Sensor position determination method

Abstract

To provide a sensor position determination method which can determine a proper location of an electric field sensor.SOLUTION: A sensor position determination method determining a location of an electric field sensor detecting electric field intensity generated on a surface of an airframe of an aircraft comprises the steps of: setting an airframe shape model, a plurality of candidate positions, and a parallel electrode to acquire the electric field intensity of respective candidate positions through electrostatic field analysis at a determined relative pitch angle and relative roll angle; acquiring, while changing at least one of the relative pitch angle and the relative roll angle, the electric field intensity of respective candidate positions and repeating it whenever changing at least one of the relative pitch angle and the relative roll angle; specifying a candidate position whose dispersion of the electric field intensity acquired whenever changing at least one of the relative pitch angle and the relative roll angle is relatively larger to configure the specified candidate position as the location of the electric field sensor.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a sensor positioning method for determining the installation position of an electric field sensor.

Background Art

[0002] For example, Patent Document 1 discloses providing an electric field sensor on the airframe of an aircraft to detect the electric field strength generated on the surface of the airframe. In such a technique, based on the detection result of the electric field sensor, the distribution of the surface electric field strength of the aircraft is derived, and by using the distribution of the surface electric field strength to perform attitude control of the aircraft, the influence of lightning strikes can be suppressed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, in order to reduce the installation cost and operation cost of the electric field sensor, a small number of electric field sensors are installed on the aircraft, and an electric field distribution table showing a reference electric field distribution is prepared in advance. Then, in Patent Document 1, based on the detection results of the small number of electric field sensors and the electric field distribution table, the distribution of the surface electric field strength at a plurality of positions is estimated.

[0005] However, depending on the positions where a small number of electric field sensors are installed, the accuracy of the electric field strength detected by the electric field sensors may decrease. When the accuracy of the electric field strength decreases, the surface electric field strength distribution cannot be appropriately estimated. From these, it is necessary to install the small number of electric field sensors at appropriate positions on the airframe.

[0006] Therefore, an object of the present invention is to provide a sensor positioning method capable of determining an appropriate installation position of an electric field sensor.

Means for Solving the Problems

[0007] To solve the above problems, a sensor positioning method according to an embodiment of the present invention is a sensor positioning method for determining an installation position of an electric field sensor that detects an electric field strength generated on the surface of an aircraft fuselage, in an analysis space for performing electrostatic field analysis, a fuselage shape model simulating the shape of the fuselage is set, in the fuselage shape model, a plurality of candidate positions that are candidates for the installation position of the electric field sensor are set, in the analysis space, a flat parallel electrode that generates an electric field is set so as to sandwich the fuselage shape model therebetween, a relative pitch angle indicating a relative pitch angle of the fuselage shape model with respect to the parallel electrode and a relative roll angle indicating a relative roll angle are determined, at the determined relative pitch angle and relative roll angle, the electric field strength at each of the plurality of candidate positions is obtained by electrostatic field analysis, changing at least one of the relative pitch angle and the relative roll angle and obtaining the electric field strength at each of the plurality of candidate positions is repeated each time at least one of the relative pitch angle and the relative roll angle is changed, among the plurality of candidate positions, a candidate position where the variance of the electric field strength obtained each time at least one of the relative pitch angle and the relative roll angle is changed is relatively large is specified, and the specified candidate position is set as the installation position of the electric field sensor.

Effects of the Invention

[0008] According to the present invention, it becomes possible to determine an appropriate installation position of the electric field sensor.

Brief Description of the Drawings

[0009]

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DETAILED DESCRIPTION OF THE INVENTION

[0010] [[ID=2ό]]Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The specific dimensions, materials, numerical values, etc. shown in such embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to omit redundant description, and elements not directly related to the present invention are not shown.

[0011] FIG. 1 is a schematic perspective view of the aircraft 1. As shown in FIG. 1, the aircraft 1 includes a fuselage 10, a main wing 12, a horizontal tail 14, a vertical tail 16, an attitude sensor 18, a flight mechanism 22, and a flight control device 26. Here, a passenger aircraft is illustrated as the aircraft 1, but various machines flying in the atmosphere can be adopted.

[0012] The fuselage 10 is provided to extend in the roll axis direction connecting the nose side and the tail side of the aircraft 1. The main wings 12, the horizontal tail 14, and the vertical tail 16 are fixed to the fuselage 10 and contribute to the stable flight of the aircraft 1. The main wings 12 extend from the fuselage 10 in the pitch axis direction perpendicular to the roll axis near the center in the roll axis direction of the fuselage 10. The horizontal tail 14 extends from the fuselage 10 in the pitch axis direction near the tail of the fuselage 10. The vertical tail 16 extends from the fuselage 10 in the yaw axis direction perpendicular to the roll axis and the pitch axis near the tail.

[0013] The rotation around the roll axis may be called roll, and the rotation angle around the roll axis may be called the roll angle. The rotation around the pitch axis may be called pitch, and the rotation angle around the pitch axis may be called the pitch angle. The rotation around the yaw axis may be called yaw, and the rotation angle around the yaw axis may be called yaw. The pitch angle corresponds to the nose angle, the roll angle corresponds to the bank angle, and the yaw angle corresponds to the flight azimuth.

[0014] The attitude sensor 18 is composed of, for example, an IMU (Inertial Measurement Unit) and detects the attitude of the airframe of the aircraft 1.

[0015] The flight mechanism 22 is composed of fixed wings such as the main wings 12, the horizontal tail 14, and the vertical tail 16, and an internal combustion engine (for example, a jet engine or a reciprocating engine) that obtains thrust, and generates lift around the wings by the thrust to maintain the state where the airframe floats in the atmosphere. However, the mechanism for generating lift is not limited to such a case, and it is also possible to obtain lift or thrust by a rotatable rotor. The flight mechanism 22 can also control the nose angle (pitch angle), the bank angle (roll angle) through the elevator and the aileron, and adjust the output of the internal combustion engine, etc., to control the airframe attitude, the flight azimuth (yaw angle), the altitude, and the flight speed.

[0016] The flight control device 26 is composed of a semiconductor integrated circuit including a central processing unit (CPU), a ROM storing programs and the like, a RAM serving as a work area, and the like. The flight control device 26 cooperates with a program to realize various functions related to the flight of the aircraft 1. For example, the flight control device 26 performs various processes according to the detection results of various sensors such as the attitude sensor 18. The flight control device 26 receives the operation input of the pilot who controls the aircraft 1, controls the flight mechanism 22, and maintains the flight of the aircraft 1.

[0017] In the example of FIG. 1, it is assumed that the aircraft 1 is flying near the lower part of the cloud CL charged on the negative electrode side. In this example, due to the influence of the electric field (e.g., electrostatic induction) of the negative charge of the cloud CL, the upper side of the fuselage of the aircraft 1 is polarized to the positive electrode side, and the lower side of the fuselage of the aircraft 1 is polarized to the negative electrode side.

[0018] Depending on the relative positional relationship between the aircraft 1 and the cloud CL, there may be a part on the fuselage of the aircraft 1 where positive or negative charges are concentrated. The strong electric field generated at the site where positive or negative charges are concentrated causes dielectric breakdown in the atmosphere, and the charge of the fuselage leaks into the atmosphere in the form of a streamer and then a leader. In addition, the charge that can no longer be held in the cloud CL may move toward such a site where positive or negative charges are biased, and there is a risk that the leader from the cloud CL and the leader extending from the fuselage are connected and discharge. Thus, lightning may strike the aircraft 1.

[0019] Here, for example, it is conceivable to obtain the surface electric field strength of the aircraft 1 and use the obtained surface electric field strength to perform attitude control of the aircraft 1 and suppress the influence of lightning strikes. As a method for obtaining the surface electric field strength, an electric field sensor for detecting the electric field strength on the surface of the fuselage of the aircraft 1 can be installed at each part of the aircraft 1. However, if electric field sensors are installed at every position on the fuselage, it will inevitably increase the installation cost and operation cost.

