engleski

Stability, performance and power flow of active U- tube anti-roll tank

In this paper active control of ship roll using a U-tube anti roll tank (ART) is considered. A linearized model of the ship and active ART with two degrees of freedom is developed. The two degrees of freedom are the ART fluid free surface angle and the ship roll angle. The active control approach is based on the absolute roll- rate feedback assuming an idealised positive displacement pump that delivers a pressure difference proportional to the roll rate via a negative feedback gain. First, the stability of the feedback loop is analysed using the Nyquist criterion. The stability analysis indicates that the ART natural frequency should be set below the ship roll natural frequency. The performance analysis is carried out in terms of the reductions of the frequency response function between the wave slope exciting the ship roll and the roll angle. It is found that the active control performance improves with reducing the natural frequency of the ART. Finally, the analysis of the power flow through the system indicates that the pump power can be reduced with the reduction of the ART natural frequency and the ART fluid passive damping ratio without a loss of the control performance.

Active control of ship roll, Anti-roll tanks, U-tube tanks, Stability of control systems, Performance of control systems, Power flow in control systems

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