CN117270009A - Center offset determining method of FPSO single-point mooring system - Google Patents
Center offset determining method of FPSO single-point mooring system Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/50—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/45—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement
- G01S19/47—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/53—Determining attitude
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/50—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
- B63B2021/505—Methods for installation or mooring of floating offshore platforms on site
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Abstract
The application discloses a center offset determining method of an FPSO single-point mooring system, which relates to the technical field of FPSOs. The circle center of the longitudinal parameter circular contour line obtained by fitting is the true stress balance point of the single-point mooring system and is not the equivalent physical circle center, the radial direction of the longitudinal parameter circular contour line is the longitudinal parameter of the ship body, the longitudinal parameter of the ship body can be accurately obtained, and the requirement on accurate mapping and data measurement accuracy is reduced by the big data analysis method, so that the accurate center offset can be realized, and the inversion accuracy of the tension of the mooring cable is improved.
Description
Technical Field
The application relates to the technical field of FPSO (floating production storage and offloading), in particular to a method for determining a center offset of a single point mooring system of an FPSO.
Background
FPSO (floating production storage vessel, floating Production Storage and Offloading) is one of the important facilities for offshore oil and gas production, and the safety and stability of the underwater cables directly relate to the life safety, ecological safety, asset safety, economic benefit and operation and maintenance operation of the operation area. The FPSO is fixed in the setting position of oil field through single point mooring system, and the structural schematic diagram of the single point mooring system of FPSO is as shown in FIG. 1, and single point mooring system is including being located the revolving tower 2 of hull 1 bow, be located mooring line 4 and submarine pipe 5 under water, and revolving tower 2 takes place synchronous rotation along with hull 1, and revolving tower 2 lower extreme is flotation pontoon 3, and flotation pontoon 3 is located under water and does not take place synchronous rotation along with hull 1, and flotation pontoon 3 receives buoyancy more than its own gravity, and then strengthens the connecting effort with revolving tower 2. The single point mooring system generally comprises a plurality of mooring lines 4, one end of all mooring lines 4 being connected to a buoy 3 at the lower end of the turret 2, and the ends of all mooring lines 4 being moored to the sea floor and located on the same virtual circumference, as shown in fig. 1 by the virtual circumference. The mooring rope 4 is a main bearing member, the mooring rope 4 is used for limiting the motion of the FPSO, protecting the underwater pipe cable 5 from being broken due to overlarge stress, the underwater pipe cable 5 is used for conveying mediums such as crude oil, slurry and the like, providing signals, electric power and the like for an underwater system, is in a curve state, does not bear mooring tension, and is subjected to ship body transmission load and seabed hydrodynamic load.
Considering the tidal level variation, a certain displacement margin is reserved for the heave motion of the hull 1, so that the mooring lines 4 are not in a linear pre-tightening state, and only the mooring lines 4 with larger stress are in a linear state. Under the action of wind, waves and currents, the ship body can continuously fluctuate, so that the stress of different mooring ropes changes, and if the tensile force of the mooring ropes is too large, the structural strength of the mooring ropes 4 is damaged to break, and the whole mooring effect is achieved. Therefore, in the FPSO working process, monitoring the tension of each mooring rope to timely find the abnormal state of the mooring rope is important to guaranteeing the mooring safety. One would clamp the tilt sensor on the mooring line 4 and calculate the mooring line tilt angle measured by the tilt sensor to obtain the tension the mooring line is subjected to. However, the tilt force sensor is arranged below the water surface, the tilt force sensor is easily damaged due to corrosion of seawater, an additional signal cable is required to be used for transmitting signals of the tilt force sensor, the signal cable is easily damaged by wave currents, and the underwater maintenance is difficult and the cost is too high.
