Reflector detection system, position estimation system, reflector detection device

Abstract

This technology provides a method for accurately determining the presence or absence of highly reflective materials. [Solution] The DK-ECU is connected to a plurality of anchors, including a first anchor and a second anchor. Each anchor is configured to perform ranging communication, including sending and receiving CW signals on multiple channels, with a portable device and other anchors. The DK-ECU has a memory 232 in which direct wave IQ data for each channel is registered. The DK-ECU obtains observed IQ data for each channel by having the first anchor communicate ranging with the second anchor. Next, it generates differential IQ data corresponding to the reflected wave IQ data by subtracting the direct wave IQ data registered in memory from the observed IQ data. Then, the DK-ECU calculates a representative value of the reflected wave intensity based on the differential IQ data, and determines that a strong reflector exists in the target area if the representative value of the reflected wave intensity is greater than the detection threshold.

Description

Technical Field

[0001] The present disclosure relates to a technique for identifying the position of a portable device relative to a vehicle by wireless communication.

Background Art

[0002] Patent Document 1 discloses a technique for identifying the position of a portable device relative to a vehicle using multiple sets of ranging data obtained by performing ranging communication between a plurality of anchors and the portable device. Here, the ranging communication is wireless communication for measuring distance. For example, the distance can be calculated based on phase information determined by transmitting and receiving a predetermined continuous wave (CW) signal. Transmitting and receiving a continuous wave can also be referred to as tone exchange or the like.

[0003] Patent Document 2 discloses a configuration for determining whether there is an object that can reflect radio waves around a vehicle based on the communication results of ranging communication between anchors, and switching parameters used for determining the device position according to the determination result. Here, the device position means the relative position of the portable device with respect to the vehicle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The results of determining the presence or absence of a strong reflector can be used to switch position estimation algorithms, etc. The developers of this disclosure were investigating a technique to determine the presence or absence of a strong reflector from IQ data obtained by anchors performing distance measurement communication, and obtained the following findings. That is, the IQ data observed through actual communication corresponds to a composite wave of direct waves and reflected waves. When a strong reflector is in the vicinity of the vehicle (e.g., within 1m), the reflected wave from the strong reflector is dominant over the direct wave, so the presence or absence of a strong reflector can be determined with a certain degree of accuracy even from the IQ data observed through actual communication alone. However, when a strong reflector is located far from the vehicle (e.g., 2m away), the difference in intensity between the reflected wave and the direct wave from the strong reflector becomes small, and it is difficult to determine the presence or absence of a strong reflector using only the IQ data observed through actual communication. Here, the direct wave refers to a signal that arrives without being reflected by walls, the ground, etc. (i.e., directly).

[0006] One of the purposes of this disclosure is to provide a technology that can accurately determine the presence or absence of a highly reflective surface. [Means for solving the problem]

[0007] The reflector detection system disclosed herein comprises a first anchor (3B) and a second anchor (3C) configured to perform distance measurement communication, including sending and receiving continuous wave signals on multiple channels, and a control unit (23) that determines whether or not a strong reflector exists around a vehicle based on the results of distance measurement communication performed by the first anchor with the second anchor, wherein the results of distance measurement communication include IQ data for each channel, and the control unit includes a memory (232) which stores direct wave IQ data, which is IQ data observed when the first anchor performs distance measurement communication with the second anchor under a predetermined test environment where no reflectors exist around the vehicle, and the control unit is configured to acquire the channel-specific IQ data obtained by having the first anchor perform distance measurement communication with the second anchor as observed IQ data, generate differential IQ data indicating IQ data originating from reflected waves based on the observed IQ data and the direct wave IQ data, calculate the reflected wave intensity based on the differential IQ data, and determine whether or not a strong reflector exists in a target area determined with respect to the vehicle by comparing the reflected wave intensity with a predetermined detection threshold.

[0008] The position estimation system included in this disclosure comprises a first anchor (3B) and a second anchor (3C) configured to perform distance measurement communication, including sending and receiving continuous wave signals on multiple channels; and a control unit (23) that obtains multiple sets of distance measurement values ​​indicating the distance from each of the first and second anchors to the mobile device by having the first and second anchors perform distance measurement communication with the mobile device, and estimates the device position, which is the position of the mobile device relative to the vehicle, based on the multiple sets of distance measurement values, wherein the result of the distance measurement communication includes IQ data for each channel, and the control unit determines when the first anchor performs distance measurement communication with the second anchor under a predetermined test environment in which there are no reflectors around the vehicle. The control unit is configured to perform the following actions: acquire channel-specific IQ data obtained by having the first anchor communicate with the second anchor for distance measurement as observed IQ data; generate differential IQ data indicating IQ data originating from reflected waves based on the observed IQ data and the direct wave IQ data; calculate reflected wave intensity based on the differential IQ data; determine whether or not a strong reflector exists in a target area defined with respect to the vehicle by comparing the reflected wave intensity with a predetermined detection threshold; and change the method for estimating the position of the mobile device depending on whether or not it has been determined that a strong reflector exists.

[0009] The reflector detection device included in this disclosure is a reflector detection device for determining whether a strong reflector exists around a vehicle, and comprises a control unit (23) that performs processing for determining the presence or absence of a strong reflector, and a communication circuit (22) for the control unit to communicate with a first anchor (3B) and a second anchor (3C) configured to perform distance measurement communication including sending and receiving continuous wave signals on multiple channels, wherein the distance measurement communication is communication for generating IQ data for each channel, and the control unit comprises a memory (232) which stores direct wave IQ data, which is IQ data for each channel observed when the first anchor performs distance measurement communication with the second anchor under a predetermined test environment in which no reflectors exist around the vehicle, and the control unit is configured to perform the following: acquire the IQ data for each channel obtained by having the first anchor perform distance measurement communication with the second anchor as observed IQ data, generate differential IQ data indicating IQ data originating from reflected waves based on the observed IQ data and the direct wave IQ data, calculate the reflected wave intensity based on the differential IQ data, and determine whether a strong reflector exists in a predetermined target area by comparing the reflected wave intensity with a predetermined detection threshold.

[0010] According to the above technology, the control unit generates differential IQ data based on direct wave IQ data pre-registered in memory and observed IQ data obtained by the actual distance measurement communication between the first and second anchors. This differential IQ data has fewer components originating from direct waves compared to the observed IQ data and can represent IQ data originating from reflected waves. Therefore, the reflected wave intensity generated from the differential IQ data can indicate the intensity of the reflected wave with higher accuracy. By using this reflected wave intensity to determine whether or not a strong reflector is present, the accuracy of the determination can be improved.

[0011] The reference numerals in parentheses in the claims indicate the correspondence with the specific means described later in the embodiments, and do not limit the technical scope of this disclosure. [Brief explanation of the drawing]

[0012] [Figure 1] It is a diagram showing the overall configuration of an electronic key system for a vehicle. [Figure 2] It is a block diagram showing the configuration of an in-vehicle key system and a portable device. [Figure 3] It is a diagram showing the mounting position of an anchor. [Figure 4] It is a diagram for explaining the test conditions for examining the influence of a reflector on the estimation of device distance and device position. [Figure 5] It is a diagram for explaining the constituent components of IQ data obtained by ranging communication. [Figure 6] It is a diagram showing the relationship between the IQ level of a reflected wave from a strong reflector and the IQ level of a direct wave in the back pocket state. [Figure 7] It is a diagram showing the outline of a test for specifying the maximum reflected wave level. [Figure 8] It is a diagram showing the outline of a test for specifying the minimum direct wave level. [Figure 9] It is a flowchart of an environment determination process. [Figure 10] It is a diagram for explaining a method of calculating the distance to a strong reflector. [Figure 11] It is a diagram showing a boundary line and a recalculation area set based on the reflector distance. [Figure 12] It is a flowchart of a position identification process. [Figure 13] It is a diagram exemplifying a case where the device position is erroneously determined by reflection. [Figure 14] It is a diagram showing the outline of a positioning operation process by a second estimation method. [Figure 15] It is a flowchart showing another operation example of a DK-ECU. [Figure 16] It is a diagram for explaining the design concept of the directivity of an antenna provided in an outer anchor. [Figure 17] It is a flowchart showing another example of an environment determination process. [Figure 18]It is a flowchart of a monitoring process using the reception intensity of advertisements.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments. The configurations disclosed below may be variously modified and implemented without departing from the gist. Various modifications may be appropriately combined and implemented within a range where no technical contradiction occurs. The present disclosure also includes configurations not explicitly stated that are combinations of multiple modifications. In the following description, members having the same function may be given the same reference numerals, and the specific description thereof may be omitted. Also, members having the same function may be given the same or similar names, and the specific description thereof may be omitted. When only a part of the configuration is mentioned, the description given elsewhere may be applied to other parts.

[0014] <Overall Configuration> One embodiment of a vehicle electronic key system according to the present disclosure will be described with reference to the drawings. FIG. 1 is a diagram showing an example of a schematic configuration of a vehicle electronic key system. As shown in FIG. 1, the vehicle electronic key system includes an in-vehicle key system 1 and one or more portable devices 9. The portable device 9 is a communication device that functions as a key for the vehicle Hv. Information of the portable device 9 (for example, device ID) is registered in advance in the in-vehicle key system 1. The portable device 9 may be understood as a communication device that is registered in advance in the in-vehicle key system 1 as a key for the vehicle Hv.

[0015] As shown in Figures 1 and 2, the in-vehicle key system 1 comprises a digital key ECU (hereinafter referred to as DK-ECU) 2, a plurality of anchors 3, and an object detection sensor 4. ECU stands for Electronic Control Unit. DK stands for Digital Key. The information of the aforementioned portable device 9 may be registered in the DK-ECU2. The in-vehicle key system 1 corresponds to the position estimation system and the reflector detection system. The DK-ECU2 corresponds to the reflector detection device.

[0016] The in-vehicle key system 1 and the portable device 9 are configured to perform short-range communication with each other according to a predetermined communication protocol. Short-range communication is a communication method that conforms to a predetermined short-range wireless communication standard, with an effective communication range of 1m to 30m, and a maximum of approximately 100m. In this embodiment, the short-range communication method is BLUETOOTH® Low Energy (hereinafter referred to as BLUETOOTH LE). Communication conforming to the BLUETOOTH LE standard will also be referred to as LE communication below. In LE communication, multiple channels (0-39Ch) belonging to the 2.4GHz band are used. Hereafter, LE signal refers to a communication packet transmitted and received in LE communication. The terms short-range communication and LE communication may be replaced with SRWC (Short Range Wireless Communication). LE signal may be replaced with SRWC signal.

[0017] The LE signal contains information indicating the source or destination. The source and destination of the LE signal may be represented, for example, by a device ID. The DK-ECU2 and the portable device 9 are pre-paired and each holds its own device ID. The anchor 3 and the portable device 9 perform distance measurement communication using the LE signal. Distance measurement communication is a type of communication that measures the distance between communication devices. Details of distance measurement communication will be described separately later.

[0018] <Mobile devices> As described above, the portable device 9 is a communication device equipped with LE communication functionality. The portable device 9 in this embodiment is a dedicated communication device (hereinafter also referred to as the dedicated device) that serves as the electronic key for the vehicle Hv. The dedicated device is a communication device that is transferred to the owner along with the vehicle Hv at the time of purchase. The dedicated device can be understood as one of the accessories of the vehicle Hv. The dedicated device as portable device 9 may be called a smart key, vehicle portable device, key fob, key card, access key, etc.

[0019] The mobile device 9 may be a portable, general-purpose information processing terminal equipped with LE communication capabilities. A general-purpose information processing terminal can be understood as a wireless communication device on which various application software can be installed. The mobile device 9 may be a smartphone with a digital key app installed, a wearable device, or the like. The digital key app is application software that enables the general-purpose communication device to function as a key for a vehicle hybrid. The term "mobile device 9" may be replaced with "key device" or "user device," etc.

[0020] As shown in Figure 2, the portable device 9 includes a device controller 91 and an LE module 92. The device controller 91 and the LE module 92 may be mounted on a circuit board (not shown). The device controller 91 is configured as a computer, including a processor 911, memory 912, storage 913, and input / output circuits, etc.

[0021] The device controller 91 is configured to control the operation of the LE module 92. The storage 913 stores the device ID of the portable device 9, the key code used for authentication with the DK-ECU2, and other information. The key code is a confidential code used to prove the authenticity of the portable device 9.

[0022] The LE module 92 is a communication module for LE communication provided in the mobile device 9. The LE module 92 may include an LE antenna 921, an RF (Radio Frequency) core 922, and a microcontroller unit (MCU) 93.

[0023] The LE antenna 921 is an antenna element for transmitting and receiving radio waves in the frequency band used for LE communication (e.g., the 2.4 GHz band). The portable device 9 is equipped with one LE antenna 921. In other embodiments, the portable device 9 may be equipped with multiple LE antennas 921.

[0024] One or more LE antennas 921 may be patterned on a circuit board of the portable device 9. Various methods can be used to pattern the LE antennas 921 on the surface of the circuit board, such as electroplating, metal deposition, or application of conductive paint. The LE antennas 921 may be monopole antennas, inverted L antennas, inverted F antennas, etc. For example, the LE antennas 921 may be patch antennas. The LE antennas 921 may also be three-dimensional antennas formed three-dimensionally on the circuit board. The portable device 9 may have multiple three-dimensional antennas.

[0025] The RF core 922 is a circuit module that performs processing related to the transmission and reception of wireless signals. The RF core 922 demodulates the signal received by the LE antenna 921 and provides it to the device controller 91. The RF core 922 also modulates the transmission data input from the device controller 91 and radiates it as radio waves from the LE antenna 921. The RF core 922 may include a local oscillator, a VCO (Voltage-controlled oscillator), a mixer, a phase shifter, an amplifier, a filter, and the like.

[0026] The RF core 922 is configured to transmit and receive continuous wave signals for each channel using the LE antenna 921, in addition to modulated signals for data communication, as a function for CS (Channel Sounding) ranging described later. The continuous wave signal will also be referred to as the (CW: Continuous Wave) signal below. The waveform of the CW signal may be a sine wave or a triangular wave. The CW signal used for CS ranging may also be called a CS tone or tone signal.

