Local positioning and global positioning integrated offshore platform positioning method and device

Abstract

The invention provides an offshore platform positioning method fusing local positioning and global positioning. The method comprises the following steps: acquiring absolute position information and attitude information of a ship under a geodetic coordinate system through a global positioning module deployed on the ship; the relative position and deflection angle data between the ship and the target platform are measured through a laser distance measuring sensor and a microwave distance measuring sensor which are arranged on the ship; a relative position transfer algorithm is adopted to convert the absolute position information, the relative position and the deflection angle data to a local coordinate system with the target platform as the center; performing data fusion on the global positioning data and the local positioning data acquired by different sensors by adopting a dynamic fusion algorithm based on confidence measurement to generate high-precision ship position information and ship attitude information; multi-ship data are synchronized through wireless networking, and ship position information and ship attitude information of multiple ships are synchronously sent to a display interface, so that accurate positioning of the ships and a target platform is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore engineering positioning, and particularly relates to a positioning method and device for an offshore platform that integrates local positioning and global positioning. Background Art

[0002] With the motorization of offshore operations, the use of dynamically positioned vessels for offshore collaborative operations is gradually replacing the original mooring operations. Dynamically positioned vessel collaborative operations play an increasingly important role in the field of offshore engineering, such as scenarios like multi-vessel collaborative disassembly and assembly of platforms, installation of offshore wind turbines by dynamically positioned vessels, and offshore rocket launches. Compared with traditional offshore mooring operations, dynamically positioned vessels save operation time and greatly improve operation efficiency, but they also pose further requirements for the monitoring of the relative positions between multiple vessels.

[0003] The current mainstream ship positioning technologies include DGPS differential positioning systems, laser ranging sensors, microwave radars, etc. The DGPS differential positioning system can provide all-weather real-time continuous measurements for ships, but its accuracy is affected by weather and the measurement base station, and there are large deviations in the signals. The actual positioning accuracy at sea is at the meter level, and the stability for multi-vessel close-range collaborative operations is poor; laser ranging radars and microwave ranging sensors estimate distances and angles by capturing the signal reflections of markers, and the accuracy can reach the centimeter level. However, considering the reflection ability and range limitations of the markers, positioning cannot be performed when the activities of the ship exceed a certain area. In addition, current positioning software can only display the position of the ship itself and cannot display the relative positions between the ship and other ships participating in the operation, which poses a huge challenge to the synchronous movement between multiple vessels. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention proposes a positioning method and device for an offshore platform that integrates local positioning and global positioning, which can accurately provide the pose information of the working ships in a local area and provide guidance for multi-vessel cooperation.

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

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

[0007] Global positioning data acquisition: Obtain the absolute position information and attitude information of the ship in the geodetic coordinate system through a global positioning module deployed on the ship;

[0008] Local positioning data acquisition: Measure the relative position and deflection angle data between the ship and the target platform through a laser ranging sensor and a microwave ranging sensor deployed on the ship;

[0009] Coordinate system conversion: The absolute position information, relative position, and declination data are respectively converted to a local coordinate system centered on the target platform by using a relative position transfer algorithm;

[0010] Multi-source data fusion: The global positioning data and local positioning data obtained by different sensors are fused by using a dynamic fusion algorithm based on confidence measure to generate high-precision ship position information and ship attitude information;

[0011] Real-time display and communication: The ship data of multiple ships are synchronized through wireless networking, and the ship position information and ship attitude information of multiple ships are synchronously sent to the display interface to achieve accurate positioning of the ship and the target platform.

[0012] A further technical solution of this embodiment is that the relative position transfer algorithm includes a single-target capture mode coordinate conversion algorithm and a multi-target capture mode coordinate conversion algorithm; when the global positioning data and local positioning data come from a single ship, the single-target capture mode coordinate conversion algorithm is called, and 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 of this embodiment is that the single-target capture mode coordinate transfer algorithm includes the following steps:

[0014] Taking the center of the target platform as a reference to establish an operation reference coordinate system, the value of the laser range finder in this coordinate system can be obtained as:

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

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

[0017] The coordinate value of the ship center point in this coordinate system is:

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

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

[0020] where x c represents the abscissa of the ship center in the coordinates of the laser ranging sensor;

[0021] y c represents the ordinate of the ship center in the coordinates of the laser ranging sensor;

[0022] X target represents the abscissa of the marked point on the target platform in the platform operation reference coordinates;

[0023] Y target represents the ordinate of the marked point on the target platform in the platform operation reference coordinates;

[0024] x BS represents the coordinate relative to the S axis returned by the laser ranging sensor;

[0025] y BS represents the coordinate relative to the B axis returned by the laser ranging sensor;

[0026] θ is the angle between the ship's bow direction and the longitudinal axis of the target platform. The angle data between the ship and the due north direction is obtained through a gyrocompass, and the angle between the ship and the longitudinal axis of the target platform is calculated based on the angle data between the target platform and the north-east coordinate system.