In general, the lengths of the mooring ropes 4 are equivalent to each other, the physical circle center of the virtual circle where the tail ends of the mooring ropes 4 are located is the stress balance point of each mooring rope, in an ideal state, when the rotating tower 2 of the FPSO is located at the physical circle center of the virtual circle, the stress of each mooring rope 4 is the same, and under the action of stormy waves, the larger the central offset of the rotating tower 2 relative to the physical circle center is, the larger the tensile force exerted on part of the mooring ropes is. Therefore, based on the principle, some methods exist at present to solve the projection distance between the rotating tower and the physical center of the virtual circumference where the tail end of the mooring rope is positioned to obtain a center offset, and the center offset can calibrate the tensile force born by each root system mooring rope and monitor the state of the mooring rope. The GPS positioning device is deployed on the ship body 1 to determine the rotation tower coordinates, the physical circle center coordinates of the virtual circumference are mapped and determined, and then the solution is carried out, but the positioning measurement of the rotation tower coordinates is limited by the positioning precision, random errors of 1-5 meters often exist, and the mapping result of the physical circle center coordinates of the virtual circumference is inevitably also error. The actual seabed is not an ideal plane, the actual lengths of the mooring ropes are not the same, and the physical circle center of the virtual circumference is not a stress balance point of each mooring rope in a strict sense, so that the center offset obtained by solving the method in the prior art has larger error, and the state monitoring of the mooring ropes is affected.
Disclosure of Invention
Aiming at the problems and the technical requirements, the application provides a method for determining the center offset of an FPSO single-point mooring system, and the technical scheme of the application is as follows:
a center offset determination method of a FPSO single point mooring system, the center offset determination method comprising:
acquiring historical stability data of the FPSO in a plurality of historical stability states in a historical working process, wherein each set of historical stability data comprises first position motion data acquired by first position motion monitoring equipment and second position motion data acquired by second position motion monitoring equipment in the historical stability state; the first position motion monitoring equipment is arranged at a rotating tower of a single-point mooring system of the FPSO hull, the second position motion monitoring equipment is arranged at the stern of the FPSO hull, and the two position motion monitoring equipment are both arranged at the center position of the width of the FPSO hull, and the position motion data comprise position coordinates and six-degree-of-freedom motion data;
solving a rotating tower coordinate, a ship heading angle and a ship longitudinal parameter of the FPSO ship under the current historical steady state based on a group of historical steady data under each historical steady state;
the method comprises the steps that rotation tower coordinates in each history steady state are used as tangent points on a longitudinal parameter circular contour, a ship heading angle is the direction that the current tangent point is perpendicular to the tangential direction and points to the center of a longitudinal parameter circular contour, the longitudinal parameter circular contour is obtained by fitting the rotation tower coordinates, the ship heading angle and the longitudinal parameters in each history steady state, the center of the longitudinal parameter circular contour is a stress balance point of a single-point mooring system, and the radial direction is a longitudinal parameter of a ship body;
in the FPSO working process, real-time hull longitudinal parameters of the FPSO hull are determined according to six-degree-of-freedom motion data acquired by two position motion monitoring devices, and the distance between the real-time hull longitudinal parameters and the circle center on a longitudinal parameter circular contour is determined to obtain the central offset of the single-point mooring system.
The further technical scheme is that solving the rotation tower coordinate, the ship heading angle and the longitudinal ship parameters of the FPSO ship body in the current historical steady state based on a set of historical steady data in each historical steady state comprises the following steps of for each set of historical steady data:
solving a first position coordinate in first position motion data in the historical stable data by using a density estimation method, and taking the first position coordinate with the maximum probability density as a rotating tower coordinate in the current historical stable state;
obtaining heading angle candidate values according to a first position coordinate in first position motion data and a second position coordinate in second position motion data at the same moment in the historical stable data, solving each heading angle candidate value by using a density estimation method, and taking the heading angle candidate value with the highest probability density as a ship heading angle in the current historical stable state;
and solving the longitudinal parameters of the ship body in the six-degree-of-freedom motion data in the historical stable data by using a density estimation method, and taking the longitudinal parameter with the highest probability density as the longitudinal parameter of the ship body in the current historical stable state.
The further technical scheme is that a circular contour line of longitudinal parameters is obtained by utilizing the rotation tower coordinates, the ship heading angle and the longitudinal parameters of the ship body under each historical stable state, and the method comprises the following steps:
initializing the center coordinates of a longitudinal parameter circular contour, and iteratively solving and determining the center coordinates by using a gradient descent method on the basis that the direction of a vector between the center coordinates and the rotating tower coordinates in each historical stable state is parallel to the direction of a ship heading angle in the current historical stable state;
and drawing a circular contour line of the rotating tower coordinate in each historical stable state based on the determined circle center coordinate to obtain a longitudinal parameter circular contour line, and determining that the circular contour line of the rotating tower coordinate in each historical stable state has the longitudinal parameter of the ship body in the historical stable state.
