WO2024242156A1 - Direction estimation device, direction estimation system, direction estimation method, and direction estimation program - Google Patents

Abstract

This direction estimation device comprises: an information acquisition unit that acquires listening result information indicating time-series listening results obtained through measurement using a sonar that emits a sound wave beam in a plurality of directions, the listening results being results of listening to sound waves from a plurality of listening directions including at least some of the plurality of directions; and a direction estimation unit that estimates a perpendicular incident direction in which the sound wave beam strikes an object of interest at a right angle on the basis of the listening result information.

Description

Direction estimation device, direction estimation system, direction estimation method, and direction estimation program CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Application No. 2023-84885, filed on May 23, 2023, the contents of which are incorporated herein by reference.

The present invention relates to a direction estimation device, a direction estimation system, a direction estimation method, and a direction estimation program.

There is a mooring line load monitoring system that remotely monitors the failure and breakage of mooring lines of floating bodies such as ships (for example, non-patent document 1).

LCM SYSTEMS., Mooring Line Load Monitoring (MLM)., [Retrieved April 21, 2023], Internet <URL: https://www.lcmsystems.com/Applications/load-cells-load-pins-for-mooring-line-load-monitoring-mlm>

In the mooring rope load monitoring system described in Non-Patent Document 1, a sensor such as a strain gauge is attached to the upper end or middle of the mooring rope, and the output value of the sensor is constantly monitored. This monitoring makes it possible to detect critical events such as the breakage of the mooring rope and to predict the risk of breakage due to excessive tension.
However, the strain and other information obtained from the sensors is merely fragmentary information at a certain point on the mooring line, making it difficult to accurately monitor the overall shape and behavior of the mooring line, as well as the amount and distribution of biological fouling.

In order to monitor these accurately, technology is required that can measure the position of mooring lines with minimal error.

The present disclosure therefore aims to provide a direction estimation device, a direction estimation system, a direction estimation method, and a direction estimation program that are capable of suppressing errors when measuring the position of an object.

A direction estimation device according to one aspect of the present invention includes an information acquisition unit that acquires listening result information indicating a time series of listening results measured by a sonar that emits sound beams in multiple directions, the listening results being sound waves from multiple listening directions including at least some of the multiple directions, and a direction estimation unit that estimates a perpendicular incidence direction in which the sound beam perpendicularly enters an object based on the listening result information.

　Although conventional sonar can measure the direction of an object as seen by the sonar and the distance between the sonar and the object, it is difficult to accurately obtain the angle of incidence of the sound beam on the object, which results in errors in measuring the object's position. In contrast, with an aspect that estimates the perpendicular incidence direction in which the sound beam perpendicularly enters the object, it is possible to determine the position of the object with reduced error as a position that is the distance measured by the sonar in the estimated perpendicular incidence direction. Therefore, errors can be reduced when measuring the object's position.

In the above aspect, the listening result information may indicate the listening results of the sound waves from the multiple listening directions for each zenith angle and each deviation angle.

In this embodiment, multiple listening directions can be expressed in polar coordinates based on the sonar, simplifying the process of estimating the perpendicular incidence direction.

In the above aspect, the information acquisition unit may acquire, as the listening result information, image information for each zenith angle, which indicates a fan-shaped image having a radius and a central angle that are the elapsed time from the time the sound beam was emitted and the deflection angle, respectively, and which includes an image corresponding to the echo of the sound beam from the target, and the direction estimation unit may estimate the vertical incidence direction based on the image information for each zenith angle.

According to this embodiment, the change in the image with respect to the zenith angle, i.e., the change with respect to the image's angle of incidence, can be easily obtained. This makes it easy to estimate the vertical incidence direction by utilizing the property that the image length changes depending on the angle of incidence of the sound beam on the target object.

In the above aspect, the direction estimation unit may estimate the vertical incidence direction based on the length of each of the images included in each of the images indicated by the image information for each of the zenith angles.

According to this aspect, for example, when the target object is linear, the perpendicular incident direction can be accurately determined by utilizing the property that the closer the angle at which the sound beam is incident on the target object is to perpendicular, the shorter the image length becomes.

In the above aspect, the direction estimation unit may further calculate the distance between the sonar and the target object based on the image information when the estimated perpendicular incident direction is included in the sound beam.

In this embodiment, in an image in which the sound beam includes a perpendicular incidence direction, the distance between the center of the fan and the image is the distance between the position where the sound beam perpendicularly enters the object and the sonar, making use of this property to accurately calculate the distance between the position where the sound beam perpendicularly enters the object and the sonar.

In the above embodiment, the object may appear to be linear when viewed from the sonar.

If the object is planar, it is necessary to estimate its direction in advance and measure from the appropriate direction. For example, if the object is a flat seabed, it is necessary to measure from above, and if it is a vertical wall, it is necessary to measure from the side. With this aspect, the shape of the object can be treated as linear, so it is possible to measure without estimating the appropriate direction in advance. Also, the relational expression between the angle at which the sound beam is incident on the object and the image length can be easily derived. This makes it easy to estimate the perpendicular incidence direction.

In the above aspect, the distance between the sonar and a plane including the target object may be smaller than a value determined based on the distance between the sonar and the target object.

In this way, by positioning the sonar near a plane that includes the target object, it is possible to suppress deterioration in the accuracy of estimating the vertical incidence direction.

In the above aspect, the direction estimation device may further include a memory unit that stores pairs of the perpendicular incidence direction and the distance, and a shape estimation unit that estimates the shape of the object based on the multiple pairs stored in the memory unit.

According to this aspect, for example, a curve that closely approximates the multiple positions represented by each of the multiple pairs can be calculated, and the shape of the entire object can be estimated by assuming that the curve represents the shape of the object. This makes it possible to estimate the shape of the entire object based on the measurement results of some positions on the object.

In the above embodiment, the sonar may be a multi-beam sonar.

According to this aspect, it is possible to efficiently obtain the results of listening to sound waves from multiple listening directions, and it is also possible to suppress variation in the listening directions, thereby suppressing deterioration in the estimation accuracy of the perpendicular incidence direction.

In the above embodiment, the sonar may be a scanning sonar.

According to this embodiment, sound wave listening results from multiple listening directions can be obtained at low cost.

A direction estimation system according to another aspect of the present invention includes an underwater robot equipped with a sonar and the above-mentioned direction estimation unit, the sonar emits sound beams in multiple directions, listens to sound waves from multiple listening directions including at least some of the multiple directions, and generates listening result information indicating the listening results in a time series.

　Although conventional sonar can measure the direction of an object as seen by the sonar and the distance between the sonar and the object, it is difficult to accurately obtain the angle of incidence of the sound beam on the object, which results in errors in measuring the object's position. In contrast, according to an aspect that estimates the perpendicular incidence direction in which the sound beam perpendicularly enters the object, a position that is a distance away from the estimated perpendicular incidence direction measured by the sonar can be obtained as the position of the object with reduced errors. Therefore, errors when measuring the object's position can be reduced. In addition, because the sonar is installed on an underwater robot that can move freely underwater, many positions of the object can be measured. This makes it possible to obtain the overall shape of the object.

