Introduction

Abstract

The subject of this book is the application of nonlinear control theory to control underactuated ocean vessels and to analyze stability of their controlled systems. A vessel is said to be underactuated if it has more degrees of freedom to be controlled than the number of independent control inputs. Many ocean ships are equipped with propellers and rudders for surge and yaw motions only, but without any actuators for direct control of their sway motion. The control of underactuated ocean vessels has become an active area of research in recent years not only because it poses many challenging questions in applied nonlinear control theory, but also because of its practical importance. This chapter starts with a brief review of the development in nonlinear control theory and its applications. Next, difficulties in control of underactuated ocean vessels are discussed. The chapter ends with a description of the organization of the book.