November 9, Dr. Andrew Rawicz School of Engineering Science Simon Fraser University Burnaby, BC V5A 1S6

Transcription

1 November 9, 2015 Dr. Andrew Rawicz School of Engineering Science Simon Fraser University Burnaby, BC V5A 1S6 Re: ENSC 440W Design Specification for Auto-adjustable Spoiler System Dear Dr. Rawicz: The enclosed document to this letter is a design specification for an Auto-adjustable Spoiler Control System. We intend to design and implement a spoiler control system that makes driving safer, more fuel efficient and more enjoyable. Our design is a cross-disciplinary engineering project which involves aerodynamics, electronics, mechanical system, programming and control theory. Our design specifications refer to a previous document Functional Specification for Auto-adjustable Spoiler Control System, and discuss the design details to achieve the functional requirements for three parts, includes Front Panel, Main Controller and Spoiler System.Our engineers at Veroptimal Solution will also use this document to stay focused on the project development progress and on the implementation of the desired functionality in a safe and reliable manner. Sincerely, Zhendong Cao President and CEO Veroptimal Solutions Enclosure: Design Specification for Auto-adjustable Spoiler Control Systems

2 Auto-adjustable Spoiler Control System Design Specification Project Team: Zhengdong Cao CEO Yueying Li COO Tianye Zhou CFO Tianlin Yang CTO Contact Person: ZhengDong Cao Phone: Submitted to: Dr. Andrew Rawicz Mr. Steve Whitemore School of Engineering Science Simon Fraser University Issued Date: Nov 9, 2015 Revision: 1.3

3 Executive Summary There are mainly two types of car spoiler in the market. One of them is a fixed car spoiler installed onto the surface of a car back trunk. Another type is a car wing which is held a distance above the car back trunk. When a car is travelling at high speed, more than 80% of the total drag applied on the vehicle is caused by air. Also, the rear body of the car is suffering from an aerodynamic lift in range of hundred pounds which leads to reduced grips of vehicle s back wheels onto the ground. Therefore, it lowers the vehicle s stability and maneuverability. Moreover, car spoiler installed on the surface of the trunk lid is to lower fuel consumption through reducing the drag. While a car wing which is held a distance above the car back trunk is aiming for a better safety performance with the usage of applying higher downforce to decrease the lift force. Veroptimal Solution is able to solve both the drag and lift issues with the latest product Auto-adjustable Spoiler Control System, or ASCS. It is an intelligent feedback control system which allows users to control the spoiler. Our product provides a friendly-looking user interface panel which allows the driver having full control of the spoiler: the operation mode of the entire system can be set to either automatic or manual depends on user preference. More specifically, with automatic mode, the ASCS will automatically adjust itself until the vehicle has reached to the optimal aerodynamic state. Particular scenarios can be detected, such as hitting emergency brake, driving downhill and being in a slippery road condition. With manual, the ASCS will listen to the user s command during security scope. The design specification for ASCS provides a set of detailed descriptions for implementations and developments of our prototype. In this document, design improvements for future iteration of ASCS are also discussed. Detailed system operations and aerodynamic principles are discussed with flowchart and analysis. As the user interface, our front panel is designed to have the RF module, LCD circuit, and different control buttons on the layout. All circuit designs, modules and board layout in the main controller are specified with details. A DC motor and a linear actuator are used for height and angle adjustments. This document also provides the test plans for future function verifications. ii

4 Table of Contents Executive Summary... ii List of table... vi List of Glossary... vi 1 Introduction System Specifications System Level Diagram System Operation Aerodynamics Downforce Improvement Drag Reduction Mechanical Design Electronics System Design Safety Design Front Panel Electronic Hardware Design Central Processing Unit Power Tree Control Buttons RF Module LCD Circuit Board Layout Design Firmware Design Control buttons RF Module LCD display Enclosure Design Exterior Enclosure Interior Enclosure Main Controller Electronic Hardware Design Power Tree Motor Driving Circuit Angle Measuring Circuit Force Measuring Circuit Brake Detection Circuit GPS Module Board Layout Design Firmware Design RF Module Angle sensors and pressure sensors iii

5 4.2.3 GPS Module LA, Motor and Motor driver Auto mode and Manual mode Enclosure Design Exterior Enclosure Exterior Enclosure Spoiler System Electrical Design Power Line Signal Line Mechanical Design Mechanical Power Source Arm Mechanism Hand Mechanism Rigid-body Dynamics Building Materials Test Plan Units Test System Test Conclusion Reference Appendix Appendix A: Complete Circuit Schematic Appendix B: Coast Down Method for Drag Estimation Appendix C: Motor Driver Test Appendix D: Angle Sensor Test iv

6 LIST OF FIGURES Figure 1: System Level Diagram... 2 Figure 2: System Flowchart... 2 Figure 3: Simulation of airflow around a high speed car... 3 Figure 4: Downforce coefficient vs AOA... 4 Figure 5: Drag Reduction by Adding a Spoiler... 4 Figure 6: General Design of the Spoiler System... 5 Figure 7: Installing a real spoiler onto the ASCS... 5 Figure 8: Front Panel Power Distribution... 7 Figure 9: Mode Selection Switch... 8 Figure 10: Spoiler Height and Angle Control Circuit... 8 Figure 11: Set Preference Button circuit... 9 Figure 12: RF Module Circuit Design... 9 Figure 13: I2C conversion of the 16x2 LCD Figure 14: LCD Circuit Design Figure 15: Component Layout (showing only faces) Figure 16: Arduino Nano Figure 17: Flow diagram of Manual Control of the Spoiler Height and Angle Figure 18: Exterior view of Front Panel Enclosure Figure 19: Interior view of Front Panel Enclosure Figure 20: Main Controller Power Tree Figure 21: Dual Bridge L298N Motor Driver Breakout Board Figure 22: Motor Driving Circuit design Figure 23: Components used for Angle Measuring Circuit design Figure 24: Angle Measuring Circuit Design Figure 25: Force Sensing Resistor used for measuring the downforce Figure 26: Non-inverting Summing Amplifier Circuit Figure 27: Brake Detection Circuit Figure 28: GPS Module Figure 29: GPS Module circuit design in Main Controller Figure 30: Layout of Main Controller Components Figure 31: Flowchart for Automatic Mode Figure 32: Exterior view of Main Controller Enclosure Figure 33: Interior view of Main Controller Enclosure Figure 34: Typical Boot Lid Design Figure 35: Linear Actuator Figure 36: DC Motor Figure 37: General Arm Design Prototype of Spoiler System Figure 38: Lowest Elevation (a) and Highest Elevation (b) Figure 39: Spoiler Components, (a) Linear Actuator (b) Linear Actuator Stand Figure 40: General Hand Design Prototype of Spoiler System Figure 41: Hand Mechanism Design Figure 42: Hand Mechanism Angle Adjustment Figure 43: Spoiler System Detailed Dimension Front View Figure 44: Spoiler System Detailed Dimension Top View v

