A Balance Controller of the Humanoid Robot Based on Momentum Under External Impact

Abstract

Humanoid robot can generate not only extra linear momentum but also angular momentum when suffering external force. This paper presents a momentum-based balance controller to control the linear and angular momenta of the robot. Firstly, the desired ground reaction force (GRF) and center of pressure (CoP) are designed through the conditions of the center of mass (CoM) and angular momentum. Secondly, the relation map between GRF and joint torques is established. Besides, the joint torques to recover balance in the presence of external force can be obtained through optimization. Finally, the robustness of the balance controller is thorouhly examined, and its capabilities are verified by simulation. The simulation results show that the balance controller can realize recovery from unknown external force and standing up. When the robot’s back is hit, the hip consumes the most energy (60%). Meanwhile, the knee costs the most energy (45%) when the impact is on the chest. In the case of suffering large impact, the anti-interference ability of the robot can be improved by properly bending down.