Whole-Body Anti-Input Saturation Control of a Bipedal Robot

Abstract

Bipedal locomotion requires a multi-level control strategy for balance and tracking, with the zero-moment point (ZMP) serving as a heuristic balance criterion.Maintaining the ZMP location within the stability margin indicates stability, but ankle joint actuation behavior restrictions are required.This paper focuses on whole-body control of a bipedal robot, considering control input limitations.Two dynamical models of bipedal dynamics are introduced, integrating center-of-mass (CoM)-based dynamics with joint space dynamics.The controlled outputs are the CoM position and joint displacements, while the control inputs are the ZMP position and joint torques.Anti-input saturation control is considered to ensure safe values for the control inputs, especially for the ZMP and ankle joint torque signals.A decentralized adaptive approximation control (DAAC) with a saturation compensator is designed.The stability of the proposed controller is proven using Lyapunov theory.Simulation experiments are conducted on a planar 6-degrees-offreedom (DOF) bipedal robot.The results demonstrate the robustness of the control architecture even under a disturbance torque of 10 N.m., ensuring safe stability margins for the ZMP and precise tracking for the multi-DOF bipedal system.