A Conceptual Approach of Passive Human-Intention-Orientated Variable Admittance Control using Power Envelope

Abstract

Two main challenges that need to be addressed in physical human-robot interaction (pHRI) are efficient recognition of human intention and interaction safety. In this paper, a general human intention framework was summarized, firstly, according to the robot's roles: a passive follower and a compliant leader. Secondly, we proposed variable admittance control models governed by human intentions. Power envelope approaches were then proposed to impose constraints on the variable admittance parameters inferred from human intention for maintaining passivity conservatively. Our passivity preserving approaches were validated via simulation and shown to avoid mismatching of time-varying admittance parameters that restrain drastic changes of admittance controller dynamics, which usually result in instability. Finally, the relationship between the robot's passivity and stability when it interacts with the human was analyzed.