Sensorless variable impedance compliant control for human–robot interaction

Abstract

In order to improve compliance in human–robot interaction, a sensorless variable impedance control method is proposed. Variable impedance control is constructed using the end-effector velocity and the human–robot interaction force. Then, the impedance parameters are adjusted online to make the end-effector velocity more compliant with human behavior. Next, a velocity controller is designed to stabilize the end-effector velocity, and a compensation force is designed to avoid the measurement of the interaction force. Based on the velocity controller and the compensation force, an integrated controller is constructed to achieve stable end-effector velocity while compensating the interaction force online. The Lyapunov theory proves that with the sensorless variable impedance control, the system is stable, and the velocity tracking is bounded; simulation results demonstrate its feasibility. The sensorless variable impedance control can achieve more stable velocity and better compliance in human–robot interaction.