Ship navigation assisting apparatus

Abstract

To provide a technique capable of causing a target ship to avoid a polygonal area where there is a risk of collision between the target ship and another ship.SOLUTION: An information acquisition unit which acquires target ship information indicating a position of the target ship; with respect to a first collision risk region indicating a range where there is a risk of collision between the target ship and a first other ship by a polygonal shape in which a plurality of constituent points are connected, calculating a course range of the first collision risk region around the position of the target ship indicated in the target ship information; And a collision avoidance course calculator configured to calculate, as a collision avoidance course candidate of the target ship, a starting azimuth course passing through a constituent point at a starting azimuth of the course range or passing through an outer side of the first collision risk area around the position of the target ship with respect to the constituent point, and an ending azimuth course passing through a constituent point at an ending azimuth of the course range or passing through an outer side of the first collision risk area around the position of the target ship with respect to the constituent point.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a technology for assisting the navigation of a ship. [Background technology]

[0002] Conventionally, research and development has been conducted on technologies for supporting ship navigation, such as generating an avoidance route to avoid collision between a target ship and another ship different from the target ship. Indicators that indicate the possibility of collision between the target ship and another ship and are used to generate an avoidance route include the collision risk, the danger direction range, and the collision risk area.

[0003] Furthermore, an index showing the possibility of collision between a target ship and another ship is the Dangerous Area of ​​Collision (DAC) shown in Patent Documents 1 and 2. The DAC is calculated by connecting multiple collision points calculated based on a polygonal safe passage area surrounding the target ship or another ship, and the polygonal shape made up of multiple points represents an area where there is a risk of collision between the target ship and another ship. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-246998 [Patent Document 2] Japanese Patent Application Publication No. 2019-166865 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem that the embodiments of the present invention aim to solve is to provide a technology that allows a target ship to avoid a polygonal area where there is a risk of collision between the target ship and another ship. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, a ship navigation support device that calculates an avoidance course for a target ship and provides navigation support is provided, and is equipped with an information acquisition unit that acquires target ship information indicating the position of the target ship, and an avoidance course calculation unit that calculates a course range of the first collision risk area around the position of the target ship shown in the target ship information for a first collision risk area that indicates an area where there is a risk of collision between the target ship and a first other ship using a polygonal shape formed by connecting multiple constituent points, and calculates as candidate avoidance courses for the target ship a constituent point at the start heading of the course range or a starting heading course that passes outside the first collision risk area around the position of the target ship from that constituent point, and an ending heading course that passes outside the first collision risk area around the position of the target ship from that constituent point. [Effects of the Invention]

[0007] According to the present invention, it is possible to cause a target ship to avoid a polygonal area where there is a risk of collision between the target ship and another ship. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating a configuration of a vessel navigation support system according to an embodiment. [Figure 2] 1 is a block diagram showing a hardware configuration of a vessel navigation support device according to an embodiment. [Figure 3] 1 is a block diagram showing a functional configuration of a vessel navigation support device according to an embodiment; [Figure 4] 3 is a flowchart showing the overall operation of the vessel navigation support device according to the embodiment. [Figure 5] FIG. 10 is a schematic diagram showing an example of setting a target point. [Figure 6] FIG. 1 is a schematic diagram showing the current DAC display screen. [Figure 7] FIG. 10 is a schematic diagram showing the DAC display screen when the first waypoint is reached. [Figure 8] FIG. 10 is a schematic diagram showing the DAC display screen when the second waypoint is reached. [Figure 9] 10 is a flowchart showing the operation of information acquisition processing. [Figure 10] 10 is a flowchart showing the operation of a navigation determination process. [Figure 11] FIG. 10 is a schematic diagram showing DAC calculated based on a safe passage area set for a vessel to be assisted. [Figure 12] FIG. 10 is a schematic diagram showing DAC calculated based on a safe passage area set for another ship. [Figure 13] 10 is a flowchart showing operations of a collision avoidance target registration process. [Figure 14] FIG. 10 is a schematic diagram showing an example of the shape of a search region. [Figure 15] FIG. 2 is a schematic diagram showing parameters of a search area. [Figure 16] FIG. 10 is a schematic diagram showing a modified example of a search area. [Figure 17] FIG. 10 is a schematic diagram illustrating a case where the search area and the DAC do not overlap. [Figure 18] FIG. 10 is a schematic diagram illustrating a case where the search area and the DAC overlap. [Figure 19] 10 is a flowchart showing the operation of a collision avoidance route calculation process. [Figure 20] FIG. 1 is a schematic diagram showing a method for calculating an escape route. [Figure 21] FIG. 10 is a schematic diagram showing a method for calculating an avoidance route. [Figure 22] FIG. 2 is a schematic diagram showing candidate avoidance routes. [Figure 23] 10 is a flowchart showing the operation of a waypoint calculation process. [Figure 24] FIG. 10 is a schematic diagram showing a method for calculating a collision avoidance end point. [Figure 25] 10 is a flowchart showing the operation of an end point direction calculation process. [Figure 26] FIG. 1 is a schematic diagram showing two end points and a nearest neighbor point. [Figure 27] FIG. 10 is a schematic diagram showing the transition of the start orientation end points and the end orientation end points when component points are selected clockwise. [Figure 28]FIG. 10 is a schematic diagram showing the transition of the start orientation end points and the end orientation end points when component points are selected counterclockwise. [Figure 29] FIG. 1 is a schematic diagram showing two endpoints calculated for a DAC ahead of a target vessel. [Figure 30] FIG. 10 is a schematic diagram showing two endpoints calculated for a DAC aft of a target vessel. [Figure 31] FIG. 10 is a schematic diagram showing a DAC surrounding a target vessel from which configuration points are selected in a clockwise direction. [Figure 32] FIG. 10 is a schematic diagram showing a DAC surrounding a target vessel with configuration points selected counterclockwise. [Figure 33] 10 is a flowchart showing the operation of an area determination process. [Figure 34] 1 is a schematic diagram showing an infringement area, a non-infringement area, and a candidate non-infringement area; [Figure 35] 1 is a schematic diagram showing an infringement area, a non-infringement area, and a non-infringement area candidate in Cartesian coordinates. [Figure 36] 10 is a flowchart showing the operation of a course range update process. [Figure 37] FIG. 4 is a schematic diagram showing the course range when the first condition is satisfied. [Figure 38] FIG. 10 is a schematic diagram showing the course range when the second condition is satisfied. [Figure 39] FIG. 10 is a schematic diagram showing the course range when the third condition is satisfied. [Figure 40] FIG. 10 is a schematic diagram showing the course range when the fourth condition is satisfied. [Figure 41] FIG. 10 is a schematic diagram showing the course range when the fifth condition is satisfied. [Figure 42] 10 is a flowchart showing the operation of a ranking determination process. [Figure 43] FIG. 10 is a schematic diagram illustrating weighting based on user selection. [Figure 44] FIG. 10 is a schematic diagram showing a collision avoidance end point according to a first modified example. [Figure 45] FIG. 10 is a schematic diagram showing a collision avoidance end point according to a second modified example. [Figure 46]FIG. 10 is a schematic diagram showing a collision avoidance end point according to a third modified example. [Figure 47] FIG. 10 is a schematic diagram showing a collision avoidance end point according to a fourth modified example. [Figure 48] FIG. 10 is a schematic diagram showing a collision avoidance end point according to a fifth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] (Configuration of ship navigation support device) The configuration of the vessel navigation support device according to this embodiment will be described. Fig. 1 is a schematic diagram showing the configuration of the vessel navigation support system according to this embodiment. Fig. 2 and Fig. 3 are block diagrams showing the hardware configuration and functional configuration of the vessel navigation support device according to this embodiment, respectively.

