Object estimation device and program

Abstract

To prevent a situation in a radar device where a certain object inhibits detection of an object with a reflection intensity lower than the certain object.SOLUTION: An instruction unit 111 instructs a radar 2 to perform first scanning. An acquisition unit 112 acquires an IF signal from the first scanning. An application unit 113 applies a first window function to the IF signal. A conversion unit 114 performs discrete Fourier transform on the IF signal applied with the first window function to extract a frequency component. An estimation unit 115 estimates the direction of a high-intensity object based on the frequency component. The instruction unit 111 instructs the radar 2 to perform second scanning for an area excluding the estimated direction of the high-intensity object. The acquisition unit 112 acquires an IF signal from the second scanning. The application unit 113 applies a second window function to the IF signal. The conversion unit 114 performs discrete Fourier transform on the IF signal applied with the second window function to extract a frequency component. The estimation unit 115 estimates the direction of a low-intensity object based on the frequency component.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to the technology of an object estimation device.

Background Art

[0002] There is a TOF (Time of Flight) method in the measurement method by a radar device. The TOF method is a method of measuring the distance to an object using the time from when the transmitted electromagnetic wave hits the object and is reflected back. The electromagnetic wave to be transmitted may be a pulse wave, but in order to improve the resolution, a technique called pulse compression using a chirp signal obtained by applying frequency modulation to the pulse wave is also often used. The estimation of the position of an object by a radar device is applied to, for example, detecting obstacles within a level crossing.

[0003] Regarding signal processing in a radar device, various techniques have been developed. For example, Patent Document 1 removes a value corresponding to the frequency of a frequency mask for removing external interference waves from frequency domain data obtained by performing a Fourier transform on a received signal of a synthetic aperture radar that transmits a chirp signal, performs pulse compression, determines whether resolution degradation or side lobe increase occurs in the data, selects one window function corresponding to the determination result from a plurality of window functions, multiplies them, and performs an inverse Fourier transform to obtain a time domain signal, and discloses a signal processing method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when using radar equipment to monitor, for example, a level crossing, the area to be monitored is the area where there is a risk of collision between vehicles (hereinafter also referred to as the hazardous area). This hazardous area is, for example, the area corresponding to the tracks through which trains pass and / or the roadway through which automobiles pass.

[0006] On the other hand, within a level crossing, safe areas that do not belong to these dangerous areas (hereinafter also referred to as safe areas) include, for example, the median strip and the space between the tracks. Objects such as power distribution panels, utility poles, planted areas, and advertisements / signboards may be installed in the safe areas.

[0007] If an object with relatively high reflectivity (hereinafter also referred to as a high-intensity object or first object) is placed in these safety areas, the electromagnetic waves reflected by this high-intensity object may interfere with electromagnetic waves reflected from other objects, potentially hindering the detection of other objects.

[0008] For example, even if an object with relatively low reflectivity (hereinafter also referred to as a low-intensity object or second object) is in the direction of the main lobe of electromagnetic waves transmitted by a radar device, if a high-intensity object placed in a safe area is detected in the direction of the side lobe of those electromagnetic waves, this low-intensity object may be overlooked due to its influence.

[0009] In this case, it is conceivable to improve the resolution by using a window function as shown in Patent Document 1. However, in radar signal processing, there is a trade-off between reducing side lobes and improving resolution. Therefore, there is a limit to the improvement in resolution depending on the acceptable side lobe conditions. Furthermore, the technology shown in Patent Document 1 merely applies a single selected window function, so when detecting an object that has entered a defined range, it is difficult to eliminate the influence of high-intensity objects that are already present within that range.

[0010] Furthermore, objects installed in the safety zone may be moved due to construction work, etc., and even if they are not moved, their reflectivity may change depending on the season, weather, time of day, etc.

[0011] Furthermore, even when high-intensity and low-intensity objects coexist within a hazardous area, the low-intensity objects may become undetectable due to the influence of the high-intensity objects. In this case, if the type of alarm must be changed depending on whether only high-intensity objects are detected or both high-intensity and low-intensity objects are detected within the hazardous area, it is difficult to distinguish the latter from the former.

[0012] One of the objectives of the present invention is to prevent a radar system from failing to detect objects with lower reflectivity than a given object due to the influence of that object. [Means for solving the problem]

[0013] This invention relates to radar The first intermediate frequency obtained by performing a first scan that scans the entire area to be scanned is Applying a first window function to the signal estimates the direction of the first object, and avoids that direction. The scanned area scanning The second scanning The second intermediate frequency obtained by performing this procedure The signal is better than the first window function. Wide dynamic range As a first embodiment, we provide an object estimation device that estimates the direction of a second object having a lower reflectivity than the first object by applying a second window function with low resolution.