7 List of table Table 1: System Mode Pin Definition Table 2: Array elements from Front Panel to Main Controller Table 3: Array elements from Main Controller to Front Panel Table 4: Detailed Dimensions of Front Panel Enclosure Table 5: Motor Control Logic Table 6:Detailed Dimension of Main Controller Enclosure Table 7: Wires for Signal Line between Main Controller and Spoiler System Table 8: Steel Properties Table 9: Material Choices List of Glossary AOA Angle of Attack ASCS Auto-adjustable Spoiler Control System CAN Controller Area Network FS Function Specification FS-R# Functional Specification Requirement # FSR Force Sensing Resistor GPS Global Positioning System I 2 C Inter-integrated Circuit I/O Input and Output KPH Kilometers per Hour LCD Liquid Crystal Display PCB Printed Circuit Board ROM Read Only Memory SDA Serial Data Line SCL Serial Clock vi

8 1 Introduction The Auto-adjustable Spoiler Control System (ASCS) is a feedback control system in which drivers are capable of adjusting the elevation and angle of attack (AOA) of the car spoiler manually or automatically. As research indicates, the car spoiler, which stays very close to the surface of the boot lid, helps to decrease the drag and increase the fuel efficiency with the method of spoiling out the undesirable flows and reshaping airflow streams around the vehicle. In addition, the AOA of the spoiler with high elevation plays a crucial role in determining how much air will be deflected upwards, which lead to the generation of down force at the rear of the vehicle [1], [2], [3]. As consequence, higher safety performance can be achieved with car spoiler being held a distance above the trunk. Our goal is to enable a single car spoiler to be multifunctional, not only to provide better safety performance but also reduce the fuel consumption. This design specification provides detailed technical descriptions for the design of each component of the ASCS. 1.1 Scope This document provides detailed design of the ASCS and specifies implementations to meet the functional requirements proposed in the previous Auto-Adjustable Spoiler Control System Functional Specification. All requirements for a proof-of concept system and a partial set of requirements for the final product are included in the design specification. 1.2 Intended Audience This document is intended to be used by all engineers of Veroptimal Solution for product development including the project manager, the hardware designers, the mechanical designers, the firmware developers and the test engineers. It will be reference as a design guideline throughout the development stage of the product. The project manager shall refer to the design requirements as consistent criteria and ensure all requirements are met in the final product. The test engineers will use this document to implement the test plans and confirm that the product follows the design goal. 2 System Specifications The ASCS product is transitioning from proof-of-concept phase to prototype phase. With more funding and time, further modifications and improvements will be implemented in the final production stage. This document provides the design details that are only for prototyping of the project. Particular functions for the production stage of the design will be briefly mentioned in the following sections. 2.1 System Level Diagram A system level diagram of ASCS is shown below as Figure 1. The power lines are marked with red color; signals are represented by black arrows solid line is for wire signals whereas dashed line indicates wireless signals. 1

9 Figure 1: System Level Diagram The design of ASCS can be divided into three major subsystems: Front Panel, Main Controller and Spoiler System based on their designated functionalities. The Front Panel will be used as a media for the user to control the system therefore it focuses on the wireless communication and user interface design. The Main Controller is an electronics system which involves most of the circuit design and programming. The Spoiler System is essentially a mechanical system controlled by the Main Controller to adjust the spoiler movements therefore it focuses on the mechanical design. 2.2 System Operation The system flow chart below in Figure 2 describes the behavior of the system. The functional blocks marked with orange represent the operations done by the Front Panel; operations executions marked by blue are commands from the Main Controller and Spoiler System. Figure 2:System Flowchart 2

10 2.3 Aerodynamics As shown in the function blocks in Figure 2, when the system is try to activate Economy Mode or Safety Mode, the vehicle aerodynamics, in which we interpreted in the form of downforce and drag in this context, are the crucial factors that determine the system performance. In Economy Mode, the system should reduce the drag applied on the vehicle; in Safety Mode, the system attempts to increase the downforce applied on the rear of the vehicle Downforce Improvement In analogous to an airplane wing, the car spoiler is able to generate downforce by flipping the wing. The downforce, F DOWN, of the spoiler can be numerally evaluated by, Where, ρ is 1.255kg/m 3 (air density at 15 C) v is the air flow speed in m/s A is the spoiler area in m 2 C DOWN is the downforce coefficient F DOWN = 1 2 ρv2 AC DOWN (1) The simulated airflow around a high speed car is shown in Figure 3 where the color represents the speed (red means fast and blue means slow). It is clear that the air speed is faster at position above the boot lid surface; therefore, in Safety Mode, the ASCS should lift the spoiler to a reasonably high position off from the boot lid in order obtain large downforce. Figure 3: Simulation of airflow around a high speed car From the downforce equation (1) above, we can see that the other variable C DOWN also determines the downforce. Though both the wing shape and AOA can affect the downforce coefficient, AOA of the spoiler is the major determinant parameter [4]. The ASCS is able to control AOA of the spoiler, and the resultant downforce can be monitored by the sensors. To achieve the Safety Mode, the system will adjust the AOA until the measured downforce reaches to maximum. 3

11 For theoretical approximation, we assume the car spoiler area to be 0.225m 2 (1.5m x 0.15m) and it is driving at 120kph (or 34m/s); for simplicity we also assume the air flow speed is same with the car speed, so we obtain that, F DOWN = 163C DOWN (2) Figure 4 shows the relationship between the downforce coefficient (interpreted as coefficient of lift) and AOA for a particular airfoil [5]. The downforce coefficient reaches to maximum (about 1.7) when AOA is about 17 degrees which will result a 277N downforce in this situation. Based on multiple research results and take consideration of higher speed situations [6], we expect the maximum downforce applied on the spoiler to be 400N. Figure 4: Downforce coefficient vs AOA Drag Reduction The Economy Mode should reduce the drag of the vehicle. By comparing the two pictures in Figure 5, adding a spoiler on the surface of the boot lid can spoil out the undesirable flows and thus reshape airflow streams around the vehicle to decrease drag. Figure 5: Drag Reduction by Adding a Spoiler The amount of the reduced drags very difficult to be theoretically approximated since we have to model the mechanical design of the car as well. Another issue to quantify the air drag reduction is due to the unavailability 4

