A Passivity-Based Approach for Stable Patient–Robot Interaction in Haptics-Enabled Rehabilitation Systems: Modulated Time-Domain Passivity Control

Abstract

In this paper, a novel passivity-based technique is proposed to 1) analyze and 2) guarantee the stability of haptics-enabled robotic/telerobotic systems when there is a possibility of having a source of nonpassivity (namely, a nonpassive environment) in addition to the conventional nonpassive component in teleoperation systems (namely, a delayed communication channel). The need for the proposed technique is motivated by safe and optimal implementation of the haptics-enabled robotic, cloud-based, and remote rehabilitation systems. The objective of the controller proposed in this paper is to perform minimum alteration to the system transparency, in a dynamic and patient-specific manner, by utilizing quantifiable biomechanical capability of the user’s limb (i.e., excess of passivity) in dissipating interactive energies to guaranteeing human–robot interaction safety, in the context of the strong passivity theorem. The proposed controller is named modulated time-domain passivity control (M-TDPC) approach and is a new member of the family of the state-of-the-art TDPC techniques. Simulations and experimental results are presented in support of the proposed technique and the developed theory.