In the above aspect, the sonar may be a multi-beam sonar that measures the sound waves from the multiple listening directions for each declination angle, and the underwater robot may include a mechanism that directs the sonar to the multiple listening directions for each zenith angle.

According to this aspect, it is possible to easily generate listening result information that indicates the listening results of sound waves from multiple listening directions for each zenith angle and each deviation angle.

A direction estimation method according to another aspect of the present invention is a direction estimation method in a direction estimation device, which includes acquiring listening result information indicating the listening results of sound waves from a plurality of listening directions including at least a portion of the plurality of directions, the listening result information being a time series of listening results measured by a sonar that emits sound beams in a plurality of directions, and estimating a perpendicular incidence direction in which the sound beam is perpendicularly incident on an object based on the listening result information.

　Although conventional sonar can measure the direction of an object as seen by the sonar and the distance between the sonar and the object, it is difficult to accurately obtain the angle of incidence of the sound beam on the object, which results in errors in measuring the object's position. In contrast, with an aspect that estimates the perpendicular incidence direction in which the sound beam perpendicularly enters the object, it is possible to determine the position of the object with reduced error as a position that is the distance measured by the sonar in the estimated perpendicular incidence direction. Therefore, errors can be reduced when measuring the object's position.

A direction estimation program according to another aspect of the present invention is a direction estimation program used in a direction estimation device, and is a program for causing a computer to function as an information acquisition unit that acquires listening result information that indicates a time series of listening results measured by a sonar that emits sound beams in multiple directions, the listening results being sound waves from multiple listening directions that include at least some of the multiple directions, and a direction estimation unit that estimates the perpendicular incidence direction in which the sound beam is perpendicularly incident on an object based on the listening result information.

　Although conventional sonar can measure the direction of an object as seen by the sonar and the distance between the sonar and the object, it is difficult to accurately obtain the angle of incidence of the sound beam on the object, which results in errors in measuring the object's position. In contrast, with an aspect that estimates the perpendicular incidence direction in which the sound beam perpendicularly enters the object, it is possible to determine the position of the object with reduced error as a position that is the distance measured by the sonar in the estimated perpendicular incidence direction. Therefore, errors can be reduced when measuring the object's position.

The present disclosure provides a direction estimation device, a direction estimation system, a direction estimation method, and a direction estimation program that can reduce errors when measuring the position of an object.

1 is a diagram for explaining the position of an underwater robot relative to a mooring line according to an embodiment of the present disclosure. FIG. FIG. 1 is a diagram illustrating a configuration of a direction estimation system according to an embodiment of the present disclosure. FIG. 1 is a diagram showing a configuration of an underwater robot according to an embodiment of the present disclosure. FIG. 2 is a diagram for explaining the orientation of the MBS in an underwater robot according to an embodiment of the present disclosure. FIG. 2 is a diagram for explaining the orientation of the MBS in an underwater robot according to an embodiment of the present disclosure. FIG. 2 is a diagram for explaining the orientation of the MBS in an underwater robot according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of an acoustic image according to an embodiment of the present disclosure. FIG. 13 illustrates an example of a swivel mechanism according to an embodiment of the present disclosure. 1 is a diagram for explaining the principle of direction estimation performed by a direction estimation device according to an embodiment of the present disclosure. FIG. 1 is a diagram for explaining the principle of direction estimation performed by a direction estimation device according to an embodiment of the present disclosure. FIG. FIG. 13 is a diagram showing an example of a change in a theoretical solution of an image length L ^* _image with respect to a head angle α according to an embodiment of the present disclosure. FIG. 1 is a diagram illustrating a configuration of a direction estimation device according to an embodiment of the present disclosure. FIG. 13 is a diagram showing an example of a change in image length L ^* _image over time according to an embodiment of the present disclosure. FIG. 13 is a diagram showing an example of a result of fitting by a fitting unit according to an embodiment of the present disclosure. FIG. 13 is a diagram showing an example of a target angle α ₀ calculated for each scan by a fitting unit according to an embodiment of the present disclosure. FIG. 13 is a diagram showing an example of a distance d calculated for each scan by a fitting unit according to an embodiment of the present disclosure. FIG. 13 is a diagram for explaining a method for calculating coordinates of a mooring line according to an embodiment of the present disclosure. FIG. 13 is a diagram showing an example of measurement results of absolute coordinates of a mooring line according to an embodiment of the present disclosure. FIG. 13 is a diagram showing an example of measurement results of absolute coordinates of a mooring line according to an embodiment of the present disclosure. FIG. 13 is a diagram showing an example of measurement results of absolute coordinates of a mooring line according to an embodiment of the present disclosure. FIG. 13 is a diagram showing an example of measurement results of absolute coordinates of a mooring line according to an embodiment of the present disclosure. 4 is a flowchart defining an operation procedure when a direction estimation device 11 according to an embodiment of the present disclosure performs a direction estimation process. 1 is a flowchart defining an operation procedure when a direction estimation device according to an embodiment of the present disclosure performs a measurement process. 1 is a flowchart defining an operation procedure when a direction estimation device according to an embodiment of the present disclosure performs information acquisition processing. 1 is a flowchart defining an operation procedure when a direction estimation device according to an embodiment of the present disclosure performs a process of calculating object position coordinates. FIG. 13 is a diagram showing an example of a target angle α ₀ calculated for each scan by a fitting unit in a first modified example of a direction estimation device according to an embodiment of the present disclosure.

A preferred embodiment of the present invention will be described with reference to the attached drawings. In each drawing, the same reference numerals denote the same or similar configurations.

[First embodiment]
FIG. 1 is a diagram for explaining the position of an underwater robot relative to a mooring line according to one embodiment of the present disclosure.

Each drawing may show an X-axis, a Y-axis, and a Z-axis. The X-axis, the Y-axis, and the Z-axis are coordinate axes fixed to the Earth, and form a right-handed three-dimensional Cartesian coordinate system. The vertical downward direction is the positive direction of the Z-axis. In other words, the X-axis and the Y-axis are oriented horizontally. Hereinafter, the direction of the X-axis arrow may be referred to as the X-axis + side, and the direction opposite the arrow may be referred to as the X-axis - side, and the same applies to the other axes. The Z-axis + side and Z-axis - side may be referred to as the "lower side" and "upper side", respectively. The Z-axis direction may also be referred to as the "depth direction". The planes perpendicular to the X-axis, Y-axis, or Z-axis, respectively, may be referred to as the YZ plane, ZX plane, or XY plane.

The mooring line 401 (object) is, for example, a chain that moor a float supporting a wind turbine from the seabed surface Pb in a floating wind power generation system. When one end of the mooring line 401 is fixed to the float and the other end of the mooring line 401 is fixed to the seabed surface Pb, the mooring line 401 hangs down under its own weight to form a catenary curve (suspended curve). This mooring method in which mooring force is obtained by the weight of the hanging mooring line 401 is called catenary mooring. Hereinafter, the plane including the mooring line 401 may be referred to as the moving plane Pm. In this embodiment, the moving plane Pm is parallel to the ZX plane.

