​Method and device for improving the safety of a maritime platform

​The present invention relates to a method for improving the safety of a maritime platform, installed at sea or sailing at sea, comprising an observation of waves impacting said platform and a characterization of a level of danger of said waves with respect to an operation of the maritime platform. The invention also relates to a corresponding device and computer program.

​The invention is in the field of maritime operations, and relates to various maritime, fixed or mobile platforms, for example wind turbines, ships.

​Such maritime platforms are constantly impacted by waves. In a known manner, successive high-amplitude waves can cause hardware and dramatic damage and endanger the safety of maritime operations.

​In particular, when the maritime platform is a ship, the movement of this ship under the effect of waves is all the more important that the period of each wave is close to the period of the own movements of the ship.

​There Are observation means for acquiring the wave rise level above sea level, which is the zero altitude level.

​However, in order to improve the safety of a maritime platform, it is not only useful for observing waves, but also to analyze whether they are likely to carry out a maritime operation implemented by sniT characterized in that it comprises the following steps: peril platform by being interesting to one or more characteristic quantities of the waves (amplitude, period, energy, etc.)

​For example, such maritime operations include apbridging operations, drone recovery, adapting the wind turbine control to secure its structure or command for navigating a ship.

​Wave field modeling methods that are deterministic are known at the present time, which require deep knowledge of the physical amplitude and phase parameters of the waves, and which require high programming power due to the complexity of the calculations to be performed.

​The object of the invention is to remedy at least some of the drawbacks of known methods, by proposing a method for improving the safety of a maritime platform faster and requiring lightened computational resources.

​For this purpose, the invention proposes A method for improving the safety of A maritime platform, installed at sea or sailing at sea, comprising a wave observation impacting said maritime platform, an operation of the maritime platform being controlled via a control system.

​The method comprises the steps of:

​-Acquiring elevation values of the surface of the sea at a plurality of points, for characterizing at least one group of waves, a wave being assimilated to a wave defined by a period and an amplitude,

​Calculating at least one characteristic variable of each group of waves, comparing the calculated characteristic quantity with a danger threshold,

​-If the comparison indicates an exceeding of the danger threshold, alarm lift intended for said control system.

​Advantageously, the invention proposes an analysis of groups of waves, and an evaluation of the danger according to a characteristic variable of a group of waves, said characteristic variable being preferably chosen according to the operation of the maritime platform.

​The method may also have one or more of the features below, taken independently or according to any technically acceptable combination.

​The method further comprises estimating a propagation time of the group of waves up to a position of said operation of the maritime platform, and said alert lift indicates said propagation time.

​The propagation time of the group of waves up to the position of said operation of the maritime platform is calculated as a function of a calculated speed, the calculated speed being a group speed or a speed calculated as a function of said selected characteristic variable and corrected for any propagation errors.

La grandeur caractéristique est sélectionnée en fonction de ladite opération de la plateforme maritime.

​The calculation of at least one characteristic quantity comprises an acquisition of a matrix of observations at a given time instant, each element of the observation matrix being equal to an elevation value above a reference level of the surface of the sea, at a given observation point of a grid of a domain of observations.

​The observation domain is rectangular, one of the sides of the observation domain being collinear with a main direction of wave propagation.

​The method comprises applying a convolution mask to said observation matrix.

​It comprises a directional spectrum estimation of waves characterizing the sea in a vicinity of the maritime platform, and the dimensions of the convolution mask are selected based on parameters of the directional spectrum.

​It comprises the calculation of a matrix of significant height of group, each element of which is associated with a given spatial index observation point, and has a value representative of the energy of the waves whose observation points are included in a spatial domain defined by the convolution mask and centered on said observation point.

​According to a second aspect, the invention relates to a device for improving the safety of a maritime platform, installed at sea or navigating at sea, comprising a wave observation impacting said maritime platform, an operation of the maritime platform being controlled via a control system.

