Ship collision prevention system, ship collision prevention method, and ship collision prevention program

Abstract

A ship collision prevention system (100) comprises: a millimeter wave radar (1) that detects an obstacle candidate on the sea as a millimeter wave symbol point in each processing cycle; a GNSS receiver (2) that obtains the position and orientation of a ship; and a processing device (3) that extracts a region of a marine obstacle that has a possibility of colliding with the ship. The processing device (3) includes: a millimeter wave point group generation unit (30) that calculates a plurality of millimeter wave symbol points on map coordinates from a plurality of millimeter wave symbol points, detected by the millimeter wave radar (1) in each processing cycle, on the basis of received values of the GNSS receiver (2); a millimeter wave point group integration unit (31) that performs integration processing on the plurality of millimeter wave symbol points on the map coordinates calculated by the millimeter wave point group generation unit (30); and an obstacle extraction unit (32) that performs threshold processing on the integrated values at each coordinate point integrated by the millimeter wave point group integration unit (31) and extracts the region of the marine obstacle from the obstacle candidate.

Description

Ship collision avoidance system, ship collision avoidance method, and ship collision avoidance program

[0001] This disclosure relates to a ship collision avoidance system, a ship collision avoidance method, and a ship collision avoidance program capable of detecting maritime obstacles that could potentially cause collisions.

[0002] Traditionally, ship operators had to visually monitor for potential obstacles at sea. Collisions with obstacles can cause equipment damage and hull damage. The risk of collision with obstacles is particularly high at night, during rain, or in fog. Therefore, ships are equipped with marine radar, such as X-band or S-band radar, to monitor other ships or buoys at sea. However, because these marine radars are designed for long-distance viewing, they generally cannot measure distances of less than 100 meters. Furthermore, the maps on marine radar do not show the locations of obstacles such as rafts, oyster farms, fishing nets, buoys, and markers installed by fishing cooperatives.

[0003] Incidentally, for example, Patent Document 1 discloses a radar image target detection device that detects targets based on radar signals from a radar transceiver and camera images from a camera imaging device. The radar transceiver can detect the distance to a target with high accuracy. The camera imaging device can detect the direction with high accuracy. This radar image target detection device accurately detects targets by utilizing the respective features of the radar transceiver and camera imaging device.

[0004] Japanese Patent Publication No. 2022-39102

[0005] However, in the technology disclosed in Patent Document 1, there is a risk that the camera imaging device may not be able to adequately photograph obstacles at sea due to factors such as nighttime, rainfall, or fog. Furthermore, ships may sway significantly up and down and side to side due to the effects of waves, which may prevent the camera imaging device from adequately photographing obstacles at sea.

[0006] This disclosure is made in view of the above and aims to provide a ship collision avoidance system that can detect areas of maritime obstacles that may collide with a ship.

[0007] To solve the above-mentioned problems and achieve the objectives, the ship collision avoidance system according to this disclosure comprises a millimeter-wave radar that detects candidate obstacles at sea as millimeter-wave symbol points at each processing cycle, a GNSS (Global Navigation Satellite System) receiver that determines the position and attitude of the ship on which the millimeter-wave radar is installed, and a processing unit that extracts the region of a sea obstacle that has the potential to collide with a ship from among the candidate obstacles detected by the millimeter-wave radar. The processing unit comprises a millimeter-wave point cloud generation unit that calculates multiple millimeter-wave symbol points on a map coordinate system from multiple millimeter-wave symbol points detected by the millimeter-wave radar at each processing cycle based on the received values ​​of the GNSS receiver, a millimeter-wave point cloud integration unit that integrates the multiple millimeter-wave symbol points on the map coordinate system calculated by the millimeter-wave point cloud generation unit, and an obstacle extraction unit that thresholds the integrated values ​​at each coordinate point integrated by the millimeter-wave point cloud integration unit and extracts the region of a sea obstacle from among the candidate obstacles.

[0008] The ship collision avoidance system described herein has the effect of being able to detect areas of maritime obstacles that could potentially collide with a ship.

[0009] Block diagram showing the ship collision avoidance system according to Embodiment 1 Explanatory diagram showing an example of radar reference coordinates of the millimeter-wave radar provided in the ship collision avoidance system according to Embodiment 1 Explanatory diagram showing multiple millimeter-wave symbol points on a map coordinate calculated by the millimeter-wave point cloud generation unit provided in the ship collision avoidance system according to Embodiment 1 Explanatory diagram showing multiple millimeter-wave symbol points on a map coordinate calculated by the millimeter-wave point cloud generation unit provided in the ship collision avoidance system according to Embodiment 1 in chronological order Explanatory diagram showing part of the processing of the millimeter-wave point cloud integration unit provided in the ship collision avoidance system according to Embodiment 1, which determines the detection coverage area of ​​the millimeter-wave radar Explanatory diagram showing part of the processing of the millimeter-wave point cloud integration unit provided in the ship collision avoidance system according to Embodiment 1, which shows the voting results of millimeter-wave symbol points enclosed by the detection coverage area Explanatory diagram showing part of the processing of the millimeter-wave point cloud integration unit provided in the ship collision avoidance system according to Embodiment 1, which determines the detection coverage area Diagram illustrating a modified version of the voting results for wave symbol points Diagram illustrating the area of ​​marine obstacles extracted by the obstacle extraction unit of the ship collision avoidance system according to Embodiment 1 Diagram illustrating a modified version of the area of ​​marine obstacles extracted by the obstacle extraction unit of the ship collision avoidance system according to Embodiment 1 Diagram illustrating a flowchart illustrating the operation procedure of the ship collision avoidance system according to Embodiment 1 Block diagram illustrating the ship collision avoidance system according to Embodiment 2 Diagram illustrating the attitude angle error Δθ and translation error ΔL calculated by the docking control unit of the ship collision avoidance system according to Embodiment 2 Diagram illustrating the processing procedure of the docking control unit of the ship collision avoidance system according to Embodiment 2 Diagram illustrating how to calculate the attitude angle error Δθ and translation error ΔL in the docking control unit of the ship collision avoidance system according to Embodiment 2 Diagram illustrating an example of the configuration of a computer system that realizes the ship collision avoidance system according to this embodiment

