Multi-point mooring positioning and four-point mooring model control method

Abstract

The present invention discloses a control method for a four-point mooring model for multi-point mooring positioning, the method comprising: establishing a four-point mooring positive solution absolute motion model and a four-point mooring positive solution relative motion model; obtaining a four-point mooring inverse solution model according to the four-point mooring positive solution absolute motion model and the four-point mooring positive solution relative motion model; establishing a drive control model between a mooring motor and a mooring cable; establishing a four-point mooring multi-motor collaborative positioning control model according to the four-point mooring inverse solution model and the drive control model, and adjusting the position deviation of the working positioning point by adjusting the four mooring motor rotation angles in the four-point mooring multi-motor collaborative positioning control model to realize the four-point mooring multi-motor collaborative positioning control, and positioning the mooring platform within a preset area. The present invention decomposes the multi-point mooring positioning into a plurality of groups of four-point mooring controls with four-corner symmetry, and the stability, rapidity and accuracy of the mooring platform positioning can be effectively realized through the distributed collaborative control of the plurality of groups of four-point moorings.

Description

Technical Field

[0001] The invention relates to the technical field of mooring control, and in particular to a control method for a four-point mooring model of multi-point mooring positioning. Background Art

[0002] Multi-point mooring is used for fixed-point positioning and regional shifting mooring control of engineering ships, semi-submersible offshore platforms, etc. The number of mooring points used varies with the size of the moored objects, and is generally 4 to 16 points. In multi-point mooring control, the mooring cables affect each other, and each mooring winch drives the mooring cable to tighten / relax in a forward / reverse direction. The mooring winches must coordinate with each other to achieve mooring positioning or shifting mooring control. However, most of the literature in the field of mooring control is a functional description of mooring characteristic analysis and control methods. There is no clear and detailed study of mooring control methods, and there is a lack of description of the mathematical relationship between multi-point moorings; for multi-point mooring control that requires propeller propulsion to assist, there are still problems of complex control and energy-saving, and it does not give full play to the control function of multi-point mooring; the existing multi-point mooring control literature lacks research on forward and inverse solution models, and the coordination between multi-point moorings lacks mathematical model analysis. Therefore, the present invention studies the four-point mooring model method for multi-point mooring control, which is of great significance, and can fill the gap in the application of multi-point mooring forward solution-inverse solution control technology in this field. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in mooring positioning technology to at least some extent. To this end, one object of the present invention is to provide a four-point mooring model control method for multi-point mooring positioning, which decomposes multi-point mooring positioning into a plurality of groups of four-point mooring controls that are symmetrical at four corners, and achieves the stability, rapidity and accuracy of mooring platform positioning through the distributed collaborative control of the plurality of groups of four-point moorings.

[0004] To achieve the above object, the present invention is implemented through the following technical solutions:

[0005] A control method for a four-point mooring model of multi-point mooring positioning is provided. The working positioning point of a mooring platform is determined, and four anchor points are symmetrically arranged with the working positioning point as the center. The four anchor points are rectangular. Four mooring cable outlets of the mooring platform are respectively connected to the corresponding four anchor points with mooring cables. The mooring cables are adjusted in length by mooring winches. The mooring winches are driven by mooring motors. The directions of the long side and the short side of the rectangle are respectively the X-axis direction and the Y-axis direction, and a geodetic coordinate system is established with the working positioning point as the origin. The method comprises:

[0006] Determine the long side spacing and the short side spacing of the rectangle based on the geodetic coordinate system, and establish a four-point mooring forward solution absolute motion model and a four-point mooring forward solution relative motion model according to the long side spacing, the short side spacing and the position of the working positioning point, wherein the four-point mooring forward solution absolute motion model is a mathematical relationship model between the mooring line length and the working positioning point position, and the four-point mooring forward solution relative motion model is a mathematical relationship model between the mooring line length deviation and the working positioning point position deviation;

[0007] Obtaining a four-point mooring inverse solution model according to the four-point mooring forward solution absolute motion model and the four-point mooring forward solution relative motion model;

[0008] Establishing a drive control model between a mooring motor and a mooring cable, wherein the drive control model is a mathematical relationship model between a rotation angle of the mooring motor and a length of the mooring cable;

[0009] A four-point mooring multi-motor collaborative positioning control model is established according to the four-point mooring inverse solution model and the drive control model. The position deviation of the working positioning point is adjusted by adjusting the rotation angles of the four mooring motors in the four-point mooring multi-motor collaborative positioning control model to realize four-point mooring multi-motor collaborative positioning control and position the mooring platform within a preset area.

