Method for calculating a ship horizontal attitude oscillation period

Abstract

The present application relates to a kind of ship horizontal posture swing period calculation method, swing period selects peak period, comprising the following steps: step 1, the horizontal posture swing period boundary value determination facing user actual demand;Step 2, to the effective horizontal posture angle number is respectively carried out curve fitting and extraction extreme point, wherein horizontal posture angle number includes ship dynamic pitch angle data and ship dynamic roll angle;Step 3, ship horizontal posture swing period quantitative calculation;Step 4, the quantitative display of ship horizontal posture swing period facing user actual demand.This calculation method can provide online calculation for user ship recent time swing period and duration swing period.

Description

Technical Field

[0001] This invention belongs to the field of ship and vessel equipment technology, and specifically relates to a method for calculating the horizontal attitude sway period of a ship. Background Technology

[0002] Currently, the inertial navigation equipment on naval vessels (including inertial navigation equipment, attitude control equipment, and compass equipment based on electrostatic gyroscopes, liquid-float gyroscopes, flexible gyroscopes, laser gyroscopes, fiber optic gyroscopes, etc.) all output pitch and roll angle information, but do not calculate the corresponding oscillation period values ​​for the pitch and roll angles. However, naval personnel urgently need to understand the ship's oscillation period in scenarios such as the sortie and recovery of fixed-wing carrier-based aircraft and carrier-based helicopters, in order to make timely decisions on actions such as carrier-based aircraft landings, thereby improving mission safety and other mission characteristics. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for calculating the horizontal attitude swaying period of a ship.

[0004] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0005] A method for calculating the horizontal attitude roll period of a ship, characterized by selecting the peak period of the roll period, comprising the following steps:

[0006] Step 1: Determine the boundary values ​​of the horizontal attitude swaying period based on actual user needs;

[0007] Step 2: Perform curve fitting and extract extreme points on the valid horizontal attitude angle data, which includes the ship's dynamic pitch angle data and the ship's dynamic roll angle data.

[0008] Step 3: Quantitative calculation of the ship's horizontal attitude swaying period;

[0009] Step 4: Quantitative display of the ship's horizontal attitude swaying period based on actual user needs.

[0010] Further: In step 1, the boundary values ​​of the horizontal attitude sway period are determined. The boundary conditions include: the sampling frequency of the inertial navigation sway angle is not less than 10 Hz; the maximum measurement error of the inertial navigation sway angle is less than 2 arcminutes; and the ship's sway angle is not less than 30 arcminutes.

[0011] Further: Step 2 includes:

[0012] 2.1. Using 1s of data, a 3rd-order polynomial is used for fitting, with a sliding window used for 0.1s after each fitting. Let the highest degree of the fitting polynomial be n, then the polynomial can be expressed as:

[0013]

[0014] Where y is the measured attitude angle, t is time, and a i These are the parameters to be fitted;

[0015] Inertial navigation output time t k and the corresponding swing angle y k Substituting into the above equation, we obtain the equation concerning the polynomial coefficients:

[0016]

[0017] In the formula, time t k It is the time interval relative to the start time of the data segment to be fitted, where N is the total number of data points to be fitted; denoted as...

[0018]

[0019] The coefficients obtained by the least squares algorithm are:

[0020] x=(A T A) -1 A T y………………………………(10)

[0021] 2.2. The fitting error is defined as the maximum difference between the fitted curve and the original curve at discrete time. The formula for calculating the fitting error Δy is as follows. The maximum acceptable fitting error for this scheme is set to 1 point.

[0022] Δy=max(Y)…………………………(11)

[0023] In the formula, Y={|y i -y(t i The set of fitting errors at each fitting time point is represented by ||i=1,……,N}.

[0024] 2.3 Calculate the derivative and discriminant of the fitted curve. The formula for calculating the derivative is as follows:

[0025]

[0026] The formula for calculating the discriminant is as follows:

[0027] Δ=(2a2) 2 -12a3a1…………………………(13)

[0028] 2.4 Calculate the extreme points:

[0029] When the discriminant is greater than 0, calculate the two extreme points using the following formula:

[0030]

[0031] When a3 is greater than 0, the smaller extreme point is the maximum point and the larger extreme point is the minimum point; when a3 is less than 0, the smaller extreme point is the minimum point and the larger extreme point is the maximum point.

[0032] When an extreme point is in the interval [0.3, 0.7], after compensating for the initial fitting time, if it is 0.4s larger than similar extreme points, it is determined to be a valid extreme point.

[0033] Furthermore: The rule for the quantitative calculation of the ship's horizontal attitude sway period in step 3 is as follows: two consecutive maximum points contain a minimum point in between, and the difference in sway angle amplitude between the two maximum points and the minimum point is greater than 30 arcminutes. The time interval between the two maximum points is defined as the sway period at the current moment.

