JP7120034B2 - Vehicle position estimation system and vehicle position estimation device - Google Patents

Description

The present disclosure relates to technology for estimating the relative position of a communication device (hereinafter referred to as a mobile terminal) carried by a user with respect to a vehicle using radio waves.

Conventionally, three or more reference stations with known positions perform wireless communication with mobile terminals such as smartphones to identify the distance from each reference station to the mobile terminal, and estimate the position of the mobile terminal based on the distance information from each reference station. A method for doing so has been proposed (for example, Patent Document 1). As a method of specifying the distance from the reference station to the mobile terminal, a method using the propagation time of radio waves (in other words, flight time), a method using received signal strength (RSS), and the like have been proposed.

Hereinafter, for the sake of convenience, the method of positioning using the reception intensity is also referred to as the reception intensity method. In the reception intensity method, it is assumed that the signal radiated from the antenna spreads evenly in all directions (that is, concentrically), and the reception intensity information is converted into distance information. Specifically, the reception intensity is converted into a distance using a model formula that the reception intensity is attenuated in inverse proportion to the cube or square of the distance. Positioning methods using the propagation time of radio waves (so-called time-of-arrival methods) include the TOA (Time Of Arrival) method, the TDOA (Time Difference Of Arrival) method, and the like.

JP 2017-32486 A

In the time-of-arrival method, measurement errors in the propagation time of radio waves have a large effect on the accuracy of distance and position estimation. Specifically, a deviation of 1 nanosecond in the propagation time causes a deviation of 30 centimeters in the observation distance. Therefore, the time-of-arrival method requires a device and a mechanism for accurately measuring the propagation time of radio waves, resulting in a relatively high cost.

On the other hand, the reception strength method can be realized relatively inexpensively because the reception strength determination can be realized using inexpensive elements/circuits. However, the reception strength is affected not only by the propagation distance of the signal, but also by various factors such as metallic bodies existing around the antenna and directivity of the antenna. Therefore, even if the received signal strength is low, it does not necessarily mean that the mobile terminal is located far away from the antenna. Therefore, the reception intensity method has a large positioning error.

As one assumed configuration for increasing the positioning accuracy of the reception intensity method, for example, the following configuration is conceivable. That is, a plurality of terminal position candidate points are set within the search range, and data (hereinafter referred to as an intensity distribution map) in which the reception intensity at each candidate point is mapped by testing or the like is prepared in advance. The position estimation device converts the received intensity into an observed distance using the intensity distribution map. Then, the sum of squares of residuals between the observed distance and the estimated distance is calculated for each combination of the candidate point and the reference station, and the candidate point with the smallest sum of squares of residuals is adopted as the position of the mobile terminal. Estimated distance refers to the straight-line distance from the candidate point to the reference station.

Such a method corresponds to a method of searching for the optimum solution by round-robin. Therefore, the above method is hereinafter also referred to as a round-robin search method.

In the brute force search method, it is necessary to calculate the residual sum of squares for each of a plurality of candidate points set within the search range. In order to improve the accuracy of estimating the position of the mobile terminal, it is necessary to reduce the setting interval of the candidate points and increase the number of candidate points within the search range. Therefore, in the brute-force search method, if an attempt is made to improve the position estimation accuracy, the amount of calculation increases.

Of course, the computational load for position estimation is less of an issue with relatively high performance processors. However, from the viewpoint of environmental resistance such as vibration resistance and heat resistance, and cost, it is difficult to use processors as high-performance as computers used in offices and homes for electronic devices for vehicles. In other words, it is preferable for the vehicle position estimation device to be able to estimate the position in a relatively short time without using a high-performance processor. The search range for the vehicle position estimation device is, for example, the entire vehicle interior or a three-dimensional space within 1 m from the side of the vehicle.

The present disclosure has been made based on this situation, and the purpose thereof is to provide a vehicle position estimation system capable of estimating the terminal position with higher accuracy while suppressing price increases, and a vehicle position estimation system. An object of the present invention is to provide a position estimation device.

A vehicle position estimation system for achieving this purpose performs wireless communication between a mobile terminal (2) carried by a vehicle user and a vehicle-side device (3) used in the vehicle, thereby A vehicle position estimation system (1) for estimating a terminal position that is a position of a mobile terminal, wherein a search range, which is a range for setting candidate points as terminal position candidates, is set in advance with reference to the vehicle, The vehicle-side device includes a plurality of vehicle-side antennas (32, 32a to 32d) that transmit radio signals to the mobile terminal, and the mobile terminal includes a mobile-side receiver ( 22) and an intensity determination unit (221) for determining the reception intensity, which is the intensity of the signal received by the mobile-side receiving unit, and the vehicle-side device or the mobile terminal is determined by the intensity determination unit. , based on the strength observation value, which is the received strength of the signal transmitted from each vehicle-side antenna, and the corresponding area preset for each vehicle-side antenna, a candidate area, which is an area in which the mobile terminal may exist, is determined. An error evaluation value indicating the degree of divergence between the candidate point and the true terminal position is calculated for each candidate point based on the area identification unit (F3) to be identified and the strength observation value for each vehicle antenna, and the error evaluation is performed. A position estimating unit (F4) that adopts as the terminal position a candidate point with the smallest value or a candidate point with an error evaluation value equal to or less than a predetermined allowable threshold, and the position estimating unit is located in the area within the search range The position of the terminal is specified by calculating the error evaluation value for the candidate points existing in the candidate area specified by the specifying unit.

According to the above configuration, it is not necessary to calculate the error evaluation value for candidate points existing in areas other than the candidate area specified by the area specifying unit among all the candidate points within the search range. Therefore, the computational complexity of the position estimator can be suppressed. Since the amount of calculation can be suppressed, the need to use a high-performance processor or the like is weakened. Therefore, the price of the system can be suppressed. Also, the above arrangement estimates the terminal position based on the received strength. Therefore, there is no need for a device and mechanism for accurately measuring the propagation time of radio waves. Therefore, it can be realized at a lower cost than a system that performs positioning by the time-of-arrival method.

Moreover, in the above configuration, the terminal position is specified based on the error evaluation value for each candidate point. According to such a configuration, it is possible to improve the positioning accuracy by reducing the setting interval of the candidate points. That is, according to the above configuration, it is possible to estimate the terminal position with higher accuracy while suppressing price increases.

Further, a vehicle position estimating device for achieving the above object is a vehicle position estimating device that estimates a terminal position, which is the position of a mobile terminal with respect to a vehicle, by performing wireless communication with a mobile terminal carried by a vehicle user. An estimating device, in which a search range, which is a range for setting candidate points as terminal position candidates, is set in advance with reference to a vehicle, receives a radio signal transmitted from a mobile terminal, and receives the received radio signal A plurality of vehicle-side receivers (34, 34a to 34d) configured to be able to detect the reception intensity of the vehicle-side receiver, an intensity observation value that is the reception intensity at each vehicle-side receiver, and a preset value for each vehicle-side receiver An area specifying unit (F3) that specifies a candidate area in which the mobile terminal may exist based on the corresponding area that has been determined, and based on the strength observation value at each vehicle-side receiver, for each candidate point , an error evaluation value indicating the degree of divergence between the candidate point and the true terminal position is calculated, and the candidate point with the smallest error evaluation value or the candidate point with the error evaluation value equal to or less than a predetermined allowable threshold value is adopted as the terminal position. and a position estimating unit (F4), wherein the position estimating unit calculates the error evaluation value for candidate points existing in the candidate area specified by the area specifying unit within the search range, thereby determining the terminal position is configured to identify

Although the vehicle position estimation device and the vehicle position estimation system differ in whether the mobile terminal or the vehicle side device has the strength determination unit, other configurations are the same. be. That is, the vehicle position estimation device estimates the position of the mobile terminal by the same procedure as the vehicle position estimation system. Therefore, the same effects as those of the vehicle position estimation system described above can be obtained.

It should be noted that the symbols in parentheses described in the claims indicate the corresponding relationship with specific means described in the embodiments described later as one aspect, and limit the technical scope of the present disclosure. is not.

1 is a block diagram showing the overall configuration of a vehicle position estimation system 1; FIG. 2 is a block diagram showing the configuration of a mobile terminal 2; FIG. FIG. 3 is a diagram showing an example of mounting positions and mounting postures of LF transmitting antennas 32a to 32d. 3 is a functional block diagram showing the configuration of an information processing unit 311; FIG. FIG. 4 is a conceptual diagram showing an example of a setting mode of a corresponding area Cs; FIG. 4 is a conceptual diagram showing an example of a setting mode of a search range SR; FIG. 10 is a diagram showing a simulation result of reception intensity distribution of each LF transmission antenna 32; 6 is a flowchart for explaining position estimation processing; 3 is a diagram showing the interrelationship between the coordinate space distance r, the pitch angle θ, the mounting position of the LF transmission antenna 32, and the positions of candidate points. FIG. FIG. 4 is a diagram showing distance residual g; It is a figure which shows the modification of the setting aspect of a candidate point. FIG. 12 is a diagram showing the overall configuration of a vehicle position estimation system 1 in Modification 7; FIG. 14 is a block diagram showing a configuration of an in-vehicle communication device 34 included in a vehicle-side device 3 of Modification 7; FIG. 10 is a diagram showing a modified example of the search range SR;

Hereinafter, embodiments and the like of the present disclosure will be described with reference to the drawings. For convenience of explanation, in some embodiments, parts having the same functions as the parts shown in the drawings used in the explanation so far are denoted by the same reference numerals, and the explanation thereof may be omitted. be. The description in the other embodiments can be referred to for the parts with the same reference numerals.

