A method for predicting the motion of a dynamically positioned offshore platform during pile insertion

Abstract

The application relates to the technical field of ship motion control, and discloses a dynamic positioning motion prediction auxiliary pile driving method for a self-elevating offshore platform, which comprises the following steps: recording the stable drift speed and direction of the platform under a target heading near a target pile driving position; calculating an initial maneuvering target position according to drift information, water depth and pile driving speed; after the platform reaches the initial target position, performing motion prediction and adjusting the position of the platform in the longitudinal direction so that the predicted motion track passes through the target pile driving position; driving the pile under the guidance of the prediction, slowing down the platform by using the pile leg to touch the bottom, and making the pile leg enter the mud to fix the position and the heading when the platform reaches the target pile driving position. The application can overcome the difficulty that it is difficult to perform normal point pile driving operation under strong sea currents due to insufficient transverse propulsion capacity of the platform, and can provide decision guidance for the operator by combining motion prediction with longitudinal control, so that the pile driving operation is assisted to be completed, and the engineering application value is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ship motion control, and particularly relates to a dynamic positioning motion prediction auxiliary pile driving method for a self-elevating offshore platform. BACKGROUND

[0002] The main function of a dynamic positioning system of a surface ship or platform is to resist the environmental forces of wind, wave and current by automatic control of the equipped propeller, so as to realize automatic control of three degrees of freedom of position and heading, so that the ship can maintain the set position, heading and trajectory to meet the needs of specific operation tasks.

[0003] When the self-elevating offshore platform is in pile driving operation, the platform propelling capacity may be insufficient to resist the environmental forces of wind, wave and current, especially the transverse propelling capacity. At this time, it is unrealistic to control the platform near the pile driving target point by using the fixed point positioning mode of dynamic positioning. This puts forward the demand for platform pile driving positioning under the condition of insufficient propelling capacity of the dynamic positioning system.

[0004] In view of this demand, a motion prediction technology is proposed, which uses a model-based motion prediction method to calculate the motion state of the platform in a future period of time, and provides an auxiliary decision for the operator to select the pile driving time. This technology effectively solves the pile driving positioning problem under the condition of insufficient propelling capacity which cannot be solved by the conventional dynamic positioning system, and can assist the operator to complete the pile driving positioning and ensure the subsequent sea operation tasks. SUMMARY

[0005] The present application aims to at least solve one of the technical problems in the related art. To this end, the present application provides a dynamic positioning motion prediction and auxiliary pile driving method for a self-elevating offshore platform.

[0006] A dynamic positioning motion prediction and auxiliary pile driving method for a self-elevating offshore platform,

[0007] S1: Obtain the target pile driving position, target pile driving heading, water depth, platform draft and pile driving speed, set the platform heading to the target pile driving heading when the platform moves to a distance within a first threshold range from the target pile driving position, and collect the drift speed and drift direction of the platform;

[0008] S2: Obtain the initial maneuver target position of the platform according to the target pile driving position, target pile driving heading, water depth, platform draft and pile driving speed;

[0009] S3: Adjust the platform heading and move to the initial maneuver target position, and adjust the platform heading to the target pile driving heading when the platform moves to the initial maneuver target position;

[0010] S4: Establish a low-frequency motion prediction model of the platform, perform motion prediction based on the low-frequency motion prediction model, and output a position prediction sequence in a future period of time; adjust the longitudinal position of the platform based on the prediction sequence, so that the trajectory of the prediction sequence passes through the target pile insertion position;

[0011] S5: While continuously outputting the motion prediction, start the pile leg insertion operation, and monitor the remaining time, water depth, and pile leg lowering length to reach the target pile insertion position;

[0012] The remaining time to reach the target pile insertion position is the time required for the berth position to move to the target pile insertion position in the motion prediction;

[0013] S6: When the platform moves to a distance within a second threshold range from the target pile insertion position, determine whether the pile leg has touched the bottom, and use the friction between the pile leg and the seabed to slow down the platform;

[0014] S7: When the platform reaches the target pile insertion position, control the pile leg to enter the mud, maintain the position and heading of the platform, and terminate the dynamic positioning operation.

