JP5002823B2 - Hull Surrounding UEP Calculation Method - Google Patents

Description

  The present invention relates to a hull peripheral UEP calculation method for estimating and calculating UEP (Underwater Electric Potential) generated around a hull such as surface ships and submarines.

  When two metals having different ionization tendencies exist in the electrolytic solution, a potential difference is generated between the two metals, and an underwater electric field is generated. Looking at this for ships, the hull is composed of various dissimilar metals (the hull is steel, for example, and the propeller is copper, for example). A potential difference occurs, and an underwater electric field is generated. The underwater potential resulting from this underwater electric field is generally referred to as UEP.

  The metal in the hull, which has a high ionization tendency, becomes cations and dissolves in the seawater, so the metal in the hull corrodes. Therefore, as a means to prevent hull corrosion, the galvanic anode method in which sacrificial protective zinc is stretched around the hull instead of the hull, and current is applied to keep the hull potential constant to prevent corrosion. There is an external power supply anticorrosion system. Although these methods can prevent hull corrosion, UEP is generated in seawater around the hull in any method.

  In order to estimate and calculate the peripheral UEP around these hulls generated from the hull at an arbitrarily set position, it is first necessary to determine the position of the electrode serving as the current generation source of the hull and the current value between the electrodes. Conventionally, an engineer repeatedly changes the position of the hull electrodes and the current value between the electrodes, repeatedly calculates UEP using the electro-image method or boundary element method, and measures the surrounding UEP measured by the UEP sensor. The position of the hull electrode and the current value between the electrodes were determined so as to most closely match the values.

  In the above method, it is necessary for an engineer to determine the positions and the number of electrodes of a complicated hull. In addition, the current value varies depending on the determined position and number of electrodes, and it is impossible to quantitatively grasp the size of the current generation source of the entire hull. In addition, the conductivity of air, seawater, and seabed during measurement is required.

  The present invention has been made in view of such a situation, and the purpose of the present invention is to determine an arbitrary position in a simple and short time regardless of the skill and experience of the engineer without determining the electrode arrangement and current value of the hull. It is an object of the present invention to provide a hull peripheral UEP calculation method capable of estimating and calculating UEP.

One aspect of the present invention is a hull periphery UEP calculation method. This method
A method for calculating a UEP generated by a hull,
The peripheral UEP of the hull in a predetermined harmonic function expansion method corresponding to the electric moment of the hull based on the peripheral UEP of the hull measured by the UEP sensor outside the hull and the relative position of the hull and the UEP sensor. A step of calculating each expansion coefficient of the calculation formula by an optimal parameter search method;
And a step of estimating and calculating a peripheral UEP of the hull by an electric moment of the hull in an arbitrarily set estimation plane or estimation line based on each calculated expansion coefficient.

  In a method of a certain mode, the UEP sensor may measure a potential difference between two points in at least one of X, Y, and Z directions orthogonal to each other as UEP.

  In the method of a certain aspect, the calculation formula in the predetermined harmonic function expansion method may represent the peripheral UEP of the hull as a potential difference between any two points.

  In the method of an aspect, the calculation formula in the predetermined harmonic function expansion method may be a representation of the surrounding UEP of the hull as an integral of an electric field between any two points.

  In a certain aspect of the method, the predetermined harmonic function expansion method may be a long sphere harmonic function expansion method.

  In a certain aspect of the method, the predetermined harmonic function expansion method may be an eccentric spherical harmonic function expansion method.

  In a certain aspect of the method, the predetermined harmonic function expansion method may be a spherical harmonic function expansion method.

  In the method of an aspect, the optimal parameter search method may be a least square method.

  In the method of an embodiment, the optimal parameter search method may be a genetic algorithm.

  In the method of an embodiment, the optimum parameter search method may be a steepest descent method.

  In a method according to an aspect, the optimum parameter search method may be an annealing method.

  It should be noted that any combination of the above-described constituent elements and a representation obtained by converting the expression of the present invention between apparatuses and systems are also effective as an aspect of the present invention.

