Characteristic Extraction Of Pressure And Engineering Application Of Beat Vibration In Variable Speed Pump-controlled Motor System

With the continuous improvement of modern industrial technology,high speed,high pressure,energy saving and reliability have become the development trend of hydraulic system.This trend is the target of the design and research of variable speed pump-controlled motor system.In the actual work of hydraulic system,due to the hydraulic pump’s own structural characteristics,the hydraulic pump outlet will output pressure and flow,but the output pressure and flow is not absolutely stable,it always output with a certain oscillation.When the oil flows through the hydraulic motor,pressure pulsation will also occur due to the working characteristics and structural parameters of the plunger motor.Under certain conditions of pressure and speed,if the design parameters are not appropriate and the pulsation frequency of the pump and the pulsation frequency of the motor are close to each other,the system will produce a strong pressure beat.When pressure patting occurs in hydraulic system,it can enhance the destructiveness of oil pressure and the non-stationarity of dynamic information transmission.In the phenomenon of patter vibration,the modulated pressure signal contains rich information about the running state of the hydraulic system.Therefore,it has important practical engineering significance to carry out the research on the accurate extraction of the characteristics of the pressure patter vibration signal of the hydraulic system and its engineering application.Aiming at the hydraulic system of variable speed pump-controlled motor,this paper makes a theoretical analysis on the mechanism of pressure patter vibration in the system.On the basis of theoretical analysis,this paper accurately extracts the characteristics of the vibration pressure signal by variational mode decomposition(VMD).This provides technical support for the study of the law of action and the method of application of patting vibration under the conditions of varying speed and load.The main work of this paper is as follows:(1)In this paper,the mathematical model of pressure tapping of hydraulic system of pump control motor is established,and the conditions of pressure tapping are analyzed theoretically:The pressure of the plunger pump is close to the pulsation frequency of the plunger motor。The maximum value of the synthesized new pressure is the sum of the pressure pulsation amplitudes of the pump and the motor,and the frequency is the difference between the pump and the motor pressure。(2)Based on AMEsim software,the simulation model of closed hydraulic system of pump-controlled motor is built in this paper.The validity and accuracy of the model are verified by the electromechanical hydraulic integration test platform.(3)Simulation model and experimental results show that:With the increase of the rotational speed,the amplitude of the hydraulic system pressure beat increases and the period decreases;With the increase of the system pressure,the pressure beat period of the hydraulic system remains unchanged and the amplitude increases.The intensity of pressure tapping in hydraulic system is negatively correlated with pipe length and pipe diameter.The intensity of pressure patting in hydraulic system is positively correlated with the temperature and gas content of hydraulic oil.(4)The pressure beat signal can be regarded as the gain signal of pump and motor pressure pulsation signal.The pressure beat vibration signal contains rich information about the running state of the hydraulic system.However,the traditional timefrequency analysis method has some limitations because the pressure beat signal of the hydraulic system is time-varying and non-stationary.Therefore,this paper based on the variational mode decomposition of the pump control motor hydraulic system pressure patter vibration signal feature extraction method.This method can accurately separate the component of beat vibration from the complex pressure signal.This provides methodological support for subsequent experimental studies.(5)Based on the simulation model of the closed hydraulic system of the pumpcontrolled motor and the mechatronic-hydraulic integration test platform,this paper studies the engineering application of the pressure tapping vibration of the pumpcontrolled motor hydraulic system.The results indicate that:The frequency of pressure beat vibration in hydraulic system can simplify the calculation of damping ratio of hydraulic system of pump-controlled motor;The pressure patter plays a significant role in amplifying the fault characteristics of common hydraulic system faults,such as plunger wear.It can provide reference for the rich fault diagnosis methods of hydraulic system.The accumulator has an obvious weakening effect on the pressure beat of hydraulic system.However,the accumulator can not completely suppress the generation of pressure beat.