Researches On System Characteristics Analysis And Control Methods Of Underwater Vehicle

Underwater vehicle, as marine tool explored and developed by human, is playing animportant role in both military and civilian fields. Underwater vehicle that will be furtherdeveloped and more sophisticated along with development and utilization of marine resources,protection of marine, and human knowledge, will be widely used in21st century. So far,many control methods have been applied to system of underwater vehicle, and contributed tomany outstanding achievements. However, there are still a lot of problems to be solved incontrol of underwater vehicle.Taking into account the complexity of the existing environmentof underwater vehicle, it is necessary to conduct further research concerning how to determinethe hydrodynamic coefficients in different marine conditions at any time and establish aprecise relatively mathematical model, how to design a more effective controller to makeunderwater vehicle move, and how to design a stable controller to help underwater vehicle tocomplete work when the systems have faults of actuator and sensor, etc.Firstly, from the perspective of system characteristics of underwater vehicle, therelationships between hydrodynamic coefficients and marine conditions of underwater vehiclewill be researched by using potential flow theory with the velocity potential function as abridge. Secondly, under the considering that system is no fault, design method of diving depthcontroller and underwater vehicle heading are both proposed through linearization ofunderwater vehicle system. Finally, some methods of fault-tolerant control are describedtaking into account the actuator and sensor failure, as well as the characteristics in strongcoupling and nonlinear.The contents and innovations in this paper are as follows on the basis of absorption ofthe previous results and research advanced:Firstly, robust H∞heading controller and diving depth controller have been designed.Without taking into account the fault of actuator and sensor, the robust H∞heading controllerand diving depth controller have been designed respectively by using linear matrix inequalityin heading control system and diving depth control system of underwater vehicle. The part ofstate nonmeasurable problems in heading control system of underwater vehicle can be solvedby robust H∞controller of state observer which has been designed, and achieve asimultaneous design of state observer and controller. It has advantage of fast convergence rateand less unknown parameter matrix comparing to the previous. In addition, in the base of dynamic model in existing underwater vehicle, it will make more practical significance incontrol problem though introducing hardness limited in control input. The existing problem ofdiving depth controller of underwater vehicle is converted to the problem whether linearmatrix inequality has feasible solution.It will provide a new idea to design diving depthcontroller of underwater vehicle by using methods mentioned above.Secondly, based on linear matrix inequality, a method of H∞fault-tolerant control ispresented. The methods of H∞fault-tolerant control on the conditions that only actuatorfaults or simultaneous sensor and actuator faults exist have been designed respectively using aclass of nonlinear systems satisfying Lipschitz condition. The methods above have beenapplied to heading controller successfully. The methods of H∞fault-tolerant control not onlyensure the system to achieve stability in fault or normal circumstances, but inhibit interferenceeffectively. It applies not only to the course in heading control system of underwater vehicle,but also applies to multi-input nonlinear systems satisfying Lipschitz conditions, whichprovide a new way to achieve fault-tolerant control of nonlinear system.Thirdly, based on feedback linearization theory, a method of guaranteed costfault-tolerant control in underwater vehicle is proposed, which not only can make the systemin stability in sensor failure, but make the system fulfill the specified performance indicators.It certainly has some theoretical and practical significance to provide a new way to reslovesensor fault of underwater vehicle.Fourthly, the fault-tolerant control method is proposed based on fault diagnosis observer,fault diagnosis observer and fault-tolerant controller are respectively designed correspondingto the nonlinear systems of constant fault and time-varying fault. The fault-tolerant controlmethod applied to the linear system is extended to a special class of nonlinear systems,broadening the range of application, and applying to heading control system of underwatervehicle. The fault-tolerant controller designed not only can guarantee the asymptotic stabilityin fault system, but meet multi-performance index. It will be simple and convenient when theform of partitioned matrix is used.