Occupant detection device

Abstract

To provide an occupant detection device with high detection accuracy.SOLUTION: An occupant detection device comprising a rader that transmits an electromagnetic wave in a room of a vehicle and receives a signal as a reflection wave of the electromagnetic wave to detect the presence or absence of a crew member in the room of the vehicle on the basis of the received signal is characterized in that the rader includes a first filter that makes a signal of a component of vibration of the vehicle in a run state among the signals that the rader has received pass through, a second filter that makes a signal of a component of human motion among the signals that the rader has received pass through, a signal intensity measurement unit that measures the intensity of the signal that has passed through the first filter and the second filter, and a detector comparing the intensity of the signal that has passed through the second filter measured by the signal intensity measurement unit with a threshold to detect a crew member according to the comparison result and altering the threshold according to the intensity of the signal that has passed through the first filter.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an occupant detection device. [Background technology]

[0002] Conventionally, there has been an occupant detection device that includes a radar that transmits electromagnetic waves into a vehicle cabin and receives reflected waves of the electromagnetic waves, and detects the status of occupants in the vehicle cabin based on the reflected waves, characterized in that one radar is provided in the vehicle cabin, and the radar is positioned closest to the driver's seat among the seats in the vehicle cabin, and is positioned so that the distances to each seat are different (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-181225 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional occupant detection devices, there is a possibility that false detection may occur when the vehicle vibrates while traveling, causing the occupants or objects inside the vehicle to shake, and there is a risk that the detection accuracy may decrease.

[0005] Therefore, an object of the present invention is to provide an occupant detection device with high detection accuracy. [Means for solving the problem]

[0006] An occupant detection device according to an embodiment of the present invention includes a radar that transmits electromagnetic waves into a vehicle cabin and receives a signal as a reflected wave of the electromagnetic waves, and detects the presence or absence of an occupant in the vehicle cabin based on the received signal, and is characterized in that it includes a first filter that passes a signal component of the vibration of the vehicle while it is moving from the signal received by the radar, a second filter that passes a signal component of the human movement from the signal received by the radar, a signal strength measuring unit that measures the strength of the signal that has passed through the first filter and the second filter, and a detection unit that compares the strength of the signal that has passed through the second filter measured by the signal strength measuring unit with a threshold value and detects an occupant based on the comparison result, and changes the threshold value based on the strength of the signal that has passed through the first filter. Effect of the Invention

[0007] It is possible to provide an occupant detection device with high detection accuracy. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of a configuration of an occupant detection device 100 according to an embodiment. [Diagram 2] 1 is a diagram showing an example of a passenger compartment of a vehicle 1 in which an occupant detection device 100 is arranged. [Diagram 3] 3A and 3B are diagrams illustrating a transmission signal and a reception signal of the occupant detection device 100. [Figure 4] FIG. 13 is a flowchart showing the processing executed by a detection unit 180. [Diagram 5] FIG. 11 is a flowchart showing a process executed by a detection unit 180 according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment to which the occupant detection device of the present invention is applied will be described.

[0010] <Embodiment> FIG. 1 is a diagram showing an example of a configuration of an occupant detection device 100 according to an embodiment. The occupant detection device 100 includes a transmitting antenna 101Tx, a receiving antenna 101Rx, a PA (Power Amplifier) ​​110Tx, an LNA (Low Noise Amplifier) ​​110Rx, a switch 115A, a signal output unit 115B, a mixer 120, a DEMUX (demultiplexer) 130, a HPF (High Pass Filter) 140A, a BPF (Band Pass Filter) 140B, a signal strength measurement unit 150A, a signal strength measurement unit 150B, a short-distance data averaging unit 160A1, a long-distance data averaging unit 160A2, a total distance data averaging unit 160A3, a short-distance data averaging unit 160B1, a long-distance data averaging unit 160B2, a total distance data averaging unit 160B3, an LPF (Low Pass Filter) 165, a MUX (multiplexer) 170, and a detection unit 180. The HPF 140A is an example of a first filter, and the BPF 140B is an example of a second filter. The PA 110Tx, the LNA 110Rx, the switch 115A, the signal output unit 115B, and the mixer 120 constitute the radar 110.

[0011] The occupant detection device 100 is provided inside the vehicle, transmits a radar transmission signal (electromagnetic wave) from a transmitting antenna 101Tx, receives a signal as a reflected wave reflected by an occupant or object inside the vehicle by a receiving antenna 101Rx, and detects the presence or absence of an occupant inside the vehicle based on the received signal. An occupant or object inside the vehicle is an example of an object that can be detected. Since the signal strength of the reflected wave varies depending on the material of the object and the shape (orientation) of the reflecting surface, if the object moves, the strength of the reflected wave changes. Since it is the occupant that moves inside the vehicle, the occupant can be detected.

[0012] The transmitting antenna 101Tx is connected to a signal output unit 115B via the PA 101Tx and a switch 115A, and transmits a transmission signal output from the signal output unit 115B, via the switch 115A, and amplified by the PA 101Tx to the interior of the vehicle.

[0013] The receiving antenna 101Rx is connected to the LNA 110Rx, receives the signal output from the transmitting antenna 101Tx as a reflected wave reflected by an occupant or an object in the vehicle cabin, and outputs the signal to the LNA 110Rx.

