Appendix A: Sample Technical Report

Transcription

1 Appendix A: Sample Technical Report This appendix presents an example technical report. This report describes initial work on the design of a personal human transporter. The main focus was on problem understanding and there was little time to do formal analysis of the design performance. Therefore, a mathematical treatment and the associated equations are not included. However, this report does demonstrate how to describe drawings, cite references, and how to prepare simple drawings to illustrate designs. This sample report also illustrates a standard technical format. This report uses most of the format guidelines displayed in Table A.1. (Single-line spacing, rather than 1.5 line spacing was used.) PAGE DESIGN SETTINGS FOR ME2110 Table A.1: Standard Format Guidelines PAGE DESIGN SETTINGS Margins: 1.0 inches on left, right, top and bottom. Justification of text: Full justification. Display of figures: Display of tables: Display of plots: Figures should be centered. Figures should be displayed after they are first mentioned in the text. Every figure must be discussed in the text of the report. Figures must be numbered and captioned below the figure. Tables should have light internal grid lines. Tables should be numbered and captioned above the table. Plots should be at least 3 ½ X 2 ¼ in. Plot backgrounds should be white. Legends should not obscure the data. Fonts should be roughly the same size as the report text. Axes: Solid lines. Scaled to fit data tightly. TYPOGRAPHY NORMS AND SETTINGS Typeface for written reports: Times or Times New Roman Base font size for written reports: 12 point TYPE STYLE SETTINGS Title: Section Head: Subhead: Indented Paragraph: Equation Display: 16 Point, bold, Centered. 12 Point, Bold, Centered or Left aligned. 12 Point, Italic, Left aligned. 12 Point, Left justified, 1.5 lines/feed. Indent 0.25 in. No blank lines between paragraphs. Equations are centered. Equation label number is right justified. 91

2 92 Appendix A: Sample Technical Report ME 2110-C A Safe and Society-Friendly Personal Human Transporter Motion Masters (Team C3): Julia Love Peter Petit Georgiana Woodruff Submitted to: Professor Andrés García TA: Jacob Kunz August 29, 2012

3 Appendix A: Sample Technical Report 93 Abstract The Segway personal transporter has had marginal success due to design flaws, high cost, and poor acceptance by the public. Two specific problems are: it is unsafe because it falls over in a wide range of conditions, and it is often banned from sidewalks. The goal of this project was to develop a safe and sidewalk-friendly personal transporter that can succeed where the Segway has failed. An initial problem assessment for the personal transporter is presented using a House of Quality. A conceptual design is proposed for a self-balancing transporter with an auxiliary stabilizing wheel that deploys when critical conditions are detected. Experimental tests prove that the auxiliary wheel can be deployed in approximately 0.3 seconds. The problem assessment, conceptual design, and experimental results indicate that a self-stabilizing personal transporter can be improved by using an auxiliary stabilizing wheel. 1. Introduction The Segway personal transporter is a technologically impressive device that targets a potentially lucrative market, but it has failed as a product. Given its notoriety, there have been many explanations for its failure. For example, many people believe that the failure was related to its over-hyped marketing campaign [1]. However, that is secondary to its more fundamental problem: The Segway fails to satisfy a number of customer needs [2]. Most importantly, it is expensive and it is unsafe due to design flaws. The goal of this project was to clearly define the customer requirements for a personal transporter and to present a conceptual design that satisfies these requirements. The Segway is an inverted pendulum device that is naturally unstable. It must be actively balanced at all times by a complex and expensive feedback control system. Even with such technology, there is a large range of conditions that cause it to fall over. Two especially challenging conditions are rough terrain and slick ground conditions such as sand, water, snow, wet leaves, etc. The Segway is unsafe in these conditions because it contacts the ground at only two points. It must apply forces at both of these points to operate safely. Therefore it requires excellent traction and fairly level terrain in order to stabilize the rider. Additionally, even on level terrain it is possible to accelerate and turn the vehicle too fast, causing the operator to fall off [3]. Injuries have also been reported in cases where the Segway powered down without warning, causing the machine and user to fall unexpectedly. Given the dangerous properties of the Segway, several cities and even entire countries have banned the use of Segways on sidewalks because they are dangerous for both riders and pedestrians [4, 5]. In addition to its dangerous properties, the Segway s cost is also a problem. The various models range from approximately $6,000- $7,000. This is too expensive for most consumers who would use the device only for short-distance transportation. For the same cost a consumer can buy a good used car that can provide both short- and long-distance transportation. The transporter concept described in this report is designed to be inexpensive and to provide enhanced safety. In addition to presenting a conceptual design, this report presents the problem assessment as well as an experimental validation of the auxiliary wheel feature of the design.