[0014] According to the object estimation device of the first embodiment, it is possible to prevent objects with a lower reflectivity than a certain object from being failed to be detected due to the influence of that object.

[0015] In the object estimation apparatus of the first embodiment, two or more phased array radars are arranged at different positions around the area to be scanned. The first intermediate frequency signal and the second intermediate frequency signal A second embodiment may be adopted in which the directions of the first object and the second object are estimated using [a specific method / tool].

[0016] According to the object estimation apparatus of the second embodiment, the blind spots in the scanned area are reduced compared to the case where the received signal of a single phased array radar is used.

[0017] In the object estimation device according to the first or second aspect, after estimating the direction of the first object, the process of estimating the direction of the second object is repeated a plurality of times, and when the number of times the direction is continuously estimated does not satisfy a predetermined condition, the estimation may be canceled, which may be adopted as a third aspect.

[0018] According to the object estimation device of the third aspect, it is possible to prevent the second object from being erroneously detected by the rescan reception signal.

[0019] In the object estimation device according to the first or second aspect, the First intermediate frequency distance to the first object is estimated by applying the first window function to the signal and performing Fourier transform, and the Second intermediate frequency distance to the second object is estimated by applying the second window function to the signal and performing Fourier transform, which may be adopted as a fourth aspect.

[0020] According to the object estimation device of the fourth aspect, the distance to the object is estimated based on the components in the frequency domain obtained by performing Fourier transform on the reception signal to which the window function is applied in the time domain.

[0021] In the object estimation device of the fourth aspect, the radar transmits a chirp signal, and combines the transmitted chirp signal and the reception signal The first intermediate frequency signal And obtain the second intermediate frequency signal. to obtain, which may be adopted as a fifth aspect.

[0022] According to the object estimation device of the fifth aspect, the resolution is improved compared to the case where a chirp signal is not used.

[0023] In the object estimation device according to the first or second aspect, the first window function is a Hamming window function, and the second window function is a Blackman window function, which may be adopted as a sixth aspect.

[0024] According to the object estimation device of the sixth embodiment, the distance to the first object is estimated by applying a Hamming window function, and the distance to the second object is estimated by applying a Blackman window function.

[0025] This invention provides a computer with radar The first intermediate frequency obtained by performing a first scan that scans the entire area to be scanned is The steps include applying a first window function to the signal to estimate the direction of the first object, and avoiding the said direction The second scanning area scanning The second intermediate frequency obtained by performing this procedure At the traffic light 、 The first window function is Wide dynamic range A seventh aspect of the present invention provides a program for performing the steps of: applying a second window function with low resolution to estimate the direction of a second object having a lower reflectivity than the first object.

[0026] According to the program of the seventh embodiment, it is possible to prevent objects with a lower reflectivity than a certain object from being undetected due to the influence of that object. [Brief explanation of the drawing]

[0027] [Figure 1] A block diagram showing an example of the configuration of an object estimation system 9 according to an embodiment of the present invention. [Figure 2] A diagram showing an example of the placement of radar 2 at a level crossing. [Figure 3] A diagram showing examples of the areas monitored by each of the two radars 2. [Figure 4] A diagram showing an example of the configuration of object estimation device 1. [Figure 5] A diagram showing an example of the configuration of radar 2. [Figure 6] A diagram showing an example of the functional configuration of object estimation device 1. [Figure 7] A flowchart illustrating an example of the operation flow in the first scan. [Figure 8] A flowchart illustrating an example of the operation flow for the second scan. [Figure 9] This figure shows examples of scanned regions R in the first and second scans, respectively. [Modes for carrying out the invention]

[0028] <Embodiment> <Configuration of the object estimation system> Figure 1 is a block diagram showing an example of the configuration of an object estimation system 9 according to an embodiment of the present invention. The object estimation system 9 shown in Figure 1 includes an object estimation device 1, a communication line 3, and a management device 4. The object estimation system 9 also includes radars 2a and 2b (hereinafter referred to simply as "radar 2" when they are not distinguished) connected to the object estimation device 1. The object estimation system 9 also includes circuit breakers 5a and 5b (hereinafter referred to simply as "circuit breaker 5" when they are not distinguished) connected to the management device 4. Note that each of these components in the object estimation system 9 may be multiple or one.