​The device comprises modules adapted to:

​-Acquiring elevation values of the surface of the sea at a plurality of points, for characterizing at least one group of waves, a wave being assimilated to a wave defined by a period and an amplitude,

​-Calculating at least one characteristic quantity of each group of waves,

​Comparing the calculated characteristic quantity with a danger threshold,

​-If the comparison indicates an exceeding of the danger threshold, lifting an alert intended for said control system.

​In a third aspect, a computer program product having code instructions is provided, when implemented by one or more programmable device computation processors implement a method as briefly described above.

​Other features and advantages of the invention will emerge from the description given below, by way of indication and in no way limiting, with reference to the appended figures, among which:

​FIG. 1 schematically represents a vessel comprising a device implementing an embodiment of the invention;

​FIG. 2 is a block diagram of the main blocks of a programmable device capable of implementing the invention;

​FIG. 3 is a graph illustrating a signal representative of a wave; FIG. 4 schematically illustrates a wave observation domain;

​FIG. 5 schematically illustrates wave characteristic parameters;

​FIG. 6 is a flowchart of the main functional blocks of a device for improving the safety of a maritime platform according to one embodiment;

​FIG. 7 is a flowchart of the main steps implemented by a method for improving the safety of a maritime platform according to one embodiment.

​FIG. 1 schematically illustrates a ship 2, which is a maritime platform, in movement at sea.

​This is a non-limiting example of a maritime platform for which the invention applies. In particular, the invention applies to maritime platforms installed at sea, for example a farm of wind turbines.

​The ship 2 is equipped with geolocation instruments 4 and an inertial unit 6 making it possible to calculate the position and the speed of movement at each instant.

​The vessel is also equipped with a set of sensors 8, for example of LIDAR Or RADAR Type, for analyzing the surface of the sea 12, in an observation domain d the range of these sensors is at least equal to the prenotice necessary for implementing the desired maritime operation.

​In one embodiment, the observation domain d has, for example, a rectangular perimeter, located at a given distance from the vessel.

​Alternatively, the observation domain has a circular or oval ring-shaped perimeter, the set of sensors 8 being capable of rotating at 360°, making it possible to acquire several sets of data around the ship 2.

​The surface of the sea 12 is analyzed in the vicinity of the vessel 2 carrying the sensors 8, and a level of danger of groups of waves is estimated.

​The sensors are capable of analyzing the surface of the sea to a given observation distance of the vessel 2, for calculating a corresponding prenotice.

​By way of non-limiting example, an observation distance of A nautical half-thousand makes it possible to obtain A waypoint prenotice of 30-60 seconds according to the sea state encountered and the speed of advance of the maritime platform.

​The groups of waves having a level of dangerousness greater than a predetermined danger threshold are propagated to one or more maritime platforms including the vessel 2 to allow the operator to anticipate, with a given notice, and to adjust the performance of various maritime operations on these maritime platforms.

​The vessel also comprises a programmable device 10, for example a computer, which receives data obtained by the sensors 8, as well as the data of the geolocation instruments 4 and of the inertial unit 6

​This programmable device 10 is part of or is associated with a control system 14 and provides information enabling the security improvement of the maritime platform according to the invention.

​The control system, controlled remotely or by an operator, makes it possible to control various maritime operations on the maritime platform, for example a weighbridge on the ship. In the case where the maritime platform is a farm of wind turbines, the control system makes it possible, for example, to orient the wind turbines.

​FIG. 2 schematically illustrates the main functional blocks of a programmable computer device, workstation, capable of implementing the method of the invention.

​In one embodiment, the programmable device is a computer of a control system 14 of the ship 2

​A programmable device 20 capable of implementing the method of the invention comprises a central processing unit 28, comprising one or more processors, capable of executing computer program instructions when the device 20 is powered up. In one embodiment, a central multiprocessor processing unit is provided for performing parallel calculations. ​The device 20 also comprises information storage means 30, for example registers, capable of storing executable code instructions enabling the implementation of programs comprising code instructions capable of implementing the methods according to the invention.

​The device 20 comprises control means 24 for updating parameters and for receiving commands from an operator. When the programmable device 20 is an on-vehicle device, the control means 24 comprise a telecommunication device for receiving commands and remote parameter values.