[0014] The PA 110Tx is provided between the switch 115A and the transmitting antenna 101Tx, and amplifies the transmission signal that is output from the signal output unit 115B and input via the switch 115A, and outputs the amplified signal to the transmitting antenna 101Tx.

[0015] The LNA 110Rx is provided between the receiving antenna 101Rx and the mixer 120, and amplifies the signal received by the receiving antenna 101Rx in a low-noise state and outputs the amplified signal to the mixer 120.

[0016] The switch 115A is provided between the signal output unit 115B and the PA101Tx, and is turned on at a predetermined sampling period by being controlled by the detection unit 180, and outputs a transmission signal to the PA101Tx. The predetermined sampling frequency is, for example, 20 Hz.

[0017] The signal output unit 115B outputs a transmission signal used to detect an occupant or object in the vehicle. The signal output unit 115B has two output terminals, which are connected to the switch 115A and the mixer 120, respectively. The occupant detection device 100 receives a signal as a reflected wave reflected by an occupant or object in the vehicle, and detects the distance to the occupant or object based on the round-trip time from transmission from the transmitting antenna 101Tx to reception of the reflected wave. For this reason, the radar 110 may be a pulse coherent radar, for example, as long as it is capable of detecting such a round-trip time.

[0018] The mixer 120 is connected to the output terminal of the LNA 110Rx, the output terminal of the signal output unit 115B, and the input terminal of the DEMUX 130. The mixer 120 combines (down-converts) the signal input from the LNA 110Rx with a signal of the same frequency as the transmission signal input from the signal output unit 115B, and outputs the result as a received signal indicating the reflection level of the reflected wave to the input terminal of the DEMUX 130. When there is no reflection, the reflection level becomes the noise floor.

[0019] The DEMUX 130 has one input terminal and five output terminals. The input terminal is connected to the output terminal of the mixer 120. Each of the five output terminals is connected to one of the five signal strength measurement units 150A via one of the five HPFs 140A, and is also connected to one of the five signal strength measurement units 150B via one of the five BPFs 140B.

[0020] Here, a configuration is shown as an example in which the DEMUX 130 has five output terminals, and five signal strength measurement units 150A and five signal strength measurement units 150B are connected to the five output terminals. However, the number of output terminals of the DEMUX 130, the number of signal strength measurement units 150A, and the number of signal strength measurement units 150B are not limited to five, and may be three or more.

[0021] Here, a number of reception periods (here, five reception periods as an example) corresponding to the number of output terminals are provided in one detection, and radar 110 transmits the transmission signal a number of times corresponding to the number of output terminals. One detection is performed by turning on switch 115A once, so detection is performed in a sampling period in which switch 115A is turned on.

[0022] As an example, a transmission signal is sent from the transmitting antenna 101Tx and the receiving antenna 101Rx toward the seat surface of a seat placed inside the vehicle, and the presence or absence of an occupant in the seat is determined. A single detection means that the space between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface of the seat placed inside the vehicle is divided into a number of regions (five regions in this example) corresponding to the number of output terminals in the direction connecting the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface, and the presence or absence of an occupant is determined once in each region.

[0023] In this way, the space between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface of the seat placed in the vehicle cabin is divided into multiple regions corresponding to the number of output terminals, and the radar 110 transmits the transmission signal a number of times corresponding to the number of output terminals. Therefore, the signals transmitted multiple times and received multiple times are multiple signals with different round trip times to the occupant or object. The radar 110 transmits the transmission signal toward multiple regions with different measurement distances.

[0024] Here, as an example, the space between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface of the seat arranged in the vehicle is divided into five regions in the direction connecting the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface of the seat, and the presence or absence of an occupant is determined in each region. Therefore, in one detection, the transmitting signal is transmitted from the transmitting antenna 101Tx and the receiving antenna 101Rx to five regions at different distances, and reception is performed in five reception periods. Also, as an example, the transmission frequency of the transmission signal output by the signal output unit 115B may be set to 100 Hz or more, which is five times the sampling frequency (20 Hz). In other words, when the area is divided into five regions by distance and sampling is performed at a period of 50 ms, the transmission period of the transmission signal is set to 10 ms or less. Note that the transmission signal does not have to be transmitted at equal intervals. For example, the transmission signal may be transmitted five times at a period of 1 ms, and then the transmission may be stopped for a period of 45 ms.

[0025] The DEMUX 130 selects one output terminal in each reception period. The DEMUX 130 selects one of the five output terminals in order each time the reception periods are switched, and outputs the reception signal input from the mixer 120 of the radar 110 in each reception period.

[0026] As an example here, the DEMUX 130 selects five reception signals in sequence, one at a time, from the upper output terminal to the lower output terminal in Fig. 1. Therefore, the reception signal output to the uppermost output terminal is the reception signal obtained in the first reception period of the five reception periods, and the reception signal output to the lowermost output terminal is the reception signal obtained in the last reception period of the five reception periods.

[0027] In the first reception period of the five reception periods, the DEMUX 130 obtains reception signals for the area closest to the transmitting antenna 101Tx and the receiving antenna 101Rx among the five areas obtained by dividing the area between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface into five, from the mixer 120. If no passenger or object is present in the area closest to the transmitting antenna 101Tx and the receiving antenna 101Rx among the five areas and no reflected waves are generated, the level of the reception signal in the first reception period becomes the noise floor.

