Experimental Comparison of Skid Steering Vs. Explicit Steering for a Wheeled Mobile Robot

Abstract

Robotic tasks call for a range of steering activity: one extreme is highway driving with negligible turning for hundreds of kilometers; another is forklift handling, which calls for agile turning. The scope of this thesis considers steady state turning of a wheeled vehicle on natural terrain with slow but capable locomotors characteristic of planetary robotic vehicles . Experiments are performed using a single vehicle that can exhibit both skid and explicit steering while driving steady state circles. Skid steering is accomplished by creating a differential velocity between the inner and outer wheels. Explicit steering is accomplished by changing the heading of the wheels to cause a change in heading of the vehicle. Experimental results are gathered to provide information regarding power draw, individual wheel torque, and position information. The experimental results show that power and torque for skid and explicit turning degenerate to equal values at infinite radius (straight driving). As the turn radius decreases from straight driving to a point turn, greater power and torque are required as a greater sideslip angle is encountered. For all turns skid steering requires greater power and torque than for explicit turning because sideslip angles are greater in all cases. In the limiting case of a point turn, the power for skid steering is approximately double that of an explicit point turn. The primary contribution of this research is the experimental quantification of the power and torque requirements over turn radii from zero to infinity.