Position identification system, position identification device, and position identification method

Abstract

In the present invention, a DK-ECU determines whether or not a reflective object such as a wall is present on the right side of a vehicle on the basis of the result of anchor-to-anchor distance measurement communication. Upon determining that the reflective object is present, the DK-ECU calculates the distance (L) from the vehicle to the reflective object, and sets a virtual line (VL) and a recalculation area (CA). The DK-ECU sets a virtual anchor point (VAP) by moving an anchor (3C) in a line-symmetric manner using the virtual line (VL) as the axis of symmetry if the provisional device position calculated through a normal positioning computation process is positioned in the recalculation area. The DK-ECU then identifies the device position using a circle defining the virtual anchor point as the center and defining a distance measurement value (Dc) at the anchor (3C) as the radius.

Description

Location determination system, location determination device, and location determination method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2024-140013 filed in Japan on August 21, 2024, and the contents of the original application are incorporated by reference in their entirety.

[0002] The present disclosure relates to techniques for wirelessly determining the location of a mobile device relative to an object.

[0003] Patent Literature 1 discloses a technology for determining the position of a mobile device relative to a vehicle using multiple sets of ranging data obtained by multiple anchors performing ranging communications with the mobile device. The ranging communications here refer to wireless communications for measuring distance. For example, the distance can be calculated from the round trip time (RTT).

[0004] Japanese Patent Application Laid-Open No. 2022-114258

[0005] In ranging communications, reflections from reflective objects such as walls can cause the distance from the anchor to the mobile device to be misspecified as being greater than the actual distance. If the distance from the anchor to the mobile device is incorrect, the location of the mobile device may be misspecified as being farther away than the actual location.

[0006] One of the objectives of the present disclosure is to provide a technique that can reduce the risk of erroneously determining the location of a mobile device.

[0007] The location identification system disclosed herein includes a portable device that is a wireless communication device carried by a user; a plurality of anchors that are configured to be able to perform ranging communication with the portable device and other anchors according to a specific communication protocol; a memory unit that stores anchor setting data indicating the positions of the plurality of anchors; and a control unit that executes processing to identify the position of the portable device relative to an object based on the results of ranging communication between the plurality of anchors and the portable device. The control unit is configured to: determine whether a reflector is present in a predetermined target area based on the results of ranging communication between the specific anchors or the detection results of the object detection sensor; if it is determined that a reflector is present in the target area, determine a reflector distance that is the distance between the object and the reflector; cause the plurality of anchors to perform ranging communication with the portable device, thereby obtaining multiple sets of ranging values ​​that indicate the distance from each of the multiple anchors to the portable device; if it is determined that a reflector is present in the target area, calculate a tentative device position that is a tentative position of the portable device using the multiple sets of ranging values ​​and information on the positions of the plurality of anchors; and verify the validity of the tentative device position based on the relationship between the tentative device position and an area where a reflector may be present, as determined from the reflector distance.

[0008] The positioning device of the present disclosure is a positioning device that determines the position of a mobile device relative to an object, and includes: a communication circuit for communicating with each of a plurality of anchors configured to be able to perform ranging communication with the mobile device and other anchors according to a specific communication protocol; a memory unit that stores anchor setting data that is data indicating the positions of the plurality of anchors; and a control unit that executes processing to determine the position of the mobile device based on data received from the plurality of anchors via the communication circuit and the anchor setting data stored in the memory unit, and the control unit determines whether a reflective object is present in a predetermined target area based on the results of ranging communication between specific anchors or the detection results of an object detection sensor associated with the object. The system is configured to determine whether a reflecting object exists in the target area, and if it is determined that a reflecting object exists in the target area, identify a reflecting object distance, which is the distance between the target object and the reflecting object, obtain multiple sets of distance measurement values ​​indicating the distance from each of the multiple anchors to the mobile device by having the multiple anchors perform distance measurement communication with the mobile device, and if it is determined that a reflecting object exists in the target area, calculate a tentative device position, which is a tentative position of the mobile device, using the multiple sets of distance measurement values ​​and position information of the multiple anchors, and verify the validity of the tentative device position based on the relationship between the area where a reflecting object may exist, which is determined from the reflecting object distance, and the tentative device position.

[0009] The positioning method of the present disclosure is a computer-executed positioning method for determining the position of a mobile device relative to an object, and includes the steps of: communicating with each of a plurality of anchors configured to be able to perform ranging communication with the mobile device and other anchors according to a specific communication protocol via a communication circuit; reading anchor setting data that is data indicating the positions of the plurality of anchors by referring to a specific storage unit; acquiring, via the communication circuit, an inter-anchor ranging result that is a result of the specific anchors performing ranging communication with each other, or a detection result of an object detection sensor associated with the object; and determining the position of the specific object based on the acquired inter-anchor ranging result or detection result. The method includes determining whether a reflective object exists in an area, and if it is determined that a reflective object exists in the target area, specifying a reflective object distance, which is the distance between the target object and the reflective object, having multiple anchors perform ranging communication with the mobile device to obtain multiple sets of distance measurement values ​​indicating the distance from each of the multiple anchors to the mobile device, and if it is determined that a reflective object exists in the target area, calculating a tentative device position, which is a tentative position of the mobile device, using the multiple sets of distance measurement values ​​and position information of the multiple anchors, and verifying the validity of the tentative device position based on the relationship between the area where a reflective object may exist, which is determined from the reflective object distance, and the tentative device position.

[0010] According to the above technology, when a reflector is detected in a predetermined target area, the validity of the tentative device position is determined based on the tentative device position and the distance to the reflector. This reduces the risk of an incorrect tentative device position being adopted as the mobile device's position. In other words, it reduces the risk of erroneously determining the mobile device's position.

[0011] Note that the symbols in parentheses in the claims indicate a correspondence with the specific means described in the embodiments described below as one aspect, and do not limit the technical scope of the present disclosure.

[0012] 1 is a diagram showing the overall configuration of a vehicle electronic key system. FIG. 2 is a block diagram showing the configuration of an in-vehicle key system and a portable device. FIG. 3 is a diagram showing an example of an LE antenna. FIG. 4 is a diagram showing the mounting position of an anchor. FIG. 5 is a flowchart of an environment determination process. FIG. 6 is a diagram for explaining a method of calculating the distance to a reflecting object. FIG. 7 is a diagram showing a boundary line and a recalculation area set based on the reflecting object distance. FIG. 8 is a flowchart of a position identification process. FIG. 9 is a diagram showing an example of a case where the device position is erroneously determined due to reflection. FIG. 10 is a diagram showing an overview of a positioning calculation process using a second method. FIG. 11 is a flowchart showing another example of the operation of a DK-ECU. FIG. 12 is a flowchart showing another example of the operation of a DK-ECU. FIG. 13 is a diagram showing an example of a configuration including multiple LE antennas. FIG. 14 is a diagram showing another example of a configuration including multiple LE antennas. FIG. 15 is a block diagram showing another example of the configuration of an in-vehicle key system and a portable device.

[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 modified in various ways without departing from the spirit of the present disclosure. Various modified examples may be appropriately combined as long as no technical contradictions arise. The present disclosure also includes configurations that are not explicitly stated and are formed by combining multiple modified examples. In the following description, components having the same function may be given the same reference numerals, and specific descriptions thereof may be omitted. Furthermore, components having the same function may be given the same or similar names, and specific descriptions thereof may be omitted. When only a portion of a configuration is mentioned, descriptions given elsewhere may apply 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 illustrating an example of the schematic configuration of a vehicle electronic key system. As shown in FIG. 1, the vehicle electronic key system includes a 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 hybrid vehicle. Information about the portable device 9 (e.g., a device ID) is pre-registered in the vehicle key system 1. The portable device 9 may be interpreted as a communication device that is pre-registered in the vehicle key system 1 as a key for the vehicle hybrid vehicle.

[0015] As shown in Figures 1 and 2, the vehicle key system 1 includes a digital key ECU (hereinafter referred to as DK-ECU) 2 and multiple anchors 3. ECU stands for Electronic Control Unit. DK stands for Digital Key. Information about the portable device 9 may be registered in the DK-ECU 2.

[0016] The vehicle key system 1 and the portable device 9 are configured to be able to perform short-range communication with each other according to a predetermined communication protocol. The short-range communication is communication that complies with a predetermined short-range wireless communication standard, with a practical communication distance of 1 m to 30 m, and up to approximately 100 m. In this embodiment, the short-range communication method is Bluetooth (registered trademark) Low Energy (hereinafter, Bluetooth LE). Communication that complies with the Bluetooth LE standard will also be referred to as LE communication below. LE communication uses multiple channels (Ch 0 to 39) in the 2.4 GHz band. Hereinafter, the term LE signal refers to a wireless signal transmitted and received via LE communication.

[0017] The LE signal includes information indicating the sender or destination. The sender and destination of the LE signal may be expressed, for example, by a device ID. The DK-ECU 2 and the portable device 9 are paired in advance and each holds its own device ID. The anchor 3 and the portable device 9 perform ranging communication using the LE signal. Ranging communication is communication that measures the distance between communication devices. Details of ranging communication will be described separately later. The terms short-range communication and LE communication may be replaced with SRWC (Short Range Wireless Communication). The LE signal may be replaced with the SRWC signal.

[0018] <Portable Device> As described above, the portable device 9 is a communication device equipped with an LE communication function. The portable device 9 of this embodiment is a dedicated communication device (hereinafter also referred to as a dedicated device) that serves as an electronic key for the vehicle Hv. The dedicated device is a communication device that is transferred to the owner along with the vehicle Hv when the vehicle Hv is purchased. The dedicated device can be considered one of the accessories of the vehicle Hv. The dedicated device as the portable device 9 may be called a smart key, a vehicle portable device, a key device, a key fob, a key card, an access key, etc.

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

[0020] 2 , the portable device 9 includes a device controller 91 and an LE module 92. The portable device 9 also includes a circuit board 99. The device controller 91 is configured as a computer including a processor 911, a memory 912, a storage 913, an input / output circuit, etc. Electronic components that configure the portable device 9 may be mounted on the circuit board 99.

[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, a key code used in the authentication process with the DK-ECU 2, and the like. 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 (Micro Controller 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 (here, the 2.4 GHz band). The portable device 9 of this embodiment includes one LE antenna 921 as shown in Fig. 3. The LE antenna 921 may be patterned on a circuit board 99 included in the portable device 9. As a method for patterning the LE antenna 921 on the surface of the circuit board 99, various methods can be used, such as electroplating, metal vapor deposition, or application of conductive paint.

[0024] The LE antenna 921 may be a monopole antenna, an inverted-L antenna, an inverted-F antenna, etc. In FIG. 3 , the LE antenna 921 is illustrated as an inverted-L antenna. The inverted-L antenna serving as the LE antenna 921 may be arranged along a corner of the circuit board 99.

[0025] When the LE antenna 921 is formed along the circuit board 99, the LE antenna 921 handles linearly polarized waves whose electric field vibration direction is parallel to the circuit board 99. In other words, the LE antenna 921 does not have a polarization plane whose electric field vibration direction is perpendicular to the circuit board 99. Hereinafter, linearly polarized waves whose electric field vibration direction is perpendicular to the circuit board 99 will be referred to as substrate vertical polarization. Furthermore, linearly polarized waves whose electric field vibration direction is parallel to the circuit board 99 will be referred to as substrate horizontal polarization. As shown in FIG. 3 , the LE antenna 921 formed as a pattern on the circuit board 99 operates as an antenna that handles substrate parallel polarization.

[0026] Polarized waves whose electric field oscillation direction is perpendicular to the surface of the human body tend to travel around the human body. However, as described above, the portable device 9 of this embodiment is configured so that the portable device 9 does not transmit or receive substrate-vertically polarized waves. This configuration in which the portable device 9 does not handle substrate-vertically polarized waves can reduce the propagation of LE signals along the surface of the human body when the portable device 9 is placed in a back pocket. In other words, the difference in reception strength depending on whether or not a human body is present can become more pronounced. As a result, the accuracy of the positional relationship determination process described below can be improved.

[0027] 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 a signal received by the LE antenna 921 and provides the demodulated signal to the device controller 91. The RF core 922 also modulates transmission data input from the device controller 91 and radiates the data as radio waves from the LE antenna 921.

