Annals of Biomedical Engineering

, Volume 44, Issue 5, pp 1613–1624

A Cyber Expert System for Auto-Tuning Powered Prosthesis Impedance Control Parameters

  • He Huang
  • Dustin L. Crouch
  • Ming Liu
  • Gregory S. Sawicki
  • Ding Wang
Article

DOI: 10.1007/s10439-015-1464-7

Cite this article as:
Huang, H., Crouch, D.L., Liu, M. et al. Ann Biomed Eng (2016) 44: 1613. doi:10.1007/s10439-015-1464-7

Abstract

Typically impedance control parameters (e.g., stiffness and damping) in powered lower limb prostheses are fine-tuned by human experts (HMEs), which is time and resource intensive. Automated tuning procedures would make powered prostheses more practical for clinical use. In this study, we developed a novel cyber expert system (CES) that encoded HME tuning decisions as computer rules to auto-tune control parameters for a powered knee (passive ankle) prosthesis. The tuning performance of CES was preliminarily quantified on two able-bodied subjects and two transfemoral amputees. After CES and HME tuning, we observed normative prosthetic knee kinematics and improved or slightly improved gait symmetry and step width within each subject. Compared to HME, the CES tuning procedure required less time and no human intervention. Hence, using CES for auto-tuning prosthesis control was a sound concept, promising to enhance the practical value of powered prosthetic legs. However, the tuning goals of CES might not fully capture those of the HME. This was because we observed that HME tuning reduced trunk sway, while CES sometimes led to slightly increased trunk motion. Additional research is still needed to identify more appropriate tuning objectives for powered prosthetic legs to improve amputees’ walking function.

Keywords

Powered prosthetic legs Biomechanics Gait Expert system Calibration Transfemoral amputation 

List of symbols

k

Stiffness

θE

Equilibrium position

C

Damping coefficient

θp

Prosthesis knee joint angle

\(\dot{\theta }_{\text{p}}\)

Prosthesis knee joint angular velocity

θpeak

Peak knee angle

Tdura

Gait phase duration

\(\dot{\theta }_{\text{peak}}\)

Peak angular velocity

m

Membership function value

D

Rule degree

N

Negative

P

Positive

CES

Cyber expert system

HME

Human expert

CV

Coefficient of variation

DF

Statistical degrees of freedom

GRF

Ground reaction force

IC

Impedance control

IDS

Initial double support

PKP

Powered knee prosthesis

RMS

Root-mean-square

SI

Symmetry index

SS

Single support

SWE

Swing extension

SWF

Swing flexion

TDS

Terminal double support

Supplementary material

10439_2015_1464_MOESM1_ESM.pdf (151 kb)
Supplementary material 1 (PDF 151 kb)

Funding information

Funder NameGrant NumberFunding Note
National Science Foundation (US)
  • 1361549
  • 1406750
  • 1527202
NCSU/UNC Rehabilitation Engineering Core

    Copyright information

    © Biomedical Engineering Society 2015

    Authors and Affiliations

    • He Huang
      • 1
      • 2
    • Dustin L. Crouch
      • 1
      • 2
    • Ming Liu
      • 1
      • 2
    • Gregory S. Sawicki
      • 1
      • 2
    • Ding Wang
      • 1
      • 2
    1. 1.UNC/NCSU Joint Department of Biomedical EngineeringNorth Carolina State UniversityRaleighUSA
    2. 2.UNC/NCSU Joint Department of Biomedical EngineeringUniversity of North Carolina at Chapel HillChapel HillUSA

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