[0028] Furthermore, in the last (fifth) reception period of the five reception periods, the DEMUX 130 obtains reception signals for the region farthest from the transmitting antenna 101Tx and the receiving antenna 101Rx among the five regions obtained by dividing the area between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat cushion from the mixer 120. Since the seat cushion is present in the region farthest from the transmitting antenna 101Tx and the receiving antenna 101Rx among the five regions, a reflected wave is obtained in the region farthest from the transmitting antenna 101Tx and the receiving antenna 101Rx when no passenger is present.

[0029] In this way, the DEMUX 130 distributes and outputs five reception signals obtained in five reception periods for five regions obtained by dividing the space between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface into five regions to five output terminals, so that the reception signals output from each output terminal indicate the reflection level of the reflected wave in each of the divided regions obtained by dividing the space between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface into five regions. The DEMUX 130 outputs the reception signals indicating the reflection level of the reflected wave in the five divided regions from separate output terminals in a time-division manner, so that the space between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface can be divided into five regions, and it is possible to determine whether an occupant or object is present in each region.

[0030] Here, the five reception periods may be set, as an example, based on the period required for the reflected wave to be received by the receiving antenna 101Rx when the transmitted signal is reflected by an occupant or an object in each of five regions divided between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface of the seat.

[0031] One HPF 140A is provided between each output terminal of the DEMUX 130 and each of the five signal intensity measuring units 150A. The HPF 140A has a cutoff frequency for passing high frequency band components (hereinafter referred to as vehicle signal components) corresponding to vehicle vibration components contained in each received signal, and blocks frequency components below the cutoff frequency.

[0032] The cutoff frequency of the HPF 140A is, for example, 5 Hz. Here, as an example, a high frequency band corresponding to the vibration components of the vehicle is 5 Hz or more, and a mode in which the cutoff frequency of the HPF 140A is set to 5 Hz will be described, but the cutoff frequency of the HPF 140A may be set to an appropriate value according to the type of vehicle and other factors.

[0033] When vibrations occur in the vehicle 1 while it is moving, the components of 5 Hz or higher in the received signal as reflected waves increase, and the signal strength of the components passing through the HPF 140A increases. Therefore, if the signal strength of the components passing through the HPF 140A increases, it can be determined that the vehicle 1 is moving. The running state of the vehicle 1 can be determined by using the HPF 140A.

[0034] The BPF 140B is provided between each output terminal of the DEMUX 130 and the five signal intensity measuring units 150B. The BPF 140B has two cutoff frequencies for passing components in a frequency band corresponding to vibration components related to the occupant's movements contained in each received signal (hereinafter, occupant movement components), and passes components with frequencies equal to or higher than the lower cutoff frequency and lower than the higher cutoff frequency. As an example, the two cutoff frequencies of the BPF 140B are 0.5 Hz and 5 Hz. Therefore, the BPF 140B passes signals in a frequency band equal to or higher than 0.5 Hz and lower than 5 Hz. Here, as an example, a form in which the frequency band corresponding to the vibration components related to the occupant's movements is equal to or higher than 0.5 Hz and lower than 5 Hz will be described.

[0035] If the detectable object in the vehicle 1 does not move, the output of the BPF 140B is the noise floor, but if the occupant moves, the direction and intensity of the reflected wave change, and the output of the BPF 140B increases. The occupant detection device 100 can also detect the movement caused by the breathing of the occupant.

[0036] The signal strength measurement unit 150A is connected to the output side of each HPF 140A and measures the signal strength of the vehicle vibration component of the received signal. The five signal strength measurement units 150A shown in Fig. 1 are input with the received signal obtained in the first reception period to the last reception period of the five reception periods, in order from top to bottom. Each signal strength measurement unit 150A outputs the signal strength of the vehicle vibration component of each received signal.

[0037] The signal strength measurement unit 150B is connected to the output side of each BPF 140B and measures the signal strength of the occupant movement component of the received signal. The five signal strength measurement units 150B shown in Fig. 1 are input with the received signal obtained in the first reception period to the last reception period, in order from top to bottom. Each signal strength measurement unit 150B outputs the signal strength of the occupant movement component of each received signal.

[0038] The short-distance data averaging unit 160A1 is connected to the topmost and second-topmost signal strength measuring units 150A of the five signal strength measuring units 150A shown in Fig. 1, and outputs the average strength of the signal strength of the vehicle vibration component for the first reception period of the five reception periods and the signal strength of the vehicle vibration component for the second reception period. Therefore, the short-distance data averaging unit 160A1 outputs the average value (short-distance components) of the signal strength of the vehicle vibration component obtained in two regions, the closest divided region to the transmitting antenna 101Tx and receiving antenna 101Rx and the second closest divided region, among the five divided regions obtained by dividing the space from the transmitting antenna 101Tx and receiving antenna 101Rx to the seat surface.

[0039] The long-distance data averaging unit 160A2 is connected to the two signal strength measuring units 150A, the lowest and the second from the bottom, of the five signal strength measuring units 150A shown in Fig. 1, and outputs the average strength of the signal strength of the vehicle vibration component for the last reception period of the five reception periods and the signal strength of the vehicle vibration component for the second from the last reception period. Therefore, the long-distance data averaging unit 160A2 outputs the average value (long-distance component) of the signal strength of the vehicle vibration component obtained in two regions, the divided region closest to the seat surface and the divided region second closest to the seat surface, among the five divided regions obtained by dividing the space from the transmitting antenna 101Tx and the receiving antenna 101Rx to the seat surface.

