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As my senior Capstone at Northeastern, I worked on a team of five to design a device to simulate the forces experienced while riding a bike. The bike is used to study bike lane design in Boston and allow researchers to safety observe realistic biker reactions.
The bike recreates the feeling of swerving in a lane by accelerating the rider laterally via two separately controlled carts. It also simulates the feedback on the handlebars by using gyroscopic effects and the geometry of the front linkage. My role on the team was design of the front linkage and the carts. My partner and I designed, analyzed, manufactured, and assembled the front linkage. The major challenge to this part of the project was designing to minimize machining time and overall cost. Some analysis included hand calculations to determine the necessary degrees of freedom and to size the flywheel inertia and speed. I manufactured the shafts, friction wheel, and turntable using the school’s machine shop.
Front Linkage
Cart Assembly
I was also part of the design team for the carts. I worked with my team to brainstorm design solutions. This included analysis and design of the transmission system. Some of the analysis completed included FEA, hand calculations, MATLAB analysis, and Simulink analysis. Early on, we performed initial testing to determine the power requirements of typical bike maneuvers in a bike lane. Through modeling, we decided on 1000 watt DC brushless motor and a 4:1 gear ratio for each cart to meet our torque and speed requirements.
Assembled Front Cart
Several of the challenges came from the electrical and control side of the system. Due to cost and ease of integration, we decided to control each motor using an on-board Arduino microcontroller. The microcontroller interpreted steer angle and speed feedback inputs from a potentiometer and the DC tachometer circuit. It also controlled the motors via a separate motor controller and communicated with the other carts for safety. I was heavily involved with selecting and filtering the feedback tachometer and programing the closed loop control.
My teammate and I used Simulink to make a simplified model of our mechanical and electrical systems. Using this model, we were able to simulate the response of our system and select appropriate PID gains.
My team was successfully able to assemble both the mechanical and electrical system. During low power testing, the simulator responded as expected to rider inputs and we were able to recreate biking phenomena such as rear wheel lag, self-steering, and the need to counter-steer to initiate a lean. Due to time constraints and a damaged motor controller, we were unable to perform high power testing with a rider. Through this project, I gained experience in electronic systems and control of electromechanical systems. More details are located in the full report.
Initial Run of Prototype
Project Takeaways
Project Takeaways
Electronics, motor, and sensor selection and implementation
Design for manufacture and minimal budget
Dynamics and controls modeling
Machine shop and test experience
Project management
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