[0020] Therefore, a small number of electric field sensors are installed on the aircraft body, and an electric field distribution table showing a reference electric field distribution is prepared in advance. Then, based on the detection results of the small number of electric field sensors installed on the aircraft body and the pre-prepared electric field distribution table, it is conceivable to estimate the distribution of the surface electric field strength at a plurality of positions including positions other than the positions where the electric field sensors are installed.

[0021] However, depending on the positions where the small number of electric field sensors are installed, the accuracy of the electric field strength detected by the electric field sensors may decrease. When the accuracy of the electric field strength decreases, the surface electric field strength distribution cannot be appropriately estimated. From these, it is necessary to install the small number of electric field sensors at appropriate positions on the aircraft body.

[0022] Therefore, in the present embodiment, a sensor positioning method for determining the installation positions of electric field sensors that detect the electric field strength generated on the surface of the aircraft body 1 is disclosed. By using the sensor positioning method of the present embodiment, appropriate installation positions of a small number of electric field sensors can be determined. As a result, by actually mounting electric field sensors at the installation positions determined by using the sensor positioning method of the present embodiment and performing attitude control of the aircraft 1 based on the detection results of the electric field sensors during the operation of the aircraft 1, the influence of lightning strikes can be suppressed.

[0023] FIG. 2 is a schematic diagram showing the configuration of an analysis device 50 for realizing the sensor positioning method of the present embodiment. The analysis device 50 is a computer such as a personal computer, for example. The analysis device 50 includes a user interface 60, a storage device 62, and an arithmetic device 64.

[0024] The user interface 60 includes a display device 70 and an input device 72. The display device 70 is, for example, a liquid crystal display or an organic EL display, and displays various images and information. Note that the user interface 60 may include, in addition to the display device 70, an output device such as a speaker that presents various information to the user. The input device 72 includes, for example, a keyboard or a mouse, and receives input operations from the user.

[0025] The storage device 62 is composed of non-volatile memory elements. The storage device 62 may be composed of, for example, electrically rewritable non-volatile memory elements such as flash memory. Various data used for various processes executed by the analysis device 50 are stored in the storage device 62.

[0026] The arithmetic device 64 includes one or more processors 80 and one or more memories 82 connected to the processor 80. The memory 82 includes a ROM in which programs and the like are stored and a RAM as a work area. The processor 80 executes various processes in cooperation with the programs included in the memory 82. The processor 80 also functions as a pre-analysis processing unit 90, a first analysis processing unit 92, and a second analysis processing unit 94 by executing programs.

[0027] The pre - analysis processing unit 90 executes pre - processing for the first analysis processing and the first reference position analysis processing by the first analysis processing unit 92, and the second analysis processing and the second reference position analysis processing by the second analysis processing unit 94. After the pre - processing is performed, the first analysis processing unit 92 executes the first analysis processing and the first reference position analysis processing. After the pre - processing is performed, the second analysis processing unit 94 executes the second analysis processing and the second reference position analysis processing. The first analysis processing is a process of determining the installation position of an electric field sensor suitable for the aircraft 1 to perform attitude control in the pitch direction to suppress the influence of lightning strikes. Since the surface of the aircraft 1 is always charged during flight, when performing attitude control to suppress the influence of lightning strikes, it is preferable to detect the degree of this charged component and perform attitude control considering this charged component. The first reference position analysis processing is a process of determining the installation position of a reference electric field sensor suitable for obtaining the charged component of the aircraft 1 when the aircraft 1 performs attitude control in the pitch direction to suppress the influence of lightning strikes. The second analysis processing is a process of determining the installation position of an electric field sensor suitable for the aircraft 1 to perform attitude control in the roll direction to suppress the influence of lightning strikes. The second reference position analysis processing is a process of determining the installation position of a reference electric field sensor suitable for obtaining the charged component of the aircraft 1 when the aircraft 1 performs attitude control in the roll direction to suppress the influence of lightning strikes. Hereinafter, the pre - processing, the first analysis processing, and the second analysis processing will be described in detail.

[0028] Figure 3 is a flowchart for explaining the operation flow of the arithmetic unit 64. When the arithmetic unit 64 receives a start signal instructing the start of the process of determining the installation position of the electric field sensor, for example, through the input device 72, it executes a series of processes shown in Figure 3. When receiving the start signal, the pre - analysis processing unit 90 of the arithmetic unit 64 executes the pre - processing (S10).

[0029] In the preprocessing (S10), the analysis preprocessing unit 90 first sets a fuselage shape model that simulates the shape of the fuselage in the analysis space for electrostatic field analysis (S11). Next, the analysis preprocessing unit 90 sets a plurality of candidate positions in the fuselage shape model that are candidates for the installation positions of the electric field sensors (S12). Next, the analysis preprocessing unit 90 excludes positions in the fuselage shape model that are vulnerable to direct lightning strikes from the plurality of candidate positions (S13). The positions vulnerable to direct lightning strikes may be determined in advance by experiments or analysis, etc. Next, the analysis preprocessing unit 90 sets a flat parallel electrode that generates an electric field in the analysis space so as to sandwich the fuselage shape model therebetween (S14).

[0030] Here, an example in which the parallel electrodes are set after the setting of the fuselage shape model has been described. However, the fuselage shape model may be set after the setting of the parallel electrodes.

[0031] FIG. 4 is a diagram showing an example of the fuselage shape model 100 and a plurality of candidate positions 102. As shown in FIG. 4, the fuselage shape model 100 is created by simulating the shape of the entire surface of the fuselage. The fuselage shape model 100 is arranged in the analysis space 104 so as to simulate the state in which the fuselage is floating. The fuselage shape model 100 is used for the subsequent electrostatic field analysis as a floating conductor.

[0032] In FIG. 4, a plurality of candidate positions 102 are illustrated by black circles. The plurality of candidate positions 102 are respectively set on the fuselage 10, the main wing 12, the horizontal tail 14, and the vertical tail 16. Note that the candidate positions 102 and the number thereof are not limited to the positions and the number illustrated in FIG. 4, and can be arbitrarily set in consideration of the structure and scale of the aircraft 1. For example, the analysis preprocessing unit 90 may analyze the fuselage shape model 100 to set a plurality of candidate positions 102. Further, the user of the analysis device 50 may set the plurality of candidate positions 102 through the input device 72.

[0033] As described above, the analysis preprocessing unit 90 excludes positions in the aircraft shape model 100 that are vulnerable to direct lightning strikes from a plurality of candidate positions 102. That is, an electric field sensor is not installed at a position vulnerable to direct lightning strikes.

[0034] Positions vulnerable to direct lightning strikes are, for example, the ends such as the wingtips of the aircraft 1. For example, the analysis preprocessing unit 90 excludes the tip of the main wing 12 in the pitch axis direction, the tip of the horizontal tail 14 in the pitch axis direction, the tip of the vertical tail 16 in the yaw axis direction, the tip of the aircraft nose, etc. from the candidate positions 102 as positions vulnerable to direct lightning strikes. Thereby, the risk of the electric field sensor being damaged by a direct lightning strike can be reduced.

[0035] Note that in the preprocessing, the process of excluding positions vulnerable to direct lightning strikes from the plurality of candidate positions 102 may not be performed. That is, positions vulnerable to direct lightning strikes may also be included in the plurality of candidate positions 102. In this case, a position vulnerable to direct lightning strikes may be specified as the installation position of the electric field sensor. If an electric field sensor is installed at a position vulnerable to direct lightning strikes, that electric field sensor is highly likely to be damaged by a direct lightning strike. However, until it is damaged, the electric field strength can be detected by that electric field sensor, and based on the detected electric field strength, it can be determined whether the aircraft is in a state where it is highly likely to be struck by a direct lightning strike. In the case of a design concept of wanting to accurately detect the electric field strength until a direct lightning strike occurs, the process of excluding positions vulnerable to direct lightning strikes from the plurality of candidate positions 102 may not be performed. On the other hand, in the case of a design concept of wanting to suppress the cost and labor required for repair when the electric field sensor is damaged by a direct lightning strike, the process of excluding positions vulnerable to direct lightning strikes from the plurality of candidate positions 102 may be performed.

