JP2002173079A - Method for estimating capacity of propulsion actuator for ocean platform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for estimating capacity of a propulsion actuator for an ocean platform allowing estimating required capacity of plural propulsion actuators without experiment. SOLUTION: This method for estimating required capacity of the plural propulsion actuators 11 mounted on the ocean platform 10 consists of a step to set previously a static external force acting on the platform 10 and a thrust of the actuators 11, a step to perform a static equilibrium calculation between the static external force and the thrust of the actuators 11, and a step to evaluate the static equilibrium calculation results by an evaluation function for setting required capacity for each thruster 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating a required capacity and an arrangement position of a plurality of propulsion actuators provided on an offshore platform.

[0002]

2. Description of the Related Art The development of oil fields in the marine environment is in the search for new petroleum resources, from the conventional continental shelf to the continental slope, gradually to deeper waters, and the size of the discovered oil fields is decreasing year by year. It is in. In the future, along with the deepening of the water, it is expected that the water will expand to the marine areas where the natural environmental conditions are more severe. In such a situation,
Floating production systems using offshore platforms
The system is increasing as a system suitable for small-scale marine oil fields.

[0003]

As small-scale marine oil fields have advanced to medium and deep water depths, it has become difficult from a technical and economic point of view to maintain the position of the platform only by the conventional mooring method. Therefore, DP using thruster
Position holding control by S (Dynamic Positioning System) becomes indispensable. The above-mentioned platform is provided with a plurality of thrusters as propulsion actuators.However, conventionally, there has been no means for appropriately evaluating and setting the required capacity and arrangement position of the thrusters. There was no problem.

An object of the present invention is to provide a method for estimating the capacity of a propulsion actuator on an offshore platform which can estimate the required capacities of a plurality of propulsion actuators in view of such a situation without experimentation. is there. Another object of the present invention is to provide a method for estimating the capacity of a propulsion actuator for an offshore platform, which can estimate not only the required capacity of the actuator but also the position of the actuator.

[0005]

SUMMARY OF THE INVENTION The present invention is a method for estimating a required capacity of a plurality of propulsion actuators provided on an offshore platform, the method comprising: a static external force acting on the platform; a thrust of each actuator; Pre-setting, performing a static balance calculation between the static external force and the thrust of each of the actuators, and evaluating a result of the static balance calculation with an evaluation function, thereby obtaining each of the thrusters. Setting the required capacity of the vehicle. In the embodiment of the present invention, a thruster having a swing function is used as the actuator. In an embodiment of the present invention, the static balance calculation includes calculating a balance between a static external force acting in the front-rear direction of the platform and a sum of the component forces in the front-rear direction of the actuators, And the total moment of the platform generated based on the static external force and the thrust of each actuator. And a balance calculation between the sum of In an embodiment of the present invention,
A step of setting a constraint condition for the capacity of each actuator is added, and a penalty function relating to the constraint condition of the capacity is included in the evaluation function, and the evaluation function is diverted. Further, in the embodiment of the present invention, a step of designating a mounting area of each actuator and a step of setting a constraint condition for the mounting area of each actuator are added, and a penalty function related to the mounting area is added to the evaluation function. I try to include it.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An offshore platform which is a component of a floating oil production system includes a monocolumn hull platform 10-1 shown in FIG. Platform 10-2 and the like. The monocolumn hull platform 10-1 has
For example, four thrusters 11 are provided at equal angular intervals on the same circumference, and a semi-sub boat platform 10-
2 is provided with, for example, three or four thrusters 11. Note that the xyz coordinate system (the z axis is a direction perpendicular to the paper surface) in FIG. 1 is an object fixed coordinate system set on the platform 10, and the XYZ coordinate system is a space fixed coordinate system set in space. .

As shown in FIG. 3, the thruster 11 has a propeller rotating motor 111 and a swinging motor 112. The rotation force of the propeller rotation motor 111 is determined by the rotation shaft 113 and the gear 1 that penetrate the swing motor 112.
The rotational force of the swinging motor 112 is transmitted to the neck 118 via the rotating shaft 117.

FIG. 4 shows a static analysis program DP-TOP (Dynamic Positionin) of the platform 10.
g system Thruster force Optima1 distribution
Program). (1) Outline This DP-TOP is composed of a static external force acting on the platform 10 under the influence of wind, waves, tidal current, etc., and a thruster 11
This is an algorithm for performing a static balance calculation with the thrust according to the formula (1) and obtaining the required minimum capacity and mounting position of the thruster 11 based on the calculation result. This algorithm is called DPS
It can be used for the initial planning of the attached platform and for the examination of the necessary thruster capacity and thruster mounting position at the examination stage.

(2) Function and configuration This algorithm is created on a personal computer, and a GUI is used for input and output.
(Graphical user interface)
A wide range of users can be used. G
The entire DP-TOP program is composed of an input / output unit using a UI and a calculation unit created in an appropriate language. The basis of the mathematical logic of the present algorithm is to formulate and solve the thrust distribution problem of the thruster 11 as a mathematical programming problem that minimizes evaluation problems such as performance and cost under a plurality of constraint conditions. Hereinafter, this algorithm will be described.

