Sliding mode tracking for pneumatic muscle actuators in opposing pair configuration

Sliding mode techniques are applied to pneumatic muscle actuators arranged in an agonist/antagonist, or opposing pair configuration. The pneumatic muscle (PM) pair actuates a planar elbow manipulator, with PMs in place of bicep and tricep. The control objective is elbow angle tracking under load. A nonlinear mathematical model is derived for this system and a sliding mode controller is designed to give elbow angle tracking to within a guaranteed accuracy despite modeling errors. Static pressure requirements are also derived for stable arm behavior in the absence of a control signal. Stability results are derived, and the results of simulation studies are presented. The simulation studies also address the effects of PM heating.