[0036] FIG. 5 is a diagram showing an example of the setting of the parallel electrodes 110. As shown in FIG. 5, the parallel electrodes 110 are composed of an upper electrode 112 and a lower electrode 114. The upper electrode 112 is disposed, for example, above the analysis space 104. The lower electrode 114 is disposed, for example, below the analysis space 104. The upper electrode 112 and the lower electrode 114 extend, for example, in a planar shape and are arranged to face each other in parallel. The body shape model 100 is located between the upper electrode 112 and the lower electrode 114. That is, the parallel electrodes 110 are set so as to sandwich the body shape model 100 therebetween. Also, the area of the plane of the upper electrode 112 is larger than the projected area when the body shape model 100 is projected onto the upper electrode 112, and the area of the plane of the lower electrode 114 is larger than the projected area when the body shape model 100 is projected onto the lower electrode 114. The relationship between the size of the analysis space 104 and the size of the body shape model 100 is set to a relationship that enables appropriate analysis.

[0037] During the electrostatic field analysis after the preprocessing, a positive potential is applied to the upper electrode 112, and a negative potential is applied to the lower electrode 114. Further, on each side surface orthogonal to the upper electrode 112 and the lower electrode 114 in the analysis space 104, a potential that changes linearly as it progresses from the upper electrode 112 to the lower electrode 114 is applied. When such a potential is applied to the upper electrode 112, the lower electrode 114, and each side surface, the parallel electrodes 110 generate a parallel electric field in the analysis space 104 between the upper electrode 112 and the lower electrode 114.

[0038] Returning to FIG. 3, after the preprocessing (S10), the first analysis processing unit 92 executes the first analysis processing (S20) and the first reference position analysis processing (S22). Thereafter, the second analysis processing unit 94 executes the second analysis processing (S24) and the second reference position analysis processing (S26), and the series of processes shown in FIG. 3 ends.

[0039] FIG. 6 is a diagram for explaining the outline of the first analysis process (S20). In FIG. 6, the aircraft shape model 100 and the parallel electrodes 110 arranged in the analysis space 104 are shown as viewed from the right wing side of the aircraft. In FIG. 6, for convenience of explanation, the aircraft shape model 100 is exaggerated and shown large with respect to the size of the analysis space 104. Also, in FIG. 6, for convenience of explanation, the roll axis, pitch axis, and yaw axis of the aircraft shape model 100 are also shown.

[0040] Hereinafter, the relative pitch angle of the aircraft shape model 100 with respect to the parallel electrodes 110 may be referred to as the relative pitch angle. The relative roll angle of the aircraft shape model 100 with respect to the parallel electrodes 110 may be referred to as the relative roll angle. The relative yaw angle of the aircraft shape model 100 with respect to the parallel electrodes 110 may be referred to as the relative yaw angle.

[0041] In the example of FIG. 6, the parallel electrodes 110 shown by the thick solid line are arranged parallel to the pitch axis and roll axis of the aircraft shape model 100. At this time, the relative pitch angle of the aircraft shape model 100 with respect to the parallel electrodes 110 is zero.

[0042] Here, fixing the position of the aircraft shape model 100, as shown by the dashed arrow A10, assume that the parallel electrodes 110 are rotated counterclockwise by a predetermined angle (for example, 10°) around the pitch axis at the center of the analysis space 104 in FIG. 6. An example of the parallel electrodes 110 at that time is shown by the thick dashed line in FIG. 6. In this state, the nose side end 112a of the upper electrode 112 and the nose side end 114a of the lower electrode 114 have moved upward, and the tail side end 112b of the upper electrode 112 and the tail side end 114b of the lower electrode 114 have moved downward. Then, with reference to the rotated thick dashed parallel electrodes 110, the relative pitch angle of the aircraft shape model 100 becomes a value on the depression angle side rather than zero.

[0043] Also, with the position of the airframe shape model 100 fixed, as indicated by the arrow A12 of the dashed line, assume that the parallel electrodes 110 are rotated clockwise by a predetermined angle (e.g., 10°) around the pitch axis at the center of the analysis space 104 in FIG. 6. An example of the parallel electrodes 110 at that time is shown by the thick dashed line in FIG. 6. In this state, the nose-side end 112a of the upper electrode 112 and the nose-side end 114a of the lower electrode 114 have been moved downward, and the tail-side end 112b of the upper electrode 112 and the tail-side end 114b of the lower electrode 114 have been moved upward. Then, with reference to the rotated parallel electrodes 110 of the thick dashed line, the relative pitch angle of the airframe shape model 100 becomes a value on the elevation angle side from zero.

[0044] In this way, by rotating the parallel electrodes 110 around the pitch axis, the relative pitch angle can be changed. Here, an example of fixing the airframe shape model 100 and rotating the parallel electrodes 110 has been described. However, the relative pitch angle may be changed by fixing the position of the parallel electrodes 110 and rotating the airframe shape model 100 around the pitch axis. However, in the electrostatic field analysis described later, for example, the analysis space 104 is divided into a mesh shape such that the analysis space 104 is divided into a plurality of triangular tetrahedrons, and the analysis is performed by representing each position in the analysis space 104 by each tetrahedron. At the time of this analysis, the spatial coordinates of the tetrahedron corresponding to the candidate position 102 are used as the candidate position 102. In the example of rotating the airframe shape model 100, since the tetrahedron corresponding to the candidate position 102 changes one by one as the airframe shape model 100 is rotated, the electrostatic field analysis becomes more laborious and complicated than the example of rotating the parallel electrodes 110. For this reason, the example of rotating the parallel electrodes 110 is more preferable than the example of rotating the airframe shape model 100.

[0045] In the first analysis process, the relative roll angle and the relative yaw angle are fixed at predetermined values respectively. The first analysis processing unit 92 extracts any four candidate positions 102 from the plurality of candidate positions 102 and creates a combination of the four candidate positions 102. Hereinafter, the number of combinations may be referred to as the combination composition number. Note that the combination composition number is not limited to four and may be set to any number of two or more.

[0046] The first analysis processing unit 92 determines an arbitrary value for the relative pitch angle, generates an electric field in the parallel electrodes 110, and obtains the electric field strength at each candidate position 102 of the combination of the four candidate positions 102 by electrostatic field analysis. Then, while maintaining the relative roll angle and the relative yaw angle at predetermined values, the first analysis processing unit 92 changes the relative pitch angle and repeats obtaining the electric field strength at each candidate position 102 of the plurality of candidate positions 102 each time the relative pitch angle is changed. For example, the first analysis processing unit 92 changes the relative pitch angle by 1° while maintaining the relative roll angle at zero and the relative yaw angle at zero. Note that the example of changing the relative pitch angle by 1° each time is not limiting, and the relative pitch angle may be changed by any angle each time.

[0047] When these processes are performed, the electric field strength is obtained for each candidate position 102 of the combination of the four candidate positions 102 for each relative pitch angle. The electric field strength at each candidate position 102 is different for each relative pitch angle.

[0048] The first analysis processing unit 92 derives the variance based on the electric field strength at each candidate position 102 of the combination of the four candidate positions 102 at an arbitrary relative pitch angle. The first analysis processing unit 92 repeats this derivation of the variance each time the relative pitch angle is changed. Then, the first analysis processing unit 92 adds the variance derived each time the relative pitch angle is changed each time the relative pitch angle is changed to derive the total variance.

[0049] More specifically, the first analysis processing unit 92 derives an average value according to the following formula (1), and derives a variance according to the following formula (2) using the average value. In formulas (1) and (2), a represents the average value. D1 represents the electric field strength at the first candidate position among the four candidate positions 102. D2 represents the electric field strength at the second candidate position among the four candidate positions 102. D3 represents the electric field strength at the third candidate position among the four candidate positions 102. D4 represents the electric field strength at the fourth candidate position among the four candidate positions 102. In formula (2), s represents the variance. a = (D1 + D2 + D3 + D4) / 4 ···(1) s = ((D1 - a) 2 + (D2 - a) 2 + (D3 - a) 2 + (D4 - a) 2 ) / 4 ···(2)

[0050] That is, the first analysis processing unit 92 squares the value obtained by subtracting the average value (a) of the electric field strengths at the four candidate positions 102 that make up the combination from the respective values (D1, D2, D3, D4) of the electric field strengths at the four candidate positions 102, and takes the average value of the four squared values by the number of combination configurations (4) to derive the variance.

