| The large scale reflecting telescope is the main target which modern telescopes develop towards.It is widely used in different fields including space observation,military detection and celestial motion observation.The primary mirror supporting system is one of key technics of reflecting telescope and its performance will affect the accuracy of telescope observation directly.Among solutions of the primary mirror supporting system which are under studying and applying,the hydraulic supporting system is regarded as a better choice because of its advantages such as high accuracy,uniform supporting force and fast adjustment.However,it is difficult for this hydraulic supporting system to achieve the target of high accuracy and fast response,which is related to the rationality of the design and many different factors in every section of this system.This thesis gave a lot of information of the large scale reflecting telescope on studying and applying in China and abroad,which was the basement of the design of one test platform about the primary mirror hydraulic system.And the bulk-modulus of the oil in the hydraulic section of this test platform was regarded as the key object of this thesis and was used to analyze its influence on the dynamic performance of the primary mirror hydraulic system.Through being improved by a vacuum-pump deaerating device designed in this thesis,the bulk-modulus of the oil became a variable affecting the dynamic response and dynamic accuracy of the primary mirror hydraulic system in simulation and experiment.The major contents are summarized as follows:In chapter 1,the research background and the significance of this thesis were presented.On the basis of existing primary mirror supporting techniques in domestic and overseas,one technic difficulty that the primary mirror hydraulic system needs to have high accuracy and fast dynamic response was concluded.By analyzing general hydraulic system,the studying direction of this thesis on the influence of the bulk-modulus of the oil towards the dynamic performance of the primary mirror hydraulic system was proposed.Several factors affecting the bulk-modulus of oil were analyzed and many ways of improving the bulk-modulus of oil were compared.The way of vacuum-pump deaerating was a good one because of its clear theory and easy design.At last,the major contents were proposed.In chapter 2,according to the requirements of control accuracy and response speed of the primary mirror system,one test platform consisting of a oil compensation device and an electronic control unit was designed.Compared with other driving solutions,the solution of a servo motor and a screw was determined.The displacement of the servo motor was controlled by control board and driver.The performance experiment of the primary mirror hydraulic supporting unit in chapter 5 was based on this platform.In chapter 3,the bulk-modulus of oil was analyzed and optimized,which was the basement of the simulation in chapter 4 and experiments in chapter 5.By way of theory and numerical analysis,the relationship among the bulk-modulus of oil,gas content,pressure and temperature in a closed container was clear.Based on this relationship,a vacuum-pump deaerating device was designed.It was used to process the oil under different conditions and the results of gas content experiments verified its usage and the correctness of the relationship above.At last,different values of the bulk-modulus of oil were present by oiling experiment and calculation.In chapter 4,a mathematical model with electricity,mechanics and hydraulics was built towards the primary mirror hydraulic supporting unit composed of a supporting hydraulic cylinder and an oil compensation device designed in chapter 2.Several factors including the bulk-modulus of the oil,the displacement of amplifying hydraulic cylinder and the supporting hydraulic cylinder in this model's hydraulic section were analyzed and were regarded as variables to simulate their influence laws on the primary mirror hydraulic supporting unit through MATLAB software.In chapter 5,an experiment platform made up of the oil compensation device and electronic control unit designed in chapter 2 was built.Firstly,the mathematical model of hydraulic section in chapter 4 was verified.Secondly,the vacuum-pump deaerating device designed in chapter 3 processed the oil in different conditions and achieved different values of the bulk-modulus of the oil.Thirdly,the dynamic response and dynamic accuracy experiments were done to verify on the influence of the bulk-modulus of the oil towards the dynamic performance of the primary mirror hydraulic system.In chapter 6,the full text of the work was summarized and the following research work was prospected. |
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