AUV position error detection system, program, and method using Hough transform

Abstract

To provide an AUV position error detection system, a program, and a method for accurately detecting an error included in a self position estimation of an AUV by a method different from a conventional one.SOLUTION: A position error detection system comprises: sound positioning means 10, 11 provided in a support ship 1 or the like and performing sound positioning of an AUV2; control means 30 that controls the AUV2; and an INS20 provided in the AUV2. The control means 30 includes: a circulation / measurement instruction section 31 for instructing the AUV2 to wait for circulation, instructing the INS20 to estimate a position during the execution of waiting for the circulation, and instructing the sound positioning means 10, 11 to sound position the AUV2; and a position error detection section 32 for deriving an INS circular orbit as a circular orbit obtained by Hough transforming position coordinates of the AUV2 acquired by the INS20, deriving a sound circular orbit as a circular orbit obtained by Hough transforming the position coordinates of the AUV2 acquired by the sound positioning means 10, 11, and detecting an error of the position estimated by the INS20 on the basis of difference between the INS circular orbit and the sound circular orbit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a system, program, and method for detecting positional errors in an AUV (Autonomous Underwater Vehicle) when it is deployed from a support vessel or an ASV (Autonomous Surface Vehicle) or the like. [Background technology]

[0002] AUVs are widely used as a platform for detailed and efficient exploration of the seabed. Compared to ROVs (Remotely Operated Vehicles), AUVs can navigate without being constrained by a tether cable from a support vessel, making them particularly useful for detailed exploration of the deep seabed. Here, Patent Document 1 discloses a method for eliminating sound wave competition in an underwater observation system, in which an offshore repeater periodically acquires various data, an overlap state determination unit calculates the range of sound wave competition between the sound wave beam emitted by the offshore repeater itself and the sound wave beams emitted by a mother ship and / or other offshore repeaters included in another group of vessels based on the acquired data, and determines the state of sound wave beam overlap, an avoidance action determination unit determines the necessity of avoidance action to eliminate sound wave competition based on the overlap state, and if it determines that avoidance action is necessary, an avoidance action execution unit executes the avoidance action, and paragraph 0032 describes that the offshore repeater and the autonomous underwater vehicle circle and wait at the end point. Furthermore, Patent Document 2 discloses a method for correcting the self-position estimation error of an underwater vehicle equipped with a detection means for detecting a target object and a self-position estimation means, which involves setting the position of a target object on the underwater vehicle, navigating it to approach the target object, acquiring detection data when the target object is detected by the detection means, transmitting the detection data to a monitoring means using wireless communication, and in the monitoring means monitoring the positional error between the target object and the underwater vehicle based on the detection data, and if there is a positional error, performing a process by an operating means to eliminate the positional error caused by the error in the self-position estimation means. Furthermore, Patent Document 3 discloses a connection system between a surface repeater and an underwater vehicle, comprising a surface repeater having a repeater propulsion means and a repeater position measurement means, an underwater vehicle having a vehicle position estimation means, an information transmission line for transmitting acquired information including image information obtained by the underwater vehicle, a position setting means for setting target latitude and target longitude for the surface repeater and the underwater vehicle, and a control means for controlling the surface repeater and the underwater vehicle. The system is configured such that the underwater vehicle and the surface repeater travel in parallel while maintaining a vertical positional relationship between the water surface and the underwater vehicle until they reach the target latitude and target longitude, by driving the repeater propulsion means based on the set target latitude and target longitude and the surface position measured by the repeater position measurement means to control the position of the surface repeater with the control means, and controlling the position of the underwater vehicle based on the set target latitude and target longitude and the underwater position estimated by the vehicle position estimation means. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-041281 [Patent Document 2] Japanese Patent Publication No. 2021-116019 [Patent Document 3] Japanese Patent Publication No. 2022-145659 [Overview of the project] [Problems that the invention aims to solve]

[0004] Due to the significant attenuation of radio waves in water, it is not possible to determine the position of an AUV (Aircraft Underwater Vehicle) by relying on GNSS (Global Navigation Satellite System). Therefore, dead reckoning is used with INS (Inertial Navigation System), which integrates information from sensors such as AHRS (Attitude Heading Reference System), DVL (Doppler Velocity Log), and PDS (Pressure Depth Sensor) to estimate the position. However, when using AUVs in deep water, the INS (Inertial Navigation System) cannot obtain ground speed from the DVL (Deep Velocity Line) until the AUV approaches the seabed, resulting in pure inertial navigation and a large accumulation of positional errors. To solve this problem, offshore stations such as support vessels and ASVs that transmit commands via acoustic communication measure the AUV's position using acoustic underwater positioning systems such as USBL (Ultra-short baseline) and transmit correction commands to reduce the AUV's positional errors. However, acoustic positioning has many outliers, and positional data may not be obtainable due to noise. Therefore, accurately determining the position of an AUV navigating underwater is difficult. Outlier location data negatively impacts prediction filters. While some research has been conducted to remove these outliers, the large number of outliers and missing measurements makes it difficult for AUV operators to predict the future position of the AUV and perform error correction. Furthermore, acoustic communication and acoustic positioning in underwater environments are affected by noise from support vessels, the AUV itself, and multiple reflections. To mitigate the adverse effects of positioning errors, outliers, and missing data caused by such instability, error estimation based on the shape pattern of the AUV's trajectory is effective. For example, one method is to calculate the error using the least squares method from the position data of an AUV moving along a straight or circular orbit. However, while the least squares method can minimize the influence of fluctuations in each position data, in principle all values ​​are considered in the calculation, so outliers may adversely affect the results.

