Transient Response of an Hydraulic Servomechanism Flexibly Connected to An Inertial Load

Abstract

The transient response of a powerful hydraulic servomechanism, flexibly connected to an inertial load is investigated theoretically and experimentally. The results indicate that a linearized fifth-order transfer function, taking into account inertial load, compressibility, leakage, and structural flexibility and damping, gives a reliable indication of the main characteristics of behaviour of this type of control in such a realistic environment. Extension of the theory to include the effects of the principal non-linearity, Coulomb friction, by simulation on an analogue computer increases the viability of the analysis. It is found that the response is of an oscillatory, biharmonic character; the low-frequency component of which is attributable mainly to effects external to the jack and the high-frequency component to internal effects. Consistently, it is found that the subsidence ratio of the former is sensitive to structural damping and of the latter to Coulomb friction and leakage.