to operating the go-kart at intense speeds. Running the engine not only propels the go-kart but it also will generate current via the alternator. This will recharge the battery and provide power for all of the electrical components. Minor maintenance such as changing the oil and cleaning the go-kart occasionally will extend the lifetime of the vehicle. This go-kart has been designed to withstand collisions and operate in harsh environments. Under typical driving conditions the go-kart should operate without fail for a long time with the proper maintenance and care. Manufacturability Obtaining the majority of the parts for this go-kart would pose little challenge if it were to be manufactured on a large scale. If a particular part such as the Motion System linear actuator was not longer manufactured or could no longer be found, a suitable replacement would be easy to find. With a parts list, the proper mechanical and wiring diagrams, and the code needed to program the microprocessors, the majority of the go-kart ready to go. However, the chassis for this go-kart is custom made and would have to be fabricated in order to make a new go-kart. With the CAD files for the go cart the materials to make the frame it would be possible to manufacture the frame and install all of the components on the frame with little challenge. Health and Safety The primary concern of this project and most other engineering projects are safety. The intended operator of this go-kart is a child with Cerebral Palsy. Having any child operate a go-kart or other motorized vehicle has the potential to be dangerous, compounded with the fact that this child has under developed motor skills means that this go-kart has to be designed with the highest safety standards in mind. This go-kart is designed with multiple control methods. The onboard controls can be overridden at any time by a remote operator in the event that the driver is in danger, i.e., about to crash or roll the vehicle. The wheel base of the go-kart is wide and weight is distributed as low as possible to ensure that 48

50 the go-kart cannot roller over. In the unlikely event that the go-kart does roll over, a roll bar able to withstand thousands of pounds of force will protect the driver. The chassis of the go-kart has been designed to withstand impacts without deforming or breaking. A multi-point harness will secure the driver safely in the seat and keep them from being ejected from the vehicle. A two kill switches have been included in the design, one remote and one onboard, which will stop the gas engine and apply the brake in the event of an emergency. A speed governor has been implemented into the system which will limit the maximum speed of the go-kart. The operator will be able to select between a low, medium, or high speed. A logic unit with multiple processing units has been designed in a way that if one component were to fail, the system would shut down safely. The go-kart has been designed to operate under a variety of environmental conditions so malfunction due to water, dirt, or temperature is unlikely. Social One of the main goals of this project is to allow a disabled child to provide a release from the daily hardships of life and to give them a way to interact with the surrounding world. Building this go-kart allows them to live life as a normal child would and show that there really are not many differences between an average child and a child that suffers from a disability. This go-kart is build in such a way that it could be operated by anyone, disabled or not, and when looking at the design it would not look any different than a normal go-kart that could be purchased. 4. Safety Issues Safety, as mentioned earlier, is the primary concern of this project. This requires that the operator be safe at all times whether they be sitting in the vehicle or anywhere nears the go-kart. Starting with the electrical systems, all wires carrying a current will be routed through conduits to protect the wires from environmental hazards, but also protect the operator from any currents the wires may be carrying. The conduit will be secured to the chassis so the operator will not become hung up in it when operating the vehicle, or trip over it when entering or exiting the vehicle. There will be no bare wires anywhere in the go-kart. This will prevent any arcing that could potentially start a fire. All electrical equipment used in the go-kart is rated for currents that are higher than what will be experience during the operation of the go-kart. This will keep components from overheating and catching fire. For the mechanical components of the go-kart, all moving parts will be situated in a way that it would be impossible for the operator to become caught in them. A chain guard will protect the chain from being dislocated as well as protecting the operator from accidently becoming caught in the chain. The steel chassis will protect both the components of the go-kart as well as the operator of the go-kart in the event of a collision. The roll bar provides protection in the case of a roll over. All part on the go-kart will be secured to the chassis and there will be no parts that could become dislodged and come off during operation. The engine, gearbox, and torque converter have been located in a position that is inaccessible to the operator during operation of the vehicle. It will not be possible for the operator to become caught in the belt of the torque converter based on its location and where the driver will be positioned when operating the go- 49

51 kart. The chemical hazards of this project include corrosive materials leaking from the battery, gasoline in the engine, and oil also for the engine. It is unlikely that the sealed battery will leak any chemicals even in the event of a collision of roll over. The same is true for the gasoline and oil which should remain inside of the engine or in the gas tank in the event of an accident. It should be noted that gasoline and oil can be dangerous is swallowed or come in contact with cuts, and also pose a fire hazard if there is a fire nearby when refueling the vehicle or adding engine oil. Other chemical hazards are from the emissions of the vehicle. The go-kart should not be operated inside, especially if there is not adequate ventilation, as this poses a major health risk. Thermal hazards include warm electronic components and a hot engine exhaust. To keep electrical components as cool as possible, active cooling will be employed on the speed controller and h-bridge. Both of these components are rated to operate under currents well above the conditions present in the go-kart. This will also keep the components from overheating. These components will be encased in ventilated boxes to keep the operator from accessing them when they could potentially be hot. The engine exhaust will be situated in a way that the operator will not be able touch it when operating the vehicle. It is also well known that the exhaust on a vehicle is hot to the touch and should not be touched during operation or after operation until it has had time to cool down. 5. Impact of Engineering Solutions There should be little to no impact based upon the engineering solutions present in this design. This gokart is intended to be operated by a single client and was designed specifically based on the needs of the client. However, in the event that this go-kart becomes mass produced there could be some considerable effects on economics, society, the environment, and even far reaching global effects. This go-kart could potentially provide a release for any physically handicapped person and it was designed to cost less than other go-karts that have electronic controls. The market for this product is large and there currently are no suitable designs that can provide the same function as this go-kart. By creating a new product for a market that has no other products like it, this go-kart has the potential to make a lot of money for the manufacturer. If this product were to be purchased by a multitude of people, then society would begin to see disabled people in a new way. They would be seen out riding in go-karts, enjoying activities that which are normally reserved for non-disabled people. Handicapped people would be seen as not being all that different and the differences between people would become less apparent. On the whole society could become more understanding, more accepting, and less judgmental. The environmental impact is not favorable however. These go-karts are gas powered and release carbon dioxide and other emissions into the atmosphere. Whether or not these emissions lead to global warming has yet to be adequately determined, however it is known that these emissions can lead to acid rain, smog, and unhealthy air to breath. Disposing of a go-kart with these electrical components would be cause trouble as well. Just as a laptop computer should not be disposed of in the garbage, 50

