Ship characteristic arithmetic operation system

Abstract

To provide a ship characteristic arithmetic operation system that computes a sideways metacenter height in consideration of a loading condition of a ship.SOLUTION: A ship characteristic arithmetic operation system 10 includes a memory unit 3 that measures draft data and vibration data and stores ship inherent information, a drainage quantity arithmetic unit 11 that computes a drainage quantity on the basis of the draft data and ship inherent information, a roll damping force coefficient arithmetic unit 12 that computes a roll damping force coefficient on the basis of the draft data, vibration data, drainage quantity, and ship inherent information, a natural frequency arithmetic unit 13 that computes a natural frequency on the basis of the vibration data, a damping coefficient arithmetic unit 14 that computes a damping coefficient on the basis of the vibration data, an apparent moment-of-inertia arithmetic unit 15 that computes an apparent moment of inertia on the basis of the roll damping force coefficient and damping coefficient, a GM arithmetic unit 16 that computes a GM on the basis of the drainage quantity, natural frequency, and apparent moment of inertia, and a display unit 4 that displays the GM.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to an arithmetic unit for calculating the characteristics of a ship.

Background Art

[0002] Generally, methods for obtaining various characteristics of ships are known. For example, Patent Document 1 describes calculating the transverse metacentric height (GM) as hull state data. Non-Patent Document 1 describes the hull motion equation and the theoretical calculation of hull motion in waves. Non-Patent Document 2 describes the time-series theoretical analysis of ship rolling. Non-Patent Document 3 describes a method for estimating the damping coefficient and the transverse rolling natural angular frequency of a ship. Non-Patent Document 4 describes a method for obtaining the transverse rolling damping force coefficient of a ship by a simple estimation formula.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

[0005] However, the known calculation method of the transverse metacentric height does not consider the loading condition of the ship. This embodiment aims to provide a ship characteristic calculation device that calculates the transverse metacentric height considering the loading condition of the ship. [Effects of the Invention]

[0006] According to the embodiment, a ship characteristic calculation device that calculates the transverse metacentric height considering the loading condition of the ship can be provided. [Means for Solving the Problems]

[0007] A ship characteristic calculation device according to an embodiment of the present invention includes a draft data receiving unit that receives draft data measured by a plurality of draft gauges provided on a ship, a roll data receiving unit that receives roll data regarding the roll of the ship measured by a roll meter, a ship unique information storage unit that stores ship unique information including information regarding the dimensions of the hull and being unique information of the ship, a displacement calculation unit that calculates displacement based on the draft data received by the draft data receiving unit and the ship unique information stored in the ship unique information storage unit, a roll damping force coefficient calculation unit that calculates a roll damping force coefficient based on the draft data received by the draft data receiving unit, the roll data received by the roll data receiving unit, the displacement calculated by the displacement calculation unit, and the ship unique information stored in the ship unique information storage unit, a roll natural angular frequency calculation unit that calculates a roll natural angular frequency based on the roll data received by the roll data receiving unit, a damping coefficient calculation unit that calculates a damping coefficient based on the roll data received by the roll data receiving unit, an apparent moment of inertia calculation unit that calculates an apparent moment of inertia based on the roll damping force coefficient calculated by the roll damping force coefficient calculation unit and the damping coefficient calculated by the damping coefficient calculation unit, a transverse metacentric height calculation unit that calculates a transverse metacentric height based on the displacement calculated by the displacement calculation unit, the roll natural angular frequency calculated by the roll natural angular frequency calculation unit, and the apparent moment of inertia calculated by the apparent moment of inertia calculation unit, and an output unit that outputs the transverse metacentric height calculated by the transverse metacentric height calculation unit.

Brief Description of Drawings

[0008]

Figure 1

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Figure 6

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Figure 10

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Figure 12

Mode for Carrying Out the Invention

[0009] (Embodiment) FIG. 1 is a configuration diagram showing the configuration of a ship characteristic calculation device 10 according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the positions of various sensors 2a, 2b, 2c, 2d, 2e provided on a ship 20 according to this embodiment.

