Digital controller design considering hardware constraints: application in a paraplegic patient

Abstract

Introduction: A methodology was developed for implementing closed-loop control algorithms and for evaluating the behavior of a system, considering certain component restrictions used in laboratory implementation. Methods:Mathematical functions representing a model of the biological system were used for knee extension/fl exion movements. A Proportional Integral Derivative (PID) controller and another one using the root locus method were designed to control a patient's leg position by applying functional electrical stimulation (FES). The controllers were simulated in Matlab and ISIS Proteus. After the simulations were performed, the codes were embedded in a microcontroller, and tests were conducted on a paraplegic volunteer. To the best of the authors' knowledge, this is the fi rst time that ISIS Proteus software resources have been used prior to implementing a closed-loop system designed to control the leg position of patients. Results: This method obviates the application of initial controller tests directly to patients. The response obtained in the experiment with a paraplegic patient complied with the specifi cations set in terms of the steady-state error, the settling time, and the percentage overshoot.The proposed procedure was successfully applied for the implementation of a controller used to control the leg position of a paraplegic person by electrical muscle stimulation. Conclusion: The methodology presented in this manuscript can contribute to the implementation of analog and digital controllers because hardware limitations are typically not taken into account in the design of controllers.

Electrical stimulation tracking control for paraplegic patients using T–S fuzzy models

“…In [39] and [40], are considered only constant reference signals and all set of the desired operation points for obtaining the maximum and minimum values of the plant nonlinear functions, to get the local models following the method proposed in [30]. The proposed method can be implemented the same as [50] and [51]. By the authors knowledge, in [50], the Takagi-Sugeno fuzzy models method to control the knee joint of paraplegic patients was implemented for the first time.…”

Robust Control of the Knee Joint Angle of Paraplegic Patients considering Norm-Bounded Uncertainties

“…As a consequence, the oscillation was eliminated from the pulse width curve, stabilizing in values of very close to one another in both simulations. As mentioned by Sanches et al in [8] "An electric current with a balanced, biphasic, rectangular waveform with a pulse width of 220 s was applied to the skin surface of the volunteer. The signal amplitude was then held constant for 3 seconds and considered a "step pattern" [5].…”

“…When electrical stimulation is applied to the quadriceps of a patient, using the controller, the knee joint angle can be varied from 0 ∘ to 30 ∘ . The authors considered the leg mathematical model proposed by [5], and they showed that, for the conditions considered in their experiments, a simple one-pole transfer function was able to model the relationship between stimulus pulse width and active muscle torque [8].…”

Discrete Takagi-Sugeno Fuzzy Models Applied to Control the Knee Joint Movement of Paraplegic Patients

“…Finally, the discrete T-S fuzzy model is obtained, using local models (24) and the membership functions (23):…”

“…In [18] and subsequent articles [19]- [22], and [23] published by our research group, some theories are employed to control knee joint movement using neuromuscular electrical stimulation. In [24], an article was published describing control application in paraplegic patients.…”