Design Of Antenna Servo Control System Of The Large Telescope

Large aperture radio telescopes are the crucial observation facility of astronomy, as theantenna structure growing huge, it is ineligible that the problem of structural vibration isserious. To improve the pointing accuracy and the performance of disturbance rejection, it isurge to improve the design level of large diameter antenna system.Optimal control theory is advanced control algorithm developed from modern controltheory, considering the problems of system optimal performances, energy consumption,minimum time and other specifications under given constraint conditions. By studyinginternal states in system, optimal control theory is more appropriate for analyzing antennaservo system possessing complex dynamic.However, optimal control theory requires accurate model to study all the internal statesof system, and the order of identified model could be too high because of the measured noise,what’s worse, high order controllers are also related to the design of observer highrequirement. Therefore, solving the problem of the accuracy of identification and theimplementation of high-order controller is the key of realizing optimal controller. For thesereasons, this article put forward modal truncation solving order-swelling in modelidentification, and also makes the reduced-order controller practicable; applyingcomprehensive high-accuracy optimal control algorithm based on internal model to improvepointing accuracy and tracking performance of the servo system. The system model, derivedfrom physical modeling or simple system identification, is too simple or too complicated.Also, servo system designed by PI controller, presenting simple control structure， isincapable of reaching high-precision servo performance facing to the control problem inantenna structure presenting high-frequency resonance. The reduction algorithm that thisarticle puts forward combines the experience knowledge and the objective information fromphysical modeling and system identification, applying advanced system identificationalgorithm acquired valid reduced model through modal truncation. Under these performancerequirements for large aperture antenna recently, we put forward LQR and H optimalreduced-order controller based on internal model, and conclude that with these controllers the antenna servo system presents better servo performance and disturbance rejection.Aimed at model identification, model reduction and control system design, this articleapplies modal truncation to real antenna and design the servo system applying H optimalcontrol algorithm based on internal model principle. This experience can not only provideeffective solution for the design of large aperture antenna control system, but also be anexample for the servo control systems of the same kind.