Ocean wave analysis device, radar device, and ocean wave analysis method

Abstract

To provide an ocean wave analysis device, a radar device, and an ocean wave analysis method that allow ocean wave analysis to be performed by using less radar videos and at a small processing load.SOLUTION: A relative speed calculation section 81 is configured to: receive sweep data from a sweep memory 5 to acquire a radar video for one scan; apply Doppler processing to the sweep data in multiple directions centered on an own ship to calculate relative speeds of sea clutter included in the sweep data. An absolute speed calculation section 82 is configured to: calculate absolute speeds of the sea clutter in multiple directions, on the basis of the relative speeds of the sea clutter, and a course and a speed of the own ship; and identify, as an arrival direction of ocean waves, a direction in which the absolute speed is maximal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wave analysis device, a radar device, and a wave analysis method for analyzing waves around a own ship.

Background Art

[0002] In a ship, in order to navigate safely, wave information such as the arrival direction of waves around the own ship and the wave speed is necessary. Therefore, a ship radar device that can measure the wave arrival direction and wave speed using signals from sea surface reflection is known (see Patent Document 1).

[0003] In the above radar device, two-dimensional FFT processing is performed on the radar video obtained by transmitting and receiving radar waves, and a cross vector between the two-dimensional FFT image of the latest radar video and the two-dimensional FFT image of the radar video obtained immediately before that is calculated, and the wave arrival direction and wave speed are calculated from the calculated cross vector. In recent radar devices, a method of increasing the measurement accuracy by repeating the calculation of the cross vector dozens of times and integrating them, and calculating the wave arrival direction and wave speed based on the average value is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In conventional wave analysis using a cross vector, at least two radar videos are required. Further, when calculating the cross vector a plurality of times to improve the measurement accuracy, even more radar videos are required. Therefore, in conventional wave analysis, there has been a problem that it takes time to acquire a large number of radar videos and the load of calculation processing increases.

[0006] Therefore, an object of the present invention is to provide a wave analysis device, a radar device, and a wave analysis method that can perform wave analysis with a smaller processing load using less radar video.

Means for Solving the Problems

[0007] In order to solve the above problems, the invention according to claim 1 is used in a marine radar device that repeats a process of transmitting a pulsed radar wave while rotating an antenna, receiving an echo reflected by the radar wave, and generating sweep data based on the echo. A wave analysis device that analyzes waves around the own ship, obtains radar video composed of the sweep data for one scan of the antenna, performs Doppler processing on the sweep data at a plurality of azimuths centered on the own ship, and calculates the relative speed of clutter existing in the plurality of azimuths. Relative speed calculation means, and absolute speed calculation means for calculating the absolute speed of the clutter in the plurality of azimuths based on the relative speed of the clutter, the course and speed of the own ship. It is characterized by comprising.

[0008] The invention according to claim 2 is the wave analysis device according to claim 1, characterized in that the arrival direction of the wave with respect to the own ship is specified based on the absolute speed of the clutter in the plurality of azimuths.

[0009] The invention according to claim 3 is the wave analysis device according to claim 1, characterized by comprising clutter removal means for generating the radar video from which the clutter has been removed by removing a target corresponding to the absolute speed of the clutter from each of the plurality of sweep data corresponding to the plurality of azimuths.

[0010] The invention according to claim 4 is a marine radar device that repeatedly performs a process of transmitting a pulsed radar wave while rotating an antenna, receiving an echo reflected by the radar wave, and generating sweep data based on the echo, and is characterized by comprising the wave analysis device according to any one of claims 1 to 3.

[0011] The invention according to claim 5 is a wave analysis method used for a marine radar device that repeatedly performs a process of transmitting a pulsed radar wave while rotating an antenna, receiving an echo reflected by the radar wave, and generating sweep data based on the echo, and analyzes waves around the own ship. The method includes acquiring radar video composed of the sweep data for one scan of the antenna, performing Doppler processing on the sweep data at a plurality of azimuths centered on the own ship, calculating the relative velocity of clutter existing at the plurality of azimuths, and calculating the absolute velocity of the clutter at the plurality of azimuths based on the relative velocity of the clutter, the course and speed of the own ship.

