The fluctuating force generated by a ship's propeller leads to axial and radial vibrations which are subsequently transmitted to the hull. The simulation study presented here demonstrates how a tuneable vibration absorber utilizing a magnetic thrust bearing and inertial mass employed in prallel with a hydrodynamic thrust bearing can reduce propeller drive shaft axial vibrations. The sensitivity to controller errors and the influence of vibration absorber mass are examined. It is shown that a practical device using well proven magnetic actuation techniques could be developed. The variable stiffness and damping characteristics of hydrodynamic thrust bearings mean that a fixed parameter closed loop controller will not perform well at all operating conditions. It is argued that the use of self tuning or model-reference type of closed-loop adaptive control is impractical. An open-loop speed-dependent control strategy is developed. This inherently stable but may increase vibration amplitudes at frequencies other than the propeller passage frequency.
The control of propeller-induced vibrations in ship transmission shafts
Kontrolle der durch Propeller verursachten Schwingungen in der Schiffstriebwerkswelle
1990
6 Seiten, 6 Bilder, 1 Tabelle, 11 Quellen
Conference paper
English
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