Nonlinear model-based control of pneumatic artificial muscle servo systems

This paper proposes a control methodology of the pneumatic artificial muscle (PAM) actuated servo systems. The four major processes in such systems, including the flow dynamics, pressure dynamics, force dynamics, and load dynamics, are studied to develop a full nonlinear model that encompasses all the major nonlinearities. The developed single-input-single-output model takes the valve command as the input and calculates the third-order derivative of the load position as the output. Since this model is expressed in the control canonical form, nonlinear control approaches can be easily applied. Based on this model, a sliding model controller is developed to obtain robust control in the existence of model uncertainties and disturbances. The controller is implemented on an experimental system, and the effectiveness of the proposed approach demonstrated by step response and sinusoidal tracking at different frequencies.