Research On The Parameters Identification And Attitude Tracking Coupling Control For The Mass Body Attached Spacecraft

For future advanced space mission, it would be a general problem for spacevehicle which carries unknown characteristic body (can be called as Mass BodyAttached Spacecraft MBAS) to implement orbit maneuver and attitude tracking. Forexample, during the missions of cleaning space junk to derelict orbit or atmosphere,executing samples return; spacecraft vehicles all need orbit maneuver to implementmissions. Different from the traditional spacecraft, these attached masses willchange the spacecraft system characters on its configuration and parameters,resulting in strong couple between orbit and attitude dynamics, and bringingenormous challenges for the control system to stay stable. Hence, it’s of importanttheoretical significance and wide application prospects to implement research onthe dynamics and control of such complicated nonlinear uncertain system as MBAS.Based on background of the attitude tracking stability control during the orbitpropulsion of the MBAS, this dissertation focuses on the mathematical model, masscharacteristic parameters identification and attitude tracking coupled controlproblem. The major contents of this dissertation are consisted the following parts.Firstly, the mathematical model of the MBAS is studied. As is known, anyresearch and analysis to system should be stretched out under correct mathematicalmodel. Hence, to establish the mathematical model of the MBAS is the basis andkey to the science research. According to the characteristics of the MBAS, thispaper abstract it as a multi-body system which considered the spacecraft as theplatform and the attached mass bodys as daughter bodys around the platform. Thegeneral mathematical models of the MBAS are proposed, in case that the quality ofthe spacecraft is constant or variable, and the relative movement of the attachedmass bodys is motorial or locked and etc. The mechanism of two interference suchas parameter interference and input interference caused by the attached mass bodysare analyzed in this paper, which will impact the stability of the attitude trackingcontrol system.Secondly, for parameter interference problem, the identification theory isadopted to estimate the mass characteristic parameters for the compensation in thecontrol system. The mass characteristic parameters of the MBAS are all unknown,and the perfect approach to identify these parameters is still studied. Through theanalysis of the unknown parameters and the optional signal source in themathematic models, the swing motion of the swivel engine is choosed as the signal source, angular velocity and acceleration are considerd as observed quantity. Onthis basis, the scheme for mass characteristic parameters identification is proposed.Because of the large change in parameters of the MBAS, a set of initial valuecalculating method is proposed to make the results convergence, considering theinitial momentum maybe not zero and noise in measured data. With the calculatedinitial value, the Levenberg-Marquardt algorithm is used for estimation of the masscharacteristics parameters. Furthermore, the numerical simulation is used to analyzethe affected factors to the accuracy of estimation, such as instrument error, engineoscillation time, engine oscillation amplitude and engine mass ratio, etc; andvalidate the algorithms and theory to solve the union identification problem for themass characteristic parameters.Finally, the attitude tracking coupled control problem during the propulsion ofthe MBAS is studied. For the parameters interference, the quasi-Euler angles andquasi-Euler angular velocities are proposed to convert the dynamics system of theMBAS with identified parametes into a perturb double-integral system. The controllogic is designed by the slide variable structure control theory. The stability of theclosed loop control system is anyalyed with input interference and identificationerrors. For the input interference problem caused by the engine during the orbitpropulsion, a strategy is proposed by using the swing of engine to make the thrustpoint to the platform centroid to avoid thrust interference. The command angles ofthe engine during the swing motion are derived. To make the thrust point theguidance direction, the coupled control attitude is establied with the quaterniontheory; on account of the relative state between the swivel engine and platform andthe guidance direction. Numerical simulation has verified that the proposed strategyand control logic can overcome the strong coupling interference and solve attitudetracking coupling control problem of the MBAS during the orbit propulsion.