[0028] The RF core 922 is configured to be able to transmit and receive, using the LE antenna 921, a continuous wave (CW) signal for each channel as a function for CS (Channel Sounding) ranging (described later), in addition to modulated signals for data communication. The waveform of the CW signal may be a sine wave or a triangular wave. The RF core 922 also includes a reception strength detection unit and a reception phase detection unit. The reception strength detection unit is a functional unit that measures the reception strength of a received signal. The reception strength detection unit outputs data indicating the detected reception strength to the MCU 923. The measurement value of the reception strength itself may also be called RSSI (Received Signal Strength Indicator / Indication).

[0029] The reception phase detector is a circuit that detects the reception phase, which is the phase angle of the reception signal relative to the output signal of the local oscillator, when a CW signal is received. The reception phase may be the output value of the arctangent whose input value is the ratio of the Q (Quadrature-Phase) component to the I (In-Phase) component of the reception signal. The reception phase may also be determined based on an IQ signal whose frequency has been reduced to baseband. The detected reception phase information is used to calculate the distance, as described in the CS ranging section.

[0030] The RF core 922 outputs the detected value of the reception phase of the CW signal in association with information indicating the frequency in use (e.g., a channel number) to the MCU 923. The RF core 922 switches from the data communication mode to the CS ranging mode based on, for example, an instruction from the MCU 923, and transmits the CW signal while switching the frequency in use 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 the transmission or reception of the CW signal is performed.

[0031] The MCU 923 exchanges data between the RF core 922 and the device controller 91. The MCU 923 processes data input from the RF core 922 and outputs the data to the device controller 91. The MCU 923 inputs a baseband signal corresponding to the transmission data input from the device controller 91 to the RF core 922, thereby causing the RF core 922 to transmit the data wirelessly.

[0032] The MCU 923 also switches the operating mode of the RF core 922 under the control of the device controller 91. For example, the MCU 923 switches the RF core 922 from data communication mode to CS ranging mode, or vice versa. The MCU 923 may also have a function to calculate a ranging value based on the reception phase for each channel observed in CS ranging. The MCU 923 may transmit data indicating the measured reception strength together with transmission 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, when the portable device 9 is not connected to the DK-ECU 2, the device controller 91 uses the LE module 92 to perform LE advertising. Advertising is a process of transmitting an advertising signal using a predetermined channel. The advertising signal is a wireless signal for notifying other devices of its presence. When the DK-ECU 2 receives an advertising signal from the portable device 9, it may transmit a connection request in response. When the device controller 91 receives a connection request from the DK-ECU 2, the LE module 92 communicatively connects the LE module 92 to the DK-ECU 2. Based on the communication connection with the vehicle key system 1, the device controller 91 may perform authentication processing, ranging communication, and the like using LE communication. The wireless authentication processing may be performed, for example, using a challenge-response method.

[0034] <DK-ECU> The DK-ECU 2 is connected to an in-vehicle network that is constructed as a communication network within the vehicle Hv. Standards for in-vehicle networks include Controller Area Network (CAN: registered trademark), Ethernet (registered trademark), and FlexRay (registered trademark). The DK-ECU 2 is connected to each of the multiple anchors 3 via the in-vehicle network or via a dedicated communication cable. The DK-ECU 2 is mounted at any position in the vehicle Hv.

[0035] The DK-ECU 2 controls multiple anchors 3. The DK-ECU 2 functions as a location identification device that identifies the location of the portable device 9 (hereinafter referred to as the device location) in cooperation with the multiple anchors 3. The device location refers to the relative location of the portable device 9 with respect to the vehicle Hv. Because the portable device 9 is linked to a user, determining the device location corresponds to determining the user location. The DK-ECU 2 may be configured to unlock the vehicle Hv when it determines that the portable device 9 is present in an entry area that is preset for the vehicle Hv and receives a predetermined unlocking operation. The entry area may be an area within a predetermined distance (e.g., 1.5 m) from the vehicle Hv.

[0036] The DK-ECU 2 includes a gateway module 21, an in-vehicle communication circuit 22, and a main controller 23. Hereinafter, the term "gateway" may be abbreviated to "GW." For example, a "GW module" refers to a gateway module.

[0037] The GW module 21 is a communication module provided in the DK-ECU 2 and configured to be able 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 supply is set to off. The GW module 21 is in a standby state constantly or intermittently using the power supplied from the vehicle battery even while the vehicle Hv is parked. The GW module 21 periodically scans and attempts to connect to the portable device 9.

[0038] The GW module 21 may include a GW controller 211, which is a microcomputer that executes processing related to LE communication. The GW controller 211 controls the exchange of data with the main controller 23. Upon connection with the portable device 9, the GW controller 211 performs procedures such as starting encrypted communication with the connected device. The connected device here refers to the portable 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-ECU 2. The GW module 21 may be provided outside the DK-ECU 2. In this case, the GW module 21 and the DK-ECU 2 may be connected to each other so as to be able to communicate with each other via a dedicated communication line or an in-vehicle network.

[0039] 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 a cable connector that comply with the communication method of the anchor 3. The in-vehicle communication circuit 22 converts signals input from the anchor 3 into a format that can be received by the main controller 23, and outputs the signals 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 the data to the anchor 3.

[0040] The main controller 23 is hardware that controls the operation of the DK-ECU 2. The main controller 23 includes a processor 231, a memory 232, a storage 233, an input / output circuit, etc. The storage 233 stores a location identification program that causes the processor 231 to execute processing related to identifying the device location.

[0041] The main controller 23 functions as a computer that executes various processes related to identifying the device location by the processor 231 executing the location identification program. Execution of the location identification program by the processor 231 corresponds to execution of a location identification method.

[0042] The functions of the DK-ECU 2 described below are basically provided by the main controller 23. In other embodiments, the main controller 23 may be integrated into the GW controller 211. The GW controller 211 may be configured to control the anchor 3 and execute processes related to determining the device position. The functional layout within the vehicle key system 1 may be changed as appropriate. The DK-ECU 2, the main controller 23, or the GW controller 211 corresponds to the control unit. The vehicle key system 1 corresponds to the location identification system.

[0043] <Anchor> The anchor 3 is a wireless communication module used to identify the device location. The anchor 3 is configured to be able to perform LE communication. The general configuration of the anchor 3 may be the same as that of the LE module 92. The anchor 3 includes an LE antenna, an RF core, an MCU, and the like. Note that the anchor 3 only needs to be configured to be able to perform CS ranging, and the anchor 3 does not need to have a data communication mode.

[0044] Based on an instruction from the DK-ECU 2, the anchor 3 performs CS ranging communication, which is a type of ranging communication, with the portable device 9. Based on an instruction from the DK-ECU 2, the anchor 3 also performs CS ranging communication with other anchors 3.

[0045] CS ranging is a method of measuring distance based on the difference in reception phase for each channel, which is obtained by transmitting and receiving CW (Continuous Wave) signals on multiple channels. CS ranging is sometimes called High Accuracy Distance Measurement (HADM) or multi-channel phase difference ranging. CS ranging involves performing bidirectional or unidirectional communication of CW signals on multiple channels to obtain the reception phase for each channel as a distance-related value. CS ranging communication may be understood as wireless communication performed as part of CS ranging. The distance-related value is a parameter indicating the length of the propagation path of the LE signal from the mobile device 9 to the anchor 3.

[0046] In this embodiment, the anchor 3 acquires the reception phase for each channel during CS ranging with the portable device 9, and calculates the device distance, which is the distance to the portable device 9, based on the reception phase. Furthermore, in CS ranging with another anchor 3, the anchor 3 acquires the reception phase for each channel, and calculates the inter-anchor distance, which is the distance to the other anchor 3, based on the reception phase. The device distance and the inter-anchor distance are also collectively referred to as the target distance. The reception phase is the phase difference between the CW signal transmitted by the portable device 9 and the CW signal received by the GW module 21. The reception phase can be called the transmission / reception phase difference, the single-frequency phase difference, or the first-order phase difference.

[0047] The anchor 3 may acquire the reception phase for each channel using, for example, a one-way method. The one-way method is a method in which, on the premise that the initial phase of the CW signal for each channel transmitted from the portable device 9 is constant, the reception phase of the CW signal transmitted from the portable device 9 is directly used as material for calculating the inter-frequency phase difference. Details of CS ranging will be described later. Note that the reception phase (in other words, single-frequency phase difference) used as material for calculating the inter-frequency phase difference can also be acquired using a passive two-way method, an active two-way method, or the like.

[0048] The MCU of the anchor 3 performs CS ranging communication with the mobile device 9 / other anchor 3 based on instructions from the DK-ECU 2, and acquires the reception phase for each channel from the RF core.The MCU then calculates the distance to the communication partner based on the data indicating the reception phase for each channel and transmits the calculated distance to the DK-ECU 2.

[0049] <Anchor Position> As shown in FIG. 4, the vehicle Hv is equipped with a plurality of anchors 3A, 3B, 3C, 3D, 3P, and 3Q. The number of anchors 3 equipped on the vehicle Hv and the arrangement of each anchor 3 may be changed as appropriate for each vehicle model. The configurations, functions, and performance of the plurality of anchors 3A to 3D, 3P, and 3Q may be substantially the same. Of the plurality of anchors 3, anchors 3A to 3D are outdoor units or exterior anchors, and are attached to the exterior surface of the vehicle Hv. In contrast, anchors 3P and 3Q are indoor units or interior anchors, and are attached to the interior of the vehicle Hv.

[0050] The anchor 3A is disposed at the left front corner of the vehicle Hv. Specifically, the anchor 3A is disposed near the left front wheel, at the left end of the front bumper, at the left side mirror, etc. Such an anchor 3A may be referred to as a left front anchor, etc. The anchor 3B is disposed at the right front corner of the vehicle Hv. Specifically, the anchor 3B is disposed near the right front wheel, at the right end of the front bumper, and at the right side mirror, etc. Such an anchor 3B may be referred to as a right front anchor, etc.

[0051] Anchor 3C is disposed at the right rear corner of vehicle Hv. Specifically, anchor 3C is disposed near the right rear wheel and at the right end of the rear bumper, etc. Such anchor 3C may be referred to as a right rear anchor, etc. Anchor 3D is disposed at the left rear corner of vehicle Hv. Specifically, anchor 3D is disposed near the left rear wheel and at the left end of the rear bumper, etc. Such anchor 3D may be referred to as a left rear anchor, etc.

[0052] Anchor 3P and anchor 3Q are arranged offset in the front-to-rear direction in the vehicle interior. Anchor 3P is mounted forward of anchor 3Q. Specifically, anchor 3P is arranged on the instrument panel, the upper edge of the windshield, the center console, etc. Anchor 3P may be referred to as an interior front anchor, etc. On the other hand, anchor 3Q is mounted rearward of anchor 3P. Specifically, anchor 3Q is arranged on the center of the rear seat, the ceiling above the rear seat, the trunk, etc. Anchor 3Q may be referred to as an interior rear anchor, etc.

[0053] Hereinafter, 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 an anchor pair associated with the right area of ​​the vehicle Hv. The second pair is an anchor pair associated with the left area of ​​the vehicle Hv. The third pair is an anchor pair associated with the rear area of ​​the vehicle Hv. The fourth pair is an anchor pair associated with the front area of ​​the vehicle Hv. Unless otherwise noted, the terms front, rear, left, and right below mean the front, rear, left, and right of the vehicle Hv (i.e., basically).

[0054] The right area may be a range on the right side of the vehicle Hv that is within a predetermined distance (for example, 5 m) from the vehicle Hv. The left area may be a range on the left side of the vehicle Hv that is within a predetermined distance (for example, 5 m) from the vehicle Hv. The rear area may be a range within 2 m from the rear end of the vehicle Hv. The front area may be a range within 2 m from the front end of the vehicle Hv. The specific range of each area may be changed as appropriate. Each area is determined outside the vehicle Hv and based on the vehicle Hv. The right area, etc., corresponds to the target area.

[0055] As will be described later, the first pair is used to determine whether there is a reflective object on the right side of the vehicle Hv, i.e., to determine the environment in the right area. The second, third, and fourth pairs are also used to determine the environments in the left area, rear area, and front area.