[0010] The ship characteristic calculation device 10 is a device that calculates the characteristics of the ship 20. The ship characteristic calculation device 10 calculates the characteristics of the ship. The characteristics of the ship include at least the transverse metacentric height (GM). For example, the ship characteristic calculation device 10 is an electronic inclinometer. The ship characteristic calculation device 10 includes an arithmetic processing unit 1, four draft gauges 2a, 2b, 2c, 2d, a motion meter 2e, a storage unit 3, and a display unit 4.

[0011] The arithmetic processing unit 1 receives the detection data detected by various sensors 2a to 2e, calculates the characteristics of the ship 20 based on the received detection data and various data stored in the storage unit 3, and outputs the calculation result to the display unit 4. Specifically, the arithmetic processing unit 1 obtains GM and displays GM on the display unit 4. The arithmetic processing unit 1 is mainly composed of a computer. The computer includes a semiconductor for performing arithmetic processing and a storage medium necessary for arithmetic processing. The computer realizes various functions of the arithmetic processing unit 1 by executing arithmetic processing according to various programs.

[0012] The arithmetic processing unit 1 may be provided on the ship 20 or may be provided outside the ship 20. For example, the arithmetic processing unit 1 may be installed in a building on the ground. The arithmetic processing unit 1 can be installed at an arbitrary location by being configured to receive the detection data of various sensors 2a to 2e. The ship characteristic calculation device 10 only needs to include at least the arithmetic processing unit 1, and other configurations do not have to be included as the configuration of the ship characteristic calculation device 10.

[0013] The draft gauges 2a to 2d are mounted on the ship 20. The first draft gauge 2a is provided at the bow portion of the ship 20. The second draft gauge 2b is provided on the port side of the central portion in the longitudinal direction of the ship 20. The third draft gauge 2c is provided on the starboard side of the central portion in the longitudinal direction of the ship 20. The fourth draft gauge 2d is provided at the stern portion of the ship 20. That is, the first draft gauge 2a and the fourth draft gauge 2d are respectively provided before and after in the longitudinal direction (the propulsion direction of the ship 20) with respect to the center O of the upper surface of the hull of the ship 20 (for example, the upper surface of the deck). Further, the second draft gauge 2b and the third draft gauge 2c are respectively provided on the left and right in the width direction (the direction perpendicular to the longitudinal direction on the upper surface of the hull) with respect to the center O.

[0014] The draft gauges 2a to 2d measure the draft (the height from the bottom of the ship to the water surface) at the installed positions. The draft gauges 2a to 2d transmit data (draft data) related to the measured draft to the arithmetic processing unit 1.

[0015] The motion sensor 2e is mounted on the ship 20. The motion sensor 2e measures surge (fore-and-aft sway), sway (side-to-side sway), heave (up-and-down sway), roll (roll), pitch (pitch), and yaw (yaw). The motion sensor 2e transmits data related to the measured motion (motion data) to the arithmetic processing unit 1. For example, the motion data includes at least one of acceleration, angular velocity, or tilt angle. Note that the motion sensor 2e may measure in any manner and may be composed of a plurality of devices.

[0016] The storage unit 3 stores data necessary for calculating the characteristics of the ship including GM. Specifically, the storage unit 3 stores unique information of the ship 20 (ship unique information) such as the dimensions of the hull. The arithmetic processing unit 1 reads out the data necessary for arithmetic processing from the storage unit 3.

[0017] The display unit 4 displays the calculation result by the arithmetic processing unit 1. Specifically, the display unit 4 displays the characteristics of the ship 20 including GM. For example, the display unit 4 is a display. Note that as long as it outputs the calculation result by the arithmetic processing unit 1, it is not limited to display on the display unit 4, and it may be printed by a printer or transmitted to an external device.

[0018] Here, the theory of the method for estimating GM using the time series of roll and the displacement will be explained. The roll Φ in irregular waves is expressed by the following equation (reference: Non-Patent Document 1), including the combined effect of side-to-side sway y and yaw ψ.

