JPH1016882A - Fin control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fin control device for suppressing cavitation by detecting the occurrence of cavitation in a fin. SOLUTION: A fin control device for controlling the inclined turning angle of a fin 1 used in the water close to a water surface includes a cavitation detecting means 22 for detecting the occurrence of cavitation in the vicinity of the outer plate 20 of the fin 1 and a control means 23 for controlling, when the occurrence of cavitation is detected by the cavitation detecting means 22 and if a specified fin angle exceeds a fin angle at the time of the cavitation occurrence, the specified fin angle to be maintained equal to the fin angle at the time of the cavitation occurrence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fin control device for preventing cavitation of a movable fin, and more particularly to a fin control of a fin stabilizer and a fin control of a high-speed hydrofoil ship having a movable fin.

[0002]

2. Description of the Related Art A fin stabilizer is known as a device for preventing a ship from rolling in waves. This means that the movable fins that protrude outside the hull are tilted, and the lift obtained by generating the angle of attack of the fins with respect to the water flow flowing along the hull is opposed to the external force. It is to prevent.

FIG. 3 is a diagram showing a configuration of a conventional fin stabilizer. This fin stabilizer has a hull 10
Of the hull 10 from the roll sensor 12
Of the seawater, that is, the ship speed VH, is input to the anti-oscillation controller 11 from a ship speed sensor 13 such as a log for navigation. Then, the fin lift LD required for preventing the hull 10 from rolling is calculated by the anti-rolling controller 11 in accordance with the rolling angular velocity ωH of the hull 10.

[0004] Next, the anti-oscillation controller 11 calculates the required fin angle of attack αD from the required fin lift LD and the boat speed VH from the following equation (1) (derived in the form of αD =...). A command fin attack angle αD is output to the fin drive devices 3 and 3 via the limiter 14.

LD = (ρ / 2) VH ² CL (αD) A (1) CL (αD): lift coefficient, function of αD A: fin area ρ: seawater density The direction in which the chord of the fin 1 matches the direction of the water flow when navigating
As the neutral position of F (βF = 0), the fin tilt angle βF is detected by a tilt angle sensor (not shown) to reduce the numerical deviation between the command fin attack angle αD and the fin tilt angle βF. The fin tilt angle βF is corrected to control the tilt of the fin 1 so that αD = βF.

As described above, by controlling the fin tilt angle βF so as to follow the command fin attack angle αD, an actual fin lift LF that follows the required fin lift LD is generated, and is incorporated in the vibration reduction controller 11. The intended reduction in roll of the calculated operation is almost achieved.

By the way, when the fin is tilted in the shallow water of about the draft of the ship, when the angle of attack αF of the fin becomes large and reaches a certain angle of attack (hereinafter referred to as critical angle of attack αCR),
Cavitation occurs. Although the critical angle of attack αCR depends on the ship speed (a function of the ship speed), here, the ship speed VH is kept constant.

FIG. 4 is a diagram showing the relationship between the angle of attack αF of the fin and the lift LF of the fin. In FIG. 4, the solid line shows the relationship between the angle of attack αF of the fin and the lift LF in the deep sea. In FIG. 4, the broken line indicates the relationship between the angle of attack αF of the fins arranged in the shallow water of about the draft of the ship and the lift LF. In the range where the angle of attack of the fin αF is small, the lift of the fin in the deep sea and in the shallow sea is the same,
When the angle of attack αF exceeds the critical angle of attack αCR, the lift LF in shallow water becomes smaller than the lift LF in deep sea.

This is because the local pressure on the suction side of the fin in the shallow sea decreases to the saturated water vapor pressure, which causes cavitation composed of minute water vapor bubbles. The local pressure becomes lower than the water vapor pressure. It does not decrease, and a decrease in lift occurs.

Accordingly, in FIG. 4, if the angle of attack αF is increased beyond the angle of attack αCR at the point P, which is the branch point between the solid line and the broken line, cavitation will occur. The generated water vapor bubbles flow down along the fin surface and are instantaneously destroyed when the pressure starts to increase. The pressure generated at this time reaches a pressure sufficient to erode the metal near the bubbles. Therefore, it is necessary to prevent the occurrence of cavitation from the viewpoint of preventing damage to the fins and suppressing noise.

[0011]

In the above-mentioned conventional fin stabilizer, basically, when the commanded fin elevation angle αD calculated based on the roll of the hull exceeds the critical fin angle αCR, the commanded fin elevation angle αD is reduced. Cavitation is prevented from occurring by limiting the critical fin angle αCR equally.