[0015] Further, S1 includes the following steps:

[0016] B1: Start the fixed-point positioning mode of dynamic positioning at the target pile insertion position within a radius threshold range, and record the coordinates in the geodetic coordinate system as ;

[0017] B2: Set the heading of the platform to the target pile insertion heading ;

[0018] B3: After the platform rotates to the target pile insertion heading and the drift speed stabilizes under the action of environmental forces, record the cross drift speed and the cross drift direction at this time; when the platform drifts to the port side, record ; when the platform drifts to the starboard side, record .

[0019] Further, S2 includes the following steps:

[0020] C1: Obtain the water depth of the target pile insertion position, the draft of the platform, and the pile insertion speed information; calculate the pile insertion time as formula (1):

[0021] Formula (1)

[0022] In the formula, is the pile insertion speed, is the water depth, is the water depth at the platform;

[0023] C2: initial target position of the maneuvering target in the earth coordinate system is denoted as , and is calculated as equation (2):

[0024] Equation (2)

[0025] The initial target position of the maneuvering target is upstream of the target pile position.

[0026] Further, S3 comprises the following steps:

[0027] D1: in the fixed-point positioning mode, setting the target position of the platform as the initial target position of the maneuvering target , and setting the target heading of the platform as ;

[0028] D2: after the platform moves to the target position and the target heading set in D1, setting the target heading of the platform as the target pile heading .

[0029] Further, S4 comprises the following steps:

[0030] E1: establishing a dynamic positioning motion prediction mathematical model, which is a simplified form of the low-frequency dynamics model in the state estimation model as equation (3):

[0031] Equation (3)

[0032] wherein and are the north position and the east position of the platform in the earth coordinate system, respectively; denotes the first derivative of n, i.e., the north acceleration; denotes the first derivative of e, i.e., the east acceleration; is the cross-ship velocity; denotes the first derivative of , i.e., the cross-ship acceleration; is the mass of the platform, is the cross-ship hydrodynamic acceleration derivative; is the cross-ship hydrodynamic velocity derivative; is the cross-ship thrust generated by the thruster; is the cross-ship wind load; and are the environmental disturbance loads in the north and the east, respectively; the predicted state vector in the model is a 3-dimensional state vector;

[0033] E2: Based on the model in E1, motion prediction is performed, 1 position is output per second, a sequence of geodetic coordinate system positions within the prediction time threshold is output, the prediction initial value uses the state estimation value output by the current dynamic positioning control period, the lateral thrust, lateral wind load, and environmental disturbance load also use the calculation results used by the state estimation;

[0034] E3: The longitudinal motion uses the hand-operated mode of dynamic positioning, the platform forward and backward position is adjusted through the hand-operated lever, and the predicted position passes through the target insertion position.

[0035] Further, E3 is specifically operated as follows:

[0036] E31: Calculate the target insertion position The foot of the straight line on which the predicted position sequence is located , The coordinates in the geodetic coordinate system Obtained by solving equation (4);

[0037] Equation (4)

[0038] In the formula, The coordinates of the first point of the predicted position sequence , The coordinates of the last point of the predicted position sequence ;

[0039] E32: Calculate the vector using equation (5) The coordinates in the geodetic coordinate system ,

[0040] Equation (5)

[0041] The geodetic coordinate system takes the insertion target point as the origin, x points north, and y points east;

[0042] E33: Calculate the vector using equation (6) The coordinates in the platform coordinate system ,

[0043] Equation (6)

[0044] The origin of the platform coordinate system is the center of gravity of the berth, x points to the bow, and y points to the right side;

[0045] E34: According to Adjust the platform forward and backward position, when , the platform moves forward; when , the platform moves backward.

[0046] Further, S5 includes the following steps:

[0047] F1: calculate the remaining time to reach the target pile insertion position, F2: continuously monitor the water depth and the length of the pile leg lowering by using the water depth sensor and the pile leg monitoring system.

