Study On Release Region Calculation For Guided Bombs

As a precision-guided weapon, guided bomb is cheap and highly effective. With the increase of modern warfare demand for precision strike, it is becoming more and more important in arms family. Compared with conventional gravity bomb, it has not only high accuracy but also the ability of mid-high altitude region release. This character can effectively reduce burden on the operation of the pilot and improve carrier survivability. Therefore, a comprehensive evaluation of the performance of guided weapons, particularly the scope of application of guided bomb is essential and critical. Where, the scope is always called as release region of guided bombs. Taking the typical guided bomb as an example, this dissertation studies systematically release region calculation for guided bombs, and through the application analysis of engineering, the practical value of release region is pointed out. The main content of this dissertation is shown as follows:Release region calculation model of a guided bomb is established, including dynamic model of guided bomb and geometric model of release region. Allowing for altitude scope and calculation accuracy, a suitable environmental model is constructed and overload is taken as control input. Then particle trajectory models on surface-launched and off-axis are set up. Synthesizing various definitions, a general definition of release region is given out. Because release region boundary is related with the utmost trajectory of guided bombs, the boundary issue was put into many rounds of optimal range calculation, through a simple translation transformation. According to guidance mode, release direction and whether or not disturbance, release region are classified into three kinds: guidance and program, on surface-launched and off-axis, ideal and actual.The homotopy method based on maximum principle is developed to calculate program release region whose demand for precision is higher than efficiency. The homotopy map for maximum range problem is built by using homotopy method with a large scope convergence property, and the control law of maximum lift-drag ratio is deduced. Then the maximum lift-drag ratio trajectory is regarded as the initial solution, and the optimal solution of original maximum range is obtained through successively increasing the adjustment parameter from zero to one. The method overcomes initial costates guess puzzle and has a fast convergence rate which thanks to maximum lift-drag ratio trajectory close to true optimal solution. Finally, program release regions on surface-launched and off-axis are calculated by using proposed method.Proper flat outputs are introduced and used to reformulate trajectory model, then the direct method is adopted to calculate guidance release region on the basis of the reformulated trajectory model. Guidance law is not only used to generate trajectory online but also as a path constraint. If above homotopy method is adopted to calculate release region of guidance type, the path constraint is complicated to deal with and the convergence rate is low. Most differential constraints of reformulated trajectory model are transformed into algebraic ones. Hence, less differential constraints need discretizing and less decision variables need optimizing. When direct method is utilized to solve maximum range problem, the cost on computation is not a troublesome problem. Finally, guidance release regions on surface-launched and off-axis are calculated based on the reformulated trajectory model.Range and off-axis angle of the release region of guidance type are smaller than those of program type under the same conditions. The reason is that solution space becomes smaller while guidance path constraint is imposed. Therefore, compound guidance scheme is adopted to expand release region. After maximum final velocity in horizon for midcourse is taken as performance indicator and smooth handover is designed from the midcourse to the terminal, the expanding type release region is calculated. Expanding type release region has both advantages of program type and guidance type through analysis of the calculation results.The problems are discussed from the practical application of release region. 1) A data preprocessing method is brought forward in order to select appropriate fitting variables, fitting queue and units of measurement, and effectiveness of proposed method is validated by illustration. 2) According to the time span of effection, the disturbances are divided into two classes: initial state error and flight course interference. The hit probability expressions are given when the former acts individually. But the latter influences each period of trajectory integral, deflection tests are necessary to analyze hit probability when flight course interference acts individually. After that, the shift mode of ideal release region is obtained by monte carlo examination considering disturbances of both classes. 3) The generality of release region calculation is expatiated from three points of view, so the conclusion is that efficiency of trajectory optimization, error disposal on group trajectories computation and relation between release region and trajectory parameters are the ways to generality.This dissertation introduces new methods for numerical calculation to obtain release region of guided bomb, and explored the problems in the appliction of release region and puts forward corresponding solutions. Referring the actual guided bomb's characters during shooting, some typical instances are designed and release regions are worked out by using proposed methods under various release conditions. What's more, detailed analysis is made and some conclusions are drawn according to above calculated results, which shows proposed methods will be helpful in development of new types of guided bombs.