Research On Coordinated Control Technology For Multiple Autonomous Underwater Vehicles

The technology of autonomous underwater vehicle(AUV) has achieved an impressive de-velopment during the last decades. AUV is playing an important role in such tasks as oceano-graphic data collection, resource exploration and underwater object inspection. As tasks get more complex, some times the single AUV can not full fill the requirements of tasks. Robust-ness, efficiency and flexibility are the advantages offered by multiple autonomous underwater vehicles(MAUV) over a single autonomous underwater vehicle system and hence has drawn more attention from research institutions all over the world than ever before.Although fast developed, some of the problems concerned with MAUV were not well solved. In this thesis, several key techniques concerned with cooperation of multiple au-tonomous underwater vehicle system were studied:1. A modularized, distributed software architecture was established for coordinated control of multiple autonomous underwater vehicle system. In this architecture,each AUV was abstracted as a group of software modules which has different functionality of their own while depends on the information provided by each other. The network protocol based information exchange mechanism provides a fast and stable means for exchange of information between software modules belong to the same AUV. The unified information exchange mechanism also makes it possible for modules of the same AUV to run in distributed fashion. Functionality of communication between different AUVs was realized by an relatively independent communi-cation module(which provides the software abstraction of the communication devices such as underwater modem),which provides a unified format for communication between AUVs.2. "Behavior-based" control theory was applied to the coordinated control of multiple autonomous vehicles. In order to improve the autonomy and adaptability of the AUVs in dy-namical undersea environments, behavior-based intelligent control strategy was studied. In the execution of cooperative tasks, motion command was generated by a set of interacting behav-iors.The multiple objective optimization based behavior fusion method was used in behavior fusion. IvP model was applied to ensure the realtime demand and optimized output of behavior fusion.3. As the jump of behavior fusion results will have influences on stability of AUV motion control,Nonlinear control theory and hybrid system theory was applied to the problem of "stability of behavior based control of AUV". A nonlinear motion controller of AUV based on command filtered backstepping(CFBS) was established. Control stability of AUV under jump of behavior output was studied and the conditions under which the AUV would remain stable was derived based on theory of multiple Lyapunov function.4. The problem of task allocation of MAUV was studied and "market-based" allo-cation strategy was applied to solve the problem.By inspecting the "Synergy effect" between tasks, an improved auction-based task allocation algorithm(cluster based task bidding algo-rithm) was proposed to improve the optimality of task allocation results.5. The problem of coordinated formation control was studied. Simplification was made on the motion model of MAUV coordinated formation control, graph theory was used to describe communication topologies between AUVs in the system. Consensus theory of multi-agent system was used to design distributed control laws of AUVs in formation control. The control law can be calculated by local information collected by the AUV and the direction of all the AUVs can be driven to the same value under the control law. Lyapunov function was design to prove stability of the system.6. Simulation environment for coordinated control of multiple autonomous under-water vehicle system was established, some typical task cases were designed to verify the feasibility and effectiveness of the methods proposed in this thesis.