Control of pneumatic artificial muscle system through experimental modelling

This paper deals with position control of a single degree of freedom (sdof) manipulator actuated by Pneumatic Artificial Muscle (PAM) actuator. Though the compliance characteristics of these actuators are desirable, their inherent non-linearities due to compressibility of air and non-linear load-contraction characteristics make them difficult to model and design of controller becomes very complex. To overcome this, a novel method is hereby proposed to establish an accurate empirical model for the system. The quasi-static characteristics of the PAM are first modelled followed by the dynamic characteristics through spectral analysis. For cost competitiveness, the present work incorporates inexpensive on-off switching valves operated using a novel model based proportional pressure regulator developed using a modified PWM algorithm. Finally, a conventional PID position controller is extended using the empirical PAM model and an inner pressure regulation loop to achieve trajectory tracking of a sdof manipulator. Results for pressure regulation and position control confirm the effectiveness of the adopted approach in achieving performance comparable to the state-of-the-art results at a reduced control complexity and total set-up cost. (C) 2012 Elsevier Ltd. All rights reserved.