<Schematic configuration of vehicle position estimation system 1>
As shown in FIG. 1, the vehicle position estimation system 1 includes a mobile terminal 2 carried by a vehicle user and a vehicle-side device 3 mounted on the vehicle. The mobile terminal 2 is a mobile communication device (so-called mobile terminal) associated with the vehicle-side device 3, and is configured to function, for example, as a vehicle key. Note that "being carried by the user" is not limited to being carried by the user, but also includes being left uncarried by the user.

The portable terminal 2 and the vehicle-side device 3 are capable of wireless communication with each other using radio waves in a predetermined frequency band. That is, when the mobile terminal 2 and the vehicle-side device 3 are within communication range of each other, the signal transmitted by one is received by the other by wireless communication.

Here, as an example, the portable terminal 2 has a function of receiving an LF (Low Frequency) band signal transmitted from the vehicle-side device 3 and a function of receiving a signal in the LF (Low Frequency) band transmitted from the vehicle-side device 3 as a function for performing wireless communication with the vehicle-side device 3 . 3 has a function of returning a signal of a predetermined frequency belonging to the UHF band. The vehicle-side device 3 has a function of transmitting a signal of a predetermined frequency belonging to the LF band and a function of receiving a UHF band signal transmitted from the mobile terminal 2 as functions for performing wireless communication with the mobile terminal 2 . have Note that the LF band here refers to a frequency band of 300 kHz or less, and includes frequencies such as 20 kHz to 30 kHz. UHF band refers to 300 MHz to 3 GHz.

The LF band frequency (hereinafter referred to as first frequency) used for signal transmission from the vehicle-side device 3 to the mobile terminal 2 is, for example, 125 kHz or 134 kHz. Further, the UHF band frequency (hereinafter referred to as the second frequency) used for signal transmission from the mobile terminal 2 to the vehicle-side device 3 is, for example, 315 MHz or 920 MHz. Here, as an example, a case where 134 kHz is adopted as the first frequency and 315 MHz is adopted as the second frequency will be taken as an example to describe the configuration of each section.

The first frequency and the second frequency may be set to frequencies other than those described above. The second frequency may be a frequency used in near field communication. The frequency used in short-range wireless communication is, for example, a frequency belonging to a band from 2400 MHz to 2480 MHz (hereinafter referred to as 2.4 GHz band). Also, the first frequency and the second frequency may belong to the same frequency band. Note that the first frequency is preferably set to a frequency belonging to a frequency band from 20 kHz to 200 kHz from the viewpoint of ease of forming a communication area, which will be described later.

Hereinafter, for the sake of convenience, the LF band radio signal transmitted by the vehicle-side device 3 is referred to as the LF signal, and the UHF band radio signal transmitted by the portable terminal 2 is also referred to as the UHF signal. Note that the radio signal emitted by the mobile terminal 2 is also called an RF signal. RF is an abbreviation for Radio Frequency.

<About the configuration of the vehicle>
First, the configuration of the vehicle will be explained. The vehicle is, for example, a passenger car with a seating capacity of five people. Here, as an example, the vehicle includes front seats and rear seats, and a driver's seat (in other words, a steering wheel) is provided on the right side. A vehicle interior space located behind the backrests of the rear seats is configured as a space (hereinafter referred to as a trunk area) that functions as a luggage compartment (in other words, a trunk room). The space for the rear seat of the vehicle communicates with the luggage compartment above the backrest for the rear seat.

In this specification, for the sake of convenience, the space in the vehicle interior that is ahead of the backrests of the front seats is referred to as the front area. The front area also includes the interior space above the instrument panel. A vehicle interior space that is located behind the backrests of the front seats and ahead of the backrests of the rear seats is also referred to as a rear area.

Of course, the vehicle may have a structure other than the example described above. For example, the vehicle may be a vehicle with a driver's seat on the left side. It may also be a vehicle without rear seats. Additionally, the vehicle may be a vehicle with a luggage compartment that is separate from the vehicle interior space. The vehicle may have a plurality of rows of rear seats. The vehicle may be a freight vehicle such as a truck. Also, the vehicle may be a taxi or a camper.

A vehicle body is made of a material such as resin that allows radio waves to pass through. The body here includes, for example, side sills, center pillars, and the like, which form the main body of the body, as well as body panels that provide the exterior shape of the vehicle. Body panels include side body panels, roof panels, rear end panels, bonnet panels and door panels. The radio waves here refer to radio waves of a first frequency, a second frequency, or the like, that is, radio waves in a frequency band used for wireless communication between the vehicle-side device 3 and the mobile terminal 2 . A material that allows radio waves to pass means a material that has a degree of signal attenuation (in other words, loss) within 3 dB. At least the door panel of the vehicle may be made of resin, and the main body portion may be made of metal.

<Schematic configuration of mobile terminal 2>
Here, the mobile terminal 2 will be described with reference to FIG. As shown in FIG. 2 , the mobile terminal 2 includes an LF receiving antenna 21 , an LF receiving section 22 , a mobile side control section 23 , a UHF transmitting section 24 and a UHF transmitting antenna 25 . It should be noted that the mobile terminal 2 only needs to have the following configuration, and the mobile terminal 2 may be a dedicated terminal for the PEPS system, a smartphone, a wearable device, a tablet terminal, a portable music player, a portable It may be a game machine or the like.

The LF reception antenna 21 is an antenna that receives an LF signal transmitted from an LF transmission antenna 32 provided in the vehicle-side device 3 . The LF receiving antenna 21 is a magnetic field type antenna, and is configured as, for example, a loop antenna or a bar antenna. The LF receiving antenna 21 is connected to the LF receiving section 22 , converts received radio waves into electrical signals, and outputs the electrical signals to the LF receiving section 22 .

The LF reception unit 22 is configured to receive the LF signal transmitted from the vehicle-side device 3 via the LF reception antenna 21 . The LF receiving section 22 is electrically connected to the LF receiving antenna 21 and receives an electrical LF signal received by the LF receiving antenna 21 . The LF receiving unit 22 extracts data contained in the received signal by subjecting the signal input from the LF receiving antenna 21 to predetermined processing such as analog-to-digital conversion, demodulation, and decoding. Then, it provides the extracted data to the mobile-side control unit 23 . The LF receiver 22 corresponds to the mobile-side receiver.

The LF receiver 22 of the present embodiment also includes a reception strength determination section 221 that measures the strength of the signal received by the LF reception antenna 21 (hereinafter referred to as reception strength). Here, the LF receiving antenna 21 is configured as a magnetic field antenna. Therefore, the received strength indicates the magnetic field strength of the signal received by the LF receiving antenna 21 .

As a method of measuring the reception intensity, various methods such as a method of calculating the reception intensity from the current flowing through the LF receiving antenna 21 can be used. The reception strength determination unit 221 can be realized by various circuit configurations. When the LF receiving antenna 21 is a multiaxial coil antenna arranged so as to be orthogonal to each other, the magnitude of the magnetic field strength vector obtained by synthesizing the magnetic field strength in each axial direction is adopted as the receiving strength. may be configured. The magnetic field intensity for each axial direction may be specified, for example, from the current amount and current direction of the coil antenna on each axis. The reception intensity detected by the reception intensity determination unit 221 is sequentially provided to the mobile-side control unit 23 in association with the received data.

The mobile-side control unit 23 is configured to control the operation of the mobile terminal 2 and is realized using, for example, a dedicated IC. Note that the mobile-side control unit 23 may be implemented using a computer including a CPU, a RAM, a ROM, and the like. In addition, the mobile-side control unit 23 may be implemented using an MPU or GPU. Also, the mobile-side control unit 23 may be implemented using an FPGA (field-programmable gate array) or an ASIC (application specific integrated circuit).

When the reception data is input from the LF reception section 22, the mobile-side control section 23 generates a baseband signal corresponding to the response signal corresponding to the reception data. The response signal includes information indicating the reception strength of the received data determined by reception strength determination section 221 (hereinafter referred to as reception strength information). After generating a baseband signal as a response signal including the reception intensity information, the mobile-side control unit 23 outputs the baseband signal to the UHF transmission unit 24 . A baseband signal as a response signal output from the mobile-side control unit 23 to the UHF transmission unit 24 is subjected to predetermined modulation processing in the UHF transmission unit 24 and transmitted as a radio signal.

The UHF transmission section 24 is electrically connected to the mobile-side control section 23 and the UHF transmission antenna 25 . The UHF transmission unit 24 performs predetermined processing such as modulation processing and digital-analog conversion on the baseband signal input from the mobile-side control unit 23 and outputs the result to the UHF transmission antenna 25 . The UHF transmission antenna 25 is a UHF transmission antenna used for transmitting UHF band signals. The UHF transmission antenna 25 converts the electrical signal input from the UHF transmission section 24 into a UHF band radio wave and radiates it into space.

In the above configuration, the mobile terminal 2 generates and returns a response signal each time it receives an LF signal. Therefore, when LF signals are sequentially transmitted from a plurality of LF transmission antennas 32 as will be described later, the mobile terminal 2 responds to each of the plurality of LF signals from different transmission sources. It returns a response signal indicating the reception strength. Hereinafter, for the sake of convenience, the reception strength of the LF signal transmitted from each of the plurality of LF transmission antennas 32 at the mobile terminal 2 is also simply described as the reception strength of each antenna.

