A novel pneumatic actuator based on high-frequency longitudinal vibration friction reduction

Abstract

Seals are an indispensable component of ordinary piston type pneumatic cylinders, but their presence inevitably introduces friction. Given that the friction is time-varying, uncertain and difficult to capture precisely, the output force of the pneumatic cylinder is difficult to obtain accurately. In addition, due to the serious negative damping effect in the low speed phase of the pneumatic cylinder friction characteristics, the motion servo control accuracy of pneumatic cylinders at low speeds is relatively poor. In this study, a novel longitudinal-vibration-mode pneumatic actuator with integrated piezoelectric stacks is developed with a resonant frequency of 5908 Hz for first-order longitudinal vibration. A new friction test system is set up and the test results show a maximum reduction of about 38.6 % in the static friction and 46.6 % in the dynamic friction of the pneumatic actuator for the high-frequency longitudinal resonance case. In the study of the effect of two-chamber pressure on friction reduction, it is found that the friction reduction rate decreases with the increase of two-chamber pressure. The preliminary motion trajectory tracking control results show that the high-frequency longitudinal resonance of the pneumatic actuator does help to reduce the maximum tracking error during the reverse process and improve the tracking accuracy of the motion trajectory.