| Spindle rotation accuracy is an important index for evaluating the processing performance of the machine tool.Precision measurement of the rotation accuracy can monitor the operating status of the machine tool,and the obtained rotation error value is the basis for motion compensation to improve processing accuracy.In order to meet the demand for high-precision measurement of spindle rotation accuracy,the thesis proposes a laser heterodyne measurement technology based on fiber structure with adaptive measurement distance and designs a detection system.The outgoing light of the fiber optic probe is highly collimated and the beam is concentrated,and the distance adaptive detection is combined with the measurement principle;The application of optical heterodyne enables the measurement of gyration accuracy to the level of micron nanometers;On the basis of spectrum analysis,a secondary autocorrelation algorithm is used to extract the Doppler frequency shift,and the measurement signal-to-noise ratio is further improved.Firstly,the thesis analyzes the evaluation method of rotation error and the principle of error separation technology in detail,and establishes a high-precision mathematical model of rotation accuracy detection.The measurement model is based on the principle of laser Doppler,using acousto-optic modulation technology to obtain a stable frequency difference of 100MHz to form an optical heterodyne measurement optical path,which makes the system have higher measurement accuracy;Investigate the transmission characteristics of optical fiber and replace the traditional air optical path to enhance the anti-interference ability of the system;Based on the dual-fiber probe,an error separation model based on bidirectional measurement and inverse method is derived.Then,according to the measurement model,the overall measurement optical path and circuit module are designed after conducting performance investigation and selection of the required key components.The self-focusing coupler improves the collimation of the measurement light,and forms an adaptive measurement probe with the characteristics of the measurement model independent of the distance,which reduces the difficulty of debugging the optical path and improves the applicability and measurement efficiency of the measurement system;The light intensity test determines the 500mm adaptive detection threshold,which ensures a high signal-to-noise ratio of the measurement system within the distance adjustment range;According to the characteristics of noisy output signal of the photodetector,a signal conditioning circuit is designed to amplify,select,demodulate,and filter the photocurrent,and realized the screening of Doppler frequency-shifted signals.Then based on the spectrum analysis,an auto-correlation algorithm is used to accurately extract the frequency of the Doppler signal after performing two auto-correlation operations on the Doppler signal,thereby improving the signal-to-noise ratio of the measurement system;The LABVIEW and MATLAB programming are performed on the PC side for signal processing and human-computer interaction interface design,and the frequency shift signal is converted into a measurement result and displayed on the PC-side interface,thereby completing the overall design of the measurement system.Finally,the measurement experiment and the uncertainty evaluation of the system are performed.Comparative experiments of radial and axial measurements at various speeds are carried out for the spindle of Cincom-A12 CNC lathe in the laboratory,the feasibility of the probe distance adaptation and the practicality of the roundness error separation model are verified.The uncertainty evaluation of the system shows that the maximum effective value of the radial rotation error is 11.732?m at the speed of 1200r/min,achieved micro-nano measurement accuracy;The synthetic standard uncertainty is3.746?10-3?m,the measurement system has high reliability and a certain practical value. |
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