[0051] The first analysis processing unit 92 changes the combination of the four candidate positions 102, and derives the total sum of variances for each combination of the candidate positions 102. The first analysis processing unit 92 derives the total sum of variances for all patterns of the combination of the four candidate positions 102.

[0052] FIG. 7 is a diagram showing an example of the relationship between the relative pitch angle and the total sum of variances. FIG. 7 shows an example when the total sum of variances regarding the relative pitch angle is relatively large. FIG. 8 is a diagram showing another example of the relationship between the relative pitch angle and the total sum of variances. FIG. 8 shows an example when the total sum of variances regarding the relative pitch angle is relatively small.

[0053] The first analysis processing unit 92 identifies a combination of four candidate positions 102 with the largest sum of variances regarding the relative pitch angle, and sets each candidate position 102 constituting the identified combination of four candidate positions 102 as the installation position of the electric field sensor.

[0054] The fact that the sum of variances is the largest means that, if electric field sensors are installed at the four candidate positions 102 constituting the combination, it can be estimated that the electric field intensities detected by the electric field sensors at the four candidate positions 102 will have the most scattered values. The fact that the electric field intensities of the respective electric field sensors vary the most corresponds to the fact that it includes both a candidate position 102 capable of detecting a high electric field intensity and a candidate position 102 capable of detecting a low electric field intensity. Then, when electric field sensors are installed at the four candidate positions 102, the resolution of the electric field sensors as a set of four electric field sensors can be made higher than that of other sets of four electric field sensors. From this, by setting each candidate position 102 constituting the combination of candidate positions 102 with the largest sum of variances as the installation position of the electric field sensor, the installed electric field sensor can effectively detect the electric field intensity.

[0055] Next, the outline of the first reference position analysis process will be described. In the first reference position analysis process, the relative roll angle and the relative yaw angle are each fixed at a predetermined value, and the relative pitch angle is determined to be an arbitrary value. In that state, the first analysis processing unit 92 generates an electric field in the parallel electrodes 110 and acquires the electric field intensity at each candidate position 102 of the plurality of candidate positions 102 by electrostatic field analysis. Then, while maintaining the relative roll angle and the relative yaw angle at predetermined values, the first analysis processing unit 92 changes the relative pitch angle and repeats the process of acquiring the electric field intensity at each candidate position 102 of the plurality of candidate positions 102 each time the relative pitch angle is changed. For example, the first analysis processing unit 92 changes the relative pitch angle by 1° while maintaining the relative roll angle at zero and the relative yaw angle at zero. Note that the example is not limited to changing the relative pitch angle by 1° each time, and the relative pitch angle may be changed by an arbitrary angle each time.

[0056] When these processes are performed, the electric field strength is obtained for each relative pitch angle at each candidate position 102. The electric field strength at each candidate position 102 is different for each relative pitch angle.

[0057] FIG. 9 is a diagram showing an example of the relationship between the relative pitch angle and the electric field strength at one candidate position 102. FIG. 10 is a diagram showing an example of the relationship between the relative pitch angle and the electric field strength at another candidate position 102.

[0058] Here, at any one candidate position 102, among the electric field strengths obtained for each relative pitch angle, the difference value obtained by subtracting the minimum value from the maximum value and taking the absolute value is defined as the second variance of the electric field strength with respect to the relative pitch angle. In other words, the second variance of the electric field strength with respect to the relative pitch angle corresponds to the fluctuation range of the electric field strength when the relative pitch angle is changed to obtain the electric field strength.

[0059] FIG. 9 shows an example when the second variance of the electric field strength with respect to the relative pitch angle is relatively large. FIG. 10 shows an example when the second variance of the electric field strength with respect to the relative pitch angle is relatively small.

[0060] The first analysis processing unit 92 identifies a candidate position 102 having a relatively small second variance of the electric field strength with respect to the relative pitch angle among the plurality of candidate positions 102, and the identified candidate position 102 may be used as the installation position of the reference electric field sensor. The reference electric field sensor is an electric field sensor for detecting a reference electric field strength that serves as a reference for the electric field strength.

[0061] The fact that the second variance of the electric field strength is small means that, if a reference electric field sensor is installed at that position, even if the pitch angle of the aircraft 1 actually changes, the change in the electric field strength detected by the reference electric field sensor will be small. Then, the electric field strength detected by the reference electric field sensor can be made roughly constant within the allowable error range regardless of the actual pitch angle of the aircraft 1. By using the electric field strength detected by this reference electric field sensor as a reference for the electric field strength, the surface electric field strength distribution of the aircraft 1 can be estimated more appropriately.

[0062] More specifically, the first analysis processing unit 92 identifies a predetermined number of candidate positions 102 from among the candidate positions 102 where the second variance is the smallest, and the identified predetermined number of candidate positions 102 may be used as the installation positions of the electric field sensors. By identifying the candidate position 102 of the installation position of the reference electric field sensor from the ones where the second variance is the smallest, the fluctuation of the electric field strength detected by the reference electric field sensor can be reduced more, and the surface electric field strength distribution can be estimated more appropriately.

[0063] The predetermined number here may be, for example, one. As long as there is at least one reference electric field strength, the surface electric field strength distribution can be estimated appropriately. Note that the predetermined number is not limited to one, and may be set to any number of two or more.

[0064] FIG. 11 is a flowchart for explaining the flow of the first analysis process (S20). When the first analysis process (S20) is started, the first analysis processing unit 92 first determines the relative roll angle to a specific relative roll angle such as zero (S30). Although omitted in FIG. 11, the relative yaw angle is also determined to a specific relative yaw angle such as zero.

[0065] Next, the first analysis processing unit 92 sets the change range of the relative pitch angle (S31). The change range of the relative pitch angle is set within a realistic range that can actually be taken in the attitude control of the aircraft 1.

[0066] Next, the first analysis processing unit 92 sets the number of combination configurations (S32). For example, the first analysis processing unit 92 sets 4 as the number of combination configurations. Note that the number of combination configurations is not limited to 4 and may be set to any number of 2 or more.

[0067] Next, the first analysis processing unit 92 extracts the number of candidate positions 102 corresponding to the number of combination configurations set in step S32 from among the plurality of candidate positions 102, and determines a combination of the candidate positions 102 corresponding to the number of combination configurations (S33).

[0068] Next, the first analysis processing unit 92 determines an arbitrary relative pitch angle within the change range of the relative pitch angle (S34).

[0069] The first analysis processing unit 92 performs an electrostatic field analysis at the determined relative pitch angle, and acquires the electric field strength at each of the candidate positions 102 constituting the combination determined in step S33 (S35). The first analysis processing unit 92 may store the relative pitch angle, the candidate positions 102 at which the electric field strength has been acquired, and the acquired electric field strength in association with each other.

[0070] The first analysis processing unit 92 derives the average value of the acquired electric field strengths, and based on the average value, derives the variance of the electric field strengths of the candidate positions 102 constituting the combination (S36). The first analysis processing unit 92 derives the sum of the variances derived in a state where the combination of candidate positions is the same and the relative pitch angle is the same (S37). For example, the first analysis processing unit 92 derives the sum of the variances by adding the variance derived this time to the variance derived previously in a state where the combination of the candidate positions 102 is the same and the relative pitch angle is the same.

[0071] Next, the first analysis processing unit 92 determines whether there is a remaining relative pitch angle for which electrostatic field analysis has not been performed (S38). If there is a remaining relative pitch angle (YES in S38), the first analysis processing unit 92 repeats the processing after step S34. At this time, the first analysis processing unit 92 determines an arbitrary relative pitch angle among the remaining relative pitch angles (S34), and acquires the electric field strength again at the relative pitch angle thus changed (S35).

