Design And Optimization Of The Cusped Filed Thruster Controller Based On Multiple Control Methods

The detection of space gravitational wave is of great significance for human astronomical observation and spatiotemporal change information understanding.Micro-newton electric propulsion system is vital for gravitational wave detection.In order to ensure the static and stable operation of gravitational wave detection spacecraft,the requirements of wide range continuously adjustable thrust,low thrust noise,high thrust precision,fast response and long life-span are put forward for the micro-newton electric propulsion system.When the satellite is in orbit,the micronewton electric thruster should compensate the non-conservative force in time so that the satellite is in a drag-free state.Cusped field thruster has the advantages of wide thrust range and stable discharge,thus it becomes one of the alternative thrusters for gravitational wave detection mission.In the laboratory of the author,microwave is creatively fed into the cusped field thruster,which can effectively reduce the lower limit of working fluid.However,at present,there is no precise understanding about the characteristics of microwave cusped field thruster,such as micro-newton adjustability,thrust noise,thrust output model and so on,yet the feasibility of its application in high-precision gravitational wave detection mission is not clear.Therefore,the measurement,evaluation and optimization of the thrust characteristics and the design of the controller based on the thrust characteristics have become the focus of this paper.In this paper,the thrust range and adjustability of the microwave cusped field thruster will be explored through the thrust steady-state and adjustment experiments.Next,the output thrust noise evaluation experiment of microwave cusped field thruster is carried out,the influence of input and environmental parameters on thrust noise is analyzed.On the basis of the experimental results,the output thrust model is established with fitting algorithm by using the steady-state thrust data of the microwave cusped field thruster.Fitting error is calculated and input parameter fluctuation is substituted to evaluate thrust model.Then,under the consideration of three input parameters,the command of output thrust is decomposed,the allocation strategy of input parameters is obtained,and the sensitivity and dynamic response characteristics of multi parameters are analyzed.Finally,combined with the measured thrust noise of the microwave cusped field thruster,a noise suppression method of closed-loop feedback thrust control for the internal of thruster is proposed,and an appropriate PID controller is designed.The high-frequency closed-loop adjustment is carried out by using the fast response characteristics of the electrical signal parameters,and the open-loop adjustment gain is increased for the slow flow response,so as to realize the closed-loop control of the output thrust and restrain the influence of disturbance on thrust noise.Through the research of this topic,we have a deep understanding of the steadystate and dynamic characteristics of the microwave cusped field thruster,verify the feasibility of its application in the gravitational wave detection satellite,and lay a foundation for the application of the micro-newton propulsion system in the space gravitational wave detection mission.