Occurrence conditions of stick-slip in a pneumatic actuation system

Abstract

In a system driven by a pneumatic actuator, friction at the seals between parts is one of the nonlinear elements that has an undesirable influence on the system's stable motion and control accuracy. In particular, when the system works at extremely low speed, the friction causes oscillation, and frequently this evolves into oscillation with sticking phases; i.e., stick-slip. The objective of this paper is to analytically derive the occurrence conditions of stick slip. In the process of derivation, we analyze system stability under some assumptions and specify the main factor affecting oscillatory behavior. In addition, we investigate the behavior of solution trajectories on a phase plane with numerical simulation by choosing an effective sectional area of restrictors as a parameter then varying it. Based on the cases that the trajectories reach a negative region, the occurrence conditions with respect to pressure are finally found. Their validity is confirmed by applying them to experimental results.