Whole-body disturbance rejection control for quadruped robots based on variable bandwidth nonlinear extended state observer

This paper proposes a novel whole-body disturbance rejection control framework for quadruped robots to enhance robustness against model uncertainty and external disturbances. Firstly, a variable-bandwidth nonlinear extended state observer (VBNESO) is designed to estimate the lumped disturbances acting on the system. Subsequently, optimal contact forces are computed based on the estimation results to counteract the disturbances, and footholds are adjusted adaptively to improve gait stability. Finally, a disturbance-aware whole-body controller is developed to generate joint torque commands that achieve desired task-space trajectories and contact forces while respecting both kinematic and dynamic constraints. The proposed approach is validated through simulations in Gazebo and real-world disturbance rejection experiments on the Go2 quadruped robot.