​Alternatively and optionally, the control means 24 are means for inputting commands from an operator, for example a keyboard.

​The programmable device 20 comprises a screen 22 and an additional pointing means 26, such as a mouse

​The various functional blocks of the device 20 described above are connected via a communication bus 32.

​The sensors 8 are capable of measuring an elevation of the surface of the sea, relative to a reference level, at a plurality of points distributed in the observation domain, at successive temporal instants. The reference level is typically the sea level, of zero altitude.

​The observation of the elevation of the surface of the sea at a plurality of points of observation P-iota to Pn At a given instant t0, makes it possible to reconstitute the temporal profile of a wave representative of a wave, as illustrated in FIG. 3

​In this figure, a graph is represented, comprising along the x-axis the time axis (t) and on the y-axis the elevation axis (eta) with respect to the sea level.

​For example, the temporal instants are expressed in seconds (s) with respect to an original time, corresponding to the observation of a first point Pi Of the surface of the sea and the values of elevation (or amplitude) are expressed in metres.

​Knowing the wave propagation speed, the observation can be placed at each point P, at time t0 at a time instant t, on the basis of the distance between the point P, and the origin point of the observation

​Points Pi To Pn, in an observation direction d, are illustrated in the right upper corner of figure 3

​In one embodiment, the direction d is the direction of wave propagation and shortages observation points are distributed in an observation domain d schematically illustrated in FIG. 4, with an associated three-dimensional spatial repository (chi, upsilon, zeta).

​In this example, the observation domain and the associated marker are preferably oriented in a manner so as to appear is characterized in that it comprises at least one of the following: one of the X Or Y directions Is collinear with the main direction of propagation of the waves d in this example, the domain d has a rectangular surface in the plane (X,Y) of respective dimensions and L2.

​A set of points P, j, of the domain D, with (, /) D, i ∈ [1, j,'G [l, 2], Mi Being the number of points observed in the direction

​X, M2 The number of points observed in the Y direction

​Example embodiment illustrated by way of example, one of the sides of the rectangular domain d is collinear with the wave propagation direction d

​In one embodiment, the points are distributed over a regular grid on the surface of the D-domain

​Alternatively, the tiling of points is not regular.

​The coordinates of the points can be represented in a cartesian coordinate system or in polar coordinates.

​Alternatively, the observation domain has another geometric shape (oval, circular...)

​The elevation eta (x1, gamma], 1) observed is the Z-axis coordinate Of the D-point of the D-domain, of spatial coordinates (x ^ yj), at instant t

​As illustrated in FIG. 5, a wave is defined by a time signal, from the observed elevations, between two zero-to-zero crossings at the time instants tk and toff + l the retained characteristic parameters are its period Tw And its amplitude

​Hw, which is the height between the lowest point (hollow) and the highest point (the peak of the wave)

​Waves are observed and analyzed to detect groups of waves using methods known to those skilled in the art. A group of waves is defined for example by a succession of at least sniT wherein the first and second temperatures are different from each other waves having similar characteristics (large amplitude, period...)

​FIG. 6 is a block diagram of the main modules implemented by a programmable device capable of implementing the invention.

​The device 40 comprises an observation data acquisition module 42, in particular data relating to the rise of the waves at each point P, j observed.

​It also comprises a module 44 for calculating one or more characteristic quantities of groups of waves.

​For example, one choice from several characteristic quantities C Is envisaged, according to the maritime operation to be monitored, or the movement characteristic of the ship in question.

​According to one embodiment, for certain types of operation, a characteristic quantity is energy, as detailed in the embodiment described below with reference to FIG. 7

​Alternatively, the characteristic variable may be the period of the waves to avoid the occurrence of parametric rolling phenomena.

​A module 46 implements parameter calculations, such as calculating the group velocity of observed waves, as well as the associated directional spectrum in a vicinity of the maritime platform.

​The directional spectrum of the observed waves is characterized by parameters including in particular the peak period Tp, the significant group Hs height, the main direction of propagation d, the directional spread Δβ.

​The values of the calculated parameters are stored in a memory unit 52.