[0010] Hereinafter, a ship collision avoidance system, a ship collision avoidance method, and a ship collision avoidance program according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] Embodiment 1. Figure 1 is a block diagram showing a ship collision avoidance system 100 according to Embodiment 1. The ship collision avoidance system 100 according to Embodiment 1 automatically detects marine obstacles that may collide with a ship. In this embodiment, marine obstacles refer to rafts, oyster farms, fishing nets, buoys, and markers installed by fishing cooperatives that have few protruding parts from the water surface, have low reflectivity in the millimeter wave band, and have a small difference in reflectivity from the sea surface. As shown in Figure 1, the ship collision avoidance system 100 includes a millimeter wave radar 1, a GNSS receiver 2, and a processing unit 3.

[0012] Figure 2 is an explanatory diagram showing an example of the radar reference coordinates of the millimeter-wave radar 1 provided in the ship collision avoidance system 100 according to Embodiment 1. The white circles in Figure 2 are millimeter-wave symbol points detected by the millimeter-wave radar 1. As shown in Figure 2, the millimeter-wave radar 1 uses millimeter-wave radio waves to detect potential obstacles on the sea surface as millimeter-wave symbol points in each processing cycle and displays them in the radar reference coordinates. The millimeter-wave radar 1 detects potential obstacles on the sea surface in each processing cycle and saves the detection result as a frame at the time of detection. That is, in one frame, multiple millimeter-wave symbol points at the time of detection are displayed in the radar reference coordinates. The threshold for the millimeter-wave radar 1 to extract potential obstacles on the sea surface is set lower than the reflection intensity of the sea surface. Therefore, potential obstacles on the sea surface include not only obstacles on the sea surface but also the sea surface itself. That is, the millimeter-wave radar 1 can detect obstacles on the sea surface and the sea surface simultaneously. By detecting potential obstacles with the millimeter-wave radar 1, the distance and angle of the potential obstacles relative to the antenna of the millimeter-wave radar 1 can be measured. The radar reference coordinates of the millimeter-wave radar 1 shown in Figure 2 are two-dimensional coordinates with the center of the antenna of the millimeter-wave radar 1 as the origin 0 and the antenna's viewing axis as the Y axis. The millimeter-wave radar 1 is, for example, a 77 GHz band or 79 GHz band millimeter-wave radar, which detects millimeter-wave symbol points at each processing cycle and displays multiple millimeter-wave symbol points for each frame. The millimeter-wave radar 1 detects potential obstacles, for example, every 50 ms or 100 ms.

[0013] The millimeter-wave radar 1 is an all-weather type that does not easily experience a decrease in detection performance even at night, during rainfall, or when fog occurs. The millimeter-wave radar 1 is installed on a ship. The number of millimeter-wave radars 1 installed on a ship may be one or two or more. The millimeter-wave radar 1 is installed on the ship at a different location from the GNSS receiver 2. The mounting position and orientation of the millimeter-wave radar 1 relative to the GNSS receiver 2 are stored in advance in the processing unit 3.

[0014] The GNSS receiver 2 is installed on the ship. The mounting position and orientation of the GNSS receiver 2 relative to the ship's center position are pre-stored in the processing unit 3. The GNSS receiver 2 receives radio waves transmitted from GNSS satellites and determines the ship's center position, attitude, and speed. The GNSS receiver 2 is, for example, a single positioning receiver for code positioning, a DGPS (Differential Global Positioning System) receiver, or a carrier phase multi-GNSS receiver. The GNSS receiver 2 may also be configured to include an inertial measurement unit (IMU). In this case, the ship's attitude can be determined by composite positioning using the GNSS receiver 2. Furthermore, two or more GNSS receivers 2 may be installed on the ship. In this case, the ship's attitude can be determined by the change in the relative positions of the multiple GNSS receivers 2.

[0015] The processing unit 3 extracts areas of marine obstacles that could potentially collide with a ship from among the candidate marine obstacles detected by the millimeter-wave radar 1. As shown in Figure 1, the processing unit 3 comprises a millimeter-wave point cloud generation unit 30, a millimeter-wave point cloud integration unit 31, and an obstacle extraction unit 32.

[0016] The millimeter-wave point group generation unit 30 calculates a plurality of millimeter-wave symbol points on the map coordinates from the plurality of millimeter-wave symbol points detected by the millimeter-wave radar 1 for each processing cycle based on the reception values of the GNSS receiver 2. The millimeter-wave point group refers to a collection of a plurality of millimeter-wave symbol points. FIG. 3 is an explanatory diagram showing a plurality of millimeter-wave symbol points on the map coordinates calculated by the millimeter-wave point group generation unit 30 provided in the ship collision prevention system 100 according to the first embodiment. In FIG. 3, in addition to the millimeter-wave point group composed of a plurality of millimeter-wave symbol points, the center position of the ship is added as coordinates. The white circles shown in FIG. 3 are the millimeter-wave symbol points detected by the millimeter-wave radar 1. That is, the white circles shown in FIG. 3 indicate the positions of potential obstacles at sea. The black circles in the figure indicate the center position of the ship. The vertical axis in FIG. 3 indicates the north-south coordinate values. The horizontal axis in FIG. 3 indicates the east-west coordinate values.

