Design and Analysis of H-infinity Force Control of a Series Elastic Actuator for Impedance Control of an Ankle Rehabilitation Robotic Platform

Author(s)

Perez-Ibarra, Juan C. ; Jutinico Alarcon, Andres L. ; Campo Jaimes, Jonathan ; Escalante Ortega, Felix M. ; Terra, Marco Henrique ; Siqueira, Adriano A. G. ; IEEE

• Document type: Journal article
• Source: 2017 AMERICAN CONTROL CONFERENCE (ACC); v. N/A, p. 6-pg., 2017-01-01.

Abstract

Impedance control based on robust force control can improves rehabilitation therapies. In this paper, we formulate and validate a model of a series-elastic-actuator-based ankle rehabilitation device that includes a second-order description of the human joint dynamics. In order to control the output impedance of the platform we used a cascade configuration with a PD position controller as outer loop and a force controller in the inner loop. We present the design and analysis of an H-infinity force controller that guarantees robust stability in the inner loop of the impedance control strategy. H-infinity mixed-sensitivity synthesis method was used for robust control loop-shaping design of the force controller. Experimental results of humanrobot interaction tests are presented. Performance and stability analysis using frequency and temporal responses are conducted. We found that our controller, actually any fixed-gain controller, can not guarantee the same performance among the different human-robot conditions. Results obtained in this work are a departure point to improve performance of the force controllers and therefore impedance-controlled rehabilitation therapies. (AU)

• FAPESP's process: 11/04074-3 - Development of an interactive robotic device for rehabilitation of injuries of the knee
• Grantee: Wilian Miranda dos Santos
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 13/14756-0 - Adaptive variable impedance applied to robotic rehabilitation of walking
• Grantee: Adriano Almeida Gonçalves Siqueira
• Support Opportunities: Regular Research Grants