[0011] As shown in Figure 1(a), the vessel navigation assistance system according to this embodiment includes equipment mounted on a target vessel 1, which is a vessel to be assisted in navigation, and equipment mounted on another vessel 2, which is a vessel that is not the target vessel. The target vessel 1 is equipped with a vessel navigation assistance device 10, sensors 11, an AIS (Automatic Identification System) 12, radar 13, and a camera 14. The other vessel 2 is equipped with an AIS 22.

[0012] The sensors 11 include a speed log that detects the target ship 1's speed through the water, a gyrocompass that detects the target ship 1's heading, and a GNSS sensor that detects the target ship 1's position, ground heading, and ground speed from a global navigation satellite system (GNSS) such as GPS.

[0013] Both AIS 12 and 22 are devices capable of transmitting and receiving signals and receive vessel data from other AISs, including the maritime mobile service identification code, vessel name, vessel type, draft, destination, estimated time of arrival, vessel name, voyage status, latitude, longitude, speed, course, vessel length, vessel breadth, and heading.

[0014] Each radar 13 captures targets, including ships, by receiving reflected waves of emitted radio waves. Each camera 14 is installed so that it can capture images of the surrounding area, and is a component of an image recognition system that detects and tracks ships included in the captured images and acquires movement information (position and speed) of the ships.

[0015] As shown in FIG. 1(b), a land station 3 may be equipped with a ship navigation support device 30 instead of the ship navigation support device 10. The land station 3 includes the ship navigation support device 30, sensors 31, an AIS 32, a radar 33, and a camera 34. The land station 3 is required to include at least the ship navigation support device 30 and the AIS 32. The sensors 31 include a GNSS sensor that detects the position, ground course, and ground speed of the target ship 1. The ship navigation support devices 10 and 30 have similar hardware and functional configurations, and the functions and processing operations described below can be similarly executed by either the ship navigation support device 10 or 30. In the following explanation, the configuration, functions, and processing of the ship navigation support device 10 installed on the target ship 1 will be described as a representative example.

[0016] In this embodiment, the vessel navigation support device 10 is realized as a function incorporated into an Electronic Chart Display and Information System (ECDIS) or an Electronic Chart System (ECS), but may be another device communicatively connected to an ECDIS or ECS. As shown in Fig. 2, the vessel navigation support device 10 includes, as hardware, a CPU (Central Processing Unit) 101, a RAM (Random Access Memory) 102, a storage device 103, an external I / F (Interface) 104, and a network I / F 105.

[0017] The CPU 101 and RAM 102 work together to execute various functions, and the storage device 103 stores various data used in the processes executed by the various functions. The external I / F 104 inputs and outputs data to and from output devices such as a display, a mouse, a keyboard, and an input / output device such as a touch panel. The network I / F 105 is an interface for communicating with the sensors 11, the AIS 12, the radar 13, and the camera 14.

[0018] The ship navigation support device 10 has the following functions: a TT processing unit 201, an information acquisition unit 202, a navigation judgment unit 203, a DAC calculation unit 204, a registration unit 205, an avoidance course calculation unit 206, a course display unit 207, and a return course calculation unit 208.

[0019] The TT processing unit 201 automatically detects / tracks the other ship 2 from the radar video signal acquired from the radar 13 or the image captured by the camera 14, and calculates the position coordinates and velocity vector of the other ship 2, and also calculates the position coordinates and velocity vector of the target ship 1 from the measurement data regarding the target ship 1 measured by the sensors 11.

[0020] The information acquisition unit 202 acquires the planned route, target ship information, and other ship information. The planned route is the route of the target ship 1 created using ECDIS or ECS and includes multiple waypoints. The target ship information includes the speed, course or heading, and position coordinates of the target ship 1. The speed of the target ship 1 is measured by a speed log or GNSS sensor in the sensors 11. The heading of the target ship 1 is measured by a gyrocompass in the sensors 11. The course of the target ship 1 is measured by a GNSS sensor. The other ship information includes the true heading, true course, true speed, and relative distance between the target ship 1 and the other ship 2, which are received by the AIS 12 or obtained by detection / tracking by the TT processing unit 201 using the radar 13 or camera 14. The information acquisition unit 202 of the vessel navigation support device 30 acquires the planned route, target ship information, and other ship information by sending and receiving information via the AIS 32 and by measurements using a GNSS sensor.

[0021] The navigation determination unit 203 determines the need for avoidance or return of the target ship 1. Here, avoidance means that the target ship 1 navigates a course that does not follow the planned route in order to avoid collision with another ship 2, and return means that the target ship 1 navigates away from the planned route and then heads toward the planned route.

[0022] The DAC calculation unit 204 calculates a Dangerous Area of ​​Collision (DAC) based on the target ship information and other ship information acquired by the information acquisition unit 202. The DAC calculation unit 204 does not necessarily need to calculate the DAC, but rather must at least calculate a collision risk area, which is an area where there is a risk of collision between the target ship 1 and the other ship 2, based on multiple constituent points connected to each other. It is preferable that the collision risk area varies over time based on the relative relationship between the target ship 1 and the other ship 2. In this embodiment, the DAC is calculated by connecting multiple collision points calculated based on the target ship information, other ship information, and a polygonal safe passage area surrounding the target ship 1 or the other ship 2. For detailed information on how to calculate the DAC based on the safe passage area, please refer to Patent Document 1 or Patent Document 2.

[0023] The registration unit 205 registers the other ship 2 that the target ship 1 corresponding to the DAC should give way to as an avoidance target, based on the DAC calculated by the DAC calculation unit 204. The avoidance course calculation unit 206 calculates an avoidance course or an avoidance route for the target ship 1 to avoid the DAC corresponding to the avoidance target. The return course calculation unit 208 calculates a return course for the target ship 1. The course display unit 207 displays the avoidance course or the avoidance route calculated by the avoidance course calculation unit 206 on a display, and also displays time-series changes in the DAC on a display. The course display unit 207 also displays the return course calculated by the return course calculation unit 208 on a display.

[0024] (Operation of marine navigation aids) The operation of the vessel navigation support device according to this embodiment will be described. Fig. 4 is a flowchart showing the overall operation of the vessel navigation support device according to this embodiment. Fig. 5 is a schematic diagram showing an example of setting a target point. Figs. 6 to 8 are schematic diagrams showing the DAC display screen at the current time, when the first waypoint has been reached, and when the second waypoint has been reached, respectively.

[0025] As shown in Figure 4, first, the information acquisition unit 202 executes the information acquisition process described below (S101), then the navigation determination process described below is executed (S102), and the return course calculation unit 208 determines whether the determination result of the navigation determination process indicates that the target ship 1 needs to return (S103).

