Research On Extrapolation And Compilation Method Of Pressure Load Spectrum Of Excavator Main Pump

In recent years,the growth of excavator market demand puts forward higher requirements for excavator quality and reliability.Reliability test is an important means to analyze the potential problems of excavator products at this stage,and the compilation of load spectrum is the core step of reliability test.The accuracy of its compilation method directly affects the rationality of reliability test.Based on the national key R ＆ D project-"Research on reliability and life test evaluation technology of high-pressure piston pump / motor"（Project No.: 2018yfb2000902）,this paper selects the non research object of 20 t medium-sized excavator,and comprehensively considers the influence of various factors on the test results from the load data test stage.After extrapolating the data.Aiming at the problems of traditional load spectrum extrapolation in time domain,an improvement is proposed,and the extrapolated load spectrum is compiled into load spectrum.The main research contents of this paper are as follows:1.Formulate excavator test plan.According to the market feedback,put forward requirements for the excavated materials,operation specifications and operation modes in the load test,and establish the test system on this basis to clarify the installation position of each measuring point and sensor.In order to study the influence of individual differences on the test results,three drivers were selected for data collection.After completing the data test,divide the load of each working stage,and check whether the length of the test sample meets the requirements.2.After completing the load test,preprocess the data of zero drift and noise in the load.The commonly used least square method is used to separate the trend term in the data and eliminate the zero drift.The method of wavelet noise reduction is used to realize noise reduction,and the correlation coefficient and signal-to-noise ratio before and after noise reduction are calculated to judge the noise reduction effect.After completing the data processing,analyze the influence of human factors on the test results,and test the difference of each data by comparing the statistical value and average time of the load data of three drivers in each stage.3.Extrapolate the preprocessed load data in time domain to obtain the full cycle life load spectrum.The basic steps of pot extreme value extrapolation method are introduced,and the pot model is established from the selection of distribution function,primary threshold and optimal threshold.Aiming at the problems of large amount of calculation and low accuracy in the traditional optimal threshold selection,an improvement is proposed.The grey correlation degree is used as the goodness of fit,and the optimal threshold is selected based on genetic algorithm.After the load spectrum extrapolation is completed,the cumulative distribution function diagram and Q-Q diagram of the sample data and the extrapolation results are compared to verify the rationality of the extrapolation results.4.Transform the extrapolated load spectrum into the load spectrum that can be recognized by the test bench.According to the whole life cycle load spectrum,the load of each working stage is equivalent by using the principle of equivalent damage,the respective load spectrum of four kinds of excavated materials is completed,and the number of loading cycles is determined according to the feedback of market investigation.In order to reduce the test cost,combined with the material characteristics of the plunger pump,the appropriate acceleration factor is selected and the acceleration spectrum is compiled.