<Schematic configuration of vehicle-side device 3>
The vehicle-side device 3 performs predetermined vehicle control according to the position of the mobile terminal 2 (hereinafter also referred to as the terminal position) by performing wireless communication with the mobile terminal 2 using radio waves in a predetermined frequency band. A passive entry passive start system (hereinafter referred to as PEPS system) is realized.

For example, when the vehicle-side device 3 can confirm that the mobile terminal 2 exists within the operation area preset for the vehicle, the vehicle-side device 3 locks the door based on the user's operation of the door button described later. and unlocking. Further, when the vehicle-side device 3 can confirm that the mobile terminal 2 is present in the vehicle compartment by wireless communication with the mobile terminal 2, the vehicle-side device 3 performs engine start control based on the user's operation of a start button described later. to run.

The operation area is an area for the vehicle-side device 3 to execute predetermined vehicle control such as locking and unlocking the doors based on the presence of the mobile terminal 2 in the area. For example, the vicinity of the driver's seat door, the vicinity of the front passenger seat door, and the vicinity of the trunk door are set as operation areas. The vicinity of the door refers to a range within a predetermined working distance from the outer door handle. The outer door handle refers to a gripping member provided on the outer surface of the door for opening and closing the door. In this embodiment, as an example, an area outside the passenger compartment that is within the operating distance from the outer door handle for the driver's seat and the outer door handle for the passenger's seat is set as the operating area. The working distance that defines the size of the working area is, for example, 0.7 m. The working distance may be 1 m or 1.5 m.

The vehicle-side device 3 includes a smart ECU 31, a plurality of LF transmission antennas 32a-32d, and at least one UHF receiver 33, as shown in FIG. The LF transmission antennas 32a to 32d correspond to vehicle-side antennas.

All of the LF transmission antennas 32a-32d are antennas that transmit LF signals. The LF transmission antennas 32a to 32d are also referred to as the LF transmission antennas 32 when the description is made without distinguishing between the LF transmission antennas 32a to 32d. The LF transmission antenna 32 is a magnetic field antenna. As the LF transmission antenna 32, for example, a uniaxial loop antenna, a bar antenna, or the like can be employed. Here, as an example, it is assumed that the LF transmission antenna 32 is realized using a bar antenna. Note that the loop antenna forms a magnetic field in a direction orthogonal to the loop plane. A bar antenna also creates a magnetic field in the axial direction of the core member. Further, the axial direction of the LF transmission antenna 32 hereinafter refers to the direction in which the magnetic field is generated in the magnetic field antenna.

An example of arrangement of the LF transmission antennas 32a to 32d will now be described with reference to FIG. As shown in FIG. 3, the LF transmit antenna 32a is arranged on the right side of the driver's seat of the vehicle. For example, the LF transmission antenna 32a is built in the vicinity of the inner door handle of the door for the driver's seat with the axial direction along the longitudinal direction of the vehicle. As another aspect, the LF transmitting antenna 32a may be arranged on the right side surface of the body. For example, the LF transmitting antenna 32a may be built into the outer door handle of the driver's door.

The LF transmit antenna 32b is arranged on the left side of the driver's seat of the vehicle. For example, the LF transmission antenna 32b is incorporated in the vicinity of the inner door handle of the door for the front passenger seat in such a posture that the axial direction of the antenna is along the longitudinal direction of the vehicle. As another aspect, the LF transmitting antenna 32b may be arranged on the left side of the body. For example, the LF transmitting antenna 32b may be built into the outside door handle of the passenger door.

The LF transmission antenna 32c is arranged in the front area of the vehicle interior. For example, the LF transmitting antenna 32c is attached in the vicinity of the center console with the axial direction of the antenna along the vehicle width direction. The LF transmission antenna 32d is arranged in the rear area of the vehicle interior. For example, the LF transmitting antenna 32d is attached to a portion of the ceiling surface of the passenger compartment above the backrest of the rear seat in such a manner that the axial direction of the antenna extends along the vehicle width direction.

Each LF transmission antenna 32 has spheroidal directivity with its major axis in the axial direction. Therefore, the LF transmitting antennas 32a to 32b transmit relatively stronger signals in the longitudinal direction of the vehicle than in the height direction and width direction of the vehicle. In addition, the LF transmitting antennas 32c to 32d transmit relatively stronger signals in the vehicle width direction than in the vehicle height direction and vehicle front-rear direction. A spheroid corresponds to a body of revolution obtained by rotating an ellipse around its long axis, and is also called a long ellipsoid. The spheroid here mainly refers to an ellipsoid having a major axis that is 1.1 times or more as long as the minor axis.

A dashed line in FIG. 3 conceptually indicates the directivity of each LF transmission antenna 32 . In addition, the signal transmitted from each LF transmitting antenna 32 is not limited to the area surrounded by the dashed line, and propagates outside the area surrounded by the dashed line. Each LF transmission antenna 32 wirelessly transmits a signal input from an LF driver 312, which will be described later, with predetermined transmission power. The transmission power of the LF transmission antenna 32 may be adjusted so as to form a desired communication area. Each LF transmitting antenna 32 is configured such that the transmitted signal reaches at least the entire/large portion of the vehicle interior.

The number, installation position, and installation attitude of the LF transmission antennas 32 mounted on the vehicle can be changed as appropriate. The vehicle-side device 3 may be provided with an LF transmission antenna 32 whose communication area is inside the trunk and an LF transmission antenna 32 whose communication area is near the trunk door outside the vehicle, in addition to the positions described above.

The UHF receiver 33 is configured to receive a response signal including reception strength information transmitted from the mobile terminal 2 using radio waves in the UHF band. The UHF receiver 33 includes a UHF receiving antenna (not shown), a demodulation circuit, and the like. The UHF receiving antenna is an antenna for receiving radio waves in the UHF band transmitted from the mobile terminal 2 . The UHF receiver 33 extracts data contained in the received signal by subjecting the signal input from the UHF receiving antenna to predetermined processing such as analog-to-digital conversion, demodulation, and decoding. Then, the smart ECU 31 is provided with the extracted data.

The smart ECU 31 is configured to control the operation of each LF transmission antenna 32 and UHF receiver 33 . The smart ECU 31 has an information processing section 311 and an LF driver 312 as a more detailed configuration. The smart ECU 31 is electrically connected to the LF transmission antennas 32a-32d, the UHF receiver 33 and the like.

The information processing unit 311 controls the operation of each LF transmitting antenna 32 and the UHF receiver 33 using data input from the UHF receiver 33, various sensors mounted on the vehicle, and the ECU. Arithmetic processing for estimating the position of the terminal 2 is executed. The information processing unit 311 includes, for example, a processor such as a CPU, memory, I/O, and a bus connecting these, and performs various processes such as processing related to estimation of the position of the mobile terminal 2 by executing a control program stored in the memory. process. Execution of the control program by the processor corresponds to execution of the method corresponding to the control program. This method corresponds to the terminal position estimation method.

Memory, as used herein, is a non-transitory tangible storage medium for non-transitory storage of computer-readable programs and data. Various storage media such as semiconductor memories and magnetic disks can be used as the non-transitional physical storage media. The memory stores data indicating the mounting positions of the LF transmitting antennas 32a to 32d. The mounting position of each LF transmitting antenna 32 is expressed as a point of a three-dimensional orthogonal coordinate system with an arbitrary point on the vehicle as a reference point (in other words, the origin). Here, as an example, it is assumed that the mounting position of the LF transmitting antenna 32 is represented by a three-dimensional coordinate system having X, Y, and Z axes with the center of the front wheel axle as the origin. The X-axis is parallel to the vehicle width direction and the positive direction is the right side of the vehicle. The Y-axis is parallel to the front-rear direction of the vehicle, and the forward direction of the vehicle is the positive direction. The Z-axis is parallel to the height direction of the vehicle and has a positive direction toward the top of the vehicle. Of course, as another aspect, the mounting position of each LF transmitting antenna 32 may be represented by polar coordinates.

Note that the information processing unit 311 may be implemented using an MPU or GPU instead of the CPU. Also, the information processing section 311 may be implemented by combining multiple types of arithmetic processing modules such as a CPU, an MPU, and a GPU. Furthermore, the information processing section 311 may be implemented using an FPGA (field-programmable gate array) or an ASIC (application specific integrated circuit). Details of the functions provided by the information processing unit 311 will be described separately later.

The LF driver 312 is configured to transmit LF signals from the LF transmitting antennas 32a-32d. The LF driver 312 is implemented using an IC, for example. The LF driver 312 causes the LF transmission antennas 32a to 32d to transmit LF signals in order according to the request from the transmission processing unit F1. Specifically, the LF driver 312 sequentially outputs modulated signals to the LF transmission antennas 32 so that the transmission timings of the signals in the LF transmission antennas 32 do not overlap. Thereby, each LF transmission antenna 32 is caused to transmit in order. By shifting the timing of transmitting radio waves from each LF transmitting antenna 32, it is possible to prevent signals transmitted from a certain LF transmitting antenna 32 from interfering with signals transmitted from other LF transmitting antennas 32.例文帳に追加

<Functions of Information Processing Unit 311>
The information processing unit 311 includes a transmission processing unit F1, a response acquisition unit F2, an area identification unit F3, and a position estimation unit F4, as shown in FIG. 4 as functional blocks realized by the CPU executing a predetermined control program. Prepare. It also includes a corresponding area storage unit M1 and an intensity distribution storage unit M2, both of which use non-volatile storage media.