The underwater robot 111 is a remotely operated unmanned underwater robot (Remotely Operated Vehicle: ROV) that is remotely controlled by an operator from outside the underwater robot 111 (e.g., on a ship or on land). The underwater robot 111 may be an underwater robot that is directly operated by a human, or it may be an underwater robot that performs missions autonomously without assistance such as human operation.

The underwater robot 111, for example, has five thrusters and can control five degrees of freedom: surge, sway, heave, pitch, and yaw.

The underwater robot 111 is equipped with a multibeam imaging sonar 114 (hereinafter sometimes referred to as MBS 114).

In response to remote control from outside, the underwater robot 111 moves to a position (hereinafter sometimes referred to as the preferred position) suitable for measuring the position of the mooring line 401 when the underwater robot 111 is used as a reference (hereinafter sometimes referred to as the relative position).

The preferred position is, for example, a position that satisfies the condition that the distance between the moving plane Pm and the MBS 114 is smaller than the distance between the MBS 114 and the mooring line 401.

Preferably, this position satisfies the condition that the distance between the moving plane Pm and the MBS 114 is smaller than a value determined based on the distance between the MBS 114 and the mooring line 401. Specifically, the distance between the moving plane Pm and the MBS 114 is smaller than 100% (preferably, 20%) of the distance between the MBS 114 and the mooring line 401.

More preferably, the preferred position is, for example, a position that satisfies the condition that the MBS 114 intersects with the moving plane Pm. In this case, the distance between the moving plane Pm and the MBS 114 is, for example, less than 2% of the distance between the MBS 114 and the mooring line 401.

Specifically, five thrusters in the underwater robot 111 operate in response to remote control from outside, causing the underwater robot 111 to change depth and move horizontally within the moving plane Pm. When the underwater robot 111 is in a suitable position, the mooring line 401 appears straight when viewed from the MBS 114.

FIG. 2 is a diagram showing the configuration of a direction estimation system according to an embodiment of the present disclosure. As shown in FIG. 2, the direction estimation system 201 includes a computer 101 and an underwater robot 111.

The computer 101 is installed, for example, on land. The computer 101 may also be installed on a floating body, a ship, or an underwater robot 111.

The computer 101 includes a processor 21, a bus 22, a communication I/F (interface) 23, a memory 24 (storage unit), and a disk 25 (storage unit). The computer 101 is, for example, a personal computer.

In computer 101, processor 21, communication unit 23, memory 24, and disk 25 are connected via bus 22 so that data can be exchanged among them.

The memory 24 is a volatile storage device such as a dynamic random access memory (DRAM). The communication unit 23 and the underwater robot 111, which is provided outside the computer 101, are connected, for example, by a cable. The communication unit 23 communicates with the underwater robot 111 via the cable.

The communication unit 23 transmits various data to the underwater robot 111 according to instructions from the processor 21. The communication unit 23 also receives various data transmitted from the underwater robot 111 and outputs the received data to the processor 21.

The disk 25 is a readable/writable non-volatile storage device such as a hard disk drive (HDD) or a solid state drive (SSD), and stores programs (code).
The disk 25 is not limited to an HDD or an SSD, and may be a memory card, a read-only CD-ROM (Compact Disc Read Only Memory), or a DVD-ROM (Digital Versatile Disc-Read Only Memory). The program can be installed from an external source. The program is distributed in a state stored in a storage medium such as the disk 25 that can be read by the computer 101.
The program may be distributed over the Internet connected via a communication interface.

When executing a program, the processor 21 transfers the program stored on the disk 25 and the data required to execute the program to the memory 24. The processor 21 reads the processing instructions and data required to execute the program from the memory 24, and executes arithmetic processing according to the contents of the processing instructions. At this time, the processor 21 may generate new data required to execute the program and store it in the memory 24. Note that the processor 21 is not limited to a configuration in which it obtains the program and data from the disk 25, and may also be configured to obtain the program and data from a server via the Internet.

FIG. 3 is a diagram showing the configuration of an underwater robot according to one embodiment of the present disclosure. As shown in FIG. 3, the underwater robot 111 includes a communication unit 112, a swivel mechanism 113, an MBS 114, a thruster control unit 115, an absolute coordinate measurement unit 116, and a swivel angle measurement unit 117.

The communication unit 112 in the underwater robot 111 communicates with the computer 101. The thruster control unit 115 controls the five thrusters based on control information received from the computer 101 via the communication unit 112.

The absolute coordinate measurement unit 116 measures, for example, coordinates (hereinafter sometimes referred to as absolute coordinates) that indicate the position of the underwater robot 111 when a reference point on the Earth is used as the reference point.

The absolute coordinate measurement unit 116 includes, for example, a one-axis fiber optic gyro (FOG) and a Doppler velocity log (DVL). The amount of movement of the underwater robot 111 is calculated, for example, by integrating the horizontal ground speed measured by the DVL along the azimuth angle obtained by integrating the angular velocity of the azimuth angle measured by the FOG. The absolute coordinate measurement unit 116 measures the absolute coordinates of the underwater robot 111 by adding the calculated amount of movement to the absolute coordinates of the initial position.

The absolute coordinate measuring unit 116, for example, measures the absolute coordinates of the underwater robot 111 at a predetermined period and transmits absolute coordinate information indicating the measured absolute coordinates to the computer 101 via the communication unit 112.

Figures 4 to 6 are diagrams for explaining the orientation of the MBS 114 in an underwater robot according to one embodiment of the present disclosure.

As shown in Figures 4 to 6, the x-axis, y-axis, and z-axis are defined as Cartesian coordinates fixed to the MBS 114. The x-axis, y-axis, and z-axis form a right-handed three-dimensional Cartesian coordinate system. When the underwater robot 111 moves as designed and is in a suitable position, the x-axis is parallel to the Y-axis, and the y-axis and z-axis are parallel to the moving plane Pm.

Figure 4 shows MBS 114 as viewed from the negative side of the y-axis. Figure 5 shows MBS 114 as viewed from the negative side of the x-axis. Figure 6 shows MBS 114 as viewed from the positive side of the z-axis.

The MBS 114 emits an acoustic beam 411 (sound wave beam) in multiple directions, listens to sound waves from multiple listening directions that include at least some of the multiple directions, and generates listening result information that indicates the listening results in a time series.

In detail, in one measurement, the MBS 114 emits an acoustic beam 411 in multiple directions in the zx plane and listens to sound waves from the multiple directions. The direction in which the acoustic beam 411 travels and the direction in which the sound waves are listened to (e.g., listening direction Da) are, for example, the same. The listening direction Da in the zx plane is defined by the deflection angle β when the z axis is used as a reference. Note that the direction in which the acoustic beam 411 travels and the direction in which the sound waves are listened to may be different.

