A ship anti-capsize self-righting control method based on attitude fitting prediction

Abstract

This invention provides a method for controlling a ship's anti-capsize self-righting function based on attitude fitting prediction. The method is primarily applicable to the field of maritime ship safety and can be installed on rescue boats, lifeboats, and other small craft with special requirements. Based on the principles of ship kinematics, the method analyzes and identifies the changing patterns of a ship's roll attitude and establishes a ship attitude prediction model. This method can quickly, accurately, and reasonably predict the ship's attitude change trends over a certain period of time in complex maritime environments, determine whether it is at risk of capsizing, and proactively respond to potential roll shocks, triggering the deployment of self-righting airbags on both sides of the hull to prevent capsizing and minimize personal injury and property damage.

Description

Technical Field

[0001] The present invention relates to the field of marine ship safety, and in particular to a ship anti-capsize self-righting control method based on attitude fitting prediction. Background Art

[0002] Ship safety is a crucial issue in maritime navigation. Capsizing a vessel due to improper loading, forward displacement, hull damage, improper maneuvering, flooding, rudder changes, storms, swells, tsunamis, or other severe environmental impacts, resulting in the righting moment being less than the capsizing moment, is a serious maritime accident. Capsizing can lead to water ingress into exhaust ports, ventilation holes, and vents, fuel leaks, and cabin flooding, often resulting in significant loss of life and property, as well as marine pollution. Consequently, various fields are striving to explore effective means to prevent ship capsizing.

[0003] Ships float in water, maintaining equilibrium under the combined effects of buoyancy and gravity. The point of buoyancy is the center of buoyancy, and the point of gravity is the center of gravity. Generally speaking, for a floating ship, the center of gravity must be lower than the center of buoyancy. The difference between the two is called the initial stability height. The greater the initial stability height, the better the ship's stability. The quality of a ship's stability determines its ability to resist capsizing. Ship dynamic stability refers to the fact that ships are affected by wind and waves in the water, which generate a torque that causes the ship to deflect to one side. The submerged volume on that side increases, which in turn increases the buoyancy on that side, causing the center of buoyancy to shift toward the capsizing side. The inward buoyancy and the downward gravity act together to generate a torque on the ship opposite to the direction of the capsizing, causing the ship to return to its original equilibrium position under the action of this torque. This torque is called the righting moment. Generally speaking, the maximum angle at which a ship can maintain a certain turning arm to restore its own posture stability is defined as the critical angle of the ship's capsizing. As long as the degree of the ship's capsizing does not exceed this limit value, the ship can be restored to a balanced state under the action of the ship's restoring torque.

[0004] Some rescue boats, lifeboats, and small boats with special requirements designed based on this principle can right themselves after capsizing, a feature known as self-righting capability. However, self-righting capability places high demands on both ship design and external sealing, making it unsuitable for all ships. For ships without self-righting capability, the automation field has designed self-righting controllers to right the ship after capsizing. However, both self-righting capability and self-righting controllers only take effect after the ship capsizes, at which point the damage has already occurred, and righting only mitigates it. When a ship is sailing at sea, its left and right rolling attitude changes periodically, while the ship's fixed transport characteristics are relatively stable. Therefore, changes in attitude, combined with angular velocity and angular acceleration, can be used to infer whether the ship is at risk of capsizing, and then respond accordingly.

[0005] In summary, there is a need for a ship anti-capsize self-righting control system and method based on attitude fitting prediction, which can quickly, accurately and reasonably predict the ship's attitude change trend within a certain period of time in a complex marine environment, and judge whether it has a capsizing risk. It can take action in advance for rolling impacts with capsizing risks, trigger the deployment of self-righting airbags on both sides of the hull, avoid capsizing of the hull, and reduce personal injury and property loss. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a ship anti-capsize self-righting control method based on attitude fitting prediction.

[0007] The present invention comprises the following steps:

[0008] Step 100: Establish a ship roll attitude prediction model based on the ship kinematics and dynamics equations.

