Development and Control of Supernumerary Robotic Limbs for Overhead Tube Manipulation Task

The foreign objects on utility poles may damage power lines and cause significant disruptions in electricity supply. A widely used approach to address this issue is for qualified personnel to climb on the pole and remove the foreign objects in a timely manner using an insulating tube. However, prolonged overhead manipulation of the insulating tube in the constrained environment not only leads to considerable upper-limb fatigue but also makes accurate tube positioning increasingly challenging. To address these challenges, wearable robotic limbs with an active control strategy have the potential to effectively reduce upper-limb fatigue and assist in tube positioning. This work presents supernumerary robotic limbs (SRLs) designed to assist electrical workers in a simulated overhead foreign objects removal task. We further propose a shared control method based on finite-horizon non- zero-sum game theory. This method models the cooperation between the SRL and the worker to adaptively modulate the input of the SRL, thereby providing rapid and accurate assistance in tube positioning. Experimental results show that the proposed SRL can reduce primary upper-limb muscle activity (deltoid, biceps brachii, brachioradialis and flexor carpi radialis) by up to 59.73% compared with performing the task without the SRL. Moreover, compared with a method that ignores human input, the proposed control strategy achieves more accurate positioning during human-SRLs cooperation. These results demonstrate the potential of both the SRL and the control strategy for the live-line overhead foreign objects removal task.