52 these electrical components should not be just thrown out if the circuits were to malfunction or the gokart was to be disposed of. The battery would also need to be disposed of properly as it contains corrosive materials that cannot just be thrown away. The same goes for the engine oil when it needs to be changed. Disposing of these materials properly is much better than throwing them out in the garbage, but even when disposed of properly, some materials cannot be recycled and ultimately must be thrown out. This go-kart could potentially have a global impact. The awareness for disabilities on the global level could rise, resulting in more funding going to research for curing ailments such as Cerebral Palsy. The acceptance of disabled people on the global level would increase as well. If the go-kart became popular in other countries that would result in an increase in the products that the United States exports and bring in more foreign money thereby lowering the trade deficit. The United States would be seen in a friendlier manner globally. If this go-kart were to become popular in a global setting then it would lead to improvements and innovations of the go-kart that could be applied to other engineering specialties. 6. Life-long Learning In the course of designing this go-kart many new skills have been developed. Designing the chassis for the go-kart required a 3D CAD program. The CAD program that was learned was Solidworks 2007 to create parts and put them together. A method for mechanical stress testing of the components had to be discovered and luckily Solidworks was able to perform this task as well. The system for steering the go-kart involved the most learning. Three systems of controlling the go-kart had to be developed that would not interfere with one another. This required acquiring some programming knowledge in embedded C and how to upload the programs to the processors. In order to be able to have the gearmotors working in both the forward and reverse directions h-bridges had to be made and tested to prove that it would be an acceptable method for quickly changing the direction of the gearmotors. Other options had to be researched as well for this task and the principles behind relays and how to incorporate relays into circuit had to be looked into. The both the speed controller for steering the gokart and the h-bridge for the braking system take PWM signals as their inputs. Understanding the basic concept of the PWM signal and how to apply it to a particular situation had to be discovered. After understanding how a PWM signal works a method for getting the processors to output such signals had to be determined and programming such a method also had to be done. To generate a smooth ride for the go-kart different types of suspensions had to be investigated. An independent front suspension and a semi-independent rear suspension was determined to be the best overall suspension for the purposes of this go-kart. Different engines had to be researched when choosing the best possible engine for the go-kart. An electrical engine would be the most environmentally friendly engine, but a gas powered engine like the one chosen for this design is able to keep the electronics operational without relying on an array of batteries and refueling a gas engine is much faster than recharging batteries for an electric motor. Aside from technical aspects that were learned when designing this go-kart, much research about Cerebral Palsy had to be done, including how it affects a person both physically and mentally. 51

53 Understanding how our client was affected helped to determine how the go-kart needed to be designed in terms of control methods and how his body would be positioned. A body position with the thighs and chest at a 90 degree angle was discovered to be the optimal body position and the client s arms needed to be as close to their body as possible. Maintaining this position allows the client to have the best control over their arms and legs. 7. Budget and Timeline 52

54 7.1 Budget Budget breakdown Free Parts Parts to Buy Item # Part Name Value Item # Part Name Price Shipping 0 Rear Wheels Engine Rack and Pinion Simple H bridge Brake controller steering wheel Steering PWM Direction controller Front Wheels Steel for Chassis " disk brake rotor Hardware series Torque Convertor Paint Tapered bearings (front) Misc. Equipment Spindles (front wheel) Linear position Transducer " axle Electronic components /4" pillow block Wire/connectors pedals Grease/grease fittings Axle Bearings Sheet metal Rear Axle Hubs Seat Safety Harness Front Shocks Fwd/Rev Gearbox Rear Shocks Remote Control reciever Deep Cycle Marine Battery Brake Gearmotor Steering Gearmotor Linear Actuator Sprockets Linear Position encoder Special Seat Electronic Components 100 Free Parts Total Value: Total Cost: Total Project Value:

55 7.2 Timeline ID Name Duration Start Finish 1 Statement and Specifications 6.d 9/1/2008 8:00 9/8/ :00 2 Design 1 28.d 9/1/2008 8:00 10/8/ :00 3 Design 2 28.d 9/1/2008 8:00 10/8/ :00 4 Design 3 28.d 9/1/2008 8:00 10/8/ :00 5 Optimal Design 31.d 9/8/2008 8:00 10/20/ :00 6 Rear Chassis Fabrication 4.d 11/22/2008 8:00 11/26/ :00 7 Front Chassis Fabrication 4.d 11/22/2008 8:00 11/26/ :00 8 Seat Mount Fabrication 4.d 11/22/2008 8:00 11/26/ :00 9 Roll Bar Fabrication 22.d 11/22/2008 8:00 12/20/ :00 10 Rear Suspension Fabrication 4.d 11/22/2008 8:00 11/26/ :00 11 Front Suspension Fabrication 4.d 11/22/2008 8:00 11/26/ :00 12 Install Engine 14.d 1/1/2009 8:00 1/18/ :00 13 Install Gearbox 15.d 1/1/2009 8:00 1/19/ :00 14 Install Brake Motor 15.d 1/1/2009 8:00 1/19/ :00 15 Install Steering Motor 15.d 1/1/2009 8:00 1/19/ :00 16 Install throttle Servo 15.d 1/1/2009 8:00 1/19/ :00 17 Install Gearbox Linear Actuator 15.d 1/1/2009 8:00 1/19/ :00 18 Install Seat Linear Actuator 15.d 1/1/2009 8:00 1/19/ :00 19 Assemble Full Frame 8.d 1/1/2009 8:00 1/12/ :00 20 Install Battery 14.d 1/2/2009 8:00 1/19/ :00 21 Install Processing Unit 5.d 1/19/2009 8:00 1/23/ :00 22 Design Processing Unit 16.d 12/15/2008 8:00 1/2/ :00 23 Assemble Circuitry 11.d 1/6/2009 8:00 1/18/ :00 24 Program: Joystick 77.d 9/30/2008 8:00 1/12/ :00 25 Program: Steering Wheel and Pedals 77.d 9/30/2008 8:00 1/12/ :00 26 Program: Remote Control 77.d 9/30/2008 8:00 1/12/ :00 27 Program: Input Selector 77.d 9/30/2008 1/12/

56 8:00 17:00 28 Program: Emergency Stop 77.d 9/30/2008 8:00 1/12/ :00 29 Program: Speed Governor 77.d 9/30/2008 8:00 1/12/ :00 30 Steering Limit Switches Installation 14.d 1/1/2009 8:00 1/18/ :00 31 Gearbox Limit Switches Installation 14.d 1/1/2009 8:00 1/18/ :00 32 Parts Order 6.d 10/20/2008 8:00 10/27/ :00 33 Steel Stock Preparation 10.d 11/10/2008 8:00 11/21/ :00 34 Processing Unit Testing 5.d 1/12/2009 8:00 1/16/ :00 35 Rack and Pinion Installation 15.d 1/1/2009 8:00 1/19/ :00 36 Steering Wheel Installation 15.d 1/1/2009 8:00 1/19/ :00 37 Pedals Installation 15.d 1/1/2009 8:00 1/19/ :00 38 Linear Position Encoder Installation 15.d 1/1/2009 8:00 1/19/ :00 39 String Potentiometer Installation 15.d 1/1/2009 8:00 1/19/ :00 40 Run Power Cables 5.d 1/12/2009 8:00 1/16/ :00 41 Run Feedback Wires 5.d 1/12/2009 8:00 1/16/ :00 42 Keystart Installation 15.d 1/1/2009 8:00 1/19/ :00 43 State Selector Installation 15.d 1/1/2009 8:00 1/19/ :00 44 Run Wire Conduits 15.d 1/1/2009 8:00 1/19/ :00 45 Hydraulic Brake Installation 15.d 1/1/2009 8:00 1/19/ :00 46 Seat and 5-point Harness Installation 15.d 1/1/2009 8:00 1/19/ :00 Assemble Engine/Torque Converter/Gearbox 1/19/ Unit 15.d 1/1/2009 8:00 17:00 1/19/ Braking H-Bridge Installation 15.d 1/1/2009 8:00 17:00 49 Steering Speed Controller Installation 15.d 1/1/2009 8:00 1/19/ :00 50 Seat Bracket Fabrication 4.d 11/22/2008 8:00 11/26/ :00 51 Testing Phase 25.d 1/26/2009 8:00 2/27/ :00 52 Steering Wheel Assembly Fabrication 5.d 11/10/2008 8:00 11/14/ :00 53 Gearbox Mount Fabrication 4.d 11/22/2008 8:00 11/26/ :00 54 Gearbox Mount Installation 4.d 11/22/2008 8:00 11/26/ :00 55 Install Killswitch 15.d 1/1/2009 8:00 1/19/

57 56 Painting/Cosmetics 1.d 1/23/2009 8:00 57 Speed Transducer Installation 7.d 1/1/2009 8:00 1/26/ Write Operator's manual 25.d 8:00 11/21/ Transport Metal Stock to Andover 2.d 8:00 1/12/ Transport Fabricated Chassis to Uconn 7.d 8:00 17:00 1/25/ :00 1/11/ :00 2/27/ :00 11/22/ :00 1/18/ :00 It is estimated that the project will require 650 man hours to complete. The start date in the timeline refers to the earliest time it is estimated that a task will begin. The finish date refers to the date which the task must be completed by. 8. Team Members Contributions to the Project James Paolino James Paolino has been the lead mechanical designer for the project. The majority of the linkages were designed by James. He has also done all of the computer drafting for the project using Solidworks James chose many of the mechanical parts for the project to be used. Metal preparations have been done by James and he will be fabricating the chassis of the go-kart as the most experienced welder on the team. James will also be taking part in the assembly of the mechanical systems of the go-kart. Eric Leknes Eric Leknes is the lead programmer for the project, writing the embed C code for the pic microproecssors. The programs for the control systems, the kill switch, the speed governor, the input selector, and other software will be programmed by Eric. Eric will also be dealing with the various inputs and outputs going into the microprocessor. The wireless interface for the remote control of the go-kart will be handled primarily by Eric. The power management for the speed controllers will be handled by Eric as well. Eric will be working to design the circuitry of the go-kart. Alexander Jadczak Alex Jadczak will be working on the fabrication of the go-kart doing preparatory work required for welding the chassis and the finishing work required post welding. Alex will also be working on the assembly of the mechanical systems once the chassis has been completed. Alex will be working to design the circuitry of the go-kart and will be soldering all of the circuitry once it has been designed. The interfaces between the electronics and the mechanics of the go-kart will be handled by Alex. Tarek Tantawy Tarek Tantawy has been working on the mechanical systems of the go-kart, focusing on the systems required for the seat of the go-kart. Tarek worked to design the seat assembly for the design of the gokart. Tarek also has been doing preparatory work on the steel stock so it will be ready for welding and 56

