Some Effects of Cavitation and Flow Forces in the Electro-Hydraulic Servomechanism

Linearized analysis has already been used to demonstrate the de-stabilizing effect of valve flow forces. In this paper an analogue simulation of an electro-hydraulic servomechanism is described and flow force effects are discussed. The results are compared with the linearized analysis. Various types of load and damping are considered. When large accelerations are demanded, the pressure in the actuating cylinder falls to zero and cavitation occurs. During the time this condition exists cylinder pressures in excess of supply pressure occur. A digital computer is used to analyse the performance of a hydraulic servomotor when cavitation exists and the results are presented in dimensionless form. Experimental results are presented for comparison with the theoretical results.