Restoring Force Model of a Pneumatic Artificial Muscle Actuator

This article will analyze the contribution of the compressed air to the restoring force of a commercial pneumatic artificial muscle (PAM) actuator relied up on the continuously symmetric configuration of the bladder. The restoring force model is then modified regardless of the shape of the bladder, which is a nonlinear function of the contractible length and the pressure inside the bladder. An experimental rig is set up to identify the parameters of the modified model through the genetic algorithm with minimum error of the predicted force and the experimental data. Besides, the effective volume of the muscle expressed approximately by the second-order polynomials is also determined by least square algorithm. The result indicates that by applying the modified model, the calculated values of the hysteresis curve are in a good agreement with the measured values. This study will offer a useful insight to analyze the dynamic response of vibration isolation systems using PAMs as elastic elements.