[0040] 1, and outputs the average strength of the signal strength of the vehicle vibration component for all five reception periods. Therefore, the total distance data averaging unit 160A3 outputs the average strength of the signal strength of the vehicle vibration component (total distance component) in all divided regions obtained by dividing the space between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface into five.

[0041] The short-distance data averaging unit 160B1 is connected to the topmost and second-topmost signal strength measuring units 150B of the five signal strength measuring units 150B shown in Fig. 1, and outputs the average strength of the signal strength of the occupant movement component for the first reception period of the five reception periods and the signal strength of the occupant movement component for the second reception period. Therefore, the short-distance data averaging unit 160B1 outputs the average value (short-distance components) of the signal strength of the occupant movement component obtained in two regions, the closest divided region to the transmitting antenna 101Tx and receiving antenna 101Rx and the second closest divided region, among the five divided regions obtained by dividing the space from the transmitting antenna 101Tx and receiving antenna 101Rx to the seat surface.

[0042] The long-distance data averaging unit 160B2 is connected to the two signal strength measuring units 150B, the lowest and the second from the bottom, of the five signal strength measuring units 150B shown in Fig. 1, and outputs the average strength of the signal strength of the occupant movement component for the last reception period of the five reception periods and the signal strength of the occupant movement component for the second from the last reception period. Therefore, the long-distance data averaging unit 160B2 outputs the average value (long-distance components) of the signal strength of the occupant movement component obtained in two regions, the divided region closest to the seat surface and the divided region second closest to the seat surface, among the five divided regions obtained by dividing the space from the transmitting antenna 101Tx and the receiving antenna 101Rx to the seat surface.

[0043] 1, and outputs the average strength of the signal strength of the occupant movement components for all five reception periods. Therefore, the total distance data averaging unit 160B3 outputs the average strength of the signal strength of the occupant movement components (total distance components) in all divided regions obtained by dividing the space between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface of the seat into five.

[0044] LPF165 is provided on the output side of each of short-distance data averaging section 160A1, long-distance data averaging section 160A2, total-distance data averaging section 160A3, short-distance data averaging section 160B1, long-distance data averaging section 160B2, and total-distance data averaging section 160B3, and outputs the EMA (Exponential Moving Average) of the average value of the signal strength input to each of them to MUX170.

[0045] MUX 170 has six input terminals connected to the output terminals of the six LPFs 165, and an output terminal connected to detection unit 180, and selects in sequence the EMAs for the signal strengths output from the six LPFs 165 and outputs them to detection unit 180.

[0046] The detection unit 180 is realized by a computer including a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), an input / output interface, an internal bus, and the like.

[0047] The detection unit 180 controls the PA 110Tx, LNA 110Rx, switch 115A, signal output unit 115B, mixer 120, DEMUX 130, HPF 140A, BPF 140B, signal strength measurement unit 150A, signal strength measurement unit 150B, short distance data averaging unit 160A1, long distance data averaging unit 160A2, total distance data averaging unit 160A3, short distance data averaging unit 160B1, long distance data averaging unit 160B2, total distance data averaging unit 160B3, LPF 165, and MUX 170.

[0048] Furthermore, detection unit 180 sets a threshold value for determining the presence or absence of an occupant depending on the state of vehicle 1 (running on a flat road, running on a non-flat road, or stopped), compares the intensities of signals output from short-distance data averaging unit 160B1, long-distance data averaging unit 160B2, and total-distance data averaging unit 160B3 with the threshold value, and detects an occupant depending on the comparison result. Details of the process executed by detection unit 180 will be described later using the flowchart of FIG. 4.

[0049] FIG. 2 is a diagram showing an example of a room of a vehicle 1 in which an occupant detection device 100 is arranged. A seat 2 is arranged in the room of the vehicle 1. As an example, a rear seat is shown as the seat 2, in which three occupants are seated. A transceiver unit 105 is provided on the ceiling of the room of the vehicle 1. The transceiver unit 105 is a part including a transmitting antenna 101Tx and a receiving antenna 101Rx in the occupant detection device 100 shown in FIG. 1. The transceiver unit 105 shown in FIG. 2 has three antennas 101. Each antenna 101 includes a transmitting antenna 101Tx and a receiving antenna 101Rx. The three antennas 101 are directed toward the seating surfaces of the three-seater seat 2, and are configured to detect the presence or absence of an occupant on each seating surface of the three-seater seat 2.

[0050] Fig. 3 is a diagram showing a transmission signal and a reception signal of the occupant detection device 100. As shown in Fig. 3(A), the frequency of the transmission signal of the occupant detection device 100 is 60.5 GHz, for example. It is preferable to use millimeter waves (30 GHz to 300 GHz) for occupant detection. The distance to the occupant or object is detected based on the round-trip time from when the transmission signal is sent to when the reception signal is received.

[0051] 3B, when transmitting the transmission signal output from the signal output unit 115B, the sampling frequency for turning on the switch 115A is, for example, 20 Hz. Here, as an example, the DEMUX 130 has five output terminals, and in one detection, in order to obtain reception signals for five regions obtained by dividing the space between the transmitting antenna 101Tx and the receiving antenna 101Rx and the seat surface into five, the transmission frequency of the transmission signal output from the signal output unit 115B may be set to 100 Hz or more, which is five times the sampling frequency (20 Hz).

