A differential drive rimless wheel that can move straight and turn

Abstract

A rimless wheel, or a wheel without a rim, is the simplest example of a legged robot and is an ideal testbed to understand the mechanics of locomotion. This paper presents the design and control of a differential drive rimless wheel robot that achieves straight-line movement and turning. The robot design comprises of a central axis with two 10-spoked springy rimless wheels on either side and a central body that houses the electronics, motors and transmission, computers, and batteries. To move straight, the current in each motor is servoed to a constant torso pitch angle. To turn, while maintaining constant pitch, a differential current is added and subtracted from either motor. In separate tests, the robot achieved the maximum speed of 9.66 miles per hour, the lowest total cost of transport (power per unit weight per unit velocity) of 0.13, and the smallest turning radius of 0.5 m.