Improvised Fuzzy Logic Controller Using Feedforward, Feedback Offset, And Proportional Integral For Knee Extension Rehabilitation With Nonlinearities Influences

Abstract

Rehabilitation through exercise using functional electrical stimulation (FES) is an effective approach to aiding recovery for individuals with spinal cord injuries (SCI). FES devices induce muscle contractions via electrode pads, generating force and torque. Precise control is essential to prevent overstimulation, which could lead to fatigue, pain, or injury. However, nonlinear effects such as fatigue, spasticity, and time delays pose challenges to feedback control systems, often resulting in performance degradation. Fuzzy logic controllers (FLCs) are known for their robustness in addressing these issues but face constraints in control bandwidth and time delay management, which can lead to oscillations. This study proposes an enhanced FLC by designing fuzzy input membership functions, rules, and outputs and incorporating tuning strategies to address these limitations. Additionally, the integration of feedback offset, and proportional-integral strategies is emphasized to improve control bandwidth and mitigate the effects of time delays. The proposed control algorithm is simulated and evaluated using MATLAB/Simulink in the context of knee extension rehabilitation, which is characterized by nonlinearities. The results demonstrated that the newly enhanced FLC architecture could effectively overcome bandwidth and time delay challenges, validating its suitability for knee extension rehabilitation in SCI patients.