[0010] Optionally, the four-point mooring forward solution absolute motion model and the four-point mooring forward solution relative motion model are respectively expressed by the following formulas:

[0011]

[0012]

[0013] Among them, L1~L4 are the lengths of the four mooring cables, a and b are half of the distance between the short and long sides of the four-point mooring rectangle, (x, y, z) are the position coordinates of the working positioning point, ΔL1~ΔL4 are the length deviations of the four mooring cables, and (Δx, Δy, Δz) are the position deviation coordinates of the working positioning point.

[0014] Optionally, the four-point mooring inverse solution model is expressed by the following formula:

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021] Optionally, the drive control model between the mooring motor and the mooring cable is expressed by the following formula:

[0022]

[0023] Among them, L m is the corresponding mooring line length, K m is the proportionality coefficient, θ m is the corresponding mooring motor rotation angle, ΔL m is the corresponding mooring line length deviation, Δθ m is the corresponding mooring motor angle deviation.

[0024] Optionally, the four-point mooring multi-motor collaborative positioning control model is expressed by the following formula:

[0025]

[0026]

[0027] Among them, Δθ m1 ~Δθ m4 is the motor rotation angle deviation from the mooring motor 1 to the mooring motor 4.

[0028] Optionally, the four-point mooring multi-motor collaborative positioning control process includes a mooring cable length-tension control and a mooring joint positioning control process.

[0029] Optionally, a tension sensor and a length encoder are provided at the cable outlet of the mooring cable to measure the tension and length of the mooring cable. The mooring cable length-tension control method includes:

[0030] Establish the mooring motor angle-speed-torque-current control model. The mooring motor is equipped with an angle encoder to measure the position of the mooring motor shaft.

[0031] According to the detected tension and length of the mooring cable, the torque and angle of the mooring motor are controlled by the mooring motor angle-speed-torque-current control model to feedback-adjust the tension and length of the mooring cable;

[0032] The mooring motor angle-speed-torque-current control model is expressed by the following formula:

[0033]

[0034]

[0035] I m =K φ T m

[0036] Among them, T s is the sampling period, is the mooring motor speed, ΔQ m is the mooring motor speed deviation; T m is the mooring motor torque, I m is the mooring motor current, K Φ is the coefficient of servo motor current and torque, K Φ is a constant, K p1 , K i1 and K d1 is the position loop / angle loop PID coefficient, K p2 , K i2 and K d2 is the speed loop PID coefficient, △θ m (k) is the k-th sampling angle deviation of the mooring motor, △θ m (k-1) is the angular deviation of the mooring motor at the k-1th sampling time; △Ω m (k) is the speed deviation of the mooring motor at the kth sampling, △Ω m (k-1) is the speed deviation of the mooring motor at the k-1th sampling; k is the number of sampling times.

[0037] Optionally, the mooring joint positioning control method includes:

[0038] The position deviation of the first working positioning point is obtained by determining the positioning point position through the GPS positioning system or Beidou positioning system of the mooring platform;

[0039] The position deviation of the second working positioning point is calculated by the four-point mooring multi-motor collaborative positioning control model;

[0040] Determine whether the first working positioning point position deviation and the second working positioning point position deviation are both within a preset error range;

[0041] If both are within the preset error range, the control enters the mooring line constant tension control mode;

[0042] If there is at least one working positioning point whose position deviation is not within the preset error range, the control enters the mooring line length control mode according to the joint positioning error identification result.

[0043] Optionally, controlling the mooring cable to enter the constant tension control mode is to control the tension of the mooring cable to be a preset tension, and to make the length of the mooring cable vary within a positioning error range.

[0044] Optionally, when the control enters the mooring line length control mode, the method further includes:

[0045] Determine whether the mooring line tension is less than or equal to the tension limit value;

[0046] When the mooring cable tension is less than or equal to the tension limit value, the motor cable reeling or releasing control is performed according to the offset direction of the mooring platform until the position deviation of the first working positioning point and the position deviation of the second working positioning point are both within the preset error range, and the control enters the mooring cable constant tension control mode.

[0047] The present invention has at least the following technical effects:

[0048] 1. The present invention decomposes multi-point mooring positioning into multiple groups of four-point mooring control with four-corner symmetry, and realizes the stability, rapidity and accuracy of mooring platform (ship) positioning through multiple groups of four-point mooring distributed collaborative control.

