| Circular grating encoder is widely used in aerospace,robotics,high-end machine tools,coordinate measuring machines and other industries.With the rapid development of these industries,the accuracy requirement of the angle measurement for circular grating encoder is higher and higher.The installation eccentricity error of circular grating has a great influence on the angle measurement accuracy of circular grating encoder.Therefore,it is very important to calculate the eccentricity error parameters and compensate the angle measurement error caused by the installation eccentricity.For the measurement and compensation of the circular grating eccentricity error,the circular grating installation eccentricity parameter measuring system based on machine vision is designed.And the eccentricity error parameter identification algorithm is proposed.At the same time,the eccentricity parameters measurement and compensation model with double reading heads is studied,and the circular grating eccentricity error compensation algorithm is presented.The experimental results show that the designed eccentricity error measurement system can effectively identify the eccentricity error,and the proposed compensation algorithm can effectively improve the circular grating angle measurement accuracy.Aiming at the technical requirements of machine vision eccentricity error measuring system,the overall scheme of circular grating installation eccentric ity measurement system is designed firstly.On this basis,the eccentric ity parameter identification algorithm based on machine vision is studied.The overall structure of the measuring device is analyzed.The design process of lens position adjustment structure and the circular grating rotation structure are introduced in detail.Secondly,according to the requirement of eccentricity error measurement,the key components of the motion control system and the image acquisition system including core controller,driving motor,industrial camera,optical lens and the light source are selected.Finally,the core control algorithms of the motion control system and image processing system are studied.The realization process of motion control function module and image processing function module of the machine vision eccentricity error measurement system are analyzed in detail.Aiming at the problems such as tedious measurement process and low compensation accuracy of the existing double reading head grating installation eccentricity error measurement and compensation.O n the basis of the existing eccentricity error model of circular grating installation,the influence of eccentricity error on the angle measurement accuracy is analyzed,and the measurement and compensation model is researched.The effectiveness of the proposed error measurement and compensation model is verified through simulation.Finally,in order to verify the error parameters measurement accuracy of the designed machine vision eccentricity error meas uring system,and the Error measurement and compensation effectiveness of proposed models for double reading head mode,the twenty-three plane prism and photoelectric autocollimator are used.The experimental results show that the eccentric error parameters can be measured and compensated effectively for double reading head mode.And the angle measurement accuracy of the circular grating can reach within 1 ”.The difference between the machine vision measurement and double reading head mode is less than 1um.The accuracy and reliability of the designed machine vision eccentricity error measuring system can be verified wel.Through the above research,the measurement and compensation to circular grating installation eccentricity are achieved.It is key to improve the angle measurement accuracy of circular grating. |
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