A High-precision Intelligent Measurement System For Hole And Shaft Parts Based On Optical-mechanical Cooperation

In precision mechanical systems,the assembly clearance between the functional hole and the shaft is an important factor affecting the accuracy and performance of the machine.From the technical goal of the assembly,even if the hole and the shaft whose dimensions exceed the design tolerance,as long as the direction of the out-of-tolerance is the same and the difference is similar,the ideal fit relationship can be formed.Therefore,compared with the traditional tolerance fit theory,the large-volume matching can obtain better assembly quality and economical parts manufacturing.And the key technology of large-volume matching is quickly and accurately measuring the size parameters of the holes and shafts.The existing measuring tools of shafts and holes are mainly suitable for manual operation of single-piece or small-batch measurement occasions.For large-volume matching measurement,there is no automatic intelligent measuring equipment with high measurement precision,stable precision and good consistency.In this paper,a high-precision intelligent measurement scheme combining industrial robot,visual guidance and pneumatic measurement method is proposed.The intelligent identification technology of parts based on the industrial integration of CAD model and visual image information are studied.The calibration technology of the robot vision system,and large-volume parts matching technology based on the network's maximum flow are also researched.Finally,the measurement system is designed and realized.Due to the lack of feature information of the hole and shaft parts in the measurement system,the intelligence cannot be realized simply by relying on machine vision.To solve this problem,this paper proposes the intelligent recognition technology that combines CAD model and visual information.The key size information of the parts automatically obtained through the program is used as the main information of part identification,and the soft-code of the program is realized.For the shaft parts,the target recognition algorithm combining contour point loop search and least-squares method is developed.For the hole parts,the target recognition algorithm based on the target features is developed.Through the above algorithms,the pixel coordinates of the target are obtained.In order to complete the conversion from pixel coordinates to world coordinates,the calibration technology of industrial robot vision system is studied.The D-H model is used to establish the motion matrix of industrial robots,and the small hole imaging model is established.Based on the above work,the calibration methods of pixel equivalent,hand-eye relationship and tool coordinate are given.Then,the target recognition and positioning method based on sequence image is introduced.Finally,a high-precision intelligent measurement system is realized,which discusses the functions of the vision guidance subsystem,the grabbing and positioning subsystem,the vision measurement subsystem,the compliant subsystem,the pneumatic measurement subsystem,the security protection subsystem,and the data storage and processing subsystem.Besides,the construction of subsystems and mechanical structure of each module is completed.The control strategy named of “look and move” is adopted to design the measurement process.The calibration of hand-eye relationship and tool coordinate is completed by using the calibration technology of industrial robot vision system.At last,the intelligent measurement system complete the measurement of the parts,and the optimal assembly group of the shafts and holes are given.The research results of this paper can provide theoretical and experimental basis for the research on the high-precision measurement of holes and shafts,intelligent recognition technology,calibration technology of industrial robot vision system,and the intelligent system combining optical and mechanical technology.