[0049] 2. The present invention simplifies multi-point mooring into a four-point mooring model, establishes a forward / inverse solution model of the mooring cable and the mooring platform (ship) position, and converts the mooring platform (ship) position control into mooring cable length control, making the control relationship clear and improving the control performance.

[0050] 3. The present invention establishes a mooring cable and mooring motor drive model, converts the mooring cable length control into the position (angle) control of the mooring motor, and realizes the constant length control and constant tension control of the mooring cable through the position control torque limit of the driving motor, thereby improving the positioning accuracy and safety of the mooring platform (ship).

[0051] 4. The present invention clarifies the mathematical relationship between the mooring cable and its driving motor for positioning control, as well as the synergistic relationship between them, thus filling the gap in control in the mooring field.

[0052] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 A schematic diagram of setting four anchor points provided in one embodiment of the present invention;

[0054] Figure 2 A flowchart of a four-point mooring model control method for multi-point mooring positioning provided by an embodiment of the present invention;

[0055] Figure 3 A working principle diagram of a four-point mooring model for multi-point mooring positioning provided by an embodiment of the present invention;

[0056] Figure 4 A flowchart of a four-point mooring model for multi-point mooring positioning provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0057] The present embodiment is described in detail below, and examples of the embodiment are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0058] The following describes the control method of the multi-point mooring positioning and four-point mooring model of this embodiment with reference to the accompanying drawings.

[0059] In multi-point mooring, three-point mooring can achieve positioning control, but four-point mooring has high reliability and good redundancy. The moored objects are of different sizes, and each mooring point is distributed with 1 to 4 mooring cables. Each mooring point corresponds to 1 to 4 mooring anchor points. The combined force of multiple mooring cables at each mooring point can be simplified to one mooring cable, which requires that multiple mooring cables under the same mooring point need to be controlled synchronously at the same time. In this embodiment, it is feasible and necessary to simplify the multi-point mooring to four-point mooring.

[0060] For the four-point mooring model control method, the working positioning point of the mooring platform can be determined first, and four anchor points are symmetrically set with the working positioning point as the center. The four anchor points are rectangular, and the four mooring cable outlets of the mooring platform are connected to the corresponding four anchor points with mooring cables. The mooring cable is adjusted by a mooring winch. The mooring winch is driven by a mooring motor. The directions of the long and short sides of the rectangle are respectively the X-axis direction and the Y-axis direction, and a geodetic coordinate system is established with the working positioning point as the origin.

[0061] Specifically, after the mooring platform (ship) reaches the working position in the designated sea area, this working point (x0, y0) can be determined as the working positioning point, and then the point is detected as (x′0, y′0) by GPS (positioning device) or Beidou (positioning device). Further, four anchor points are arranged symmetrically with the working positioning point (x0, y0) as the center, and they are in a rectangular shape. Then, the long side is taken as the X-axis direction, and the distance between the two anchors on the long side is 2b; the short side is taken as the Y-axis direction, and the distance between the two anchors on the short side is 2a. The schematic diagram of the four-anchor arrangement is as follows: Figure 1 As shown, the geodetic coordinate system XYZ satisfies the right-hand rule.

[0062] like Figure 1As shown, A, B, C, and D are the mooring cable holes of the mooring platform (ship); O1, O2, O3, and O4 are four mooring fixed anchor points; AO1, BO2, CO3, and DO4 are the lengths of the mooring cables, which are AO1=L1, BO2=L2, CO3=L3, and DO4=L4 respectively; XYZ is the positioning coordinate system (geodetic coordinate system), and O is the coordinate origin; the Z-axis direction is the draft of the mooring platform (ship), which represents the height of the mooring platform (ship) from the seabed and can be approximately constant; wherein the X-axis is parallel to the longitudinal direction of the mooring platform (ship), and the Y-axis is parallel to the transverse direction of the mooring platform (ship). In this embodiment, O1O4=O2O3=2b; O1O2=O3O4=2a can be set, and the coordinates of the working center point (positioning point) of the mooring platform (ship) are (x, y, z).

