With the increase in developments in underwater infrastructure, the demand for development of autonomous vehicle navigation system in structured environment is also increased. However, the localization in a structured environment is a challenging problem due to signal uncertainties and distortions. In order to overcome these problems, we propose the camera and sonar aided integrated navigation system. In the proposed sensor-fusion-based localization scheme, the AUV estimates its own position continuously using artificial landmarks. The artificial landmarks for image sonar is deployed along the path to guide the AUV to the structure. The active vision markers are installed on the jacket structure, and they function as both landmarks and waypoints. This approach prevents the inherent drift of dead-reckoning velocities and collision with structures. The proposed approach was verified through a real sea experiment. The AUV conducted the full autonomous navigation from the dock to the jacket structure, and then returned to the dock without collision or significant localization error. These results show the feasibility of full autonomous navigation in a structured environment.

We propose an adaptive generation method of desired velocity field for leader-follower type cooperative mobile robots with decentralized passive velocity field control (PVFC) which is a decentralized control algorithm of multiple robots handling a common object in coordination. The proposed control method for cooperative mobile robots is constructed by extending the PVFC. This research is different from the previous work in which a common desired velocity field for cooperative PVFC and all cooperative mobile robots was only following the same desired velocity field using the proposed method supervisor can easily specify the behavior of the mobile robots. The stability and boundedness of the resultant system with the proposed control algorithm is also guaranteed. Finally, the proposed control algorithm is examined by computer simulations for cooperative tasks with two mobile robots, and the results illustrate the validity of the proposed control algorithm.

We have proposed a decentralized control method based on passive velocity field control (PVFC) in previous works (1997, 1998). However, the feedback was localized and the desired velocity field was given by a central controller. The geometry cooperative multiple mobile robot system whose subsystem is under nonholonomic constraints and which conveys a common rigid object in a horizontal plain was proposed. In this paper, we propose a method to generate the desired velocity field for cooperative mobile robots with decentralized PVFC. The proposed control method for cooperative mobile robots is constructed by extending the PVFC and ensures the stability and boundedness using projection algorithm. Finally, the efficiency of the proposed method is examined by computer simulations for cooperative tasks with two manipulators.