[0009] Step 200: The attitude sensor collects real-time attitude data and inertial data of the hull, takes the prior impact data over a period of time as input, and brings it into the hull roll attitude prediction model in step 001 to calculate and obtain a hull roll state characteristic parameter data set as a result; the elements in the characteristic parameter data set include the roll characteristic frequency of the ship type and the swing amplitude attenuation coefficient of the ship type.

[0010] Step 300: Taking the characteristic parameter data set in step 200 as input, the polynomial fitting relationship between the hull roll state characteristic parameters and the speed is estimated based on the least squares linear fitting model, and the optimal hull roll state characteristic parameters that meet the current environmental parameters are estimated according to the current speed to obtain the adjusted hull roll attitude prediction model.

[0011] Step 400: inputting the attitude sensor data into the adjusted ship roll attitude prediction model to calculate the ship roll attitude change curve;

[0012] The system determines whether there is a capsizing risk based on the peak value of the curve, and takes action in advance for roll impacts that pose a capsizing risk, triggering the deployment of self-righting airbags on both sides of the hull to prevent the hull from capsizing.

[0013] Step 500: When a violent impact causes the hull to capsize or the anti-capsize self-righting control system fails to effectively prevent the hull from capsizing, causing the hull to flip 90 degrees and unable to rely on the turning lever to right the hull, after a certain period of time has accumulated, the anti-capsize self-righting control system will trigger the left and right self-righting airbags to deploy in sequence to ensure that the capsized hull gradually rights itself.

[0014] The present invention has the following advantages:

[0015] 1. The present invention analyzes the changing laws of the ship's roll attitude based on the principles of ship kinematics and dynamics, approximating the ship's roll as simple harmonic motion. Through experiments and analysis of ship characteristic parameters, the characteristic parameters of the ship's roll state can be obtained, which are brought into the prediction model to estimate the ship's attitude change curve. Action is taken in advance for roll impacts that pose a risk of capsizing, triggering the deployment of self-righting airbags on both sides of the hull to prevent the hull from capsizing and reduce personal injury and property loss. For a hull that has already capsized, the self-righting airbags are immediately activated to right the hull.

[0016] 2. Since the roll characteristics of the hull will be affected by the hull speed and environmental parameters, the present invention adopts a linear regression method based on the least squares method, taking the data in the period before the hull sailing as the sample input, and combining the change law of the hull roll attitude under the current environmental conditions, inverse fitting is performed to obtain the characteristic parameters of the hull roll state under the current conditions. The adjusted hull roll state parameters are brought into the prediction model to estimate the hull attitude change curve, which can weaken or offset the impact of external environmental changes on the hull swing characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the arrangement of the self-righting airbag;

[0018] Figure 2 It is the composition and flow chart of the anti-overturning self-righting control system based on attitude fitting prediction;

[0019] Figure 3 This is an example of a curve showing the change in the ship's roll attitude. DETAILED DESCRIPTION

[0020] To make the objects, technical solutions, and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings. This description introduces specific embodiments consistent with the principles of the present invention by way of example and not limitation. The descriptions of these embodiments are sufficiently detailed to enable those skilled in the art to practice the present invention. Other embodiments may be used and the structures of the various elements may be changed and / or replaced without departing from the scope and spirit of the present invention. Therefore, the following detailed description should not be understood in a restrictive sense.

[0021] The present invention provides a ship anti-capsize self-righting control system and method based on attitude fitting prediction, comprising the following steps:

[0022] Step 100: Establish a ship roll attitude prediction model based on the ship kinematics and dynamics equations.

[0023] Step 200: The attitude sensor collects the real-time attitude data and inertial data of the hull, and uses the prior impact data within a period of time As input, the ship roll attitude prediction model in step 001 is used to calculate the ship roll state characteristic parameter data set {R i (σ i ,w Ti )} as the result, where i represents a piece of data in the dataset and T represents the feature parameter.

[0024] Step 300: Using the data set in step 002 as input, the polynomial fitting relationship between the ship's roll state characteristic parameters and the speed is estimated based on the least squares linear fitting model. The optimal ship's roll state characteristic parameters that meet the current environmental parameters are estimated based on the current speed to obtain the adjusted ship's roll attitude prediction model.

