Adaptive Attitude Controller for a Six Wheel-Legged Robot Based on Impedance Control

Abstract

To remain the attitude of the robot during moving, an adaptive controller is proposed for a wheeled-legged robot on an irregular terrain. Our contributions are as follows: we develop a six-wheeled legged robot based on PRR structure and an adaptive attitude controller. The controller is comprised of three modules: which are adaptive impedance controller module, attitude controller module and centroid height controller module. When moving in wheeled mode, attitude adjustment primarily relies on elongation of each leg, it is crucial to avoid any suspended legs. An adaptive impedance control (AIC) is employed to track the leg force, adapt to terrain changes-induced disturbances, and compensate for terrain uncertainty by self-adaptively adjusting target damping. The comparative simulations were conducted to verify the effectiveness and robustness of the proposed adaptive controller in maintaining the robot’s attitude stability across various motion modes. AIC could track the desired force within 0.3 s and the force error is less than 20 N. The robotic attitude angles are maintained within a range of ±0.5° and the centroid height error fluctuates within −2 mm to + 5 mm.