Multi-constrained Guidance Law And Cooperative Encirclement Hunting Guidance Strategy For Medium-range Air-to-ground Missile

In recent years,the world military powers represented by the United States and Russia have carried out in-depth exploration on the performance improvement and operational use of air-to-ground missiles.The medium-range air-to-ground missile is a precision-to-ground combat weapon with a maximum flight range of about 20～100 km.It has the characteristics of mid-guidance boost acceleration and terminal guidance precision strike.Because of its advantages of fast flight speed,high strike precision and strong damage ability,it is widely used in modern warfare.With the development of combat missions towards complexity,intelligence,clustering and systematization,how to improve the strike capability of medium-range air-to-ground missiles under multiple constraints is an important problem in the development of guidance technology,which is directly related to the success or failure of combat missions.Therefore,this paper conducts in-depth research on the precise attack and cooperative hunting guidance strategy of medium-range air-to-ground missiles under multiple constraints,focusing on solving the problem of time-varying speed of midcourse guidance law,the problem of time / angle constraint of terminal guidance attack,the problem of keeping the angle of view of guidance law under attack time constraint,the problem of fast acquisition of intelligent guidance law parameters,and the design of multi-missile cooperative hunting guidance strategy.The specific research contents include:Firstly,the coordinate system and its transformation relationship required for the guidance law design of medium-range air-to-ground missiles are defined,and then the missile motion equations are derived by force analysis.Then,according to the geometric relationship of relative motion,the vector expression of relative motion between missile and target is constructed and deduced into scalar form,which lays a model foundation for the design of guidance law in subsequent chapters.Finally,taking a typical mediumrange air-to-ground missile as the research object,the overall flight parameters and typical flight profiles are given,which provide typical flight parameters and operational application scenarios for subsequent guidance law simulation.In order to solve the problem that the optimal midcourse guidance law is difficult to solve under the condition of unsteady velocity,and to meet the multiple handover constraints of midcourse and terminal guidance handover time,an optimal midcourse guidance law considering time-varying velocity is designed.Firstly,the relative motion equation of time-varying missile-target with relative distance as the independent variable under the action of thrust and gravity is established.By setting the heading angle constraint of the handover point,a good initial condition is provided for the start-up of the seeker,and the energy minimization performance index function including the relative distance is constructed.Based on the minimum principle,the optimal midcourse guidance law is derived to ensure that the angle of attack command converges to zero at the handover time,so as to significantly reduce the initial overload pressure of the terminal guidance.Finally,the superiority and optimality of the algorithm are verified by numerical simulation and comparative simulation in different scenarios.In order to solve the influence of the residual time estimation error on the accuracy of the attack time guidance law under the assumption of small angle,and considering the difficulty of designing multi-constraint guidance law under three-dimensional conditions,a three-dimensional impact time and angle sliding mode guidance law is designed.Firstly,taking the impact time error and the missile-target range as the sliding surface parameters,the equivalent guidance law of the impact time independent of the time-to-go estimation is designed.The equivalent guidance law of impact angle is designed based on nonsingular terminal sliding mode surface.Based on the idea of hierarchical sliding mode,the design of two-dimensional impact time and angle sliding mode guidance law is realized by introducing nonsingular fast convergence reaching law,which improves the accuracy of impact time.The two-dimensional impact plane error angle is defined and the three-dimensional convergence condition is analyzed.The fixed-time convergence impact plane tracking guidance law is designed.The complex three-dimensional coupling problem is processed in different planes,which effectively improves the accuracy of impact angle constraint under three-dimensional coupling condition and improves the convergence speed of angle constraint.Finally,the effectiveness and superiority of the algorithm are verified by different scene simulation and different algorithm comparison.In the application of the three-dimensional guidance law of impact time,the trajectory bending leads to the increase of the angle of view of the missile and even the situation beyond the field of view(FOV)of the seeker.Therefore,aiming at the limitation of the FOV and the tedious debugging of the optimal guidance parameters,the threedimensional impact time intelligent guidance law considering the FOV constraint is studied.By accurately solving the time-to-go function of the three-dimensional proportional navigation law,the accuracy of the impact time error is effectively improved.Based on the Lyapunov principle,a three-dimensional guidance law of impact time is designed.By introducing a bias term with FOV angle error,the expected impact time constraint is effectively guaranteed within the FOV angle constraint.Then,the convergence accuracy of the impact time is further improved by designing the time error attractor.Based on the deep learning framework,the Deep Deterministic Policy Gradient(DDPG)algorithm is used to train the optimal guidance law parameters in different scenarios,and the intelligent and fast acquisition of the optimal gain coefficient under different initial conditions is realized,which effectively avoids the tedious manual setting of parameters.Finally,the effectiveness and superiority of the algorithm are verified by simulation analysis and comparative simulation under different conditions.In order to improve the coverage of the target,a new multi-missile cooperative hunting guidance strategy is designed when the ground target moves quickly or escapes.An impact angle control guidance law is designed for high-performance leader missiles,and an extended state observer is introduced to observe the unknown items,so as to obtain the nominal trajectory of the leader’s line-of-sight angle.The follower missiles adopt the distributed time-varying line-of-sight angle formation tracking guidance law,and by introducing the distributed extended state observer,the unknown acceleration and nonlinear uncertainties in the state equation are observed with high precision,and the overload saturation compensation function is designed for the overload saturation of the follower,which effectively improves the algorithm’s ability to cope with target maneuvering interference and anti-saturation.It is ensured that the new cooperative hunting guidance strategy can effectively perform fan-shaped cooperative hunting on ground targets,which greatly improves the strike ability of ground targets when they maneuver or turn around.