A method for calculating the real-time load of a ship

Abstract

This invention discloses a method for real-time ship load calculation, relating to ship load calculation technology. It involves obtaining the ship's average draft from its periphery using a three-point detection method; determining the ship's center of buoyancy; and obtaining the average draft of the ship's trim based on the trigonometric relationship between the center of buoyancy and the midships; applying a weighted correction to the average draft of the ship to obtain the average draft; determining an interpolation interval based on the average draft; and calculating the ship's load capacity using linear interpolation. This invention provides highly accurate ship weight measurement; it enables real-time acquisition of ship load capacity, timely and effective assessment of ship energy efficiency, and has a wide range of applications.

Description

Technical Field

[0001] This invention relates to ship load calculation technology, and more specifically, to a method for real-time ship load calculation. Background Technology

[0002] Faced with the inefficient management of inland waterway fleets and increasingly stringent national requirements for energy conservation and emission reduction, optimizing real-time navigation status through real-time vessel load data is crucial for achieving green and ecological development of inland waterway transportation. This allows vessels to maintain high energy efficiency, reducing emissions while achieving high economic benefits. Currently, vessel load capacity is primarily calculated using draft surveying, which uses the vessel as a measuring tool and applies Archimedes' principle to calculate cargo capacity. The key technology lies in measuring the vessel's draft.

[0003] The most common method for determining the draft of inland waterway vessels in my country is manual observation. However, with the continuous development of intelligent ship technology, intelligent measurement technologies such as ultrasonic detection, multi-sensor information fusion, pressure sensor technology, and laser ranging are gradually being applied to the draft determination of inland waterway vessels. However, the state of a vessel in the water is highly variable, including states such as list and trim, and hull sagging. Furthermore, due to the unevenness of the water surface, the draft at the stern and bow is not consistent. Therefore, improving the accuracy of measurement data has become an important issue in this field. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for real-time load calculation of ships, which addresses the shortcomings of the existing technology. Based on ultrasonic detection technology, the method measures the current draft of the ship with the ship's deck as a reference, and then calculates the actual load of the ship using formulas according to the relevant water gauge charts. This method comprehensively considers changes in the ship's state and changes in the water surface, which greatly improves the accuracy of the measurement data.

[0005] The technical solution of this invention is as follows: a method for real-time load calculation of a ship, which uses a three-point detection method to obtain the average draft of the ship's periphery; determines the ship's center of buoyancy, and obtains the average draft of the ship's heel based on the trigonometric function relationship between the ship's center of buoyancy and the ship's midships; performs weighted correction processing on the average draft of the ship's heel to obtain the average draft of the ship; determines the interpolation interval based on the average draft of the ship, and calculates the load capacity of the ship using a linear interpolation method.

[0006] The three-point detection method is specifically as follows:

[0007] An ultrasonic sensor is installed at the bow, and two ultrasonic sensors are installed on both sides of the stern, with the three ultrasonic sensors positioned on the same horizontal plane. The real-time distances between the three ultrasonic sensors and the water surface are collected sequentially. The fixed distances between the ultrasonic sensors and the bottom of the ship are then compared with the three real-time distances to obtain three fixed-point drafts. The average of the sum of the three fixed-point drafts is taken as the outer average draft.

[0008] When collecting the real-time distance between the ultrasonic sensor and the water surface, temperature compensation is applied to the propagation speed of the ultrasonic waves generated by the ultrasonic sensor in the medium.

[0009] The speed of ultrasonic wave propagation after temperature compensation is:

[0010]

[0011] In the formula, v is the ultrasonic propagation speed after temperature compensation; T is the ambient temperature in Celsius.

[0012] The method for determining the ship's center of gravity is as follows:

[0013] The draft at a fixed point on the bow is taken as the bow draft, and a first marker is taken on the bow perpendicular line of the vessel, such that the distance between the first marker and the bottom of the vessel is the bow draft; the average of the sum of the two fixed drafts at the stern is taken as the stern draft, and a second marker is taken on the stern perpendicular line of the vessel, such that the distance between the second marker and the bottom of the vessel is the stern draft; the first marker and the second marker are connected to form a marker line, and the intersection of the marker line and the horizontal plane is taken as the center of the vessel's float.

