Crawling Locomotion Enabled by a Novel Actuated Rover Chassis

Traversing soft soils represents a major concern of planetary rover missions. In this paper, we present a new chassis mechanism capable of a crawling gait that enhances trafficability on soft soil while relying on as few actuators as possible. Articulated by two actuated joints, MARCEL is a four-wheeled rover chassis which name stands for Mobile Active Rover Chassis for Enhanced Locomotion. MARCEL's crawling leverages a continuous adjustment of the load distribution on the four wheels using an internal torque applied between two halves of the chassis by series elastic actuation. This allows the pressure on two wheels to be minimized while they are moving forward with the assistance of the chassis's articulated motion. As a result, the wheels can be propelled forward one pair after another while avoiding the bulldozing resistance of the sand. This crawling motion is tested experimentally and is shown to generate more drawbar pull than both rolling or using a mere “push-pull” locomotion. Its ability to extricate the rover from deep sand entrapment is also tested successfully. This will allow future missions to deal with unforeseen terrain properties or to venture in more challenging areas while minimizing design complexity.