JPS6136089A - Reduction of rolling - Google Patents

Abstract

PURPOSE:To secure safety by controlling a valve in a duct so that the phase difference between the natural period in a rolling reducing tank and that in the movement of a hull is set within a prescribed range and obtain a constant flow- rate by fixing the opening degree of the valve in anomaly exceeding a prescribed range. CONSTITUTION:The right and left broadside tanks 4 and 6 are connected with a water duct 8 and an air duct 10, and the natural period of a rolling reducing tank 2 is set smaller than that of a hull. Onto the water duct 8, a valve 16 whose opening degree is controlled on the basis of the output of a metering device 18 for detecting the direction of rolling of the hull from the level hull of the broadside tank 6 is installed. The valve 16 is controlled so that the both natural period values are set within a prescribed range. In anomaly outside the prescribed range, the opening degree of the valve 16 is fixed at a constant value so that the amount of shift of the fluid which passes through the duct 8 becomes constant. Therefore, the stability of rolling can be secured by allowing the natural period of the hull to accord with that of the rolling reducing tank.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rocking reduction method for obtaining a rocking reduction function for suppressing the rocking of a ship or the like.

Conventional technology In the past, tanks installed on the starboard and port sides of a ship were connected by water ducts and air ducts, and the fluid inside the tanks moved in response to the roll of the ship, thereby suppressing the roll of the ship. A shaking method has been proposed. This method of reducing rocking has the advantage of being inexpensive and providing a rocking reducing effect even when the ship is at rest.

Problems to be Solved by the Invention Conventionally, this type of vibration reduction method involves installing a valve in the water duct to control the flow of water, or injecting high-pressure air into each tank to reduce the flow of water. Various methods have been proposed, such as those that change the period, but all of them have the drawback that they cannot achieve a sufficient effect of reducing the shaking of the ship. The aim is to make this process easier.

Means for Solving the Problems This invention sets the natural period of the anti-sway tank to be smaller than the natural period of the ship's hull, and sets the phase difference between the motion of the fluid in the anti-sway tank and the motion of the ship within a predetermined range. If the fluid passing through the water duct is controlled so that the phase difference between the motion of the fluid in the anti-sway tank and the motion of the ship exceeds the specified range, the natural period of the ship and the natural period of the tank are It is designed to match.

By setting the natural period of the anti-sway tank to be smaller than the natural period of the ship's hull, the period of motion of the fluid in the tank to reduce the amount of movement of the fluid in the tank against rolling of the ship is made faster, and the movement of the fluid in the tank and the movement of the hull are reduced. The phase difference between the water duct and the water duct is controlled within a predetermined range, and the fluid passing through the water duct is controlled to obtain a vibration reduction function.

In addition, when the phase difference between the motion of the fluid in the anti-sway tank and the motion of the ship's hull is out of a predetermined range, by keeping the amount of movement of the fluid passing through the water duct constant, the natural period of the ship and the motion of the ship are adjusted. Match the natural period of the tank.

Embodiments Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

FIG. 1 shows an embodiment of the vibration reduction method of the present invention.

The anti-sway tank 2 is connected by a water duct 8 and an air duct 10 to a port side tank 4.6 installed on each of the port and starboard sides of the hull, and a predetermined amount of water 12 as a fluid is stored therein. ing. In this case, the natural period of the anti-sway tank 2 is set smaller than the natural period of the hull.

Further, a control valve 16 whose opening degree is controlled according to the control output of the control device 14 is installed in the overboard duct 8, and a control valve 16 is installed to detect the direction of the ship's rocking from the height of the water 12 in the side tank 6. A detector 18 is installed, and the detection output of this detector 18 is applied to the control device 14.

The control device 14 corresponds to the output of the detector 18 and controls the control valve 1.
Water I2 passes through water duct 8 by adjusting the opening degree of 6.
The opening of the control valve 16 is adjusted in accordance with an arbitrary operational input in addition to the output of the detector 18.

In the above configuration, the motion of the water 12 in the rock reduction tank 2 due to the rolling of the ship is detected by the detector 18, and the position of the natural period of the rock reduction tank 2 and the natural period of the ship is detected. The water 12 passing through the water duct 8 is controlled by adjusting the opening degree of the control valve 16 so that the phase difference is within a predetermined range.

Further, the occurrence of an abnormal situation in which the phase difference between the natural period of the vibration reduction tank 2 and the natural period of the hull is out of a predetermined range is detected by the detector 18 based on the water level of the water 12 in the vibration reduction tank 2. In this case, the control valve 16 is fixed at a constant opening degree so that the amount of movement of the fluid passing through the water duct 8 is constant according to the output of the detector 18, and the control valve 16 is fixed at a constant opening degree and Match the natural period of .

This vibration reduction method advances the phase of the water level fluctuation in the vibration reduction tank compared to the conventional vibration reduction method, and the phase of the water level fluctuation in the vibration reduction tank is delayed by changing the diameters of the control valve 16 and water duct 8. be able to. Therefore, the control range is wide and a high vibration reduction effect can be obtained.

