Method for evaluating probability of ship riding wave in irregular wave based on AIS data

Abstract

The application discloses a method for evaluating ship riding wave probability in irregular waves based on AIS data, which comprises the following steps: 1, establishing a probability density function of ship density based on ship AIS data; 2, selecting a representative route and multiple test points at equal intervals, and obtaining the probability of occurrence of a specific random sea state in a target sea area according to a wave scatter diagram of a sea area near the test points; 3, calculating the riding wave probability of a ship in random waves; 4, calculating the riding wave probability of a ship in a specific irregular wave of a test point of the representative route in random waves; 5, calculating the riding wave probability of the ship under each random sea state of the test point, and calculating the riding wave probability of the ship of other test points according to the same steps. The application solves the related problem of solving the riding wave motion of a ship in irregular waves, can predict the probability of the riding wave motion of the ship in irregular waves, the calculation result can directly obtain the riding wave motion probability of the ship in irregular waves, the solving precision is high, the efficiency is high, and the application is suitable for various ship types.

Description

Technical Field

[0001] This invention belongs to the field of ship nonlinear motion analysis, and in particular relates to a method for evaluating the probability of a ship riding waves based on AIS data in irregular waves. Background Technology

[0002] Wave riding / flare motion is one of the failure modes in second-generation intact stability of ships. During wave riding / flare motion, the nonlinear dynamic characteristics are the most significant among ship instability modes. From a mechanical perspective, wave riding is an equilibrium state where longitudinal wave force, thrust, and drag reach dynamic equilibrium when the ship speed equals the wave speed. Typically, the wavelength of a wave-riding motion is about 1 to 3 times the ship's length, the waves are sufficiently steep, and the ship speed is comparable to the wave speed, approximately 75% of the wave speed.

[0003] Unlike wave-riding motion under regular waves, wave-riding motion of ships in irregular waves manifests as abnormally high-speed motion exceeding the ship's rated speed over a period of time. Internationally, Grim first confirmed the existence of this abnormal motion phenomenon and conducted statistical analysis on its duration. Subsequently, Spyrou et al. established the differential equation for the single-degree-of-freedom sway motion of ships in irregular waves, solving for the ship's instantaneous velocity. They also solved for the instantaneous wave velocity in the waves from both time and space dimensions, using the lower of the instantaneous wave velocity and the nominal speed as the critical velocity for determining wave-riding, thus defining the phenomenon of high runs in irregular waves. Currently, there is limited research on high runs in China. Current research on wave-riding motion of ships in irregular waves mainly focuses on optimizing wave-riding calculation models, defining the boundaries of wave-riding motion, and theoretical research on the probability and correlation of subsequent yaw motion. There is a lack of research combining actual sea conditions and route probabilities to analyze wave-riding motion and thus conduct practical research on ship route optimization. Summary of the Invention

[0004] Purpose of the Invention: The purpose of this invention is to provide a method for assessing the probability of a ship riding waves in irregular waves based on AIS data. A ship density calculation model is established based on AIS data and a standard ship. A nonparametric kernel density method is used to estimate the probability density function of the ship density. The ship density map obtained from the probability density function is used to find representative shipping routes in a certain sea area. The probability of a ship riding wave on a representative route is studied. Furthermore, to overcome the limitations of numerical methods in nonlinear wave riding motion of ships in irregular waves, a nonlinear dynamic probability analysis method for ship wave riding in irregular waves is proposed. This method uses nonlinear dynamic analysis to analyze the probability of a ship riding waves in irregular waves, providing an analytical method and a basis for safe navigation.