[0014] The average draft of the ship's trim is determined by the following formula.

[0015]

[0016] In the formula, d m1 d1 is the average draft of the ship with a tilt; d2 is the draft of the port stern; d3 is the draft of the starboard stern; X is the draft of the ship with a bow. f L is the distance between the center of the ship's buoyancy and the midships. BF It is the distance between the bow perpendicular and the stern perpendicular.

[0017] The formula for calculating the average draft of the ship is as follows:

[0018]

[0019] In the formula, d m θ is the average draft of the ship; k is the weighting coefficient; θ is the angle between the punctuation mark and the horizontal plane.

[0020] The formula for calculating the deadweight of the vessel is as follows:

[0021]

[0022] In the formula: m is the deadweight of the ship; m i The load value at the left endpoint of the interpolation interval; m i+1 d represents the load value at the right endpoint of the interpolation interval. mi d represents the draft depth at the left endpoint of the interpolation interval. mi+1 The draft is the right endpoint of the interpolation interval.

[0023] Beneficial effects

[0024] The advantages of this invention are as follows: By correcting the propagation speed of ultrasonic waves in the medium through temperature compensation, the ranging accuracy can be effectively improved, thereby enhancing the accuracy of ship weight measurement. Furthermore, this invention employs a correction algorithm to adjust the ship's average draft under conditions of heeling, trimming, and sag deformation, and uses linear interpolation based on the measured ship draft to calculate the ship's load capacity. This further improves measurement accuracy while maintaining the original accuracy of the sensor. It enables real-time acquisition of ship load capacity, timely and effective assessment of ship energy efficiency, and has a wide range of applications. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the working principle of a single-probe ultrasonic sensor.

[0026] Figure 2 This is a schematic diagram of the installation of the ship ultrasonic sensor of the present invention;

[0027] Figure 3 This is a schematic diagram of the ship exhibiting a small angle of trim according to the present invention.

[0028] Figure 4 This is a schematic diagram of the ship in the central arch state according to the present invention;

[0029] Figure 5 This is a schematic diagram of the ship in a drooping state according to the present invention;

[0030] Figure 6 This is a schematic diagram of the linear interpolation method of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0032] See Figures 1-6The present invention provides a method for real-time load calculation of ships, which is based on ultrasonic sensors.

[0033] Ultrasonic ranging measures distance using the reflection and absorption characteristics of ultrasonic waves, with reflection being the most commonly used characteristic. When a plane sound wave passes through the interface between two media of different densities, the sound wave will be reflected and refracted by the interface. If sound absorption does not occur, the relationship between the sound intensity of the reflected wave, incident wave, and refracted wave is as follows:

[0034]

[0035]

[0036] In the above formula: I o The incident wave acoustic intensity; I r The intensity of the reflected wave; I t α is the refracted wave intensity; α is the incident angle of the sound wave. Z is the angle of refraction of the sound wave; Z1 and Z2 are the wave resistances in the two media, respectively, Z1 = ρ1v1, Z2 = ρ2v2; ρ i v is the density of the i-th medium; i Let be the speed of sound propagation in medium i; i is a natural number.

[0037] like If a sound wave is incident perpendicularly, it will not be reflected.

[0038] When a sound wave encounters the interface between two media and is reflected during propagation, the ratio of the intensity of the reflected wave to the intensity of the incident wave is called the reflection coefficient, and its calculation formula is shown below:

[0039]

[0040] In the above formula: R is the sound wave reflection coefficient.

[0041] The ratio of the transmitted wave intensity to the incident wave intensity is called the transmission coefficient, which is defined as follows:

[0042]

[0043] In the above formula: T is the sound wave transmission coefficient.

