This rover mobility system was designed as a part of my Capstone project at Northeastern University, by me and my capstone team, Rithin Tirumalasetti, Henry Silverstein, Lucia Marquez, and Micheal Nunes.
The design features four high-power large wheels, mounted to custom harmonic swerve drive steering actuators. In addition, it is mounted to an adjustable-height pnematic suspension system, allowing traversal of very steep terrain with increase traction and reduced risk of tipping. The differential maintains all four wheel’s contact with the ground and keeps the chassis as level as possible.
Improvements and adapations for the systems use in next year’s rover are currently in progress to allow aspects of the system to be used in competition.
CAD: https://grabcad.com/library/rover-drive-system-capstone-project-1
Steering is accomplished using a custom integrated harmonic actutor, driven by a Cubemars RI60 frameless motor, and controlled by a Moteus C1 controller. The AS5047p integrated moteus encoder tracks absolute position, while commutation of the motor is accomplished via the integrated hall sensors.
The wheel drive is accomplished both with a belt reduction, as well as a single stage planetary. The prior also allows for offset motor mounting, improving packaging and ground clearance. The wheel is of a custom design, which was loosely based off past designs but scaled up, and then FEA and real world deflection testing was performed to achieve a suitable spring rate for increased traction on loose surfaces.
The system features both independent wheel suspension to absorb large impacts without signifigantly moving the chassis, as well as a differential to keep all wheels on the ground at all times. The suspension is also adjustable pressure in order to change the height and length of the wheelbase, which can permit much higher chassis stability and traction on steep slopes, enabling traversal of extreme terrain.
Dynamic analysis was performed by other members of my team using Matlab simulink, which both allowed us to charcterize our suspension geometry, as well as derive worst-case impact loads which were used in our FEA analysis of all structural components.
The design was fully master sketched, which allowed for rapid changes to major design aspects and control of all aspects of interfacing parts within one document, greatly simplifing the design process.