[0034] If no valid maximum point is found, slide one maximum point forward in the maximum point column and judge again. If there is no valid maximum point pair within 1 minute of the current time, the ship is considered to be stable and without obvious swaying.

[0035] Furthermore: Step 4 includes the quantitative display of the ship's horizontal attitude sway period, which includes: 1. the average horizontal attitude sway period of the ship within 30 seconds; 2. the average horizontal attitude sway period of the ship within 60 seconds; and 3. the average horizontal attitude sway period of the ship within 5 minutes.

[0036] The advantages and positive effects of this invention are as follows:

[0037] The method for calculating the ship's roll period in this invention mainly uses the ship's dynamic pitch and roll angle parameters as input data. It establishes a roll period calculation scheme through methods such as sliding window fitting, assigns values ​​using methods such as extreme value judgment, and finally realizes the dynamic determination of the ship's roll period. It can provide users with online calculations of the ship's roll period at the most recent moment and the roll period over time. Attached Figure Description

[0038] Figure 1 This is a flowchart of the ship roll peak calculation method of the present invention. Detailed Implementation

[0039] The structure of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that these embodiments are descriptive and not limiting.

[0040] A method for calculating the horizontal attitude roll period of a ship mainly includes: (1) determining the boundary values ​​of the horizontal attitude roll period based on actual user needs; (2) performing curve fitting and extracting extreme points from the effective horizontal attitude angle data, wherein the horizontal attitude angle data includes the ship's dynamic pitch angle data and the ship's dynamic roll angle; (3) quantitatively calculating the ship's horizontal attitude roll period; and (4) quantitatively displaying the ship's horizontal attitude roll period based on actual user needs. Specifically:

[0041] Under the influence of external excitations such as ocean waves, ships oscillate back and forth around their equilibrium position. Due to the complexity of these external excitations, the oscillation curve of the ship exhibits a complex shape and rich spectral components. Therefore, there are multiple ways to define the ship's motion period, such as peak period, spectral peak period, and spectral average period. The peak period is defined as the time interval between two peak oscillation angles, reflecting the short-term characteristics of the oscillation motion and the period of the previous oscillation, exhibiting a certain time delay. The spectral peak period is defined as the period with the largest amplitude among the oscillation spectral components over a period of time. The spectral average period is a comprehensive evaluation of the oscillation spectrum, reflecting the period of the main distribution of oscillation energy over a period of time.

[0042] This invention aims to reflect the characteristics of short-term swaying periods, and selects the peak period as the calculation method for the swaying period motion of ships.

[0043] The boundary value for the horizontal attitude roll period, which addresses actual user needs, is determined as follows: when the ship's roll amplitude is too small, the need to calculate the roll period does not exist. Therefore, the application conditions of this invention are as follows:

[0044] 1. The sampling frequency of the inertial navigation swing angle is not less than 10Hz;

[0045] 2. The maximum measurement error of the inertial navigation system's swing angle is less than 2 arcminutes;

[0046] 3. The ship's roll angle is not less than 30 arcminutes; if it is less than 30 arcminutes, the ship is considered to be in a stable state.

[0047] The calculation process for curve fitting and extreme point extraction of the effective horizontal attitude angle data is as follows:

[0048] 1. Take 1 second of data and fit it using a 3rd-order polynomial. After each fit, use a sliding window to slide for 0.1 seconds. Let the highest degree of the fitting polynomial be n, then the polynomial can be expressed as:

[0049]

[0050] Where y is the measured attitude angle, t is time, and ai is the parameter to be fitted.

[0051] Inertial navigation output time t kand the corresponding swing angle y k Substituting into the above equation, we obtain the equation concerning the polynomial coefficients:

[0052]

[0053] In the formula, time t k It is the time interval relative to the start time of the data segment to be fitted, where N is the total number of data points to be fitted; denoted as...

[0054]

[0055] The coefficients obtained by the least squares algorithm are:

[0056] x=(A T A) -1 A T y………………………………(17)

[0057] 2. Define the fitting error as the maximum difference between the fitted curve and the original curve at discrete time. The formula for calculating the fitting error Δy is as follows. Set the maximum acceptable fitting error of this scheme to 1 point.

[0058] Δy=max(Y)…………………………(18)

[0059] In the formula, Y={|y i -y(t i The set of fitting errors at each fitting time point is represented by ||i=1,……,N}.

[0060] 3. Calculate the derivative and discriminant of the fitted curve. The formula for calculating the derivative is as follows:

[0061]

[0062] The formula for calculating the discriminant is as follows:

[0063] Δ=(2a2) 2 -12a3a1…………………………(20)

[0064] 4. Calculate the extreme points:

[0065] When the discriminant is greater than 0, calculate the two extreme points using the following formula:

[0066]

[0067] When a3 is greater than 0, the smaller extreme point is the maximum point and the larger extreme point is the minimum point; when a3 is less than 0, the smaller extreme point is the minimum point and the larger extreme point is the maximum point.

