Abstract
Pressure ripple has always been a major drawback in hydraulic circuits, since it is the main source of the overall noise emitted by the pump. This article presents a theoretical analysis on the active control of the pressure ripple in an axial piston pump by properly moving the swash plate. The reduction of the pressure oscillations is studied in an active way and for this purpose a mathematical model of the whole pump has been developed, focusing on both the fluid dynamic aspects and the component dynamics. An experimental activity has been performed in order to validate the pump mathematical model. The results of the simulation, compared with the experimental data, highlight a suitable capability of the model to predict both the dynamics of the swash plate and the delivery pressure ripple. The validated model has been used for implementing an active control of the pressure ripple with the aim of properly modifying the machine displacement at high frequency in order to vary the instantaneous delivery flow rate and, consequently, the outlet pressure. The control strategy is grounded on moving the swash plate for modifying the motion law of the pistons through a servo valve integrated into the displacement control system. The simulations results have demonstrated that acting on the pump displacement control is possible to considerably reduce the amplitude of the pressure oscillations.
Highlights
Variable displacement axial piston pumps are widespread in hydraulic circuits, because they are robust machines able to guarantee great reliability, considerable flexibility and to transmit high power density with significant energy savings [1]
Piston pumps deliver an oscillating flow rate, generating a pressure ripple that is a huge drawback in hydraulic circuits
Many previous studies have focused on how to solve this problem, concentrating mainly on passive techniques in order to reduce the amplitude of the pressure ripple: these methodologies generally consist of geometric optimizations of some components with the aim of limiting the flow and pressure fluctuations between internal pump chambers at different pressure values
Summary
Variable displacement axial piston pumps are widespread in hydraulic circuits, because they are robust machines able to guarantee great reliability, considerable flexibility and to transmit high power density with significant energy savings [1]. Liquid bulk modulus is constant, simplified way, treating a gas-liquid mixture ashypotheses: Because of this assumption, it the surface tension effects are ignored; fluid and temperature are the[29,30], same for gas and liquid; is not possible to account for delays in pressure both air release and re-dissolution but both for the purpose of this study the development such a complex model is not necessary. Volume is the sum of the volume of each component, expressed for the unit of mass as: The gaseous phase is modelled through the state equation for ideal gases neglecting any contribution of oil vapor and the effects of high pressure on the gas compressibility factor.
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