In the first year of HURC doing the rover challenge in 2024, I became the lead mechanical engineer and designed the rover using Solidworks. The rover design has 3 main subsystems: the 5-DOF arm, the rocker-bogie suspension, and the aluminum-welded chassis. After designing the rover, I made drawings for each of the custom parts using GD&T to send to our in-house machinists. Additionally, I machined many of the parts myself including the structure of the chassis, and the robotic arm joints
The 5-DOF robotic arm is actuated using stepper motors with the base, and two wrist joints using planetary gearboxes, and the shoulder and elbow using harmonic drive strain wave gearboxes. The arm structure is made of carbon fiber with the joint structures machined out of 6061 aluminum. Since the club has access to a waterjet, it was important to design the arm around that being our primary machine, so there is broad use of sheet metal parts. Certain rotary components had to be done on the lathe, and some structural components required the mill. The gripper is a 4-bar parallel linkage design actuated using a stepper motor and a worm gear drive to actuate both fingers at the same time.
The chassis was decided to be aluminum welded due to the reduced mechanical complexity and low weight while ensuring a high strength system. Due to the chassis being the main structure that holds the load of all of the subsystems, I performed FEA on the chassis. Given the expected load on the chassis, it has a safety factor of 10.
As this was the first rover made by HURC, the decision was made to design a traditional rocker-bogie suspension with 6 wheels. The differential coupling either side was initially a complex linkage system, but was heavily simplified to be a system of ball joint struts. I went through many design iterations of this suspension including a sprung and damped design, and a design where the wheels could rotate independently. However, I ultimately landed on a simple tank-driven system where the tires do the damping. The motors running the wheels of this suspension are brushless DC motors from maxon with planetary reducers.