In other words, in one measurement, the MBS 114 emits an acoustic beam 411 in multiple listening directions Da, each determined by multiple deflection angles β, and listens to sound waves from the multiple listening directions Da.

FIG. 7 is a diagram showing an example of an acoustic image according to an embodiment of the present disclosure. As shown in FIGS. 4 to 7, the MBS 114 generates a sector-shaped acoustic image 301 whose radius and central angle are the elapsed time from the time the acoustic beam 411 was emitted and the deflection angle β, respectively, and which includes an image 302 corresponding to the echo of the acoustic beam 411 from the mooring line 401. In this embodiment, the acoustic image 301 further includes an image 303 corresponding to the echo of the acoustic beam 411 from the sea surface.

The range of the fan-shaped acoustic image 301 is the area where an image can exist. The measurement origin of the MBS 114 is located at the intersection of two radii that pass through both ends of the fan-shaped arc, i.e., the center of the fan.

As a coordinate representation within the acoustic image 301 (hereinafter sometimes referred to as acoustic image coordinates), the above intersection point is set as the origin, and a u-axis and a v-axis that are orthogonal to each other are defined. The u-axis direction is, for example, a direction that bisects the central angle of the sector, and is taken so as to show the time-series listening results based on the acoustic beam 411 emitted in the z-axis direction. The direction Dr defined by the deflection angle β when the u-axis is used as the reference shows the time-series listening results based on the acoustic beam 411 emitted in the listening direction Da (see Figure 5).

The radius of the sector is the maximum distance R that can be measured by the MBS 114 (hereinafter, sometimes referred to as the measurement range R). The measurement range R of the MBS 114 is set appropriately according to the size of the mooring line 401.

When MBS114 receives an echo based on an acoustic beam, the position of the image is determined by its direction and the time that has elapsed from when acoustic beam 411 was emitted until the echo is received. The shorter the time that elapses until the echo returns, the closer the image is to the origin (0,0) of the acoustic image coordinates, and the longer the time that elapses, the closer the image is to the sector arc.

Furthermore, the stronger the reverberation, the whiter the image appears. The white rod-shaped image 302 that appears inside the sector-shaped area in the acoustic image 301 is the image of the mooring line 401. When the underwater robot 111 moves as designed and is positioned in a suitable position, the image 302 of the mooring line 401 appears as an image that extends straight on the u-axis.

In this embodiment, the MBS 114 generates an acoustic image 301 for each measurement. The MBS 114 performs measurements at a predetermined interval, for example, and transmits image information indicating the acoustic image 301 to the computer 101 via the communication unit 112.

FIG. 8 is a diagram showing an example of a swivel mechanism 113 according to one embodiment of the present disclosure. As shown in FIG. 8, the swivel mechanism 113 is fixed to the underwater robot 111 (not shown).

The oscillating mechanism 113 has a rotation shaft (not shown) that is rotated by, for example, a motor. The rotation shaft is parallel to the x-axis. The MBS 114 is attached to the rotation shaft of the oscillating mechanism 113. This allows the MBS 114 to rotate around the rotation shaft.

In this embodiment, the oscillating mechanism 113 rotates the rotation shaft back and forth at a predetermined angular velocity within a predetermined angle range, thereby causing the MBS 114 to perform a continuous oscillating motion.

As shown in Figures 4 and 8, the swivel angle measurement unit 117 measures the swivel angle (zenith angle) of the MBS 114. In this embodiment, the swivel angle measurement unit 117 includes, for example, an angle sensor, and acquires the angle of the rotation axis of the swivel mechanism 113 detected by the angle sensor, i.e., the swivel angle, at a predetermined interval. The swivel angle measurement unit 117 transmits swivel angle information indicating the acquired angle to the computer 101 via the communication unit 112.

It is preferable that the measurement timing of the angle sensor and the measurement timing of the MBS 114 are approximately the same. However, the measurement timing of the angle sensor and the measurement timing of the MBS 114 may be different.

[Measurement principle]
9 and 10 are diagrams for explaining the principle of direction estimation performed by a direction estimation device according to an embodiment of the present disclosure. As shown in Fig. 9 and 10, how the length L ^* _image (see Fig. 7) of the image 302 of the mooring line 401 changes depending on the distance from the MBS 114 to the mooring line 401 and the incident angle of the acoustic beam to the mooring line 401 is theoretically derived.

As shown in FIG. 9, when the MBS 114 is located at point O, assume that the perpendicular line from point O to the mooring line 401 is not included in the acoustic beam 411.

When MBS114 is viewed from the front side (z-axis + side), the angle between the axis of rotation TA of the swing and the direction in which the mooring line 401 extends is 90 degrees (see Figure 6). In addition, the mooring line 401 is positioned exactly in the center of the viewing angle of MBS114 (see Figure 4).

Furthermore, to simplify the discussion, the following five assumptions are made. The first assumption is that in the region of the mooring line 401 where the acoustic beam 411 hits when the MBS 114 performs a swiveling motion, the mooring line 401 is considered to be locally straight.

The second assumption is to ignore the thickness of the mooring line 401. This is equivalent to considering that the acoustic beam 411 reflects from the central axis of the mooring line 401.

The third assumption is that the MBS 114 is considered to be a point. The fourth assumption is that the acoustic beam 411 is uniformly distributed only within a certain symmetrical angular range (e.g., 2δ) as viewed from the body of the MBS 114 (see Figures 5, 9, and 10).

The fifth assumption is to ignore the pulse width of the acoustic beam 411 and to assume that the acoustic beam 411 spreads out like a widthless arc.

With these assumptions, consider the length of the image 302 of the mooring line 401 reflected in the acoustic image 301. 2δ is the distribution angle of the acoustic beam 411 in the yz plane. Distance d is the length of the perpendicular line OH drawn from point O to the mooring line 401.

α is the swivel angle of the MBS 114, with the reference direction Ds from point O as the reference and the counterclockwise direction as viewed from the x-axis + side to the x-axis - side as the positive direction. The reference direction Ds is, for example, the horizontal direction. α ₀ is the swivel angle α when the acoustic beam 411 is perpendicularly incident on the mooring line 401.

Point A is the intersection of the center line of the acoustic beam 411 and the mooring line 401. Points B and C are the upper and lower intersections of the mooring line 401 and a line indicating the distribution range of the acoustic beam, which is taken δ above and below the center line of the acoustic beam 411, respectively.

First, for simplicity, consider the case where α ₀ =0°. When the acoustic beam 411 is reflected by the mooring line 401 and returns to the MBS 114, the acoustic beam 411 is distributed in the area inside the triangle OBC. The length L ₁ of the longest reflection path in this area is the longer of the line segments OB and OC. The length L 1 is calculated by using d=OH as follows:
This is expressed as:

On the other hand, the shortest reflection path depends on whether point H is located between points B and C. When point H is located between points B and C (see Figure 10), the length of the shortest path is equal to d = OH.

