| The wheel brake device is one of the commonly used deceleration devices in modern aircraft.For the large aircraft,multi-wheel parallel main landing gear is usually used.And the application of multiple wheel brake devices in parallel will cause some adverse problems such as strong non-linearity,parameter time-variation and complex random load force etc.And it will cause vibration and instability of the multi-wheel brake system.Such problems are widespread in military and civilian aircraft at home and abroad.However,due to the technical blockade imposed on China,our self-developed military aircraft still failed to solve this problem well.Such a situation restricts the development of our own military aircraft and threatens national defense security.In order to solve the stability problem of the multi-valve parallel brake system of large aircraft and improve the strategic support capabilities of large military aircraft,this paper will carry out a series of research work.The vibration phenomenon,vibration mechanism and influencing factors of the brake pressure servo valve-actuator system are analyzed.And the research work during this period includes dynamic model establishment,vibration mechanism analysis and model modification,parameter sensitivity analysis and nonlinear dynamic behavior analysis.On this basis,a dynamic model of the system with multi brake pressure servo valve in parallel is established.The vibration characteristics of the system are analyzed,and a vibration suppression method is proposed.Based on the general idea of this paper,the following research work has been completed.(1)Dynamic model of brake servo valve-actuator system.The special working principle of brake pressure servo valve which is different from general flow control servo valve is analyzed.Then the mathematical model of such a system was established which concludes dynamic model of brake pressure servo valve and brake actuator.The performance test platform of brake servo valve-actuator system and load simulation platform are built,the performance of brake servo valve-actuator system under different working condition is verified by experiments.(2)Vibration mechanism analysis and dynamic model optimization of brake servo valve-actuator system.The vibration mechanism of the brake servo valve-actuator system is analyzed.The original dynamic model was optimized by introducing the intrinsically nonlinear factors and the dynamic change factors of oil return channel.The experiment platform was used to verify simulation analysis accuracy improvement effect of the optimized model.(3)Parameter sensitivity analysis of brake servo valve-actuator system.The state space model of brake servo valve-actuator system is established.The dynamic sensitivity of 41 parameters is analyzed under typical working conditions.And two sensitivity indexes is used to quantization the results from sensitivity analysis.The experiment platform was used to verify the sensitivity analysis results.(4)Nonlinear dynamic analysis and stability analysis of brake servo valve-actuator system.The effect of parameter changes on the nonlinear dynamic behavior of brake servo valve-actuator system is studied by combining phase diagram analysis with direct solution of nonlinear dynamic behavior.On this basis,the stability of the system is studied.The experiment platform was used verify the analysis results.(5)Vibration characteristics and vibration suppression method of multi-brake servo valve system.The natural frequency of hydraulic pipes,the fluid-structure coupling resonance and the vibration characteristics of the system under different working conditions are analyzed.Based on the above research work,a new type of brake pressure servo valve is proposed.An experimental test platform for the new brake pressure servo valve was established,and the vibration suppression effect is verified. |
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