Research On Application Of Missile Guidance Laws Based On Fuzzy Logic Control

Missile guidance system function is to guide the missile to hit the target with the highest probability. To ensure high accuracy and low error, guidance technology need have adaptive features. Thus, a single traditional guidance law can not meet the requirements of the increasingly sophisticated intercept conditions. This dissertation takes missile guidance law as the background, the theory and application of fuzzy logic control in the composite guidance and the variable structure guidance are investigated. The main contributions are as follows:First, based on two-dimensional kinematical model of the missile interceptor, classical simple guidance laws were analyzed and simulated, including proportional navigation (PN), augmented proportional navigation guidance (APN) and Bang-Bang guidance (BB). The results are fully consistent with the theoretical ones.Secondly, based on the theory of serial composite guidance and on the characteristics of each fundamental guidance law, a fuzzy composite guidance law is proposed, compositing PN, APN and BB. To obtain the precision target acceleration, in practice, a second order extended state observer (ESO) is designed. Meanwhile, in order to eliminate measurement noise, a tracking-differentiator (TD) based on fal-function feedback is introduced. On the results of intercept simulation between fuzzy-logic-based composite guidance law and classical guidance laws, it is known that fuzzy composite guidance law is better than the classical ones, whether miss distance or intercept performance.Finally, according to line of sight (LOS) rate and relative velocity, traditional PN with a constant gain is improved by fuzzy logic control, and then a fuzzy proportional guidance law with a variable gain is put forward. For large maneuvering targets, two-dimensional kinematics model will be extended to three-dimensional one. Thus, under this model, a variable structure guidance law (VSG) considering missile's dynamics of autopilot will be derived. On basis of fuzzy PN and this VSG, fuzzy logic control is introduced into proportional navigation item and dynamic compensation term in this proposed VSG. Then, a fuzzy variable structure guidance law (FVSG) is presented. Compared to conventional VSG, the FVSG has a high guidance precision. At the same time, comparative analysis of the conventional VSG and FVSG considering missile's dynamics of autopilot is investigated. Simulation results show missile's interceptor performances ignoring dynamic characteristics of missile's autopilot are affected. Simultaneously, introducing fuzzy logic into consider the dynamic characteristics of the variable structure guidance law, Most of interception performances are improved.