Horizon-stability control for wheel-legged robot driving over unknow, rough terrain

Abstract

Maintaining the horizontal and stable posture of a robot while traversing unfamiliar, rugged terrain poses a significant challenge in various applications such as wounded rescue and disability assistance. This paper introduces a horizontal-stability control framework designed for a wheel-legged hybrid robot to ensure the stability and horizontal orientation of the robot's trunk when encountering unknown and rough terrain conditions. This framework primarily comprises a compliance controller and a terrain adaptation controller. The compliance controller is geared towards establishing compliant interactions with the terrain and tracking the desired ground reaction forces. This is achieved through the implementation of a novel adaptive impedance control method to uphold torque equilibrium in the robot's trunk. To conform to the variable terrain, the terrain adaptation controller is employed. This controller decouples posture adjustments and regulates control outputs to adapt to terrains featuring unknown topographical changes. A series of numerical simulations and experimental trials are carried out to validate the proposed methods on a wheel-legged hybrid robot, followed by comparative evaluations to assess its performance.