The corresponding area storage unit M1 is a storage device that stores data indicating the corresponding area Cs for each LF transmission antenna 32 within the search range SR, as shown in FIG. The search range SR here corresponds to the entire range in which the position of the mobile terminal 2 is searched, and specifically refers to the space in which candidate points for the terminal position are set. Although the search range SR is shown two-dimensionally in FIG. 5, it is actually three-dimensionally set so as to include the vehicle as shown in FIG. In FIGS. 5 and 6, the area inside the dashed-dotted line corresponds to the search range SR.

In this embodiment, the search range SR is set to a space within Dx from the left and right sides of the vehicle, less than Dz in height, behind the front end, and within Dy from the rear end of the vehicle. Dx and Dy are set to 1 m, for example. Dz is set to 2 m, for example. If the size of the own vehicle is, for example, 2 m in width and 4 m in length, the length of the search range SR in the width direction is 6 m, and the length in the longitudinal direction of the vehicle is 5 m. Therefore, the volume of the design space to be searched is 6m×5m×2m=60m ³ . The candidate points are set, for example, at 2 cm intervals in the X, Y, and Z axis directions within the search range SR.

The corresponding area Cs of a certain LF transmitting antenna 32 means that the reception strength at the mobile terminal 2 of the signal transmitted from the LF transmitting antenna 32 within the search range SR is the same as the signal transmitted from the other LF transmitting antenna 32. This space is expected to have a higher reception intensity than the (A) of FIG. 5 conceptually shows the coverage area Cs of the LF transmission antenna 32a, and (B) conceptually shows the coverage area Cs of the LF transmission antenna 32b. Further, (C) of FIG. 5 conceptually shows the coverage area Cs of the LF transmission antenna 32c, and (D) conceptually shows the coverage area Cs of the LF transmission antenna 32d. In FIG. 5, the area enclosed by the two-dot chain line (in other words, the area hatched with dot patterns) indicates the corresponding area Cs. Although the corresponding area is shown two-dimensionally in FIG. 5, it is actually set three-dimensionally like the search range SR.

The data indicating the corresponding area Cs for each LF transmitting antenna 32 may be represented by coordinates in the same three-dimensional coordinate system as the mounting position of the LF transmitting antenna 32 . The corresponding area Cs of each LF transmitting antenna 32 may overlap with the corresponding area Cs of another LF transmitting antenna 32 . Each corresponding area Cs corresponds to a sub-region formed by dividing the search range SR.

The intensity distribution storage unit M2 is a storage device that stores data (intensity distribution map) indicating the distribution of reception intensity for each antenna within the search range SR. The intensity distribution map may be generated by actually measuring/simulating the reception intensity for each antenna at each candidate point. The intensity distribution map corresponds to the intensity distribution model.

FIG. 7A conceptually shows the reception intensity distribution for the LF transmission antenna 32a with contour lines, and FIG. 7B conceptually shows the reception intensity distribution for the LF transmission antenna 32b with contour lines. ing. In addition, (C) of FIG. 7 conceptually shows the reception intensity distribution for the LF transmission antenna 32c by contour lines, and (D) conceptually shows the reception intensity distribution for the LF transmission antenna 32d by contour lines. shown in A contour line here is a line formed by points having the same reception intensity. Contour lines can be rephrased as isointensity lines. For the sake of simplification, FIG. 7 shows an aspect in which the interval between contour lines is set to 7.5 dBμV/m.

Strictly speaking, FIG. 7 shows the result of simulating the magnetic field strength distribution of the signal wirelessly transmitted from each LF transmission antenna 32. FIG. Although the magnetic field intensity and the received intensity of the transmitted signal are different physical quantities, they are in a proportional relationship due to the reversibility of transmission and reception, and can be adopted as an alternative characteristic.

Although FIG. 7 shows the reception intensity distribution of each LF transmission antenna 32 two-dimensionally, the reception intensity of each LF transmission antenna 32 is three-dimensionally distributed. The contour lines and isointensity lines described above correspond to one section of a curved surface (hereinafter referred to as a contour surface) formed by points having the same reception intensity. A contour surface can be rephrased as an iso-intensity surface.

The intensity distribution map only needs to indicate the reception intensity for each antenna at each candidate point, and various formats such as a map format and a table format can be adopted as the representation format. The intensity distribution map held by the intensity distribution storage unit M2 is referred to by the position estimation unit F4.

The transmission processing unit F1 is configured to execute processing related to transmission of the LF signal. The transmission processing unit F1 requests the LF driver 312 to transmit LF signals in order from the LF transmission antennas 32a to 32d at a predetermined timing. Hereinafter, for the sake of convenience, transmitting LF signals in a predetermined order from each of the LF transmitting antennas 32a to 32d will be referred to as sequential LF transmission processing.

For example, when the vehicle is parked and a door button provided on the outer door handle of the vehicle door is operated, the transmission processing unit F1 requests the LF driver 312 to sequentially execute the LF transmission processing. do. In addition, the transmission processing unit F1 is configured to sequentially request the LF driver 312 to execute the LF transmission processing when the start button is operated while the vehicle is parked. good too. The start button is a push switch for requesting the start of the driving source of the vehicle, and is provided in the vicinity of the driver's seat (for example, the instrument panel) inside the vehicle.

The information processing unit 311 may determine whether or not the vehicle is parked based on the vehicle speed detected by the vehicle speed sensor, the shift position detected by the shift position sensor, the parking brake switch signal, and the like. Various determination algorithms can be employed as a method of determining whether or not the host vehicle is in a parked state. The information processing section 311 may determine that the door button has been operated based on a signal from the door button.

The response acquisition unit F2 acquires a response signal including reception strength received from the mobile terminal 2 by the UHF receiver 33 . Each time the mobile terminal 2 receives the LF signal sequentially transmitted from the LF transmitting antennas 32a to 32d, it returns a response signal including the reception strength. Therefore, the smart ECU 31 (mainly the response acquisition unit F2) can uniquely identify the LF transmitting antenna 32 that transmitted the LF signal to which the mobile terminal 2 responded from the timing of receiving the response signal to the LF signal. That is, the response acquisition unit F2 determines from which LF transmission antenna 32 the mobile terminal 2 responded to the LF signal transmitted from the relationship between the signal transmission timing of each LF signal and the reception timing of the response signal. can be identified. As a result, the response acquisition unit F2 acquires the reception strength of the LF signal transmitted from each LF transmission antenna 32 at the mobile terminal 2. FIG. The response acquisition unit F2 outputs data indicating the reception strength of each antenna to the position estimation unit F4.

If the response signal contains a code for authentication, authentication is performed using this code. It is sufficient to perform locking/unlocking of the vehicle doors, permission to start the driving source (for example, engine) of the vehicle, and the like. Various methods such as a challenge-response method can be adopted as an authentication method for the mobile terminal 2 .

The area specifying unit F3 compares the reception strength of each antenna, and specifies the LF transmission antenna 32 with the highest reception strength at the mobile terminal 2 (hereinafter referred to as nearest neighbor antenna) among the plurality of LF transmission antennas 32 . Then, it is determined that the mobile terminal 2 exists within the corresponding area Cs of the nearest neighbor antenna. That is, the coverage area Cs of the nearest neighbor antenna is set as a candidate area where the mobile terminal may exist. Such an area specifying unit F3 corresponds to a configuration that specifies (in other words, narrows down) an area in which the mobile terminal 2 may exist within the search range SR. Also, from another point of view, this configuration corresponds to a configuration that excludes areas within the search range SR in which there is no/sufficiently low possibility of the presence of the mobile terminal 2 from the search targets.

Note that the area specifying unit F3 obtains the highest reception strength when the difference between the highest reception strength and the second highest reception strength is less than a predetermined integration threshold as a result of comparing the reception strength for each antenna. and the corresponding area Cs of the LF transmitting antenna 32 with the second highest reception strength are set as candidate areas. good. Further, even if the area specifying unit F3 is configured to include, in the candidate areas, areas Cs corresponding to the LF transmitting antennas 32 in which the difference from the highest received strength is less than a predetermined integration threshold is obtained. good. According to the above configuration, it is possible to reduce the possibility that the true terminal position will leak out of the candidate area when there is no significant difference in the reception strength of each antenna. Note that the integration threshold may be set to, for example, 3 dB.

The position estimation unit F4 estimates the position of the mobile terminal 2 using the reception strength of each antenna acquired by the response acquisition unit F2. The operation of the position estimator F4 will be separately described later.

<Regarding position estimation processing>
Next, processing related to estimation of the terminal position in the smart ECU 31 (hereinafter referred to as position estimation related processing) will be described using the flowchart shown in FIG. The flowchart in FIG. 8 may be executed when a predetermined position estimation condition is satisfied, such as when a door button or a start button is pressed. Note that the position estimation process may be performed periodically (for example, every 200 milliseconds). In this embodiment, as an example, the position estimation process includes steps S101 to S109.

First, in step S101, the transmission processing unit F1 cooperates with the LF driver 312 to sequentially execute LF transmission processing. That is, the transmission processing unit F1 requests the LF driver 312 to transmit LF signals in order from the LF transmission antennas 32a to 32d. As a result, the LF driver 312 causes the LF transmission antennas 32a to 32d to transmit LF signals in order. Each time the mobile terminal 2 receives the LF signal that is sequentially transmitted, it returns a response signal indicating the reception strength of the received signal.