[0027] The RF core 922 has the function of detecting received signal strength and received phase. When the RF core 922 receives a CW signal, it detects the received phase, which is the phase angle of the received CW signal with respect to the output signal of the local oscillator. For example, the RF core 922 generates IQ data by analyzing the IQ signal. The IQ data may be a dataset containing pairs of I and Q values. The I value is a parameter that indicates the in-phase component of the received signal. The I value indicates the magnitude of the in-phase component of the received signal. The I value can be understood as the real component of the received signal. The I value can be determined by analyzing the signal obtained by multiplying the received signal by the carrier signal. The Q value is a parameter that indicates the quadrature-phase component of the received signal. The Q value indicates the magnitude of the quadrature-phase component of the received signal. The Q value can be understood as the imaginary component of the received signal. The Q value can be determined by analyzing the signal obtained by multiplying the received signal by a carrier signal shifted by 90° in phase. The IQ data may also be called an IQ sample.

[0028] In other embodiments, IQ data may consist of a pair of received phase and amplitude values. The received phase is determined by the I and Q values ​​of the received signal. The received phase may be the output value of an arctangent with the ratio of the Q value to the I value as the input value. The amplitude is a parameter corresponding to the received strength or RSSI (Received Signal Strength Indicator / Indication). The RF core 922 determines the IQ level as received strength based on the IQ signal. The IQ level may be the square root of the sum of the squared I value and the squared Q value. The received phase and amplitude values ​​indirectly indicate the I and Q values. The IQ data may be a dataset that directly or indirectly indicates the I and Q values.

[0029] The RF core 922 may generate a dataset that includes, in addition to or alternatively to, a pair of I-values ​​and Q-values, a pair of received phase and IQ level. The IQ data may be understood as a dataset that shows the characteristics of the IQ signal (magnitude of each component). The RF core 922 may generate a dataset that includes I-values, Q-values, phase angle, and IQ level. The IQ data is used to calculate distance as described in the CS ranging section.

[0030] The RF core 922 outputs the IQ data of the received CW signal to the MCU 923, associating it with information indicating the operating frequency (e.g., channel number). Based on instructions from the MCU 923, for example, the RF core 922 switches from data communication mode to CS ranging mode and transmits or receives CW signals while switching the operating frequency at predetermined intervals. The data communication mode is a mode in which normal data communication can be performed, and the CS ranging mode may be a mode in which CW signals are transmitted or received. In addition to CW signals, the RF core 922 may also detect the received strength of normal LE signals (e.g., advertiser / data packets) and output it to the MCU 923.

[0031] The MCU923 handles data exchange between the RF core 922 and the device controller 91. The MCU923 processes the data input from the RF core 922 and outputs it to the device controller 91. The MCU923 transmits wirelessly by inputting a baseband signal corresponding to the transmission data input from the device controller 91 to the RF core 922.

[0032] The MCU923 switches the operating mode of the RF core 922 under the control of the device controller 91. For example, the MCU923 can switch the RF core 922 from data communication mode to CS ranging mode, or vice versa. The MCU923 may also have a function to calculate the ranging value based on the channel-specific IQ data observed by CS ranging. The MCU923 can transmit data indicating the measured received signal strength, along with source information, to the device controller 91.

[0033] The LE module 92 transmits and receives LE signals under the control of the device controller 91. For example, if the mobile device 9 is not connected to the DK-ECU2, the device controller 91 uses the LE module 92 to perform advertising in LE. Advertising is the process of transmitting an advertising signal using a predetermined channel. The advertising signal is a wireless signal used to notify other devices of its own presence. When the DK-ECU2 receives an advertising signal from the mobile device 9, it may send a connection request in response. When the device controller 91 receives a connection request from the DK-ECU2, it establishes a communication connection between the LE module 92 and the DK-ECU2. Based on the communication connection with the in-vehicle key system 1, the device controller 91 may perform authentication processing using LE communication, distance measurement communication, etc. Wireless authentication processing may be performed, for example, by a challenge-response method.

[0034] <dk-ecu> The DK-ECU2 is connected to an in-vehicle network established as a communication network within the vehicle Hv. The DK-ECU2 is connected to each of the multiple anchors 3, either via the in-vehicle network or via a dedicated communication cable. The DK-ECU2 is also connected to the object detection sensor 4. The DK-ECU2 is mounted at any location within the vehicle Hv.

[0035] The DK-ECU2 controls multiple anchors 3. In cooperation with the multiple anchors 3, the DK-ECU2 functions as a location identification device that determines the location of the mobile device 9 (hereinafter referred to as the device location). The device location refers to the relative position of the mobile device 9 with respect to the vehicle Hv. Since the mobile device 9 is associated with the user, determining the device location is equivalent to determining the user location. The DK-ECU2 may be configured to unlock the vehicle Hv when it determines that the mobile device 9 is in a pre-set entry area relative to the vehicle Hv and when it accepts a predetermined unlocking operation. The entry area may be an area within a predetermined distance (e.g., 1.5m or 2.0m) from the vehicle Hv.

[0036] Furthermore, the DK-ECU2 may also be able to control object detection sensors mounted on the vehicle Hv. The object detection sensor 4 may be a sonar, camera, millimeter-wave radar, or LiDAR. The object detection sensor 4 is driven based on instructions from the DK-ECU2 and provides the DK-ECU2 with detection results regarding three-dimensional objects such as walls. The object detection sensor 4 is an optional element and may be omitted.

[0037] The DK-ECU2 includes a gateway module 21, an in-vehicle communication circuit 22, and a main controller 23. Hereafter, gateway may be abbreviated as GW. For example, GW module refers to the gateway module.

[0038] The GW module 21 is a communication module installed in the DK-ECU2 that is configured to perform LE communication. The configuration and functions of the GW module 21 may be the same as those of the LE module 92. The GW module 21 is supplied with power from the vehicle battery even when the vehicle power is set to off. Using the power supplied from the vehicle battery, the GW module 21 remains in standby mode continuously or intermittently, even when the vehicle Hv is parked. The GW module 21 periodically scans and attempts to connect with the mobile device 9.

[0039] The GW module 21 may include a GW controller 211, which is a microcomputer that performs processing related to LE communication. The GW controller 211 controls the exchange of data with the main controller 23. Based on the connection with the mobile device 9, the GW controller 211 performs procedures such as initiating encrypted communication and exchanging distance measurement settings with the connected device. The connected device here is the mobile device 9 with which an LE communication connection has been established. The GW module 21 does not necessarily have to be built into the DK-ECU2. The GW module 21 may be located outside the DK-ECU2. In that case, the GW module 21 and the DK-ECU2 may be connected to communicate with each other via a dedicated communication line or an in-vehicle network.

[0040] The in-vehicle communication circuit 22 is a circuit that performs signal processing related to data communication between the main controller 23 and the anchor 3. The in-vehicle communication circuit 22 includes a PHY chip and cable connectors that conform to the communication method of the anchor 3. The in-vehicle communication circuit 22 converts the signal input from the anchor 3 into a format that the main controller 23 can receive and outputs it to the main controller 23. The in-vehicle communication circuit 22 performs predetermined signal processing on the data input from the main controller 23 and outputs it to the anchor 3. The in-vehicle communication circuit 22 corresponds to the communication circuit.

[0041] The main controller 23 is hardware that controls the operation of the DK-ECU2. The main controller 23 includes a processor 231, memory 232, and input / output circuits 233, etc. Memory 232 may be RAM (Random Access Memory). Memory 232 may contain multiple types of storage media. Memory 232 may contain non-volatile storage media such as flash memory. Memory 232 stores a location identification program, which is a program that causes the processor 231 to execute processing related to device location identification.

[0042] The main controller 23 functions as a computer that performs various processes related to device location determination by having the processor 231 execute a location determination program. The execution of the location determination program by the processor 231 is equivalent to the execution of a location determination method.

[0043] The functions of the DK-ECU2 described below are provided by the main controller 23 in this embodiment. In other embodiments, some of the functions of the DK-ECU2 may be provided by the GW controller 211. The main controller 23 may be integrated with the GW controller 211. The GW controller 211 may be configured to perform processing related to the control of the anchor 3 and the determination of the device position. The arrangement of functions within the in-vehicle key system 1 may be changed as appropriate. The DK-ECU2, main controller 23, or GW controller 211 correspond to the control unit. The in-vehicle key system 1 corresponds to the position identification system.

[0044] <Anchor> Anchor 3 is a wireless communication module used to locate a device. Anchor 3 is configured to perform LE communication. Anchor 3 includes an antenna 31, an RF core 32, and an MCU 33. Antenna 31, RF core 32, and MCU 33 may be the same as LE antenna 921, RF core 922, and MCU 923, respectively. In other words, anchor 3 has roughly the same functions and configuration as LE module 92. Of course, anchor 3 and LE module 92 may differ in performance and components (e.g., chip model numbers). Multiple anchors 3 may have roughly the same functions and configurations. There may be individual differences between anchors 3. For example, the directivity, antenna type, and number of antennas of antenna 31 may differ for each anchor 3.

[0045] Anchor 3 performs CS ranging communication, a type of ranging communication, with the mobile device 9 based on instructions from DK-ECU2. Anchor 3 also performs CS ranging communication with other Anchor 3s based on instructions from DK-ECU2. CS ranging communication includes sending and receiving CW signals on each of multiple channels.

[0046] CS ranging is a method of measuring distance based on the difference in received phases between channels, obtained by transmitting and receiving CW signals on multiple channels. CS ranging is sometimes called High Accuracy Distance Measurement (HADM), Phase-based Ranging (PBR), or Multi-channel Phase Difference Ranging. CS ranging involves acquiring the received phase for each channel by performing bidirectional or unidirectional communication of CW signals on multiple channels.

[0047] When Anchor 3 performs CS ranging communication with the mobile device 9, it acquires the received phase for each channel and calculates the device distance, which is the distance to the mobile device 9, based on the received phases of multiple channels. Also, when Anchor 3 performs CS ranging communication with another Anchor 3, it acquires the received phase for each channel and calculates the inter-anchor distance, which is the distance to the other Anchor 3, based on the received phases.

[0048] CS distance measurement between the portable device 9 and the anchor 3, and CS distance measurement between the anchor 3s themselves, may be performed using a one-way method. The one-way method assumes that the initial phase of the CW signal for each channel transmitted from the reflector is constant, and the initiator uses the received phase of the CW signal transmitted from the reflector directly as the material for calculating the inter-frequency phase difference. In CS distance measurement, the initiator may be understood as a device that collects the received phase for each channel and calculates the distance measurement value. In CS distance measurement, the reflector may be understood as a device that transmits the CW signal toward the initiator. In this embodiment, the reflector in CS distance measurement between the portable device 9 and the anchor 3 may be the portable device 9. The reflector in CS distance measurement between the anchor 3s may be designed as appropriate. In the one-way method, the reflector may be referred to as a tag, transmitter, tone transmitter, etc. The initiator may be referred to as a ranging device, etc.

[0049] In a one-way system, the reflector transmits multiple channels of CW signals sequentially according to a procedure agreed upon with the initiator. Details of CS ranging will be described separately. The received phase (in other words, single-frequency phase difference) used for distance calculation can also be obtained using other methods such as passive two-way systems and active two-way systems.

[0050] Anchor 3, based on instructions from DK-ECU2, performs CS ranging communication with the mobile device 9 / other Anchor 3 and generates data indicating the received phase for each channel (e.g., IQ data). Then, Anchor 3 calculates the distance to the communication partner based on the IQ data for each channel and transmits it to DK-ECU2.

[0051] <Anchor position> As shown in Figure 3, the vehicle Hv is equipped with multiple anchors 3A, 3B, 3C, 3D, 3P, and 3Q. The number of anchors 3 installed on the vehicle Hv and the arrangement of each anchor 3 may be changed as appropriate for each vehicle model. The configuration, function, and performance of the multiple anchors 3A-3D, 3P, and 3Q may be substantially identical. Of the multiple anchors 3, anchors 3A-3D are outdoor unit or external anchors and are attached to the exterior of the vehicle Hv. In contrast, anchors 3P and 3Q are indoor unit or interior anchors and are attached to the interior of the vehicle Hv.

[0052] Anchor 3A is located at the left front corner of the vehicle Hv. Specifically, anchor 3A is located near the left front wheel, at the left edge of the front bumper, and near the left side mirror, etc. Such anchor 3A may be referred to as the left front anchor, etc. Anchor 3B is located at the right front corner of the vehicle Hv. Specifically, anchor 3B is located near the right front wheel, at the right edge of the front bumper, and near the right side mirror, etc. Anchor 3B may be referred to as the right front anchor, etc.

[0053] Anchor 3C is located at the right rear corner of the vehicle Hv. Specifically, Anchor 3C is located near the right rear wheel and at the right edge of the rear bumper. Anchor 3C may be referred to as the right rear anchor, etc. Anchor 3D is located at the left rear corner of the vehicle Hv. Specifically, Anchor 3D is located near the left rear wheel and at the left edge of the rear bumper, etc. Anchor 3D may be referred to as the left rear anchor, etc. Multiple anchors 3A, 3B, 3C, and 3D are located at a distance of 1 meter or more from each other.

[0054] Anchor 3P and Anchor 3Q are positioned offset from each other in the front-to-rear direction within the vehicle interior. Anchor 3P is mounted further forward than Anchor 3Q. Specifically, Anchor 3P is located on the instrument panel, the upper edge of the windshield, and the center console, etc. Anchor 3P may be referred to as the front interior anchor. On the other hand, Anchor 3Q is mounted further back than Anchor 3P. Specifically, Anchor 3Q is located in the center of the rear seats, the ceiling above the rear seats, and the trunk, etc. Anchor 3Q may be referred to as the rear interior anchor, etc.

