Design And Study Of Guidance And Control System Based On Variable Structure Control Theory For SINS/GPS Guided Bomb

The design of guidance and control system for the project of Strapdown Inertial Navigation System/Global Positioning System(SINS/GPS) guided bomb is confronted with two main practical problems. First, how to present a guidance law for the guided bomb with no thruster to satisfy tactical guideline of'large range, big hitting angle, high hitting accuracy'. Second,how to solve the problem of robust flight control with uncertain pneumatic parameters and various random outside disturbances due to the guided bomb maneuvering in huge airspace.In this dissertation, acording to the above practical engineering problems, key technolog--ies of guidance and control system are deeply studied based on variable structure control theory for the guided bomb. Simulations and tests are carried out to validate the validity and feasibility of above methods. The main research points done of the dissertation are listed as follows:1. According to the constraint of terminal trajectory angle of the guided bomb with no thruster, a compound guidance law is developed, consisting of midcourse guidance and terminal guidance with hitting angle constraint, which makes the tactical guideline of'large range, big hitting angle, high hitting accuracy'achieved effectively.In the midcourse guidance phase, optimal attack angle with maximal lift-drag ratio is obtained to add the guided bomb's flight range. In the terminal guidance phase, two guidance laws with hitting angle constraint are designed. One is named as fuzzy variable structure guidance law. The time-varied sliding mode surface and exponential apporach law are designed, adjusting the speed of approaching sliding mode surface automaticly on the basis of the distance between the guided bomb and target. In order to reduce system's chattering, fuzzy control is used to select the gain of the switching term adaptively. The other is non-singular terminal sliding mode(NTSM) guidance law.It is designed via the method of NTSM control, and the time of the guidance system state reaching the sliding mode surface is guaranteed to be finite without singularity. And more overload can be afforded by the NTSM guidance law compareing with the fuzzy variable structure guidance law, which provides opportunities for guided flying with quick maneuver.2. When the SINS/GPS guided bomb maneuvers in huge airspace, parameters uncertain and various random outside disturbances are existent. Taking these into account, autopilots are designed using model reference adaptive variable structure control method. Thus, both model reference adaptive control and variable structure control's advantages are hold by the autopilots. On the one side, system state is pledged to approach sliding mode surface in conformity to the stated dynamic, which redounds to improve the system's dynamic trait. On the other side, the variable structure control's excellent robust is useful to resist system parameters disturbation and enhance control precision. In succession, the adaptive model reference variable structure autopilots are proved to be effectual by several classes of representative simulations.3. In order to obtain better integrative performance, integrated guidance and control system is designed using NTSM control. Firstly, integrated guidance and control state equations are established. Then uncertainties of guidance loop and control loop are taken into consideration adequately, the integrated guidance and control feedback law is designed based on NTSM method. By means of numerical simulations, it is compared with the conventional method of which guidance loop and control loop are designed separately. Simulation results indicate that integrated guidance and control system can not only keep hitting accuracy and terminal angular constraint well, but also can rectify control output dynamicly and make control signal smooth, which provides academic reference for even more complicated flight control conditions.4. The capability of variable structure guidance and control system is studied by the guided bomb's release regions and hitting accuracy. Six degrees of freedom model to compute release regions is established, and the technique for calculating release regions is proposed based on optimized theory. By calculation and simulation, guided bomb's release regions under various bombing conditions are obtained and factors affecting the boundary of release regions are also analyzed. And then, all kinds of guidance errors and none-guidance errors are analyzed roundly and relevant error models are established for the guided bomb maneuvering in huge airspace. Simulations of target practice with various errors are carried out using Monte Carlo method. Simulation results show that the tactical guideline demand of hitting accuracy is still satisfied primely, which proves favorable robustness of variable structure guidance and control system.5. Finally, validity and feasibility of variable structure guidance and control system of the guided bomb are testified in virtue of researching on hardware-in-loop simulations with three-axis turntable and vehicle tests of simulating bombing.All the research results are very valuable and important to the guided bomb's overall design, aeroplane'taking test and bombing test etc.