[0025] Step 400: Input the attitude sensor data into the adjusted hull roll attitude prediction model, calculate the hull roll attitude change curve, judge whether there is a capsizing risk based on the curve peak, take action in advance for roll impacts with capsizing risks, trigger the self-righting airbags on both sides of the hull to deploy, and avoid capsizing.

[0026] Step 500: When a violent impact causes the hull to capsize or the anti-capsize self-righting control system fails to effectively prevent the hull from capsizing, causing the hull to flip 90 degrees and unable to rely on the turning lever to right the hull, after a certain period of time has accumulated, the anti-capsize self-righting control system will trigger the left and right self-righting airbags to deploy in sequence to ensure that the capsized hull gradually rights itself.

[0027] In step 100 of the present invention, the rolling law of the ship under damping state after being impacted can be approximately treated as simple harmonic motion. The hull rotation torque is defined as M f , the hull roll attitude angle is θ, the hull rotation torque generation proportional factor is K, the hull moment of inertia is J, the hull heading is ψ, the hull rotation angular velocity is w, the hull angular momentum is L, the hull gravity is Mg, the hull center of gravity force arm is R, the initial angle is θ0, and the initial angular velocity is w0.

[0028] First, the hull rotation moment is M f The relationship with the ship's roll attitude angle θ is simplified to a direct proportional function, that is, it satisfies Equation 1-1. Then, based on the principle of conservation of angular momentum, Equation 1-2 can be obtained. The relevant formulas for the approximate treatment of simple harmonic motion of a ship at sea in a damped state after being impacted are derived as follows:

[0029] M f =Kθ Formula 1-1

[0030] L=Jw Formula 1-2

[0031]

[0032] Jα=MgRsinθ-Mf =MgRsinθ-kθ Formula 1-4

[0033] Since the maximum safe tilt angle of the hull is generally not greater than 45 degrees, When , based on the linear fitting principle, it can be obtained that sinθ is approximately proportional to the function N γ θ, and the error is no more than 5%, that is:

[0034] sinθ≈N γ θ,N γ =0.9384 Formula 1-5

[0035] Substituting Equation 1-5 into Equation 1-4 yields:

[0036] Jα=N γ MgRθ-Kθ formula 1-6

[0037] Performing Laplace transformation on Equation 1-6 yields:

[0038] J(Θs 2 -sθ0-w0)=(N γ MgR-K)Θ Formula 1-7

[0039] Θ(Js 2 +KN γ MgR)=J(sθ0+w0) Formula 1-8

[0040]

[0041] The Laplace inverse transform of equation 1-9 yields:

[0042]

[0043] definition is the roll characteristic frequency of the ship type, then Equation 1-10 can be simplified to:

[0044]

[0045] Definition A T The amplitude and value in Equation 1-11 are expressed as Expressing the phase in Equation 1-11, we can obtain the simple harmonic motion equations in Equation 1-12:

[0046]

[0047] Considering that the movement of the hull in seawater is a periodic damped oscillation, and the oscillation amplitude shows a periodic reduction trend due to the friction of seawater, an attenuation link e is added. -σt , σ is the attenuation coefficient, as shown in the following formula 1-13:

[0048]

[0049] From the above formula, we can see that there are two unknowns in the time domain expression of θ: σ and w T The rest can be determined by w T Calculated with the initial state X0(θ0,w0), the ship rolling state characteristic parameter R(σ,w T ), so we can get R(σ,w T ) can obtain the time-domain variation equation of the hull inclination angle θ, and then predict whether the hull is at risk of capsizing and take targeted preventive actions.

