CSurvey—An autonomous optical inspection head for AUVs

• We are using a structured light system on an autonomous pan–tilt unit (PTU) which acts as sensor carrier for an AUV.
• The system has been especially designed to work in turbid water.
• The influences of turbidity in water on the PTU are investigated in detail with a special experiment.
• The results of the first integration of the PTU on its target AUV and of the turbidity tests are presented in this work.

The inspection of underwater structures and facilities by autonomous underwater vehicles (AUVs) is of an increasing interest in the offshore industry. The big advantage of AUVs compared to the currently used method of deploying remotely operated vehicles (ROVs) or divers is, that AUVs require significantly less operational overhead and can be operated in parallel to other tasks. Currently AUVs are primary used for hydrographic and scientific applications and are therefore not suited for the demands of inspection tasks. The autonomous inspection unit developed within the CSurvey project and presented in this paper acts as an intelligent sensor package, allowing the deployment of a sensor package suitable for different tasks on a commercial AUV. The main focus of this article is to introduce the mechatronics and control of this inspection system and present the results of experiments done with its primary high-resolution sensor, which is based on laser-projected structured light. The main focus of these experiments was to quantify the impact of water quality on the sensor system, especially within respect to sensing range.