Research On Large Gear Measurement Method Based On Articular Arm Measuring Instrument

As a key component of large equipment,large gear measurement requirements are increasing with the application and development of large equipment in engineering in recent years.The articular arm measuring instrument is widely used in measuring industry because of its advantages of stability,reliability,portability,flexibility and wide measuring range.This thesis presents a measuring method of big gear based on articular arm measuring instrument.This method mainly includes three parts: data acquisition of tooth surface,reconstruction of tooth surface,calculation of tooth profile deviation and tooth pitch deviation.The structure characteristics and sampling accuracy of the articular arm measuring instrument were analyzed.Therefore,the data acquisition method of big gear tooth surface was determined.The articular arm data acquisition had problems with the inability to aim the target point and the uncertainty of the sampling point position on the tooth surface of the large gear.Therefore,the articular arm tooth surface measurement auxiliary ruler was designed.The tooth surface of big gear was picked by the collection method of row and row matrix.The position of the coordinate system after the arm movement was determined based on the principle of triangulation.The full coverage measurement of the oversize gear was realized by moving the articular arm several times.The collected data points were used as control vertices to form an interpolation sequence in both U and V directions.The node vector was determined by a uniform parameterization method.NURBS surfaces were generated by bicubic NURBS interpolation method.The coordinate data points on the theoretical tooth surface were obtained by means of the geometric characteristics and parametric equations of involute gears.The coordinate points were generated into tooth surfaces by using the method.The error of this method generates NURBS tooth surface was obtained by calculating the distance between each point on the tooth surface and the corresponding point on the theoretical tooth surface.The results show that the NURBS interpolation tooth surface error were less than 0.7μm.The calculation model of big gear error were established according to the involute tooth profile equation.The pitch deviation and profile deviation of big gear were calculated by this error calculation model.According to this measurement method,the data of the big gear(m=8,d=640mm)tooth surface were collected.The pitch deviation and tooth profile deviation of large gear were calculated by using the measurement method in this thesis,and the uncertainty of the measurement results was calculated.The accuracy of the measurement method in this thesis was verified by comparing with the measurement results of three coordinates.