Moving body detection system, processing device, and non-transitory computer-readable medium

Abstract

In the present invention, a transmission antenna (11) transmits radio waves (W) toward a detection region (20). A first reception antenna (121) receives, at a first position (P1), a radio wave (W) arriving from the detection region (20) and outputs a first detection signal (S1) corresponding to the radio wave strength at the first position (P1). A second reception antenna (122) receives, at a second position (P2), a radio wave (W) arriving from the detection region (20) and outputs a second detection signal (S2) corresponding to the radio wave strength at the second position (P2). A processing device (13) estimates the presence or absence of a moving body (30) in the detection region (20) on the basis of an index value corresponding to the magnitude of a directionally statistical variance related to a phase difference between the first detection signal (S1) and the second detection signal (S2).

Description

MOTION DETECTION SYSTEM, PROCESSING DEVICE, AND NON-TRANSITORY COMPUTER-READABLE MEDIUM

[0001] The present disclosure relates to a motion detection system, a processing device that may be included in the system, and a non-transitory computer-readable medium having stored thereon a computer program executable by a processor included in the device.

[0002] Japanese Patent Application Publication No. 2011-519288 discloses a technology that estimates the presence or absence of a moving object in a detection area based on the radar principle from a signal corresponding to the reception intensity of radio waves arriving from the detection area.

[0003] There is a demand for improving the accuracy of detecting moving objects based on radar principles.

[0004] One example of an aspect that the present disclosure can provide is a moving object detection system comprising: a transmitting antenna that transmits radio waves toward a detection area; a first receiving antenna that receives the radio waves arriving from the detection area at a first position and outputs a first detection signal corresponding to the radio wave intensity at the first position; a second receiving antenna that receives the radio waves arriving from the detection area at a second position and outputs a second detection signal corresponding to the radio wave intensity at the second position; and a processing device that estimates the presence or absence of a moving object in the detection area based on an index value that corresponds to the magnitude of directional statistical variance related to the phase difference between the first detection signal and the second detection signal.

[0005] One example of an aspect that the present disclosure can provide is a processing device comprising: a processor that causes a transmitting antenna to transmit radio waves toward a detection area; and an interface that receives a first detection signal corresponding to the radio wave intensity at a first position from a first receiving antenna that receives the radio waves arriving from the detection area at a first position, and receives a second detection signal corresponding to the radio wave intensity at a second position from a second receiving antenna that receives the radio waves arriving from the detection area at a second position, wherein the processor estimates the presence or absence of a moving object in the detection area based on an index value that corresponds to the magnitude of directional statistical variance related to the phase difference between the first detection signal and the second detection signal.

[0006] One example aspect that the present disclosure can provide is a non-transitory computer-readable medium storing a computer program executable by a processor mounted on a processing device, wherein execution of the computer program causes the processing device to: cause a transmitting antenna to transmit radio waves toward a detection area; receive a first detection signal corresponding to the radio wave intensity at a first position from a first receiving antenna that receives the radio waves arriving from the detection area at a first position; receive a second detection signal corresponding to the radio wave intensity at a second position from a second receiving antenna that receives the radio waves arriving from the detection area at a second position; and estimate the presence or absence of a moving object in the detection area based on an index value corresponding to the magnitude of directional statistical variance of the phase difference between the first detection signal and the second detection signal.

[0007] The inventors of the present application discovered that the magnitude of the directional statistical variance of the phase difference between radio waves transmitted from a transmitting antenna and received by a first receiving antenna and a second receiving antenna correlates with the presence or absence of a moving object in the detection area. Since the phase difference can be obtained regardless of the radio wave reception strength by defining different first and second positions, the influence of fluctuations in the radio wave reception strength on moving object detection can be reduced by estimating the presence or absence of a moving object based on an index value corresponding to the magnitude of the variance. This improves the accuracy of moving object detection based on the radar principle.

[0008] 1 illustrates an example of the functional configuration of a moving object detection system according to an embodiment. 2 illustrates an example of processing executed by the processing device of FIG. 1. 3 illustrates another example of processing executed by the processing device of FIG. 1. 4 illustrates another example of processing executed by the processing device of FIG. 1. 5 illustrates a vehicle equipped with the moving object detection system of FIG. 1.

[0009] The following detailed description of exemplary embodiments will be given with reference to the accompanying drawings. In the drawings used in the following description, the scale of each element is appropriately changed so that it can be recognized.

