Research On Stability Of Binary Asteroids System And Mission Orbit Design

Due to its unique form of movement,binary asteroids have the capacity to provide significant clues for the evolution of the planets.Thus general interest for asteroids detection.mission is aroused.In this paper,based on the detection of the binary asteroids system,the equilibrium state and the stability of the binary asteroids system,the design of natural capture and escape orbits,the design of optimal transfer in binary asteroids system,and the binary asteroids landing control are investigated.In addition,binary asteroids system,Lundia,is aimed for mission orbit design and research.The main research results are as follows:Firstly,directed at the full two-body problem of the double-ellipsoid model,the equation of motion of the binary asteroids system is established through the Lagrangian equation,and the equilibrium state and stability of binary asteroids system are obtained.Based on the equilibrium state of binary asteroids system,the control equation is obtained for determining the stability of the two-body asteroid system.For binary asteroids system with different physical parameters,the influence of physical parameters exerted on the stability limits and the type of stability is discussed.Secondly,based on the stability set theory,the design of natural capture and escape orbits meeting certain conditions under equilibrium state is targeted at.The initial condition parameters space is spatially discretized.And According to the criteria of stability,escape,and impact,the initial condition parameters are classified,acquiring initial condition parameters of natural capture and escape satisfied.Thus,the corresponding capture and escape orbits satisfied with certain conditions are constructed.Thirdly,the optimal transfer orbit planning problem in binary asteroids system is studied.Based on the convex optimization,exploiting the lossless convexification of the nonlinear dynamics and nonlinear constraints corresponding to the transfer problem,the optimal transfer orbits of finite-thrust in the binary asteroids system are optimized by successive solution method(SSM).The influences of transfer time,thrust amplitude and initial mass of vehicle on transfer process are analyzed,which provided design basis for the optimal transfer orbit.Finally,the higher-order sliding control strategy is employed to design the precision landing trajectory on the surface of a primary in binary asteroids system.The impact of various control parameters on the landing process is analyzed.In addition the PWPF(Pulse-Width Pulse-Frequency)method is applied to convert the continuous control acceleration obtained by the second-order sliding method into a discrete control acceleration in the bang-bang form.The optimized control parameters and PWPF parameters are used to performe Monte-Carlo simulation to verify the robustness of the control law.