[0005] Patent Document 1 does not detect errors in self-position estimation by AUVs. Furthermore, while Patent Documents 2 and 3 disclose methods for correcting errors in AUV self-position estimation, these methods utilize underwater targets or the like for error correction. Therefore, the present invention aims to provide an AUV position error detection system, program, and method that accurately detects errors included in the AUV's self-estimated position using a method different from conventional methods. [Means for solving the problem]

[0006] The AUV position error detection system according to claim 1 is an AUV position error detection system for detecting position errors when navigating an AUV (autonomous underwater vehicle) deployed from a support vessel, ASV (Autonomous Offshore Vehicle), or monitoring station, comprising: acoustic positioning means provided in the water surrounding the support vessel, ASV, monitoring station, or AUV for acoustic positioning of the AUV; control means provided on the support vessel, ASV, monitoring station, or AUV for controlling the AUV; and an INS (Inertial Navigation System) provided on the AUV, wherein the control means provides a stationary station for the AUV to orbit on a designated orbit. The system is characterized by comprising: a rotation and measurement instruction unit that gives instructions to the aircraft and instructions for position estimation by INS during the execution of rotation and standby, and instructions for acoustic positioning of the AUV to support vessels, ASVs, monitoring bases, or acoustic positioning means installed in the water around the AUV; and a position error detection unit that derives an INS circular orbit as a circular orbit obtained by performing a Hough transform on the AUV's position coordinates acquired by the INS, derives an acoustic circular orbit as a circular orbit obtained by performing a Hough transform on the AUV's position coordinates acquired by the acoustic positioning means, and detects the error in the position estimated by the INS based on the difference between the INS circular orbit and the acoustic circular orbit. According to the present invention as described in claim 1, errors included in the position estimated by the INS of the AUV can be accurately detected using the Hough transform.

[0007] The present invention as described in claim 2 is characterized in that the position error detection unit determines the center coordinates for both the INS circular orbit and the acoustic circular orbit, determines the distance between the center of the INS circular orbit and the center of the acoustic circular orbit based on their respective center coordinates as the difference between the INS circular orbit and the acoustic circular orbit, determines that the error in position estimation by INS is outside the acceptable range if the distance is not within a predetermined range, and determines a position error correction value that includes the distance and direction to be corrected for position estimation by INS. According to the present invention as described in claim 2, a position error correction value can be accurately derived, and the position estimated by the INS can be corrected with the position error correction value.

[0008] The present invention as described in claim 3 is characterized in that the control means is provided on a support vessel, ASV, or monitoring base, and the orbiting and measurement instruction unit sequentially transmits the position error correction value obtained by the position error detection unit from the support vessel, ASV, or monitoring base to the AUV via acoustic communication means, instructs the AUV to orbit and wait for a specified period, and instructs position estimation by INS that reflects the position error correction value. According to the present invention as described in claim 3, the AUV continues to orbit (orbit standby) in an orbit while repeatedly correcting its position based on the received position error correction value, thereby enabling more accurate correction of the position estimated by the INS.

[0009] The present invention as described in claim 4 is characterized in that the control means repeatedly transmits a position error correction value to the AUV from the orbiting and measurement instruction unit, and instructs orbiting waiting for a specified period and position estimation reflecting the position error correction value by the INS, until the distance between the center of the INS circular orbit and the center of the acoustic circular orbit falls within a predetermined range set in the position error detection unit. According to the present invention as described in claim 4, the error included in the position estimated by the INS can be kept within a predetermined value.

[0010] The present invention as described in claim 5 is characterized in that the control means uses a position estimation method that integrates output information from an AHRS (Aircraft Heading and Attitude Reference System), DVL (Doppler Velocity Log), and PDS (Pressure Depth Sensor) mounted on the AUV, in addition to INS, to estimate the position of the AUV. According to the present invention as described in claim 5, after approaching the seabed, the ground velocity can be obtained from the DVL and position information can be determined with high accuracy.

[0011] The AUV position error detection program corresponding to claim 6 is an AUV position error detection program for detecting position errors when an AUV (autonomous unmanned underwater vehicle) equipped with an INS (inertial navigation system) deployed from a support vessel, ASV (autonomous offshore relay vehicle), or monitoring base is operated, characterized in that it causes a computer to execute: a waiting orbit step instructing the AUV to wait orbit in a specified orbit; an INS step instructing the AUV performing waiting orbit to perform position estimation by the INS; an acoustic positioning step instructing acoustic positioning means installed in the water around the support vessel, ASV, monitoring base, or AUV to perform acoustic positioning of the AUV; a conversion step in which an INS circular orbit is derived as a circular orbit obtained by performing a Hough transform on the AUV's position coordinates obtained by the INS, and an acoustic circular orbit is derived as a circular orbit obtained by performing a Hough transform on the AUV's position coordinates obtained by the acoustic positioning means; and a position error detection step in which the computer executes the error of position estimation by the INS based on the difference between the INS circular orbit and the acoustic circular orbit. According to the present invention as described in claim 6, a computer can accurately detect the error included in the position estimated by the INS of the AUV using the Hough transform.

