Research On Fuzzy Guidance Law For Intercepting Maneuvering Targets

The design of guidance law is one of the key technologies to attack or intercept a target precisely. Missile guidance and control system is a multi-variable, nonlinear, time-varying system with model uncertainty. With the development of technology, the working environment of a missile is becoming more and more complex and the maneuverability of a target is becoming stronger. So the design of advanced guidance law is attracting more and more attention. At present, the commonly used methods, e.g.,the proportional guidance law, are not available to intercept the target with large varying maneuver. It is hard to meet the requirement of attacking or intercepting the large maneuvering target with high precision. Therefore, this thesis is to design more effective guidance laws with stronger adaptability and robustness.The miss distance of traditional proportional guidance law is becoming bigger when intercepting maneuvering targets. Because the fuzzy logic can use people’s experience knowledge effectively and it does not rely on accurate mathematical model, it is applied to improve the precision of guidance law. As an effective method to improve the precision of fuzzy control, varying domain strategy is introduced in fuzzy guidance law. The fuzzy rules are optimized through choosing an appropriate contraction-expansion factor and the accuracy of the guidance is improved. The simulation results prove the effectiveness of the designed guidance law.Next, considering the long reasoning time of fuzzy rules under semantic description during large amount of calculations, a kind of adaptive fuzzy guidance law based on the analytic fuzzy rules is designed. Analytical rules are described by an analytical expression with a correction factor. The proposed fuzzy rules are able to adaptively adjust their correction factors according to the change of target speed and acceleration.Finally, considering the large mount of simulation experiments to determine the formula of the correction factor, and in order to improve the adaptability of the guidance law, the variable structure theory is introduced. The presented adaptive rules are designed by using the Lyapunov stability theory, which ensure that the line of sight (LOS) angle rate approaches zero and the missile hits the target precisely. The simulation results show that the designed guidance law is an advanced guidance law with higher guidance accuracy and stronger adaptability.