Utilisation of manipulator redundancy for torque reduction during force interaction

Abstract

The integration of robots into environments shared by humans has been enhanced through the use of redundant robots capable of executing primary tasks and secondary objectives such as obstacle avoidance and null space impedance control. A critical secondary objective involves optimizing manipulator configurations to reduce torque and prevent torque saturation, similar to how athletes distribute loads to minimize the risk of injury. This paper suggests employing robotic redundancy to evenly distribute joint loads, thereby improving performance and avoiding torque saturation. Prior studies primarily focused on either endpoint stiffness control or kinetic energy minimization, each having its drawbacks. This paper introduces a novel objective function that responds to all external disturbances at the end effector, aiming to lower joint torques via redundancy for precise trajectory tracking amidst disturbances. This method, which provides an inverse kinematics solution adaptable to various controllers, demonstrated a 29.85% reduction in peak torque and a 14.69% decrease in cumulative torques in the KUKA LBRiiwa 14 R820 robot.