[0056] Here, the term "reflecting object" refers to a wall- or plate-like three-dimensional object that faces the vehicle Hv. The reflecting object is made of a material that reflects radio waves, such as concrete or metal. Specifically, the reflecting object may be a relatively large reflector with a substantially flat surface, such as a wall or the side of another vehicle. A relatively large reflecting object may be understood to be an object with a width of 1 m or more. A wall- or plate-like three-dimensional object may include a metal partition or divider. In this disclosure, the term "reflecting object" may be replaced with "wall," "other vehicle," "large reflector," etc. When such a reflecting object is present on the side of the vehicle Hv facing the vehicle Hv, the reflected wave may be dominant over the direct wave. Here, the direct wave refers to a signal that arrives without being reflected by an object such as a wall, the ground, the ceiling, or another vehicle. The direct wave may also include a diffracted wave, which is a signal that arrives by deflection (diffraction). Hereinafter, a situation in which a reflecting object such as a wall or another vehicle exists around the vehicle Hv is also referred to as a "reflective environment." Determining the environment corresponds to determining whether or not a reflective object is present, in other words, whether or not the environment is reflective.

[0057] <Anchor Setting Data> Anchor setting data is stored in the storage 233 of the main controller 23. The anchor setting data indicates the mounting position of each anchor 3 in the vehicle Hv. The mounting position of each anchor 3 may be expressed in a two-dimensional coordinate system in which the longitudinal direction of a given vehicle Hv is the X-axis and the width direction is the Y-axis. The storage 233 corresponds to a memory unit.

[0058] The anchor setting data may also include actual values ​​of the inter-anchor distance for each combination of anchors 3. The inter-anchor distance means the distance from one anchor 3 to another anchor 3. The actual value of the inter-anchor distance may be a design value of the inter-anchor distance 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 a value measured by each anchor pair actually performing ranging communication in a so-called line-of-sight environment where there are no reflective objects around the vehicle Hv. The anchor setting data may include actual values ​​of the inter-anchor distances for the first to fourth pairs.

[0059] The coordinates of the mounting position of each anchor 3 are data that indirectly indicate the inter-anchor distance and are data that can identify the inter-anchor distance. Data indicating the actual inter-anchor distance does not necessarily have to be stored in the storage 233. The DK-ECU 2 may be configured to calculate the actual inter-anchor distance from the position coordinates of each anchor 3 included in the anchor setting data and use the calculated value for the environment determination process, which will be described later.

[0060] <CS Ranging> This section describes CS ranging performed between the vehicle key system 1 and the portable device 9. The series of processes for CS ranging (hereinafter referred to as CS ranging process) includes a phase collection phase and a calculation phase. The phase collection phase is a phase in which the reception phase is collected by actually transmitting and receiving a CW signal. Wireless communication for acquiring the phase difference between frequencies, such as transmitting and receiving a CW signal across multiple channels, corresponds to CS ranging communication. The calculation phase is a phase in which the distance is calculated based on the reception phase for each collected frequency.

[0061] The CS ranging process may include a preparation phase prior to the execution of CS ranging communication. For example, the GW module 21 communicates with the mobile device 9 to exchange and agree on ranging settings prior to the execution of CS ranging communication. The GW module 21 may transmit the ranging settings based on the establishment of a communication connection with the mobile device 9. The ranging settings are an LE signal indicating parameters related to the execution of communication for CS ranging. The parameters related to the execution of ranging communication may include at least one of a setting value of an initial phase, a hopping interval, a channel transition amount, an initial channel, and a ranging start time.

[0062] The initial phase setting value specifies the initial phase when transmitting a CW signal. The initial phase may basically be set to 0. The hopping interval represents the time required to switch channels, in other words, the time required to maintain one channel. The hopping interval may be the same as the connection interval used for data communication. The channel transition amount is a parameter indicating the amount of channel change when switching channels. The channel transition amount may be the same value as the hop increment used for data communication, or may be a different value. The initial channel specifies the channel of the CW signal to be transmitted first in a series of ranging communications. The initial channel can be determined randomly. Information on the channel (frequency) used for communication may be expressed, for example, by a channel number. The ranging start time is a parameter that specifies the timing at which transmission and reception of a CW signal actually begins. The ranging start time may be the waiting time, such as 200 milliseconds or 400 milliseconds, from the completion of the preparation phase until the start of transmission and reception of a CW signal on the initial channel.

[0063] Upon receiving the ranging configuration, the mobile device 9 returns an Ack to the GW module 21. The preparation for CS ranging communication may be completed by the return of the Ack from the mobile device 9. Upon receiving the Ack from the mobile device 9, the GW module 21 distributes the ranging configuration to each anchor 3.

[0064] The anchor 3 transitions to a state of waiting for a signal on the initial channel according to the ranging start time determined by the ranging setting. The portable device 9 starts transmitting a CW signal on the initial channel when a predetermined time has elapsed since returning the Ack. After the ranging start time, the anchor 3 and the portable device 9 transmit and receive CW signals while switching channels at regular intervals. The anchor 3 and the portable device 9 may start CS ranging communication when they receive a predetermined ranging start signal from the DK-ECU 2.

[0065] The transmission of a CW signal on one channel may be stopped, for example, after a certain time has elapsed since the start of transmission. When the anchor 3 receives a CW signal from the mobile device 9, it detects the reception phase based on the IQ signal and stores this reception phase data in memory together with frequency information (e.g., channel number). The CW signal transmitted by the mobile device 9 may be received in parallel by multiple anchors 3. Each of the multiple anchors 3 may receive the CW signal transmitted from the mobile device 9 in accordance with the ranging settings and collect the reception phase for each channel.

[0066] The anchor 3 and the portable device 9 may repeatedly switch channels and transmit and receive CW signals until they have collected reception phases for all channels available for LE communication. The GW module 21 and the portable device 9 may terminate the repetitive process when they have collected a predetermined number of reception phases for each channel. The required number here may be the same as or smaller than the number of data channels. The required number may be set to 37, which is the number of channels available for data communication. The greater the number of channels from which reception phases are collected, the higher the ranging accuracy described below. However, the time and power consumption required for ranging communication may increase. The required number may be 5, 16, 32, or the like. For example, if the number of channels available for LE communication is 80, the required number may be set to 80.

[0067] The GW module 21 or any of the anchors 3 may transmit a ranging end notification to the portable device 9 when it has collected the reception phases of a necessary and sufficient number of channels. The ranging end notification is a data signal for notifying that ranging communication is to be terminated. Upon receiving the ranging end notification, the portable device 9 may transition to a normal data communication mode. The normal data communication mode corresponds to a state in which data such as voice data, rather than a CW signal, can be transmitted and received. The transmission and reception of the ranging end notification is an optional element and may be omitted.

[0068] When the anchor 3 completes collection of the reception phase for each channel, it calculates a phase change coefficient (α) in step S111. The phase change coefficient is a parameter that indicates the degree to which the reception phase changes in response to a change in frequency. The phase change coefficient can also be called the phase change degree, the phase shift amount, or the correlation coefficient between phase and frequency.

[0069] The phase change coefficient is calculated based on the reception phase observed at two arbitrary frequencies, a first frequency and a second frequency, for example. If the difference frequency between the first and second frequencies is Δf, the inter-frequency phase difference between the reception phases observed at the first and second frequencies is Δφ, and the phase change coefficient is α, then the relationship is α = Δφ / Δf. The inter-frequency phase difference (Δφ) is the difference between the reception phases observed at two different frequencies. The inter-frequency phase difference can also be called a two-frequency phase difference or a quadratic phase difference. The inter-frequency phase difference corresponds to the amount of phase angle shift due to a change in the frequency used.

[0070] The anchor 3 of this embodiment calculates a regression line indicating the relationship between frequency and reception phase based on the reception phase for each frequency, and uses 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 reception phase relative to the amount of frequency shift. The regression line and its slope can be calculated using various methods, such as the least squares method. If the regression line is expressed as y = ax + b, the coefficient a of x corresponds to the slope of the regression line. In other words, the anchor 3 can calculate the coefficient (a) as the phase change coefficient (α). Here, x is a variable parameter representing frequency, and y is a variable parameter representing reception phase. A configuration that uses the regression line to calculate the phase change coefficient enables calculation of a more accurate phase change coefficient. The regression line can also be referred to as an approximation line.

[0071] The anchor 3 may calculate the inter-frequency phase difference (Δφ), the differential frequency (Δf), and the tentative phase coefficient (Δφ / Δf) for each combination of frequencies for which the reception phase can be observed. The anchor 3 may use the average value or median value of the tentative phase coefficients for each combination of frequencies as the phase change coefficient to be used in distance calculation.

[0072] In this step, anchor 3 calculates the device distance (D) using the phase change coefficient (α) after calculating it. If the device distance is D, there is a relationship between the differential frequency Δf and the inter-frequency phase difference (Δφ): D∝C Δφ / (2π Δf) = C α / 2π. The parameter "C" in the above equation indicates the propagation speed of radio waves (3 x 10^8 m / sec). Anchor 3 calculates the device distance based on this relational equation.

[0073] For example, the anchor 3 calculates the device distance using Equation 1: D = k C α / 2π. The parameter k in Equation 1 is a design value that is set to 1.0 or 0.5. The value of k may be determined depending on whether the transmission and reception phase difference is calculated as a phase change coefficient for one way or a round trip.

[0074] The anchor 3 transmits the calculated device distance to the DK-ECU 2. In the present disclosure, the device distance calculated as a result of ranging communication may also be referred to as a distance measurement value. If the anchor 3 is unable to receive a signal from the portable device 9 during ranging communication, the anchor 3 may output an error value, which is a specific value indicating that measurement was not possible, as the distance measurement value. The error value may be, for example, Nan (Not a Number). The error value may be a sufficiently large predetermined value. The error value may also be an error code, etc. Note that phase information such as the phase change coefficient (α) corresponds to the distance. Therefore, the anchor 3 may transmit a phase change coefficient or a data set of the reception phase for each channel to the DK-ECU 2 as a result of CS ranging communication. The process of converting the phase change coefficient or the reception phase information for each channel into the device distance may be performed by the DK-ECU 2.

[0075] In addition to the distance measurement value, the anchor 3 may transmit data on the reception strength of the signal received from the portable device 9 (hereinafter also referred to as the device signal) to the DK-ECU 2. Hereinafter, the reception strength of the device signal observed by the anchor 3 will also be referred to as the device signal strength. The device signal strength may be the magnitude of the IQ signal. The reception strength reported to the DK-ECU 2, in other words, the reception strength used by the DK-ECU 2 for the determination described below, may be the maximum value of the reception strength for each channel. Furthermore, if the anchor 3 has multiple antennas, the maximum value of the reception strength for each antenna may be provided to the DK-ECU 2.

[0076] In CS ranging in the one-way system, the anchor 3 can calculate the distance measurement 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 receive (sniffer) the CW signal emitted from the portable device 9 in parallel to collect phase information and calculate the distance.

[0077] In other embodiments, each anchor 3 may individually perform CS ranging communication with the mobile device 9. For example, when an active two-way system is adopted, multiple anchors 3 may individually perform CS ranging communication with the mobile device 9. Not only the anchors 3, but also the GW module 21 may be configured to perform CS ranging.

[0078] CS ranging communication between anchors 3 may also be performed using a procedure similar to that described above. For convenience, ranging communication between anchors 3 is referred to as inter-anchor ranging communication. Inter-anchor ranging communication may be one-way CS ranging communication. In inter-anchor ranging communication, the DK-ECU 2 (GW module 21) can determine the ranging settings independently. Furthermore, the ranging settings for inter-anchor ranging communication may be pre-designed settings. The combination of anchors 3 performing ranging communication and their role allocation (initiator / reflector) may be determined by the DK-ECU 2. An initiator in CS ranging may be understood as a device responsible for collecting reception phases and calculating ranging values. An initiator in CS ranging may be understood as a device responsible for transmitting CW signals to the initiator.

[0079] <Environment Determination Process> The DK-ECU 2 executes the environment determination process shown in Fig. 5 at a predetermined timing. The environment determination process is a process for determining whether or not a reflective object such as a wall exists in the target area. If it is determined that a reflective object exists, the environment determination process may include estimating the distance to the reflective object and setting a recalculation area CA based on the estimation result.

[0080] The recalculation area CA is an area used to determine whether the device position needs to be calculated using a second method different from the basic first method. As will be described later, if the tentative device position calculated using the first method is within the recalculation area CA, the device position is recalculated using the second method. The recalculation area CA is an area where a reflecting object is expected to exist, and is an area where the calculated device position is inappropriate. The term "recalculation area CA" may be replaced with expressions such as an obstacle presence area or an invalid area.

