Research On Technology Of Reproducing Instantaneous Dynamic Load And Reliability Loading Test For Motorized Spindle Based On Fourier Transform

In the industry of equipment manufacturing,NC(numerical control)machine tools is commonly known as “the mother of machines”.The function,accuracy and reliability of NC machine tools dramatically affect the function,accuracy and reliability of products in other industries.In a word,the technology level of NC machine tools determines the level of equipment manufacturing of a country.In the last decade,under the support of the “state key projects of science and technology”,the domestic NC machine tools are making progress in high speed,high accuracy,multi-axis coordination and high reliability,and the progress is supported by the research and development of various advanced technologies,of which the most attracting is the high-speed motorized spindle.However,the highest level of technology of the motorized spindle is reliability,which is also the key obstacle for developing the domestic motorized spindle.It is significant to improve the reliability level of the domestic high-speed motorized spindle,which is benefit for improving the reliability level of the entire NC machine tools and further the level of equipment manufacturing.The ultimate target of reliability research on motorized spindle is to improve the reliability,and the reliability experiment technology is the basis to achieve this target.Therefore,this paper focuses on the technology of reliability experiment.Nowadays,the existing reliability test bench of motorized spindle can apply static force or dynamic force of simple laws,such as sinusoid or linear function.As is known to all,in the time domain,the real entire load curve is jagged,approximately periodic,and random.Thus,the existing test bench of motorized spindle cannot simulate the real working load well.For now,the frontier of loading technology for motorized spindle is based on load spectrum,which is able to simulate the real working condition in the sense of statistics.But in the sense of instantaneous dynamic load,the spectrum-based loading method still applies the static force or dynamic force of sinusoid or linear function.Thus,to solve the problem that the existing loading technology of reliability test bench cannot simulate the real working condition with a high level,this paper proposes a method of analyzing,decomposing and simulating the real load with a high level and then applying the simulated load on the motorized spindle based on Fourier transform.The detailed idea is as follows:(1)Research the theory of reproducing the real load of motorized spindle based on Fourier transform.Build the measuring system to measure the load curve of the spindle in the time domain under the real working conditions.Map the time-domain load curve into the frequency domain.Analyze the amplitude,phase and frequency of each sine harmonic curve in the frequency domain.Map the sine harmonic curves back into the time domain using the inverse Fourier transform.Design algorithms to generate the simulated signals of the real load.(2)Build the test bench of reliability experiment for motorized spindle,which mainly consists of the mechanical system and control system.The mechanical system consists of designing general structure and loading device.The control system consists of software,sensors,amplifier and electro-hydraulic valves.(3)Implement the reliability experiment on a domestic motorized spindle using the test bench,based on the load spectrum and the loading method of transient dynamic load proposed in this paper.The motorized spindle is loaded under the simulated real working conditions,and the fault and operation data are collected simultaneously.(4)Implement the reliability assessment for the motorized spindle based on the test data,that is,to calculate the MTBF(mean time between failures).Since the reliability level of motorized spindle is high,the sample size of the collected reliability data sample is small,and this paper turns to the Bayes reliability theory for help to calculate MTBF.In this paper,a technique of reconstructing dynamic load of motorized spindle based on Fourier transform is proposed,and in the process of reliability test,loading the simulated transient dynamic load on the motorized spindle is realized,which is based on the load spectrum and close to the actual working condition.The proposed technique provides the method and basis for the reliability test and evaluation of the motorized spindle.