Design Method Of Terminal Guidance Law For Reusable Launch Vehicle

Reusable Launch Vehicle (RLV) will deliver various payloads, such as cargoes and military weapons on the Earth's surface with angle constraint, while the terminal velocity is required to be within a permissible range. Terminal angle constraint and velocity constraint must be considered, while design the terminal guidance law for RLV, This thesis focuses on the design of terminal guidance laws for RLV with the above requirements.Firstly, this thesis builds up the mathematical kinetics model and motion model in view of the dynamical characteristics of RLV and the problem at high velocity. Target model and the missile-target engagement geometry model are established, and the navigation calculation method is given. The research work lays the groundwork for the successive research.Secondly, the design of the terminal guidance law with the angle constraint is described as a mathematics problem. Two such guidance laws are derived by solving a constrained problem using optimal control theory and robust control theory. Numerical simulations are performed to compare the two guidance laws with and without disturbances. The optimality of the optimal guidance method and the robust guidance method's robustness against disturbances are proved by simulation results. Thirdly, the velocity control method of RLV with the velocity constraint is developed in detail. The design method of the ideal velocity curve and the detailed mehtod of controlling the velocity are discussed, and the control of velocity depends on the ideal velocity curve. Velocity control is achieved by increasing the angle of attack.Finally, according to the requirements of the RLV's terminal flight task, the simulation codes for the RLV's terminal guidance system are programmed. Simulation results demonstrate that the proposed guidance laws have good miss distance performance with the required impact angle and velocity even under model uncertainty and disturbance condition.