Occupant detection device and occupant detection method

Abstract

The present invention comprises a transmission control unit (2001) that controls transmission of impulse signals sequentially transmitted at prescribed intervals from an in-vehicle UWB anchor (20), a reflected wave information acquisition unit (2002) that acquires reflected wave information including at least the signal intensity of reflected waves of the impulse signals, and an occupant detection unit (2003) that, on the basis of the reflected wave information, detects the presence or absence of an occupant in a vehicle compartment. The occupant detection unit (2003) detects the presence or absence of occupants in the vehicle compartment by using the reflected wave information not only of the first reflected wave for which the signal intensity thereof first reaches or exceeds a threshold from among the reflected waves received by the in-vehicle UWB anchor (20) between transmission of the impulse signal by the transmission control unit (2001) and the next transmission interval, but also reflected wave information of second and subsequent reflected waves for which the signal intensity thereof reaches or exceeds the threshold.

Description

Occupant Detection Device and Occupant Detection Method Cross-Reference to Related Applications

[0001] This application is based on Japanese Patent Application No. 2025-30729 filed with Japan on February 27, 2025, the entire content of which is incorporated herein by reference.

[0002] The present disclosure relates to an occupant detection device and an occupant detection method.

[0003] Techniques for detecting an occupant in a vehicle cabin are known. Patent Document 1 discloses a technique of receiving a reflected wave of a radio wave transmitted from a radio sensor installed in a vehicle and obtaining a distance to a reflector. In Patent Document 1, an occupant is detected by measuring a distance from the reflector to the radio sensor. In Patent Document 1, it is determined that an occupant exists when a temporal variation in the detected distance to the reflector is equal to or greater than a predetermined value. In Patent Document 1, a plurality of radio sensors are installed in the vehicle to remove or eliminate influences of disturbance, multipath, diffuse reflection, other obstacles and the like.

[0004] Japanese Unexamined Patent Application Publication No. 2018-202921

[0005] In the technique disclosed in Patent Document 1, as it attempts to remove or eliminate the influence of multipath, it intends to detect an occupant based on a distance to a reflector obtained from a direct wave. However, when attempting to detect an occupant using a direct wave, in order to reduce blind spots such as rear seats and footwells, it has been necessary to increase the number of sensors installed in the vehicle cabin as disclosed in Patent Document 1.

[0006] One object of the present disclosure is to provide an occupant detection device and an occupant detection method that make it easy to detect even an occupant located in a position with poor visibility in a vehicle cabin while suppressing the number of sensors for detecting an occupant in the vehicle cabin.

[0007] Reference signs in parentheses in the claims indicate correspondence relationships with specific means described in embodiments below as one aspect, and do not limit the technical scope of the present disclosure.

[0008] To achieve the above objective, the occupant detection device of this disclosure comprises a transmission control unit that controls the transmission of an impulse signal from a radar that can be used inside a vehicle, which transmits an impulse signal and receives a reflected wave of the impulse signal; a reflected wave information acquisition unit that acquires reflected wave information, which is information about the reflected wave of the impulse signal received by the radar; and an occupant detection unit that detects the presence or absence of an occupant inside the vehicle based on the reflected wave information acquired by the reflected wave information acquisition unit. The transmission control unit causes the impulse signal to be transmitted sequentially at predetermined intervals, the reflected wave information acquisition unit acquires reflected wave information including at least the signal strength of the reflected wave, and the occupant detection unit detects the presence or absence of an occupant inside the vehicle using not only the reflected wave whose signal strength is first above a threshold, but also the reflected wave information of the second and subsequent reflected waves whose signal strength is above a threshold, from among the reflected waves received by the radar between the time the transmission control unit transmits the impulse signal and the next transmission interval.

[0009] To achieve the above objective, the occupant detection method of this disclosure includes a transmission control step which controls the transmission of an impulse signal from a radar usable in the passenger compartment of a vehicle, which transmits an impulse signal and receives a reflected wave of the impulse signal, and is performed by at least one of a processor and a circuit; a reflected wave information acquisition step which acquires reflected wave information, which is information about the reflected wave of the impulse signal received by the radar; and an occupant detection step which detects the presence or absence of an occupant in the passenger compartment based on the reflected wave information acquired in the reflected wave information acquisition step. The transmission control step causes the impulse signal to be transmitted sequentially at predetermined intervals, the reflected wave information acquisition step acquires reflected wave information, which includes at least the signal strength of the reflected wave, and the occupant detection step detects the presence or absence of an occupant in the passenger compartment using reflected wave information of the second and subsequent reflected waves whose signal strength is above the threshold, as well as the reflected wave information of the first reflected wave whose signal strength is above the threshold, from the time the impulse signal is transmitted in the transmission control step until the next transmission interval.

[0010] According to this, in detecting the presence or absence of occupants, the radar will use not only the reflected wave whose signal strength is the first to exceed the threshold, but also the reflected wave information of the second and subsequent reflected waves whose signal strength is the threshold, from the time the radar transmits an impulse signal until the next transmission interval. Therefore, it becomes possible to detect the presence or absence of occupants using multipath waves as well. Consequently, even occupants in positions with poor line of sight inside the vehicle, where it is difficult for the radar to directly receive the waves, can be easily detected by multipath waves. Furthermore, since the presence or absence of occupants can be detected using multipath waves even when direct reception is not possible, there is no need to increase the number of radars to eliminate positions with poor line of sight inside the vehicle. As a result, it becomes possible to detect occupants in positions with poor line of sight inside the vehicle while keeping the number of sensors for detecting occupants inside the vehicle low.

[0011] This figure shows an example of a schematic configuration of a vehicle system. This figure shows an example of a schematic configuration of a mobile terminal. This figure shows an example of the arrangement of an in-vehicle UWB anchor, a BLE anchor, and an external UWB anchor. This figure shows an example of a schematic configuration of a BLE anchor. This figure shows an example of a schematic configuration of an external UWB anchor. This figure shows an example of a schematic configuration of an in-vehicle UWB anchor. This figure shows an example of the time variation of the received intensity of the reflected wave. This is a schematic diagram showing an example of the direct wave and multipath wave of an in-vehicle UWB anchor. This figure illustrates an example where the child to be detected is located in a position with good line of sight inside the vehicle. This figure illustrates an example where the child to be detected is located in a position with poor line of sight inside the vehicle. This figure illustrates how the variation in the peak level and frequency of the reflected wave can be obtained from multiple data points. This figure illustrates how the variation in the peak level and frequency of the reflected wave differs depending on the presence or absence of a respiratory component. This figure shows the correspondence between the measured distance and the calculated likelihood. This figure shows the correspondence between the frequency of the reflected wave, the measured distance, and the peak level. This is a flowchart showing an example of the flow of occupant detection processing at an in-vehicle UWB anchor. This figure shows an example of a general configuration of a DigiKey ECU.

[0012] Multiple embodiments for disclosure will be described with reference to the drawings. For the sake of clarity, in some embodiments, parts having the same function as those shown in the drawings used in previous descriptions will be denoted by the same reference numerals, and their descriptions may be omitted. For parts denoted by the same reference numerals, refer to the descriptions in other embodiments.

[0013] (Embodiment 1) <Outline Configuration of Vehicle System 1> This embodiment will be described below with reference to the drawings. First, the vehicle system 1 will be described using Figure 1. As shown in Figure 1, the vehicle system 1 includes an in-vehicle system 2 and a mobile terminal 3. The in-vehicle system 2 is a system mounted on a vehicle. The vehicle using the in-vehicle system 2 will be assumed to be, for example, an automobile, in the following description. The vehicle on which the in-vehicle system 2 is mounted will be referred to as "the vehicle" below. The mobile terminal 3 is carried by the user of the vehicle. The mobile terminal 3 is an information processing terminal such as a multi-function mobile phone. Various communication terminals such as wearable devices can be used as the mobile terminal 3. In the following description, the case where the mobile terminal 3 is a multi-function mobile phone will be used as an example.

[0014] The in-vehicle system 2 and the mobile terminal 3 are configured to perform bidirectional wireless communication using radio waves in a predetermined frequency band. Here, as an example, the in-vehicle system 2 and the mobile terminal 3 are configured to perform wireless communication using the UWB-IR (Ultra Wide Band - Impulse Radio) method. That is, the in-vehicle system 2 and the mobile terminal 3 are configured to send and receive impulse-like radio waves (hereinafter referred to as impulse signals) used in ultra-wideband (UWB) communication. An impulse signal used in UWB communication is a signal with an extremely short pulse width (e.g., 2 ns) and a bandwidth of 500 MHz or more (i.e., ultra-wideband). Various modulation methods can be used for UWB-IR communication, such as on-off keying (OOK), pulse position modulation (PPM), and pulse width modulation (PWM).