[0052] Fig. 4 is a diagram showing a flowchart showing the processing executed by the detection unit 180. When executing the processing shown in Fig. 4, the detection unit 180 controls the PA110Tx, the LNA110Rx, the switch 115A, the signal output unit 115B, the mixer 120, the DEMUX130, the HPF140A, the BPF140B, the signal strength measurement unit 150A, the signal strength measurement unit 150B, the short distance data averaging unit 160A1, the long distance data averaging unit 160A2, the total distance data averaging unit 160A3, the short distance data averaging unit 160B1, the long distance data averaging unit 160B2, the total distance data averaging unit 160B3, the LPF165, and the MUX170.

[0053] When the flow starts, the detection unit 180 controls the radar 110 to acquire a received signal (step S1).

[0054] The detection unit 180 determines whether the output of the long-distance data averaging unit 160A2 obtained from the MUX 170 is equal to or greater than a first threshold value for determining the running state of the vehicle 1 (step S2). The first threshold value may be set as a value that is a boundary between the output in the running state and the output in the stopped state by previously acquiring the output of the long-distance data averaging unit 160A2 obtained when the vehicle 1 is running and the output of the long-distance data averaging unit 160A2 obtained when the vehicle 1 is stopped. Since the vehicle 1 experiences greater vibrations when it is running than when it is stopped, if the output of the long-distance data averaging unit 160A2 is equal to or greater than the first threshold value, it can be determined that the vehicle 1 is in the running state.

[0055] The reason why the output of long distance data averaging unit 160A2 is used in step S2 is that, in determining whether the vehicle 1 is moving or stopped based on the fluctuation in the received signal caused by vibration, the longer the measured distance, the easier it is to determine the fluctuation in the received signal caused by vibration. Note that the output used for the determination in step S2 is not limited to the output of long distance data averaging unit 160A2, and the output of short distance data averaging unit 160A1 or all distance data averaging unit 160A3 may also be used.

[0056] When the detection unit 180 determines that the output of the long-distance data averaging unit 160A2 is equal to or greater than the first threshold (S2: YES), it determines whether the output of the long-distance data averaging unit 160A2 is equal to or greater than the second threshold (step S3). The second threshold is a threshold for determining whether the road on which the vehicle 1 is traveling is a flat road or a rough road. When traveling on a flat road, the vehicle 1 vibrates relatively little, and when traveling on a rough road such as an unpaved road or a rough land, the vehicle 1 vibrates greatly. For this reason, the output of the long-distance data averaging unit 160A2 when traveling on a flat road and the output of the long-distance data averaging unit 160A2 when traveling on a rough road are acquired in advance, and the second threshold is set to a value that is the boundary between the output on a flat road and the output on a rough road. If the output of the long-distance data averaging unit 160A2 is equal to or greater than the second threshold, it is possible to determine that the road on which the vehicle 1 is traveling is a non-flat road.

[0057] The reason for using the output of long-distance data averaging unit 160A2 in step S3 is the same as that for step S2. However, if the output of close-distance data averaging unit 160A1 or all-distance data averaging unit 160A3 is used in the judgment of step S2, the output of close-distance data averaging unit 160A1 or all-distance data averaging unit 160A3 should also be used in the judgment of step S3.

[0058] When the detection unit 180 determines that the output of the long-distance data averaging unit 160A2 is equal to or greater than the second threshold (S3: YES), it sets the threshold used in step S8 for determining the presence or absence of an occupant to the third threshold (step S4A). The third threshold is a threshold for distinguishing between an occupant and an object when the vehicle 1 is traveling on a rough road. An occupant has body movements associated with breathing, and if the occupant is a driver, there is a motion for driving operation, and an occupant other than the driver is accompanied by an action such as operating a smartphone or a game console. In contrast, an object other than an occupant does not have a motion like a human motion. For this reason, when traveling on a rough road, the output of the long-distance data averaging unit 160A2 when an occupant with the above-mentioned motion is sitting on the seat 2 and the output of the long-distance data averaging unit 160A2 when an occupant is not sitting may be acquired in advance, and the third threshold may be set to a boundary value that can distinguish the presence or absence of an occupant.

[0059] Furthermore, when the detection unit 180 determines in step S3 that the output of the long-distance data averaging unit 160A2 is not equal to or greater than the second threshold (S3: NO), the detection unit 180 sets the threshold used in step S8 for determining the presence or absence of an occupant to a fourth threshold (step S4B). The fourth threshold is a threshold for distinguishing between an occupant and an object when the vehicle 1 is traveling on a flat road. For this reason, the output of the long-distance data averaging unit 160A2 when an occupant performing the above-mentioned actions is sitting in the seat 2 while the vehicle 1 is traveling on a flat road and the output of the long-distance data averaging unit 160A2 when no occupant is sitting may be acquired in advance, and the fourth threshold may be set to a boundary value that allows the presence or absence of an occupant to be determined.

[0060] The fourth threshold value is smaller than the third threshold value because the vehicle 1 experiences less vibration when traveling on a flat road than when traveling on a non-flat road, and thus has less effect on the detection of occupants and objects.