​It should be noted that several methods for estimating the directional spectrum of the waves observed are known to a person skilled in the art (MLM For maximum best method, entropy maximum, with partitioning spectral partitioning methods to discretize a plurality of sea state systems...)

​The device comprises a comparison module 48, capable of comparing one or each of the characteristic quantities C Calculated with a threshold of danger Sc associated with this characteristic quantity, previously calculated and stored in the memory unit 52.

​For example, observation history H data is recorded, and a calculation module 50 is able to use this data to determine various danger thresholds Sc.

​Thus, in one embodiment, at temporal instants t, a set of parameter values associated with the contemplated operation, for example the amplitudes of movement of the vessel according to various degrees of freedom, and these parameter values are stored. Furthermore, the value of the characteristic quantity of a selected group of waves is calculated, for example energy, related to the envisaged maritime operation reaching the platform at instant t, ​Accordingly, it is possible, in an automatic or semi-automatic manner, with the aid of an operator, for determining the danger thresholds Sc of a characteristic quantity as a function of the parameter values associated with the envisaged operation.

​When the comparison module 48 indicates an exceeding of the corresponding danger threshold Sc, a propagation module simulates the propagation of the observed wave group to the position of the operation performed by the respective maritime platform.

​For example, the position of the operation is the spatial position of the maritime platform at a given instant.

​Alternatively, the propagation module simulates the propagation of the observed wave group to the position of the student operation performed by the maritime platform in question regardless of the level of danger of the waves.

​This propagation simulation makes it possible to estimate the propagation time, and thus predicting the arrival of a group of waves detected as being dangerous for a given operation, with a given time prenotice, for example of the order of 30 seconds.

​A module 56 makes it possible to lift an alert to prevent the control system of the maritime platform from the arrival of the group of waves detected as dangerous

​For example, in the case where the control system has man-machine interfaces and is controlled by an operator, visual or audible alerts are sent.

​In one embodiment, the modules 42,44,46, 48, 50, 54 and 56 are software modules.

​FIG. 7 is a flowchart of the main steps of a method for improving the safety of a maritime platform according to the invention, in which the calculated characteristic quantity is representative of the energy of the wave packets representative of the observed wave groups.

​In a first preliminary step 70, parameters are calculated and stored, in particular the parameters of the directional spectrum of the waves observed around the maritime platform, characterizing the condition of the sea.

​This step is followed by a step 72 of acquiring the observations of the elevation values eta (χi, gamma], 1) at each point P, j of the domain d, of spatial coordinates

​(JC; yj), at a current instant t

​A matrix of observations Obt Of size M1 xM2 is obtained. If it is noted

​Eta (χi, gamma], i) = j i (t) the index element (i,j) of the matrix has the following formula:

​In the filtering step 74, A convolution mask P Is applied at each point of the observation matrix Obt.

​In this embodiment, P Is a rectangular mask all the coefficients of which are equal to 1

​More generally, this convolution mask may cover different shapes, for example a gaussian, circular kernel,

​The dimensions of this convolution mask depend on the dark sea state. For example, by choosing as a large feature the energy, it is set according to the peak period of the waves and the directional spread.

​Filtering by application of the convolution mask P Consists in calculating, for each point (i,j) of the matrix of the observations Obt, a filtered value. The convolution mask may be directly applied to the matrix of the Obt Observations or on a quantity derived from the matrix of the observations selected according to the envisaged maritime operation, for example the period of waves if it is sought to study parametric roll phenomena.

​The filtering step 74 is followed by a step 76 of calculating a significant height of group HSG T at each point (i,j), which is a significant magnitude of the energy of the waves, the observation points of which are included in the domain of the convolution mask P -750 T around the point P Associated with the point associated with the spatial index (i,j) of the matrix of the observations.

​According to one variant, the filtering and the calculation of the significant height are carried out in a single step.

​The calculated values of the significant group height are compared, during a comparison step 78, each, to a danger threshold S, associated with the Characteristic variable HSG t, previously calculated and stored.

​If the danger threshold S is exceeded by a value HSG t (i, j), step 78 is followed by a step 80 of propagation of the matrix containing the values of significant height of group HSG T to the maritime platform under consideration.

