Research On Guidance Law Design With Terminal Impact Angle Constraints In Air-to-surface Guided Weapon

With the tide of the multi-roles, complexity, currency and precision in the air-to-surface guided weapons, we need to improve the precision of the guidance law for impact with angular constraints. In order to design the guidance law with terminal impact angle constraints, we study on the key techonology of optimal, robust, target moving, model-mismatching and kinematic coupling in guidance law step by step. The main work and contributions can be exhibited as follows:1.The trajectory model of air-to-surface guided weapon and the simulation system are presented for the convenience of the tests of guidance laws in the dissertation. Accordingly, the deficiencies of the tradition guidance law were analyzed from the simulation results.2.The design of the optimal guidance law with terminal impact angle constraints is accomplished in the dissertation, because the parameter optimization is the core problem. After the 3-dimensional (3D) terminal movement of aerial vehicles is divided into the movements of pitching plane and swerve plane, the guidance law is designed independently. Considering the terminal impact constraints of miss-distance, angle of trajectory inclination, angle of trajectory rotation and system dynamics, the 3D optimal guidance law is computed by the differential matrix Riccati equation of optimal control. And the traditional algorithm of max-velocity control is also improved by the adaptive gradient methods and Takagi-Sugeno fuzzy theory. The parameters of late guidance laws can refer optimization parameters to tuning.3.Aiming at enhancing the robust of guidance law, an optimal sliding mode guidance law with terminal impact angle constraints is proposed to depress the influence of parameter perturbation and outside disturbance during flight. The optimal sliding mode controller and the optimal guidance law are used to design the guidance law based on the channels decoupling in 3D guidance model. The robust of guidance law is tested through the simulation. So the robust of other guiandance laws can refer the study of the optimal sliding mode guidance law.4.When the target moves, it is difficulty to generalize the optimal guidance law directly. To solve the problem of undershoot, the engagement geometry between missile and target is established using virtual displacement. Based on the sliding-mode variable structure control theory and Lyapumov function, a new 3D variable structure guidance law for maneuvering target is deduced, which is satisfied with the multi-constraint conditions of precision, impact angular and incidence angular. In order to estimate and predict the unmeasured parameters, a nonlinear sliding-model observer is designed.5.A model-reference adaptive variable structure guidance law is deduced from the model reference adaptive variable structure control law, while mismatching of guidance model is resulted from the time-varying and system uncertainty in flight. After a kind of typical nonlinear time-varing system is analyzed, two kinds of model reference adaptive variable structure control law are designed based on the model reference adaptive control theory and the variable structure control theory. Then the linear guidance model and the optimal guidance law are taken as the nominal system and reference guidance law, respectively. Through model matching condition and integral sliding mode, a model-reference adaptive variable structure guidance law with terminal impact angle constraints is proposed by model reference adaptive variable structure control law.6. There are some disadvantages during the guidance law design using the channels decoupling assumption, because the rotation of aircraft body can result in strong kinematics coupling. Once a model of 3D guidance is formulated using vectors, the 3D sliding mode guidance law based on Lie group can be developed from the Lie group control theory and sliding mode contol theory. And then the guidance command of BTT (Bank-to-turn) control and STT (Skid-to-turn) control is shown. Based on the loss of guidance information, a new viewpoint on decoupling of guidance command is proposed.In summary, the dissertation concentrates on the basic theoretical and key technologies of the guidance law with the flight velocity and impact angle constraints. During the studying of guidance law design, the optimal control theory, variable structure control theory, Lie group control theory etc are introduced and utilized. A series of 3D guidance law with terminal impact angle constraints are achieved and tested by theory deduction and simulation. These research results are meaningful for the application of the new concept and principles of the guidance law with terminal impact angle constraints in precision strike.