[0015] Data transmission via UWB communication is achieved using multiple impulse signals. Hereafter, data signals exchanged in UWB communication will be referred to as UWB signals. UWB signals such as response request signals and response signals, which will be described later, refer to signal sequences in which multiple impulse signals are arranged at time intervals corresponding to the transmitted data. Since these UWB signals contain multiple impulses, they can also be called pulse sequence signals.

[0016] Furthermore, the in-vehicle system 2 and the mobile terminal 3 are each configured to enable wireless communication compliant with the Bluetooth® Low Energy standard (hereinafter referred to as BLE communication) as a second short-range communication means other than UWB communication.

[0017] <Outline Configuration of Mobile Terminal 3> Here, the outline configuration of mobile terminal 3 will be explained using Figure 2. Mobile terminal 3 is an information processing terminal equipped with UWB communication function and BLE communication function. As shown in Figure 3, mobile terminal 3 comprises a device control unit 30, a UWB communication unit 31, and a BLE communication unit 32. In this embodiment, for convenience, the explanation of the mobile terminal 3 other than the configuration related to wireless communication with the in-vehicle system 2 has been omitted.

[0018] The UWB communication unit 31 is a communication module capable of performing UWB communication. The UWB communication unit 31 may consist of components such as an IC, an antenna, and a communication circuit. The UWB communication unit 31 performs UWB communication by transmitting and receiving impulse signals. The frequency bands that can be used for UWB communication (hereinafter referred to as the UWB band) include 3.1 GHz to 10.6 GHz, 3.4 GHz to 4.8 GHz, 7.25 GHz to 10.6 GHz, and 22 GHz to 29 GHz.

[0019] The BLE communication unit 32 is a communication module capable of performing BLE communication. The BLE communication unit 32 may consist of, for example, an IC, an antenna, a communication circuit, etc. The BLE communication unit 32 establishes a communication connection with the in-vehicle system 2 and performs short-range wireless communication.

[0020] The device control unit 30 is configured as a computer, for example, equipped with a processor, memory, storage, etc. Memory can be described as volatile memory. Storage can be described as non-volatile memory. The storage stores the device ID and key code. The device ID is an identification number used to identify each mobile terminal 3 individually. For example, the device ID can be a device address, UUID (Universally Unique Identifier), etc. The key code here is data used in the authentication process described later. The key code is data used to prove that the person trying to access the vehicle is a legitimate user. The key code may also be called an encryption key. The device ID and key code are different for each mobile terminal 3. The device control unit 30 performs processing related to the control of the UWB communication unit 31 and the BLE communication unit 32, and processing related to authentication.

[0021] For example, the mobile terminal 3 periodically transmits an advertisement signal from its BLE communication unit 32. The advertisement signal is a signal to notify the surroundings of the presence of the mobile terminal 3 and includes source information. The mobile terminal 3 accepts a connection request transmitted from the in-vehicle system 2, which has received the advertisement signal, and establishes a communication connection between the BLE communication unit 32 and the in-vehicle system 2. Note that the establishment of the communication connection between the BLE communication unit 32 and the in-vehicle system 2 may be performed by receiving an advertisement signal from the in-vehicle system 2. Based on the establishment of the communication connection between the in-vehicle system 2 and the BLE communication unit 32, the mobile terminal 3 performs data communication with the in-vehicle system 2 via BLE communication. The following explanation will continue with an example of a case where the mobile terminal 3 transmits an advertisement signal to establish a communication connection with the in-vehicle system 2.

[0022] For example, the mobile terminal 3 performs wireless authentication processing based on the establishment of a BLE communication connection with the in-vehicle system 2. The wireless authentication processing may be performed, for example, by a challenge-response method. In this case, when the BLE communication unit 32 receives a challenge code from the in-vehicle system 2, the mobile terminal 3 generates a response code using a predetermined procedure and function based on the challenge code and key code. The generated response code is then sent back to the in-vehicle system 2 from the BLE communication unit 32. The challenge code is a random number of a predetermined length generated, for example, using a pre-prepared random number table. The challenge code may also be a random number generated using the current time information as the SEED. The challenge code can be determined in various ways. The in-vehicle system 2 generates a verification code using the vehicle's key code and the challenge code sent to the mobile terminal 3 according to a predetermined procedure. This verification code is used to verify the legitimacy of the response code returned from the mobile terminal 3, that is, the legitimacy of the user of the mobile terminal 3. In the in-vehicle system 2, if the verification code and the received response code match, the system authenticates that the mobile terminal 3 belongs to a legitimate user. The wireless authentication process can consist of both authentication on the mobile terminal 3 using a challenge code sent from the in-vehicle system 2, and authentication on the in-vehicle system 2 using a challenge code sent from the mobile terminal 3. In other words, the in-vehicle system 2 can perform the same process based on the challenge code sent from the mobile terminal 3. Then, if both are authenticated, the system can authorize the mobile terminal 3 to control its own vehicle.

[0023] Furthermore, when the mobile terminal 3 receives a response request signal transmitted from the in-vehicle system 2 via the UWB communication unit 31, it sends back a response signal. The mobile terminal 3 can send back a UWB signal as a response signal, which may include source information such as a device ID.

[0024] Note that the mobile device 3 may be a smart key, which is a dedicated device that serves as the vehicle's electronic key. A smart key is a device that is transferred to the owner along with the vehicle when it is purchased. A smart key is also called a vehicle portable device, key fob, key card, or access key.

[0025] <Outline Configuration of In-Vehicle System 2> Next, the in-vehicle system 2 will be explained using Figure 1. As shown in Figure 1, the in-vehicle system 2 includes an in-vehicle UWB anchor 20, a digital key ECU 21, a BLE anchor 22, an external UWB anchor 23, a door sensor 24, a start switch 25, a power ECU 26, and a body ECU 27. These should be configured to be connected to the in-vehicle LAN (see LAN in Figure 1).

[0026] The BLE anchor 22 is a communication module for performing BLE communication. The BLE anchor 22 is located, for example, inside the vehicle. The BLE anchor 22 is located, for example, at the upper edge of the windshield, on the ceiling inside the vehicle, etc. The BLE anchor 22 may also be built into the DigiKey ECU 21. Multiple BLE anchors 22 may be provided in the vehicle. The BLE anchor 22 transmits data received from the mobile terminal 3 and data related to the communication status with the mobile terminal 3 to the DigiKey ECU 21 as needed. Data related to the communication status includes, for example, the device ID of the mobile terminal 3 with which communication is connected. The operation of the BLE anchor 22 may be controlled, for example, by the DigiKey ECU 21.

[0027] The in-vehicle UWB anchor 20 and the out-of-vehicle UWB anchor 23 are communication modules for performing UWB communication. The in-vehicle UWB anchor 20 is located inside the vehicle's cabin. The in-vehicle UWB anchor 20 may be configured to have at least one located inside the cabin. The in-vehicle UWB anchor 20 may be located, for example, at the upper edge of the windshield or on the ceiling inside the cabin. The out-of-vehicle UWB anchor 23 is located on the exterior of the vehicle. The exterior refers to the part facing the outside of the vehicle and includes the sides, front end, rear end, and roof. For example, the outer surfaces of each pillar, door panels, door handles, bumper, side sills, side mirrors, roof edges, front grille, etc., are included in the exterior. The out-of-vehicle UWB anchor 23 may be configured to have multiple anchors located on the exterior of the vehicle.

[0028] Here, using Figure 3, we will explain an example of the arrangement of the in-vehicle UWB anchor 20, BLE anchor 22, and external UWB anchor 23. As shown in Figure 4, one in-vehicle UWB anchor 20 and one BLE anchor 22 are placed inside the vehicle. Four external UWB anchors 23 are placed on the exterior of the vehicle. Here, the four external UWB anchors 23 are distinguished and referred to as external UWB anchors 23a, 23b, 23c, and 23d. If it is not necessary to explain the four external UWB anchors 23 separately, they will be collectively referred to as external UWB anchors 23 below. External UWB anchor 23a is placed near the left corner of the front end of the vehicle. External UWB anchor 23b is placed near the right corner of the front end of the vehicle. External UWB anchor 23c is placed near the left corner of the rear end of the vehicle. The external UWB anchor 23d is positioned near the right corner of the rear end of the vehicle. The internal UWB anchor 20 and BLE anchor 22 are positioned on the ceiling inside the vehicle. This is to reduce the effects of multipath interference from the vehicle body and facilitate wireless communication with the mobile terminal 3 outside the vehicle.