[0044] Clearly, R + T = 1. From the above two equations, we can see that when z1 = z2, R = 0 and T = 1, meaning all sound waves are transmitted and no reflection occurs. When z1 >> z2 or z1 >> z2, R = 1 and T = 0, meaning all sound waves are reflected and no transmission occurs. When sound waves reach the interface between two media with significantly different wave resistances, most of the sound waves will be reflected, which can be used to locate the two media with different wave resistances and obtain the distance between them.

[0045] The basic method of ultrasonic ranging is the time-of-flight (TOF) method. A pulsed electrical signal is input to the ultrasonic transmitter sensor. The piezoelectric crystal deforms, generating vibrations at frequencies above 20 kHz, thus producing ultrasonic waves. These waves are amplified by a conical resonant disk and emitted directionally. When the ultrasonic waves encounter obstacles or interfaces in the propagation medium, significant reflection echoes occur. By measuring the time difference between the ultrasonic sensor's transmission and reception times, as well as the propagation speed of the ultrasonic waves in the medium, the distance between the measurement point and the measured object can be calculated. This invention uses a self-transmitting and self-receiving single-probe ultrasonic sensor.

[0046] Depend on Figure 1 The working principle of a single-probe ultrasonic sensor shows that the ultrasonic propagation distance L1 can be calculated based on the time difference between the emitted and received echoes measured by the timer.

[0047]

[0048] The distance between the probe and the object being measured can be calculated based on the distance between the ultrasonic transceiver transducers.

[0049]

[0050] In the single-probe mode with self-transmitting and self-receiving capabilities, the transducers are very close together, i.e., d is very small. When the distance between the probe and the object being measured is much greater than the distance between the transducers, it can be considered that the distance between the probe and the object being measured is approximately equal to the ultrasonic wave propagation distance, i.e.:

[0051]

[0052] The propagation speed of ultrasound in a medium is easily affected by factors such as temperature, humidity, and pressure, with temperature having a significant impact. For example, when ultrasound propagates in air, its propagation speed increases by approximately 0.6 m / s for every 1°C increase in temperature. Therefore, temperature compensation is used to correct the propagation speed of ultrasound in the medium, thereby improving ranging accuracy. The temperature compensation correction formula is as follows:

[0053]

[0054] In the formula, v is the ultrasonic propagation speed after temperature compensation; T is the ambient temperature in Celsius.

[0055] The following is a detailed description of the steps of the real-time load calculation method for ships according to the present invention.

[0056] This method first uses a three-point detection method to obtain the average draft of the ship's outer perimeter.

[0057] like Figure 2 As shown, the three-point detection method specifically involves installing an ultrasonic sensor at the bow and two ultrasonic sensors on either side of the stern, ensuring all three sensors are positioned on the same horizontal plane. The real-time distances between the three ultrasonic sensors and the water surface are sequentially collected. The fixed distance between the ultrasonic sensors and the hull bottom is then calculated as the difference between these three real-time distances to obtain the draft at three fixed points. The average of the sum of these three fixed-point drafts is taken as the outer average draft.

[0058] according to Figure 2 The ultrasonic sensor installation diagram shows that the distance H from the bottom of the ship to the plane formed by the three ultrasonic sensors installed on the ship is known. Therefore, the final draft of the ship measured by the three ultrasonic sensors installed on the port, starboard, and bow of the stern are as follows:

[0059] d1 = |H - H1|;

[0060] d2 = |H - H2|;

[0061] d3 = |H-H3|.

[0062] In the formula: H1 is the measured value of the ultrasonic sensor at the port stern, that is, the real-time distance between the ultrasonic sensor and the water surface; H2 is the measured value of the ultrasonic sensor at the port stern; H3 is the measured value of the ultrasonic sensor at the bow; d1, d2, and d3 are three fixed-point drafts, defined as follows: d1 is the draft at the port stern, d2 is the draft at the starboard stern, and d3 is the draft at the bow.

[0063] Based on the above measurements, when the ship reaches the ideal state of upright buoyancy and no deformation after loading, the ideal average draft d of the ship is determined. m0 for:

[0064]

[0065] Under ideal conditions, the ideal average draft of a ship is d. m0 It is equal to the draft d0 at the midships.

