Research On Optimal Terminal Guidance Law And Seeker Tracking Control

Recently, rights and interests of China have been constantlychallenged around. Thus, how to effectively protect the national security isan extremely urgent and significant issue that needs to be tackled. As oneof the most important national security defense components, interceptiontechnique has to be adapted to the development of long-range attackingweapons. Firstly, guidance law is definitely the influential factor ofinterception performance. When exposed to the current situation that targetpossesses high speed, even hypersonic speed, the traditional guidance lawsconfronted with challenges like largely diminished interception windowand lack of interception speed so that they could not effectively guide themissile to attack targets. In addition, onboard seeker is also the componentthat determines the interception performance. The roll-pitch strapdownseeker which is mainly developed today is superior on simple structure andlarge off-axis angle. However, few attentions have been paid on this. Thecontrol problem confronts difficulties such as deformation of fractionfunction, extremely short responding time and large input varyingmagnitude therefore is a very difficult problem. On the other hand, seekercontrol problem influences some significant factors such as themeasurement of the angle of Line of Sight (LOS) and response speed, thusit is a noteworthy area. This dissertation based on the study of controltheory and missile guidance law, conducted research on novel guidance laws and controlling discipline of roll-pitch strapdown seeker. Presents theachievements as follow:(1) This dissertation proposed a novel head pursuit optimal adaptivesliding mode guidance law. Above all, it has been studied which theadvanced head pursuit guidance strategy which is superior on interceptinghigh speed target. But it does not provided the optimal energy consumption.The fuel consumption is an important study direction of targetminiaturization and battlefield expansion. The dissertation studied theoptimal energy consumption on the premise of satisfied accuracy, and thesuppression of target maneuver acceleration. After modeled and linearizedthe relative movement of interceptor and target, we picked cost functionwhich matches reality situation to drive interceptor acquiring optimalenergy consumption with interception accuracy and utilized optimalcontrol method-Linear Quadratic Regulation (LQR) to derive the guidancelaw. Then we adopted the sliding mode control method to suppress thestate error brought by target acceleration and augment the robustness. Thefluctuation problem was dealt with saturation function. Compared withother guidance laws, this approach could lead to optimal energyconsumption and satisfied interception accuracy as well as strongrobustness.(2) A new adaptive head pursuit guidance law with attacking angle isproposed in this dissertation. Firstly, head pursuit requires both target andinterceptor fly on the same trajectory. To increase the performance ofinterception, there needs some angle difference between the two aircrafts.This dissertation modified the geometry conditions of head pursuit so thata flying angle difference exists when interception occurs. On thefoundation of relative motion model of Head Pursuit and considering thedynamics of autopilot, we derived the adaptive head pursuit guidance lawwith sliding mode control. The stability was proved by Lyapunov stabilityprinciple. Via simulation, this guidance law possesses some advantages onattacking angle, low relative speed and high accuracy. (3) A controller was designed for the roll-pitch strapdown seeker inthis dissertation. After the analysis of seeker model, designed a structurewith switchover between two controllers to handle the sudden variation offriction which has large influence on system model. The H2optimalcontrol theory could achieve the optimal performance of the system and berobust to the model deformation. Based on H2optimal control theory wederived roll-pitch strapdown seeker controller which could effectivelycontrol system with large variation of input by switching controller. Thiscontroller possesses satisfied robustness and the performance of unit stepresponse largely exceeds the requirement.