[0055] Hereafter, a combination of two anchors 3 may also be referred to as an anchor pair. The combination of anchors 3B and 3C may be referred to as the first pair, the combination of anchors 3A and 3D as the second pair, the combination of anchors 3C and 3D as the third pair, and the combination of anchors 3A and 3B as the fourth pair. The first pair is the anchor pair associated with the right area of ​​the vehicle Hv. The second pair is the anchor pair associated with the left area of ​​the vehicle Hv. The third pair is the anchor pair associated with the rear area of ​​the vehicle Hv. The fourth pair is the anchor pair associated with the front area of ​​the vehicle Hv. Below, front, back, left, and right refer to the front, back, left, and right of the vehicle Hv unless otherwise noted (i.e., basically).

[0056] The right area may be the area outside the vehicle, to the right of the vehicle Hv, within a predetermined distance (e.g., 2m or 3m) from the vehicle Hv. The left area may be the area to the left of the vehicle Hv, within a predetermined distance from the vehicle Hv. The rear area may be the area within 2m from the rear end of the vehicle Hv. The front area may be the area within 2m from the front end of the vehicle Hv. The specific boundaries of each area may be changed as appropriate. Each area is outside the vehicle Hv and is defined with respect to the vehicle Hv. The right area, etc., corresponds to the target area.

[0057] The first pair, as described later, is used to determine whether or not there is a highly reflective object on the right side of the vehicle Hv, that is, to determine the environment of the right area. The second, third, and fourth pairs are also used to determine the environment of the left area, rear area, and front area. Highly reflective objects will be described separately.

[0058] <CS distance measurement between mobile devices and anchors> This section describes CS distance measurement performed between the in-vehicle key system 1 and the portable device 9. The following describes the case where CS distance measurement is performed using a one-way method. In this embodiment, the portable device 9 is responsible for transmitting the CW signal (i.e., the reflector), and the anchor 3 is responsible for performing distance calculations based on the received CW signal (the initiator).

[0059] The series of processes for CS ranging (hereinafter referred to as CS ranging process) includes a phase acquisition phase and a calculation phase. The phase acquisition phase is the phase in which received phase information from multiple channels is collected by actually transmitting and receiving CW signals from multiple channels. The received phases of multiple channels may be identified based on IQ data from multiple channels. The calculation phase is the phase in which the distance is calculated based on the collected received phases for each frequency.

[0060] The CS ranging process may include a preparation phase prior to the execution of CS ranging communication. The preparation phase involves communication with the mobile device 9 to exchange and agree on ranging settings. The GW module 21 may transmit the ranging settings based on the communication connection with the mobile device 9. The ranging settings are LE signals indicating the parameters for conducting the communication for CS ranging. The parameters for conducting the ranging communication may include at least one of the following: initial phase setting value, hopping interval, initial channel, and ranging start time.

[0061] The initial phase setting specifies the initial phase of the CW signal. The initial phase can basically be set to 0, but other values ​​may be specified. The hopping interval represents the time it takes to switch channels, in other words, the time it takes to maintain one channel. The initial channel specifies the channel of the CW signal to be transmitted first in a series of distance measurement communications. Channel (frequency) information may be expressed, for example, by a channel number. The distance measurement start time is a parameter that specifies the timing at which transmission and reception of the CW signal actually begins. The distance measurement start time may be a waiting time, for example, 200 milliseconds or 400 milliseconds, from the completion of the preparation phase until transmission and reception of the CW signal on the initial channel begins. The portable device 9 may send an Ack to the GW module 21 based on receiving the distance measurement settings. The preparation for CS distance measurement communication may be completed by the Ack sent by the portable device 9. The GW module 21 distributes the distance measurement settings to each anchor 3 based on receiving the Ack from the portable device 9.

[0062] Multiple anchors 3 transition to a state where they wait for a signal on the initial channel according to the distance measurement start time specified in the distance measurement settings. The portable device 9 also starts transmitting a CW signal on the initial channel after a predetermined time has elapsed since sending back an Ack. After the distance measurement start time, CW signals are transmitted and received between the anchors 3 and the portable device 9, with the channel being switched at regular intervals. In another embodiment, the anchors 3 and the portable device 9 may start CS distance measurement communication triggered by receiving a predetermined distance measurement start signal from the DK-ECU2.

[0063] Transmission of a CW signal on a single channel may be stopped, for example, after a certain period of time has elapsed since the start of transmission. When Anchor 3 receives a CW signal from the mobile device 9, it generates IQ data based on the received signal. This IQ data is then stored in memory along with frequency information (e.g., channel number). The CW signal transmitted by the mobile device 9 may be received in parallel by multiple Anchor 3s. Each of the multiple Anchor 3s may receive the CW signal transmitted from the mobile device 9 according to the distance measurement settings and generate IQ data for each channel.

[0064] Anchor 3 and portable device 9 may repeatedly transmit and receive CW signals on all channels available for LE communication. GW module 21 and portable device 9 may terminate the repetition process when they have collected IQ data for a predetermined number of channels. The required number here may be the same as the number of data channels, or it may be less. The required number may be 5, 16, 32, etc.

[0065] Anchor 3 calculates the phase shift coefficient (α) once it has finished collecting the received phase for each channel. The phase shift coefficient is a parameter that indicates the degree to which the received phase changes in response to changes in frequency. The phase shift coefficient can also be called the degree of phase change or the amount of phase shift.

[0066] In one embodiment, the phase shift coefficient may be calculated based on the received phase observed at two arbitrary frequencies, a first frequency and a second frequency. If we assume that the difference frequency, which is the difference between the first and second frequencies, is Δf, the inter-frequency phase difference, which is the difference between the received phases observed at the first and second frequencies, is Δφ, and the phase shift coefficient is α, then the relationship α = Δφ / Δf holds. The inter-frequency phase difference (Δφ) is the difference between the received phases observed at two different frequencies. The inter-frequency phase difference corresponds to the amount of phase angle displacement due to the change in operating frequency.

[0067] In this embodiment, anchor 3 calculates a regression line showing the relationship between frequency and received phase based on the received phase for each frequency, and adopts the slope of the regression line as the phase change coefficient (α). This is because the slope of the regression line indicates the amount of change in the received phase in response to a change in frequency. The regression line and its slope can be calculated using various methods, such as the least squares method. If the regression line is represented as y = a·x + b, the coefficient a of x corresponds to the slope of the regression line. In other words, anchor 3 can calculate the phase change coefficient (α) using the coefficient a of x. Here, x is a variable parameter representing frequency, and y is a variable parameter representing received phase. By using a regression line to determine the phase change coefficient, it becomes possible to calculate a phase change coefficient with higher accuracy. The regression line can also be called an approximation line.

[0068] In other embodiments, anchor 3 may calculate the inter-frequency phase difference (Δφ), the difference frequency (Δf), and the pseudo-phase coefficient (Δφ / Δf) for each combination of frequencies in which the received phase can be observed. Anchor 3 may also use the average or median value of the pseudo-phase coefficients for each combination of frequencies as the phase change coefficient (α) for distance calculation.

[0069] Anchor 3 calculates the phase shift coefficient (α), and then uses the phase shift coefficient (α) to calculate the device distance (D). If the device distance is D, then the relationship between the difference frequency Δf and the inter-frequency phase difference (Δφ) is D∝C·Δφ / (2π·Δf)=C·α / 2π. In the above equation, the parameter "C" represents the propagation speed of radio waves (3×10^8 m / sec). Anchor 3 calculates the device distance based on this relationship.

[0070] For example, Anchor 3 calculates the device distance using Equation 1: D = k·C·α / 2π. The parameter k in Equation 1 is a design value and is set to 1.0 or 0.5. The value of k may be determined by whether the transmission-reception phase difference is calculated as a phase change coefficient for one path or as a phase change coefficient for both paths.

[0071] Anchor 3 transmits the calculated device distance to DK-ECU2. In this disclosure, the device distance calculated as a result of the distance measurement communication may also be referred to as the distance measurement value. If a signal from the mobile device 9 cannot be received during the distance measurement communication, Anchor 3 may output an error value as the distance measurement value, which is a specific value indicating that measurement was not possible. The error value may be, for example, NaN (Not a Number). The error value may also be a sufficiently large predetermined value. The error value may also be an error code.

[0072] In other embodiments, the DK-ECU2 may perform the process of converting the phase shift coefficient or channel-specific IQ data into device distance. The anchor 3 may transmit the phase shift coefficient data or channel-specific IQ data to the DK-ECU2 as a result of CS ranging communication with the mobile device 9. The functional arrangement may be changed as appropriate.

[0073] In addition to the distance measurement value, Anchor 3 may transmit data on the received strength of the signal received from the mobile device 9 (hereinafter also referred to as the device signal) to the DK-ECU2. Hereafter, the received strength of the device signal observed by Anchor 3 will also be referred to as the device signal strength. The device signal strength may be the magnitude (i.e., amplitude, IQ level) of the IQ signal. The device signal strength reported to the DK-ECU2 may be the maximum value of the IQ level for each channel. The device signal strength may also be the median or average value of the IQ level for each channel.

[0074] In CS ranging using a one-way system, anchor 3 can calculate the distance value if it can observe the CW signal emitted by the portable device 9. Therefore, in one embodiment, after the GW module 21 exchanges the ranging settings with the portable device 9, multiple anchors 3 may collect phase information and perform distance calculations by receiving (sniffering) the CW signal emitted from the portable device 9 in parallel. In other words, by applying sniffer technology, multiple anchors 3 may simultaneously perform CS ranging communication with a single portable device 9.

[0075] In other embodiments, each anchor 3 may individually perform CS ranging communication with the mobile device 9. Furthermore, the channel-specific received phase used to calculate the phase shift coefficient (α) can also be obtained using methods such as a so-called passive two-way method or an active two-way method. When an active two-way method or a passive two-way method is adopted as the CS ranging method with the mobile device 9, multiple anchors 3 may individually perform CS ranging communication with the mobile device 9. Passive two-way and active two-way methods will be discussed separately as supplementary information. Not only the anchors 3, but also the GW module 21 may be configured to perform CS ranging.

[0076] <CS distance measurement between anchors> CS distance measurement between anchors 3 may also be performed using the same procedure as CS distance measurement between anchor 3 and the portable device 9. For convenience, distance measurement communication between anchors 3 will be referred to as inter-anchor distance measurement communication or inter-anchor communication. Inter-anchor communication may be a communication in which one of the two anchors 3 transmits multiple channels of CW signals sequentially, and the other generates IQ data for each channel. Inter-anchor distance measurement communication may be performed for each anchor pair. The division of roles (initiator / reflector) in the anchor pair performing distance measurement communication may be determined by the DK-ECU2. The settings for distance measurement communication may be determined by the DK-ECU2 and distributed to the anchors 3. Pre-designed distance measurement settings may be applied for inter-anchor distance measurement communication. Inter-anchor distance measurement communication may be performed using one-way, active two-way, or passive two-way methods.

[0077] As an initiator, Anchor 3 transmits the IQ level for each channel to DK-ECU2 as a result of the inter-anchor distance measurement communication being performed. For example, Anchor 3 may transmit the IQ data for each channel to DK-ECU2. Anchor 3 may also calculate a representative IQ level, which is the median of the IQ levels for each channel, and transmit it to DK-ECU2. The representative IQ level may be the average or maximum value of the IQ levels for each channel. In addition to data related to the IQ levels, Anchor 3 may also transmit distance measurement values ​​to DK-ECU2.

[0078] <Effect of reflectors> The developers of this disclosure investigated the effect of a reflector RO on the accuracy of device distance estimation when the reflector RO is located to the right of the vehicle Hv, as shown in Figure 4. Three types of reflectors RO were used in the verification test: (1) a metal plate, (2) a reinforced concrete wall, and (3) a metal pole. The metal plate was approximately the same width as the total length of the vehicle Hv and 2 m high. The reinforced concrete wall was a 0.1 m thick wall with 10 mm diameter reinforcing bars inside. Inside the reinforced concrete wall, the reinforcing bars were arranged in a grid pattern with 250 mm spacing. The metal pole was a 150 mm diameter pole. The metal pole as a reflector RO was positioned at the location indicated by Rop in Figure 4, i.e., to the side of the B-pillar. The distance Dt from the vehicle to the reflector RO in the verification test was 1.0 m, 1.5 m, and 2.0 m. The anchors used for distance measurement are anchors 3B and 3C, which correspond to the right area, and the distance between the anchors is 3.5m.

[0079] In addition to the static conditions described above, the way the mobile device 9 is held can also affect the accuracy of the device distance estimation. Therefore, the verification test was conducted in two patterns: one where the mobile device 9 is in a back pocket, and another where the mobile device 9 is not in a back pocket. Figure 4 shows the back pocket state.

[0080] The "back pocket state" refers to a state in which the tester / user has the portable device 9 in their back pocket and is facing the vehicle Hv. In a broader sense, the back pocket state can be understood as a state in which the user's body is positioned between the vehicle Hv and the portable device 9. The back pocket state may also include a state in which the portable device 9 is in the chest pocket of a user who is facing away from the vehicle Hv. The back pocket state is a state in which the portable device 9 is located behind the user's body as viewed from the vehicle. The expression "back pocket state" can be replaced with "backside state" or "LOS (Non-Line of Sight) state," etc.

[0081] In contrast, the non-back pocket state primarily refers to a state in which the tester / user, holding the portable device 9 in their hand, is facing the vehicle Hv. The non-back pocket state can be understood as a state in which the user's body is not interposed between the vehicle Hv and the portable device 9, and the portable device 9 is within the LOS of the anchor 3. The non-back pocket state may also include a state in which the portable device 9 is stored in the chest pocket of a user who is facing their abdomen towards the vehicle Hv. The non-back pocket state is a state in which the portable device 9 is on the front side of the user's body as seen from the vehicle. The non-back pocket state can also be rephrased as front-side possession state or LOS state.

[0082] The distance estimation accuracy (error) under various test conditions was evaluated multiple times while changing the position of the portable device 9. The general evaluation results of the test are as follows: When the reflector RO is a concrete wall or a metal pole, the desired estimation accuracy can be obtained by the first estimation method described later, regardless of how the portable device is held or where it is located. On the other hand, when the reflector RO is a metal wall, the estimation accuracy may be partially degraded. In particular, when the reflector RO is a metal wall and the portable device 9 is in a back pocket, the estimation error increases compared to other cases.