Advantages of the Invention

[0012] According to the inventions described in claim 1, claim 4, and claim 5, since the wave velocity can be measured based on the radar video for one scan, the measurement time can be significantly shortened compared to the conventional process using cross vectors, and the processing load required for the measurement can be reduced.

[0013] According to the invention described in claim 2, since the wave arrival direction can be measured based on the radar video for one scan, the measurement time can be significantly shortened compared to the conventional process using cross vectors, and the processing load required for the measurement can be reduced.

[0014] According to the invention described in claim 3, since clutter can be removed from the radar video based on the radar video for one scan, the processing time can be significantly shortened and the processing load can be reduced compared to clutter removal using conventional CFAR (Constant False Alarm Rate) processing.

Brief Description of the Drawings

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Modes for Carrying Out the Invention

[0016] Hereinafter, this invention will be described based on the illustrated embodiments.

[0017] (Embodiment 1) FIG. 1 is a block diagram showing a schematic configuration of a radar device 1 according to Embodiment 1 of the present invention. The radar device 1 is mounted on a ship, for example, and includes an antenna 2, a transceiver 3, an A / D conversion unit 4, a sweep memory 5, a display control unit 6, a display unit 7, and a wave analysis unit (wave analysis device) 8. The radar device 1 is solid-state using a solid-state device for generating radar waves and is capable of performing Doppler processing.

[0018] The antenna 2 repeatedly performs a sweep process of transmitting a pulsed radar wave while rotating in the horizontal plane and receiving an echo of the radar wave reflected by a target. The transceiver 3 generates a radar wave to be transmitted from the antenna 2 and inputs it to the antenna 2. Further, the transceiver 3 detects and amplifies the echo received by the antenna 2 to generate an analog echo signal.

[0019] The A / D conversion unit 4 performs A / D conversion on the echo signal output from the transceiver 3 to generate digital sweep data. The sweep data is in a polar coordinate system indicated by an azimuth θ and a distance R.

[0020] The sweep memory 5 stores the sweep data for one sweep output from the A / D conversion unit 4 and outputs the sweep data for this one sweep to the display control unit 6 and the wave analysis unit 8 until the next sweep process is executed and new sweep data is input.

[0021] The wave analysis unit 8 measures the arrival direction of waves around a ship (hereinafter also referred to as the own ship) on which the radar device 1 is mounted and the wave speed, and outputs the measurement results to the display control unit 6.

[0022] The display control unit 6 sequentially receives the sweep data from the sweep memory 5 and generates radar video composed of the sweep data for one scan (for example, one rotation) of the antenna 2. Here, as shown in FIG. 2, when one transmission and reception from the transmission of the radar wave by the antenna 2 to the reception of the echo is defined as one sweep and one rotation of the antenna 2 is defined as one scan, the radar video for one scan includes a large number of sweeps, that is, sweep data.

[0023] Further, the display control unit 6 generates a measurement result display image or the like based on the measurement result of the wave analysis unit 8. The measurement result display image is a graphic image for displaying the arrival direction of the wave and the wave velocity measured by the wave analysis unit 8, and is displayed superimposed on the radar video.

[0024] The display unit 7 is a display having a function of displaying the radar video and the measurement result display image generated by the display control unit 6, and is configured by, for example, a liquid crystal display or the like.

[0025] The wave analysis unit 8 includes a relative velocity calculation unit (relative velocity calculation means) 81 and an absolute velocity calculation unit (absolute velocity calculation means) 82. As shown in FIG. 3, when the own ship is denoted by symbol S and the waves around the own ship S are denoted by symbol W, the wave analysis unit 8 measures the velocity of the wave W around the own ship S and the arrival direction of the wave W based on the law that the velocity of the wave W can be obtained by subtracting the vector Sv of the own ship S from the vector Wv of the wave W.

[0026] The relative velocity calculation unit 81 sequentially receives sweep data from the sweep memory 5 and acquires (generates) a radar video composed of sweep data for one scan of the antenna 2. The relative velocity calculation unit 81 performs Doppler processing on the sweep data at a plurality of azimuths centered on the own ship S, and calculates the relative velocity of the clutter (i.e., the wave) included in the sweep data.

