Most of this group has no electronics at all. Chassis, wheels, hubs and linear actuators are sizing decisions — match shaft diameter, bore and mounting pattern before torque specs.
Robot chassis (2WD miniQ, 4WD mecanum, 6WD outdoor), mecanum wheels (48–97mm), brass hex hubs (4–6mm), shaft couplers, 2GT timing pulleys and uArm robotic arms.