[0048] Further, the step of calculating the remaining time to reach the target pile insertion position comprises:

[0049] F11: calculate the coordinates of the current predicted position in the geodetic coordinate system and the northward and eastward deviations of the target pile insertion position, respectively and ; and calculate the coordinates of the last predicted position in the geodetic coordinate system and the northward and eastward deviations of the target pile insertion position, respectively and :

[0050] Equation (7)

[0051] In the equation, K and K-1 represent the Kth and K-1th in the prediction sequence, respectively;

[0052] F12: calculate the lateral deviation of the current predicted position from the target pile insertion position in the platform coordinate system, denoted as ; and calculate the lateral deviation of the last predicted position from the target pile insertion position, denoted as :

[0053] Equation (8)

[0054] F13: calculate the remaining time to reach the target pile insertion position,

[0055] If , output the predicted remaining time to reach the target pile insertion position as K-1 seconds; when the prediction time threshold is reached, the result is always greater than 0, output the predicted remaining time to reach the target pile insertion position > prediction time threshold.

[0056] Further, S7 comprises the following steps:

[0057] G1: according to the motion prediction result, when the platform reaches the target pile insertion position, make the pile leg mud entering position and the heading remain,

[0058] G2: after the pile insertion is completed, the dynamic positioning operation is released, and the subsequent ballast and leveling operations are completed by the pile leg lifting facility.

[0059] Further, the method is suitable for self-elevating offshore platforms with insufficient lateral propulsion capacity, and the motion prediction and longitudinal adjustment compensate for the insufficient lateral positioning to ensure the accuracy of the pile insertion operation.

[0060] The one or more technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0061] The motion prediction and longitudinal adjustment compensate for the insufficient lateral propulsion capacity of the platform, and realize accurate pile insertion.

[0062] The motion prediction model provides a position sequence and a remaining time in a certain time threshold in the future, and provides real-time guidance for the operator.

[0063] In combination with the fixed-point positioning of the dynamic positioning, the manual operation mode and the state estimation, an efficient assisted pile insertion process is realized.

[0064] In summary, the method can overcome the difficulty of pile insertion in the fixed-point mode caused by the large current and insufficient lateral capacity of the platform, and by combining different operation modes of the dynamic positioning and the state estimation output, the motion prediction result of the platform in a future period of time is given, and the assisted pile insertion operation is guided, which has high engineering application value.

[0065] Additional aspects and advantages of the present application will be described in part below, some will become apparent from the following description, or will be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0066] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0067] Figure 1 is a flow chart of a dynamic positioning motion prediction assisted pile insertion method of a self-elevating offshore platform provided by an embodiment of the present application. DETAILED DESCRIPTION

[0068] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely in combination with the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The following embodiments are used to illustrate the present application, but cannot be used to limit the scope of the present application.

[0069] The following will describe the dynamic positioning motion prediction assisted pile insertion method of a self-elevating offshore platform of the present application. Figure 1 The following will describe the dynamic positioning motion prediction assisted pile insertion method of a self-elevating offshore platform of the present application.

[0070] The present application aims at the situation that the jack-up offshore platform may encounter insufficient transverse capacity to cause failure in normal pile driving in the dynamic positioning mode during pile driving, and proposes a method of motion prediction assisted pile driving by the dynamic positioning system. The method combines the fixed positioning of the dynamic positioning, the manual control mode and the state estimation output, and designs an operation method of assisted pile driving, which can guide the jack-up offshore platform to complete the pile driving operation even when the flow rate is high.

[0071] The present application provides a method of motion prediction assisted pile driving of a jack-up offshore platform by dynamic positioning, comprising:

[0072] S1: obtaining target pile driving position and target pile driving heading information, setting the heading of the platform as the target pile driving heading when the platform moves to a distance within a first threshold range from the target pile driving position, and collecting the drift speed and drift direction of the platform;

[0073] comprising the following steps:

[0074] B1: starting the fixed positioning mode of dynamic positioning within a radius of 50 meters around the target pile driving position , and recording the coordinates in the geodetic coordinate system as ; ;

[0075] B2: setting the heading of the platform as the target pile driving heading ;

[0076] B3: after the platform rotates to the target pile driving heading and the drift speed is stable under the action of environmental forces, recording the transverse speed and the transverse direction at this time. When the platform drifts to the port side, record ; when the platform drifts to the starboard side, record .

