First Trial of Underwater Excavator Work Supported by Acoustic Video Camera

Abstract

[abstFig src='/00280002/04.jpg' width=""300"" text='The experiment of recognition by acoustic video camera' ]External recognition is important for underwater machinery works. However, acquisition of external field information from optical camera images may not be possible, owing to muddiness of water caused by such work. Furthermore, in order to improve the workability of machines in the scenario of their remote operation, it is important to know the positional relation information between a target object and the end effector. To solve these problems, an acoustic video camera was developed and performance test experiments were conducted at a caisson dockyard. In the experiments, a prototype of acoustic video camera was used to measure and to recognize a target objects and an underwater construction machine. And the feasibility of monitoring for underwater construction using the acoustic videos was evaluated. As a result, it was found that despite the lower accuracy of shape recognition on account of a resolution problem, the positional relation could be recognized satisfactorily since the video images could be presented from an arbitrary viewpoint.

Verification of resolution on self-focusing effect of polarization-inverted transmitter by up-chirp signal for subaperture array

“…However, the required distance range is the acoustic near field of the 3D underwater acoustic video camera, and the transmission field is changed in a complicated manner; hence, false acoustic images tend to be captured. [22][23][24] To solve this problem, we studied the self-focusing effect of the polarization-inverted transmitter by up-chirp signal driving for subaperture arrays in the acoustic near field. 25) In this study, we examined these effects experimentally by (1) self-focusing without giving a delay to the driving up-chirp signal of each element of the polarization-inverted transmitter, (2) improving the focusing effect of the subaperture, and (3) moving the focal point to change the frequency component of the driving up-chirp signal.…”