In step S102, the response acquisition unit F2 cooperates with the UHF receiver 33 to acquire observed values of reception strength for each antenna (hereinafter also referred to as observed strength values) Bo1 to Bo4. The strength observation value Bo1 represents the reception strength of the LF signal transmitted from the LF transmission antenna 32a at the mobile terminal 2, and the strength observation value Bo2 represents the reception at the mobile terminal 2 of the LF signal transmitted from the LF transmission antenna 32b. represents strength. The strength observation value Bo3 represents the reception strength of the LF signal transmitted from the LF transmission antenna 32c at the mobile terminal 2, and the strength observation value Bo4 represents the reception at the mobile terminal 2 of the LF signal transmitted from the LF transmission antenna 32d. represents strength. The strength observation values Bo1 to Bo4 are also described as the strength observation value Bo when the source is not distinguished. The "o" in "Bo" stands for Observation.

If no response signal could be received, or if the number of LF transmission antennas 32 that could receive response signals was less than 3, this flow should be stopped. When this flow is canceled, for example, the process may be executed again from step S101 when a predetermined retry time (for example, 200 milliseconds) has elapsed from the point of cancellation.

In step S103, the area specifying unit F3 selects candidate Determine area. For example, if the strength observation value Bo1 of the LF transmission antenna 32a is the highest among the strength observation values Bo for each antenna, the corresponding area Cs of the LF transmission antenna 32a is set as the candidate area.

In step S104, the position estimation unit F4 sets any one candidate point existing in the candidate area determined by the area identification unit F3 in the previous step S103 as the target candidate point, and the process proceeds to step S105.

In step S105, the intensity distribution map stored in the intensity distribution storage unit M2 is referenced, and estimated values (hereinafter referred to as intensity estimation values) Be1 to Be4 of the reception intensity for each antenna at the target candidate point are obtained. The strength estimation value Be1 represents the reception strength of the LF signal transmitted from the LF transmission antenna 32a at the mobile terminal 2, and the strength estimation value Be2 represents the reception at the mobile terminal 2 of the LF signal transmitted from the LF transmission antenna 32b. represents strength. The strength estimation value Be3 represents the reception strength of the LF signal transmitted from the LF transmission antenna 32c at the mobile terminal 2, and the strength estimation value Be4 represents the reception at the mobile terminal 2 of the LF signal transmitted from the LF transmission antenna 32d. represents strength. The intensity estimation values Be1 to Be4 are also referred to as the intensity estimation value Be when the source is not distinguished. "e" of "Be" means estimate.

ステップＳ１０６での処理が完了すると、ステップＳ１０７に移る。ステップＳ１０７では、候補エリア内に位置する全ての候補点について残差平方和ＲＳＳを算出したか否かを判定する。候補エリア内の全ての候補点について残差平方和ＲＳＳを算出している場合にはステップＳ１０７を肯定判定してステップＳ１０９を実行する。一方、候補エリアの中に、まだ残差平方和を算出していない候補点が残っている場合にはステップＳ１０７を否定判定してステップＳ１０８を実行する。 In step S106, the RSS of the residual sum of squares (hereafter referred to as the residual sum of squares) RSS of the reception strength of each antenna at the target candidate point is calculated using the following formulas 1 to 5. The residual sum of squares RSS is a parameter that indicates the degree of deviation (in other words, the degree of divergence) between the candidate point and the true terminal position. That is, the residual sum of squares RSS corresponds to the error evaluation value. Note that the error index value may be the sum of the absolute values of the residuals.

When the processing in step S106 is completed, the process moves to step S107. In step S107, it is determined whether or not the residual sum of squares RSS has been calculated for all the candidate points located within the candidate area. If the residual sum of squares RSS has been calculated for all the candidate points in the candidate area, an affirmative decision is made in step S107 and step S109 is executed. On the other hand, if there are candidate points for which residual sums of squares have not yet been calculated in the candidate area, a negative decision is made in step S107 and step S108 is executed.

In step S108, any candidate point belonging to the candidate area and for which the residual sum of squares RSS has not yet been calculated is set as the target candidate point, and step S105 is executed. For example, in step S108, a candidate point adjacent to the current target candidate point in the X-axis direction is set as the target candidate point. The order of setting the target candidate points (in other words, the search direction) may be appropriately designed.

In step S109, among all the candidate points existing in the candidate area, the candidate point with the smallest residual sum of squares RSS is adopted as the terminal position, and this flow ends. The residual sum of squares RSS is a parameter that comprehensively evaluates the magnitude of the residual corresponding to each of the plurality of LF transmission antennas. The candidate point with the smallest residual sum of squares RSS can be expected to be the candidate point closest to the true terminal position.

As the processing after step S109, for example, the position estimating unit F4 determines whether or not the terminal position adopted in step S109 corresponds to the operating area or the vehicle interior. If the terminal position falls within the operating area, the door is unlocked or locked. Further, when the terminal position corresponds to the inside of the vehicle, the travel drive source is started.

<Effects of this embodiment>
Here, three comparative configurations, that is, first, second and third comparative configurations are introduced to describe the effects of this embodiment.

なお、上記式における（Ｘ_ｐ，Ｙ_ｐ，Ｚ_ｐ）は候補点の座標を表す。（Ｘ_ｉ，Ｙ_ｉ，Ｚ_ｉ）は、ＬＦ送信アンテナ３２ａ～３２ｄの位置を表す。Δｔ_ｉは、ＬＦ送信アンテナ３２から送信されたＬＦ信号の伝搬時間を表す。ｉ＝１～４は、ＬＦ送信アンテナ３２ａ～３２ｄに順に対応する。例えば、（Ｘ_１，Ｙ_１，Ｚ_１）はＬＦ送信アンテナ３２ａの設置位置を示し、Δｔ_１は、ＬＦ送信アンテナ３２ａから送信されたＬＦ信号の伝搬時間を示す。ｉの最大値は、車両側装置３が備えるＬＦ送信アンテナ３２の数に相当する。 The first comparative configuration uses the propagation time (in other words, flight time) Δt of the radio wave and the propagation speed C of the radio wave, such as TOA (Time Of Arrival) and TDOA (Time Difference Of Arrival), to obtain a distance as an observation value is calculated, and the degree of deviation (that is, the residual) between the candidate point and the true terminal position is evaluated based on the concept of the distance. In the first comparison configuration, the residual sum of squares RSS is expressed by Equation 6 below.

Note that (X _p , Y _p , Z _p ) in the above formula represent the coordinates of the candidate points. (X _i , Y _i , Z _i ) represent the positions of the LF transmit antennas 32a-32d. Δt _i represents the propagation time of the LF signal transmitted from the LF transmit antenna 32 . i=1-4 correspond to the LF transmit antennas 32a-32d in order. For example, (X ₁ , Y ₁ , Z ₁ ) indicates the installation position of the LF transmission antenna 32a, and Δt ₁ indicates the propagation time of the LF signal transmitted from the LF transmission antenna 32a. The maximum value of i corresponds to the number of LF transmission antennas 32 provided in the vehicle-side device 3 .

According to the above-described first comparison configuration, the terminal position can be approximately estimated by iterative calculation about 3 to 4 times using the Newton method or the like. However, in the first comparison configuration, the radio wave propagation time Δt is used for distance estimation. Since the propagation speed C of radio waves is very high, a deviation of 1 nanosecond in the propagation time Δt results in a deviation of 30 centimeters from the observation distance. That is, the first comparative configuration must be configured to be able to measure the propagation time Δt of radio waves (speed of light) with very high accuracy. Since the highly accurate time measurement function requires expensive elements, the cost of the first comparative configuration increases relatively.

第２比較構成においても、第１比較構成と同様に、ニュートン法等を用いて３～４回程度の反復計算によって近似的に端末位置を推定できる。また、電波の信号強度は電波の伝搬時間Δｔを計測するよりも安価な素子／回路を用いて検出可能であるため、第２比較構成によれば、第１比較構成よりもシステムのコストを抑制できる。 A second comparison configuration assumes that the signal radiated from the LF transmit antenna 32 spreads evenly (i.e., concentrically) in all directions, and the LF transmit antenna 32 from candidate points based on the intensity observations Bo. This configuration calculates the distance to and evaluates the residual. In the second comparison configuration, the residual sum of squares RSS is calculated by Equation 7 below. Note that D(Bo) in the formula is a function for converting the intensity observation value Bo into a distance. For example, the signal strength in the near field of the antenna is inversely proportional to the cube of the distance. That is ^, it has a relationship of B=κ/d3. Therefore, D(Bo)=(κ/Bo)̂(1/3). Note that κ is a constant.

In the second comparison configuration, similarly to the first comparison configuration, it is possible to approximately estimate the terminal position by iterative calculation of about 3 to 4 times using the Newton method or the like. In addition, since the signal strength of the radio wave can be detected using an element/circuit that is cheaper than measuring the propagation time Δt of the radio wave, the second comparative configuration reduces system costs more than the first comparative configuration. can.

