Nonlinear Guidance Law For Interception Of Maneuvering Target

In modern war, the engagement of targets which possess higher speed and maneuverability has been the new challenges for ballistic missile. For improving the maneuver of missile, the missile must fly at big attack angle. In addition, the dynamics of missile are highly nonlinear and the nonlinear effect increase when flight conditions vary quickly. Besides, the unmodeled dynamics or parametric perturbations are usually remained in the plant modeling procedure. Therefore, one does not know exactly what the true missile model is, and the missile behavior may change in unpredictable ways. Consequently, recently developed intelligent cybernetics theory and nonlinear control system theory are used to synthesize the guidance strategies.Under these situations, different guidance laws based on fuzzy logic control and feedback linearization theory have been developed in this paper. The main contents of the dissertation are listed as follows:The analytical description fuzzy logic guidance law is developed to effectively speed up the fuzzy logic inference and fuzzy strategy. The command line of sight guidance law is designed based on error feedback control theory. The principle aim to the guidance law is to zeroing the line sight of rate and to reduce the miss distance, so an on-line tuning factor is introduced to adjust the acceleration command based on the target's maneuver.The adaptive fuzzy guidance law is derived to eliminate the parametric perturbation effect and defence larger maneuver targets. The combination of output error and error change is defined as the sliding surface. The adaptive laws of parameters based on a Lyapunov function are developed to adjust the parameters of the fuzzy rules and the uncertainty bound. The simulation results show that adaptive fuzzy logic control guidance law reduces the missile distance and flight time of attack missile.The nonlinear output regulation guidance law based on Takagi-Sugeno fuzzy model via state or error feedback is developed. The guidance problem is formulated as a tracking problem of a time-varying nonlinear system. The acceleration command is determined considering the target acceleration as external disturbances. First, the missile-target dynamics in different sample time can be expressed as Takagi-Sugeno fuzzy model. Then linear feedback control technique was utilized as in the case of feedback stabilization. Finally, the resulting overall controller is a fuzzy blending of each individual linear controller.Feedback guidance law, based on feedback linearization technique was presented here. Feedback linearization, one of the commonly used geometric nonlinear control techniques, is a powerful technique that takes the nonlinearities into account directly. It focus on driving line of sight rates to zero which mainly aims at movement of pursuer along the ling of sight to intercept the evader for sure hit to kill. However, feedback guidance law depend on the accurate the missile-target model and exact parameters. A robust terminal guidance law was developed that combines feedback linearization and adaptive control theory. In the presence of various unknown target accelerations, the guidance law keeps the LOS rate converging to zero.An integrated guidance and control law is designed for the case of intercepting maneuvering target. The fourth order state equation for integrated guidance and control loop is derived through analysis of the influences of aerodynamic uncertainties. The state equation is further changed into the normal form by nonlinear coordinate transformation. Using the derived model, adaptive guidance law based on a reference model for estimating unknown bounds of uncertain parameters is developed. Simulation results show that the proposed guidance law can reduce the performance degradation due to uncertainties.Finally, the work of this dissertation is summarized and the prospective of future research is discussed.