On The Three-Dimensional Robust Nonlinear Guidance Law Design

The interception of high maneuvering targets is one of the important issues of guid-ance law design. The pursuit-evasion motion and kinematics model between missile and target are sophisticatedly nonlinear and strongly coupled. For the interception of high maneuvering targets, since the limited capacity of dynamic actuators and sensors, there exist the phenomenon of input saturation and incomplete measurement information, which create considerable requirement of research on the guidance law design problem with input saturation and incomplete measurement information. This dissertation focus-es on the guidance law design problems for the interception of high maneuvering targets with input saturation, incomplete measurement information, external disturbances, ac-tuator failures, and target maneuvers. The main works are summarized as follows:First of all, assume that all measurements are available, the guidance law design problem with input constraints, external disturbances, actuator failures, and target ma-neuvers is considered. For the interception of high maneuvering targets, accepting the intuition that nullifying light-of-sight (LOS) rate will lead to successful interception, the input-to-state stability (ISS) method is introduced to design a fault-tolerant con-trol guidance law to guarantee robust interception of a maneuvering target without the input constraints. The convergence of line-of-sight rate to a small neighborhood of ori-gin is ensured in theory, and the performed simulations results show that the presented approach is effective in achieving a successful interception. Then, a saturated fault-tolerant control guidance law is constructed to ensure that the resulting control signal will never incur input constraints using a modified saturation function. The convergence to a small neighborhood of origin is ensured in Lyapunov theory. the theoretical anal-ysis as well as simulation results show that the performance of the closed-loop system under the saturated fault-tolerant control guidance law can be guaranteed.Next, after simple considerations of input saturation using a sample input satura-tion function, the guidance law design and implementation problem is discussed only using LOS azimuths in the presence of incomplete measurement information. More-over, in the practical problems of the interception, the LOS rate is always combined with pursuer body rates, and not easy to compensate for the affects of body rate, espe-cially in a complicated and volatile situation. Besides that, more sensors and estimators may increase the complexity and the cost of the guidance system. First, a guidance law without input saturation only using LOS rate is proposed. Second, based on the guidance law only using LOS rate and a simple saturation function, a nonlinear robust H∞observer is introduced to estimate LOS rate. The LOS rate and error dynamics are input-to-state stability. The theoretical analysis as well as simulation results show that the performance of the closed-loop system under the guidance law with LOS rate measurement can be recovered by using a nonlinear robust H∞observer.Then, the guidance law design problem in the presence of input saturation and incomplete measurement information is studied. A dead zone operator based model is introduced to describe the saturation phenomenon, and a novel three-dimensional law based on input-to-state stability (ISS) and backstepping method is proposed such that the LOS rate is globally input-to-state stable. The theorem analyses illustrates the LOS rate can converge to a neighborhood of zero by adjusting the parameters. Using nonlinear robust H∞observer to estimate LOS rate, a novel three-dimensional law is proposed relative range, speed, and LOS azimuths by replacing LOS rate by its estimate against input saturation and target maneuvers. Moreover, the guidance law design problem is discussed using LOS azimuths in the presence of measurement noise. The simulation results show that the proposed approach is effective.Finally, in order to consider the attitude control in the process of guidance law de-sign, the attitude control problem of rigid body is discussed, and it lays a foundation for further study. The ISS small-gain approach can be efficiently applied to the con-troller design of the attitude control system for rigid bodies, and can realize a successful track of the predetermined attitude angles. And the information used for feedback con-trol is much easier to obtain. The external disturbances can be sufficiently suppressed. The theoretical analysis and simulation results have confirmed the effectiveness of the proposed approach.