Robust Control of A Missile System

Abstract

Missiles, known for their high agility and fast speed, are becoming increasingly important for defense purposes and they are frequently encountered, especially in air defense scenarios. In an air defense scenario, the missile is guided towards the target with the goal of intersecting the target's trajectory as quickly as possible or minimizing the deviation that will occur at the intersection point. Since these trajectories are produced in the missile guidance unit, this unit is vital to achieving the expected results from the missile. For years, intensive studies on this unit have been carried out by using different control methods, intelligent approaches as well as classical guidance laws.

Within this thesis, novel alternative structures are developed based on robust control methodologies with the purpose of designing the guidance laws that demand more than enough high accuracy in a short, finite amount of time. The first structure is based on two conventional control methods, which are the proportional-integral-derivative (PID) and the sliding mode control (SMC), while two traditional guidance controls, the Proportional Navigation (PN) guidance law and the Augmented Proportional Navigation (APN) guidance law, are designed for comparison of results. In the second structure, a novel composite 3D guidance law based on an adaptive integral sliding mode (AISM) control method utilizing an nonlinear disturbance observer technique is proposed for missiles. Firstly, the integral sliding mode control is proposed to get rid of the reaching phase of traditional SMC, as well as the adaptive law is used to design without the upper bound of the target information. Moreover, the NDOB is designed to estimate the target acceleration by handling as the disturbance to minimize the chattering phenomenon. The third proposed new guidance law includes a high-order sliding mode control technique that utilizes an adaptive algorithm and fuzzy gain scheduling to obtain its parameters online. In this guidance law, the super-twisting sliding mode guidance law, which is a high-order sliding mode control technique, is designed to overcome the chattering phenomenon, and also an adaptive law and fuzzy control are used to determine the controller parameters and gains. Stability analyzes of the proposed guidance laws are performed using the Lyapunov method. In the last structure, a new law based on the APN guidance law utilizing an NDOB technique is proposed. Thus, a different approach has been brought to classical guidance law. Here, an NDOB technique is used to obtain the target acceleration, and so when designing the APN guidance law, it can be designed without the need for target acceleration information.

Through numerical simulations, all designed and proposed guidance laws are evaluated and compared with different guidance laws according to several cases of the target. In addition, all guidance laws are evaluated in terms of the miss distance and interception time, and the results are presented. Throughout this thesis, it was clearly observed that the proposed guidance laws outperform the other schemes regarding the miss distance and interception time.