However, when navigating in waves, the motion of water particles due to waves and the relative motion between the hull and seawater due to the swaying of the hull occur, and the water flow flowing into the fins in the case of navigating in flat water. Fin tilt angle βF which is the direction of water flow
Is 0, the direction of the chord of the fin differs from that direction. This difference is, as the case may be, the critical fin angle αCR of 20
%. Then, an angle difference equal to the above difference occurs between the fin tilt angle βF and the fin attack angle αF. That is,

[0013]

(Equation 1)

[0014]

(Equation 2) Δα: Deviation of the water flow flowing into the fins in waves from the direction of the water flow in plain water (Δα takes both positive and negative values) Therefore, cavitation is prevented even when sailing in waves The command fin elevation angle αD is output via the elevation angle limiter 14 so as to be, for example, 0.8 αCR or less. Limiting the command lift by limiting the angle of attack in this way causes a problem in that the size of the fins increases and the cost increases in order to secure the required reduced swing lift.

[0015] Such a problem of the prior art arises from the fact that there is no means for detecting the direction and the flow velocity of the water flowing into the fin. However, means for reliably detecting the flow velocity and direction of the water flow immediately before each fin requires measures such as collision with driftwood or the propagation of marine organisms on the surface. Not in practical use. An object of the present invention is to provide a fin control device that suppresses cavitation by detecting cavitation generated in fins.

[0016]

Means for Solving the Problems To solve the above problems and achieve the object, a fin control device of the present invention is configured as follows. (1) A fin control device of the present invention is a fin control device for controlling a tilt angle of a fin used in water near a water surface, and includes a cavitation occurrence detecting means for detecting cavitation occurring near an outer plate of the fin. When the cavitation occurrence detecting means detects the occurrence of cavitation, when the commanded fin angle exceeds the fin angle at the time when the cavitation occurs,
Control means for controlling the instructed fin angle to be maintained at the fin angle at the time when the cavitation occurs. (2) The fin control device of the present invention is the device described in (1) above, and the cavitation occurrence detecting means includes:
It is configured to detect the occurrence of cavitation of the fin based on the magnitude of the ultrasonic signal obtained by band-pass filtering the ultrasonic band signal in the stress fluctuation signal detected by the ultrasonic sensor mounted on the inner surface of the fin. ing.

As a result of taking the above-mentioned measures, the following effects are produced. (1) According to the fin control device of the present invention, cavitation generated near the outer plate of the fin is detected, and if the commanded fin angle exceeds the fin angle at the time when the cavitation occurs, the commanded fin angle is detected. Since the angle is controlled to be maintained at the fin angle at the time when the cavitation occurs, by detecting the occurrence of the cavitation by the ultrasonic wave generated when the cavitation bubbles are destroyed, over the period during which the cavitation continues , The command angle of attack can be limited to the fin tilt angle when cavitation first occurs. (2) According to the fin control device of the present invention, the ultrasonic band signal in the stress fluctuation signal detected by the ultrasonic sensor mounted on the inner surface of the fin is subjected to band-pass filtering based on the magnitude of the ultrasonic signal. In addition, since the occurrence of cavitation of the fin is detected, the occurrence of cavitation can be detected when the output of the filtered ultrasonic signal exceeds the output corresponding to the cavitation occurrence that has been verified in advance.

[0018]

FIG. 1A is a plan view showing a hull equipped with a fin stabilizer as a fin control device according to an embodiment of the present invention, and FIG. 1B is an ultrasonic wave. It is sectional drawing of the fin equipped with the sensor. 1A and 1B, the same parts as those in FIG. 4 are denoted by the same reference numerals.

The fins 1, 1 protruding into the seawater outside the hull outer panel 10 are provided with fin drive devices 3, 3 installed inside the hull by fin shafts 2, 2 fixed to the fins 1, 1, respectively. And is supported rotatably. The fin drive device 3 tilts the fin shaft 2 at a tilt speed substantially proportional to the difference between the input command fin attack angle αD and the current fin tilt angle βF, and sets the value of the fin tilt angle βF to the command fin tilt angle βF. Angle αD
The fin 1 is tilted so as to be equal to the value of. The anti-rolling controller 11 inputs the roll angular velocity ωH of the hull from the roll sensor 12 and receives the ship speed VH from the boat speed sensor 13.
And outputs the required fin angle of attack αD.

In the present embodiment, the command fin elevation angle αD, which is the output of the vibration reduction controller 11, is transmitted to the cavitation controllers 23, 23 associated with the individual fins 1, 1, respectively. Further, an ultrasonic sensor 21 which is a stress detector such as a piezoelectric element is newly mounted on a portion near the front edge of the fin 1.