[0081] The timing for executing the environment determination process may be when communication is established with the portable device 9. The DK-ECU 2 may also execute the environment determination process when the vehicle Hv is parked. The DK-ECU 2 may be configured to execute the environment determination process periodically (for example, every 20 minutes) while the vehicle Hv is parked.

[0082] The following describes a case where a reflective object is determined to exist in the right area using anchors 3B and 3C as a first pair. One of the two anchors 3 associated with the target area corresponds to the first anchor, and the other corresponds to the second anchor. The DK-ECU 2 may also be configured to determine whether a reflective object exists on the left side, rear, and front of the vehicle Hv. The environment determination in each direction may be performed using an anchor pair associated with the area to be determined. For example, the determination of whether an obstacle exists in the left area may be performed using anchors 3A and 3D that form a second pair.

[0083] The environment determination process generally includes steps S101 to S110. The DK-ECU 2 that executes the following process may be replaced with the vehicle key system 1, the main controller 23, the processor 231, the gateway controller 211, etc. The functional layout of the vehicle key system 1 may be changed as appropriate, and the vehicle key system 1, the DK-ECU 2, the main controller 23, the processor 231, and the gateway controller 211 may be replaced with each other.

[0084] Step S101 is a step in which the DK-ECU 2 causes the anchors 3 associated with the target area to perform ranging communication. In this example, the anchors 3 associated with the target area are anchors 3B and 3C. In step S101, ranging communication between the anchors in the first pair is performed. For example, the DK-ECU 2 notifies the anchors 3B and 3C that make up the first pair of ranging settings, and then transmits a ranging start instruction. The ranging settings may include information specifying the role assignment in ranging communication, for example, the anchor 3 that will play the role of initiator.

[0085] When the distance measurement communication between anchors 3B and 3C is completed, the DK-ECU 2 acquires a distance measurement value from anchor 3B, anchor 3C, or both in step S102. The distance measurement value here is the distance measurement value from anchor 3B to anchor 3C, and corresponds to the measured value of the distance between anchors. The distance measurement value obtained as a result of distance measurement communication between specific anchors 3 corresponds to the inter-anchor distance measurement result.

[0086] When the DK-ECU 2 acquires the measured value of the inter-anchor distance for the combination of anchors 3B and 3C, in step S103, it reads the actual value of the inter-anchor distance for the combination of anchors 3B and 3C from the storage 233. Then, in step S104, the DK-ECU 2 determines whether the measured value is greater than the actual value by a predetermined value or more.

[0087] S104 corresponds to a step of determining whether a reflecting object is present in a predetermined determination area set on the right side of the vehicle by comparing the measured value with the actual value. The developers of the present disclosure have found through testing that when a wall-like reflecting object is present in the right area, the measured value of the distance between anchors may be larger than when no reflecting object is present. Furthermore, this measured value indirectly represents the distance to the reflecting object. S104 was created based on this finding.

[0088] For example, if the measured value is Lo and the actual value is Ld, the DK-ECU 2 calculates the distance difference ΔL based on the formula ΔL = Lo - Ld. Then, using a predetermined threshold ThL, it determines whether ΔL ≧ ThL holds. The threshold ThL may be set to absorb accidental measurement errors and increases in distance due to vehicle turning. For example, the threshold ThL may be set to 0.5 m. ΔL ≧ ThL holds when the measured value is greater than the actual value by the threshold or more.

[0089] If ΔL≧ThL is established (YES in S104), the DK-ECU 2 sets the reflection object flag to ON in step S105. The reflection object flag is a flag that indicates whether or not a reflection object is present. For example, when the reflection object flag is ON (1), it means that it is determined that a reflection object is present. When the reflection object flag is OFF (0), it means that it is not determined that a reflection object is present, in other words, it means that it is determined that a reflection object is not present. A reflection object flag may be prepared for each of the front, rear, left, and right areas. Here, an example is given of determining the environment of the right area, so the reflection object flag may be interpreted as a reflection object flag for the right area.

[0090] The processing from step S104 to step S105 corresponds to a configuration in which the DK-ECU 2 determines that a reflecting object is present in the right-hand area based on the fact that the measured value is greater than the actual value by a predetermined value or more. When the DK-ECU 2 determines that a reflecting object is present in the right-hand area, it calculates the reflecting object distance L in step S106. The DK-ECU 2 of this embodiment calculates the reflecting object distance L based on, for example, the measured value of the distance between the anchors.

[0091] If the measured distance corresponds to the path length of the reflected wave, the measured distance is likely to correspond to the shortest path among various reflection paths. Therefore, the path of the reflected wave corresponding to the measured distance may be symmetric between the outbound and inbound paths, as shown in FIG. 6 . That is, the path of the reflected wave corresponding to the measured distance and the line segment connecting anchors 3B and 3C may form an isosceles triangle with the line segment connecting anchors 3B and 3C as its base. Based on this assumption, the DK-ECU 2 can determine the distance L to the reflecting object using the measured value of the distance between the anchors (Lo) and the actual distance (Ld) according to Pythagoras' theorem. That is, the DK-ECU 2 determines the distance L to the reflecting object by solving the relational expression L = √{(Lo / 2)^2 - Ld^2}. Hereinafter, the assumed distance L from the vehicle Hv to the reflecting object will also be referred to as the reflecting object distance L. Note that the reflecting object is indicated by "WL" in FIG. 6 .

[0092] After calculating the reflector distance L, the DK-ECU 2 sets a recalculation area CA using the reflector distance L in step S107. The DK-ECU 2 may set the recalculation area CA to an area whose distance from the right side of the vehicle Hv is equal to or greater than the reflector distance L. Specifically, as shown in FIG. 7 , the DK-ECU 2 sets a virtual line VL, which is a straight line parallel to the longitudinal direction of the vehicle Hv, at a position on the right side of the vehicle Hv that is the reflector distance L to the right from a predetermined reference point P. The virtual line VL corresponds to the outline of the reflector. The DK-ECU 2 then sets the recalculation area CA to an area on the opposite side of the vehicle Hv from the virtual line VL. The reference point P may be the midpoint between the anchors 3B and 3C. The reference point P may also be the location of the door handle or the B-pillar in a top view. In FIG. 7 , the recalculation area CA is indicated by hatching using a dot pattern.

[0093] When the setting of the recalculation area CA is completed, the DK-ECU 2 stores the reflective object flag and the data of the recalculation area CA in the storage 233 or the like in step S107, and ends the flow. Step S107 corresponds to a step of updating environmental data, which is data indicating the determination result regarding the environment around the vehicle.

[0094] On the other hand, if ΔL<ThL (NO in S104), the DK-ECU 2 sets the reflective object flag to OFF in step S109. This step corresponds to the step of determining that no reflective object is present on the right side of the vehicle. After setting the reflective object flag to OFF, the DK-ECU 2 saves the setting value of the reflective object flag in the storage 233 and ends the flow. Step S110 also corresponds to the step of updating the environmental data.

[0095] The above describes the case where the DK-ECU 2 determines whether or not a reflective object exists in the right area based on the results of distance measurement communication from anchors 3B and 3C. The DK-ECU 2 may use other anchor pairs to determine whether or not a reflective object exists in other directions. The DK-ECU 2 may use the second anchor pair to perform environment determination processing for the left area. The DK-ECU 2 may use the third anchor pair to perform environment determination processing for the rear area. The DK-ECU 2 may use the fourth anchor pair to perform environment determination processing for the front area. The storage 233 may store environmental data for the front, rear, left, and right.

[0096] <Position Identification Process> The DK-ECU 2 executes the position identification process illustrated in FIG. 8 at a predetermined timing. The position identification process is a process for identifying the device position. Here, as an example, the identification of the device position involves calculating the position coordinates of the portable device 9 relative to the vehicle Hv. The device position may be expressed in a two-dimensional coordinate system with the vehicle longitudinal direction as the X axis and the vehicle width direction as the Y axis. The origin of the coordinate system may be set at any position, for example, the mounting position of the anchor 3B may be set as the origin.

[0097] The timing at which the DK-ECU 2 executes the location identification process may be, for example, the timing at which the GW module 21 establishes a communication connection with the portable device 9. That is, the DK-ECU 2 may execute the location identification process in response to the GW module 21 establishing a communication connection with the portable device 9. The DK-ECU 2 may execute the location identification process periodically (for example, every 400 milliseconds) while the GW module 21 establishes a communication connection with the portable device 9.

[0098] The DK-ECU 2 may execute the position identification process in response to a user action on the vehicle hybrid vehicle. A user action on the vehicle hybrid vehicle may also be referred to as an operation or instruction from the user on the vehicle hybrid vehicle. The user action may be an unlocking operation, a locking operation, opening or closing a door, pressing a start switch, etc. An unlocking operation is an operation for unlocking the vehicle hybrid vehicle. A locking operation is an operation for locking the vehicle hybrid vehicle. The user action may be detected based on an input signal from a door handle sensor, a courtesy switch, a start switch, a gesture sensor, a microphone, etc. The door handle sensor may be a touch sensor or a push switch provided on the outer door handle. The gesture sensor may be an infrared sensor, a photoelectric sensor, or a sonar for detecting the action of waving a foot under the door.

[0099] The position identification process includes steps S201 to S211. Step S201 is a step in which the DK-ECU 2 accesses the storage 233 and reads out environmental data. If no environmental data is stored, the DK-ECU 2 may execute an environmental determination process for all or part of the target area. Step S201 may be a step in which the DK-ECU 2 obtains data regarding the presence or absence of reflective objects around the vehicle Hv by reading out data or executing the environmental determination process.

[0100] Upon completion of step S201, the DK-ECU 2 causes all or some of the anchors 3 to perform CS ranging communication with the portable device 9. When the vehicle Hv is locked, the DK-ECU 2 may cause only exterior anchors, such as anchors 3A, 3B, 3C, and 3D, to perform CS ranging communication. Furthermore, when the vehicle Hv is locked, all exterior anchors and one interior anchor (e.g., anchor 3P) may perform CS ranging communication with the portable device 9. A locked vehicle Hv may be interpreted as being parked. The combination of anchors 3 that perform CS ranging communication may be determined depending on the situation. For example, when performing a location determination process in response to a touch on an exterior door handle on the right side, the DK-ECU 2 may cause only anchors 3B and 3C to perform CS ranging communication with the portable device 9. This is because the user is likely to be located on the right side of the vehicle Hv.

[0101] When the distance measurement communication between the multiple anchors 3 and the portable device 9 in step S202 is completed, the DK-ECU 2 acquires multiple sets of distance measurement values ​​as a result of the distance measurement communication from the multiple anchors 3. The multiple sets of distance measurement values ​​each have a different source (output source). For example, the distance measurement value received from anchor 3B and the distance measurement value received from anchor 3C correspond to an example of multiple sets of distance measurement values.

[0102] Then, in step S203, the DK-ECU 2 simply determines the device orientation based on the results of the distance measurement communication in step S202. The device orientation is the direction in which the portable device 9 is located as viewed from the vehicle Hv. The device orientation may be categorized into general directions such as front, rear, left, and right. The DK-ECU 2 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.

[0103] Specifically, the DK-ECU 2 compares multiple distance measurements to identify the nearest anchor and the near-neighbor anchor from among the multiple anchors 3. The nearest anchor is the anchor 3 that outputs the smallest distance measurement value. The near-neighbor anchor is the anchor 3 that outputs the second smallest distance measurement value. The DK-ECU 2 determines the device direction from the combination of the nearest anchor and the near-neighbor anchor.

[0104] For example, if the nearest anchor and the near-neighbor anchor are a combination of anchors 3B and 3C, the DK-ECU2 may determine the device direction to be right. If the nearest anchor and the near-neighbor anchor are a combination of anchors 3C and 3D, the DK-ECU2 may determine the device direction to be rearward. If the nearest anchor and the near-neighbor anchor are anchors 3A and 3D, the DK-ECU2 may determine the device direction to be left. If the nearest anchor and the near-neighbor anchor are anchors 3A and 3B, the DK-ECU2 may determine the device direction to be forward. If the nearest anchor is anchor 3B or 3C and the near-neighbor anchor is anchor 3P or 3Q, the DK-ECU2 may also determine the device direction to be right. Details of the method for determining the device direction may be changed as appropriate.

