On the dynamics of hydraulic lines supplying servosystems

Measures for achieving an almost quiescent state of hydraulic power supply pressure are outlined. Models for hydraulic pipelines supplying hydraulic control systems, which integrate dynamic behavior of the pipelines, the pressure control valve, or pressure controlled variable displacement pump, gas accumulators, and Helmholtz resonators are developed. Experiments show that pressure fluctuations due to pump flow pulsations are suppressed by a selective filter or by a small gas accumulator. Helmholtz resonator is most effective for eliminating one specific frequency of pump flow pulsation. A gas accumulator close to the pump suppresses pulsations in a wide frequency range. Pressure fluctuations due to the varying servomotor oil consumption are suppressed by an accumulator near the servovalve.