SHIP MANEUVERING ASSISTANCE SYSTEMS

When it comes to ship maneuvering assistance systems, the first technology that comes to mind is the 'Dynamic Positioning System (DPS).'

Although this system, which we will explain in detail in a subsequent article, is not the main subject of this writing, we can briefly summarize it as follows:

Today, it is a maneuvering system that performs maneuvers with extreme precision for marine vehicles that require very high positional accuracy, such as platform support vessels and specialized tugboats handling anchorage.

The 'Dynamic Positioning System' achieves this by utilizing DGPS position data, which is expressed with an error margin of only centimeters, in addition to radar and sonar signals from beacons fixed on the platform. The system executes the desired maneuver with minimal deviation using a method called the 'Kalman Filter.' In fact, we can say that this filtering method is a much more complex and precise form of the working principle of autopilots.

The 'Dynamic Positioning System' performs its function with a precision expressed in centimeters, and frankly, it is not possible to execute the mentioned maneuvers with the same precision and minimal deviation values using human perception.

'Dynamic Positioning System Operators' are trained and certified through specialized courses.

Currently, the 'Dynamic Positioning System,' which is a relatively expensive technology, has found widespread use only in the special vessels mentioned above. However, with the advancements in artificial intelligence in this field, the technology has started to become relatively cheaper and has begun to be used in some passenger ships as well.

Although the 'Dynamic Positioning System' continues to be a relatively expensive technology, it is crucial to be aware that the performance of computer and artificial intelligence-supported technologies in applications like DPS has long surpassed the accuracy and precision of human perception in the field of ship maneuvering.

After providing a brief summary of the 'Dynamic Positioning System,' we will discuss another tool that has been widely used for a long time, especially in tanker and gas terminals, which can be defined as the 'Docking Aid Systems (DAS).'

The main parameters of the docking aid system are shown in Figure-2 and consist of the following headings:

1. Laser Sensors

2. Display Board

3. Main Computer

4. Maneuver Screen

5. Auxiliary Sensors

a. Current Sensor

b. Tide Sensor

c. Weather Sensor

If we take a closer look at these parameters:

1. Laser Sensors: Laser sensors are placed at least 25 meters apart from the dock where the docking will take place.

The number and spacing of laser sensors are determined based on the various ship sizes that will approach the dock, ensuring that they will control the bow and stern points of the approaching ship.

Laser sensors use non-harmful Class 1 infrared energy beams to calculate the bow-stern distance and bow-stern approach speed of the ship from approximately 300 meters away.

Laser sensors are generally made of stainless steel or aluminum and are placed on a telescopic base that can be extended or shortened. This prevents them from coming into contact with water depending on tide conditions.

Laser sensors take the contact surface of the fenders as the zero point.

2. Display Board: Display boards are large panels that allow the ship's captain and pilot to see the calculated bow-stern distance and bow-stern approach speeds, which are computed from the beams sent by the laser sensors, from approximately 250 meters away, both day and night.

They are generally mounted on bases that vary between 1 to 4 meters in height. The display board can typically rotate +/- 35 degrees both vertically and horizontally, thus adapting to variable bridge heights and ship length changes.

As seen in Figure-4, the top part of the panel displays the bow and stern distances in three digits side by side (0.0-19.9 m, 20-200 m). Below the panel, the bow and stern approach speed is displayed in two digits as cm/s (0-99 cm/s).

Additionally, the panel features three colored warning lights: red, yellow, and green.

Red indicates that the maximum speed parameter for a certain distance is being exceeded very quickly.

When yellow is lit, it means the ship is approaching the dock at a speed above the designated ideal speed parameter from the bow or stern, or both.

If green is lit, the ship is approaching the dock at a safe speed below the designated speed parameter.

Generally, when there is a distance of 100-150 meters to the dock, an approach speed of 24 cm/s is considered normal, while in the final stages of docking, this parameter is adjusted to below 10 cm/s.

3-4. Main Computer and Processor Unit: The data from the laser sensors and other auxiliary sensors (current, tide, wind sensors) pass through the processor unit on the main computer, providing us with speed and distance values.

Other computers in the terminal can be connected in parallel to the main computer. These processors are designed by manufacturers to be completely independent and unaffected by power outages.

5. Portable Pilot Unit (PPU): Portable handheld units, which can be described as pagers, allow the ship user to view the information displayed on the panel on a small device that can be carried. Depending on the antenna and frequency power, these devices can start receiving information from approximately 2-3 km away. Information is transmitted via UHF frequency (464-468 MHz).

Distance and speed information is transmitted on an LCD screen, which can be illuminated if desired, across four lines, each capable of holding 20 characters, as shown in Figure-8.

The angle value seen in the bottom line of the figure indicates the angle at which the ship is approaching the dock line. If this angle is positive, the bow of the ship is closer to the dock than the stern (Bow-in). If the angle value is negative, the stern of the ship is closer to the dock than the bow.

6. Auxiliary Sensors: One of the auxiliary elements of the system, the current sensor operates on the Doppler principle and measures current speed, direction, and water temperature through the acoustic signals it sends into the water.

The tide parameter is detected through laser sensors under all kinds of snow, rain, and sea conditions.

The weather station in the system is equipped with sensors that measure wind speed and direction, precipitation, barometric pressure, temperature, and relative humidity. All this information is instantly transmitted to the main computer within the system and can be viewed on the screen.

7. Maneuver Screen: Depending on various manufacturers, the screen presentation may have slight differences, but the maneuver can be monitored at every stage from the terminal and all connected computers, either from a bird's-eye view or as a graphical representation of bow-stern distance and speeds. All this information is recorded and stored in the system's memory.

On the screen, information such as bow-stern distance, bow-stern approach speed, the ship's lateral transfer track, points where the ship should stop and begin lateral transfer, wind speed and direction, current speed and direction, etc., can be displayed as desired. When we look at the maneuver screen shown in Figure-9, we will see that in addition to all the mentioned information, the positions of the laser sensors are also displayed on the screen. The wind and current direction and forces are shown on the left side of the screen. One noteworthy difference here is that when the bow of the ship is close, the angle value is generally expressed positively, while in this example, it is shown negatively. The section where the stern of the ship will dock is indicated as North, and the section where the bow will dock is indicated as South.

The ship is approaching the dock at a speed of 58 cm/s from the bow, which is higher than the stern.

Figure-10 shows a screen that graphically represents the situation instead of a real image.

Upon examining the graph, it is clear that initially, the bow of the ship is approaching the dock more closely, but at 08:45, with a distance of 31 meters from the bow and 39 meters from the stern, the ship's approach has stopped and it has started to move away from the dock.

This is clearly visible from the U profile on the graph. Shortly after 08:47, the stern of the ship was closer to the dock than the bow for a while, but soon the situation reverted to its previous state. Additionally, after 08:47, the ship noticeably began to approach the dock again.

Conclusion: Docking assistance systems contribute positively by providing critical information to ship users at every moment of the docking maneuver, thus eliminating the risk of errors and inadequacies in human perception.

In the arrangement of 'Docking Assistance Systems,' including the 'Dynamic Positioning System,' human perception acts almost as a secondary element alongside technology.

With artificial intelligence rapidly making its impact felt in every aspect of life, we can foresee that these developments will significantly enhance and change traditional ship maneuvering consultancy and formats in the not-so-distant future.

Source: SeaNews Türkiye