The further technical scheme is that the iterative solution to determine the center coordinates by using the gradient descent method comprises the following steps:
initializing the center coordinates of a longitudinal parameter circular contour as (lon c ，lat c )；
Calculating a loss valueWherein the rotation tower coordinate in the ith historical steady state is (lon [ i ]]，lat[i]) Θ is the set of all historical steady state formations;
when the maximum iteration number is not reached and the Loss value Loss is not smaller than the Loss threshold value, updating the center coordinates of the longitudinal parameter circular contour asAnd calculating the loss value again;
and when the maximum iteration times or the Loss value Loss is smaller than the Loss threshold value, solving to obtain the circle center coordinates.
The further technical scheme is that the method for acquiring the historical stability data of the FPSO in a plurality of historical stability states in the historical working process comprises the following steps:
acquiring first historical monitoring data acquired by a first position motion monitoring device and second historical monitoring data acquired by a second position motion monitoring device of the FPSO in a historical working process, wherein the historical monitoring data comprise position coordinates and six-degree-of-freedom motion data;
and screening out the period of time when the FPSO is in the history steady state according to the six-degree-of-freedom motion data in the history monitoring data, and extracting the history monitoring data of the FPSO in the history steady state as history steady data.
The further technical scheme is that the screening out the period of time when the FPSO is in the historical stable state comprises the following steps:
and when the roll angular speed, the bow angular speed and the triaxial acceleration of the FPSO are smaller than the respective corresponding maximum threshold values within a period of a preset duration, and the stability of the pitch angular speed meets the stability requirement, determining that the FPSO is in a historical stable state.
The further technical scheme is that when the time domain curve of the pitching angular velocity of the FPSO in a time period of a preset duration, when the time domain duty ratio of the waveform and the period of the time domain curve of the pitching angular velocity is stable and reaches a duty ratio threshold, the stability of the pitching angular velocity is determined to reach the stability requirement, otherwise, the stability of the pitching angular velocity is determined to not reach the stability requirement.
According to the further technical scheme, for any one of the motion data of the roll angular speed, the bow angular speed and the triaxial acceleration, the maximum threshold corresponding to the motion data is determined based on the statistical values of all the historical monitoring data.
The further technical scheme is that the parameter type of the longitudinal parameter of the ship body is pitching amplitude, pitching angular acceleration or pitching acceleration of the FPSO ship body.
The further technical scheme is that each position movement monitoring device comprises a GPS device and an IMU device which are integrated together, the GPS device is used for collecting position coordinates, and the IMU device is used for collecting six-degree-of-freedom movement data.
The beneficial technical effects of this application are:
the utility model discloses a center offset determining method of FPSO single point mooring system, this method obtains the historical stable data of FPSO under a plurality of historical steady state in the historical course of working, obtains vertical parameter circular contour through big data analysis method fit, big data analysis method has reduced the requirement to accurate survey and drawing and data measurement accuracy. The circle center of the longitudinal parameter circular contour line obtained by fitting is the true stress balance point of the single-point mooring system and is not the equivalent physical circle center, the radial direction of the longitudinal parameter circular contour line is the longitudinal parameter of the ship body, and the longitudinal parameter of the ship body can be accurately obtained, so that the central offset of the single-point mooring system can be accurately obtained by utilizing the longitudinal parameter circular contour line, and the inversion accuracy of the tension of the mooring cable is improved.
The historical stable data used by the method is obtained by two position movement monitoring devices which are only required to be installed above the water surface, so that the problems of easy damage and high maintenance difficulty caused by installation under water are avoided, the operation reliability is improved, and the hardware maintenance difficulty is reduced.
Drawings
Fig. 1 is a schematic structural view of a FPSO single point mooring system.
Fig. 2 is a schematic diagram of two position motion monitoring devices deployed on the FPSO hull when the center offset determination method of the present application is applied.
Fig. 3 is a method flow diagram of a center offset determination method of one embodiment of the present application.
Fig. 4 is a schematic representation of a longitudinal parameter circular contour fitted in one example.
Detailed Description
The following describes the embodiments of the present application further with reference to the accompanying drawings.