[0026] If return is not necessary (S103, NO), the registration unit 205 determines whether or not the determination result of the navigation determination process indicates that avoidance by the target ship 1 is necessary (S104).

[0027] If collision avoidance is necessary (S104, YES), the registration unit 205 executes the collision avoidance target registration process described below (S105), and the collision avoidance course calculation unit 206 determines whether or not there is a collision avoidance target registered by the collision avoidance target registration process (S106).

[0028] If a target for avoidance exists (S106, YES), the avoidance course calculation unit 206 sets a target point and a reference course (S107), and the avoidance course calculation process described below is executed (S108). Here, the avoidance course calculation process calculates an avoidance course candidate that includes at least one or more waypoint candidates. The waypoint candidates will be described in detail later.

[0029] Regarding the setting of the target point, if a planned route exists, more specifically, if the planned route has been acquired by the information acquisition unit 202, the location to be set as the target point can be a plurality of positions based on the planned route. If the target ship 1 is sailing on the planned route, the target point is set on a leg of the planned route. If the target ship 1 is not sailing on the planned route, four methods of setting the target point are possible, as shown in Figure 5. Figure 5(a) shows a target point DP set on the nearest leg of the planned route PR. Figure 5(b) shows a target point DP set at the nearest waypoint WPT of the planned route PR. Figure 5(c) shows a target point DP set at the intersection of the nearest leg and the next leg of the nearest leg when the target ship 1 sails parallel to the nearest leg of the planned route PR. Figure 5(d) shows the target point DP set at the intersection with a virtual line extending forward from the next leg of the nearest leg of the planned route PR when the target ship 1 sails parallel to the nearest leg of the planned route PR. If there is no planned route, the target point is set on the current course of the target ship 1 or on the course set as the reference course. The reference course is set in the direction from the starting point, which is the current position of the target ship 1, to the target point, unless a separate course is set.

[0030] Next, as will be described in detail later, the course display unit 207 executes a ranking determination process to determine priorities for multiple candidate avoidance routes when multiple candidate avoidance routes have been calculated (S109), and displays at least one of the highest-priority avoidance routes on the display so that the user can select it, and also displays the avoidance route selected by the user and the time-series changes in DAC corresponding to the other ship 2 that is the target of avoidance on the display (S110), as shown in Figures 6 to 8, and then the operation of the ship navigation assistance device 10 related to the calculation of the avoidance course / return course is terminated.

[0031] Figures 6 to 8 show an avoidance route including a first waypoint VP_1 and a second waypoint VP_2. Figure 6 shows a display screen displaying the DAC at the current time, specifically, when the position TS of the target ship 1 is heading toward the first waypoint VP_1. Figure 7 shows a display screen displaying the predicted DAC when the position TS reaches the first waypoint VP_1. Figure 8 shows a display screen displaying the predicted DAC when the position TS reaches the second waypoint VP_2.

[0032] Furthermore, in step S106, if there is no target for avoidance (S106, NO), the operation of the vessel navigation support device 10 relating to calculation of the avoidance course / return course is terminated.

[0033] Furthermore, in step S104, if no collision avoidance is required (S104, NO), that is, if neither collision avoidance nor return is required, the operation of the vessel navigation support device 10 relating to calculation of the collision avoidance course / return course is terminated.

[0034] Furthermore, in step S103, if return is necessary (S103, YES), the return course calculation unit 208 calculates a return course toward the planned route, specifically, an arbitrary point or waypoint on the leg of the planned route (S111), the course display unit 207 displays the calculated return course on the display (S112), and the operation of the ship navigation support device 10 related to the calculation of the avoidance course / return course is terminated.

[0035] (Information acquisition processing) The operation of the information acquisition process will now be described with reference to a flowchart of FIG.

[0036] As shown in FIG. 9, the information acquisition unit 202 determines whether or not a planned route has been created for the target ship 1 (S201).

[0037] If a planned route exists (S201, YES), the information acquisition unit 202 acquires the planned route (S202), acquires target ship information (S203), acquires other ship information (S204), and the information acquisition process ends.

[0038] On the other hand, if the planned route does not exist (S201, NO), the information acquisition unit 202 acquires the target ship information (S203).

[0039] (Navigation determination processing) The operation of the navigation determination process will be described. Fig. 10 is a flowchart showing the operation of the navigation determination process. Figs. 11 and 12 are schematic diagrams showing DAC calculated based on the safe passage areas set for the support target ship and the other ship, respectively.

[0040] First, the DAC calculation unit 204 calculates a DAC for each of the other ships 2 surrounding the target ship 1 (S301). Here, a brief explanation of the calculation of the DAC will be given. As described above, there are two methods for calculating the DAC: one based on the safe passage area set for the target ship 1, and the other based on the safe passage area set for the other ships 2. As shown in FIGS. 11 and 12, the safe passage area SPA is a circular area surrounding the position TS of the target ship 1, or an arbitrary two-dimensional area surrounding the position OS of the other ships 2, with multiple constituent points SP connected to form the area. The DAC shown in FIG. 11 is calculated by calculating constituent points P, which are the collision points between the other ships 2 and each vertex of the safe passage area set for the target ship 1, based on the relative position and velocity vector of the other ships 2 relative to the target ship 1 obtained from the target ship information and other ship information, and the speed of the target ship 1, and then connecting the calculated constituent points P. The DAC shown in FIG. 12 differs from the DAC shown in FIG. 11 in that it calculates constituent points P, which are the collision points between the target ship 1 and each vertex of the safe passage area set for the other ships 2. With this type of DAC, not only can the current area where there is a possibility of collision be calculated, but also the positions of the target ship 1 and the other ship 2 after a certain period of time has elapsed, virtually advancing time from the present, based on the target ship information and the other ship information, and the area where there is a possibility of collision in the future can be calculated as a future DAC, as described below.

[0041] After calculating the DAC, the navigation determination unit 203 determines whether or not the target ship 1 satisfies the conditions for avoidance (S302). Here, the navigation determination unit 203 determines that the conditions for avoidance are met when the distance between the target ship 1 and the DAC closest to the target ship 1 is equal to or less than a preset distance threshold, but may also determine that the conditions for avoidance are met when an index indicating the degree of danger regarding the navigation of the target ship 1 is equal to or greater than a preset level threshold.

[0042] If the target ship 1 does not satisfy the collision avoidance conditions (S302, NO), the navigation determination unit 203 determines whether the achievement level is equal to or lower than a preset level threshold (S303). Here, the achievement level indicates the degree of achievement of collision avoidance, and for example, the achievement level becomes lower the more the portion of the target ship 1's current navigation course or navigation route that overlaps with the DAC, and becomes higher the more the portion that does not overlap with the DAC.

[0043] If the achieved level is not equal to or lower than the level threshold (S303, NO), the navigation determination unit 203 determines whether the target ship 1 satisfies the return condition (S304). Here, the navigation determination unit 203 determines that the target ship 1 satisfies the return condition if the target ship 1 has deviated from the planned route and is sailing, and the current navigation course or navigation route is not connected to the planned route.

