Precision Initiation Theory And Technology For Complex Encounter

Complex encounter is the composite encounter of the relative trajectory and attitudebetween the ammunition and the target. With the rapid development of smart ammunition,it has become an important trend in the technical field of future ammunition that equippedwith the focus warhead with high energy efficiency and minimized collateral damage. Inthis paper, loitering ammunition equipped with multi-mode EFP warhead, which is atypical representative of smart ammunition, is considered as the research object. Theaffection of the impact factor on the hit accuracy of kill element, which is the relativeposition and attitude between the ammunition and the target at the blast moment, is heretranslated into the precise hitting control problem of the focus warhead and the target underthe complex encounter condition. Relevant research work was carried out, and it laidtheoretical and technical foundation for this problem. The main contents are described asfollows:(1) Under the complex encounter condition, the precise hitting of the kill element in thefocus warhead requires proper cooperation among the relative trajectory of the ammunitionand the target, attitude of the ammunition and the initiation time. In this paper, thescheduling relationship between guidance and flight control and fuse warhead system wasfirst analyzed, and then a design method for coordination of these systems was proposed,i.e., based on the time-scale separation theory in the ammunition flight mechanics and theguidance integrated fuse technology, apply time-division multiplex in flight control systemand give up tracking of guidance command at the end of the trajectory, and adjust theattitude of the ammunition to meet the requirement of the precise hitting of the kill element,without changing the original terminal trajectory. This method makes a full use ofinformation from the ammunition and an optimal scheduling of the hardware resource,which can increase the hit accuracy without the additional components.(2) The encounter information obtained by the ammunition is analyzed and the6-DOFmotion model was established. According to the size of the target’s vulnerable part, therelationship between the maximum allowable lateral deviation of the trajectory, availableoverload and maneuver time were studied. And the ammunition attitude control timeinterval, also named as time window of the attitude controlin the terminal trajectory, wasproposed. Within this interval, only the ammunition attitude would be changed, and the terminal trajectory remains the same. Taking a maximum available overload calculation asan example, the calculated method of the time window was proposed, which is a theoreticalsupport for the time-division multiplex in the flight control system.(3) Considering the kill characteristics of the focus warhead, installation angles, and therequirements of precise hitting on the intersection angle and the optimal initiation height, aguidance law was designed based on the virtual target. Firstly, a completethree-dimensional pursuit-evasion kinematics model was established. Secondly, theparameters of the practical encounter are transferred to the aim point. Furthermore, theinitial position and movement of the aim point were designed. Thirdly, the quadraticperformance index was proposed and the guidance law was solved by the proposed method.Then the receding horizon method is used to improve the hit accuracy for the maneuveringtarget interception as well. Finally, the performance of the guidance law was verified bysimulation with the loitering ammunition equipped with the multi-mode EFP warhead.Numerical results show that the guidance law can meet the requirements of the intersectionangle and the detonation height has a high precision. So a better trajectory intersectionconditions are provided.(4) Concerning the kill characteristics of the focus warhead and the complex encountercondition, the killing axis was chosen as the research object. To begin with, the concept ofthe killing plane was proposed, the intersection angle is defined from the point of view ofthe kill element precise hitting. Then the initiation time algorithm in the killing plane wasdeduced. In addition, the constraints of precise hitting were established, feasible region ofdetonation was defined and the sensitivities of hit point coordinates to different parameterswere analyzed. What is more, the cost function of optimal damage was presented and theconcept of fuse promoter region is discussed. Besides, a new formula of fuse warheadcoordination efficiency is established. Therefore, the problems of initiation time, attituderequirements of the initiation, and the assessment of fuse warhead coordination efficiencyare solved. And the research mentioned above laid a theoretical foundation for the precisieinitiation of the focus warhead in a complex encounter condition.(5) Because it is difficult to establish an accurate model for the ammunition, and the inputof the ammunition attitude control based on kill element hit is usually constant and the system needs fast response, a design method for attitude control system was proposedcombining the characteristic modelling and optimal control theory. Through the onlinemissile identification, which applied the recursive least squares method with the forgettingfactor, the characteristic model of the ammunition attitude motion was built. In addition,the receding horizon control method was introduced to obtain the optimal control law in thereceding horizon based on the ammunition attitude characteristic model. And this controllaw will solve the ammunition attitude control problem in the terminal trajectory under themulti-variable, strong coupling and multiple interferences.(6) A certain type of the loitering ammunition was taken as an example, and the charactersof the warhead, integration system of guidance/arming/fusing and the target were analyzed.The coupling of the rudder angle among different channels was analyzed with aerodynamicparameters. And then the attitude control performance proposed was verified by computersimulation and numerical results show that, compared with the conventional controlmethod for the same loitering ammunition, the method mentioned above provided fasterresponse and stronger anti-interference, and it also can meet the attitude controlrequirements. Next, its performances further verified by the hardware in the loopsimulation. Finally, the Monte Carlo method was used in the algorithm simulation ofinitiation time and initiation attitude, and the results show that the method proposed cangreatly improve the hit accuracy of kill the element.