For our final project, my team and I needed to design, construct, and program a robot to collect "solar panels" off a roof at various angles, and deposit them on a platform. To accomplish this goal, we designed a four-bar linkage system and custom gearbox to lift light PLA panels as well as heavy aluminum ones. I 3D printed our final design and we assembled it using VEX shafts and shaft collars.

In order to determine the required output torque of the gearbox, I performed a motion study on the crank in Solidworks. We verified the resulting torque required (with a safety factor) by setting up the equations of equilibrium for the three moving linkages and solving for all of the forces in MathCAD. Based on the resulting data and the input torque of the motor in our kit, we decided to use a 1:27 gear ratio.

Our robot used reflectance and ultrasonic sensors with PID to navigate the field. Using PID control allowed us to maintain a specific position with respect to the line while driving, and stop a set distance from the target. For the overall control, we used a state machine which allowed the robot to move between various actions such as line following, picking up plates, and adjusting the height of the arm. Because the arm needed to reach a very specific angle and height in order to place the plates on the roof, we used PID control to account for the "dead zone" in our system and return the arm to the same position each time.