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

[0028] Taking the center of the target platform as the reference, establish an operation reference coordinate system, and the values of the laser ranging sensor in this coordinate system are:

[0029] X C = X target + x AB

[0030] Y C = Y target + y AB

[0031] The coordinate value of the ship center point in this coordinate system is:

[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 represents the abscissa of the ship center under the coordinates of the laser ranging sensor;

[0035] y c represents the ordinate of the ship center under the coordinates of the laser ranging sensor;

[0036] X target represents the abscissa of the marked point on the jacket platform under the platform operation reference coordinates;

[0037] Y target represents the ordinate of the marked point on the jacket platform under the platform operation reference coordinates;

[0038] x AB represents the coordinate relative to the A-axis returned by the laser ranging sensor;

[0039] y AB represents the coordinate relative to the B-axis returned by the laser ranging sensor;

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

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

[0042] Calculating the confidence interval of the measurement data of the same type of sensors, and rejecting the data of a certain sensor if it exceeds the threshold range;

[0043] Dynamically allocating weights according to the variance of the historical data of the sensors, and the smaller the variance, the higher the weight;

[0044] Using the weighted average method to fuse the remaining valid data and output the final positioning result.

[0045] A further technical solution of this embodiment is that calculating the confidence interval of the measurement data of the same type of sensors and rejecting the data of a certain sensor if it exceeds the threshold range includes the following steps:

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

[0047]

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

[0049]

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

[0051]

[0052] Set the parameter K m , in a single reference system, if the number of systems supporting the measurement data of this system is greater than K m , then it is considered that the measurement data of this position reference system is correct, otherwise it is considered that the measurement data is incorrect.

[0053] A further technical solution of 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 represents the weight value occupied by the corresponding sensor measurement data, and ω i satisfies

[0057]

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

[0059]

[0060] Make σ 2 the smallest, obtain the following expression, calculate the variance size in real time, and dynamically adjust the weight value:

[0061]

[0062] In this embodiment, a positioning device for implementing the above method is also proposed, which is arranged on a ship and is characterized by including:

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

[0064] A local positioning module, including laser ranging sensors and microwave radars arranged along the ship's side, used to capture the reflection markers deployed on the target platform to measure the relative position and deflection angle data between the ship and the target platform;

[0065] An attitude detection module, including a gyrocompass and an attitude sensor, used to measure the ship's heading and roll and pitch angles;

[0066] A coordinate conversion module, which is used to convert the absolute position information, relative position and declination data to a local coordinate system centered on the target platform through a relative position transfer algorithm;

[0067] A data fusion module, which is used to perform data fusion on the global positioning data and local positioning data obtained by different sensors through a dynamic fusion algorithm based on confidence measure to generate high-precision ship position information and ship attitude information;

[0068] A wireless communication module, which is used to realize synchronous data transmission among multiple ships through a multi-point networking protocol.

[0069] A further technical solution of this embodiment is that the laser range sensors are arranged on the same side of the ship's side or on the forecastle deck.

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

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

[0072] In the present invention, global positioning data acquisition: the absolute position information and attitude information of the ship in the geodetic coordinate system are obtained through a global positioning module deployed on the ship; local positioning data acquisition: the relative position and declination data between the ship and the target platform are measured through laser range sensors and microwave range sensors deployed on the ship; coordinate system unified conversion: the relative position transfer algorithm is used to convert the absolute position information, relative position and declination data to a local coordinate system centered on the target platform respectively; multi-source data fusion: a dynamic fusion algorithm based on confidence measure is used to perform data fusion on the global positioning data and local positioning data obtained by different sensors to generate high-precision ship position information and ship attitude information; real-time display and communication: the data of multiple ships are synchronized through wireless networking, and the ship position information and ship attitude information of multiple ships are synchronously sent to the display interface to achieve precise positioning of the ship and the target platform.