[0012] A method for detecting the position error of an AUV corresponding to claim 7, the method for detecting the position error of an AUV (autonomous unmanned underwater vehicle) equipped with an INS (inertial navigation system) deployed from a support vessel, ASV (autonomous offshore relay vehicle), or monitoring base, the method comprising: a waiting orbit step in which the AUV waits while orbiting on a designated orbit; an INS step in which the position estimation of the AUV by INS is performed on the AUV while waiting orbit; an acoustic positioning step in which the acoustic positioning of the AUV is performed on acoustic positioning means installed in the water around the support vessel, ASV, monitoring base, or AUV; a conversion step in which an INS circular orbit is derived as a circular orbit obtained by performing a Hough transform on the position coordinates of the AUV obtained by the INS, and an acoustic circular orbit is derived as a circular orbit obtained by performing a Hough transform on the position coordinates of the AUV obtained by the acoustic positioning means; and a position error detection step in which the error of the position estimation by INS is detected based on the difference between the INS circular orbit and the acoustic circular orbit. According to the present invention set forth in claim 7, an error included in the position estimated by an INS provided in an AUV can be detected with high accuracy using Hough transform.

Effects of the Invention

[0013] According to the AUV position error detection system of the present invention, an error included in the position estimated by an INS provided in an AUV can be detected with high accuracy using Hough transform.

[0014] Further, the position error detection unit obtains center coordinates for each of the INS circular orbit and the acoustic circular orbit, obtains a distance between the center of the INS circular orbit and the center of the acoustic circular orbit based on the respective center coordinates as a difference between the INS circular orbit and the acoustic circular orbit. When the distance is not within a predetermined range, it is determined that the error in position estimation by the INS is outside the allowable range, and when obtaining a position error correction value including the distance and direction to be corrected for the position estimation by the INS, the position error correction value can be derived with high accuracy, and the position estimated by the INS can be corrected with the position error correction value.

[0015] Further, when the control means is provided in a support vessel, an ASV, or a monitoring base, and the orbit / measurement instruction unit sequentially transmits the position error correction value obtained by the position error detection unit from the support vessel, the ASV, or the monitoring base to the AUV via acoustic communication means, causes the AUV to wait in orbit for a specified period, and instructs position estimation by the INS reflecting the position error correction value, the AUV continues orbiting (orbit standby) on the circular orbit while repeatedly correcting the position based on the received position error correction value. Therefore, the position estimated by the INS can be corrected with higher accuracy.

[0016] Further, when the control means repeats transmission of the position error correction value to the AUV from the orbit / measurement instruction unit, standby in orbit for the specified period, and the instruction for position estimation reflecting the position error correction value by the INS until the distance between the center of the INS circular orbit and the center of the acoustic circular orbit falls within a preset predetermined range in the position error detection unit, the error included in the position estimated by the INS can be kept within a predetermined value.

[0017] Furthermore, when the control means uses a position estimation method that integrates output information from the INS, as well as the AHRS (Aircraft Heading and Attitude Reference System), DVL (Doppler Velocity Log), and PDS (Pressure Depth Sensor) mounted on the AUV to estimate the AUV's position, the position information can be accurately determined by obtaining the ground velocity from the DVL after approaching the seabed.

[0018] Furthermore, according to the AUV position error detection program of the present invention, a computer can accurately detect the error included in the position estimated by the INS (Inspection System) of the AUV using the Hough transform.

[0019] Furthermore, according to the AUV position error detection method of the present invention, the error included in the position estimated by the INS (Inspection Network System) of the AUV can be accurately detected using the Hough transform. [Brief explanation of the drawing]

[0020] [Figure 1] Functional block diagram of the AUV position error detection system according to an embodiment of the present invention. [Figure 2] Conceptual diagram showing the AUV in a rotating, waiting position. [Figure 3] Flowchart for positional error correction [Figure 4] Flowchart of circle detection process using the Hough transform [Figure 5] This figure shows an example of transforming the same observation location into a Huff parameter space. [Figure 6] A conceptual diagram showing the state in which the AUV is waiting to rotate in order to detect the position error of the AUV according to another embodiment of the present invention. [Figure 7] A conceptual diagram showing the state in which the AUV is waiting to rotate in the detection of the AUV's position error according to yet another embodiment of the present invention. [Figure 8] This diagram shows the trajectory of the AUV's position during submersion in the sea trial. [Figure 9] This figure shows the results of detecting circular orbits in the sea trials. [Figure 10] This figure shows the time-series variation of the radius of the detected circle in the sea trial. [Figure 11] This figure shows the distance difference based on timestamps between the INS-LOG position data recorded by the AUV during the sea trial and the USBL position data from the support vessel. [Figure 12] This figure shows the detection results from simulations related to the sea trials. [Figure 13] This figure shows the Huff parameter space of the original USBL data and the data with added errors in a simulation related to the sea trial. [Modes for carrying out the invention]