58 fabrication of the chassis. The parts ordering for the project was completed by Tarek. Tarek will be in charge of painting the go-kart and the cosmetics of the go-kart. 9. Conclusion The goal of this project is to design a go-kart for a client suffering from Cerebral Palsy. Safety is the most important aspect of this design, therefore a remote control system and a remote kill switch must be incorporated into the design along with the control methods the operator will be using in order for this go-kart to be safe for the client. A reinforced chassis has been designed to keep the operator safe in the event of a collision. The current design fulfils these safety requirements and exceeds the safety requirements for a collision as demonstrated by the structural analysis. The proposed go-kart will allow the client to experience driving a go-kart on his own while still remaining safe while operating it. 10. References 1. Alex Peslak, Alex Kattamis and Steve Ricciardelli. E-Racer: An Electric Go-Kart. University of Connecticut. NSF 2001 Engineering Senior Design Projects to Aid Persons with Disabilities. Retrieved on 25 September < 2. Joel G. Landau, James J. LaPenna and Todd M. Piche. Recreational Electra-Scooter for Special Children: A Fixed-Radius-Turn, On-Off-Control Wheelchair Carrier. State University of New York-Buffalo. NSF 1994 Engineering Senior Design Projects to Aid the Disabled. Retrieved on 25 September < 3. Kevin Arpin, Michael Marquis, Allison Meisner and Travis Ward. E-Racer. University of Connecticut. NSF 2008 Engineering Senior Design Projects to Aid Persons with Disabilities. Retrieved on 25 September < 4. Go-Kart by Mobility4Kids. ABLEDATA. Retrieved on 25 September < 5. Roberts, Keith Alan. Handi-Driver. United States Patent Application Publication. Retrieved on 25 September < 6. Simple H Bridge information Retrieved on 20 October 2008 < > 7. IFI Thor 883 Speed Controller Retrieved on 20 October 2008 < 57

59 8. Tecumseh Formula Horizontal Engine with Electric Start Retrieved 20 October 2008 < ductid=394&r=394> 9. Gearbox Retrieved on 20 October 2008 < 10. Torque Convertor Retrieved 20 October 2008 < 11. Dayton Gearmotor Retrieved 20 October 2008 < 11. Acknowledgements The S-90 Go-kart team thanks the following for their support in this project: Rich and Serj of the University of Connecticut Machine Shop for the use of tools, space, and all of their wisdom. The National Science Foundation Projects to Aid Persons with Disabilities Project for funding. Dr. John Enderle of the University of Connecticut Mr. David Price of the University of Connecticut 12. Appendix 12.1 Updated Specifications All specifications are up to date 12.2 Purchase Requisitions 58

60 59

61 PURCHASE ORDER REQUISITION - UCONN BME SENIOR DESIGN LAB Instructions: Students are to fill out boxed areas with white background Each Vendor will require a different purchase requisition Date: October 27, 2008 Team # 1 Student Name: Tarek Tantawy Total Expenses 0 Ship to: University of Connecticut Lab Admin only: Biomedical Engineering FRS # U-2247, 260 Glenbrook Road Student Initial Budget Storrs, CT Student Current Budget Attn: Tarek Tantawy Project Sponsor Project Name: S-90 Go Kart ONLY ONE COMPANY PER REQUISITION Catalog # Description Unit QTY Unit Price Amount RustOleum 12oz Sp Gray Auto Primer 6 each 2 $23.79 $47.58 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 Comments Price Quote Shipping $12.45 File Name: Total: $47.58 Yes or No Vendor Accepts Purchase Orders? Vendor: Hardware World Address: Authorization: customerservice@hardwareworld.com Phone: Contact Name: 60

62 PURCHASE ORDER REQUISITION - UCONN BME SENIOR DESIGN LAB Instructions: Students are to fill out boxed areas with white background Each Vendor will require a different purchase requisition Date: October 27, 2008 Team # 1 Student Name: Tarek Tantawy Total Expenses 0 Ship to: University of Connecticut Lab Admin only: Biomedical Engineering FRS # U-2247, 260 Glenbrook Road Student Initial Budget Storrs, CT Student Current Budget Attn: Tarek Tantawy Project Sponsor Project Name: S-90 Go Kart ONLY ONE COMPANY PER REQUISITION Catalog # Description Unit QTY Unit Price Amount 1095K65 grease fittings 10 pack $ T211 tie rod end each $ k21 Plain bore spur gear each $ k16 Plain bore spur gear each $ t3 Mounted Bearings each $5.06 $0.00 $0.00 $0.00 Comments Price Quote Shipping $0.00 File Name: Total: $88.72 Yes or No Vendor Accepts Purchase Orders? Vendor: McMaster-Carr Address: 200 New Canton Way Robbinsville, NJ Authorization: Phone: (609) Contact Name: 61

