A Null-space based Approach for a Safe and Effective Human-Robot Collaboration

TL;DR

This paper introduces a null-space based method to enhance human-robot collaboration by maintaining stability without degrading performance, using energy harvesting to avoid spurious dynamics in admittance control.

Contribution

It proposes a novel null-space energy harvesting approach to prevent spurious dissipative effects in time-varying admittance control during human-robot collaboration.

Findings

Validated through simulations and experiments with a collaborative robot.

Achieved stable, effective human-robot interaction without performance degradation.

Abstract

During physical human robot collaboration, it is important to be able to implement a time-varying interactive behaviour while ensuring robust stability. Admittance control and passivity theory can be exploited for achieving these objectives. Nevertheless, when the admittance dynamics is time-varying, it can happen that, for ensuring a passive and stable behaviour, some spurious dissipative effects have to be introduced in the admittance dynamics. These effects are perceived by the user and degrade the collaborative performance. In this paper we exploit the task redundancy of the manipulator in order to harvest energy in the null space and to avoid spurious dynamics on the admittance. The proposed architecture is validated by simulations and by experiments onto a collaborative robot.