[0021] This document describes an AUV position error detection system, an AUV position error detection program, and an AUV position error detection method according to embodiments of the present invention. Figure 1 is a functional block diagram of the AUV position error detection system, and Figure 2 is a conceptual diagram showing the AUV in a state of waiting to rotate. As shown in Figure 2, the AUV (Autonomous Underwater Vehicle) 2 conducts seabed resource exploration and other activities under the control of a support vessel 1 located on the water. Alternatively, an ASV (Autonomous Offshore Vehicle) may be used together with or instead of the support vessel 1. As shown in Figure 1, the position error detection system includes an acoustic positioning means 10 for acoustically positioning the AUV2 underwater, an INS (Inertial Navigation System) 20 used for self-position estimation of the AUV2, and a control means 30 used for controlling the AUV2. The acoustic positioning means 10 and the control means 30 are mounted on the support vessel 1 which controls the AUV2 underwater, while the INS 20 is mounted on the AUV2 which performs underwater exploration. The acoustic positioning means 10 performs acoustic positioning using USBL (ultrashort baseline) and may be referred to as "USBL positioning means" in the following description. The control means 30 has a rotation / measurement instruction unit 31 and a position error detection unit 32. The control means 30 can also be installed inside the AUV2. In addition to the USBL positioning means 10 and control means 30, the support vessel 1 is equipped with a GNSS (Global Navigation Satellite System) 40 for acquiring position coordinates and an acoustic communication means 50 (first acoustic communication means 50A) for acoustic communication with the AUV 2. In addition to the INS20, the AUV2 is equipped with an acoustic communication means 50 (second acoustic communication means 50B) used for acoustic communication with the support vessel 1, an AHRS (Aircraft Heading and Attitude Reference System) 60 for acquiring the heading and attitude, a DVL (Doppler Velocity Log) 70 for acquiring ground speed and altitude, and a PDS (Pressure and Depth Gauge) 80 for acquiring pressure and depth. When navigating, the AUV2 can move freely underwater and draw a precise trajectory without being constrained by cables like an ROV when approaching the seabed. Therefore, when cruising, the AUV2 waits while maintaining a circular trajectory as a steady turn before starting a survey voyage in order to maintain control when approaching the seabed.

[0022] Figure 3 is a flowchart of the position error correction process. The operator monitoring the AUV2 on the support vessel 1, or the orbit / measurement instruction unit 31 of the control means 30, instructs the AUV2 to perform orbital standby, orbiting along a designated orbital (rotating) trajectory. The AUV2, deployed from the support vessel 1 into the exploration area, descends towards the seabed and performs orbital standby (steady rotation) before the start of the survey voyage along a designated trajectory (radius) and for a period (hour, designated time) (S1: orbital standby step). Furthermore, the operator or the orbiting / measurement instruction unit 31 instructs the AUV2 to determine its position coordinates using position estimation by the INS20 of the AUV2 alone. Upon receiving this instruction, the AUV2 sequentially reports its acquired position coordinates in Earth coordinates to the operator or the orbiting / measurement instruction unit 31 via the second acoustic communication means 50B (S2: INS step). The control means 30 preferably uses a position estimation method that integrates output information from the AHRS60, DVL70, and PDS80 sensors mounted on the AUV2, in addition to the INS20, to estimate the position of the AUV2. This allows for accurate determination of position information by obtaining the ground velocity from the DVL70 after approaching the seabed. The operator or the orbiting / measurement instruction unit 31 begins receiving position data (position coordinates) from the INS 20 and USBL positioning means 10 when the AUV2 begins submerging. The position of the AUV2 in Earth coordinates (i.e., latitude and longitude) can be measured from the support vessel 1 using the GNSS 40 and USBL positioning means 10. The operator or the orbiting / measurement instruction unit 31 instructs the USBL positioning means 10 to acoustically position the AUV2, which is waiting to orbit, and determine its position coordinates. Upon receiving this instruction, the USBL positioning means 10 sequentially transmits the position coordinates obtained by acoustically positioning the AUV2 to the operator or the orbiting / measurement instruction unit 31 (S3: acoustic positioning step).

[0023] Next, a Hough transform is performed to determine the orbit (circular orbit) of the waiting AUV2 (S4: Transformation Step). The Hough transform is a method for extracting geometric patterns that can be represented using parameters such as lines and circles. Since the most appropriate parameters are determined by voting and majority rule, it is robust to noise components that do not belong to geometric elements and to missing geometric elements such as occlusion (hideout, objects in the foreground obscuring the image). Here, Figure 4 is a flowchart of the circle detection process using the Hough transform. Circle detection using the Hough transform is determined by voting on candidate coordinates in the Hough parameter space, which is a three-dimensional discrete space. When the operator or position error detection unit 32 starts detecting the orbit using the Hough transform, it first grasps the approximate distribution of position data acquired by the USBL positioning means 10 and manually or automatically sets a reference coordinate which is the origin of the Hough parameter space. This is because it is difficult to predict the errors that occur in the INS 20. Determining the origin and initializing other parameters is the initialization process of the Hough parameter space. Next, the operator or position error detection unit 32 applies the Hough transform calculation process to each position data (position coordinate) received from the INS 20 and the USBL positioning means 10. It detects each circle until the radii of both circles converge to a predetermined value and determines the distance between their centers.

[0024] FIG. 5 is a diagram showing an example of converting observation positions into Hough parameter space. In the example of FIG. 5, the following parameters are set in advance. - Reference position coordinates define the origin of the Hough parameter space, and convert observation positions from an absolute geographic coordinate system to a relative coordinate system. Note that in FIG. 5, the Hough parameter space is denoted as "HPS". - The search range specifies the range of each axis of the Hough parameter space from the reference position coordinates. The search area is composed of an N range in the north-south direction and an E range in the east-west direction. The R range is the search range of the radius to be detected. - The N range, E range, and R range are each discretized with resolutions ΔN, ΔE, and ΔR. First, a newly observed position (point α) is converted from world coordinates (latitude and longitude). The World Geodetic System (WGS84) is converted into a two-dimensional Cartesian coordinate system. The north direction and east direction from the reference position are based on the distance and azimuth θ calculated by the following formula (1) according to the Karney method. In the discretized Hough parameter space, the coordinates of the observation position are n i , e i ), the center of the circle is n c , e c ), and the radius is assumed to be r. [Numerical]

[0025] The observed position (n i , e i ) is a candidate for obtaining circular components. For each r, votes are collected for center candidate coordinates of (n,e) combinations that include the circumference of a circle centered at (n i , e i ). The estimated center position and radius (n c ^, e i ^, r^) can be obtained by maximum value search of the following formula (2) when three or more pieces of observation position data are converted into the Hough parameter space and voted. [Numerical] The value of r^ is unstable and fluctuates when the number of votes is small because each observed position data point contains an error. Until the value of r^ converges to a constant value, the process of receiving position coordinates, voting in the Hough parameter space, searching for the maximum vote value, and calculating the circle's center and radius is repeated. After convergence, the circle detection process using the Hough transform is terminated, with the estimated values ​​being the most probable center position coordinates and radius values.

