Design and Control of a Passively Steered, Dual Axle Vehicle

In this paper we describe the steering, suspension and control systems of the rover Zoë, a solar-powered robot designed to explore the Mars-like landscapes of the Atacama Desert in Chile. We are developing the Zoë chassis as an alternative to the traditional six-wheeled, rocker-bogie system used by Mars rovers flown in the past ten years. Zoë travels over rough terrain using only four independent drive motors. Steering is accomplished by differentially driving pairs of these motors to passively articulate front and rear steering axles. In this paper we present a detailed mechanical design of the chassis, a description of Zoë’s steering controller and results of steering controller tests that validate this design. We also include lessons learned after field experiments in the Atacama Desert of Chile.