Study On Measurement Design Of Form And Position Error For Center Block In Large Telescope

With increasing of the aperture of domestic large optical telescope, the size of center block in the telescope increase. A fine machine equipment requires very high tracking precision, which requires pitch shaft of telescope has a high rotation accuracy. In many factors the form and position error of center block is not negligible error sources. Now for the center block of 2-meter telescope and larger telescope, because there is not effective detection means to accurately measure its form and position error, which cannot accurately guide the follow-up repair. So now the accuracy of large center block can only rely on the accuracy of machine tools. The research on detection method of form and position error for center block is put forward urgent requirements, but due to size of the center block, two cylindrical end span, accuracy higher characteristic, and two cylinder distance of center block in 4-meters aperture telescope can reach 6 meters,so the form and position error detection is much more difficult. The main research contents of this paper:Study the laser tracker system structure and working principle, and analyze the main factors that affect the laser tracker ranging and angular measurement accuracy. According to the center block structure of single station measurements can only be measured characteristics of the coordinates of the four through the end of the proposed transfer station measurement method, and through the experiment to determine the laser tracker in the transfer station accuracy. Last, center block form and position error is measured precisely.According to the requirement of the center block form and position error measurement, study of existing measuring method on form and position error for large structure, built up a more convenient and efficient optical measurement method and analyze its accuracy. Through the experiment, the feasibility of the measurement method of center block perpendicularity, parallelism measurement is verified.The least square mathematical model of the form and position error is established, and the results are processed by MATLAB. The uncertainty of measurement results is evaluated by GUM method and Monte Carlo method.The proposed measurement method can not only meet the 2m telescope center block form and position error measurement requirement. And compared with laser tracker, it has obvious advantages about 4-meter telescope and larger telescope. But also it will play a certain reference significance for large shaft-hole structure.