[0029] Object estimation device 1 controls a radar 2 that monitors a predetermined space and performs signal processing on the signals received by the radar 2 (hereinafter also referred to as received signals) to estimate the direction of an object in space and the distance to that object. Object estimation device 1 is, for example, a computer.

[0030] Radar 2 is a device that transmits and receives electromagnetic waves and outputs a signal corresponding to the distance and direction to an object using the TOF (Time-of-Flight) method. Radar 2 shown in Figure 1 is a phased array radar having multiple antenna elements arranged at predetermined positions. Phased array radars can perform beam scanning by controlling the phase of the electromagnetic waves transmitted from each antenna, and therefore have the advantage of faster scanning compared to mechanical scanning.

[0031] Communication line 3 is a line that connects the object estimation device 1 and the management device 4 in a way that enables communication, either by wire or wireless connection. Communication line 3 may be, for example, a LAN (Local Area Network), a WAN (Wide Area Network), the Internet, or a combination of these. Furthermore, communication line 3 may include public switched telephone networks (PSTN), integrated services digital networks (ISDN), etc.

[0032] Barrier 5 is a device that blocks the roadway when a train enters the tracks at a level crossing where a railway and a road intersect at grade. Barrier 5 is controlled by the control device 4.

[0033] The control device 4 is a device that controls and manages the barrier gates 5 installed at level crossings, and the warning devices attached to the barrier gates 5. The control device 4 determines the position of the train on the track and controls the barrier gates 5 according to that position. The position of the train is determined, for example, by sensors installed along the track, or by positioning devices installed on the train. This control device 4 may be installed, for example, at each level crossing or at each station. Alternatively, this control device 4 may be a central control device that manages all the barrier gates 5 installed at multiple level crossings at once.

[0034] Furthermore, the management device 4 shown in Figure 1 is connected to the object estimation device 1 via a communication line 3. Before a train enters the level crossing, the management device 4 activates the barrier 5 installed at the level crossing to block the roadway and notifies the object estimation device 1 of this fact. When the object estimation device 1 receives the above notification from the management device 4 via the communication line 3, it activates the radar 2 to determine whether there is an obstruction that has entered the level crossing. The object estimation device 1 does not need to receive this notification. In this case, the object estimation device 1 may keep the radar 2 activated at all times to monitor the inside of the level crossing.

[0035] Figure 2 shows an example of the arrangement of radar 2 at a level crossing. The radar 2 shown in Figure 2 consists of radar 2a and radar 2b, respectively, positioned at different locations around the scan area R. Here, the scan area R is the area scanned by radar 2. The scan area R includes the area of ​​the level crossing where the railway track and the road intersect at the same level. Barriers 5a and 5b each block the road to prevent automobile C from entering the scan area R before the train enters the level crossing area. Barriers 5a and 5b then cease blocking the road after the train has left the level crossing area.

[0036] Figure 3 shows an example of the areas monitored by each of the two radars 2. Radar 2a, shown in Figure 3, monitors the monitoring area Ra by scanning an electromagnetic wave beam. Radar 2b monitors the monitoring area Rb. Both monitoring areas Ra and Rb are fan-shaped regions within a predetermined angle and radius centered on radars 2a and 2b, respectively. The scanned area R is covered by the union of monitoring areas Ra and Rb.

[0037] Because radars 2a and 2b are positioned in different locations, they can compensate for each other's blind spots. Furthermore, in areas where monitoring area Ra and monitoring area Rb overlap, even if detection of low-intensity objects becomes difficult in one area due to the influence of high-intensity objects, detection of those low-intensity objects may become possible in the other area because the receiving direction is different.

[0038] In this way, by arranging two or more radars 2 at different positions around the scanned area R, the object estimation device 1 uses the other radars 2 to monitor areas and objects that cannot be monitored by any of the radars 2. In particular, when radar 2 is a phased array radar, the object estimation device 1 that controls these two or more radars 2 is an example of an object estimation device that estimates the directions of a first object and a second object using the received signals of two or more phased array radars arranged at different positions around the scanned area.

[0039] <Configuration of the object estimation device> Figure 4 shows an example of the configuration of the object estimation device 1. The object estimation device 1 includes a processor 11, a memory 12, and a communication unit 13. These are connected to each other via a bus so that they can communicate with one another.

[0040] Memory 12 is a storage means for storing the operating system, various computer programs (hereinafter simply referred to as "programs"), data, etc., which are loaded into the processor 11. Memory 12 has RAM (Random Access Memory) and ROM (Read Only Memory). Memory 12 may also have a solid-state drive, a hard disk drive, etc.