[0005] Technical Solution: The present invention provides a method for assessing the probability of ships riding waves in irregular waves based on AIS data. This method selects AIS data of ships in a target sea area within a target time period, establishes a probability density function of ship density, determines representative shipping routes in the target sea area using the probability density function, and determines the probability of ships riding waves in irregular waves based on a nonlinear dynamic probability analysis method for ships riding waves in irregular waves. The method includes the following steps:

[0006] Step 1: Select AIS data of ships in the target sea area within the target time, establish the probability density function of ship density, and solve the probability density function of ship density using the nonparametric kernel density estimation method to obtain the ship density map;

[0007] Step 2: Select the critical density threshold of ships based on the ship density map and define areas with high traffic volume. Identify and characterize representative route areas from these areas. Select at least two test points at equal intervals within the representative route areas. Based on the wave scattering map of the sea area near the test points, obtain the probability P1 of irregular waves appearing in a specific combination of meaningful wave height and characteristic period in the target sea area.

[0008] Step 3: Based on the nonlinear dynamic probability analysis method of ships riding waves in irregular waves, calculate the probability P2 of ships riding waves in irregular waves in the target sea area;

[0009] Step 4: Calculate the probability P of a ship riding the waves at a specific irregular wave at a test point on a representative route in the irregular wave based on the probability P1 of irregular waves appearing in the target sea area and the probability P2 of a ship riding the waves in the irregular waves; by analogy, calculate the probability of a ship riding the waves at each random sea state at the test point based on the wave scattering map of the area covered by the representative route, and obtain the probability map of the ship riding the waves at the test point.

[0010] Step 5: Repeat steps 2-4 to calculate the probability of a ship riding the waves in different irregular waves at other test points, obtain the probability diagram of riding the waves at each test point, and solve for the total probability of a ship riding the waves on a representative route.

[0011] Furthermore, step 1 specifically includes the following steps:

[0012] Step 1.1: Assume x1, x2…x n Let x be a sample of random variable x, and let x be the probability density function of random variable x. The probability density function of the ship's density is shown in the following equation:

[0013]

[0014] Where x is a random variable, Indicates ship density, x iLet h represent the i-th ship density sample, h represent the bandwidth length, n represent the number of samples, and K represent the kernel function.

[0015] Step 1.2: Select the Gaussian kernel function as the kernel function in the nonparametric kernel density estimation method. The formula for the Gaussian kernel function is as follows:

[0016]

[0017] Step 1.3: Select h as the bandwidth;

[0018] Step 1.4: Obtain the probability density function of the ship density using the nonparametric kernel density estimation method to get the ship density map. The probability density function is shown below:

[0019]

[0020] Furthermore, in step 2, five test points are selected.

[0021] Furthermore, step 3 specifically includes the following steps:

[0022] Step 3.1: Establish the differential equations of the ship's sway motion in irregular waves:

[0023]

[0024] Where, ξ′ G Here, m represents the ordinate of the ship's center of gravity in the geodetic coordinate system, and m represents the ship's displacement. x Let u be the mass added to the hull in the sway direction, R(u) be the instantaneous velocity in the sway direction, T(u,n) be the ship's resistance in still water, and X be the propeller thrust in still water. ω (ξ G ,t) represents the wave force in the oscillation direction, and t represents time;

[0025] Step 3.2: Determine the coefficients of each term in the differential equation of the sway motion: the mass m of the ship, and the additional mass m of the hull in the sway direction. x The longitudinal resistance R(u) of the ship, the propeller thrust T(u,n) in the pitch direction, and the wave force X experienced by the ship in the pitch direction. ω (ξ G ,t);

[0026] The longitudinal resistance R(u) of the hull is fitted using a cubic polynomial as follows:

[0027] R(u) = r1u + r2u 2 +r3u 3 (5)

[0028] Among them, r1, r2, and r3 are obtained by calculation and fitting from hull resistance test data or hydrodynamic numerical simulation software;

[0029] The propeller thrust T(u,n) in the oscillation direction is approximated by a polynomial:

[0030] T(u,n)=(1-t p )ρn 2 D p 4 K T (6)

[0031] Where n represents the propeller speed, t p ρ represents thrust reduction, D represents seawater density, and D represents the thrust reduction. p K represents the propeller diameter. T The thrust coefficient of the propeller is calculated using the following formula:

