Evaluation of Gait Phase Detection Delay Compensation Strategies to Control a Gyroscope-Controlled Functional Electrical Stimulation System During Walking.

Nicole Zahradka,Ahad Behboodi,Samuel Lee,Henry Wright,Barry Bodt

doi:10.3390/s19112471

Abstract

Functional electrical stimulation systems are used as neuroprosthetic devices in rehabilitative interventions such as gait training. Stimulator triggers, implemented to control stimulation delivery, range from open- to closed-loop controllers. Finite-state controllers trigger stimulators when specific conditions are met and utilize preset sequences of stimulation. Wearable sensors provide the necessary input to differentiate gait phases during walking and trigger stimulation. However, gait phase detection is associated with inherent system delays. In this study, five stimulator triggers designed to compensate for gait phase detection delays were tested to determine which trigger most accurately delivered stimulation at the desired times of the gait cycle. Motion capture data were collected on seven typically-developing children while walking on an instrumented treadmill. Participants wore one inertial measurement unit on each ankle and gyroscope data were streamed into the gait phase detection algorithm. Five triggers, based on gait phase detection, were used to simulate stimulation to five muscle groups, bilaterally. For each condition, stimulation signals were collected in the motion capture software via analog channels and compared to the desired timing determined by kinematic and kinetic data. Results illustrate that gait phase detection is a viable finite-state control, and appropriate system delay compensations, on average, reduce stimulation delivery delays by 6.7% of the gait cycle.

Highlights

Functional electrical stimulation (FES) is the application of electrical stimulation to assist functional movements such as standing [1,2,3], walking [4,5,6], and grasping [7,8] in individuals with upper motor neuron lesions
FES systems are used as neuroprosthetic devices [9] in the rehabilitative settings and the delivery of stimulation relies on open-or closed-loop controllers
The purpose of this paper is to evaluate five finite-state FES system triggers, designed to compensate for the inherent gait phase detection delays, by comparing stimulation delivery time to the desired timing during walking in typically-developing (TD) children

Summary

Introduction

Functional electrical stimulation (FES) is the application of electrical stimulation to assist functional movements such as standing [1,2,3], walking [4,5,6], and grasping [7,8] in individuals with upper motor neuron lesions. FES systems are used as neuroprosthetic devices [9] in the rehabilitative settings and the delivery of stimulation relies on open-or closed-loop controllers. Open-loop controlled FES systems are typically used in clinical settings because they are easy to don/doff; provide less accurate movement control because these systems rely on manual input to trigger the delivery of stimulation [14]. Sensors 2019, 19, 2471 and RehaStim (Hasomed Inc., Germany) are two examples of commercially-available FES systems that utilize open-loop controllers. Both systems require pushing a button to start the stimulation program and, once initiated, stimulation parameters such as timing are fixed and require the user to try to match their gait speed to the timing of the stimulation program

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