[0017] First, the millimeter-wave point group generation unit 30 converts the coordinates of the millimeter-wave symbol points detected by the millimeter-wave radar 1 for each processing cycle from the reference coordinates of the millimeter-wave radar 1 to the reference coordinates by the GNSS receiver 2. The radar reference coordinates of the millimeter-wave radar 1 are two-dimensional coordinates with the center of the antenna of the millimeter-wave radar 1 as the origin 0 and the antenna line of sight as the Y axis. That is, in order to display the position of the millimeter-wave symbol point displayed in the radar reference coordinates on the map coordinates, it is necessary to convert it to the reference coordinates with the GNSS receiver 2 as the origin. The conversion from the radar reference coordinates to the reference coordinates of the GNSS receiver 2 is performed based on the attachment position and attachment orientation of the millimeter-wave radar 1 with respect to the GNSS receiver 2. Thereby, the distance and angle of the millimeter-wave symbol point with the GNSS receiver 2 as the origin are obtained. <000,092>Next, the millimeter-wave point cloud generation unit 30 synchronizes the time detected by the millimeter-wave radar 1 with the time received by the GNSS receiver 2 using a time offset value. Since the millimeter-wave radar 1 and the GNSS receiver 2 operate independently and asynchronously, it is necessary to synchronize the detection time detected by the millimeter-wave radar 1 with the reception time received by the GNSS receiver 2. Then, based on the values ​​received by the GNSS receiver 2, the millimeter-wave point cloud generation unit 30 determines the ship's center position, attitude, and speed, as well as the coordinate values ​​of the millimeter-wave symbol points relative to the ship's center position. For each processing cycle, it calculates multiple millimeter-wave symbol points on the map coordinates from multiple millimeter-wave symbol points detected by the millimeter-wave radar 1. Note that the ship's center position is different from the position where the GNSS receiver 2 is installed. Therefore, the ship's center position is determined based on the mounting position and orientation of the GNSS receiver 2 relative to the ship's center position. This makes it possible to calculate a millimeter-wave point cloud consisting of multiple millimeter-wave symbol points relative to the ship's center position on the map coordinates. Map coordinates include, for example, the plane rectangular coordinate system used in surveying, or the coordinate system of the Mercator projection.

[0019] Figure 4 is an explanatory diagram showing multiple millimeter-wave symbol points on a map coordinate system calculated by the millimeter-wave point cloud generation unit 30 of the ship collision avoidance system 100 according to Embodiment 1, in chronological order. In Figure 4, as an example, the processing cycle detected by the millimeter-wave radar 1 is set to approximately 1 second, and multiple millimeter-wave symbol points on the map coordinate system are calculated for each frame. In Figure 4, the center position of the ship, indicated by the black circle in the lower left, can be seen to be moving slightly northeast in the order shown from (a) to (e). On the other hand, among the white circles that represent millimeter-wave symbol points that are candidates for obstacles at sea, the white circles that become obstacles at sea have a fixed position at sea and therefore do not change position, while only the white circles that represent the sea surface change position. The position of the white circles changes because the points on the sea surface that are reflected by the millimeter-wave radar 1 are constantly changing.

[0020] FIG. 5 is an explanatory diagram for obtaining the detection coverage area of the millimeter-wave point cloud integration unit 31 included in the ship collision prevention system 100 according to Embodiment 1. The millimeter-wave point cloud integration unit 31 integrates the millimeter-wave point cloud on the map coordinates calculated by the millimeter-wave point cloud generation unit 30. The integration process is, for example, a process of voting millimeter-wave symbol points to each coordinate point on the map plane. Specifically, first, as shown in FIG. 5, the millimeter-wave point cloud integration unit 31 obtains the moving direction of the ship for each processing cycle, that is, for each frame, based on the reception value of the GNSS receiver 2, and sets the detection coverage area A of the millimeter-wave radar 1. The detection coverage area A is, as an example, rectangular, and is set as an area where it is necessary to detect marine obstacles according to the performance of the millimeter-wave radar 1. The detection coverage area A is, as an example, an area that is about 100 m to 200 m away from the center position of the ship shown by a black circle in the moving direction of the ship, and has a width of about 50 m. Note that the detection coverage area A is not limited to the illustrated rectangle, and may be other shapes such as a circular shape or an elliptical shape. In short, the detection coverage area A may have any shape as long as it can be set as an area where it is necessary to detect marine obstacles.

[0021] FIG. 6 is a part of the processing of the millimeter-wave point cloud integration unit 31 included in the ship collision prevention system 100 according to Embodiment 1, and shows the detection coverage area A １ , A ２ surrounded by a three-dimensional graph showing the voting results of millimeter-wave symbol points. The vertical axis indicates the count number of millimeter-wave symbol points. Two orthogonal axes in the plane perpendicular to the vertical axis indicate the north-south coordinate value and the east-west coordinate value. A １ , A ２ shown in FIG. 6 indicate the detection coverage areas of the millimeter-wave radar 1 detected at different times. As shown in FIG. 6, the millimeter-wave point cloud integration unit 31 votes the millimeter-wave symbol points of each coordinate point surrounded by the detection coverage areas A １ , A ２ on the map coordinates. Voting is the integration of the number of millimeter-wave symbol points surrounded by the detection coverage areas A １ , A ２ and is represented by a histogram. In FIG. 6, for the sake of illustration, two detection coverage areas A １ , A２ While this is shown, the detection coverage area is not limited to just two. The height of the histogram is the sum of millimeter-wave symbol points, which corresponds to the probability of the presence of a sea obstacle at that coordinate position. Since sea obstacles are fixed on the sea, their position does not change whether the ship is moving or stationary, resulting in a high sum of millimeter-wave symbol points. On the other hand, the sea surface has an uneven wave front and occurs randomly within the detection coverage area A of the millimeter-wave radar 1, resulting in a low sum of millimeter-wave symbol points. In other words, the high part of the histogram corresponds to the area of ​​sea obstacles, and the low part of the histogram corresponds to the sea surface.