[0105] The following describes the case where it is determined that the device direction is to the right. In step S204 following step S203, the DK-ECU 2 refers to the environmental data read in step S201 and determines whether or not a reflective object is present in the device direction. If it is determined in step S203 that the device direction is to the right, in step S204 the DK-ECU 2 determines whether or not a reflective object is present in the right-hand area.

[0106] If the DK-ECU 2 does not determine that a reflective object is present on the right side (NO in S204), in step S205, it executes a process of calculating device position coordinates based on the distance measurement values ​​of multiple anchors 3. The device position coordinates can be calculated by multipoint positioning (for example, three-point positioning). Multipoint positioning is a method of obtaining the device position coordinates from the intersection of multiple circles (spheres in the case of three dimensions) with the mounting positions of each anchor 3 as the center and the distance measurement values ​​as the radius. The DK-ECU 2 calculates the device position coordinates based on the distance measurement values ​​of the multiple anchors 3 and the mounting positions of each anchor 3.

[0107] In principle, three or more anchors 3 are used in multipoint positioning. However, for the sake of simplicity and simplification of the calculation process, the case where the device position coordinates are determined using the distance measurement values ​​of two anchors 3 will be described here. When only two anchors 3 are used in multipoint positioning, two circles are generated. When only two anchors 3 are used in multipoint positioning, two candidate points for the device position, which are the intersections of the circles, may be generated. The DK-ECU 2 may adopt, as the device position, one of the two candidate points that matches the device orientation. For example, if the device orientation is determined to be right, and intersections P1 and P2 occur on the left and right sides of the vehicle Hv, the intersection located on the right side of the vehicle Hv may be considered the device position. Of course, the device position coordinates may be calculated using three or more anchors 3. Hereinafter, the process of calculating the device position coordinates using two or more anchors and the principles of multipoint positioning will also be referred to as the positioning calculation process. The positioning calculation process method in step S205 corresponds to the first method. The first method is a method of estimating the position by locating the center of a virtual circle at the mounting position of the anchor 3.

[0108] The DK-ECU 2 of this embodiment determines the combination of anchors 3 to be used in the positioning calculation process based on the device orientation. For example, if the device orientation is determined to be right-hand, the positioning calculation process is performed using anchors 3B and 3C. If the device orientation is determined to be left-hand, the positioning calculation process is performed using anchors 3A and 3D.

[0109] In this flow, since the device direction is determined to be right, in step S205, the device position coordinates are calculated using anchors 3B and 3C. That is, of the intersections P1 and P2 between the first circle C1 corresponding to anchor 3B and the second circle C2 corresponding to anchor 3C, the intersection P1 that matches the device direction is adopted as the device coordinate.

[0110] The first circle C1 corresponding to anchor 3B is a circle whose center is the mounting position (0,0) of anchor 3B and whose radius is the distance measurement value Db at anchor 3B. The first circle C1 is expressed as x^2 + y^2 = Db^2. The distance measurement value Db at anchor 3B corresponds to the first distance measurement value. The second circle C2 corresponding to anchor 3C is a circle whose center is the mounting position (Ld,0) of anchor 3C and whose radius is the distance measurement value Dc at anchor 3C. The second circle C2 is expressed as (x-Ld)^2 + y^2 = Db^2. The distance measurement value Dc at anchor 3C corresponds to the second distance measurement value. The coordinates of the intersection points P1 and P2 can be determined by solving these simultaneous equations.

[0111] On the other hand, if the DK-ECU 2 determines that a reflective object is present in the right-hand area (YES in S204), it calculates a provisional device position in step S206. The method for calculating the provisional device position may be the same as the positioning calculation process in step S205. That is, the DK-ECU 2 calculates the provisional device position using the first method. Step S206 corresponds to a step of determining device position coordinates by positioning calculation process using multiple (e.g., two) anchors 3 associated with the device direction, and treating the device position coordinates as the provisional device position.

[0112] Upon completion of the processing of step S206, the DK-ECU 2 determines in step S207 whether the tentative device position calculated in step S206 is located within the recalculation area CA set in the environment determination processing. For example, as shown in FIG. 9 , if the anchor 3C outputs a distance measurement value Dc derived from a wave reflected from a reflecting object rather than a direct wave, the radius of the second circle C2 corresponding to the anchor 3C will be greater than the straight-line distance from the anchor 3C to the portable device 9. As a result, the tentative device position TP may be located within the recalculation area CA. Paradoxically, if the tentative device position TP is located in the recalculation area CA, this means that the anchors 3 used in the positioning calculation processing include an anchor 3 that outputs a distance measurement value corresponding to the path of the reflected wave.

[0113] Generally, the intensity of the reflected wave is smaller than the intensity of the direct wave. Therefore, in many cases, the distance measurement value may correspond to the direct wave. However, if a human body or other object that attenuates the direct wave is present on the propagation path of the direct wave, the intensity of the direct wave may be lower than the intensity of the reflected wave. An example of a case where a human body or other object that attenuates the direct wave is present on the propagation path of the direct wave is when the portable device 9 is carried in the user's back pocket. In such a case, the anchor 3 may output a distance measurement value derived from the reflected wave.

[0114] If the tentative device position TP is located within the recalculation area CA (YES in S207), the DK-ECU 2 executes steps S209 to S211 to calculate a more valid device position. This process includes discarding the tentative device position. On the other hand, if the tentative device position TP is not located within the recalculation area CA, the DK-ECU 2 adopts the tentative device position TP as the device position coordinates and ends this flow. Step S207 corresponds to a step of verifying the validity of the tentative device position TP based on the positional relationship between the tentative device position TP and the virtual line VL or the recalculation area CA. The virtual line VL or the recalculation area CA is determined by the reflector distance L. Therefore, step S207 may be interpreted as a step of verifying the validity of the tentative device position TP based on the reflector distance L.

[0115] Note that step S207 may be replaced with a process for verifying the validity of the tentative device position TP using a simpler method. For example, the DK-ECU 2 may verify the validity of the tentative device position TP based on whether the distance from the vehicle Hv to the tentative device position TP is equal to or greater than the reflector distance L. The DK-ECU 2 may be configured to execute the processes of step S209 and subsequent steps if the distance from the vehicle Hv to the tentative device position TP is equal to or greater than the reflector distance L, and to execute step S208 if the distance from the vehicle Hv to the tentative device position TP is less than the reflector distance L.

[0116] In step S209, the DK-ECU 2 identifies an NLOS (Non Line Of Sight) anchor 3 from among the anchors 3 used in the positioning calculation process in step S206. An NLOS anchor refers to an anchor 3 that outputs a distance measurement value derived from a reflected wave rather than a direct wave. An NLOS anchor may be referred to as a reflected wave observation anchor, etc. The distance measurement value derived from a reflected wave output by an NLOS anchor may also be referred to as a reflected path value, etc.

[0117] In step S209, the DK-ECU 2 may, for example, regard an anchor 3 used in the positioning calculation process as an NLOS anchor if the observed device signal strength is less than a predetermined NLOS threshold. If the device signal strength observed by anchor 3B is equal to or greater than the NLOS threshold, while the device signal strength observed by anchor 3C is less than the NLOS threshold, the DK-ECU 2 regards anchor 3C as an NLOS anchor. As for anchor 3B, since the device signal strength is equal to or greater than the NLOS threshold, it is not regarded as an NLOS anchor.

[0118] 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 present within the target area and there are no reflecting objects or human bodies around the mobile device 9. The NLOS threshold may be determined by testing the NLOS threshold by collecting, under specific conditions, multiple samples of the reception strength that can be observed when receiving a direct wave and multiple samples of the reception strength that can be observed when receiving a reflected wave. The NLOS threshold may be set to distinguish between the reception strength due to the direct wave and the reception strength due to the reflected wave. The NLOS threshold may be adjusted so that the accuracy rate reaches a desired target value.

[0119] The DK-ECU 2 may also include distance-intensity data indicating a normal range of device signal strength according to the distance measurement value. The DK-ECU 2 may acquire the device signal strength according to the distance measurement value as the NLOS threshold based on the distance-intensity data prepared in advance. The normal range may be designed through the above-described testing. The distance-intensity data may be a data set in a map or table format, or may be a function (program) that outputs a lower limit value of the device signal strength according to the distance measurement value.

[0120] The following describes a case where only anchor 3C is determined to be an NLOS anchor. However, depending on the situation, both anchors 3B and 3C may be determined to be NLOS anchors.

[0121] Once the NLOS anchor has been identified, the DK-ECU 2 sets a virtual anchor point VAP corresponding to the NLOS anchor in step S210. The virtual anchor point VAP is a point obtained by moving the NLOS anchor symmetrically with respect to the virtual line VL, as shown in FIG. 10 . When the position of anchor 3C is represented by (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 that is located on the opposite side of the NLOS anchor from the virtual line VL. The virtual anchor point VAP may also be referred to as a virtual wave source.

[0122] After completing the setting of the virtual anchor point VAP, the DK-ECU 2 executes positioning calculation processing by the second method using the virtual anchor point VAP in step S211. Specifically, the DK-ECU 2 calculates the intersections P3 and P4 of the first circle C1 corresponding to the 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 expressed as (x-Ld)^2 + (y-2L)^2 = Dc^2.

[0123] In this case, two intersections are obtained. Of the two intersections P3 and P4, the DK-ECU 2 may use the intersection P4 located outside the recalculation area CA, i.e., 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 finally determined based on the distance measurement value of the third anchor 3.

[0124] In this manner, the positioning calculation process using the virtual anchor point VAP corresponds to the position determination by the second method. For convenience in this disclosure, the series of processes from step S209 to step S211 is also referred to as the positioning calculation process using the virtual anchor or the positioning calculation process by the second method.

[0125] Although the above description deals with the case where anchor 3B is determined not to be an NLOS anchor, if anchor 3B is determined to be an NLOS anchor, a virtual anchor point may be set for anchor 3B. The coordinates of the virtual anchor point for anchor 3B are (0, 2L). If anchor 3B is an NLOS anchor, DK-ECU 2 may perform positioning calculation processing using a fourth circle whose center is the virtual anchor point for anchor 3B and whose radius is the measured distance Db.

[0126] According to the above configuration, even if some anchors 3 output distance measurements affected by reflected waves, it is possible to identify the device position with fewer errors. Note that a case where an anchor 3 outputs a distance measurement value affected by reflected waves may occur when there is a reflective object such as a wall around the portable device 9 and the portable device 9 is in the NLOS from the anchor 3. A case where the portable device 9 is in the NLOS of the anchor 3 may occur when a human body is interposed between the portable device 9 and the anchor 3, for example, when the portable device 9 is carried in the user's back pocket. Taking this situation into consideration, according to this embodiment, it is possible to accurately calculate the device position even when there is a reflective object such as a wall around the portable device 9 and the portable device 9 is in the NLOS of the anchor 3.

[0127] <Modification (1)> Even if the DK-ECU 2 determines that a reflective object exists and that the tentative device position is between the virtual line VL and the vehicle Hv, if the DK-ECU 2 determines that the portable device 9 is located behind the user as seen from the vehicle Hv, the DK-ECU 2 may execute positioning calculation processing using a virtual anchor. If the DK-ECU 2 determines that a reflective object exists in the direction of the device (YES in S204), the DK-ECU 2 may execute steps S301 to S307 shown in FIG. 11 instead of steps S206 to S211 shown in FIG. 8.

[0128] Steps S301 and S302 may be the same as steps S206 and S207. When a reflective object is present and the tentative device position is located in the recalculation area CA (YES in S302), the DK-ECU 2 executes positioning calculation processing using the virtual anchor in step S303. Step S303 corresponds to steps S209 to S211 described above, and its specific content is as described above.

[0129] On the other hand, if the tentative device position is located between the virtual line VL and the vehicle Hv (NO in S302), the DK-ECU 2 executes a positional relationship determination process in step S305. The positional relationship determination process is a process for determining whether a human body (i.e., the user's body) is present between the portable device 9 and the vehicle Hv. The positional relationship determination process can be interpreted as a process for determining whether the portable device 9 is located behind the user as viewed from the vehicle Hv. An example of a case in which the user's body is interposed between the vehicle Hv and the portable device 9 is when the portable device 9 is placed in a back pocket or backpack of a user facing the vehicle Hv. Another example of a case in which the user's body is interposed between the vehicle Hv and the portable device 9 is when the portable device 9 is placed in a breast pocket of a user facing away from the vehicle Hv. The positional relationship determination process may also be referred to as a back pocket determination or a backside determination.

