Research On High Accuracy Navigation And Control Method Of Fractionated Spacecraft

Fractionated Spacecraft System(FSS)has received growing attention for its unique technical advantages and extensive application prospect,which will bring great innovation to spacecraft applications.Currently the research of FSS mainly focused on dynamic/kinematic modeling and navigation control method,which covered modeling and controlling of orbital dynamics/attitude dynamics,integrated navigation,sensors and actuators,data processing and computation,etc.This paper systematically studied the integrated navigation and cooperative control of FSS in view of spacecraft dynamics,navigation,and control.The content of this paper summed up as follows.Firstly,for the problem of orbit and attitude dynamic modeling of FSS,the orbital/attitude dynamics equations are established according to the operation characteristics of spacecraft.FSS orbital characteristics are analyzed,and on the basis of spacecraft's single-body model this paper established FSS sub-function module's relative orbital dynamic equation.Secondly,this paper researched the navigation problem of FSS,designed the integrated navigation algorithm for position measurementbased on multi-sensors.Considering the characteristics of FSS's sub-modules,which topological structure built through communications,this paper designed the multi-sensor multi-spacecraft cooperative positioning algorithm of FSS and conducted analysis of numerical simulations.Simulations shown that the integrated algorithm designed is capable of improving satellite navigation precision and fulfilling the complex task's requirement.Thirdly,through the study of FSS onboard star-sensors' operation characteristics,this paper presented multi-info attitude determination algorithm and star identification process,which use innovational star feature extraction methods to solve the problem of observation reliance and poor anti-interferences of existed methods.Based on star-sensor/gyroscope's multi-info attitude determination method,this paper designed their measurement model,proposed modified AIEKF algorithm for the nonlinear approximate error problem.Also,an attitude measurement scheme is proposed in case of star-sensor unavailable,based on the study on star-sensors visibility calculation method in different space environment and star-sensors visibility's influence on attitude determination accuracy.The simulation verified the effectiveness of proposed star identification method and improved attitude filtering algorithm.Fourthly,FSS configuration's adjustment and preserve processes require attitude tracking.Due to the uncertainty of FSS dynamic model and the feature of tracking control,this paper designed a new sliding-mode observer based on the advantage of integral in control principle.On the basis of this observer,its self-adapt integral slider-mode controller is designed.Considering FSS attitude control system's model parameter uncertainty and the nature of the sliding-mode controller system's trembles,Lyapunov stability theorem is used to prove designed controller's slide-mode accessibility and overall stability.Finally,spacecraft's cooperative features of multiple sub-modules are studied based on the topological configuration of FSS's sub modules.Due to the attitude control system,application of homogeneous theory in control system is researched in this paper.Consulted the attitude description method of Modified Rodrigues Parameters(MRP),this paper researched both single and multiple spacecraft in FSS,designed corresponding controller to ensure the finite-time convergence of attitude control system.Multiple simulation results and mathematical analysis proved the effectiveness of the developed controllers.