The application discloses a center offset determining method of FPSO single-point mooring system, based on the structural expansion of the FPSO single-point mooring system shown in the prior art figure 1, and the tensile force born by each root mooring cable is calculated and monitored according to the center offset according to the prior art, the center offset determining method is not expanded for the two parts, and the center offset of the single-point mooring system is accurately determined.
When the center offset determining method is applied, two groups of position motion monitoring devices are additionally arranged on the hull of the FPSO, please refer to a schematic diagram shown in FIG. 2, the first position motion monitoring device 6 is arranged at the rotating tower 2 of the single-point mooring system of the FPSO hull 1, the second position motion monitoring device 7 is arranged at the stern of the FPSO hull, the two position motion monitoring devices are all arranged at the center position of the width of the FPSO hull, and the two position motion monitoring devices are generally and directly arranged on the deck of the FPSO hull.
Each positional movement monitoring device may monitor positional movement data including positional coordinates and six degrees of freedom movement data. In one embodiment, each of the positional movement monitoring devices includes a GPS device and an IMU device integrated together. The GPS equipment is used for collecting position coordinates, and can be replaced by other equipment with the same technical specification by using the Beidou satellite positioning system. The IMU device is configured to collect six-degree-of-freedom motion data of the FPSO hull, and the physical quantities output by the IMU device include triaxial acceleration and triaxial angular velocity of the FPSO hull, and the triaxial angle, triaxial velocity and displacement can be converted by integration.
The center offset determining method based on the two position motion monitoring devices includes the following steps, please refer to the flowchart shown in fig. 3:
step 1, acquiring historical stability data of the FPSO in a plurality of historical stability states in a historical working process.
Each set of historical stability data in each historical stability state obtained comprises first position motion data collected by the first position motion monitoring device and second position motion data collected by the second position motion monitoring device in the current historical stability state.
In practical application, wind, wave and current are not always in a stable state, so that the FPSO is not always in a stable state, and therefore, the historical stable data of the FPSO cannot be directly acquired, the two position motion monitoring devices are generally utilized to continuously acquire data in the historical working process of the FPSO, the first historical monitoring data acquired by the first position motion monitoring device and the second historical monitoring data acquired by the second position motion monitoring device in the historical working process of the FPSO are acquired, and the acquired historical monitoring data comprise position coordinates and six-degree-of-freedom motion data.
And then screening out the time period of the FPSO in the history steady state according to the six-degree-of-freedom motion data in the history monitoring data, and extracting the history monitoring data of the FPSO in the history steady state as history steady data. During screening, when the yaw angular velocity, the bow angular velocity and the triaxial acceleration of the FPSO are smaller than the respective corresponding maximum threshold values within a period of a preset time, and the stability of the pitch angular velocity reaches the stability requirement, the FPSO is determined to be in a historical stable state, and the preset time can be set in a self-defined mode, for example, can be set to 8 hours.
In the screening process, for any one of the roll angular velocity, the yaw angular velocity and the triaxial acceleration, the maximum threshold corresponding to the motion data may be set manually and empirically based on the situation of the local sea area, or the maximum threshold corresponding to the motion data may be determined based on the statistical values of all collected historical monitoring data, for example, all the collected historical monitoring data for the motion data are cut out proportionally from large to small as the maximum threshold.
In the screening process, for the pitch angular velocity, a time domain curve of the pitch angular velocity in a time period of a preset time length is drawn, when the waveform of the time domain curve of the pitch angular velocity and the curve time period duty ratio of the period of the time domain curve of the pitch angular velocity are stable reach a duty ratio threshold value, the stability of the pitch angular velocity is determined to reach a stability requirement, otherwise, the stability of the pitch angular velocity is determined to not reach the stability requirement.
By the method, some periods of time when the FPSO is in a stable state can be screened from all the historical monitoring data of the FPSO in the historical working process, so that the historical stable data of each historical stable state are extracted, and errors caused by the data in an unstable state are avoided.
And 2, solving the rotation tower coordinates, the ship heading angle and the longitudinal parameters of the FPSO hull in the current historical stable state based on a set of historical stable data in each historical stable state.
