MICRO STICK-SLIP VIBRATION IN HYDRAULIC SERVO SYSTEMS

Abstract

This paper treats stick-slip vibrations occurring in a typical computer controlled hydraulic servo system. The relevant system consists of hydraulic cylinder, servo-valve and personal computer. First, experiment was performed to reveal three different types of vibrations occurring in a conventional feedback control system. Detailed numerical analysis has been then performed to identify the main factors for occurrence of these self-excited vibrations. It is shown that the control signal generated through the D/A converter causes stick-slip vibration of small amplitude over the wide range of the control feedback gain. Increasing the feedback gain results in the other type of stick-slip vibration of larger amplitude due to the locally increased flow gain within the underlap of the servo-valve.