| Gear measurement technology is the foundation for evaluating gear quality.Traditional gear measurement mainly focuses on measuring a few points and lines on the tooth surface,which only includes local information of the complex-shaped tooth surface and cannot reflect the overall quality of the whole gear.Additionally,it suffers from low measurement efficiency.In recent years,optical measurement technology,including laser triangulation measurement,laser holographic measurement,industrial CT measurement,and machine vision measurement,has gradually been developed in gear measurement to obtain the complete 3D shape of the tooth surface.Among them,line laser measurement,as a typical laser triangulation measurement technology,is an effective means to achieve rapid measurement of 3D tooth surfaces and is beginning to be applied.However,compared with the mature conventional gear measurement based on point and line measurement,the line laser 3D gear measurement method is not yet perfect,especially in the acquisition and utilization of three-dimensional tooth surface measurement data.Through theoretical research and technological innovation,this thesis solves the calibration of position and attitude parameters of line laser sensors in line laser 3D gear measurement.It clarifies the influence and law of the measuring angle on tooth surface in line laser 3D gear measurement,analyzes the occlusion phenomenon of adjacent gear teeth on the measuring light and proposes corresponding improvement strategies,providing technical supports for fast and high-precision acquisition of 3D tooth surfaces.Based on the principle of line laser 3D gear measurement,a line laser3 D gear measurement instrument is developed,which not only meets the measurement needs of accuracy evaluation indicators in current standards,but also has new functions such as measuring the profile of the path of contact and the flank twist,expanding the utilization of 3D tooth surface data.The main research contents of this thesis are as follows:(1)A calibration method of the position and attitude parameters of the line laser sensor have been proposed in line laser 3D gear measurement.Using a gear rotation scanning method based on a line laser sensor,the spatial transformation relationship between the machine coordinate system,gear coordinate system,sensor coordinate system,and measuring light coordinate system is established.a line laser 3D gear measurement model has been established to solve the problem of obtaining 3D tooth surface information of the gear.A dedicated artefact with specific geometric features has been invented,and a calibration method for the spatial position and attitude parameters of the line laser sensor has been proposed to determine the accurate position and attitude of the line laser sensor in the machine coordinate system.The dynamic repeatability after five repeated calibrations is less than 2 μm,ensuring the accuracy of the measurement data.(2)A model of measuring angle on tooth surface has been established,and the impact of the measuring angle on the loss of gear surface data has been revealed.To address the problem of gear surface data loss caused by excessively large incident angles in line laser 3D gear measurement,the definition of the measuring angle on tooth surface has been clarified,and a model of the measuring angle on tooth surface has been established.The correctness of the model has been verified through simulation analysis and actual experiments for involute cylindrical gears.Based on the model of measuring angle,the loss of gear surface data has been analyzed.If the influence of measuring angles is effectively controlled,the efficiency of measuring the full tooth width of the gear under current experimental conditions will be greatly improved,with a maximum efficiency increase of 50%.For the tested gears with different geometric parameters,the impact of the measuring angle on the acquisition of gear surface data can be reduced by adjusting the position and attitude parameters of the line laser sensor,thereby avoiding the problem of gear surface data loss in line laser 3D gear measurement.(3)A model of the occlusion area between adjacent gear teeth has been established,and its formation law has been revealed,and improvement strategies have been proposed.In line laser 3D gear measurement,a large offset of the line laser sensor along the tangent of tested gears will cause the adjacent gear teeth to block the measuring light.By using the parallel projection principle of projective geometry,the occlusion problem of spatial surfaces has been simplified into the relative position relationship of planar curves,and the occlusion process to the measuring light has been analyzed and a model of the occlusion area has been established.The correctness of the model has been verified through simulation analysis and actual experiments for involute cylindrical gears.The formation law of the occlusion area between adjacent gear teeth has been analyzed.If the occlusion phenomenon is effectively controlled,the efficiency of measuring the full tooth width of the gear under current experimental conditions will be greatly improved,with a maximum efficiency increase of 70%.Based on simulation and experimental analysis,the threshold conditions for the occurrence of occlusion under different offsets of the line laser sensor and different the inclination angle of the measuring light plane have been clarified.Improvement strategies for reducing the occlusion area have been proposed,providing a basis for sensor path planning and avoiding occlusion between adjacent gear teeth in line laser3 D gear measurement,and ensuring the integrity of the 3D tooth surface data.(4)The optimal position and attitude parameters of the line laser sensor in gear3 D measurement has been determined.In gear 3D measurement,the tangential offset along the tested gear for the line laser sensor directly affects the measuring angle on tooth surface and the occlusion phenomenon between adjacent gear teeth,and the action law of the two is opposite.To reduce the influence of measuring angle and avoid the occlusion phenomenon,the minimum offset in the model of measuring angle on tooth surface and the maximum offset in the model of the occlusion area between adjacent gear teeth should be calculated.By comprehensively considering and selecting reasonable weights,the optimal offset along the tangential direction of the measured gear for the line laser sensor is determined.At the same time,the inclination angle of the line laser sensor should follow the principle of determining the inclination direction of the line laser sensor based on the rotation direction of the tested gear.The measuring light plane should be illuminated on the tested tooth surface as much as possible in a direction perpendicular to the helix.(5)A line laser 3D gear measurement instrument has been developed.Based on the principle of line laser 3D gear measurement,the overall design scheme of the measurement instrument was determined,and a line laser 3D gear measurement instrument is developed.Based on this measurement instrument,considering the influence of the measuring angle and the adjacent gear occlusion problem,the spatial position and attitude of the line laser sensor was adjusted.The position and attitude parameters of the line laser sensor in the machine coordinate system were accurately calibrated using a dedicated artefact with specific geometric features,and gear measurement experiments were conducted.The measurement repeatability of the original point cloud,profile deviation,and pitch deviation is analyzed,and the experimental results had good measurement consistency.According to the gear accuracy standard ISO 1328-1:2013,profile deviation,helix deviation,pitch deviation,and topological error are measured and compared with the inspection report issued by the National Institute of Metrology,China,which verified that the line laser 3D gear measurement instrument meets the measurement requirements of grade 5 accuracy gears.(6)Utilization of the 3D gear surface data have been extended.Based on the normal error of the 3D tooth surface,not only were the accuracy evaluation indicators in the current standards extracted,but new evaluation indicators are also defined to more comprehensively characterize the quality of the actual tooth surface.Profile deviation of the path of contact,as a functional indicator with comprehensiveness,uniformity,and uniqueness,is defined and extracted.Based on the tolerance calculation formula for the profile deviation and helix deviation,the tolerance calculation method for the profile deviation of the path of contact is proposed.The flank twist is extracted,which can be used to evaluate the overall the flank twist of measured tooth surface. |
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