[0026] As shown in Figure 3, when the operator or the position error detection unit 32 has finished the circle detection process using the Hough transform for either the position data received from the INS 20 or the position data received from the USBL positioning means 10, it determines whether the circle detection using the Hough transform for the other has also been completed. If it determines that the circle detection for the other has not been completed (NO), it continues the circle detection for the other. On the other hand, if it is determined that circle detection for the other circle has also been completed, i.e., that both circle detections have been completed (YES), the distance between the centers of the two detected circles is calculated (S5: Position Error Detection Step). This distance between the centers of the circles represents the error distance (INS error) that needs to be corrected when both circles are detected. The operator or the position error detection unit 32 determines whether this error distance is within an acceptable range (predetermined range), and if it is determined to be outside the acceptable range (NO), it transmits a position correction command (error information) including the distance and direction to be corrected as a position error correction value to the AUV2 via acoustic communication. The AUV2, having received the position correction command, corrects and updates its own position information based on the command and continues to transmit the position information acquired by the INS20. The operator or the position error detection unit 32 continues to perform circle detection processing using the Huff transform based on the position information received from the AUV2 and the position information received from the USBL positioning means 10, and repeats this procedure until it is determined that the error distance is within an acceptable range (YES).

[0027] Thus, by using the position error detection system or method of this embodiment, it is possible to accurately detect the error included in the position coordinates obtained by the INS20 of the AUV2 using the Hough transform. Furthermore, the position error correction value can be accurately derived, and the position estimated by INS20 can be corrected using the position error correction value. Furthermore, since AUV2 continues to orbit (orbit standby) while repeatedly correcting its position coordinates based on the received position error correction values, it can correct the position estimated by INS20 with greater accuracy. Furthermore, the position error detection unit 32 corrects the position error by repeating the correction until the distance between the center coordinates of the INS orbit and the USBL orbit falls within a predetermined range, thereby keeping the error included in the position estimated by the INS 20 within a predetermined value.

[0028] In this embodiment, the support vessel 1 (or ASV) is equipped with a control means 30, which detects the error in the position estimated by the INS 20 and sends a position correction command from the support vessel 1 to the AUV 2 so that the AUV 2 can correct its own position information. However, as described above, the control means 30 can also be equipped on the AUV 2. When the control means 30 is installed on the AUV2, the AUV2 still performs self-position estimation using the INS 20, but it differs in that the position coordinates obtained by acoustic positioning of the AUV2 from the support vessel 1 (or ASV) using the USBL positioning means 10 are transmitted to the AUV2 via the acoustic communication means 50, and the control unit 30 of the AUV2 performs the conversion step S4 and the position error detection step S5. In other words, in this case, the error detection of the position estimated by the INS 20 and the derivation of a position error correction value are performed within the AUV2, and its own position information is corrected accordingly.

[0029] Furthermore, positional error detection for AUV2 can be performed using a program. The AUV2 position error detection program causes the computer to execute the following steps: an orbiting standby step (corresponding to the orbiting standby step S1 above) which instructs the AUV2 to orbit in a specified orbit; an INS step (corresponding to the INS step S2 above) which instructs the AUV2, which is orbiting, to perform position estimation using the INS20; an acoustic positioning step (corresponding to the acoustic positioning step S3 above) which instructs the acoustic positioning means (USBL positioning means) 10 provided on the support vessel 1 to perform acoustic positioning of the AUV2; a conversion step (corresponding to the conversion step S4 above) which derives an INS circular orbit as a circular orbit obtained by performing a Hough transform on the position coordinates of the AUV2 acquired by the INS20, and derives an acoustic circular orbit as a circular orbit obtained by performing a Hough transform on the position coordinates of the AUV acquired by the acoustic positioning means (USBL positioning means) 10; and a position error detection step (corresponding to the position error detection step S5 above) which detects the error in the position estimation by the INS20 based on the difference between the INS circular orbit and the acoustic circular orbit. This allows the computer to accurately detect the errors in the position estimated by the INS20 of the AUV2 using the Hough transform. The computer that executes the position error detection program may also be the control means 30 described above, or it may be provided separately from the control means 30 and linked to the control means 30.

[0030] Next, an AUV position error detection system, an AUV position error detection program, and an AUV position error detection method according to other embodiments of the present invention will be described. Note that equipment and other components similar to those described in the above embodiments are denoted by the same reference numerals and their descriptions are omitted. Figure 6 is a conceptual diagram showing an AUV in a rotating, waiting position. This embodiment differs from the above-described embodiment in that the monitoring base 3 is equipped with acoustic positioning means (USBL positioning means) 10 and control means 30, but is otherwise basically the same as the above-described embodiment. Monitoring Station 3 is a base for monitoring seabed exploration conducted by support vessel 1 (or ASV) and AUV2. It consists of a first monitoring station (offshore platform) 3A located at sea and a second monitoring station 3B located on the quay. The AUV2 can be deployed into the water from support vessel 1, or from either the first monitoring station 3A or the second monitoring station 3B. Support vessel 1 is capable of wireless communication with the first monitoring station 3A and the second monitoring station 3B, and support vessel 1 and the second monitoring station 3B are capable of wireless communication with the positioning satellite 4. In addition, the first monitoring station 3A and the second monitoring station 3B are equipped with USBL positioning means 10 and control means 30, respectively. Note that the USBL positioning means 10 of the second monitoring station 3B may be installed on the quay where the second monitoring station 3B is located.