[0050] In steps 200 and 300 of the present invention, the self-stabilizing characteristics of the hull are related to the speed when the hull is sailing. In the low-speed state, as the speed increases, the hull pitch amplitude will decrease under the constraint of the water flow, thereby improving the hull's straight-line stability. Therefore, σ and w at a certain state of the hull are obtained. T After that, the influence of speed on hull stability still needs to be considered. The present invention adopts the least square method to fit the parameters σ, w using N-order polynomial fitting T The relationship with the speed v is as follows:

[0051] Step 201: Collect valid wave impact data: Data that meets certain conditions within a period of time before the ship capsizes will be considered valid data and added to the data set. The judgment condition is that the angular velocity w of the hull increases significantly in a short period of time, and when the angular acceleration α is at the zero point, the hull tilt angle θ at this time is recorded. 0i , angular velocity w i and speed v i , and then calculate the rolling angle amplitude A of the hull due to this impact i and arrival time ΔT i , using the arrival time ΔT i The phase of simple harmonic motion can be obtained So we get a priori shock data where ψ i As the basis for data classification, a data set is formed. Based on this data, the characteristic parameter R of the hull rolling state in the current state can be obtained by substituting it into formula 1-10. i (σ i ,w Ti );

[0052] Step 202: Repeat step 201 to obtain a priori shock data set within a period of time and roll state characteristic parameter dataset {R i (σ i ,w Ti )};

[0053] Step 203: Use the least square method to obtain σ and w at a certain speed T Polynomial relationship with ship speed v.

[0054] The general polynomial model expression of the least squares method is as follows:

[0055]

[0056] For m sample sampling set M(x i ,y i ), define x i ,y i is the actual sampling value, The predicted value is a polynomial fitting function, which satisfies the following polynomial relationship:

[0057]

[0058] The calculation expression of the sum of squared errors E is:

[0059]

[0060] Calculate the minimum value of E, and the right side of the equation for a i , i=0,1,2…n, find the partial derivatives and get the following n+1 equations:

[0061]

[0062] Arranging formula 2-4 gives

[0063]

[0064] Solving n+1 groups of n+1 linear equations in equation 2-5 yields a0…a n The value of , thus obtaining a polynomial relationship between y and x.

[0065] Based on the above principle, the characteristic parameter of the ship rolling state R(σ,w T ) respectively satisfy the following relations:

[0066]

[0067] Shock the dataset a priori Rolling state characteristic parameter dataset {R i (σ i ,w Ti )} and equation 2-6 are substituted into equation 2-5 to obtain the parameter set {α0,α1…α n} and {{β0,β1…β n}}, and then obtain σ, w at a certain speed T The polynomial relationship with the speed v,

[0068] In steps 400 and 500 of the present invention:

[0069] 1) Critical judgment angle θ of anti-overturning self-righting control system Limit

[0070] Generally speaking, the maximum angle at which a ship can maintain a certain turning arm to restore its own attitude stability is defined as the ship's capsizing critical angle θ1. In addition, when the ship tilts too much, the ship's side will be lower than the water surface, which will cause the ship to sink and capsize. The minimum angle at which the ship tilts and causes water to enter is defined as the water inflow critical angle θ2. In summary, when the anti-capsulation self-righting control system predicts whether the ship has a capsizing risk, it should ensure that the expected maximum angle of the ship is less than the capsizing critical angle θ1 and the water inflow critical angle θ2, that is, the critical judgment angle θ Limit Take the minimum value of θ1 and θ2.

[0071] θ Limit =min(θ1,θ2) Formula 3-1

[0072] 2) Anti-overturning judgment logic

[0073] Considering the ship rolling period T1 and the self-righting airbag deployment time T2, the prediction time length of the anti-capsize self-righting control system is defined as T f When the anti-capsize self-righting control system predicts whether the hull has a capsize risk, if T f If T is too small, the self-righting airbag cannot be deployed smoothly. f If it is too large, the prediction accuracy cannot be guaranteed. In order to ensure that the anti-capsize self-righting control system can effectively and reliably predict whether the hull has the risk of capsizing, the following equation is used to calculate T f :

[0074]

[0075] T1 can be obtained from formula 1-13:

[0076]

[0077] Self-righting airbags are installed on both sides of the hull. When the hull is at risk of capsizing to the starboard side, the anti-capsize self-righting control system will trigger the deployment of the right self-righting airbag, and vice versa for the left side.

