Study On Formation Configuration Control Of Distributed Satellites

Distributed Satellite System (DSS) has been well concerned because of its unique technical advantages and good prospects in applications. Control of formation configuration is an important section of coordinate control, which is the key technique to enable distributed satellite. Therefore, control of formation configuration is of great importance to the development of DSS. Considering some certain missions, control of formation configuration and its correlative techniques were studied in the thesis.Firstly, the constitution mechanism of formation configuration was studied. The dynamic equations and the kinematic equations of relative motion were derived and analyzed separately. Based on the definition of formation configuration parameters, the determination formulas for formation configuration were given, followed with a detailed analysis on the effect of the orbit elements'errors on the formation configuration.Secondly, the stability of perturbed configuration in LEO was analyzed on the basis of the kinematic equations of relative motion. The change of the configuration general parameters was studied with the use of perturbed equations described with non-dimensional Delaunay variables, and then the adjustment of semi-major axis was derived to compensate the J 2 perturbation. Using the model of atmosphere density including daily effect, the difference of orbital energy consumption between the formation flying satellites is analyzed, from which the along-track drift law of the formation configuration was derived. And then two methods for the adjustment of area-mass-ratio were designed to compensate the atmosphere perturbation.Thirdly, formation optimized design was studied for the distributed SAR. On the research of the coverage performance of the distributed SAR, the reference orbit was designed to meet with the requirement of the integrated design, and the effect of the technical parameters on the mapping duration was analyzed. Taking the system performance as the sufficiency function, genetic algorithm was used to optimize the formation configuration. Based on the parameters of several typical SAR satellites, a number of formation configurations were designed. The result indicated that the configurations can guarantee the accuracy of the height measurement or the ratio of the measurable velocity to fulfill the mission.Fourthly, the control of the along-track drift of the formation was studied based on atmosphere drag. With a detailed analysis on the principle of the control, phase-plane method and fuzzy control method were presented. According to the phase trajectory of along-track drift, the switching function with the oblique lines was designed in order to converge the initial errors, and the limit cycle was analyzed correspondingly. To deal with the instability of the along-track drift of the configuration, the fuzzy control method was presented. Based on the fuzzification of the inputs and outputs, the fuzzy rules and the defuzzification algorithm were designed, followed with the analysis of the stability of the controller.Fifthly, the control of the formation was studied based on impulse thrust. According to the limitation of the baselines, the control scheme was designed using the drag panels and impulse thrusters. In order to prolong the control duration to meet the requirement of the mission, the adjustment strategy of the configuration was presented by offsetting the parameters. The cross-track control and co-plane control were studied based on impulse thrust, by which the permanent control of the formation could be enabled. The fuel consumption of the method was analyzed, and the simulation result indicated that the mass of propellant used in the formation control was only 1.73% in proportion to the total mass, on the condition of the control scheme proposed in the thesis.Finally, precise maintenance of formation was studied based on continuous micro-thrust. Nonlinear feedback control law was derived using Krassowski's theorem. Then, the effects of the feedback coefficient, navigation error and thrust error were studied with numerical simulation. Based on the nonlinear feedback control law, the precise maintenance of the inner formation for the gravity field observation was studied at the end.