When point H is not located between point B and point C (see FIG. 9), the shorter of the line segments OB and OC is the shortest path. Therefore, the length L2 of the shortest reflection path is given by
Here, max(A, B) is a function that returns the larger of A and B.

From the above, the difference L _diff between the lengths of the shortest routes is
This is expressed as:

If the measurement range of the MBS 114 is R and the length of the image 302, L ^* _image , is expressed as a ratio of _Ldiff to R, then:
It becomes.

Here, let us consider the case where α ₀ ≠ 0°. When α ₀ ≠ 0°, if we consider that the mooring line 401 is rotated around the point O by the symmetric angle α ₀ , the theoretical solution for the length L ^* _image of the image 302 is finally given by
It becomes.

11 is a diagram showing an example of a change in the theoretical solution of the length L ^* _image of the image 302 according to an embodiment of the present disclosure with respect to the swivel angle α. In FIG. 11, the vertical axis indicates L ^* _image . The horizontal axis indicates the swivel angle α in degrees.

As shown in FIG. 11, for example, when L ^* _image (α) is plotted with d=2.0 m, R=7.5 m, _α0 =-45.0°, and δ=10.0°, a downward convex curve is obtained that has a minimum value at α= _α0 in the range of -90°≦α≦0°.

This means that when the oscillation angle is such that the acoustic beam 411 of the MBS 114 is perpendicularly incident on the mooring line 401, the image 302 of the mooring line 401 appears at its shortest in the acoustic image 301.

Even in the case of an actual mooring line 401, which is not necessarily straight, by considering it as locally straight, the property that "when the length L _image of the image 302 of the mooring line 401 is minimum, the acoustic beam 411 of the MBS 114 is perpendicularly incident on the mooring line 401" is assumed.

FIG. 12 is a diagram showing the configuration of a direction estimation device according to an embodiment of the present disclosure. FIG. 12 shows the software configuration of the direction estimation device 11. The direction estimation device 11 is configured, for example, by executing a program in the processor 21 of the computer 101.

As shown in FIG. 12, the direction estimation device 11 includes, as functional blocks, a hearing result information acquisition unit 31, a head-swivel angle information acquisition unit 32, a control unit 33, an image processing unit 34, a data set generation unit 35, a direction estimation unit 36, an object coordinate calculation unit 37, an absolute coordinate information acquisition unit 38, and an overall shape estimation unit 39.

The control unit 33 in the direction estimation device 11 controls the underwater robot 111 through the bus 22 and the communication unit 23. Specifically, the control unit 33 controls the thrusters of the underwater robot 111, the swing mechanism 113, and the MBS 114.

The listening result information acquisition unit 31 acquires the listening result information. In this embodiment, the listening result information indicates the results of listening to sound waves from multiple listening directions for each swivel angle α and each deflection angle β.

Specifically, the listening result information acquisition unit 31 receives image information showing an acoustic image 301 as listening result information from the underwater robot 111 at each measurement timing of the MBS 114.

Because the MBS 114 is swiveled at a predetermined angular velocity by the swiveling mechanism 113, the image information is also information for each swiveling angle α. The hearing result information acquisition unit 31 outputs the acquired acoustic image 301 to the image processing unit 34.

When the image processing unit 34 receives the acoustic image 301 from the hearing result information acquisition unit 31, it acquires the length L ^* _image of the image 302 based on the acoustic image 301 (see FIG. 7).

Specifically, the image processing unit 34, for example, sets an area that includes the image 302 and binarizes that area. The image processing unit 34 performs an opening morphological transformation on the binarized area (hereinafter sometimes referred to as the binarized area) to remove small noise points, and then performs a closing morphological transformation to connect small gaps.

The image processing unit 34 selects the contour having the closest point to the measurement origin (u = 0, v = 0) from among the multiple contours in the binarized region. However, points that are too close to the measurement origin may be considered noise points and excluded.

The image processing unit 34 gives the smallest rectangle that circumscribes the selected contour and has each side parallel to the sides of the original image.

The image processing unit 34 calculates the position (u1, v1) that is the midpoint of the bottom side of the rectangle as the position of the bottommost part of the image 302 of the mooring line 401. The image processing unit 34 also calculates the height of the rectangle as the length L ^* _image of the image 302 of the mooring line 401.

The image processing unit 34 outputs bottom position information indicating the calculated position (u1, v1) of the bottom of the image 302 and length information indicating the length L ^* _image of the image 302 to the data set generating unit 35.

The swivel angle information acquisition unit 32 receives swivel angle information from the MBS 114 at each measurement timing of the swivel angle measurement unit 117 in the MBS 114, and outputs the swivel angle information to the data set generation unit 35.

13 is a diagram showing an example of a change in length L ^* _image of the image 302 over time according to an embodiment of the present disclosure. In FIG. 13, the vertical axis indicates L ^* _image , and the horizontal axis indicates time.

The data set generator 35 receives the bottom position information and length information from the image processor 34, and stores the bottom position (u1, v1), the length L ^* _image of the image 302, and the measurement time in association with each other. This generates a first data set in which the bottom position (u1, v1), the length L ^* _image of the image 302, and the measurement time are arranged in chronological order. The graph shown in Fig. 13 plots the change in L ^* _image over time when the MBS 114 swings back and forth once.

The data set generator 35 also receives the swing angle information from the swing angle information acquirer 32 and stores the swing angle α in association with the measurement time. This generates a second data set in which pairs of the swing angle α and the measurement time are arranged in chronological order.

The data set generator 35 generates a third data set in which the position (u1, v1) of the bottom of the image 302, the length L ^* _image of the image 302, and the swing angle α correspond to each other based on the relationship between the measurement times in the first data set and the measurement times in the second data set. As a result, the horizontal axis of the graph in Fig. 13 is converted from time to the swing angle α based on the third data set. The data set generator 35 outputs the third data set to the direction estimator 36.

Fig. 14 is a diagram showing an example of a result of fitting by a fitting unit according to an embodiment of the present disclosure. In Fig. 14, the vertical axis indicates L ^* _image , and the horizontal axis indicates the swing angle α in "°".

The direction estimation unit 36 estimates the perpendicular incidence direction based on the length L ^* _image of each image 302 indicated by the image information for each swing angle α.

In this embodiment, when the direction estimation unit 36 receives the third data set from the data set generation unit 35, it estimates the vertical incidence direction based on the third data set.

Specifically, the direction estimation unit 36 performs fitting based on the third data set and formula (5) to calculate the target angle α ₀ that gives the curve Cb when formula (5) best fits the third data set. The direction estimation unit 36 calculates the target angle α ₀ for each one-way swing of the MBS 114.

In this embodiment, the shape of the mooring rope 401 is approximated by a straight line, so that a point on the linear mooring rope 401 that is the shortest distance from the MBS 114 is located in the direction of the target angle α ₀ .

The direction estimation unit 36 also calculates the distance d between the MBS 114 and the mooring line 401 based on the image information when the estimated vertical incidence direction is included in the acoustic beam 411.