[0032] K T =k0+k1J P +k2J P 2 (7)

[0033] Among them, J P Represents the advance rate coefficient. k0, k1, and k2 can be obtained by fitting the open-water test data of the propeller;

[0034] Step 3.3: Under random sea states, the wave force is solved by linear superposition, as shown below:

[0035]

[0036] In the formula, ki is the wave number of the i-th regular wave, and ω i Let φ be the frequency of the i-th regular wave. i For random phase angles, γ i For phase shift, a i For the i-th regular amplitude value, RAO(k) i ) represents the amplitude of the oscillating wave force generated by the i-th regular wave unit amplitude, where N is a positive integer;

[0037] Step 3.4: Calculate the probability P2 of the ship riding the waves in irregular waves using analytical or numerical methods.

[0038] Furthermore, in step 3.4, the analytical method specifically involves using the Melnikov method to solve for the probability of a ship riding the waves in irregular waves. The specific steps are as follows:

[0039] Substituting equation (8) into equation (4) and performing dimensionless transformation, let y = kξ G , Considering the changes in wave force caused by irregular waves in addition to regular waves, we have:

[0040]

[0041] The equation can be rewritten in the following form, with the left side representing the undamped Hilmiton system:

[0042]

[0043] in:

[0044]

[0045] η is a time-dependent random process related to irregular waves, and its spectral density function is S. η For the purpose of analytical calculation, the irregular wave force is considered as a variable, random wave force superimposed on the regular wave force, η, expressed in the following form:

[0046]

[0047] Where: ω n Let be the peak frequency of the wave spectrum, and c1(t) be the random phase angle;

[0048] The Melnikov method uses the following function to characterize the distance between stable and unstable manifolds, as shown below:

[0049]

[0050] The necessary condition for a ship to ride the waves in irregular waves is that M(τ0) < 0. The excitation generated by the irregular waves is approximately a Gaussian random process, and the Melnikov process M(τ0), which is derived from its linear transformation, is also a Gaussian process with a mean μ. M and variance σ z 2 The expression is:

[0051]

[0052]

[0053] Where H(ω) is the frequency response function, calculated by the following formula:

[0054]

[0055] The probability density function of the normal distribution is:

[0056]

[0057] Integrating equation (16), we obtain the probability distribution function of the normal distribution:

[0058]

[0059] According to the probability distribution function of the normal distribution, the probability of wave riding in an irregular wave is:

[0060]

[0061] Furthermore, the numerical method in step 3.4 specifically includes:

[0062] Substituting equation (8) into equation (4), the Runge-Kutta method is used to obtain the ship speed time history curve, where time is the abscissa, and the ship's relative displacement and relative velocity are the ordinates. The instantaneous wave velocity of the random wave is shown in the following equation:

[0063]

[0064] In the formula, ω(ξ) s ,t) is the frequency of the random wave, k(ξ) s ,t) is the wavenumber of the random wave;

[0065] The instantaneous wave speed diagram of random waves is plotted according to formula (19). The upper cross threshold value is selected as the intersection of instantaneous wave speed and ship speed, and the lower cross threshold value is selected as the intersection of instantaneous wave speed and ship rated speed. The time node when the ship speed exceeds the instantaneous wave speed is defined as the start time of riding the wave, and the time node when the ship speed is lower than the rated speed is defined as the end time of riding the wave. The probability of a ship riding the wave under a certain random working condition is the ratio of the sum of the intermittent wave riding time t0 to the numerical simulation duration t1.

[0066] For the same sea state, the sway motion response under multiple random seed numbers is calculated, and all results are statistically analyzed to reduce errors, so that the probability of the ship riding the waves in random waves is P2 = t0 / t1.