[0083] This is presumably because (1) when the mobile device 9 is in the back pocket state, the intensity of the direct wave decreases, and (2) when the reflector is a metal plate, the loss due to reflection is small and the reflected wave is strong. Here, the direct wave means a signal that reaches without being reflected by an object such as a wall, the ground, the ceiling, or another vehicle. The direct wave can include a diffracted wave that is a signal that reaches by diffraction (wrapping around). When there is a metal wall around the vehicle Hv and the mobile device 9 is in the back pocket state, it becomes easy to output the distance of the reflection path as the ranging value, and as a result, it becomes easy to erroneously detect the device position. On the other hand, it was found that even when there is a concrete wall around the vehicle Hv, the intensity of the reflected wave due to the concrete wall is not strong enough to cause an erroneous detection of the device distance, and the influence on the ranging result is small.

[0084] The present disclosure was created based on the above findings, and includes switching the method for estimating the device position (in other words, the estimation algorithm) according to whether there is a strong reflector around the vehicle Hv as one feature. From another perspective, the DK-ECU 2 in one embodiment is characterized by not changing the method for estimating the device position even when there is a concrete wall.

[0085] Here, the strong reflector means a plate-like member having a certain area with a high radio wave reflectivity. Conceptually, the strong reflector is a reflector that causes an error of 0.5 m or more in the estimated result of the device distance. Specifically, the strong reflector may be a metal plate, a metal wall, or a side surface of another vehicle having a size of 1 square meter or more. The metal wall may include a metal partition or partition. The metal partition may be a steel plate that can be used as a fence surrounding a construction site. The metal wall also includes metal siding.

[0086] <Determination of the presence or absence of a strong reflector and estimation of the reflector distance based on IQ data> The IQ level obtained by anchor-to-anchor distance measurement communication can change depending on the presence or absence of a strong reflector. In the above test, it was confirmed that the representative IQ level observed when a strong reflector was near vehicle Hv was higher than when a concrete wall or metal pole was present at the same location. Therefore, by comparing the IQ level obtained by anchor-to-anchor distance measurement communication with a predetermined threshold, it is possible to determine with a certain degree of accuracy whether or not a strong reflector is present.

[0087] On the other hand, the IQ data from anchor-to-anchor distance measurement communication exhibits the characteristics of a composite wave, which is a mixture of the reflected wave and the direct wave. As shown in Figure 5, the composite wave is the sum of the complex vectors of the direct wave and the reflected wave. There is a risk of misjudging the presence or absence of a strong reflector due to the influence of the direct wave. In fact, up to a distance of 1.5m between the metal wall and the vehicle, the presence or absence of a strong reflector can be identified with a certain degree of accuracy by comparing the representative IQ level with a threshold. However, when the distance between the metal wall and the vehicle exceeds 2.0m, the influence of the direct wave becomes greater, and the accuracy of the judgment may deteriorate.

[0088] For these reasons, the main controller 23 of this disclosure determines the presence or absence of a strong reflector using differential IQ data, which is IQ data obtained by subtracting the IQ value derived from the direct wave from the IQ data obtained by inter-anchor ranging communication, as described below. With this configuration, the determination accuracy can be improved compared to a configuration that determines the presence or absence of a strong reflector using the IQ data observed in actual communication as is.

[0089] In addition to the above, the developers of this disclosure also investigated a method for calculating the distance to a strong reflector using the Pythagorean theorem based on the distance measurement value determined from the inter-anchor distance measurement communication. This method, as will be explained separately with reference to Figure 10, is based on the premise that the distance measurement value (Lo) obtained by the inter-anchor distance measurement communication represents the length of the reflection path.

[0090] However, as mentioned above, the IQ data from anchor-to-anchor distance measurement communication is affected by the direct wave. When a strong reflector is close to the vehicle's Hv, the reflected wave component is relatively large in the composite wave. Therefore, the distance measurement value based on the IQ data from anchor-to-anchor distance measurement communication can indicate the reflected path length with relatively high accuracy. On the other hand, when a strong reflector is located far from the vehicle, the difference in intensity between the reflected wave and the direct wave from the strong reflector becomes small, and the difference between the distance measurement value and the actual reflected path length becomes large. As a result, the accuracy of determining the distance to the strong reflector may deteriorate. For example, when the distance between the vehicle and the strong reflector is 2m or more, the accuracy of estimating the distance to the strong reflector using the distance measurement value obtained by anchor-to-anchor distance measurement communication may deteriorate.

[0091] For these reasons, the main controller 23 of this embodiment determines the distance to the strong reflector using differential IQ data obtained by removing the direct wave component from the IQ data obtained by inter-anchor distance measurement communication, as described below. With this configuration, the accuracy of estimating the reflector distance can be improved compared to a configuration that estimates the reflector distance from distance information determined by using the IQ data observed in actual communication as is.

[0092] <Direct wave IQ data and anchor setting data> The memory 232 of the main controller 23 stores direct wave IQ data for each channel. Direct wave IQ data is IQ data for direct waves. Direct wave IQ data is IQ data observed when anchor-to-anchor distance measurement communication is performed under predetermined test environments where no reflectors are present around the vehicle Hv. As mentioned above, the IQ data here may be a set of I value and Q value. The test environment for measuring direct wave IQ data may be, for example, an environment where no reflectors are present within at least 4m of the vehicle Hv. Direct wave IQ data may be generated by prior testing and registered in memory 232. Memory 232 may store direct wave IQ data for each anchor pair. Direct wave IQ data may be measured and registered at manufacturing plants, dealer shops, repair shops, etc. Direct wave IQ data may also be referred to as registered IQ data.

[0093] Furthermore, memory 232 stores anchor setting data. The anchor setting data indicates the position information of the anchor 3 mounted on the vehicle Hv. The mounting position of the anchor 3 may be represented in a two-dimensional coordinate system where the longitudinal direction of the vehicle Hv is the X-axis and the width direction is the Y-axis.

[0094] Furthermore, the anchor setting data may include the actual values ​​of the distance between anchors for each combination of anchors 3. The distance between anchors refers to the distance from one anchor 3 to another anchor 3. The actual value of the distance between anchors may be the design value of the distance between anchors based on the mounting position of each anchor 3. The actual value may be the straight-line distance between anchors. The actual value may also be called the true value. The anchor setting data may include the actual values ​​of the distance between anchors for the first to fourth pairs.

[0095] The coordinates of the mounting position for each anchor 3 are data that indirectly indicates the distance between anchors, and are data that can determine the distance between anchors. The memory 232 does not necessarily have to store data that shows the actual value of the distance between anchors. The DK-ECU2 may be configured to calculate the actual value of the distance between anchors from the position coordinates of each anchor 3 included in the anchor setting data and use it for position determination processing, etc., as described later.

[0096] <Threshold for determining the presence or absence of a highly reflective surface> Memory 232 stores the detection threshold used in the following processes. The detection threshold is a parameter used to determine whether or not there is a strong reflector based on the IQ level obtained by inter-anchor distance measurement communication. The detection threshold may be a parameter of the same dimension as the IQ level. For example, the IQ level may be expressed as dBμV / m.

[0097] The detection threshold may be the value obtained by subtracting an offset value from a reference level determined by testing. The reference level is the representative IQ level of anchor-to-anchor ranging communication that can be observed in an environment where a strong reflector exists within a predetermined assumed distance. Tests have determined that the representative IQ level observed in anchor-to-anchor ranging communication will be within a few dB from a certain value (γ) even when the distance between the vehicle and the strong reflector is varied in the range of 1.0 m to 2.0 m.

[0098] The tests to determine the baseline level were conducted not only for the right-side pattern but also for the rear-side pattern. The results obtained in the rear-side pattern test were the same as those obtained in the right-side pattern test. The right-side pattern test refers to measuring the IQ level using the first pair with a metal wall positioned in the right area facing the vehicle. The rear-side pattern test refers to measuring the IQ level using the third pair with a metal wall positioned in the rear area facing the vehicle. In addition, the tests to determine the baseline level were also conducted with patterns with and without a metal ceiling, and it was confirmed that the presence or absence of a ceiling did not affect the test results.

[0099] The reference level may be a representative value (e.g., median) of the IQ level observed by the above test. If the representative IQ level observed in the rear pattern and the representative IQ level observed in the right pattern differ by a predetermined value or more due to the shape of the vehicle Hv or the positional relationship of anchor 3, a separate reference level for the rear may be set in addition to the reference levels for the left and right sides.

[0100] The offset value may correspond to a level difference that allows us to assume that reflected waves do not affect the results of distance measurement communication with the mobile device 9. Even if there are reflectors around the vehicle Hv, if they are walls with high loss, such as concrete walls, these reflectors can be ignored. The offset value defines the conditions under which we can assume that there are no reflectors that affect the distance measurement results, such as metal walls.

[0101] Here, when a strong reflector is present around the vehicle Hv, the IQ level of the reflected wave from the strong reflector may exceed the IQ level of the direct wave attenuated by the human body, as shown in Figure 6. The offset value may correspond to the excess of the maximum value of the reflected wave relative to the minimum value of the direct wave. For example, the offset value may be the value obtained by subtracting the minimum direct wave level from the maximum reflected wave level.

[0102] In the figure, "REF_MAX" represents the maximum reflected wave level, and "DIR_MIN" represents the minimum direct wave level. Figure 6 conceptually represents the observation probability of IQ levels, with the vertical axis representing IQ levels and the horizontal axis representing observation probability. The solid line conceptually represents the distribution of IQ levels for direct waves, and the dashed line conceptually represents the distribution of IQ levels for reflected waves.

[0103] Qualitatively, if a reflector surrounding the vehicle Hv has a reflection loss greater than or equal to the offset value, that reflector can be ignored. This is because the reflected wave from that object is sufficiently weak and does not affect the distance measurement result. The IQ level of the reflected wave from an object with a reflection loss greater than or equal to the offset value will be smaller than the value obtained by subtracting the offset value from the reference level. On the other hand, objects with a reflection loss less than the offset value may affect the distance measurement result. The IQ level of the reflected wave from an object with a reflection loss less than the offset value will be larger than the value obtained by subtracting the offset value from the reference level. Therefore, for these reasons, the detection threshold may be set to the value obtained by subtracting the offset value from the reference level.

[0104] The maximum reflected wave level used to determine the offset value is the maximum IQ level of the reflected wave that can be observed when the mobile device 9 is located within the entry area. The reflective material may be a strong reflector. The maximum reflected wave level may be a representative IQ level of the reflected wave observed by the mobile device 9, which is placed near the point Pn closest to the anchor 3 among the strong reflectors, as shown in Figure 7, for example. When measuring the maximum reflected wave level, a radio wave absorber or the like may be placed between the mobile device 9 and the vehicle so that the mobile device 9 does not receive direct waves from the anchor 3.

[0105] The minimum direct wave level is the minimum IQ level of the direct wave that can be observed when the mobile device 9 is within the entry area. For example, as shown in Figure 8, it may be the value obtained by subtracting the attenuation due to the human body from the representative IQ level observed at mobile devices 9 that are a predetermined distance (e.g., 4 m) apart from each other. The minimum direct wave level may be evaluated in a test environment where there are no reflectors around the vehicle Hv. The attenuation due to the human body may be an assumed value such as 10 dB. Thus, the minimum direct wave level may be the representative IQ level when there are no reflectors around the vehicle and the user with the mobile device 9 in their back pocket is located at the furthest point in the entry area.

[0106] Figures 7 and 8 illustrate the case where the minimum direct wave level and maximum reflected wave level are evaluated using anchor 3C. The minimum direct wave level and maximum reflected wave level may be evaluated using other anchors 3, not just anchor 3C. When the minimum direct wave level is L1, the maximum reflected wave level is L2, and the reference level is L3, the detection threshold (Rth) may be determined by L3 - (L2 - L1). The detection threshold determined based on the test results is registered in memory 232 and referenced by the processor 231 in the environment determination process described later.

[0107] Furthermore, a detection threshold determined for a particular vehicle model may be applied to multiple vehicles of the same vehicle model. The detection threshold may be determined by machine learning methods such as deep learning. Also, test data (training data) used to determine the detection threshold for a particular vehicle model may be reused to determine detection thresholds for other vehicle models. The detection threshold for each vehicle or vehicle model may be efficiently determined using transfer learning.

[0108] <Environmental Determination Process> The DK-ECU2 executes the environmental determination process illustrated in Figure 9 at a predetermined timing. The environmental determination process determines whether or not a highly reflective object exists in the target area. If the environmental determination process determines that a highly reflective object exists, it may include estimating the distance from the vehicle to the highly reflective object and setting the recalculation region CA based on the estimation result.

[0109] The recalculation region CA is the region used to determine whether the device position needs to be calculated using a second estimation method different from the basic first estimation method. As will be described separately, if the provisional device position calculated by the first estimation method is located in the recalculation region CA, the device position will be recalculated using the second estimation method. The recalculation region CA is the region beyond the strong reflector and is an area where the device position calculation result is incorrect. The expression "recalculation region CA" may be replaced with expressions such as "obstacle presence region" or "ineffective region".

[0110] The timing for executing the environmental determination process may be designed as appropriate. The DK-ECU2 may be configured to execute the environmental determination process upon receiving notification that the vehicle Hv is parked. This may also occur when a communication connection is established with the mobile device 9. The DK-ECU2 may also execute the environmental determination process upon receiving notification that the vehicle Hv is parked. The DK-ECU2 may be configured to execute the environmental determination process periodically (for example, every 30 minutes) while the vehicle Hv is parked. The parked state may include the state in which the vehicle Hv is locked.

[0111] The parked state may be a state in which the vehicle Hv is stopped and all doors are closed. In other words, the DK-ECU2 may be configured to perform environmental determination processing using the anchor 3 when the vehicle Hv is stopped and all doors are closed. Alternatively, the DK-ECU2 may be configured to perform environmental determination processing when the vehicle Hv is locked and multiple anchor 3 or GW modules (corresponding to other in-vehicle communication devices) receive signals from the portable device 9.