63 PURCHASE ORDER REQUISITION - UCONN BME SENIOR DESIGN LAB Instructions: Students are to fill out boxed areas with white background Each Vendor will require a different purchase requisition Date: November 12, 2008 Team # 1 Student Name: Tarek Tantawy Total Expenses 0 Ship to: University of Connecticut Lab Admin only: Biomedical Engineering FRS # U-2247, 260 Glenbrook Road Student Initial Budget Storrs, CT Student Current Budget Project Attn: Tarek Tantawy Sponsor Project Name: S-90 Go Kart ONLY ONE COMPANY PER REQUISITION Catalog # Description Unit QTY Unit Price Amount 6.0 R /4 inch Alloy 4140 Steel Round - Cold Drawn Annealed Ft. 2 $40.50 $81.00 T OD x.120 wall x.760 ID DOM Seamless Structural Round Steel Tube 4.0 Ft. 1 $23.80 $23.80 $0.00 $0.00 $0.00 Comments Price Quote Shipping $10.56 File Name: Total: $ Yes or No Vendor Accepts Purchase Orders? Vendor: Metals Depot Address: 4200 Revilo Road, Winchester, KY USA Authorization: Phone: Contact Name: 62

64 PURCHASE ORDER REQUISITION - UCONN BME SENIOR DESIGN LAB Instructions: Students are to fill out boxed areas with white background Each Vendor will require a different purchase requisition Date: October 27, 2008 Team # 1 Student Name: Tarek Tantawy Total Expenses 0 Ship to: University of Connecticut Lab Admin only: Biomedical Engineering FRS # U-2247, 260 Glenbrook Road Student Initial Budget Storrs, CT Student Current Budget Attn: Tarek Tantawy Project Sponsor Project Name: S-90 Go Kart ONLY ONE COMPANY PER REQUISITION Catalog # Description Unit QTY Unit Price Amount T /2 OD x.250 wall x 1.00 ID DOM Seamless Structural Round Steel Tube 8.0 Ft. 1 $ $ SQ11 1 x 1 Square Bar Hot Rolled A-36 Steel Square 4.0 Ft. 1 $22.08 $22.08 T X 1 X 11 GA (.120 wall) A513 Steel Structural Square Tube 12.0 Ft. 4 $24.96 $99.84 R158 5/8 inch Dia. Round Bar Hot Rolled A-36 Steel Round 2.0 Ft. 1 $4.68 $4.68 T /8 OD X.120 wall X.635 ID DOM Seamless Structural Round Steel Tube 2.0 Ft. 1 $12.18 $12.18 R /4 inch Alloy 4140 Steel Round - Cold Drawn Annealed 12.0 Ft. 1 $64.80 $64.80 T OD x.120 wall x.760 ID DOM Seamless Structural Round Steel Tube 8.0 Ft. 1 $47.60 $47.60 F3182 1/8 X 2 Cold Finished C1018 Flat Bar 4.0 Ft. 1 $12.72 $12.72 C wide X 1/2 legs X 1/8 web A-36 Steel Channel 4.0 Ft. 1 $10.08 $10.08 A /2 X 1-1/2 X 1/8 Steel Angle A-36 Steel Angle 6.0 Ft. 1 $14.16 $14.16 T /2 X 1-1/2 X 11 GA (.120 wall) A513 Steel Structural Square Tube 12.0 Ft. 1 $51.24 $51.24 Comments Price Quote Shipping $58.19 File Name: Total: $ Yes or No Vendor Accepts Purchase Orders? Vendor: Metals Depot Address: 4200 Revilo Road, Winchester, KY USA Authorization: Phone: Contact Name: 63

65 PURCHASE ORDER REQUISITION - UCONN BME SENIOR DESIGN LAB Instructions: Students are to fill out boxed areas with white background Each Vendor will require a different purchase requisition Date: October 27, 2008 Team # 1 Student Name: Tarek Tantawy Total Expenses 0 Ship to: University of Connecticut Lab Admin only: Biomedical Engineering FRS # U-2247, 260 Glenbrook Road Student Initial Budget Storrs, CT Student Current Budget Project Attn: Tarek Tantawy Sponsor Project Name: S-90 Go Kart ONLY ONE COMPANY PER REQUISITION Catalog # Description Unit QTY Unit Price HM T Amount Tecumseh Formula Horizontal Engine with Electric Start 10 HP, 1in. x 2 7/8in. Shaft each 1 $ $ $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 Comments Price Quote Shipping $25.71 File Name: Total: $ Yes or No Vendor Accepts Purchase Orders? Vendor: Northern Tools Address: 2800 Southcross Drive West Burnsville, Minnesota Authorization: Phone: Contact Name: 64

66 PURCHASE ORDER REQUISITION - UCONN BME SENIOR DESIGN LAB Instructions: Students are to fill out boxed areas with white background Each Vendor will require a different purchase requisition Date: October 27, 2008 Team # 1 Student Name: Tarek Tantawy Total Expenses 0 Ship to: University of Connecticut Lab Admin only: Biomedical Engineering FRS # U-2247, 260 Glenbrook Road Student Initial Budget Storrs, CT Student Current Budget Attn: Tarek Tantawy Project Sponsor Project Name: S-90 Go Kart ONLY ONE COMPANY PER REQUISITION Catalog # Description Unit QTY Unit Price Amount 0C-WI10Gb 10 gauge high-strand count wire - Black per foot 20 $0.79 $ C-WI10Gr 10 gauge high-strand count wire - Red per foot 20 $0.79 $15.80 $0.00 $0.00 $0.00 $0.00 $0.00 Comments Price Quote Shipping $7.20 File Name: Total: $31.60 Yes or No Vendor Accepts Purchase Orders? Vendor: Robot Marketplace Address: th Street E. Bradenton, FL Authorization: Phone: (877) Contact Name: 65