[0010] 1 illustrates the functional configuration of a moving object detection system 10 according to an embodiment. The moving object detection system 10 is configured to detect a moving object 30 located within a detection area 20 based on the radar principle.

[0011] The moving object detection system 10 includes a transmitting antenna 11. The transmitting antenna 11 is configured to transmit radio waves W toward a detection area 20. The frequency of the radio waves W can be determined as appropriate. The radio waves W in this example have a frequency that is classified as a microwave.

[0012] The moving object detection system 10 includes a first receiving antenna 121. The first receiving antenna 121 is configured to receive radio waves W arriving from the detection area 20 at a first position P1. In other words, the first receiving antenna 121 is configured to be sensitive to the frequency of the radio waves W.

[0013] The first receiving antenna 121 is configured to output a first detection signal S1 corresponding to the radio wave intensity at the first position P1. The first detection signal S1 may be an analog signal or a digital signal depending on the specifications of the first receiving antenna 121.

[0014] The moving object detection system 10 includes a second receiving antenna 122. The second receiving antenna 122 is configured to receive radio waves W arriving from the detection area 20 at a second position P2 different from the first position P1. In other words, the second receiving antenna 122 is also configured to be sensitive to the frequency of the radio waves W.

[0015] The second receiving antenna 122 is configured to output a second detection signal S2 corresponding to the radio wave intensity at the second position P2. The second detection signal S2 may be an analog signal or a digital signal depending on the specifications of the second receiving antenna 122.

[0016] The moving object detection system 10 includes a processing device 13. The processing device 13 includes an input interface 131, a processor 132, and an output interface 133.

[0017] The input interface 131 is configured as a hardware interface capable of receiving the first detection signal S1 and the second detection signal S2. When the first detection signal S1 and the second detection signal S2 are analog signals, the input interface 131 is provided with an appropriate conversion circuit including an A / D converter.

[0018] The processor 132 is configured to output, from an output interface 133 configured as a hardware interface, a transmission control signal TC for causing the transmitting antenna 11 to transmit radio waves W. The transmission control signal TC includes information capable of specifying the time when the transmitting antenna 11 is to transmit radio waves W.

[0019] The transmission control signal TC may be an analog signal or a digital signal depending on the specifications of the transmitting antenna 11. When the transmission control signal TC is an analog signal, the output interface 133 includes an appropriate conversion circuit including a D / A converter. This description also applies to other signals that can be output from the output interface 133, which will be described later.

[0020] The processor 132 is configured to execute a process for estimating the presence or absence of a moving object 30 in the detection area 20 based on the first detection signal S1 and the second detection signal S2. The process will be described in detail with reference to FIGS. 2 and 3.

[0021] The processor 132 of the processing device 13 outputs a transmission control signal TC from the output interface 133, thereby causing the transmitting antenna 11 to repeatedly transmit radio waves W. The radio waves W are reflected by an object present in the detection area 20 and received by the first receiving antenna 121 and the second receiving antenna 122.

[0022] The processor 132 identifies the I component and the Q component of the radio wave W received by the first receiving antenna 121 based on the first detection signal S1 output from the first receiving antenna 121. The identified I component and Q component correspond to one point on the complex coordinate plane illustrated in FIG.

[0023] A first data set is acquired by identifying the I and Q components of all radio waves W transmitted from the transmitting antenna 11 and received by the first receiving antenna 121. The first data set corresponds to a first point distribution D1 formed on a complex coordinate plane. A similar process is performed on the second detection signal S2 output from the second receiving antenna 122, to acquire a second data set. The second data set corresponds to a second point distribution D2 formed on a complex coordinate plane.

[0024] When a moving object 30 that vibrates periodically is present within the detection area 20, a periodic variation occurs in the time it takes for the reflected radio waves W to reach the first receiving antenna 121 and the second receiving antenna 122. As a result, each of the first point distribution D1 and the second point distribution D2 exhibits an arc shape on the complex coordinate plane.

[0025] Next, processor 132 calculates the average value of the Q coordinate values ​​and the average value of the I coordinate values ​​of all points forming first point distribution D1. This process corresponds to specifying an average position AP1 in first point distribution D1. Similarly, processor 132 calculates the average value of the Q coordinate values ​​and the average value of the I coordinate values ​​of all points forming second point distribution D2. This process corresponds to specifying an average position AP2 in second point distribution D2.

