CN104050370B - Method for performing dynamic positioning ability analysis based on dichotomy - Google Patents

Abstract

The invention provides a method for performing the dynamic positioning ability analysis based on the dichotomy. The method comprises the steps of formulating a dichotomy judgment function I; determining a wind speed action range [a, b]; setting a solving error tolerance epsilon as 1 m/s; calculating and updating the wind speed action range; estimating the overall optimization step number. The method for performing the dynamic positioning ability analysis based on the dichotomy can obtain the maximum environmental force (generally expressed by the maximum wind speed) resisted under different heading angles of the ocean structure, the solving process is simplified, the solving efficiency is improved, and the stability is better compared with the traditional method.

Description

The method that dynamic positioning capability analysis are carried out based on two way classification

Technical field

The present invention relates to a kind of method of dynamic positioning capability analysis, especially for have multiple pusher-type or Multiple angle of rake marine structures.

Background technology

Field of exploring with the mankind extends to the ocean of the length and breadth of land, in the marine structure of deepwater regions operation, such as ocean Platform, what the orientation problem of all kinds of workboats etc. became becomes increasingly conspicuous.In shallow water area, the positioning of marine structure even can be led to Cross anchoring approach to solve, but the increasing with the depth of water, exponentially trend raises the cost of anchoring positioning, so needing new determining Position mode solves the problems, such as that marine structure positions.Dynamic positioning occurs in this context and grows up.Ocean On works, the dynamic positioning system of configuration passes through satellite or underwater sound array obtains works current location, and controller is by itself and mesh The deviation of cursor position calculates works and is returned to target location required thrust and torque, and push system produces required thrust And torque, so that marine structure is maintained near target location.

Dynamic positioning capability analysis can obtain dynamic positioning ability under different bows are to angle for the marine structure.In design With during using a set of new dynamic positioning system, safe operation always first wants position.In order to expection reach a kind of safety and Operate effectively, this system is it should be understood that clearly in the working sea area difference maximum environmental forces that can bear downwards of bow. Therefore when designing new dynamic positioning system marine structure it is necessary to carry out dynamic positioning capability analysis.

When carrying out dynamic positioning capability analysis, traditional method for solving is to calculate under angle at certain, is stepped up wind speed, Distributed by thrust, determine whether feasible solution.If there are feasible solution, then represent marine structure and can resist this wind speed and produced Power.Continue to increase wind speed, until no feasible solution produces, that is, obtain the strong wind that under this angle, marine structure can be resisted Speed, the stationkeeping ability analysis of this angle completes.Transform to other angles again to be analyzed.But the shortcoming existing for the method is just The process that is to solve for is slower, during being solved, generally is intended to travel through all values in computational fields, to judge whether Feasible solution.In addition, the scale calculating and to calculate step number in advance also and unknowable and estimate.

Content of the invention

The present invention is exactly that in dynamic positioning capability analysis calculate, calculating speed is relatively slow and solves step number thing in order to solve A kind of method that dynamic positioning capability analysis are carried out based on two way classification that first can not estimate and propose.

The principle of the invention is as follows：

The method using two points of designed discriminant functions as the Rule of judgment solving flow process, ask by the interval composition of wind speed effect The initial condition of solution preocess and successive iterations condition, solve the criterion whether allowable error terminates as solution.At two points Under discriminant function, wind speed effect collective effect that is interval and solving allowable error, dynamic positioning capability analysis not only can be carried out Rapid solving, also can estimate overall optimizing step number simultaneously.

Solve allowable error be selected to distinguish different solving precision, affect overall optimizing step number simultaneously.

The technology of the present invention solution is as follows：

Step 1, formulates two points of discriminant functions according to dynamic positioning ability fast solution method.

$I=\left\{\begin{array}{cc}1,& x\∈A\\ 0,& x\∉A\end{array}\right.$

Wherein, I is two points of discriminant functions, and x ∈ A represents there is feasible solution in the region being solved, now, I=1, table Show that the wind speed that finally can bear can be more than present calculation of wind speed；Expression does not exist feasible in the region being solved Solution, now I=0, represent that the wind speed that finally can bear can be not more than present calculation of wind speed.

