Harbors must have a certain minimum depth to allow ships to use them. Silt is constantly being washed in through locks. Dredgers remove the sediment from the seabed. This can also be done by an autonomous dredger.
The German Aerospace Center (DLR), together with its partners Niedersachsen Ports and Mareval, is researching ways to make the process more environmentally friendly and productive at the same time. Field tests were conducted in the port of Emden in September 2023. The deposited silt is not dredged there, but rather suctioned up using a recirculation process and briefly exposed to atmospheric oxygen. This causes the sediments to remain suspended in the water, allowing ships to navigate through these suspended particles. To prevent the silt particles from settling back on the harbor floor, it is necessary for a dredger to continuously and systematically traverse all harbor basins.
A project called AMISIA will also explore a suitable operating concept. AMISIA stands for "Advanced Port Maintenance: Intelligent, Sustainable, Innovative and Automated Dredging". The DLR research vessel "Sally", which is powered entirely by batteries and electricity, will be used for the investigations.
“This project is particularly exciting because highly automated navigation on water is virtually nonexistent in regular operation,” says Mirjam Bogner from the DLR Institute of Systems Engineering for Future Mobility, who is responsible for test design and data analysis for the field tests. “A particular challenge for the dredger lies in safe navigation in the harbor environment, which is constantly changing, for example, due to anchored ships. Therefore, we are researching a sensor concept that enables safe automated navigation in these unpredictable areas. We are also working on an assistance system to help avoid collisions with the harbor infrastructure.”
Object detection on board the test vessel
Sally is equipped with sensors and cameras that monitor its surroundings. This allows it to detect passing ships and its distance from the quay wall. Sally is also equipped with a variety of assistance systems, such as collision avoidance sensors, autopilots, and object recognition systems. These assistance systems are designed to handle most navigational tasks. For the test, Sally was fitted with a standard remote control. The researchers aim to assess the limitations of this system and its suitability for future use in a dredger.
Automation in three stages
In Emden, scientists tested three levels of automation. In the first stage, DLR employees controlled the vessel from on board. In the second, a researcher remotely controlled the boat from a container converted into a ship's bridge. The third stage aimed to automate the vessel to the point where it could react independently to any problems that arose. Sally is already capable of automatically maintaining its course and avoiding obstacles. For safety reasons, the obstacles are only simulated within the system. At each stage, a person remained on board to intervene at any time if a problem occurred.
The data from newly installed radar sensors and the point clouds generated from them will be analyzed in more detail over the coming months. Researchers expect this to enable the detection of unexpected obstacles or ships ahead, even under challenging environmental conditions. The findings from these tests will be incorporated into the final design and operational concept, which the project partners will present in autumn 2024.
Furthermore, AMISIA's concept envisions an alternative propulsion system to reduce CO2 emissions during the future operation of the floating dredger. The range of propulsion alternatives extends from hydrogen and synthetic methane to methanol and hybrid solutions combining combustion engines and battery power. Fully electric propulsion systems are also being considered.
Support crew in waiting position. Photos: DLR
The volume of AMISIA amounts to 3.23 million euros and is 78 percent financed by the German Federal Ministry of Transport.