In this embodiment, the direction estimation unit 36 acquires the position (u1, v1) of the bottom of the image 302 in the acoustic image 301 corresponding to the swing angle α closest to the target angle α ₀ in the third data set.

The direction estimation unit 36 calculates the distance d _image from the acquired position (u1, v1) to the origin (0, 0) of the acoustic image coordinates in the acoustic image 301, and calculates the result of multiplying the distance d _image by the measurement range R as the distance d from the MBS 114 to the mooring line 401.

Fig. 15 is a diagram showing an example of a target angle _α0 calculated for each scan by a fitting unit according to an embodiment of the present disclosure. In Fig. 15, the vertical axis indicates the target angle _α0 in units of "°". The horizontal axis indicates the number of scans. For example, when the number of scans is an odd number and an even number, the swing motion of the MBS 114 is the result of the forward and backward paths, respectively.

16 is a diagram showing an example of the distance d calculated for each scan by the fitting unit according to an embodiment of the present disclosure. The vertical axis indicates the distance d in units of "m". The horizontal axis can be read in the same way as in FIG. 15. The direction estimation unit 36 outputs the target angle α ₀ and the distance d to the target coordinate calculation unit 37 for each scan, i.e., for each one-way swing of the MBS 114.

When the absolute coordinate information acquisition unit 38 receives absolute coordinate information from the underwater robot 111 via the bus 22, it outputs the absolute coordinate information to the object coordinate calculation unit 37.

The target coordinate calculation unit 37 calculates the absolute coordinates of the mooring rope 401 based on the target angle α ₀ and distance d received from the direction estimation unit 36 and the absolute coordinate information received from the absolute coordinate information acquisition unit 38 .

12 and 17, the absolute coordinates of the position of the MBS 114 are (xs, zs), the pitch angle of the robot is θ, the swing angle at normal incidence is the target angle α ₀ , and the absolute coordinates of the point where the center plane 411a of the acoustic beam 411 and the mooring line 401 intersect are (xt, zt).
In addition, θ is positive in the counterclockwise direction as viewed from the Y-axis + side, and α ₀ is positive in the clockwise direction as viewed from the Y-axis + side. In this case, (xt, zt) ^T can be obtained as follows.

If the absolute coordinates of the positioning center of the underwater robot 111 are (xb, zb) and the absolute coordinates of the relative mounting position of the MBS 114 as viewed from that point are (xsb, zsb), then (xs, zs) ^T can be expressed as follows using (xb, zb) ^T and (xsb, zsb) ^T :

By eliminating (xs, zs) ^T from equations (6) and (7), (xt, zt) ^T can be expressed as follows using (xb, zb) ^T and (xsb, zsb) ^T , which are parameters that can be easily extracted in an actual device.

The object coordinate calculation unit 37 calculates (xt, zt) as the absolute coordinates of the mooring line 401, and stores the object coordinate information indicating the calculated absolute coordinates in the memory 24 or disk 25 via the bus 22.

FIGS. 18 to 21 are diagrams showing an example of the measurement results of the absolute coordinates of a mooring line according to one embodiment of the present disclosure. In FIG. 18 to FIG. 21, the vertical axis indicates the Z coordinate in units of "m". The horizontal axis indicates the X coordinate in units of "m".

As shown in Figures 18 to 21, multiple markers are attached to a mooring line 401. Symbol 401a is located at the absolute coordinates of the markers measured, for example, by underwater motion capture.

As shown in FIG. 18, the multiple symbols included in symbol group Sr1 are each located at the absolute coordinates when the underwater robot 111 generates the listening result information.

The absolute coordinates of the mooring line 401 calculated based on the listening result information generated at the positions of the multiple symbols included in the symbol group Sr1 are located at the multiple symbols included in the symbol group St1.

The multiple symbols included in symbol group Sr2 are each located at the absolute coordinates when the underwater robot 111 generated the listening result information.

The absolute coordinates of the mooring line 401 calculated based on the listening result information generated at the positions of the multiple symbols included in the symbol group Sr2 are located at the multiple symbols included in the symbol group St2.

The multiple symbols included in symbol group Sr3 are each located at the absolute coordinates when the underwater robot 111 generated the listening result information.

The absolute coordinates of the mooring line 401 calculated based on the listening result information generated at the positions of the multiple symbols included in the symbol group Sr3 are located at the multiple symbols included in the symbol group St3.

As shown in FIG. 19, the multiple symbols included in symbol group Sr4 are each located at the absolute coordinates when the underwater robot 111 generated the listening result information.

The absolute coordinates of the mooring line 401 calculated based on the listening result information generated at the positions of the multiple symbols included in the symbol group Sr4 are located at the multiple symbols included in the symbol group St4.

The multiple symbols included in symbol group Sr5 are each located at the absolute coordinates when the underwater robot 111 generated the listening result information.

The absolute coordinates of the mooring line 401 calculated based on the listening result information generated at the positions of the multiple symbols included in the symbol group Sr5 are located at the multiple symbols included in the symbol group St5.

As shown in FIG. 20, the multiple symbols included in symbol group Sr6 are each located at the absolute coordinates when the underwater robot 111 generated the listening result information.

The absolute coordinates of the mooring line 401 calculated based on the listening result information generated at the positions of the multiple symbols included in the symbol group Sr6 are located at the multiple symbols included in the symbol group St6.

As shown in FIG. 21, the multiple symbols included in symbol group Sr7 are each located at the absolute coordinates when the underwater robot 111 generated the listening result information.

The absolute coordinates of the mooring line 401 calculated based on the listening result information generated at the positions of the multiple symbols included in the symbol group Sr7 are located at the multiple symbols included in the symbol group St7.

In this way, each symbol included in the symbol groups St1 to St7 closely reproduces the curve (not shown) connecting each symbol 401a. In other words, the direction estimation device 11 can accurately calculate the absolute coordinates of the mooring rope 401.

As shown in FIG. 12, if the overall shape of the mooring line 401 is known, it is useful for monitoring the mooring line 401, so a technique for estimating the shape of the mooring line 401 is required. In this embodiment, the overall shape estimation unit 39 in the direction estimation device 11 estimates the shape of the mooring line 401 based on multiple pairs of the vertical incidence direction and distance d stored in the memory 24 or disk 25.

In this embodiment, the overall shape estimation unit 39 acquires multiple pieces of object coordinate information stored in the memory 24 or disk 25 via the bus 22, and estimates the overall shape of the mooring line 401 based on the multiple pieces of object coordinate information acquired.

Specifically, for example, after the control unit 33 has finished controlling the underwater robot 111, the overall shape estimation unit 39 acquires multiple pieces of target coordinate information stored in the memory 24 or disk 25.

The overall shape estimation unit 39 assumes, for example, a curve that closely approximates the shape of the mooring line 401. In this embodiment, the overall shape estimation unit 39 assumes a catenary curve whose shape is determined by parameters, and calculates the parameters when the catenary curve best fits each absolute coordinate indicated by the multiple object coordinates by performing fitting based on the multiple object coordinate information acquired and the assumed catenary curve.

