Research On Orbit Control Technology Of On-orbit Maintenance To GEO Satellite Based On AOTV

Conforming to the developing upsurge of space technologies in our country, it is aintending space technology’s development trend of taking a research on the technologyof geostationary earth orbit (GEO) satellite’s on-orbit maintenance by using a reusablelaunch vehicle which travels between space station and geostationary earth orbit.Aeroassisted orbital transfer vehicle, to be a new type of trans-atmospheric orbitaltransfer vehicle, while compared with the all-propulsive mode, the cost for orbitchange can be saved effectively as a result of exploiting the atmosphere. The relatedtechnologies among GEO satellite’s on-orbit maintenance based on AOTV are studiedin this dissertation. The main work and contributions can be summarized as follows:1. The on-orbit separation model for AOTV and space station is built, and thecorresponding problems after they are apart are studied.1) The separation mode forAOTV and space station is analyzed. On this basis, the design scheme of on-orbitseparation organ and the concept of safety distance are proposed.2) The dynamicalmodel for the mission of discrete mass-energy transfer is built. The formulation ofseparation velocity is deduced, and the disturbances to the space station’s orbit bydifferent separation velocities are analyzed.3) The process of relative motion after theseparation is studied. Under the circumstance of constant separation velocity, thedirection of separation velocity is optimized by genetic algorithm.4) The problem ofspace station’s orbital maintenance after the separation is studied. The method ofsolving the orbital elements of the virtual center for arbitrary configuration is proposed.The orbit keeping controller is designed based on Linear Quadratic Regulator (LQR)and the effectivity is validated by simulations.2. The problem of optimal orbital transfer outside the atmosphere is studied.1)Assuming the thrust is impulsive, the analytic method of solving optimal transfer orbitis presented. The parameters of optimal transfer orbit can be obtained only by solvinga transcendental equation with one variable. Regarding the deorbit position, reorbitposition and transfer time as the optimization parameters, the optimal transfer orbit isobtained by intelligent optimization algorithm. The first-order optimality of the twomethods are demonstrated based on the theory of Lawden’s prime vector.2) Assumingthe thrust is finite, the problem of orbital transfer from GEO to low earth orbit isstudied by the hybrid method. Combined with the work pattern of the engine, themathematical model of parameter optimization problem is presented and it is solved bySequential Quadratic Programming (SQP).3. The problem of trajectory planning for spacecraft formation flying’s orbitmaneuver is studied. A new programming strategy is presented. Firstly the referencespacecraft’s transfer orbit is planned according to the flight mission, then the accompanied spacecraft’s trajectory is planned by the condition of periodic relativemotion. Simulation results show the approach is simple and can satisfy all therequirements of the coordinated maneuver.4. The problem of optimal orbital transfer by aeroglid is studied.1) The process ofaeroassisted orbital transfer is analyzed in depth. It is divided into three phases whichare deorbit phase, atmospheric flight phase and reorbit phase. The atmospheric flightphase is established as the optimization object.2) The optimal control model of planarorbital transfer is built which contains nondimensional dynamical equations,constrained conditions and performance indices. The two point boundary valueproblem derived from the indirect problem is solved by the Broyden shooting method,and the technique of initial value guess for the costate variables is discussed. TheAOTV’s atmospheric flight trajectory is optimized by Gauss pseudospectral mehodwhen the heating rate and over loading are considered.3) The optimal control modelof nonplanar orbital transfer is built. Two-level optimization method of “Geneticalgorithm+Gauss pseudospectral method” is adopted to solve the optimal controlproblem which includes variable optimization, and compassion is carried on with theindirect method and sequential grads restoring method.5. The problem of optimal orbital transfer by aerocruise is studied.1) Thedynamical equations by aerocruise are built. For the convenience of optimality analysis,the equations are simplified legitimately.2) The optimal control model of nonplanarorbital transfer by aerocruise is built, and the corresponding optimization strategy isproposed. The heating-rate-constrained aerocruise conditions which consist of cruisealtitude, cruise velocity and angle of attack are optimized by using SQP. Theoptimality of the aerocruise maneuver is guaranteed by considering the optimizedaerocruise conditions as performance index of descent trajectory optimization.3)Based on the dynamical equations which are expressed by orbital elements, theanalytical solution of the orbit transfer during the cruise phase is deduced. Thus theintegral process is avoided and the analytical solution can be applied into theoptimization computation of cruise phase.The related technologies of GEO satellite’s on-orbit maintenance based on AOTVare studied in this dissertation. The accomplished work expands the applicationdomain of orbital transfer vehicle. It will provide scheme references and theoreticalsupport for the over design and key technology development of GEO satellite’son-orbit autonomous servicing.