[0041] The processor 11 controls the object estimation device 1 by reading and executing a program from the memory 12. The processor 11 is, for example, a CPU (Central Processing Unit). Alternatively, the processor 11 may be, for example, an FPGA (Field Programmable Gate Array), or may include an FPGA. Furthermore, this processor may have an ASIC (Application Specific Integrated Circuit) or other programmable logic device, and control may be performed by these.

[0042] The communication unit 13 is a communication circuit that connects the object estimation device 1 to the radar 2 via wired or wireless means. The communication unit 13 is also a communication circuit that connects to the management device 4 via wired or wireless means through the communication line 3. In addition to these, the communication unit 13 may connect various external devices to the object estimation device 1.

[0043] <Radar Configuration> Figure 5 shows an example of the configuration of radar 2. Radar 2 includes an array antenna 20, an oscillator 21, a modulation unit 22, a transmitting unit 23, a switching unit 24, a receiving unit 25, an amplification unit 26, a demodulation unit 27, and a communication unit 28.

[0044] The array antenna 20 is an antenna composed of multiple antenna elements (radiating elements) arranged at predetermined positions. The arrangement of the multiple antenna elements can be, for example, linear, circular, or grid-like.

[0045] The oscillator 21 is a device that emits coherent electromagnetic waves. The electromagnetic waves emitted by the oscillator 21 are, for example, microwaves, millimeter waves, terahertz waves, etc.

[0046] The modulation unit 22 is a device that frequency modulates the electromagnetic wave oscillated by the oscillator 21 to obtain a chirp signal. This chirp signal may be a linear chirp signal in which the frequency increases and decreases at a predetermined rate with respect to time, or it may be a nonlinear chirp signal. For example, the modulation unit 22 may use a surface acoustic wave (SAW) device that converts an electrical signal into ultrasonic vibrations to provide delay characteristics.

[0047] The transmitting unit 23 controls the array antenna 20 based on instructions from the object estimation device 1 and transmits the chirp signal generated by the modulation unit 22 toward the scanned area R. The object estimation device 1 causes each antenna element constituting the array antenna 20 to transmit a chirp signal with a phase corresponding to the beam scanning direction. As a result, the array antenna 20 transmits electromagnetic waves indicating the chirp signal in a predetermined direction.

[0048] The switching unit 24 is, for example, a circulator, which switches the transmission and reception functions of the array antenna 20 in a time-division manner. The receiving unit 25 acquires a received signal indicating electromagnetic waves from the array antenna 20 that has received electromagnetic waves reflected after hitting an object. The amplification unit 26 amplifies the received signal received by the receiving unit 25.

[0049] The demodulation unit 27 detects and demodulates the received signal amplified by, for example, the amplification unit 26. This demodulation corresponds to the frequency modulation performed by the modulation unit 22. The demodulation unit 27 includes, for example, a mixer, and uses the signal transmitted by the transmission unit 23 (referred to as the transmitted signal) to convert the received signal into an intermediate frequency signal (hereinafter also referred to as the IF signal). By converting the received signal into an IF signal, pulse compression is performed.

[0050] The communication unit 28 transmits the IF signal converted by the demodulation unit 27 to the object estimation device 1. The communication unit 28 also receives control signals from the object estimation device 1 for controlling the radar 2.

[0051] <Functional Configuration of an Object Estimation Device> Figure 6 shows an example of the functional configuration of the object estimation device 1. The processor 11 of the object estimation device 1 functions as an instruction unit 111, an acquisition unit 112, an application unit 113, a conversion unit 114, and an estimation unit 115 by reading and executing a program stored in the memory 12.

[0052] The instruction unit 111 instructs the radar 2 via the communication unit 13 to perform a scan of the entire scan area R (hereinafter also referred to as the first scan). Upon receiving this instruction, the radar 2 performs the first scan and generates an IF signal from the received signal.

[0053] The acquisition unit 112 acquires an IF signal from the radar 2 via the communication unit 13 through a first scan. When the IF signal acquired by the acquisition unit 112 is obtained through a first scan, the application unit 113 applies a first window function (hereinafter also referred to as the first window function) to this IF signal. The first window function is a window function that prioritizes frequency resolution over dynamic range.

[0054] An example of a window function is the following: A rectangular window is a window that extracts the original signal in the time domain over a certain interval and sets values ​​outside that interval to 0. The window function that represents a rectangular window is called a rectangular window function. The rectangular window function is expressed by the following equation (1) when the interval is [0,1].

