Integrated Adaptive Compliance Control for Wheeled-legged Platforms Based on State Estimation

As a new type of special vehicle, the wheeled-legged platform (WLP) extends the degrees of freedom at the wheel ends, and has the potential of traveling at high-speed in complex terrain. However, the vertical-longitudinal coupled dynamics of two-stage actuation unit and the unmeasurable states pose significant challenges to speed tracking and terrain-adaptive compliance control on uneven roads. To address these issues, this paper proposes an integrated adaptive compliance control method based on state estimation. Firstly, the forward and inverse kinematic models of the WLP are developed based on its movement configuration, and the reference dynamic models for vertical vibration damping and longitudinal compliance are constructed using the virtual model approach. Then an integrated adaptive compliance control framework in vertical-longitudinal directions is established. It incorporates longitudinal terminal sliding mode control, vertical optimal vibration damping control, and Kalman filtering to finally achieve the speed tracking and terrain adaptation under a reference posture. Tests under various conditions validate the effectiveness and stability of the newly proposed integrated compliance control method. For example, the peak vertical acceleration under the bumpy road condition is less than 1.1m/s^2.