Effect of Solid Friction on Global Stability on a Hydraulic Servo System

This paper deals with the dynamic behavior and stability of a hydraulic system subjected to solid friction of a typical friction model, for example, the “negative slope” characteristic. Numerical simulation reveals a particular phenomenon in which hard self-excited vibration occurs for a disturbance beyond some critical value, despite the fact that the neutral operating point of the system is stable for the whole region of the supply pressure. Vibratory waveform is stick-slip for a smaller disturbance or sinusoidal for a larger disturbance. This multi-structural stability can occur for any friction model studied here, and can be confirmed experimentally.