[0029] The operation of the in-vehicle UWB anchor 20 and the out-of-vehicle UWB anchor 23 may be controlled, for example, by the DigiKey ECU 21. While driving, the in-vehicle UWB anchor 20 and the out-of-vehicle UWB anchor 23 transmit data to the DigiKey ECU 21 indicating the reception status of signals from the mobile terminal 3. The reception status includes whether or not a signal was received, the reception strength, and the distance measurement value. The in-vehicle UWB anchor 20 and the out-of-vehicle UWB anchor 23 are used to determine the position of the mobile terminal 3. More specifically, they are used in distance measurement communication, which is bidirectional communication for measuring the distance to a communication target. Distance measurement communication means wireless communication for measuring the distance between communication devices based on the time of flight of the signal or the phase information of the received signal. The in-vehicle UWB anchor 20 is also used as a radar for detecting occupants inside the vehicle. This in-vehicle UWB anchor 20 corresponds to the radar.

[0030] The DigiKey ECU 21 is implemented using a computer. The DigiKey ECU 21 includes, for example, a processor, memory, storage, I / O, and bus lines connecting these components. The processor is a processing core such as a CPU (Central Processing Unit). The memory is volatile memory such as RAM (Random Access Memory). The processor performs various processes to realize the functions of the DigiKey ECU 21 by accessing the memory. The storage includes a non-volatile storage medium such as flash memory. This storage stores the device ID of the legitimate user's mobile terminal 3, associated with the key code. The I / O is a circuit module for communicating with other devices. The storage also stores a control program executed by the processor. The DigiKey ECU 21 performs the various processes described later in the DigiKey ECU 21 by executing this control program.

[0031] The DigiKey ECU 21 has a function to perform wireless authentication processing. Wireless authentication processing is the process of authenticating whether the mobile terminal 3, which has established a communication connection with the BLE anchor 22, is the mobile terminal 3 of a legitimate user. The DigiKey ECU 21 also has a function to perform terminal location determination processing. Terminal location determination processing is the process of determining the position of the mobile terminal 3 relative to the vehicle in cooperation with the in-vehicle UWB anchor 20 and the external UWB anchor 23. In addition, the DigiKey ECU 21 has a function to perform a process that notifies the results of the occupant detection processing performed by the in-vehicle UWB anchor 20 (hereinafter referred to as occupant detection result notification processing). Occupant detection processing is the process of detecting whether or not there is an occupant inside the vehicle. Occupant detection result notification processing is the process of notifying the system if an occupant is detected by the occupant detection processing.

[0032] The door sensor 24 is a sensor that allows the user to unlock and lock the doors of their vehicle. The door sensor 24 may be a touch sensor or a push-button switch. In the following explanation, we will use the case where the door sensor 24 is a touch sensor as an example. The door sensor 24 is installed on the outer door handle of each door of the vehicle. The door sensor 24 outputs an electrical signal to the digital key ECU 21 indicating that it has been touched by the user.

[0033] The start switch 25 is a push switch used by the user to switch the vehicle's power supply on and off. The power supply is the power source for the vehicle to move, and if the vehicle's power source is the engine, it refers to the ignition power supply. If the vehicle's power source is the motor, the power supply refers to the system main relay. When the start switch 25 is pushed by the user, it outputs an electrical signal to the digital key ECU 21 indicating that the switch has been pressed.

[0034] The power ECU 26 is an electronic control unit that controls the on / off state of the vehicle's power supply. For example, the power ECU 26 switches the power supply from off to on based on a request signal from the digital key ECU 21. If the vehicle's power source is the engine, the power ECU 26 starts the engine based on an instruction signal from the digital key ECU 21.

[0035] The Body ECU 27 is an electronic control unit that controls the vehicle's electrical components. The Body ECU 27 controls the vehicle's door lock motor. The door lock motor is a motor that switches the locking and unlocking mechanism of each door of the vehicle. The Body ECU 27 controls the vehicle's turn signals. Turn signals are also called turn signal lamps, turn lamps, or indicator lamps. Turn signals are located on both the left and right sides of the vehicle. When only one of the left or right turn signals is lit, it indicates that the vehicle is changing direction. When both of the left and right turn signals are lit, it functions as a hazard light and indicates an emergency. The Body ECU 27 controls the vehicle's horn. The horn is an audible device used to draw attention to the area around the vehicle. The Body ECU 27 monitors the open and closed status of the vehicle's doors based on signals input from the courtesy switch.

[0036] <Outline Configuration of BLE Anchor 22> Here, the outline configuration of the BLE anchor 22 will be explained using Figure 4. As shown in Figure 4, the BLE anchor 22 comprises a control unit 220, an interface (hereinafter referred to as I / F) unit 221, and a BLE communication unit 222.

[0037] The I / F unit 221 is a module for the BLE anchor 22 to communicate with the digital key ECU 21 via the in-vehicle LAN. The BLE communication unit 222 is a communication module capable of performing BLE communication. The BLE communication unit 222 may consist of, for example, an IC, an antenna, a communication circuit, etc. The BLE communication unit 222 establishes a communication connection with the mobile terminal 3 and performs BLE communication. The BLE anchor 22 may be powered, for example, by a backup power supply, so that it remains operational even when the vehicle is parked.

[0038] The control unit 220 controls the operation of the BLE anchor 22. For example, an IC can be used as the control unit 220. The control unit 220 causes the BLE communication unit 222 to transmit the aforementioned challenge code and response code, which are input from the DigiKey ECU 21. The control unit 220 outputs the received data, such as the challenge code and response code, which are received from the mobile terminal 3 by the BLE communication unit 222, to the DigiKey ECU 21.

[0039] <Outline Configuration of the External UWB Anchor 23> Next, we will explain the outline configuration of the external UWB anchor 23. As shown in Figure 5, the external UWB anchor 23 comprises a control unit 230, an I / F unit 231, and a UWB communication unit 232.

[0040] The I / F unit 231 is a module for the external UWB anchor 23 to communicate with the digital key ECU 21 via the in-vehicle LAN. The UWB communication unit 232 is a communication module capable of performing UWB communication. The UWB communication unit 232 may consist of, for example, an IC, an antenna, a communication circuit, etc. The UWB communication unit 232 performs UWB communication with the mobile terminal 3 by sending and receiving impulse signals. The UWB communication unit 232 sends a response request signal to the mobile terminal 3 via UWB communication. The UWB communication unit 232 receives a response signal sent from the mobile terminal 3 via UWB communication.

[0041] The control unit 230 controls the operation of the external UWB anchor 23. For example, an IC may be used as the control unit 230. The control unit 230 performs processing related to distance measurement communication. The processing related to distance measurement communication is as follows: The control unit 230 outputs a response request signal to the UWB communication unit 232 to be transmitted to the mobile terminal 3, in accordance with the instructions of the digital key ECU 21. The control unit 230 outputs the response signal received from the mobile terminal 3 by the UWB communication unit 232 to the digital key ECU 21.

[0042] The control unit 230 measures an elapsed time (hereinafter, round trip time) from transmitting a fast pulse of a response request signal to receiving a fast pulse of a response signal. A fast pulse is an impulse signal positioned at the head among a plurality of impulse signals constituting transmission / reception data. The control unit 230 may identify the transmission timing of the impulse signal by receiving a notification from the UWB communication unit 232. The control unit 230 may identify the transmission timing of the impulse signal by monitoring a voltage level of a signal line leading to an antenna of the UWB communication unit 232. After transmitting the response request signal, the control unit 230 may set, as the reception timing of the fast pulse, a timing at which the reception intensity of the response signal first exceeds a predetermined detection threshold. The round trip time may alternatively be measured using a trailing pulse of the transmission / reception data. Various methods can be adopted as the method for measuring the round trip time. The round trip time corresponds to a time obtained by adding the length of the response request signal and the response processing time in the mobile terminal 3 to the round-trip flight time of the impulse signal. The control unit 230 outputs the round trip time to the digital key ECU 21.

[0043] <Schematic Configuration of In-Vehicle UWB Anchor 20> Next, a schematic configuration of the in-vehicle UWB anchor 20 will be described. As shown in FIG. 6, the out-of-vehicle UWB anchor 23 includes a control unit 200, an I / F unit 201, and a UWB communication unit 202.