[0072] If there is no remaining relative pitch angle (NO in S38), the first analysis processing unit 92 determines whether there is a remaining combination that has not been combined (S39). If there is a remaining combination (YES in S39), the first analysis processing unit 92 repeats the processing after step S33. At this time, the first analysis processing unit 92 determines an arbitrary combination among the remaining combinations (S33), and repeats the processing after the determination of the relative pitch angle for the combination thus changed.

[0073] If there is no remaining combination (NO in S39), the first analysis processing unit 92 specifies the combination with the maximum sum of variances (S40). The first analysis processing unit 92 sets the candidate position 102 constituting the combination specified in step S40 as the installation position of the electric field sensor (S41), and ends the first analysis processing.

[0074] FIG. 12 is a flowchart for explaining the flow of the first reference position analysis processing (S22). When the first reference position analysis processing (S22) is started, the first analysis processing unit 92 first determines the relative roll angle to a specific relative roll angle such as zero (S50). Although omitted in FIG. 12, the relative yaw angle is also determined to a specific relative yaw angle such as zero.

[0075] Next, the first analysis processing unit 92 sets the change range of the relative pitch angle (S51). The change range of the relative pitch angle is set within a realistic range that can be actually taken in the attitude control of the aircraft 1.

[0076] The first analysis processing unit 92 determines an arbitrary relative pitch angle within the range of change of the relative pitch angle (S52).

[0077] The first analysis processing unit 92 performs an electrostatic field analysis at the determined relative pitch angle and acquires the electric field strength at each of the plurality of candidate positions 102 (S53). The first analysis processing unit 92 may store the relative pitch angle, the candidate position 102 at which the electric field strength is acquired, and the acquired electric field strength in association with each other.

[0078] Next, the first analysis processing unit 92 determines whether there is a remaining relative pitch angle for which the electrostatic field analysis has not been performed (S54). If there is a remaining relative pitch angle (YES in S54), the first analysis processing unit 92 repeats the processing after step S32. At this time, the first analysis processing unit 92 determines an arbitrary relative pitch angle among the remaining relative pitch angles (S52), and again acquires the electric field strength at the relative pitch angle thus changed (S53).

[0079] If there is no remaining relative pitch angle (NO in S54), the first analysis processing unit 92 derives a second variance of the electric field strength with respect to the relative pitch angle (S55). For example, the first analysis processing unit 92 derives the second variance of the electric field strength at an arbitrary candidate position 102 by subtracting the minimum value from the maximum value of the electric field strength at the arbitrary candidate position 102 and taking the absolute value, and similarly derives the second variance of the electric field strength at all candidate positions 102.

[0080] Next, the first analysis processing unit 92 identifies the candidate position 102 at which the second variance of the electric field strength derived in step S55 is relatively small (S56). For example, the first analysis processing unit 92 identifies the candidate position 102 among the plurality of candidate positions 102 at which the second variance of the electric field strength is the smallest. The first analysis processing unit 92 sets the candidate position 102 identified in step S56 as the installation position of the reference electric field sensor (S57), and ends the first reference position analysis processing (S22).

[0081] FIG. 13 is a diagram showing an example of the installation position of the electric field sensor determined by the first analysis process (S20) and the installation position of the reference electric field sensor determined by the first reference position analysis process (S22). In FIG. 13, the hatched circle B10 indicates an example of the installation position of the electric field sensor determined in step S41 of the first analysis process. In FIG. 13, the hatched square B12 indicates an example of the installation position of the reference electric field sensor determined in step S57 of the first reference position analysis process.

[0082] In the example of FIG. 13, as shown by the hatched circle B10 in FIG. 13, for example, a total of four locations, namely the left and right nose sides on the nose side of the aircraft 1 and the lower surfaces of the left and right horizontal tails 14, are determined as the installation positions of the electric field sensors. By actually installing the electric field sensors at these positions, when the aircraft 1 performs attitude control in the pitch direction, the electric field intensity can be effectively detected, and the surface electric field intensity distribution of the aircraft 1 can be more appropriately estimated.

[0083] Also, in the example of FIG. 13, as shown by the hatched square B12 in FIG. 13, for example, the position between the fuselage 10 and the engine on the lower surface of the main wing 12 of the aircraft 1 is determined as the installation position of the reference electric field sensor. By actually installing the reference electric field sensor at this position, the reference of the electric field intensity when the aircraft 1 performs attitude control in the pitch direction becomes clear, and the electric field intensity distribution of the aircraft 1 can be more appropriately estimated.

[0084] FIG. 14 is a diagram for explaining the outline of the second analysis process (S24). In FIG. 14, a state of the airframe shape model 100 and the parallel electrodes 110 arranged in the analysis space 104 as viewed from the nose side of the airframe is shown. In FIG. 14, for the sake of convenience of explanation, the airframe shape model 100 is exaggerated and shown large with respect to the size of the analysis space 104. Also, in FIG. 14, for the sake of convenience of explanation, the roll axis, pitch axis, and yaw axis of the airframe shape model 100 are also shown.

[0085] In the example of FIG. 14, the parallel electrodes 110 shown by the thick solid line are arranged parallel to the pitch axis and the roll axis of the airframe shape model 100. At this time, the relative roll angle of the airframe shape model 100 with respect to the parallel electrodes 110 is zero.

[0086] Here, assuming that the position of the airframe shape model 100 is fixed and the parallel electrodes 110 are rotated counterclockwise by a predetermined angle (for example, 10°) in FIG. 14 with the roll axis at the center of the analysis space 104 as the rotation center as indicated by the dashed arrow A20. An example of the parallel electrodes 110 at that time is shown by the thick dashed line in FIG. 14. In this state, the left-wing side ends 112c of the upper electrode 112 and the left-wing side ends 114c of the lower electrode 114 have moved upward, and the right-wing side ends 112d of the upper electrode 112 and the right-wing side ends 114d of the lower electrode 114 have moved downward. Then, with reference to the rotated parallel electrodes 110 of the thick dashed line, the relative roll angle of the airframe shape model 100 becomes a value on the left bank side from zero.

[0087] Also, assuming that the position of the airframe shape model 100 is fixed and the parallel electrodes 110 are rotated clockwise by a predetermined angle (for example, 10°) in FIG. 14 with the roll axis at the center of the analysis space 104 as the rotation center as indicated by the dash-dotted arrow A22. An example of the parallel electrodes 110 at that time is shown by the thick dash-dotted line in FIG. 14. In this state, the left-wing side ends 112c of the upper electrode 112 and the left-wing side ends 114c of the lower electrode 114 have moved downward, and the right-wing side ends 112d of the upper electrode 112 and the right-wing side ends 114d of the lower electrode 114 have moved upward. Then, with reference to the rotated parallel electrodes 110 of the thick dash-dotted line, the relative roll angle of the airframe shape model 100 becomes a value on the right bank side from zero.

[0088] In this way, by rotating the parallel electrodes 110 around the roll axis, the relative roll angle can be changed. Here, an example of fixing the aircraft shape model 100 and rotating the parallel electrodes 110 has been described. However, the relative roll angle may also be changed by fixing the position of the parallel electrodes 110 and rotating the aircraft shape model 100 around the roll axis. However, in the example of rotating the aircraft shape model 100, since the tetrahedron corresponding to the candidate position 102 changes one by one as the aircraft shape model 100 rotates, it takes more time and becomes more complicated for the electrostatic field analysis than the example of rotating the parallel electrodes 110. For this reason, the example of rotating the parallel electrodes 110 is more preferable than the example of rotating the aircraft shape model 100.

[0089] In the second analysis process, the relative pitch angle and the relative yaw angle are fixed at predetermined values. The second analysis processing unit 94 extracts any four candidate positions 102 from among the plurality of candidate positions 102 and creates a combination of the four candidate positions 102.

