A sea platform positioning method and device fusing local positioning and global positioning

Abstract

This invention proposes a method for positioning a marine platform that integrates local and global positioning. The method includes: acquiring the ship's absolute position and attitude information in a geodetic coordinate system using a global positioning module deployed on the ship; measuring the relative position and deflection angle data between the ship and the target platform using laser and microwave ranging sensors deployed on the ship; converting the absolute position, relative position, and deflection angle data to a local coordinate system centered on the target platform using a relative position transfer algorithm; fusing the global and local positioning data acquired by different sensors using a confidence metric-based dynamic fusion algorithm to generate high-precision ship position and attitude information; and synchronizing multiple ship data via wireless networking to simultaneously send the ship position and attitude information of multiple ships to a display interface, thereby achieving precise positioning of the ship and the target platform.

Description

Technical Field

[0001] This invention relates to the field of marine engineering positioning technology, specifically to a method and apparatus for positioning offshore platforms that integrates local and global positioning. Background Technology

[0002] With the increasing mobility of maritime operations, the use of dynamically positioned vessels for collaborative maritime operations is gradually replacing traditional mooring operations. Dynamically positioned vessel collaborative operations are playing an increasingly important role in the field of marine engineering, such as multi-vessel collaborative platform assembly and disassembly, offshore wind turbine installation via dynamically positioned vessels, and offshore rocket launches. Compared to traditional offshore mooring operations, dynamically positioned vessels save operation time and greatly improve operational efficiency, but they also place higher demands on the monitoring of the relative positions of multiple vessels.

[0003] Currently, mainstream ship positioning technologies include DGPS differential positioning systems, laser rangefinders, and microwave radar. DGPS differential positioning systems can provide all-weather, real-time, and continuous measurements for ships; however, their accuracy is affected by weather and the location of the measurement base station, resulting in significant signal deviations. Actual positioning accuracy at sea is only at the meter level, and their stability is poor for close-range collaborative operations involving multiple ships. Laser rangefinders and microwave rangefinders estimate distance and angle by capturing signal reflections from markers, achieving centimeter-level accuracy. However, considering the reflectivity and range limitations of markers, positioning becomes impossible once a ship's movement exceeds a certain area. Furthermore, current positioning software can only display the ship's own position, not its relative position to other participating ships, posing a significant challenge to synchronized movement among multiple vessels. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a method and apparatus for positioning offshore platforms that integrates local and global positioning. This method can accurately provide the position and orientation information of working vessels within a local area, providing guidance for multi-vehicle collaboration.

[0005] The technical solution of this invention is implemented as follows:

[0006] A method for positioning a marine platform that integrates local and global positioning includes the following steps:

[0007] Global positioning data acquisition: The ship's absolute position and attitude information in the geodetic coordinate system are acquired through a global positioning module deployed on the ship.

[0008] Local positioning data acquisition: The relative position and deflection angle between the ship and the target platform are measured by laser ranging sensors and microwave ranging sensors deployed on the ship;

[0009] Coordinate system transformation: The absolute position information, relative position, and deflection angle data are transformed to a local coordinate system centered on the target platform using a relative position transfer algorithm.

[0010] Multi-source data fusion: A dynamic fusion algorithm based on confidence measure is used to fuse the global positioning data and local positioning data acquired by different sensors to generate high-precision ship position information and ship attitude information;

[0011] Real-time display and communication: Through wireless networking, multiple ship data are synchronized, and the ship position information and attitude information of multiple ships are sent to the display interface in a synchronized manner to achieve precise positioning of ships and target platforms.

[0012] A further technical solution in this embodiment is that the relative position transfer algorithm includes a single-target capture mode coordinate transformation algorithm and a multi-target capture mode coordinate transformation algorithm; when the global positioning data and local positioning data come from a single ship, the single-target capture mode coordinate transformation algorithm is called; when the global positioning data and local positioning data come from no less than two ships, the multi-target capture mode coordinate transfer algorithm is called.

[0013] A further technical solution in this embodiment is that the single-target capture mode coordinate transfer algorithm includes the following steps:

[0014] By establishing a reference coordinate system based on the center of the target platform, the values ​​of the laser rangefinder sensor in this coordinate system can be obtained as follows:

[0015] X C =X target +x BS cosθ+y BS sinθ

[0016] Y C =Y target +y BS cosθ-x BS sinθ

[0017] The coordinates of the ship's center point in this coordinate system are:

[0018] X K =X target +(x BS+ x c )cosθ+(y BS +y c sinθ

[0019] Y K =Y target +(y BS +y c)cosθ-(x BS+ x c sinθ

[0020] Where, x c This represents the x-coordinate of the ship's center in the laser ranging sensor coordinate system.

