JP2024002224A - Wireless ranging device and position determination system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless ranging device and a position determination system that can reduce the risk of erroneously calculating the distance to a target.

SOLUTION: A plurality of communication devices are connected to a smart ECU. A standard rise time, which is a model value of a time from the rise point to the peak of a received pulse (so-called rise time), is registered in a controller of each communication device. The standard rise time is a parameter generated based on a measured value of the rise time in an ideal environment. The controller calculates a measured distance value by regarding a time point later than the rise point of the received pulse by the standard rise time on the time axis as a peak. That is, the controller calculates the measured distance value by regarding a value obtained by adding the standard rise time to a rise detection time as a round trip time.

SELECTED DRAWING: Figure 7

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present disclosure provides a wireless ranging device that calculates a distance to a target based on the time from transmitting a wireless signal toward the target to receiving a signal corresponding to the transmitted signal, and the wireless ranging device. This invention relates to a position determination system using.

There is a technique for estimating the distance to a target using the round trip time, which is the time from when an impulse signal, which is a pulsed radio wave, is transmitted toward a target until the impulse signal is received back from the target. For example, Patent Documents 1-2 disclose a configuration in which a vehicle-mounted communication device that performs UWB-IR wireless communication performs two-way communication with the mobile device to determine the distance from the vehicle-mounted communication device to the mobile device. ing.

JP2020-26996A JP2020-122727A

The reception timing of the impulse signal can be specified based on the peak of the received waveform. However, the interior of the vehicle and the surroundings of the vehicle correspond to a so-called multipath environment where metal bodies such as the vehicle body are present. Therefore, a communication device may receive a direct wave in such a manner that a reflected wave is combined with (superimposed on) the direct wave. When a reflected wave is coupled to a direct wave, the peak of the received pulse may be detected behind the peak (true peak) of the direct wave. If the peak position of the received pulse is incorrectly detected, the error included in the distance to the target may increase.

The present disclosure has been made based on the above considerations or points of view, and one of its purposes is to provide a wireless ranging device and a position determination system that can reduce the risk of miscalculating the distance to a target. It's about doing.

The wireless ranging device disclosed herein includes a transmitter (12) that transmits an impulse signal in a predetermined frequency band, a receiver (13) that detects the reception strength of radio waves in the frequency band, and a receiver that detects A received pulse detection unit (142) that detects the rising point of a received pulse based on time series data of received intensity, and a model value memory in which a model value of the time from the rising point to the peak of the received pulse is registered in advance. (141), and a distance calculation unit (143) that calculates a distance value indicating the distance to the target using the rise detection time, which is the time from when the impulse signal is transmitted until the rise point is detected, and the model value. ) and.

The time from transmitting the impulse signal until the peak of the received pulse is observed is the first period from transmitting the impulse signal until the rising point is observed, and the second period from the rising point to the peak. It can be divided into two periods. According to the above configuration, the length of the second period can be specified based on the pre-registered model value. Therefore, even if the peak position is erroneously detected due to superimposition of the reflected wave on the direct wave, the influence can be alleviated, and the error in the measured distance value can be reduced.

Further, the position calculation system of the present disclosure is a position determination system including a plurality of wireless ranging devices (1) and a position calculating device (2), each of which has a predetermined frequency. A transmitting section (12) that transmits an impulse signal of the frequency band, a receiving section (13) that detects the received strength of the radio wave of the frequency band, and a rising edge of the received pulse based on the time series data of the received strength detected by the receiving section. A received pulse detection unit (142) that detects the point, a model value storage unit (141) in which model values of the time from the rising point to the peak of the received pulse are registered in advance, and a model value storage unit (141) that stores the model value of the time from the rising point to the peak of the received pulse, and the A distance calculation unit (143) calculates a distance value indicating the distance to the target using the rise detection time, which is the time until a point is detected, and the model value; a reporting unit (144) that transmits data to the calculation device; and a position calculation unit (F1) that calculates the position coordinates of the target based on the distance measurement data received from a plurality of wireless distance measurement devices.

The above position determination system is a system using a plurality of the above radio distance measuring devices. As explained above, since the distance measurement values provided by the individual wireless distance measurement devices become more accurate, the accuracy of position estimation based on them can also be improved.

