Designing Within Guidelines
The design of the Roll Car was largely limited by the Roll Track that was available for experimentation. We knew the sensors and hardware that were necessary to create an Advanced Cruise Control System. Therefore, the challenge was to package all these components into the allotted space while reducing weight and ensuring proper ground clearance.
Instead of a 3D printed chassis, which can be both dense and expensive, a simply sheetmetal chassis was produced. At 1/8 inch thickness, the metal provided surprisingly rigidity and offered maximum internal space. In order to fit all hardware —Arduino, battery, H-Bridge, and motors— flaps were added to the chassis to introduce a second layer.
The hardware proved difficult to manage as wiring and hardware interconnections were tightly packed together. In order to minimize electrical failures with the metal chassis, an ample use of electrical tape and precise soldering was necessary. The breadboard was replaced with direct wiring in order to open up space for larger 12V batteries to fully drive the 900 RPM DC motors.
The cruise control and vehicle following algorithm was designed using a PID controller modeled from data collected using three velocities of the lead vehicle, which used the exact same hardware aside from ultrasonic. Due to excessive sensor noise, a Kalman filter was implemented within the code alongside a 115,200 baud rate in order to rapidly respond to the everchanging environment.