The overall shape estimation unit 39 estimates the overall shape of the mooring rope 401 based on the calculated parameters and catenary curve. In other words, it is possible to estimate the overall shape of the mooring rope 401 based on fragmentary measurement results.

[Direction Estimation Processing]
FIG. 22 is a flowchart that defines an operation procedure when the direction estimation device 11 according to an embodiment of the present disclosure performs a direction estimation process.

As shown in FIG. 22, the underwater robot 111 moves, for example, along a predetermined path. The path includes, for example, a number of preferred positions in the vicinity of the mooring line 401.

First, the direction estimation device 11, for example, moves the underwater robot 111 along a travel path (step S102).

Next, the direction estimation device 11 performs a measurement process (step S104). The measurement process is started when a predetermined condition is satisfied, for example, when the underwater robot 111 reaches a predetermined measurement position or when a predetermined measurement timing arrives.

Next, the direction estimation device 11 determines whether the underwater robot 111 has reached the end point of the specified movement path (step S106).

If the direction estimation device 11 determines that the underwater robot 111 has not reached the end point (NO in step S106), it moves the underwater robot 111 further along the travel path (step S102).

On the other hand, when the direction estimation device 11 determines that the underwater robot 111 has reached the end point (YES in step S106), it outputs the shape of the mooring lines 401 based on the calculated absolute coordinates of the multiple mooring lines 401 (step S108).

FIG. 23 is a flowchart that defines the operation procedure when a direction estimation device according to an embodiment of the present disclosure performs measurement processing. FIG. 23 shows details of the operation in step S104 in FIG. 22.

As shown in FIG. 23, first, the direction estimation device 11 performs a measurement start process (step S202). Specifically, the direction estimation device 11 activates the swivel mechanism 113, MBS 114, absolute coordinate measurement unit 116, and swivel angle measurement unit 117 in the underwater robot 111. This causes the underwater robot 111 to transmit swivel angle information, image information, and absolute coordinate information to the direction estimation device 11. The swivel mechanism 113 causes the MBS 114 to perform a swivel motion.

Next, the direction estimation device 11 performs information acquisition processing (step S204) until the MBS 114's swivel angle α reaches its upper limit (NO in step S206).

Next, the direction estimation device 11 performs a process of calculating the target object position coordinates (step S208).

Next, the direction estimation device 11 performs information acquisition processing (step S210) until the swing angle α of the MBS 114 reaches the lower limit (NO in step S212).

Next, the direction estimation device 11 performs a process of calculating the target object position coordinates (step S214).

Next, if the direction estimation device 11 determines that the predetermined termination condition is not satisfied (NO in step S216), it performs information acquisition processing (step S204) until the swing angle α of the MBS 114 reaches its upper limit (NO in step S206).

The specified end condition is, for example, that a specified time has elapsed since the start of measurement, or that the oscillating mechanism 113 has moved the oscillating angle of the MBS 114 back and forth a specified number of times.

On the other hand, if the direction estimation device 11 determines that the specified termination condition is satisfied (YES in step S216), it terminates the measurement process.

FIG. 24 is a flowchart that defines the operation procedure when a direction estimation device according to an embodiment of the present disclosure performs information acquisition processing. FIG. 24 shows details of the operations in steps S204 and S210 in FIG. 23.

As shown in FIG. 24, first, the direction estimation device 11 waits until it receives image information, swing angle information, or absolute coordinate information from the underwater robot 111 (NO in step S302, NO in step S308, and NO in step S314).

When the direction estimation device 11 receives image information from the underwater robot 111 (YES in step S302), it processes the acoustic image 301 indicated by the image information and obtains the position (u1, v1) of the bottom of the image 302 and the length L ^* _image of the image 302 (step S304).

Next, the direction estimation device 11 stores the position (u1, v1) of the bottom portion and the length L ^* _image of the image 302 in the first data set in association with the measurement time (step S306).

In addition, when the direction estimation device 11 receives the swing angle information from the underwater robot 111 (YES in step S308), it stores the swing angle α indicated by the swing angle information in the second data set in association with the measurement time (step S310).

In addition, when the direction estimation device 11 receives absolute coordinate information from the underwater robot 111 (YES in step S312), it stores the swing angle α indicated by the swing angle information in association with the measurement time (step S314).

FIG. 25 is a flowchart that defines the operation procedure when a direction estimation device according to an embodiment of the present disclosure performs a process of calculating object position coordinates. FIG. 25 shows details of the operations in steps S208 and S214 in FIG. 23.

As shown in FIG. 25, first, the direction estimation device 11 generates a third data set in which the position (u1, v1) of the bottom of the image 302 and the length L ^* _image of the image 302 correspond to the swing angle α, based on the relationship between the measurement time in the first data set and the measurement time in the second data set (step S402).

Next, the direction estimation device 11 performs fitting based on the third data set and equation (5) to calculate the target angle α ₀ that gives the curve Cb when equation (5) best fits the third data set (step S404).

Next, the direction estimation device 11 acquires the position (u1, v1) of the bottom of the image 302 corresponding to the swing angle α closest to the target angle _α0 in the third data set, and calculates the distance d _image from the origin (0, 0) of the acoustic image coordinates to the position (u1, v1) by the measurement range R as the distance d from the MBS 114 to the mooring line 401 (step S406).

Next, the direction estimation device 11 calculates the absolute coordinates of the mooring rope 401 based on the target angle α ₀ and the distance d, and the absolute coordinates indicated by the absolute coordinate information (step S408).

(First Modification)
26 is a diagram illustrating an example of a target angle α ₀ calculated for each scan by a fitting unit in a first modified example of a direction estimation device according to an embodiment of the present disclosure. Note that the way to view FIG. 26 is the same as that of FIG. 15.

For example, the timing when the MBS 114 generates the acoustic image 301 may differ from the timing when the swing angle information acquisition unit 32 acquires the swing angle α. In this case, the target angle α ₀ during the forward swing motion (e.g., when the number of scans is an odd number) becomes larger or smaller than the target angle α ₀ during the return swing motion (e.g., when the number of scans is an even number).

In more detail, for example, if on the outbound journey, the swivel angle information acquisition unit 32 measures an angle greater than the swivel angle α at which the MBS 114 generated the acoustic image 301, on the return journey, the swivel angle information acquisition unit 32 will measure an angle smaller than the swivel angle α at which the MBS 114 generated the acoustic image 301.

In addition, for example, if on the outbound journey, the swivel angle information acquisition unit 32 measures an angle smaller than the swivel angle α at which the MBS 114 generated the acoustic image 301, on the return journey, the swivel angle information acquisition unit 32 will measure an angle larger than the swivel angle α at which the MBS 114 generated the acoustic image 301.

In contrast, in the first modified example of the direction estimation device 11, the direction estimation unit 36 calculates the average of two target angles _α0 for two consecutive scan numbers as the target angle _α0 for one of the two consecutive scan numbers.