The component force of the environmental load from wind, wave, current and the like borne by the FPSO on the horizontal plane is balanced with the component force of the environmental load from the mooring rope borne by the FPSO on the horizontal plane, the magnitude of the environmental load is represented by the magnitude of the central offset of the FPSO, and the resultant force direction of the environmental load is represented by the direction of the heading of the FPSO, so that the central offset and the pulling force of the mooring rope can be inverted by solving the coordinates of the rotating tower and the heading angle of the ship.
(1) For the rotating tower coordinates, a density estimation method is used for solving first position coordinates contained in each first position motion data in a group of historical stable data, and the first position coordinates with the maximum probability density are used as the rotating tower coordinates in the current historical stable state instead of taking an average value, so that accuracy is improved.
(2) For the ship bow angle. When the FPSO is in a stable state, the environment of the ocean power plant where the FPSO is located is also in a stable state, namely, sea waves, wind directions and seabed flow directions are all kept in a stable state, and the bow direction of the FPSO is usually pointed to the circle center of the virtual circumference where the mooring lines are located or deviates from the circle center by a fixed included angle. Because the two position motion monitoring devices are both arranged at the center position of the width of the FPSO hull, please refer to FIG. 2, the vectors of the position coordinates collected by the two position motion monitoring devices can be used for calibrating the heading of the FPSO, therefore, the heading angle candidate values can be calculated according to the first position coordinates in the first position motion data and the second position coordinates in the second position motion data at the same moment, then, the density estimation method is used for solving the heading angle candidate values, and the heading angle candidate value with the maximum probability density is used as the heading angle of the ship in the current historical stable state.
(3) For hull longitudinal parameters. When the FPSO is in a steady state, the FPSO is typically free of roll and yaw, and only pitch motion. Thus, the greater the combined wind, wave, and current environmental load, the greater the hull longitudinal parameters of the FPSO will cause the rotational tower position of the single point mooring system to deviate from the single point mooring center point by a greater distance, i.e., resulting in a greater center offset. The present application thus also determines the longitudinal parameters of the hull at each historical steady state for calibrating the center offset. And solving the longitudinal parameters of the ship body in the six-degree-of-freedom motion data in the historical stable data by using a density estimation method, and taking the longitudinal parameter with the highest probability density as the longitudinal parameter of the ship body in the current historical stable state.
The type of the longitudinal parameter of the hull is pitch amplitude, pitch angular acceleration or pitch acceleration of the FPSO hull, and the pitch amplitude is generally selected.
And 3, taking the rotating tower coordinates in each history steady state as a tangent point on a longitudinal parameter circular contour line, wherein the ship heading angle is the direction that the current tangent point is perpendicular to the tangential direction and points to the center of the longitudinal parameter circular contour line, and obtaining the longitudinal parameter circular contour line by utilizing the fitting of the rotating tower coordinates, the ship heading angle and the longitudinal parameters in each history steady state, wherein the center of the longitudinal parameter circular contour line is a stress balance point of the single-point mooring system, and the radial direction is the longitudinal parameter of the ship body.
The data in each historical stable state can be used as a scattered point, and the fitting solution problem can be equivalently abstracted into the following problems: assuming that some scattered points are distributed in concentric circles with different radiuses, the longitude and latitude coordinates and the normal direction of the scattered points are known, but the scattered points are not distributed on an ideal circle, then the scattered points with known parameters need to be used for fitting a longitudinal parameter circular contour.
Considering that data in practical engineering application are all interfered by noise, three centers of circles may be drawn by scattered points in three historical stable states so as to fit different longitudinal parameter circular contour lines, so that the method provided by one embodiment is as follows: firstly initializing the center coordinates of a longitudinal parameter circular contour, and iteratively solving and determining the center coordinates by using a gradient descent method on the basis that the direction of a vector between the center coordinates and a rotating tower coordinate in each historical stable state is parallel to the direction of a ship heading angle in the current historical stable state, wherein the method comprises the following steps:
(1) Initializing the center coordinates of a longitudinal parameter circular contour as (lon c ，lat c )。
(2) Calculating a loss valueWherein the rotation tower coordinate in the ith historical steady state is (lon [ i ]]，lat[i]) Θ is the set of all historical steady state formations.
(3) When the maximum iteration number is not reached and the Loss value Loss is not smaller than the Loss threshold value, updating the circle center of the longitudinal parameter circular contour lineCoordinates areAnd the loss value is calculated again.
