A Passivity-Based Optimal Contact Force Control for Humanoid Robots with Redundant Joints and Multiple Contact Points

Abstract

This paper proposes a practical contact force control framework for force-controllable legged robots with redun-dant joints, which is applicable to automatic/semi-automatic control for mobile robots, construction robots, bipedal humanoid robots, and assisitive devices. The proposed method requires: (1) no contact forces measurements; (2) no inverse kinematics; (3) nor inverse dynamics in achieving the desired contact forces. Combined with a passivity-based redundancy resolution technique, a contact force closure is optimally solved and transformed directly into joint torques in real-time. Experimental results on a full-sized biped humanoid robot show that the proposed method can simultaneously control the multiple contact forces without generating internal forces, and can naturally interact with unknown external forces.