FIG. 1B shows an example in which the ultrasonic sensor 21 is mounted. The ultrasonic sensor 21 is superposed on the inner surface of the outer plate 20 of the fin 1 at a position symmetrical to the chord of the fin 1 and near the front edge. The stress detection surface of the acoustic wave sensor 21 is provided by bonding.
The reason that two ultrasonic sensors 21 are mounted on the upper and lower surfaces of the fin 1 is that the cavitation when the fin 1 is raised and the cavitation when the head is lowered are efficiently detected by the ultrasonic sensor 21 close to the cavitation generating position. To do that.

Fin outer plate 2 detected by ultrasonic sensor 21
The zero stress fluctuation signal is transmitted to the corresponding cavitation determiner 22. The cavitation determiner 22 filters the input stress fluctuation signal with a band-pass filter that picks up a part at several tens of kHz of the stress fluctuation signal. Next, when the output of the filtered signal exceeds the output corresponding to the cavitation occurrence that has been verified in advance, a signal indicating the occurrence of cavitation is output from the cavitation determiner 22 to the cavitation controller 23.

The cavitation controller 23 uses the cavitation generation signal input from the cavitation determiner 22 and the fin tilt angle βF input from the fin drive device 3 to generate a command fin elevation angle αD input from the anti-oscillation controller 11. The signal is output to the fin drive device 3 with some restrictions.

FIG. 2 is a flowchart showing a control procedure of the cavitation controller 23. Hereinafter, a control procedure of the cavitation controller 23 will be described with reference to FIG. First, the cavitation controller 23 inputs the commanded fin elevation angle αD from the vibration reduction controller 11 and the actual fin tilt angle βF from the fin drive device 3 in step S101. Next, in step S102, the presence or absence of cavitation is determined based on the input from the cavitation determination unit 22.

If cavitation does not occur in step S102, the command fin elevation angle αD is directly output as the command tilt angle βD in step S103. If cavitation has occurred, step S201
It is determined whether or not cavitation has occurred in the immediately preceding time cycle. If cavitation has not occurred in the immediately preceding time step in step S201, it is determined in step S202 that cavitation has occurred for the first time, and the fin tilt angle βH to be maintained in the future is set to the current fin tilt angle βF. I do. Next, step S
At 203, the command fin tilt angle βD is made to coincide with the fin tilt angle βH to be maintained.

In step S201, if cavitation has occurred in the immediately preceding time step, it is determined in step S301 whether the magnitude of the command attack angle αD is greater than the magnitude of the fin tilt angle βH to be maintained. I do. If the command fin elevation angle αD is larger,
In step S203, the command fin tilt angle βD is made to coincide with the fin tilt angle βH to be maintained.

If the command fin elevation angle αD is smaller in step S301, the command fin tilt angle βD is made equal to the command attack angle αD in step S103. Generally, when passing through this route, the fin tilt angle β
The control returns to the normal control (the route from step S102 to step S103) when the size of F is gradually reduced and no cavitation occurs. The command fin tilt angle βD determined in each of the above cases is output to the fin drive device 3 in step S401, and then a new time cycle is calculated.

As described above, when cavitation does not occur in the fin 1, the fin tilt angle βF is set to be equal to the command angle of attack αD, or when cavitation occurs, cavitation occurs first. Control can be performed so that the fin tilt angle βF does not increase beyond the fin tilt angle βH at the time.

In the present embodiment, as in the conventional case, the detection of the direction and the flow velocity of the water flow in the immediate vicinity of the fin is abandoned.
The occurrence of cavitation is detected by ultrasonic waves generated when the cavitation bubbles collapse, and the fin's angle of attack αF
Has a cavitation determiner 22 for determining that has reached the critical angle of attack αCR. This cavitation determiner 2
By performing control to maintain the tilt angle βF of the fin from the time when the occurrence of cavitation is detected to the tilt angle βH at the time when the occurrence of cavitation is detected,
It is intended to suppress cavitation generated in the fin 1.

Actually, since the tilt angle of the fin is maintained at that angle after the occurrence of cavitation is detected, cavitation occurs.
The cavitation that occurs near the angle of attack αCR shown in the figure is so-called aeration in which air dissolved in water is gasified, the pressure at which bubbles are destroyed is small, and damage to the fins is small enough to be a problem, Practical cavitation prevention control can be performed.