[0067] Furthermore, in step 4, the probability P of a ship riding the waves in a specific irregular wave in the test point area representing a typical route within the irregular wave is calculated based on the probability P1 of irregular waves occurring in the target sea area and the probability P2 of a ship riding the waves in random waves, where:

[0068] P = P1P2 (20)

[0069] By analogy, based on the wave scattering map of the area covered by the representative route, the probability of a ship riding the waves at each random sea state at the test point is calculated, and the probability map of the ship riding the waves at the test point is obtained.

[0070] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0071] 1. The present invention provides a nonlinear dynamic probability calculation and analysis method for ships under irregular wave excitation, which solves the problem of solving the relevant problems of ships riding waves in irregular waves and can predict the probability of ships riding waves in irregular waves;

[0072] 2. Based on modern nonlinear dynamics theory and methods, the calculation results can directly obtain the probability of a ship riding waves in irregular waves, with high accuracy and efficiency.

[0073] 3. The nonlinear dynamics calculation and analysis method for ships under irregular wave excitation of the present invention is applicable to various ship types and has strong versatility;

[0074] 4. Based on the theories of ship and marine engineering hydrodynamics and nonlinear dynamics, this invention presents a nonlinear dynamic probabilistic analysis method for ship wave-riding in irregular waves, enabling rapid solution of ship instability conditions through nonlinear dynamics. Addressing the nonlinear problem of ship wave-riding motion in irregular waves, this invention combines numerical analysis and nonlinear dynamics theory to determine the unstable dynamic conditions and wave-riding motion patterns of ships in irregular waves, thereby predicting potential ship motion risks. Attached Figure Description

[0075] Figure 1 For the ship's motion coordinate system;

[0076] Figure 2 A ship density map for representative shipping routes;

[0077] Figure 3 A schematic diagram showing five test points A, B, C, D, and E taken at equal intervals along the selected schematic route;

[0078] Figure 4 A wave scatter plot for one point on the flight path;

[0079] Figure 5 This is a schematic diagram of the ship speed time history curve and the instantaneous wave speed of random waves;

[0080] Figure 6 This is a diagram illustrating the probability of riding the wave.

[0081] Figure 7 This is a flowchart illustrating the method for assessing the probability of a ship riding the waves based on AIS data in irregular waves according to the present invention. Detailed Implementation

[0082] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0083] This invention combines ship motion theory with nonlinear dynamics theory, proposes new indicators and concepts for measuring ship motion instability, and establishes an analysis method and process for nonlinear dynamics.

[0084] In the nonlinear dynamics calculation and analysis method of ships under irregular wave excitation, the ship's motion coordinate system is as follows: Figure 1 As shown. Where O(x,y,z) is the geodetic fixed coordinate system, O′(x′,y′,z′) is the ship-borne coordinate system, O″(x″,y″,z″) is the wave coordinate system, and ξ... G Let ζ be the position of the ship's center of gravity in the geodetic coordinate system. G This represents the position of the ship's center of gravity in the wave coordinate system.

[0085] This invention is a nonlinear dynamic calculation and analysis method for calculating the probability of a ship riding waves based on its density under irregular wave excitation. The specific method for analyzing the probability of a ship riding waves is described below:

[0086] Step 1: Select AIS data for any time period in a certain sea area, such as ship AIS data from April 2 to May 24, 2020, establish a probability density model of ship density, and use the nonparametric kernel density estimation method to solve the probability density function of ship density.

[0087] Assume x1, x2…x n Let x be a sample of random variable x, and let x be the probability density function of random variable x. The probability density function of the ship's density is shown in the following equation:

[0088]

[0089] Where x is a random variable, Indicates ship density, x i Let represent the i-th ship density sample, h represent the bandwidth length, n represent the number of samples, and K represent the kernel function.

