PID Control of Knee Extension for FES-Assisted Walking with Spring Brake Orthosis

This paper presents a simulation of bipedal locomotion to control the stimulation pulses of functional electrical stimulation (FES) for activating muscles for paraplegic walking with spring brake orthosis (SBO). The work is a first effort towards restoring natural like swing phase in paraplegic gait through a new hybrid orthosis, referred to as spring brake orthosis (SBO). This mechanism simplifies the control task and results in smooth motion and more-natural like trajectory produced by the flexion reflex for gait in spinal cord injured subjects. The study is carried out with a model of humanoid with wheel walker using the Visual Nastran (Vn4D) dynamic simulation software. Stimulated muscle model of quadriceps is developed for knee extension. Proportional integral derivative (PID) control is developed in Matlab/Simulink to regulate the muscle stimulation pulse-width required to drive FES-assisted walking gait and the computed motion is visualised in graphic animation from Vn4D. The results show that SBO can reduce torque and stimulation pulses required for FES-assisted paraplegic walking with wheel walker and PID control is found to be appropriate controller for the leg extension.