A robust control of the pressure in a control-cylinder for the variable displacement axial piston pump
ABSTRACT In order to achieve energy-efficient hydraulic systems, an accurate flow rate and pressure required by a load should be supplied to the systems. The discharge flow from the variable displacement swash-plate type axial piston pump is mainly determined by the angle of the swash-plate and it is adjusted by controlling the pressure in the control-cylinder which is a mechanical regulator for the swash-plate. In this paper, a robust pressure control system of the control-cylinder using a direct drive valve is proposed to control the discharge flow from the variable displacement swash-plate type axial piston pump precisely. In order to design a robust pressure control system, a mathematical model of a pressure control system is derived and system parameters are identified by using the signal-compression method. Also, the sliding mode controller is designed based on the identified mathematical model to guarantee the control performance of the pressure control system. Experiments verified the satisfactory performance of the proposed pressure control system that uses a direct drive even with non-linearity and uncertainties such as flow characteristics, unknown discharge coefficient of the valve orifice, variation of the bulk-modulus, leakage and disturbance induced by the pressure fluctuation in the pressure control system.
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ABSTRACT: As a supplying component of airborne hydraulic power actuator, the stability and accuracy of flow discharged by pump supplying directly impact the working stability of the whole hydraulic system loop. A robust controller of airborne pump supplying displacement regulation is designed by using H∞ mixed sensitivity control algorithm in this paper. It is aimed at the characters of sensitivity function and complementary sensitivity function, based on the requirement of frequency-domain of displacement regulation loop, achieved satisfactory closed-loop control performance by selecting suitable weight function. The impacts originated from disturbance and parameters uncertainty in the model were depressed. The desired frequency-domain performance could directly achieved by using the control algorithm, it is useful for practicing. The simulation and test show that the controller present in this paper demonstrate a better robustness and effectiveness on disturbance depression and parameter variation. It is a development direction on pump supplying intelligent control.