Stability Analysis Of Special Controller Design Method For Underwater Vehicle

With the continuous development of science and technology of mankind,the demand for the development of the ocean is also becoming higher and higher.The abundance of marine resources goes far beyond the land and the ocean will become the main field for the future development of human,therefore,the marine exploration,research and protective development have become the main problem confronted by many coastal countries.As the intelligent tool which can replace humans for ocean exploration to a large extent,the underwater vehicle has been more and more applied into practice,including civil and military aspects where it is of irreplaceable importance.The underwater vehicle system is an intelligent system which requires high autonomy and security,Its motion control technology has always been a hot research topic.Although the design and control of the underwater vehicle depends on the specific requirements of the underwater operation,its control principle is consistent while what is different is the design of the function module in upper layer.Currently,with the extensive application of underwater vehicle and the continuous innovation of its structure,there are still many problems to be solved or improved in the control of it.This paper firstly introduces and analyzes the method and process in which the hydrodynamic theory is applied to construct the mathematical model of motion of underwater vehicle and describes the underwater vehicle model in detail,moreover,it also points out that the moving system of underwater vehicle can be depicted as a system determined by differential equations.Further,it also mentions that some important parameters in the system will be affected by the environment and sea conditions.From the perspective of control theory,it can be formulated as a stochastic control system changing with time.The random variation of the correlation coefficient matrix in the system model makes the underwater vehicle system operate in the form of generalized system.Therefore,the research on such dynamics model of underwater vehicle is carried out for the analysis of the possible problems that may occur in the process of control,after that,the paper highlights on this aspect and determines the preliminary control scheme,at the same time some innovative achievements have been made as well.The main contents of this paper are shown in the following aspects:1.The control problem of stochastic jump system is carried out and two problems are solved in this aspect.(1)In order to reduce the conservatism and improve the control efficiency of the stochastic jump system,the Lyapunov functional method is used to design the controller for the stochastic jump system.After referring to the relevant information and literature of many years,it is found out that there is no Ito formula for Lyapunov function required by the relevant theory.According to the situation,this paper derives the form of Ito formula solution where the Lyapunov functional complex is applied to stochastic differential system,moreover,the strict proof is presented as well.(2)In the control process of the stochastic jump system,the real-time data of the correlation coefficient of the system is required.But these time-varying data,such as the hydrodynamic coefficients must be calculated by a large number of real-time data as submarine and sea currents data in the classical theory of potential flow,so it is difficult to determine them to some extent.On such basis,this paper has obtained a identification method for correlation coefficient.These two innovations not only help to solve the problem of random jump system control of underwater vehicle in the paper,but also provide theoretical support for other control of this category.2.Since the underwater robot system can be expressed as a generalized system in some cases,in this paper,the characteristic of the generalized system is analyzed in detail.On the basis of the existing three kinds of standardized modes of restricted equivalent type,a new one is obtained and the uniqueness of the model is proved.By using the standardized modes of restricted equivalent type,the proof for the existence of the impulse in the generalized systems is obtained.Finally,the identification method for the fast subsystem of the generalized system is proposed,which is based on the decomposition of the generalized system into the slow subsystem and the fast subsystem.In this paper,the research results of generalized systems have met the requirements of underwater vehicle control and it can be completely generalized into the general descriptor systems so as to provide theoretical support for the research of other generalized systems.3.In view of the situation that the underwater vehicle system may confront failure in the process of operation,the paper has carried out the research on fault tolerance control to ensure that it is still able to continue working in failure.The fault tolerance control is divided into the active fault tolerance control and the negative one.(1)A fault diagnosis method is proposed which can be applied for diagnosis of executor and sensor,in the unit operation cycle of the system according to active fault tolerant control problem,standing on the diagnosis of failure and by using the D-stability theory based on linear matrix inequalities.So,it has solved the problem of limited time diagnosis.(2)According to the control problem of passive fault tolerant,a partial order relation is proposed by using the defined stable fault set.The existence condition of the state feedback H_?control law is analyzed and the design method of fault tolerant controller H_?in multiple step formats is put forward.The method not only ensures that the system can operate normally when the combination of the fault types is included as many as possible in the situation that the fault of system occurs.Furthermore,the fewer the number of faults is,the better the system performance for its fault tolerant control will be.