[0078] 3) Self-righting judgment strategy

[0079] When a violent impact causes the hull to capsize or the anti-capsize self-righting control system fails to effectively prevent the hull from capsizing, causing the hull to flip 90 degrees and the hull cannot be righted by the turning lever arm, a certain cumulative time T is reached. s(usually set to 60s), the anti-capsize self-righting control system will trigger the left and right self-righting airbags to deploy in sequence to ensure that the capsized hull is gradually righted. The deployment order of the left and right self-righting airbags is related to the angle of the hull capsizing. If the hull capsizes to the starboard side, the starboard self-righting airbag will be deployed first to generate a turning arm for the hull. When the hull roll angle is less than θ Limit Then deploy the left self-righting airbag, and vice versa.

[0080] Example:

[0081] Figure 1 This is a schematic diagram of the arrangement of self-righting airbags. Ship A001 is generally a rescue boat, lifeboat or a small boat with special requirements. The left self-righting airbag A002 and the right self-righting airbag A003 are arranged on both sides of the ship A001 respectively, and are triggered to deploy when the hull is at risk of capsizing.

[0082] Figure 2 This is the composition and flow chart of the anti-rollover self-righting control system based on attitude fitting prediction. The anti-rollover self-righting control system consists of attitude sensor 1-A004, attitude sensor 2-A005, anti-rollover self-righting controller A006, driver unit A007, left self-righting airbag A002 and right self-righting airbag A003. The two attitude sensors are redundant and calibrated with each other. The anti-rollover self-righting controller A006 is responsible for the anti-rollover self-righting control algorithm. The algorithm flow is as follows:

[0083] Step 100: Establishing a ship roll attitude prediction model based on the ship kinematics and dynamics equations;

[0084] Step 200: The attitude sensor collects the real-time attitude data and inertial data of the hull, and uses the prior impact data within a period of time As input, the ship roll attitude prediction model in step 001 is used to calculate the ship roll state characteristic parameter data set {R i (σ i ,w Ti )} as result;

[0085] Step 300: Using the data set in step 200 as input, the polynomial fitting relationship between the ship's roll state characteristic parameters and the speed is estimated based on the least squares linear fitting model, and the optimal ship's roll state characteristic parameters that meet the current environmental parameters are estimated based on the current speed;

[0086] Step 400: Input the attitude sensor data into the adjusted hull roll attitude prediction model, calculate the hull roll attitude change curve, judge whether there is a capsizing risk based on the curve peak, take action in advance for roll impacts with capsizing risks, trigger the self-righting airbags on both sides of the hull to deploy, and avoid capsizing.

[0087] Figure 3 The following is an example of the curve of the ship's rolling attitude change. The ship's rolling attitude is stable during the time period 0-t1. During the time period t1-t2, there is an attitude peak, which is lower than θ Limit , there is no capsizing risk, the ship's rolling attitude remains stable during the t2-t3 period, and the attitude peak is greater than θ during the t3-t4 period Limit If there is a risk of capsizing, the anti-capsize self-righting controller will trigger the self-righting airbag in advance some time before the peak arrives to avoid capsizing.