[0090] The Gaussian kernel function is chosen as the kernel function in the nonparametric kernel density estimation method. The formula for the Gaussian kernel function is as follows:

[0091]

[0092] Bandwidth selection: In this article, the bandwidth is directly taken as h;

[0093] Finally, the probability density function of the ship density obtained by the nonparametric kernel density estimation method is shown below:

[0094]

[0095] The probability density function of ship density is calculated using a nonparametric kernel density estimation method, resulting in a ship density map. The ship density map for the selected route area is shown below. Figure 2 As shown.

[0096] Step 2: According to Figure 2 The ship density map is used to define areas with high traffic volume by selecting a critical ship density threshold. Representative route areas are identified and characterized, and five test points (A, B, C, D, and E) are selected at equal intervals within the areas covered by these representative routes (e.g., the Italian Mediterranean route). Figure 3 (As shown by the black line).

[0097] Based on the wave scattering maps of the sea areas near five locations (A, B, C, D, and E) within the area covered by this route, such as the wave scattering map of one of the points... Figure 4 As shown, the probability of an irregular wave appearing in a specific combination of meaningful wave height and characteristic period in the sea area at this test point can be obtained as P1.

[0098] Step 3: A nonlinear dynamic analysis method for ships riding waves in irregular waves is shown below:

[0099] Establish the differential equations for the sway motion of a ship in irregular waves:

[0100]

[0101] Where, ξ′ G Here, m represents the ordinate of the ship's center of gravity in the geodetic coordinate system, and m represents the ship's displacement. x Let u be the mass added to the hull in the sway direction, R(u) be the instantaneous velocity in the sway direction, T(u,n) be the ship's resistance in still water, and X be the propeller thrust in still water. ω (ξ G ,t) represents the wave force in the oscillation direction, and t represents time.

[0102] Determine the coefficients of the differential equations for the sway motion: the mass m of the ship, and the additional mass m of the hull in the sway direction. x The longitudinal resistance R(u) of the ship, the propeller thrust T(u,n) in the pitch direction, and the wave force X experienced by the ship in the pitch direction. ω (ξ G ,t).

[0103] The longitudinal resistance R(u) of the hull is fitted using a cubic polynomial as follows:

[0104] R(u) = r1u + r2u 2 +r3u 3 (5)

[0105] Among them, r1, r2, and r3 can be obtained by calculation and fitting from hull resistance test data or hydrodynamic numerical simulation software.

[0106] The propeller thrust T(u,n) in the oscillation direction is approximated by a polynomial:

[0107] T(u,n)=(1-t p )ρn 2 D p 4 K T (6)

[0108] Where n represents the propeller speed, t p ρ represents thrust reduction, D represents seawater density, and D represents the thrust reduction. p K represents the propeller diameter. T The thrust coefficient of the propeller is calculated using the following formula:

[0109] K T =k0+k1J P +k2J P 2 (7)

[0110] Among them, J P Represents the advance rate coefficient. k0, k1, and k2 can be obtained by fitting the open-water test data of the propeller.

[0111] Under random sea states, wave forces are solved by linear superposition, as shown below:

[0112]

[0113] In the formula, k i Let ω be the wave number of the i-th regular wave. i Let φ be the frequency of the i-th regular wave. i For random phase angles, γ i For phase shift, a i For the i-th regular amplitude value, RAO(k) i ) represents the amplitude of the oscillating wave force generated by the i-th regular wave unit amplitude, where N is a positive integer.

[0114] The probability of a ship riding the waves under the influence of irregular waves can be calculated using both analytical and numerical methods, with the specific steps as follows.

[0115] (1) Analytical method: The Melnikov method is mainly used to solve the probability of a ship riding the waves in irregular waves. The specific steps are as follows:

[0116] Substitute equation (8) into equation (4) and perform dimensionless transformation. Let y = kξ G , Considering the changes in wave force caused by irregular waves in addition to regular waves, we have:

[0117]

[0118] The equation can be rewritten in the following form, with the left side representing the undamped Hilmiton system:

[0119]

[0120] in:

[0121]

[0122] η is a time-dependent random process related to irregular waves, and its spectral density function is S. η For the purpose of analytical calculation, the irregular wave force is considered as a varying, random wave force superimposed on the regular wave force. Based on the above assumptions, η can be expressed in the following form:

[0123]

[0124] Where: ω n c1(t) is the peak frequency of the wave spectrum and c1(t) is the random phase angle.