  According to the present invention, as long as the peripheral UEP of the hull and the relative position between the hull and the UEP sensor can be obtained, the electrode arrangement and current value of the hull are not determined, and it is simple and short regardless of the skill and experience of the engineer. In addition, the UEP at an arbitrary position can be estimated and calculated. In addition, the magnitude of the current source of the entire hull can be quantitatively grasped from the magnitude of the electric moment of the hull. Furthermore, the present invention is also effective for applications such as canceling the UEP around the hull by forcibly applying a current that cancels the electrical moment of the hull.

The flowchart which shows the flow of the surrounding UEP calculation method of the hull which concerns on embodiment of this invention. The schematic diagram of the long sphere coordinate used for the long sphere harmonic function expansion method. The schematic diagram of the oblate ball coordinate used for the oblate ball harmonic function expansion method. The schematic diagram of the spherical coordinate used for the spherical harmonic function expansion method.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, process, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  FIG. 1 is a flowchart showing a flow of a hull periphery UEP calculation method according to an embodiment of the present invention. Here, an example in which the least square method is used as the optimum parameter search method used when calculating each expansion coefficient corresponding to the electric moment of the hull (electric multipole moment such as electric dipole moment) is shown. Each step is basically realized by the cooperation of a computer and software. Details will be described below.

  First, the peripheral UEP of the hull is measured by a UEP sensor installed in the sea or on the seabed, and the relative position between the hull center and the UEP sensor is measured by a positioning system such as GPS (Global Positioning System) (STl). The UEP sensor is configured to measure a potential difference between two points. Here, with respect to the coordinate axes, the center of the hull is defined as the origin, the forward direction of the tail line is defined as the X axis, the right lateral direction is defined as the Y axis, and the vertical downward direction is defined as the Z axis.

Subsequently, the following data is input (ST2).

  In addition, although the space | interval of each axial direction both ends of a triaxial UEP sensor is set to l (m), the space | interval may not be the same about each axial direction. Moreover, it is also possible to use a 1-axis UEP sensor or a 2-axis UEP sensor instead of the 3-axis UEP sensor. In this case, only the data in the 1-axis direction or the 2-axis direction is input as the UEP measurement data. However, the calculation accuracy of the later-described expansion coefficient is higher when the 2-axis UEP sensor is used than the 1-axis UEP sensor and the 3-axis UEP sensor is used rather than the 2-axis UEP sensor. Further, the number of 1-axis to 3-axis UEP sensors may be one, or two or more. As the number of UEP sensors is increased, the calculation accuracy of the expansion coefficient described later increases.

  Next, the order nn and the order mm (nn ≧ mm) in various harmonic function expansion methods are set (ST3). The harmonic function expansion method is, for example, a long sphere harmonic function expansion method, an oblate spherical harmonic function expansion method, or a spherical harmonic function expansion method. FIG. 2 shows the long spherical coordinates used in the long spherical harmonic expansion method, FIG. 3 shows the eccentric spherical coordinates used in the partial spherical harmonic expansion method, and FIG. 4 shows the spherical coordinates used in the spherical harmonic expansion method. For example, c is half of the hull length.

  Here, in order to calculate UEP between two arbitrary points, there are a method of calculating the difference between the two points after obtaining the potential between the two points, and a method of integrating the electric field between the two points. First, calculation formulas in various harmonic function expansion methods using a method of calculating a potential difference between two points will be shown.

In the long spherical harmonic expansion method,
It becomes.

In the oblate spherical harmonic expansion method,
It becomes.

In the spherical harmonic expansion method,
It becomes.

  Subsequently, calculation formulas in various harmonic function expansion methods using a method of integrating an electric field between two arbitrary points will be shown.

In the long spherical harmonic expansion method,
It becomes.

In the oblate spherical harmonic expansion method,
It becomes.

In the spherical harmonic expansion method,
It becomes.

In the above formulas 2 to 7,
It is.

