Adaptive Multi-dimensional Compliance Control of a Humanoid Robotic Arm with Anti-Windup Compensation

Safety is very important for physical human-robot interaction. Compliance control can solve an important aspect of the safety problem by dealing with impact and other forces arising during close contact between humans and robots. An adaptive ompliance model reference controller was implemented in real-time on a 4 degrees of freedom(DOF) humanoid robotic arm in Cartesian space. The robot manipulator has been controlled in such a way as to follow the compliant passive behaviour of a reference mass-spring-damper system model subject to externally sensed forces/torques in all DOF. The relevant reference model converts all measured torques into their equivalent forces at the end-effector and reacts accordingly. The suggested control scheme takes in particular account the multi-variable aspect and the problem of body own torques when measuring external torques. The redundant DOF were used to control the robot motion in a human-like pattern via effort minimization. Associated actuator saturation issues were addressed by incorporating a novel anti-windup (AW) compensator. The controller was tested on the arm of the humanoid Bristol-Elumotion-Robotic-Torso II (BERT II).