Research On Attitude-Orbit Coupled Dynamic Modeling And Control For Flexible Spacecraft

With the rapid development of aerospace technology,there are higher requirements for spacecraft dynamics modeling and control.Traditional spacecraft orbital and attitude dynamics modelling and control problems are divided and conquered.Today,since the application of technology is becoming more and more complex and the demand for precision is becoming more and more stringent,potential problems of the traditional method are gradually revealed.On the other hand,when a spacecraft with flexible appendages performs high-precision space missions,the influence of attitudeorbit coupling on control accuracy should be taken into account,as well as the influence factors of flexible appendages.Aiming at the above problems,this dissertation deeply studies the integrated attitude-orbit dynamics modeling and control method of spacecraft with flexible appendages,mainly including the following four aspects:Firstly,a rigid-flexible coupling attitude-orbit integrated dynamic model of spacecraft with flexible appendages is established.In this dissertation,dual quaternion and screw mathematical tools are selected to describe the spacecraft attitude-orbit integrated dynamics model.The dynamic equations of flexible spacecraft in body coordinate system are derived.Then,based on the dynamic model of general motion of rigid body,the integrated attitude-orbit dynamic model of flexible spacecraft based on dual quaternion is deduced,and then the integrated error dynamic model of attitudeorbit of flexible spacecraft is obtained.Aiming at the problem of integrated attitude and orbit control for flexible spacecraft,based on the derived attitude-orbit coupling error dynamic model,a linear sliding mode robust controller is designed by using logarithm of dual quaternion.The controller can realize asymptotic convergence of state error,i.e.asymptotic tracking of desired state.A terminal sliding mode robust controller is proposed,which can realize finite-time convergence of state error,i.e.,finite-time tracking of the desired state.A fast terminal sliding mode robust controller is designed,which can accelerate the convergence speed on the basis of finite-time tracking of the desired state.Aiming at unmeasurable velocity information or the inaccurate angular velocity information caused by gyroscope faults of spacecraft during on-orbit flight,the attitudeorbit coupling controller of flexible spacecraft without velocity screw is designed.Firstly,a velocity-screw-free attitude-orbit coupling controller for rigid spacecraft is deduced based on output feedback without disturbance.Then the controller design is extended to a velocity-screw-free attitude-orbit coupling controller for flexible spacecraft with measurable modal information and without external disturbance.Then an extended state observer is designed for more general cases.Based on the observer,the attitude-orbit coupling controller of flexible spacecraft is designed.In order to suppress the vibration of flexible appendages in attitude and orbit control of flexible spacecraft,some kinds of robust attitude-orbit coupling controller for suppressing the vibration of flexible appendages are designed.Firstly,when the flexible modal coordinates are known,the flexible vibration suppression controllers are designed for the full column rank of the coupling coefficient matrix and the unsatisfactory rank of the column respectively.Then,in the case of unknown and undisturbed flexible modal coordinates,based on observer technology,feedback controllers are designed for full rank of coupling coefficient matrix and non-full rank of column respectively,which ensures the finite-time tracking performance of state trajectory and achieves effective suppression of flexible vibration.