Research On Measurement Method Of Radial Error Motion Of High-Speed Spindle Based On Target Trajectory Tracking

As the foundation of modern industry,the machining accuracy of machine tools has been continuously improved.In order to ensure the performance of machine tools,it is particularly important to monitor and compensate the radial rotary motion of the spindle in machine tool,especially for the measurement of radial error motion of high-speed spindle.As the rotational speed of the spindle gradually increases from thousands of revolutions to tens of thousands or even hundreds of thousands of revolutions,advanced machine tools have put forward extremely stringent requirements for high-speed spindle measurement technology.The existing classical measurement method for spindle radial error motion is with extremely high measurement accuracy in the low-speed rotation state of the spindle,but limited by the response frequency of the measurement system,the existing measurement method is difficult to be used for the spindle in the high-speed state.The measurement for radial error motion of the spindle can not meet the requirements of the above-mentioned technical field for the measurement of the radial error motion of the high-speed spindle.This paper "Research on measurement method of radial error motion of high-speed spindle based on target trajectory tracking" aims to solve the above problems,and propose a measurement method for radial error motion with large dynamic measurement range for high-speed spindle measurement technology.The principle analysis and experimental verification of the high-speed spindle at 30 000r/min were carried out under laboratory conditions.The research results of this paper can be applied to the frontier engineering fields such as the measu rement and compensation of the axis motion error of the advanced CNC machine tool.The main research contents of this paper are as follows:The development status of measurement technology in spindle radial error motion at home and abroad is systematically analyzed,and the main problems that restrict the measurement for radial error motion of high-speed spindle to higher rotation speed are pointed out: the acquisition capacity of measurement data per unit time in the measurement system in the classical measurement method is insufficient,it is difficult to complete the large-bandwidth sampling in measurement for high-speed spindle;the spindle rotation period is shortened due to the increase in the rotation speed of the measured spindle.In order to ensure sufficient sampling points within the rotation period of the measured spindle,it is necessary to improve the response frequency of the displacement sensor.Limited by the data acquisition capability of the measurement system,when the classical measurement method for spindle radial error motion is applied to the measurement of high-speed spindle,due to insufficient sampling points,the high-frequency information in the measurement results is lost.Therefore,developing a method that can realize the large bandwidth sampling in the measurement for the radial error motion of the high-speed spindle is the key technical problem to be solved urgently in the meas urement of the error motion of the high-speed spindle.Aiming at the problem of insufficient response frequency of the measurement system in the existing measurement methods for radial rotation error of spindle,a measurement model for radial error motion of high-speed spindle based on the single-point motion trajectory of the end face is established,and a target trajectory tracking based method is proposed.The measurement method of radial error motion of high-speed spindle.The image sensor is used to directly record the movement trajectory of the marked points on the spindle end face during the rotation,so as to directly measure the radial error motion at the spindle end face.Compared with the measurement model specified in ISO 230-7:2015,this model converts single-point serial sampling measurement into multi-point parallel measurement,thereby breaking through the restriction of measurement system response frequency on the measurement of radial error motion of high-speed spindle,which has laid a theoretical foundation for the realization of the measurement of the radial error motion of the high-speed spindle.Aiming at the problem of SNR degradation caused by image degradation in high-speed object measurement in existing machine vision methods,an SNR enhancement method based on signal light source wavelength selection and fusion of environmental noise spectral line compression is proposed.This method establishes the SNR degradation model of the target moving trajectory image under the condition of unequal time integration of signal and noise.Based on the difference of the spectral components between the active light source and the background stray light,through the design of the optical filter curve of the optical window,the environmental protection is realized.The significant compression of the noise integral spectrum section solves the problem of reducing the SNR of the target trajectory image in the high-speed rotation of the spindle.A measurement system for radial error motion of high-speed spindle based on target trajectory tracking is designed,and most of the existing digital image processing algorithms focus on edge localization and object extraction while ignoring the object center localization.When locating the center of the light spot of the topographic target,the problem of inaccurate center positioning is caused by solving the center of the light spot based on the classical edge localization algorithm.A target trajectory center localization method based on radial Gaussian fitting is proposed.On the basis of the simulation and experimental analysis of the spot shape based on the active light source,the edge localization method based on the local area effect is adopted to obtain the least square fitting circle center of the target trajectory,and then the radial Gaussian fitting-based method is adopted.The target trajectory centroid positioning method can obtain a more accurate target trajectory.According to the above content,a method for measuring the radial error motion of high-speed spindle based on target trajectory tracking is carried out,including a cooperative target based on active light source,a high-sensitivity image sensor,a target trajectory edge extraction algorithm based on regional edge effect,and a radial Gaussian-based algorithm.The complete design of the measurement system for the method of centroid positioning of the fitted target trajectory.On this basis,the radial error motion measurement of a high-speed hydrostatic air-floating electric spindle is carried out,and the measurement repeatability of the built high-speed spindle radial rotation error measurement system is tested.The maximum standard deviation is 0.07 μm,the measured radial rotation error at the spindle speed of30 000 r/min is 2.58 μm,and the measurement uncertainty is 1.2 μm(k=2).