June 22, 2008
June 22, 2008
June 25, 2008
13.194.1 - 13.194.13
An Investigation of Acceleration and Jerk Profiles of Public Transportation Vehicles
Abstract The acceleration and braking profiles of several public transportation vehicles were investigated as part of an independent undergraduate student research project in Electro-Mechanical Engineering Technology. In particular, vehicles in which the passengers are often required to stand while the vehicle is moving were studied. These vehicles include city buses and subway trains. Vehicle acceleration, either positive or negative (braking), and the time rate of change of acceleration, jerk, can have a significant impact on the safety and comfort of passengers. The effects of acceleration and jerk are especially troublesome for passengers that either choose to stand or must stand in the vehicle because no empty seats are available. A standing passenger has a higher center of mass and smaller base footprint than one that is seated. The standing position is also less stable than the seated position. Therefore as the vehicle accelerates or changes its acceleration, standing passengers must exert significant forces with their limbs to maintain their balance. In this paper, the instrumentation and software used to measure the acceleration and jerk of some public transportation vehicles are presented and discussed. Instrumentation hardware and software typically used in an engineering technology laboratory was used for these measurements. The data obtained from the testing of several vehicles is analyzed and interpreted using software and techniques familiar to undergraduate engineering technology students. Fundamental dynamics associated with the human passengers is also presented and discussed. Careful control of the acceleration and braking profile of the vehicle can greatly improve the comfort and safety of the passengers. A suggested instrumentation and display system to help drivers control the acceleration profiles to improve passenger safety is presented. This project utilizes many aspects of the course and laboratory work of the four-year electro-mechanical engineering technology program. No human subjects were used in this study.
Every year, commuters travel more than 20 billion miles by bus and 9 billion miles by commuter rail in the United States1. During the national average 24.4 minute commute to work, there are many factors affecting ride comfort2. Some of these factors are noise, temperature, humidity, and motion3. The factor of motion, including acceleration and jerk, will be examined as a transit vehicle comes to a complete stop. As the vehicle reaches zero velocity and does not reverse direction, the acceleration exhibits a very rapid (nearly discontinuous) change. This rapid change in acceleration imposes a large jerk on all elements in motion with the vehicle, including its passengers. Note that jerk is also referred to as jolt which is equally descriptive of this action. To better understand the physics of the linear motion experienced by ground vehicle passengers,
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