Oscillations Caused by Solid Friction in a Hydraulic Driving System (In Consideration of Friction-Velocity Characteristics of Hysteresis Curves for Increasing and Decreasing Velocity Motions)

The phenomena of ‘stick-slip’ oscillations in the hydraulic driving system are studied both experimentally and analytically. The system consists of a table lying on a rectilinear sliding surface, an actuator cylinder, a 4-way servo valve, a relief valve and an oil pump. In our experiment, some of the friction-velocity curves are observed to become the hysteresis curves with increasing and decreasing velocity motions of the table. Here, also in the theoretical analysis, the accelerated and decelerated portions of the friction-velocity curves are assumed to be distinct. The variations of friction are modelled as follows: (1) Kinetic friction varies with impressed electric current and sliding velocity. (2) Static friction varies with electric current passing through the servo valve and the sliding velocity. The principal experimental variables are lubricant viscosity and the mass of the table. Their influences are studied on the characteristics of ’stick-slip’ oscillations.