[0073] In this embodiment, by adopting measurement systems with different measurement principles and complementing each other through a data fusion algorithm, high-precision and strong-stability position information feedback is obtained. In addition, through a wireless transmission system, synchronous monitoring of multiple ships is realized, and with a visual display interface, the operation of multiple ships is made more intuitive, providing more accurate guidance for multiple-ship operations. Description of the Drawings

[0074] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0075] Figure 1 It is a flowchart of the steps of a positioning method for an offshore platform that integrates local positioning and global positioning according to the present invention;

[0076] Figure 2 It is a detailed flowchart of a positioning method for an offshore platform that integrates local positioning and global positioning according to the present invention;

[0077] Figure 3 It is a schematic diagram of the coordinate transfer algorithm for the single-target capture mode according to the present invention;

[0078] Figure 4 It is a schematic diagram of the coordinate transfer algorithm for the multi-target capture mode according to the present invention;

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

[0080] Figure 6 It is an overall layout diagram of the positioning device according to the present invention. Specific embodiments

[0081] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0082] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third", "fourth", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0083] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0084] Large offshore facilities such as jacket platforms, drilling platforms, and wind power facilities can currently be installed and disassembled by the method of dynamic floating installation. This technology involves the position positioning of multiple ships and the target platform. The existing ship positioning methods include GPS positioning, laser ranging sensor positioning, and microwave radar positioning. From a global perspective, the actual positioning accuracy of GPS at sea is at the meter level, which can provide all-weather real-time continuous measurement for ships. However, its accuracy is affected by weather and the measurement base station, and there are large deviations. For the cooperative operation of multiple ships at close range, the stability is poor. From a local perspective, laser positioning and microwave positioning estimate the distance and angle by capturing the signal reflection of the markers set on the platform, and the accuracy can reach the centimeter level. However, considering the reflection ability and range limitation of the markers, the ship cannot be positioned after its activity exceeds a certain area. When used independently, neither of the two positioning methods can achieve accurate positioning, and the anti-interference ability is poor, and it is easily affected by factors such as the environment and platform occlusion. With the development of the ship dynamic positioning system from DP-0 in the 1960s to the modern DP-2 and DP-3, the requirement for anti-interference ability has been improved. Therefore, a single positioning method can no longer meet the existing offshore engineering positioning requirements.

[0085] Based on this, see Figures 1 to 2 , an embodiment of the present invention discloses a positioning method for an offshore platform that integrates local positioning and global positioning. Taking the demolition operation of an offshore platform as an example, this method includes the following steps:

[0086] S1 Global positioning data acquisition: Obtain the absolute position information and attitude information of the ship in the geodetic coordinate system through the global positioning module deployed on the ship;

[0087] It can be understood that in this embodiment, the global positioning module uses the commonly used GPS positioning system, VRU attitude sensor and gyrocompass on the ship to obtain the absolute position information and attitude information, so as to reduce the use cost of the system. During the operation of offshore platform demolition, when the double-ship floating jacket platform transfers the load, the attitude monitoring between the ships is also necessary, so as to have an overall understanding of the loading state of the ships. In terms of the out-of-plane motion monitoring of the ships, the VRU attitude sensor usually uses the combination of an accelerometer and a gyroscope to measure the tilt angles (roll and pitch), and the built-in algorithm is used to obtain the original sensor data and convert it into the angles in the three-axis directions of the ship, so as to restore the attitude of the ship at sea. The gyrocompass can determine the heading of the ship's bow. Since the ranging sensors used in local positioning cannot calculate the included angle between the current ship and the reference target, it is crucial to perform the conversion of the phase included angle based on the north-east coordinate system at this time for more accurate position calculation. Therefore, the gyrocompass that autonomously finds the true north and establishes a stable true north azimuth reference on the moving object to accurately determine the moving direction of the moving object can calculate the accurate bow angle of the ship. Through the cooperation of the GPS and the gyrocompass, the position and heading information of the ship are restored in real time on the operation interface, providing accurate reference data for subsequent fusion.

