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research-article

VARIABLE IMPEDANCE CONTROL OF POWERED KNEE PROSTHESES USING HUMAN-INSPIRED ALGEBRAIC CURVES

[+] Author and Article Information
Alireza Mohammadi

Dept. Electrical & Computer Engineering, The University of Michigan, Dearborn, Dearborn, MI 48128
amohmmad@umich.edu

Robert D. Gregg

Dept. Bioengineering and Dept. Mechanical Engineering, The University of Texas at Dallas, Richardson, TX 75080
rgregg@utdallas.edu

1Corresponding author.

ASME doi:10.1115/1.4043002 History: Received October 02, 2018; Revised February 23, 2019

Abstract

Achieving coordinated motion between transfemoral amputee patients and powered prosthetic joints is of paramount importance for powered prostheses control. In this article we propose employing an algebraic curve representation of nominal human walking data for powered knee prosthesis controller design. The proposed algebraic curve representation encodes the desired holonomic relationship between the human and the powered prosthetic joints with no dependence on joint velocities. For an impedance model of the knee joint motion driven by the hip angle signal, we create a continuum of equilibria along the gait cycle using a variable impedance scheme. Our variable impedance-based control law, which is designed using the parameter-dependent Lyapunov function framework, realizes the coordinated hip-knee motion with a family of spring and damper behaviors that continuously change along the human-inspired algebraic curve. In order to accommodate variability in the user's hip motion, we propose a computationally efficient radial projection-based algorithm onto the human-inspired algebraic curve in the hip-knee plane.

Copyright (c) 2019 by ASME
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