Research On Trajectory Planning And Guidance For Space-Based Strike Weapon

The space-based strike weapon which has characteristics of arbitrary-time launch, fast response, accurate access, high-level autonomy and large-area maneuver, is a new strategic platform for long-range precise strike mission and force delivering. The problems of trajectory planning and guidance for space-to-ground kinetic weapon (SGKW) and orbital bombing vehicle (OBV) are focused on this dissertation. The main results achieved are summarized as follows:A whole trajectory optimization approach for SGKW is studied. Firstly the optimal control problem is translated into two-point-boundary-value problem by Pontryagin maximum principle, and then a combined optimization algorithm based on genetic algorithm and sequential quadratic programming is used to calculate the initial values of costates and reentry designed parameters. Simulation results show effectiveness of the approach presented under different performance indices including maximum cross range, minimum strike time and minimum fuel consumption. Furthermore, the problems of surface coverage of weapon system, quadrant determination of control variables and transition phase partition are researched.Two methods of fast whole trajectory generation for SGKW are proposed. The one is indirect method, which first establishes BP neural network prediction models by offline optimization data samples and then uses sequential quadratic programming to modify the network predicted values. Since the predicted values can be derived in real time and near to the optimal values, the calculation time is decreased remarkably. Another is direct method, which translates the trajectory optimization problem into nonlinear programming problem on a series of algebraic equations by pseudospectral method. After the discrete approximation values of states variables and control variable are obtained, sequential quadratic programming is applied to iteration. The need of fast trajectory generation is satisfied without integral calculation.A reentry analytical predictive guidance logic for SGKW is researched. Firstly the three dimensional analytical solution of trajectory parameters under ballistic reentry is deduced and subsequently modified by analysis of error sources. Then an iterative correction algorithm for velocity inclination and heading angle is devised following the Newton iteration method, which is finally used for guidance command generation. Simulation results indicate that the analytical predictive guidance presented is able to improve the impact precision effectively and has good real-time performance.The technique of transition trajectory planning and guidance for OBV is studied. On condition that initial location and reentry location and velocity inclination are constrained, the time-fixed transfer orbit and the energy-minimum transfer orbit are respectively designed based on impulse hypothesis and two-body theory, which is substantially for deciding braking position and braking velocity. A scheme of limited thrust guidance with virtual reentry point compensation is presented to eliminate planning error. For some power systems with depleted shutdown, the redundant fuel can be dissipated by energy management, which is validated by simulation.A scheme of on-board reentry flight trajectory planning and tracking guidance for OBV is discussed. The quasi-equilibrium glide condition is utilized to convert reentry corridor constraints to the constraints of control variables. Accordingly the longitudinal reference trajectory is computed through the parameter search of bank angle model and the corresponding tracking law is designed using linear quadratic regulator theory. To enhance the maneuvering capability, a geometrical control mode considering no-fly zone constraints is analyzed and applied to OBV's lateral guidance. Moreover, for the precision achievement, an approach of on-line end-corrected phase trajectory planning and tracking guidance based on inverse dynamics is proposed. The effectiveness of the scheme presented is illustrated by numerical simulation.Three guidance laws with terminal angular constraint are derived. The adaptive proportional guidance law introduces closed-loop correction of guided coefficients for the sake of robustness enhancement. The quasi-slide mode guidance law determines the guidance parameters by optimization algorithm. The integrated guidance law improves the antijamming ability by adding variable structure controller to the optimal guidance law, which uses RBF neural network to adjust switching gain adaptively. Simulation results indicate that the three guidance laws proposed are applicable to different cases, but compared with the classical optimal guidance law, the robustness is remarkably enhanced.This dissertation will provide theoretical support for the overall design and key technology development of future space-based strike weapon, and also are a good reference to the orbit transfer of space vehicle, reentry guidance of hypersonic aircraft and exact terminal guidance of tactical missile.