[0022] Figure 7 is an explanatory diagram showing a modified example of the voting results for millimeter-wave symbol points enclosed by the detection area, which is part of the processing of the millimeter-wave point group integration unit of the ship collision avoidance system according to Embodiment 1. Figure 7(A) shows the case where the number of millimeter-wave symbol points is accumulated, and Figure 7(B) shows the case where the reflection intensity of the millimeter-wave symbol point detected by the millimeter-wave radar 1 for each millimeter-wave symbol point is added to the integration process. As shown in Figure 7(B), when the millimeter-wave point group integration unit 31 integrates the millimeter-wave symbol points enclosed by the detection area A, it may also add the reflection intensity of the millimeter-wave symbol point detected by the millimeter-wave radar 1 for each millimeter-wave symbol point to the integration process. Specifically, the millimeter-wave point group integration unit 31 accumulates the number of millimeter-wave symbol points and performs weighting by multiplying each millimeter-wave symbol point by a coefficient corresponding to the reflection intensity of the millimeter-wave symbol point detected by the millimeter-wave radar 1 and accumulating the accumulated weights. For example, in the example shown in Figure 7, the millimeter-wave symbol points are a ｘｘ This is shown, and its millimeter-wave symbol point a ｘｘ The reflectance intensity at is converted into a coefficient b ｘｘ This is shown by b. ｘｘ The value of is standardized at 1, with values ​​less than 1 when the reflectance is low and values ​​greater than 1 when the reflectance is high. For example, as shown in Figure 7(B) b １１ The value of is set to the standard 1. Figure 7(B) shows b １２ The value of is set to a value less than 1, indicating a low reflectance. Figure 7(B) shows b １３ from b １５The value of is defined as a value greater than 1 due to a high reflectance. Maritime obstacles such as rafts, oyster farms, fishing nets, buoys, and markers have a higher reflectance than the sea surface. Therefore, by accumulating the number of millimeter-wave symbol points and multiplying them by a coefficient corresponding to the reflectance of the millimeter-wave symbol points, the total value of millimeter-wave symbol points indicating maritime obstacles increases, thereby improving the detection accuracy of maritime obstacles.

[0023] Figure 8 is an explanatory diagram showing the region R of a marine obstacle X extracted by the obstacle extraction unit 32 of the ship collision avoidance system 100 according to Embodiment 1. As shown in Figure 8, the obstacle extraction unit 32 thresholds the cumulative value at each coordinate point integrated by the millimeter-wave point group integration unit 31, i.e., the count of millimeter-wave symbol points, to extract the region R of the marine obstacle X from among the obstacle candidates. Thresholding is a process that removes millimeter-wave symbol points with low counts, judging them to be the sea surface, and extracts millimeter-wave symbol points with high counts. The threshold is a value that distinguishes marine obstacle X from the sea surface in terms of the count of millimeter-wave symbol points. The threshold is set according to, for example, the S / N (Signal / Noise) ratio performance of the millimeter-wave radar 1 used. Then, the obstacle extraction unit 32 extracts the centroid P of all millimeter-wave symbol points that have been judged to be marine obstacle X by thresholding. １ We will find the centroid P of all points. １ The method for determining the center of gravity P is carried out using known techniques. Next, the obstacle extraction unit 32 determines the center of gravity P １ The distance from the position of point X to the positions of all millimeter-wave symbol points identified as marine obstacle X is calculated. Then, the centroid P is determined. １ A circle with radius r is extracted from the position of the object to the furthest millimeter-wave symbol point, and this circle is approximated as the region R of the maritime obstacle X.

[0024] Figure 9 is an explanatory diagram showing a modified example of the region R of a marine obstacle X extracted by the obstacle extraction unit 32 of the ship collision avoidance system 100 according to Embodiment 1. As shown in Figure 9, the region R of the marine obstacle X is not limited to a circle and may be approximated as a polygonal region. In this case, for example, the edge portions of the thresholded millimeter-wave symbol points are determined, and the polygon formed by connecting these edges is extracted as the region R of the marine obstacle X. By approximating the region R of the marine obstacle X as a polygon, the shape of complex marine obstacles can be precisely modeled, and the region R of the marine obstacle X can be extracted more accurately.

