After evaluating several existing stair-climbing technologies, including transformable wheels, linkage leg systems, and continuous tank treads, the team selected a six-wheeled rocker-bogie suspension system as the most promising approach. The design was specifically optimized for the Engineering Gateway staircase, with steps measuring 5.75 inches in height and 17 inches in depth, including two extended landings at steps 6 and 13.
The chassis consists of two laser-cut 1/4-inch plywood segments forming the rocker and bogie linkage arms (4-inch front rocker, 8-inch rear rocker, 5.5-inch bogie arm), connected by threaded rods to minimize weight. Wheels were 3D printed in PETG filament at 30% gyroid infill for strength-to-weight efficiency, then dip-coated in Plasti-Dip rubber to maximize traction on concrete stair surfaces.
The drivetrain uses six 12V DC worm-gear motors, one per wheel, selected after torque analysis confirmed they could meet stair-climbing demands within the project budget. The worm gear configuration also provides passive self-locking, preventing the robot from sliding back when pausing mid-climb. After prototyping and testing, the team determined that a simplified direct-wired electrical configuration was sufficient, eliminating the need for motor drivers or control software.
The team performed SolidWorks-based geometric simulation to validate that the chassis could articulate through four distinct climbing phases without contacting the stair edges, with calculated pitch angles of 63.4°, 101.8°, 27.6°, and 49.0° respectively. These were verified during proof-of-concept testing, with measured angles of 60°, 105°, 35°, and 55°, within acceptable tolerance. A three-step proof-of-concept climb was successfully completed during Fall Quarter, validating the geometry before full fabrication.
Development followed an iterative test-and-refine methodology across Winter Quarter, progressing from motor and electronics integration testing through full staircase runs and friction optimization, ultimately culminating in a successful timed climb of all 19 steps.
