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In recent years, forward-scan sonar is widely applied to the underwater inspection, which is not subject to the influence
of light and turbidity. For expanding the monitoring scope, the image sonar is generally mounted on the pan-tilt platform
of a ROV (Remotely Operated Vehicle) or survey boat. However, there are still some problems such as: 1) The field-of-view
is narrow, i.e. the horizontal view angle of DIDSON (Dual-frequency identification sonar) is 29°; 2) The dynamic
change of a ROV or survey boat by the water disturbances will cause the target to escape from the sonar image easily; 3)
The image sonar is fixed on the pan-tilt platform, and its position and posture are unceasingly changed. As a result of
these problems, the obtained images may be distorted and not on the same plane. To solve the above problems, stability
augmentation of pan-tilt platform based on the principle of bionic eye movements and a mosaic method of sonar images
are presented. According to the principle of the vestibule-ocular reflex, an active compensation control system of the
mechanical pan-tilt platform is developed. It can compensate the sonar image instability resulting from attitude variation
of a ROV or survey boat during operation. Applying multi-sensor fusion technology can rectify the sonar images with
different position and posture to be on a single geodetic coordinate frame for image matching. Finally, sonar images can
be mosaic. A stable large-scale sonar image can be obtained. The experimental results validate that the presented method
is valid.
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