[0077] The platform is preliminarily controlled near the target pile driving position by the fixed positioning mode, providing a basis for subsequent calculation of the initial maneuvering target position. The drift speed and direction are recorded to quantify the influence of environmental forces on the transverse motion of the platform, providing key input data for motion prediction. By adjusting the heading to the target pile driving heading, the attitude consistency of the platform in the subsequent pile driving process is ensured.

[0078] S2: obtaining the initial maneuvering target position of the platform according to the target pile driving position, the target pile driving heading, the water depth of the target pile driving position, the draft of the platform and the pile driving speed; the initial maneuvering target position is located upstream of the target pile driving position;

[0079] comprising the following steps:

[0080] C1: The specific steps include: obtaining the target pile driving position water depth, platform draft and pile driving speed information; calculating the pile driving time As formula (1):

[0081] (1)

[0082] In the formula, is the pile driving speed, is the water depth, is the platform draft.

[0083] C2: Initial mobile target position in the geodetic coordinate system The coordinate is denoted as , and is calculated as follows:

[0084] (2)

[0085] By calculating the pile driving time, the motion time window of the platform from the initial mobile target position to the target pile driving position is determined; the initial mobile target position takes into account the drift speed and direction of the platform, ensuring that the platform can reach the target pile driving position through natural drift and longitudinal adjustment in the case of insufficient lateral propulsion capacity; and providing a clear starting point for subsequent positioning and motion prediction of the dynamic positioning system.

[0086] S3: Adjusting the heading of the platform and moving to the initial mobile target position, and when the platform moves to the initial mobile target position, adjusting the heading of the platform to the target pile driving heading;

[0087] The method comprises the following steps:

[0088] D1: In the fixed-point positioning mode, setting the target position of the platform as the initial mobile target position , and setting the target heading of the platform as ; is in the opposite direction of , and this setting ensures that the platform can move to the initial mobile target position upstream of the target pile driving position, so as to reach the target pile driving position through the subsequent combined action of longitudinal adjustment and lateral movement of the platform.

[0089] D2: After the platform moves to the target position and target heading set in D1, setting the target heading of the platform as the target pile driving heading .

[0090] This ensures that the platform starts pile driving operation from a known and optimized starting position, reducing the complexity of subsequent adjustment. Adjusting the heading to the target pile driving heading provides a correct platform attitude for subsequent pile driving operation, and the platform can still maintain a relatively stable position in the case of insufficient lateral propulsion capacity.

[0091] S4: Establish a low-frequency motion prediction model of the platform transversely, take the current state estimation value as the initial state to perform motion prediction, and output a position prediction sequence in the future period of time; adjust the longitudinal position of the platform based on the position prediction sequence, so that the trajectory of the position prediction sequence passes through the target pile position;

[0092] comprising the following steps:

[0093] E1: Establish a dynamic positioning motion prediction mathematical model. In the present application, it is considered that the longitudinal and bow propulsion capacity of the platform is sufficient to resist environmental forces, and the transverse capacity is insufficient, so motion prediction and auxiliary pile insertion are performed. Therefore, only transverse motion is predicted. Moreover, the high-frequency motion of the ship caused by the first-order wave force is reciprocating motion, so the present application only predicts low-frequency motion. The dynamic positioning motion prediction mathematical model established is a simplified form of the low-frequency dynamics model in the state estimation model, as shown in equation (3):

[0094] (3)

[0095] wherein, and are the northward position and eastward position in the platform geodetic coordinate system, represents the first derivative of n, i.e., the northward acceleration; represents the first derivative of e, i.e., the eastward acceleration; is the transverse velocity; represents the first derivative of , i.e., the transverse acceleration; is the mass of the platform, is the transverse hydrodynamic acceleration derivative; is the transverse hydrodynamic velocity derivative; is the transverse thrust generated by the thruster; is the transverse wind load; and are the environmental disturbance loads in the northward and eastward directions, respectively.

[0096] In the above model, the predicted state vector is a 3-dimensional state vector;

[0097] E2: Based on the model in E1, motion prediction is performed, 1 position is output per second, a geodetic coordinate system position sequence in 30 minutes is output, the initial value of the prediction is the state estimation value output by the dynamic positioning control cycle, and the transverse thrust, the transverse wind load, and the environmental disturbance load are also calculated using the state estimation value.

