Robustness evaluation of the improved NCTF controller for a pneumatic artificial muscle driven stage

This paper presents robustness evaluation of the improved nominal characteristic trajectory following (NCTF) controller in the presence of mass variation for a pneumatic artificial muscle (PAM) driven stage. The improved NCTF controller consists of a nominal characteristic trajectory (NCT), a PI compensator, an acceleration feedback compensator, and a reference rate feedforward. The improvements have been realized on the conventional NCTF controller by adding the acceleration feedback compensator to increase the damping characteristic of the PAM mechanism, and the reference rate feedforward is to improve the following characteristic. The controller parameters can be determined easily without the need of an exact model parameters. The design procedure remains simple and straightforward. The robustness of the improved NCTF controller is evaluated and compared experimentally with a classical PI controller in continuous motion. The default weight of a mover is 2 kg, and an additional mass with 4 kg of weight is added on it. The comparative experimental results demonstrate that the improved NCTF controller has better tracking performance and higher robustness to mass variation, as compared to the PI controller.