[0063] It should be noted that for multi-point moorings with more than 4 points, such as 8-, 12-, and 16-point moorings, this method is also used to group them into 2 four-point moorings, 3 four-point moorings, and 4 four-point moorings in sequence. Each group of four-point moorings is arranged symmetrically in a four-point rectangle. After the positioning anchor is in place, it is necessary to conduct an anchor pulling test. On the one hand, it allows the anchor to be gripped into the soil, and on the other hand, it is used to detect whether the anchor can be fixed to prevent the anchor from dragging. After the four-point positioning anchor is fixed, the multi-point mooring motors work together to adjust the mooring platform to within the specified range. At this time, the mooring motor enters the constant tension control mode, and the mooring cable tension at this time is pre-tension. The mooring platform (ship) begins to lay anchors and position. At this time, the sea conditions are required to be good. Among them, the key to the arrangement of the four-point mooring anchor is that the four anchor points form a rectangle, and the positioning point is set within the range near the center of the rectangle.

[0064] Figure 2 This is a flow chart of a four-point mooring model control method for multi-point mooring positioning provided by an embodiment of the present invention. Figure 3 The working principle diagram of the four-point mooring model for multi-point mooring positioning provided by one embodiment of the present invention. Figure 2 and Figure 3 As shown, the method includes:

[0065] Step S1: Determine the long side spacing and short side spacing of the rectangle based on the geodetic coordinate system, and establish a four-point mooring correct solution absolute motion model and a four-point mooring correct solution relative motion model according to the long side spacing, the short side spacing and the position of the working positioning point. The four-point mooring correct solution absolute motion model is a mathematical relationship model between the mooring cable length and the working positioning point position, and the four-point mooring correct solution relative motion model is a mathematical relationship model between the mooring cable length deviation and the working positioning point position deviation.

[0066] Among them, the absolute motion model of the four-point mooring positive solution and the relative motion model of the four-point mooring positive solution are expressed by the following formulas:

[0067]

[0068]

[0069] Among them, L1~L4 are the lengths of the four mooring cables, a and b are half of the distance between the short and long sides of the four-point mooring rectangle, (x, y, z) are the position coordinates of the working positioning point, ΔL1~ΔL4 are the length deviations of the four mooring cables, and (Δx, Δy, Δz) are the position deviation coordinates of the working positioning point.

[0070] Thus, the mathematical relationship model between the mooring line length Lm (the number of mooring points m=1, 2, 3, 4) and the mooring working positioning point (x, y, z) and the mathematical relationship model between the mooring line deviation △Lm and the position deviation of the mooring working positioning point (△x, △y, △z) can be obtained.

[0071] Step S2: Obtain a four-point mooring inverse solution model according to the four-point mooring forward solution absolute motion model and the four-point mooring forward solution relative motion model.

[0072] Among them, the four-point mooring inverse solution model is expressed by the following formula:

[0073]

[0074]

[0075]

[0076]

[0077]

[0078]

[0079] Therefore, the inverse motion model of the position relationship between the mooring cable and the mooring platform (ship) can be established through formulas (3)-(8), thereby determining the analytical expressions of the working positioning point (x, y, z) and (△x, △y, △z) changing with the mooring cable length Lm and the length deviation △Lm, and clarifying the quantitative relationship of the influence of the mooring cable on the mooring positioning.

[0080] Step S3: establishing a drive control model between the mooring motor and the mooring cable, wherein the drive control model is a mathematical relationship model between the rotation angle of the mooring motor and the length of the mooring cable.

[0081] Specifically, the mooring motor is a variable frequency motor. When the variable frequency motor drives the mooring winch, the mooring winch can tighten / relax the mooring cable. Therefore, the drive control model between the mooring motor and the mooring cable can be determined, that is, the relationship between the forward / reverse control of the mooring motor angle and the length of the mooring cable can be determined. The drive control model between the mooring motor and the mooring cable is expressed by the following formula:

[0082]

[0083] Among them, L m is the corresponding mooring line length, K m is the proportionality coefficient, which is related to the reduction ratio of the mooring motor driven winch, the winch drum diameter and the cable diameter, θ m is the corresponding mooring motor rotation angle, ΔL m is the corresponding mooring line length deviation, Δθ m is the corresponding mooring motor angle deviation.

[0084] Therefore, the mooring cable length control can be converted into the position (rotation angle) control of the mooring motor through formula (9), thereby determining the control effect of the mooring motor control on the moored platform (ship) and reducing the control difficulty and complexity.

[0085] Step S4: A four-point mooring multi-motor collaborative positioning control model is established according to the four-point mooring inverse solution model and the drive control model. The position deviation of the working positioning point is adjusted by adjusting the rotation angles of the four mooring motors in the four-point mooring multi-motor collaborative positioning control model to realize the four-point mooring multi-motor collaborative positioning control and position the mooring platform within the preset area.