[0019]

Equation

[0020] Here, if both sides are divided by the apparent moment of inertia (I xx +A 44 ) and the right side is represented by f, Equation (1) is represented as follows.

[0021]

Equation

[0022] Here, since f is mainly caused by irregular waves, it is reasonable to treat it as a stochastic process. However, it should be noted that its statistical properties do not satisfy the whiteness because the wave has a peak at a specific frequency.

[0023]

Number

[0024] Equation (6) can be solved analytically. If the discrete interval is Δt, it becomes the following equation (10).

[0025]

Number

[0026] Equation (10) has the same form as the two-variable first-order autoregressive (AR) model of the statistical model. However, as described above, v t+Δt does not satisfy the assumption of whiteness as a statistical property. That is, this term needs to be whitened in some way. Here, let ε t+Δt ≡ Bv t+Δt and whiten it as follows using an autoregressive process following the method of Yamauchi (see Non-Patent Document 2). Hereafter, for simplicity, t + Δt is denoted as n and t as n - 1.

[0027]

Number

[0028] Substituting Equation (10) into Equation (13) and rearranging, x n is represented by a two-variable AR model of order L + 1 as in the following Equation (14).

[0029]

Number

[0030] The roll angular velocity and the roll angle can be expressed by a two-variable AR model as a discrete model of the equation of motion as described above. The parameters of the equation of motion and the parameters of the AR model are related by equations (7), (11) and (15). Therefore, if the roll angular velocity and the roll angle are measured with a motion sensor, the AR coefficient matrix A in equation (14) l can be estimated, and based on equations (15) and (11), the damping coefficient α and the roll natural angular frequency (hereinafter referred to as "natural frequency") ω can be estimated. For example, the Hamiltonian Monte Carlo method and the Markov chain Monte Carlo method are used for the estimation of these parameters (see, for example, Non-Patent Document 3). Further, since the roll damping force coefficient B which is a parameter of equation (1) 44 can be estimated by a known method (for example, Ikeda's method: see Non-Patent Document 4), the apparent moment of inertia (I xx +A 44 ) can be estimated based on equation (3).

[0031] In addition, GM can be obtained from the displacement W using the following equation which is a transformation of equation (4). Note that the natural frequency ω in the following equation can be obtained by any method.

[0032]

Equation

[0033] Furthermore, by transforming the above equation, GM is expressed as follows.

[0034]

Equation

[0035] In addition, the apparent moment of inertia (I xx +A 44 ) is obtained from the following equation which is a transformation of equation (3).

[0036]

Equation

[0037] Furthermore, by calculating the displacement W during navigation, GM can be obtained by Equation (4) using each value obtained so far.

[0038] Next, with reference to FIGS. 3 to 12, a method for calculating the displacement W will be described. Note that the method for calculating the displacement W described here is an example, and the displacement W may be obtained in any manner. Also, FIGS. 3 to 12 assume a specific ship, and the content varies for each ship.

[0039] The displacement W is obtained using the draft values acquired from draft meters 2a to 2d and a displacement table. The displacement table is included in the ship-specific information stored in the storage unit 3. Specifically, the displacement table includes various fixed values such as the dimensions of the hull as information necessary for obtaining the displacement.

[0040] The first draft meter 2a measures the bow draft Fore and transmits the measurement result to the arithmetic processing unit 1. The second draft meter 2b measures the midship port draft Mid(P) and transmits the measurement result to the arithmetic processing unit 1. The third draft meter 2c measures the midship starboard draft Mid(S) and transmits the measurement result to the arithmetic processing unit 1. The fourth draft meter 2d measures the aft draft Aft and transmits the measurement result to the arithmetic processing unit 1.

[0041] First, the arithmetic processing unit 1 calculates each draft based on the data of the specifications table indicating the dimensions etc. of the ship 20 stored in the storage unit 3 and the measurement values by the draft meters 2a to 2d. For example, as shown in FIG. 3, the following data is described in the specifications table. These data are as shown in FIGS. 4 to 7. FIG. 4 shows the data for draft mark correction. FIG. 5 shows the data for perpendicular correction. FIG. 6 is a cross-sectional view showing the attachment positions of the bow draft meter and the aft draft meter. FIG. 7 is a cross-sectional view showing the attachment position of the midship draft meter.