12 of a large power wind tunnel which simulates the airflow around the car. As an alternative solution, we will use coast down method to estimate the reduction of the air drag once we build the prototype, see Appendix B for method details. 2.4 Mechanical Design The Spoiler System occupies most of the mechanical design portion which involved with power source, structural design, rigid body mechanics and engineering materials. Figure 6 shows the general mechanical design of the ASCS Spoiler System when it stays at a specific instance of movement. Technical details regarding are provided in section 5.2 which illustrating the mechanical design of the Spoiler System. Figure 6: General Design of the Spoiler System The Spoiler System is designed with a specific manner such that it can grip an additional spoiler as shown in Figure 7 instead of having a spoiler as an integrated part of the system. In this way, we do not need to spend money and time on fabricating a spoiler; also it makes the ASCS being more compatible, that is, users can upgrade their old spoiler (if they had one) to a more versatile and intelligent version by simply mount it onto our system. Figure 7: Installing a real spoiler onto the ASCS 2.5 Electronics System Design The electronics system in ASCS involved with hardware circuit design, board prototyping and firmware programming. 5

13 When designing the circuit two options were considered: Microcontroller based circuit design PCB based circuit design Eventually we decided to follow the microcontroller based circuit design scheme and particularly we will use Arduino microcontroller as the central processing unit. Arduino microcontroller is small, light, inexpensive and reliable. As a well-developed open source device, Arduino is highly compatible with many hardware shields such as the RF module, motor driver and GPS module used in our project; much hardware and coding support can be found online. More importantly, the time spent on the design, debugging and prototyping of a microcontroller based breakout circuit board is much faster than designing a PCB board. As ASCS is a complex system which involves cross-disciplinary engineering fields, we have very limited time spending on the electronics system design. Some market available modules such as H bridge motor driver, GPS module, angle sensor module and RF module can be directly used for the hardware circuit design. Also there are circuitries with particular functions need to be specifically designed, e.g. downforce measuring circuit, break detection circuit and many control buttons. The performance of each circuitry will be first verified by using power supply, multi-meters and oscilloscope on breadboard; then a small test programs will be uploaded into the microcontroller circuit to validate the functions of the circuitry. Once the functions of all modules are tested on the breadboard, we will arrange the layout of components on perf-boards for soldering and prototyping. Suitable mechanical enclosures will be designed for the circuit boards for protection. The complete circuit schematic is in Appendix A. 2.6 Safety Design Design for safety is a crucial part of this project. We identified the major hazards or disasters that could be caused by this system as: Fracture of the structural materials under heavy loads Vehicle instability caused by improper adjustment of the spoiler AOA System operation failure due to the interference of the wireless communication Structural materials must be chosen carefully to prevent fracture. Quantitative analysis and justifications in terms of structural mechanics and material properties will be addressed in the Spoiler System design section. The factor causing instability of the vehicle is the aerodynamic lift generated by the spoiler due to the improper adjustment of the AOA of the spoiler. The instability scenario is most likely happened in the manual operation mode where the user mistakenly adjusted the Spoiler Angle Knob. Such mistakes could by avoided by providing user with clear and easy understandable instructions about the device control in the user document. Lastly, reliance on wireless communication is another potential for system operation failures. To prevent cascading failures, if the wireless communication is lost, the system will remain its previous states and will not do any further dangerous movements. 6

14 3. Front Panel This section specifies the Front Panel design in the prototype stage including electronics design, programming and enclosure. In the production stage of the project, the electronics will be integrated to the CAN bus of the vehicle computer which has higher stability in data transmission. 3.1 Electronic Hardware Design The hardware design of the Front Panel in the proof-of-concept stage is divided into two subjects: circuit design and board prototyping which can be further break down into smaller design pieces. The hardware design for the future production product will be mentioned in the last part of this section Central Processing Unit We will use Arduino Nano microcontroller as our central processing unit. Nano is small (45mm x 18mm) and light (5g) therefore is a perfect candidate used in the Front Panel design. The electrical specification of Nano is given in Table 4. Table 1: Arduino Nano Electrical Specification Power Tree The power flow diagram in Figure 8 below highlights the current flow direction in the Front Panel circuitry. There are three components: Arduino Nano, LCD and RF Module are consuming power; the power consumption of other units such as switch and potentiometer is insignificant as others; therefore, they are not shown in the diagram. In the diagram, it shows that the LCD and RF Module are taking power from the 5V and 3.3V power rail from Nano whereas Nano is powered by the battery. Figure 8: Front Panel Power Distribution 7

15 The regulator on Nano is type of 7805 therefore the regulator is able to deliver 1A when the input power is 12V. Since the operation current of LCD is normally below 30mA and the maximum current for the RF Module is 20mA [7], [8], therefore using the regulator on Nano as the power source of LCD and RF Module will be sufficient Control Buttons The Mode Selection Switch, as shown in Figure 9, is a 3-way switch with pull-up resistors R14, R15 and R16. By closing the switch on one of the three terminals, e.g. the middle terminal as shown in the picture, then the node U1_D1 will be short to ground therefore is 0V; the other two nodes are pulled up by the VCC1_5V which is the Nano 5V rail. The three nodes, U1_D0, U1_D1 and U1_D2 will be connected to Nano digital I/O pins to indicate the selection of modes. Figure 9: Mode Selection Switch The circuit for Spoiler Height and Spoiler Angle adjustment is shown in Figure 10. The Spoiler Height Lever uses a slide potentiometer and the Spoiler Angle Knob is a rotary potentiometer. The output voltage, U1_A1 and U1_A0 will be fed into Nano analog input pins. Figure 10: Spoiler Height and Angle Control Circuit The last control button is the Set Preference Button. When this button is pressed, the Nano shall record the current spoiler position information and save it in ROM so that this information can be retained even the Nano is rebooted. In Figure 11, we again use a pull-up resistor for the SET_PREF button; also we shunt a capacitor so that R17 and C6 consist of a low pass filter to eliminate high frequency bounce when the switch is pressed. 8