[0021] y c This represents the ordinate of the ship's center in the laser rangefinder sensor coordinate system.

[0022] X target This indicates the x-coordinate of the marked point on the target platform under the platform's operational reference coordinates;

[0023] Y target This represents the ordinate of the marker point on the target platform in the platform's operational reference coordinates;

[0024] x BS This represents the coordinates relative to the S-axis returned by the laser rangefinder.

[0025] y BS This represents the coordinates relative to the B-axis returned by the laser rangefinder.

[0026] θ is the angle between the ship's bow and the longitudinal axis of the target platform. The angle between the ship and the due north direction is obtained by using an electric gyroscope. The angle between the ship and the longitudinal axis of the target platform is calculated based on the angle between the target platform and the northeast coordinate system.

[0027] A further technical solution in this embodiment is that the multi-target capture mode coordinate transformation algorithm includes the following steps:

[0028] A reference coordinate system for the operation is established with the center of the target platform as the datum, and the values ​​of the laser rangefinder sensor in this coordinate system are obtained as follows:

[0029] X C =X target +x AB

[0030] Y C =Y target +y AB

[0031] The coordinates of the ship's center point in this coordinate system are:

[0032] X K =x c cosθ+y c sinθ+X target +x AB

[0033] Y K =Y c cosθ+Xc sinθ+Y target +y AB

[0034] Where, x c This represents the x-coordinate of the ship's center in the laser ranging sensor coordinate system.

[0035] y c This represents the ordinate of the ship's center in the laser rangefinder sensor coordinate system.

[0036] X target This indicates the x-coordinate of the marked point on the jacket platform under the platform's operational reference coordinates.

[0037] Y target This indicates the ordinate of the marked point on the jacket platform in the platform's operational reference coordinates;

[0038] x AB This represents the coordinates relative to the A-axis returned by the laser rangefinder.

[0039] y AB This represents the coordinates relative to the B-axis returned by the laser rangefinder.

[0040] θ is the angle between the ship's bow and the longitudinal axis of the jacket platform.

[0041] A further technical solution in this embodiment is that the dynamic fusion algorithm includes:

[0042] Calculate the confidence interval for measurement data from similar sensors, and discard any sensor data that exceeds the threshold range.

[0043] Weights are dynamically assigned based on the variance of historical sensor data; the smaller the variance, the higher the weight.

[0044] The remaining valid data are fused using a weighted average method to output the final positioning result.

[0045] A further technical solution in this embodiment is that the calculation of the confidence interval for measurement data of similar sensors, and the rejection of sensor data if it exceeds the threshold range, includes the following steps:

[0046] Introducing variable d ij d ij This represents the confidence interval between two measurement data points, specifically:

[0047]

[0048] When there are m sensors of the same type, d ij The values ​​can form an m×m ordinal interval matrix D, whose expression is as follows:

[0049]

[0050] According to D m Find the relationship matrix R between them. ij The expression is as follows:

[0051]

[0052] Setting parameter K m In a single reference system, if the number of systems supporting the system's measurement data is greater than K m If the measurement data of the reference system is correct, then the measurement data of that location is considered correct; otherwise, the measurement data is considered incorrect.

[0053] A further technical solution in this embodiment is that the weight calculation of the measurement data includes the following steps:

[0054] Let the final result of data fusion be

[0055]

[0056] In the formula, ω i This represents the weight of the corresponding sensor measurement data, and ω i satisfy

[0057]

[0058] The total mean square error after data fusion is:

[0059]

[0060] Make σ 2 To minimize the variance, the following expression is obtained, and the weights are dynamically adjusted in real time:

[0061]

[0062] This embodiment also proposes a positioning device for implementing the method described above, which is installed on a ship and is characterized by comprising:

[0063] A global positioning module, including satellite positioning sensors configured at different locations on the ship to obtain absolute position information;

[0064] The local positioning module includes a laser rangefinder and a microwave radar arranged along the ship's side, used to capture reflective markers deployed on the target platform to measure the relative position and deflection angle data between the ship and the target platform;

[0065] Attitude detection module, including gyrocompass and attitude sensor, is used to measure the ship's heading and pitch angles;

[0066] The coordinate transformation module is used to transform the absolute position information, relative position, and deflection angle data to a local coordinate system centered on the target platform using a relative position transfer algorithm.

[0067] The data fusion module is used to fuse the global positioning data and local positioning data acquired by different sensors through a dynamic fusion algorithm based on confidence measure, so as to generate high-precision ship position information and ship attitude information.

[0068] The wireless communication module is used to achieve synchronous data transmission between multiple ships through a multi-point networking protocol.

[0069] A further technical solution in this embodiment is that the laser rangefinder is installed along the same side of the ship's hull or on the forecastle deck.