[0044] If the target ship 1 satisfies the return condition (S304, YES), the navigation determination unit 203 determines that the target ship 1 needs to return (S305), and the navigation determination process ends.

[0045] On the other hand, if the target ship 1 does not satisfy the return condition (S304, NO), it is determined that neither return nor avoidance is necessary, and the navigation determination process is terminated.

[0046] Furthermore, in step S303, if the achieved level is equal to or lower than the level threshold (S303, YES), the navigation determination unit 203 determines that avoidance is necessary for the target ship 1 (S306), and the navigation determination process ends.

[0047] Furthermore, in step 302, if the target ship 1 satisfies the navigation conditions (S302, YES), the navigation determination unit 203 determines that avoidance is necessary for the target ship 1 (S306), and the navigation determination process ends.

[0048] (Collision avoidance target registration processing) The operation of the collision avoidance target registration process will be described. Fig. 13 is a flowchart showing the operation of the collision avoidance target registration process. Fig. 14 is a schematic diagram showing an example of the shape of the search area. Fig. 15 is a schematic diagram showing parameters of the search area. Fig. 16 is a schematic diagram showing a modified example of the search area. Figs. 17 and 18 are schematic diagrams showing cases where the search area does not overlap with the DAC and where the search area overlaps with the DAC, respectively.

[0049] First, the registration unit 205 determines whether or not there is a DAC that has not been selected in the collision avoidance target registration processing among the DACs calculated by the DAC calculation unit 204 (S401).

[0050] If an unselected DAC exists (S401, YES), the registration unit 205 selects the unselected DAC (S402), and determines whether or not an unselected composition point exists in the selected DAC (S403).

[0051] If an unselected component point exists (S403, YES), the registration unit 205 selects the unselected component point (S404) and determines whether the component point exists within the search area (S405).

[0052] Here, the search area will be explained. As shown in FIG. 14, the search area SA is a two-dimensional area that starts at the position TS of the target ship 1 and extends in the course direction from the position TS toward the destination point DP, as well as in a direction perpendicular to the course direction. Examples of such a search area SA include the shapes shown in FIGS. 14(a) to 14(d). FIG. 14(a) shows a search area SA formed in a fan shape with the vertex of the central angle coinciding with the position TS of the target ship 1. FIG. 14(b) shows a search area SA formed in a rectangular shape with two opposing sides parallel to the reference course direction and an arbitrary point on one side coinciding with the position TS. FIG. 14(c) shows a search area SA formed in a triangular shape with one vertex coinciding with the position TS. FIG. 14(d) shows a search area SA formed by curving inward the two radii of the fan shape shown in FIG. 14(a). In this embodiment, the fan-shaped search area SA shown in FIG. 14(a) is used.

[0053] As shown in Figure 15, the sector-shaped search area SA is set by two parameters: a search distance range SDR and a search course range SHR. The search course range SHR corresponds to the radius of the sector and is set to at least 0, for example, 12 nautical miles, or the distance traveled in one hour at the speed of the target ship 1. The search course range SHR corresponds to the central angle of the sector and is set to at least 360° or less, and is set to the angle β of the starboard side radius relative to the reference course. s ° and the port angle β relative to the reference course p ° and are given as parameters that determine the search course range SHR.

[0054] As shown in Figure 16, a fan-shaped search area SA may be used in which the apex of the central angle is advanced by a forward advance distance FAD toward the target point DP, i.e., forward. Generally, when a ship starts to change course from a straight sailing state, it advances forward by a new course distance corresponding to the reach, turning radius, and course angle until it reaches the desired course angle. By appropriately setting the forward advance distance FAD, it is possible to search for a DAC that takes such a new course distance into consideration. The forward advance distance FAD may be set, for example, between 0 and 3 nautical miles. In the following explanation, it is assumed that a search area SA with the forward advance distance FAD set to 0 is used.

[0055] In the judgment of step S405 shown in Figure 11, the registration unit 205 determines that the constituent point is located within the search area if the direction of the line segment connecting the position TS of the target ship 1 and the selected constituent point is within the search course range and the length of this line segment is less than or equal to the search distance range SDR.

[0056] If the configuration point is present within the search area (S405, YES), the registration unit 205 registers the other ship corresponding to the selected DAC as a target for avoidance (S406), and again determines whether there is an unselected DAC (S401).

[0057] On the other hand, if the constituent point does not exist within the search region (S405, NO), the registration unit 205 again determines whether or not there is an unselected constituent point in the currently selected DAC (S403).

[0058] Furthermore, in step S403, if there is no unselected configuration point (S403, NO), the registration unit 205 again determines whether there is an unselected DAC (S401).

[0059] Furthermore, in step S401, if there is no unselected DAC (S401, NO), the collision avoidance target registration process is terminated.

[0060] According to this collision avoidance target registration process, if none of the constituent points P of any DAC are included within the search area SA, as shown in Figure 17, none of the other ships 2 are registered as collision avoidance targets. Also, as shown in Figure 18, if only the constituent point P of DAC_A is present within the search area SA, only the other ship 2A corresponding to DAC_A is registered as a collision avoidance target, and the other ship 2B corresponding to DAC_B is not registered as a collision avoidance target. In this way, by registering collision avoidance targets prior to calculating the collision avoidance route, the time required to calculate the collision avoidance route can be reduced.

[0061] (Evasion route calculation processing) The operation of the avoidance route calculation process will now be described. Fig. 19 is a flowchart showing the operation of the avoidance route calculation process. Figs. 20 and 21 are schematic diagrams showing the calculation method of an avoidance course and an avoidance route, respectively. Fig. 22 is a schematic diagram showing candidates for avoidance routes.

[0062] As shown in FIG. 19, first, the avoidance course calculation unit 206 determines whether or not the current avoidance route calculation process is a recursive process that has been recursively called by the avoidance route calculation process itself (S500).

[0063] If the current avoidance route calculation process is a recursive process (S500, YES), the avoidance course calculation unit 206 selects as the target route an avoidance route that has at least one waypoint calculated by the avoidance course process that directly or indirectly calls the current avoidance route calculation process (S501).

[0064] Next, the avoidance course calculation unit 206 selects the last waypoint on the target route as the starting point (S502), and the DAC calculation unit 204 calculates the future DAC (S503). Here, the DAC calculation unit 204 calculates the time required for the target ship 1 to reach the starting point based on a predetermined course and speed, and calculates the predicted position of the other ship 2 that is the target of avoidance after the required time based on the course and speed of the other ship 2, and calculates the DAC between the other ship 2 at the predicted position and the target ship 1 at the starting point as the future DAC.

[0065] Next, the avoidance course calculation unit 206 adjusts parameters such as the reference course, search area, and target point as necessary (S504), and executes the waypoint calculation process described below (S505). According to this waypoint calculation process, as shown in Fig. 20, for one starting point, up to two waypoint candidates are calculated, which are the destination points of a course that passes through the end points of DAC. Fig. 20 shows the waypoint candidate VP_A, which is the destination point of a course that passes through the port end point of DAC_A, and the waypoint candidate VP_B, which is the destination point of a course that passes through the starboard end point of DAC_A. After executing the waypoint calculation process, the avoidance course calculation unit 206 determines whether or not there are any unprocessed waypoint candidates (S506).