Claims

1. A ship anti-capsize self-righting control method based on attitude fitting prediction, characterized in that The following steps are involved: Step 100: Establishing a ship roll attitude prediction model based on the ship kinematics and dynamics equations; Step 200: The attitude sensor collects real-time attitude data and inertial data of the hull, uses a priori impact data over a period of time as input, and uses the data to calculate the hull roll attitude prediction model in step 100 to obtain a hull roll state characteristic parameter dataset as a result; the elements of the characteristic parameter dataset include the roll characteristic frequency of the ship and the swing amplitude attenuation coefficient of the ship; Step 300: Using the characteristic parameter data set in step 200 as input, a polynomial fitting relationship between the ship's roll state characteristic parameters and the speed is estimated based on a least squares linear fitting model. The optimal ship's roll state characteristic parameters that meet the current environmental parameters are estimated based on the current speed, and an adjusted ship's roll attitude prediction model is obtained. Step 400: inputting the attitude sensor data into the adjusted ship roll attitude prediction model to calculate the ship roll attitude change curve; The ship determines whether there is a capsizing risk based on the curve peak, and takes early action for any rolling impact that could cause a capsizing risk, triggering the deployment of the self-righting airbags on both sides of the hull to prevent the ship from capsizing. Step 500: When a violent impact causes the hull to capsize or the anti-capsize self-righting control system fails to effectively prevent the hull from capsizing, causing the hull to roll over 90 degrees and the hull cannot be righted by the turning lever arm, after a certain period of time has accumulated, the anti-capsize self-righting control system will trigger the left and right self-righting airbags to deploy in sequence to ensure that the capsized hull gradually rights. The ship roll attitude prediction model in step 100 refers to a periodic roll motion model of a ship at sea in a damped state after being impacted. The time domain attitude prediction equations based on the model are as follows: The hull rotation moment is M f , the ship's rolling attitude angle is θ, the ship's turning torque generation proportional factor is K, the ship's rotational inertia is J, the ship's angular velocity is w, the ship's angular momentum is L, the ship's gravity is Mg, the ship's center of gravity arm is R, and the ship's turning torque is M f The ship's roll angle is θ, the initial angle is θ0, the initial angular velocity is w0, and N γ for The approximate coefficients of the sine function and the proportional function, σ is the attenuation coefficient of the swing amplitude of the ship, t is the time, A T is the swing characteristic amplitude, w T is the ship's rolling characteristic frequency.

2. The method for controlling a ship to prevent capsizing and self-righting based on attitude fitting prediction according to claim 1, characterized in that: The a priori impact data in step 100 include the angle of the hull at the initial moment, the hull rotation angular velocity, the hull speed, the heading, the hull swing amplitude and the phase corresponding to the hull swing amplitude.

3. The method for controlling a ship to prevent capsizing and self-righting based on attitude fitting prediction according to claim 1, characterized in that: The process described in step 400 is to determine whether there is a capsizing risk based on the curve peak value, and to take action in advance for a roll shock that poses a capsizing risk, triggering the deployment of the self-righting airbags on both sides of the hull to prevent the hull from capsizing. Specifically, the process is as follows: 1) Select the minimum value between the critical angle of hull capsizing θ1 and the critical angle of water inflow θ2 as the critical judgment angle θ of the anti-capsulation self-righting control system Limit ,Right now: i Limit =min(θ1,θ2) 2) Anti-overturning judgment logic Considering the ship rolling period T1 and the self-righting airbag deployment time T2, the prediction time length of the anti-capsize self-righting control system is defined as T f When the anti-capsize self-righting control system predicts whether the hull has a capsizing risk, it uses the following equation to calculate T f : Where T1 is: Self-righting airbags are installed on both sides of the hull. When the hull is at risk of capsizing to the starboard side, the anti-capsize self-righting control system will trigger the deployment of the right self-righting airbag, and vice versa for the left side.

4. The method for controlling a ship to prevent capsizing and self-righting based on attitude fitting prediction according to claim 1, characterized in that: The anti-capsize self-righting control system comprises two attitude sensors, an anti-capsize self-righting controller, a driver unit, a left self-righting airbag and a right self-righting airbag. The two attitude sensors are redundant and calibrated with each other. The inputs of the two attitude sensors are connected to the anti-capsize self-righting controller, which controls the left and right self-righting airbags located on both sides of the ship through the driver unit.

5. The method for controlling a ship's anti-capsize self-righting according to claim 4, characterized in that: Step 500 specifically includes: The anti-capsize self-righting control system triggers the deployment of the left and right self-righting airbags in sequence to ensure that the capsized hull gradually returns to the right position. The deployment order of the left and right self-righting airbags is related to the angle of the hull capsizing. If the hull capsizes to the starboard side, the starboard self-righting airbag will be deployed first to generate a turning arm for the hull. When the hull roll angle is less than the critical judgment angle θ, the starboard self-righting airbag will be deployed first to generate a turning arm for the hull. Limit Then, deploy the left self-righting airbag, and vice versa.

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