16 Figure 11: Set Preference Button circuit RF Module We use a pair of nrf24l01 of 2.4GHz for wireless communication. To prevent current surges of the module during transmission, we connect a 10uF capacitor at its 3.3V power rail. Also, some special pins such as CS, SCK, MOSI and MISO of the nrf24l01 shall be reserved and mapped to the same family pins on Nano. As a result, the pin connection is given as in Figure 12. Figure 12: RF Module Circuit Design LCD Circuit A 16x2 LCD will be displaying information such as the downforce and spoiler angle for user s knowledge. For the purpose of saving I/O pins, we will use the LCD with I 2 C adapter such that all communication can be achieved via the I 2 C bus line (SCA and SCL). The I 2 C adapter circuit connection is shown in the left of Figure 13. The three address pins, A2, A1 and A0 are pulled up by the 10KΩ resistors which correspond to the slave address of 27 in hexadecimal value. 9

17 Figure 13: I2C conversion of the 16x2 LCD The LCD circuit, after being converted into I 2 C communication, ends up being a very simple circuit seen by the microcontroller. Note that the SDA and SCL should be specifically connected to analog input pins A4 and A5 on the Nano which support for I 2 C communication [9]. Figure 14: LCD Circuit Design Board Layout Design We will use a perf-board of 15cm x 9cm for prototyping the circuit. The layout of the components by showing their faces is shown in Figure 15 below. Figure 15: Component Layout (showing only faces) 10

18 For wiring, due to the availability of resources, we do not many different types of wires; however, we will stick with some basic rules to ensure the hardware is reliable: Use thick wires (22AWG or less) for power lines Red wires for positive terminals and black wires for ground Use thin and flexible wires for signals Minimum wire crossing is desired All connections will be nicely soldered (good contact, smooth and shiny soldering surface) 3.2 Firmware Design The main idea of developing Front Panel firmware is to program on Arduino Nano microcontroller, pictures are shown in Figure 16, which functions with hardware circuit, Knob, switch, button, and lever respectively. Also, we will program on a RF2.4MHz to complete data exchange. The Main controller feedback information will be displayed on the LCD Screen. Figure 16: Arduino Nano Control buttons Mode Selection Switch: A 3-way switch is used to connect the 3 digital pins D0, D1 and D3 of the Nano. As explained in section 3.1.3, D0, D1 and D3 have digital value of 1 by default and will be digital 0 when one of the pins is connected to the switch. Based on the property specified above, the program defines the three modes, Automatic, Manual and Preference in the given Table 2. Table 2: System Mode Pin Definition Angle Knob & Height Lever: the spoiler height and AOA can be manually adjusted by using the Angle Knob and Height Lever which correspond to the A1 and A0 pin of the microcontroller on the Front Panel. The actual spoiler 11

19 height and angle are reflected by analog feedback signals which fed to the analog pins of the microcontroller on the Main Controller. As described in the flow diagram, by comparing the control signal value sent from the user to the feedback signal values measured from sensors, the system can execute the correct operations. Set Preference Button: this button will work only under the manual mode. Once the button is pushed, the microcontroller ROM will be updated to the latest spoiler position including the spoiler height and angle. Even if the system is power cycled the recorded information will not be lost. When the Preference Mode is being activated, the system will adjust the spoiler according to the spoiler position data read from the ROM. Figure 17 is flow diagram to show the system chain of the spoiler Height and angle in manual control. Mode Selection Manual Mode Adjust spoiler height and angle Compare desired Height and angle with Current positon Is current height and angle - current positon > 2(tolerance) Raise spoiler height or spoiler angle Is current height and angle - current positon <= 2 or >= -2(tolerance) Stop moving Is current height and angle - current positon < -2(tolerance) Lower spoiler height or angle Figure 17: Flow diagram of Manual Control of the Spoiler Height and Angle 12

20 3.2.2 RF Module The data packages exchanged between the Front Panel to the Main Controller are two arrays A and B of both size 5 described in Table 3 and Table 4. Table 3: Array elements from Front Panel to Main Controller Table 4: Array elements from Main Controller to Front Panel The nrf24l01 has to be defined as either a transceiver or receiver before data transmission proceeds therefore cannot achieve a real time 2-way communication. In practice, the program swiftly switches the role as a transceiver/receiver of the RF module on each side LCD display The information that the user shall acquire are stored in array B in Table #. Signals and information will be displayed by the LCD installed on the Front Panel. The program will also intentionally lower the refresh frequency of the LCD to ensure the driver not being distracted. 3.3 Enclosure Design The ASCS product will have an enclosure for Front Panel to prevent unintentional damages. More importantly, it will provide a user-friendly interface for customers to understand and operate the system. The case is designed to be manufacture with 3D printer. Details for Front Panel enclosure design are illustrated as below Exterior Enclosure The exterior of the enclosure aims to provide users an instructional panel to operate the ASCS. Figure 18 shows the actual design from CAD drawings. Front Panel will fit the circuit layout design to allow users operate the system. The front is intended to expose adjustments from circuit board, which are LCD screen, Set Preference Mode Button, Mode Selection Switch, Spoiler Height Level Adjuster and Spoiler Angle Knob. 13

21 Figure 18: Exterior view of Front Panel Enclosure Interior Enclosure The Figure19 shows the detailed dimensions for Front Panel. Figure 19: Interior view of Front Panel Enclosure 14

22 Actual measurements and design dimensions are listed in Table 4 below. All measurements are in centimetre Letter d is stand for diameter Table 1: Detailed Dimensions of Front Panel Enclosure (Unit: cm) ACTUAL DESIGNED LCD Width LCD Length Mode Selection Switch d=4.0 d=4.5 Set Preference Button d=1.0 d=1.6 Spoiler Angle Knob d=3.0 d=2.0 Spoiler Height Lever Width Spoiler Height Lever Long Case Width Case Long Case Round Depth Main Controller The electronics design of the Main Controller in the prototyping stage are microcontroller-based which will be changed to a PCB-based design in the production stage. 4.1 Electronic Hardware Design The circuit design of the Main Controller involves Microcontroller, RF Module, GPS Module, Brake Detection Circuit, Force Measuring Circuit, Angle Measuring Circuit and Motor Driving Circuit. The Microcontroller and RF Module have the same hardware design as in Front Panel therefore will not be included in this section Power Tree Figure 20 shows the Main Controller power tree diagram. The power source of the Main Controller will be the car battery. As specified in FS-R11, the maximum power required by the system is 40W. Car batteries are lead-acid type and they can deliver over 100W therefore will be sufficient for powering our Main Controller. 15

