This paper reports a theoretical and experimental evaluation of the pressure transients in a hydraulic servo used to position a mass when the oil volumes on the two sides of the jack are substantially different.
Application of small perturbation theory to the closed loop shows that the pressure transients are smallest when the oil volumes are equal. The worst condition is shown to be at the stroke ends, the peak pressure increasing as the volume ratio increases. Predicted values obtained by analogue computer are in good accord with measurements made on an experimental rig.
An approximate guide is suggested for the relationship of peak pressures in the unequal and equal volume conditions.
Get full access to this article
View all access options for this article.
References
1.
CoombeJ E M, ‘Hydraulic remote position controllers’, J Instn Elec Engrs London, 1949, Vol 94 (Part 2a), p 270.
2.
HarperN F, ‘Some design considerations of hydraulic servos of the jack type’, Proc Conf Hydraulic Servomechanisms, 1953, p. 41 (I Mech ELondon).
3.
LambertT HDaviesR M, ‘Investigation of the response of a hydraulic servomechanism with inertia load’, J Mech Engng Sci, 1963, Vol 5, No 3, p 281.
4.
GlazeS G, ‘Analogue technique and the non-linear jack servo mechanism’, Proc Symp Recent Mech Engng Dev in Automatic Control, 1960, p 178 (I Mech E, London).
5.
ParnabyJ, ‘Electronic analogue computer study of nonlinear effects in a class of hydraulic servomechanisms’, J Mech Engng Sci, 1968, Vol 10, No 4, p 346.
6.
MartinK F‘Stability and step response of a hydraulic servo with special reference to unsymmetrical oil volume conditions’, J Mech Engng Sci1970, 12, 5, p. 331.
7.
NikiforukP NWestlundD R, ‘The large signal response of a loaded high pressure hydraulic servomechanism’, Proc Instn Mech Engrs, London, 1965–6, Vol 180, Part 1.
8.
McCloyD, ‘Pressure peaks in the hydraulic actuator’, Trans ASME Journal of Basic Engng, Dec 1965, p 953.
9.
McCloyDMartinH R, ‘Some effects of cavitation and flow forces in the electrohydraulic servomechanism’, Proc I Mech E (London)1964, Vol 178, p 539.
10.
MartinH RLichtarowiczA, ‘Theoretical investigation into the prevention of cavitation in hydraulic actuators, Proc I Mech E (London)1966–7, Vol 181, Part I.
11.
RoyleJ K, ‘Inherent non-linear effects in hydraulic control systems with inertia loading’, Proc I Mech E, London, 1959, Vol 173, p 257.
