Structure tracing with a ranging system using a sheet laser beam

Autonomous Underwater Vehicles (AUVs) are suitable for condition survey of artificial structures such as pillars and caissons in harbors. The authors have developed a method to investigate the structures using AUVs. The method has been successfully demonstrated in tank tests and sea trials as reported in the previous papers. Since the ranging system in this method used an array of pinpoint lasers, it is oversensitive to noise, for example small obstacles and floating particles. This paper describes a method to trace the structure's surface using a sheet laser beam that overcomes the difficulties previously encountered. This ranging system determines the continuous shape of the target objects over a wide area by light-sectioning. The vehicle navigates referencing the principal shape of the structure, tracing its surface while taking video images. The method is implemented using testbed AUV "Tri-Dog 1" and verified by tank tests. It is proved that the new method is more robust against noise and trivial objects than the previous method that used a pinpoint laser ranging system. This ranging system can also be used for 3D mapping of the surface and bottom structure.

[1]  Hayato Kondo,et al.  Underwater structure observation by the AUV with laser pointing device , 2002, Proceedings of the 2002 Interntional Symposium on Underwater Technology (Cat. No.02EX556).

[2]  Tamaki Ura,et al.  Visual investigation of underwater structures by the AUV and sea trials , 2003, Oceans 2003. Celebrating the Past ... Teaming Toward the Future (IEEE Cat. No.03CH37492).

[3]  J. Kojima.  Cable tracking by autonomous underwater vehicle , 2003, 2003 International Conference Physics and Control. Proceedings (Cat. No.03EX708).

[4]  Hayato Kondo,et al.  Object observation in detail by the AUV "Tri-Dog 1" with laser pointers , 2001, MTS/IEEE Oceans 2001. An Ocean Odyssey. Conference Proceedings (IEEE Cat. No.01CH37295).

[5]  T. Ura,et al.  Construction and operation of four autonomous underwater vehicles for lake survey , 2002, Proceedings of the 2002 Interntional Symposium on Underwater Technology (Cat. No.02EX556).

[6]  R. L. Wernli.  AUVs-a technology whose time has come , 2002, Proceedings of the 2002 Interntional Symposium on Underwater Technology (Cat. No.02EX556).

[7]  Hayato Kondo,et al.  Development of an Autonomous Underwater Vehicle "Tri-Dog" Toward Practical Use in Shallow Water , 2001, J. Robotics Mechatronics.