Whole-Body Locomotion and Posture Control on a Torque-Controlled Hydraulic Rover

This letter presents the control method and system of a four-legged, four-wheel-drive hydraulic powered rover that can traverse irregular terrain such as agricultural or forest landscapes while carrying manipulators and other tools to do heavy-duty work. The rover is equipped with driving wheels at the tip of its legs and passive wheels at its knees or the bottom of its belly. By directly controlling the whole-body joint torque using hydraulic actuators, the multiple contact forces at its rolling contact points can be distributed optimally according to the rover state. This allows the acceleration of the rover's center of gravity and posture to be controlled while the active/passive wheels accommodate the terrain. The proposed control method is applied to our new fully torque-controlled rovers produced from low-cost hydraulic components. The simulation and experiments on balancing on moving ground, or running over slopes validates the proposed algorithm and the system.