[0130] In the positional relationship determination process, first, the DK-ECU 2 selects the larger of the device signal strengths at the two anchors 3 used in calculating the tentative device position in step S301 as the representative strength. If the representative strength is less than a predetermined backside threshold, it may determine that the user's body is interposed 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.

[0131] For example, the backside threshold may be set based on first test data and second test data. The first test data is data of the reception strength for each channel observed when the portable device 9 is present at a predetermined position and no human body is present between the portable device 9 and the vehicle Hv. The second test data is data of the device signal strength for each channel observed when the portable device 9 is present at a predetermined position near the vehicle Hv and a human body is present between the portable device 9 and the vehicle Hv. The second test data may be, for example, device signal strength measured when a tester holds the portable device 9 in his or her back pocket and stands at a predetermined position with his or her body (mainly his or her chest and abdomen) facing the vehicle Hv.

[0132] For convenience, the state in which the tester / user who has the portable device 9 in their back pocket faces the vehicle Hv is also referred to as the back pocket state. The state in which the tester / user who has the portable device 9 in their hand faces the vehicle Hv is also referred to as the non-back pocket state. The measurement point, which is a predetermined position used in the test, may be, for example, a location 1 m away from the vehicle Hv. The measurement point may be set at multiple locations within the target area.

[0133] The backside threshold may be set according to the maximum value of the device signal strength in the back pocket state. The backside threshold may be determined taking into account the minimum value of the device signal strength in the non-back pocket state. The backside threshold may be set so as to maximize the sum of the detection rate for the back pocket state and the value obtained by subtracting the false detection rate from 100%. The detection rate for the back pocket state means the probability of determining that the ball is in a back pocket state when it is actually in a back pocket state. The false detection rate for the back pocket state means the probability of erroneously determining that the ball is in a back pocket state when it is actually not in a back pocket state. These probability values ​​may be determined by testing. The positional relationship determination process may be interpreted as a process of determining whether or not the ball is in a back pocket state in a single situation.

[0134] If the representative intensity is less than the backside threshold, the DK-ECU 2 determines that the user's body is between the portable device 9 and the vehicle Hv (YES in S305) and executes step S307. On the other hand, if the representative intensity is equal to or greater than the backside threshold, the DK-ECU 2 determines that the user's body is not between the portable device 9 and the vehicle Hv (NO in S305) and executes step S306. Step S306 is a step in which the tentative device position is officially adopted as the device position.

[0135] In step S307, similar to step S303, a positioning calculation process using virtual anchors is performed. Note that in step S307, virtual anchor points corresponding to the two anchors 3 used in calculating the tentative device position may be set, and the intersection of the third and fourth circles may be determined as the device position. This is because if the representative strength is below the backside threshold, the device signal strength at both anchors 3 is likely to be below the NLOS threshold. The NLOS threshold and the backside threshold may be the same value. That is, the backside threshold may be integrated into the NLOS threshold. Furthermore, 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. If the NLOS threshold and the backside threshold are set to different values, then in step S307, it may also be possible to determine whether each anchor 3 corresponds to an NLOS anchor, as described in step S209, before setting the virtual anchor point.

[0136] According to the above configuration, the accuracy of determining the device position can be improved in a situation where the mobile device 9 is in a back pocket and in front of a reflective object such as a wall.

[0137] <Modification (2)> The DK-ECU 2 may be configured to execute the positional relationship determination process and change the post-processing depending on the determination result even when it has determined that no reflective object is present. For example, when it has determined that no reflective object is present in the direction of the device (NO in S204), the DK-ECU 2 may execute steps S401 to S405 shown in FIG. 12 instead of step S205 shown in FIG. 8.

[0138] Step S401 is executed when it is determined in step S204 that no reflective object is present, and its content is the same as step S304. That is, the DK-ECU 2 executes a positional relationship determination process in step S401.

[0139] If it is determined in step S401 that the user's body is not present between the vehicle Hv and the portable device 9 (NO in step S402), step S403 is executed. In step S403, the DK-ECU 2 executes a positioning calculation process by the first method using the distance measurement values ​​observed by each anchor 3. The content of step S403 is the same as that of step S205.

[0140] On the other hand, if it is determined that the user's body is present between the vehicle Hv and the portable device 9 (YES in S402), the DK-ECU 2 corrects the distance measurement values ​​of each anchor 3 by a predetermined correction amount in step S404. The correction here may be a subtraction. The correction amount may be set to a value corresponding to the length of the path that the LE signal takes around the human body, i.e., the length of the detour path. The correction amount may be set to 0.2 m, 0.3 m, 0.4 m, 0.5 m, or the like. The correction amount corresponds to a correction parameter. The correction amount may be registered in the storage 233 as a parameter. Once the correction of the distance measurement values ​​is complete, the DK-ECU 2 executes step S405.

[0141] In step S405, the DK-ECU 2 executes positioning calculation processing using the distance measurement value corrected in step S404. The method of positioning calculation processing itself may be the same as that in steps S403 and S205. The difference is that step S403 uses the observed distance measurement value as is, whereas step S405 uses the corrected distance measurement value.

[0142] The developers of the present disclosure tested the effect of a human body on distance measurements in an environment where there are no reflective objects such as walls around the vehicle Hv, and discovered the following: In an environment where there are no reflective objects, when the portable device 9 is in a back pocket, the observed distance measurement value can be 0.3 m or more longer than when the portable device 9 is not in a back pocket. This modification was created based on this finding, and according to the above processing flow, when there is no wall in the direction of the device and the portable device 9 is in a back pocket, the distance measurement value is corrected and treated as shorter by a predetermined amount. This makes it possible to reduce errors in estimating the device position that result from the LE signal going around the human body.

[0143] This modification may be implemented in combination with the other modifications described above. If the DK-ECU 2 determines in step S204 that a reflecting object is present in the direction of the device, it may execute the process from step S301 onward shown in Fig. 11, whereas if it determines that no reflecting object is present in the direction of the device, it may execute the process from step S401 onward shown in Fig. 12.

[0144] <Anchor Arrangement> Within the communication range of anchor 3, null points are formed concentrically around anchor 3. Here, a null point is a point where the signal strength drops compared to the surrounding area due to overlap with reflected waves. Such null points can be formed primarily by waves reflected from the floor. Null points can occur discretely and periodically depending on the distance from anchor 3. Points that are not null points are also referred to as non-null points. When portable device 9 is located at the null point of anchor 3C, the device reception strength at anchor 3C can fall below the backside threshold even when not in a back pocket. When the null points of anchor 3C and anchor 3B are arranged to coincide, the representative strength is more likely to fall below the backside threshold, which can degrade the accuracy of the positional relationship determination process.

[0145] For this reason, anchor 3B may be placed at a position that complements the null point of anchor 3C. A mounting position that complements the null point of anchor 3C is a mounting position where a non-null point of anchor 3B is located at the null point of anchor 3C. A person skilled in the art can identify the null point of anchor 3C through simulation. Similarly, the null point and non-null point of anchor 3B can be identified through simulation. Therefore, by combining the simulation results of the propagation characteristics of anchors 3B and 3C, a person skilled in the art can determine the position of anchor 3B that can roughly complement the null point of anchor 3C within the entry area.

[0146] The above technical concept is not limited to the first pair, but may also be applied to the second, third, and fourth pairs. By arranging the anchors 3 constituting a pair in this way so that they complement each other's null points, the accuracy of the positional relationship determination process as a system can be improved. Specifically, the rate of false detection of the back pocket state can be reduced.

[0147] <Configuration of Antenna in Portable Device> The portable device 9 may have multiple LE antennas 921. The multiple LE antennas 921 may be pattern antennas that utilize the ground layer of the circuit board 99. A pattern antenna that utilizes the ground layer may be a monopole antenna, an inverted-L antenna, an inverted-F antenna, or the like, patterned on the surface of the circuit board 99. The LE antenna 921 may be an antenna element having a length of λ / 4. Here, "λ" represents the wavelength of the operating frequency. By making the LE antenna 921 a pattern antenna that utilizes the ground layer of the circuit board 99, it is possible to reduce costs.

[0148] If the portable device 9 has multiple LE antennas 921, the RF core 922 may selectively use the multiple LE antennas 921 or may implement receive diversity. For example, the RF 922 may be configured to perform data communication or ranging communication with the vehicle key system 1 using an LE antenna 921 with a high reception strength among the multiple LE antennas 921.

[0149] The mobile device 9 may have a first antenna A1 and a second antenna A2 as the LE antenna 921, as shown in FIG. 13 . The first antenna A1 and the second antenna A2 may both be monopole antennas. The second antenna A2 may be patterned in an orientation perpendicular to the first antenna A1. As shown in FIG. 13 , the first antenna A1 and the second antenna A2 may be configured to handle polarization parallel to the substrate. In other words, the first antenna A1 and the second antenna A2 may not be configured to handle polarization perpendicular to the substrate. Note that the first antenna A1 is not limited to a monopole antenna, and may be an inverted-L antenna, an inverted-F antenna, a patch antenna, a dipole antenna, a loop antenna, or the like. The second antenna A2 may also be any of various types of antennas. The specific shape of the antenna element serving as the LE antenna 921 may be designed as appropriate.

[0150] The second antenna A2 may be an antenna that is erected on the circuit board 99, as shown in Fig. 14. Although Fig. 14 illustrates an example in which the second antenna A2 is an inverted-L antenna, the second antenna A2 may be an inverted-F antenna or a monopole antenna that is erected on the circuit board 99. When the second antenna A2 has a section that is perpendicular to the circuit board 99, the second antenna A2 partially handles polarization that is perpendicular to the board.

[0151] The second antenna A2 may be configured to handle substrate-vertically polarized waves. However, the three-dimensional second antenna A2 may be formed with a sufficiently low profile so that the substrate-vertically polarized wave gain is less than half the gain of substrate-parallel polarized waves. For example, the height of the three-dimensional second antenna A2 may be set to less than λ / 10. With this configuration, the radiation intensity of the substrate-vertically polarized wave is reduced, thereby reducing the components propagating along the surface of the human body when the portable device 9 is placed in a back pocket. In other words, the difference in reception strength depending on whether or not a human body is present may become more pronounced. As a result, the accuracy of the positional relationship determination process based on reception strength may be improved.

[0152] The second antenna A2 may be a metamaterial antenna. A metamaterial antenna is a mushroom-shaped antenna including a ground plane, which is a flat metal conductor, that functions as a ground; a counter conductor plate, which is a flat metal conductor, that is arranged opposite the ground plane; and a short-circuit portion that electrically connects the center of the counter conductor plate to the ground plane. In a metamaterial antenna, a parallel resonance occurs at a frequency corresponding to the capacitance and inductance formed between the ground plane and the patch portion. Among the dispersion characteristics of a metamaterial, the phenomenon of resonance at a frequency where the phase constant β is zero (0) is called zeroth-order resonance. The phase constant β is the imaginary part of the propagation coefficient γ of a wave propagating through a transmission line. A metamaterial antenna is also sometimes called a zeroth-order resonance antenna.

[0153] When the portable device 9 has two LE antennas 921, the RF core 922 may measure a distance measurement value and a reception strength at each of the two LE antennas 921. The MCU 923 may be configured to selectively output the smaller distance measurement value of two distance measurement values ​​measured using the two LE antennas 921. The MCU 923 may be configured to selectively output the larger reception strength of two reception strengths measured using the two LE antennas 921. A configuration in which multiple LE antennas 921 are provided can reduce variations in the magnitude of the reception strength.

[0154] <UWB Introduction> The vehicle key system 1 and the portable device 9 may be configured to communicate with each other using UWB (Ultra Wide Band) technology. That is, as shown in FIG. 15 , the vehicle key system 1 may include a UWB module 4, which is a module for UWB communication. The portable device 9 may also include a UWB module 93, which is a module for UWB communication. The UWB communication may be wireless communication using the UWB-IR (Impulse Radio) method. As specified in IEEE 802.15.4z, UWB communication may use frequencies ranging from 3.1 GHz to 4.8 GHz and 6.0 GHz to 10.6 GHz. For example, the vehicle key system 1 and the portable device 9 may be configured to use channel 9 for UWB communication. Channel 9 is a frequency band of 7987.2 MHz ±250 MHz.