[0061] Furthermore, when the detection unit 180 determines in step S2 that the output of the long-distance data averaging unit 160A2 is not equal to or greater than the first threshold (S2: NO), the detection unit 180 sets the threshold used in step S8 for determining the presence or absence of an occupant to a fifth threshold (step S4C). The fifth threshold is a threshold for distinguishing between an occupant and an object when the vehicle 1 is in a stopped state. For this reason, the output of the long-distance data averaging unit 160A2 when an occupant performing the above-mentioned actions is seated on the seat 2 in the stopped state, and the output of the long-distance data averaging unit 160A2 when no occupant is seated may be acquired in advance, and the fifth threshold may be set to a boundary value that allows the presence or absence of an occupant to be determined in the stopped state.

[0062] The fifth threshold value is smaller than the fourth threshold value because the vibration of the vehicle 1 is smaller when the vehicle 1 is stopped than when the vehicle 1 is moving, and thus the effect on the detection of passengers and objects is smaller.

[0063] After completing the process of step S4A, S4B, or S4C, detection unit 180 starts the loop process of steps S5 to S10 (step S5). In this loop process, the presence or absence of an occupant is determined for all outputs of short distance data averaging unit 160B1, long distance data averaging unit 160B2, and total distance data averaging unit 160B3 using any of the third threshold, fourth threshold, and fifth threshold set in any of steps S4A, S4B, or S4C as the threshold to be used in step S8.

[0064] In the loop processing, when selecting the outputs of short distance data averaging section 160B1, long distance data averaging section 160B2, and total distance data averaging section 160B3, i=1, i=2, and i=3 are used as identification numbers i.

[0065] The detection unit 180 determines whether the identification number i is 1 (step S6A). This is to determine whether it is the turn to select the output of the short-distance data averaging unit 160B1.

[0066] If detection unit 180 determines that identification number i is 1 (S6A: YES), it selects the output of short-distance data averaging unit 160B1 (step S7A).

[0067] After completing the process of step S7A, the detection unit 180 uses one of the third threshold, the fourth threshold, and the fifth threshold as a threshold and determines whether the output of the short-distance data averaging unit 160B1 is equal to or greater than the threshold (step S8). Step S8 is a determination process in which the output of the short-distance data averaging unit 160B1 is compared with the threshold.

[0068] When the detection unit 180 determines that the output of the short-distance data averaging unit 160B1 is equal to or greater than the threshold (S8: YES), it notifies the upper system that an occupant has been detected (step S9). That is, the detection unit 180 detects an occupant according to the comparison result (determination result) obtained in step S8, and notifies the upper system of the detection. Note that the upper system is, for example, an ECU (Electronic Control Unit) that manages the fastening state of the seat belt of the vehicle 1, an ECU that controls the opening and closing of the power window, etc.

[0069] When the detection unit 180 finishes the process of step S9, the detection unit 180 returns the flow to step S5 (step S10), whereby a loop process from step S5 to S10 is performed.

[0070] Moreover, when detection unit 180 determines that the output of short-distance data averaging unit 160B1 is not equal to or greater than the threshold value (S8: NO), it causes the flow to proceed to step S10.

[0071] Furthermore, if detection unit 180 determines in step S6A that identification number i is not 1 (S6A: NO), it determines whether identification number i is 2 (step S6B). This is to determine whether it is the turn to select the output of long distance data averaging unit 160B2.

[0072] If detection unit 180 determines that identification number i is 2 (S6B: YES), it selects the output of long distance data averaging unit 160B2 (step S7B).

[0073] After completing the processing of step S7B, detection unit 180 uses one of the third threshold, the fourth threshold, or the fifth threshold as a threshold and determines whether the output of long distance data averaging unit 160B2 is greater than or equal to the threshold (step S8).

[0074] When the detection unit 180 determines that the output of the long distance data averaging unit 160B2 is equal to or greater than the threshold value (S8: YES), it notifies the upper system that an occupant has been detected (step S9).

[0075] When the detection unit 180 finishes the process of step S9, the detection unit 180 returns the flow to step S5 (step S10), whereby a loop process from step S5 to S10 is performed.

[0076] Moreover, when detection unit 180 determines that the output of long distance data averaging unit 160B2 is not equal to or greater than the threshold value (S8: NO), it causes the flow to proceed to step S10.

[0077] Furthermore, if detection unit 180 determines in step S6B that identification number i is not 2 (S6B: NO), it selects the output of all distance data averaging unit 160B3 (step S7C).

[0078] After completing the processing of step S7C, the detection unit 180 uses one of the third threshold, the fourth threshold, or the fifth threshold as a threshold and determines whether the output of the total distance data averaging unit 160B3 is greater than or equal to the threshold (step S8).

[0079] When the detection unit 180 determines that the output of the total distance data averaging unit 160B3 is equal to or greater than the threshold value (S8: YES), it notifies the upper system that an occupant has been detected (step S9).

[0080] When the detection unit 180 finishes the process of step S9, the detection unit 180 returns the flow to step S5 (step S10), whereby a loop process from step S5 to S10 is performed.

[0081] Moreover, when detection unit 180 determines that the output of total distance data averaging unit 160B3 is not equal to or greater than the threshold value (S8: NO), it causes the flow to proceed to step S10.

[0082] When detection unit 180 has completed the loop process of steps S5 to S10 for all outputs from short distance data averaging unit 160B1, long distance data averaging unit 160B2, and total distance data averaging unit 160B3, it ends the series of processes (END).

[0083] Furthermore, the detection unit 180 can detect the movement of the occupant in the cabin of the vehicle 1 based on the temporal change in the position of the occupant by repeatedly executing the process shown in FIG.