(4) And when the maximum iteration times or the Loss value Loss is smaller than the Loss threshold value, solving to obtain the circle center coordinates.
After the circle center coordinates of the longitudinal parameter circular contour lines are determined, the circular contour lines of the rotation tower coordinates in each historical stable state are respectively drawn based on the determined circle center coordinates to obtain the longitudinal parameter circular contour lines, and the circular contour lines of the rotation tower coordinates in each historical stable state are determined to have the longitudinal parameters of the ship body in the historical stable state.
In the longitudinal parameter circular contour line drawn by the method, distances from all points on the same circular contour line to the circle center are equal, which means that the center offset is equal at the moment, and the mooring force resultant force applied to the mooring cable is the same. For example, in one example, with the longitudinal parameter of the hull as the pitching amplitude, the circular contour of the longitudinal parameter obtained by fitting is shown in fig. 4, and each oval shadow in fig. 4 represents a scattered point obtained by data abstraction under each historical steady state.
And 4, determining real-time hull longitudinal parameters of the FPSO hull according to the six-degree-of-freedom motion data acquired by the two position motion monitoring devices in the working process of the FPSO, and determining the distance between the real-time hull longitudinal parameters and the circle center on a longitudinal parameter circular contour line to obtain the central offset of the single-point mooring system.
The real-time ship longitudinal parameters can be obtained by taking the average value of the ship longitudinal parameters acquired by the two position motion monitoring devices, and can also be obtained by directly taking the ship longitudinal parameters acquired by the first position motion monitoring device. Because the longitudinal parameter circular contour line constructed takes the longitudinal parameter of the ship body as the value in the radial direction, rather than taking the position distance as the value in the radial direction as in the conventional method, no matter what parameter type the longitudinal parameter of the ship body is specifically adopted, the longitudinal parameter of the ship body can be accurately acquired through the IMU equipment, the accuracy of the longitudinal parameter of the ship body which can be acquired by the IMU equipment at present is very high and far higher than the accuracy of the position acquired by the GPS equipment, and therefore, the method can accurately acquire the central offset of the single-point mooring system. The obtained center offset is the center offset relative to the real stress balance point, and is not the center offset relative to the physical center of the virtual circumference of the equivalent mooring rope, so that the accuracy is higher.
What has been described above is only a preferred embodiment of the present application, which is not limited to the above examples. It is to be understood that other modifications and variations which may be directly derived or contemplated by those skilled in the art without departing from the spirit and concepts of the present application are to be considered as being included within the scope of the present application.
Claims (10)
1. A method for determining a center offset of a FPSO single point mooring system, the method comprising:
acquiring historical stability data of the FPSO in a plurality of historical stability states in a historical working process, wherein each set of historical stability data comprises first position motion data acquired by first position motion monitoring equipment and second position motion data acquired by second position motion monitoring equipment in the historical stability state; the first position motion monitoring equipment is arranged at a rotating tower of a single-point mooring system of the FPSO hull, the second position motion monitoring equipment is arranged at the stern of the FPSO hull, the two position motion monitoring equipment are both arranged at the center position of the ship width of the FPSO hull, and the position motion data comprise position coordinates and six-degree-of-freedom motion data;
solving a rotating tower coordinate, a ship heading angle and a ship longitudinal parameter of the FPSO ship under the current historical steady state based on a group of historical steady data under each historical steady state;
the method comprises the steps that rotation tower coordinates in each history steady state are used as tangent points on a longitudinal parameter circular contour, a ship heading angle is the direction that the current tangent point is perpendicular to the tangential direction and points to the center of a longitudinal parameter circular contour, the longitudinal parameter circular contour is obtained by fitting the rotation tower coordinates, the ship heading angle and the longitudinal parameters in each history steady state, the center of the longitudinal parameter circular contour is a stress balance point of a single-point mooring system, and the radial direction is a longitudinal parameter of a ship body;
in the FPSO working process, real-time hull longitudinal parameters of the FPSO hull are determined according to six-degree-of-freedom motion data acquired by two position motion monitoring devices, and the distance between the real-time hull longitudinal parameters and the circle center on a longitudinal parameter circular contour line is determined to obtain the central offset of the single-point mooring system.