[0086] Specifically, formula (9) can be substituted into formulas (6) and (7) to obtain the four-point mooring multi-motor collaborative positioning control model. The four-point mooring multi-motor collaborative positioning control model is expressed by the following formula:

[0087]

[0088]

[0089] Among them, Δθ m1 ~Δθ m4 is the motor rotation angle deviation from the mooring motor 1 to the mooring motor 4.

[0090] The △x control of the moored platform (ship) can be realized through the four-point mooring multi-motor collaborative positioning control model of formula (10), and the △y control of the moored platform (ship) can be realized through the four-point mooring multi-motor collaborative positioning control model of formula (11). It can be seen from formulas (10) and (11) that a mooring motor position control can affect △x and △y at the same time, so that the adjustment direction and coordinate quadrant can be determined according to the positive and negative values ​​of △x and △y, and the mooring platform can be positioned within the specified range (in the coordinate origin area) through the collaborative control of four mooring motors.

[0091] like Figure 4 As shown, the four-point mooring multi-motor collaborative positioning control process specifically includes the mooring cable length-tension control and the mooring joint positioning control process.

[0092] Among them, mooring line length-tension control includes:

[0093] Establish the mooring motor angle-speed-torque-current control model;

[0094] According to the detected tension and length of the mooring cable, the torque and angle of the mooring motor are controlled through the mooring motor angle-speed-torque-current control model to feedback adjust the tension and length of the mooring cable;

[0095] Among them, the mooring motor angle-speed-torque-current control model is expressed by the following formula:

[0096]

[0097]

[0098] I m =K φ T m (14)

[0099] Among them, T s is the sampling period, is the mooring motor speed, △Ω m is the mooring motor speed deviation; T m is the mooring motor torque, I m is the mooring motor current, K Φ is the coefficient of servo motor current and torque, K Φ is a constant, K p1 , K i1 and K d1 is the position loop / angle loop PID coefficient, K p2 , K i2 and K d2 is the speed loop PID coefficient, △θ m (k) is the k-th sampling angle deviation of the mooring motor, △θ m (k-1) is the angular deviation of the mooring motor at the k-1th sampling time; △Ω m (k) is the speed deviation of the mooring motor at the kth sampling, △Ω m (k-1) is the speed deviation of the mooring motor at the k-1th sampling; k is the number of sampling times.

[0100] Specifically, since the change in the length of the mooring cable is proportional to the rotation angle of the mooring winch and also proportional to the rotation angle of the mooring motor, the position control of the mooring motor is the position control of the mooring platform (ship), and since the speed (rotation speed) control of the mooring motor can improve the dynamic performance of the mooring, and the torque control of the mooring motor can achieve tension control and limit control of the mooring cable to ensure the safety and reliability of the mooring cable, a mooring motor rotation angle-rotation speed-torque-current control model can be established in this embodiment to achieve length-tension control of the mooring cable through the model.

[0101] In this embodiment, a roller and a tensioning wheel can be added at the mooring cable outlet hole, and the length change of the mooring cable can be detected by the absolute value encoder on the roller, that is, the angle encoder, and the mooring motor has its own encoder to detect its rotation angle and speed, and the tension of the mooring cable can be detected by the tension sensor set on the tensioning wheel, thereby realizing accurate feedback of the dynamic characteristics of the mooring cable, and further realizing the position (rotation angle), speed and torque feedback and closed-loop control of the mooring winch motor. In this embodiment, in order to improve the control accuracy, the position and torque control of the mooring winch motor can be calibrated by the length change and tension value of the mooring cable detected by the above sensors.

[0102] In one embodiment of the present invention, the mooring joint positioning control includes:

[0103] The position of the positioning point determined by the GPS positioning system or Beidou positioning system of the mooring platform is used to obtain the position deviation of the first working positioning point; the position deviation of the second working positioning point is calculated by the four-point mooring multi-motor collaborative positioning control model; it is determined whether the position deviation of the first working positioning point and the position deviation of the second working positioning point are both within the preset error range; if both are within the preset error range, the control enters the mooring cable constant tension control mode; if there is at least one working positioning point position deviation that is not within the preset error range, the control enters the mooring cable length control mode according to the joint positioning error identification result.

[0104] Specifically, GPS or Beidou can be used to detect the position (x′0, y′0) of the moored platform (ship) to obtain the position deviation (△x′, △y′) of the first working positioning point, and at the same time, the position deviation (△x, △y) of the second working positioning point of the moored platform (ship) can be calculated through the four-point mooring multi-motor collaborative positioning control model.