67 PURCHASE ORDER REQUISITION - UCONN BME SENIOR DESIGN LAB Instructions: Students are to fill out boxed areas with white background Each Vendor will require a different purchase requisition Date: November 13, 2008 Team # 1 Student Name: Tarek Tantawy Total Expenses 0 Ship to: University of Connecticut Lab Admin only: Biomedical Engineering FRS # U-2247, 260 Glenbrook Road Student Initial Budget Storrs, CT Student Current Budget Attn: Tarek Tantawy Project Sponsor Project Name: S-90 Go Kart ONLY ONE COMPANY PER REQUISITION Catalog # Description Unit QTY Unit Price Amount MB-SBPP /8 bore SBPP Pillow Block each 2 $13.05 $26.10 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 Comments Price Quote Shipping $14.26 File Name: Total: $26.10 Yes or No Vendor Accepts Purchase Orders? Vendor: Robot Marketplace Address: th Street E. Bradenton, FL Authorization: Phone: (877) Contact Name: 66

68 PURCHASE ORDER REQUISITION - UCONN BME SENIOR DESIGN LAB Instructions: Students are to fill out boxed areas with white background Each Vendor will require a different purchase requisition Date: October 27, 2008 Team # 1 Student Name: Tarek Tantawy Total Expenses 0 Ship to: University of Connecticut Lab Admin only: Biomedical Engineering FRS # U-2247, 260 Glenbrook Road Student Initial Budget Storrs, CT Student Current Budget Attn: Tarek Tantawy Project Sponsor Project Name: S-90 Go Kart ONLY ONE COMPANY PER REQUISITION Catalog # Description Unit QTY Unit Price Amount IFI-T883 IFI Thor 883-with 12V fan each 1 $185 $ SYREN25 SyRen 25A Regenerative Motor Driver each 1 $74.99 $ C-WI10Gb 10 gauge high-strand count wire - Black per foot 20 $0.79 $ C-WI10Gr 10 gauge high-strand count wire - Red per foot 20 $0.79 $15.80 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 Comments Price Quote Shipping $19.20 File Name: Total: $ Yes or No Vendor Accepts Purchase Orders? Vendor: Robot Marketplace Address: th Street E. Bradenton, FL Authorization: Phone: (877) Contact Name: 67

69 12.3 Stress Analysis Appendix A: Gear Stress Analysis Author: James Paolino Company: UConn Date: 10/21/08 1. File Information 2. Materials 3. Load & Restraint Information 4. Study Property 5. Results a. Stress b. Displacement c. Deformation d. Design Check 6. Appendix 1. File Information Model name: drive Gear Model location: C:\Documents and Settings\JFP\My Documents\Solidworks\Senior Design\drive Gear.SLDPRT Results location: C:\Documents and Settings\JFP\My Documents\Solidworks\Senior Design\Analysis Study name: COSMOSXpressStudy (-Default-) 68

70 2. Materials No. Part Name Material Mass Volume 1 drive Gear [SW]Plain Carbon Steel lb in^3 3. Load & Restraint Information Restraint Restraint1 <drive Gear> on 1 Face(s) immovable (no translation). Description: Load Load1 <drive Gear> on 33 Face(s) apply normal force 2 lb using uniform distribution Description: 4. Study Property Mesh Information Mesh Type: Mesher Used: Automatic Transition: Solid mesh Standard Off 69

71 Smooth Surface: Jacobian Check: Element Size: Tolerance: Quality: On 4 Points in in High Number of elements: Number of nodes: Time to complete mesh(hh;mm;ss): 00:00:13 Computer name: JAMES Solver Information Quality: Solver Type: High Automatic 5. Results 5a. Stress Name Type Min Location Max Location Plot1 VON: von Mises stress N/m^2 (0.25 in, in, e+008 N/m^2 ( in, in, 70

72 in) in) drive Gear-COSMOSXpressStudy-Stress-Plot1 JPEG 71

73 5b. Displacement Name Type Min Location Max Location Plot2 URES: Resultant displacement 0 mm (1.125 in, in, mm (0.25 in, in, in) in) drive Gear-COSMOSXpressStudy-Displacement-Plot2 JPEG 72

74 5c. Deformation drive Gear-COSMOSXpressStudy-Deformation-Plot3 JPEG 73

75 5d. Design Check drive Gear-COSMOSXpressStudy-Design Check-Plot4 JPEG 74

76 6. Appendix Material name: [SW]Plain Carbon Steel Description: Material Source: Used SolidWorks material 75

77 Material Library Name: Material Model Type: Linear Elastic Isotropic Property Name Value Units Elastic modulus e+007 psi Poisson's ratio 0.28 NA Mass density lb/in^3 Yield strength psi 76

78 Appendix B: Roll Bar Stress Analysis Author: James Paolino Company: UConn Date: 10/22/08 1. File Information 2. Materials 3. Load & Restraint Information 4. Study Property 5. Results a. Stress b. Displacement c. Deformation d. Design Check 6. Conclusion 7. Appendix 1. File Information Model name: Roll Bar Model location: C:\Documents and Settings\JFP\My Documents\Solidworks\Senior Design\Roll Bar.SLDPRT Results location: C:\Documents and Settings\JFP\My Documents\Solidworks\Senior Design\Analysis Study name: COSMOSXpressStudy (-Default-) 77