[0042] LPP is the length between perpendiculars. LDD is the distance from fore draft mark to aft draft mark. LMF is the distance from fore draft mark to mid draft mark. LMA is the distance from mid draft mark to aft draft mark. LP is the distance from centerline to port hull. LS is the distance from centerline to stbd hull. LMf is the distance from fore draft level transmitter to fore draft mark. LMa is the distance from aft draft level transmitter to aft draft mark. Ls is the distance from mid draft mark or midship to mid draft level transmitter. WF is the distance from centerline to fore draft level transmitter. WA is the distance from centerline to aft draft level transmitter. WP is the distance from the centerline to the mid draft level transmitter on the center port side. WS is the distance from the centerline to the mid draft level transmitter on the center starboard side. W’ is the distance from the mid draft level transmitter to the port (stbd) hull on the left (right) side.

[0043] There are two methods to obtain the draft: the method using the draft mark and the method using the perpendicular position (fore perpendicular (FP) / aft perpendicular (AP)). Either method can be adopted. Figure 8 shows how to obtain each parameter for calculating the draft using the draft mark. Figure 9 shows how to obtain each parameter for calculating the draft using the perpendicular position. Here, CAL_FORE, CAL_AFT, CAL_MIDP, and CAL_MIDS are obtained.

[0044] The average value dMID of the mid draft is calculated by the following formula. dMID = (CAL_MIDP + CAL_MIDS) / 2... Equation (20) Next, deflection correction is performed, and the trim (draft difference) is calculated from the fore draft Fore and the aft draft Aft. The trim is obtained by the following formula. AFT - FORE [m] = CAL_AFT - CAL_FORE... Equation (21) Refer to the trim correction table shown in Figure 10 to refer to the correction value from the trim. For example, if the trim (AFT - FORE [m]) is "2.2", it is decomposed into the integer part "2.0" and the decimal part "0.2", and the correction values "FORE: -12, AFT: +119" are obtained from the table shown in Figure 10. The corrected CAL_FORE and corrected CAL_AFT are obtained by the following formula. Corrected CAL_FORE = CAL_FORE + FORE correction value... Equation (22) Correction: CAL_AFT = CAL_AFT + AFT correction value... Equation (23) Calculate the corrected trim from the calculated trim using the following equation. dm [m] = (Correction CAL_AFT + Correction CAL_FORE) / 2... Equation (24) TRIM(t) [m] = Correction CAL_AFT - Correction CAL_FORE... Equation (25) Next, calculate hogging and sagging. δd [m] = dMID - dm... Equation (26) Compare dm with "DRAFT ext" in the hydrostatic table shown in Figure 11 to find a close value. Refer to the table of even keel (trim = 0.0 m) to correct the trim.

[0045] For example, when dm [m] is "6.58", refer to the row with the approximate value of "6.60" in the table of Figure 11 to obtain the values of TPC (ton per centimeter) and DISP (displacement). TPC is an index representing how many centimeters the draft increases per ton of load. DISP represents the displacement. Thus, TPC = 63.5 [t / cm] and DISP = 39420 [m.t].[[]END]]

[0046] Next, identify the approximate displacement of the mean draft (approximate value) that matches the corrected trim using the correction table of the displacement by trim shown in Figure 12.

[0047] Compare dm with DRAFT ext and TRIM(t) with Trim(m) to find close values.

[0048] δΔ1 [m.t] = -360... Equation (27) The correction of the displacement due to deflection is obtained by the following equation. δΔ2 [m.t] = 3 / 4 × δd × TPC × 100... Equation (28) Next, obtain an approximate value of the trim from the calculated displacement. The total displacement is obtained by the following equation. Δ' [m.t] = Δ0 + δΔ1 + δΔ2... Equation (29) Next, correction is performed based on the difference between the seawater specific gravity and the actual specific gravity using the following formula. Δ[m.t]=Δ'×ρ / 1.025 … Equation (30) Here, ρ is the coefficient indicating the actual specific gravity, which becomes 1.025 when it is the same as the seawater specific gravity. Δ[m.t] obtained in this way becomes the displacement W.

