Research On Dynamics And Control Of Spacecraft Electromagnetic Manipulation

With the development of astronautical technology and the increasing number of spacecrafts,on-orbit manipulate technology has gradually become research hotspot in aerospace field.Spacecraft electromagnetic manuipulate is achieved by installation of electromagnetic coils on both active spacecraft and target spacecraft.Electromagnetic fields are generated by the controllable coil currents to generate electromagnetic force / moment with each other,so as to realize the non-contact control of the target spacecraft.Not only effectively avoid the inherent shortcomings of traditional thrusters and contact control methods(such as plume pollution,propellant consumption,optical pollution,collision risk,etc.),electromagnetic manipulate also has characteristics of non-contact,continuous and reversible control.It has wide application prospects including spacecraft docking and separation,on-orbit assembly,formation flying,faulty satellite rescue and de-orbit of satellite,etc.In this paper,two situations of the full controllability(all current of electromagnetic-coils on active spacecrafts and target spacecraft are controllable)and under-actuated(coil current of the target satellite is constant and uncontrollabe)are considered.Concentrating on dynamics and control problems of spacecraft electromagnetic manipulate,this paper mainly investigates the system modeling,the relative position control of electromagnetic de-orbit,the angular momentum management,the relative attitude control of electromagnetic attitude correction and coupling control of attitude and orbit.(1)Spacecraft electromagnetic manipulate system modeling.Based on the assumption of magnetic dipole,the far-field model of electromagnetic force / torque is deduced by electromagnetic theory,and its error characteristics are analyzed.Taking into account the internal force characteristics of the electromagnetic force and the linearity of the Hill model,the trajectory of the orbital coordinate system is taken as the reference system.The governing equations of the electromagnetic derailment are derived using the Hill equation,the electromagnetic force model and the linear superposition principle.Based on the Euler equations,the dynamics model of attitude correction electromagnetic control is deduced.The dynamic characteristics of electromagnetic control are analyzed,including strong nonlinearity,coupling,model uncertainty and control ability.(2)Relative position control of electromagnetic de-orbit.Without considering the attitude control problem,the research on the derailment electromagnetic control under both driving conditions and under-driving conditions is carried out.Under full driving conditions,the energy distribution and optimization strategy under mixed thrust is designed.The nonlinear robust control of long-term state keeping and the electromagnetic steering method of orbital transfer are studied.For the non-contact electromagnetic control of under-driving,the electromagnetic control ability was analyzed.The orbit control scheme with under-actuated spacecraft was designed,and the electromagnetic derailment control algorithm was designed based on the artificial potential field method.(3)Angular momentum management of spacecraft electromagnetic manipulate.Based on the geomagnetic field model,the influence of the geomagnetic field on the accumulation of angular momentum during electromagnetic control of the spacecraft is analyzed.The angular momentum management is divided into the normal working mode and the angular momentum unloading mode.The normal and cosine-based coil current control strategies and the angular momentum management strategy based on the optimization of the magnetic moment distribution are designed under the normal driving mode.An angular momentum unloading method based on AC-DC hybrid is designed.Under normal driving conditions,the optimization strategy of angular momentum distribution and the passive angular momentum unloading strategy under angular momentum unloading mode are designed.(4)Relative attitude control of electromagnetic attitude correction.Based on the previous part of the strategy of angular momentum management,the non-contact attitude correction control strategy considering the optimal cumulation of angular momentum under all driving conditions is studied.The attitude control algorithm based on sliding mode variable structure is designed.For the under-driving attitude correction Electromagnetic control and its control ability are analyzed.Considering the influence on the target spacecraft orbit during the attitude correction,two control configurations of "one-to-one" and "two-to-one" are designed.On the basis of that,the under-actuated attitude correction control algorithm is presented.(5)Coupling electromagnetic control of attitude and orbit.Considering the coupling of electromagnetic manipulator,the relative attitude of the manipulator during electromagnetic de-oribt is achieved by designing a reasonable control scheme and relative configuration.Based on the designed control scheme,parameters and control ability analysis,and design of the attitude and rail coupling off-track electromagnetic control law.In summary,the thesis studies the dynamics and control of spacecraft electromagnetic control,verifies the feasibility of non-contact electromagnetic de-orbit and non-contact attitude correction technology from the perspective of dynamics and control.On the other hand,the task provides the basic control model and algorithm support.In the future launch of space missions,if the electromagnetic coil can be installed as a standard accessory on the spacecraft,it can play an important role in satellite docking separation,formation flying,rescue of faulty satellites,and de-orbit of failed satellites.Research work for electromagnetic manipulation theory and application of useful exploration,laid a solid foundation for further in-depth study.