[0105] It should be noted that multi-point mooring positioning control based on GPS or Beidou position feedback can be adopted, and position feedback control indirectly obtained by the calculation method of the four-point mooring multi-motor collaborative positioning control model can also be adopted. In this embodiment, a combined positioning control combining the two can be adopted. In the mooring joint positioning control, if one of the position deviations (△x′, △y′) and (△x, △y) exceeds the preset error range such as (3-5)% of the water depth H, an audible and visual alarm is issued. In this embodiment, the four-point mooring model control based on the position deviation (△x, △y) can be used, and then the position deviation (△x′, △y′) of GPS or Beidou positioning can be referred to to perform mooring platform positioning control until each position deviation is ≤ (3-5)% of the water depth H, and the mooring positioning adjustment is completed. In this embodiment, the use of position dual closed-loop control can improve the safety, reliability and accuracy of mooring platform positioning.

[0106] In one embodiment of the present invention, controlling the mooring line to enter the constant tension control mode is controlling the tension of the mooring line to be a preset tension, and making the length of the mooring line vary within a positioning error range.

[0107] Specifically, the tension value of the constant tension control mode is variable as the length of the mooring cable changes, and its variation law is determined by formula (9) and formula (12)-(14). The mooring cable has a maximum tension limit value, that is, the breaking tension of the mooring cable. The working range of the tension control mode is between the pre-tension and the maximum tension limit value. Since the mooring positioning will move under the action of external wind and wave currents, the length of the mooring cable will also change, that is, the mooring cable on the upwind side becomes longer and the mooring cable on the leeward side becomes shorter, which causes the tension value of the constant tension control mode to change. The tension value on the upwind side becomes larger and the tension value on the leeward side becomes smaller. The two change synchronously, which can prevent the platform position from changing suddenly and limit the platform inclination angle to no more than 1° (the value required by the classification society regulations) until the platform stops moving, and then enters the constant value control mode under the new tension value. When the position deviation of the mooring positioning is within the allowable positioning range, the system can automatically perform constant tension control of the mooring cable, that is, control the tension of the mooring cable to be constant tension, and allow the length of the mooring cable to change within the positioning error range. At this time, the mooring cable is equivalent to a spring effect. Due to the different interference directions of wind, waves and currents, the tension control values ​​of each mooring cable are different. Therefore, the constant tension control mode can also detect whether the mooring anchor moves. If the mooring position does not change, but the length of the mooring cable changes direction, the system can automatically determine that the anchor is dragging, or the connection between the mooring cable and the anchor is loose, and then the system will issue an audible and visual alarm.

[0108] As mentioned above, tension control can be achieved through the mooring motor angle-speed-torque-current control model. Since the mooring cable tension control can be achieved through the mooring motor torque control, the mooring cable tension change can be detected and feedback adjustment can be performed through the model to control the entry into the mooring cable constant tension control mode.

[0109] In one embodiment of the present invention, when the control enters the mooring cable length control mode, the method further includes: determining whether the mooring cable tension is less than or equal to the tension limit value; when the mooring cable tension is less than or equal to the tension limit value, controlling the motor to retract or release the cable according to the offset direction of the mooring platform until the position deviation of the first working positioning point and the position deviation of the second working positioning point are both within a preset error range, and then controlling the mooring cable to enter the constant tension control mode.

[0110] Specifically, if the moored platform (ship) exceeds the allowable range, the system will alarm and automatically switch to the mooring cable length control mode. At this time, the tension will no longer remain at a constant value. The position motor in the opposite direction (windward side) of the drift direction of the moored platform (ship) reels in the cable, and the tension increases, but it cannot exceed the breaking tension of the mooring cable. Then the position motor on the offset direction side (leeward side) releases the cable. It should be noted that the motors on both sides are required to be synchronized at the same time to prevent the platform from tilting. If the influence of wind, waves and currents is large, causing the tension on the windward side to reach the breaking tension of the mooring cable, the system can automatically switch the windward side motor to a fixed value control with tension amplitude limitation. In this case, for 8-point / 12-point / 16-point multi-point mooring systems, the system will automatically start the second set of four-point mooring model control; for 4-point mooring systems, only the motor on the same side of the windward side can be used for cable reeling control. When the moored platform (ship) returns to the predetermined position, that is, the position deviation (△x′, △y′) and (△x, △y) ≤ (3-5)% of the water depth H, the adjustment is completed, and then all motors of the multi-point mooring are subjected to secondary tension adjustment, and each motor bears the additional wind, wave and current loads.