[0025] Figure 10 is a flowchart showing the operation procedure of the ship collision avoidance system 100 according to Embodiment 1. First, the millimeter-wave radar 1 uses millimeter-wave radio waves to detect potential obstacles on the sea as millimeter-wave symbol points in each processing cycle and displays them as symbols on the radar reference coordinates (Step S11). Next, the millimeter-wave point cloud generation unit 30 converts the coordinates of the millimeter-wave symbol points detected by the millimeter-wave radar 1 from the reference coordinates of the millimeter-wave radar 1 to the reference coordinates of the GNSS receiver 2 in each processing cycle (Step S12). Next, the millimeter-wave point cloud generation unit 30 synchronizes the time detected by the millimeter-wave radar 1 with the time received by the GNSS receiver 2 (Step S13). Next, the millimeter-wave point cloud generation unit 30 calculates multiple millimeter-wave symbol points on the map coordinates from multiple millimeter-wave symbol points detected by the millimeter-wave radar 1 in each processing cycle based on the received value of the GNSS receiver 2 (Step S14). Next, the millimeter-wave point cloud integration unit 31 determines the ship's direction of movement for each processing cycle based on the received values ​​from the GNSS receiver 2 and sets the detection coverage area A of the millimeter-wave radar 1 (step S15). Next, the millimeter-wave point cloud integration unit 31 integrates the millimeter-wave symbol points enclosed by the detection coverage area A on the map coordinates in each frame (step S16). Next, the obstacle extraction unit 32 thresholds the accumulated values ​​at each coordinate point integrated by the millimeter-wave point cloud integration unit 31, i.e., the count of millimeter-wave symbol points, and extracts the region R of the offshore obstacle X from the obstacle candidates (step S17). As a result, the ship collision avoidance system 100 can determine not only the presence or absence of the offshore obstacle X, but also the position and size of the offshore obstacle X in the map coordinate system, and can calculate the relative distance and angle between its own ship and the offshore obstacle X.

[0026] As described above, the ship collision avoidance system 100 according to Embodiment 1 includes a millimeter-wave radar 1 that detects candidate obstacles at sea as millimeter-wave symbol points at each processing cycle, a GNSS receiver 2 that determines the position and attitude of the ship on which the millimeter-wave radar 1 is installed, and a processing device 3 that extracts the region R of a sea obstacle X that has the potential to collide with a ship from among the candidate obstacles detected by the millimeter-wave radar 1. The processing device 3 includes a millimeter-wave point cloud generation unit 30 that calculates a plurality of millimeter-wave symbol points on a map coordinate system from a plurality of millimeter-wave symbol points detected by the millimeter-wave radar 1 at each processing cycle based on the received values ​​of the GNSS receiver 2, a millimeter-wave point cloud integration unit 31 that integrates the plurality of millimeter-wave symbol points on the map coordinate system calculated by the millimeter-wave point cloud generation unit 30, and an obstacle extraction unit 32 that thresholds the integrated values ​​at each coordinate point integrated by the millimeter-wave point cloud integration unit 31 and extracts the region R of a sea obstacle X from among the candidate obstacles. This allows for the accurate and automatic detection of areas R of low-reflectivity marine obstacles X that could potentially collide with a vessel, even at night, during rainfall, or in foggy conditions. As a result, vessels can steer to avoid marine obstacles X or smoothly decelerate, enabling safe and secure operation.

[0027] Embodiment 2. Next, the ship collision avoidance system according to Embodiment 2 will be described with reference to Figures 11 to 14. The ship collision avoidance system 101 according to Embodiment 2 has a configuration that allows a ship to automatically dock at a pier, in addition to the configuration described in Embodiment 1. Figure 11 is a block diagram of the ship collision avoidance system 101 according to Embodiment 2. As shown in Figure 11, the ship collision avoidance system 101 according to Embodiment 2 includes a millimeter-wave radar 1, a GNSS receiver 2, a processing unit 3, a docking control unit 4, and a ship control unit 5. The configurations of the millimeter-wave radar 1, GNSS receiver 2, and processing unit 3 are the same as in Embodiment 1, so their description will be omitted.

[0028] Figure 12 is an explanatory diagram showing the attitude angle error Δθ and translation error ΔL calculated by the docking control unit 4 of the ship collision avoidance system 101 according to Embodiment 2. Point P shown in Figure 12 ２The dotted line L in Figure 12 indicates the position of the ship. １ The solid line L in Figure 12 shows the approximate straight line of the sea obstacle X. ２ The dashed line L in Figure 12 shows the trajectory of the ship's navigation. ３ This indicates the planned course of the ship.

[0029] As shown in Figure 12, the docking control unit 4 determines the position of the ship P relative to the sea obstacle X determined by the obstacle extraction unit 32. ２ Approximate straight line L of a marine obstacle X that is close to it １ Determine the position P of the ship. ２ Approximate line L from the posture １ The attitude angle error Δθ and translation error ΔL are calculated. The docking control unit 4 transmits the calculated attitude angle error Δθ and translation error ΔL to the ship control unit 5.

[0030] Next, the processing procedure of the docking control unit 4 will be described with reference to Figures 13 and 14. Figure 13 is a flowchart showing the processing procedure of the docking control unit 4 included in the ship collision avoidance system 101 according to Embodiment 2. Figure 14 is an explanatory diagram for calculating the attitude angle error Δθ and the translation error ΔL in the docking control unit 4 included in the ship collision avoidance system 101 according to Embodiment 2. The dashed line L in Figure 14 １ The solid line L in Figure 14 shows an approximate straight line of the sea obstacle X. ２ The dashed line L in Figure 14 shows the trajectory of the ship's navigation. ３ The arrow indicates the planned course of the ship. The vertical axis in Figure 14 represents the north-south coordinate axis. The horizontal axis in Figure 14 represents the east-west coordinate axis.

[0031] First, as shown in Figure 14, the docking control unit 4 selects three arbitrary millimeter-wave symbol points from among the multiple millimeter-wave symbol points that constitute the offshore obstacle X calculated by the obstacle extraction unit 32 (step S21). In Figure 14, the three millimeter-wave symbol points are shown as S1, S2, and S3. Note that the number of millimeter-wave symbol points to be selected is not limited to three; two or more are sufficient.

