| As large-scale low-Earth-orbit（LEO）constellations are rapidly deployed,the scarcity issue of LEO resources is becoming increasingly pronounced.The application value and strategic significance of very-low-Earth-orbit（VLEO）micro/nano satellites below 300km in fields such as disaster warning,military reconnaissance,and internet communication have garnered significant attention and importance.The ability to maneuver the attitude and orbit is an essential technical prerequisite for satellites to perform complex space missions.However,the denser and highly uncertain space atmosphere environment in VLEO poses significant challenges to the attitude and orbit control systems of micro/nano nanosatellites with limitations in mass,volume,and power consumption.This thesis focuses on the research of aerodynamic control technology for the micro/nano satellite in VLEO,and specifically delves into the schemes and algorithms of mass-moment attitude control,differential aerodynamic formation control,and attitude-orbit coupling system control.The main work contents are as follows:（1）Aiming at the problem of complex and uncertain dynamics of VLEO satellites,research on the attitude,formation,and aerodynamic models of multi-rigid body satellites is conducted,and a universal model building method for the attitude dynamics of active component satellites based on vector mechanics and an aerodynamic force analysis method based on the Maxwell distribution are proposed.Firstly,based on the generalized moment of inertia theorem,the attitude dynamics equations and the moving mass dynamics equations of the mass-moment satellite considering parameter uncertainties are derived;the existence forms and action mechanisms of system disturbances are analyzed.Secondly,based on the assumption of circular orbit and close distance,the relative motion dynamics equations of the satellite formation considering the average J2 perturbation effects are derived.Then,by simulating the flow form,density,and velocity of atmospheric particles,the variations and influencing factors of the VLEO atmospheric environment are analyzed.Finally,the interactions between the satellite surface and atmospheric particles in space and aerodynamic force generation mechanisms are clarified;the complete expression of aerodynamic coefficients based on the Maxwell distribution is derived,and the aerodynamic drag and lift models are provided.It is concluded that the density,direction,and velocity of space atmosphere particles exhibit periodic fluctuations related to orbital periods and have significant uncertainties.As the accommodation coefficient of the satellite surface material decreases,the lift-to-drag ratio increases,and the aerodynamic control ability for the satellite’s attitude and orbit is correspondingly improved.（2）Aiming at the problem of poor attitude control stability in mass-moment satellites caused by inertial disturbances,research on the dynamics characteristics,additional disturbances,and attitude control mechanisms is conducted,and a composite attitude control scheme is proposed based on the filter observer and the adaptive backstepping algorithm.Firstly,from the perspective of dynamics and numerical simulation results,the motion characteristics of the mass-moment attitude control system are analyzed,and the influence mechanism of factors such as stroke,mass and installation position deviation on additional disturbances is clarified.Secondly,based on the aforementioned dynamic characteristics analysis,the dynamics model of the mass-moment mechanism with double symmetrical layout is simplified,and the error attitude control equation is given.Then,a compensation method for strong aerodynamic disturbances of VLEO satellites using mass moment control technology is proposed,and a double-loop attitude stabilization control scheme based on a filter observer is designed.Finally,a combined attitude maneuvering control method of aerodynamic torque and magnetic torque is designed,and an adaptive backstepping control algorithm considering multiple constraints on control inputs is proposed.Numerical simulation results show that the compensation control and the maneuvering control accuracy reach±0.05°and±0.5°,respectively.The filter disturbance observer accurately tracks the slow time-varying system disturbances,and the gain of filtering additional disturbance can reach-6d B.The adaptive convergence parameter reduces the input overshoot of the actuator,and improves the attitude convergence speed by 40%.