[0044] The I / F unit 201 is a module for the in-vehicle UWB anchor 20 to communicate with the digital key ECU 21 via an in-vehicle LAN. The UWB communication unit 202 is a communication module capable of performing UWB communication. The UWB communication unit 202 may be the same as the UWB communication unit 232 of the out-of-vehicle UWB anchor 23.

[0045] The control unit 200 controls the operation of the in-vehicle UWB anchor 20. For example, an IC or the like may be used as the control unit 200. A microcomputer including a processor may be used as the control unit 200. Similarly to the control unit 220 of the outside-vehicle UWB anchor 23, the control unit 200 performs processing related to ranging communication. The control unit 200 outputs a response request signal to be transmitted to the portable terminal 3 to the UWB communication unit 202 in accordance with an instruction from the DigiKey ECU 21. The control unit 200 outputs the response signal received from the portable terminal 3 by the UWB communication unit 202 to the DigiKey ECU 21. Further, the control unit 230 measures the round trip time and outputs the measurement result to the DigiKey ECU 21.

[0046] In addition to the processing related to ranging communication, the control unit 200 also performs the aforementioned occupant detection processing. The control unit 200 performs the occupant detection processing using the in-vehicle UWB anchor 20 as a radar. That is, in the example of the present embodiment, the in-vehicle UWB anchor 20 is commonly used for both radar and ranging communication. According to this configuration, it is possible to reduce the effort of installing a new UWB anchor in the cabin of the own vehicle for the occupant detection processing. Note that a configuration may be adopted in which a UWB anchor for ranging communication and a UWB anchor for occupant detection processing are respectively provided in the cabin of the own vehicle.

[0047] When the in-vehicle UWB anchor 20 is used as a radar, the in-vehicle UWB anchor 20 transmits an impulse signal and receives a reflected wave of the impulse signal. The reflected wave is reflected by an object in the cabin of the own vehicle.

[0048] The following describes the functional blocks used in the crew detection process. As shown in Figure 6, the control unit 200 includes a transmission control unit 2001, a reflected wave information acquisition unit 2002, a crew detection unit 2003, and a result notification unit 2004 as functional blocks used in the crew detection process. The control unit 200 corresponds to the crew detection device. Furthermore, the execution of the processing of each functional block of the control unit 200 by a circuit or processor corresponds to the execution of the crew detection method. Note that some or all of the functions executed by the control unit 200 may be configured in hardware using one or more ICs, etc. Also, some or all of the functional blocks provided by the control unit 200 may be realized by a combination of software execution by a processor and hardware components.

[0049] The transmission control unit 2001 controls the transmission of impulse signals from the in-vehicle UWB anchor 20. The processing in the transmission control unit 2001 corresponds to the transmission control process. The transmission control unit 2001 is used for the radar function of the in-vehicle UWB anchor 20. For example, the transmission control unit 2001 should transmit impulse signals sequentially at predetermined intervals. The predetermined interval should be a time interval that is sufficiently short compared to the cycle of human respiration. For example, the predetermined interval may be 5 ms. When the transmission control unit 2001 receives an occupant detection instruction, which will be described later, from the DigiKey ECU 21, it should start transmitting the impulse signals used for the radar function. The timing of the transmission of the impulse signals used for the radar function should be different from the timing of the distance measurement communication. The occupant detection instruction is transmitted from the DigiKey ECU 21, for example, when the doors of the vehicle are locked.

[0050] The reflected wave information acquisition unit 2002 acquires information about the reflected wave of the impulse signal received by the in-vehicle UWB anchor 20 (hereinafter referred to as reflected wave information). The processing in the reflected wave information acquisition unit 2002 corresponds to the reflected wave information acquisition process. It is preferable that the reflected wave information acquisition unit 2002 acquires reflected wave information that includes at least the signal strength of the reflected wave. It is more preferable that the reflected wave information acquisition unit 2002 acquires reflected wave information that includes at least the signal strength and phase of the reflected wave. In this embodiment, the explanation will continue with an example in which the reflected wave information acquisition unit 2002 acquires CIR (Channel Impulse Response) data including the signal strength and phase of the reflected wave as reflected wave information.

[0051] The occupant detection unit 2003 detects the presence or absence of occupants in the vehicle based on the reflected wave information acquired by the reflected wave information acquisition unit 2002. The occupant detection unit 2003 can detect the presence or absence of occupants by analyzing the reflected wave information and determining whether the reflected wave information shows a tendency characteristic of occupants. For example, the presence of an occupant may be detected if the amount of temporal variation in the received intensity shows a degree of agreement with the respiratory variation amount, which is the amount of variation caused by the occupant's breathing, that is above a threshold. The occupants to be detected may be configured so as not to distinguish between adults and children, or they may be configured to distinguish between adults and children. Adults may be replaced with adults, and children with infants. As an example, it is preferable to target children for detection in order to detect if a child has been left unattended in the vehicle. In this embodiment, the explanation will continue with an example where the occupant to be detected is a child.

[0052] The occupant detection unit 2003 detects the presence or absence of occupants in the vehicle by using not only the reflected wave information of the first reflected wave whose signal strength exceeds the threshold, but also the reflected wave information of the second and subsequent reflected waves whose signal strength exceeds the threshold, from the time the transmission control unit 2001 transmits an impulse signal until the next transmission interval. The threshold here is a threshold set to distinguish it from noise, and can be set to any arbitrary value. The processing in the occupant detection unit 2003 corresponds to the occupant detection process.

[0053] The first reflected wave whose signal strength exceeds the threshold is presumed to be the direct wave. If the target of detection is located in a place where a direct wave can be obtained, as shown in Figure 7, after a direct wave with a signal strength exceeding the threshold is obtained, multiple multipath waves with a signal strength exceeding the threshold are obtained. Figure 7 shows an example of the time change of the received intensity of the reflected wave. The vertical axis in Figure 7 shows the received intensity, and the horizontal axis shows time. Also, DW in Figure 7 shows the direct wave, and MPW shows the reflected wave. Note that the first reflected wave whose signal strength exceeds the threshold is not necessarily the direct wave. If the target of detection is located in a blind spot where it is difficult to obtain a direct wave, the first reflected wave with a signal strength exceeding the threshold may not be the direct wave. The second and subsequent reflected waves with a signal strength exceeding the threshold are multipath waves. In other words, the occupant detection unit 2003 uses not only the reflected wave presumed to be the direct wave, but also the reflected wave information of the multipath wave, as well as the reflected wave information, to detect the presence or absence of occupants in the vehicle. For example, in CIR analysis, the first pass, where the signal strength initially exceeds a threshold, is identified, and multipath signals are excluded. In contrast, this embodiment does not exclude multipath signals, but instead uses reflected wave information from the second pass and subsequent multipath signals to detect the presence or absence of occupants inside the vehicle.

[0054] When attempting to detect occupants using direct waves, time window filtering may be performed to exclude multipath waves by selecting within the time range in which reflected waves can be obtained. Therefore, the first reflected wave whose signal strength exceeds the threshold can be rephrased as a reflected wave received by the in-vehicle UWB anchor 20 within a time range pre-set as the time range in which direct waves can be obtained from the detection target. On the other hand, the second and subsequent reflected waves whose signal strength exceeds the threshold can be rephrased as reflected waves received by the in-vehicle UWB anchor 20 beyond the time range pre-set as the time range in which direct waves can be obtained from the detection target. The processing in the occupant detection unit 2003 corresponds to the occupant detection process.

[0055] With the above configuration, it becomes possible to detect the presence or absence of occupants using multipath waves as well. Therefore, even occupants in positions with poor line of sight within the vehicle interior, where it is difficult for the in-vehicle UWB anchor 20 to directly receive waves, can be easily detected by multipath waves. For example, when attempting to detect occupants using direct waves, as in the technology disclosed in Patent Document 1, as shown in Figure 8, it is difficult to receive direct waves (see DW in Figure 8) from occupants in positions with poor line of sight within the vehicle interior (see Ch in Figure 8). As a result, there is a risk that occupants may not be detected even if they are present in the vehicle interior. In contrast, radio waves radiated within the vehicle interior are reflected by the body and interior components and fill the vehicle interior. Therefore, in a closed environment such as a vehicle interior, it becomes possible to detect occupants using multipath waves (see MPW in Figure 8). Figure 8 is a schematic diagram showing an example of direct waves and multipath waves from the in-vehicle UWB anchor 20.