Step 2, determines that wind speed effect is interval [a, b].For guaranteeing computational efficiency and the stability of this method, wind speed active region Between should include minimum and maximum wind speed on the premise of, little as far as possible, to reduce the calculating time.Generally choose 180 ° and 90 ° of bows are to the maximum wind velocity in the case of angle as reference.This method advises that the interval initial choosing of wind speed effect is worth：

$\left\{\begin{array}{c}a=\mathrm{\α}\·V_{\max }^{90}\\ b=\mathrm{\β}\·V_{\max }^{180}\end{array}\right.$

The value of wherein factor alpha (possible value 30%) and β (possible value 120%) is entered according to the feature of marine structure Row is chosen.

Step 3, sets and solves allowable error ε.The solution allowable error of wind speed is generally chosen for 1m/s, according to actual need Will, solution allowable error can be reduced.Reduce this value, it is possible to increase solving precision, but the calculating time can be increased.

Step 4, is solved according to calculation process and the effect of real-time update wind speed is interval.Calculation process as shown in figure 1, Each calculating, all carries out two points to wind speed effect interval [a, b], and determines that according to two points of discriminant functions the wind speed after renewal acts on Interval [a, b], carries out subsequent calculations, until interval mould | the b-a | of wind-force effect is less than or equal to allowable error ε, just must go to sea The maximum wind velocity that foreign works can bear under this bow is to angleOther bows follow-up are flowed to the calculating of angle with this Journey is similar, and after completing the angled calculating of institute, the dynamic positioning capability analysis of marine structure just complete.

Step 5, overall optimizing step number is estimated.This method can be estimated to the totally maximum step number of optimizing.False Initial wind speed interval during design is calculated is [a₀, b₀], solution allowable error is ε₀, then interval [a₀, b₀] in calculate point sum For：

$P_{\mathrm{total}}=\frac{b_0-a_0}{{\mathrm{\ϵ}}_0}$

Two points of calculating are exactly in overall calculating point P_totalIn carry out two points, constantly close to final result of calculation.Real Any one point in the windward power effect interval of border can be expressed as：

$x=(\frac{1}{2}{P}_{\mathrm{total}}\±\frac{1}{4}{P}_{\mathrm{total}}\±\·\·\·\±\frac{1}{2^N}{P}_{\mathrm{total}})\·{\mathrm{\ϵ}}_0$

Wherein, optimizing step number N meets 2^N-1＜ P_total≤2^N, optimizing N step, calculating points can for 2N-1 max calculation step number To be estimated by following formula：

N=[log₂P_total]

Wherein [.] represents and rounds.As can be seen here, by given initial wind-force effect interval and solution allowable error, Can be obtained by the step number of optimizing.

Compared with existing computational methods, this computational methods has the characteristics that the solution step number less solution time is shorter, with When optimizing step number can pre-estimate, thus there is higher stability and the efficiency of Geng Gao.If adopting this method, permissible Lifting dynamic positioning capability analysis efficiency, solve points larger in the case of, this efficiency lifting embody more bright Aobvious.

Brief description

Fig. 1 asks for maximum wind velocity flow chart for two way classification.

Fig. 2 is two way classification result of calculation and traditional method result of calculation comparison diagram

Specific embodiments

In order that technological means, creation characteristic, reached purpose and effect that the present invention realizes are easy to understand, tie below Close drawings and Examples, the present invention is expanded on further.

Fig. 1 asks for maximum wind velocity flow chart for two way classification, and according to flow chart, we are carried out point with reference to concrete instantiation Analysis.Certain semi-submerged platform needs to carry out dynamic positioning capability analysis, and analytic angle is 0 ° to 180 °.

Step 1 is first carried out, determines two points of discriminant function I, according to definition：

$I=\left\{\begin{array}{cc}1,& x\∈A\\ 0,& x\∉A\end{array}\right.$

Execution step 2, determines that wind-force effect is interval [a, b], and the initial value formula of this method suggestion is：

$\left\{\begin{array}{c}a=\mathrm{\α}\·V_{\max }^{90}\\ b=\mathrm{\β}\·V_{\max }^{180}\end{array}\right.$

According to the real work situation of platform, wind-force effect interval is set as [a, b]=[0,100].

Execution step 3, sets and solves allowable error ε.The solution allowable error of wind speed is generally chosen for 1m/s, according to reality Need, solution allowable error can be reduced.Choosing in this example and solving allowable error is 1m/s.

