Discrete Windowed-Energy Variable Structure Passivity Signature Control for Physical Human-(Tele)Robot Interaction

Abstract

In this letter, we propose a novel adaptive iterative stabilization method for physical human-(tele)robot interaction, named Discrete Windowed-Energy Variable Structure Passivity Signature Control (DWE-VSPSC). The proposed stabilizer is capable of adaptively translating the knowledge domain regarding the capacity of the user's biomechanics in absorbing physical interaction energy to reduce the transparency distortion (induced for stabilization) while enhancing system performance through a flexible design of stabilizer. The contributions of this letter are: (1) the design of a novel discrete adaptive stabilizer with proof of stability; allowing for digital implementation of the intelligent algorithm; (2) introducing the concept of “windowed energy stabilization” for the proposed variable structure passivity-signature controller in order to allow for tuning the energy behavior of the interconnected system while making a balance between conservatism and agility of the system; (3) relaxing any assumption on the passivity behavior of the environment while being able to handle stochastic variable network delays without any restriction on the rate of change of delay or the delay. The mathematical design of the stabilizer is provided alongside the stability proof. Also, the performance of the system is evaluated using a systematically-designed grid simulation study for a large range of delay and environmental impedances ranging from passive to non-passive behaviors. A direct application of the outcome is for telerobotic rehabilitation and telerobotic surgery.