Single Mass Drag-free Control Based On The High-gain Observer

With more and more tasks for science measurement based on the satellite,the application of drag-free control is becoming more and more common,and for the current gravitational wave detection mission which is being vigorously promoted,the accuracy of drag-free control is further improved.In the high orbit of the earth,the thrust noise of micro level thruster and the disturbance of solar light pressure are one of the main reasons to affect the detection accuracy.The thrust noise mechanism is different because of different types of thrusters.In this paper,the thrust noise data of micro level thruster collected in practice is taken as the main disturbance model,and the disturbance suppression of drag-free control is studied by using the control method of feedback control based on the high-gain observer.Firstly,the relative motion equation of the satellite platform and the detection mass is established for the translational direction of the single mass drag-free system,aiming at the displacement mode of the drag-free control adopted in the gravitational wave detection.The main disturbance models including thruster thrust noise and solar light pressure are established,and the mechanism of other small disturbance forces is established.And the corresponding noise signal model is designed for the measurement noise of the sensor,which provides the basis for the subsequent simulation analysis.Then,the design of the high-gain observer and its main characteristics,including the disturbance immunity,peak phenomenon and separation theorem,are analyzed and the design method of the extended high gain observer is given.The PD feedback controller based on extended high-gain observer and the appropriate parameter design are given in combination with the drag free model,and the Bode curve analysis for the performance of the controller is given.Combined with the deduced control transfer function,a group of equivalent PID design methods are given,and a comparative analysis is made.Finally,the simulation platform is built.For the disturbance signal sources such as thrust noise,PD feedback controller based on extended high gain observer is designed.Through the analysis of the disturbance suppression effect,the effectiveness of the controller is verified.Combined with the measurement noise model,the influence of the measurement noise on the controller is analyzed.