Parameters uncertainty analysis of posture control of a four-wheel-legged robot with series slow active suspension system

Abstract

This paper focuses on the posture control performance on uneven terrain for a wheel-legged robot (WLR). Firstly, a novel four-wheel-legged robot (FWLR) with series slow active suspension system (SSASS) is proposed. Secondly, the parameters uncertainty of posture control is studied, and an 11 DOF dynamic model and the corresponding system state equation are presented. Thirdly, to suppress the chattering problem and enhance the robustness of traditional sliding mode controller (TSMC), the second order low-pass filter (SOLPF), equivalent speed control, saturation function, terrain estimation model and the actuator model are introduced into the control system, and an improved sliding mode controller (ISMC) is proposed. Finally, both the co-simulation and experiment on uneven terrain are carried out, the results show that even if the system parameters have 30% variation, the robot posture angle can be improved effectively. That is, the proposed robot and ISMC control strategy have good posture control performance with low parameters sensitivity on uneven terrain. Overall, this paper attempts to provide an effective way for the application of WLR on uneven terrain.