Research On Motion Control System Architecture Of Underwater Vehicle

Ocean is the second strategic space among the land, ocean, sky and outer space. It is the exploitation base of biology, energy, water, metal resources and the most practical and potential space. The development of ocean will have direct and enormous influence on the development of economics and society. Underwater vehicle, as a sophisticated system integration of artificial intelligence, is a highly autonomous, self-learning unmanned platform to adapt to the volatile surroundings in complex ocean environment. Underwater vehicle will show its potential uses in maritime research and ocean development. The operator only needs to give the command to the underwater vehicle, which will complete the tactical and strategic missions by itself. As the most basic and essential part of underwater vehicle, the research on motion control system architecture have important meaning for implementing underwater vehicle design comprehensively. The motivation of the thesis is to establish synthetic motion control system architecture of underwater vehicle, which is not only compatible with intelligent planning system, but also have the advantages of expansibility and generality. The system architecture can be applied not only to autonomous underwater vehicles (AUV), but also underwater vehicles with specified missions.The author launches dissertation research under the topic of "Research on Motion Control System Architecture of Underwater Vehicle". Starting from system architecture of underwater vehicles, the author proposed a perception-control-executive (PCE) based motion control system architecture according to the characteristics of underwater vehicle. In perception layer, the following topics are included: perception of volatile surroundings, comprehension of motion state and underwater environment, command analysis of trajectory planning system and fault diagnose technology. In control layer, intelligent control theories, especially neural network control theory, are applied to design motion controller of underwater vehicle. In executive layer, various algorithms of force allocation are proposed by analyzing the hydrodynamics of different executive systems. The PCE based motion control system architecture is a kind of hierarchical architecture with definite task distribution, explicit relation and concrete requirement. However, perception layer can send command directly to executive layer in emergency which solves slow reaction problem of hierarchical architecture.Following the method of combining theory with engineering application, the PCE based motion control system architecture is proposed based on the rules of integrality, generality and extensibility and discussed from the viewpoint of subsystems, resources, distribution, safe and reliability and concrete application. The techniques of perception layer, control layer and executive layer are discussed in turns. The thesis includes the research of theory and methods, the engineering application and the experiment.Theory and methods:(1) Perception-control-executive (PCE) based motion control system architecture is proposed according to the characteristics of underwater vehicle, which provides a kind of standard and reference for the motion system design of underwater vehicle.(2) Virtual sonar based guidance law is presented by considering the ability of motion controller and the objective state specified by trajectory planning system both, which coordinates the behavior of motion control system and planning system.(3) Parallel neural network controller and neural network based adaptive sliding mode controller are investigated theoretically. By introducing self-learning part and desired state programming in parallel neural network controller, the shortcoming of slow convergence of neural network controller can be overcome. However, by introducing neural network and observer to estimate compensation function of underwater vehicle's model online, sliding mode controller can be improved even with high model uncertainty.(4) By conducting a series thruster and executive instruments hydrodynamic experiments, the hydrodynamic performances of normal executive instruments are discussed, which provides instructional meaning for design and configuration of executive system.Engineering Application:(1) Semi-physical motion simulation system of underwater vehicle is established. Not only the software logic but also the hardware architecture, information interface and reliability could be verified with the semi physical motion simulation system, which is essential to the practical application of underwater vehicle.(2) Modified S controller is presented for engineering application, which can handle the difficulties of heading control of underwater vehicle with high speed forward and the depth control besides the advantages of simple control model and parameter adjustment method.(3) Various algorithms of force allocation are proposed by analyzing the hydrodynamics of various executive systems. According to the task requirement, the highly efficient force allocation algorithm is adopted, which provides solution to various executive systems.(4) Underwater vehicle control software and graphic user interface are designed. UML language is utilized to design control software according to various configuration of underwater vehicle and object oriented methods are used to design the graphic user interface.Experiments:PCE based motion control system architecture is applied to some underwater vehicles with different mission requirements, such as autonomous underwater vehicle, remotely operated vehicle and fin-controlled underwater vehicle. The feasibility, expansibility and reliability of PCE based motion control system architecture are verified by sea trials, lake trials and tank experiments. Dealing with autonomous underwater vehicle, perception layer, control layer and executive layer are embedded inside underwater vehicle and the perception and control ability are emphasized. As to remotely operated vehicle, GDROV (General Detective Remotely Operated Vehicle), traditional client and PC architecture is adapted. However, to fulfill the requirement of GDROV, automatic control of dam-scanning, dead-reckoning algorithm and graphic user interface are introduced in system architecture. For fin-controlled underwater vehicle, the executive layer is emphasized to verify force allocation algorithm. The results of experiments show the feasibility and reliability of PCE based motion control system.A perception-control-executive (PCE) based motion control system architecture is proposed to fulfill control system's requirements of underwater vehicle. The techniques of perception layer, control layer and executive layer are discussed in turns. As the experiment results indicate, PCE based motion control system architecture is expansible and general to be applied to various underwater vehicles. The research production has comparable meaning for implementing underwater vehicle design comprehensively and has important practical meaning and application value.