[0055]

number

[0056] The Hamming window is one of the windows that has relatively high frequency resolution but a narrow dynamic range. Because the Hamming window has good resolution, it can accurately estimate the position of an object, but because its dynamic range is narrow, it is difficult to detect low-intensity objects with low reflectivity. The window function that represents the Hamming window (called the Hamming window function) is given by the following equation (2) when the interval is [0,1].

[0057]

number

[0058] The Blackman window is a window with a lower frequency resolution but a wider dynamic range compared to the Hamming window. Because of its wide dynamic range, the Blackman window can detect even low-intensity objects, but its poor resolution results in lower accuracy in position estimation. The window function representing the Blackman window (called the Blackman window function) is given by the following equation (3) when the interval is [0,1].

[0059]

number

[0060] A rectangular window can detect objects with a reflectance difference of approximately 13 dB, while a Hamming window can detect objects with a difference of approximately 40 dB, and a Blackman window with a difference of approximately 60 dB. If the resolution of a rectangular window is set to 1, the resolution of a Hamming window is approximately 1.5, and the resolution of a Blackman window is approximately 1.93.

[0061] The first window function applied by the application unit 113 to the IF signal obtained by the first scan is, for example, a Hamming window function, in order to prioritize high frequency resolution over wide dynamic range.

[0062] The conversion unit 114 extracts frequency components by performing a discrete Fourier transform on the IF signal to which the first window function has been applied. For example, the Fast Fourier Transform is used for the discrete Fourier transform.

[0063] The estimation unit 115 estimates the direction of the detected object and the distance to this object based on the frequency components obtained by the conversion unit 114. The frequency components extracted from the IF signal obtained by the first scan and to which the first window function has been applied indicate the direction and distance of the high-intensity object because the dynamic range of the first window function is relatively narrow. The estimation unit 115 stores the estimated direction and distance of the high-intensity object in the memory 12. The estimation unit 115 also transmits the estimated direction and distance of the high-intensity object to the instruction unit 111.

[0064] When the instruction unit 111 receives the direction of a high-intensity object from the estimation unit 115, it instructs the radar 2 to perform a rescan (hereinafter also referred to as a second scan) on the area excluding this direction from the entire scanned area R. The radar 2 receives this instruction, performs this second scan, and generates an IF signal from the received signal.

[0065] The acquisition unit 112 acquires the IF signal from the radar 2 via the communication unit 13 through the second scan. When the IF signal acquired by the acquisition unit 112 is obtained through the second scan, the application unit 113 applies a second window function (hereinafter also referred to as the second window function) to this IF signal. The second window function is a window function with a wider dynamic range and lower frequency resolution compared to the first window function. The second window function that the application unit 113 applies to the IF signal obtained through the second scan is, for example, the Blackman window function.

[0066] The conversion unit 114 performs a discrete Fourier transform on the IF signal to which the second window function has been applied to extract frequency components. The estimation unit 115 estimates the direction of the detected object and the distance to this object based on the frequency components obtained by the conversion unit 114. The frequency components extracted from the IF signal to which the second window function has been applied indicate the direction and distance of low-intensity objects, as the direction of high-intensity objects has been avoided in advance by the second scan. The estimation unit 115 stores the estimated direction and distance of the low-intensity object in the memory 12.

[0067] In other words, the object estimation device 1 that implements these functions is an example of an object estimation device that estimates the direction of a first object by applying a first window function to the radar received signal, and then estimates the direction of a second object with lower reflectivity than the first object by applying a second window function, which has lower resolution than the first window function, to the radar rescan received signal that has been rescanned while avoiding this direction. The first window function used in this object estimation device 1 is a Hamming window function, and the second window function is a Blackman window function.

[0068] Furthermore, this object estimation device 1 is an example of an object estimation device that estimates the distance to the first object by applying a first window function to the received signal and performing a Fourier transform, and estimates the distance to the second object by applying a second window function to the rescanned received signal and performing a Fourier transform.

[0069] Furthermore, this object estimation device 1 is an example of an object estimation device that estimates distance by having a radar emit a chirp signal, and then performing a Fourier transform on an intermediate frequency signal obtained by combining the emitted chirp signal and the received signal.

[0070] <Operation of the distance image sensor> <Overall processing> The processor 11 of the object estimation device 1 performs a first scan as step S100, which scans the entire area R to be scanned, and then performs a second scan as step S200, which rescans the area of ​​the area R to be scanned, avoiding the direction of the high-intensity object estimated in the first scan.