[0098] E3: The longitudinal motion uses the hand-operated mode of dynamic positioning, the forward and backward positions of the platform are adjusted through the hand-operated lever, so that the predicted position passes through the target pile position. The specific operation is as follows:

[0099] E31: Calculate target spud position The foot of the perpendicular on the straight line on which the predicted position sequence lies , The coordinates in the geodetic coordinate system , obtained by solving the equation set of formula (4),

[0100] (4)

[0101] In the formula, The coordinates of the first point of the predicted position sequence , The coordinates of the last point of the predicted position sequence .

[0102] E32: Calculate vector The coordinates in the geodetic coordinate system , using formula (5) as follows:

[0103] (5)

[0104] The geodetic coordinate system takes the spud target point as the origin, with x pointing north and y pointing east;

[0105] E33: Calculate vector The coordinates in the platform coordinate system , using formula (6) as follows:

[0106] (6)

[0107] The origin of the platform coordinate system is the center of gravity of the berth, with x pointing towards the bow and y pointing to the right side;

[0108] E34: Adjust the front and rear positions of the platform according to When , use the hand control lever to move the platform forward; when , use the hand control lever to move the platform backward.

[0109] The mathematical model predicts the trajectory of the platform's lateral movement, providing a decision basis for the operator to determine the spud time. Through the longitudinal hand control mode, the platform position is adjusted in real time to make up for the lack of lateral propulsion capacity, ensuring that the platform trajectory can accurately pass through the target spud position. The prediction results provide an intuitive movement trend for the operator, reducing the blindness of manual operation.

[0110] S5: While maintaining the continuous output of the movement prediction, start the spud leg spud operation, monitor the remaining time, water depth, and spud leg lowering length to reach the target spud position;

[0111] Comprising the following steps:

[0112] F1: Calculate the remaining time to reach the target pile driving position,

[0113] The remaining time to reach the target pile driving position is the time required for the berth position movement in motion prediction to reach the target pile driving position;

[0114] The calculation step includes:

[0115] F11: In the loop function of motion prediction, calculate the coordinates of the current predicted position in the geodetic coordinate system and the north and east deviations from the target pile driving position, respectively and ; and calculate the coordinates of the last predicted position in the geodetic coordinate system and the north and east deviations from the target pile driving position, respectively and :

[0116] (7)

[0117] In the formula, K and K-1 represent the Kth and K-1th in the prediction sequence, respectively.

[0118] F12: Calculate the lateral deviation of the current predicted position from the target pile driving position in the platform coordinate system, denoted as ; and calculate the lateral deviation of the last predicted position from the target pile driving position, denoted as :

[0119] (8)

[0120] F13: Calculate the output prediction time to reach the target pile driving position:

[0121] If , the output prediction time to reach the target pile driving position is K-1 seconds; if until the end of the prediction loop function, the result is always greater than 0, the output prediction time to reach the target pile driving position is > 30 minutes.

[0122] F2: Continuously monitor water depth and pile leg lowering length using water depth sensor and pile leg monitoring system.

[0123] Through continuous pile driving and real-time monitoring, it is ensured that the pile leg lowering process is synchronized with the platform motion. The remaining time calculation provides accurate pile driving opportunity for the operator, optimizing the operation efficiency. Real-time monitoring of water depth and pile leg lowering length ensures accurate preparation before the pile leg touches the bottom.

[0124] S6: When the platform motion is within the second threshold range from the target pile driving position, use the friction between the pile leg and the seabed to slow down the platform;

[0125] Pile leg bottoming increases the friction between the pile leg and the seabed, slows down the platform, and attention should be paid to judging whether the pile leg has bottomed out according to the pile leg vertical load measured by the pile leg monitoring system.

[0126] When the pile leg contacts the seabed, the pile leg vertical load will have a clear positive and negative sign change, at this time the force of the pile leg on the platform changes from the downward resultant force (gravity, buoyancy difference) to the upward supporting force.

[0127] Through the friction between the pile leg and the seabed, the drift speed of the platform under the condition of insufficient lateral propulsion capacity is effectively slowed down. The timing of pile leg bottoming is accurately judged through load change, which provides guarantee for subsequent pile insertion into the mud. The deceleration process avoids missing the target pile insertion position due to too fast drift speed of the platform.