[0049] Next, the general method for obtaining the roll damping force coefficient B 44 based on Ikeda's formula will be described (see Non-Patent Document 3). Note that the roll damping force coefficient B 44 can be obtained in any way.

[0050] The roll damping at zero forward speed is divided into a frictional component Bf, a wave component Bw, a vortex component Be, and a bilge keel component Bbk, and at forward speed, a lift component Bl is added. Each component Bf, Bw, Be, Bl, Bbk is obtained based on the draft, displacement W, ship dimensions, and the measured motion data by the motion meter 2e. Here, the draft may be the average of two measured values by the second draft meter 2b and the third draft meter 2c provided on both sides of the ship 20, respectively.

[0051] The roll damping force coefficient B 44 (= roll damping moment (kgfm) / roll angular velocity (rad / sec)) is obtained by the following formula. B 44 =Bf+Bw+Be+Bl+Bbk … Equation (31) The arithmetic processing unit 1 includes a displacement arithmetic unit 11, a roll damping force coefficient arithmetic unit 12, a natural frequency arithmetic unit 13, a damping coefficient arithmetic unit 14, an apparent moment of inertia arithmetic unit 15, and a GM arithmetic unit 16.

[0052] Each arithmetic unit 11 - 16 is mainly composed of software such as a program or a module, but may be divided hardware-wise. Also, each arithmetic unit 11 - 16 does not necessarily need to be clearly divided, and may be configured in any way as long as the same GM as the configuration described here is calculated substantially, and some calculations may be shared.

[0053] The displacement calculation unit 11 calculates the displacement W based on the draft values measured by the four draft gauges 2a to 2d and the ship-specific information stored in the storage unit 3. The displacement calculation unit 11 outputs the calculated displacement W to the roll damping force coefficient calculation unit 12 and the GM calculation unit 16.

[0054] The roll damping force coefficient calculation unit 12 calculates the roll damping force coefficient B based on the ship-specific information stored in the storage unit 3, the displacement W calculated by the displacement calculation unit 11, the mid-port draft Mid(P) and mid-starboard draft Mid(S) measured by the second draft gauge 2b and the third draft gauge 2c provided on both sides of the ship 20, respectively, and the motion data measured by the motion meter 2e. 44 calculates. The roll damping force coefficient B 44 The type draft used for the calculation of is calculated using the mid-port draft Mid(P) and the mid-starboard draft Mid(S). The roll damping force coefficient calculation unit 12 outputs the calculated roll damping force coefficient B 44 to the apparent moment of inertia calculation unit 15.

[0055] The natural frequency calculation unit 13 calculates the natural frequency ω based on the motion data measured by the motion meter 2e. For example, the natural frequency calculation unit 13 estimates the natural frequency ω using the Markov chain Monte Carlo method after fitting a two-variable AR model (see Non-Patent Document 3). The natural frequency calculation unit 13 outputs the calculated natural frequency ω to the GM calculation unit 16.

[0056] The damping coefficient calculation unit 14 calculates the damping coefficient α based on the motion data measured by the motion meter 2e. For example, the damping coefficient calculation unit 14 estimates the damping coefficient α using the Markov chain Monte Carlo method after fitting a two-variable AR model (see Non-Patent Document 3). The damping coefficient calculation unit 14 can use the same two-variable AR model as that used by the natural frequency calculation unit 13. Therefore, the damping coefficient calculation unit 14 may perform calculations shared with the natural frequency calculation unit 13. The damping coefficient calculation unit 14 outputs the calculated damping coefficient α to the apparent moment of inertia calculation unit 15.

[0057] The apparent moment of inertia calculation unit 15 calculates the apparent moment of inertia (I 44 + A xx ) based on the roll damping force coefficient B calculated by the roll damping force coefficient calculation unit 12 44 and the damping coefficient α calculated by the damping coefficient calculation unit 14. The apparent moment of inertia calculation unit 15 outputs the calculated apparent moment of inertia (I xx + A 44 ) to the GM calculation unit 16.