[0056] Here, we will explain how reflected waves are obtained under different line-of-sight conditions inside the vehicle using Figures 9 and 10. Figures 9 and 10 are diagrams showing the correspondence between the frequency of the reflected wave, the measurement distance, and the peak level. Figure 9 is a diagram illustrating an example where the child to be detected is located in a position with a good line-of-sight environment inside the vehicle. Figure 10 is a diagram illustrating an example where the child to be detected is located in a position with a poor line-of-sight environment inside the vehicle. In Figures 9 and 10, the vertical axis shows the frequency of the reflected wave, and the horizontal axis shows the measurement distance. The measurement distance should be the distance calculated by TOF from the time from when the impulse signal is transmitted from the in-vehicle UWB anchor 20 until the reflected wave is received at the in-vehicle UWB anchor 20. The measurement distance does not necessarily coincide with the actual distance from the in-vehicle UWB anchor 20 to the target to be detected. The measurement distance calculated from the multipath wave will be longer than the actual distance from the in-vehicle UWB anchor 20 to the target to be detected. AD in Figures 9 and 10 shows the actual distance from the in-vehicle UWB anchor 20 to the target to be detected. Furthermore, in Figures 9 and 10, the intensity of the frequency peak level is indicated by the shade of color. The frequency peak level can be determined by analyzing the CIR data of the reflected wave and detecting the peak. In the examples in Figures 9 and 10, 0.5 Hz, which is characteristic of a child's frequency, is used as the detection target in order to detect children.

[0057] As shown in Figure 9, when the line of sight is good, reflected waves can be seen at the actual distance AD ​​from the target to be detected. In other words, direct waves are obtained. On the other hand, as shown in Figure 10, when the line of sight is poor, reflected waves cannot be seen at the actual distance AD ​​from the target to be detected. In other words, direct waves cannot be obtained. As shown in Figure 10, when the line of sight is poor and direct waves cannot be obtained, it becomes impossible to detect occupants even if an attempt is made to detect them using direct waves. In contrast, with the configuration of this embodiment, by also utilizing multipath waves, it becomes possible to detect occupants even when the line of sight is poor.

[0058] Thus, according to the configuration of this embodiment, even if direct waves cannot be received, the presence or absence of occupants can be detected using multipath waves. Therefore, there is no need to increase the number of in-vehicle UWB anchors 20 to eliminate positions in the vehicle interior where the line of sight is poor for the in-vehicle UWB anchors 20. As a result, it becomes possible to detect occupants even in positions in the vehicle interior where the line of sight is poor, while keeping the number of sensors for detecting occupants in the vehicle interior to a minimum. In addition, by using multipath waves in addition to direct waves, it is possible to amplify the signal, which also makes it possible to improve the SNR (signal-to-noise ratio) in occupant detection.

[0059] Preferably, the occupant detection unit 2003 further detects the presence or absence of an occupant in the vehicle cabin based on the amount of fluctuation in the signal strength and phase of the reflected wave acquired by the reflected wave information acquisition unit 2002. The amount of fluctuation in the signal strength and phase of the reflected wave differs between occupants and objects. This is because occupants experience body movements due to breathing. The amount of fluctuation in the signal strength and phase of the reflected wave also differs depending on whether the occupant is an adult or a child. This is because the magnitude of body movements due to breathing differs between adults and children. The occupant detection unit 2003 can utilize these differences in the amount of fluctuation in the signal strength and phase of the reflected wave. As a result, the occupant detection unit 2003 can distinguish and detect occupants from objects, or distinguish and detect adults from children.

[0060] The occupant detection unit 2003 preferably uses the peak level and frequency standard deviation of the reflected wave as the above-mentioned fluctuation amounts. The peak level and frequency standard deviation of the reflected wave are determined from the signal intensity and phase of the reflected wave. The occupant detection unit 2003 can then detect the presence or absence of an occupant in the vehicle based on whether the combination of the peak level and frequency standard deviation is similar to the combination of the peak level and frequency standard deviation characteristic of occupant body movements. The frequency standard deviation can be determined from the reflected waves for multiple impulse signal transmissions from the in-vehicle UWB anchor 20. The peak level of the reflected wave may be determined as an average value or the like from the reflected waves for multiple impulse signal transmissions from the in-vehicle UWB anchor 20.

[0061] Here, using Figures 11 and 12, we will explain how the standard deviation of the peak level and frequency of the reflected wave correlates with the occupant's body movements. Here, we will use the example where the occupant's body movements are due to breathing. Figure 11 is a diagram to explain how the variation (i.e., standard deviation) of the peak level and frequency of the reflected wave can be obtained from data from multiple measurements. As shown in Figure 11, the data for the standard deviation of the peak level and frequency of the reflected wave is obtained from data obtained from multiple impulse signal transmissions from the in-vehicle UWB anchor 20. In the example of Figure 11, a diagram (hereinafter referred to as the correspondence diagram) showing the relationship between the data for the peak level and standard deviation of the frequency of the reflected wave for a certain measurement distance is extracted and shown. In this correspondence diagram, the vertical axis represents frequency, and the horizontal axis represents the number of measurements. The number of measurements corresponds to the number of impulse signal transmissions from the in-vehicle UWB anchor 20. Figure 11 is just one example, and combinations of data for the peak level and standard deviation of the frequency of the reflected wave can be obtained for each measurement distance.

[0062] Figure 12 illustrates how the peak level and frequency variation of reflected waves differ depending on the presence or absence of a breathing component. Figure 12 shows correspondence diagrams for the case with and without a breathing component. In Figure 12, correspondence diagrams for the same measurement distance are shown side by side. "With breathing component" indicates that the reflected wave is based on a child who is breathing. "Without breathing component" indicates that the reflected wave is based on an object. In the case without a breathing component, the frequency is noise, so as shown in Figure 12, the frequency variation is large and the peak level intensity is small. On the other hand, in the case with a breathing component, the frequency due to breathing is observed, so as shown in Figure 12, the frequency variation is small and the peak level intensity is large. Thus, because the peak level and frequency variation of reflected waves differ depending on the presence or absence of a breathing component, it becomes possible to accurately detect occupants by distinguishing them from noise by using the standard deviation of the peak level and frequency of the reflected wave.

[0063] Furthermore, as mentioned above, if the occupant is located in a position with poor line of sight, the signal strength of the reflected wave from the occupant to be detected will be weaker. Also, when using multipath waves, there is a problem that the signal strength of the multipath waves is weaker compared to the direct wave. In response to this, by using not only the peak level of the reflected wave but also the standard deviation of the frequency for occupant detection, the SNR in occupant detection can be improved.

[0064] The following describes the details of occupant detection using the peak level and frequency standard deviation of reflected waves. As an example, the occupant detection unit 2003 detects occupants by referring to dictionary data and using a combination of the peak level and frequency standard deviation of reflected waves. The dictionary data is data used to calculate the likelihood of detection for each of the multiple labels. The dictionary data is divided into four labels, for example, "noise," "DeepSeep," "Awake," and "Disturb." "Noise" corresponds to a classification of nothing moving. "DeepSeep" corresponds to movements that reproduce the breathing of a child during sleep. "Awake" corresponds to breathing and limb and head movements of a child when awake. "Disturb" corresponds to a classification of disturbance. In this embodiment, since the detection target is a child, adult body movements are also classified as disturbances. The dictionary data is data that associates combinations of peak levels and frequency standard deviations of multiple types of reflected waves with four labels. The dictionary data may be created in advance through machine learning or similar learning. The in-vehicle UWB anchor 20 should be configured to have the dictionary data within the algorithm for detecting occupants. For example, the dictionary data may be stored in the non-volatile memory of the in-vehicle UWB anchor 20. Note that the labels in the dictionary data are not limited to four classifications, but may be multiple classifications other than four. For example, there may be two labels to distinguish between occupants and non-occupants. The following explanation will continue using the case where there are the four types of labels mentioned above as an example. The dictionary data may be configured to be created according to the type of occupant to be detected, and switched when changing the detection target. For example, a dictionary data for detecting children and a dictionary data for detecting adults may be switched between.

[0065] The occupant detection unit 2003 calculates the likelihood that the detected object corresponds to each label by referring to dictionary data based on the combination of the peak level and standard deviation of the reflected wave. The likelihood can be calculated by determining how similar the combination of the peak level and standard deviation of the reflected wave is to the set of combinations that correspond to each label in the dictionary data. Various methods can be used to calculate the likelihood. The occupant detection unit 2003 can detect that there is a child, who is the occupant to be detected, inside the vehicle if the likelihood of "DeepSeep" or "Awake" is the highest among the four labels. On the other hand, the occupant detection unit 2003 can detect that there is no child, who is the occupant to be detected, inside the vehicle if the likelihood of neither "DeepSeep" nor "Awake" is the highest among the four labels.

