Terminal Guidance Law For Homing Missiles With Multiple Constraints

As a precision-guided weapon with long-range capturability,homing missiles have a great significance to the military and national defense.In recent years,with the rapid development of electromagnetic interference and communication technology,targets in modern warfare are often capable of detecting,confronting,and destroying incoming missiles.For instance,ships equipped with close-in weapon systems,tanks equipped with defensive armor,etc.,have put forward more stringent requirements on the survivability and penetration capabilities of missiles.An effective way to solve this problem is to design a terminal guidance law that satisfies various constraints,which can enhance the combat capability and damage effectiveness of missiles.However,the existing guidance approaches still face technical challenges,such as low stability,high computational cost,poor robustness,and inability to intercept maneuvering targets.By considering the development direction and practical demands of future guidance technology,this dissertation tries to solve the multi-constraint terminal guidance problem of homing missiles and design new guidance laws with both theoretical innovation and engineering applicability.This dissertation includes the following contents:For the impact time control problem with the seeker’s field-of-view constraint,the polynomial shaping method and switching control concept are utilized to design a two-dimensional nonlinear feedback guidance law,which can satisfy the impact time and field-of-view constraints simultaneously.After that,the proposed guidance law is further extended to obtain a three-dimensional impact time guidance law.The new guidance approach has a concise structure and a strict analytical expression.Moreover,the achievable range of impact times is investigated under various field-of-view constraints.In the meantime,the new guidance approach does not require any form of model linearization and online numerical iterations.This means that it can save the computational cost of the whole guidance system.For the impact time control problem with the seeker’s blind zone,a circular arc tracking guidance law is designed based on the classical differential geometry theory.By introducing a virtual-target concept,the guidance command can strictly converge to zero at the collision point.Then,the proposed planar guidance law is extended to a three-dimensional engagement geometry,resulting in a three-dimensional guidance law for impact time control.In comparison with related literature,the unique feature of the proposed approach is it can provide a terminal gliding phase for the guidance system.During such a terminal gliding phase,the missile can intercept the target and meet the impact time constraint without any control input.Thus,the new guidance approach can cope with the blind zone and improve the accuracy of the guidance system.For the impact time and angle control problem against a stationary target,a complete framework of look-angle design and tracking is presented from a theoretical point of view.First of all,the look angle of the missile is modeled as a time-varying inverse tangent function with two independent variables,and the methodology for designing the independent variables is also introduced.Then,a feedback guidance law based on finitetime control is designed to track the desired look angle.The proposed guidance law can achieve the impact time and angle constraints without involving any form of model linearization and parameter online optimization process,which is more stable and suitable for onboard implementations.In addition,a variety of desired look angles and guidance laws can be obtained by using the proposed guidance approach.Thus,the new guidance approach is said to be a generalized methodology,which provides a novel mentality of designing for the guidance problem with various constraints.For the impact time and angle control problem against a constant-velocity target,this dissertation develops a desired trajectory of the line-of-sight angle with one tuning parameter.A fixed-time guidance law is then presented to guide the missile to track such a desired trajectory,and a derivative-free method is involved to online determine the proper value of the tuning parameter.For the impact time and angle control problem against a maneuvering target,this dissertation proposes a desired trajectory of the flight path angle with two tuning parameters.A finite-time convergent guidance law is then developed to nullify the tracking error,and a conjugate gradient descent method is used for online parameter searching.The proposed two guidance approaches are able to achieve the guidance objectives without using any form of the predicted collision point.They provide new insight into the terminal guidance problem with impact time and impact angle constraints.