[0125] The basic principle of the Melnikov method is to characterize the distance between stable and unstable manifolds using the following function, called the Melnikov function, as follows:

[0126]

[0127] Studies have shown that for a ship to ride the waves in irregular waves, the necessary condition is M(τ0) < 0. The excitation generated by irregular waves approximates a Gaussian random process; therefore, the Melnikov process M(τ0), which is derived from its linear transformation, is also a Gaussian process with a mean μ. M and variance σ z 2 The expression is:

[0128]

[0129]

[0130] Where H(ω) is the frequency response function, calculated by the following formula:

[0131]

[0132] The probability density function of the normal distribution is:

[0133]

[0134] Integrating equation (16), we obtain the probability distribution function of the normal distribution:

[0135]

[0136] According to the probability distribution function of the normal distribution, the probability of wave riding in an irregular wave is:

[0137]

[0138] (2) The steps of the numerical method are as follows:

[0139] Substituting equation (8) into equation (4), the Runge-Kutta method is used to obtain the ship speed-time history curve, where time is the abscissa and the ship's relative displacement and relative speed are the ordinates, as shown below. Figure 5 As shown.

[0140] The instantaneous wave velocity of a random wave is shown in the following formula:

[0141]

[0142] In the formula, ω(ξ) s ,t) is the frequency of the random wave, k(ξ) s ,t) is the wavenumber of the random wave.

[0143] The instantaneous wave velocity diagram of the random wave is plotted according to equation (19) as follows: Figure 5 As shown.

[0144] The upper crossover threshold can be selected as the intersection of the instantaneous wave speed and the ship speed, while the lower crossover threshold can be selected as the intersection of the instantaneous wave speed and the ship's rated speed. The time point when the ship speed exceeds the instantaneous wave speed is defined as the start time of wave riding (shown by dots), and the time point when the ship speed falls below the rated speed is defined as the end time of wave riding (shown by square dots). The probability of a ship riding a wave under a certain random operating condition is the ratio of the total intermittent wave riding time t0 to the numerical simulation duration t1.

[0145] For the same sea state, the sway motion response under multiple random seed numbers is calculated, and all results are statistically analyzed to reduce errors, so that the probability of the ship riding the waves in random waves is P2 = t0 / t1.

[0146] Step 4: Based on the probability P1 of irregular waves occurring in the target sea area and the probability P2 of a ship riding the waves in random waves, calculate the probability P of a ship riding the waves in a specific irregular wave in the test point area representing the irregular wave route, as shown in the following formula:

[0147] P = P1P2 (20)

[0148] By analogy, based on the wave scattering diagram of the area covered by the representative route, the probability of a ship riding the waves at the test point under each random sea state is calculated, resulting in the wave-riding probability diagram for that test point, as shown below. Figure 6 As shown.

[0149] Step 5: Then, calculate the probability of the ship riding the waves in different irregular waves at other test points using the same steps as above, and finally obtain the total probability of riding the waves.

[0150] In summary, the flowchart of the method for assessing the probability of a ship riding the waves based on AIS data in irregular waves according to this invention is as follows: Figure 7 As shown.

