Simplified Stable Admittance Control Using End-Effector Orientations

Abstract

Admittance control is used mainly for human–robot interaction. It transforms forces and torques to the desired position and orientation of the end effector. When the admittance control is in the task space, it needs the Jacobian matrix, while in the joint space, it requires the inverse kinematics. This paper modifies the admittance control using only the orientation components of the end-effector to avoid the calculation of the inverse kinematics and the Jacobian matrix. We use geometric properties, adaptive control and sliding mode control to approximate them. The stability of those controllers is proven. Experiments are presented in real time with a 2-DOF pan and tilt robot and a 4-DOF exoskeleton. The results of the experiment show the effectiveness of the proposed controllers.