[0155] The UWB module 4 includes an antenna and a signal processing circuit for UWB communication. The UWB module 4 is configured to be capable of transmitting and receiving pulsed radio waves (hereinafter, UWB pulses) used in UWB communication. The UWB pulses used in UWB communication may be signals having an extremely short pulse width (e.g., 2 nanoseconds) and a bandwidth of 500 MHz or more (i.e., ultra-wide bandwidth). Hereinafter, a radio signal using UWB pulses transmitted and received in UWB communication will be referred to as a UWB signal. The function and configuration of the UWB module 93 may be similar to those of the UWB module 4.

[0156] In the vehicle Hv, the UWB module 4 may be disposed in a position such as on the ceiling of the vehicle interior where it can communicate via UWB with a portable device 9 located outside the vehicle. The DK-ECU 2 and the UWB module 4 may be connected to each other so as to be able to communicate with each other via a dedicated communication line or an in-vehicle network.

[0157] The UWB module 4 and the portable device 9 may be configured to perform UWB ranging, which is distance measurement using a UWB signal. UWB ranging is a process of generating a distance measurement value based on the propagation time (i.e., time of flight) of a UWB signal from the UWB module 4 to the portable device 9. The UWB ranging may include a process of performing UWB ranging communication and a process of calculating the distance based on the result of the ranging communication.

[0158] UWB ranging communication includes a step in which a communication device serving as an initiator transmits a poll signal, and a step in which a communication device serving as a responder transmits a response signal in response to receiving the poll signal. The poll signal is a UWB signal of a predetermined pattern that requests the responder to return a response. The response signal is a UWB signal serving as a response signal, and may be referred to as an answer signal. UWB ranging communication may include a step in which the initiator transmits a final signal in response to receiving the response signal.

[0159] In one embodiment, the UWB module 4 may correspond to an initiator in UWB ranging, and the mobile device 9 may be configured to act as a responder. The roles of initiator and responder in ranging communications may be reversed.

[0160] The UWB module 4 as the initiator measures the round trip time (RTT), which is the time elapsed from transmitting a poll signal to receiving a response signal from the mobile device 9, and generates a ranging value based on the RTT. The RTT corresponds to the round-trip flight time of the UWB signal. The ranging value represents the distance from the UWB module 4 to the mobile device 9. For convenience, the ranging value generated by UWB ranging is also referred to as a UWB ranging value to distinguish it from the ranging value generated by CS ranging.

[0161] In addition to the function of generating UWB distance measurements, the UWB module 4 also includes a circuit for measuring the reception strength of UWB signals transmitted from the portable device 9. The reception strength of UWB signals is also referred to as UWB signal strength to distinguish it from the reception strength of LE signals. The UWB module 4 performs UWB distance measurement communication with the portable device 9 at a predetermined timing and outputs the UWB signal strength together with the UWB distance measurement value to the DK-ECU 2.

[0162] The UWB module 4 may perform UWB ranging communication based on the connection between the DK-ECU 2 and the portable device 9 via LE communication. Furthermore, the UWB module 4 may periodically perform UWB ranging communication while the DK-ECU 2 is connected to the portable device 9 via LE communication. Prior to UWB ranging, the DK-ECU 2 may exchange UWB ranging settings (start timing, execution interval, etc.) with the portable device 9 via LE communication. The UWB module 4 and the portable device 9 may operate according to the UWB ranging settings agreed upon in advance.

[0163] In such a system configuration, the DK-ECU 2 may execute the positional relationship determination process using the UWB signal strength observed by the UWB module 4 instead of the reception strength of the LE signal observed by the anchor 3. That is, the DK-ECU 2 may determine that the portable device 9 is in the back pocket state in steps S305 and S404 based on the UWB signal strength being equal to or less than a predetermined value. Alternatively, the DK-ECU 2 may determine that the portable device 9 is in the back pocket state when the UWB signal strength is sufficiently low compared to the UWB distance measurement value.

[0164] As described above, UWB communication uses a higher frequency band than LE communication. The higher the frequency of a wireless signal, the more it is attenuated by the human body. By using the reception strength of UWB signals, which are attenuated by the human body more than LE signals, to determine the positional relationship, the accuracy of determining whether or not a device is in a back pocket state can be improved. Tests have confirmed that the level attenuation of LE signals by the human body is approximately 20 dB, while the level attenuation of UWB signals in the 8 GHz band (i.e., channel 9) by the human body is approximately 35 dB.

[0165] <Ranging Method> The method of measuring the distance between the anchor 3 and the mobile device 9 is not limited to CS ranging, but may also be RTT ranging using RTT. In other words, ranging communication may be bidirectional communication for measuring RTT. Furthermore, the communication method used for ranging is not limited to LE communication. Ranging communication may be performed using UWB communication. The anchor 3 may have UWB communication function in addition to LE communication function. The anchor 3 may be equipped with a UWB module 4 instead of or in addition to a module for performing LE communication. For multiple anchors 3, ranging between the anchor 3 and the mobile device 9 may be performed using UWB ranging. The anchor 3 may be configured to provide UWB ranging values ​​to the DK-ECU 2. Ranging communication between anchors may also be UWB ranging communication. The communication protocol compatible with the anchors may be UWB-IR. Like the anchor 3, the GW module 21 may also be configured to perform CS ranging or RTT ranging using LE communication.

[0166] <Environment Determination Process> The DK-ECU 2 may determine whether an obstacle exists around the vehicle Hv using an object detection sensor such as a camera, sonar, millimeter-wave radar, or LiDAR mounted on the vehicle Hv. After the vehicle Hv is parked, the DK-ECU 2 may use an object detection sensor (e.g., sonar) to sense whether an obstacle exists in the front or rear direction of the vehicle Hv. While the vehicle Hv is parked, the DK-ECU 2 may intermittently activate the object detection sensor at a predetermined interval to update the environmental data. The DK-ECU 2 may execute an environment determination process using the object detection sensor after the GW module 21 connects to the portable device 9 via LE communication. In this way, the environment determination process may be performed using the object detection sensor instead of the anchor-to-anchor ranging communication. Furthermore, when the DK-ECU 2 determines that a reflecting object exists based on the results of the anchor-to-anchor ranging communication or the detection results of the object detection sensor, it may acquire the reflecting object distance L using the object detection sensor.

[0167] <Target Area> The size of the right area as the target area may be determined based on the mounting positions of anchors 3B and 3C. The range within 5 m from anchor 3B and within 5 m from anchor 3C may be considered to be the right area. The right area may be a range in which an inversion phenomenon of reception strength may occur at either anchor 3B or anchor 3C when a reflecting object is present. The inversion phenomenon of reception strength means that the reception strength of the reflected wave exceeds the reception strength of the direct wave.

[0168] <Application Examples of the Present Disclosure> The present disclosure is applicable not only to vehicles but also to electronic key systems for buildings and facilities. For example, the present disclosure is applicable to a system that controls the locking state of building doors. The mobile device 9 may be a wireless key for a building door, or a wireless key for a door such as a locker or a safe. The target object is not limited to a vehicle, and may be various objects such as a building, a safe, a locker, or a delivery box.

[0169] <Supplementary Remarks (1)> The present disclosure also includes the following technical ideas and configurations. The present disclosure also includes an apparatus, a method, a computer program, and a recording medium on which a computer program is recorded, which correspond to the following technical ideas.

[0170] [Technical Idea 1] A positioning system comprising: a portable device (9) that is a wireless communication device carried by a user; a plurality of anchors (3B, 3C) configured to be able to perform ranging communications with the portable device and other anchors according to a specific communication protocol; a storage unit (233) that stores anchor setting data indicating positions of the plurality of anchors; and a control unit (23) that executes processing to identify the position of the portable device relative to an object (Hv) based on results of ranging communications executed by the plurality of anchors with the portable device, wherein the control unit: determines whether a reflecting object exists in a predetermined target area based on results of ranging communications between specific anchors or detection results of an object detection sensor; if it is determined that the reflecting object exists in the target area, specifies a reflecting object distance that is the distance between the object and the reflecting object; causes the plurality of anchors to perform ranging communications with the portable device, thereby obtaining a plurality of sets of ranging values ​​indicating the distance from each of the plurality of anchors to the portable device; When it is determined that the reflector is present in the target area, the location identification system is configured to: calculate a tentative device position, which is a tentative position of the mobile device, using the multiple sets of distance measurement values ​​and information on the positions of the multiple anchors; and verify the validity of the tentative device position based on the relationship between the area where the reflector may be present, which is determined from the reflector distance, and the tentative device position.

[0171] [Technical Idea 2] The positioning system according to Technical Idea 1, wherein the plurality of anchors include a first anchor and a second anchor, and the control unit is configured to: acquire a measurement value of the distance between the anchors by causing the first anchor and the second anchor to perform ranging communication; determine whether the reflecting object is present in the target area based on the measurement value of the distance between the anchors; and, if it is determined that the reflecting object is present in the target area, determine the reflecting object distance based on the measurement value of the distance between the anchors.

[0172] [Technical Idea 3] The memory unit stores data that can identify the actual value of the inter-anchor distance for a combination of the first anchor and the second anchor, and the control unit is configured to: acquire a measurement value of the inter-anchor distance by having the first anchor perform ranging communication with the second anchor over a plurality of channels; determine whether the reflecting object is present by comparing the measurement value of the inter-anchor distance with the actual value of the inter-anchor distance obtained by referring to the data stored in the memory unit; and, if it is determined that the reflecting object is present, calculate the reflecting object distance based on the measurement value of the inter-anchor distance.

[0173] [Technical Idea 4] The control unit is configured to: set a recalculation area (CA) based on the distance to the reflecting object; if it is determined that the reflecting object exists in the target area and the tentative device position is not located in the recalculation area, adopt the tentative device position as the position of the mobile device; if it is determined that the reflecting object exists in the target area and the tentative device position is located in the recalculation area, discard the tentative device position; and if the tentative device position has been discarded, determine the position of the mobile device using the reflecting object distance in addition to the multiple sets of distance measurement values ​​and position information of the multiple anchors.

[0174] [Technical Idea 5] The plurality of anchors include a first anchor and a second anchor, and the control unit sets a recalculation area (CA) based on the distance to the reflecting object, causes the first anchor or the second anchor to perform ranging communication with the portable device over a plurality of channels to acquire reception strength data for each of the channels, and determines whether a human body is present between the portable device and the object based on the reception strength data for each of the channels, adopts the tentative device position as the position of the portable device when it is determined that the reflecting object is present in the object area, the tentative device position is not located in the recalculation area, and there is no human body between the portable device and the object, and discards the tentative device position when it is determined that the tentative device position is located in the recalculation area or there is a human body between the portable device and the object in a situation where it is determined that the reflecting object is present in the object area, A location determination system as described in Technical Idea 1, configured to determine the location of the mobile device using the reflector distance in addition to the multiple sets of distance measurements and information on the positions of the multiple anchors when the tentative device location is discarded.

[0175] [Technical Idea 6] The position identification system according to Technical Idea 5, wherein the control unit is configured to: when it determines that the reflective object exists, execute a positional relationship determination process that determines whether or not a human body exists between the portable device and the target object; and when it determines that the reflective object does not exist, omit the positional relationship determination process.

[0176] [Technical Idea 7] The positioning system according to any one of Technical Ideas 1 to 6, wherein the plurality of anchors include a first anchor and a second anchor; and the control unit is configured to: acquire reception strength data for each channel by having the first anchor or the second anchor perform ranging communication with the portable device over multiple channels; determine whether a human body is present between the portable device and the object based on the reception strength for each channel; identify the position of the portable device using the plurality of sets of distance measurement values ​​and information on positions of the plurality of anchors when it is determined that the reflecting object is not present and that no human body is present between the portable device and the object; correct the distance measurement values ​​using correction parameters registered in advance when it is determined that the reflecting object is not present and that a human body is present between the portable device and the object; and when the distance measurement values ​​have been corrected, identify the position of the portable device using the corrected distance measurement values.

[0177] [Technical Idea 8] The positioning system according to any one of Technical Ideas 5 to 7, wherein the control unit is configured to: acquire reception strength data for each channel from the first anchor by having the first anchor perform ranging communication with the portable device over multiple channels; acquire reception strength data for each channel from the second anchor by having the second anchor perform ranging communication with the portable device over multiple channels; and determine that a human body is present between the portable device and the target object based on the reception strengths for each channel acquired from the first anchor and the second anchor both being below a predetermined threshold.

