Research On Variable Structure Guidance Law Based On Approach Law Method

With the rapid development of military science and technology,modern battlefield has put forward the requirements of fast,precise and accurate missile guidance.The design of terminal guidance law has become one of the most important factors to influence the accuracy of missile guidance and has gradually become a research hotspot in the field of military guidance.Because the battlefield is a complex and changeable strategic decisive battle place,the targets distributed on the battlefield will be distributed in different positions.Therefore,in order to improve the destruction efficiency of the terminal warhead of the missile,the terminal angle of landing is expected to become an important key factor for the missile to hit the target.Therefore,the angle of fall problem should be regarded as a key constraint problem in the guidance law.In addition,according to different position and different maneuver performance target,inevitable in the process of missile in flight,external disturbance and perturbation of internal problems on the convergence rate of the missile system and status may be the influence of different level,and general proportional guidance law only to motor speed target is of high precision guidance ability,more and more difficult to meet the motor speed and motor form complex target’s guidance,and,in the form of variable structure control method to design guidance law for improving guidance accuracy,robustness and convergence speed problem is of great significance.In view of the missile attacking or intercepting targets at different positions in the longitudinal plane,the relative motion models of the projectiles are established in the line of sight coordinate system,and the relative motion relations among the relative distance,angle of sight and angular velocity of the projectiles are analyzed.In order to solve the problem of high miss distance and slow convergence speed of terminal drop angle in the guidance process of missile intercepting high-altitude target,a sliding mode guidance law based on the law of variable power approach is proposed.Considering the target maneuver as interference,the slide-mode observer is designed to accurately detect the interference and compensate it to the guidance instruction,which improves the guidance effect of the missile.The improved law of variable power approach is adopted to improve the dynamic convergence speed and stability accuracy of the sliding mode.Finally,compared with the exponential approach law method,in the process of attacking the maneuvering target,the missile’s sight angle rate and sight angle error converge to 0 faster,and effectively reduce the chattering problem.After adding in the external interference,the missile can still maintain high precision and maintain better guidance performance.In order to solve the problem of high miss distance and slow convergence speed of terminal drop angle in the guidance process of missile attacking ultra-low altitude target,improving missile radar seeker looking down a low-level target detection and tracking precision,minimize the influence of multipath interference effect,in the process of guidance,the angle of the line of sight to constrain to near brewster Angle,make the earth sea clutter reflection coefficient,the smallest design based on Sigmoid function modular target reaching law to intercept a low-level guidance law.A sliding surface with line-of-sight velocity and line-of-sight deviation approaching zero is established to reduce chattering.In the case that the maneuvering acceleration of the target is difficult to obtain,the extended state observer is used to estimate and compensate,and is added to the guidance law designed.Finally,the simulation of intercepting targets by multiple interceptors and the comparison with the ballistic shaping guidance law show that the designed guidance law can not only guide the interceptor to hit the target at the desired brewster angle,but also effectively improve the performance of ultra-low altitude interception.In order to solve the problem of high miss distance and slow convergence speed of terminal angle during the guidance of missile attacking the ground target,an angle of fall constrained guidance law based on double power approach law is proposed.Based on double exponential reaching law is established the first missile terminal sliding mode guidance method,the first to use the terminal sliding mode control method combining nonlinear function,construct the Terminal sliding mode surface,in order to improve the dynamic response of missile speed,using the double exponential reaching law,combining with the Terminal sliding mode control idea and the super-twisting disturbance observer.design a new Terminal sliding mode guidance law,and carries on the Lyapunov stability analysis and simulation.In the second,a fixed-time convergence guidance method based on the double power law of approach is established,and it is proved that the missile can reach the desired angle quickly and the global fixed-time convergence is maintained,and the influence of the parameters of the guidance law on the guidance performance is analyzed.Finally,simulation shows that the guidance law in this chapter has higher guidance precision when attacking ground targets.The results show that the new guidance law has a faster convergence rate than the traditional power approximation law,which makes the missile better in practical application.