[0112] The following describes how to determine whether or not a strong reflector exists in the right area using anchors 3B and 3C as the first pair. Of the two anchors 3 associated with the target area, one corresponds to the first anchor and the other to the second anchor. In one example, anchor 3B may be the first anchor and anchor 3C may be the second anchor.

[0113] The DK-ECU2 may be configured to determine whether or not a highly reflective object is present on the left side, rear, and front of the vehicle Hv. Environmental determination in each direction may be performed using anchor pairs associated with the area to be determined. For example, the determination of whether or not an obstacle is present in the left area may be performed using anchors 3A and 3D that constitute the second pair.

[0114] The environmental determination process generally includes S101 to S110. The description of DK-ECU2 as the entity executing the following processes may be replaced with the in-vehicle key system 1, main controller 23, processor 231, or GW controller 211, etc. The functional arrangement in the in-vehicle key system 1 may be changed as appropriate, and the descriptions of in-vehicle key system 1, DK-ECU2, main controller 23, processor 231, and GW controller 211 may be interchangeable.

[0115] S101 is a step in which the DK-ECU2 causes the anchors 3 associated with the target area to perform distance measurement communication. The anchors 3 associated with the target area are, in this case, anchors 3B and 3C. In S101, distance measurement communication between anchors is performed in the first pair. For example, the DK-ECU2 notifies anchors 3B and 3C, which constitute the first pair, of the distance measurement settings and then sends a distance measurement start instruction. The distance measurement settings may include information specifying the roles of the distance measurement communication, for example, the anchor 3 that will play the role of initiator. The following describes the case where anchor 3B is the initiator and anchor 3C is the reflector.

[0116] Once the distance measurement communication between anchors 3B and 3C is complete, in S102, the DK-ECU2 acquires channel-specific IQ data from anchor 3B. To distinguish it from the direct-wave IQ data registered in memory 232, the IQ data observed by the actual distance measurement communication in S101 will also be referred to as observed IQ data below. After acquiring the channel-specific observed IQ data in S102, the DK-ECU2 then generates differential IQ data in S103. Differential IQ data is IQ data obtained by subtracting the direct-wave IQ data from the observed IQ data. Differential IQ data is generated for each channel.

[0117] Differential IQ data, like observed IQ data and direct-wave IQ data, is also a pair of I-values ​​and Q-values. The I-value of the differential IQ data for the first channel may be the value obtained by subtracting the I-value of the direct-wave IQ data for the first channel from the I-value of the observed IQ data for the first channel. The Q-value of the differential IQ data for the first channel may be the value obtained by subtracting the Q-value of the direct-wave IQ data for the first channel from the Q-value of the observed IQ data for the first channel. Differential IQ data is generated by subtracting corresponding elements. Differential IQ data may be a vector obtained by subtracting the vector of the direct-wave IQ data for the corresponding channel from the vector of the observed IQ data.

[0118] As explained using Figure 5, the observed IQ data shows the amplitude and phase of the composite wave. The difference IQ data generated in this way corresponds to the data obtained by subtracting the component originating from the direct wave from the composite wave. In other words, the difference IQ data can be understood as IQ data for the reflected wave. The difference IQ data roughly shows the phase and amplitude of the reflected wave. Such difference IQ data can be rephrased as reflected wave IQ data.

[0119] For convenience, the phase determined by the differential IQ data is referred to as the reflected wave phase. The amplitude of the differential IQ data is also referred to as the reflected wave intensity. Since the reflected wave intensity is the IQ level determined by the I and Q values ​​of the differential IQ data, it can also be called the differential IQ level. The differential IQ data for each channel indirectly or directly indicates the reflected wave phase and reflected wave intensity for each channel. Of course, the differential IQ data for each channel can also directly or indirectly indicate the I and Q values ​​for each channel.

[0120] When the DK-ECU2 generates differential IQ data for each channel, in S104 it calculates a representative value (Rp) of the reflected wave intensity based on the differential IQ data. The representative value of the reflected wave intensity may be the median value of the reflected wave intensity for each channel. The representative value of the reflected wave intensity may also be the average or maximum value of the reflected wave intensity for each channel.

[0121] The DK-ECU2 calculates a representative value of the reflected wave intensity and, in step S105, determines whether this representative value is greater than the detection threshold. In the diagram, "Rp" represents the representative value of the reflected wave intensity, and "Rth" represents the detection threshold. Step S105 corresponds to the step of determining whether or not a strong reflector exists in the target area (in this case, the right area) by comparing the representative value of the reflected wave intensity with the detection threshold.

[0122] If Rp > Rth is true (S105 YES), the DK-ECU2 sets the strong reflector flag to ON in S106. The strong reflector flag indicates whether or not a strong reflector exists around the vehicle Hv. For example, if the strong reflector flag is ON, it means that it has been determined that a strong reflector exists. Conversely, if the strong reflector flag is OFF, it means that it has been determined that a strong reflector does not exist. A strong reflector flag may be provided for each of the front, rear, left, and right areas. Here, we are illustrating the case of determining the environment of the right area, so the strong reflector flag handled in S106 and S110 (described later) may be understood as the strong reflector flag for the right area.

[0123] The processing from S101 to S105 corresponds to the process by which the DK-ECU2 determines whether or not a strong reflector exists in the right area based on the distance measurement communication results of the first pair. If the DK-ECU2 determines that a strong reflector exists in the right area, it calculates the reflector distance L in S107. The reflector distance L is the distance from the vehicle Hv to the detected strong reflector. In this example, the reflector distance L can be understood as the distance from the right side of the vehicle Hv to the strong reflector. Since the strong reflector is a metal plate in a lower-level concept, the strong reflector distance can also be rephrased as the metal plate distance. The metal plate may include the body panel of another vehicle parked next to the vehicle Hv.

[0124] The DK-ECU2 in this embodiment calculates the reflector distance L based on the differential IQ data for each channel. Specifically, the DK-ECU2 extracts channel-specific phase information (reflected wave phase as described above) from the channel-specific differential IQ data. Next, the DK-ECU2 calculates a phase change coefficient (α) from the channel-specific phase information, similar to the normal method for calculating distance values ​​in CS distance measurement. Then, using Equation 1 described above, the phase change coefficient (α) is converted into a distance value. For convenience, the differential IQ-based distance value is referred to as the distance value of the reflection path.

[0125] The distance measurement value of the reflection path calculated by the above method is highly likely to correspond to the shortest path among various reflection paths. Therefore, the reflection wave path corresponding to the distance measurement value may have symmetry between the outward and return paths, as shown in Figure 10. That is, the line segment connecting the reflection wave path corresponding to the distance measurement value and anchors 3B and 3C may form an isosceles triangle with the line segment connecting anchors 3B and 3C as the base. Based on this assumption, the DK-ECU2 can determine the distance L to the strong reflector using the Pythagorean theorem with the distance measurement value of the reflection path (Lo) and the actual value of the distance between anchors (Ld). That is, the DK-ECU2 determines the distance L to the strong reflector by solving the relationship L = √{(Lo / 2)^2 - Ld^2}. Hereafter, the distance L from the assumed vehicle Hv to the strong reflector will also be referred to as the reflector distance L. Note that in Figure 10, the strong reflector is indicated by "WL".

[0126] When DK-ECU2 calculates the reflector distance L, in S108 it sets the recalculation region CA using the reflector distance L. For example, DK-ECU2 sets the recalculation region CA to be the area where the distance from the right side of the vehicle Hv is greater than or equal to the reflector distance L. Specifically, as shown in Figure 11, DK-ECU2 sets a virtual line VL, which is a straight line parallel to the longitudinal direction of the vehicle Hv, at a position to the right of a predetermined reference point P on the right side, at a distance of reflector distance L. The virtual line VL corresponds to the contour of the strong reflector. Then, DK-ECU2 sets the recalculation region CA to be the area farther than the virtual line VL. The reference point P may be the midpoint between anchors 3B and 3C. The reference point P may also be the location of the door handle or B-pillar in a top view. In Figure 11, the recalculation region CA is shown with a dot pattern hatching.

[0127] Once the recalculation area CA setting is complete, the DK-ECU2 saves the highly reflective flag and the recalculation area CA data to memory 232 or similar in S109, and terminates the flow. S109 corresponds to the step of updating the environmental data, which is data indicating the judgment result regarding the environment around the vehicle.

[0128] On the other hand, if Rp > Rth is not true (S105 NO), DK-ECU2 sets the strong reflector flag to off in S110. This step corresponds to determining that there are no strong reflectors on the right side of the vehicle. After setting the strong reflector flag to off, DK-ECU2 saves the setting value of the strong reflector flag to memory 232 in S111 and terminates the flow. S111 also corresponds to updating the environmental data.

[0129] The above describes the case where DK-ECU2 determines whether or not a strong reflector exists in the right area based on the results of the distance measurement communication of anchors 3B and 3C. DK-ECU2 may use other anchor pairs to determine whether or not a strong reflector exists in other directions. DK-ECU2 may use a second anchor pair to perform environmental determination processing for the left area. DK-ECU2 may use a third anchor pair to perform environmental determination processing for the rear area. DK-ECU2 may use a fourth anchor pair to perform environmental determination processing for the front area. Memory 232 may store environmental data for the front, rear, left, and right.

[0130] <Location identification processing> The DK-ECU2 executes a positioning process, as illustrated in Figure 12, at a predetermined timing. The positioning process determines the location of the device. Here, as an example, determining the device location involves calculating the position coordinates of the portable device 9 relative to the vehicle Hv. The device location may be represented in a two-dimensional coordinate system with the vehicle's longitudinal direction as the X-axis and the vehicle's width direction as the Y-axis. The origin of the coordinate system may be set at any position; for example, the mounting position of anchor 3B may be set as the origin.

[0131] The timing at which the DK-ECU2 executes the location determination process may be, for example, when the GW module 21 establishes a communication connection with the mobile device 9. That is, the DK-ECU2 may execute the location determination process in response to the GW module 21 establishing a communication connection with the mobile device 9. The DK-ECU2 may periodically (for example, every 400 milliseconds) execute the location determination process while the GW module 21 is communicating with the mobile device 9.

[0132] The DK-ECU2 may perform location determination processing in response to user actions on the vehicle Hv. User actions on the vehicle Hv may be rephrased as user operations or instructions on the vehicle Hv. User actions may include unlocking, locking, opening and closing doors, pressing the start switch, etc. Unlocking is an operation to unlock the vehicle Hv. Locking is an operation to lock the vehicle Hv. User actions may be detected based on input signals from a door handle sensor, courtesy switch, start switch, gesture sensor, microphone, etc. The door handle sensor may be a touch sensor or push switch provided on the outside door handle. The gesture sensor may be an infrared sensor, photoelectric sensor, or sonar for detecting the act of waving a foot under the door.

[0133] The location determination process includes steps S201 to S211. Step S201 is the step in which the DK-ECU2 accesses memory 232 and reads environmental data. If environmental data is not stored, the DK-ECU2 may perform environmental determination processing for all or part of the target area. Step S201 may be the step in which the DK-ECU2 obtains data regarding the presence or absence of highly reflective objects around the vehicle Hv by reading the data or performing environmental determination processing.

[0134] Once S201 is complete, the DK-ECU2 instructs all or some of the anchors 3 to perform CS ranging communication with the mobile device 9. For example, the DK-ECU2 outputs ranging instructions to all or some of the anchors 3. An anchor 3 that receives a ranging instruction performs CS ranging communication with the mobile device 9. As described above, the CS ranging communication between multiple anchors 3 and the mobile device 9 may be performed in parallel using a one-way method.

[0135] If the vehicle Hv is locked, the DK-ECU2 may only allow external anchors such as anchors 3A, 3B, 3C, and 3D to perform CS distance measurement communication. Alternatively, if the vehicle Hv is locked, all external anchors and one internal anchor (e.g., anchor 3P) may perform CS distance measurement communication with the mobile device 9. The vehicle Hv being locked can be understood as being parked. The combination of anchors 3 that perform CS distance measurement communication may be determined on a case-by-case basis. For example, if location determination processing is performed in response to an external door handle on the right side being touched, the DK-ECU2 may only allow anchors 3B and 3C to perform CS distance measurement communication with the mobile device 9, because the user is likely to be on the right side of the vehicle Hv.

[0136] Once the distance measurement communication between the multiple anchors 3 and the mobile device 9 in S202 is complete, the DK-ECU2 acquires multiple sets of distance measurement values ​​from the multiple anchors 3 as a result of the distance measurement communication. Each of the multiple sets of distance measurement values ​​has a different source (output source). For example, the distance measurement value received from anchor 3B and the distance measurement value received from anchor 3C are examples of multiple sets of distance measurement values.

[0137] Then, in S203, the DK-ECU2 roughly determines the device orientation based on the results of the distance measurement communication in S202. The device orientation is the direction in which the portable device 9 is located relative to the vehicle Hv. The device orientation may be divided into general directions such as front, back, left, and right. The DK-ECU2 may determine the device orientation from the mounting position of the anchor 3 that outputs a relatively small distance measurement value among the multiple anchors 3.

[0138] Specifically, the DK-ECU2 identifies the nearest neighbor anchor and the quasi-neighbor anchor from among multiple anchors 3 by comparing multiple distance measurements. The nearest neighbor anchor is the anchor 3 that outputs the smallest distance measurement value. The quasi-neighbor anchor is the anchor 3 that outputs the second smallest distance measurement value. The DK-ECU2 determines the device orientation from the combination of the nearest neighbor anchor and the quasi-neighbor anchor.