[0070] A further technical solution in this embodiment is that each ship is equipped with no less than three sets of satellite positioning sensors, three sets of electric compasses, and three attitude sensors.

[0071] Compared with the prior art, the present invention has the following advantages:

[0072] This invention employs the following methods: Global positioning data acquisition: The absolute position and attitude information of the ship in the geodetic coordinate system are acquired through a global positioning module deployed on the ship; Local positioning data acquisition: The relative position and deflection angle data between the ship and the target platform are measured through laser ranging sensors and microwave ranging sensors deployed on the ship; Coordinate system transformation: The absolute position information, relative position, and deflection angle data are transformed to a local coordinate system centered on the target platform using a relative position transfer algorithm; Multi-source data fusion: The global positioning data and local positioning data acquired by different sensors are fused using a dynamic fusion algorithm based on confidence measures to generate high-precision ship position and attitude information; Real-time display and communication: Data from multiple ships is synchronized through wireless networking, and the ship position and attitude information of multiple ships are simultaneously sent to the display interface to achieve precise positioning of the ship and the target platform.

[0073] This embodiment employs measurement systems based on different measurement principles, which complement each other through data fusion algorithms to obtain highly accurate and stable position information feedback. Furthermore, a wireless transmission system enables synchronous monitoring of multiple vessels, coupled with a visual display interface, making multi-vessel operations more intuitive and providing more precise guidance for multi-vessel operations. Attached Figure Description

[0074] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0075] Figure 1 This is a flowchart illustrating the steps of a method for merging local and global positioning of a marine platform according to the present invention.

[0076] Figure 2 This is a detailed flowchart of a method for locating offshore platforms that integrates local and global positioning according to the present invention.

[0077] Figure 3 This is a schematic diagram of the coordinate transfer algorithm for the single-target capture mode in this invention;

[0078] Figure 4 This is a schematic diagram of the coordinate transfer algorithm for the multi-target capture mode in this invention;

[0079] Figure 5 This is a schematic diagram of the structure of a positioning device according to the present invention;

[0080] Figure 6 This is an overall layout diagram of the positioning device in this invention. Detailed Implementation

[0081] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0082] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," "third," and "fourth," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0083] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0084] Large offshore facilities such as jackets, drilling platforms, and wind power facilities can currently be installed and dismantled using powered floating systems. This technology involves the positioning of multiple vessels relative to the target platform. Existing vessel positioning methods include GPS positioning, laser rangefinder positioning, and microwave radar positioning. From a global perspective, GPS positioning at sea offers meter-level accuracy and provides continuous, real-time measurements for vessels around the clock. However, its accuracy is significantly affected by weather and the location of the measurement base station, resulting in substantial deviations. It also exhibits poor stability for close-range collaborative operations involving multiple vessels. From a local perspective, laser and microwave positioning estimate distance and angle by capturing signal reflections from markers placed on the platform, achieving centimeter-level accuracy. However, considering the reflectivity and range limitations of these markers, positioning becomes impossible once the vessel's movement exceeds a certain area. Neither of these positioning methods can achieve precise positioning independently, and both have poor anti-interference capabilities, easily affected by environmental factors and platform obstructions. As ship dynamic positioning systems have evolved from DP-0 in the 1960s to the modern DP-2 and DP-3, the requirements for anti-interference capabilities have increased. Therefore, a single positioning method can no longer meet the current positioning needs of marine engineering.

[0085] Based on this, see Figures 1 to 2 This invention discloses a method for locating offshore platforms that integrates local and global positioning. The following description uses offshore platform dismantling operations as an example. The method includes the following steps:

[0086] S1 Global Positioning Data Acquisition: The absolute position and attitude information of the ship in the geodetic coordinate system are acquired through the global positioning module deployed on the ship;

[0087] Understandably, in this embodiment, the global positioning module uses the GPS positioning system, VRU attitude sensor, and gyrocompass commonly used on ships to obtain absolute position and attitude information, thereby reducing the system's operating costs. During offshore platform dismantling operations, when the dual-ship floating jacket platform is transferring loads, attitude monitoring between the ships is also necessary to gain an overall understanding of the ships' loading status. In terms of monitoring the ship's out-of-plane motion, the VRU attitude sensor typically uses a combination of accelerometers and gyroscopes to measure the tilt angles (roll and pitch). The built-in algorithm is used to acquire the raw sensor data and convert it into angles along the ship's three axes to reconstruct the ship's attitude at sea. The gyrocompass can determine the ship's heading. Since the ranging sensor used in local positioning cannot calculate the angle between the ship and the reference target, it is crucial to convert the phase angle using the northeast coordinate system as a reference for more accurate position calculation. Therefore, the gyrocompass, which autonomously finds true north and establishes a stable true north reference on the moving object to accurately determine the direction of the moving object's movement, can calculate the ship's heading angle precisely. With the cooperation of GPS and the gyrocompass, the ship's position and heading information can be restored in real time on the operating interface, providing accurate reference data for subsequent fusion.