[0066] Because ships may list or trim during navigation and after loading cargo, and because the weight and buoyancy acting on different parts of the ship are uneven, the hull will undergo longitudinal deformation, also known as yaw. Therefore, since the drafts at the bow, midships, and stern of a ship are different, small-angle corrections for list and yaw are needed when calculating the ship's average draft.

[0067] In an ideal, upright, and undeformed state, a ship's average draft corresponds to a fixed displacement or volume. When the ship's cargo load is constant, both heeling and trimming only affect the shape of the displacement volume, not the displacement itself. Therefore, by finding the invariants when a ship heels or trims, the average draft under ideal, upright, and undeformed conditions can be calculated. The center of float is the center of the waterline area formed by the ship's contact with the water surface. During a small trim, the center of float does not change; that is, when the ship undergoes isochoric heeling, the waterline rotates around the center of float by an angle. Therefore, the draft at the center of float is the ship's average draft.

[0068] like Figure 3 This is a schematic diagram of a ship experiencing a small angle of trim. Figure 3 It can be seen from this that the draft d at the center of the ship's buoyancy is... m The difference in depth between the midship draft d0 and the midship draft is δ. According to trigonometric relationships, we can obtain:

[0069]

[0070] In the formula: X f L is the distance between the center of the ship's buoyancy and the midships. BP d is the distance between the bow and stern perpendiculars; t is the difference in draft between the bow and stern, t = d3 - (d1 + d2) / 2.

[0071] Therefore, considering the ship's tilt, its average draft is:

[0072]

[0073] In the formula, d m1 The average draft of the ship when tilted.

[0074] Furthermore,

[0075]

[0076] See also Figure 3 According to its trigonometric function relationship, the draft d0 at the midships is:

[0077]

[0078] In the formula: L is the overall length of the ship; l is the distance from the ultrasonic sensor to the ship's side; θ is the ship's trim angle.

[0079] Based on the above principle, the average draft of the ship when tilted is:

[0080]

[0081] A schematic diagram of the sag deformation of a ship is shown below. Figures 4-5 As shown. When a ship experiences midship sag, the draft at the bow and stern is greater than the draft amidship, leading to an overestimation of the upward displacement volume and an inflated average draft. Conversely, when a ship experiences hag, the draft at the bow and stern is less than the draft amidship, resulting in an underestimation of the downward displacement volume and an inflated average draft. Therefore, when considering sag deformation, the above formula introduces significant errors, necessitating a correction for sag deformation in the calculation of the average draft.

[0082] In engineering practice, a weighted correction to the midship draft is used to eliminate the effects of sag deformation caused by the ship. The calculation formula is as follows:

[0083]

[0084] In the formula: k is a weighting coefficient, which is generally taken as 6. For ships with a longer length and a longer parallel midhull, k can be taken as 7; for ships with a shorter length and a shorter parallel midhull, k can be taken as 5.

[0085] In summary, when a ship experiences both list and trim and sag deformation, its corrected mean draft is as follows:

[0086]

[0087] After obtaining the ship's average draft, the interpolation interval is determined based on the ship's average draft, and the ship's load capacity is calculated using linear interpolation.

[0088] Since the ship's deadweight is determined from the "Ship Deadweight and Draft Chart" provided by the shipyard, some deadweight values ​​cannot be found in the chart. Therefore, this invention uses linear interpolation to calculate the ship's deadweight based on the "Ship Deadweight and Draft Chart." That is, linear interpolation can calculate values ​​not found in the chart during the lookup process.

[0089] Linear interpolation is a relatively simple interpolation method. Geometrically, it approximates the original function with a straight line formed by two interpolation nodes, and the interpolation function is a first-order polynomial. For example... Figure 5 The diagram shown is a schematic of the linear interpolation method.

