Research On Vibration Characteristics Of Poppet Valve Core Based On Virtual Binocular Vision

Hydraulic poppet valves are widely used in various hydraulic systems because of their simple structure,good sealing and strong flow capacity.However,the poor stability of the quality system of "spool-spring" will cause the phenomenon of pressure fluctuation of the hydraulic system,and when the hydraulic system is disturbed,the spool is easy to deviate from the equilibrium state and enter an unstable state,causing poppet valve vibration.The vibration of the poppet valve affects the control accuracy and stability of the hydraulic system,and in severe cases,it can cause the failure of the hydraulic control system or the damage of components.In recent years,with the high pressure,high speed and high power of hydraulic technology,more stringent requirements have been put forward for the performance of poppet valves,so the study of vibration characteristics of hydraulic poppet valves is of great practical significance.In this thesis,the vibration characteristics of poppet valve spools are studied by combining theoretical analysis and experimental analysis.In order to obtain a high-speed image sequence to measure the spatial distribution characteristics of poppet valve spool,a virtual binocular system composed of a total mirror and a semi-translucent prism is built to realize the synchronous acquisition of the projected image of the poppet valve spool in both directions.The high-speed camera in the image information acquisition system is calibrated by Zhang Zhengyou calibration method,which effectively realizes the correction of the valve core image,and provides an experimental basis for the study of the vibration characteristics of the poppet valve core.For the spool image collected by the virtual binocular system,the super-resolution reconstruction method is used to improve the spool image quality.By comparing five super-resolution network structures,the ESRGAN model was selected for superresolution reconstruction,which significantly improved the image quality of the spool vibration sequence.The image processing methods such as filtering,sharpening,binarization and edge detection of the super-resolution reconstructed image are extracted to the contour of the spool,and the virtual vertex of the spool vibration is obtained by the contour approximation method,and the three-dimensional curve of the spool vibration is obtained after batch processing.According to the characteristic parameters affecting the vibration of the valve core,such as inlet pressure,outlet pressure,spring precompression,spring rate and spool half cone angle,the vibration characteristics of poppet valve spool are studied by the control variable method,and the amplitude,skewness,steepness and waveform factor of spool vibration are obtained.The results show that with the increase of the inlet pressure of the poppet valve,the amplitude,skewness,steepness and waveform factor of the valve core become larger.The amount of spring precompression is opposite to the influence of inlet pressure on the vibration characteristics of the spool,and the vibration degree of the spool intensifies as the amount of spring precompression decreases;With the increase of spring rate,the parameters of valve core vibration show a trend of first decreasing and then increasing,and the vibration state of the valve core is the most stable when the spring rate is 2N/mm;With the increase of the half-cone angle of the poppet valve core,the intensity of the valve core vibration first decreases and then increases,when the half-cone angle of the valve core is 30°,the degree of vibration of the valve core is the smallest,and the working state is the most stable;Poppet valve spool vibration and outlet pressure is also related,with the increase of outlet pressure,the intensity of spool vibration first decreases and then increases,when the outlet pressure is 1.2MPa,the valve core is affected by the flow field condition is the least,the performance is the most stable.Among the three directions of spool vibration,the radial direction of the side has the greatest degree of vibration,followed by the radial direction of the front,and the smallest in the axial direction.In order to study the spatial distribution characteristics of poppet valve core vibration,this thesis proposes to characterize the distribution of valve core vibration characteristic points with dispersion,and the results show that the dispersion is consistent with the amplitude with the structural parameters of the valve core and the change law of various working conditions.The density of the vibration characteristic point is affected by the working condition and the valve core structure,and when the vibration state of the valve core tends to be flat,the more concentrated the distribution of the vibration feature points,the steeper the density curve.In addition,this thesis combines the dispersion values under various working conditions and spool structure parameters,and obtains the influence factors of each parameter on the vibration of the spool through orthogonal analysis.The results show that the structural parameters of the spool itself have a greater influence on the vibration stability,and among the three structural parameters that affect the vibration of the spool,the precompression amount has the greatest influence on the vibration of the spool.The thesis has 80 figures,4 tables and 96 references.