Oscillation Caused by Solid Friction in a Hydraulic Driving System (In Consideration of Friction-Velocity Characteristics of Hysteresis Curves for Accelerating and Decelerating Phases)

The phenomena of 'stick-slip' oscillation in a 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 servovalve, a relief valve and an oil pump. In our experiment, certain friction-velocity curves are observed to exhibit hysteresis with increasing-and decreasing-velocity motion of the table. Here and in the theoretical analysis, the acceleration and deceleration portions of the frictio-velocity curves are assumed to be distinct. The variations of friction are modeled as follows. (1) Kinetic friction varies with applied electric current and sliding velocity. (2) Static friction varies with electric current passing through the servovalve and the sliding velocity. The principal experimental variables are lubricant viscosity and the table mass. Their influences on the characteristics of 'stick-slip' oscillation are studied.