The formation of biological fouling on a ship’s hull can affect the fuel efficiency and environmental impact of a ship. A layer of slime can increase the frictional drag of a ship by up to 40%, reducing fuel efficiency. This increases the potential emissions and operational costs. Fouling is also transported from port to port, increasing the risk of introducing invasive species and damaging a port’s ecology.
Current cleaning systems available have to be used while in port or in a dry dock and some use divers in order to operate the machinery. By designing an autonomous robot which can be operated while the ship is underway a number of benefits are gained. The vessel need not spend as much time in port, minimising operational impact. In addition, by not requiring divers, both the cost of cleaning and the human risk involved can also be significantly reduced.
In order to design the robot, a number of focus areas were identified - the hydrodynamic hull form, the attachment and propulsion method, and the autonomous system. Using Computational Fluid Dynamics (CFD), an outer shell was developed in order to minimise drag and lift caused by the robot, both of which would cause detachment from the ship’s hull. The forces on this shell were then used to determine an appropriate attachment and propulsion method - magnetic caterpillar tracks driven by two high torque DC motors. The autonomous system was developed alongside these and produced a system capable of planning a route and detecting and avoiding obstacles on that route using ultrasonic sensors.
Testing of the components consisted of wind tunnel testing in order to validate the CFD, pull tests in order to test the attachment and motor strengths and autonomous tests requiring Remora to navigate around an obstacle. Through these tests it was found that while the robot would only be able to operate at ship speeds of up to 8 knots in her current configuration, some simple design changes to the track and suspension systems would be able to increase that speed to at least 15 knots. The autonomous systems test showed Remora could successfully navigate around obstacles.
More comprehensive testing, as well as future development to the track, suspension, and autonomous system could see Remora operating in a wider
Current cleaning systems available have to be used while in port or in a dry dock and some use divers in order to operate the machinery. By designing an autonomous robot which can be operated while the ship is underway a number of benefits are gained. The vessel need not spend as much time in port, minimising operational impact. In addition, by not requiring divers, both the cost of cleaning and the human risk involved can also be significantly reduced.
In order to design the robot, a number of focus areas were identified - the hydrodynamic hull form, the attachment and propulsion method, and the autonomous system. Using Computational Fluid Dynamics (CFD), an outer shell was developed in order to minimise drag and lift caused by the robot, both of which would cause detachment from the ship’s hull. The forces on this shell were then used to determine an appropriate attachment and propulsion method - magnetic caterpillar tracks driven by two high torque DC motors. The autonomous system was developed alongside these and produced a system capable of planning a route and detecting and avoiding obstacles on that route using ultrasonic sensors.
Testing of the components consisted of wind tunnel testing in order to validate the CFD, pull tests in order to test the attachment and motor strengths and autonomous tests requiring Remora to navigate around an obstacle. Through these tests it was found that while the robot would only be able to operate at ship speeds of up to 8 knots in her current configuration, some simple design changes to the track and suspension systems would be able to increase that speed to at least 15 knots. The autonomous systems test showed Remora could successfully navigate around obstacles.
More comprehensive testing, as well as future development to the track, suspension, and autonomous system could see Remora operating in a wider
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- Magnetic vertical pull test on coated tracks
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- Track curvature visualisation
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- Above Wind tunnel testing of Remora’s hydrodynamic shell with smoke visualisation
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- Robot hull form in CFD
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- Artifical Potential Field Path Planning Algorithm
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- DC motor attached to mounting