[0139] For example, if the nearest neighbor anchor and the quasi-neighbor anchor are a combination of anchors 3B and 3C, DK-ECU2 may determine the device direction to be to the right. If the nearest neighbor anchor and the quasi-neighbor anchor are a combination of anchors 3C and 3D, DK-ECU2 may determine the device direction to be to the rear. If the nearest neighbor anchor and the quasi-neighbor anchor are anchors 3A and 3D, DK-ECU2 may determine the device direction to be to the left. If the nearest neighbor anchor and the quasi-neighbor anchor are anchors 3A and 3B, DK-ECU2 may determine the device direction to be to the front. DK-ECU2 may also determine the device direction to be to the right if the nearest neighbor anchor is anchor 3B or 3C and the quasi-neighbor anchor is anchor 3P or 3Q. Details of the device direction determination method may be modified as appropriate.

[0140] The following describes the case where the device direction is determined to be to the right. Following S203, S204 refers to the environmental data read in S201 and determines whether or not a strong reflector exists in the direction of the device. If S203 determines that the device direction is to the right, in S204 DK-ECU2 determines whether or not a strong reflector exists in the right area.

[0141] If the DK-ECU2 does not determine that a strong reflector is present on the right side (S204 NO), in S205 it executes a process to calculate the device position coordinates based on the distance measurements of multiple anchors 3. The device position coordinates can be calculated by multi-point positioning (e.g., 3-point positioning). Multi-point positioning is a method of determining the device position coordinates by finding the intersection points of multiple circles (spheres in the case of 3D) with the mounting position of each anchor 3 as the center and the distance measurement value as the radius. The DK-ECU2 calculates the device position coordinates based on the distance measurements of multiple anchors 3 and the mounting position of each anchor 3.

[0142] In multi-point positioning, three or more anchors 3 are generally used. However, for the sake of simplicity in explanation or calculation, this document describes the case where the device position coordinates are determined using the distance measurements of two anchors 3. When only two anchors 3 are used for multi-point positioning, two circles are generated. When only two anchors 3 are used for multi-point positioning, there can be two candidate points for the device position, which are the intersections of the circles. The DK-ECU2 may adopt the candidate point that aligns with the device direction as the device position. For example, if the device direction is determined to be the right side, and intersections P1 and P2 occur on the left and right sides of the vehicle Hv, then intersection P1, located on the right side of the vehicle Hv, may be considered the device position.

[0143] Of course, the device position coordinates may be calculated using three or more anchors 3. Hereafter, the process of calculating the device position coordinates using two or more anchors and the principle of multi-point positioning will also be referred to as the positioning calculation process. The positioning calculation method in S205 corresponds to the first estimation method. The first estimation method is a method of estimating the position by placing the center of a virtual circle at the mounting position of the anchor 3.

[0144] The DK-ECU2 may determine the combination of anchors 3 used for positioning calculation based on the device direction. For example, if the DK-ECU2 determines that the device direction is to the right, it will perform positioning calculation using anchors 3B and 3C. If the DK-ECU2 determines that the device direction is to the rear, it will perform positioning calculation using anchors 3C and 3D. If the DK-ECU2 determines that the device direction is to the left, it will perform positioning calculation using anchors 3A and 3D.

[0145] In this flow, the device direction is determined to be to the right, so in S205, the device position coordinates are calculated using anchors 3B and 3C. Specifically, of the intersection points P1 and P2 of the first circle C1 corresponding to anchor 3B and the second circle C2 corresponding to anchor 3C, the intersection point P1 that aligns with the device direction is adopted as the device coordinate.

[0146] The first circle C1, corresponding to anchor 3B, is a circle centered at the mounting position of anchor 3B (0,0) and with radius Db, the distance measured at anchor 3B. The first circle C1 is expressed as x^2 + y^2 = Db^2. The distance measured at anchor 3B, Db, corresponds to the first distance measured. The second circle C2, corresponding to anchor 3C, is a circle centered at the mounting position of anchor 3C (Ld,0) and with radius Dc, the distance measured at anchor 3C. The second circle C2 is expressed as (x - Ld)^2 + y^2 = Db^2. The distance measured at anchor 3C, Dc, corresponds to the second distance measured. The coordinates of intersection points P1 and P2 can be determined by solving this system of equations.

[0147] On the other hand, if DK-ECU2 determines that a strong reflector exists in the right area (S204 YES), in S206 it calculates a provisional device position, which is a temporary device position. The method for calculating the provisional device position may be the same as the positioning calculation process in S205. In other words, DK-ECU2 calculates the provisional device position using the first estimation method. S206 corresponds to the step of determining the device position coordinates by positioning calculation processing using multiple (e.g., two) anchors 3 associated with the device direction, and treating those device position coordinates as the provisional device position.

[0148] Once processing in S206 is complete, in S207, the DK-ECU2 determines whether the provisional device position calculated in S206 is located within the recalculation region CA set in the environment determination process. For example, as shown in Figure 13, if anchor 3C outputs a distance value Dc derived from a reflected wave at a strong reflector rather than a direct wave, the radius of the second circle C2 corresponding to anchor 3C will be larger than the actual distance from anchor 3C to the mobile device 9. As a result, the provisional device position TP may be located within the recalculation region CA. Conversely, if the provisional device position TP is located within the recalculation region CA, it means that the anchor 3 used in the positioning calculation process includes an anchor 3 that outputs a distance value corresponding to the path of a reflected wave.

[0149] Generally, the intensity of a reflected wave is lower than the intensity of a direct wave. Therefore, in many cases, the measured distance can correspond to the direct wave. However, if there is a human body or other object in the propagation path of the direct wave that attenuates the direct wave, the intensity of the direct wave may be lower than the intensity of the reflected wave. An example of a situation where a human body or other object attenuating the direct wave is in the propagation path of the direct wave is when the portable device 9 is placed in the user's back pocket. In such cases, the anchor 3 may output a measured distance value derived from the reflected wave.

[0150] If the temporary device location TP is located within the recalculation region CA (S207 YES), DK-ECU2 discards the temporary device location TP and executes the processes in S209 to S211 to calculate a more valid device location. On the other hand, if the temporary device location TP is not located within the recalculation region CA, DK-ECU2 adopts the temporary device location TP as the device location coordinate and terminates this flow.

[0151] Such a step S207 corresponds to verifying the validity of the provisional device position TP based on the positional relationship between the provisional device position TP and the virtual line VL or the recalculation region CA. The virtual line VL or the recalculation region CA is determined by the reflector distance L. Therefore, S207 may also be understood as a step to verify the validity of the provisional device position TP based on the reflector distance L.

[0152] The content of S207 may be replaced with a process to verify the validity of the temporary device position TP using a simpler method. For example, the DK-ECU2 may verify the validity of the temporary device position TP by checking whether the distance from the vehicle Hv to the temporary device position TP is greater than or equal to the reflector distance L. The DK-ECU2 may be configured to execute the processes from S209 onward if the distance from the vehicle Hv to the temporary device position TP is greater than or equal to the reflector distance L, and to execute S208 if the distance from the vehicle Hv to the temporary device position TP is less than the reflector distance L.

[0153] In S209, the DK-ECU2 identifies an NLOS (Non-Line Of Sight) anchor 3 from among the anchors 3 used in the positioning calculation process in S206. An NLOS anchor refers to an anchor 3 that outputs distance values ​​derived from reflected waves rather than direct waves. An NLOS anchor can also be called a reflected wave observation anchor. The distance values ​​derived from reflected waves output by an NLOS anchor can also be called indirect distance values.

[0154] In S209, DK-ECU2 may consider, for example, one of the anchors 3 used in the positioning calculation process that has observed a device signal strength below a predetermined NLOS threshold as an NLOS anchor. The following describes the case where the device signal strength observed at anchor 3B is above the NLOS threshold, while the device signal strength observed at anchor 3C is below the NLOS threshold. If the device signal strength observed at anchor 3C is below the NLOS threshold, DK-ECU2 considers anchor 3C to be an NLOS anchor. If the device signal strength observed at anchor 3C is below the NLOS threshold, DK-ECU2 does not determine anchor 3B to be an NLOS anchor.

[0155] The NLOS threshold used in the above determination may be determined by testing. The NLOS threshold may be set to a value approximately 6 dBV / m lower than the device signal strength that can be observed when the mobile device 9 is within the target area and there are no strong reflectors or human bodies around the mobile device 9. The test to determine the NLOS threshold may include multiple samples of the IQ level (in other words, received intensity) that can be observed when anchor 3 receives a direct wave from the mobile device 9 in a non-back pocket state in an environment where there are no reflectors around vehicle Hv. These multiple samples represent the direct wave-based IQ level.

[0156] The test to determine the NLOS threshold may further include collecting multiple samples of IQ levels that can be observed when anchor 3 receives a direct wave from a handheld device 9 in a back pocket position in an environment where no reflectors are present around vehicle Hv. These multiple samples represent attenuated direct wave-based IQ levels, which are direct waves attenuated by the human body. The NLOS threshold may be set to distinguish between direct wave-based IQ levels and attenuated direct wave-based IQ levels. The NLOS threshold may be adjusted so that the accuracy rate reaches a desired target value.

[0157] The DK-ECU2 may also include distance-intensity data, which indicates the normal range of device signal intensity corresponding to the measured distance. The DK-ECU2 may acquire the device signal intensity corresponding to the measured distance as an NLOS threshold based on pre-prepared distance-intensity data. The normal range may be designed by the above test. The distance-intensity data may be a dataset in map or table format, or it may be a function (program) that outputs a lower limit of the device signal intensity corresponding to the measured distance.

[0158] The following describes the case where only anchor 3C is determined to be an NLOS anchor. Note that, depending on the circumstances, both anchors 3B and 3C may be determined to be NLOS anchors.

[0159] Once the NLOS anchors have been identified, the DK-ECU2 sets a virtual anchor point VAP corresponding to the NLOS anchor in S210. The virtual anchor point VAP is the point obtained by moving the NLOS anchor symmetrically across the virtual line VL, as shown in Figure 14. When the position of anchor 3C is represented as (Ld, 0), the coordinates of the virtual anchor point VAP corresponding to anchor 3C may be set to (Ld, 2L). The virtual anchor point VAP corresponds to a virtual anchor where the NLOS anchor is placed on the opposite side of the virtual line VL. The virtual anchor point VAP may also be referred to as a virtual wave source.

[0160] Once the virtual anchor point VAP is set, the DK-ECU2 performs positioning calculation processing using a second estimation method with the virtual anchor point VAP in S211. Specifically, it calculates the intersection points P3 and P4 of the first circle C1 corresponding to anchor 3B and the third circle C3 corresponding to the virtual anchor point. Each coordinate can be calculated by solving the simultaneous equations of the first circle C1 and the third circle C3. The third circle C3 is represented by (x-Ld)^2+(y-2L)^2=Dc^2.

[0161] In this case as well, two intersection points are obtained. Of the two intersection points P3 and P4, DK-ECU2 may adopt intersection point P4, which is located outside the recalculation region CA, that is, between the virtual line VL and the vehicle Hv, as the device position. If the distance measurement value of a third anchor 3, such as anchor 3P, is available, the device position may be finalized based on the distance measurement value of that third anchor 3.

[0162] Thus, the positioning calculation process using the virtual anchor point VAP corresponds to position determination by the second estimation method. For convenience, in this disclosure, the series of processes from S209 to S211 will also be referred to as the positioning calculation process using the virtual anchor, or the positioning calculation process by the second estimation method.

[0163] The above describes the case where anchor 3B is determined not to be an NLOS anchor. However, if anchor 3B is determined to be an NLOS anchor, a virtual anchor point for anchor 3B may be set. The coordinates of the virtual anchor point for anchor 3B are (0, 2L). If anchor 3B is an NLOS anchor, DK-ECU2 may perform positioning calculations using a fourth circle centered on the virtual anchor point for anchor 3B and with the distance measurement value Db as its radius.

[0164] With the above configuration, even if some of the anchors 3 output distance values ​​affected by reflected waves, it becomes possible to determine the device position with less error. Note that when anchors 3 output distance values ​​affected by reflected waves, it may be when there is a strong reflector around the portable device 9 and the portable device 9 is in a back pocket. Taking these circumstances into account, according to this embodiment, even when there is a strong reflector such as a wall around the portable device 9 and the portable device 9 is stored in a back pocket or the like, the device position can be calculated with high accuracy.

[0165] <Other operational examples when a highly reflective surface is present> Even if the DK-ECU2 determines that a strong reflector is present and the temporary device position is between the virtual line VL and the vehicle Hv, it may perform positioning calculation processing using a virtual anchor if it determines that the portable device 9 is in a back pocket position relative to the vehicle Hv. If the DK-ECU2 determines that a strong reflector is present in the direction of the device (S204 YES), it may perform S301 to S306 shown in Figure 15 instead of S206 to S211 shown in Figure 8.

[0166] Steps S301 to S302 may be the same as steps S206 to S207. In the presence of a strong reflector, if the temporary device position is located in the recalculation region CA (S302 YES), DK-ECU2 performs positioning calculation processing using a virtual anchor in S303. Step S303 corresponds to steps S209 to S211 described above, and its specific content is as described above.

[0167] On the other hand, if the temporary device position is located between the virtual line VL and the vehicle Hv (S302 NO), the DK-ECU2 performs a possession-type determination process in S304. The possession-type determination process determines whether the portable device 9 is in a back pocket, that is, whether a human body (i.e., the user's body) is present between the portable device 9 and the vehicle Hv. The possession-type determination process can be understood as determining whether the portable device 9 is located on the user's back side as seen from the vehicle Hv. The possession-type determination process may also be called a back pocket determination or backside determination.

[0168] In the possession type determination process, the DK-ECU2 first selects the larger of the two device signal strengths used in the calculation of the provisional device position in S301 as the representative strength. If this representative strength is less than a predetermined backside threshold, it may be determined that the user's body is between the vehicle Hv and the portable device 9. The backside threshold may be set based on testing so that the false detection rate is less than a predetermined target value.

[0169] The backside threshold may be set according to the maximum device signal strength in the back pocket state. The backside threshold may be determined by considering the minimum device signal strength in the non-back pocket state. It may be set so that the sum of the back pocket state detection rate and the value obtained by subtracting the false detection rate from 100% is maximized. The back pocket state detection rate means the probability that the device can be determined to be in the back pocket state when it is actually in the back pocket state. The back pocket state false detection rate means the probability that the device is incorrectly determined to be in the back pocket state when it is not actually in the back pocket state. These probability values ​​may be determined by testing. The possession form determination process may be understood as the process of determining whether or not the device is in the back pocket state in a given situation.