[0066] If there are any unprocessed waypoint candidates (S506, YES), the avoidance course calculation unit 206 connects the unprocessed waypoint candidate as a waypoint to the currently selected starting point (S507) and determines whether the recursion upper limit condition is satisfied (S508). Here, the recursion upper limit condition is a condition for terminating the recursion of the avoidance course calculation process. Examples of the recursion upper limit condition include the total distance of the avoidance course exceeding a distance threshold that defines the upper limit, the total navigation time of the avoidance course assuming a constant speed of the target ship 1 exceeding a time threshold that defines the upper limit, the number of recursion processes exceeding a count threshold that defines the upper limit, or the total number of calculated waypoint candidates exceeding a count threshold that defines the upper limit. Note that if the upper limit of the number of recursion processes is set to 0 as the recursion upper limit condition, the avoidance course calculation process calculates an avoidance course that includes only one waypoint that is essentially the destination point, i.e., an avoidance course.

[0067] If the recursion upper limit condition is satisfied (S508, YES), the avoidance course calculation unit 206 stores at least one calculated avoidance route as an avoidance route candidate (S509), and the avoidance route calculation process is terminated.

[0068] On the other hand, if the recursion upper limit condition is not satisfied (S508, NO), the avoidance course calculation unit 206 recursively calls the avoidance course calculation process (S510) and determines again whether or not there are any unprocessed waypoint candidates (S506).

[0069] Furthermore, in step S506, if there are no unprocessed maneuvering point candidates (S506, NO), the avoidance route calculation process is terminated.

[0070] Furthermore, in step S500, if the current avoidance route calculation process is not a recursive process (S00, NO), the avoidance course calculation unit 206 selects the current position TS of the target ship 1 as the starting point (S502).

[0071] According to this avoidance route calculation process, two candidate waypoints VP_A1 and VP_A2 starting from candidate waypoint VP_A as shown in Figure 21(a), and two candidate waypoints VP_B1 and VP_B2 starting from candidate waypoint VP_B as shown in Figure 21(b) are calculated by a single recursive process. Furthermore, by executing the recursive process multiple times, multiple candidate avoidance routes branching into two for each candidate waypoint are calculated as shown in Figure 22. For example, in Figure 22, as candidate avoidance routes starting from the current position TS of the target ship 1 and passing through candidate waypoint VP_A1, a candidate avoidance route that passes through VP_A and VP_A1 to reach VP_A11 and a candidate avoidance route that passes through VP_A and VP_A1 to reach the destination point DP are calculated.

[0072] (Varying course point calculation process) The operation of the waypoint calculation process will be described below. Fig. 23 is a flowchart showing the operation of the waypoint calculation process. Fig. 24 is a schematic diagram showing a method for calculating a collision avoidance end point.

[0073] 23, first, the avoidance course calculation unit 206 executes an end point bearing calculation process to calculate two end points of the DAC corresponding to the other ship 2 that is the object of avoidance (S601), and then executes an area setting process to set an infringement area and a non-infringement area for the search area SA (S602). The end point bearing calculation process and the area setting process will be described in detail later.

[0074] Next, as shown in Fig. 24, the avoidance course calculation unit 206 calculates two avoidance end points for each DAC corresponding to the other ship 2 that is the target of avoidance, based on the two endpoints calculated by the endpoint direction calculation process (S603). Here, the avoidance end point is calculated as a position moved forward from the current position TS of the target ship 1, which is the starting point, on a course that passes through the endpoints of the DAC. Examples of the amount of movement relative to the endpoints include a preset distance, and the distance that the target ship 1 will travel in a preset time if its speed is constant.

[0075] After calculating the collision avoidance end point, the collision avoidance course calculation unit 206 selects one of the unselected collision avoidance end points (S604), and determines whether the selected collision avoidance end point is within the area set as a non-infringement area by the area setting process (S605).

[0076] If the collision avoidance end point is within the non-infringement area (S605, YES), the collision avoidance course calculation unit 206 registers the selected collision avoidance end point as a candidate waypoint (S606), and determines whether or not there is an unselected collision avoidance end point (S607).

[0077] If there is no unselected avoidance end point (S607, NO), the waypoint calculation process is terminated.

[0078] On the other hand, if there is an unselected collision avoidance end point (S607, YES), the collision avoidance course calculation unit 206 again selects one unselected collision avoidance end point (S604).

[0079] Furthermore, in step S605, if the collision avoidance end point is not within the non-infringement area (S605, NO), the collision avoidance course calculation unit 206 selects one unselected collision avoidance end point (S604).

[0080] (End point direction calculation process) The operation of the end point bearing calculation process will be described. Figure 25 is a flowchart showing the operation of the end point bearing calculation process. Figure 26 is a schematic diagram showing two end points and the nearest point. Figures 27 and 28 are schematic diagrams showing the transition of the start bearing end point and the end bearing end point when component points are selected clockwise and counterclockwise, respectively. Figures 29 and 30 are schematic diagrams showing two end points calculated for DACs located in front and behind the target ship, respectively. Figures 31 and 32 are schematic diagrams showing DACs surrounding the target ship in which component points are selected clockwise and counterclockwise, respectively. Note that the end point bearing calculation process shown in Figure 25 is executed for each DAC corresponding to another ship that is the target of avoidance.

[0081] 25, the avoidance course calculation unit 206 initializes parameters used in the end point direction calculation process (S701). Here, the parameters to be initialized are pnt_azim[], stt_azim, end_azim, idx_stt, idx_end, last_azim, and i.

[0082] pnt_azim[] is an array indicating the orientation of each of the component points in the DAC around the current position TS of the target ship 1, and point[0].orientation is assigned as the initial value to ptn.azim[0]. point[] is an array whose elements contain objects representing the component points of the closed space drawn in one stroke in the DAC, and ".orientation" is a property indicating the orientation of the component point. In the array used in the endpoint orientation calculation process, numbers assigned to each component point of the DAC, as shown in Figure 26, are used as indexes to specify each component point, which is an element of the array and an object. point[0] is the start point and end point of the DAC. Note that point[0] indicates the component point indicated by the maximum index in the DAC for which the endpoint is to be calculated; in the example DAC shown in Figure 26, it indicates the same component point as point

[16] . Furthermore, the indexes specifying the component points are assigned so that the numerical value increases clockwise. Therefore, each component point of the DAC is processed clockwise sequentially for each processing cycle of the endpoint orientation calculation process according to this embodiment.

[0083] Please note that in the following explanation, the term "clockwise" used when referring to the processing order of component points is different from the term "clockwise" used when referring to the range in which the DAC surrounds the target ship 1 in the rotation range centered on the target ship 1. Furthermore, the "starting heading" indicates the heading around the target ship 1 of the component point that forms the end point of the DAC where the DAC begins to surround the target ship 1, and the "ending heading" indicates the heading around the target ship 1 of the component point that forms the end point of the DAC where the DAC ends to surround the target ship 1. The angular range from the starting heading to the ending heading indicates the course range in which the DAC exists.

[0084] stt_azim is a variable indicating the start azimuth of DAC, and end_azim is a variable indicating the end azimuth of DAC. pnt_azim[0] is substituted for stt_azim and end_azim as their initial values.

