Ports must have a certain minimum depth so that ships can easily use them. Silt is regularly washed into the harbor via the locks with the tide and settles at the bottom. Dredging vessels ensure that the sediment is removed from the ground.
The German Aerospace Center (DLR) is researching with its partners Niedersachsen Ports and MAREVAL to make this process more environmentally friendly and at the same time more productive using an autonomous dredger. Field tests took place in the port of Emden in September 2023.
The settled silt is not dredged in Emden, but rather sucked in using the recirculation process and briefly exposed to atmospheric oxygen. Back in the water, the sediments remain suspended and the ships can sail through these suspended particles. In order to prevent the silt particles from settling back on the harbor floor, it is necessary for a dredging ship to continuously and systematically travel through all harbor basins.
New ship and new operating concept
The AMISIA project aims not only to research an autonomous dredging vessel, but also a suitable operating concept. AMISIA stands for “Advanced Port Maintenance: Intelligent, Sustainable, Innovative and Automated Dredging”. The DLR research boat “Sally” is used for the investigations. It is very maneuverable, can turn on the spot and is purely battery-electric powered.
“The project is particularly exciting because highly automated driving on water in regular operation is almost non-existent,” says Mirjam Bogner from the DLR Institute for Systems Engineering for Future Mobility , who is responsible for the test design and data evaluation for the project Responsible for field tests. “A particular challenge for the dredger is safe navigation in the port environment, which is constantly changing, for example due to ships at anchor. We are therefore researching a sensor concept that enables safe, automated navigation in these imponderable areas. We are also working on assistance to avoid collisions with the port infrastructure.”
Everything in view with sensors and cameras
There are sensors and cameras attached to Sally that keep an eye on the surroundings. Moving ships or the distance to the quay wall can be recorded in this way. Sally is also equipped with all kinds of assistance systems, such as collision avoidance sensors, autopilot and object recognition systems. The assistance systems are intended to take on most navigational tasks. For the test, Sally was equipped with a commercially available remote control. Here, the researchers want to test the limits of this system and future approval in a dredging vessel.
Remote controlled to autonomous through the port
The scientists tested three levels of automation in Emden. In the first stage, DLR employees controlled the ship from on board. In the second, a researcher remotely controlled the boat from a container converted into a ship’s bridge. In the third stage, the ship should be automated to such an extent that it can react independently to any problems that arise. Sally is already able to automatically stay on track and avoid obstacles. For safety reasons, the obstacles are only simulated in the system. In each phase there was another person on board so that if a problem occurred, they could intervene at any time.
The data from newly installed radar sensors and the point clouds generated from them will be examined in more detail over the next few months. The researchers expect to be able to detect unexpected obstacles or ships ahead, even under difficult environmental conditions. The findings from the tests will be incorporated into the final design and operating concept of an autonomous dredging vessel. Those involved in the project will present this in autumn 2024.
Better for the environment
In addition, AMISIA’s concept envisages an alternative ship propulsion system in order to make maintaining the floating excavator less CO2 – intensive in the future. The selection of drive alternatives ranges from hydrogen and synthetic methane to methanol to mixed solutions consisting of combustion engines and battery power – so-called hybrid drives. But fully electric drives can also be considered.