Claims

1. A method for assessing the probability of a ship riding waves based on AIS data in irregular waves, characterized in that, Select AIS data of ships in the target sea area within the target time period, establish a probability density function of ship density, determine representative routes in the target sea area through the probability density function, and solve the total probability of ship wave-riding motion on the representative routes based on the nonlinear dynamics probability analysis method of ships riding waves in irregular waves, including the following steps: Step 1: Select AIS data of ships in the target sea area within the target time, establish the probability density function of ship density, and solve the probability density function of ship density using the nonparametric kernel density estimation method to obtain the ship density map; Step 2: Select the critical density threshold of ships based on the ship density map and define areas with high traffic volume. Identify and characterize representative route areas from these areas. Select at least two test points at equal intervals within the representative route areas. Based on the wave scattering map of the sea area near the test points, obtain the probability P1 of irregular waves appearing in a specific combination of meaningful wave height and characteristic period in the target sea area. Step 3: Based on the nonlinear dynamic probability analysis method of ships riding waves in irregular waves, calculate the probability P2 of ships riding waves in irregular waves in the target sea area; Step 4: Calculate the probability P of a ship riding the waves at a specific irregular wave at a test point on a representative route in the irregular waves, based on the probability P1 of irregular waves appearing in the target sea area and the probability P2 of a ship riding the waves in the irregular waves; calculate the probability of a ship riding the waves at each random sea state at the test point based on the wave scattering map of the area covered by the representative route, and obtain the probability map of the ship riding the waves at the test point. Step 5: Repeat steps 2-4 to calculate the probability of a ship riding the waves in different irregular waves at other test points, obtain the probability diagram of riding the waves at each test point, and solve for the total probability of a ship riding the waves on a representative route.

2. The method for assessing the probability of a ship riding waves based on AIS data in irregular waves according to claim 1, characterized in that, Step 1 specifically includes the following steps: Step 1.1: Assume x1, x2…x n Let x be a sample of random variable x, and let x be the probability density function of random variable x. The probability density function of the ship's density is shown in the following equation: Where x is a random variable, Represents ship density, x i Let h represent the i-th ship density sample, h represent the bandwidth length, n represent the number of samples, and K represent the kernel function. Step 1.2: Select the Gaussian kernel function as the kernel function in the nonparametric kernel density estimation method. The formula for the Gaussian kernel function is as follows: Step 1.3: Select h as the bandwidth; Step 1.4: Obtain the probability density function of the ship density using the nonparametric kernel density estimation method to get the ship density map. The probability density function is shown below:

3. The method for assessing the probability of a ship riding waves based on AIS data in irregular waves according to claim 1, characterized in that, In step 2, five test points are selected.

4. The method for assessing the probability of a ship riding waves based on AIS data in irregular waves according to claim 1, characterized in that, Step 3 specifically includes the following steps: Step 3.1: Establish the differential equations of the ship's sway motion in irregular waves: Where, ξ′ G Here, m represents the ordinate of the ship's center of gravity in the geodetic coordinate system, and m represents the ship's displacement. x Let u be the mass added to the hull in the sway direction, R(u) be the instantaneous velocity in the sway direction, T(u,n) be the ship's resistance in still water, and X be the propeller thrust in still water. ω (ξ G ,t) represents the wave force in the oscillation direction, and t represents time; Step 3.2: Determine the coefficients of each term in the differential equation of the sway motion: the mass m of the ship, and the additional mass m of the hull in the sway direction. x The longitudinal resistance R(u) of the ship, the propeller thrust T(u,n) in the pitch direction, and the wave force X experienced by the ship in the pitch direction. ω (ξ G ,t); The longitudinal resistance R(u) of the hull is fitted using a cubic polynomial as follows: R(u)=r1u+r2u 2 +r3u 3 (5) Among them, r1, r2, and r3 are obtained by calculation and fitting from hull resistance test data or hydrodynamic numerical simulation software; The propeller thrust T(u,n) in the oscillation direction is approximated by a polynomial: T(u,n)=(1-t p )ρn 2 D p 4 K T (6) Where n represents the propeller speed, t p ρ represents thrust reduction, D represents seawater density, and D represents the thrust reduction. p K represents the propeller diameter. T The thrust coefficient of the propeller is calculated using the following formula: K T =k0+k1J P +k2J P 2 (7) Among them, J P Represents the advance rate coefficient. k0, k1, and k2 can be obtained by fitting the open-water test data of the propeller; Step 3.3: Under random sea states, solve for wave forces by linear superposition: In the formula, ki is the wave number of the i-th regular wave, and ω i Let φ be the frequency of the i-th regular wave. i For random phase angles, γ i For phase shift, a i For the i-th regular amplitude value, RAO(k) i ) represents the amplitude of the oscillating wave force generated by the i-th regular wave unit amplitude, where N is a positive integer; Step 3.4: Calculate the probability P2 of the ship riding the waves in irregular waves using analytical or numerical methods.