[0090] The second analysis processing unit 94 determines the relative roll angle to an arbitrary value, generates an electric field in the parallel electrodes 110, and acquires the electric field strength at each of the candidate positions 102 of the combination of the four candidate positions 102 by electrostatic field analysis. Then, the second analysis processing unit 94 repeats, each time the relative roll angle is changed, while maintaining the relative pitch angle and the relative yaw angle at predetermined values, to acquire the electric field strength at each of the candidate positions 102 of the plurality of candidate positions 102. For example, the second analysis processing unit 94 changes the relative roll angle by 1° while maintaining the relative pitch angle at zero and the relative yaw angle at zero. Note that the example is not limited to changing the relative roll angle by 1° each time, and the relative roll angle may be changed by an arbitrary angle each time.

[0091] When these processes are performed, the electric field strength is obtained for each candidate position 102 of the combination of the four candidate positions 102 for each relative roll angle. The electric field strength at each candidate position 102 is different for each relative roll angle.

[0092] The second analysis processing unit 94 derives the variance based on the electric field strengths of each of the candidate positions 102 in the combination of the four candidate positions 102 at an arbitrary relative roll angle. The method for deriving the variance here is the same as the method for deriving the variance in the first analysis processing unit 92. The second analysis processing unit 94 repeats this derivation of the variance each time the relative roll angle is changed. Then, the second analysis processing unit 94 adds the variances derived each time the relative roll angle is changed, and derives the total sum of the variances.

[0093] The second analysis processing unit 94 changes the combination of the four candidate positions 102 and derives the total sum of the variances for each combination of the candidate positions 102. The second analysis processing unit 94 derives the total sum of the variances for all patterns of the combinations of the four candidate positions 102.

[0094] FIG. 15 is a diagram showing an example of the relationship between the relative roll angle and the total sum of the variances. FIG. 15 shows an example when the total sum of the variances related to the relative roll angle is relatively large. FIG. 16 is a diagram showing another example of the relationship between the relative roll angle and the total sum of the variances.

[0095] The second analysis processing unit 94 specifies the combination of the four candidate positions 102 with the largest total sum of the variances related to the relative roll angle, and sets each candidate position 102 constituting the specified combination of the four candidate positions 102 as the installation position of the electric field sensor.

[0096] As described above, by setting each candidate position 102 constituting the combination of the candidate positions 102 with the maximum total sum of the variances as the installation position of the electric field sensor, the installed electric field sensor can effectively detect the electric field strength.

[0097] Next, the outline of the second reference position analysis process will be described. In the second reference position analysis process, the relative pitch angle and the relative yaw angle are fixed to predetermined values, respectively, and the relative roll angle is determined to be an arbitrary value. In this state, the second analysis processing unit 94 generates an electric field in the parallel electrodes 110, and acquires the electric field strength at each candidate position 102 of the plurality of candidate positions 102 by electrostatic field analysis. Then, while maintaining the relative pitch angle and the relative yaw angle at predetermined values, the second analysis processing unit 94 changes the relative roll angle, and repeats, each time the relative roll angle is changed, the acquisition of the electric field strength at each candidate position 102 of the plurality of candidate positions 102. For example, the first analysis processing unit 92 changes the relative roll angle by 1° while maintaining the relative pitch angle at zero and the relative yaw angle at zero. Note that the present invention is not limited to the example in which the relative roll angle is changed by 1° each time, and the relative roll angle may be changed by an arbitrary angle each time.

[0098] When these processes are performed, the electric field strength is obtained for each relative roll angle at each candidate position 102. The electric field strength at each candidate position 102 is different for each relative roll angle.

[0099] FIG. 17 is a diagram showing an example of the relationship between the relative roll angle and the electric field strength at one candidate position 102. FIG. 18 is a diagram showing an example of the relationship between the relative roll angle and the electric field strength at another candidate position 102.

[0100] Here, at any one candidate position 102, among the electric field strengths acquired for each relative roll angle, the difference value obtained by subtracting the minimum value from the maximum value and taking the absolute value is defined as the second variance of the electric field strength with respect to the relative roll angle. In other words, the second variance of the electric field strength with respect to the relative roll angle corresponds to the amplitude of the electric field strength when the relative roll angle is changed to acquire the electric field strength.

[0101] FIG. 17 shows an example in which the second variance of the electric field strength with respect to the relative roll angle is relatively large. FIG. 18 shows an example in which the second variance of the electric field strength with respect to the relative roll angle is relatively small.

[0102] The second analysis processing unit 94 identifies a candidate position 102 with a relatively small second variance of the electric field strength with respect to the relative roll angle among the plurality of candidate positions 102, and the identified candidate position 102 may be used as the installation position of the reference electric field sensor. The reference electric field sensor is an electric field sensor for detecting a reference electric field strength that serves as a reference for the electric field strength.

[0103] As described above, the fact that the second variance of the electric field strength is small means that if a reference electric field sensor is installed at that position, even if the roll angle of the aircraft 1 actually changes, the change in the electric field strength detected by the reference electric field sensor will be small. Then, the electric field strength detected by the reference electric field sensor can be made roughly constant within an allowable error range regardless of the actual roll angle of the aircraft 1. By using the electric field strength detected by this reference electric field sensor as the reference for the electric field strength, the surface electric field strength distribution of the aircraft 1 can be estimated more appropriately.

[0104] More specifically, the second analysis processing unit 94 identifies candidate positions 102 corresponding to a predetermined number among the candidate positions 102 having the smallest second variance among the plurality of candidate positions 102, and the identified predetermined number of candidate positions 102 may be used as the installation positions of the electric field sensors. By identifying the candidate position 102 for the installation position of the reference electric field sensor starting from the one with the smallest second variance, the variation in the electric field strength detected by the reference electric field sensor can be reduced more, and the surface electric field strength distribution can be estimated more appropriately.

[0105] Here, the predetermined number may be, for example, one. As long as there is at least one reference electric field strength, the surface electric field strength distribution can be estimated appropriately. Note that the predetermined number is not limited to one and may be set to any number of two or more.

[0106] FIG. 19 is a flowchart for explaining the flow of the second analysis process (S24). When the second analysis process (S24) is started, the second analysis unit 94 first determines the relative pitch angle to a specific relative pitch angle such as zero (S60). Although omitted in FIG. 19, the relative yaw angle is also determined to a specific relative yaw angle such as zero.

[0107] Next, the second analysis unit 94 sets the change range of the relative roll angle (S61). The change range of the relative roll angle is set within a realistic range that can be actually taken in the attitude control of the aircraft 1.

[0108] Next, the second analysis unit 94 sets the number of combined configurations (S62). For example, the second analysis unit 94 sets 4 as the number of combined configurations. Note that the number of combined configurations is not limited to 4 and may be set to any number of 2 or more.

[0109] Next, the second analysis unit 94 extracts the number of candidate positions 102 corresponding to the number of combined configurations set in step S62 from among the plurality of candidate positions 102, and determines the combination of the candidate positions 102 corresponding to the number of combined configurations (S63).

[0110] Next, the second analysis unit 94 determines an arbitrary relative roll angle within the change range of the relative roll angle (S64).

[0111] The second analysis unit 94 executes an electrostatic field analysis at the determined relative roll angle, and acquires the electric field strength at each of the candidate positions 102 constituting the combination determined in step S63 (S65). The second analysis unit 94 may store the relative roll angle, the candidate positions 102 at which the electric field strength is acquired, and the acquired electric field strength in association with each other.

[0112] The second analysis processing unit 94 derives the average value of the acquired electric field strength, and based on the average value, derives the variance of the electric field strength at the candidate position 102 that constitutes the combination (S66). The second analysis processing unit 94 derives the sum of the variances derived in a state where the combination of candidate positions is the same and the relative roll angle is the same (S67). For example, the second analysis processing unit 94 derives the sum of the variances by adding the variance derived this time to the variance derived previously in a state where the combination of candidate positions 102 is the same and the relative roll angle is the same.

