IIUM Press, International Islamic University Malaysia
Abstract
Improvement of stability has been going for decades. Anti-rolling system like bilge keel, anti-rolling tank, and weight stabilizer, those basic ideas were first proposed by researchers in the period of latter half of 19th century. While on the other hand, fin stabilizer was invented around 1920`s. Some of the ideas remain undeveloped for years while others turned out to be a successful system in years to come.
Among those system there is weight stabilizer which offers wide concept of anti-rolling system. As the horizontal type has been treated as common, researchers now have pay high interest to vertical type weight stabilizer. Vertical type can change both the height of the center of gravity and the moment of inertia of the system or in other word change the radius of gyration (gyradius). By using movable weight, gyradius will change as the weight position is moved upward or downward. VWS system mass only take few percent of total ship displacement and is positioned at the back upper deck of the ship.
The development of VWS is actually the key to doubts and problems from previous research. From anti-rolling tank, the result has shown that the system demands large space for the installation while from the Air Fin Stabilizer(AS) research, we found out that system has 0% efficiency in immobile state. VWS has been improved to overcome these problems and meet the requirements of more promising system.
With new ideas and skills, VWS works even when the ship is at rest condition. Moreover, the space used is minimal and loads can be adjust based on ship`s condition. As the device is installed above draught level, water friction also can be reduced. VWS is controlled by PID control system which analyses GAIN`s value needed for weight’s movement. The optimization of the control system will be further discussed and confirmed by carrying out numerical and physical simulation