[0031] In this embodiment, in INS step S2, the AUV2 sequentially transmits its acquired position coordinates from the second acoustic communication means 50B to the operator or control means 30 of the first monitoring station 3A or the second monitoring station 3B. Also, in acoustic positioning step S3, the support ship 1 acoustically positions the AUV2 using the USBL positioning means 10 and sequentially transmits the obtained position coordinates to the operator or control means 30 of the first monitoring station 3A or the second monitoring station 3B. The operator or control means 30 of the first monitoring station 3A or the second monitoring station 3B, which has received position coordinates from the support vessel 1 and AUV2, detects the error in the position estimated by INS20 and sends a position correction command to AUV2. As a result, AUV2 corrects its own position information.

[0032] Furthermore, since USBL positioning means 10 are provided at both the first monitoring station 3A and the second monitoring station 3B, if acoustic positioning information of the AUV2 cannot be obtained from the support vessel 1, the AUV2 can be acoustically positioned using the USBL positioning means 10 provided at the first monitoring station 3A or the second monitoring station 3B to obtain its position coordinates, and the error in the position estimated by the INS 20 can be detected.

[0033] Next, an AUV position error detection system, an AUV position error detection program, and an AUV position error detection method according to yet another embodiment of the present invention will be described. Note that equipment and other components similar to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted. Figure 7 is a conceptual diagram showing an AUV in a rotating, waiting position. This embodiment differs from the first embodiment in that the acoustic positioning means consists of multiple underwater devices (transponders) 11 installed in the water surrounding the AUV2 (on the seabed of the AUV2's exploration area), but is otherwise basically the same as the first embodiment. AUV2 is equipped with a transducer 90 for acoustic communication with the transponder 11.

[0034] In this embodiment, in INS step S2, the AUV2 sequentially transmits its acquired position coordinates to the operator or control means 30 of the support vessel 1 via the second acoustic communication means 50B. Furthermore, in acoustic positioning step S3, acoustic positioning is performed using the LBL (Long Baseline) method with the transponder 11, and the obtained position coordinates of the AUV2 are sequentially transmitted to the operator or control means 30 of the support vessel 1 via the second acoustic communication means 50B of the AUV2. The control means 30 of the support vessel 1, which receives the position coordinates from the INS20's self-position estimation and the position coordinates from the transponder 11's acoustic positioning from the AUV2, detects the error in the position estimated by the INS20 and sends a position correction command to the AUV2. As a result, the AUV2 corrects its own position information. In this embodiment, when performing acoustic positioning using the LBL method, it is not necessary to perform acoustic positioning from the support vessel 1, and it is possible to perform acoustic positioning of the AUV2 more accurately (with greater precision) than when performing acoustic positioning from the support vessel 1.

[0035] Next, we will describe the sea trials conducted with respect to the first embodiment. The sea trials were conducted in Suruga Bay, Shizuoka Prefecture, at a depth of approximately 100m. A total of 12 dives were performed during the trial period, but here we will describe the results of the 10th dive (Dive #10), the 11th dive (Dive #11), and the 12th dive (Dive #12). The tests used two AUVs developed by the National Maritime Research Institute (NMRI) of the National Maritime, Port and Aviation Technology Institute. The specifications of the two AUVs used are shown in Table 1 below. AUV#2 was used in the 12th dive, and AUV#4 was used in the 10th and 11th dives. The two AUVs were controlled using the same software, and the radius of the orbiting waiting circle could be specified in a predefined scenario file. During navigation, the estimated position was calculated using an INS consisting of AHRS, DVL, and PDS. [Table 1]

[0036] The AUV (Autonomous Underground Vehicle) was equipped with an ATM (Acoustic telemetry modem) and a transponder for the Global Acoustic Positioning System. Since the AUV does not have a GNSS receiver, initializing the INS position requires overwriting via correction commands over the Wi-Fi and ATM. INS data such as latitude, longitude, depth, and attitude can be acquired as uplink data via ATM, and position correction commands can be transmitted to the AUV as downlink data while the support vessel is waiting to turn. Recorded INS data (INS-LOG) is stored in the AUV, and the INS data transmitted to the support vessel (INS-TX) is the most recent INS-LOG data from the AUV's navigation. On the support vessel side, the software developed for AUV control has been extended and implemented using a robot operating system and the Python programming language.