​Alternatively, multiple hazard thresholds may be used, each hazard threshold having an associated confidence level.

​The propagation step 80 implements the group speed Cg =-- Tp For

​Propagating hazardous ocean waves

​Alternatively, another propagation speed depending on the chosen criterion is applied.

​According to an alternative, the calculated propagation speed is adjusted as a function of the observed propagation errors.

​The step 78 is followed, on the other hand, with a step 82 of updating the observation time instant taken into consideration, the current instant t being set at the following instant ts = t + dt, where dt is the measurement sampling frequency, and step 82 is followed by the previously described step 72.

​Step 80 is followed by a step 84 of lifting alert to the control system of the maritime platform, for example in the form of a display on a graphical user interface to an operator, when the calculated characteristic value exceeds the one or more danger thresholds.

​Advantageously, the arrival of groups of waves having a level of dangerous dangesity for example ratio to an operation performed on a maritime platform is thereby provided, sufficient prenotice is transmitted so that the operator of the control system can take corrective action. The safety of maritime operations is thus increased.

CLAIMS

1. - Method for improving the safety of a maritime platform, installed at sea or navigating at sea, comprising an observation of waves striking the said maritime platform, a operation of the sea platform being controlled by means of a control system, the characterized in that it comprises steps of:

acquisition (72) of elevation values ​​of the sea surface at a plurality of points, making it possible to characterize at least one group of waves, a wave being assimilated to a wave defined by a period and an amplitude,

calculating (74, 76) at least one characteristic quantity of each wave group,

comparison (78) of the characteristic quantity calculated with a threshold of danger,

- if the comparison indicates an exceeding of the threshold of danger, raising alert (84) for said control system.

2. - Method according to claim 1, characterized in that it further comprises an estimate (80) of a duration of propagation of the wave group to a position of said operation of the maritime platform, and in that said alert raising indicates said propagation time.

3. - Method according to claim 2, characterized in that the duration of propagation of the wave group to the position of said operation of the marine platform is calculated according to a calculated speed, the calculated speed being a speed of group or a speed calculated according to said selected characteristic value and adjusted according to detected propagation errors.

4. - Method according to any one of claims 1 to 3, characterized in that the characteristic quantity is selected according to said operation of the marine platform.

5. - Method according to any one of claims 1 to 4, characterized in that the calculation of at least one characteristic quantity comprises an acquisition of a matrix of observations at a given time instant, each element of the matrix d observations being equal to an elevation value above a reference level of the sea surface at a given observation point (P, j ) of a grid of a field of observations.

6. - Method according to claim 5, characterized in that the field of observation is rectangular, one side of the field of observation being collinear with a main direction of wave propagation.

7. - Method according to one of claims 5 or 6, characterized in that it comprises the application of a convolution mask to said observation matrix.

8. - Method according to claim 7, characterized in that it comprises a directional spectrum estimate (70) of waves characterizing the sea in a vicinity of the maritime platform, and in that the dimensions of the convolution mask are selected in function of directional spectrum parameters.

9. - Method according to any one of claims 7 or 8, characterized in that it comprises the calculation (76) of a matrix of significant height of group of which each element is associated with a point of observation index given space, and has a value representative of the wave energy whose observation points are included in a spatial domain defined by the convolution mask and centered on said observation point.

10. - Device for improving the safety of a maritime platform, installed at sea or navigating at sea, including an observation of waves striking the said maritime platform, an operation of the sea platform being controlled by means of a control system , the device being characterized in that it comprises modules adapted to:

acquiring (42) elevation values ​​of the sea surface at a plurality of points, making it possible to characterize at least one group of waves, a wave being assimilated to a wave defined by a period and an amplitude,

calculating (44) at least one characteristic quantity of each group of waves,

comparing (48) the characteristic quantity calculated with a threshold of danger,

- if the comparison indicates an exceeding of the danger threshold, raise (56) an alert for said control system.

1 1 .- Computer program comprising code instructions which, when implemented by one or more programmable device calculation processors implement a method according to any one of claims 1 to 9.