Radar signal processing device, radar signal processing program, radar image display device, and autonomous navigation device

Abstract

This disclosure aims to determine whether to appropriately enhance target signals of ships, etc., when using radar images or sonar images to facilitate navigation decisions by crew members, regardless of frequency band, antenna length, or mounting position. [Solution] This disclosure acquires radar images before clutter suppression from multiple radar transceivers A-1, A-2 having the same or different frequency bands or antenna lengths. Then, among the radar images after target signal extraction, if there are target signals that are not displayed in one radar image after target signal extraction, unlike in other radar images after target signal extraction, the clutter suppression parameters are feedback controlled so that the previously undisplayed target signals are displayed again in the radar image after target signal extraction.

Description

Technical Field

[0001] The present disclosure relates to a technology for autonomous navigation using radar images.

Background Art

[0002] There has conventionally been a technology for autonomous navigation of ships and the like using radar images or sonar images. By performing autonomous navigation of ships and the like, the safety of ships and the like can be improved, and the shortage of crew and the like can be eliminated. On the other hand, by passing through the navigation judgment of crew and the like, obstacles of ships and the like can be avoided in areas such as straits where ships are congested.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By controlling the clutter suppression parameters such as waves or rain and snow and using a radar image that emphasizes the target signal of a ship or the like when passing through the navigation judgment of crew and the like, stable target display can be performed regardless of the skills of crew and the like.

[0005] Here, in Patent Document 1, a radar image that emphasizes the target signal of a ship or the like is displayed after controlling the clutter suppression parameters such as waves or rain and snow for the sensor signal of one system of radar devices. However, one system of radar devices has advantages or disadvantages in terms of resolution, maximum distance, or visible area depending on the frequency band, antenna length, or mounting position. Therefore, it has not been possible to clearly determine whether or not the target signal of a ship or the like is appropriately emphasized when passing through the navigation judgment of crew and the like in one system of radar images.

[0006] Therefore, in order to solve the aforementioned problems, this disclosure aims to determine whether to appropriately enhance the target signal of a ship or the like when using radar images or sonar images to make navigation decisions with the crew or others, regardless of the frequency band, antenna length, or mounting position. [Means for solving the problem]

[0007] To address the aforementioned issues, and in preparation for navigation decisions made by crew members or others, radar images after target signal extraction are output for multiple radar devices (with identical or different frequency bands or antenna lengths; their mounting positions will inevitably differ) that have the same or different frequency bands or antenna lengths.

[0008] Here, multiple radar systems compensate for each other's shortcomings in terms of resolution, maximum range, or visible area, depending on the frequency band, antenna length, or mounting position. Therefore, when there are target signals that are not displayed in one radar image, unlike in the other, the clutter suppression parameters are feedback-controlled so that the previously undisplayed target signals are redisplayed in the radar image of the other.

[0009] Specifically, the present disclosure is a radar signal processing device characterized by comprising: a radar image acquisition unit that acquires radar images before clutter suppression from a plurality of radar transceivers having the same or different frequency bands or antenna lengths; a target signal extraction unit that extracts both or one of the target signals and land signals from each of the radar images before clutter suppression, suppresses both or one of the wave clutter and rain / snow clutter, and outputs each radar image after target signal extraction; and a radar image comparison unit that, when there is a target signal that is not displayed in one of the radar images after target signal extraction, unlike in other radar images after target signal extraction, feedback-controls the suppression parameters of both or one of the wave clutter and rain / snow clutter so that the undisplayed target signal is displayed again in the radar image after target signal extraction.

[0010] With this configuration, when sailors make navigation decisions using radar or sonar images, it is possible to determine whether to appropriately enhance the target signal of a ship or other object, regardless of the frequency band, antenna length, or mounting position. If it is determined that the target signal of a ship or other object is not appropriately enhanced, the target signal of the ship or other object can be displayed again.

[0011] Furthermore, this disclosure relates to a radar signal processing device characterized in that the radar image comparison unit provides feedback control to the suppression parameters of both or one of the wave clutter and the rain / snow clutter so that, in a radar image after the extraction of a target signal, the suppression of both or one of the wave clutter and the rain / snow clutter is weakened so that the target signal that was not displayed is displayed again.

[0012] With this configuration, when sailors or other personnel make navigation decisions using radar or sonar images, if it is determined that the clutter is being excessively suppressed and therefore the target signals of ships or other objects are not being properly emphasized, the target signals of ships or other objects can be displayed again.

[0013] Furthermore, this disclosure relates to a radar signal processing device characterized in that the target signal extraction unit outputs a radar image after the extraction of each target signal based on either or both of the target information and land information acquired from an external source.

[0014] With this configuration, when navigation decisions are made by crew members or others using radar or sonar images, the control method for clutter suppression parameters can be adjusted based on target information and land information (highly reliable information not obtained from radar) acquired from external sources.

[0015] Furthermore, this disclosure relates to a radar signal processing device characterized in that the target signal extraction unit feedback-controls the suppression parameters of both or one of the wave clutter and rain / snow clutter based on the degree of agreement between each radar image after target signal extraction (current or past radar image) and information of both or one of the target information and the land information (the current or past information).

[0016] With this configuration, when navigation decisions are made by crew members or others using radar or sonar images, the control method for clutter suppression parameters can be feedback-controlled based on current target information and land information (highly reliable information acquired externally) or past target information and land information (even more reliable information verified afterward).

[0017] Furthermore, this disclosure is a radar signal processing program that causes a computer to execute each processing step performed by each processing unit of the radar signal processing device described above.

[0018] This configuration makes it possible to provide a program that has the effects described above.

[0019] In addition, the present disclosure is a radar video display device that separately displays each of the radar videos after target signal extraction output by the radar signal processing device described above.

[0020] According to this configuration, a video display device having the effects described above can be provided.

[0021] In addition, the present disclosure is an autonomous navigation device that performs autonomous navigation using each of the radar videos after target signal extraction output by the radar signal processing device described above.

[0022] According to this configuration, an autonomous navigation device having the effects described above can be provided.

[0023] Note that the inventions of the above disclosures can be combined as much as possible.

Effects of the Invention

[0024] As described above, the present disclosure can determine whether to appropriately emphasize target signals of ships, etc., regardless of the frequency band, antenna length, or mounting position, when using radar video or sonar video and passing through the navigation judgment of crew members, etc.

Brief Description of the Drawings

[0025] [Figure 1] It is a diagram showing the configuration of the radar system of the present disclosure. [Figure 2] It is a diagram showing the procedure of the target signal extraction process of the present disclosure. [Figure 3] It is a diagram showing a specific example of the target signal extraction process of the present disclosure. [Figure 4] It is a diagram showing the procedure of the radar video comparison process of the present disclosure. [Figure 5] It is a diagram showing a specific example of the radar video comparison process of the present disclosure. [Figure 6] It is a diagram showing a specific example of the radar video comparison process of the present disclosure. [Figure 7] ​ [Modes for carrying out the invention]

[0026] Embodiments of the present disclosure will be described with reference to the attached drawings. The embodiments described below are examples of the implementation of the present disclosure, and the present disclosure is not limited to these embodiments.

[0027] (Configuration of the radar system in this disclosure) The configuration of the radar system of this disclosure is shown in Figure 1. The radar system R comprises radar transceivers A-1 and A-2, a target information acquisition device T, a radar signal processing device S, a radar image display device D, and an autonomous navigation device N. The radar signal processing device S comprises target signal extraction units 1-1 and 1-2 and a radar image comparison unit 2, and can be implemented by installing the radar signal processing program shown in Figures 2 and 4 onto a computer.

[0028] As shown in Figures 4-6, in preparation for navigation decisions made by crew members or others, multiple radar transceivers (mounted in different locations) with the same or different frequency bands or antenna lengths output radar images after target signal extraction from each device.

[0029] Here, multiple radar transceivers compensate for each other's shortcomings in terms of resolution, maximum distance, or visible area, depending on the frequency band, antenna length, or mounting position. Therefore, when there are target signals that are not displayed in one radar image, unlike in the other, the clutter suppression parameters are feedback-controlled so that the previously undisplayed target signals are displayed again in the radar image of the other.

[0030] (Procedure for target signal extraction processing as described herein) Figure 2 shows the procedure for the target signal extraction process of this disclosure. Figure 3 shows a specific example of the target signal extraction process of this disclosure. Radar transceivers A-1 and A-2 transmit an illumination radar signal and receive a reflected radar signal. Target information acquisition device T acquires either or both of the following information from an external source: target information (AIS information and buoy information, etc.) and land information. However, for small boats, yachts, and fallen objects, etc., target information acquisition device T cannot acquire information, and radar transceivers A-1 and A-2 can acquire images.

[0031] The radar signal processing device S acquires pre-clutter suppression radar images from multiple radar transceivers A-1 and A-2 (which are necessarily mounted in different locations) that have the same or different frequency bands or antenna lengths (step S1). Here, the multiple radar transceivers A-1 and A-2 compensate for each other's shortcomings with the advantages of the other in terms of resolution, maximum distance, or visible area, depending on the frequency band, antenna length, or mounting location.

[0032] The target signal extraction units 1-1 and 1-2 extract both or one of the target signal and land signal from the radar images obtained from each of the multiple radar transceivers A-1 and A-2 before clutter suppression, based on both or one of the target information and land information acquired from an external source, suppress both or one of the wave clutter and rain / snow clutter, and output the radar image after the target signal extraction (step S2).

[0033] In other words, the target signal extraction units 1-1 and 1-2 control the wave clutter and rain / snow clutter suppression parameters for each pre-clutter suppression radar image in such a way that target signals and land signals are not suppressed at the target and land positions included in the target and land information, and that wave clutter and rain / snow clutter are suppressed.

[0034] In the left column of Figure 3, in each radar image before clutter suppression, land signals are not obscured by wave clutter and rain / snow clutter, while target signals are obscured by wave clutter and rain / snow clutter. In the middle column of Figure 3, in each radar image during clutter suppression, target information (AIS information and floating marker information, etc.) includes target locations, and land information includes land locations. In the right column of Figure 3, in each radar image after target signal extraction, land signals are not obscured by wave clutter and rain / snow clutter, and target signals (including small boats, yachts, and fallen objects, etc.) are also not obscured by wave clutter and rain / snow clutter.

[0035] The target signal extraction units 1-1 and 1-2 provide feedback control to suppress both or one of the wave clutter and rain / snow clutter based on the degree of agreement between the radar image after target signal extraction (current or past radar image) and the information (current or past) of either the target information or the land information. (Steps S3 to S5)

[0036] In other words, the target signal extraction units 1-1 and 1-2 determine the degree of agreement between the radar image after target signal extraction and the target information and land information (step S3). Then, if the degree of agreement is low (step S4, NO), the target signal extraction units 1-1 and 1-2 perform feedback control of the suppression parameters for wave clutter and rain / snow clutter (step S5, right column of Figure 3) and return to step S3. On the other hand, if the degree of agreement is high (step S4, YES), the target signal extraction units 1-1 and 1-2 finish the feedback control of the suppression parameters for wave clutter and rain / snow clutter (right column of Figure 3) and proceed to step S6.

[0037] Here, the target signal extraction units 1-1 and 1-2 can precisely feedback control the suppression parameters for wave clutter and rain / snow clutter in the present when determining the degree of agreement between the radar image after extraction of each target signal in the present and the current target information and land information (highly reliable information acquired externally).

[0038] Furthermore, when the target signal extraction units 1-1 and 1-2 determine the degree of agreement between the radar images after the extraction of each target signal from the "past" and the target information and land information from the "past" (more reliable information verified afterward), they can provide even more precise feedback control of the suppression parameters for wave clutter and rain / snow clutter in the "present".

[0039] The target signal extraction units 1-1 and 1-2 output the radar images after target signal extraction (after coordinate transformation, coordinate rotation, and range adjustment, etc., but before radar image comparison and before recontrol of suppression parameters) to the radar image comparison unit 2 (step S6).

[0040] In this way, when navigation decisions are made by crew members using radar or sonar images, the control method for clutter suppression parameters can be adjusted based on target information and land information acquired from external sources (highly reliable information not obtained by radar). Furthermore, the control method for clutter suppression parameters can be feedback-controlled based on current target information and land information (highly reliable information acquired from external sources) or past target information and land information (even more reliable information verified afterward).

[0041] As a variation, the target signal extraction units 1-1 and 1-2 may output radar images after target signal extraction using CFAR processing or STC processing, etc., without relying on either or both of the target information and land information acquired from an external source.

[0042] (Procedure for radar image comparison processing as disclosed herein) The procedure for the radar image comparison processing of this disclosure is shown in Figure 4. Specific examples of the radar image comparison processing of this disclosure are shown in Figures 5 and 6. The radar signal processing device S acquires pre-clutter suppression radar images from a plurality of radar transceivers A-1 and A-2 (mounting positions are necessarily different) that have the same or different frequency bands or antenna lengths (step S1). Here, the plurality of radar transceivers A-1 and A-2 compensate for each other's shortcomings with the advantages of the other in terms of resolution, maximum distance, or visible area, depending on the frequency band, antenna length, or mounting position. The advantages and disadvantages of resolution, maximum distance, or visible area are described below.

[0043] Firstly, the higher the frequency band (e.g., X-band), the higher the distance and azimuthal resolution, but the shorter the maximum distance corresponding to the amount of water vapor. On the other hand, the lower the frequency band (e.g., S-band), the longer the maximum distance corresponding to the amount of water vapor, but the lower the distance and azimuthal resolution.

[0044] Next, the longer the antenna length, the higher the azimuth resolution, but the lower the antenna rotation rate. Furthermore, the lower the antenna rotation rate, the lower the frequency of radar image updates, but the higher the number of hits (number of radar irradiations) per target. On the other hand, the shorter the antenna length, the lower the azimuth resolution, but the higher the antenna rotation rate. Furthermore, the higher the antenna rotation rate, the higher the frequency of radar image updates, but the lower the number of hits (number of radar irradiations) per target.

[0045] Next, if the mounting position is not obstructed by a mast or similar structure, the target signal can be displayed in all directions. On the other hand, if the mounting position is obstructed by a mast or similar structure, the target signal will not be displayed in the direction of the obstruction. However, even in the direction of the obstruction, diffraction may occur at long distances, resulting in diffuse reflection or multipath reflection, but the target signal may still be displayed.

[0046] The radar image comparison unit 2 determines, among the radar images after target signal extraction input from multiple target signal extraction units 1-1 and 1-2, whether there are any target signals (including small boats, yachts, and fallen objects, etc.) that are not displayed in one radar image after target signal extraction, unlike in other radar images after target signal extraction (step S11).

[0047] Then, if there is a target signal that is not displayed (step S12, YES), the radar image comparison unit 2 feedback-controls the suppression parameters of both or one of the wave clutter and rain / snow clutter so that the target signal that was not displayed is displayed again in the radar image after a target signal has been extracted (step S13), and returns to step S11.

[0048] Here, the radar image comparison unit 2 provides feedback control to the suppression parameters of both or one of the wave clutter and rain / snow clutter so that the suppression of both or one of the wave clutter and rain / snow clutter is weakened in the radar image after a target signal has been extracted, so that the target signal that was not displayed is displayed again (step S13).

[0049] On the other hand, when there are no target signals that are not displayed (step S12, NO), the radar image comparison unit 2 finishes feedback control of the suppression parameters of both or one of the wave clutter and rain / snow clutter in both the radar image after extracting one target signal and the radar image after extracting another target signal, and proceeds to step S14.

[0050] In the left column of Figure 5, six target signals are displayed in the radar image after S-band or X-band target signal extraction. In the middle column of Figure 5, four target signals are displayed in the radar image after X-band or S-band target signal extraction. In the middle column of Figure 5, two target signals are not displayed compared to the left column of Figure 5, due to shortcomings in resolution or maximum range.

[0051] In the right-hand column of Figure 5, in the radar image after controlling the X-band or S-band suppression parameters, the clutter suppression parameters are reduced, weakening the clutter suppression. As a result, some clutter is displayed, but two target signals that were previously not displayed are now displayed. In other words, the disadvantage of one in terms of resolution or maximum range is compensated for by the advantage of the other.

[0052] In the left column of Figure 6, six target signals are displayed in the radar image after target signal extraction from a radar with no obstructions. In the middle column of Figure 6, five target signals are displayed in the radar image after target signal extraction from a radar with obstructions. In the middle column of Figure 6, one target signal is not displayed compared to the left column of Figure 6 due to the limitations of the visible field.

[0053] In the right column of Figure 6, in the radar image after controlling the suppression parameters of a radar with obstructions, the clutter suppression parameter is reduced, weakening the clutter suppression. As a result, some clutter is displayed, but one target signal that was previously not displayed is now displayed. In other words, in the visible region, at long distances, the disadvantage of one aspect is compensated for by the advantage of the other.

[0054] The radar image comparison unit 2 displays the radar images after each target signal extraction (after coordinate transformation, coordinate rotation, and range adjustment, etc., and after radar image comparison and recontrol of suppression parameters) on the radar image display device D (step S14).

