Simulation and Control of a Pneumatic Muscle Actuator for a Rehabilitation Robot

Abstract The perfomance of a pneumatic muscle actuator, invented by Jim Hennequin and used in a prototype wheelchair-mounted robot ann designed by the first author is reported. Experimental measurements were made of the output torque versus rotary motion and internal pressure. The torque available for a muscle of size 60 mm width by 90 mm length ranges from 1 to 15 Nm. The rotary stiffness of this muscle is 0.081 Nm/deg. A simulation model of the dynamic behaviour of the muscle attached to the robot arm using one-dimensional flow theory was written in ACSL (Advanced Continuous Simulation Language). The resultant simulation gives good agreement to within ± 5% of the experimental values. Control using proportional and a PID controller is shown to be effective.