[0113] Next, the second analysis processing unit 94 determines whether there is a remaining relative roll angle for which the electrostatic field analysis has not been performed (S68). If there is a remaining relative roll angle (YES in S68), the second analysis processing unit 94 repeats the processing from step S64 onwards. At this time, the second analysis processing unit 94 determines an arbitrary relative roll angle among the remaining relative roll angles (S64), and acquires the electric field strength again at the relative roll angle changed in this way (S65).

[0114] If there is no remaining relative roll angle (NO in S68), the second analysis processing unit 94 determines whether there is a remaining combination that has not been combined (S69). If there is a remaining combination (YES in S69), the second analysis processing unit 94 repeats the processing from step S63 onwards. At this time, the second analysis processing unit 94 determines an arbitrary combination among the remaining combinations (S64), and repeats the processing after determining the relative roll angle in the combination changed in this way.

[0115] If there is no remaining combination (NO in S69), the second analysis processing unit 94 specifies the combination for which the sum of the variances is the maximum (S70). The second analysis processing unit 94 sets the candidate position 102 that constitutes the combination specified in step S70 as the installation position of the electric field sensor (S71), and ends the second analysis processing.

[0116] FIG. 20 is a flowchart for explaining the flow of the second reference position analysis process (S26). When the second reference position analysis process (S26) starts, the second analysis unit 94 first determines the relative pitch angle to a specific relative pitch angle such as zero (S80). Although omitted in FIG. 20, the relative yaw angle is also determined to a specific relative yaw angle such as zero.

[0117] Next, the second analysis unit 94 sets the change range of the relative roll angle (S81). The change range of the relative roll angle is set within a realistic range that can be actually taken in the attitude control of the aircraft 1.

[0118] The second analysis unit 94 determines an arbitrary relative roll angle within the change range of the relative roll angle (S82).

[0119] The second analysis unit 94 performs an electrostatic field analysis at the determined relative roll angle and acquires the electric field strength at each of the plurality of candidate positions 102 (S83). The second analysis unit 94 may store the relative roll angle, the candidate position 102 at which the electric field strength is acquired, and the acquired electric field strength in association with each other.

[0120] Next, the second analysis unit 94 determines whether there is a remaining relative roll angle for which the electrostatic field analysis has not been performed (S84). If there is a remaining relative roll angle (YES in S84), the second analysis unit 94 repeats the processes after step S82. At this time, the second analysis unit 94 determines an arbitrary relative roll angle among the remaining relative roll angles (S82), and acquires the electric field strength again at the relative roll angle thus changed (S83).

[0121] If there is no remaining relative roll angle (NO in S84), the second analysis unit 94 derives a second variance of the electric field strength with respect to the relative roll angle (S85). For example, the second analysis unit 94 derives the second variance of the electric field strength at an arbitrary candidate position 102 by subtracting the minimum value from the maximum value of the electric field strength at the arbitrary candidate position 102 and taking the absolute value, and derives the second variance of the electric field strength in the same manner at all the candidate positions 102.

[0122] Next, the second analysis processing unit 94 identifies candidate positions 102 where the second variance of the electric field strength derived in step S85 is relatively small (S86). For example, the second analysis processing unit 94 identifies the candidate position 102 with the smallest second variance of the electric field strength among the plurality of candidate positions 102. The second analysis processing unit 94 sets the candidate position 102 identified in step S86 as the installation position of the reference electric field sensor (S87), and ends the second reference position analysis processing (S26).

[0123] FIG. 21 is a diagram showing an example of the installation position of the electric field sensor determined by the second analysis processing (S24) and the installation position of the reference electric field sensor determined by the second reference position analysis processing (S26). In FIG. 21, the hatched circle B20 indicates an example of the installation position of the electric field sensor determined in step S71 in the second analysis processing. In FIG. 21, the hatched square B22 indicates an example of the installation position of the reference electric field sensor determined in step S87 in the second reference position analysis processing.

[0124] In the example of FIG. 21, as indicated by the hatched circle B20 in FIG. 21, for example, a total of four positions near the tip portions rather than the fuselage 10 on the upper and lower surfaces of the left and right main wings 12 of the aircraft 1 are determined as the installation positions of the electric field sensors. By actually installing the electric field sensors at these positions, when the aircraft 1 performs attitude control in the roll direction, the electric field strength can be effectively detected, and the surface electric field strength distribution of the aircraft 1 can be more appropriately estimated.

[0125] Also, in the example of FIG. 21, as indicated by the hatched square B22 in FIG. 21, for example, the position between the fuselage 10 and the engine on the lower surface of the main wing 12 of the aircraft 1 is determined as the installation position of the reference electric field sensor. By actually installing the reference electric field sensor at this position, the reference of the electric field strength when the aircraft 1 performs attitude control in the roll direction becomes clear, and the electric field strength distribution of the aircraft 1 can be more appropriately estimated.

[0126] From the above description, the appropriate installation position of the electric field sensor with respect to the relative pitch angle was determined by the first analysis process, and the appropriate installation position of the electric field sensor with respect to the relative roll angle was determined by the second analysis process. Based on these, it is preferable to actually install the electric field sensor at both the installation position determined by the first analysis process and the installation position determined by the second analysis process. Note that the electric field sensor may be actually installed at at least one of the installation positions determined by the first analysis process and the installation position determined by the second analysis process.

[0127] Further, the arithmetic unit 64 is not limited to the mode of performing both the first analysis process and the second analysis process, and may perform only one of the first analysis process and the second analysis process. Also, in the mode of performing both the first analysis process and the second analysis process, it is not limited to the mode of performing the second analysis process after the first analysis process, and the second analysis process may be performed first, and the first analysis process may be performed after the second analysis process.

[0128] Also, the first reference position analysis process and the second reference position analysis process may be omitted.

[0129] Note that it is not limited to the mode of obtaining the electric field strength by fixing the relative pitch angle and changing the relative roll angle, or the mode of obtaining the electric field strength by fixing the relative roll angle and changing the relative pitch angle, and the electric field strength may be obtained by changing both the relative pitch angle and the relative roll angle at once. However, in the mode of changing both at once, the total variance when changing the relative pitch angle may be larger than the total variance when changing the relative roll angle, and the accuracy of specifying the combination with the maximum total variance may decrease. For this reason, the mode of fixing one of the relative pitch angle and the relative roll angle and changing the other is more preferable than the mode of changing both at once.

[0130] As described above, in the sensor positioning method of the present embodiment, at least one of the relative pitch angle and the relative roll angle is changed, and obtaining the electric field strength at each candidate position 102 of the plurality of candidate positions 102 is repeated each time at least one of the relative pitch angle and the relative roll angle is changed. Then, in the sensor positioning method of the present embodiment, among the plurality of candidate positions 102, a candidate position 102 in which the variance of the electric field strength obtained each time at least one of the relative pitch angle and the relative roll angle is changed is relatively large is specified, and the specified candidate position 102 is set as the setting position of the electric field sensor.

[0131] Therefore, according to the sensor positioning method of the present embodiment, an appropriate installation position of the electric field sensor can be determined. As a result, by actually installing the electric field sensor at the determined installation position, the surface electric field strength distribution of the aircraft 1 can be appropriately estimated, and the influence of lightning strikes can be suppressed.

[0132] FIG. 22 is a flowchart for explaining another example of the first analysis process (S20). In FIG. 22, instead of determining the installation position of the electric field sensor based on the sum of the variances for each combination of candidate positions 102, the installation position of the electric field sensor is determined based on a second variance of the electric field strength of each individual candidate position 102.

[0133] When the first analysis process (S20) is started, the first analysis processing unit 92 first determines the relative roll angle to a specific relative roll angle such as zero (S100). Although omitted in FIG. 22, the relative yaw angle is also determined to a specific relative yaw angle such as zero. Next, the first analysis processing unit 92 sets a change range of the relative pitch angle (S101). The first analysis processing unit 92 determines an arbitrary relative pitch angle within the change range of the relative pitch angle (S102).

[0134] The first analysis processing unit 92 executes electrostatic field analysis at the determined relative pitch angle and acquires the electric field strength at each of the plurality of candidate positions 102 (S103). The first analysis processing unit 92 may store the relative pitch angle, the candidate position 102 at which the electric field strength is acquired, and the acquired electric field strength in association with each other.