Here, referring to the sway reduction device model in Fig. 1 and describing the equation of motion consisting of the hull-tank-pump system for the hull and tank, in the hull, Jsφ + Bs1fi + K
sdr+Js tQ+Kt Ω-F ・
・・(1), and in the anti-sway tank 2, JtΩ+BtΩ+KtΩ+Jstφ+Ktφ+==P...(2). These are cases of active control.

Now, considering the function of the control valve 16 as one pump, the flow rate of the water 12 passing through the water duct 8 can be set to O by adjusting the opening degree of the valve 16.

Assuming that this pump is an ideal pump, the second
As shown in the figure, the pump is able to instantaneously apply 1 to a flow rate of 2, and the action time can be considered as a δ function.

In addition, pumps generally have the effect of increasing the flow rate,
In this case, it can be considered that there is only the effect of -■.

Then, as shown in FIG. 3, when the opening degree of the control valve 16 is made zero at a certain time 10, the water level will be
6 (pump), but this is considered to be a type of overshoot, as shown by the broken line a in FIG.

From the above, regarding P in formula (2), P=PaΩ, Pa<O---(3) it is conceivable that.

Further, assuming that the opening/closing time of the valve 16 is very short, the phase delay between the signal from the detector 18 and the opening/closing of the valve 16 can be ignored.

However, if the signal is taken from the flow velocity or water level, there will be a delay due to the mass force of the fluid after the valve 16 is opened and closed.

However, if a little more detailed control is to be performed, Pa=αPa' (4) can also be considered. However, α is the opening degree (0 to π/2) of the valve.

This α is α=αΩ+αφ (5), αφ=g1 φ1 +g2φz +gs φ3...(
6) αΩ=e, (TI)Ω+Ω) ・・□・(Consider phase correction including force.

Figure 5 shows the control model given above.
The same parts as those shown in the figures are given the same reference numerals. In addition, 20 shows the hull, and 22.24 shows the return system.

Here, consider opening and closing of the valve 16 at a cycle of aθ-bθ.

This provides a phase compensation of tan-'(bω/a) for θ.

Tm=2.214 (sec), fm=0.452
(Hz), ωm = 2.838 (1/rad) control model is set, and f = 1 (Hz), π/4 ~
If we create a phase difference of π/2, then 1<bω/a ω=,,6.283, and from this, b becomes b/a>0.159, and if a=L, then b>0. It turns out that 1'59 is good.

Figure 6 shows the phase difference with respect to the ratio e between the natural frequency ωt of the anti-sway tank and the natural frequency ωm of the hull, and A is the conventional method;
B is a vibration reduction method according to the present invention. As is clear from FIG. 6, as the natural frequency ωt of the anti-sway tank becomes larger than the natural frequency ωm of the hull, in other words, as the natural period of the anti-sway tank 2 becomes smaller than the natural period of the hull, the phase difference decreases. It becomes larger, and the vibration reduction control becomes easier.

In practice, it is sufficient to set ωt to approximately 1.5, and it has been confirmed through experiments that control becomes difficult when the damping characteristic of the anti-sway tank 2 is small.

Note that even if the control valve 16 of the above embodiment is replaced with an opening/closing means 26 for controlling the flow rate of the water duct 8 as shown in FIG. 7, the same effect can be expected.

In addition, in the example, the phase difference between the motion of the fluid due to rolling and the motion of the ship is controlled to be optimal, and in the event of an abnormality, the opening degree of the valve is set at a certain angle, and the natural period of the ship and the natural period of the tank are controlled. Although we have explained the case where control is performed using a control device to match the above, even if the control is switched to manual in the event of an abnormality, it is possible to ensure the ship's lateral stability and stability.

Advantages of the Invention As explained above, according to the present invention, the following effects can be obtained.

fil Set the natural period of the anti-sway tank to be smaller than the natural period of the hull, and control the fluid passing through the duct so that the phase difference between the motion of the fluid in the anti-sway tank and the motion of the hull is within a predetermined range. In particular, it is possible to obtain a stable and high vibration reduction effect and to easily control it.

(2) If there is an abnormality in which the phase difference between the natural period of the rock reduction tank and the natural period of the hull is out of the specified range, the opening degree of the control valve is changed manually or automatically to a constant value. By matching the period with the natural period of the vibration reduction tank, safety against rolling can be ensured.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining the oscillation reduction method of the present invention, FIG. 2 is a graph showing the operation of the control valve,
FIG. 5 is a program diagram showing a control model, FIG. 6 is a graph showing the occurrence of a phase difference in the vibration reduction method of the present invention, and FIG. 7 is an explanatory diagram showing a modification of the control valve. 2... Anti-sway tank, 4.6... Side tank, 8...
・Walk duct, 12...Water as a fluid, 16・
... Control valve, 26... Opening/closing means. Figure 1 Figure 6 Figure 7

Claims (1)

[Claims] The natural period of the vibration reduction tank is set to be smaller than the natural period of the ship's hull, and the fluid passing through the duct is controlled so that the phase difference between the motion of the fluid in the vibration reduction tank and the movement of the ship is within a predetermined range, In addition, when the phase difference between the motion of the fluid in the vibration reduction tank and the motion of the ship exceeds a predetermined range, the natural period of the ship and the natural period of the vibration reduction tank are made to match. Method.