# A Review of Autonomous Tugboat Operations for Efficient and Safe Ship Berthing
## 2 Current Developments of Unmanned/Autonomous Towing Technology
### Projects Related to Autonomous Towing  
Figure 1 illustrates the global efforts being made to automate the process of ship berthing using autonomous/remote tugboats. Many countries have presented concept point models of autonomous tugboats and have achieved complete remote control and smart tugboats. The automation of tugboats can be categorized into several levels based on their degree of autonomy. These levels provide a standardized framework for the development and assessment of autonomous tugboats. The first level involves automated process and decision-making support, the second and third levels allow for remote control with or without a crew member on board, and the fourth level represents fully autonomous tugboats capable of making decisions and taking actions on their own. Currently, various countries are conducting research and development projects aimed at achieving different levels of automation in the field of tugboat operations [8]. In November 2017, Maersk Line, a Danish shipping company, collaborated with Rolls-Royce to achieve a significant milestone in the maritime industry. The world's first remote tugboat, named \"Svitzer Hermod\", was remotely operated in Copenhagen Harbor. During the navigation test, the vessel was remotely controlled by the Remote Operation Center (ROC) located at the pier. The ship successfully proceeded along the pier, anchored at the target point, and rotated 360 degrees before safely returning to the pier and docking, as shown in Figure 2. The remote control system was made possible by the Dynamic Positioning System (DPS), which is the core of the system, and the ROC, as depicted in Figures 2 and 3. It is worth noting that while the operation was successful, due to the presence of the crew on board, it was not a completely unmanned operation [10]. Figure 1: Ship berthing process using Intellitug developed by Wartsila [9]. Figure 2: Description of pilot test scenario of the tugboat \"Svitzer Hermod\" [11]. Maersk Line and its subsidiary Svitzer, in collaboration with Kongsberg and the American Bureau of Shipping (ABS), have jointly developed the RECOTUG, which is the world's first fully remotely operated tugboat. This breakthrough has led to a significant increase in research in this area [12]. By remotely controlling the tugboat, it is possible to significantly reduce the risks to human life associated with towing operations, as well as to increase the efficiency and reliability of tugboat services. The ABB/KEPPEL project provides another example of a successful remotely piloted project. Singapore-based Keppel O&M (Keppel Offshore & Marine) and ABB(Asea Brown Boveri) collaborated to remotely control a tugboat for the first time in South Asia using a joystick, which was carried out in Singapore. The ABB Ability(tm) Marine Pilot Vision digital solution, shown in Figure 4, was used to provide sensor fusion in an onboard system that increased digital situational awareness. Additionally, the ABB Ability(tm) Marine Pilot Control system, shown in Figure 5, was used to achieve remote control by executing intelligent start-up and control commands. Since more than 130,000 vessels pass through the Port of Singapore annually, it is one of the most complex autonomous port operating environments globally. As a result, this test is a significant step towards demonstrating the safety and efficiency of using digital solutions that are already available for ships' towing operations [13]. Figure 4: ABB Ability(tm) Marine Pilot Vision Digital Solutions [14]. Figure 5: ABB Ability(tm) Marine Pilot Control system [15]. Figure 3: Tugboat ”Svitzer Hermod” (left) and Remote Operation Center (ROC) (right) used in the project [11]. In 2015, [PERSON] of the United States presented a conceptual model of an autonomous tugboat that involves the installation of a towline between the mothership and the tugboat, as shown in Figure 6[16].