[0090] exist Figure 6 In the above, let the function y = f(x) be applied at x. i x i+1 The values ​​of the two points are y t y t+1 Find the polynomial:

[0091]

[0092] Make it satisfy:

[0093]

[0094] From analytic geometry, we know that:

[0095]

[0096] In the formula: y is the interpolation result of the i-th interpolation interval; x is the independent variable of the i-th interpolation interval; x i x is the independent variable at the left endpoint of the interpolation interval. i+1 y is the independent variable at the right endpoint of the interpolation interval; i The function value at the left endpoint of the interpolation interval; y i+1 The function value is the right endpoint of the interpolation interval.

[0097] Based on the measured ship draft d m Determine the interpolation interval from the "Correspondence Table of Ship Load Capacity and Draft Water" Then, the ship's deadweight is calculated using linear interpolation, and the calculation formula is shown below.

[0098]

[0099] In the formula: m is the deadweight of the ship; m i The load value at the left endpoint of the interpolation interval; m i+1 d represents the load value at the right endpoint of the interpolation interval. mi d represents the draft depth at the left endpoint of the interpolation interval. mi+1 The draft is the right endpoint of the interpolation interval.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for calculating the real-time load of a ship, characterized in that, The average draft of the vessel's perimeter is obtained using a three-point detection method; the vessel's center of buoyancy is determined, and the average draft of the trim is obtained based on the trigonometric relationship between the center of buoyancy and the midships; the average draft of the trim is then weighted and corrected to obtain the vessel's average draft; an interpolation interval is determined based on the average draft, and the vessel's deadweight is calculated using a linear interpolation method; The three-point detection method is specifically as follows: An ultrasonic sensor is installed at the bow, and two ultrasonic sensors are installed on both sides of the stern, with the three ultrasonic sensors positioned on the same horizontal plane. The real-time distance between the three ultrasonic sensors and the water surface is collected sequentially. The fixed distance between the ultrasonic sensors and the bottom of the ship is calculated by subtracting the three real-time distances to obtain the draft at three fixed points. The average of the sum of the three fixed-point drafts is taken as the average draft at the outer perimeter. The method for determining the ship's center of gravity is as follows: The draft at a fixed point on the bow is taken as the bow draft, and a first marker is taken on the bow perpendicular line of the vessel, such that the distance between the first marker and the bottom of the vessel is the bow draft; the average of the sum of the two fixed drafts at the stern is taken as the stern draft, and a second marker is taken on the stern perpendicular line of the vessel, such that the distance between the second marker and the bottom of the vessel is the stern draft; the first marker and the second marker are connected to form a marker line, and the intersection of the marker line and the horizontal plane is taken as the center of the vessel's float. The average draft of the ship's trim is determined by the following formula. ； In the formula, The average draft of the ship when tilted; This refers to the draft at the port stern. This refers to the draft at the starboard stern. The draft at the bow; The distance between the center of the vessel's buoyancy and the midships; The distance between the bow perpendicular and the stern perpendicular; The overall length of the vessel; The distance from the edge of the ship to which the ultrasonic sensor extends; The angle between the line connecting the punctuation marks and the horizontal plane; The formula for calculating the average draft of the ship is as follows: ； In the formula, The average draft of the vessel; These are the weighting coefficients.

2. The method for calculating the real-time load of a ship according to claim 1, characterized in that, When collecting the real-time distance between the ultrasonic sensor and the water surface, temperature compensation is applied to the propagation speed of the ultrasonic waves generated by the ultrasonic sensor in the medium.

3. The method for calculating the real-time load of a ship according to claim 2, characterized in that, The speed of ultrasonic wave propagation after temperature compensation is: ； In the formula, The speed of ultrasonic wave propagation after temperature compensation; The ambient temperature is in Celsius.

4. The method for calculating the real-time load of a ship according to claim 1, characterized in that, The formula for calculating the deadweight of the vessel is as follows: ； In the formula: The deadweight tonnage of the ship; The load value is the left endpoint of the interpolation interval; The load value is the right endpoint of the interpolation interval; The draft is the left endpoint of the interpolation interval; The draft is the right endpoint of the interpolation interval.

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