23 Figure 20: Main Controller Power Tree There are two major current branches flow out from the battery: microcontroller branch and motor driver branch. The Motor Driving Circuit is most power thirsty as it will be driving the mechanical power sources on the Spoiler System. The Motor Driver Circuit is consisted with two L298N Dual H-Bridge motor drivers with total maximum power near 40W [10]. Other circuits such as RF Module and GPS are much less power thirsty than the motor driver therefore can be directly powered by the Arduino Nano regulator outputs (5V and 3.3V) Motor Driving Circuit The Motor Driving Circuit contains two L298N Dual H-Bridge motor driver breakout boards as shown in Figure 21. Each driver can only supply up to 20W, therefore we will use two motor drivers to control the Linear Actuator and DC motor individually. Figure 21: Dual Bridge L298N Motor Driver Breakout Board The Motor Driving Circuit design is shown in Figure 22. The ENABLEA pin shorted to the 5V output to have to motor driver stay at the stand-by mode as long as the Main Controller is powered. The logic inputs, INPUT1 and INPUT2 are PWM signals which control the current flow direction as well as the average output power. The logical table is summarized in Table 5. 16

24 Figure 22: Motor Driving Circuit design Table 2: Motor Control Logic ENABLEA INPUT1 INPUT2 Motor Direction HIGH LOW LOW STOP HIGH LOW HIGH TURN LEFT HIGH HIGH LOW TURN RIGHT HIGH HIGH HIGH STOP When the motor driver is running at 20W, the heat is dissipated from the heat sink; our pre-test shows that the heat sink temperature can exceed 100 C at this condition see Appendix C. The design of Main Controller Enclosure shall have windows near the heat sinks to allow thermal dissipation. More details will be given in section 4.3 about Enclosure Design Angle Measuring Circuit We will be using an SCA60C based angle sensing breakout board for our Angle Measuring Circuit. SCA60C is accelerometer consists of a sensing element chip and a signal conditioning circuit which gives the analog signal indicating the change of angle respect to horizon. The breakout board model is shown in Figure 14 (a) and the SCA60C schematic is shown in Figure 14(b). 17

25 (a) Breakout Board (b) SCA60C Schematic Figure 23: Components used for Angle Measuring Circuit design By performing the test of the breakout board (Appendix D), we concluded that the output analog voltage and the angles of the module are able to sense has a linear relationship within 50 degree. Based on the test result, we confirm that the SCA60C based breakout board is appropriate for our application of angle measuring. Figure 24 shows the circuit in our design. We only power the module with 5V and take feed its output to the analog input pin of the Nano. It is important to note that when the breakout board is placed horizontally, the output voltage will be half the VCC therefore is 2.5V in this case. Figure 24: Angle Measuring Circuit Design Force Measuring Circuit We will use three force sensing resistors (FSR) as shown in Figure 25 to measure the downforce applied by the spoiler. Each FSR is electrically equivalent to a variable resistor of which the resistance changes linearly with respect to the force applied on its active region (the inner rectangular area). The resistance of each FSR is 10kΩ when no force applied and close to 100Ω when 100N is applied. Since each FSR is only able to accurately measuring up to 100N force, we will use three of them for measuring the downforce. 18

26 Figure 25: Force Sensing Resistor used for measuring the downforce The Force Measuring Circuit is shown in the circuit diagram Figure 26 below where the three FSRs are modeled as variable resistors R4, R5 and R6. The FSRs along with the 10KΩ resistors R3, R2 and R1 consist of three pairs of voltage divider. The divided signals v1, v2 and v3 will be summed by the summing amplifier. Figure 26: Non-inverting Summing Amplifier Circuit We used LM358 Op-amp for the design due to its single rail supply structure and cheap price. The output U2_A4 is a function of the three inputs described in the equation: U2_A4 = (1 + R11 R10 )(v1+v2+v3 3 ) (3) In this circuit, the ratio of R11 and R10 is 2 which leads the output of the Op-amp U2_A4 essentially equal to the sum of three voltage divider signals. Therefore, the output of the Force Measuring Circuit represents the sum of the forces applied onto the three FSRs. 19

27 4.1.5 Brake Detection Circuit The Brake Detection Circuit in Figure 27 is able to tell if the car is braking by sending a triggered pulse at the output U2_D1. The triggering mechanism is achieved using a comparator circuit shown in Figure 18. The input signal, Brake_Sig, will be taken from the vehicle brake light. When the driver brakes, the brake light turns on immediately and the Brake_Sig will also rise from 0V to 12V within 1ms. The Brake_Sig will be divided by a ratio of 2.5 to feed to the non-inverting input of the LM311. The inverting input of the LM311 is the trigger level which stays at 0.45V. The output stage of LM311 is an open drain mechanism so we add a pull up resistor R25 in the circuit design. Figure 27: Brake Detection Circuit GPS Module The GPS Module is used to sense the car speed. We use the Ultimate GPS Breakout v3 in out circuit as shown in Figure 28. To receive better signals from the satellite we also need an antenna. Figure 28: GPS Module The connection of GPS Module in our circuit is straightforward: need two pins for power and two pins for communication as shown in Figure

28 Figure 29: GPS Module circuit design in Main Controller Board Layout Design The layout of components on Main Controller is shown below. Additionally, 2 cables will be sticking out. One cable is used as the power cord for powering the Main Controller. We refer the other cable as the Spoiler System Cable which will be mentioned more specifically in section 5.1. The Spoiler System Cable serves as a bridge between the Main Controller and Spoiler System for both power delivery and signal transmission. Figure 30: Layout of Main Controller Components 21

29 4.2 Firmware Design The main idea of firmware development of the Main Controller is to control the hardware circuits by Arduino programs. Also, we will program on an RF2.4MHz to complete data exchange. Meanwhile, one of the most important function is controlling Spoiler position by adjusting LA length and Motor angle RF Module The module will send information to front panel to display, as well as receive data packages from front panel. When data package received, the micro-controller will determine which mode is selected, what the height and angle of the spoiler would the driver like. Then, the micro-controller will send signals to motor drivers to complete adjustment action Angle sensors and pressure sensors Those sensors will be connected with analog input pins through the electric circuits. The micro-controller will read those analog voltage value and convert them into unsigned char data and store into package. Then, those data will be transmitted and displayed on the LCD display at front panel. However, the micro-controller will process those data to adjust LA and Motor under Auto mode GPS Module Since it is very hard to get car speed directly form car, we will use GPS module to get car speed information. The GPS Module will connect with analog pins to send the speed information to the micro-controller to process. Also, the information will pack into packages and send to front panel to display LA, Motor and Motor driver The micro controller cannot provide enough power to drive LA and motor, so we will use external power source combined with motor driver to drive them. The LA and Motor will connect with Motor drivers, and Motor drivers will connect in PWM pins on the micro-controller. The micro controller will send signal to let LA and motor work. The signal will also include the moving speed of LA and Motor Auto mode and Manual mode Under Manual mode, the logic of the firmware will be in the following Figure 31, which controlled by height lever and angle knob. However, the whole logic of auto mode firmware will be controlled by main controller. The Figure 31 is shown the control logic of main controller under auto mode. 22