However, the signal radiated from the LF transmitting antenna 32 does not spread evenly in all directions (that is, concentrically). For example, the signal radiated from the LF transmit antenna 32 spreads out like a spheroid. In addition, even if the LF transmission antenna 32 is an omnidirectional antenna, the signal from the LF transmission antenna 32 is concentrically spherical because it is affected by reflection and diffraction from the body of the vehicle and the structures in the vehicle interior. does not spread. For example, if there is a metal body such as a center pillar or a rear pillar near the LF transmitting antenna 32, the contour lines (actually contour planes) of the intensity distribution may be distorted by the metal body. Therefore, the observed intensity value Bo does not always correspond to the linear distance between the two points. Even near the LF transmission antenna 32, there may be a portion where the reception strength is relatively low due to the influence of structures and directivity. This tendency is particularly strong on the back side of the metal plate. Therefore, the position estimation by the method of the second comparison configuration can actually have an error of several tens of centimeters or more.

On the other hand, in the configuration of the present embodiment, the residual and residual sum of squares RSS are evaluated using the estimated value Be of the reception intensity for each candidate point set in advance by simulation or the like. In other words, the residual is calculated using an estimated value that takes into consideration the effects of the vehicle structure and the like. Therefore, the terminal position can be estimated more accurately than the second comparison configuration. In other words, it can be said that the configuration of the present embodiment is suitable when the vehicle-side antenna is configured using an antenna having non-spherical (for example, prolate) radiation characteristics. Further, it can be said that the configuration of the present embodiment is suitable when the reception strength of the signal transmitted from the vehicle-side antenna is distributed in a non-spherical shape due to the influence of the body of the vehicle and the interior structure of the vehicle.

The third comparative configuration is a configuration for calculating residuals by a method similar to that of the present embodiment. However, in the third comparison configuration, the residual sum of squares RSS is calculated for all candidate points in the search range SR, and the candidate point with the smallest residual sum of squares RSS is adopted as the terminal position.

In such a third comparison configuration, it is necessary to calculate the residual sum of squares RSS for all the candidate points within the search range SR in one position estimation process. becomes huge. For example, if candidate points are set at intervals of 2 cm in the X-axis, Y-axis and Z-axis directions in a space of 6 m×5 m×2 m=60 m ³ , the total number of candidate points is 7.5 million. Therefore, in the third comparison configuration, the calculation of the residual sum of squares RSS must be repeated 7,500,000 times in one position estimation process.

In contrast to such a third comparison configuration, according to the configuration of the present embodiment, the area specifying unit F3 determines the candidate areas, thereby limiting the candidate points for which the residual sum of squares RSS is to be calculated. Specifically, the position estimator F4 calculates the residual sum of squares RSS only for the candidate points within the corresponding area Cs of the LF transmitting antenna 32 with the highest observed intensity value Bo. According to such a configuration, it is possible to reduce the calculation load of the position estimator F4.

It should be noted that the mobile terminal 2 can basically be expected to exist within the corresponding area Cs of the LF transmitting antenna 32 with the highest intensity observed value Bo. Therefore, by limiting the calculation target of the residual sum of squares RSS (in other words, the terminal position search range) as in the present embodiment, the position estimation accuracy is less likely to deteriorate than in the third comparison configuration. That is, according to the above configuration, it is possible to suppress the amount of calculation while improving the position estimation accuracy more than the first comparison configuration and the second comparison configuration.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications described below are also included in the technical scope of the present disclosure. Various modifications can be made without departing from the scope of the present invention. For example, the various modified examples below can be implemented in combination as appropriate within a range that does not cause technical contradiction.

It should be noted that members having the same functions as those of the members described in the above-described embodiments are denoted by the same reference numerals, and description thereof will be omitted. Also, when only part of the configuration is mentioned, the configuration of the previously described embodiments can be applied to the other portions.

上記式は、アンテナコイルのループ半径ａよりも距離ｒのほうが十分に大きいものとして近似している。式８の「μ_０」は、磁気定数である。「Ｉ」はアンテナコイルに流す電流値を示す。式８中の「ｒ」は、ＬＦ送信アンテナ３２の搭載位置（Ｘ_ｉ，Ｙ_ｉ，Ｚ_ｉ）から任意の候補点Ｐ（Ｘ_ｐ，Ｙ_ｐ，Ｚ_ｐ）までの距離を表す。また、θは、アンテナの搭載位置から候補点Ｐに向かうベクトルとアンテナの軸とがなす角度を表す。なお、上記式８に示すｒとθは、アンテナ軸がＹ軸に平行となる姿勢においては式９ａ、９ｂ（以降、式９とまとえて記載）の関係を満たす。図９は、座標空間距離ｒ、ピッチ角θ、ＬＦ送信アンテナ３２の搭載位置（Ｘ_ｉ，Ｙ_ｉ，Ｚ_ｉ）、候補点の位置（Ｘ_ｐ，Ｙ_ｐ，Ｚ_ｐ）の相互関係を示す図である。式９ｂの内容（主として分子）は、アンテナ軸の向きに応じて適宜変更されればよい。

ところで、強度観測値Ｂｏ１～Ｂｏ４や、各アンテナの座標を式８、式９に代入すると、Ｘ_ｐ，Ｙ_ｐ，Ｚ_ｐの３つを変数とする連立方程式が得られる。よって、当該連立方程式を解けば、端末位置としての候補点（Ｘ_ｐ，Ｙ_ｐ，Ｚ_ｐ）を特定可能なように思われる。しかしながら、これらの連立方程式を解くことは現実的には容易でない。加えて、受信強度，ＬＦ送信アンテナ３２の位置，定数ｋ等に誤差を含む場合には、解が不定になる。対して、以上で述べた方法によれば、より確からしい端末位置を推定できるといった利点を有する。 [Modification 1]
In the above-described embodiment, a mode is disclosed in which the intensity estimation value for each candidate point is specified using an intensity distribution map, but the present invention is not limited to this. The magnetic field strength of the LF transmitting antenna 32 at an arbitrary candidate point P (X _p , Y _p , Z _p ) can be formulated as in Equation 8 below using the Biot-Savart law. Therefore, the intensity estimated value (in other words, theoretical value) for each candidate point may be calculated by Equation 8 below. Whether the LF transmission antenna 32 is a loop antenna or a bar antenna, the magnetic field strength distribution of the LF transmission antenna 32 can be approximately obtained by the above equation (8).

The above formula is approximated assuming that the distance r is sufficiently larger than the loop radius a of the antenna coil. “μ ₀ ” in Equation 8 is the magnetic constant. "I" indicates the value of the current flowing through the antenna coil. “r” in Equation 8 represents the distance from the mounting position (X _i , Y _i , Z _i ) of the LF transmitting antenna 32 to any candidate point P (X _p , Y _p , Z _p ). Also, θ represents the angle formed by the axis of the antenna and the vector directed from the mounting position of the antenna to the candidate point P. Note that r and θ shown in Equation 8 above satisfy the relationships of Equations 9a and 9b (hereinafter collectively described as Equation 9) in a posture in which the antenna axis is parallel to the Y-axis. FIG. 9 shows the mutual relationship among the coordinate space distance r, the pitch angle θ, the mounting position (X _i , Y _i , Z _i ) of the LF transmitting antenna 32, and the candidate point position (X _p , Y _p , Z _p ). It is a diagram. The contents of Equation 9b (mainly the numerator) may be changed as appropriate according to the direction of the antenna axis.

By the way, by substituting the observed intensity values Bo1 to Bo4 and the coordinates of each antenna into Equations 8 and 9, simultaneous equations with three variables X _p , Y _p , and Z _p are obtained. Therefore, it seems that the candidate point (X _p , Y _p , Z _p ) as the terminal position can be identified by solving the simultaneous equations. However, solving these simultaneous equations is not easy in practice. In addition, if the received intensity, the position of the LF transmitting antenna 32, the constant k, etc. contain errors, the solution becomes indefinite. On the other hand, the method described above has the advantage of being able to estimate a more probable terminal position.

[Modification 2]
For example, as shown in FIG. 10, the position estimating unit F4 uses an intensity distribution map to identify a curved surface (that is, a contour surface) in which the received intensity is the observed intensity value Bo, and a contour surface from the target candidate point to the contour surface. It may be configured to calculate the distance as the residual g. The residual g may be calculated for each combination of candidate points and antennas. The residual sum of squares RSS for a certain target candidate point may be the sum of squares of the residuals g for each antenna for the target candidate point.

Alternatively, the residual g may be the difference between the coordinate space distance r from the candidate point P to the antenna and the estimated distance s determined based on the intensity observation value Bo. The coordinate space distance r is a straight line distance from the candidate point P to the mounting position of the antenna in the three-dimensional space coordinate system, and may be calculated using respective coordinates. The estimated distance s is a parameter corresponding to the distance r, determined by substituting the pitch angle θ and the intensity observed value Bo into Equation (8). The estimated distance s may be calculated by the following Equation 10, which is a modified Equation 8. k in Equation 10 is a constant parameter determined according to μ ₀ , I, and a, for example, k=μ ₀ Ia ² /2.

[Modification 3]
In the above-described embodiment, a configuration is disclosed in which the residual sum of squares RSS is calculated for all candidate points existing in the candidate area, and then the candidate point with the smallest residual sum of squares RSS is adopted as the terminal position. However, it is not limited to this. For example, the position estimator F4 may be configured to adopt a candidate point whose residual sum of squares RSS is less than a predetermined allowable threshold as the terminal position. This configuration corresponds to a configuration that terminates the search process when a candidate point whose residual sum of squares RSS is less than a predetermined allowable threshold is found in the process of repeating steps S104 to S108. According to such a configuration, it is possible to further reduce the amount of calculation related to position estimation.