[0088] S2 Local Positioning Data Acquisition: The relative position and deflection angle between the ship and the target platform are measured by laser ranging sensors and microwave ranging sensors deployed on the ship;

[0089] It is understandable that GPS-collected global data has relatively low accuracy, with actual positioning accuracy at sea at the meter level. This results in poor stability for the precise positioning requirements of close-range collaborative operations involving multiple vessels. Therefore, this embodiment further provides positioning data by using high-precision laser ranging radar and microwave ranging sensors within a local area, achieving a complementary effect. The choice of installation location is crucial for both the GPS system and the radar ranging sensor; they should be placed in areas with minimal obstruction to ensure measurement accuracy. Taking the collaborative demolition of a marine platform's superstructure by multiple vessels as an example, the location and number of laser ranging sensors vary depending on the semi-submersible vessel type. This embodiment primarily uses two types of semi-submersible vessels: Class X and Class K (both virtual classes). On the Class K semi-submersible vessel, two sensors are arranged along one side of the hull. It is important to note that the relative position of the laser ranging sensor on the semi-submersible vessel relative to the center of the deck must be accurately obtained; subsequent coordinate system conversions are based on this. To avoid signal obstruction during the vessel's approach to the platform, which would affect the continuity and accuracy of the measurement, the two sensors are arranged at a certain distance apart. There are also certain requirements regarding the distance between the sensor and the side of the ship carrying the load-bearing unit. Since the minimum measuring distance of the laser rangefinder is 10m, this must be considered during sensor installation. To achieve redundancy in the measurement principle, an additional set of radar rangefinder sensors is installed on both ships.

[0090] For the X-class semi-submersible vessel, a laser rangefinder and a radar rangefinder system are deployed on the forecastle deck, with their corresponding markers installed at the corresponding height on the jacket platform. The coordinates of these markers on the jacket platform are recorded. It is important to note that the line connecting the markers must be parallel to the Y-axis of the jacket platform (the length direction of the semi-submersible vessel).

[0091] Considering the relatively little shielding between the jacket platform and the X-class vessel, only redundancy in the measurement principle was taken into account, and only one additional set of radar ranging sensors was added. Positioning the sensors in the forecastle reduces the difficulty of outfitting and data transmission.

[0092] The positions of all the markers and sensors must be accurately determined during installation to ensure accurate distance conversion results are received. Regarding the installation height of the sensors, since the sensors receive signals at a certain pitch angle, their height should not exceed their adjustment range, provided that they are not obstructed.

[0093] The structure of microwave ranging sensors is very similar to that of laser ranging sensors, consisting of a radar computer host, a radar interrogator, a reflector, and a display. The installation location of the radar interrogator can be referenced from the laser ranging radar described above.

[0094] S3 coordinate system transformation: The absolute position information, relative position and deflection angle data are transformed to a local coordinate system centered on the target platform using a relative position transfer algorithm;

[0095] Specifically, after the position coordinates are read by the sensor, they are transformed to obtain a consistent description under a unified coordinate system. Taking the coordinate transformation of a laser rangefinder as an example, the coordinate transformation algorithm is derived. The feedback information of the laser rangefinder is inconsistent in different working modes. In this case, there are two situations: single-target acquisition mode coordinate transformation algorithm and multi-target acquisition mode coordinate transformation algorithm. When the global positioning data and local positioning data come from a single ship, the single-target acquisition mode coordinate transformation algorithm is called. When the global positioning data and local positioning data come from no less than two ships, the multi-target acquisition mode coordinate transformation algorithm is called.

[0096] For single-target acquisition mode, the coordinates output by the sensor are as follows: Figure 4 As shown, since the angle between the semi-submersible vessel and the jacket platform cannot be determined during single-target acquisition, the angle between the platform's longitudinal axis and the semi-submersible vessel's bow axis can only be calculated using data from the vessel's own gyrocompass as the basis for coordinate system transformation. The coordinate transformation algorithm includes the following steps:

[0097] By establishing a reference coordinate system based on the center of the target platform, the values ​​of the laser rangefinder sensor in this coordinate system can be obtained as follows:

[0098] X C =X target +x BS cosθ+y BS sinθ

[0099] Y C =Y target +y BS cosθ-x BS sinθ

[0100] The coordinates of the ship's center point in this coordinate system are:

[0101] X K =X target +(x BS+ x c )cosθ+(y BS +y c sinθ

[0102] Y K =Y target +(y BS +y c )cosθ-(x BS+ xc sinθ

[0103] Where, x c This represents the x-coordinate of the ship's center in the laser ranging sensor coordinate system.