79 2. Materials No. Part Name Material Mass Volume 1 Roll Bar [SW]Plain Carbon Steel lb in^3 2 Roll Bar [SW]Plain Carbon Steel lb in^3 3 Roll Bar [SW]Plain Carbon Steel lb in^3 3. Load & Restraint Information Restraint Restraint1 <Roll Bar> on 2 Face(s) immovable (no translation). Description: Load Load1 <Roll Bar> on 1 Face(s) apply force lb normal to reference plane with respect to selected reference Right Plane using uniform distribution Description: 4. Study Property Mesh Information Mesh Type: Solid mesh 78

80 Mesher Used: Automatic Transition: Smooth Surface: Jacobian Check: Element Size: Tolerance: Quality: Standard Off On 4 Points in in High Number of elements: Number of nodes: Time to complete mesh(hh;mm;ss): 00:00:07 Computer name: JAMES Solver Information Quality: Solver Type: High Automatic 5. Results 5a. Stress Name Type Min Location Max Location Plot1 VON: von Mises stress N/m^2 ( in, e+008 N/m^2 (21.25 in,

81 in, 0 in) in, 0 in) Roll Bar-COSMOSXpressStudy-Stress-Plot1 JPEG 80

82 5b. Displacement Name Type Min Location Max Location Plot2 URES: Resultant displacement 0 mm ( in, 0 in, 0.25 in) mm ( in, in, in) Roll Bar-COSMOSXpressStudy-Displacement-Plot2 JPEG 81

83 5c. Deformation Roll Bar-COSMOSXpressStudy-Deformation-Plot3 JPEG 82

84 5d. Design Check Roll Bar-COSMOSXpressStudy-Design Check-Plot4 JPEG 83

85 6. Conclusion This analysis shows that the roll bar can easily withstand a direct side impact force of 1000lbs without any extra supports, and since there will be extra supports and the vehicle with a 200lb passenger is estimated to weigh 750lbs, this means that the roll bar is more than strong enough to withstand a vehicle rollover with minimal strain effects. 7. Appendix 84

86 Material name: [SW]Plain Carbon Steel Description: Material Source: Used SolidWorks material Material Library Name: Material Model Type: Linear Elastic Isotropic Property Name Value Units Elastic modulus e+007 psi Poisson's ratio 0.28 NA Mass density lb/in^3 Yield strength psi 85

87 Appendix C: Rear Suspension Bar Stress Analysis Author: James Paolino Company: UConn Date: 10/22/08 1. File Information 2. Materials 3. Load & Restraint Information 4. Study Property 5. Results a. Stress b. Displacement c. Deformation d. Design Check 6. Conclusion 7. Appendix 1. File Information Model name: Rear Chassis Model location: C:\Documents and Settings\JFP\My Documents\Solidworks\Senior Design\Rear Chassis.SLDPRT Results location: C:\Documents and Settings\JFP\My Documents\Solidworks\Senior Design\Analysis 86

88 Study name: COSMOSXpressStudy (-Default-) 2. Materials No. Part Name Material Mass Volume 1 Rear Chassis [SW]Plain Carbon Steel lb in^3 2 Rear Chassis [SW]Plain Carbon Steel lb in^3 3 Rear Chassis [SW]Plain Carbon Steel lb in^3 4 Rear Chassis [SW]Plain Carbon Steel lb in^3 5 Rear Chassis [SW]Plain Carbon Steel lb in^3 6 Rear Chassis [SW]Plain Carbon Steel lb in^3 7 Rear Chassis [SW]Plain Carbon Steel lb in^3 8 Rear Chassis [SW]Plain Carbon Steel lb in^3 9 Rear Chassis [SW]Plain Carbon Steel lb in^3 10 Rear Chassis [SW]Plain Carbon Steel lb in^3 11 Rear Chassis [SW]Plain Carbon Steel lb in^3 3. Load & Restraint Information Restraint Restraint1 <Rear Chassis> on 2 Face(s) immovable (no translation). 87

89 Description: Load Load1 <Rear Chassis> on 1 Face(s) apply force 200 lb normal to reference plane with respect to selected reference Front Plane using uniform distribution Description: 4. Study Property Mesh Information Mesh Type: Mesher Used: Automatic Transition: Smooth Surface: Jacobian Check: Element Size: Tolerance: Quality: Solid mesh Standard Off On 4 Points in in High Number of elements: 4926 Number of nodes: 8918 Time to complete mesh(hh;mm;ss): 00:00:01 Computer name: JAMES 88

90 Solver Information Quality: Solver Type: High Automatic 5. Results 5a. Stress Name Type Min Location Max Location Plot1 VON: von Mises stress N/m^2 ( in, in, e+007 N/m^2 ( in, in, in) in) Rear Chassis-COSMOSXpressStudy-Stress-Plot1 JPEG 89

91 5b. Displacement Name Type Min Location Max Location Plot2 URES: Resultant displacement 0 mm (13 in, in, mm (5.2377e-007 in, in, 90