Note that the concept of the allowable threshold may also be introduced in the above-described embodiment. If the minimum value of the residual sum of squares RSS is equal to or greater than a predetermined allowable threshold, the position may be treated as indeterminate. With such a configuration, it is possible to reduce the risk of adopting an uncertain position as the terminal position. A specific value of the allowable threshold may be appropriately adjusted based on the required position estimation accuracy and the like.

[Modification 4]
The mounting positions of the LF transmitting antennas 32a to 32d are not limited to those described above. Each LF transmit antenna 32 can be mounted in a variety of positions. For example, the LF transmitting antenna 32a may be arranged near the right end of the ceiling. The right end portion of the ceiling portion corresponds to the portion with which the upper end portion of the door for the driver's seat abuts. Also, the LF transmitting antenna 32a may be arranged at the center arranged on the right side of the vehicle. The LF transmission antenna 32b may be arranged at a position symmetrical to the LF transmission antenna 32a. The LF transmitting antenna 32c may be attached to an overhead console, a central portion of the ceiling surface of the vehicle interior, an instrument panel, or the like. The LF transmitting antenna 32d may be arranged on the seating surface of the rear seat or inside the backrest.

Also, the mounting posture of the LF transmitting antennas 32a to 32d is not limited to the above-described mode. The LF transmitting antennas 32a to 32b may be mounted with the axial direction of the antenna along the vehicle width direction, or may be mounted with the antenna axial direction along the vehicle height direction. The LF transmitting antenna 32a and the LF transmitting antenna 32b may be mounted in different mounting postures. For example, the LF transmitting antenna 32a may be mounted with its axial direction along the vehicle longitudinal direction, while the LF transmitting antenna 32b may be mounted with its axial direction along the vehicle longitudinal direction. The LF transmitting antenna 32c and the LF transmitting antenna 32d may be attached in a posture in which the axial direction of the antenna is along the vehicle front-rear direction or the vehicle height direction. The LF transmitting antenna 32c and the LF transmitting antenna 32d may be mounted in different mounting postures. For example, the LF transmitting antenna 32c may be mounted with its axial direction along the vehicle longitudinal direction, while the LF transmitting antenna 32b may be mounted with its axial direction along the vehicle longitudinal direction.

[Modification 5]
In the above-described embodiment, a manner in which candidate points are set uniformly (at regular intervals) within the search range SR is disclosed, but the manner in which candidate points are set is not limited to this. As shown in FIG. 11, candidate points may be set more densely in the vicinity of the window than in areas other than the vicinity of the window. For example, the candidate points may be set every 4 cm in the area other than the vicinity of the window, while the candidate points may be set every 2 cm in the vicinity of the window. d1 shown in FIG. 11 indicates the setting interval of the candidate points outside the vicinity of the window, and d2 indicates the setting interval of the candidate points near the window. The window portion here refers to a region within 10 cm from the window.

According to the above setting mode, it is possible to improve the determination accuracy near the window portion where erroneous determination of the terminal position is likely to occur. As a result, it is possible to improve the accuracy of determining whether the mobile terminal 2 exists inside the vehicle or outside the vehicle. Further, in a configuration in which the body of the vehicle transmits radio waves, candidate points may be set more densely in the vicinity of the side portion of the vehicle than in the area other than the vicinity of the window portion. Alternatively, the set density of the candidate points may be made sparse as the distance from the vehicle increases.

[Modification 6]
In the embodiment described above, a mode in which the vehicle-side device 3 includes the area specifying unit F3 and the position estimating unit F4 has been disclosed, but the arrangement of various functions is not limited to this. The mobile terminal 2 may include the area specifying unit F3 and the position estimating unit F4. In this case, it is preferable that the portable terminal 2 is configured to wirelessly transmit to the vehicle-side device 3 data indicating the result of estimating the position of the terminal with respect to the vehicle.

[Modification 7]
Although a mode of estimating the position of the mobile terminal 2 using the received strength of the signal transmitted from the vehicle at the mobile terminal 2 has been disclosed above, the present invention is not limited to this. In a configuration in which a vehicle-side device includes a plurality of configurations (in-vehicle receivers) for receiving signals from the mobile terminal 2, the terminal position is estimated based on the reception strength of the signal from the mobile terminal 2 at each in-vehicle receiver. It may be configured as follows. Hereinafter, an embodiment corresponding to such a technical idea will be described as Modified Example 7. FIG. Note that the vehicle-side device 3 of this modified example corresponds to the vehicle position estimation device. Various technical ideas disclosed as Modifications 1 to 6 and Modification 8 to be described later can be appropriately applied to this modification as well.

The vehicle-side device 3 and the mobile terminal 2 in this modified example are each configured to be able to perform communication (hereinafter referred to as short-range communication) conforming to a predetermined short-range wireless communication standard. As a short-range wireless communication standard, for example, Bluetooth Low Energy (Bluetooth is a registered trademark), Wi-Fi (registered trademark), ZigBee (registered trademark), or the like can be adopted. Any short-range wireless communication standard may be used as long as it can provide a communication distance of, for example, several meters to several tens of meters. The vehicle-side device 3 and the mobile terminal 2 of this embodiment are configured to perform wireless communication in compliance with the Bluetooth Low Energy standard, for example.

As shown in FIG. 12 , the mobile terminal 2 in this modified example includes a mobile-side control section 23 and a mobile-side communication section 26 . The mobile-side communication unit 26 is a communication module for implementing short-range communication. The configuration and function of the mobile-side communication unit 26 are the same as those of the vehicle-mounted communication device 34, which will be described later. However, the mobile-side communication unit 26 does not have to include the reception intensity determination unit C3. The mobile-side communication unit 26 is connected to the mobile-side control unit 23 so as to be mutually communicable. The mobile-side control unit 23 controls the operation of the mobile-side communication unit 26 .

A signal transmitted by the mobile terminal 2 as short-range communication includes source information. The sender information is, for example, unique identification information (hereinafter referred to as terminal ID) assigned to the mobile terminal 2 . The terminal ID functions as information for identifying the mobile terminal 2 from other communication terminals. In addition, the portable terminal 2 notifies surrounding communication terminals equipped with a short-range communication function of its own existence by wirelessly transmitting communication packets containing source information at predetermined transmission intervals (i.e., advertise). Hereinafter, for the sake of convenience, a communication packet that is periodically transmitted for the purpose of advertising will be referred to as an advertisement packet.

The vehicle-side device 3 receives a signal (for example, an advertisement packet) transmitted from the mobile terminal 2 by the above-described short-range communication function, so that the mobile terminal 2 and the vehicle-side device 3 are within a range where short-range communication is possible. Detect that it exists. In this embodiment, as an example, the vehicle-side device 3 is configured to detect the presence of the mobile terminal 2 within the communication area by receiving advertisement packets sequentially transmitted from the mobile terminal 2. However, it is not limited to this. As another aspect, the mobile terminal 2 exists within the communication area of the vehicle-side device 3 based on the fact that the vehicle-side device 3 sequentially transmits advertising packets and a communication connection (so-called connection) with the mobile terminal 2 is established. It may be configured to detect that

As shown in FIG. 12, the vehicle-side device 3 of this embodiment includes a plurality of vehicle-mounted communication devices 34a to 34d as communication modules for carrying out short-range communication with the portable terminal 2. FIG. When the vehicle-mounted communication devices 34a to 34d are not distinguished, they are referred to as the vehicle-mounted communication device 34. FIG. Each in-vehicle communication device 34 is connected to the smart ECU 31 via a dedicated communication line or an in-vehicle network so as to be able to communicate with each other. Each vehicle-mounted communication device 34 is assigned a unique communication device number. The communication device number is information corresponding to the terminal ID for the mobile terminal 2 . The communication device number functions as information for identifying a plurality of vehicle-mounted communication devices 34 .

The in-vehicle communication devices 34a to 34d are mounted in appropriately designed locations in the vehicle. For example, the in-vehicle communication devices 34a to 34d are attached to the positions exemplified as the mounting positions of the LF transmission antenna 32 in the above-described embodiment and modification 4. FIG. Of course, the mounting position of each in-vehicle communication device 34 can be changed as appropriate.

FIG. 13 schematically shows the electrical configuration of the vehicle-mounted communication device 34. As shown in FIG. As shown in FIG. 13 , the vehicle-mounted communication device 34 includes an antenna 341 , a transmission/reception section 342 and a communication microcomputer 343 . Antenna 341 is an antenna for transmitting and receiving radio waves in a frequency band (for example, 2.4 GHz band) used for short-range communication. Antenna 341 is electrically connected to transmitter/receiver 342 . Various antenna structures such as a patch antenna, a dipole antenna, a monopole antenna, an inverted F antenna, and an inverted L antenna can be employed as the antenna 341 .

The transmitter/receiver 342 is a circuit module that performs signal processing related to signal transmission/reception. The transmission/reception unit 342 is connected to the communication microcomputer 343 so as to be able to communicate with each other. The transmitting/receiving section 342 includes a transmitting circuit C1, a receiving circuit C2, and a reception strength determining section C3. The transmission circuit C1 modulates a signal input from the smart ECU 31 via the communication microcomputer 343, outputs it to the antenna 341, and radiates it as radio waves.