[0027] The speed of the own ship S is input to the wave analysis unit 8 from a ship speed meter (not shown), and the course (ship's head azimuth) of the own ship S is input from a course meter (not shown). The absolute velocity calculation unit 82 calculates the absolute velocity of the clutter at a plurality of azimuths based on the relative velocity of the clutter calculated by the relative velocity calculation unit 81, the course of the own ship S, and the speed.

[0028] Note that the directions for obtaining the relative speed and absolute speed of the sea clutter may be determined for all sweep data constituting the video data for one scan, or may be determined for the sweep data corresponding to the directions of the front, rear, left, and right of the own ship S.

[0029] FIG. 4 is a chart showing the relationship between the direction centered on the own ship S and the absolute speed of the sea clutter. As shown in this figure, the direction in which the absolute speed of the sea clutter is maximum (i.e., the direction in which the speed approaching the own ship S is maximum) is the wave arrival direction. Conversely, the direction in which the absolute speed of the sea clutter is in the negative direction (i.e., the direction in which the speed moving away from the own ship S is maximum) is 180° with respect to the wave arrival direction. Also, the direction in which the absolute speed of the sea clutter becomes zero is 90° with respect to the own ship S (i.e., the direction straight toward the side of the own ship S).

[0030] The wave analysis unit 8 applies the absolute speeds of a plurality of directions calculated by the absolute speed calculation unit 82 to the chart of FIG. 4, and specifies the direction in which the absolute speed is the largest as the wave arrival direction. The wave analysis unit 8 inputs the specified wave arrival direction and the wave speed (the maximum value of the absolute speed of the sea clutter) to the display control unit 6.

[0031] Note that the absolute speed of the sea clutter can be calculated from only the radar video for one scan, but may be calculated by averaging a plurality of absolute speeds obtained from the radar video for a plurality of scans. According to this, it becomes possible to measure the wave arrival direction and the wave speed more accurately.

[0032] FIG. 5 shows an example of a radar screen RS displayed on the display unit 7 by the display control unit 6. On the radar screen RS, a circular PPI scope RS1 with an indicator Sa indicating the own ship S at the center is displayed. Inside the PPI scope RS1, radar video input from the display control unit 6 is displayed. Also, on the outer periphery of the PPI scope RS1, an inverted triangle wave direction marker RS2 indicating the wave arrival direction is displayed. In the lower right of the PPI scope RS1, the wave arrival direction (relative to the bow) and the wave speed RS3 with respect to the own ship S are displayed. The helmsman of the own ship S can safely navigate by adjusting the course, ship speed, etc. while checking the wave arrival direction and wave speed based on the radar screen RS.

[0033] The operation of the above-described first embodiment will be described with reference to the flowchart shown in FIG. 6.

[0034] The transmission / reception unit 3 transmits a pulsed radar wave while rotating the antenna 2 and receives an echo reflected by the radar wave. The A / D conversion unit 4 converts the analog echo signal into digital sweep data and stores it in the sweep memory 5.

[0035] The relative velocity calculation unit 81 of the wave analysis unit 8 sequentially receives sweep data from the sweep memory 5 and acquires radar video consisting of sweep data for one scan of the antenna 2 (step S1).

[0036] The relative velocity calculation unit 81 performs Doppler processing on the sweep data in a plurality of azimuths centered on the own ship S based on the acquired radar video, and calculates the relative velocity of the clutter included in the sweep data (step S2).

[0037] The absolute velocity calculation unit 82 calculates the absolute velocity of the clutter in a plurality of azimuths based on the relative velocity of the clutter calculated by the relative velocity calculation unit 81 and the course and speed of the own ship S (step S3).

[0038] When the number of scans, i.e., the number of acquired radar videos, is 1 (NO in step 4), the wave analysis unit 8 identifies the direction of wave arrival as the azimuth at which the absolute speed of the sea clutter is maximum based on the absolute speed of the sea clutter calculated based on only that one radar video (step S6).

