Realization of Whole-Body Torque-Controlled Hydraulic Wheel-On-Leg Rover

This paper presents a realization of a four-legged, four-wheel-drive hydraulic powered rover that can traverse irregular terrain such as agricultural or forest land. The fabricated rover is 331[kg] in weight, with a base of 1,200[mm] length, 700[mm] width and standard height at 1,000[mm] on nominal configuration. The rover can control the whole-body joint torque using the pressure servo on hydraulic actuators, thereby optimally manipulate the ground reaction force and traction of the wheel according to the rover states. In this paper, we describe the design concept of the rover, followed by the details of the realized mechanical system, control system, and the control methods. We validate the proposed system by demonstrating the experimental results on compliant balancing on a moving seesaw and traveling on a slope.