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Active Controlled Tank (ACT) systems are sophisticated roll damping mechanisms that utilize the controlled movement of fluid within tanks to counteract the rolling motion of a vessel. They typically consist of the following main components:

1. Tanks:

• Usually, there are two tanks, one on each side of the ship, located at a strategic position, often near the midship section to maximize the leverage against the rolling motion.
• The tanks can be U-shaped or separate tanks connected by a duct at the bottom.   1. On the development of ship anti-roll tanks | Request PDF – ResearchGate www.researchgate.net
• They are partially filled with water or another suitable fluid.

2. Pumps or Valves:

• Active control is achieved through the use of pumps or valves that regulate the flow of fluid between the tanks.   1. Antiroll tanks – Wikipedia en.wikipedia.org
• Pumps actively transfer the fluid from one tank to the other, while valves control the flow rate and direction.

3. Control System:

• A sophisticated control system, typically consisting of sensors, a controller, and actuators, manages the operation of the pumps or valves.
• Sensors, such as accelerometers or gyroscopes, measure the ship’s roll motion.
• The controller processes this information and sends signals to the actuators (pumps or valves) to adjust the fluid flow in response to the roll.

4. Air Vents (in some designs):

• Some ACT systems may incorporate air vents or valves to control the air pressure above the fluid in the tanks.   1. WO2019143257A1 – U-tank active roll dampening system for and method for active roll dampening of a vessel – Google Patents patents.google.com
• This can further influence the fluid flow and enhance the system’s response to the roll motion.

Operation

1. Sensing Roll Motion:

• The control system’s sensors continuously monitor the ship’s roll motion, measuring its amplitude, frequency, and phase.

2. Control Algorithm:

• The controller uses sophisticated algorithms to analyze the sensor data and predict the ship’s upcoming roll motion.
• It calculates the required fluid transfer to counteract the roll and sends commands to the actuators (pumps or valves).

3. Fluid Transfer:

• The pumps or valves respond to the controller’s commands and transfer the fluid between the tanks.   1. WO2019143257A1 – U-tank active roll dampening system for and method for active roll dampening of a vessel – Google Patents patents.google.com
• The timing and amount of fluid transfer are precisely controlled to create a counteracting force that opposes the ship’s roll.

4. Roll Damping:

• As the fluid shifts to the opposite side of the roll, it creates a moment that opposes the ship’s rolling motion.
• This dampens the roll, reducing its amplitude and making the ship’s motion more stable and comfortable.

Advantages:

• High Effectiveness: Active controlled tanks offer greater roll reduction compared to passive tank systems, particularly in severe sea conditions.   1. Control of ship roll using passive and active anti-roll tanks | Request PDF – ResearchGate www.researchgate.net
• Adaptability: The control system can adapt to varying sea states and ship loading conditions, optimizing the stabilization effect.
• Space Efficiency: They can be designed to be relatively compact and integrated into the ship’s structure, minimizing the impact on internal space.

Disadvantages:

• Complexity and Cost: They are more complex and expensive than passive tank systems, requiring sophisticated control systems and actuators.
• Power Consumption: The pumps or valves require electrical power to operate, increasing the ship’s overall energy consumption.
• Maintenance: The system’s moving parts and control components require regular maintenance to ensure optimal performance and reliability.

Overall, active controlled tank roll damping systems provide a powerful and adaptable solution for reducing ship roll, particularly in challenging sea conditions. They offer advantages in terms of effectiveness and space efficiency compared to passive systems, but their complexity and cost need to be considered.  

1. Control of ship roll using passive and active anti-roll tanks | Request PDF – ResearchGate