[0039] Also, when the number of scans, i.e., the number of acquired radar videos, is 2 or more (YES in step 4), the wave analysis unit 8 averages the absolute speeds of the sea clutter calculated based on each radar video (step S5), and based on the averaged absolute speed of the sea clutter, identifies the direction of wave arrival as the azimuth at which the absolute speed of the sea clutter is maximum (step S6).

[0040] As described above, according to the radar device 1 according to the first embodiment, the speed of the wave can be measured based on the radar video for one scan. Also, the direction of wave arrival can be measured based on the radar video for one scan. Thereby, compared with the conventional processing using cross vectors, the measurement time can be significantly shortened, and the processing load required for the measurement can be reduced.

[0041] (Second Embodiment) Next, the radar device according to the second embodiment will be described. The radar device according to the second embodiment is different from the first embodiment in that it removes sea clutter from the radar video using the absolute speed of the sea clutter. In the configuration of the second embodiment, for the same configurations as those in the first embodiment, the same reference numerals are used and detailed descriptions are omitted.

[0042] FIG. 7 is a block diagram showing a schematic configuration of a radar device 1A according to the second embodiment of the present invention. The radar device 1A is a solid-state radar device for ships, similar to the first embodiment, and includes an antenna 2, a transceiver unit 3, an A / D conversion unit 4, a sweep memory 5, a display control unit 6, a display unit 7, a wave analysis unit 8, and a target detection unit 9.

[0043] The object detection unit 9 includes a clutter removal unit (clutter removal means) 91 that removes clutter from the radar video. The clutter removal unit 91 generates a radar video with clutter removed by removing objects corresponding to the absolute speed of the clutter from each of the plurality of sweep data corresponding to a plurality of azimuths.

[0044] Specifically, as shown in FIG. 8, a plurality of sweep data 0 to N are sequentially input from the sweep memory 5 to the clutter removal unit 91. Also, the absolute speed of the clutter in each azimuth is input from the absolute speed calculation unit 82 of the wave analysis unit 8 to the clutter removal unit 91. The clutter removal unit 91 removes an object having the absolute speed of the corresponding azimuth from the input sweep data 0. Also, the clutter removal unit 91 removes an object having the absolute speed of the corresponding azimuth from the input sweep data 1. Similarly, the clutter removal unit 91 removes an object having the absolute speed of the corresponding azimuth from the input sweep data N. The sweep data 0 to N with clutter removed are output to the display unit 6, and the radar video with clutter removed is displayed on the display unit 7.

[0045] FIG. 9(A) shows a part of an example of the radar video before clutter removal, and FIG. 9(B) shows a part of an example of the radar video after clutter removal. Reference numerals S1 to S3 in the figure indicate other ships detected by the radar device 1A of the own ship S. As is clear from this figure, the clutter surrounded by the broken line in FIG. 9(A) is removed in FIG. 9(B), so that it becomes possible to clearly identify the other ships S1 to S3.

[0046] Next, the operation of the above-described Embodiment 2 will be described with reference to the flowchart shown in FIG. 10.

[0047] The transceiver unit 3 transmits a pulsed radar wave while rotating the antenna 2 and receives an echo reflected by the radar wave. The A / D conversion unit 4 converts the analog echo signal into digital sweep data and stores it in the sweep memory 5.

[0048] The relative velocity calculation unit 81 of the wave analysis unit 8 sequentially receives sweep data from the sweep memory 5 and acquires radar video consisting of sweep data for one scan of the antenna 2 (step S1).

[0049] Based on the acquired radar video, the relative velocity calculation unit 81 performs Doppler processing on the sweep data in a plurality of azimuths centered on the own ship S, and calculates the relative velocity of the sea clutter included in the sweep data (step S2).

[0050] Based on the relative velocity of the sea clutter calculated by the relative velocity calculation unit 81 and the course and speed of the own ship S, the absolute velocity calculation unit 82 calculates the absolute velocity of the sea clutter in a plurality of azimuths (step S3).

[0051] When the number of scans, that is, the number of acquired radar videos is one (NO in step 4), the wave analysis unit 8 removes the target with the corresponding absolute velocity for each sweep based on the absolute velocity of the sea clutter calculated based on only that one radar video (step S10).