4 94 Appendix A: Sample Technical Report 2. Problem Analysis In order to thoroughly define the problems that a personal human transporter must address, the House of Quality shown in Figure 1 was developed. The column on the left lists the customer needs, which are ranked on an importance scale of 1 to 10. The row at the top displays the engineering requirements that have been identified at this point in the project. The most important customer needs are Safe Operation, Ease of Use, Reliability, and Terrain Robustness, which are ranked 10 and 9 in importance. Engineering Requirements Importance Production Cost Machine Weight Customer Needs Low Purchase Cost Low Operation Cost Safe Operation Ease of Storage Reliability Mobility Ease of Maintenance Aestethics Transport Speed Sidewalk Compatibility Ease of Use Terrain Robustness Poor Weather Operation Column Σ Σ(Ιmportance*Relationship) Relative Value {Σ/TotalΣ} Load Capacity Energy Usage..... Recharge Time Training Time Sidewalk Safety Operating Footprint Terrain Stability Ground Clearance = Correlations.. Strong Pos. Positive Negative Strong Neg. Ratings of Current Products Nike Shoes Bicycle Segway Target Values < $2000 < 25 kg 40 kg kg 2 Hrs./Charge 4 Hrs. 5 min. = Jogger < Wheelchair 15 deg. stable 10 cm Figure 1: Human Transporter House of Quality. The matrix in the center of the diagram shows the relationships between the customer needs and the engineering requirements. Because there are no blank rows in this

5 Appendix A: Sample Technical Report 95 relationship matrix, it is clear that the engineering requirements will address all of the customer needs to some extent. Two needs, Ease of Storage and Ease of Maintenance are addressed by only one or two engineering requirements. However, these needs have low importance values, so the engineering requirements are adequate. The rows at the bottom of the relationship matrix show the sums and the weighted sums of the vertical columns. Based on analysis of these values, the greatest engineering effort should be directed at Sidewalk Compatibility, Terrain Stability, and Ground Clearance. The column on the far right of the House of Quality provides a comparison with a few current products that provide personal transportation: shoes, a bicycle, and a Segway. With a score of 4, the shoes score highly in the satisfaction of most customer needs, except for transport speed. This is the critical limitation of human-powered shoes and reveals the need for a device that actively powers human transportation. The bicycle also scores highly in most categories, except Poor Weather Operation and Terrain Robustness. The Segway scores highly in transport speed and provides head-turning aesthetic appeal, but it scores low in a large number of customer needs. Based on this analysis of the problem, the design presented here addresses community acceptance in the requirement of Sidewalk Compatibility, and it addresses safety in the requirements of Terrain Stability and Ground Clearance. 3. Design Overview A conceptual sketch of the proposed human transporter is shown in Figure 2. The device rolls on two large powered wheels; a third stabilizing wheel is deployed from the front handlebar stem when the vehicle speed falls below a threshold value or the forward pitch angle of the device exceeds a critical angle. This wheel travels up and down a slot that is located in the handlebar stem. A seat is mounted between the wheels. Height adjustments give the user control over the seat and handlebar stem, and a width adjustor allows the user to modify the handlebar location. The vehicle is stabilized by a feedback controller using gyroscopic sensors [6], allowing the user to control the forward motion by simply leaning forward. This design offers several safety enhancements over the Segway. The forward stabilizing wheel prevents the vehicle from falling over in the event of a user error or a mechanical error resulting in sudden loss of speed or large increase in forward pitch. The configuration using a seated operator lowers the system s moment of inertia, so that the required balancing torques applied to the wheels are reduced. Furthermore, in the unlikely event that the stabilizing wheel fails to prevent a tip-over accident, the operator will fall a smaller distance than the Segway s standing operator. Any risk of injury due to falling forward will be greatly reduced because the system s potential energy is comparatively low. The seat height and the handlebar position can be adjusted by the operator; the adjustment knobs are represented on Figure 2, and two-sided arrows illustrate the potential motions. The addition of an auxiliary stabilizing wheel reduces risks from mechanical or human failures that may cause the vehicle to pitch forward due to loss of control. This capability compares favorably with the Segway, where failures in the loss-of-batterypower warning have resulted in serious injuries.