[0026] Subsequently, the processor 132 performs a process on each of the first data set and the second data set that corresponds to an operation of moving each of the average positions AP1 and AP2 to the origin O of the complex coordinate plane.

[0027] As described above, the transmission control signal TC output from the processing device 13 includes information related to the time point at which the radio waves W are transmitted from the transmitting antenna 11, and therefore the processor 132 can identify which point on the complex coordinate plane was acquired by the radio waves W transmitted at which time point. This allows the processor 132 to identify data acquired in conjunction with reception of the same radio waves W from each of the first data set and the second data set. This processing corresponds to identifying point p1 included in the first point distribution D1 and point p2 included in the second point distribution D2 on the complex coordinate plane.

[0028] The two identified data correspond to the reception state at a first position P1 and the reception state at a second position P2 of radio waves W transmitted from the transmitting antenna 11 at a certain point in time. Because the first position P1 and the second position P2 are different, a phase difference occurs between the radio waves W received by the first receiving antenna 121 and the radio waves W received by the second receiving antenna 122. The processor 132 acquires information corresponding to this phase difference. Specifically, this information can be acquired by identifying the angle θ formed by points p1 and p2 with the origin O of the complex coordinate plane as the center.

[0029] By determining the phase difference for all radio waves W transmitted from the transmitting antenna 11 as described above, the processor 132 obtains time series data TS indicating the relationship between the time at which the radio waves W were received and the phase difference.

[0030] 3 illustrates the results of the above processing when no moving object 30 is present in the detection area 20. The first point distribution D1 and the second point distribution D2 on the complex coordinate plane each exhibit a more aggregated form than when a periodically vibrating moving object 30 is present. Identifying the average position of each point distribution, moving the point distribution to the coordinate origin, identifying the angle θ corresponding to the phase difference, and acquiring the time-series data TS are also performed in the same manner as in the example described with reference to FIG. 2, although the angle θ is not shown.

[0031] The processor 132 acquires an index value corresponding to the magnitude of the directional statistical variance of the phase differences included in the time-series data TS. Examples of the index value include the value of the variance itself, as well as a function of the variance, the standard deviation, and a function of the standard deviation. As can be seen from a comparison between FIGS. 2 and 3, the variance of the phase difference values ​​is greater when no moving object 30 is present in the detection area 20. Therefore, when an index value corresponding to a situation in which the magnitude of the variance is below a threshold is obtained, the processor 132 estimates that a moving object 30 is present in the detection area 20.

[0032] The inventors of the present application have found that the magnitude of the directional statistical variance of the phase difference occurring between radio waves W transmitted from the transmitting antenna 11 and received by the first receiving antenna 121 and the second receiving antenna 122 correlates with the presence or absence of a moving object 30 in the detection area 20. Since the phase difference can be obtained regardless of the reception strength of the radio waves W by defining different first and second positions P1 and P2, the influence of fluctuations in the reception strength of the radio waves W on moving object detection can be suppressed by estimating the presence or absence of a moving object 30 based on an index value corresponding to the magnitude of the variance. Therefore, the accuracy of moving object detection based on the radar principle can be improved.

[0033] The first detection signal S1 output from the first receiving antenna 121 and the second detection signal S2 output from the second receiving antenna 122 each contain information corresponding to the time elapsed from when the radio wave W is transmitted from the transmitting antenna 11 until it is received. The elapsed time corresponds to the distance to the object that reflected the radio wave W.

[0034] 4 and 5 illustrate the relationship between the elapsed time and the index value obtained as described above. The index value in this example is defined as the reciprocal of the magnitude of the variance of the phase difference values. Therefore, a larger value corresponds to a situation with a smaller variance. FIG. 4 corresponds to the case where a moving object 30 is present in the detection area 20 (time-series data TS illustrated in FIG. 2). FIG. 5 corresponds to the case where a moving object 30 is not present in the detection area 20 (time-series data TS illustrated in FIG. 3).

[0035] The processor 132 can be configured to estimate the distance to the moving object 30 based on the elapsed time since the radio waves W associated with each index value were transmitted. In this example, as illustrated in Fig. 4, the distance corresponding to the elapsed time during which the index value exceeds a predetermined threshold value Th is identified as the distance to the moving object 30.