[0037] Table 2 below shows the conditions and parameters used in the orbit (circular orbit) detection algorithm. Since the duration and radius of the circular motion on the seabed must be specified in advance, the duration of the 10th and 11th dives was set to 180 seconds, the duration of the 12th dive to 600 seconds, and the radius of each dive to 50m. The size of the Huff parameter space was determined by narrowing the ranges of the N, E, and R ranges to reduce computational complexity. The search range was set to cover a circle with a radius of 50m, located 100m in the east-west and north-south directions (i.e., 200m in both the vertical and horizontal directions) from the reference coordinates, and the R range was set to a range of ±10m from a position 50m away from the reference coordinates (40-60m). The reference coordinates were manually selected after confirming that the AUV had started submerging and orbiting (steady rotation), so that the orbit based on INS and USBL data was included within the search range. In addition, the resolution values ​​ΔN, ΔE, and ΔR were set to 1m, which is within a range that does not impair the real-time nature of the calculations. The data acquisition intervals were 16 seconds for INS-TX position reporting via ATM and 4 seconds for USBL positioning using USBL positioning means. [Table 2]

[0038] Figure 8 shows the trajectory of the AUV position during dive, plotted using INS-LOG, INS-TX, USBL data manually placed by the operator during circular orbit detection, and data from the search area. Figure 8(a) is from the 10th dive, Figure 8(b) is from the 11th dive, and Figure 8(c) is from the 12th dive. Figure 9 shows the results of detecting circular orbits; Figure 9(a) is from the 10th dive, Figure 9(b) is from the 11th dive, and Figure 9(c) is from the 12th dive. The dotted circles in each graph in Figure 9 represent the results of circle detection using INS-TX and USBL data when the radius of the detected circles converges to a predetermined value of 50m. The distance between the centers of the circles represents the position error distance, which needs to be corrected using a position correction command. Table 3 below shows the results of position error detection and correction. [Table 3]

[0039] Figure 10 shows the time-series variation of the detected circle radius, with Figure 10(a) representing the 10th dive, Figure 10(b) the 11th dive, and Figure 10(c) the 12th dive. The origin of the time series (0 s) marks the start of voting into the Huff parameter space. Each time the support vessel receives position data from INS-TX and USBL, the estimated radius value is calculated sequentially. The numbers on each data point (e.g., 0, 1, 41, 48 in Figure 10(a)) are the time-series readings corresponding to the numbers on each data point in Figure 9. Figure 11 shows the distance difference based on timestamps between the INS-LOG position data recorded by the AUV and the USBL position data from the support vessel. Figure 11(a) is from the 10th dive, Figure 11(b) is from the 11th dive, and Figure 11(c) is from the 12th dive. Since the starting point of the time series is the beginning of each dive, the moments of "Start," "Updated," and "End" correspond to the positions shown in the plots in Figure 8, and "Updated" is the moment when the AUV receives correction instructions (position correction command) from the support vessel.

[0040] As shown in Figures 9(a), (b) and 10(a), (b), the detection of a circle using INS-TX data reached a predetermined radius (50m) after receiving four data points during the 10th and 11th dives. As shown in Figures 11(a), (b), the error distances between the positions based on INS-LOG and USBL data immediately after the AUV received a position correction command were 1.6m and 1.3m, respectively. Considering that these position errors were corrected to be smaller than the length of AUV#4 used (3.9m), the accuracy of position error detection according to this embodiment is sufficiently practical. This result suggests that a circular orbit can be detected even with a small amount of data. Therefore, since the position error detection of this embodiment can estimate errors more quickly than methods that average many positions, it may be effective not only for navigating AUVs but also for hovering AUVs capable of waiting in place, as long as they are able to wait on a circular orbit. Furthermore, the 12th dive took longer to detect the error distance than the 10th and 11th dives, and both the INS-TX and USBL measurements took 218 seconds to reach the predetermined radius (50m). This was because there was a period of 42 to 202 seconds during which INS-TX data was unavailable for an extended period.

[0041] The USBL positioning data obtained from sea trials was satisfactory and contained few outliers. Therefore, a simulation was performed using the USBL data from the 11th dive to verify the performance when outliers are present. Although this assumption is excessive, new data was created for each data point with an error of 100m standard deviation. Figure 12 shows the detection results from the simulation. Even if outliers are included, the parameters of the desired circle are determined by majority vote, so positions that do not constitute the circle do not have an effect (see Figure 9(b)). Figure 13 shows the Hough parameter space for the original USBL data and the data with added errors in the simulation. Figure 13(a) is for the original data without added outliers (see Figure 9(b)), and Figure 13(b) is for the data with added outliers (see Figure 12). In these Hough parameter spaces, the desired radius value was 50m (i.e., Hough parameter space (n,e,50)). The edges of the circles voted for by the outliers do not intersect at this point and therefore do not affect the maximum vote value. Therefore, the selected combination of parameters (n c ^,e c ^,50) is counted as 7 in both cases and is invariant to outliers as long as the non-outlier component dominates the overall position data, demonstrating that the position error detection according to this embodiment is robust to outliers. In the examples given for carrying out the invention, a circular orbit parallel to the water surface was used, but a circular orbit perpendicular to the water surface or a circular orbit oblique to the water surface may also be used. These can be appropriately selected when estimating not only horizontal errors but also three-dimensional errors in the INS (Inertial Navigation System), including vertical and diagonal directions. Furthermore, the orbit does not necessarily have to be a circular orbit; elliptical or round-square orbits, etc., can be selected as appropriate. In such cases, the center coordinates can be those of the foci of the elliptical orbit or the geometric center coordinates of the round-square orbit. In addition, any orbit other than a circular orbit, such as a hyperbolic or linear orbit, is acceptable as long as the difference between the INS orbit and the acoustic orbit can be determined. The term "circular orbit" in the claims should be interpreted to include these as well. [Industrial applicability]

[0042] This invention can be used to correct the position of an AUV before the start of a survey voyage, and if necessary, a circular orbit pattern can be inserted for the AUV during the mission to repeat the correction operation. Furthermore, the equipment or functions used for position error detection are expected to be present in general AUV operating systems, and if position error detection is performed on the support vessel, ASV, or monitoring base side, it can be implemented without making major changes to the AUV itself. [Explanation of symbols]