[0104] y c This represents the ordinate of the ship's center in the laser rangefinder sensor coordinate system.

[0105] X target This indicates the x-coordinate of the marked point on the target platform under the platform's operational reference coordinates;

[0106] Y target This represents the ordinate of the marker point on the target platform in the platform's operational reference coordinates;

[0107] x BS This represents the coordinates relative to the S-axis returned by the laser rangefinder.

[0108] y BS This represents the coordinates relative to the B-axis returned by the laser rangefinder.

[0109] θ is the angle between the ship's bow and the longitudinal axis of the target platform. The angle between the ship and the due north direction is obtained by using an electric gyroscope. The angle between the ship and the longitudinal axis of the target platform is calculated based on the known angle between the target platform and the northeast coordinate system.

[0110] For multi-target capture modes, such as Figure 3 As shown, a unified standard is used, with a right-handed rotating coordinate system originating from a selected reference point. Under this definition, the angle output by the sensor is the angle between the ship's bow and the longitudinal axis of the jacket platform to be dismantled. The coordinate transformation algorithm includes the following steps:

[0111] A reference coordinate system for the operation is established with the center of the target platform as the datum, and the values ​​of the laser rangefinder sensor in this coordinate system are obtained as follows:

[0112] X C =X target +x AB

[0113] Y C =Y target +y AB

[0114] The coordinates of the ship's center point in this coordinate system are:

[0115] X K =x c cosθ+y c sinθ+X target +x AB

[0116] Y K =Y c cosθ+X c sinθ+Y target +y AB

[0117] Where, x c This represents the x-coordinate of the ship's center in the laser ranging sensor coordinate system.

[0118] y c This represents the ordinate of the ship's center in the laser rangefinder sensor coordinate system.

[0119] X target This indicates the x-coordinate of the marked point on the jacket platform under the platform's operational reference coordinates.

[0120] Y target This indicates the ordinate of the marked point on the jacket platform in the platform's operational reference coordinates;

[0121] x AB This represents the coordinates relative to the A-axis returned by the laser rangefinder.

[0122] y AB This represents the coordinates relative to the B-axis returned by the laser rangefinder.

[0123] θ is the angle between the ship's bow and the longitudinal axis of the jacket platform.

[0124] S4 Multi-source data fusion: A dynamic fusion algorithm based on confidence measure is used to fuse the global positioning data and local positioning data acquired by different sensors to generate high-precision ship position information and ship attitude information.

[0125] Specifically, multi-sensor data fusion technology analyzes data from multiple different types of sensors separately and then synthesizes them to obtain a more reliable and accurate optimal value. This embodiment employs a dynamic data fusion algorithm based on confidence intervals. This method primarily identifies the interrelationships between measurement data from sensors of the same type. If the measurement data from sensors of this type are close, the data is considered fusionable and reliable; if a measurement data point differs significantly from the others, it is considered unreliable and not included in the fusion process. The specific method is as follows:

[0126] First, we introduce a variable d. ij The expression is as follows:

[0127]

[0128] In the formula, d ij This represents the confidence interval between two measurements. Where d ij The physical meaning is: if xi The probability density function is P i (x), then d ij This is represented by the probability density curve P. i (x) below x i and x j The area of ​​the region between x. i and x j The greater the distance between them, the greater the interval d ij The larger the value, the greater the difference between the measurements from the two sensors. ij The range of values ​​for is 0 ≤ d ij ≤1. When there are m sensors of the same type, d ij The values ​​can form an m×m orientation interval matrix D.

[0129] The orientation interval matrix D is calculated as follows:

[0130] Assuming the measurement data all follow a normal distribution, the expression is as follows:

[0131]

[0132] In the formula, x i Let represent the measurement value of the i-th sensor (i = 1, 2, ..., n). To measure variance, and in the above formula

[0133] There are n sensors measuring the ship's position, and the measurement data is X. i (i = 1, 2, ..., n), and the measurement data all follow a normal distribution. Because different sensors have different characteristics, the measured data X i Their characteristics also differ.