Further, when the material of the fin surface and the structure of the fin are improved, cavitation may occur, so that it is possible to select using the maximum lift of the fin (point Q shown in FIG. 4). In this case, the tilt angle βH of the fin at the time when the occurrence of cavitation is detected is shown in FIG.
The tilt angle βST βST = βH + (αST−αCR) shown in the following equation (4), which is obtained by adding the difference between the angles of attack at the points P and Q: Stall prevention control can be performed.

Further, since the occurrence of cavitation is actually detected and the fin tilt angle βF can be controlled to be maintained near the cavitation occurrence limit even when the command fin attack angle αD is further increased, the command fin attack angle can be controlled. It is not necessary to limit αD to about 0.8αCR unlike the conventional technology, and the lift of the fin can be used effectively,
The area of the fin mounted on the hull can be reduced by about 20%. Further, damage to the fin due to cavitation can be prevented.

It should be noted that the present invention is not limited to only the above-described embodiment, and can be implemented with appropriate modifications without departing from the scope of the invention. (Summary of Embodiment) The configuration, operation and effect shown in the embodiment are summarized as follows. [1] The fin control device described in the embodiment is a fin control device that controls the tilt angle of the fin 1 used in water near the water surface such as a fin stabilizer, and is generated near the outer plate 20 of the fin 1. Cavitation occurrence detecting means (22) for detecting cavitation to occur, and when the cavitation occurrence is detected by the cavitation occurrence detecting means (22), when the commanded fin angle exceeds the fin angle at the time when the cavitation occurs. And control means (23) for controlling the fin angle instructed to be maintained at the fin angle at the time when the cavitation occurs.

As described above, the fin control device detects cavitation generated near the outer plate 20 of the fin 1 and, if the commanded fin angle exceeds the fin angle at the time when the cavitation occurs, the command is issued. Since the fin angle is controlled to be maintained at the fin angle at the time when the cavitation occurs, the occurrence of the cavitation is detected by ultrasonic waves generated when the cavitation bubbles are destroyed, so that the cavitation continues during the generation of the cavitation. Over time, the command angle of attack can be limited to the fin tilt angle when cavitation first occurs. [2] The fin control device described in the embodiment is the device according to the above [1], and the cavitation occurrence detecting means (22) is an ultrasonic sensor 21 mounted on the inner surface of the fin 1. It is configured to detect the occurrence of cavitation of the fin 1 based on the magnitude of the ultrasonic signal obtained by bandpass-filtering the ultrasonic band signal in the stress fluctuation signal detected in step (1).

As described above, in the above fin control device, the ultrasonic sensor 21 mounted on the inner surface of the fin 1
The cavitation of the fins 1 is detected based on the magnitude of the ultrasonic signal obtained by band-pass filtering the ultrasonic band signal in the stress fluctuation signal detected in step (1), so that the output of the filtered ultrasonic signal is determined in advance. The cavitation can be detected when the output corresponding to the cavitation occurrence that has been tested is exceeded.

[0036]

According to the present invention, it is possible to provide a fin control device that suppresses cavitation by detecting cavitation occurring in fins.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hull equipped with a fin stabilizer that is a fin control device according to an embodiment of the present invention,
(A) is a plan view, (b) is a cross-sectional view of a fin equipped with an ultrasonic sensor.

FIG. 2 is a flowchart showing a control procedure of a cavitation controller in the fin control device according to the embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a fin stabilizer according to a conventional example.

FIG. 4 is a diagram showing the relationship between the angle of attack of a fin and the lift of the fin according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fin 2 ... Fin shaft 3 ... Fin drive device 10 ... Hull (outer plate) 11 ... Decline controller 12 ... Roll sensor 13 ... Ship speed sensor 14 ... Angle of attack limiter 20 ... Hull (outer plate) 21 ... Ultrasonic sensor 22 Cavitation judgment device 23 Cavitation controller

Claims (2)

[Claims] 1. A fin control device for controlling a tilt angle of a fin used in water near a water surface, a cavitation occurrence detecting means for detecting cavitation occurring near an outer plate of the fin, and a cavitation occurrence detecting means. When the occurrence of cavitation is detected in step (b), when the commanded fin angle exceeds the fin angle at the time of the occurrence of the cavitation, the control is performed such that the commanded fin angle is maintained at the fin angle at the time of the occurrence of the cavitation. A fin control device, comprising: 2. The method according to claim 1, wherein the cavitation occurrence detection means is configured to perform a band-pass filter on an ultrasonic band signal in the stress fluctuation signal detected by an ultrasonic sensor mounted on an inner surface of the fin, based on a magnitude of the ultrasonic signal. The fin control device according to claim 1, wherein occurrence of cavitation of the fin is detected.