Closed-Loop Neuromuscular Electrical Stimulation Method Provides Robustness to Unknown Time-Varying Input Delay in Muscle Dynamics

Serhat Obuz, Victor H. Duenas, Ryan J. Downey, Justin R. Klotz, Warren E. Dixon

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Neuromuscular electrical stimulation (NMES) is commonly used to rehabilitate people with motor impairment (e.g., following stroke or spinal cord injury). Closed-loop NMES holds the promise to facilitate coordinated limb motion, but technical challenges remain. In particular, there is a potentially destabilizing delay between the application of the electrical stimulation and the ensuing muscle contraction, which changes as muscle fatigues. In this brief, a closed-loop NMES method is developed to yield lower limb tracking, despite an unknown time-varying input delay, uncertain nonlinear limb dynamics, and additive bounded disturbances. A novel filtered error signal is designed using the past states in a finite integral over a constant estimated delay interval. The control development is based on an approach that uses Lyapunov-Krasovskii functionals in a Lyapunov-based stability analysis to prove ultimately bounded tracking. Experimental results in healthy individuals and participants with neurological conditions are provided to demonstrate the performance of the developed controller.

Original languageEnglish (US)
Article number8781760
Pages (from-to)2482-2489
Number of pages8
JournalIEEE Transactions on Control Systems Technology
Volume28
Issue number6
DOIs
StatePublished - Nov 2020
Externally publishedYes

Keywords

  • Delay systems
  • Lyapunov methods
  • neuromuscular electrical stimulation (NMES)
  • nonlinear control systems
  • robust control
  • uncertain systems
  • unknown time-varying input delay

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Electrical and Electronic Engineering

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