Coupling-reduction Control Of Satellite Platform And Antenna

This dissertation is a pre-research project of civil aerospace, to study asynchronous orbit communication satellite with a deployable antenna, for solving thedynamics coupling problem of satellite platform and flexible antenna. Theoretically, thework starts with a new concept and control method of reducing dynamical coupling, theintensive research are carried out on engineering standard.In the view of engineering, flexible satellite attitude control problem has not beencompletely resolved as presented solutions all have some disadvantages to apply to thesatellite with large flexible antenna. It is needed to develop new solutions.The key nut of the flexible satellite attitude control is dynamical coupling ofsatellite platform and antenna, and coupling dynamics is always accompanied with poorcontrollability. Simply counting on controller design, to improve the performance ofattitude control system, is fruitless in this predicament. Unfortunately, current researchworks of flexible satellite attitude control are mostly localized to this way, so theproblem can not be resolved successfully.To cope with the difficulty of controlling satellite with large flexible antenna, thiswork finds its way by taking measures to change the to be controlled object, to improveits dynamical controllability. Then, better conttrol performace is obtained. Specificworks are as follows.Fundamentally, upon deep investigating the characterisatic of dynamics of flexibleatenna and satellite platform, a new control method of reducing dynamical coupling isproposed. Based on this concept, a coupling-reduction-mechanism for flexible antennaconnected to satellite platform is designed. The introduction ofcoupling-reduction-mechanism fundamentally changes the dynamical controllability ofsatellite.Dynamical model of a satellite with large flexible antenna connected to platformby coupling-reduction-mechanism is established. Derivation proves thecoupling-reduction-mechanism can reduce the degree of dynamical coupling.Comparative analysis of coupling-reduction and coupling control shows the degree ofcontrollability and observability. This tells qualitatively the reason ofcoupling-reduction-mechanism makes the satellite platform and flexible antenna becontrolled more easily. By combining dynamics equations of the satellite platform andflexible antenna, the entire satellite eigenvalue mobility is calculated, which indicatesquantitively that the controllability has been greatly improved.In accordance with engineering implementation constraints, an attitude controlsystem using scheme of pre-compensation and coupling-reduction is designed. The antenna angular position measurement relative to the satellite platform is the outer loopfeedback signal, and the inner loop employs the angular velocity of the antenna withrespect to inertial space. This constitutes a dual loop control system. Low bandwidthouter loop is to isolate antenna vibration, and high bandwidth inner loop to suppressfriction torque. Analysis of entire satellite demonstrates that the control system has agreat coupling-reduction performance.The control performance of coupling-reduction and coupling control system iscompared. The simulation datum show that the coupling-reduction control methodcould meet the system pointing accuracy and stability requirements. Furtherly, by usingdynamics model under condition of the centroid position uncertainty and addingcorresponding nonlinear elements, a more real model is established, to validate theeffectiveness of coupling-reduction control system under the influence of uncertainfactors. The robustness of the control system is verified with parameters perturbation inwide range in the model.In conclusion, this work carrys out the reserch on coupling-reduction control tosatellites with large deployable antenna, a new concept of control to reduce dynamicscoupling is proposed, and the new control system of coupling-reduction with satisfatoryperformance is designed. The putout theories in this dissertation are of theoreticalsignificance for some flexible satellite attitude control, and the designed control systemhas certain practical referential value for national satellite with large deployable antennain engineering.