Research On Catastrophe Control Method And Its Application In Ship Motion

With the development of social economy and science and technology, the characteristic of control object in practical engineering becomes more variety of form. Especially in some complex manufacture process such as aeronautic and marine engineering, and electric system, catastrophe phenomena would appear which may affect normal state. So, to describe and analysis and control these catastrophe phenomena would be urgent for discussion. The found of catastrophe theory make this possible. But to control these catastrophes in accordance with peoples' intention, a new theoretical method would be formed based on the combination of control theory. This thesis devotes to establish catastrophe control methodology by combining with control theory, to investigate its theoretical framework, and to apply this theory to ship motion and stability control system.The proceeding of preliminary catastrophe control theory establishment is based on the comprehension and summary of existing research results. The theoretical framework includes many aspects:catastrophe definition, the content of catastrophe control, catastrophe control system model, catastrophe analysis method, catastrophe control method, and catastrophe control system design and so on, which purport is to provide programmatic guidance for catastrophe control applications.As a theoretical system, it contains two main positive and negative aims:one is to create new beneficial catastrophe while preserve all initial equilibriums, named catastrophe control; the other is to eliminate or restrain harmful catastrophe, called averse-catastrophe. For this study clue, this paper studies the catastrophe creation or restraining control arithmetic respectively, and succeeds to apply them in various navigational ship motions.The purpose of catastrophe creation control is to establish requisite catastrophe which includes static catastrophe characteristic and dynamic catastrophe characteristic at a desired location by inputting control law. For the main form of static one, the static catastrophe control method is put forward. Combining with static bifurcation distinguish conditions, many kinds of static catastrophe can be designed. And the control law is very easy and convenient. For dynamic catastrophe, tow controllers respectively in the low dimension based on transversality condition and high dimension on implicit criterion are given, which extends the application of control technology.In engineering, a majority of systems need restrain the entire catastrophe phenomena which would make system couldn't work in normal state and lose stability. In this paper, the three typical catastrophes as static, dynamic and embranchment types are investigated. In ship motion models, these three catastrophe characteristics are concretely analyzed. The control arithmetic are schemed out to restrain different catastrophes respectively.The static transcritical bifurcation catastrophe in submersible near-surface motion under wave disturbance force is discussed by qualitative and quantitative methods. The variable structure controller based on feedback linearization is designed to eliminate the static catastrophe phenomena.In analysis of the ship nonlinear rolling equation the Hopf dynamic bifurcation catastrophe is described. So the linear state feedback controller is employed to control this dynamic catastrophe. The influence of control parameters with different values are also presented to prove the control effects.A tow-degree-of-freedom ship nonlinear motion was investigated for double page cusp catastrophe and force-response embranchment catastrophe characteristics. By utilize of coupled state feedback method, the controller is derived to retrain these catastrophes.