[0085] idx_stt is a variable indicating the number of the component point in the start direction, and idx_end is a variable indicating the number of the component point in the end direction. 0 is assigned to idx_stt and idx_end.

[0086] last_azim is a variable that stores the azimuth of the component point processed in the previous cycle, and is initially set to pnt_azim[0]. i is a variable used as an iterator that sequentially specifies each element of the array, and is initially set to 1.

[0087] After initializing the parameters, the avoidance course calculation unit 206 determines the nearest point among the constituent points of the DAC that has the smallest distance from the position TS of the target ship 1 by sequentially comparing the distance between the position TS and each constituent point, and calculates the distance between this nearest point and the position TS as the nearest distance (S702).

[0088] Next, the avoidance course calculation unit 206 stores point[i].direction in now_azim, which is a variable for storing the direction of the constituent point to be processed in the current cycle (S703), and determines whether now_azim is a direction between stt_azim and end_azim (S704). This determination is made to skip the comparison process of the direction of the constituent point so that the start direction is not updated when the direction of the constituent point to be processed in the current cycle is within the range from the start direction to the end direction and has transitioned in the opposite direction to the transition direction of the constituent point processed in the previous cycle.

[0089] If now_azim is not a heading between stt_azim and end_azim (S704, NO), the avoidance course calculation unit 206 determines whether or not now_azim>last_azim (S705).

[0090] If now_azim>last_azim (S705, YES), that is, if point[i] is transitioning clockwise, the avoidance course calculation unit 206 determines whether now_azim>end_azim (S706).

[0091] If now_azim>end_azim (S706, YES), the avoidance course calculation unit 206 assigns now_azim to end_azim and i to idx_end (S707), assigns i+1 to i and now_azim to last_azim (S708), and determines whether i≧total number of component points−1 (S709).

[0092] If i≧total number of component points−1 (S709, YES), the avoidance course calculation unit 206 determines whether pnt_azim[0]>last_azim and pnt_azim[0]=stt_azim (S710).

[0093] When pnt_azim[0] > last_azim and pnt_azim[0] = stt_azim (S710, YES), the avoidance course calculation unit 206 substitutes pnt_azim[0] into end_azim and substitutes 0 into idx_end (S711), and the end point azimuth calculation process ends. Here, when the constituent point at the end azimuth has made a full circle clockwise, as shown in FIG. 31, since the DAC surrounds the target ship 1 over the entire circumference, the avoidance course calculation unit 206 makes the constituent point at the start azimuth and the constituent point at the end azimuth the same. At this time, in the rotation range centered on the target ship 1, since the range in which the DAC surrounds the target ship 1 is 360°, the start azimuth and the end azimuth can be any constituent point.

[0094] On the other hand, when pnt_azim[0] > last_azim and pnt_azim[0] ≠ stt_azim (S710, NO), the avoidance course calculation unit 206 determines whether pnt_azim[0] < last_azim and pnt_azim[0] = end_azim (S712).

[0095] When pnt_azim[0] < last_azim and pnt_azim[0] = end_azim (S712, YES), the avoidance course calculation unit 206 substitutes pnt_azim[0] into stt_azim and substitutes 0 into idx_stt (S713), and the end point azimuth calculation process ends. Here, when the constituent point at the start azimuth has made a full circle counterclockwise, as shown in FIG. 32, since the DAC surrounds the target ship 1 over the entire circumference, the avoidance course calculation unit 206 makes the constituent point at the start azimuth and the constituent point at the end azimuth the same.

[0096] On the other hand, when pnt_azim[0] < last_azim and pnt_azim[0] ≠ end_azim (S712, NO), the end point azimuth calculation process ends.

[0097] Also, in step S709, if i ≠ total number of configuration points - 1 (S709, NO), the evasion course calculation unit 206 stores point[i].azimuth in now_azim, which is a variable for storing the azimuth of the configuration point to be processed in the current cycle, again (S703).

[0098] Also, in step S706, if now_azim > end_azim is not true (S706, NO), the evasion course calculation unit 206 substitutes i + 1 for i and substitutes now_azim for last_azim (S708).

[0099] Also, in step S705, if now_azim > last_azim is not true (S705, NO), that is, if point[i] has transitioned counterclockwise, the evasion course calculation unit 206 determines whether now_azim < stt_azim (S714).

[0100] If now_azim < stt_azim (S714, YES), the evasion course calculation unit 206 substitutes now_azim for stt_azim and substitutes i for idx_stt (S715), substitutes i + 1 for i and substitutes now_azim for last_azim (S708).

[0101] On the other hand, if now_azim < stt_azim is not true (S714, NO), the evasion course calculation unit 206 substitutes i + 1 for i and substitutes now_azim for last_azim (S708).

[0102] <​​​​According to this type of end point bearing calculation process, it is possible to calculate the nearest distance and the bearings of the two end points, that is, the start bearing and end bearing, for the DAC of interest, as shown in Figure 26. Furthermore, according to the end point bearing calculation process of this embodiment, the value of the index indicating the constituent point increases clockwise, so the end point having the start bearing and the end point having the end bearing transition as shown in Figure 27. The value of the index indicating the constituent point may also increase counterclockwise, in which case the two end points transition as shown in Figure 28. According to the end point bearing calculation process, it is possible to calculate the start bearing and end bearing not only for the DAC located forward of the target ship 1 as shown in Figure 29, but also for the DAC located aft of the target ship 1 as shown in Figure 30, and for the DACs that completely surround the target ship 1 as shown in Figures 31 and 32.

[0104] (Area determination processing) The operation of the area determination process will be described. Fig. 33 is a flowchart showing the operation of the area determination process. Fig. 34 is a schematic diagram showing an infringement area, a non-infringement area, and a non-infringement area candidate. Fig. 35 is a schematic diagram showing an infringement area, a non-infringement area, and a non-infringement area candidate using Cartesian coordinates.

[0105] As shown in Figure 33, first, the avoidance course calculation unit 206 sorts the DACs within the search area, i.e., all DACs corresponding to other ships 2 registered as avoidance targets, in order of shortest nearest distance calculated by the end point direction calculation process (S801), selects unselected DACs in ascending order (S802), and determines whether the nearest distance of the selected DAC is equal to or greater than a preset distance threshold (S803).

[0106] If the nearest distance is equal to or greater than the preset distance threshold (S803, YES), the avoidance course calculation unit 206 determines a fan-shaped area having a course range from the start heading to the end heading calculated for the selected DAC and with a radius equal to the nearest distance as a non-infringement area candidate (S804), and determines whether an inner DAC exists (S805). Here, the inner DAC is a DAC whose nearest distance is smaller than that of the selected DAC and whose course range overlaps.

[0107] If an inner DAC exists (S805, YES), the avoidance course calculation unit 206 executes a course range update process to update the course range of the non-infringement area candidate corresponding to the selected DAC (S806), registers the updated non-infringement area candidate as a non-infringement area (S807), and determines whether or not an unselected DAC exists (S808).

