Analysis and Suppression for Self-excited Vibration of Aircraft Hydraulic Braking System
The aircraft hydraulic braking system is a pressure control system,which utilises a pressure servo valve to delivery the pressure proportional to the input control signal.The pressure oscillation problem encountered has periodic fluctuations,which significantly reduces the control performance of the braking system.The mathematical model of the system is derived,and the vibration is analysed.It is pointed out that the sustainable oscillation is a self-excited vibration of valve-pipe system,which is actually a nonlinear dynamic process with positive feedback.The established ordinary differential equations are solved with Runge-kutta,and the lotus of limit circle is obtained indicating the self-excited vibration.Two suppression methods,increasing the return chamber's volume and removing the return pressure feedback passage,are proposed.The AMESim software is used to build system's model,and suppression methods are investigated by the simulation.Experiments are carried out to validate the self-excited vibration and the suppression schemes.The experimental results show that the vibration is eliminated by the suppression methods,indicating their effectiveness.The proposed theory can be used to analyse and recognise the self-excited vibration of pressure servo-valve,and is beneficial for the design of aircraft hydraulic brake systems.
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