| Large aperture optical systems have wide range of applications in the field of astronomy and defense. It is the focus of research direction both here and abroad in the optical processing institution because the characteristics of its higher angular resolution, stronger energy collection ability etc. Large aperture optical mirrors are the core components in the system, and the primary mirror has a diameter of 4m is under processing here and is up to 8m in the world.Computer controlled optical surfacing technology is widely used in the processing of small diameter of the optical mirrors. The technology represented by small polishing tools, with the development of technology, integration of processing means more to adapt to the processing needs more extensive. Although the CCOS technology in the processing of small aperture optical mirror has been mature, but when it was applied in the processing of large aperture optical mirror, we found the key technologies such as processing route and removal function stability, edge effect and optical processing center, greatly limit the efficiency of processing convergence of large aperture optical mirrors. Therefore, in this paper we propose that through the experiment and analysis improve rough polishing removal function stability and amendment technology parameters relation, and using superposition of motion synthesis for complex motor spindle suppress edge effect, tri-station machine with multi-stations is designed and developed to improve the efficiency of processing convergence of large aperture optical mirror. Based on the pioneer work done by my workmate, my work is in the following few regions.1) According to the existing technology in the processing of large aperture mirror has low convergence efficiency and uncertainty, build the experimental platform of processing parameters. Take the orbital motion which is using here as the foundation, we focus on solving the rough polishing stage which is the greatest impact on the stability of the convergence efficiency of processing. First of all, we discuss the possibility of that simulation algorithm which based on discrete matrix arithmetic can introduce the actual removal function to the algorithm, in terms of that algorithm improves the consistency of the simulation and actual machining, which provides guarantee algorithms to improve the convergence efficiency. Secondly, from the point of view of tool structure, linearity of parameters, and abrasive as the main direction of processing parameters on the effect of the stability of the removal function. The use of configuration parameters to obtain a reasonable Gauss type removal function with high uncertainty and high stability. We processed the experiment in a ? 100 mm sub aperture are based on the new technology without considering the influence of edge effect. The experiment result indicates that, with a 48 min one-step iterative process, the RMS converged from 0.079 ?(? ?632.8nm) to 1/30 ?, the convergence efficiency is 58%. The simulation and actual processing results are highly consistent. Furthermore, we processed an off-axis parabolic mirror with a full aperture diameter of ? 800 mm. The experiment result indicates that, with a one-step iterative process, the RMS convergence efficiency is 34%, which is higher than simulation processing. The simulation and actual removal are highly consistent except the edge zone.2) In this paper, in the view of the problems in the existing edge effect researches focus on the edge collapse prediction and mathematical description, we propose that in the keep orbital motion which produces Gaussian removal function high volume removal rate, and through the motion synthesis of the removal function peak removal rate to deviate from the center and re-distribution makes its to move to the edge, so that the distance tool out of to the reflector edge is not in danger of producing edge collapse can remove the peak removal rate to mirror edge, thereby achieving inhibition of edge effect in the real sense. Through the simulation convergence we proved New removal functions to enhance the convergence, thus suggesting that the theory of large aperture optical reflector has the ability of suppressing edge effect. Based on the design and control theory, we used complex motor spindle and follow the movement control algorithm to achieve the new removal function, and by removing the function experiments show that the removal function is exist. Because of the actual physical smoothing effect exists, actual removal function is more suitable for engineering application than theory design. By introducing the measured removal function to the matrix algorithm, the edge removal experiment of a rectangular 300mm×150mm SiC mirror removal experiments is processed. The experiment result indicates that removal of new function, did not produce edge effects such as warped edge and collapsed edge, and the desired processing highly similar to the results. Consequently, the validity of the new removal function to the edge effect inhibition ability is thereby demonstrated.3) Based on that, in order to process large-aperture aspherical mirrors, we designed and constructed a tri-station machine processing center with a three station device, which bears vectored feed motion of up to 10 axes. Based on this processing center, an aspherical mirror processing model is proposed, in which each station implements traversal processing of large-aperture aspherical mirrors using only two axes, while the stations are switchable, thus lowering cost and enhancing processing efficiency. The applicability of the tri-station machine is also analyzed. At the same time, a simple and efficient zero-calibration method for processing is proposed. To validate the processing model, using our processing center, we processed an off-axis parabolic SiC mirror with an aperture diameter of 1450 mm. The experimental results indicate that, with a one-step iterative process, the PV and RMS of the mirror converged from 3.441μm and 0.5203μm to 2.637μm and 0.2962μm respectively, where the RMS reduced by 43%. The validity and high accuracy of the model is thereby demonstrated. |
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