[0088] S2 Local positioning data acquisition: Measure the relative position and deflection angle data between the ship and the target platform through the laser ranging sensor and microwave ranging sensor deployed on the ship;

[0089] It is understandable that due to the relatively low accuracy of the global data collected by GPS, the actual positioning accuracy at sea is at the meter level, and it has poor stability for the precise positioning requirements of multi-ship close-range collaborative operations. Therefore, in this embodiment, a lidar and a microwave ranging sensor with high accuracy in a local range are further provided to provide positioning data, achieving a complementary effect. Whether it is a GPS system or a radar ranging sensor, the selection of the installation position is crucial, and both should be placed in an area with less occlusion to ensure the measurement accuracy. Taking the multi-ship collaborative demolition of the superstructure of an offshore platform as an example, first, the positions and quantities of lidar sensors installed for different semi-submersible ship types are different. In this embodiment, two types of semi-submersible ships, namely X-class and K-class (both are virtual classes), are mainly used. Among them, two sensors of the K-class semi-submersible ship are arranged along one side of the ship's hull. It should be noted here that the relative position of the lidar sensor relative to the center of the ship's deck on the semi-submersible ship must be accurately obtained, and the subsequent coordinate system conversion is based on this to avoid signal occlusion during the approach of the ship to the platform, affecting the continuity and accuracy of the measurement. The two sensors are arranged at a certain distance apart. At the same time, there are also certain requirements for the distance between the sensor and the side of the ship equipped with the loading unit. Since the minimum measurement distance of the lidar sensor is 10m, this point should also be considered when installing the sensor. In order to achieve redundancy in the measurement principle, a set of radar ranging sensors is installed on two ships.

[0090] For the X-class semi-submersible ship, a lidar sensor and a radar ranging sensor system are arranged on the forecastle deck, and their corresponding marker points are installed at the corresponding height of the jacket. Record the position coordinates of the marker points on the jacket platform. It should be noted here that the installation connection line of the marker points is parallel to the Y-axis (the length direction of the semi-submersible ship) of the jacket platform.

[0091] Considering that there is less occlusion between the jacket platform and the X-class ship, only the redundancy of the measurement principle is considered, and only an additional set of radar ranging sensors is added. Arranging the sensors on the forecastle can reduce the difficulty of outfitting and data transmission.

[0092] The positions of all the above markers and sensors must be accurately mastered during installation to ensure accurate distance conversion results. For the installation height of the sensors, the sensors receive signals at a certain pitch angle. Therefore, when arranging the sensors, on the premise of not being occluded, their height should not exceed their adjustment range.

[0093] The composition of the microwave ranging sensor is very similar to that of the lidar sensor, and it is divided into a radar computer host, a radar interrogator, a reflector and a display. The installation position of the radar interrogator can refer to the above-mentioned lidar.

[0094] S3 Coordinate System Transformation I: The absolute position information, relative position, and declination data are respectively transformed into a local coordinate system centered on the target platform by 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 in a unified coordinate system. Taking the coordinate transformation of the laser ranging sensor as an example, the derivation of the coordinate transformation algorithm is carried out. The feedback information of the laser ranging sensor in different working modes is inconsistent. In this case, it is divided into two situations: namely, the coordinate transformation algorithm for the single-target capture mode and the coordinate transformation algorithm for the multi-target capture mode; when the global positioning data and local positioning data come from a single ship, the single-target capture mode coordinate transformation algorithm is called, and 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.

[0096] For the single-target capture mode, the coordinate form output by the sensor is as Figure 4 shown. Since the angle between the semi-submersible ship and the jacket platform cannot be determined during single-target capture, only the data of the gyrocompass carried by the ship itself can be referred to here to calculate the angle between the longitudinal axis of the platform and the bow direction of the semi-submersible ship as the basis for coordinate system transformation. Its coordinate transfer algorithm includes the following steps:

[0097] Taking the center of the target platform as the reference to establish an operation reference reference coordinate system, the value of the laser ranging sensor in this coordinate system can be obtained as:

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

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

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

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

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

[0103] Wherein, x c represents the abscissa of the ship center under the coordinates of the laser ranging sensor;

[0104] y c represents the ordinate of the ship center under the coordinates of the laser ranging sensor;

[0105] X target represents the abscissa of the marked point on the target platform under the platform operation reference coordinates;

[0106] Y target represents the ordinate of the marked point on the target platform under the platform operation reference coordinates;

[0107] x BS represents the coordinate relative to the S axis returned by the laser ranging sensor;

[0108] y BS represents the coordinate relative to the B axis returned by the laser ranging sensor;

[0109] θ is the angle between the ship's bow direction and the longitudinal axis of the target platform. The angle data between the ship and the true north direction is obtained through the gyrocompass, and the angle between the ship and the longitudinal axis of the target platform is calculated based on the known angle data between the target platform and the north-east coordinate system.