[0066] The occupant detection unit 2003 can calculate the likelihood for each reflected wave obtained at different measurement distances from a combination of the peak level and the standard deviation of the frequency of the reflected wave. Then, it may detect whether or not there is an occupant to be detected inside the vehicle based on these multiple likelihoods. In this case, it can be done as follows.

[0067] First, as shown in Figure 13, the calculated likelihoods are plotted for each measurement distance. This likelihood should be the likelihood of "DeepSeep" or "Awake". Figure 13 is a diagram showing the correspondence between the measurement distance and the calculated likelihood. In Figure 13, Th is the threshold for distinguishing whether or not it is the breathing of the child who is the target occupant. This threshold can be set to any arbitrary value. Then, the occupant detection unit 2003 should determine from the plot results whether or not the measurement data is the breathing of the child who is the target occupant. For example, if there is a plot result that exceeds the threshold Th, it should be determined to be the breathing of the child who is the target occupant. In other words, the occupant detection unit 2003 should detect that there is a child who is the target occupant inside the vehicle. For example, even if the likelihood of "DeepSeep" or "Awake" is the highest among the four labels, if the likelihood is low, a false detection is possible. In contrast, by also detecting the presence of a target when the likelihood is greater than or equal to the threshold th, it is possible to suppress false detections. Alternatively, as shown in the elliptical plot results in Figure 13, the presence of a target can also be detected if plot results exceeding a threshold th are consecutive within a short measurement distance. In this case as well, it is possible to suppress false positives.

[0068] Furthermore, based on the plot results that are above the threshold Th, the data used to estimate the distance to the detection target and the respiratory frequency may be determined as shown in Figure 14. In this embodiment, it is sufficient to determine that the data enclosed by the ellipse in Figure 14 from the 0.5 Hz frequency data will be used to estimate the distance to the detection target and the respiratory frequency. Figure 14 is a diagram showing the correspondence between the reflected wave frequency, the measured distance, and the peak level.

[0069] The occupant detection unit 2003 uses multiple units of reflected wave information, treating the reflected wave information for a certain period from the time the transmission control unit 2001 transmits an impulse signal until the next transmission interval as one unit, to detect the presence or absence of an occupant in the vehicle. Preferably, the occupant detection unit 2003 allows setting how many units of reflected wave information to use to detect the presence or absence of an occupant in the vehicle. The number of units of reflected wave information used is in a trade-off relationship between the accuracy of occupant detection and the detection time. Therefore, by making it possible to set how many units to use, it becomes possible to adjust the accuracy of occupant detection and the detection time. In the example of this embodiment, the following explanation will use the case where 5 seconds of reflected wave information is used, with a period of 5 ms as one unit.

[0070] The occupant detection unit 2003 can detect the presence or absence of an occupant inside the vehicle when the vehicle's doors are locked. The occupant detection unit 2003 can start occupant detection processing and detect the presence or absence of an occupant inside the vehicle when triggered by an occupant detection instruction transmitted from the digital key ECU 21 when the vehicle's doors are locked. This makes it possible to quickly detect the presence or absence of an occupant inside the vehicle after the vehicle's doors are locked. Therefore, it can be suitably used to detect children being left unattended inside a vehicle. The occupant detection unit 2003 may also be triggered when it receives information from the body ECU 27 indicating that the vehicle's doors are locked.

[0071] The result notification unit 2004 sends the occupant detection result from the occupant detection unit 2003 to the DigiKey ECU 21. The occupant detection result may be, for example, an occupant detection result indicating the presence of an occupant inside the vehicle. Alternatively, the occupant detection result may be an occupant detection result indicating the presence or absence of an occupant inside the vehicle. When the result notification unit 2004 sends an occupant detection result indicating the presence of an occupant inside the vehicle to the DigiKey ECU 21, the DigiKey ECU 21 issues an alarm. The alarm may consist of sounding the vehicle's horn and / or turning on the vehicle's hazard lights. In other words, the result notification unit 2004 will issue an alarm by sounding the vehicle's horn and / or turning on the vehicle's hazard lights. Thus, the result notification unit 2004 corresponds to the alarm instruction unit. This makes it easier for those around the vehicle to notice if an occupant has been left inside the vehicle. When the DigiKey ECU 21 receives an occupant detection result indicating the presence of an occupant inside the vehicle, the DigiKey ECU 21 may perform processing other than issuing an alarm. This processing other than issuing an alarm will be described later.

[0072] <Occupant detection processing at the in-vehicle UWB anchor 20> Next, an example of the flow of occupant detection processing at the in-vehicle UWB anchor 20 will be explained using the flowchart in Figure 15. The flowchart in Figure 15 can be configured to start, for example, when the vehicle's driving power supply is turned off and switches to the backup power supply.

[0073] First, in step S1, if there is a trigger indicating that the vehicle's doors are locked (YES in S1), the process proceeds to step S2. On the other hand, if there is no trigger indicating that the vehicle's doors are locked (NO in S1), the process in S1 is repeated. Whether or not there is a trigger indicating that the vehicle's doors are locked can be determined by the occupant detection unit 2003.

[0074] In step S2, radar measurement is performed at the in-vehicle UWB anchor 20. During the radar measurement, the transmission control unit 2001 causes the in-vehicle UWB anchor 20 to transmit an impulse signal. The reflected wave information acquisition unit 2002 then acquires the CIR data of the impulse signal received by the in-vehicle UWB anchor 20. In this embodiment, the transmission interval of the impulse signal is set to 5 ms.

[0075] In step S3, the reflected wave information acquisition unit 2002 saves the CIR data acquired by radar measurement to the buffer of the in-vehicle UWB anchor 20. The buffer can also be described as the buffer area of ​​the memory. In step S4, if there is more than 5 seconds' worth of CIR data saved in the buffer (YES in S4), the process proceeds to step S5. On the other hand, if the CIR data saved in the buffer does not reach 5 seconds' worth (NO in S4), the process returns to S2 and is repeated. In step S5, the reflected wave information acquisition unit 2002 deletes the oldest CIR data in the buffer using FIFO (First In First Out) so that the CIR data in the buffer reaches 5 seconds' worth.

[0076] In step S6, the occupant detection unit 2003 obtains and records the peak level and frequency of the reflected wave from the CIR data stored in the buffer. In Figure 15, the peak level is shown as PL and the frequency as Fr. The peak level and frequency can be stored in the memory of the in-vehicle UWB anchor 20. In step S7, if 5 seconds' worth of peak level and frequency data has been stored (YES in S7), the process proceeds to step S8. On the other hand, if 5 seconds' worth of peak level and frequency data has not been stored (NO in S7), the process returns to S2 and is repeated.

[0077] In step S8, if the peak level intensity is above the aforementioned threshold (YES in S8), the process proceeds to step S9. For example, if any of the calculated peak levels are above the threshold, the process should proceed to S9. The threshold can be any value used to exclude noise and can be set arbitrarily. On the other hand, if the peak level intensity is not above the aforementioned threshold (NO in S8), the crew detection process is terminated. For example, if none of the calculated peak levels are above the threshold, the crew detection process should be terminated.

[0078] In step S9, the crew detection unit 2003 calculates the standard deviation of the frequency from the accumulated frequency records. In step S10, the crew detection unit 2003 calculates the likelihood of each label by referring to dictionary data based on the combination of the peak level of the reflected wave and the standard deviation of the frequency.

[0079] In step S11, the occupant detection unit 2003 detects whether or not there is a detection target inside the vehicle based on the likelihood calculated in S10. In this embodiment, the detection target is a child. The occupant detection unit 2003 only needs to detect the presence of a detection target inside the vehicle if the likelihood of "DeepSeep" or "Awake" is the highest among the four labels, and that likelihood exceeds the threshold Th explained in Figure 13. In S11, if the occupant detection unit 2003 detects that there is a detection target inside the vehicle (YES in S11), the process moves to step S12. On the other hand, if the occupant detection unit 2003 detects that there is no detection target inside the vehicle (NO in S11), the occupant detection process ends. In step S12, the result notification unit 2004 sends an occupant detection result indicating the presence of an occupant inside the vehicle to the digital key ECU 21, triggers an alarm, and ends the occupant detection process.