[0134] From the knowledge of normal distribution, we can obtain σ 2 σ represents the degree to which the data deviates from the mean. 2 The larger the value, the greater the deviation, and vice versa; μ represents the mean of the measurement data. From a statistical perspective, μ is the value closest to the ship's true position and can be obtained from historical data; from a probabilistic perspective, the median value has the highest probability of being close to the true value. Therefore, the median value of n sensor measurements can be used as the value of each historical data point. In this embodiment, the platform dismantling operation requires three ships, so the GPS position measurement system consists of three sets of global satellite positioning systems. The measurement data of the three sets of sensors are arranged from smallest to largest, and the median value of the three values ​​is taken. The N consecutive historical data points obtained above are denoted as x. m (m=1,2,…,N), then the mean μ is:

[0135]

[0136] If the first N consecutive historical data of a certain sensor are X m (m=1,2,…,N), then σ 2 for:

[0137]

[0138] Therefore, d ij The error function erf(θ) can be used to obtain the value. The expression for erf(θ) is as follows:

[0139]

[0140] Assumption The above formula can then be further written as:

[0141]

[0142] Again but

[0143]

[0144] Right now

[0145]

[0146] When there are multiple data points from the same type of sensor, the confidence intervals between each measurement and other measurement data can form a matrix. For example, if there are m position reference systems, the confidence matrix of the measured ship position data can be represented as:

[0147]

[0148] The number of location reference systems is m=3, resulting in the confidence interval matrix D. m Then according to D m Find the relationship matrix R between them. ij The elements in the relation matrix are calculated as follows:

[0149]

[0150] In the formula, β ij d was obtained through experiments ij The boundary value, r ij =0 indicates that the data measured by the i-th sensor and the j-th sensor are mutually incompatible, r ij =1 indicates that the data measured by the i-th sensor and the j-th sensor support each other. Therefore, the relationship matrix R m for:

[0151]

[0152] Set a K m For a given location reference system in this paper, if the number of systems supporting the system's measurement data is greater than K... m If the measurement data from the location reference system is correct, it is considered correct; otherwise, it is considered incorrect. After eliminating erroneous data through the algorithm, the remaining data is considered to have high reliability. Then, weights are calculated on the remaining correct measurement data to obtain the final fused data. Considering that there are only three sets of location reference systems and the redundancy of the other sensors is not high, determining the weights based on the level of support would lead to insufficient accuracy. Therefore, the weight calculation method adopted in this embodiment is to determine the weights based on the variance of the measurement data of the remaining sensors after elimination.

[0153] According to the knowledge of normal distribution, σ 2 A larger σ value indicates a greater deviation of the measured data from the mean and a greater fluctuation in the data, meaning that the sensor's measurement accuracy is lower. Conversely, a smaller σ value indicates a lower accuracy. 2 The smaller the value, the smaller the fluctuation in the measurement data, indicating higher sensor accuracy. Therefore, it is necessary to increase the weight of high-accuracy measurement data in data fusion to achieve optimal fusion results and obtain more accurate and reliable fused data. The specific derivation of how to calculate this weight is as follows.

[0154] Assuming the final result of data fusion is

[0155]

[0156] In the formula, ω i This represents the weight of the corresponding sensor measurement data, and ω i satisfy

[0157]

[0158] The total mean square error after data fusion is:

[0159]

[0160] As can be derived from the above formula, to make data fusion more accurate and reliable, σ 2 To minimize this value, we need to find the minimum value of the aforementioned multivariate quadratic function. Based on the extremum theorem, we introduce a correction function:

[0161]

[0162] Find ω on both sides of the above equation i partial derivatives

[0163]

[0164] when When the time is right, the correction function F reaches its minimum value, so we can solve the equation:

[0165]

[0166] have to:

[0167]

[0168] because so therefore,

[0169]

[0170] The weights of the measurement data from each sensor can be obtained from the above formula, so that the data fusion result is optimal. In this algorithm, the variance can be calculated in real time as the data is transmitted, and the weights can be dynamically adjusted.

[0171] S5 Real-time Display and Communication: Synchronizes data from multiple vessels through wireless networking, sending the vessel position and attitude information of multiple vessels to the display interface simultaneously to achieve precise positioning of vessels and target platforms.

[0172] Understandably, for communication between three ships at sea, each ship has a switch installed at its bow and stern. The system framework includes a low-level sensor layer, a low-level industrial control computer layer, an operation control interface, and a wireless communication system layer. The low-level sensor layer includes the position measurement sensors listed above; the low-level industrial control computer mainly performs unpacking, analysis, and fusion processing of sensor data, forwards messages from its own ship, receives information from other ships or targets, and finally packages and sends it to the operation control interface; the control interface unpacks the summarized data, provides visual display and corresponding conversions for easy operation; the wireless transmission system provides a means of communication between different ships, ensuring smooth information transmission and reception.