[0111] The present invention clarifies the mathematical model of mooring motor-mooring cable length and the mathematical model of mooring cable length and mooring platform (ship) position, thereby clarifying the quantitative relationship between the mooring cable length change △Lm and the mooring platform (ship) position (△x, △y), as well as the quantitative relationship between the coordinated control between multi-point mooring and the positioning control of the mooring platform (ship). The present invention converts the mooring cable length control into the position control of the mooring drive motor, and uses the position loop-speed loop-current loop of the variable frequency motor drive principle to convert the mooring cable length-tension control of the mooring platform (ship) positioning into the mooring motor rotation angle-torque control, thereby realizing the positioning control of the mooring platform (ship).

[0112] The working principle of the present invention is as follows: firstly, the initial position coordinates (x0, y0) of the mooring platform (ship) are determined, then four mooring fixed anchor points are symmetrically arranged, and the initial position coordinates (x0, y0) are used as the coordinate origins of the four mooring fixed anchor points, and the mathematical models of formulas (1) to (9) are established, then the initial length of the mooring cable is calibrated to correspond to the starting position of the mooring motor, and the corresponding relationship between the change in the length of the mooring cable and the rotation angle of the mooring motor is clarified, and then the position coordinates (x′0, y′0) of the mooring platform (ship) are detected by GPS or Beidou for reference of mooring positioning control, and finally the change amount and tension of the mooring cable are detected in real time for compensation and position calibration, so as to realize the position control of the mooring platform (ship) based on the four-point mooring model method.

[0113] In summary, the present invention decomposes multi-point mooring positioning into a plurality of groups of four-point mooring controls with four-corner symmetry, and realizes the stability, rapidity and accuracy of mooring platform (ship) positioning through a plurality of groups of four-point mooring distributed collaborative control; the present invention simplifies multi-point mooring into a four-point mooring model, establishes a forward solution / inverse solution model of the position of the mooring cable and the mooring platform (ship), and converts the position control of the mooring platform (ship) into the length control of the mooring cable, so that the control relationship is clear and the control performance is improved; the present invention establishes a mooring cable and a mooring motor driving model, converts the length control of the mooring cable into the position (angle) control of the mooring motor, and realizes the length constant value control and constant tension control of the mooring cable through the position control torque limit of the driving motor, thereby improving the positioning accuracy and safety of the mooring platform (ship); the present invention clarifies the mathematical relationship between the mooring cable and its driving motor for positioning control, as well as the collaborative relationship between them, filling the gap in the control of the mooring field; in addition, the tension control mode of the present invention can also judge whether the anchor is dragged, whether the connection between the mooring cable and the anchor is loose, and realize sound and light alarm.

[0114] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0115] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A control method for a four-point mooring model for multi-point mooring positioning, characterized in that: The working positioning point of the mooring platform is determined, four anchor points are symmetrically set with the working positioning point as the center, the four anchor points are rectangular, four mooring cable outlet holes of the mooring platform and the corresponding four anchor points are respectively connected with mooring cables, the mooring cables are adjusted in length by mooring winches, and the mooring winches are driven by mooring motors. The directions of the long side and the short side of the rectangle are respectively the X-axis direction and the Y-axis direction, and a geodetic coordinate system is established with the working positioning point as the origin. The method includes: Determine the long side spacing and the short side spacing of the rectangle based on the geodetic coordinate system, and establish a four-point mooring forward solution absolute motion model and a four-point mooring forward solution relative motion model according to the long side spacing, the short side spacing and the position of the working positioning point, wherein the four-point mooring forward solution absolute motion model is a mathematical relationship model between the mooring line length and the working positioning point position, and the four-point mooring forward solution relative motion model is a mathematical relationship model between the mooring line length deviation and the working positioning point position deviation; Obtaining a four-point mooring inverse solution model according to the four-point mooring forward solution absolute motion model and the four-point mooring forward solution relative motion model; Establishing a drive control model between a mooring motor and a mooring cable, wherein the drive control model is a mathematical relationship model between a rotation angle of the mooring motor and a length of the mooring cable; A four-point mooring multi-motor collaborative positioning control model is established according to the four-point mooring inverse solution model and the drive control model. The position deviation of the working positioning point is adjusted by adjusting the rotation angles of the four mooring motors in the four-point mooring multi-motor collaborative positioning control model to realize the four-point mooring multi-motor collaborative positioning control and position the mooring platform in a preset area. The four-point mooring positive solution absolute motion model and the four-point mooring positive solution relative motion model are respectively expressed by the following formulas: Among them, L1~L4 are the lengths of the four mooring cables, a and b are half of the distance between the short and long sides of the four-point mooring rectangle, (x, y, z) are the position coordinates of the working positioning point, △L1~△L4 are the length deviations of the four mooring cables, and (△x, △y, △z) are the position deviation coordinates of the working positioning point.

