Operational Space Control Framework for Torque Controlled Humanoid Robots with Joint Elasticity Torque controlled robots have the capability of implementing compliant behavior with backdrivability. In practice, however, joint elasticity often prevents an accurate position tracking performance of a robot. In particular, humanoid robots are influenced more by elasticity because of a long kinematic chain between the feet and hands. In this paper, we present a new inverse dynamics based control approach for torque controlled humanoid robots with joint elasticity. When formulating the operational space control framework, feedback control consists of only motorrelated parts with measured motor angle values, and the link dynamics is compensated by the feedforward terms. The experiment results of the proposed approach show a noticeable improvement in the position tracking performance in 6DoF manipulator. Finally, the proposed method was applied to a torque controlled biped robot for walking. Both stiff motion control of the CoM and compliant motion control of the foot were simultaneously achieved, demonstrating the advantage of the torque controlled robot.

Impedance Control Strategy and Experimental Analysis of Collaborative Robots Based on Torque Feedback In this paper, through the modeling and analysis of flexible joints, an impedance controller based on torque feedback is proposed, which is used to realize the active compliance of collaborative robots. The controller includes two parts: torque controller and impedance controller. The torque controller is used to compensate the robot dynamics, and the impedance controller is used to adjust the joint stiffness and damping. The theoretical analysis of the control strategy shows that the significance of torque feedback is that it can reshape the inertia of the motor, reduce friction torque and suppress unknown disturbances. In order to ensure tracking accuracy, a task errorbased disturbance observer is designed. Experiments with a 7DOF collaborative robot show that the proposed controller in this paper can realize the body compliance and obtain better compliance performance than the traditional compliance control method.