天文光学望远镜轴系驱动方式发展概述

Review of Drive Style for Astronomical Optical Telescope

该文首先介绍了已投入使用的2.5米口径以上的25架地平式光学望远镜和11架赤道式光学望远镜轴系驱动方式,并概述了天文光学望远镜轴系驱动及其相关技术的发展过程;然后对目前国际上在研的6架大型光学望远镜和预研的10架极大光学望远镜轴系所采用的驱动形式进行了归类;最后分析了未来极大光学望远镜轴系驱动的发展趋势和与之相关的研究内容.

Drive systems are indispensable for the astronomical optical telescopes to track the motion of celestial bodies. The main purpose of this paper is to generalize the drive type of the astronomical optical telescopes and to analyse the development trend of drive type to be used in the future telescopes. By summarizing the main axles drive type of 25 alt-azimuth operational telescopes and 11 equatorial operational telescopes in the world, this paper investigated the development history of drive technologies adopted in optical telescope. By analysing the main axles drive style used in the 6 large telescopes under construction and will be adopted for the 10 extremely large telescopes in the future, the preliminary conclusion has been gotten that the direct drive, which was used in VLT and Subaru successfully, will be the main drive type in the future, especially for the ELT. Each drive type has its advantagas and deficiencies. Feasibility, reliability, maintainability and cost performance are the main factors to be considered in choosing the drive type. Until the 1970s, worm gear drives are the traditional drive ways to provide the final gear stage for most ground-based telescopes because of its large gear ratio in a single stage and excellent intrinsic accuracy. Moreover, the worm gear is the only type of drive to offer absolute safety against telescope imbalance. But, the poor mechanical efficient, not allowing back driving, high precise install alignment, costly and limited in size are the main factors which affect the use of worm gear in large telescopes. Spur gears avoid the irreversibility problem of the worm gear while maintaining positive control. The helical multi-start gear drive distributes the high loading on the gear＇s teeth. Friction drive was developed to overcome many of the inherent deficiencies in both worm drives and gear drives, such as periodic error, backlash. But friction drive also has its own inherent weakness, such as slippage and creepage. Direct drive was developed to overcome the above shortcomings for large optical telescopes. This system has the simplest mechanical configuration. It is free from friction and high contact stress and stick-slip effects. A modularity drive section can generally be removed for maintenance while still leaving the telescope completely operational. It is very important for large telescope to decrease the operation cost and enable highest availability. The disadvantages of this system are relatively high cost and alight torque ripple and nonlinearities associated with electromagnetic cogging. But, with the development of material science, servo motor technology, control technology and manufacture technology, the cost of direct drive motor and its control system will be lower and lower in the future. All these make it possible for direct drive to be leading drive type adopted by future optical telescopes.