Guidance Law Based On Nonsingular Terminal Sliding Mode Control And Finite-Time Disturbance Observer

Missile is a kind of precision guided weapon which is used as defensing or attacking. Interceptor missiles are used to intercept guided bombs, fighter, cruise missile and other maneuvering targets. The missile guidance control system is the most important part of the missile. The guidance law is one of the key technologies of the guidance control system. As the development of the modern control theory and space technology, more and more advanced control algorithms are used to design guidance law.In the interception process, target maneuver is the most important factor to cause the miss distance. In the presence of target maneuver, traditional guidance laws are no longer effective. Besides, the autopilot dynamics of missile is also one of the factors to cause the miss distance. So, the advanced guidance law is needed to study with the consideration of autopilot dynamics of missile.In this paper, a composite guidance law is proposed with consideration of the autopilot dynamics of missiles. To guarantee the finite time convergence and alleviate the chattering problem, nonsingular terminal sliding mode control(NTSMC) and finite-time disturbance observer(FTDO) are introduced to design the guidance law. A first order model is used to represent the autopilot dynamics of missile. In dealing with the guidance system, target maneuver is regarded as disturbances. In the presence of the autopilot dynamics, the disturbances are not in the same channel with the guidance law. These disturbances are mismatched disturbances. These disturbances are estimated accurately by finite time disturbance observer. The estimations of disturbances are employed as feedforward compensation to reduce the influence of disturbances. By using NTSMC-FTDO guidance law, the LOS angular rate converges to zero in finite time in the presence of autopilot dynamics and target maneuvers. Different from previous work, the proposed guidance law does not need the second order differential information of LOS rate and relative distance. It has a simpler form and reduces the effect of measuring noise. The miss distance of NTSMC-FTDO guidance law is much smaller than that of PNG with the presence of autopilot dynamics and target maneuvers. The main contents are as follows:Firstly, the basic knowledge of missile guidance system and traditional guidance laws are introduced. Then the development of modern guidance laws are introduced in Chapter 1 including optimal control, sliding mode control, disturbance observer technology and finite time control theory.Then, the missile-target relative motion model is given in Chapter 2. Common coordinate system and coordinate transformation are described firstly. Then planar and three-dimensional kinematic models of missile are given.Hereafter, the nonsingular terminal sliding mode control theory and finite-time disturbance observer are introduced in Chapter 3. Lastly, planar and three-dimensional finite -time disturbance observer based guidance laws are designed with the consideration of autopilot dynamics in Chapter 4 and 5.