[0084] As described above, when detecting unit 180 compares the output (signal strength) measured by signal strength measuring unit 150A and averaged by long-distance data averaging unit 160B2 with a threshold value to determine the presence or absence of an occupant, it changes the threshold value according to the state of vehicle 1. Therefore, it is possible to determine the presence or absence of an occupant using a threshold value according to the strength of vibration of vehicle 1, and the accuracy of occupant detection is improved compared to a case where the strength of vibration of vehicle 1 is not taken into consideration.

[0085] Therefore, it is possible to provide an occupant detection device 100 with high detection accuracy.

[0086] Further, the detection unit 180 judges whether the vehicle 1 is in a running state or a stopped state based on the strength of the signal measured by the signal strength measurement unit 150A, and detects an occupant according to the judgment result. The signals received by the radar 110 are a plurality of signals with different round trip times to the occupant or object, and the detection unit 180 judges whether the vehicle 1 is in a running state or a stopped state using a long-distance signal among the plurality of signals, the distance to the occupant or object being a predetermined distance or more. In order to judge whether the vehicle 1 is in a running state or a stopped state based on the fluctuation of the received signal due to the vibration of the vehicle 1, the longer the measurement distance, the easier it is to distinguish the fluctuation of the received signal due to the vibration, so by using the output of the long-distance data averaging unit 160A2, it is possible to detect an occupant with higher accuracy.

[0087] In addition, the detection unit 180 selects a threshold value for determining whether or not an occupant is present based on the state of the vehicle 1, so that an appropriate threshold value can be used taking into account the strength of the vibrations occurring in the vehicle 1, thereby enabling occupants to be detected with higher accuracy.

[0088] In addition, the detection unit 180 determines whether the state of the vehicle 1 is stopped, traveling on a flat road, or traveling on a rough road based on the signal strength measured by the signal strength measurement unit 150A, and detects the occupant using three thresholds (third threshold, fourth threshold, and fifth threshold) according to the determination result, so that the occupant can be detected with higher accuracy by taking into account the effect on the detection result of the strength of vibrations generated in the vehicle 1 depending on the road surface condition.

[0089] Moreover, the HPF 140A is a high-pass filter that passes at least some signals of 5 Hz or more. Since the speed of human movement is expressed in terms of frequency between 0.5 Hz and less than 5 Hz, the strength of vibrations of the vehicle 1, which is a movement other than human movement, can be efficiently detected by setting the cutoff frequency of the HPF 140A to 5 Hz and passing signals of 5 Hz or more.

[0090] In addition, the BPF 140B is a band-pass filter that passes at least a part of signals having a frequency of 0.5 Hz or more and less than 5 Hz. Since the speed of human movement is expressed in terms of frequency, which is 0.5 Hz or more and less than 5 Hz, it is possible to efficiently detect human movement by eliminating components due to vibration of the vehicle 1.

[0091] Furthermore, the detection unit 180 can detect the movement of the occupant in the cabin of the vehicle 1 based on the temporal change in the position of the occupant by repeatedly executing the process shown in FIG.

[0092] In the above, a description has been given of a form in which the second threshold value is used in step S3 of the flow chart shown in Fig. 4 to determine whether the road is flat or non-flat, and the third, fourth and fifth threshold values ​​obtained in advance are set as the threshold values ​​used in step S8 in steps S4A, S4B and S4C. However, it is not necessary to determine whether the road is flat or non-flat, and the threshold values ​​used in step S8 may be set according to the strength of the signal that has passed through BPF 140B, for example. Such a modified example will be described with reference to Fig. 5.

[0093] Fig. 5 is a diagram showing a flowchart showing the processing executed by detection unit 180 of the modified embodiment. The processing shown in Fig. 5 differs from the processing shown in Fig. 4 in that step S3 in Fig. 4 is omitted and steps S4D and S4E are included instead of steps S4A to S4C. Since the rest of the processing is the same as that shown in Fig. 4, the same step numbers are given to the same steps as in Fig. 4 and the differences will be described.

[0094] When the detection unit 180 determines that the output of the long distance data averaging unit 160A2 is equal to or greater than the first threshold value (S2: YES), it sets the value obtained by multiplying the constant for driving by the signal strength measured by the signal strength measuring unit 150A as the threshold value used in step S8 for determining the presence or absence of an occupant (step S4D). The constant for driving is a value that is multiplied by the signal strength measured by the signal strength measuring unit 150A when the vehicle 1 is in a driving state to obtain the threshold value used in step S8.

[0095] In a traveling state, the vehicle 1 is more susceptible to vibration than in a stopped state, and so the constant for traveling is a larger value than the constant for stopping, which will be described later. Such a constant for traveling may be determined in advance by an experiment, a simulation, or the like, so that the threshold value used in step S8 can be obtained by multiplying the signal strength measured by the signal strength measurement unit 150A. Note that the signal strength measured by the signal strength measurement unit 150A is the strength of the signal that has passed through the HPF 140A, so the constant for traveling can also be regarded as a value that, when the vehicle 1 is in a traveling state, is multiplied by the strength of the signal that has passed through the HPF 140A to obtain the threshold value used in step S8.