[0080] <About the Functions of the DigiKey ECU 21> Next, we will explain the general configuration of the DigiKey ECU 21. As shown in Figure 16, the DigiKey ECU 21 includes a BLE instruction unit 211, a BLE acquisition unit 212, a registration unit 213, a verification unit 214, a permission unit 215, a distance measurement instruction unit 216, an RTT acquisition unit 217, a terminal distance estimation unit 218, a terminal position estimation unit 219, a door lock detection unit 240, an occupant detection instruction unit 241, a detection result acquisition unit 242, and an alarm processing unit 243. Note that some or all of the functions performed by the DigiKey ECU 21 may be configured in hardware using one or more ICs, etc. Also, some or all of the functional blocks provided by the DigiKey ECU 21 may be realized by a combination of software execution by a processor and hardware components.

[0081] The BLE instruction unit 211 performs the following processing when a communication connection is established between the BLE anchor 22 and the BLE communication unit 32 of the mobile terminal 3. The BLE instruction unit 211 causes the BLE anchor 22 to send the challenge code generated by the verification unit 214 to the mobile terminal 3. The BLE acquisition unit 212 acquires the response code when it receives the response code returned in response to the transmitted challenge code at the BLE anchor 22. The acquired response code is sent to the verification unit 214.

[0082] Furthermore, the BLE acquisition unit 212 acquires the challenge code when it receives the challenge code transmitted from the mobile terminal 3 at the BLE anchor 22. The acquired challenge code is sent to the verification unit 214. The BLE instruction unit 211 causes the verification unit 214 to send the response code it generates for this challenge code back to the mobile terminal 3 from the BLE anchor 22.

[0083] The registration unit 213 stores the aforementioned key code. A storage device can be used as the registration unit 213. The verification unit 214 starts wireless authentication processing when a communication connection is established between the BLE anchor 22 and the BLE communication unit 32 of the mobile terminal 3. First, the verification unit 214 generates a challenge code and sends it to the BLE instruction unit 211. Also, when the verification unit 214 receives a response code from the BLE acquisition unit 212, it generates a verification code using the key code stored in the registration unit 213 and the challenge code sent to the mobile terminal 3 according to a predetermined procedure. The verification unit 214 authenticates that the mobile terminal 3 is the mobile terminal 3 of a legitimate user when this verification code matches the response code sent from the BLE acquisition unit 212.

[0084] The authorization unit 215 permits the use of the vehicle if authentication is successful in the verification unit 214. Examples of permission for vehicle use include permission to lock and unlock the vehicle, and permission to start the drive source. For example, the authorization unit 215 can switch whether or not to permit the use of the vehicle depending on whether the terminal location estimated by the terminal location estimation unit 219 (described later) is within a predetermined range. For example, in the case of permission to start the drive source, the predetermined range can be the interior of the vehicle.

[0085] The distance measurement instruction unit 216 causes the in-vehicle UWB anchor 20 and the out-of-vehicle UWB anchor 23 to transmit impulse signals in sequence. Hereinafter, when the in-vehicle UWB anchor 20 and the out-of-vehicle UWB anchor 23 are not distinguished, they will be collectively referred to as UWB anchors. In this embodiment, the in-vehicle UWB anchor 20 and the out-of-vehicle UWB anchors 23a, 23b, 23c, and 23d should transmit impulse signals in sequence at predetermined time intervals. The distance measurement instruction unit 216 should start transmitting impulse signals from the UWB anchors when a communication connection is established between the BLE communication unit 32 of the mobile terminal 3 and the BLE anchor 22, or when the establishment of such a connection is triggered. This makes it possible to suppress the waste of transmitting impulse signals even when there is no mobile terminal 3 in the vicinity of the vehicle.

[0086] The RTT acquisition unit 217 acquires the round-trip time measured by the UWB anchor when distance measurement communication is performed between the mobile terminal 3 and the UWB anchor. The RTT acquisition unit 217 acquires the round-trip time output from each of the multiple UWB anchors. The RTT acquisition unit 217 can identify which UWB anchor's round-trip time it is based on the anchor ID output from the UWB anchor. In this embodiment, the RTT acquisition unit 217 acquires the round-trip time for each of the in-vehicle UWB anchors 20 and out-of-vehicle UWB anchors 23a, 23b, 23c, and 23d that were able to receive a response signal during distance measurement communication.

[0087] The terminal distance estimation unit 218 estimates the distance from the UWB anchor to the mobile terminal 3 using the round-trip time acquired by the RTT acquisition unit 217. The distance from the UWB anchor to the mobile terminal 3 will be referred to as the terminal distance below. The terminal distance estimation unit 218 may estimate the terminal distance as follows, for example: The terminal distance estimation unit 218 calculates the propagation time by dividing the value obtained by subtracting the internal processing time at the mobile terminal 3 in distance measurement communication from the round-trip time by 2. Then, it estimates the terminal distance as the value obtained by multiplying the calculated propagation time by the speed of light. Note that the internal processing time may be configured to store a standard value in the storage of the DigiKey ECU 21. Note that the terminal distance estimation may also be performed at the UWB anchor.

[0088] The terminal position estimation unit 219 estimates the position of the mobile terminal 3 relative to the vehicle using the terminal distance estimated by the terminal distance estimation unit 218. The position of the mobile terminal 3 relative to the vehicle will be referred to as the terminal position below. The terminal position estimation unit 219 only needs to estimate the terminal position using the terminal distances for the three UWB anchors as described above. For the selection of the three UWB anchors, the three with the shortest terminal distances should be selected. An example of estimating the terminal position is as follows: First, in a horizontal coordinate system (hereinafter referred to as the plane coordinate system) with the vehicle's reference point as the origin, three circles are drawn with the positions of the three UWB anchors as centers and the terminal distance as the radius. Then, the terminal position is estimated using three-point positioning based on these three circles. Three-point positioning can also be called triangulation. The vehicle's reference point can be determined as appropriate; for example, it can be the position at the center of the rear axle in the vehicle width direction. The position of the UWB anchor relative to the vehicle can be stored in the storage of the digital key ECU 21 in advance to make it available. The terminal position estimation unit 219 outputs the estimated terminal position to the in-vehicle LAN. This terminal position can be used, for example, for the digital key system or to notify users if they have left their mobile terminal 3 inside the vehicle.

[0089] The door lock detection unit 240 detects the locked / unlocked status of the vehicle's doors. The door lock detection unit 240 can detect the locked / unlocked status of the vehicle's doors by obtaining information on the locked / unlocked status of the vehicle's doors from the body ECU 27. When the door lock detection unit 240 detects that the vehicle's doors are locked, the occupant detection instruction unit 241 sends an occupant detection instruction to the in-vehicle UWB anchor 20.

[0090] The detection result acquisition unit 242 acquires occupant detection results sent from the in-vehicle UWB anchor 20. The alarm processing unit 243 triggers an alarm when the detection result acquisition unit 242 acquires occupant detection results indicating the presence of an occupant inside the vehicle. The alarm may consist of at least one of the following: sounding the vehicle's horn and / or illuminating the vehicle's hazard lights. The alarm processing unit 243 can send an instruction to the body ECU 27 to trigger this alarm. Alternatively, the alarm processing unit 243 may be configured to perform actions other than an alarm. For example, it may send an instruction to the body ECU 27 to unlock the vehicle's doors. It may also send an instruction to the body ECU 27 to open the vehicle's windows. Furthermore, it may notify the vehicle user's mobile terminal 3 that an occupant has been left inside the vehicle and trigger a warning from the display device on the mobile terminal 3.

[0091] (Disclosed Technical Concepts) This specification discloses several technical concepts as set forth in the following paragraphs. Some paragraphs may be written in a multiple dependent form, where subsequent paragraphs alternately refer to preceding paragraphs. Furthermore, some paragraphs may be written in a multiple dependent form, where they refer to other multiple dependent forms. These paragraphs written in multiple dependent forms define several technical concepts.

[0092] (Technical Concept 1) An occupant detection device comprising: a transmission control unit (2001) that controls the transmission of an impulse signal from a radar (20) that can be used inside a vehicle, which transmits an impulse signal and receives a reflected wave of the impulse signal; a reflected wave information acquisition unit (2002) that acquires reflected wave information, which is information about the reflected wave of the impulse signal received by the radar; and an occupant detection unit (2003) that detects the presence or absence of an occupant inside the vehicle based on the reflected wave information acquired by the reflected wave information acquisition unit, wherein the transmission control unit causes the impulse signal to be transmitted sequentially at predetermined intervals; the reflected wave information acquisition unit acquires the reflected wave information, which includes at least the signal strength of the reflected wave; and the occupant detection unit detects the presence or absence of an occupant inside the vehicle by using the reflected wave information of the second and subsequent reflected waves whose signal strength is above the threshold, as well as the reflected wave information of the first reflected wave whose signal strength is above the threshold, among the reflected waves received by the radar from the time the transmission control unit transmits the impulse signal until the next transmission interval.

