Fully Automatic Control of Paraplegic FES Pedaling Using Higher-Order Sliding Mode and Fuzzy Logic Control

Abstract

In this paper, a fully automatic robust control strategy is proposed for control of paraplegic pedaling using functional electrical stimulation (FES). The method is based on higher-order sliding mode (HOSM) control and fuzzy logic control. In FES, the strength of muscle contraction can be altered either by varying the pulse width (PW) or by the pulse amplitude (PA) of the stimulation signal. The proposed control strategy regulates simultaneously both PA and PW (i.e., PA/PW modulation). A HOSM controller is designed for regulating the PW and a fuzzy logic controller for the PA. The proposed control scheme is free-model and does not require any offline training phase and subject-specific information. Simulation studies on a virtual patient and experiments on three paraplegic subjects demonstrate good tracking performance and robustness of the proposed control strategy against muscle fatigue and external disturbances during FES-induced pedaling. The results of simulation studies show that the power and cadence tracking errors are 5.4% and 4.8%, respectively. The experimental results indicate that the proposed controller can improve pedaling system efficacy and increase the endurance of FES pedaling. The average of power tracking error over three paraplegic subjects is 7.4±1.4% using PA/PW modulation, while the tracking error is 10.2±1.2% when PW modulation is used. The subjects could pedal for 15 min with about 4.1% power loss at the end of experiment using proposed control strategy, while the power loss is 14.3% using PW modulation. The controller could adjust the stimulation intensity to compensate the muscle fatigue during long period of FES pedaling.

Cadence control of stationary cycling induced by switched functional electrical stimulation control

“…where λ c was defined in (14). Following the procedure described in [20] allows the solution of (21) to be determined as…”

“…Past FES-cycling control methods have utilized linear controllers [9]- [11], fuzzy logic and sliding mode controllers [12]- [14], or controllers based on experimental data or numerical optimizations [15]- [18]. All of these previous studies lack detailed stability analyses or require exact model knowledge.…”

Estimation of Relationship Between Stimulation Current and Force Exerted During Isometric Contraction

“…Jaime et al proposed a method of generating standing motion using FES by employing proportional-integral-derivative (PID) control [3]. Farhoud et al proposed a pedaling operation based on an FES system composed of a sliding mode controller and a fuzzy mode controller [4]. Bouton et al reported a method of generating desired actions read from electroencephalogram (EEG) by using FES [5].…”

“…In addition, the Hammerstein model [20], and a few subsequent improvement have been reported [21] [22]. For control using FES, a method using voltage control [6] [8] [18] and a method using current control [4] [15] [16] have been mixed, but it was not reported as to which value determines the exerted force.…”

Stationary cycling induced by switched functional electrical stimulation control

“…Many approaches have been taken in attempt to improve the efficiency and power output of FEScycling, including optimization of the cycling mechanism [5], [6], alteration of the stimulation pattern [7]- [11], and variation of the stimulation strategy [12]- [15]. Studies have explored the use of feedback control methods to automatically determine the appropriate stimulation parameters, but most use either linear approximations of the nonlinear cycle-rider system [16] or nonlinear methods lacking detailed stability analyses [17]- [19]. Previous approaches (cf.…”