[0071] <Processing of the first scan> Figure 7 is a flowchart showing an example of the operation flow of the first scan. This first scan process is step S100 described above. The processor 11 of the object estimation device 1 determines the direction in the scanned area R that has not been scanned (step S101), and transmits electromagnetic waves in this direction using radar 2 (step S102). Then, the processor 11 receives the electromagnetic waves using radar 2 (step S103). The received electromagnetic waves include reflected waves that are the result of the transmitted electromagnetic waves hitting an object and being reflected.

[0072] The processor 11 converts the received signal into an IF signal by combining it with the transmitted signal indicated by the transmitted electromagnetic wave (step S104). Once the received signal is converted into an IF signal, the processor 11 determines whether the peak of this IF signal is above a threshold (step S105).

[0073] The threshold that the processor 11 compares to the peak of the IF signal is, for example, the output of the electromagnetic wave transmitted by radar 2 plus approximately 30 dB (decibels). In other words, if the output of the electromagnetic wave transmitted by radar 2 is approximately 50 dB, the threshold compared to the peak is approximately 80 dB.

[0074] The object estimation device 1 needs to detect a person entering the railroad crossing. The ratio of the intensity of the reflected wave reflected by the person to the transmitted electromagnetic wave, i.e., the reflection loss, is approximately -10 dB. On the other hand, when the Hamming window function, which is the first window function, is applied, the object estimation device 1 can only detect reflected waves up to approximately 40 dB in intensity. Therefore, if a high-intensity object with a peak in the received signal of approximately +30 dB or more is detected, the object estimation device 1 will no longer be able to detect a person from the received signal to which the Hamming window function has been applied.

[0075] If it is determined that the peak of the IF signal is above a threshold (step S105; YES), the processor 11 applies a first window function to the IF signal (step S106), performs a Fourier transform, and converts it to the frequency domain (step S107).

[0076] Then, the processor 11 estimates the distance and direction to the high-intensity object (i.e., the first object) based on the signal converted to the frequency domain and stores it in the memory 12 (step S108).

[0077] On the other hand, if in step S105 it is determined that the peak of the IF signal is not above a threshold (step S105; NO), the processor 11 applies a second window function with lower frequency resolution than the first window function to the IF signal (step S109), performs a Fourier transform, and converts it to the frequency domain (step S110).

[0078] Then, the processor 11 estimates the distance and direction to the low-intensity object (i.e., the second object) based on the signal converted to the frequency domain and stores it in the memory 12 (step S111).

[0079] When the processes in steps S108 and S111 are completed, the processor 11 determines whether or not the scan has completed a full cycle (step S112). If it determines that the scan has not completed a full cycle (step S112; NO), the processor 11 returns to step S101.

[0080] On the other hand, if it is determined that the scan has completed one cycle (step S112; YES), the processor 11 terminates the processing of this first scan.

[0081] <Processing of the second scan> Figure 8 is a flowchart showing an example of the operation flow of the second scan. The processing of this second scan is step S200 described above. The processor 11 of the object estimation device 1 determines the direction that has not been scanned within the scanned area R (step S201), and determines whether or not this direction is the direction of the first object estimated in the first scan (step S202). If it is determined that the determined direction is the direction of the first object (step S202; YES), the processor 11 proceeds to step S209.

[0082] In this case, the processor 11 does not perform the processing from step S203 to step S208, so the direction of the first object estimated in the first scan is avoided in the second scan, and electromagnetic waves arriving from this direction are not analyzed.

[0083] On the other hand, if it is determined that the determined direction is not the direction of the first object (step S202; NO), the processor 11 transmits electromagnetic waves in this direction using radar 2 (step S203) and receives electromagnetic waves using radar 2 (step S204).

[0084] Then, the processor 11 converts the received signal into an IF signal by combining it with the transmitted signal indicated by the transmitted electromagnetic wave (step S205). Once the received signal is converted into an IF signal, the processor 11 applies a second window function to this IF signal (step S206), performs a Fourier transform on it, and converts it into the frequency domain (step S207).

[0085] Then, the processor 11 estimates the distance and direction to the detected object based on the signal converted to the frequency domain and stores it in the memory 12 (step S208). The object detected at this time is a low-intensity object (i.e., a second object) with a lower reflection intensity than the high-intensity object, because it was detected during a rescan that avoided the direction of the high-intensity object.