[0178] [Technical Idea 9] The threshold value for determining whether a human body is present between the portable device and the target object is set based on first test data, which is data on the reception strength for each channel observed when the portable device is present at a predetermined position within a target area and there is no human body between the portable device and the target object, and second test data, which is data on the reception strength for each channel observed when the portable device is present at the predetermined position and there is a human body between the portable device and the target object.

[0179] [Technical Concept 10] The position specifying system according to Technical Concept 8, wherein the first anchor and the second anchor are provided on the object in a positional relationship that complements each other's null points.

[0180] [Technical Idea 11] The mobile device comprises a circuit board and at least one antenna patterned on the surface of the circuit board, and does not comprise an antenna erected on the circuit board, a location determination system described in any one of Technical Ideas 1 to 10.

[0181] [Technical Idea 12] The portable device comprises a circuit board, a first antenna (A1) patterned on the surface of the circuit board, and a second antenna (A2) erected relative to the circuit board, wherein the second antenna has a shape such that the gain of a board parallel polarization, which is a linear polarization whose electric field vibration direction is parallel to the surface of the circuit board, is greater than the gain of a board vertical polarization, which is a linear polarization whose electric field vibration direction is perpendicular to the circuit board. This is a positioning system described in any one of Technical Ideas 1 to 10.

[0182] In addition, in technical idea 1, verifying the validity of the provisional device position based on the relationship between the area in which the reflector may exist, determined from the reflector distance, and the provisional device position may be replaced by setting a recalculation area (CA) based on the distance to the reflector, and determining whether the provisional device position is located in the recalculation area.

[0183] In addition, the control unit provided in the location identification system described in Technical Idea 1, etc. may be configured to, if it is not determined that the reflective object exists in the target area, identify the location of the mobile device according to a first method using the multiple sets of distance measurement values ​​and information on the positions of the multiple anchors, and, if it is determined that the reflective object exists in the target area, identify the location of the mobile device according to a second method different from the first method.

[0184] Furthermore, the control unit included in the position identification system described in Technical Idea 1 etc. may be configured to identify the position of the mobile device using the multiple sets of distance measurement values ​​and information on the positions of the multiple anchors when it is not determined that the reflecting object is present in the target area. Furthermore, the method of identifying the position may be multipoint positioning.

[0185] Furthermore, the control unit provided in the position determination system described in Technical Idea 4 or 5 may be configured, when discarding the tentative device position, to identify a reflected wave observation anchor from among the plurality of anchors that is outputting a distance measurement value derived from a reflected wave, set a virtual anchor point using the reflecting object distance and the position data of the reflected wave observation anchor, and determine the position of the mobile device using a virtual circle centered on the virtual anchor point and having a radius of the distance measurement value generated by the reflection observation anchor.

[0186] <Supplementary Note (2)> The various flowcharts shown in this disclosure are all examples, and the number of steps constituting the flowcharts and the execution order of the processes can be changed as appropriate. The controls shown in each flowchart may be combined / executed in parallel to the extent that there is no contradiction. Expressions such as acquisition, determination, detection, generation, and calculation may be interchangeable. When a device acquires certain data, it also includes the device generating the data based on a signal input from another device / sensor.

[0187] The apparatus, system, and methods described herein may be implemented by a special-purpose computer having a processor programmed to perform one or more functions embodied in a computer program. The apparatus and methods described herein may also be implemented using dedicated hardware logic circuitry. The apparatus and methods described herein may also be implemented by one or more special-purpose computers configured by a combination of a processor executing a computer program and one or more hardware logic circuits. The processor may be any computing core, such as a CPU, MPU, GPU, or DFP (Data Flow Processor). Some or all of the functions of the DK-ECU 2 may be implemented as hardware. Some or all of the functions of the DK-ECU 2 may be implemented using a system-on-chip (SoC), an integrated circuit (IC), or a field-programmable gate array (FPGA). The computer program includes instructions executed by a computer. The computer program may be stored on a computer-readable, non-transitory, tangible storage medium. The computer program recording medium may be a variety of media such as a hard-disk drive (HDD), a solid-state drive (SSD), or a flash memory.

Claims

1. A location identification system comprising: a portable device (9) that is a wireless communication device carried by a user; a plurality of anchors (3B, 3C) configured to be able to carry out ranging communications with the portable device and other anchors in accordance with a specific communication protocol; a memory unit (233) that stores anchor setting data indicating the positions of the plurality of anchors; and a control unit (23) that executes processing to identify the position of the portable device relative to an object (Hv) based on the results of ranging communications executed by the plurality of anchors with the portable device, wherein the control unit: determines whether a reflecting object exists in a predetermined target area based on the results of ranging communications between specific anchors or the detection results of an object detection sensor; if it is determined that the reflecting object exists in the target area, determines a reflecting object distance that is the distance between the object and the reflecting object; and causes the plurality of anchors to carry out ranging communications with the portable device, thereby obtaining a plurality of sets of ranging values ​​indicating the distance from each of the plurality of anchors to the portable device; When it is determined that the reflector is present in the target area, the location identification system is configured to: calculate a tentative device position, which is a tentative position of the mobile device, using the multiple sets of distance measurement values ​​and information on the positions of the multiple anchors; and verify the validity of the tentative device position based on the relationship between the area where the reflector may be present, which is determined from the reflector distance, and the tentative device position.

2. The positioning system of claim 1, wherein the plurality of anchors include a first anchor and a second anchor, and the control unit is configured to: obtain a measurement value of the distance between the anchors by causing the first anchor and the second anchor to perform ranging communication; determine whether the reflecting object is present in the target area based on the measurement value of the distance between the anchors; and, if it is determined that the reflecting object is present in the target area, determine the reflecting object distance based on the measurement value of the distance between the anchors.

3. The positioning system described in claim 2, wherein the memory unit stores data that can identify the actual value of the inter-anchor distance for a combination of the first anchor and the second anchor, and the control unit is configured to: acquire a measured value of the inter-anchor distance by having the first anchor perform ranging communication with the second anchor over multiple channels; determine whether the reflecting object is present by comparing the measured value of the inter-anchor distance with the actual value of the inter-anchor distance obtained by referring to the data stored in the memory unit; and, if it is determined that the reflecting object is present, calculate the reflecting object distance based on the measured value of the inter-anchor distance.

4. The location determination system of claim 1, wherein the control unit is configured to: set a recalculation area (CA) based on the distance to the reflecting object; if it determines that the reflecting object exists in the target area and the tentative device position is not located in the recalculation area, adopt the tentative device position as the position of the mobile device; if it determines that the reflecting object exists in the target area and the tentative device position is located in the recalculation area, discard the tentative device position; and if it discards the tentative device position, determine the position of the mobile device using the reflecting object distance in addition to the multiple sets of distance measurement values ​​and position information of the multiple anchors.

5. The location determination system of claim 1, wherein the multiple anchors include a first anchor and a second anchor, and the control unit is configured to: set a recalculation area (CA) based on the distance to the reflecting object; cause the first anchor or the second anchor to perform ranging communication with the portable device over multiple channels to acquire reception strength data for each of the channels; determine whether a human body is present between the portable device and the object based on the reception strength data for each of the channels; adopt the tentative device position as the location of the portable device when it is determined that the reflecting object is present in the object area, the tentative device position is not located in the recalculation area, and that no human body is present between the portable device and the object; discard the tentative device position when it is determined that the tentative device position is located in the recalculation area or that a human body is present between the portable device and the object in a situation where it is determined that the reflecting object is present in the object area; and when the tentative device position is discarded, determine the location of the portable device using the reflecting object distance in addition to the multiple sets of distance measurement values ​​and position information of the multiple anchors.

6. The location identification system of claim 5, wherein the control unit is configured to: when it determines that the reflective object exists, execute a positional relationship determination process that determines whether or not a human body exists between the portable device and the target object; and when it determines that the reflective object does not exist, omit the positional relationship determination process.

7. The location determination system of claim 1, wherein the multiple anchors include a first anchor and a second anchor; and the control unit is configured to: acquire reception strength data for each channel by having the first anchor or the second anchor perform ranging communication with the portable device over multiple channels; determine whether a human body is present between the portable device and the object based on the reception strength for each channel; identify the location of the portable device using the multiple sets of distance measurement values ​​and information on the positions of the multiple anchors if it is determined that the reflecting object is not present and that no human body is present between the portable device and the object; correct the distance measurement values ​​using pre-registered correction parameters if it is determined that the reflecting object is not present and that a human body is present between the portable device and the object; and, if the distance measurement values ​​are corrected, identify the location of the portable device using the corrected distance measurement values.

8. The location identification system described in claim 5 or 7, wherein the control unit is configured to: acquire data on the reception strength for each channel from the first anchor by having the first anchor conduct ranging communication with the portable device over multiple channels; acquire data on the reception strength for each channel from the second anchor by having the second anchor conduct ranging communication with the portable device over multiple channels; and determine that a human body is present between the portable device and the target object based on the reception strengths for each channel acquired from the first anchor and the second anchor both being below a predetermined threshold.

9. The location identification system described in claim 8, wherein the threshold value for determining whether a human body is present between the mobile device and the target object is set based on first test data, which is data on the reception strength for each channel observed when the mobile device is present at a predetermined position within the target area and no human body is present between the mobile device and the target object, and second test data, which is data on the reception strength for each channel observed when the mobile device is present at the predetermined position and a human body is present between the mobile device and the target object.

10. The positioning system according to claim 8, wherein the first anchor and the second anchor are provided on the object in a positional relationship that complements each other's null points.

11. The location system of claim 1, wherein the mobile device comprises: a circuit board; and at least one antenna patterned on a surface of the circuit board; and no antenna standing on the circuit board.

12. The positioning system of claim 1, wherein the portable device comprises: a circuit board; a first antenna (A1) patterned on the surface of the circuit board; and a second antenna (A2) erected relative to the circuit board, and the second antenna has a shape such that the gain of a board-parallel polarization, which is a linear polarization whose electric field vibration direction is parallel to the surface of the circuit board, is greater than the gain of a board-vertical polarization, which is a linear polarization whose electric field vibration direction is perpendicular to the circuit board.

13. A location determination device for determining the location of a portable device relative to an object, comprising: a communication circuit (22) for communicating with each of a plurality of anchors configured to be able to perform ranging communication with the portable device and other anchors in accordance with a specific communication protocol; a memory unit (233) storing anchor setting data which is data indicating the locations of the plurality of anchors; and a control unit (23) which executes processing for determining the location of the portable device based on data received from the plurality of anchors via the communication circuit and the anchor setting data stored in the memory unit, wherein the control unit: determines whether a reflecting object exists in a predetermined target area based on the results of ranging communication between specific anchors or the detection results of an object detection sensor associated with the object; if it is determined that the reflecting object exists in the target area, determines the reflecting object distance which is the distance between the object and the reflecting object; and acquires a plurality of sets of ranging values ​​indicating the distance from each of the plurality of anchors to the portable device by having the plurality of anchors perform ranging communication with the portable device. When it is determined that the reflector is present in the target area, the location identification device is configured to: calculate a tentative device position, which is a tentative position of the mobile device, using the multiple sets of distance measurement values ​​and information on the positions of the multiple anchors; and verify the validity of the tentative device position based on the relationship between the area where the reflector may be present, which is determined from the reflector distance, and the tentative device position.

14. A computer-implemented location method for determining the location of a portable device relative to an object, comprising: communicating with each of a plurality of anchors configured to be able to perform ranging communication with the portable device and other anchors according to a specific communication protocol via a communication circuit (22); reading anchor setting data indicating the locations of the plurality of anchors by referring to a specific storage unit (233); acquiring, via the communication circuit, an inter-anchor ranging result resulting from ranging communication between specific anchors or a detection result of an object detection sensor associated with the object; determining whether a reflector is present in a specific object area based on the acquired inter-anchor ranging result or the acquired detection result; if it is determined that the reflector is present in the object area, specifying a reflector distance which is the distance between the object and the reflector; and having the plurality of anchors perform ranging communication with the portable device to obtain a plurality of sets of ranging values ​​indicating the distance from each of the plurality of anchors to the portable device. When it is determined that the reflector is present in the target area, a tentative device position, which is a tentative position of the mobile device, is calculated using the multiple sets of distance measurements and information on the positions of the multiple anchors; and verifying the validity of the tentative device position based on the relationship between the area where the reflector may be present, which is determined from the reflector distance, and the tentative device position.

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