[0128] The second threshold in this step is adjusted according to the lateral movement speed Adjustment can be made by the driver according to the specific situation, the size of the second threshold can be adjusted by controlling the pile leg and using the size of the friction between the pile leg and the seabed.

[0129] S7: When the platform reaches the target pile insertion position, control the pile leg to enter the mud to complete the position and heading keeping of the platform.

[0130] Comprising the following steps:

[0131] G1: According to the motion prediction result, when the platform reaches the target pile insertion position, make the pile leg enter the mud to realize position and heading keeping. The motion prediction result of the dynamic positioning process assists the pile leg lifting facility to carry out pile insertion.

[0132] G2: After pile insertion is completed, the dynamic positioning operation is released, and subsequent operations such as ballast and leveling are completed by the pile leg lifting facility.

[0133] The pile leg entering the mud ensures the stability and heading keeping of the platform at the target pile insertion position, and completes the pile insertion task. After the dynamic positioning is released, the pile leg lifting facility takes over the subsequent operation to ensure that the platform enters a stable working state; which marks the successful completion of the pile insertion operation and lays a foundation for subsequent sea work (such as drilling and installation).

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for assisting pile driving of a self-elevating offshore platform by dynamic positioning motion prediction, characterized in that, S1: obtaining a target pile driving position, a target pile driving heading, water depth, platform draft and pile driving speed, setting the platform heading to the target pile driving heading when the platform moves to a distance within a first threshold range from the target pile driving position, collecting the drift speed and drift direction of the platform; S2: obtaining an initial maneuver target position of the platform according to the target pile driving position, the target pile driving heading, the water depth, the platform draft and the pile driving speed; S3: adjusting the platform heading and moving to the initial maneuver target position, and adjusting the platform heading to the target pile driving heading when the platform moves to the initial maneuver target position; S4: establishing a low-frequency motion prediction model of the platform, performing motion prediction based on the low-frequency motion prediction model, and outputting a position prediction sequence in a future period of time; adjusting the longitudinal position of the platform based on the prediction sequence so that the trajectory of the position prediction sequence passes through the target pile driving position; S5: while the motion prediction continues to output, starting the pile leg driving operation, and monitoring the remaining time to reach the target pile driving position, the water depth and the pile leg lowering length; the remaining time to reach the target pile driving position is the time required for the platform position output in the motion prediction to move to the target pile driving position; S6: when the platform moves to a distance within a second threshold range from the target pile driving position, judging whether the pile leg has touched the bottom, and using the friction between the pile leg and the seabed to slow down the platform; S7: when the platform reaches the target pile driving position, controlling the pile leg to enter the mud, realizing the retention of the platform position and heading, and terminating the dynamic positioning operation.

2. The method for assisting pile driving of a self-elevating offshore platform by dynamic positioning motion prediction according to claim 1, characterized in that, S1 includes the following steps: B1 : at the target pinning location a point positioning mode of opening the active force positioning in the radius threshold range, record the geodetic coordinate system coordinates as ; B2: Set platform heading Targeted to plug the bow ; B3: the platform is to be rotated to the target plugging bow direction , and the lateral drift speed is recorded after the drift speed is stable under the action of the environmental force and the lateral drift direction ; When the platform drifts to port, record When the platform drifts to starboard, record .

3. The method for assisting pile driving of a self-elevating offshore platform by dynamic positioning motion prediction according to claim 1, characterized in that, S2 includes the following steps: C1: Obtain target spud position water depth, platform draft and spud down speed information; calculate spud down time As formula (1): Formula (1) wherein is the speed of the pile, is the water depth, is the draft of the platform; C2: Initial maneuvering target position in geodetic coordinate system The coordinate is denoted and is calculated as in equation (2): Formula (2) the initial maneuver target position is upstream of the target pile driving position.

4. The method for assisting pile driving of a self-elevating offshore platform by dynamic positioning motion prediction according to claim 1, characterized in that, S3 includes the following steps: D1: in the point positioning mode, set the target position of the platform as the initial maneuvering target position , set the target heading of the platform as ; D2: the platform moves to the target position and target heading set in D1, and sets the target heading of the platform as the target pile driving heading .