[0086] Figure 9 shows examples of scanned areas R in the first and second scans, respectively. When radar 2a performs the first scan, it scans the monitoring area Ra, for example as shown in Figure 9(a), and detects a high-intensity object J1 when scanning in direction L1. This high-intensity object J1 is an object that is pre-installed in a safe area Rs where there is no risk of collision with a train, etc., and is, for example, a power distribution panel. In the first scan, a first window function with relatively high frequency resolution is applied to the received signal, so the position of the high-intensity object J1 is determined relatively accurately. On the other hand, because the dynamic range of the received signal is narrowed by the application of the first window function, a low-intensity object J2, for example shown in Figure 9(a), is not detected due to the influence of the reflected wave from the high-intensity object J1. This low-intensity object J2 is located in a dangerous area Rc where there is a risk of collision with a train, etc., and an alarm should be issued.

[0087] In the second scan, radar 2a, under the control of object estimation device 1, for example as shown in Figure 9(b), rescans the monitoring region Ra, avoiding the region Rp that includes the direction L1 where the high-intensity object J1 detected in the first scan is located. As a result, the low-intensity object J2 is not affected by the reflected waves of the high-intensity object J1. Furthermore, in the second scan, a second window function with a relatively wide dynamic range is applied to the received signal, so this low-intensity object J2 can be detected even if its reflection intensity is relatively low.

[0088] Next, as shown in Figure 8, the processor 11 determines whether or not the scan has completed one cycle (step S209). If it determines that the scan has not completed one cycle (step S209; NO), the processor 11 returns to step S201.

[0089] On the other hand, if it determines that the scan has completed one cycle (step S209; YES), the processor 11 terminates the processing of this second scan.

[0090] By performing the processes described above, the object estimation device 1 controls the radar 2 to perform a first scan and detects the location of high-intensity objects by applying a Hamming window function to the acquired received signal. Subsequently, the object estimation device 1 performs a second scan to rescan areas where there are no high-intensity objects, and processes the results of the rescan with a second window function such as a Blackman window function, thereby detecting low-intensity objects that could not be detected in the first scan.

[0091] Furthermore, the object estimation device 1 compares the peak of the received signal acquired by the first scan with a threshold, and if it determines that there are no peaks above the threshold, it assumes that there are no high-intensity objects in the scanning direction and applies a second window function with a wide dynamic range, suitable for detecting low-intensity objects, to the received signal.

[0092] The configurations, shapes, sizes, and arrangements described in the above embodiments are merely schematic representations to the extent that the present invention can be understood and implemented. Therefore, the present invention is not limited to the described embodiments and can be modified in various forms as long as it does not deviate from the scope of the technical idea set forth in the claims.

[0093] <Variation> The above describes the embodiment, but the contents of this embodiment can be modified as follows. Furthermore, the following modifications may be combined.

[0094] <1> In the embodiment described above, the processor 11 performs a second scan only once after the first scan, but the second scan may be repeated multiple times. In this case, if the number of times the direction of the low-intensity object is estimated consecutively does not satisfy a predetermined condition, the object estimation device 1 may cancel the estimation of the direction of the low-intensity object.

[0095] For example, after the first scan, the object estimation device 1 performs five second scans, avoiding the directions of the high-intensity objects estimated in the first scan. Then, if low-intensity objects are not estimated in the common direction for three or more consecutive scans out of the five second scans, that is, if low-intensity objects are estimated in a direction at most three times consecutively, the object estimation device 1 cancels the information for that direction. In this way, the object estimation device 1 can exclude false detections caused by fluctuations in the receiving equipment, etc., from the detection results.

[0096] In this modified example, the object estimation device 1 is an example of an object estimation device that estimates the direction of a first object, then estimates the direction of a second object, and repeats this process multiple times, canceling the estimation if the number of consecutive directions estimated does not meet a predetermined condition.

[0097] <2> In the embodiment described above, the processor 11 may terminate the second scan after only one pass if no high-intensity object is detected in the second scan, and if a high-intensity object is detected, it may re-estimate the direction of the high-intensity object and perform a second second scan to avoid that direction. In this case, the processor 11 may repeat the second scan until no more high-intensity objects are detected.

[0098] <3> In the embodiment described above, the processor 11 used a Hamming window function as the first window function and a Blackman window function as the second window function, but the selection of these window functions is not limited to this example. Examples of other window functions that can be applied to the first and second window functions include the rectangular window, cosine window, Gaussian window, Hann window, Tukey window, Kaiser window, and Blackman-Harris window, respectively.

[0099] <4> In the embodiment described above, the processor 11 applied the window function by multiplication to the received signal (original signal) in the time domain before the Fourier transform, but the window function may also be applied by convolution integral in the frequency domain after the Fourier transform.