[0170] If the representative intensity is below the backside threshold, DK-ECU2 determines that the portable device 9 is in the back pocket state (S305 YES) and executes S307. On the other hand, if the representative intensity is above the backside threshold, DK-ECU2 determines that the portable device 9 is not in the back pocket state (S305 NO) and executes S306. S306 is the step of formally adopting the provisional device position as the device position.

[0171] S307, like S303, performs positioning calculation processing using virtual anchors. In the positioning calculation processing using virtual anchors in S307, the DK-ECU2 sets virtual anchor points corresponding to each of the two anchors 3 used to calculate the provisional device position, and may determine the intersection of the third circle and the fourth circle as the device position. This is because if the representative intensity is below the backside threshold, there is a high probability that the device signal intensity at either anchor 3 will also be below the NLOS threshold.

[0172] The NLOS threshold and the backside threshold may be the same value; that is, the backside threshold may be integrated into the NLOS threshold. Alternatively, the NLOS threshold and the backside threshold may be set to different values; the backside threshold may be set to a value smaller than the NLOS threshold.

[0173] According to the above configuration, the accuracy of determining the device's position can be improved when a portable device 9 is in a back pocket position in front of a highly reflective surface such as a wall.

[0174] <Other examples of operation in the back pocket state> The processing performed in S307 as shown in Figure 15 is not limited to positioning calculation processing using a virtual anchor. Instead of performing positioning calculation processing using a virtual anchor in S307, the DK-ECU2 may perform processing that includes a first step of correcting the distance measurement value and a second step of performing positioning calculation processing using the corrected distance measurement value generated in the first step.

[0175] In the first step, the DK-ECU2 corrects the distance measurement value of each anchor 3 by a predetermined correction amount. This correction may be subtraction. The correction amount may be set to a value corresponding to the length of the path the CW signal takes around the human body, i.e., the detour path length. The correction amount may be set to 0.2m, 0.3m, 0.4m, or 0.5m, etc. The correction amount corresponds to the correction parameter. The correction amount may be registered as a parameter in memory 232.

[0176] In the second step, the DK-ECU2 uses the distance measurement value corrected in the first step to perform positioning calculation processing according to the first estimation method. The method of positioning calculation processing itself may be the same as that of S205, etc. The difference is that S205 uses the observed distance measurement value as is, while the second step uses the corrected distance measurement value. When the CW signal is transmitted around the human body in a back pocket state, the distance measurement value may be calculated to be about 0.3m longer than the original value. The above processing can further improve the distance measurement accuracy. In this disclosure, the calculation processing including the first and second steps is also referred to as positioning calculation processing that cancels out the bypass portion.

[0177] Furthermore, even if DK-ECU2 determines in S204 that there is no strong reflector (S204 YES), it may still determine whether the portable device 9 is in a back pocket. If DK-ECU2 determines in S204 that there is no strong reflector and that the portable device 9 is in a back pocket, it may perform positioning calculation processing that cancels out the detour. This also reduces the estimation error of the device position caused by the CW signal bending around the human body.

[0178] <Setting the antenna's directivity> The anchors 3 positioned on the outer surface of the vehicle Hv may be designed with a directivity that makes it difficult to receive direct waves from other anchors 3 that form a pair with them. For example, each outer anchor may have its main beam directed away from the vehicle. This reduces the influence of direct waves in the ranging communication between anchors, thereby improving the accuracy of determining the presence or absence of a strong reflector and the accuracy of estimating the reflector distance.

[0179] More specifically, the anchor 3C may be positioned on the outer surface of the vehicle Hv with its main beam facing outward in direction A1, as shown in Figure 16. For the anchor 3C, outward direction A1 is the direction perpendicular to the vehicle body surface to which the anchor 3C is attached. The dashed line in the figure schematically shows the directivity of the antenna 31 provided by the anchor 3C. In Figure 16, Am represents the direction of the main beam, and θ represents the half-power angle. The half-power angle can be relatively wide, such as 120 degrees.

[0180] In Figure 16, the arrows with diagonal hatching represent the outward direction for anchor 3C. 5 in the figure represents a component separating the interior from the exterior of the vehicle, such as a body panel, door, or frame. The outward direction varies depending on the mounting location. For example, for anchor 3 located near the license plate at the rear end, the outward direction A1 could be towards the rear of the vehicle.

[0181] In Figure 16, the white arrow labeled A2 represents the pair direction for anchor 3C. Pair direction A2 is the direction in which the other anchor 3 forming the pair exists. From one perspective, pair direction A2 for anchor 3C is the direction in which anchor 3B exists. From another perspective, pair direction A2 for anchor 3C is the direction in which anchor 3D exists. When antenna 31 of anchor 3C is considered the first antenna, antenna 31 of either anchor 3B or anchor 3C corresponds to the second antenna. The pair direction can be understood as the direction from the first antenna to the second antenna.

[0182] Anchor 3C may have its main beam oriented in a direction at least 45 degrees different from the pair direction A2. Anchor 3C may be mounted on the vehicle body in a position such that the pair direction A2 is outside the half-power range. The gain of Anchor 3C in the direction approximately 45 degrees outward from the pair direction A2 may be at least 3 dB greater than the gain in the pair direction A2.

[0183] According to the configuration of anchor 3C shown in Figure 16, the gain in the pair direction A2 is smaller than the gain in the outward direction A1. Therefore, reflected waves from strong reflectors are received relatively strongly. As a result, the accuracy of determining the presence or absence of a strong reflector and the accuracy of estimating the reflector distance can be improved. Note that the orientation of the main beam facing outward direction A1 is not limited to a state where the main beam direction and outward direction A1 are perfectly aligned. The main beam of anchor 3 may be tilted at about 45 degrees with respect to the outward direction A1. Anchor 3C may be positioned near a corner of the vehicle body with its main beam facing a predetermined angle behind the outward direction A1. In addition, anchor 3 may be positioned with its main beam within ±40 degrees in the centrifugal direction. The centrifugal direction is the direction away from the center of the vehicle Hv.

[0184] The above describes the mounting orientation of anchor 3C, but this explanation may also apply to the mounting orientation of other outer anchors. The antenna type of anchor 3 may be selected according to the above objectives. The built-in antenna of anchor 3 may be any type of antenna, such as a patch antenna, monopole antenna, or inverted L antenna.

[0185] The directivity of anchor 3 may be set using the concept of the direction of arrival of the reflected wave, which is the direction in which the LE signal from the other paired anchor 3 arrives after being reflected by a strong reflector. The direction of arrival of the reflected wave may be approximately 45 degrees outward with respect to the pair direction. Anchor 3 may be configured such that the gain in the direction of arrival of the reflected wave is 3 dB or more greater than the gain in the pair direction.

[0186] <Supplementary information on how to calculate the distance to a highly reflective object> In the embodiments described above, we have described a DK-ECU2 configured to calculate the reflector distance L based on differential IQ-based distance measurements (in other words, distance measurements of the reflection path). In other embodiments, the DK-ECU2 may be configured to determine the reflector distance L using an object detection sensor 4 after determining that a strong reflector is present based on differential IQ data.

[0187] Figure 17 shows an example of the operation of the DK-ECU2's environmental determination process described above. The environmental determination process shown in Figure 17 includes S401 to S411. S401 to S406 and S408 to S411 correspond to S101 to S106 and S108 to S111. The specific contents of S401 to S406 and S408 to S411 may be the same as those of S101 to S106 and S108 to S111.

[0188] S407, following S406, is a replacement for S107. Like S107, S407 is executed when the representative value of the reflected wave intensity (Rp) exceeds the detection threshold (Rth). S407 is a step in which the DK-ECU2 determines the reflector distance L using an object detection sensor such as sonar. S407 includes activating the object detection sensor, driving the object detection sensor, and obtaining the reflector distance L based on the output signal of the object detection sensor.

[0189] The object detection sensor to be activated may be an object detection sensor corresponding to the direction corresponding to the anchor pair that has detected a strong reflector. If a strong reflector is detected based on the results of the first pair's distance measurement communication, an object detection sensor with a detection range on the right side of the vehicle may be used to determine the reflector distance L. For example, if the representative value of the reflectance intensity generated from the results of the first pair's distance measurement communication exceeds the detection threshold, the DK-ECU2 drives the right sonar and acquires its detection result (in other words, output data). The DK-ECU2 then adopts the detection distance of the right sonar as the reflector distance L. The right sonar is a sonar that forms a detection range on the right side of the vehicle Hv. The right sonar may be a sonar or camera installed on the right side of the vehicle Hv (e.g., the right side sill or fender). By using a configuration that determines the reflector distance L based on the output data of the object detection sensor instead of the differential IQ-based distance measurement value, the estimation accuracy of the reflector distance L can be improved.

[0190] As a comparative configuration, one could also consider a system that uses only an object detection sensor to determine the presence or absence of a highly reflective object, and if a highly reflective object is detected, to determine the distance to that object. However, an object detection sensor cannot determine whether the detected object is truly a highly reflective object that would affect the results of the distance measurement communication. For example, sonar can detect concrete walls, poles, trees, etc., as reflectors and output the distance to the detected object. Furthermore, it is difficult to determine whether an object is highly reflective based on its appearance alone. Therefore, even with a camera, it is difficult to determine whether an object captured in the image is a highly reflective object. For example, a camera may mistakenly detect a resin partition with a white or silver metallic paint as a highly reflective object.

[0191] Such a comparative configuration may incorrectly determine the presence of a strong reflector even when one does not exist, potentially leading to positioning calculations using an inappropriate estimation method. The configuration disclosed in this section was created in response to the potential problems of the comparative configuration. First, the presence or absence of a strong reflector is determined from a representative value of the reflectance intensity using differential IQ data. Then, only if a strong reflector is determined to be present based on the representative value of the reflectance intensity, the distance to the strong reflector is determined using an object detection sensor.

[0192] The configuration disclosed in this section reduces the risk of misinterpreting an environment where concrete walls, resin partitions, trees, etc., are present around the vehicle Hv as an environment where highly reflective objects are present. In addition, if highly reflective objects are present, the accuracy of estimating the distance to them can be improved. Furthermore, when the system determines that no highly reflective objects are present based on the representative value of the reflectivity while the vehicle is parked, the object detection sensor is not driven. The above configuration may also have the advantage of reducing power consumption associated with driving the object detection sensor.

[0193] <Environment monitoring using advertising> The DK-ECU2 may perform an environmental assessment process once after the vehicle Hv is parked, and then periodically perform monitoring processes. The monitoring process assumes that advertisement packets are sent and received between the anchor pair and detects environmental changes from changes in the received level of the advertisement packets. Environmental changes here refer to the appearance / disappearance of a highly reflective object. An example of an environmental change is when another vehicle is parked next to the vehicle Hv after it has been parked. Another example of an environmental change is when the other vehicle moves away after the vehicle Hv has been parked next to it.

[0194] The monitoring process includes re-executing the environmental determination process in response to the detection of an environmental change. That is, the monitoring process includes S501 to S504 as shown in Figure 18. S501 may be repeatedly executed at a fixed monitoring interval while the vehicle Hv is parked, for example. The monitoring interval may be 10 minutes, 30 minutes, 1 hour, etc. The monitoring interval may be changed depending on the parking location or time of day. The monitoring interval may be set to be longer during nighttime hours compared to daytime hours. If the vehicle Hv is parked at its storage location (e.g., home), the monitoring interval may be set to be longer than when it is parked at other locations (e.g., commercial facilities).

[0195] S501 is the step in which the paired Anchor 3s exchange advertisement packets. For example, DK-ECU2 configures the roles of multiple outer anchors. For instance, it configures Anchor 3B and 3D as the central in BLUETOOTH LE, and Anchor 3A and 3C as peripherals. It then notifies Anchor 3A and 3C of the timing information for when they should send advertisement packets. It also notifies Anchor 3B and 3D of the timing information for when they should enter a listening state.

[0196] Anchor 3 transmits or scans for advertised packets at the timing notified by DK-ECU2. This ensures efficient exchange of advertised packets. To prevent packet collisions, the timing of Anchor 3A's and Anchor 3C's advertisement packet transmissions may be delayed by a predetermined amount. The scan windows (reception waiting times) of Anchors 3B and 3D may be set to a length that allows them to receive advertised packets from Anchors 3A and 3C, respectively. Anchors 3B and 3D receive the advertised packets transmitted from Anchors 3A and 3C, respectively, and report their IQ levels (in other words, received strength, received level) along with source information to DK-ECU2.

[0197] S502 is a step in which the DK-ECU2 obtains the reception level of advertisement packets from the central anchor 3. The central anchor 3 in this case refers to anchors 3B and 3D. The DK-ECU2 saves the reception level data obtained from anchors 3B and 3D to memory 232, adding a timestamp. From anchor 3B, the DK-ECU2 may obtain the reception level of advertisement packets sent from anchor 3A in addition to the reception level of advertisement packets sent from anchor 3C. From anchor 3D, the DK-ECU2 may obtain the reception level of advertisement packets sent from anchor 3C in addition to the reception level of advertisement packets sent from anchor 3A.

[0198] S503, following S502, is a step in which the DK-ECU2 determines whether a change of more than a predetermined value has occurred in the received level. S503 includes comparing the received level data stored in the previous monitoring process (i.e., the received level acquired in the previous process) with the received level data acquired in the current monitoring process (i.e., the received level acquired in the current process). The comparison may be performed for each combination of the advertised packet source and receiving device. Specifically, the DK-ECU2 compares the received level previously observed at anchor 3B with the received level observed in the current process for the advertised packet transmitted by anchor 3C. A change in the received level observed at anchor 3B for the advertised packet transmitted by anchor 3C represents a change in the environment in the right area.