Execution step 4, is solved according to calculation process and the effect of real-time update wind speed is interval.According to selected in this example The computation interval taking, carries out two points to it, the wind speed intermediate value after two points Substituted in thrust distribution calculating logic and calculated, seen under this wind conditions, if there is feasible solution.If there is feasible Solution, thenNow wind-force effect interval is updated to [a, b]=[50,100]；If do not deposited In feasible solution, thenNow wind-force effect interval is updated to [a, b]=[0,50].Judge Whether less than allowing solution error ε, now siding-to-siding block length is obviously more than allowable error to the length of wind-force effect interval [a, b], then Interval after updating is carried out two points again, and the process before repeating, till siding-to-siding block length is less than allowable error, just may be used Obtain the maximum wind velocity that this angle lower platform can bear.After converting other angles, calculating process is similar to.This platform is in segment angle As shown in table 1, the result of calculation of its result of calculation and traditional method is as shown in Figure 2 for the calculating data of degree.

Table 1

Table 1 is the actual calculation under Partial angle, in conjunction with table 1, can be best understood from the effect of the execution step of this method Rate.Shown in table four calculate under angle, have all only carried out 7 steps and have just completed calculating, whole dynamic positioning capability analysis institute It is 38373s with the time.Under the same terms, the time used by this example is solved for 46101s using traditional method for solving.Result shows This method is larger for the lifting ratio of computational efficiency, if solving, allowable error requirement is higher or calculating angular interval is bigger, Then the lifting of this efficiency will become more apparent.

In conjunction with Fig. 2 it is found that this method and traditional computational methods difference in result of calculation is little, simultaneously because Actual error will be slightly smaller than allowable error, and the result of calculation of this method will slightly be better than traditional result of calculation.

Basic skills, principal character and the advantages of the present invention of the present invention have been shown and described above.The technology of the industry The simply explanation present invention it should be appreciated that the present invention is not limited by the examples described above, described in examples detailed above and description for the personnel Method, without departing from the spirit and scope of the present invention the present invention also have various changes and modifications, these change and Improvement both falls within scope of the claimed invention.Claimed scope is by appended claims and its equivalent Define.

Claims (1)

1. a kind of the method for dynamic positioning capability analysis is carried out it is characterised in that the method comprises the steps based on two way classification：

Step 1, formulates two points of discriminant function I：

$I=\left\{\begin{array}{cc}1,& x\∈A\\ 0,& x\∉A\end{array}\right.$

Wherein, x ∈ A represents there is feasible solution in the region being solved, now, I=1, represent the wind speed meeting that finally can bear More than present calculation of wind speed；

Represent there is not feasible solution in the region being solved, now I=0, represent that the wind speed that finally can bear can be less In present calculation of wind speed；

Step 2, determines that wind speed effect is interval [a, b], if the interval initial choosing of wind speed effect is worth being：

$\left\{\begin{array}{c}a=\mathrm{\α}\·V_{\max }^{90}\\ b=\mathrm{\β}\·V_{\max }^{180}\end{array}\right.$

Wherein, the value of factor alpha and β is chosen according to the feature of marine structure；

Step 3, sets allowable error ε as 1m/s；

Step 4, calculates and the effect of real-time update wind speed is interval, and detailed process is as follows：Calculate every time, interval to wind speed effect [a, B] carry out two points, the intermediate value after then choosing two pointsSubstituted in thrust distribution logic and calculated, seen this wind speed Under, if there is feasible solution, the wind speed effect after determining to update according to two points of discriminant function I is interval [a, b], if I=1, more NewlyIf I=0, updateCarry out subsequent calculations, until interval length | the b-a | of wind speed effect less than or Equal to allowable error ε, draw the maximum wind velocity that marine structure can bear

Step 5, overall optimizing step number is estimated：Wind speed effect in assuming to calculate is interval to be [a, b], and allowable error is ε, then interval In [a, b] calculate point sum be：

$P_{total}=\frac{b-a}{\mathrm{\ϵ}}$

In overall calculating point P_totalIn carry out two points, constantly close to final maximum wind velocity；

Any one point actually in wind speed effect interval is expressed as：

$x=(\frac{1}{2}{P}_{total}\±\frac{1}{4}{P}_{total}\±...\±\frac{1}{2^N}{P}_{total})\·\mathrm{\ϵ}$

Wherein, optimizing step number N meets 2^N-1＜ P_total≤2^N；Optimizing N walks, and calculating points is 2^N- 1, max calculation step number can be led to Cross following formula to be estimated：

N=[log₂P_total]

Wherein [] represents and rounds.