[0055] In this way, when using radar or sonar images to make navigation decisions for crew members, it is possible to determine whether to appropriately enhance the target signals of ships, etc., regardless of the frequency band, antenna length, or mounting position. If it is determined that the target signals of ships, etc., are not appropriately enhanced, the target signals of ships, etc., can be displayed again. Furthermore, if it is determined that the target signals of ships, etc., are not appropriately enhanced due to excessive clutter suppression, the target signals of ships, etc., can be displayed again.

[0056] As a variation, the radar image comparison unit 2 may feedback control the suppression parameters of both or one of the wave clutter and rain / snow clutter so that, in the radar image after a target signal has been extracted, the suppression of both or one of the wave clutter and rain / snow clutter is "strengthened" so that the target signal that was not displayed is displayed again.

[0057] (Specific examples of autonomous navigation processing in this disclosure) A specific example of the autonomous navigation process of this disclosure is shown in Figure 7. The radar image display device D displays the radar images after each target signal has been extracted, output by the radar signal processing device S, separately (step S14). The autonomous navigation device N performs autonomous navigation using the radar images after each target signal has been extracted, output by the radar signal processing device S.

[0058] In the left column of Figure 7, in the radar images before clutter suppression, land signals are not obscured by wave clutter and rain / snow clutter, while target signals are obscured by wave clutter and rain / snow clutter. In the right column of Figure 7, in the radar images after target signal extraction, land signals are not obscured by wave clutter and rain / snow clutter, and target signals (including small boats, yachts, and fallen objects) are also not obscured by wave clutter and rain / snow clutter.

[0059] Then, the autonomous navigation system N confirms the destination of the vessel or other object and uses radar images to autonomously navigate in a direction where no target signals or land signals are displayed. In other words, the autonomous navigation system N confirms the destination of the vessel or other object and uses radar images to autonomously navigate in a way that avoids obstacles such as the vessel and land. [Industrial applicability]

[0060] The radar signal processing device and radar signal processing program of this disclosure can determine whether to appropriately enhance the target signal of a ship or the like, regardless of the frequency band, antenna length, or mounting position, when navigation decisions are made by a crew member or the like using radar images or sonar images.

[0061] The radar image display device of this disclosure can display radar images or sonar images necessary for navigation decisions made by crew members or other personnel, using these images. The autonomous navigation device of this disclosure can perform autonomous navigation of a vessel or other vehicle using the radar images or sonar images thus output. [Explanation of symbols]

[0062] R: Radar system A-1, A-2: Radar transceiver T:Target information acquisition device S: Radar signal processing device D: Radar image display device N:Autonomous navigation device 1-1, 1-2: Target signal extraction part 2: Radar Image Comparison Section

Claims

1. A radar image acquisition unit that acquires radar images from multiple radar transceivers having the same or different frequency bands or antenna lengths, before clutter suppression, A target signal extraction unit extracts both or one of the target signal and land signal from each of the radar images before clutter suppression, suppresses both or one of the wave clutter and rain / snow clutter, and outputs the radar image after the target signal extraction for each; A radar image comparison unit provides feedback control of the suppression parameters of both or one of the wave clutter and rain / snow clutter so that, when, among the radar images after target signal extraction, there is a target signal that is not displayed in one of the radar images after target signal extraction, unlike in other radar images after target signal extraction, the target signal that was not displayed is displayed again in the radar image after target signal extraction. A radar signal processing device characterized by comprising:

2. The radar image comparison unit provides feedback control to the suppression parameters of both or one of the wave clutter and rain / snow clutter so that, in a radar image after the extraction of a target signal, the suppression of both or one of the wave clutter and rain / snow clutter is weakened, thereby causing the previously undisplayed target signal to be displayed again. The radar signal processing device according to claim 1, characterized in that

3. The target signal extraction unit outputs radar images after the target signal extraction, based on either or both of the target information and land information acquired from an external source. The radar signal processing device according to claim 1, characterized in that

4. The target signal extraction unit provides feedback control to suppress both or one of the wave clutter and rain / snow clutter based on the degree of agreement between the radar image after each target signal extraction (current or past radar image) and the information of both or one of the target information and the land information (the current or past information). The radar signal processing device according to claim 3, characterized in that...

5. A radar signal processing program for causing a computer to perform each processing step performed by each processing unit of the radar signal processing device according to any one of claims 1 to 4.

6. A radar image display device that separately displays each of the radar images after target signal extraction output by the radar signal processing device according to any one of claims 1 to 4.

7. An autonomous navigation device that performs autonomous navigation using the radar image after extraction of each target signal output by the radar signal processing device according to any one of claims 1 to 4.

Images