[0032] Next, the docking control unit 4 uses a linear function as a mathematical model and, for three arbitrary millimeter-wave symbol points S1, S2, and S3, uses the least squares method to determine the slope and intercept of the line, thereby approximating the maritime obstacle X L. １ The docking control unit 4 then calculates the approximate straight line L of the sea obstacle X that it has found. １ and the ship's position P at that time ２ Find the distance to and the approximate line L. １ The two are paired and saved with an ID (step S23). Approximate line L １ and the position P of the ship ２ The distance to is the position P of the ship. ２ Approximate straight line L from the sea obstacle X １ This is the length of the perpendicular line drawn towards it.

[0033] Next, the docking control unit 4 determines whether all millimeter-wave symbol points calculated as sea obstacles X have been selected as arbitrary millimeter-wave symbol points (step S24). If the docking control unit 4 determines that all millimeter-wave symbol points calculated as sea obstacles X have been selected as arbitrary millimeter-wave symbol points (step S24: Yes), it selects an approximate straight line L from all the saved IDs. １ and the position P of the ship ２ The unit selects the value with the shortest distance and determines the translation error ΔL (step S25). On the other hand, if the docking control unit 4 determines that none of the millimeter-wave symbol points calculated as sea obstacles X have been selected as arbitrary millimeter-wave symbol points (step S24: No), it returns to step S21 and again selects three different arbitrary millimeter-wave symbol points from among the multiple millimeter-wave symbol points that constitute sea obstacles X calculated by the obstacle extraction unit 32.

[0034] Next, as shown in Figure 14, the docking control unit 4 controls the position P of the ship. ２ The shortest approximation line L １ The slope θ ＯＢＳ and the attitude angle θ of the ship ＴＲＪ The attitude angle error Δθ is calculated from this (step S26). ＴＲＪ This refers to the east-west coordinate axis and the trajectory of a ship's navigation L. ２ This is the angle made with the approximation line L.１ The slope θ ＯＢＳ And the attitude angle θ of the ship ＴＲＪ Since the and have been determined, the attitude angle error Δθ is tan(θ ＯＢＳ -θ ＴＲＪ This can be calculated using the formula shown. Next, the docking control unit 4 transmits the translation error ΔL and the attitude angle error Δθ to the ship control unit 5 (step S27).

[0035] The ship control unit 5 determines the ship's center position, attitude, and speed based on the values ​​received by the GNSS receiver 2, and controls the ship's rudder so that the attitude angle error Δθ becomes zero, while also controlling the ship's speed so that the translation error ΔL becomes zero. As the attitude angle error Δθ and translation error ΔL approach zero, the ship stops parallel to the pier, enabling automatic docking.

[0036] Figure 15 is an explanatory diagram showing an example configuration of a computer system that realizes the ship collision avoidance systems 100 and 101 according to this embodiment. In the ship collision avoidance systems 100 and 101 according to this embodiment, the computer system functions as the ship collision avoidance systems 100 and 101 when a computer program describing the processing in the ship collision avoidance systems 100 and 101 is executed on the computer system. As shown in Figure 15, this computer system comprises a processor 200, memory 201, storage 202, and communication device 203, which are connected via a system bus 204.

[0037] The processor 200, memory 201, storage 202, and communication device 203 can send and receive information from each other via the system bus 204. The processor 200 is, for example, an example of a processing circuit and includes one or more of the following: CPU (Central Processing Unit), DSP (Digital Signal Processor), and system LSI (Large Scale Integration). The memory 201 includes one or more of the following: RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM® (Electrically Erasable Programmable Read Only Memory). The memory 201 also includes a recording medium on which a computer-readable program is recorded. Such a recording medium includes one or more of the following: non-volatile or volatile semiconductor memory, magnetic disk, flexible memory, optical disk, compact disk, and DVD (Digital Versatile Disc). Memory 201 stores the program that the processor 200 should execute, necessary data obtained during processing, and so on. Memory 201 is also used as a temporary storage area for the program. The communication device 203 consists of a receiver and transmitter that perform communication processing. Note that the computer system is not limited to the configuration shown in Figure 15 and may include other components.

[0038] Here, an example of the operation of the computer system until the program of this embodiment becomes executable will be described. In the computer system with the above configuration, for example, a computer program is installed in the storage 202 from media such as a CD-ROM or DVD-ROM set in a CD (Compact Disc)-ROM drive or DVD-ROM drive (not shown). When the program is executed, the program read from the storage 202 is stored in the main memory area of ​​the memory 201. In this state, the processor 200 executes the processing of the ship collision avoidance system 100, 101 according to this embodiment, in accordance with the program stored in the memory 201.

[0039] In the above description, a program describing the processing in the ship collision avoidance systems 100 and 101 is provided on a CD-ROM or DVD-ROM as the recording medium. However, the system is not limited to this, and depending on the configuration of the computer system, the capacity of the program to be provided, a program provided via a transmission medium such as the internet through the communication device 203 may also be used.

[0040] The program in this embodiment causes the computer system to perform, for example, the steps of: detecting candidate obstacles at sea as millimeter-wave symbol points with the millimeter-wave radar 1 at each processing cycle; calculating multiple millimeter-wave symbol points on a map coordinate system from multiple millimeter-wave symbol points detected by the millimeter-wave radar 1 at each processing cycle based on the received values ​​of the GNSS receiver 2 which determines the position and attitude of the ship on which the millimeter-wave radar 1 is installed; integrating the multiple millimeter-wave symbol points on the map coordinate system; and thresholding the integrated values ​​at each coordinate point to extract the region R of the sea obstacle X from among the candidate obstacles.