5. The method for assisting pile driving of a self-elevating offshore platform by dynamic positioning motion prediction according to claim 1, characterized in that, S4 includes the following steps: E1: establishing a dynamic positioning motion prediction mathematical model, which is a simplified form of the low-frequency dynamics model in the state estimation model as formula (3): Equation (3) where and are the north and east positions in the platform ECEF coordinate system, respectively; denotes the first derivative of n, i.e. the north acceleration; denotes the first derivative of e, i.e. the east acceleration; is the cross-range velocity; denotes the first derivative of , i.e. the cross-range acceleration; is the platform mass, is the cross-range hydrodynamic acceleration derivative; is the cross-range hydrodynamic velocity derivative; is the cross-range thrust generated by the thrusters; is the cross-range wind load; and are the north and east environmental disturbance loads, respectively; the predicted state vector in the model is the 3-dimensional state vector; E2: based on the model in E1, performing motion prediction, outputting 1 position per second, outputting a sequence of positions in the geodetic coordinate system within a prediction time threshold, using the state estimation value output in the current dynamic positioning control period as the prediction initial value, and using the calculation results of the state estimation as the lateral thrust, lateral wind load and environmental disturbance load; E3: the longitudinal motion uses the hand-operated mode of dynamic positioning, the platform forward and backward position is adjusted through the hand-operated lever, and the predicted position passes through the target pile driving position.

6. The method for assisting pile driving of a self-elevating offshore platform by dynamic positioning motion prediction according to claim 5, characterized in that, E3 is specifically operated as: E31: Calculate target pegging position Foot of perpendicular on the straight line on which the sequence of predicted positions lies , Coordinates in the geodetic coordinate system By solving the system of equations (4) Formula (4) In the formula, The first point in the predicted location sequence coordinates The last point in the predicted location sequence The coordinates; E32: Calculate the vector using formula (5) Coordinates in the terrestrial coordinate system , Formula (5) The earth coordinate system takes the target pile insertion point as the origin, with x pointing north and y pointing east. E33: Compute the vector using formula (6) Coordinates in the platform coordinate system , Equation (6) The origin of the platform coordinate system is the center of gravity of the platform, with x pointing forward and y pointing to the right side. E34: According to Adjust the front and back position of the platform, when the platform moves forward; when the platform moves backward.

7. The method of claim 1, wherein the method further comprises: S5 comprises the following steps: F1: calculating the remaining time to reach the target pile insertion position, and F2: continuously monitoring the water depth and the pile leg lowering length using the water depth sensor and the pile leg monitoring system.

8. The method of claim 1, wherein the method further comprises: The step of calculating the remaining time to reach the target pile insertion position comprises: F11: Calculate the coordinates of the current predicted position in the geodetic coordinate system and eastward deviation of the target drilling position, respectively, are recorded as and ; and calculate the coordinates of the last predicted position in the geodetic coordinate system and eastward deviation of the target drilling position, respectively, are recorded as and : Formula (7) wherein K and K-1 represent the Kth and K-1th in the prediction sequence, respectively. F12: the lateral deviation between the current predicted position and the target splicing position in the coordinate system of the computing platform, denoted as ; and the lateral deviation between the last predicted position and the target splicing position is calculated, denoted as : Equation (8); F13: calculating the remaining time to reach the target pile insertion position, If the output is the predicted time to reach the target spiking location. If the result is always greater than 0, the output is the predicted time to reach the target spiking location > the predicted time threshold.

9. The method of claim 1, wherein the method further comprises: S7 comprises the following steps: G1: based on the motion prediction result, when the platform reaches the target pile insertion position, the pile leg mud entry implementation position and the heading are kept, G2: after the pile insertion is completed, the dynamic positioning operation is released, and the subsequent ballast and leveling operations are completed by the pile leg lifting device.

10. The method of claim 1, wherein the method is suitable for self-elevating offshore platforms with insufficient lateral propulsion capacity, and the motion prediction and longitudinal adjustment compensate for the insufficient lateral positioning to ensure the accuracy of the pile insertion operation. ​

Images