2. The method of claim 1, wherein solving for the rotation tower coordinates, the ship heading angle and the hull longitudinal parameters of the FPSO hull at the current historical steady state based on the set of historical steady data at each historical steady state comprises, for each set of historical steady data:
solving a first position coordinate in first position motion data in the historical stable data by using a density estimation method, and taking the first position coordinate with the maximum probability density as a rotating tower coordinate in the current historical stable state;
obtaining heading angle candidate values according to a first position coordinate in first position motion data and a second position coordinate in second position motion data at the same moment in the history stable data, solving each heading angle candidate value by using a density estimation method, and taking the heading angle candidate value with the highest probability density as a ship heading angle in the current history stable state;
and solving the longitudinal parameters of the ship body in the six-degree-of-freedom motion data in the historical stable data by using a density estimation method, and taking the longitudinal parameter with the highest probability density as the longitudinal parameter of the ship body in the current historical stable state.
3. The method of claim 1, wherein the fitting the longitudinal parameter circle contour using the rotation tower coordinates, the ship heading angle, and the hull longitudinal parameter at each historical steady state comprises:
initializing the center coordinates of a longitudinal parameter circular contour, and iteratively solving and determining the center coordinates by using a gradient descent method on the basis that the direction of a vector between the center coordinates and the rotating tower coordinates in each historical stable state is parallel to the direction of a ship heading angle in the current historical stable state;
and drawing a circular contour line of the rotating tower coordinate in each historical stable state based on the determined circle center coordinates to obtain a longitudinal parameter circular contour line, and determining that the circular contour line of the rotating tower coordinate in each historical stable state has the longitudinal parameter of the ship body in the historical stable state.
4. The method of claim 3, wherein the iteratively solving for determining center coordinates using a gradient descent method comprises:
initializing the center coordinates of a longitudinal parameter circular contour as (lon c ，lat c )；
Calculating a loss valueWherein the rotation tower coordinate in the ith historical steady state is (lon [ i ]]，lat[i]) Θ is the set of all historical steady state formations;
when the maximum iteration number is not reached and the Loss value Loss is not smaller than the Loss threshold value, updating the center coordinates of the longitudinal parameter circular contour asAnd calculating the loss value again;
and when the maximum iteration times or the Loss value Loss is smaller than the Loss threshold value, solving to obtain the circle center coordinates.
5. The method of claim 1, wherein the obtaining historical stability data for the FPSO at a number of historical stability conditions during historical operation comprises:
acquiring first historical monitoring data acquired by a first position motion monitoring device and second historical monitoring data acquired by a second position motion monitoring device of the FPSO in a historical working process, wherein the historical monitoring data comprise position coordinates and six-degree-of-freedom motion data;
and screening out the period of time when the FPSO is in the history steady state according to the six-degree-of-freedom motion data in the history monitoring data, and extracting the history monitoring data of the FPSO in the history steady state as history steady data.
6. The method of claim 5, wherein screening out periods when the FPSO is in a historically stable state comprises:
and when the roll angular speed, the bow angular speed and the triaxial acceleration of the FPSO are smaller than the respective corresponding maximum threshold values within a period of a preset duration, and the stability of the pitch angular speed meets the stability requirement, determining that the FPSO is in a historical stable state.
7. The center offset determination method according to claim 6, wherein the stability of the pitch angle speed is determined to reach the stability requirement when the time domain profile of the pitch angle speed of the FPSO over a predetermined period of time, when the profile period ratio of the time domain profile of the pitch angle speed, in which both the waveform and the period are stable, reaches the duty ratio threshold, and otherwise, the stability of the pitch angle speed is determined not to reach the stability requirement.
8. The center shift amount determining method according to claim 6, wherein for any one of the motion data of the roll angular velocity, the yaw angular velocity, and the triaxial acceleration, the maximum threshold value corresponding to the motion data is determined based on the statistical values of all the history monitoring data.
9. The center offset determination method according to claim 1, wherein the parameter type of the hull longitudinal parameter is a pitching amplitude, a pitching angular acceleration, or a pitching acceleration of the FPSO hull.
10. The method of claim 1, wherein each of the position motion monitoring devices comprises an integrated GPS device for acquiring position coordinates and an IMU device for acquiring six degrees of freedom motion data.
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