[0173] Example 2

[0174] This embodiment proposes a positioning device for implementing Embodiment 1, using platform dismantling operations as an example. Platform dismantling is a very complex task. After the engineering vessel arrives at the designated area, before the dismantling work begins, the reflective markers of the laser rangefinder and microwave radar rangefinder must be installed on the jacket leg. During the transfer, two K-class vessels and one X-class vessel are required. By adjusting the ballast water system of the engineering vessel, the draft is changed to achieve the required freeboard and heel angle. The K-class vessel approaches the docking position, and the two K-class vessels adjust the ballast water system to change the draft, gradually lifting the superstructure and transferring the platform weight from the jacket to the two K-class vessels. Ballasting and buoyancy continue until the platform's load-bearing structure is transferred from the jacket to the two K-class vessels, ensuring sufficient safety clearance between the superstructure and the top of the jacket. This embodiment installs a positioning device on the vessel and applies the positioning method in Embodiment 1 to monitor the corresponding vessel position and attitude data in real time. Specifically, the positioning device includes:

[0175] The global positioning module 101 includes satellite positioning sensors configured at different locations on the ship to obtain absolute position information;

[0176] The local positioning module 102 includes a laser rangefinder and a microwave radar arranged along the ship's side, used to capture reflective markers deployed on the target platform to measure the relative position and deflection angle data between the ship and the target platform;

[0177] Furthermore, laser ranging sensors are installed on Class X and Class K vessels. For the Class K semi-submersible vessel, two sensors are arranged along one side of the hull. To avoid signal obstruction during the vessel's approach to the platform, which could affect measurement continuity and accuracy, the two sensors are spaced a certain distance apart. There are also specific requirements regarding the distance between the sensors and the hull side containing the support unit; since the minimum measurement distance for the laser ranging sensor is 10m, this must be considered during sensor installation. To achieve redundancy in the measurement principle, a set of radar ranging sensors is also installed on both vessels. For the Class X semi-submersible vessel, one laser ranging sensor and one radar ranging sensor system are deployed on the forecastle deck, with their corresponding markers installed at the corresponding height on the jacket platform. The position coordinates of the markers on the jacket platform are recorded. It is important to note that the line connecting the markers is parallel to the Y-axis of the jacket platform (the length direction of the semi-submersible vessel). Since the X-class semi-submersible vessel approaches from one side of the platform, there is less obstruction between the jacket platform and the X-class vessel. Only an additional set of radar ranging sensors needs to be added. Placing the sensors on the forecastle can reduce the difficulty of outfitting and data transmission.

[0178] Furthermore, the structure of microwave ranging sensors is very similar to that of laser ranging sensors, consisting of a radar computer host, a radar interrogator, a reflector, and a display. The installation location of the radar interrogator can be referenced from the laser ranging radar described above.

[0179] Attitude detection module 103, including an electric compass and an attitude sensor, is used to measure the ship's heading and roll and pitch angles;

[0180] The coordinate transformation module 104 is used to transform the absolute position information, relative position and deflection angle data to a local coordinate system centered on the target platform through a relative position transfer algorithm.

[0181] The data fusion module 105 is used to fuse the global positioning data and local positioning data acquired by different sensors through a dynamic fusion algorithm based on confidence measure to generate high-precision ship position information and ship attitude information.

[0182] The relative position transfer algorithm and the dynamic fusion algorithm have been described in detail in Example 1, and will not be repeated here.

[0183] The wireless communication module 106 is used to achieve synchronous data transmission between multiple ships through a multi-point networking protocol.

[0184] It is understandable that switches are installed at the bow and stern of each ship to enable communication networking between ships.

[0185] Furthermore, each vessel is equipped with no fewer than three sets of satellite positioning sensors, three sets of gyrocompasses, and three sets of attitude sensors to meet the equipment redundancy requirements of the DP2 dynamic positioning floating platform technology.

[0186] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for positioning a marine platform that integrates local and global positioning, characterized in that, Includes the following steps: Global positioning data acquisition: The ship's absolute position and attitude information in the geodetic coordinate system are acquired through a global positioning module deployed on the ship. Local positioning data acquisition: The relative position and deflection angle between the ship and the target platform are measured by laser ranging sensors and microwave ranging sensors deployed on the ship; Coordinate system transformation: The absolute position information, relative position, and deflection angle data are transformed to a local coordinate system centered on the target platform using a relative position transfer algorithm. Multi-source data fusion: A dynamic fusion algorithm based on confidence measure is used to fuse the global positioning data and local positioning data acquired by different sensors to generate high-precision ship position information and ship attitude information; Real-time display and communication: Through wireless networking, multiple ship data are synchronized, and the ship position information and attitude information of multiple ships are sent to the display interface in a synchronized manner to achieve precise positioning of ships and target platforms.

2. The offshore platform positioning method integrating local and global positioning according to claim 1, characterized in that, The relative position transfer algorithm includes a single-target capture mode coordinate transformation algorithm and a multi-target capture mode coordinate transformation algorithm. When the global positioning data and local positioning data come from a single vessel, the single-target capture mode coordinate transformation algorithm is invoked. When the global positioning data and local positioning data come from at least two vessels, the multi-target capture mode coordinate transfer algorithm is invoked.