[0096] Furthermore, when the detection unit 180 determines in step S2 that the output of the long distance data averaging unit 160A2 is not greater than or equal to the first threshold value (S2: NO), it sets the value obtained by multiplying the stop constant by the signal strength measured by the signal strength measuring unit 150A as the threshold value to be used in step S8 to determine the presence or absence of an occupant (step S4E).

[0097] In a stopped state, the vehicle 1 is less susceptible to vibrations than in a running state, so the stopping constant is a smaller value than the running constant used in step S4D. Such a stopping constant may be obtained in advance by experiment, simulation, or the like so that the threshold value used in step S8 can be obtained by multiplying the signal strength measured by the signal strength measurement unit 150A. Note that the signal strength measured by the signal strength measurement unit 150A is the strength of the signal that has passed through the HPF 140A, so the stopping constant can also be regarded as a value that, when the vehicle 1 is in a stopped state, is multiplied by the strength of the signal that has passed through the HPF 140A to obtain the threshold value used in step S8.

[0098] In step S8, detection unit 180 determines whether the outputs of short-distance data averaging unit 160B1, long-distance data averaging unit 160B2, and total distance data averaging unit 160B3 are greater than or equal to the threshold value calculated based on the driving constants in step S4D or the threshold value calculated based on the stopping constants in step S4E.

[0099] 5, the threshold value is set according to the intensity of the signal that has passed through HPF 140A. Since the frequency of vibrations occurring in the vehicle 1 is high and the components of the high frequency band of the received signal are likely to include, among all the components of the received signal, an increase in intensity caused by the influence of the vibrations of the vehicle 1, by setting the threshold value according to the intensity of the signal that has passed through HPF 140A, it is possible to set an appropriate threshold value taking into account the influence of the vibrations occurring in the vehicle 1, and it is possible to detect an occupant with higher accuracy.

[0100] The above describes an occupant detection device according to an exemplary embodiment of the present invention. However, the present invention is not limited to the specifically disclosed embodiment, and various modifications and changes are possible without departing from the scope of the claims. [Explanation of symbols]

[0101] 1 vehicle 100 Occupant detection device 110 Radar 140A HPF (example of the first filter) 140B BPF (an example of a second filter) 150A, 150B signal strength measurement section 180 Detector

Claims

1. An occupant detection device having a radar disposed in a vehicle cabin, the radar having a transmitting antenna for transmitting electromagnetic waves into a vehicle cabin and a receiving antenna for receiving a signal as a reflected wave of the electromagnetic waves, the occupant detection device detecting the presence or absence of an occupant in the vehicle cabin based on a signal received by the receiving antenna, a demultiplexer having an input terminal connected to the receiving antenna and a plurality of output terminals, which selects the plurality of output terminals in sequence, and distributes a plurality of the received signals input to the input terminals during a plurality of reception periods corresponding to the number of the plurality of output terminals to the selected output terminals and outputs the signals in a time-division manner; a plurality of first filters respectively connected to the plurality of output terminals and receiving the received signals, the first filters passing signals of components of vibration of a vehicle in a traveling state among the plurality of received signals; a plurality of second filters respectively connected to the plurality of output terminals and receiving the received signals, the second filters passing signals representing components of human movement among the plurality of received signals; a plurality of first signal strength measuring units each measuring a strength of a plurality of signals that have passed through the plurality of first filters; a plurality of second signal strength measuring units each measuring a strength of a plurality of signals that have passed through the plurality of second filters; a detection unit that compares the intensities of the plurality of signals that have passed through the plurality of second filters, respectively measured by the plurality of second signal intensity measurement units, with a threshold value, and detects an occupant according to a comparison result, the detection unit changing the threshold value according to the intensities of the plurality of signals that have passed through the plurality of first filters, respectively measured by the plurality of first signal intensity measurement units; Including, The detection unit is an occupant detection device that divides the space between the transmitting antenna and the receiving antenna and the seat surface of a seat placed in the vehicle cabin into multiple regions corresponding to the number of the multiple output terminals in a direction connecting the transmitting antenna and the receiving antenna and the seat surface of the seat, and determines the presence or absence of an occupant in each region.

2. The plurality of received signals received by the receiving antenna during the plurality of reception periods are a plurality of signals having different round trip times to a detectable object in the plurality of regions, The occupant detection device according to claim 1 , wherein the detection unit changes the threshold value using a strength of a signal that passes through the first filter and is a long-distance signal, of the plurality of signals, in which the distance to the detectable object is equal to or greater than a predetermined distance.

3. The occupant detection device according to claim 2 , wherein the detection unit detects an occupant by selecting one threshold value from a plurality of threshold values ​​based on a result of determining a state of the vehicle based on the strengths of the plurality of signals measured by the plurality of first signal strength measuring units.

4. The occupant detection device according to claim 2 or 3, wherein the detection unit determines whether the vehicle is stopped, traveling on a flat road, or traveling on a rough road based on the strengths of the multiple signals measured by the multiple second signal strength measuring units, changes the threshold value in three stages, and detects an occupant according to the determination result.

5. The occupant detection device according to claim 1 , wherein the first filter is a high-pass filter that passes at least a part of signals having a frequency of 5 Hz or higher.

6. The occupant detection device according to claim 1 , wherein the second filter is a band-pass filter that passes at least a part of signals having a frequency of 0.5 Hz or more and less than 5 Hz.

7. The occupant detection device according to claim 1 , wherein the detection unit detects a movement of the occupant based on a temporal variation of the comparison result.

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