| Solid launch vehicles can be launched rapidly with maneuverability,high reliability and low cost,which has become the expected vehicles for small satellites and other responsive space loads.In order to improve the load-to-structure mass ratio and increase the strength of structure,the thrust termination mechanism has been removed from solid rocket motors,which will cause solid motors to shut off only by the fuel exhaustion instead of the main engine cut-off controlled by the guidance command.During the fight,the combustion characteristics of the rocket motors are seriously affected by the ambient temperature,and the actual thrust and the mass change rate present the large dispersion and uncertainty,which requires the guidance methods to have strong adaptability and robustness.In addition,solid launch vehicles have the characteristics of large thrust-weight ratio and short combustion time,so it is necessary to adopt the “burn-coastburn” flight mode to ensure the autonomous adaptability to different missions.Therefore,higher-level requirements are put forward for the guidance technology of solid launch vehicles to adapt to the autonomy of the missions and the robustness under the condition of the large dispersion,fulfilling the longed-for requirement of responsive launching into orbit missions with high precision.In this thesis,the multi-stage solid launch vehicles shutting off by fuel exhaustion are taken as the research object.In response to launching the sun synchronous orbit missions with multiple terminal constraints,the technical route of “analytic base-guidance” combined with “nonlinear energy management” is adopted,and the key problems are are mainly solved: the adaptive guidance in the “burn-coast-burn” flight mode,multi-constrained energy management shutting off by fuel exhaustion and high precision guidance under the condition of the parameters deviations and uncertainties.The main research results and achievements are as follows:(1)For the single stage adopting the “coast-burn” flight mode,the classical closed loop guidance method is improved by the Pointing Algorithm and multiple terminal constraints are satisfied by the ignition time.According to the variation of the vectors of the orbital momentum moment,the theoretical relations among the ignition time,the required velocity vector and the terminal multiple constraints are established,then the pointing algorithm guidance method considering the sliding ignition time is proposed.At the same time,the applicability of the closed loop and pointing algorithm guidance methods to the solar synchronous circular orbit with multiple constraints is analyzed and discussed,the conclusion of which illustrates the necessity of the energy management methods during the course of exhausting shutdown in solving the problem of solid rockets injecting into the orbit.(2)In order to solve the problem of the multi-constrained velocity increment control in the way of exhausting shutdown,a nonlinear numerical discrete velocity control method with the process constraints is designed,where using the pointing algorithm as the base guidance vectors and adopting the energy dissipation mode of the additional attitude angles.According to the limitation of the actual nonlinear engine model and the attitude tracking ability of the control system,the improved model prediction static programming method takes the attitude rate as the control variables,which improves the accuracy of the velocity control and realizes the limitation of the attitude rate.(3)For the additional position coupling effects caused by the velocity increment control process during the course of exhausting shutdown,a three-dimensional energy management method is proposed to suppress the coupling effects of the velocity increment control,which develops and improves the application of pointing algorithm in the way of exhausting shutdown.This hybrid method establishes the coupling influence model between the velocity control and the pointing guidance,and determines the implementation channels of the coupling suppression in the process of velocity control.By decomposing the coupling effect of additional position to the longitude of the ascending node,the constraint ability of the semi-major axis,eccentricity and orbit inclination can be improved,and the sun synchronous orbit missions of solid launch vehicles with the multiple terminal constraints can be achieved in the way of exhausting shutdown.(4)For the saturation tracking of the attitude rates caused by the energy management methods,a multi-stage mission planning method is proposed,which develops and improves the performances of the pointing algorithm in the practical multi-stage missions.Through the distribution and planning for the energy of the multi-stage launch vehicles,the saturation tracking of the control system is avoided in the process of the velocity increment control,and the autonomy and reliability of the onboard guidance for solid launch vehicles are improved.The guidance methods of the “burn-coast-burn” flight mode,which are difficult for the fast response of the solid rockets launching immediate missions,are studied systematically by this thesis.The multi-stage Lambert’s problem with the given velocity increments and the twopoint boundary value problem with the fixed terminal time are solved in theory,providing theoretical support for the space fast response guidance technology of solid launch vehicles.The proposed guidance methods have been experienced the Monte Carlo simulations of the whole flight through the ascending phase and entering into a variety of typical sun synchronous orbits,which not only show that they have the characteristics of the strong real-time and high reliability in the guidance calculation process,but also verify the strong robustness to the parameter deviations and model uncertainties,and the strong autonomy for immediate missions.Consequently,the research results of this paper have the important theoretical significance and the engineering application reference values. |
