4m SiC Primary Mirror Hydraulic Support System Optimization Design

In the course of the elevation of the 4m telescope, the primary mirror will produce large rigid body displacement due to its own gravity and acceleration, which will affect the imaging quality of the telescope.The traditional passive axial support means, such as lever counterweight, mechanical whiffletree support and other passive support ways can not guarantee the the relative position of the primary mirror with the cell, which difficult to to be used for 4m and above telescope, so, for the 4m telescope presents a hydraulic whiffletree supporting system which not only bear the weight of the main mirror but also ensure the relative position of the primary mirror and the cell. Foreign telescope such as:8.2m VLT, 8.1m Gemini and 3.67 m AEOS and so on,of which primary mirror have been used this hydraulic whiffletree support technology.The temperature range of 4m telescope is large, which makes the response characteristic of the hydraulic system is very large. In order to improve the response characteristics of the hydraulic system at low temperature, the hydraulic system is optimized, and the main contents are included:In the first chapter, the support method of the 4m level and above telescope at home and abroad is summarized, and the advantages and disadvantages of several common methods are analyzed.In the second chapter, the structure of VLT and AEOS telescope axial hydraulic support system is analyzed, and according to the characteristics of 4m SiC primary mirror, the suitable structure is selected. The whole of the hydraulic support system is designed and the mathematical model of it has been built. The stiffness, natural frequency, damping and pressure loss of the hydraulic support system also are analyzed.In the third chapter, according to the hydraulic system of 4m telescope, the suitable working medium, accumulator, pipeline, etc was chose, the optimum design of axial and lateral hydraulic system is optimized. The suitable diameter and connection mode are selected, the influence of the oil bubble content and pipeline length on the response characteristics of response characteristics is also analyzed.In the fourth chapter, the shrinkage ratio experience of the hydraulic support system of 4m is built by 1.23 m SiC primary mirror. The open loop response characteristics of the 3 partitions of the primary mirror are measured;the natural frequency of the primary mirror chamber is measured by the modal test apparatus, and the stiffness of the axial and lateral support system is obtained. The results are cored with the simulation results.The fifth chapter summary the main research work of this paper, innovation points and the next step of the work plan.