Specifically, the direction estimation unit 36 calculates, for example, the average of two target angles α ₀ when the number of scans is 1 and 2, as the target angle α ₀ when the number of scans is 1.

Then, the direction estimation unit 36 calculates, for example, the average of the two target angles α ₀ when the number of scans is two and three, as the target angle α ₀ when the number of scans is two.

This makes it possible to cancel out the difference between the swing angle α at which the MBS 114 generates the acoustic image 301 and the swing angle α measured by the swing angle information acquisition unit 32, thereby suppressing the variation in the target angle α ₀ .

In this embodiment, the object of shape measurement is a mooring rope 401, but this is not limited to this. The object may be, for example, a ship's rudder, or the like, which appears linear when viewed from the edge.

In addition, in this embodiment, a configuration has been described in which image information is transmitted from the underwater robot 111 to the computer 101 each time the MBS 114 generates image information, but this is not limited to this. The image information generated by the MBS 114 may be sequentially stored in a storage device provided in the underwater robot 111. In this case, after the measurement by the MBS 114 is completed, the direction estimation device 11 estimates the vertical incidence direction based on the image information stored in the storage device.

In addition, in this embodiment, a configuration in which the MBS 114 is provided on the underwater robot 111 has been described, but this is not limited to the above. A scanning sonar may be provided on the underwater robot 111 instead of the MBS 114. However, a configuration in which the MBS 114, which has good accuracy in the declination direction, is provided on the underwater robot 111 is preferable.

In addition, in this embodiment, a configuration has been described in which the orientation of the MBS 114 is changed by the oscillating motion of the oscillating mechanism 113, but this is not limited to the configuration. For example, the MBS 114 may be fixed to the underwater robot 111, and the orientation of the MBS 114 may be changed by adjusting the pitch of the underwater robot 111.

In addition, in this embodiment, the MBS 114 is provided on the underwater robot 111, but this is not limiting. The MBS 114 may be provided on a ship or held by a diver.

In addition, in this embodiment, the configuration has been described in which the target angle α ₀ at the time of vertical incidence is estimated by fitting the model function, i.e., equation (5), to the plot of L ^* _image against the swivel angle α, but this is not limited to this. For example, an algorithm may be used that compares two L ^* _images at two swivel angles α and determines that the sound beam at the swivel angle α with the smaller L ^* _image is close to vertical incidence. Since equation (5) has a minimum value, the vertical incidence direction at which the L ^* _image is smallest can be found by repeatedly executing this algorithm.

In this embodiment, the absolute coordinates are calculated from the coordinates of the relative position (target angle _α0 and distance d), but the present invention is not limited to this. For example, when a rider is on board the underwater robot 111, the rider can easily recognize the position of the target object based on the target angle _α0 and distance d.

The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The elements of the embodiments, as well as their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those exemplified, and may be modified as appropriate. Furthermore, configurations shown in different embodiments may be partially substituted or combined.

11...Direction estimation device 21...Processor 22...Bus 23...Communication unit 24...Memory 25...Disk 31...Sound listening result information acquisition unit 32...Pivot angle information acquisition unit 33...Control unit 34...Image processing unit 35...Data set generation unit 36...Direction estimation unit 37...Object coordinate calculation unit 38...Absolute coordinate information acquisition unit 39...Overall shape estimation unit 101...Computer 111...Underwater robot 112...Communication unit 113...Pivot mechanism 114...Multibeam imaging sonar 115...Thruster control unit 116...Absolute coordinate measurement unit 117...Pivot angle measurement unit 201...Direction estimation system 301...Acoustic images 302, 303...Image 401...Mooring line 411...Acoustic beam 411a...Center plane TA...Rotation axis Pm...Moving plane Pb...Seabed surface Da...Sound listening direction Ds...Reference direction R...Measurement range

Claims (14)

An information acquisition unit that acquires sound-hearing result information indicating a time series of sound-hearing results measured by a sonar that emits sound beams in multiple directions, the sound-hearing result being from multiple sound-hearing directions including at least a portion of the multiple directions;
and a direction estimating unit that estimates a normal incidence direction in which the sound wave beam is normal to the object based on the hearing result information.
Directional estimation device. The sound listening result information indicates the sound listening results of the sound waves from the multiple sound listening directions for each zenith angle and each deviation angle.
The direction estimation device according to claim 1 . The information acquisition unit acquires, as the hearing result information, image information showing a sector-shaped image having a radius and a central angle that are the elapsed time from the time when the sound beam was emitted and the deflection angle, respectively, for each zenith angle, the image including an image corresponding to the echo of the sound beam from the object;
The direction estimation unit estimates the vertical incidence direction based on the image information for each zenith angle.
The direction estimation device according to claim 2 . The direction estimation unit estimates the normal incidence direction based on a length of each of the images included in each of the images indicated by the image information for each of the zenith angles.
The direction estimation device according to claim 3 . The direction estimation unit further calculates a distance between the sonar and the object based on the image information when the estimated normal incidence direction is included in the sound wave beam.
The direction estimation device according to claim 3 . The object appears to the sonar as a straight line.
The direction estimation device according to claim 1 . The distance between the plane including the object and the sonar is smaller than a value determined based on the distance between the sonar and the object.
The direction estimation device according to claim 6 . The direction estimation device comprises:
A storage unit that stores a pair of the normal incidence direction and the distance;
A shape estimation unit that estimates a shape of the object based on the plurality of sets stored in the storage unit,
The direction estimation device according to claim 5 . The sonar is a multi-beam sonar.
The direction estimation device according to claim 1 . The sonar is a scanning sonar.
The direction estimation device according to claim 1 . An underwater robot equipped with sonar,
A direction estimation device according to any one of claims 1 to 10,
The sonar emits sound beams in a plurality of directions, listens to sound waves from a plurality of listening directions including at least a portion of the plurality of directions, and generates listening result information indicating the listening results in a time series.
Orientation Estimation System. The sonar is a multi-beam sonar that measures the sound waves from the plurality of listening directions for each declination angle,
The underwater robot comprises:
A mechanism for directing the sonar to a listening direction for each zenith angle among the plurality of listening directions,
The direction estimation system of claim 11. A direction estimation method for a direction estimation device, comprising:
Acquiring sound-sensing result information indicating a time series of sound-sensing results measured by a sonar that emits sound beams in a plurality of directions, the sound-sensing result being from a plurality of sound-sensing directions including at least a portion of the plurality of directions;
and estimating a normal incidence direction in which the sound beam is normal to the object based on the hearing result information.
Direction estimation methods. A direction estimation program for use in a direction estimation device,
Computer,
An information acquisition unit that acquires sound-hearing result information indicating a time series of sound-hearing results measured by a sonar that emits sound beams in multiple directions, the sound-hearing result being from multiple sound-hearing directions including at least a portion of the multiple directions;
a direction estimation unit that estimates a perpendicular incidence direction in which the sound wave beam is perpendicularly incident on an object based on the hearing result information,
Direction estimation program.

Images