Automatic Adjustment Technology Of Grating Encoder Based On Machine Vision

Encoder has been prevalent among many fields, such as radar, photoelectric theodolite, robots numerically-controlled machine tools, and loop-closed speed adjustment system with high precision, and it is a desire angle transducer for robotization equipment. As the modernized productivity is more automated and higher accurate, the demand for encoders becomes larger, and the requirement for the accuracy of them increases too. When the optical grating has been installed on the main axis of the encoder, the co-axiality of the optical grating and the center of gyration has a big influence on the accuracy of the encoder. The right assemble and adjustment of the optical grating can allow the performance of accuracy in all parts of the encoder to have a full play, or make up for the imperfection of some parts.Based on the machine vision, therefore, this paper designs and improves some primary techniques, such as the eccentricity measurement method and eccentric adjustment scheme of the optical grating auto-adjustment system on the encoder and so on.First of all, analyze and study of the influence on the system precision and efficiency, which is impacted by the adjustment scheme on the optical grating assemble auto-adjusting system of the encoder and pushrod promotion scheme;analyze the influence on the system precision and efficiency, which is made from the main hardware of the optical grating assemble auto-adjusting system on the encode,and based on this, make an improvement and adjustment on the main hardware.Secondary, this paper comes up with preprocessing and contour extraction method aiming at the characteristics of the surface images of the encoder optical grating, and through comparing to the traditional image preprocessing and methods of contour extraction on the surface image, it also proves the feasibility of the contour extraction method given by this paper.Besides, this paper develops the function of automatic focusing, based on the working requirements on the eccentric adjustment system of the encoder.Contrapose the features of the surface image of the encoder optical grating, this paper designs an evaluation methodology on sharpness of the optical grating surface image. It also constructs combined spotlight search scheme with depth from focusand depth from defocus, aiming at evaluation of the sharpness of the optical grating surface images on the encoder and the functional relationship between the places of the focusing mechanism.Finally, this research paper tests the highest adjustment precision and efficiency which can be reached by the system, through experiments verifying the validity of the whole eccentric adjustment of the encoder optical grating. Simultaneously, it illustrates that how to select the different eccentric adjustment standards of the optical grating in the system, according to various situations and types of the optical grating.Through the research process above, it completes the optimization to the auto-adjustment system of optical grating on the encoder, and improvements the feasibility and adjustment precision of the system.