(Step 1) For example, when the platform is the semi-sub type platform 10-2 shown in FIG. 2, the coordinates of the mounting area (see the diagonal lines) of the individual thrusters 11 are input as inequality conditions. This inequality condition is as follows. x _mini ≤x _{i ≤x maxi} (1) y _mini ≤y _{i ≤y maxi} (2) where i is the number of the thruster, and i = 1, 2,.
N x _min , y _min : minimum value x _max , y _max : maximum value

(Step 2) Initialization setting is performed. That is, the initial mounting position of the thruster 11, the thrust value in the initial state of the thruster 11, and the thrust direction are set. The initial thrust value is given as a component force value in the x and y directions in the object fixed coordinate system.

(Step 3) A dynamic constraint condition is input. That is, the force balance conditions H ₁ and H ₂ in the following equations (3) and (4) are used as force constraints, and the moment balance about the z-axis H ₃ (H _i ) shown in the following equation (5) is used. = 0,
i = 1 to 3) are input as the moment constraints. _{H 1 = F xc -ΣF ix (} 3) H 2 = F yc -ΣF iy (4) H 3 = N zc -Σ (x i F iy + y i F ix) (5) Range of Σ is i =. 1 to N Here, F _xc , F _yc : Total force in the x, y directions F _ix , F _iy : _Component force of the i th thruster in the x, y directions N _zc : Total moment about the z axis x _i , y _i : i Mounting position coordinates of the th thruster

(Step 4) According to the following equations (6) and (7)
Constraint condition G of the thruster 11_i(≧ 0, i = 1 to 6
N) and the thruster 11 according to the following equations (8) to (11).
Mounting position constraint condition G _i(≧ 0, i = 2N + 1-6N) and
Enter G_i= (F_max)^Two− (F_ix)^Two− (F_iy)^Two (6) (i = 1 to N) G_i= (F_max)^Two− (F_ix)^Two− (F_iy)^Two (7) (i = N + 1 to 2N) G_i= X_maxi-X_i (8) (i = 2N + 1-3N) G_i= X_i-X_mini (9) (i = 3N + 1-4N) G_i= Y_maxi-Y_i (10) (i = 4N + 1-5N) G_i= Y_i-X_mini(11) (i = 5N + 1-6N)

(Step 5) The following evaluation function is input. The thrust sum of squares is selected as the evaluation function, and the sum is minimized. f (x) = Σ (F ix) 2 -Σ (F iy) 2 (13) range of sigma are i = 1 to N

(Step 6) The evaluation function set in step 5 is converted into the following total evaluation function. This comprehensive evaluation function is composed of a penalty function of a mechanical constraint condition (equality condition) input in step 2 and a thruster constraint condition (inequality condition) input in step 3. F (x, r, t) = f (x) + ψ (r, H i (x)) + φ (t, G j (x)) (14) where, [psi: equality condition penalty function (= rΣ
The range of {(H _i (x)｝ ² )} is i = 1 to N φ: penalty function of inequality condition (= t ＝ 1 / G
_j (x)) is in the range of i = 1 to Nr, t: parameter

(Step 7) The minimum value of the comprehensive evaluation function is calculated by the quasi-Newton method to obtain the optimum distribution thrust of the thruster 11, that is, the required minimum capacity of the thruster 11, and the optimum mounting position of the thruster 11. . The minimum required capacity and the optimal mounting position of the thruster 11 determined as described above are determined based on the initial plan of the platform 10,
It is used as design data at the examination stage.

(3) Object of analysis ○ Hull form ・ Mono column ・ Semi-sub ・ Other ○ External force condition ・ Steady external force Wave, wind, tidal current ○ Thruster ・ Swing type ○ Type of analysis ・ Analysis of required thruster capacity ・ Optimal thruster mounting position analysis

(4) Input / output items (a) Input data ○ Hull form data ・ Drainage volume ・ Representative length ・ Representative wind pressure area ○ External force conditions ・ Irregular waves (wave direction, average wave period, significant wave height) ・ Wind (wind) Direction, wind speed) ・ Tidal current (tidal current direction, tidal current velocity) ○ External force coefficient ・ Wave drifting force coefficient ・ Wind load coefficient ・ Tidal force coefficient Built-in data: Mono-column type, semi-sub type ○ Thruster required ・ Thruster mounting position coordinates (or mounting) (Position range) ・ Maximum thruster capacity (b) Output data ○ Required thruster capacity ○ Thruster neck angle ○ Evaluation function ○ Optimal mounting position coordinates

(5) Example of Calculation Result FIG. 5 shows the mono-column type platform 10 shown in FIG.
This is an example of the result of analysis calculation by the above algorithm when four thrusters 11 each having a maximum capacity of 80 tons are mounted on a GUI screen.

