The Development Of Angle Encoder Calibrator Base On Self-calibration Method

Angle is a key measurement parameter in the important fields of national economy,such as manufacturing industry,medical industry,scientific instruments and aerospace,etc.The reliability of angle measurement results is the key factor affecting the verification results and product quality.Therefore,it is necessary to trace and transfer the angle standard through effective methods.Angle encoder is a popular linear angle measurement tool on the market.Some internal problems that can not be observed by naked eyes may occur during its manufacture or use process,which will affect the accuracy of measurement and even lead to the angle encoder can not be used normally.In order to reduce the loss caused by angle measurement errors,the accuracy calibration of angle encoder is an indispensable component.Based on the analysis of the development status of angle encoder calibrator at domestic and foreign,this paper designs an angle encoder calibrator based on self-calibration method according to the national standards.The main research contents are as follows:Angle encoder is the most popular linear angle measurement tool in the market at present.Some internal problems that can not be observed by naked eyes may occur during using,which will affect the measurement accuracy and even can not be used normally.To reduce the loss caused by the deviation of angle measurement,Calibrating angle encoder is an indispensable link.In this paper,the development of angle encoder calibrator is studied,analyzing the calibration requirements of angle encoder at domestic and foreign and the development status of calibration technology,proposing the development direction of the calibrator,and designing a new angle encoder calibrator based on the existing national standard.The main research contents are as follows:(1)According to the national standard "Photoelectric Axle Encoder Calibration Specification",a high-precision encoder calibration model is established,and the feasibility of the calibration model is verified by simulation.The harmonic suppression effect of grating system based on self-calibration method in the calibration model is analyzed;With the innovation of miniaturization,highprecision,calibration diversity and universality,the module is designed in three parts:machinery,circuit and host computer.(2)According to the encoder verification index to select the grating system;the air bearing shaft is designed to reduce the system error caused by the shaft friction;the encoder clamping device with flexible adjustment of size and coaxiality.(3)Develop a digital processing circuit based on FPGA to implement the functions of collecting,processing and uploading of the reading heads and encoder signals.Verify the validity of floating-point division to improve the accuracy of the system;function realization of self-calibration algorithm in digital circuit of FPGA;develop Slave FIFO state machine to control USB communication to ensure the stable data transmission between the circuit system and the host computer.(4)Develop human-computer interaction program which integrates self-inspection of equipment,selection of calibration mode,data collection,coder calibration,data export and chart display.Through the development of motor driver program,the automatic rotation of turntable can be effectively controlled;the USB communication program can implement data connection with circuit system;the encoder calibration program developed based on national standard calibration standard to implement the calibration automation.(5)According to the national standard "Evaluation and Representation of Measurement Uncertainty",the polygonal prism calibration error,reading heads consistency,reading heads phase relationship,circuit system accuracy error and coaxiality error of the calibrator are studied,and the overall performance uncertainty is synthesized.The calibration experiment of incremental shaft photoelectric encoder is carried out to verify the validity of the calibrator.