[0043] 1. Support ship 2 AUV 3. Monitoring bases 10 Acoustic positioning means (USBL positioning means) 11. Acoustic positioning means (transponder) 20 INS 30 Control means 31 Lap / Measurement Indicator 32 Position error detection unit 60 AHRS 70 DVL 80 PDS S1 Lap Waiting Step S2 INS Step S3 Acoustic positioning step S4 Conversion Step S5 Position error detection step

Claims

1. A system for detecting positional errors of an AUV (Autonomous Underwater Vehicle) deployed from a support vessel, ASV (Autonomous Offshore Relay Vehicle), or monitoring base, which detects positional errors when the AUV is being navigated, Acoustic positioning means provided in the water surrounding the support vessel, the ASV, the monitoring base, or the AUV for acoustic positioning of the AUV, Control means provided on the support vessel, the ASV, the monitoring base, or the AUV for controlling the AUV, The aforementioned AUV is equipped with an INS (Inertial Navigation System), The control means includes a circling and measurement instruction unit that gives instructions to the AUV to orbit on a designated circular orbit, instructions to the INS to estimate its position while the circling wait is being performed, and instructions to the support vessel, the ASV, the monitoring base, or the acoustic positioning means installed in the water around the AUV to acoustic position the AUV; and a position error detection unit that derives an INS circular orbit as a circular orbit obtained by performing a Hough transform on the position coordinates of the AUV acquired by the INS, derives an acoustic circular orbit as a circular orbit obtained by performing a Hough transform on the position coordinates of the AUV acquired by the acoustic positioning means, and detects the position error estimated by the INS based on the difference between the INS circular orbit and the acoustic circular orbit.

2. The AUV position error detection system according to claim 1, characterized in that the position error detection unit determines the center coordinates for each of the INS circular orbit and the acoustic circular orbit, determines the distance between the center of the INS circular orbit and the center of the acoustic circular orbit based on the respective center coordinates as the difference between the INS circular orbit and the acoustic circular orbit, determines that the error in position estimation by the INS is outside the acceptable range if the distance is not within a predetermined range, and determines a position error correction value including the distance and direction to be corrected for position estimation by the INS.

3. The AUV position error detection system according to claim 2, characterized in that the control means is provided in the support vessel, the ASV, or the monitoring base, and the orbiting / measurement instruction unit sequentially transmits the position error correction value obtained by the position error detection unit from the support vessel, the ASV, or the monitoring base to the AUV by acoustic communication means, instructs the AUV to orbit and wait for a specified period, and instructs the INS to estimate the position reflecting the position error correction value.

4. The AUV position error detection control system according to claim 3, characterized in that the control means repeatedly transmits the position error correction value to the AUV from the orbiting / measurement instruction unit and instructs the orbiting wait for a specified period and position estimation by the INS that reflects the position error correction value, until the distance between the center of the INS circular orbit and the center of the acoustic circular orbit falls within the predetermined range set in the position error detection unit.

5. The AUV position error detection system according to claim 1 or 2, characterized in that the control means uses a position estimation method that integrates output information from the INS, as well as from the AHRS (Aircraft Heading and Attitude Reference System), DVL (Doppler Velocity Log), and PDS (Pressure Depth Sensor) mounted on the AUV, to estimate the position of the AUV.

6. A position error detection program for an AUV (Autonomous Underwater Vehicle) equipped with an INS (Inertial Navigation System) deployed from a support vessel, ASV (Autonomous Offshore Repeater), or monitoring base, which detects position errors when the AUV is being driven, On the computer, A waiting step in which the AUV is instructed to wait in orbit on a designated orbit, An INS step in which the AUV performing the aforementioned waiting orbit is instructed to perform position estimation by the INS, Acoustic positioning step of instructing acoustic positioning means installed in the water surrounding the support vessel, the ASV, the monitoring base, or the AUV to perform acoustic positioning of the AUV, A transformation step of deriving an INS circular orbit as a circular orbit obtained by performing a Hough transform on the position coordinates of the AUV acquired by the INS, and deriving an acoustic circular orbit as a circular orbit obtained by performing a Hough transform on the position coordinates of the AUV acquired by the acoustic positioning means, An AUV position error detection program characterized by executing a position error detection step that detects the error in position estimation by the INS based on the difference between the INS circular orbit and the acoustic circular orbit.

7. A method for detecting the position error of an AUV (Autonomous Underwater Vehicle) equipped with an INS (Inertial Navigation System) deployed from a support vessel, ASV (Autonomous Offshore Relay Vehicle), or monitoring base, while navigating the AUV, The AUV is kept waiting while orbiting in a designated orbit; An INS step in which the AUV is waiting in a circuit and performs position estimation using INS, Acoustic positioning step of performing acoustic positioning of the AUV from acoustic positioning means installed in the water surrounding the support vessel, the ASV, the monitoring base, or the AUV, A transformation step of deriving an INS circular orbit as a circular orbit obtained by performing a Hough transform on the position coordinates of the AUV acquired by the INS, and deriving an acoustic circular orbit as a circular orbit obtained by performing a Hough transform on the position coordinates of the AUV acquired by the acoustic positioning means, A method for detecting the position error of an AUV, characterized by having a position error detection step that detects the error in position estimation by the INS based on the difference between the INS circular orbit and the acoustic circular orbit.

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