[0036] 1, the transmitting antenna 11, the first receiving antenna 121, and the second receiving antenna 122 may be supported on a common substrate 14. An example of the substrate 14 is a circuit board on which these antenna elements can be mounted.

[0037] When the first receiving antenna 121 and the second receiving antenna 122 approach the transmitting antenna 11 to the extent that they are supported by the common substrate 14, a phenomenon called loopback may occur, in which a portion W' of the radio waves transmitted from the transmitting antenna 11 flows into the first receiving antenna 121 and the second receiving antenna 122 without passing through the detection area 20, as illustrated in Fig. 1. In this case, observation results may be obtained that suggest the presence of an object in the area corresponding to the short distance indicated by the diagonal lines in Figs.

[0038] 4 and 5, the influence of loopback can be ignored in the index value corresponding to the magnitude of the directional statistical variance of the phase difference of the radio waves W received by the first receiving antenna 121 and the second receiving antenna 122, so it is possible to further improve the detection accuracy of the moving object 30 based on the radar principle. In addition, since additional circuits and processing for removing phenomena caused by loopback are not required, the complexity of the moving object detection system 10 can be suppressed.

[0039] 6 , the moving object detection system 10 can be mounted on a vehicle 40. In this case, the detection area 20 is set to include the interior of a passenger compartment 41 of the vehicle 40. The vehicle 40 is an example of a moving object. The passenger compartment 41 is an example of a living space.

[0040] With this configuration, it is possible to detect a moving object 30 located inside the vehicle interior 41. If the moving object 30 is a living organism, it is possible to detect body movements associated with periodic vital signs (heartbeat, breathing, etc.) as the moving object 30. This makes it possible to estimate, for example, whether a child or a pet has been left behind inside the vehicle interior 41.

[0041] 1 , the processor 132 of the processing device 13 can be configured to output a control signal CT from the output interface 133 when it is estimated that a moving object 30 is present in the detection area 20 based on the first detection signal S1 and the second detection signal S2. The control signal CT is configured to cause the controlled device 50 to perform a predetermined operation. Examples of the controlled device 50 include an alarm device and a communication device.

[0042] For example, if it is estimated that a child or a pet has been left behind in the vehicle interior 41, an alarm device mounted on the vehicle 40 may provide at least one of a visual alarm and an audible alarm to the user of the vehicle 40 or the surrounding area. Examples of notification methods include honking the horn of the vehicle 40, turning on all lighting devices of the vehicle 40, or automatically driving the vehicle 40 to a location where people are present. Additionally or alternatively, a communication device mounted on the vehicle 40 may notify a mobile device carried by the user of the vehicle 40 of the estimated fact. An image captured inside the vehicle interior 41 may be transmitted together with the notification of the fact.

[0043] In addition to or instead of the above-described notification, an intervention process may be performed to change the environment inside the vehicle compartment 41. Examples of the intervention process include automatically controlling an air conditioning device (heating and cooling), opening a window of the vehicle 40, unlocking a door of the vehicle 40, opening or closing a sunshade, and the like.

[0044] The processor 132 having the various functions described above may be realized by at least one general-purpose microprocessor operating in cooperation with at least one general-purpose memory. Examples of general-purpose microprocessors include a CPU, an MPU, and a GPU. Examples of general-purpose memory include a ROM and a RAM. In this case, a computer program for implementing the corresponding functions may be stored in the ROM. The ROM is an example of a non-transitory computer-readable medium storing a computer program. The general-purpose microprocessor specifies at least a portion of the computer program stored in the ROM, expands it on the RAM, and executes the above-described processing in cooperation with the RAM. The computer program may be pre-installed in the general-purpose memory or may be downloaded from an external server via a communication network and then installed in the general-purpose memory. In this case, the external server is an example of a computer-readable medium storing a computer program.

[0045] The processor 132 may be implemented by at least one dedicated integrated circuit capable of executing the computer program. Examples of the dedicated integrated circuit include a microcontroller, an ASIC, and an FPGA. In this case, the computer program is pre-installed in a memory element included in the dedicated integrated circuit. The memory element is an example of a computer-readable medium storing a computer program. The processor 132 may also be implemented by a combination of a general-purpose microprocessor and a dedicated integrated circuit.

[0046] The configurations described above are merely examples to facilitate understanding of the present disclosure. Each configuration example can be appropriately modified and combined with other configuration examples without departing from the spirit of the present disclosure.