[0108] If there is no unselected DAC (S808, NO), the avoidance course calculation unit 206 registers, if there is a course range in the search area where no DAC exists, this course range as a non-infringement area (S809), and the area determination process is terminated.

[0109] On the other hand, if there is an unselected DAC (S808, YES), the avoidance course calculation unit 206 selects an unselected DAC again (S802).

[0110] Furthermore, in step S805, if there is no inside DAC (S805, NO), the avoidance course calculation unit 206 registers the non-infringement area candidate corresponding to the selected DAC as a non-infringement area (S807).

[0111] Also, in step S803, if the nearest distance is less than the distance threshold (S803, NO), the avoidance course calculation unit 206 determines that the course range from the start heading to the end heading calculated for the selected DAC is an infringement area over the entire radial range of the search area (S810), and determines whether or not there is an unselected DAC (S808).

[0112] According to this area determination process, as shown in Figures 34 and 35, the search area SA can be divided into non-infringement areas that are unlikely to infringe on other ships 2 and infringement areas that are likely to infringe on other ships 2 based on the starting direction, ending direction, and nearest point of the DAC.

[0113] (Course range update processing) The operation of the course range update process will now be described. Fig. 36 is a flowchart showing the operation of the course range update process. Figs. 37 to 41 are schematic diagrams showing the course ranges when the first to fifth conditions are satisfied, respectively.

[0114] 36, first, the avoidance course calculation unit 206 selects an unselected inner DAC (S901), and determines whether or not the selected DAC and the inner DAC satisfy a first condition (S902), which will be described later. Here, the selected DAC refers to the DAC selected in the above-mentioned area determination processing, and in the following description of the course range update processing, it will be referred to as the DAC of interest to distinguish it from the inner DAC.

[0115] If the DAC of interest and the inner DAC do not satisfy the first condition (S902, NO), the avoidance course calculation unit 206 determines whether the DAC of interest and the inner DAC satisfy a second condition, which will be described later (S903).

[0116] If the DAC of interest and the inner DAC do not satisfy the second condition (S903, NO), the avoidance course calculation unit 206 determines whether the DAC of interest and the inner DAC satisfy a third condition, which will be described later (S904).

[0117] If the inner DAC of interest and the side DAC do not satisfy the third condition (S904, NO), the avoidance course calculation unit 206 determines whether the DAC of interest and the inner DAC satisfy a fourth condition, which will be described later (S905).

[0118] If the DAC of interest and the inner DAC do not satisfy the fourth condition (S905, NO), the avoidance course calculation unit 206 determines whether the DAC of interest and the inner DAC satisfy a fifth condition, which will be described later (S906).

[0119] If the DAC of interest and the inside DAC do not satisfy the fifth condition (S906, NO), the avoidance course calculation unit 206 determines whether or not there is an unselected inside DAC (S907).

[0120] If there is no unselected inside DAC (S907, NO), the course range update process is terminated.

[0121] On the other hand, if there is an unselected inside DAC (S907, YES), the avoidance course calculation unit 206 selects an unselected inside DAC again (S901).

[0122] In step S902, if the DAC of interest and the inner DAC satisfy the first condition (S902, YES), the avoidance course calculation unit 206 determines whether or not there is an unselected inner DAC (S907). As shown in FIG. 37, the first condition is (end heading of inner DAC≦start heading of DAC of interest) OR (end heading of DAC of interest≦start heading of inner DAC). Here, OR is a logical sum operator. In this case, the course ranges of the DAC of interest and the inner DAC do not overlap, so the non-infringement area candidate based on the DAC of interest is not updated.

[0123] In step S903, if the DAC of interest and the inner DAC satisfy the second condition (S903, YES), the avoidance course calculation unit 206 updates the non-violation area candidate (S908) and determines whether or not there is an unselected inner DAC (S907). As shown in FIG. 38, the second condition is (starting heading of the inner DAC≦starting heading of the DAC of interest) AND (starting heading of the DAC of interest≦ending heading of the inner DAC≦ending heading of the DAC of interest). Here, AND is a logical product operator. If the second condition is satisfied, that is, if the course ranges of the DAC of interest and the inner DAC overlap on the starting heading side, the avoidance course calculation unit 206 updates the non-violation area candidate based on the DAC of interest so as to replace the starting heading of the DAC of interest with the ending heading of the inner DAC.

[0124] In step S904, if the DAC of interest and the inner DAC satisfy the third condition (S904, YES), the avoidance course calculation unit 206 updates the non-violation area candidate (S909) and determines whether any unselected inner DACs exist (S907). The third condition, as shown in FIG. 39, is (starting heading of inner DAC≦starting heading of DAC of interest) AND (ending heading of DAC of interest≦ending heading of inner DAC). If the third condition is satisfied, that is, if the course range of the DAC of interest is included in the course range of the inner DAC, the starting heading and ending heading of the DAC of interest are cleared, and the non-violation area candidate is essentially eliminated. In this case, in step S807 of the area determination processing, the non-violation area candidate is not registered as a non-violation area.

[0125] In step S905, if the DAC of interest and the inner DAC satisfy the fourth condition (S905, YES), the avoidance course calculation unit 206 updates the non-violation area candidate (S910) and determines whether or not there is an unselected inner DAC (S907). The fourth condition, as shown in Figure 40, is (starting heading of the DAC of interest ≦ starting heading of the inner DAC ≦ ending heading of the DAC of interest) AND (ending heading of the DAC of interest ≦ ending heading of the inner DAC). If the fourth condition is satisfied, that is, if the course ranges of the DAC of interest and the inner DAC overlap on the ending heading side, the avoidance course calculation unit 206 updates the non-violation area candidate of the DAC of interest so as to replace the ending heading of the DAC of interest with the starting heading of the inner DAC.

[0126] In step S906, if the DAC of interest and the inner DAC satisfy the fifth condition (S906, YES), the avoidance course calculation unit 206 updates the non-infringement area candidate (S911) and determines whether or not there is an unselected inner DAC (S907). The fifth condition is, as shown in FIG. 41 , (starting heading of the DAC of interest≦starting heading of the inner DAC≦ending heading of the DAC of interest) AND (starting heading of the DAC of interest≦ending heading of the inner DAC≦ending heading of the DAC of interest). If the fifth condition is satisfied, that is, if the course range of the DAC of interest encompasses the course range of the inner DAC, the avoidance course calculation unit 206 divides the course range of the non-infringement area candidate into two and updates the non-infringement area candidate so that the first course range is from the starting heading of the DAC of interest to the starting heading of the inner DAC, and the second course range is from the ending heading of the inner DAC to the ending heading of the DAC of interest.

[0127] According to this course range update process, as shown in FIGS. 34 and 35, the course range of the non-infringement area candidate is updated so as to exclude the course range of the inner DAC that overlaps with the course range of the DAC of interest.

[0128] (Ranking determination process) The operation of the ranking determination process will be described below. Fig. 42 is a flowchart showing the operation of the ranking determination process. Fig. 43 is a schematic diagram showing weighting based on user selection.

[0129] As shown in FIG. 42, the course display unit 207 determines whether or not there are any candidate waypoints (S1001).

