2023 Rover Frame
Current Design
CMR’s 2023 Frame design was a collaboration between myself and various other members of the drives sub-team. The primary goal behind the redesign of the frame was to bring the footprint of the rover in and increase manufacturability. To achieve these goals the E-Core (pictured as a black box with our logo on it) was made more circuit board dense and shortened by 2in. The triangle front where the 6 DOF arm mounted in previous years was removed and replaced with a straight connection to further cut the footprint of the rover down. To increase manufacturability the small CNC’ed aluminum joints used in previous years were replaced with continuous carbon fiber reinforced 3D printed joints made on a Markforged printer. My involvement in the frame was limited to the three aluminum CNCed structural joints in the front of the frame, the E-Core, and the 3D printed carbon fiber reinforced joints.
Aluminum Structural Joints
The frame’s three structural joints are responsible for taking all of the loading on the rover. The arm base, pictured top left, connects the arm to the rest of the frame via two rectangular carbon fiber tubes. The geometry of the arm-base is dictated by the mounting holes available on the arm, the motor that fits inside the U-shaped hole in the joint, the differential bar, and the carbon fiber tubing. I performed structural analysis on a version with additional lightweight pocketing pictured bottom middle, which showed that with the addition of pocketing to reduce mass the part was too weak in max loading conditions.
The suspension pivot, pictured top right, is responsible for acting as the rocker pivot for the suspension system, mount for the back portion of the frame, and support for the arm base. Virtually all loads acting on the rover run through this single part. The suspension pivot joint dictates the distance the linkages for the differential bar are away from the rocker bogie pivot. Structural Analysis on the joint shows that it is likely over-engineered, however further pocketing would result in a part requiring too many tool changes when manufacturing and is not worth the increased complexity.
