Research On Maintenance And Reconfiguration Control Of Spacecraft Electromagnetic Formation Flight

As a novel spacecraft formation technology,the spacecraft electromagnetic formation attempts to control the relative motion of spacecraft by using the coupled electromagnetic force generated by the interaction between the electromagnetic field.Compared with the traditional thruster-based spacecraft formation,it has some prominent advantages,such as no propellant consumption,no plume contamination,and non-contacting,continuous and synchronous control features,ensuring its broad prospect of application in such fields as deep space exploration and ground monitoring.Because of the special nature of the electromagnetic force,the strong nonlinearity and coupling of the spacecraft electromagnetic formation dynamics model,the spacecraft electromagnetic formation control faces new problems and challenges in theory and method.Based on an analysis and summary of the research on spacecraft electromagnetic formation control at home and abroad,this paper focuses on the relative orbital motion control of spacecraft electromagnetic formation,and mainly investigates the reconfiguration control,formation keeping control,finite-time orbital coordinated control,and attitude-orbit coupling control of spacecraft electromagnetic formation by comprehensively applying dynamic system theory,graph theory and related control theories.The main contents include the following parts:The optimal reconfiguration between equilibria of a two-craft electromagnetic formation without considering the influence of perturbation is studied.The relative translational dynamic model of a two-craft electromagnetic formation without perturbation is derived based on the Hill equation.The three equilibrium configurations of two-craft electromagnetic formation are solved,namely,the two crafts aligned with orbital radial,normal and tangential directions respectively.And the magnetic moment collocation and stability of radial and normal relative equilibrium configurations are theoretically analyzed.The invariant manifolds of the radial and normal relative equilibrium configurations are numerically solved and analyzed.Based on the invariant manifold theory,nonlinear programming theory and particle swarm optimization algorithm,a reconfiguration optimization method is proposed to transform the reconfiguration optimization control problem into nonlinear programming problem,which is then solved by the particle swarm optimization algorithm.The numerical simulations demonstrate the effectiveness of the proposed method.The formation keeping robust control problem of a two-craft electromagnetic formation under the influence of disturbance is studied.The internal force characteristics of the inter-satellite electromagnetic force determine its inability to control the movement of the formation mass center.Considering the influence of perturbation on the formation mass center,the formation keeping control strategy of "feedforward control + feedback compensation" is proposed.The feedforward control is used to maintain the desired formation configuration,and the feedback compensation control is used to compensate for the configuration deviation caused by the disturbance.The electromagnetic force formula and magnetic moment collocation are deduced,and the uncertainty of external perturbation and far-field electromagnetic force model is regarded as the equivalent sum disturbance to derive the relative motion dynamic model of the two-craft electromagnetic formation under the influence of disturbance.The feedforward controller is designed based on the expected formation configuration.The active disturbance rejection feedback controller is designed based on the active disturbance rejection control technology and low-pass filter.The effectiveness of the proposed control strategy and controller are verified by numerical simulations.The finite-time orbit coordinated control problem of the electromagnetic formation is studied.The control strategy for electromagnetic formations is given,and the general relative translational dynamic model of spacecraft electromagnetic formations is derived.The graph theory is used to describe the communication topological relationship between spacecraft.In the case of undirected communication,based on the terminal sliding mode technology,the sliding surface of the formation system with inner-outer ring two-layer structure is designed,and a finite-time formation coordinated controller is designed.Both theoretical analysis and numerical simulation show that the designed formation coordinated controller ensures that the tracking error of the formation system converges to the origin within a finite time.In the case of directed communication containing the directed spanning tree,based on the adaptive theory and sliding mode control theory,an adaptive sliding mode extended state observer is designed to estimate the disturbance.Based on the output information of the extended state observer and adaptive control method,a robust adaptive formation coordinated controller is designed.Theoretical analysis and numerical simulation show that the designed robust adaptive formation coordinated controller can guarantee the finite-time convergence characteristics of the closed loop system.The attitude-orbit coupling stability control problem of a two-craft electromagnetic formation in deep space in a long term is studied.The application of spacecraft electromagnetic formation is extended to deep space.The nonlinear attitude-orbit coupling dynamic model of a two-craft electromagnetic formation in the circular restricted three-body problem is derived by utilizing analytical mechanics theory.Without considering the perturbation effect,a full state feedback optimal controller is designed based on the nonlinear quadratic optimal control theory.When the velocity information is unmeasurable,a finite-time state observer is developed based on the sliding mode theory to observe the velocity information.Combined with the output information of the state observer and the full state feedback optimal controller,a partial state measurable output feedback optimal controller is put forward.Then,taking the perturbations into account,the effects of the solar gravity and solar radiation pressure are analyzed.By constructing the performance index function including the perturbation threshold,the robust control problem of two-craft electromagnetic formation under perturbation is transformed into an optimal control problem,and the suboptimal control method is developed to solve the optimal control problem and indirectly obtain the attitude-orbit coupling robust optimal controller for a two-craft electromagnetic formation.Theoretical analysis and numerical simulations show that the proposed robust optimal controller not only ensures the quadratic performance index optimality,but also suppresses the state-associated disturbances.