[0130] If a candidate waypoint exists (S1001, YES), the course display unit 207 sorts the candidate avoidance routes in ascending order of deviation distance from the planned route (S1002), and determines whether a candidate avoidance route with the same deviation distance exists (S1003).

[0131] If there are candidate avoidance routes with the same departure distance (S1003, YES), the course display unit 207 sorts the candidate avoidance routes in order of proximity to the reference course (S1004), and determines whether diversity is set (S1005). Note that in step S1004, if the candidate avoidance route has two or more waypoints, i.e., if it is not an avoidance course, the candidate avoidance routes are sorted based on a comparison between the reference course and the first course in the candidate avoidance routes.

[0132] If diversity setting has been made (S1005, YES), the course display unit 207 classifies the avoidance route candidates into three types of categories (S1006), and the ranking process is terminated. Here, the three types of categories are straight ahead, turning starboard, and turning left. Straight ahead is a category that includes avoidance route candidates whose angular difference from the reference course is within a preset angle range. Turning starboard is a category that includes avoidance route candidates that turn to the right of the reference course and are outside the angle range. Turning left is a category that includes avoidance route candidates that turn to the left of the reference course and are outside the angle range. For each of these three types of categories, the highest-ranked avoidance route candidate is displayed in step S110 of the overall operation.

[0133] On the other hand, if diversity setting has not been made (S1005, NO), the ranking determination process is ended. In this case, the top three candidate avoidance routes are displayed in ascending order in step S110.

[0134] Furthermore, in step S1003, if there is no candidate avoidance route with the same departure distance (S1003, NO), the course display unit 207 determines whether or not diversity setting has been made (S1005).

[0135] Furthermore, in step S1001, if no waypoint candidate exists (S1001, NO), a condition relaxation process is executed, and the ranking process is terminated. This condition relaxation process is a process in which the conditions related to the calculation are relaxed so that more waypoint candidates can be calculated, and the overall operation is executed again. Examples of conditions that can be relaxed in the condition relaxation process include reducing the size of the safe passage area based on DAC, reducing the search area, etc.

[0136] According to such ranking determination processing, candidate avoidance routes that are closer to the reference course are displayed. Note that, as shown in Fig. 43, the ranking of candidate avoidance routes may be determined based on trends analyzed from a compilation of the user's past selection histories of candidate avoidance routes.

[0137] (Variation) The calculation of the collision avoidance end point according to the modified examples will now be described. Figures 44 to 48 are schematic diagrams showing collision avoidance end points according to the first to fifth modified examples, respectively.

[0138] In the above-described embodiment, the avoidance course calculation unit 206 calculated the avoidance end point as a position that is further forward than the end point of the DAC on a course that passes through this end point, but the avoidance course processing unit 206 in the modified example calculates the avoidance end point that is located further outward from the end point of the DAC in the circumferential direction centered on the position of the target ship TS.

[0139] The avoidance course calculation unit 206 according to the first modified example calculates an avoidance end point that is located on a virtual line that passes through the end point and faces the true vector direction of the other ship 2 corresponding to the DAC, and that is located on the outer side of the DAC, as shown in FIG.

[0140] The avoidance course calculation section 206 according to the second modified example calculates an avoidance end point that is located on an imaginary line passing through both end points and is located outward of the DAC, as shown in FIG.

[0141] The avoidance course calculation unit 206 according to the third modified example calculates an avoidance end point that is located on each of an imaginary line passing through the position of the center of gravity of the DAC and one end point, and an imaginary line passing through the position of the center of gravity of the DAC and the other end point, and that is located on the outward side of the DAC, as shown in Fig. 46. In this case, the distance between an end point and the corresponding avoidance end point is calculated by multiplying the distance between the end point and the position of the center of gravity by a coefficient that is greater than 0 and less than 1.

[0142] The avoidance course calculation unit 206 in the fourth variant calculates an avoidance end point located on the circumference of a perfect circle centered on the position of the target ship TS and passing through both end points, and located on the outer side of the DAC, as shown in Figure 47.

[0143] The avoidance course calculation unit 206 according to the fifth modified example calculates an avoidance end point located on the outer side of the DAC in a direction perpendicular to the imaginary lines connecting the target ship TS and each of the end points, as shown in FIG.

[0144] In this way, the avoidance course calculation unit 206 according to the modified example calculates a position that is spaced from the DAC circumferentially outward of the end point as the avoidance end point.

[0145] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included within the scope and spirit of the invention, and are also included in the inventions described in the claims and their equivalents. [Explanation of symbols]

[0146] 10 Navigation aids 202 Information Acquisition Department 205 Registration Department 206 Collision avoidance course calculation unit

Claims

1. A ship navigation support device that calculates an avoidance course for a target ship and provides navigation support, an information acquisition unit that acquires target ship information indicating the position of the target ship; an avoidance course calculation unit that calculates a course range of the first collision risk area around the position of the target ship shown in the target ship information, with respect to a first collision risk area that indicates an area where there is a risk of collision between the target ship and a first other ship using a polygonal shape formed by connecting a plurality of constituent points, and calculates, as avoidance course candidates for the target ship, a constituent point at the start heading of the course range or a starting heading course that passes through the outer side of the first collision risk area around the position of the target ship from said constituent point, and a constituent point at the end heading of the course range or a ending heading course that passes through the outer side of the first collision risk area around the position of the target ship from said constituent point; A ship navigation aid device comprising:

2. a registration unit that registers other ships corresponding to a collision risk area that at least partially overlaps within a search area extending forward of the target ship as a target to be avoided; The vessel navigation support device according to claim 1 , wherein the avoidance course calculation unit calculates the possible avoidance courses based on a collision risk area corresponding to the target to be avoided.

3. The vessel navigation support device described in claim 2, characterized in that the escape route calculation unit determines, in the search area, an area that does not overlap with the route range of a second collision risk area, which indicates an area where there is a risk of collision between the target vessel and a second other vessel, as a non-violation area, and calculates an escape route within the non-violation area as the escape route candidate.

4. The vessel navigation support device according to claim 3, characterized in that the avoidance course calculation unit determines the course range of the second collision risk area to be a non-infringement area when the second collision risk area is located at a distance greater than a predetermined distance threshold from the target vessel.

5. The ship navigation support device described in claim 4, characterized in that the avoidance course calculation unit indicates an area where there is a risk of collision between the target ship and a third other ship, and if there is a third collision risk area that is closer to the target ship than the second collision risk area, the course range that excludes the course range of the third collision risk area from the course range of the second collision risk area is set as a non-violation area.

6. The vessel navigation support device according to any one of claims 1 to 5, characterized in that the avoidance course calculation unit sets the end point of the start heading course to a position that is a predetermined distance away in the forward direction from a constituent point at the start heading along the start heading course, and sets the end point of the end heading course to a position that is a predetermined distance away in the forward direction from a constituent point at the end heading along the end heading course.

7. A ship navigation support device as described in any one of claims 1 to 5, characterized in that the avoidance course calculation unit calculates as candidate avoidance courses for the target ship a starting heading course that passes around the position of the target ship on the outer side of the first collision risk area relative to a constituent point at the starting heading of the course range, and an ending heading course that passes around the position of the target ship on the outer side of the first collision risk area relative to a constituent point at the ending heading of the course range.

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