Stewart-Inspired Vibration Isolation Control for a Wheel-legged Robot via Variable Target Force Impedance Control

The vibration isolation control for wheel-legged robot has been widely investigated when adapting to the undulating slope terrain. How to solve the lag problem of low accuracy of foot-end force convergence to fixed target force in traditional impedance control under continuously changing slope terrain is the main challenge. In this paper, a vibration isolation control strategy based on variable target force impedance control (VTFIC) is proposed to effectively realize the foot-end contact force to track the target force under uneven road while maintaining the stability of the body. The strategy includes foot-end disturbance force estimator (FDFE) and force convergence accelerating controller (FCAC). Firstly, FDFE includes slope angle model, slope terrain model, autoregressive comprehensive moving average (ARIMA) model and event-triggering mechanism. It is mainly used to predict and calculate the disturbance force of slope terrain, and solve the problem of high deviation between foot-end actual force and target force caused by the impulse when foot contact with slope. Secondly, FCAC is designed based on power functional feed-forward control, to accelerate the convergence speed of the foot-end contact force to the target force. Finally, the simulation and experiment results show that the foot-end contact force of the robot can effectively track the target force with high accuracy and the robot remains stable under various terrains.