Robot assistant for fueling vessels

The research project Fuel – Ship2Ship at the University of Applied Sciences in Kiel reseaches the autonomous refueling of ships with alternative fuels at sea.

A ship approaches a bunkering station—whether at sea or in a harbor. A robotic arm equipped with a fuel hose automatically moves into position, the nozzle inserts itself into the tank, and the fuel begins to flow. Within minutes, the ship is refueled. The hose retracts, and the ship departs. Researchers at Kiel University of Applied Sciences are working on making this vision a reality as part of a projekt in the framework of CAPTN Energy.

The Fuel – Ship2Ship project aims to develop a robot-assisted system for the autonomous refueling of ships under rough sea conditions. “Due to the increasing demand for green fuels such as methane, ammonia, and hydrogen, we need a dense network of bunkering stations that allow ships to refuel quickly and easily—ideally in an automated manner,” explains project engineer Max Senkbeil. Since the energy density of these fuels is significantly lower than that of fossil fuels, ships will need to refuel more frequently. “With our project, we not only aim to develop solutions for robot-assisted refueling but also to increase acceptance of environmentally friendly fuels,” says Senkbeil. The biggest challenge: the ocean itself. Waves move both the ship and, potentially, the floating refueling station.

The idea is simple: the bunkering station is equipped with a robot consisting of a crane-like, movable arm and a sensor system. This system detects the ship’s movements and transmits real-time data to the robotic control system. The robot adapts to the ship’s motion and carries out the refueling process. “We are currently working with a camera system and artificial intelligence that analyzes the images and translates them into control impulses,” says Senkbeil. The difficulty lies in tracking the relatively fast and unpredictable movement of both the ship and the nozzle at the end of the robotic arm to initiate the docking process. Researchers are still determining which type of mechanical coupling between the robot and the ship is the most practical. “Right now, we are working on how best to integrate impedance control into our system,” explains Senkbeil. This branch of robotics, which deals with force regulation, ensures that the robotic kinematics can react appropriately to external forces—helping to prevent damage during the refueling process.

In addition to the above mentioned land-to-ship refueling, the team is also researching ship-to-ship refueling solutions. They have developed a demonstrator for this purpose. This test setup, located in the automation lab at the university, consists of a sensor system, a simulation environment, and two robotic arms. One robot simulates the receiving ship, receiving position data from a simulation that models various sea conditions and ship movements. The second robot, equipped with sensors, tracks the refueling interface and performs the connection and refueling process. Simulating ship movements in waves is a crucial aspect of this experiment. Using this setup, Senkbeil determines the system’s required movement dynamics, precision, and robustness, comparing the results with real-world data.

In theory, the robotic arm designed for refueling has already demonstrated its ability to compensate for wave heights of up to 2.5 meters. Senkbeil himself designed the laboratory demonstrator, implementing both the hardware and software. Electrical control cabinets also need to be built to withstand environmental conditions, while a heavy-duty workbench serves as a stable foundation for the 120-kilogram robotic arm.

A digital twin—a virtual copy of the system—allows engineers to test motion control and sensor processing beforehand. “This is important, for example, to determine the optimal routing of the fuel hose. Is there an obstruction in the way? Is the movement range restricted?” elaborates Senkbeil. Based on the data, the team creates a requirement profile and concrete recommendations for real-world implementation on a ship. The research catamaran MS Wavelab, part of the CAPTN initiative, serves as a test case. By the end of the three-year project, not only should the refueling robot be fully designed, but the necessary ship-side requirements should also be clearly defined. These include the maximum distance between the catamaran and the robot, the design of the refueling interface, and possible nozzle-locking mechanisms.

Ultimately, the refueling process should be completed in a fraction of the time required for manual refueling by human operators. Additionally, the use of robotics should reduce the risk of accidents. “Of course, we are incorporating safety mechanisms. An emergency disconnect—a rapid disconnection process in case of errors—is absolutely necessary. It’s also conceivable to install a camera that externally monitors the refueling process and detects irregularities. Automated systems can react much faster than humans,” says Senkbeil. Therefore, transmitting refueling data to a control center might not always be practical. “Real-time capability is best ensured when all refueling process steps are executed within a centralized industrial control system. Such a system can react to events within milliseconds, enabling sensor-guided robotic movement essential for the refueling process. These reaction times are simply impossible for humans.” However, in real-world operations, data can still be transmitted to a land-based control center for monitoring purposes.

The next step is practical implementation. The first real-world trials are planned for this year.
Funding and Project Leadership

The research project is receiving €380,000 in funding from the German Federal Ministry of Education and Research (BMBF) as part of the WIR! Alliance CAPTN Energy. The project is led by Prof. Dr.-Ing. Christoph Wree and Prof. Dr.-Ing. Bernd Finkemeyer from Kiel University of Applied Sciences.