Quantitative Performance And Design Optimization Approach Of Close-Range Rendezvous Trajectory Safety

With the development of space exploration, the environment for space missions in future becomes more complicated than what we know now. Therefore, the requirement of autonomy for rendezvous and docking (RVD) technology is needed and the safety of the RVD is worth more attention. With the background of RVD mission of China manned spaceflight, this dissertation studies the design of the close range rendezvous trajectory safety in details, which involves the methods for errors propagation analysis, the quantitative performance for safety, the design optimization of passive safety trajectory and the closed-loop active safety control of rendezvous trajectory. The main results achieved in this dissertation are summarized as follows.The rendezvous errors propagation models are deduced using CADET. 1) Based on the C-W equations, the CADET propagation models of the statistical properties of the relative states and their dispersions are formulated with considering the navigation errors and actuation errors. 2) Based on the nonlinear perturbation dynamic equations, the CADET propagation models of the statistical properties of the relative states and their dispersions are deduced with considering the orbital disturbance model errors, navigation errors and actuation errors. 3) With the CADET propagation models of the nonlinear system, the different influences of the main rendezvous errors are analyzed and distinguished using the orthogonal experiment design method.The quantitative performance index for rendezvous trajectory safety with considering errors and its calculation methods are proposed. 1) Based on 3σellipsoid and collision probability theory, the quantitative performance index is presented, and the simplified calculation methods are provided which could be used for on-orbit safety performance analysis. 2) The orthogonal experiment design method is adopted to analyze the influences of transfer time, number of impulses and intervals between impulses and so forth on the trajectory safety, and some primary results of qualitative analysis are obtained.The design approach for safety-optimal rendezvous trajectory is proposed, and its characteristics are analyzed. 1) An optimization model for the safety-optimal impulsive linear rendezvous of the closing phase is formulated. Several cases involving different rendezvous directions and different number of impulses are designed and optimized, and the characteristics and the engineering application value of the safety-optimal approach trajectory are analyzed using the optimization results. 2) Using the Lambert algorithm, an optimization model for the homing safety-optimal two-body rendezvous is formulated. The homing trajectories with different number of impulses are designed, and the relationship among safety, fuel consumption, and transfer time is discussed. 3) With the two-body solution as an initial reference solution, a sequential quadratic programming algorithm is used to obtain the J2-perturbed solution. The influence of J2 on the trajectory's performance indexes is also analyzed.The optimization models and algorithms for designing multiple-objective rendezvous trajectory including objective of safety are proposed. 1) The three-objective optimization linear models including the minimum characteristic velocity, the minimum transfer time, and the minimum safety performance index are formulated. The optimization abilities of non-dominated sorting genetic algorithm (NSGA2) and strength Pareto evolutionary algorithm (SPEA2) for this problem are compared, the tradeoffs between the whole performance indexes of a rendezvous trajectory are demonstrated, and the influences of rendezvous directions and number of impulses on the optimization results are illustrated. 2) The multiple-objective optimization models for homing two-body and J2-perturbed rendezvous are formulated, NSGA2 is employed to obtain the Pareto solution sets of the homing two-body rendezvous while the physical programming method is used to obtain the designer-preferred two-body solution, and the preferred J2-perturbed solution is obtained afterwards.The closed-loop glideslope algorithms for active safety control of rendezvous trajectory are proposed. 1) An impulsive glideslope guidance algorithm for close range rendezvous is presented, which ensures the relative motion in any direction and at any time with the objective of fuel economy and also satisfying the constraints of field-of-view of navigation facilities, the minimum interval of impulses, and the maximum value of impulse. 2) On this basis, the trajectory controlled and terminal controlled closed-loop glideslope algorithms are presented which could ensure the rendezvous trajectory safety by the decrease of trajectory deviations. This dissertation has some theoretical significance in developing the error analysis methods of the rendezvous process, proposing the systemic quantitative performance index and its efficient calculation methods, investigating the characteristics of the safety-optimal trajectory by theoretical analysis and numerical optimization, and developing the design approaches of the optimal multiple-objective rendezvous. The proposed approaches could be used for on-orbit rendezvous safety performance analysis and also provide new design tools for achieving a rendezvous trajectory with better comprehensive performance index, which have high engineering application value.