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

OBUZ S., Duenas V. H., Downey R. J., Klotz J. R., Dixon W. E.

IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY, vol.28, no.6, pp.2482-2489, 2020 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 28 Issue: 6
  • Publication Date: 2020
  • Doi Number: 10.1109/tcst.2019.2926945
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, Applied Science & Technology Source, Communication Abstracts, Compendex, Computer & Applied Sciences, INSPEC, Metadex, Civil Engineering Abstracts
  • Page Numbers: pp.2482-2489
  • Eskisehir Osmangazi University Affiliated: Yes


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.