[0047] In the above embodiment, two receiving antennas are assigned to one transmitting antenna 11. However, the number of receiving antennas assigned to one transmitting antenna 11 may be three or more. If multiple receiving antennas are assigned to one transmitting antenna 11, the number of transmitting antennas 11 included in the motion detection system 10 may be two or more.

[0048] Alternatively, if a single receiving antenna can acquire the phase difference of the radio waves W by moving at high speed between a first position P1 and a second position P2, the single receiving antenna can be assigned to the transmitting antenna 11. In this case, the single receiving antenna located at the first position P1 is an example of a first receiving antenna, and the single receiving antenna located at the second position P2 is an example of a second receiving antenna.

[0049] The form of the vehicle 40 in Figure 6 is merely an example. The number of seats and wheels in the vehicle 40 in which the moving object detection system 10 is installed can be determined as appropriate. Note that the moving object detection system 10 does not necessarily have to be installed in a vehicle 40. Examples of other moving objects in which the moving object detection system 10 is installed include trains, airplanes, and ships. The moving object does not need to require a driver. The position and size of the detection area 20 can be determined as appropriate depending on the type of moving object.

[0050] The moving object detection system 10 does not necessarily have to be mounted on a moving object. The moving object detection system 10 can be installed in a suitable home, facility, equipment, etc. The position and size of the detection area 20 can be determined appropriately depending on the installation location and the type of moving object 30 to be detected. In other words, the moving object 30 does not necessarily have to be a living organism. Furthermore, the moving object 30 does not necessarily have to exhibit periodic displacement.

[0051] The contents of Japanese Patent Application No. 2023-223013 filed on December 28, 2023 are incorporated by reference as part of this disclosure.

Claims

1. A moving object detection system comprising: a transmitting antenna that transmits radio waves toward a detection area; a first receiving antenna that receives radio waves arriving from the detection area at a first position and outputs a first detection signal corresponding to the radio wave intensity at the first position; a second receiving antenna that receives radio waves arriving from the detection area at a second position and outputs a second detection signal corresponding to the radio wave intensity at the second position; and a processing device that estimates the presence or absence of a moving object in the detection area based on an index value corresponding to the magnitude of the statistical variance in the direction related to the phase difference between the first detection signal and the second detection signal.

2. The moving object detection system according to claim 1, wherein the processing device estimates the distance to the moving object based on the elapsed time since the radio wave associated with the index value was transmitted.

3. The moving object detection system according to claim 1 or 2, wherein the transmitting antenna, the first receiving antenna, and the second receiving antenna are supported on a common substrate.

4. The moving object detection system according to any one of claims 1 to 3, wherein when the presence of a moving object is estimated in the detection area, the processing device causes a controlled device to perform a predetermined operation.

5. The moving object detection system according to any one of claims 1 to 4, wherein the moving object is a living body.

6. The moving object detection system according to any one of claims 1 to 5, wherein the detection area is set to include the interior of a moving object.

7. The moving object detection system according to any one of claims 1 to 6, wherein the radio wave has a frequency classified as a microwave.

8. A processing device comprising: a processor that causes a transmitting antenna to transmit radio waves toward a detection area; and an interface that receives a first detection signal corresponding to the radio wave intensity at a first position from a first receiving antenna that receives radio waves arriving from the detection area at the first position, and receives a second detection signal corresponding to the radio wave intensity at a second position from a second receiving antenna that receives radio waves arriving from the detection area at the second position, wherein the processor estimates the presence or absence of a moving object in the detection area based on an index value corresponding to the magnitude of the statistical variance in the direction related to the phase difference between the first detection signal and the second detection signal.

9. A non-transitory computer-readable medium storing a computer program executable by a processor mounted on a processing device, wherein when the computer program is executed, the processing device causes a transmission antenna to transmit radio waves toward a detection area, receives a first detection signal corresponding to the radio wave intensity at a first position from a first reception antenna that receives radio waves arriving from the detection area at the first position, receives a second detection signal corresponding to the radio wave intensity at a second position from a second reception antenna that receives radio waves arriving from the detection area at the second position, and estimates the presence or absence of a moving object in the detection area based on an index value corresponding to the magnitude of the statistical variance in the direction related to the phase difference between the first detection signal and the second detection signal.

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