Design of an underwater positioning sensor for crawling ship hull maintenance robots

In recent years there has been a significant increase in the automation of ship hull maintenance tasks such as cleaning, paint stripping, and in-water inspection. This is driven by several factors including reduction in cost, environmental hazard, and impact on the health of workers. The development of autonomous systems has been limited by the availability of suitable position sensors capable of providing accurate and repeatable information to a robot control system. This paper presents the development of an optical position sensor (OPS) suitable for use both underwater and in air, and designed to operate on a crawling ship hull robot. The OPS provides dead-reckoning position data which may be used in conjunction with a landmark position sensor for navigation of a robot. The OPS was based on an optical mouse sensor and telecentric lens and has been shown to provide accurate position information over a range of test speeds and working distances and when operating under non-ideal conditions in terms of angle with respect to the ship hull surface.