[0041] Furthermore, the program in this embodiment provides the computer system with an approximate straight line L of the marine obstacle X closest to the ship's position for the extracted marine obstacle X. １ We determine the approximate straight line L from the ship's position and attitude. １The system performs the steps of: calculating the attitude angle error Δθ and translation error ΔL for a given object; and controlling the direction and speed of the vessel so that it approaches the obstacle X based on the calculated translation error ΔL and attitude angle error Δθ.

[0042] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention.

[0043] The various aspects of this disclosure are summarized below as an appendix.

[0044] (Note 1) A ship collision avoidance system comprising: a millimeter-wave radar that detects candidate obstacles at sea as millimeter-wave symbol points at each processing cycle; a GNSS receiver that determines the position and attitude of a ship on which the millimeter-wave radar is installed; and a processing unit that extracts the region of a sea obstacle that has the potential to collide with the ship from among the candidate obstacles detected by the millimeter-wave radar, wherein the processing unit comprises: a millimeter-wave point cloud generation unit that calculates a plurality of millimeter-wave symbol points on a map coordinate system from a plurality of millimeter-wave symbol points detected by the millimeter-wave radar at each processing cycle based on the received value of the GNSS receiver; a millimeter-wave point cloud integration unit that integrates the plurality of millimeter-wave symbol points on the map coordinate system calculated by the millimeter-wave point cloud generation unit; and an obstacle extraction unit that thresholds the integrated value at each coordinate point integrated by the millimeter-wave point cloud integration unit and extracts the region of the sea obstacle from among the candidate obstacles. (Note 2) The ship collision avoidance system according to Note 1, characterized in that the millimeter-wave point cloud generation unit converts the reference coordinates of the millimeter-wave symbol points detected by the millimeter-wave radar into reference coordinates by the GNSS receiver, synchronizes the time of detection by the millimeter-wave radar with the time of reception by the GNSS receiver, and calculates a plurality of millimeter-wave symbol points on a map coordinate system from a plurality of millimeter-wave symbol points detected by the millimeter-wave radar at each processing cycle based on the value received by the GNSS receiver. (Note 3) The ship collision avoidance system according to Note 1 or 2, characterized in that the millimeter-wave point cloud integration unit determines the direction of movement of the ship at each processing cycle based on the value received by the GNSS receiver, sets the detection coverage area of ​​the millimeter-wave radar, and integrates the millimeter-wave symbol points enclosed by the detection coverage area. (Note 4) The ship collision avoidance system according to Note 3, characterized in that when the millimeter-wave point group integration unit integrates the millimeter-wave symbol points surrounded by the detection coverage area, it also adds the reflection intensity of the millimeter-wave symbol point detected by the millimeter-wave radar to the integration process for each millimeter-wave symbol point. (Note 5) The ship collision avoidance system according to any one of Notes 1 to 4, characterized in that the obstacle extraction unit thresholds the integrated values ​​at each coordinate point integrated by the millimeter-wave point group integration unit to extract the area of ​​the offshore obstacle from among the obstacle candidates.(Note 6) The ship collision avoidance system according to Note 5, characterized in that the obstacle extraction unit determines the centroid of all millimeter-wave symbol points that have been determined to be obstacles at sea by threshold processing, determines the distance from the position of the centroid to the positions of all millimeter-wave symbol points that have been determined to be obstacles at sea, and extracts a circle with a radius equal to the distance from the position of the centroid to the millimeter-wave symbol point furthest away as the region of the obstacles at sea. (Note 7) The ship collision avoidance system according to Note 5, characterized in that the obstacle extraction unit determines the edge portions of the millimeter-wave symbol points that have been determined to be obstacles at sea by threshold processing, and extracts a polygon formed by connecting these edges as the region of the obstacles at sea. (Note 8) A ship collision avoidance system according to any one of Notes 1 to 7, further comprising: a docking control unit that, with respect to the offshore obstacle determined by the obstacle extraction unit, finds an approximate straight line of the offshore obstacle closest to the ship's position, and calculates an attitude angle error and a translation error with respect to the approximate straight line from the ship's position and attitude; and a ship control unit that controls the direction and speed of the ship so that the ship approaches the offshore obstacle based on the translation error and the attitude angle error calculated by the docking control unit. (Note 9) A ship collision prevention method characterized by comprising: detecting candidate obstacles at sea as millimeter-wave symbol points with a millimeter-wave radar at each processing cycle; calculating a plurality of millimeter-wave symbol points on a map coordinate system from a plurality of millimeter-wave symbol points detected by the millimeter-wave radar at each processing cycle based on the received values ​​of a GNSS receiver that determines the position and attitude of a ship on which the millimeter-wave radar is installed; integrating the plurality of millimeter-wave symbol points on the map coordinate system; and thresholding the integrated values ​​at each coordinate point to extract the region of a sea obstacle that has the potential to collide with a ship from among the candidate obstacles.(Note 10) A ship collision avoidance program characterized by causing a computer to perform the following steps: detecting candidate obstacles at sea as millimeter-wave symbol points with a millimeter-wave radar at each processing cycle; calculating multiple millimeter-wave symbol points on a map coordinate system from multiple millimeter-wave symbol points detected by the millimeter-wave radar at each processing cycle based on the received values ​​of a GNSS receiver that determines the position and attitude of the ship on which the millimeter-wave radar is installed; integrating the multiple millimeter-wave symbol points on the map coordinate system; and thresholding the integrated values ​​at each coordinate point to extract the area of ​​a sea obstacle that has the potential to collide with a ship from among the candidate obstacles.

