Elbow Joint Angle Control by Fuzzy-PID Controller

Functional electrical stimulation (FES) systems restore motor functions after spinal cord injury (SCI). In this study, we used a model consists of a joint, two links with one degree of freedom, and two muscles as flexor and extensor of the joint, which simulated in MATLAB using SimMechanics andSimulink Toolboxes. The muscle model is based on Zajac musculotendon actuator and composed of a nonlinear recruitment curve, a nonlinear activation-frequency relationship, calcium dynamics, fatigue/recovery model, an additional constant time delay, force-length and force-velocity factors. Inthis study, we used a classic controller for regulating the elbow joint angle; a Proportional- Integral- Derivative and Fuzzy controller. The fitness function was defined as sum square of error. The results for fuzzy controller show faster response for reaching the range of the set point than the PID controller tuned by trial and error. However the fuzzy-PID is much better in terms of the rise time and the settling time, they have no overshoot. Moreover the steady state error is zero

Keywords:

Functional Electrical Stimulation (FES) , PID Controller , Fuzzy controller , Elbow Joint