3. The offshore platform positioning method integrating local and global positioning according to claim 2, characterized in that, The single-target capture mode coordinate transfer algorithm includes the following steps: By establishing a reference coordinate system based on the center of the target platform, the values ​​of the laser rangefinder sensor in this coordinate system can be obtained as follows: ； ； The coordinates of the ship's center point in this coordinate system are: ； ； in, This represents the x-coordinate of the ship's center in the laser ranging sensor coordinate system. This represents the ordinate of the ship's center in the laser rangefinder sensor coordinate system. This indicates the x-coordinate of the marked point on the target platform under the platform's operational reference coordinates; This represents the ordinate of the marker point on the target platform in the platform's operational reference coordinates; This represents the coordinates relative to the S-axis returned by the laser rangefinder. This represents the coordinates relative to the B-axis returned by the laser rangefinder. The angle between the ship's bow and the longitudinal axis of the target platform is determined by obtaining the angle data between the ship and the due north direction using an electric gyroscope. Based on the angle data between the target platform and the northeast coordinate system, the angle between the ship and the longitudinal axis of the target platform is calculated.

4. The offshore platform positioning method integrating local and global positioning according to claim 2, characterized in that, The multi-target capture mode coordinate transformation algorithm includes the following steps: A reference coordinate system for the operation is established with the center of the target platform as the datum, and the values ​​of the laser rangefinder sensor in this coordinate system are obtained as follows: ； ； The coordinates of the ship's center point in this coordinate system are: ； ； in, This represents the x-coordinate of the ship's center in the laser ranging sensor coordinate system. This represents the ordinate of the ship's center in the laser rangefinder sensor coordinate system. This indicates the x-coordinate of the marked point on the jacket platform under the platform's operational reference coordinates. This indicates the ordinate of the marked point on the jacket platform in the platform's operational reference coordinates; This represents the coordinates relative to the A-axis returned by the laser rangefinder. This represents the coordinates relative to the B-axis returned by the laser rangefinder. The angle between the ship's bow and the longitudinal axis of the jacket platform.

5. The offshore platform positioning method integrating local and global positioning according to claim 1, characterized in that, The dynamic fusion algorithm includes: Calculate the confidence interval for measurement data from similar sensors, and discard any sensor data that exceeds the threshold range. Weights are dynamically assigned based on the variance of historical sensor data; the smaller the variance, the higher the weight. The remaining valid data are fused using a weighted average method to output the final positioning result.

6. The offshore platform positioning method integrating local and global positioning according to claim 5, characterized in that, The process of calculating the confidence interval for measurement data from similar sensors, and discarding data from a sensor if it exceeds a threshold range, includes the following steps: Introducing variables , This represents the confidence interval between two measurement data points, specifically: ； When there are sensors of the same type At that time, The values ​​can form a The set interval matrix Its expression is as follows: ； according to Find the relationship matrix between them. The expression is as follows: ； Setting parameters In a single reference system, if the number of systems supporting the system's measurement data is greater than... If the measurement data of the reference system is correct, then the measurement data of that location is considered correct; otherwise, the measurement data is considered incorrect.

7. The offshore platform positioning method integrating local and global positioning according to claim 5, characterized in that, The weighting calculation of the measurement data includes the following steps: Let the final result of data fusion be : ； In the formula, This represents the weight of the corresponding sensor measurement data, and satisfy ； The total mean square error after data fusion is: ； make To minimize the variance, the following expression is obtained, and the weights are dynamically adjusted in real time: 。 8. A positioning device for implementing the method according to any one of claims 1-7, disposed on a ship, characterized in that, include: A global positioning module, including satellite positioning sensors configured at different locations on the ship to obtain absolute position information; The local positioning module includes a laser rangefinder and a microwave radar arranged along the ship's side, used to capture reflective markers deployed on the target platform to measure the relative position and deflection angle data between the ship and the target platform; Attitude detection module, including gyrocompass and attitude sensor, is used to measure the ship's heading and pitch angles; The coordinate transformation module is used to transform the absolute position information, relative position, and deflection angle data to a local coordinate system centered on the target platform using a relative position transfer algorithm. The data fusion module is used to fuse the global positioning data and local positioning data acquired by different sensors through a dynamic fusion algorithm based on confidence measure, so as to generate high-precision ship position information and ship attitude information. The wireless communication module is used to achieve synchronous data transmission between multiple ships through a multi-point networking protocol.

9. The positioning device according to claim 8, characterized in that, It includes at least two laser rangefinders, which are positioned along the same side of the ship's hull or on the forecastle deck.

10. The positioning device according to claim 8, characterized in that, Each vessel is equipped with no fewer than three sets of satellite positioning sensors, three sets of electric compasses, and three attitude sensors.

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