Modern naval vessels, which mount a large number of advanced electronic equipment, require such equipment to be well protected against external disturbance, including particularly vibration. The conventional means of minimising vibration is to increase structural rigidity, but this entails the increase of structural mass. If vibration could be suppressed by means of a lightweight compact device, it should immensely benefit naval vessel design. To this end, a two-axis active mass damper driven by a hydraulic actuator has been developed, which effectively reduces the vibration of ship superstructures. A prototype model damper unit has been tested in a laboratory, which proved to corroborate closely the high performance of the design estimated from simulated calculations. It is shown that; 1. The acceleration generated in the model structure by a sinusoidal exciting vibration was reduced to about 1/5 upon actuation of the device, and 2. A similar reduction of acceleration, to about 1/5, was obtained when the exciting vibration wave pattern reproduced the actual movement of a ship at sea.

Active Mass Damper Demonstration for Ship Vibration Reduction

In this paper, the dynamic characteristics of a vibration absorber with passive and active devices are examined by means of an optimization technique. The optimum design parameters for the following cases of absorbers are reviews: active control for the natural frequency of absorbers; active/passive control for damping ratio of absorbers and active control for the control force between absorbers and main systems. A multiple objective fuzzy optimization technique based on Bellman and Zadeh's decision criteria is used to find a design with the best compromise of dynamic response between the main system and the absorber.

Optimum vibration absorber with active control

64) Robust Control for the Vibration Attenuation of Superstructures

A robust control methodology applied for active vibration reduction on superstructures using the H∞ synthesis is presented Based on this technique, the control law may be calculated according to the required objective The designed control system will automatically meet the performance and robustness properties, which are given in the specifications Finally, the superstructure of a cargo ship subject to wind gust and foundation oscillation is investigated The results show that the active vibration control system designed by this scheme has an effective vibration attenuation for both excitations In addition, this controller will maintain high performance even when there is a large perturbation in the system parameter

Robust Control for the Vibration Attenuation of Superstructures

A centrifugal pendulum absorber to reduce ship superstructure vibration was developed. It is compact and claimed to be easy to install. Vibration of any order caused by engine or propeller can be reduced, random variations of amplitude and phase can be automatically followed, and other structures are not excited by the absorber.

Y Yoshida

Papers

Development of the centrifugal pendulum absorber for the reduction of ship superstructure vibration