Study Of Key Techniques On High Precision Calibration Turntable Grating Angle Measuirng System

The testing turntable in the dissertation is a kind of high positioning accuracyand stability,large scale,great loading capacity,complex and precisionmechano-electronic equipment used for calibrating mapping camera. To locate withprecision we develop a kind of high precision grating angle measuring system.Thedissertation based on practical engineering project thoroughly researches the keytechniques of grating angle measuring system.The key techniques include the keydesign of optical and mechanical structure system, the key design of electronics,theanalysis and testing of error,the compensation of error etc.The dissertation dissertates the theory of grating angle measuring system basedon grating MoireFringe technique,the quality parameter and affecting factors ofgrating signal,the gauging methods of grating signal quality. The precision of theangle measuring system is distributed theoretically to directing the design.Forimproving the precision and reducing the cost effectively the error compensationmethods using software is researched.The dissertation dissertates the key techniques of optical and mechanicalstructure system. High accuracy and high stability dense ball bearing shatfing isdesigned. The primary grating is a kind of thin and big diameter grating. Fourreading heads and multilineal index gratings are used to reduce the period error ofgrating. The application of digital addition technology reduces the eccentricity errorof the primary grating and the difficulty of installation.The dissertation analyses the error source of the angle measuring system andtests the shafting movement error and grating dividing error.The dissertation analyses the key techniques of electronical design. The detecting components that have stability capability and identical characteristic ischoosed.To decreasing phase excursion correcting circuits of signals phase are used.To reduce zero offsets error the difference amplifying circuits are used. To reduceunequal amplitude error amplitude adjusting circuits are used. Because manytechnical mehods are used,the quartering of signals is ensured.The illuminationsystem that has symmetrical,parallel and stability characteristic is designed to ensurethe high quality of signals. The dissertation uses improved BP algorithm to reducethe angle measuring error and the precision of angle measuring system is improvedsignificantly.The precision is tested by the directly comparing method,permutation and entirecombination method.The result shows that the precision can achieve the target of thedesign and satisfy requirements.The dissertation is completed by combining practical engineering andsummarizes the project at the same time.The primary innovation points of thedissertation are as follows:(l)In the design of optical and mechanical structure system, The method ofusing multilineal index gratings and four reading heads is put forword to reduce theperiod error of primary grating;(2)The formula between distortion and thickness of supporting board isdeduced when duplicating thin and big diameter grating,which provides basic theorypledge to develop high precision grating.(3)Thetradition software compensation method of angle measuring system isbased on numerical value analysis mehod or error correct table method.Thedissertation uses BP neural network and improved BP algorithm to reduce the anglemeasuring error.The precision of angle measuring system is improvedsignificantly.The method of this dissetration is aflfuent in the method ofcompensation error of angle measuring system.The research of this dissertation provides pratical experience and theoreticalbasis for the developing of turntable grating angle measuring system,which isprominent in practical and theoretical significance.