[0100] <5> In the embodiments described above, the scanned area R may be scanned by a one-dimensional scan that changes the azimuth, or by a two-dimensional scan that changes both the azimuth and the elevation angle. When performing a two-dimensional scan, the object estimation device 1 may rotate the radar 2 in either the azimuth direction or the elevation direction by mechanical drive. The radar 2 may also transmit electromagnetic waves in the elevation direction using a wide fan beam. Furthermore, when receiving electromagnetic waves including reflected waves reflected by an object, the radar 2 may simultaneously form multiple received beams with different directional directions by using digital beamforming (DBF).

[0101] <6> In the embodiment described above, the processor 11 performed the first scan in step S100 and the second scan in step S200, but the second scan may also be performed within step S100. In this case, for example, after estimating the direction of the first object in step S108, the processor 11 may have the radar 2 perform a second scan, which is a rescan avoiding the estimated direction of the first object, and then perform the processing from steps S109 to S111 on the received signal obtained therefrom.

[0102] <7> In the embodiments described above, the operation of the processor 11 may not be performed solely by a single processor 11, but may also be performed collaboratively by multiple processors located in physically separate locations. Furthermore, the order of the operations of the processor 11 is not limited to the order described above and may be changed as appropriate.

[0103] <8> In the embodiments described above, the program executed by the processor 11 of the object estimation device 1 may be provided stored on a recording medium readable by a computer device, such as a magnetic recording medium like a magnetic tape or magnetic disk, an optical recording medium like an optical disk, a magneto-optical recording medium, or a semiconductor memory. Alternatively, this program may be downloaded via a communication line such as the Internet.

[0104] The program executed by the processor 11 described above is an example of a program that causes the computer to perform the following steps: apply a first window function to the radar's received signal to estimate the direction of the first object; and apply a second window function with lower resolution than the first window function to the radar's rescanned received signal, which avoids the estimated direction, to estimate the direction of the second object, which has a lower reflectance than the first object. [Explanation of Symbols]

[0105] 1...Object estimation device, 11...Processor, 111...Instruction unit, 112...Acquisition unit, 113...Application unit, 114...Conversion unit, 115...Estimation unit, 12...Memory, 13...Communication unit, 2, 2a, 2b...Radar, 20...Array antenna, 21...Oscillator, 22...Modulation unit, 23...Transmission unit, 24...Switching unit, 25...Receiver, 26...Amplifier, 27...Demodulation unit, 28...Communication unit, 3...Communication line, 4...Management device, 5, 5a, 5b...Breakdown device, 9...Object estimation system, J1...High-intensity object, J2...Low-intensity object.

Claims

1. The direction of the first object is estimated by applying a first window function to the first intermediate frequency signal obtained by performing a first scan that scans the entire area to be scanned with radar, An object estimation device that estimates the direction of a second object with lower reflection intensity than the first object by applying a second window function, which has a wider dynamic range and lower resolution than the first window function, to a second intermediate frequency signal obtained by performing a second scan that scans the scanned area while avoiding the direction.

2. The object estimation device according to claim 1, which estimates the directions of the first object and the second object using the first intermediate frequency signal and the second intermediate frequency signal of two or more phased array radars arranged at different positions around the scanning area.

3. The object estimation device according to claim 1 or 2, wherein the process of estimating the direction of the first object and then estimating the direction of the second object is repeated multiple times, and the estimation is canceled if the number of times the direction is estimated consecutively does not satisfy a predetermined condition.

4. An object estimation device according to claim 1 or 2, wherein the distance to the first object is estimated by applying the first window function to the first intermediate frequency signal and performing a Fourier transform, and the distance to the second object is estimated by applying the second window function to the second intermediate frequency signal and performing a Fourier transform.

5. The object estimation device according to claim 4, wherein the radar transmits a chirp signal, and the transmitted chirp signal and the received signal are combined to obtain the first intermediate frequency signal and the second intermediate frequency signal.

6. The object estimation device according to claim 1 or 2, wherein the first window function is a Hamming window function and the second window function is a Blackman window function.

7. On the computer, The first step involves performing a first scan to scan the entire area to be scanned using radar, and then applying a first window function to the first intermediate frequency signal obtained to estimate the direction of the first object. A second scan is performed to scan the area to be scanned while avoiding the aforementioned direction. A second window function, which has a wider dynamic range and lower resolution than the first window function, is applied to the second intermediate frequency signal obtained by this scan to estimate the direction of the second object, which has a lower reflection intensity than the first object. A program to execute.

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