[0058] The GM calculation unit 16 calculates GM based on the displacement W calculated by the displacement calculation unit 11, the natural frequency ω calculated by the natural frequency calculation unit 13, and the apparent moment of inertia (I xx + A 44 ) calculated by the apparent moment of inertia calculation unit 15. The GM calculation unit 16 outputs the calculated GM to the display unit 4.

[0059] According to the present embodiment, by calculating GM based on the displacement W, it is possible to obtain GM considering the loading state of the ship 20.

[0060] In addition, additional advantages and modifications may readily occur to those skilled in the art. Therefore, the present invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and their equivalents.

Explanation of Reference Numerals

[0061] 1... arithmetic processing unit, 2a, 2b, 2c, 2d... draft gauges, 2e... motion meter, 3... storage unit, 4... display unit, 10... ship characteristic calculation device, 11... displacement calculation unit, 12... roll damping force coefficient calculation unit, 13... natural frequency calculation unit, 14... damping coefficient calculation unit, 15... apparent moment of inertia calculation unit, 16... GM calculation unit.

Claims

1. A draft data receiving unit that receives draft data measured by a plurality of draft gauges provided on a ship; A sway data receiving unit that receives sway data regarding the sway of the ship measured by a sway meter; A ship-specific information storage unit that stores ship-specific information including information regarding the dimensions of the hull, which is the unique information of the ship; A displacement calculation unit that calculates the displacement based on the draft data received by the draft data receiving unit and the ship-specific information stored in the ship-specific information storage unit; A roll damping force coefficient calculation unit that calculates a roll damping force coefficient based on the draft data received by the draft data receiving unit, the sway data received by the sway data receiving unit, the displacement calculated by the displacement calculation unit, and the ship-specific information stored in the ship-specific information storage unit; A roll natural angular frequency calculation unit that calculates a roll natural angular frequency based on the sway data received by the sway data receiving unit; A damping coefficient calculation unit that calculates a damping coefficient based on the sway data received by the sway data receiving unit; An apparent moment of inertia calculation unit that calculates an apparent moment of inertia based on the roll damping force coefficient calculated by the roll damping force coefficient calculation unit and the damping coefficient calculated by the damping coefficient calculation unit; A transverse metacentric height calculation unit that calculates a transverse metacentric height based on the displacement calculated by the displacement calculation unit, the roll natural angular frequency calculated by the roll natural angular frequency calculation unit, and the apparent moment of inertia calculated by the apparent moment of inertia calculation unit; An output unit that outputs the transverse metacentric height calculated by the transverse metacentric height calculation unit A ship characteristic calculation device comprising the above.

2. The ship characteristic calculation device according to claim 1, further comprising the plurality of draft gauges and the sway meter.

3. The ship characteristic calculation device according to claim 1, wherein the roll natural angular frequency calculation unit and the damping coefficient calculation unit perform calculations for estimating the roll natural angular frequency and the damping coefficient, respectively, using a two-variable first-order autoregressive model.

4. A computer receives draft data measured by a plurality of draft gauges provided on a ship, and the computer receives sway data regarding the sway of the ship measured by a sway meter. The computer calculates the displacement based on the received draft data and information on the dimensions of the hull, and based on the vessel-specific information, which is the unique information of the vessel. The computer calculates the roll damping force coefficient based on the received draft data, the received motion data, the calculated displacement, and the vessel-specific information. The computer calculates the roll natural angular frequency based on the received motion data. The computer calculates the damping coefficient based on the received motion data. The computer calculates the apparent moment of inertia based on the calculated roll damping force coefficient and the calculated damping coefficient. The computer calculates the transverse metacentric height based on the calculated displacement, the calculated roll natural angular frequency, and the calculated apparent moment of inertia. The computer outputs the calculated transverse metacentric height. A method for calculating vessel characteristics, characterized by including the above.

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