FIG. 6 shows the relationship between the change in the external force direction β and the optimum mounting position of each thruster 11 when the above algorithm is applied to the semi-sub platform 10-2 shown in FIG. 2, and FIG. 7 shows the external force direction. Change of β and each thruster 11
FIG. 8 illustrates the relationship between the change in the external force direction β and the total force and total moment by each thruster 11, respectively.

In this example, the external force direction β is 0 to 90
° has been changed. And platform 10-2
The origin of the x, y coordinates set in
-2 center of gravity position (center position)
The initial mounting position of No.1 thruster 11 is (0m, 30m)
The same position of No. 2 thruster 11 is set to (−30 m, −30 m
m), the same position of the No. 3 thruster 11 is (30 m, -30
m).

The mounting area of the No. 1 thruster 11 (FIG. 2)
Hatched area) with respect to its initial mounting position (± 15
m, ± 5 m) with the initial mounting position as a reference (± 5 m, ± 5 m).
The mounting area of the No. 3 thruster 11 is set in the range of (± 5 m, ± 5 m) based on the initial mounting position.

As is apparent from the simulation results shown in FIGS. 6 to 8, when the total force and total moment in the x and y directions fluctuate with the change in the external force direction β, the force in each of the thrusters 11 in the x and y directions changes. The mounting position of each thruster 11 is determined in the direction in which the moment fluctuation is corrected while ensuring the balance.

As shown, the difference in thrust between the thrusters 11 is small. When the external force direction β is 90 °,
Although the positions of the No. 2 and No. 3 thrusters 11 are not symmetrical, it is considered that the optimum mounting position is shifted from the symmetrical position due to a slight thrust thrust error.

As described above, the above-mentioned algorithm can optimize the mounting position of the thruster 11, so that the mounting position of the thruster 1 is limited and the thruster 11 must be mounted at an asymmetric position. This is effective as a means for optimizing the thruster mounting position when there is an excellent external force direction.

The algorithm shown in steps 1 to 7 is for analyzing the capacity and the mounting position of the thruster 11 by simulation. If the analysis of the mounting position is unnecessary, step 1 is deleted and the thruster 11 is deleted. Is fixed, and the equations (8) to (11) in step 4, that is, the mounting position constraint condition of the thruster 11 may be deleted.

[0027]

According to the present invention, the required capacities of a plurality of propulsion actuators can be estimated without experiments. Therefore, the design of the platform can be facilitated by effectively utilizing it for estimating the required thruster capacity in the initial planning and study stages of the platform. Further, according to the present invention, it is possible to estimate the optimum mounting position of each actuator in addition to the required capacity. Therefore, the thruster 1 is effectively used as a means for optimizing the thruster mounting position especially when the thruster 1 is limited in the mounting position and the thruster 11 has to be mounted at an asymmetric position or when there is an excellent external force direction. Can be.

[Brief description of the drawings]

FIG. 1 is a plan view of a monocolumn platform.

FIG. 2 is a plan view of a semi-sub type platform.

FIG. 3 is a longitudinal sectional view showing a structure of a thruster.

FIG. 4 is a flowchart illustrating an algorithm for estimating a required capacity and a mounting position of a thruster.

FIG. 5 is a diagram exemplifying a display screen of a required capacity and a mounting position of a thruster.

FIG. 6 is a graph exemplifying a relationship between a change in an external force direction and an optimum mounting position of each thruster.

FIG. 7 is a graph illustrating a relationship between a change in an external force direction and a change in thrust of each thruster.

FIG. 8 is a graph exemplifying a relationship between a change in an external force direction and a total force and a total moment by each thruster.

[Explanation of symbols]

 10-1, 10-2 Offshore Platform 11 Thruster

Claims (5)

[Claims] 1. A method for estimating a required capacity of a plurality of propulsion actuators provided on an offshore platform, comprising: presetting a static external force acting on the platform and a thrust of each of the actuators; Performing a static balance calculation between a static external force and the thrust of each actuator; and evaluating a result of the static balance calculation by an evaluation function,
Setting a required capacity of each of the thrusters. A method for estimating the capacity of a propulsion actuator on an offshore platform. 2. The method according to claim 1, wherein the actuator is a thruster having a swing function. 3. The static balance calculation comprises: calculating a balance between a static external force acting in the front-rear direction of the platform and the sum of the component forces of the actuators in the front-rear direction; And the total moment of the platform generated based on the static external force and the moment generated based on the thrust of each actuator. 3. The method for estimating the capacity of a flow propulsion actuator in an offshore platform according to claim 1, comprising calculating an equilibrium with the sum of 4. The method according to claim 1, further comprising the step of setting a constraint condition for the capacity of each actuator, wherein the evaluation function includes a penalty function relating to the constraint condition of the capacity. 3. A method for estimating the capacity of a propulsion actuator on an offshore platform according to item 1. 5. The method according to claim 1, further comprising a step of designating a mounting area of each of said actuators and a step of setting constraints on the mounting area of each of said actuators, wherein said evaluation function includes a penalty function relating to said mounting area. The method for estimating the capacity of a propulsion actuator in an offshore platform according to any one of claims 1 to 4, characterized in that: