Safe Adaptive Compliance Control of a Humanoid Robotic Arm with Anti-Windup Compensation and Posture Control

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 compliance 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 an externally sensed force. The redundant DOF were used to control the robot motion in a human-like pattern via minimization of effort, a function of gravity. Associated actuator saturation issues were addressed by incorporating a novel anti-windup (AW) compensator originally developed for a neural network scheme. The controller was simulated for a robotic arm representing the Bristol-Elumotion-Robotic-Torso II (BERT II) and then tested on the real BERT II arm. BERT II has been developed in collaboration by Bristol Robotics Laboratory and Elumotion Ltd.