30 Figure 31: Flowchart for Automatic Mode 4.3 Enclosure Design The ASCS product will have an enclosure for Main Controller to keeps all the components together and protect components from unintentional damages. The case is designed to be manufacture with 3D printer with material of Figure 32. Details for Main Controller enclosure design are illustrated as below Exterior Enclosure The enclosure is designed to be light weight to fit the Main Controller components circuitries compatibly inside. However, rooms are left intentionally for circuitries to dissipate excess heat. Figure 32 shows the appearance of the interior design to house the Main Controller circuit board. The upper bound is left unseal for the wire connections. 23

31 Figure 32: Exterior view of Main Controller Enclosure 4.3.2Exterior Enclosure The Figure 33 below is the detailed dimensions for Main Controller. Besides, detailed data are list in Table 6. Figure 33: Interior view of Main Controller Enclosure 24

32 Table 3:Detailed Dimension of Main Controller Enclosure Unit:cm ACTUAL DESIGNED Case Long Case Width Case Round Depth Spoiler System 5.1 Electrical Design The hardware design involved in the Spoiler System focuses the Spoiler System Cable design as mentioned in section The cable has multiple wires serving for power delivery and signal transmission; different types of wires must be designed for different purposes. Design details are addressed in the following subsections Power Line According to FS-R97, the wire loss from Main Controller to Spoiler System shall be less than 2%. Since the Spoiler System will be installed on top of the car boot lid whereas the Main Controller stays in the boot trunk, we must not use thick wires for connections to meet the requirement. Figure 34 is a typical boot lid design. When the boot lid is closed, the very small slot marked by red color tends to be the best place for which the cable can sneak in, thus the wire dimensions shall not be large. Figure 34: Typical Boot Lid Design The length of the cable is about 1 meter. The have the cable loss less than 2%, the maximum power on the cable shall be less than 0.8W when the Main Controller is delivering 40W to the Spoiler System. When a 4A current passing through the wire, the wire resistance by ohm s law is calculated by equation (4): 25

33 R < P cable I 2 = 0.8 W 16 A2 = 50mΩ (4) By referring to the standard AWG table [11], we should use wires less or equal to AWG22 in order to have the wire resistance about 50mΩ when its length is 1 meter. Meanwhile we want to minimize the cross section area of the wire, therefore the AWG22 wires which have sectional area of 0.33m 2[12] will be best option for the power line material Signal Line As shown in the system level diagram in Figure 1, the signal lines between the Main Controller and Spoiler System contain Motor Control signals and Sensor Output signals. There are 13 wires in total for signal transmission listed in Table 7. Table 4: Wires for Signal Line between Main Controller and Spoiler System Given the fact that wire resistance does not produce significant effects at low current low frequency signals, we are allowed to use thin wires for each signal line to keep the total area small. As a result, we will be using Ribbon Cable with 14 conductors for our signal line. The end of the Ribbon Cable shall have connector which allows the Spoiler System to be electrically disconnected from the Main Controller in a simple and easy way. 5.2 Mechanical Design The general mechanical design of the Spoiler System was presented in section 2.4. This section contains technical details which illustrate the design progressively and comprehensively Mechanical Power Source A Linear Actuator and a DC Motor are used in the Spoiler System design serving as mechanical power sources. Linear Actuators are able to provide translational or linear motion whereas DC Motors generate rotational motion. They will be used to control the ASCS system outputs Spoiler Elevation and Spoiler Angle respectively. The Linear Actuator we used along with its technical specifications is shown in Figure 35. We refer the stationary part as body and the movable portion as stroke. The pushing force of the stroke is linearly proportional to the current draw; the moving speed of the stroke can be varied by the PWM control signals sending from the Main Controller. 26

34 Figure 35: Linear Actuator The specification of the DC Motor is marked with yellow color in Figure 36. It has remarkably large rated torque by satisfying the angular speed which is perfectly suitable to control the AOA of the spoiler. Figure 36: DC Motor Both mechanical power sources have self-lock mechanism, that is, they can sustain the previous states without feeding any electrical power Arm Mechanism The Spoiler Mechanism has two parts: Arm Mechanism and Hand Mechanism. Figure 37 below shows the general arm design prototype of Spoiler System. 27

35 Figure 37: General Arm Design Prototype of Spoiler System The arm mechanism is driven by the Linear Actuator and it is responsible for adjusting the spoiler height. The moment when the Arm Mechanism reaches to the lowest position and highest position are presented in the two pictures in Figure 38. As highlighted, the lowest position is 6.5cm and highest position is 25cm which meet the FS-R106 and FS-R107. (a) Lowest Position: 6.5cm (b) Highest Position: 25cm Figure 38: Lowest Elevation (a) and Highest Elevation (b) Detailed parts and the related functionalities will be listed as below. Figure 39 shows the parts overview of the arm mechanisms. 28

36 Figure 39: Spoiler Components; (a) Linear Actuator (b) Linear Actuator Stand (c) Arm Bracket (d) DC Motor (e) Motor Stabilizer (f) Motor Shaft Couple The Base of the Spoiler System is designed as shown in Figure# above. It is made with plywood and will be installed in the surface of the car trunk lid. The base has a square shape which will take up whole system weight and evenly distribute along its square surface. Linear Actuator is bridged between two Linear Actuator Stands (Figure 39.b) fixed in the Base with the flexible rotatory ability. DC motor will be mounted on the tip of the arm support link with the handmade DC motor stabilizer as shown in Figure 39. (e). Two arm support links will be fixed in the base used Arm Brackets, Figure 39. (c). The Motor Shaft Couple is planned to manufactured with 3D printer The Alloy Hand Link will be fixed though Motor Shaft Couple, Figure39. (f), with DC Motor, which is the connector of DC motor and arm link Hand Mechanism The Hand Mechanism controls the AOA of the spoiler. According to FS-R4, the ASCS should be compatible with any type of car spoilers with different width and thickness. As shown in Figure 121, the two horizontal Supporting Rods along with the Horizontal Stabilizers are able to stabilize a spoiler with arbitrary width; the two vertical Supporting Rods along with the Vertical Stabilizers can immobilize the spoiler with arbitrary thickness. The structure shown in Figure 40 is named as a spoiler clamper. Figure 40: General Hand Design Prototype of Spoiler System 29