[0093] (Technical Concept 2) An occupant detection device as described in Technical Concept 1, wherein the reflected wave information acquisition unit acquires the reflected wave information including at least the signal strength and phase of the reflected wave, and the occupant detection unit detects the presence or absence of an occupant in the vehicle interior based on the amount of variation in the signal strength and phase of the reflected wave acquired by the reflected wave information acquisition unit.

[0094] (Technical Concept 3) An occupant detection device as described in Technical Concept 2, wherein the occupant detection unit uses the standard deviation of the peak level and frequency of the reflected wave, which is obtained from the signal strength and phase of the reflected wave acquired by the reflected wave information acquisition unit, as the amount of fluctuation in the signal strength and phase of the reflected wave acquired by the reflected wave information acquisition unit, and detects the presence or absence of an occupant in the vehicle interior based on whether the combination of the peak level and the standard deviation of frequency is similar to the combination of the peak level and the standard deviation of frequency that is characteristic of the body movements of the occupant.

[0095] (Technical Concept 4) An occupant detection device according to any one of Technical Concepts 1 to 3, wherein the occupant detection unit uses multiple units of reflected wave information, treating the reflected wave information for a certain period from the time the transmission control unit transmits the impulse signal until the next transmission interval as one unit, to detect the presence or absence of an occupant in the vehicle, and the number of units of reflected wave information to be used to detect the presence or absence of an occupant in the vehicle is configurable.

[0096] (Technical Concept 5) An occupant detection device according to any one of Technical Concepts 1 to 4, wherein the occupant detection unit detects the presence or absence of an occupant inside the vehicle when the vehicle door is locked, and the occupant detection device comprises an alarm instruction unit (2004) that causes an alarm to be issued when the occupant detection unit detects the presence of an occupant inside the vehicle.

[0097] (Technical Concept 6) An occupant detection device according to Technical Concept 5, wherein the alarm instruction unit causes the alarm to be sounded by sounding the vehicle's horn and the vehicle's hazard lights to turn on.

[0098] (Technical Idea 7) An occupant detection device according to any one of Technical Ideas 1 to 6, wherein the radar, whose transmission control unit controls the transmission of the impulse signal, is an anchor that is also used in the vehicle for range-measuring communication, which is bidirectional communication for measuring the distance to a communication target.

[0099] In this disclosure or claims, the term "processor" refers to one or more hardware processors configured to execute processing defined by computer program code (i.e., one or more instructions of a computer program) contained in a computer program, by reading the code each time. In other words, a "processor" is a hardware device that executes one or more programmed processes. Therefore, computer program code can also be considered software that can define the processing of the processor according to its content. For example, a "processor" may be a general-purpose or specific-purpose processor, and may be, but is not limited to, a CPU, microprocessor, GPU, and DFP (Data Flow Processor).

[0100] In this disclosure or claims, the term “memory” means one or more hardware memories that are non-transitional tangible recording media configured to record computer program code and / or data in a manner accessible by a processor. “Memory” can be implemented by memory technologies such as SRAM, SDRAM, non-volatile / flash type memory, or other types of memory. Computer program code that constitutes a program is recorded in memory and executed by a processor, thereby enabling the processor to perform the various functions described above.

[0101] In this disclosure or claims, the term “circuit” refers to a logic circuit as one or more pieces of hardware, configured to perform specific processing defined by a pre-designed circuit configuration. In other words (and, in contrast to “processor”), “circuit” in this disclosure or claims refers to a hardware device that performs specific processing based on a circuit configuration, rather than processing defined by software such as the computer program code described above. For example, “circuit” may include custom ICs such as ASICs (Application Specific Integrated Circuits) and FPGAs (Field Programmable Gate Arrays) designed with Hardware Description Language (HDL). That is, “circuit” in this disclosure or claims includes all hardware circuits except for the processor described above, which performs processing by reading computer program code.

[0102] In this disclosure or claims, the expression "at least one of the processors and circuits" should be interpreted as a disjunctive (logical OR) and not as at least one processor and at least one circuit. Therefore, in this disclosure or claims, "at least one of the processors and circuits" includes cases where the circuit alone performs all functions. Also, in this disclosure or claims, "at least one of the processors and circuits" includes cases where the processor alone performs all functions. In this disclosure or claims, "at least one of the processors and circuits" includes cases where the circuit performs some functions and the processor performs the remaining functions.

Claims

1. An occupant detection device comprising: a transmission control unit (2001) that controls the transmission of an impulse signal from a radar (20) that can be used inside a vehicle, which transmits an impulse signal and receives a reflected wave of the impulse signal; a reflected wave information acquisition unit (2002) that acquires reflected wave information, which is information about the reflected wave of the impulse signal received by the radar; and an occupant detection unit (2003) that detects the presence or absence of an occupant inside the vehicle based on the reflected wave information acquired by the reflected wave information acquisition unit, wherein the transmission control unit causes the impulse signal to be transmitted sequentially at predetermined intervals; the reflected wave information acquisition unit acquires the reflected wave information, which includes at least the signal strength of the reflected wave; and the occupant detection unit detects the presence or absence of an occupant inside the vehicle by using the reflected wave information of the second and subsequent reflected waves whose signal strength exceeds a threshold, as well as the reflected wave information of the first reflected wave whose signal strength exceeds a threshold, among the reflected waves received by the radar from the time the transmission control unit transmits the impulse signal until the next transmission interval.

2. An occupant detection device according to claim 1, wherein the reflected wave information acquisition unit acquires the reflected wave information, which includes at least the signal strength and phase of the reflected wave, and the occupant detection unit detects the presence or absence of an occupant in the vehicle interior based on the amount of fluctuation in the signal strength and phase of the reflected wave acquired by the reflected wave information acquisition unit.

3. An occupant detection device according to claim 2, wherein the occupant detection unit uses the standard deviation of the peak level and frequency of the reflected wave obtained from the signal strength and phase of the reflected wave obtained from the reflected wave information acquisition unit as the amount of fluctuation in the signal strength and phase of the reflected wave obtained from the reflected wave information acquisition unit, and detects the presence or absence of an occupant in the vehicle interior based on whether the combination of the peak level and the standard deviation of frequency is similar to the combination of the peak level and the standard deviation of frequency characteristic of the occupant's body movements.

4. An occupant detection device according to claim 1, wherein the occupant detection unit detects the presence or absence of an occupant in the vehicle interior using multiple units of reflected wave information, with the number of units of reflected wave information used to detect the presence or absence of an occupant in the vehicle interior being configurable.

5. An occupant detection device according to claim 1, wherein the occupant detection unit detects the presence or absence of an occupant inside the vehicle when the vehicle doors are locked, and the occupant detection device further comprises an alarm instruction unit (2004) that causes an alarm to sound when the occupant detection unit detects the presence of an occupant inside the vehicle.

6. An occupant detection device according to claim 5, wherein the alarm instruction unit causes the alarm to be triggered by at least one of the following: sounding the vehicle's horn and illuminating the vehicle's hazard lights.

7. An occupant detection device according to claim 1, wherein the radar, whose transmission control unit controls the transmission of the impulse signal, is an anchor that is also used in distance measuring communication, which is bidirectional communication for measuring the distance to a communication target, in the vehicle.

8. An occupant detection method comprising: a transmission control step, which is performed by at least one of a processor and a circuit, to control the transmission of an impulse signal from a radar that can be used inside a vehicle, which transmits an impulse signal and receives a reflected wave of the impulse signal; a reflected wave information acquisition step, which is information of the reflected wave of the impulse signal received by the radar, and an occupant detection step, which detects the presence or absence of an occupant inside the vehicle based on the reflected wave information acquired in the reflected wave information acquisition step, wherein the transmission control step causes the impulse signal to be transmitted sequentially at predetermined intervals; the reflected wave information acquisition step acquires the reflected wave information, which includes at least the signal strength of the reflected wave; and the occupant detection step detects the presence or absence of an occupant inside the vehicle by using the reflected wave information of the second and subsequent reflected waves whose signal strength is above a threshold, as well as the reflected wave information of the first reflected wave whose signal strength is above a threshold, among the reflected waves received by the radar from the time the impulse signal is transmitted in the transmission control step until the next transmission interval.

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