[0110] For the multi-target capture mode, as Figure 3 shown, it is uniformly stipulated to rotate the coordinate system to the right with the selected reference point as the origin. Under this definition, the angle output by the sensor is the angle between the ship's bow direction and the longitudinal axis of the jacket platform to be demolished. The coordinate transformation algorithm includes the following steps:

[0111] Taking the center of the target platform as the reference to establish the operation reference coordinate system, the values of the laser ranging sensor in this coordinate system are:

[0112] X C = X target + x AB

[0113] Y C = Y target + y AB

[0114] The coordinate value of the ship center point in this coordinate system is:

[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 represents the abscissa of the ship center under the coordinates of the laser ranging sensor;

[0118] y c represents the ordinate of the ship center under the coordinates of the laser ranging sensor;

[0119] X target represents the abscissa of the marked point on the jacket platform under the platform operation reference coordinates;

[0120] Y target represents the ordinate of the marked point on the jacket platform under the platform operation reference coordinates;

[0121] x AB represents the coordinate relative to the A-axis returned by the laser ranging sensor;

[0122] y AB represents the coordinate relative to the B-axis returned by the laser ranging sensor;

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

[0124] S4 Multi-source data fusion: The global positioning data and local positioning data obtained by different sensors are fused by using a dynamic fusion algorithm based on confidence measure to generate high-precision ship position information and ship attitude information;

[0125] Specifically, the multi-sensor data fusion technology analyzes the data from multiple different types of sensors separately and then synthesizes them to obtain a more reliable and accurate optimal value. In this embodiment, a data dynamic fusion algorithm based on confidence interval is adopted. This method mainly finds the mutual relationship between the measurement data of each sensor of the same type. If the measurement data between these sensors are close to each other, the data is considered to be fusible and reliable. If a certain measurement data is very different from the other measurement data, the data is considered untrustworthy and does not participate in the fusion. The specific method is as follows:

[0126] First, introduce a variable d ij , and the expression is as follows:

[0127]

[0128] In the formula, d ij represents the confidence interval between two measurement data. Among them, the physical meaning of d ij is: if xi The probability density function is P i (x), then d ij represents the area under the probability density curve P i (x) between x i and x j . The farther the distance between x i and x j , the larger the interval d ij , which means the greater the difference in the measured values of the two sensors. The value range of d ij is 0 ≤ d ij ≤ 1. When there are m sensors of the same type, the values of d ij can form an m×m qualitative interval matrix D.

[0129] The calculation of the qualitative interval matrix D is as follows:

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

[0131]

[0132] In the formula, x i represents the measured value of the i-th sensor (i = 1, 2,..., n), is the measurement variance, and in the above formula

[0133] Suppose there are n sensors to measure 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 the characteristics of different sensors are different, the characteristics between the measurement data X i are also different.

[0134] According to the knowledge of normal distribution, σ 2 is the degree of deviation of the data from the mean. The larger σ 2 , the greater the degree of deviation, and vice versa; μ represents the mean of the measurement data. From a statistical perspective, μ is the value closest to the true position of the ship and can be obtained from historical data; from a probability theory perspective, the probability that the middle value is close to the true value is the largest. Then, the middle value of the n sensor measurements can be used as the value of each historical data. In this embodiment, three ships are required for the demolition platform operation. Therefore, the GPS position measurement system is 3 groups of global satellite positioning systems. Then, the measurement data of the 3 groups of sensors are arranged in ascending order, and the middle value of the three values is taken. The above-obtained N consecutive historical data are 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 is:

[0137]

[0138] Thus, d ij can be obtained by using the error function erf(θ), and the expression of erf(θ) is as follows:

[0139]

[0140] Assume Then the above formula can be further written as:

[0141]

[0142] Let Then

[0143]

[0144] That is

[0145]

[0146] When there are multiple data between sensors of the same type, the confidence intervals between each measurement data 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 expressed as:

[0147]