37 A Hand Mechanism consists of two spoiler clampers, a Hand Link and some components for connection purposes. As shown in Figure 41, the entire Hand Mechanism is driven by the DC Motor. The Motor Shaft Coupling and Motor Coupling Connectors can transfer the mechanical power of the DC motor to the movement of the Hand Link. Since the Hand Mechanism is attached onto the Hand Link, the mechanical power of the DC Motor will eventually be translated to the angular movement of the car spoiler. Figure 41: Hand Mechanism Design Refering to the picture below, the upper angle and lower angle of the Hand Mechanism movement are 40 degree and 1 degree respectively which also satisfy the FS-103 and FS-104. The angle of the Hand Mechanism will be exactly same with AOA of the spoiler. Figure 42 shows the Hand Mechnism flexible angle adjustments. Figure 42: Hand Mechanism Angle Adjustment Rigid-body Dynamics Based on the aerodynamic theory explained in section 2.3, we expect the maximum down force occurred when the spoiler has some distance off from the ground surface and the AOA is approximated 17 degrees. In this case, we expect a down force, Fd about 300N. 30

38 Figure 43: Spoiler System Detailed Dimension Front View Figure 43 shows free body diagram of the Spoiler System at an instance of movement. Assuming the 300N to be the worst case scenario, by using Newton s Equation, we obtained the result as in equation (5): F LA (sin12.87) (188) = 300 cos( ) ( ) (5) Where F LA is the pushing force for the Linear Actuator. Solving the equation above we obtained that F LA = 1750N. That is, with 300N exerted onto the system, the Linear Actuator must provide 1750N to be able to move the spoiler. Due to the fact that the Linear Actuator can only provide 900N thrust force, we obtained result in equation (6) that: 900 (sin12.87) (188) = F d cos( ) ( ) (6) And F d is solved to be 155N. In other words, the ASCS in this proof-of-concept stage is only able to lift 155N load. 31

39 Figure 44 shows the top view of the Spoiler System, the position and geometry is same as in Figure 43. Figure 44: Spoiler System Detailed Dimension Top View The two linkages, Arm Link and Hand Link, are suffering most of the load. The 300N down force will be uniformly distributed onto the two Spoiler Base hence F1 = F2 = 150N; in this case, we use our worst scenario calculation, F LA = 1750N to evaluate the torque and bending torque (twice of the torque) applied onto the two linkages. For the Arm Link, τ center = 1750N 244mm = 427N m (7) τ bending = 854N m (8) For the Hand Link, τ center = 150N 98.94mm = 15N m (9) τ bending = 30N m (10) From the calculation as in equations (7) (8) (9) (10), we see that the Arm Link is suffering a much larger bending force than the Hand Link. Reasonably we should use high stiffness material as the Arm Link and it should be thicker than the Hands Link. Details for materials are mentioned in next section. 32

40 5.2.4 Building Materials From research [13], four types of steels have the best matches and their properties are listed as the below table. Table 5: Steel Properties Properties Plywood (Hardwood core) Aluminum Alloy Stainless Steels Tool Steels Density (1000 kg/m3) Elastic Modulus (GPa) Poisson's Ratio Thermal Expansion (10-6/K) Tensile Strength (MPa) Yield Strength (MPa) Percent Elongation (%) Hardness (Brinell 3000kg) Based on the worst case scenario analysis, decisions have been made to choose the following materials. Rated the stiffness, hardness and density from level 1 to 5, which has the properties from low to high. The table below has summarized the materials decided according to their required stiffened, hardness and density. Table 6: Material Choices Components Material Stiffness Hardness Density Arm Bracket Steel Arm Supporter Aluminum Alloy Arm Link Steel Base Plywood Bracket Pin Steel DC Motor Stabilizer Plywood Hand Link Aluminum Alloy Linear Actuator Body Steel Linear Actuator Stroke Aluminum Alloy Linear Actuator Stand Stainless Steel Linear Actuator Pin Steel Motor Shaft Couple Aluminum Alloy Shaft Hand Link Stabilizer Wood Spoiler Base Wood

41 Firstly, for the arm bracket, arm link, bracket pin, Linear Actuator Body and Linear Actuator Link, tool steel will be the selection. Next, for the reason that tool steel has a related high density and tensile strength compared to the other three type of steels. More importantly, tool steel is the lowest cost among the other three. Then, for the Linear Actuator Stand, we choose Stainless Steel to secure the lifetime of the component. In addition, for the Arm shorter, Arm Longer, Hand Link, Linear actuator Stroke and Motor Shaft Couple, Aluminum Alloy is considered to use. Because Alloy steel has similar properties as tool steel. Lastly, for the rest of the components, Bas, DC Motor Stabilizer, Shaft Hand Link Stabilizer and Spoiler Base, wood will be the replacement of steel uses. Poplar wood will be the best choice for Spoiler System. It is because the properties of wood will be similar to steel. Especially, wood has much lower cost than steels. In sum, with aim of higher safety and lower cost, Veroptimal manage to balance the choices of material used. 6. Test Plan 6.1 Units Test In general, our individual module testing consists of separately testing, which include GPS Module testing, Downforce measurement module testing, Angle measurement module testing, Wireless communication module testing, and Mechanical part testing. In order to test every individual module, an Arduino program will be written for every single module. According those tests, the following results are expected: Circuit board power test o Set power supply to 12V, 3A current limit then power up the circuit board with power supply o The actual current draw of the circuit is the current reading on the power supply Individual electronics modules test o GPS module test: Design a speed comparison test for GPS when it is installed on the car Compare GPS output value with real car speed o Downforce and Angel measurement modules tests: Design test cases to read actual load and rotated angel Compare actual load and angel values with tested output values o Wireless Communication module test: Design a test for the processes of sending and receiving in every 0.1 second Determine the percentage of error occurs during transmissions o Mechanical part tests: No fractures on mechanical structure when 300N load is applied 34

