Research On Thrust Control Of Colloid Thruster For Space Gravitational Wave Detection

At present,with the continuous advancement of space gravitational wave detection projects such as the "Tianqin",the micro-newton-level thruster used to maintain a resistance-free environment has become one of the key technologies in the project.In contrast,the initial thrust level of the colloid thruster is low,and multiple emitters can work together to broaden the thrust range,which is more suitable for precision applications including space gravitational wave detection.In this paper,a physical simulation model is established to qualitatively analyze thrust characteristics,and a closed-loop multi-emitter thrust control model is established based on experimental data;in order to solve the problem of 0.5 μN initial thrust and slow start-up response of a single emitter,this paper proposes a pre-applied voltage scheme and a pulse width control scheme improve the thrust control model,and finally integrate the task indicators into a comprehensive thrust control model.The following is the introduction to each part.Specifically,this article first uses the physical simulation model to qualitatively analyze the thrust characteristics and stable operating voltage range of the colloid thruster.In terms of thrust characteristics,analyze the influence of voltage,flow,and temperature on the steady-state thrust value;in terms of thrust stability domain,the physical simulation model can qualitatively analyze the thrust stability region under a certain flow rate according to the simulation results.Secondly,based on the experimental results under multiple sets of working fluids and voltages,combined with the theory and fitting-derived thrust calculation formula,this paper establishes the thrust model of the single-emitter colloid thruster,and evaluate its open-loop steady-state response and dynamic response by directly providing voltage and current commands;closed-loop control uses PI link to calculate emitter voltage command according to thrust feedback error value,flow rate adopts open-loop scheme,and obtains closed-loop single-emitter thrust simulation results.Judging from the steady-state thrust noise results,the closed-loop control can better suppress the low-frequency thrust noise below 1 Hz;the multi-emitter grouping scheme is adopted to obtain the closed-loop multi-emitter thrust control results,and at the same time the structure of multi-emitter colloid thruster is preliminary designed.Finally,in view to the problem that the single-emitter thrust lower limit of 0.5 μN in the results of multi-emitter thrust control,a passive flow rate supply method is proposed to achieve pulse width regulation within 50 ms response time;for the problem that the response speed of direct start does not meet the mission index requirements,A pre-starting method of applying flow and voltage which is lower than the starting voltage in advance is proposed to realize the rapid start of the emitter.So far,the optimization of the multi-emitter thrust control strategy has been realized.