2. The method for controlling a four-point mooring model for multi-point mooring positioning according to claim 1, characterized in that: The four-point mooring inverse solution model is expressed by the following formula:

3. The multi-point mooring positioning four-point mooring model control method according to claim 2, characterized in that: The drive control model between the mooring motor and the mooring cable is expressed by the following formula: Among them, L m is the corresponding mooring line length, K m is the proportionality coefficient, θ m is the corresponding mooring motor rotation angle, ΔL m is the corresponding mooring line length deviation, Δθ m is the corresponding mooring motor angle deviation.

4. The control method of the four-point mooring model for multi-point mooring positioning according to claim 3, characterized in that: The four-point mooring multi-motor collaborative positioning control model is expressed by the following formula: Among them, Δθ m1 ~Δθ m4 is the motor rotation angle deviation from the mooring motor 1 to the mooring motor 4.

5. The control method of the four-point mooring model for multi-point mooring positioning according to claim 4, characterized in that: The four-point mooring multi-motor collaborative positioning control process includes the mooring cable length-tension control and the mooring joint positioning control process.

6. The control method of the four-point mooring model for multi-point mooring positioning according to claim 5, characterized in that: A tension sensor and a length encoder are provided at the cable outlet of the mooring cable to measure the tension and length of the mooring cable. The mooring cable length-tension control method includes: Establish the mooring motor angle-speed-torque-current control model; the mooring motor is equipped with an angle encoder to measure the position of the mooring motor shaft; According to the detected tension and length of the mooring cable, the torque and angle of the mooring motor are controlled by the mooring motor angle-speed-torque-current control model to feedback-adjust the tension and length of the mooring cable; The mooring motor angle-speed-torque-current control model is expressed by the following formula: I m =K φ T m Among them, T s is the sampling period, is the mooring motor speed, △Ω m is the mooring motor speed deviation; T m is the mooring motor torque, I m is the mooring motor current, K Φ is the coefficient of servo motor current and torque, K Φ is a constant, K p1 , K i1 and K d1 is the position loop / angle loop PID coefficient, K p2 , K i2 and K d2 is the speed loop PID coefficient, △θ m (k) is the k-th sampling angle deviation of the mooring motor, △θ m (k-1) is the angular deviation of the mooring motor at the k-1th sampling time; △Ω m (k) is the speed deviation of the mooring motor at the kth sampling, △Ω m (k-1) is the speed deviation of the mooring motor at the k-1th sampling; k is the number of sampling times.

7. The control method of the four-point mooring model for multi-point mooring positioning according to claim 6, characterized in that: The mooring joint positioning control method includes: The position deviation of the first working positioning point is obtained by determining the positioning point position through the GPS positioning system or Beidou positioning system of the mooring platform; The position deviation of the second working positioning point is calculated by the four-point mooring multi-motor collaborative positioning control model; Determine whether the first working positioning point position deviation and the second working positioning point position deviation are both within a preset error range; If both are within the preset error range, the control enters the mooring line constant tension control mode; If there is at least one working positioning point whose position deviation is not within the preset error range, the control enters the mooring line length control mode according to the joint positioning error identification result.

8. The control method of the four-point mooring model for multi-point mooring positioning according to claim 7, characterized in that: Controlling the mooring cable constant tension control mode is to control the tension of the mooring cable to be a preset tension, and to make the length of the mooring cable vary within a positioning error range.

9. The control method of the four-point mooring model for multi-point mooring positioning according to claim 7, characterized in that: When the control enters the mooring line length control mode, the method further comprises: Determine whether the mooring line tension is less than or equal to the tension limit value; When the mooring cable tension is less than or equal to the tension limit value, the motor cable reeling or releasing control is performed according to the offset direction of the mooring platform until the position deviation of the first working positioning point and the position deviation of the second working positioning point are both within the preset error range, and the control enters the mooring cable constant tension control mode.

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