[0135] Next, the first analysis processing unit 92 determines whether there is a remaining relative pitch angle for which electrostatic field analysis has not been performed (S104). If there is a remaining relative pitch angle (YES in S104), the first analysis processing unit 92 repeats the processing after step S102. At this time, the first analysis processing unit 92 determines an arbitrary relative pitch angle among the remaining relative pitch angles (S102), and acquires the electric field strength again at the relative pitch angle thus changed (S103).

[0136] If there is no remaining relative pitch angle (NO in S104), the first analysis processing unit 92 derives a second variance of the electric field strength with respect to the relative pitch angle (S105). For example, the first analysis processing unit 92 derives the second variance of the electric field strength at an arbitrary candidate position 102 by subtracting the minimum value from the maximum value of the electric field strength at the arbitrary candidate position 102 and taking the absolute value, and derives the second variance of the electric field strength in the same manner at all candidate positions 102.

[0137] Next, the first analysis processing unit 92 identifies candidate positions 102 at which the second variance of the electric field strength derived in step S105 is relatively large (S106). For example, the first analysis processing unit 92 identifies a predetermined number of candidate positions 102 from among the plurality of candidate positions 102, starting from the one with the largest variance of the electric field strength. The predetermined number is, for example, four, but is not limited to this example and may be set to any number. The first analysis processing unit 92 sets the candidate position 102 identified in step S106 as the installation position of the electric field sensor (S107).

[0138] If the second variance of the electric field strength is large, it can be estimated that if an electric field sensor is installed at that position, the amplitude of the electric field strength that can be detected by the electric field sensor is large. If the amplitude of the electric field strength that can be detected by the electric field sensor is large, the ratio of noise to the electric field strength that can be detected by the electric field sensor becomes small, and the resolution of the electric field sensor can be made higher than that of electric field sensors at other positions. From this, by setting the candidate position 102 where the second variance of the electric field strength is relatively large as the installation position of the electric field sensor, the installed electric field sensor can effectively detect the electric field strength.

[0139] FIG. 23 is a flowchart for explaining another example of the second analysis process (S24). In FIG. 23, instead of determining the installation position of the electric field sensor based on the sum of the variances for each combination of candidate positions 102, the installation position of the electric field sensor is determined based on the second variance of the electric field strength at each individual candidate position 102.

[0140] When the second analysis process (S24) is started, the second analysis processing unit 94 first determines the relative pitch angle to a specific relative pitch angle such as zero (S110). Although omitted in FIG. 23, the relative yaw angle is also determined to a specific relative yaw angle such as zero. Next, the second analysis processing unit 94 sets the change range of the relative roll angle (S111).

[0141] The second analysis processing unit 94 executes an electrostatic field analysis at the determined relative roll angle and acquires the electric field strength at each of the plurality of candidate positions 102 (S113). The second analysis processing unit 94 may store the relative roll angle, the candidate position 102 at which the electric field strength is acquired, and the acquired electric field strength in association with each other.

[0142] Next, the second analysis processing unit 94 determines whether there is a remaining relative roll angle for which electrostatic field analysis has not been performed (S114). If there is a remaining relative roll angle (YES in S114), the second analysis processing unit 94 repeats the processing after step S112. At this time, the second analysis processing unit 94 determines an arbitrary relative roll angle among the remaining relative roll angles (S112), and acquires the electric field strength again at the relative roll angle thus changed (S113).

[0143] If there is no remaining relative roll angle (NO in S114), the second analysis processing unit 94 derives a second variance of the electric field strength with respect to the relative roll angle (S115). For example, the second analysis processing unit 94 subtracts the minimum value from the maximum value of the electric field strength at an arbitrary candidate position 102 and takes the absolute value to derive the second variance of the electric field strength at the arbitrary candidate position 102, and similarly derives the second variance of the electric field strength at all candidate positions 102.

[0144] Next, the second analysis processing unit 94 identifies candidate positions 102 where the second variance of the electric field strength derived in step S115 is relatively large (S116). For example, the second analysis processing unit 94 identifies a predetermined number of candidate positions 102 from among the plurality of candidate positions 102, starting from the one with the largest second variance of the electric field strength. The predetermined number is, for example, four, but is not limited to this example and may be set to any number. The second analysis processing unit 94 sets the candidate position 102 identified in step S116 as the installation position of the electric field sensor (S117).

[0145] The fact that the second variance of the electric field strength is large means that, if an electric field sensor is installed at that position, it can be estimated that the amplitude of the electric field strength that can be detected by the electric field sensor is large. The fact that the amplitude of the electric field strength that can be detected by the electric field sensor is large means that the ratio of noise to the electric field strength that can be detected by the electric field sensor becomes small, and the resolution of the electric field sensor can be made higher than that of electric field sensors at other positions. From this, by setting the candidate position 102 where the second variance of the electric field strength is relatively large as the installation position of the electric field sensor, the installed electric field sensor can effectively detect the electric field strength.

[0146] The embodiments of the present invention have been described above with reference to the accompanying drawings. Needless to say, the present invention is not limited to such embodiments. It is obvious that those skilled in the art can conceive various modification examples or correction examples within the scope described in the claims, and it is naturally understood that those also belong to the technical scope of the present invention.

[0147] For example, in the above embodiment, an airliner is exemplified as the aircraft 1, and the installation position of the electric field sensor installed in the airliner has been determined. However, the sensor positioning method of the present embodiment is not limited to the mode of determining the installation position of the electric field sensor installed in the airliner. The sensor positioning method of the present embodiment can determine the installation position of the electric field sensor regardless of the type and shape of the aircraft 1 on which the electric field sensor is installed.

[0148] Also, in the above embodiment, in the preprocessing (S10), the positions vulnerable to direct lightning strikes were excluded in advance from a plurality of candidate positions, and then the first analysis process (S20), the first reference position analysis process (S22), the second analysis process (S24), and the second reference position analysis process (S26) were performed. However, the exclusion process of excluding the positions vulnerable to direct lightning strikes from a plurality of candidate positions may not be performed in the preprocessing, and after deriving the total sum of variances for all combinations, the exclusion process may be performed.

Explanation of Reference Numerals

[0149] 1 Aircraft 100 Airframe Shape Model 102 Candidate Position 104 Analysis Space 110 Parallel Electrodes

Claims

1. A sensor positioning method for determining the installation position of an electric field sensor that detects the electric field strength generated on the surface of an aircraft fuselage, comprising: In an analysis space where electrostatic field analysis is performed, a fuselage shape model simulating the shape of the fuselage is set; In the fuselage shape model, a plurality of candidate positions that are candidates for the installation position of the electric field sensor are set; In the analysis space, a flat parallel electrode that generates an electric field is set so as to sandwich the fuselage shape model therebetween; A relative pitch angle indicating the relative pitch angle of the fuselage shape model with respect to the parallel electrode and a relative roll angle indicating the relative roll angle are determined; At the determined relative pitch angle and relative roll angle, the electric field strength at each of the plurality of candidate positions is obtained by electrostatic field analysis; Repeating each time at least one of the relative pitch angle and the relative roll angle is changed to obtain the electric field strength at each of the plurality of candidate positions; Among the plurality of candidate positions, a candidate position where the variance of the electric field strength obtained each time at least one of the relative pitch angle and the relative roll angle is changed is relatively large is specified, and the specified candidate position is set as the installation position of the electric field sensor. Sensor positioning method.

2. Among the plurality of candidate positions, a candidate position where the variance of the electric field strength obtained each time at least one of the relative pitch angle and the relative roll angle is changed is relatively small is specified, and the specified candidate position is used as the reference electric field strength that is the reference for the electric field strength. The sensor positioning method according to claim 1, wherein the sensor positioning method is the installation position of a reference electric field sensor that detects the sensor.

3. The sensor positioning method according to claim 1 or 2, wherein a position on the fuselage shape model that is likely to be struck by direct lightning is excluded from the plurality of candidate positions.

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