[0068] When an extreme point is in the interval [0.3, 0.7], after compensating for the initial fitting time, if it is 0.4s larger than similar extreme points, it is determined to be a valid extreme point.

[0069] The quantitative calculation rules for the horizontal attitude roll period of the aforementioned ships are as follows:

[0070] If two consecutive maxima contain a minimum, and the difference in the swing angle amplitude between the two maxima and the minimum is greater than 30 arcminutes, the time interval between the two maxima is defined as the swing period at the current moment.

[0071] If no valid maximum point is found, slide one maximum point forward in the maximum point column and judge again. If there is no valid maximum point pair within 1 minute of the current time, the ship is considered to be stable and without obvious swaying.

[0072] To meet the actual needs of users, the following sway cycles are provided for users to use in mission decision-making: 1. Average sway cycle of the ship's horizontal attitude within 30 seconds; 2. Average sway cycle of the ship's horizontal attitude within 60 seconds; 3. Average sway cycle of the ship's horizontal attitude within 5 minutes.

[0073] The performance indicators achievable by this invention are as follows:

[0074] 1. Period calculation error ≤ 1s;

[0075] 2. The delay for periodic calculation is ≤1 minute.

[0076] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for calculating the horizontal attitude sway period of a ship, characterized in that: Selecting the peak period for the swing cycle includes the following steps: Step 1: Determine the boundary values ​​of the horizontal attitude swaying period based on actual user needs; Step 2: Perform curve fitting and extract extreme points on the valid horizontal attitude angle data, which includes the ship's dynamic pitch angle data and the ship's dynamic roll angle data. Step 3: Quantitative calculation of the ship's horizontal attitude swaying period; Step 4: Quantitative display of the ship's horizontal attitude roll period to meet actual user needs; Step 2 includes: 2.

1. Take 1s of data and fit it using a 3rd-order polynomial. After each fit, use a sliding window to slide for 0.1s. Let the highest degree of the fitting polynomial be... Then the polynomial can be expressed as: …………………………………………(1.) Where y is the measured attitude angle, t is time, and a i These are the parameters to be fitted; Inertial navigation output time and corresponding swing angle Substituting into the above equation, we obtain the equation concerning the polynomial coefficients: ………………………………(2.) In the formula, time It is the time interval relative to the start time of the fitted data segment. Let be the total number of data points to be fitted; denote ， ， ； The coefficients obtained by the least squares algorithm are: …………………………………(3.) 2.

2. The fitting error is defined as the maximum difference between the fitted curve and the original curve at discrete time. The calculation formula is as follows, and the maximum acceptable fitting error of this scheme is set to 1 arcminute; …………………………………(4.) In the formula, This represents the set of fitting errors at each fitting time point; 2.3 Calculate the derivative and discriminant of the fitted curve. The formula for calculating the derivative is as follows: ……………………………………(5.) The formula for calculating the discriminant is as follows: …………………………………(6.) 2.4 Calculate the extreme points: When the discriminant is greater than 0, calculate the two extreme points using the following formula: ……………………………………(7.) when When the value is greater than 0, the smaller extreme point is the maximum point, and the larger extreme point is the minimum point. If the value is less than 0, the smaller extreme point is the minimum point, and the larger extreme point is the maximum point; When an extreme point is in the interval [0.3, 0.7], after compensating for the initial fitting time, if it is 0.4s larger than similar extreme points, it is determined to be a valid extreme point.

2. The method for calculating the horizontal attitude swaying period of a ship according to claim 1, characterized in that: In step 1, the boundary values ​​of the horizontal attitude sway period are determined. The boundary conditions include: the sampling frequency of the inertial navigation sway angle is not less than 10 Hz; the maximum measurement error of the inertial navigation sway angle is less than 2 arcminutes; and the ship's sway angle is not less than 30 arcminutes.

3. The method for calculating the horizontal attitude swaying period of a ship according to claim 1, characterized in that: The rule for quantifying the ship's horizontal attitude roll period in step 3 is as follows: if there is a minimum point between two consecutive maximum points and the difference between the roll angle amplitudes of the two maximum points and the minimum point is greater than 30 arcminutes, the time interval between the two maximum points is defined as the roll period at the current moment. If no valid maximum point is found, slide one maximum point forward in the maximum point column and judge again. If there is no valid maximum point pair within 1 minute of the current time, the ship is considered to be stable and without obvious swaying.

4. The method for calculating the horizontal attitude swaying period of a ship according to claim 1, characterized in that: The quantitative display of the ship's horizontal attitude sway period in step 4 includes:

1. The average horizontal attitude sway period of the ship within 30 seconds; 2. The average horizontal attitude sway period of the ship within 60 seconds; 3. The average horizontal attitude sway period of the ship within 5 minutes.

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