Bio-inspired adaptive control for active knee exoprosthetics

Journal article (2017)

Authors

A.K. Pagel ETH Zürich, University of Zürich

Raffaele Ranzani ETH Zürich

Robert Riener ETH Zürich, University of Zürich

H. Vallery Biomechatronics & Human-Machine Control - Mechanical, Maritime and Materials Engineering

Research Group

Biomechatronics & Human-Machine Control (Mechanical, Maritime and Materials Engineering) (TU Delft)

Physiology Impedance Adaptive control Prosthetics Legged locomotion Knee Active knee exoprosthetics Adaptation models Joint impedance modulation Reflex-based neuromusculoskeletal model Solid modeling User-cooperative control

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Published Date

2017

Language

English

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Faculty

Mechanical, Maritime and Materials Engineering

Department

Biomechanical Engineering

Research Group

Biomechatronics & Human-Machine Control

Abstract

On the quest to bring function of prosthetic legs closer to their biological counterparts, intuitive interplay of their control with the users impedance modulation is key. We present two control features to enable more physiological and more user-adaptive control of prosthetic legs: a neuromusculoskeletal impedance model (NeurImp) including a reflexive component, and a human model reference adaptive controller (HuMRAC), which can be combined with the former. In stance-phase simulations, the NeurImp allowed to control a prosthetic leg with physiological knee joint angle and moment. When perturbations were applied, the HuMRAC reduced the resulting root mean square error (RMSE) between simulated and physiological reference angle by 96%. In a pilot experiment with two unimpaired and one amputee subject, gait with the NeurImp deviated more from a physiological reference than with a conventional visco-elastic impedance controller. Subjects, however, preferred the NeurImp. When adding the HuMRAC to either of the two impedance controllers, the RMSE between the actual and the physiological reference angle was reduced by up to 54%. Subjects confirmed this finding and reported an easier stance-toswing transition. Simulation and pilot experiment suggest that a reflex-based impedance controller combined with an adaptive controller may improve user-cooperative behavior of active knee exoprostheses.

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