[0148] The number of position reference systems m = 3, and the confidence interval matrix D m is obtained, and then based on D m the relationship matrix R ij is calculated. The calculation of each element in the relationship matrix is as follows:

[0149]

[0150] In the formula, β ij is the boundary value of d ij obtained through experiments, r ij = 0 means that the data measured by the i-th sensor and the j-th sensor do not support each other, and r ij = 1 means that the data measured by the i-th sensor and the j-th sensor support each other. Therefore, the relationship matrix R m is:

[0151]

[0152] Set a K m , for a certain position reference system in this article, if the number of systems supporting the measurement data of this system is greater than K m , then it is considered that the measurement data of this position reference system is correct, otherwise it is considered that the measurement data is incorrect. After excluding the incorrect data through the algorithm, the remaining data can be considered to have a high degree of credibility. Then, by calculating the weights of the remaining correct measurement data, the final fusion data can be obtained. Considering that there are only 3 groups of position reference systems and the redundancy of the other sensors is not high, determining the weights according to the support degree will result in insufficient accuracy. Therefore, the weight calculation method adopted in this embodiment is to determine the weights according to the variances of the measurement data of the remaining sensors after exclusion.

[0153] It is known from the knowledge of normal distribution that σ 2 The larger the value, the greater the degree of deviation of the measurement data from the mean and the greater the data fluctuation, that is, the lower the measurement accuracy of the sensor. On the contrary, the smaller σ 2 , the smaller the measurement data fluctuation, that is, the higher the measurement accuracy of the sensor. Therefore, to increase the weights of the measurement data with high corresponding accuracy in data fusion to achieve the optimal fusion effect and obtain more accurate and reliable fusion data. And how to calculate this weight is specifically deduced as follows.

[0154] Assume that the final result of data fusion is

[0155]

[0156] In the formula, ω i represents the weight occupied by the corresponding sensor measurement data, and ω i satisfies

[0157]

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

[0159]

[0160] It can be deduced from the above formula that to make the data fusion more accurate and reliable, σ 2 should be as small as possible, and it is necessary to find the minimum value of the above multivariate quadratic function. According to the extreme value theorem, a correction function is introduced:

[0161]

[0162] Take the partial derivative of ω i on both sides of the above formula

[0163]

[0164] When the correction function F reaches its minimum value, so solve the equation:

[0165]

[0166] to obtain:

[0167]

[0168] Because So Therefore,

[0169]

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

[0171] S5 Real-time Display and Communication: Synchronize the data of multiple ships through wireless networking, and synchronously send the ship position information and ship attitude information of multiple ships to the display interface to achieve precise positioning of ships and target platforms.

[0172] It can be understood that for mutual communication among three ships at sea, one switch is arranged at the bow and stern of each ship. The system framework includes the underlying sensor layer, the underlying industrial computer layer, the operation control interface, and the wireless communication system layer. The underlying sensor layer includes the position measurement sensors listed above; the underlying industrial computer mainly unpacks, analyzes, and fuses the sensor data, forwards the messages of this ship, receives the information of other ships or targets, and finally packs and sends it to the operation control interface; the control interface unpacks the aggregated data, performs visual display and corresponding conversions for the convenience of operators to master; the wireless transmission system provides a way for communication between different ships to ensure the smooth reception and transmission of information.

[0173] Embodiment 2

[0174] In this embodiment, a positioning device for implementing the positioning device of Embodiment 1 is proposed. Taking the platform demolition operation as an example, the demolition of the platform is a very complex task. When the engineering ship arrives at the designated area, before the demolition work starts, the reflection markers of the laser ranging sensor and the microwave radar ranging sensor need to be installed on the jacket leg correspondingly. When transferring, two K-class ships and one X-class ship need to be configured. By adjusting the ballast water system of the engineering ship, the draft is changed to make the ship's attitude reach the required freeboard and heel angle. The K-class ships approach the docking position. By adjusting the ballast water system of the two K-class ships and changing the draft, the superstructure is gradually lifted, and the weight of the platform starts to transfer from the jacket to the two K-class ships; continue to ballast and float until the load-bearing structure of the platform changes from the jacket to the two K-class ships, and ensure that there is enough safety clearance between the superstructure and the top of the jacket. In this embodiment, the positioning device is set on the ship, and the positioning method in Embodiment 1 is applied to monitor the corresponding ship position and attitude data in real time. Specifically, the positioning device specifically includes:

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

[0176] The local positioning module 102 includes laser ranging sensors and microwave radars arranged along the ship's side, which are used to capture the reflection 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 the X-class and K-class ships. Two sensors are installed on the K-class semi-submersible ship along one side of the ship's side. In order to avoid signal occlusion during the approach of the ship to the platform, which affects the continuity and measurement accuracy of the measurement, the two sensors are arranged at a certain distance apart. At the same time, there are also certain requirements for the distance between the sensor and the side of the ship equipped with the bearing unit. Since the minimum measurement distance of the laser ranging sensor is 10m, this point also needs to be considered when installing the sensor. In order to achieve redundancy in the measurement principle, a set of radar ranging sensors is installed on the two ships. For the X-class semi-submersible ship, a laser ranging sensor and a radar ranging sensor system are arranged on the forecastle deck, and their corresponding marker points are installed at the corresponding height of the jacket. Record the position coordinates of the marker points on the jacket platform. It should be noted here that the installation connection line of the marker points is parallel to the Y-axis (the length direction of the semi-submersible ship) of the jacket platform. Since the X-class semi-submersible ship approaches from one side of the platform, there is less occlusion between the jacket platform and the X-class ship. Only an additional set of radar ranging sensors needs to be added, and arranging the sensors on the forecastle can reduce the difficulty of outfitting and data transmission.

[0178] In addition, the composition of the microwave ranging sensor is very similar to that of the laser ranging sensor, which is divided into a radar computer host, a radar interrogator, a reflector and a display. The installation position of the radar interrogator can refer to the above-mentioned laser ranging radar.

[0179] The attitude detection module 103, including an electrocompass and an attitude sensor, is used to measure the ship's heading and roll and pitch angles.

[0180] The coordinate conversion module 104 is used to convert the absolute position information, relative position and declination data to the local coordinate system centered on the target platform through the relative position transfer algorithm.

[0181] The data fusion module 105 is used to perform data fusion on the global positioning data and local positioning data obtained 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 Embodiment 1 and will not be elaborated here.

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

[0184] It can be understood that switches are arranged at the bow and stern of each ship to realize the communication networking between ships.

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

[0186] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for positioning an offshore platform integrating local positioning and global positioning, characterized in that: The following steps are involved: Global positioning data acquisition: The absolute position information and attitude information of the ship in the geodetic coordinate system are acquired through the global positioning module deployed on the ship; Local positioning data acquisition: The relative position and deflection data between the ship and the target platform are measured by the laser ranging sensor and microwave ranging sensor deployed on the ship; Coordinate system conversion: using a relative position transfer algorithm to convert the absolute position information, relative position and deflection angle data into a local coordinate system centered on the target platform; Multi-source data fusion: A dynamic fusion algorithm based on confidence measurement is used to fuse the global positioning data and local positioning data obtained by different sensors to generate high-precision ship position information and ship attitude information; Real-time display and communication: Synchronize multi-ship data through wireless networking, and send the ship position information and ship attitude information of multiple ships to the display interface synchronously to achieve accurate positioning of ships and target platforms.

2. The offshore platform positioning method integrating local positioning and global positioning according to claim 1, characterized in that: The relative position transfer algorithm includes a single target capture mode coordinate conversion algorithm and a multi-target capture mode coordinate conversion algorithm; when the global positioning data and the local positioning data come from a single ship, the single target capture mode coordinate conversion algorithm is called, and when the global positioning data and the local positioning data come from no less than two ships, the multi-target capture mode coordinate transfer algorithm is called.

3. The offshore platform positioning method integrating local positioning and global positioning according to claim 2 is characterized in that: The single target capture mode coordinate transfer algorithm comprises the following steps: The operation reference coordinate system is established based on the center of the target platform. The value of the laser ranging sensor in this coordinate system can be obtained as follows: X C =X target +x BS cosθ+y BS sinθ AND C =And target +y BS cosθ-x BS sinθ The coordinate values ​​of the center point of the ship in this coordinate system are: X C =X target +(x BS+ x c )cosθ+(y BS +y c )sinθ AND C =And target +(and BS +y c )cosθ-(x BS+ x c )sinθ Among them, x c Indicates the horizontal coordinate of the center of the ship in the laser ranging sensor coordinates; y c Indicates the ordinate of the center of the ship in the laser ranging sensor coordinates; X target Indicates the horizontal coordinate of the mark point on the target platform under the platform operation reference coordinates; Y target Indicates the ordinate of the mark point on the target platform under the platform operation reference coordinates; x BS Indicates the coordinates relative to the S axis returned by the laser ranging sensor; y BS Indicates the coordinates relative to the B axis returned by the laser ranging sensor; θ is the angle between the ship's bow and the longitudinal axis of the target platform. The angle data between the ship and the true north direction is obtained by the gyrocompass, and the angle between the ship and the longitudinal axis of the target platform is calculated based on the angle data between the target platform and the northeast coordinate system.

