Study On Nonlinear Variable Structure Guidance Law

With the application of the new technology in military areas, terminal guidance laws are used in missile to improve the guidance precision. It is urgent to search a new precision guidance law to change this situation, since the classical guidance laws cannot satisfy the more and more complicated interceptions. Especially, for the high maneuverable target, classical guidance laws always are noneffective.The main achievements are summarized as follows:Firstly, Two-dimensional relative motion model of missile and target is established in two dimensional LOS(line-of-sight) coordinates, variable structure robust guidance law for homing missile based on zeroing normal speed of LOS is presented in intercepting the high maneuverable target, and the method has solved the problem of chattering existing in common sliding mode control. The maneuvering acceleration of target is regarded as a disturbance with boundary, and the adaptive parameters of system are designed by application of Lyapunov method. The simulation result verifies the correctness and effectiveness of the presented guidance law.Secondly, Two-dimensional guidance law is applied to there-dimensional, relative motion model of missile and target is established in three dimensional spherical coordinates, the maneuvering acceleration of target is regarded as a disturbance with boundary, 3-D variable structure robust guidance law for homing missile based on zeroing normal speed of LOS(line-of-sight) is presented in intercepting the high maneuverable target, and the adaptive parameters of system are designed by application of Lyapunov method. Numerical simulation shows that the rates of LOS approach zero. The simulation result verifies the correctness and effectiveness of the presented guidance law.Finally, 3-D adaptive fuzzy variable structure guidance law for homing missile based on zeroing speed of LOS(line-of-sight) angle is presented in intercepting the high maneuverable target. The fuzzy system is used to approximate the nonlinear function which is unknown in the guidance system so as to overcome the influence of model uncertainty and external disturbance, and the maneuvering acceleration of target is regarded as a disturbance with boundary, which is estimated. Numerical simulation shows that the rates of LOS approach zero. The simulation result verifies the correctness and effectiveness of the presented guidance law.