Design and trajectory tracking control of a novel pneumatic bellows actuator

This paper designs a pneumatic bellows actuator (PBA) and proposes a double-loop control strategy for realizing its trajectory tracking control objective. To fully utilize the advantage of the PBA's large elongation, the finite element method (FEM) is used to analyze the relationship between the elongation and the pneumatic pressure of the PBA, and on this basis, a set of appropriate physical parameters are chosen for the PBA. For the tracking control of the PBA, a double-loop control (DLC) strategy, which includes an outer loop and an inner loop, is proposed for realizing the trajectory tracking control objective of the PBA. In the proposed strategy, the outer loop is composed of a feedforward controller and a feedback controller. The feedforward controller is used to deal with the asymmetric hysteresis of the PBA, and the feedback controller is used to eliminate the control error that is caused by the uncertain factors. The inner loop is composed of a compensator, which is used to compensate for the pneumatic pressure regulation error that is caused by the dead zone and the lag of the proportional-pressure regulator. Experiments are carried out to show the effectiveness and superior performance of the proposed DLC strategy, and the experimental results show that the PBA can generate large axial elongation while the high-precision trajectory tracking control objective is realized by using the DLC strategy.