4. The offshore platform positioning method integrating local positioning and global positioning according to claim 2, characterized in that: The multi-target capture mode coordinate conversion algorithm comprises the following steps: The operation reference coordinate system is established with the center of the target platform as the reference, and the value of the laser ranging sensor in this coordinate system is obtained as follows: X C =X target +x AB AND C =And target +y AB The coordinate values ​​of the center point of the ship in this coordinate system are: X K =x c cosθ+y c sinθ+X target +x AB AND K =And c cosθ+X c sinθ+Y target +y AB Among them, x c Indicates the horizontal coordinate of the center of the ship in the laser ranging sensor coordinates; y c Indicates the ordinate of the center of the ship in the laser ranging sensor coordinates; X target Indicates the horizontal coordinate of the marked point on the jacket platform under the platform operation reference coordinate; Y target Indicates the ordinate of the marked point on the jacket platform under the platform operation reference coordinates; x AB Indicates the coordinates relative to the A axis returned by the laser ranging sensor; y AB Indicates the coordinates relative to the B axis returned by the laser ranging sensor; θ is the angle between the ship's bow and the longitudinal axis of the jacket platform.

5. The offshore platform positioning method integrating local positioning and global positioning according to claim 1, characterized in that: The dynamic fusion algorithm includes: Calculate the confidence interval of the measurement data of the same type of sensors, and remove the data of a certain sensor if it exceeds the threshold range; Dynamically assign weights based on the variance of historical sensor data. The smaller the variance, the higher the weight. The weighted average method is used to fuse the remaining valid data and output the final positioning result.

6. The offshore platform positioning method integrating local positioning and global positioning according to claim 5, characterized in that: The calculation of the confidence interval of the measurement data of the same type of sensors and the elimination of the data of a certain sensor if it exceeds the threshold range includes the following steps: Introduce variable d ij , d ij Represents the confidence interval between two measured data, specifically: When there are m sensors of the same type, d ij The values ​​of can form an m×m position interval matrix D, which is expressed as follows: According to D m Find the relationship matrix R between them ij The expression is as follows: Setting parameter K m , in a single reference system, if the number of systems supporting the measurement data of the system is greater than K m , then the measurement data of the position reference system is considered correct, otherwise it is considered wrong.

7. The offshore platform positioning method integrating local positioning and global positioning according to claim 5, characterized in that: The weight calculation of the measurement data includes the following steps: Assume that the final result of data fusion is In the formula, ω i represents the weight of the corresponding sensor measurement data, and ω i satisfy The total mean square error after data fusion is: Make σ 2 Minimum, get the following expression, calculate the variance in real time, and adjust the weight dynamically:

8. A positioning device for implementing the method according to any one of claims 1 to 7, arranged 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, which is used to capture the reflective markers deployed on the target platform to measure the relative position and deflection data between the ship and the target platform; Attitude detection module, including gyrocompass and attitude sensor, used to measure the ship's heading and pitch angle; A coordinate conversion module, which is used to convert the absolute position information, relative position and deflection angle data into a local coordinate system centered on the target platform through a relative position transfer algorithm; A data fusion module, which is used to fuse the global positioning data and local positioning data acquired by different sensors through a dynamic fusion algorithm based on confidence measurement, so as to generate high-precision ship position information and ship attitude information; The wireless communication module is used to realize synchronous data transmission between multiple ships through a multi-point networking protocol.

9. The positioning device according to claim 8, characterized in that: It comprises at least two laser distance measuring sensors, which are arranged along the same side of the ship's side or on the forecastle deck.

10. The positioning device according to claim 8, characterized in that: Each ship is equipped with no less than three sets of satellite positioning sensors, three sets of gyro compasses, and three sets of attitude sensors.

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