42 The measurements of the GPS Module, Downforce measurement module, Angle measurement module shall be accurate (less than 2% of error comparing with the physical measurements) 6.2 System Test To verify the manual mode system will meet the requirement, the following results are expected: When the driver selects manual mode, spoiler height controller, spoiler angle controller and set preference button will be enabled. Under manual mode, the driver can change to other modes in any time. When the driver adjusts spoiler height controller, the Arm Mechanism in Spoiler System will raise or descend. When the driver adjusts spoiler angle controller, the Hand Mechanism in Spoiler System will rotate clockwise or counter-clockwise. Once the driver press set preference button, the latest profile of angel and height data of Spoiler System will be stored in Arduino ROM. To verify the automatic mode system will meet the requirement, the following results are expected: When the driver selects automatic mode, spoiler height controller, spoiler angle controller and set preference button will be disabled. Under automatic mode, the driver can change to other modes in any time. The ASCS will perform routinely following the flow chart in Figure 31. To verify the preference mode system will meet the requirement, the following results are expected: When the driver selects preference mode, spoiler height controller, spoiler angle controller and set preference button will be disabled. Under manual mode, the driver can change to other modes in any time. Once preference mode is selected, the spoiler height and angle will adjust to a stored value in Arduino ROM. To verify the ASCS will help the car to reduce drag force while driving: The coast down test method will be applied. The detail test information will be attached in the Appendix B. 35

43 7. Conclusion As a detailed design guideline, the design specification specifies design goals, design details about each component, and solutions to meet the function specification. This design specification will be used as consistent criteria throughout the actual developing phase. Most of the hardware designs are finished except for some board layouts. Therefore, we will mainly focus on the firmware and mechanical design of the ASCS later on. The amount of expense and time that we invested in designing the hand and arm mechanism is beyond our expectation. As a result, we are re-designing some of the mechanical components in order to reduce the cost and increase the easiness for us to make. Due to the fact that it is rather crucial to ensure all required functionalities of the ASCS are achieved, test plans listed in the design specification will be well prepared and implemented. This design specification will be strictly followed to fulfill the design goals. 36

44 Reference [1] Y. Xu. (2009, March 08). Qi Che Feng ZuShuo Ming [Aerodynamics Analysis of Vechicles] [Online]. Available: 6%B1%BD%E8%BB%8A%E9%A2%A8%E9%98%BB%E8%AA%AA%E5%88%86%E6%98%8E.aspx?ArchID=945 [Accessed 19 October 2015]. [2] A. K. Mathews et al.(2014, June 02) Study of Aerodynamic Effect Of Spoiler On A Car [Online]. Available: [Accessed 19 October 2015]. [3] Oppositelock.(2014, Dec.01).Wings/Spoilers: You're probably doing it wrong [Online]. Available: [Accessed 19 October 2015]. [4] Abbott, Ira H (2012, April 26) Theory of Wing Sections. Appendix IV [Online] Available: [Accessed 11 November 2015]. [5] Abbott, Ira H (2012, April 26) Theory of Wing Sections. Appendix IV [Online] Available: [Accessed 11 November 2015] [6] Journal of Jiamusi University (2014, May) Aerodynamic optimization of sedan spoiler based on experimental design method [Online] Available: [Accessed 11 November 2015] 37

45 [7] XIAMEN AMOTEC DISPLAY CO.,LTD (2008, October 29). Specification of LCD Module [Online] Available: [Accessed 11 November 2015] [8] Nordic Semiconductor. nrf24l01+ Singel Chip 2.4GHz Transceiver Preliminary Product Specification v1.0 [Online] Available: on_v1_0.pdf [Accessed 11 November 2015] [9] Arduino. Arduino Nano [Online] Available: [Accessed 11 November 2015] [10] Instructables. Arduino Modules L298N Dual H-Bridge Motor Controller [Online] Available: [Accessed 11 November 2015] [11] Stranded Wire Chart (AWG) [Online] Available: [Accessed 11 November 2015] [12] HM Wire International, Inc. American Wire Gauge Square MM Cross Sectional Area Chart [Online] Available: rt_ pdf [Accessed 11 November 2015] 38

46 [13] Efunda. General Properties of Steels [Online] Available: [Accessed 11 November 2015] 39

47 Appendix Appendix A: Complete Circuit Schematic Figure A shows the schematic of the ASCS. Figure A: Circuit Schematic of the ASCS Appendix B: Coast Down Method for Drag Estimation Test Condition (for all Test cases: 1, 2, 3) 1. Same weather condition and road condition (wind speed, dry road and no elevation) 2. The initial velocity where measurement takes place should be same for all test cases 3. The car weight should be same (same passenger numbers during all cases) Test Cases Setup There are three cases in this test: without spoiler, with spoiler at Economy Mode (lowest drag) and with spoiler at Safety Mode (largest downforce). For each test case, we drive the car until it reaches to the initial velocity v1, then the car accelerator will be released so the car is free running. Then we will record the car velocity for every certain amount of time. We will repeat recording for 10 times in each test case. 40

48 Figure B: Test Cases for Coast Down Method Test Result After test, we will create a data spreadsheet as similar in Table B, the numbers are just examples for demonstration purpose. Table B: Data Recording The data in Table B indicate the drop of car speed in the same time period. We can process these numbers to calculate deaccelerate of the car hence to compute the total drag force applied on the car based on Newton s equation: F = Ma Where, M is the mass of the car a is the deceleration calculated from Table B Using this method, we can obtain many different sets of F and hence to approximate the changes of drag by comparing these forces. The estimation can be very accurate if we repeat the test many times. 41

49 Appendix C: Motor Driver Test Test Condition: Rail Power = 12V, ambient temperature = 22 C, 100% duty cycle The test is conducted in the test condition specified above. Then we use rheostat to pull current from the motor driver. The setup is shown in Figure C1. Figure C1: Test Setup The test results are summarized in Table C. At load of 500mA, 1000mA, 1500mA and 2000mA and soaking for 10 minutes, the heat distribution of the motor driver is reflected by the 4 pictures in Figure C2. Table C: Power Test of the Motor Driver Figure C1: Thermal Dissipation of Motor Driver at 500mA, 1000mA, 1500mA and 2000mA 42

50 Appendix D: Angle Sensor Test Test Condition: Vcc = 5V, ambient temperature = 22 C Figure D1: Angle Sensor Test Setup The test results are recorded and processed as shown in Figure D2. The plot shows that the relationship between voltage and angle is linear when the angles are between -50 to 50. Figure D2: Voltage and Angle Relationship of the Angle Sensor 43