The receiving circuit C 2 demodulates the signal received by the antenna 341 and provides it to the communication microcomputer 343 . The reception strength determination unit C3 is configured to sequentially detect the electric field strength (that is, the reception strength) of the signal received by the antenna 341 . The reception strength determination section C3 can be realized by various circuit configurations. The reception intensity detected by the reception intensity determination unit C3 is sequentially provided to the communication microcomputer 343 in association with the terminal ID included in the reception data. The reception intensity may be expressed in units of power [dBm], for example. For the sake of convenience, the data in which the reception strength and the terminal ID are associated will be referred to as reception strength data. The in-vehicle communication device 34 including the receiving circuit C2 and the reception intensity determination section C3 corresponds to the vehicle side receiver.

The communication microcomputer 343 is a microcomputer that controls data exchange with the smart ECU 31 . In addition, when the communication microcomputer 343 acquires the reception intensity data from the reception intensity determination unit C3, the communication microcomputer 343 sequentially provides the smart ECU 31 with the reception intensity data.

In the above configuration, the information processing section 311 of the smart ECU 31 identifies the terminal position by the same method as in the above-described embodiment. That is, the area specifying unit F3 specifies the corresponding area Cs where the mobile terminal 2 is located based on the reception strength of the signal from the mobile terminal 2 at each in-vehicle communication device. Note that the corresponding area Cs is set in advance for each in-vehicle communication device 34 . The position estimating unit F4 calculates a residual sum of squares RSS for each candidate point present in the corresponding area Cs specified by the area specifying unit F3 within the search range SR. Then, it is determined that the portable terminal 2 is present at the candidate point where the residual sum of squares RSS is the smallest in the corresponding area Cs. Since the vehicle-mounted communication device 34 incorporates the antenna 341, the corresponding area Cs for each vehicle-mounted communication device 34 corresponds to the corresponding area for each antenna. Also, the mounting position of the in-vehicle communication device 34 corresponds to the mounting position of the antenna.

[Modification 8]
In the above-described embodiment, a three-dimensional space including the exterior of the vehicle within 1 m from the side and rear ends of the vehicle is set as the search range SR. Not limited. The range used as the search range SR can be changed as appropriate. Dx, which defines the size of the search range SR in the vehicle width direction, may be set to 2 m in consideration of the Thatcham requirement. In addition, in a configuration in which a three-dimensional space including the exterior of the vehicle is set as the search range, the area above the hood, roof, and under the vehicle body may be set as the non-search area. It is preferable that the corresponding area for each antenna is set so as not to include the unsearched area.

Also, the search range SR may be limited only to the interior of the vehicle. In that case, the corresponding area Cs of each antenna should also be set in the vehicle interior. FIG. 14A conceptually shows the coverage area Cs of the LF transmission antenna 32a, and FIG. 14B conceptually shows the coverage area Cs of the LF transmission antenna 32b. Further, (C) of FIG. 14 conceptually shows the coverage area Cs of the LF transmission antenna 32c, and (D) conceptually shows the coverage area Cs of the LF transmission antenna 32d.

<Additional notes>
The controller and techniques described in this disclosure may be implemented by a special purpose computer comprising a processor programmed to perform one or more functions embodied by a computer program. The apparatus and techniques described in this disclosure may also be implemented by dedicated hardware logic circuitry. Additionally, the apparatus and techniques described in this disclosure may be implemented by one or more special purpose computers configured in combination with a processor executing a computer program and one or more hardware logic circuits. The computer program may also be stored as computer-executable instructions on a computer-readable non-transitional tangible recording medium. In other words, the means and/or functions provided by the smart ECU 31 can be provided by software recorded in a physical memory device and a computer that executes the software, only software, only hardware, or a combination thereof. Some or all of the functions provided by the smart ECU 31 may be implemented as hardware. Implementation of a function as hardware includes implementation using one or more ICs.

1 vehicle position estimation system 2 mobile terminal 3 vehicle side device 21 LF receiving antenna 22 LF receiving unit (mobile side receiving unit) 23 mobile side control unit 24 UHF transmitting unit 25 UHF transmitting antenna 26 mobile side communication unit, 31 smart ECU, 32 32a to 32d LF transmission antenna (vehicle side antenna), 33 UHF receiver, 34 34a to 34d in-vehicle communication device (vehicle side receiver), 221 C3 reception strength determination unit, 311 information processing unit, 312 LF driver, 341 antenna, 342 transmission/reception unit, 343 communication microcomputer, C1 transmission circuit, C2 reception circuit, F1 transmission processing unit, F2 response acquisition unit, F3 area identification unit, F4 position estimation unit, M1 correspondence area storage unit, M2 intensity distribution storage unit

Claims (9)

A mobile terminal (2) carried by a vehicle user and a vehicle-side device (3) used in the vehicle perform wireless communication to estimate a terminal position, which is the position of the mobile terminal with respect to the vehicle. A vehicle position estimation system (1),
a search range, which is a range for setting candidate points as candidates for the terminal position, is set in advance with reference to the vehicle;
The vehicle-side device includes a plurality of vehicle-side antennas (32, 32a to 32d) that transmit radio signals toward the mobile terminal,
The mobile terminal is
a mobile receiver (22) for receiving a signal from the vehicle antenna;
An intensity determination unit (221) that determines the reception intensity, which is the intensity of the signal received by the mobile-side reception unit,
The vehicle-side device or the mobile terminal,
Based on the strength observation value, which is the reception strength of the signal transmitted from each of the vehicle-side antennas, determined by the strength determination unit, and the corresponding area preset for each of the vehicle-side antennas, an area identification unit (F3) that identifies a candidate area that is an area in which a mobile terminal may exist;
calculating an error evaluation value indicating the degree of divergence between the candidate point and the true terminal position for each of the candidate points based on the observed strength of the signal transmitted from each of the vehicle-side antennas, and calculating the error evaluation; a position estimation unit (F4) that adopts the candidate point with the smallest value or the candidate point with the error evaluation value equal to or less than a predetermined allowable threshold as the terminal position,
The position estimating unit identifies the terminal position by calculating the error evaluation value for the candidate points existing within the candidate area identified by the area identifying unit within the search range. A configured vehicle localization system. The vehicle position estimation system according to claim 1,
The position estimation unit
identifying, for each vehicle-side antenna, an iso-intensity surface that is a curved surface in which the received strength of a signal transmitted from the vehicle-side antenna is the strength observation value corresponding to the vehicle-side antenna;
A position estimation system for a vehicle, wherein a sum of squares of distances from the candidate point to the iso-intensity surface for each of the vehicle-side antennas is calculated as the error evaluation value. The vehicle position estimation system according to claim 1,
An intensity distribution storage unit (M2) that stores an intensity distribution model, which is data indicating the distribution of reception intensity for each of the vehicle-side antennas within the search range,
The position estimation unit uses the intensity distribution model for each of the vehicle antennas stored in the intensity distribution storage unit to calculate the intensity estimated value, which is the estimated value of the reception intensity at the candidate point, from the vehicle antenna. specified for each
A position estimation system for a vehicle, wherein a sum of squares of differences between the estimated strength value and the observed strength value for each of the vehicle antennas is calculated as the error evaluation value for the candidate point. The vehicle position estimation system according to any one of claims 1 to 3,
A position estimation system for a vehicle, wherein the vehicle-side antenna is configured using an antenna having a spheroidal radiation characteristic. The vehicle position estimation system according to any one of claims 1 to 4,
A three-dimensional space within 1 m from the side of the vehicle is set as the search range,
The hood, roof, and underbody of the vehicle are set as non-search areas,
A position estimation system for a vehicle, wherein none of the corresponding areas for each of the vehicle-side antennas is set so as not to include the non-search area. The vehicle position estimation system according to any one of claims 1 to 5,
A position estimation system for a vehicle, wherein, in the search range, a region within a predetermined distance from a window of the vehicle has the candidate points set more densely than other regions in the search range. A vehicle position estimation system according to any one of claims 1 to 6,
When the difference between the highest observed strength value and the second highest observed strength value among the observed strength values for each of the vehicle-side antennas is less than a predetermined integration threshold, The range obtained by integrating the corresponding area of the vehicle-side antenna from which the highest observed intensity value is obtained and the corresponding area of the vehicle-side antenna from which the second highest observed intensity value is obtained A vehicle localization system configured to set a candidate area. 8. The vehicle position estimation system according to any one of claims 1 to 7, which is used in a vehicle whose body is constructed using a material that allows radio waves to pass through. A vehicle position estimation device that estimates a terminal position, which is the position of the mobile terminal with respect to the vehicle, by performing wireless communication with a mobile terminal carried by a user of the vehicle,
a search range, which is a range for setting candidate points as candidates for the terminal position, is set in advance with reference to the vehicle;
a plurality of vehicle-side receivers (34, 34a to 34d) configured to receive radio signals transmitted from the mobile terminal and detect the reception strength of the received radio signals;
A candidate area in which the mobile terminal may exist is determined based on the intensity observation value, which is the reception intensity at each of the vehicle-side receivers, and a corresponding area preset for each of the vehicle-side receivers. an area identification unit (F3) to be identified;
An error evaluation value indicating the degree of divergence between the candidate point and the true terminal position is calculated for each of the candidate points based on the intensity observation value at each of the vehicle-side receivers, and the error evaluation value is the highest. a position estimating unit (F4) that adopts, as the terminal position, the candidate point that becomes smaller or the candidate point that causes the error evaluation value to be equal to or less than a predetermined allowable threshold,
The position estimating unit identifies the terminal position by calculating the error evaluation value for the candidate points existing within the candidate area identified by the area identifying unit within the search range. A configured vehicle position estimator.

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