（3）To overcome the limitation of differential aerodynamic control technology being restricted to two-satellite formation control due to the differential form of the input,research on the complex feasible domain of control inputs and the decoupling method of aerodynamic drag and lift is conducted,and a multi-satellite formation extension strategy based on the PWA-MMPC（piecewise-affine Multiplexed Model Predictive Control）algorithm is proposed.Firstly,the form and feasible range of the complex input of the differential aerodynamic control method are described,and the difficulty of extending this method due to the strong nonlinearity of the control matrix and the complex constraints of the input boundary is analyzed.Secondly,a single-yaw differential aerodynamic control method is proposed,and the underactuated control system characteristics and the system state reconstruction method are clarified by comparing with the reorientation control method.Then,a multi-satellite formation extension strategy based on the idea of alternately updating inputs is proposed for this multi-input control system,Finally,to meet the requirement of alternately updating inputs,a PWA-MMPC algorithm suitable for piecewise-affine models is proposed,and its feasibility and stability conditions are analyzed.Numerical simulation results show that this algorithm can execute control according to the given input sequence,achieving relative motion accuracy of±1m and stability of±0.01m/s.The calculation time is much shorter than that of traditional MPC algorithms,and it can be distributed to each satellite for operation.The tracking ability and error compensation ability of the differential aerodynamic control increase as the control cycle shortens,and the method gradually becomes less effective as the formation size increases.（4）Aiming at the problem of inadequate attitude maneuverability of aerodynamic control for formation control,research on the specific aerodynamic configuration of satellites and the attitude-orbit coupling aerodynamic control scheme for is conducted,and a control scheme of the attitude-orbit coupling high-order cascade system is proposed combining the mass-moment control technology and the differential aerodynamic control technology.Firstly,the influence mechanism of the satellite’s specific configuration and stable flight attitude on the aerodynamic control capability is analyzed;on this basis,a vertical-diagonal-sail satellite configuration is designed,and the mathematical model of the attitude-orbit coupling control system of the mass-moment satellite in VLEO with thrust is described.Then,a double-loop control scheme and a high-order cascade control scheme are designed for this system;the applicability and similarities/differences of each scheme are compared,and the piecewise-affine linear control equations are derived.Finally,aiming at the problems of additional disturbance and convergence speed,an adaptive PWA-MMPC algorithm based on the idea of control sequence adaptive switching is proposed,and its feasibility and stability are analyzed.The numerical simulation results show that the tracking capability and disturbance response capability of the high-order cascade control scheme are better than those of the double-loop control scheme,but for the former,the selection of weight parameters is relatively difficult.The control algorithm greatly reduces the additional disturbance and the attitude dynamics coupling,and effectively improves the attitude control stability and convergence speed by real-time adaptive planning of control input sequence.The attitude control accuracy and stability reach±0.5°and±0.1°/s,respectively.（5）To promote the engineering application of the proposed aerodynamic control method,a prototype of the mass-moment actuator is developed,and a semi-physical attitude-orbit simulation platform is built.Firstly,a real-time semi-physical attitude-orbit simulation platform is designed for a 50kg micro/nano satellite in VLEO,achieving a millisecond-level iterative step size,and the attitude control actuators are physically accessed.Then,a prototype of the mass-moment actuator based on the through-type linear screw stepper motor is developed,and its related motion performance is tested;the motion information is measured by an asynchronous encoder so that it can be connected to the semi-physical simulation platform.Finally,based on the designed simulation platform,a specific flight mission for the aerodynamic control of a three-satellite formation in VLEO is designed to further verify the high-performance attitude and orbit aerodynamic control schemes and algorithms proposed in previous chapters.The semi-physical simulation results show that the composite control accuracy of the attitude of the mass-moment satellite can reach±2°.The effect of the high-order cascade attitude-orbit coupling control scheme is significantly better than that of the double-loop control scheme,and its relative motion control accuracy can reach±5m.The aerodynamic control of the VLEO satellite will only slightly speed up its orbit decay speed,but it can save propellant and greatly prolong the satellite’s orbiting time and working life.This control scheme is more suitable for the close-range formation control and the constellation phase control.This thesis conducts in-depth research on the schemes and algorithms of mass moment attitude aerodynamic control,differential aerodynamic formation control,and attitude-orbit coupling cascade system control.The accuracy and reliability of attitude and orbit aerodynamic control for micro/nano satellite formations in VLEO are improved.Relevant research will expand the ability of micro-nano satellites in VLEO to perform complex space missions and provide technical support for its large-scale application in civil aerospace,space attack and defense and other fields. |
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