[0052] Further, when the number of scans, that is, the number of acquired radar videos is two or more (YES in step 4), the wave analysis unit 8 averages the absolute velocities of the sea clutter calculated based on each radar video (step S5), and based on the averaged absolute velocity of the sea clutter, removes the target with the corresponding absolute velocity for each sweep (step S10).

[0053] In a conventional radar device, when removing sea clutter from radar video, Doppler processing is performed on the radar video for one scan, so-called threshold processing, i.e., CFAR processing, is performed for each Doppler component, and the CFAR processing results for each Doppler component are combined. Therefore, there is a problem that the processing takes time and the processing load becomes high.

[0054] On the other hand, according to the radar device 1A according to the second embodiment, clutter can be removed from the radar video based on the radar video for one scan. Therefore, compared with clutter removal using the conventional CFAR processing, the processing time can be significantly shortened and the processing load can be reduced.

[0055] As described above, the embodiments of the present invention have been described. However, the specific configuration is not limited to the above-described Embodiments 1 and 2, and even if there are design changes and the like within a range not departing from the gist of the present invention, they are included in the present invention.

[0056] For example, when calculating the absolute speed of clutter, if there is sweep data that deviates from the relationship between the azimuth and absolute speed of clutter in the chart shown in FIG. 4, the sweep data may include targets other than clutter such as other ships. In such a case, the absolute speed may be complemented using the sweep data before and after it without using the sweep data that deviates from the relationship between the azimuth and absolute speed of clutter.

[0057] In addition, in the above-described Embodiments 1 and 2, a radar device incorporating a wave analysis device has been described as an example. However, the wave analysis device may be configured separately from the radar device and connected to the radar device.

[0058] 1, 1A Radar device 2 Antenna 3 Transceiver 4 A / D conversion unit 5 Sweep memory 6 Display control unit 7 Display unit 8 Wave analysis unit (wave analysis device) 81 Relative speed calculation unit (relative speed calculation means) 82 Absolute speed calculation unit (absolute speed calculation means) 9 Target detection unit 91 Clutter removal unit (clutter removal means)

Claims

1. A wave analysis device used in a marine radar device that repeatedly performs a process of transmitting a pulsed radar wave while rotating an antenna, receiving an echo reflected by the radar wave, and generating sweep data based on the echo, and analyzes waves around the own ship, a relative velocity calculation means for acquiring a radar video composed of the sweep data for one scan of the antenna, performing Doppler processing on the sweep data in a plurality of azimuths centered on the own ship, and calculating a relative velocity of clutter existing in the plurality of azimuths; an absolute velocity calculation means for calculating an absolute velocity of the clutter in the plurality of azimuths based on the relative velocity of the clutter and the course and velocity of the own ship; A wave analysis device characterized by comprising:

2. Identifying the direction of arrival of waves with respect to the own ship based on the absolute velocities of the clutter in the plurality of azimuths, The wave analysis device according to claim 1, characterized in that:

3. Comprising clutter removal means for generating the radar video from which the clutter has been removed by removing targets corresponding to the absolute velocity of the clutter from each of the plurality of sweep data corresponding to the plurality of azimuths, The wave analysis device according to claim 1, characterized in that:

4. A marine radar device that repeatedly performs a process of transmitting a pulsed radar wave while rotating an antenna, receiving an echo reflected by the radar wave, and generating sweep data based on the echo, Comprising the wave analysis device according to any one of claims 1 to 3, A radar device characterized by:

5. A wave analysis method used in a marine radar device that repeatedly performs a process of transmitting a pulsed radar wave while rotating an antenna, receiving an echo reflected by the radar wave, and generating sweep data based on the echo, and analyzes waves around the own ship, acquiring a radar video composed of the sweep data for one scan of the antenna, performing Doppler processing on the sweep data in a plurality of azimuths centered on the own ship, and calculating a relative velocity of clutter existing in the plurality of azimuths; calculating an absolute velocity of the clutter in the plurality of azimuths based on the relative velocity of the clutter and the course and velocity of the own ship; A wave analysis method characterized by:

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