6 96 Appendix A: Sample Technical Report 4. Experimental Validation Because the auxiliary stabilizing wheel is a critical aspect of the proposed design, its feasibility was experimentally investigated. The goal of the experiment was to determine how quickly such a wheel could be deployed using a relatively low-cost actuation system. The actuator used in the experiments was a pneumatic cylinder driven by air compressed up to a maximum pressure of 100 psi. Handlebar Width Adjustor Handlebar Height Adjustor Stabilizing Wheel Seat Seat Height Adjustor Footrest Platform Main Drive Wheels Figure 2: Human Transporter with Auxiliary Stabilizing Wheel. The pneumatic cylinder was attached inside a hollow tube with its stroke piston pointed downward. A prototype of the stabilizing wheel was constructed using a 6 inch wheel attached to the end of a 15 inch long piece of aluminum bar stock. The prototype was then attached to the end of the cylinder piston. The assembly was held rigidly in a test stand and a video camera was placed to the side of the apparatus to record the motion of the prototype. The air tank used to drive the cylinder was pressurized to 10 psi, the valve was opened, and the cylinder extended the wheel downward 4 inches. An analysis of the video revealed that full deployment occurred approximately 0.55 seconds after the air valve was opened. Tests were repeated at increments of 10 psi, up to a maximum value of 100 psi. Figure 3 shows the recorded extension times as a

7 Appendix A: Sample Technical Report 97 Wheel Deployment Time (s) Air Pressure (psi) Figure 3: Wheel Deployment Time as a Function of Air Pressure. function of the air pressure. The extension time decreases as the pressure is increased above 10 psi. However, it reaches a minimum of 0.3 seconds at about 60 psi. Further increase in air pressure produced negligible improvements in deployment time. 5. Discussion The Segway failed to gain community acceptance because it was too expensive and too dangerous to use on sidewalks with pedestrians. While the new design has approximately the same footprint as the Segway, it moves slower, so that the danger the vehicle poses to pedestrians is greatly reduced. The auxiliary safety wheel further decreases dangers to both the rider and nearby pedestrians. The low center of gravity of the complete system decreases the required stabilizing torques. This allows the use of less powerful motors and reduces energy consumption. Both of these effects lower the expense of the device. 6. Conclusions In order to design a personal human transporter for mass appeal, it is necessary to thoroughly examine the problem and understand the customer needs. The House of Quality shown in Figure 1 relates engineering requirements to customer needs so that the most important requirements of the customer are identified. This analysis indicated that a more sidewalk-friendly transporter was needed. This analytical result led to a conceptual design that is safer for operators and more appropriate for use on public sidewalks. References [1] K. Weinmann. (2011 December 6). 4 Things You Can Learn from Segway s Notorious Product Fail. American Express OPEN Forum (online). Accessed Available:

8 98 Appendix A: Sample Technical Report [2] D. A. McIntyre. (2010, May 14). The 10 Biggest Tech Failures of the Last Decade. Time Magazine (electronic version). Available: /specials/packages/article/0,28804, ,00.html,00.html [3] A. Castro, W. Singhose, J. J. Potter, and C. Adams, Modeling and Experimental Testing of a Two-Wheeled Inverted-Pendulum Transporter, ASME Dynamic Systems and Control Conference, Ft. Lauderdale, FL, [4] B. Webster. (2006, August 21). Blow to inventors as Segway banned. The Times (electronic version). Available: business/entrepreneur/article ece [5] Stuff.co.nz. (2008, August 27). Pizza delivery Segways banned. Stuff.co.nz BUSINESS DAY (online). Accessed Available: [6] J. B. Morrell and D. Field, Design of a closed loop controller for a two wheeled balancing transporter, Conference on Intelligent Robots and Systems, San Diego, CA, 2007, pp