Research On Parameter Identification And Robust Control Of High-precision Servo Method For Large Radio Telescope

With the development of the times and the increasing demands for radio astronomy,radio telescopes are bound to develop towards high frequency bands and large apertures.High-frequency electromagnetic wave signals needs a higher pointing accuracy,the ever-increasing caliber leads to a further decrease in the natural frequency of the structure itself.drive flexibility and structural flexibility continue to increase,in addition,due to the effects of friction,backlash,and wind disturbance,high-precision pointing control becomes an engineering difficulty.For this reason,according to the characteristics of the large radio telescope servo pointing system,a double-loop composite control framework is constructed.based on this framework,the following contents are studied.Parameter identification.The dual-loop compound control framework includes an inner-loop controller and an outer-ring controller.The inner-loop controller adopts a PI+LQG control algorithm,The algorithm needs to know the more accurately state space equation of the controlled object.Aiming at this problem,a method is proposed.Parameter identification method based on nontraditional step signals.This method can obtain the transfer function of the system within a certain error range,and then obtain each physical parameter,obtain the system state space equation that is more accurate,and also can identify the system's lag time.Robust controller design.Large radio telescopes are affected by a variety of disturbances and uncertainties.Firstly,considering the wind disturbance,a wind disturbance model of steady wind and random wind is established,and the mechanism of random wind entering the servo control system is studied;the parameter uncertainty in the uncertainty factor can be obtained from the error range in the parameter identification process;finally,the non-linear factors such as various frictional backlash existed in electromechanical servo system of large radio telescope are analyzed.Under the influence of all the above factors,in order to keep the system stable and ensure high enough pointing accuracy,a robust controller based on Bode diagram is designed.The core idea of this controller is to embody all uncertainties and disturbances as the restricted area of the system's Bode diagram,and the a robust controller is designed to make the frequency response curve of the system not to cross the restricted area to achieve the purpose of control.Hardware-in-the-loop simulation system experiment.At the end of the paper,a two-inertia system is built on the semi-physical simulation system,and the proposed parameter identification method and robust controller are tested.The experimental results show that the parameter identification method can accurately identify the physical parameters of the system within the error range.The robust controller can suppress the unfavorable influence of the uncertainty factors on the system under the inner ring and the double ring,and ensure the high enough pointing.Accuracy.In this paper,generalized parameter identification method and robust control algorithm are proposed to provide reference for designing the controller and designing steps for designing controllers for future QTT projects.