[0199] Similarly, DK-ECU2 compares the previously observed reception level at anchor 3D with the currently observed reception level for the advertisement packet transmitted by anchor 3A. A change in reception level between anchors 3A and 3D indicates a change in the environment in the left area. DK-ECU2 may compare the previously observed reception level at anchor 3D with the currently observed reception level for the advertisement packet transmitted by anchor 3C to determine whether there is a change in the environment in the rear area. DK-ECU2 may also compare the previously observed reception level at anchor 3B with the currently observed reception level for the advertisement packet transmitted by anchor 3A to determine whether there is a change in the environment in the forward area.

[0200] If there is a change in the reception level in any of the anchor pairs (S503 YES), S504 is executed. On the other hand, if there is no change in the reception level in any of the anchor pairs (S503 NO), this flow is terminated. A change in the reception level is defined as the absolute value of the difference between the reception level observed this time and the reception level observed last time being greater than or equal to a predetermined update threshold. Conversely, if the absolute value of the difference between the reception level observed this time and the reception level observed last time is less than the update threshold, DK-ECU2 may determine that there was no change in the reception level. The update threshold is a threshold for re-executing the environment determination process, as will be explained next.

[0201] S504 is a step in which the environmental determination process is re-executed. The target area of ​​the environmental determination process may be limited to the area where a change in the received level has been observed. Therefore, the anchor pairs used in the environmental determination process of S504 may be limited to the anchor pairs where a change in the received level has been observed. The specific flow of the environmental determination process may be the flow exemplified in Figure 9 or Figure 17. In S504, the distance measurement communication is re-executed in the anchor pairs where a change in the received level has been observed, and the presence or absence of a strong reflector is re-determined.

[0202] As described above, when parked, the DK-ECU2 may be configured to perform environmental determination processing triggered by a change in the received level of advertised packets. CS ranging communication can consume more power than the exchange of advertised packets. With the above configuration, the opportunities to perform CS ranging communication can be reduced compared to a configuration that performs environmental determination processing periodically. Consequently, power consumption while parked can be reduced.

[0203] Note that S501 may include executing transmission and reception of advertisement packets a plurality of times for each anchor pair. The received level stored in S502 may be a representative value (average value, median value, or maximum value) of a plurality of received levels. The change in the received level in S503 may also be determined by comparing representative values of a plurality of received levels. The DK-ECU2 may not execute the monitoring process periodically, and may execute the monitoring process in response to the GW module 21 being connected to the mobile device 9 via LE communication.

[0204] <Supplementary Explanation of CS Distance Measurement Method> The anchor 3, GW module 21, or LE module 92 may acquire a single-cycle phase difference for each frequency by an active two-way method or a passive two-way method, and calculate an inter-frequency phase difference using them. Here, an overview of the active two-way method and the passive two-way method will be described.

[0205] The active two-way method is a method in which an initiator and a reflector transmit and receive CW signals to each other to detect the phase difference between the transmitted signal and the received signal for each, and specify the single-cycle phase difference using these two phase differences. The active two-way method includes a process in which the initiator and the reflector transmit and receive CW signals to each other, and a process in which the received phase (θr) observed by the reflector is transmitted to the initiator.

[0206] If the initial phase of the initiator is δi, the initial phase of the reflector is δr, the single-frequency phase difference that should be observed depending on the one-way distance between the initiator and the reflector is φ, and the target frequency is f, then the relationships θr = φ + δi - δr and θi = φ - δi + δr exist. Based on these relationships, the average of θi and θr is the single-frequency phase difference (φ), where the initial phase components of the initiator and reflector cancel each other out. The active two-way system corresponds to a method that calculates the single-frequency phase difference as the average of the received phase at the initiator and the received phase at the reflector. Note that here, since we are assuming a phase difference due to one-way propagation, the average of θi and θr is used as the single-frequency phase difference. In another embodiment, when assuming a phase difference due to round-trip propagation as the single-frequency phase difference, the single-frequency phase difference can be obtained as θi + θr.

[0207] The passive two-way system is also a method in which the initiator and reflector transmit and receive CW signals to and from each other. The difference from the active two-way system is that the reflector reflects the received phase of the CW signal transmitted from the initiator into the initial phase of the CW signal it transmits. For example, if the received phase at the reflector is θr, it transmits a CW signal expressed as z(t)=A·exp{-i(ωt+θr+2πn)}, where A represents the amplitude, ω is the angular frequency corresponding to the target frequency (f), and the relationship ω=2πf exists. n is a natural number and corresponds to the interval from when the reflector receives the CW signal until it transmits the CW signal.

[0208] According to this method, the received phase observed by the initiator does not include the initial phase component of the reflector. The received phase observed by the initiator is the same value as when a CW signal is received after being reflected by a reflector such as a wall. As a result, the initiator can calculate the single-frequency phase difference without obtaining the received phase from the reflector. The passive two-way method has the advantage of not requiring the reflector to transmit a received phase message compared to the active two-way method. As described above, single-frequency phase difference, and by extension, inter-frequency phase difference, can be implemented using a variety of methods.

[0209] <Additional Note> The various flowcharts shown in this disclosure are all examples, and the number of steps constituting the flowchart and the order of execution of processes can be changed as appropriate. The controls shown in each flowchart may be combined and executed in parallel to the extent that they do not contradict each other. Expressions such as acquisition, determination, detection, generation, and calculation may be used interchangeably. When a device acquires certain data, it may also include the device generating that data based on signals input from other devices / sensors.

[0210] The apparatus and methods described herein may be implemented by one or more dedicated computers comprising a processor for executing a computer program and one or more hardware logic circuits. The processor may be any arithmetic core, such as a CPU, MPU, GPU, or DFP (Data Flow Processor). Some or all of the functions of the in-vehicle key system may be implemented as hardware. Some or all of the functions of the in-vehicle key system may be implemented using a system-on-a-chip (SoC), integrated circuit (IC), or field-programmable gate array (FPGA). The computer program includes instructions executed by the computer. The above-mentioned DK-ECU may be a position estimation device. The position estimation device includes a reflector detection device. The method implemented by the DK-ECU includes a strong reflector detection method and a position estimation method. Furthermore, the programs installed on the DK-ECU may include a program for detecting strong reflectors and a program for estimating the device position. [Explanation of symbols]

[0211] 2 DK-ECU, 3 Anchor, 3B Anchor (1st Anchor), 3C Anchor (2nd Anchor), 4 Object Detection Sensor, 21 GW Module (Other In-Vehicle Communication Device), 22 In-Vehicle Communication Circuit (Communication Circuit), 23 Main Controller (Control Unit), 231 Processor, 232 Memory, CA Recalculation Area

Claims

1. A first anchor (3B) and a second anchor (3C) are configured to perform distance measurement communication, including transmitting and receiving continuous wave signals on multiple channels, The system includes a control unit (23) that determines whether or not a highly reflective object exists around the vehicle based on the results of distance measurement communication performed by the first anchor with the second anchor, The results of the distance measurement communication include IQ data for each channel. The control unit includes a memory (232) in which direct wave IQ data, which is IQ data observed when the first anchor performs distance measurement communication with the second anchor under a predetermined test environment in which no reflectors are present around the vehicle, is stored. The control unit, The IQ data for each channel obtained by having the first anchor communicate with the second anchor for distance measurement is acquired as observed IQ data, The process involves generating difference IQ data that represents IQ data originating from reflected waves based on the observed IQ data and the direct wave IQ data, The reflected wave intensity is calculated based on the aforementioned differential IQ data, A reflector detection system configured to perform the following: determine whether or not the strong reflector exists in a target area determined with respect to the vehicle by comparing the reflected wave intensity with a predetermined detection threshold.

2. A first anchor (3B) and a second anchor (3C) are configured to perform distance measurement communication, including transmitting and receiving continuous wave signals on multiple channels, The system includes a control unit (23) that performs distance measurement communication between the first anchor and the second anchor and a mobile device, thereby acquiring multiple sets of distance measurement values ​​indicating the distance from each of the first anchor and the second anchor to the mobile device, and estimating the device position, which is the position of the mobile device relative to the vehicle, based on the multiple sets of distance measurement values. The results of the distance measurement communication include IQ data for each channel. The control unit includes a memory (232) in which direct wave IQ data, which is IQ data observed when the first anchor communicates with the second anchor for distance measurement under a predetermined test environment in which no reflectors exist around the vehicle, is stored. The control unit, The IQ data for each channel obtained by having the first anchor communicate with the second anchor for distance measurement is acquired as observed IQ data, The process involves generating difference IQ data that represents IQ data originating from reflected waves based on the observed IQ data and the direct wave IQ data, The reflected wave intensity is calculated based on the aforementioned differential IQ data, The method involves comparing the reflected wave intensity with a predetermined detection threshold to determine whether or not a highly reflective object exists in a target area defined with respect to the vehicle, A position estimation system configured to change the method for estimating the position of the mobile device depending on whether or not it is determined that the aforementioned highly reflective object is present.

3. The control unit, The position estimation system according to claim 2, which is configured to determine the reflector distance, which is the distance between the vehicle and the strong reflector, based on the differential IQ data, when it is determined that the strong reflector exists in the target area.

4. The system further includes an object detection sensor (4), which is a sensor that detects objects. The control unit, The position estimation system according to claim 2, wherein when it is determined that the strong reflector exists in the target area, the object detection sensor is activated and the reflector distance, which is the distance from the vehicle to the strong reflector, is determined based on the output data of the object detection sensor.

5. The control unit, Upon the vehicle being parked, the first anchor communicates with the second anchor to measure distance and determines whether the strong reflector exists in the target area based on a comparison of the reflected wave intensity and the detection threshold, While the vehicle is parked, predetermined communication packets are periodically sent and received between the first anchor and the second anchor, thereby periodically obtaining the reception level of the communication packets at the first anchor or the second anchor. The position estimation system according to claim 2, wherein if the difference between the previously acquired reception level and the newly acquired reception level is greater than or equal to a predetermined value, the first anchor causes the second anchor to perform distance measurement communication again, and re-determines whether the strong reflector exists in the target area based on a comparison of the reflected wave intensity and the detection threshold.

6. The position estimation system according to claim 5, wherein the reception level is the average, median, or maximum value of a plurality of reception levels obtained by sending and receiving the communication packets multiple times.

7. The control unit, If it is determined that the highly reflective object exists in the target area, the temporary device position, which is the temporary position of the mobile device, is calculated using the distance measurement values ​​of the multiple sets and the position information of the first and second anchors. The position estimation system according to claim 3 or 4, configured to perform the following: verify the validity of the temporary device position based on the relationship between the reflector distance and the temporary device position.

8. The control unit, Based on the reflector distance, a recalculation region (CA) is set. If it is determined that the reflector exists in the target area, it is determined whether the temporary device position is located in the recalculation area. If the provisional device location is not located in the recalculation region, the provisional device location is adopted as the location of the portable device. If the temporary device location is located in the recalculation region, the temporary device location is discarded. The position estimation system according to claim 7, wherein, if the provisional device position is discarded, the position of the portable device is determined using the reflector distance in addition to the distance values ​​of the multiple sets and the position information of the first and second anchors.

9. The control unit, Based on the reflector distance, a recalculation region (CA) is set. If it is determined that the reflector exists in the target area, it is determined whether the temporary device position is located in the recalculation area. If the provisional device position is not located in the recalculation area, then it is determined whether the mobile device is in a back pocket state based on the IQ data obtained by the distance measurement communication between the first anchor and the mobile device or the IQ data obtained by the distance measurement communication between the first anchor and the mobile device. If the temporary device position is not located in the recalculation region and is not in the back pocket state, the temporary device position is adopted as the position of the portable device. If the temporary device location is located in the recalculation region, the temporary device location is discarded. The position estimation system according to claim 7, wherein, if the provisional device position is discarded, the position of the portable device is determined using the reflector distance in addition to the position information of the first anchor and the second anchor and the distance measurement values ​​of the multiple sets.

10. The control unit, The position estimation system according to claim 2, wherein the determination of whether or not the highly reflective body is present is performed when the vehicle is stopped and all doors are closed.

11. The control unit, The position estimation system according to claim 2, wherein the determination of whether or not the highly reflective body is present is performed when the first anchor, the second anchor, or another in-vehicle communication device receives a signal from the mobile device while the vehicle is locked.

12. The position estimation system according to claim 2, wherein the highly reflective body is a metal plate, a metal wall, or another vehicle having a size of 1 square meter or more.

13. The detection threshold is set to a value obtained by subtracting an offset value, which is obtained by subtracting the minimum direct wave level from a predetermined maximum reflected wave level, from a predetermined reference level. The aforementioned maximum reflected wave level is the maximum value of the received level that can be observed by the portable device located in the target area for a signal transmitted from the first anchor and reflected by the strong reflector. The minimum direct wave level is the minimum received level observable by the portable device located in the target area for a signal transmitted from the first anchor that is not reflected by the strong reflector. The position estimation system according to claim 2, wherein the reference level is an assumed value of the reception level that can be observed when the first anchor and the second anchor perform distance measurement communication in an environment in which the highly reflective material is present around the vehicle.

14. A reflector detection device for determining whether a highly reflective object exists around a vehicle, A control unit (23) that performs processing to determine the presence or absence of the strong reflector, The system comprises a first anchor (3B) and a second anchor (3C) configured to perform distance measurement communication, including transmitting and receiving continuous wave signals on multiple channels, and a communication circuit (22) for communication between the control unit and the first anchor (3B). Range measurement communication is a communication method for generating IQ data for each channel. The control unit includes a memory (232) in which direct wave IQ data, which is channel-specific IQ data observed when the first anchor communicates with the second anchor for distance measurement under a predetermined test environment in which no reflectors exist around the vehicle, is stored. The control unit, The IQ data for each channel obtained by having the first anchor communicate with the second anchor for distance measurement is acquired as observed IQ data, Based on the observed IQ data and the direct wave IQ data, difference IQ data is generated that shows the IQ data originating from the reflected wave. The reflected wave intensity is calculated based on the aforementioned differential IQ data, A reflector detection device configured to perform the following: determine whether or not the strong reflector exists in a predetermined target area by comparing the reflected wave intensity with a predetermined detection threshold.

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