5. The method for assessing the probability of a ship riding the waves based on AIS data in irregular waves according to claim 4, characterized in that, The analytical method in step 3.4 specifically involves using the Melnikov method to solve for the probability of a ship riding the waves in irregular waves. The specific steps are as follows: Substituting equation (8) into equation (4) and performing dimensionless transformation, let y = kξ G , Considering the changes in wave force caused by irregular waves in addition to regular waves, we have: The equation can be rewritten in the following form, with the left side representing the undamped Hilmiton system: in: r,q,p1,p2,p3∈R; η is a time-dependent random process related to irregular waves, and its spectral density function is S. η For the purpose of analytical calculation, the irregular wave force is considered as a variable, random wave force superimposed on the regular wave force, η, expressed in the following form: Where: ω n Let be the peak frequency of the wave spectrum, and c1(t) be the random phase angle; The Melnikov method uses the following function to characterize the distance between stable and unstable manifolds, as shown below: The necessary condition for a ship to ride the waves in irregular waves is that M(τ0) < 0. The excitation generated by the irregular waves is approximately a Gaussian random process, and the Melnikov process M(τ0), which is derived from its linear transformation, is also a Gaussian process with a mean μ. M and variance σ z 2 The expression is: Where H(ω) is the frequency response function, calculated by the following formula: The probability density function of the normal distribution is: Integrating equation (16), we obtain the probability distribution function of the normal distribution: According to the probability distribution function of the normal distribution, the probability of wave riding in an irregular wave is:

6. The method for assessing the probability of a ship riding waves based on AIS data in irregular waves according to claim 4, characterized in that, The numerical method in step 3.4 specifically refers to: Substituting equation (8) into equation (4), the Runge-Kutta method is used to obtain the ship speed time history curve, where time is the abscissa, and the ship's relative displacement and relative velocity are the ordinates. The instantaneous wave velocity of the random wave is shown in the following equation: In the formula, ω(ξ) s ,t) is the frequency of the random wave, k(ξ) s ,t) is the wavenumber of the random wave; The instantaneous wave speed diagram of random waves is plotted according to formula (19). The upper cross threshold value is selected as the intersection of instantaneous wave speed and ship speed, and the lower cross threshold value is selected as the intersection of instantaneous wave speed and ship rated speed. The time node when the ship speed exceeds the instantaneous wave speed is defined as the start time of riding the wave, and the time node when the ship speed is lower than the rated speed is defined as the end time of riding the wave. The probability of a ship riding the wave under a certain random working condition is the ratio of the sum of the intermittent wave riding time t0 to the numerical simulation duration t1. For the same sea state, the sway motion response under multiple random seed numbers is calculated, and all results are statistically analyzed to reduce errors, so that the probability of the ship riding the waves in random waves is P2 = t0 / t1.

7. The method for assessing the probability of a ship riding waves based on AIS data in irregular waves according to claim 1, characterized in that, In step 4, the probability P of a ship riding the waves in a specific irregular wave in the test point area representing a typical route in the irregular wave is calculated based on the probability P1 of irregular waves occurring in the target sea area and the probability P2 of a ship riding the waves in random waves. Where: P = P1P2 (20) Based on the wave scattering map of the area covered by the representative route, the probability of a ship riding the waves at the test point under each random sea state is calculated, and the probability map of the ship riding the waves at the test point is obtained.

Images