Research On Multi-constrained Guidance Law For Aircraft Protection

Traditional means of aircraft defense,such as infrared decoy and radar jammings,are not able to achieve satisfying performance when confronted with advanced incoming air-to-air missiles.Under such condition,it is more effective to intercept incoming missiles by launching defensive missiles.This defense approach has significant values and a wide range of application.This thesis studies on the midcourse and terminal cooperative guidance laws for intercepting highly maneuvering target in the aircraft defense scenario.The main research work and innovations are concluded as follows:(1)A novel cooperative guidance method considering time-varying speed,impact angle and impact time is proposed to address the two-dimensional midcourse guidance problem of inaccurate prediction of time-to-go and undeterministic control of terminal constraints.A missile kinematic model involving engine thrust and drag force is built.The flight trajectory is designed based on Bezier curves and has two phases.The impact angle constraint is satisfied by making the missile fly along the designed straight terminal phase trajectory.The entire trajectory length and maximum trajectory curvature are controlled by tuning the phase-switching point position.Linear quadratic regulator based tracking algorithm is used to track the desired trajectory.Numerical simulations demonstrate that the proposed two-dimensional cooperative guidance can control the impact angle and flight time under variable speeds and autopilot lags.(2)To solve the problem that two-dimensional midcourse guidance relies on threedimensional kinematics decomposition,a novel cooperative guidance law is proposed based on log-aesthetic space curves.A three-dimension missile kinematic modelling is built and Frenetic frame is introduced to describe the geometry characters of the threedimensional flight trajectory.A two-phase trajectory based on Log-aesthetic space curve is designed.The impact time control and missile's maximum acceleration limit is achieved by adjusting the phase-switching point along the terminal straight course.Numerical simulations demonstrate that the proposed three-dimensional cooperative guidance can control the impact angle and time as expected,which can be further used for the formation flight of missile team.(3)To intercept high-speed,highly maneuvering target,a novel intercepting formation and strategy for defensive missiles are proposed.The engagement geometry is analyzed from the perspective of reachable set and equal time line,which leads to a modified necessary condition for zero-miss-distance interception.Based on this,an interception strategy is derived by covering the target's reachable set with the union of the missiles' reachable sets.The disadvantage of defensive missiles' flight performance is compensated by their quantity advantage,which further leads to the engagement advantage.Numerical simulations demonstrate that the proposed cooperative strategy can be used to intercept high-speed,highly maneuvering target.The missile team using this strategy can be easily extended to improve interception performance.Moreover,the proposed strategy is applicative for a diversified missile team.(4)A launch planning process is designed to combine the proposed midcourse and terminal guidance methods in for the aircraft defense scenario.A six-degree-of-freedom numerical simulation platform including dynamic models and flight control systems of aircraft and missiles is established.Base on the predicted flight trajectory of the target,the whole-process simulation,consists of missile launch,midcourse guidance and terminal guidance,is conducted.The simulation results verify that the proposed midcourse guidance and interception strategy can intercept superior,high speed and highly maneuvering target effectively,which offers great value in military application.