92 in) in) Rear Chassis-COSMOSXpressStudy-Displacement-Plot2 JPEG 91

93 5c. Deformation Rear Chassis-COSMOSXpressStudy-Deformation-Plot3 JPEG 92

94 5d. Design Check Rear Chassis-COSMOSXpressStudy-Design Check-Plot4 JPEG 93

95 6. Conclusion This Analysis shows that the rear suspension bar can withstand a force of 200lbs with a safety factor of 3.2. This is important because the estimated weight of the vehicle is about 750lbs with a 200lb rider, and the force that the rear suspension bar will see will be about 1/12th of that due to the mechanical design of where the suspension pins are located and the weight distribution of the vehicle. Using a 200lb force simulates more than the bar will probably ever see, and the high safety factor of 3.2 proves that it will be stable. 7. Appendix Material name: [SW]Plain Carbon Steel Description: Material Source: Used SolidWorks material Material Library Name: Material Model Type: Linear Elastic Isotropic Property Name Value Units Elastic modulus e+007 psi Poisson's ratio 0.28 NA Mass density lb/in^3 Yield strength psi 94

96 Appendix D: Front Bumper Analysis Author: James Paolino Company: UConn Date: 10/18/08 1. File Information 2. Materials 3. Load & Restraint Information 4. Study Property 5. Results a. Stress b. Displacement c. Deformation d. Design Check 6. Appendix 1. File Information Model name: Front Bumper Model location: C:\Documents and Settings\JFP\My Documents\Solidworks\Senior Design\Front Bumper.SLDPRT Results location: C:\Documents and Settings\JFP\My Documents\Solidworks\Senior Design\Analysis Study name: COSMOSXpressStudy (-Default-) 95

97 2. Materials No. Part Name Material Mass Volume 1 Front Bumper [SW]Plain Carbon Steel lb in^3 2 Front Bumper [SW]Plain Carbon Steel lb in^3 3 Front Bumper [SW]Plain Carbon Steel lb in^3 4 Front Bumper [SW]Plain Carbon Steel lb in^3 3. Load & Restraint Information Restraint Restraint1 <Front Bumper> on 1 Face(s) immovable (no translation). Description: Load Load1 <Front Bumper> on 1 Face(s) apply normal force 1000 lb using uniform distribution Description: 4. Study Property Mesh Information Mesh Type: Solid mesh 96

98 Mesher Used: Automatic Transition: Smooth Surface: Jacobian Check: Element Size: Tolerance: Quality: Standard Off On 4 Points in in High Number of elements: 7503 Number of nodes: Time to complete mesh(hh;mm;ss): 00:00:03 Computer name: JAMES Solver Information Quality: Solver Type: High Automatic 5. Results 5a. Stress Name Type Min Location Max Location Plot1 VON: von Mises stress e+007 N/m^2 (18.5 in, e+007 N/m^2 (19 in, 97

99 0.12 in, in) 1 in, in) Front Bumper-COSMOSXpressStudy-Stress-Plot1 JPEG 98

100 5b. Displacement Name Type Min Location Max Location Plot2 URES: Resultant displacement 0 mm (18 in, 1 in, mm (19 in, 0 in, in) 9 in) Front Bumper-COSMOSXpressStudy-Displacement-Plot2 JPEG 99

101 5c. Deformation Front Bumper-COSMOSXpressStudy-Deformation-Plot3 JPEG 100

102 5d. Design Check Front Bumper-COSMOSXpressStudy-Design Check-Plot4 JPEG 101

103 6. Appendix Material name: [SW]Plain Carbon Steel Description: Material Source: Used SolidWorks material 102

104 Material Library Name: Material Model Type: Linear Elastic Isotropic Property Name Value Units Elastic modulus e+007 psi Poisson's ratio 0.28 NA Mass density lb/in^3 Yield strength psi 103

105 Appendix E: Front Suspension Arm Top Author: James Paolino Company: UConn Date: 10/18/08 1. File Information 2. Materials 3. Load & Restraint Information 4. Study Property 5. Results a. Stress b. Displacement c. Deformation d. Design Check 6. Appendix 1. File Information Model name: Front upper suspension arm Model location: C:\Documents and Settings\JFP\My Documents\Solidworks\Senior Design\Front upper suspension arm.sldprt Results location: C:\Documents and Settings\JFP\My Documents\Solidworks\Senior Design\Analysis 104

106 Study name: COSMOSXpressStudy (-Default-) 2. Materials No. Part Name Material Mass Volume 1 Front upper suspension arm [SW]Plain Carbon Steel lb in^3 3. Load & Restraint Information Restraint Restraint1 <Front upper suspension arm> on 1 Face(s) immovable (no translation). Description: Load Load1 <Front upper suspension arm> on 1 Face(s) apply normal force 1000 lb using uniform distribution Description: 4. Study Property Mesh Information Mesh Type: Solid mesh 105

107 Mesher Used: Automatic Transition: Smooth Surface: Jacobian Check: Element Size: Tolerance: Quality: Standard Off On 4 Points in in High Number of elements: 8136 Number of nodes: Time to complete mesh(hh;mm;ss): 00:00:02 Computer name: JAMES Solver Information Quality: Solver Type: High Automatic 5. Results 5a. Stress Name Type Min Location Max Location Plot1 VON: von Mises stress N/m^2 ( in, e+008 N/m^2 ( in, 106

108 in, in) in, in) Front upper suspension arm-cosmosxpressstudy-stress-plot1 JPEG 107

109 5b. Displacement Name Type Min Location Max Location (6 in, (0 in, Plot2 URES: Resultant displacement 0 mm in, mm in, e-017 in) 108

110 in) Front upper suspension arm-cosmosxpressstudy-displacement-plot2 JPEG 109

111 5c. Deformation Front upper suspension arm-cosmosxpressstudy-deformation-plot3 JPEG 110

112 5d. Design Check Front upper suspension arm-cosmosxpressstudy-design Check-Plot4 JPEG 111