The above numbers 2 to 7 are summarized as follows:
It can be expressed as. Therefore, if the expansion coefficient D _t of various harmonic function expansion methods can be obtained, the potential difference E ^k between any two points can be estimated and calculated. If the same harmonic function expansion method is used, the expansion coefficient obtained by calculating the difference between the two points after obtaining the potential between the two points, and the expansion coefficient obtained by integrating the electric field between the two points, for example, Equations 2 and The expansion coefficient D _t by 5 is the same.

  The function of the position in Equation 9 is calculated based on the measurement data of the relative position between the hull center and the UEP sensor (ST4). Next, a least squares determinant is created (ST5).

The determinant is
By solving this, the expansion coefficient D _t of various harmonic function expansion methods is calculated (ST6). Here, an example in which the least square method is used for the optimum parameter search method is shown, but ST5 is another method such as genetic algorithm (GA), steepest descent method, annealing method (SA), etc. The expansion coefficient D _t can also be calculated using a known optimum parameter search method.

  Next, an estimation plane or an estimation line is set (ST7), and a function of the position at each set point j on the estimation plane or the estimation line is calculated (ST8).

UEP at each set point j
(ST9).

  According to the present embodiment, as long as the peripheral UEP measurement data of the hull and the relative position of the hull and the UEP sensor can be acquired, anyone can easily determine the conductivity of the hull electrode arrangement, current value, seawater, etc. In addition, UEP at an arbitrary position can be estimated and calculated in a short time. In addition, the magnitude of the current source of the entire hull can be quantitatively grasped from the magnitude of the electric moment arranged at the origin. Furthermore, by forcibly applying a current that cancels the electrical moment of the hull, an application such as canceling the peripheral UEP of the hull becomes possible.

  The present invention has been described above by taking the embodiment as an example. However, it is understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiment within the scope of the claims. By the way.

5 hull

Claims (11)

A method for calculating UEP (Underwater Electric Potential) generated by a hull,
The peripheral UEP of the hull in a predetermined harmonic function expansion method corresponding to the electric moment of the hull based on the peripheral UEP of the hull measured by the UEP sensor outside the hull and the relative position of the hull and the UEP sensor. A step of calculating each expansion coefficient of the calculation formula by an optimal parameter search method;
A method for calculating a surrounding UEP for a hull, including a step of estimating and calculating a surrounding UEP of the hull by an electric moment of the hull in an arbitrarily set estimation plane or estimated line based on each calculated expansion coefficient.   The hull peripheral UEP calculation method according to claim 1, wherein the UEP sensor measures a potential difference between two points in at least one of X, Y, and Z directions orthogonal to each other as a UEP.   3. The method for calculating a peripheral UEP for a hull according to claim 1 or 2, wherein the calculation formula in the predetermined harmonic function expansion method represents the peripheral UEP of the hull as a potential difference between any two points.   3. The method for calculating a peripheral UEP for a hull according to claim 1 or 2, wherein the calculation formula in the predetermined harmonic function expansion method represents the peripheral UEP of the hull as an integral of an electric field between two arbitrary points.   The hull peripheral UEP calculation method according to any one of claims 1 to 4, wherein the predetermined harmonic function expansion method is a long sphere harmonic function expansion method.   The hull peripheral UEP calculation method according to any one of claims 1 to 4, wherein the predetermined harmonic function expansion method is an oblate ball harmonic function expansion method.   The hull peripheral UEP calculation method according to claim 1, wherein the predetermined harmonic function expansion method is a spherical harmonic function expansion method.   The method for calculating a surrounding UEP for a hull according to any one of claims 1 to 7, wherein the optimum parameter search method is a least square method.   The method for calculating a surrounding UEP for a hull according to any one of claims 1 to 7, wherein the optimum parameter search method is a genetic algorithm.   The method for calculating a surrounding UEP for a hull according to any one of claims 1 to 7, wherein the optimum parameter search method is a steepest descent method.   The method for calculating a peripheral UEP for a hull according to any one of claims 1 to 7, wherein the optimum parameter search method is an annealing method.