[0045] 1 Millimeter-wave radar, 2 GNSS receiver, 3 Processing unit, 4 Docking control unit, 5 Ship control unit, 30 Millimeter-wave point cloud generation unit, 31 Millimeter-wave point cloud integration unit, 32 Obstacle extraction unit, 100, 101 Ship collision avoidance system, 200 Processor, 201 Memory, 202 Storage, 203 Communication device, 204 System bus.

Claims

1. A ship collision avoidance system comprising: a millimeter-wave radar that detects potential obstacles at sea as millimeter-wave symbol points at each processing cycle; a GNSS receiver that determines the position and attitude of a ship on which the millimeter-wave radar is installed; and a processing unit that extracts the region of a sea obstacle that has the potential to collide with the ship from among the obstacle candidates detected by the millimeter-wave radar, wherein the processing unit comprises: a millimeter-wave point cloud generation unit that calculates a plurality of millimeter-wave symbol points on a map coordinate system from a plurality of millimeter-wave symbol points detected by the millimeter-wave radar at each processing cycle based on the received values ​​of the GNSS receiver; a millimeter-wave point cloud integration unit that integrates the plurality of millimeter-wave symbol points on the map coordinate system calculated by the millimeter-wave point cloud generation unit; and an obstacle extraction unit that thresholds the integrated values ​​at each coordinate point integrated by the millimeter-wave point cloud integration unit and extracts the region of the sea obstacle from among the obstacle candidates.

2. The ship collision avoidance system according to claim 1, characterized in that the millimeter-wave point cloud generation unit converts the reference coordinates of the millimeter-wave symbol points detected by the millimeter-wave radar into reference coordinates by the GNSS receiver, synchronizes the time of detection by the millimeter-wave radar with the time of reception by the GNSS receiver, and calculates a plurality of millimeter-wave symbol points on a map coordinate system from a plurality of millimeter-wave symbol points detected by the millimeter-wave radar at each processing cycle based on the value received by the GNSS receiver.

3. The ship collision avoidance system according to claim 1 or 2, characterized in that the millimeter-wave point group integration unit determines the ship's direction of movement for each processing cycle based on the received value of the GNSS receiver, sets the detection coverage area of ​​the millimeter-wave radar, and integrates the millimeter-wave symbol points enclosed by the detection coverage area.

4. The ship collision avoidance system according to claim 3, characterized in that when the millimeter-wave point group integration unit integrates the millimeter-wave symbol points enclosed by the detection coverage area, it also adds the reflection intensity of the millimeter-wave symbol point detected by the millimeter-wave radar to the integration process for each millimeter-wave symbol point.

5. The ship collision avoidance system according to any one of claims 1 to 4, characterized in that the obstacle extraction unit performs threshold processing on the integrated values ​​at each coordinate point integrated by the millimeter-wave point group integration unit to extract the region of the offshore obstacle from among the obstacle candidates.

6. The ship collision avoidance system according to claim 5, characterized in that the obstacle extraction unit determines the centroid of all millimeter-wave symbol points that have been determined to be marine obstacles by threshold processing, determines the distance from the position of the centroid to the positions of all millimeter-wave symbol points that have been determined to be marine obstacles, and extracts a circle with a radius equal to the distance from the position of the centroid to the millimeter-wave symbol point furthest away as the region of the marine obstacle.

7. The ship collision avoidance system according to claim 5, characterized in that the obstacle extraction unit determines the edge portion of the millimeter-wave symbol points that have been determined to be the offshore obstacles by threshold processing, and extracts the polygon formed by connecting the edges as the region of the offshore obstacle.

8. A ship collision avoidance system according to any one of claims 1 to 7, further comprising: a docking control unit that, with respect to the offshore obstacle determined by the obstacle extraction unit, finds an approximate straight line of the offshore obstacle closest to the ship's position, and calculates an attitude angle error and a translation error with respect to the approximate straight line from the ship's position and attitude; and a ship control unit that controls the direction and speed of the ship so that the ship approaches the offshore obstacle based on the translation error and the attitude angle error calculated by the docking control unit.

9. A ship collision prevention method characterized by comprising: detecting candidate obstacles at sea as millimeter-wave symbol points with a millimeter-wave radar at each processing cycle; calculating a plurality of millimeter-wave symbol points on a map coordinate system from a plurality of millimeter-wave symbol points detected by the millimeter-wave radar at each processing cycle based on the received values ​​of a GNSS receiver that determines the position and attitude of a ship on which the millimeter-wave radar is installed; integrating the plurality of millimeter-wave symbol points on the map coordinate system; and thresholding the integrated values ​​at each coordinate point to extract the region of a sea obstacle that has the potential to collide with a ship from among the candidate obstacles.

10. A ship collision avoidance program characterized by causing a computer to perform the following steps:

10. Detect potential obstacles at sea as millimeter-wave symbol points using a millimeter-wave radar at each processing cycle; 12. Based on the received values ​​of a GNSS receiver that determines the position and attitude of a ship on which the millimeter-wave radar is installed, calculate multiple millimeter-wave symbol points on a map coordinate system from multiple millimeter-wave symbol points detected by the millimeter-wave radar at each processing cycle; 13. Integrate the multiple millimeter-wave symbol points on the map coordinate system; and 14. Threshold the integrated values ​​at each coordinate point obtained through the integration process to extract areas of sea obstacles that have the potential to collide with a ship from among the obstacle candidates.

Images