Note that the numerals in parentheses described in the claims indicate correspondence with specific means described in the embodiments described later as one aspect, and limit the technical scope of the present disclosure. isn't it.

FIG. 2 is a diagram for explaining the overall image of a vehicle electronic key system. FIG. 2 is a block diagram showing the configuration of a smart ECU 2. FIG. FIG. 2 is a functional block diagram of a communication device. FIG. 3 is a diagram for explaining round trip time. FIG. 3 is a diagram showing received pulses of direct waves that can be observed in an ideal environment. FIG. 3 is a diagram for explaining a rise detection time and a peak detection time. It is a flowchart which shows an example of search processing. FIG. 3 is a diagram for explaining the reason why a distance measurement error occurs due to reflected waves. FIG. 3 is a diagram for explaining the influence of reflected waves on distance measurement values. It is a flowchart which shows another example of search processing. It is a flowchart which shows another example of search processing. FIG. 7 is a diagram showing that there is a positive correlation between rise time and distance measurement error. It is a flowchart which shows another example of search processing. FIG. 3 is a block diagram showing another configuration example of the controller.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle electronic key system to which the distance measuring device of the present disclosure is applied will be described below with reference to the drawings. The following description can be modified as appropriate to suit the laws and customs of the region where the vehicle Hv is used.

The vehicle electronic key system of this embodiment includes a plurality of communication devices 1 and a smart ECU 2, as shown in FIG. ECU is an abbreviation for Electronic Control Unit and means an electronic control device. A plurality of communication devices 1 and smart ECUs 2 are mounted at arbitrary positions on the vehicle Hv. The smart ECU 2 is connected to each of the plurality of communication devices 1 through a dedicated signal line. A vehicle electronic key system corresponds to a position determination system.

Each communication device 1 is a communication module that performs bidirectional wireless communication using radio waves in a predetermined frequency band with a portable device 9 that is a device carried by a user of the vehicle Hv. The configuration and performance of each communication device 1 are substantially the same.

Here, as an example, the communication device 1 and the mobile device 9 are configured to be able to perform wireless communication using the UWB-IR (Ultra Wide Band - Impulse Radio) method. That is, the communication device 1 and the mobile device 9 are configured to be able to transmit and receive impulse-like radio waves (hereinafter referred to as impulse signals) used in ultra-wideband (UWB) communication. The impulse signal used in UWB communication is a signal that has an extremely short pulse width (for example, 2 ns) and a bandwidth of 500 MHz or more (that is, ultra-wide bandwidth).

Note that in UWB communication, multiple channels can be used as disclosed in IEEE802.15.4z. For example, the communication device 1 communicates with the mobile device 9 using the fifth channel of UWB communication. Of course, the communication device 1 may be configured to be able to communicate with the mobile device 9 using the third channel or the ninth channel. The third channel means a frequency band from 4243 MHz to 4742 MHz (center frequency is 4492 MHz). The fifth channel refers to radio waves in the 6489.6 MHz (approximately 6.5 GHz) ±250 MHz band, that is, frequencies from 6240 MHz to 6739 MHz. The ninth channel means a frequency band from 7738 MHz to 8237 MHz (center frequency is 7987.2 MHz). Note that IEEE (registered trademark) is an abbreviation for Institute of Electrical and Electronics Engineers, and means the American Institute of Electrical and Electronics Engineers.

In addition, there are various UWB-IR modulation methods, such as on-off keying (OOK), pulse position modulation (PPM), and pulse width modulation (PWM). Adoptable. Note that the on-off modulation method is a method for expressing information (for example, 0 and 1) by the presence/absence of an impulse signal. The pulse position modulation method is a method in which modulation is performed at the pulse generation position. The pulse width modulation method is a method that expresses information by pulse width. Here, as an example, UWB communication between the communication device 1 and the mobile device 9 is performed using the OOK method.

Data transmission by UWB communication is realized using a plurality of impulse signals. Hereinafter, data signals exchanged through UWB communication will be referred to as UWB signals. That is, a UWB signal such as a response request signal or a response signal, which will be described later, means a signal sequence in which a plurality of impulse signals are arranged at time intervals corresponding to transmission data. Since the UWB signal includes a plurality of impulses, it can also be called a pulse sequence signal.

For example, a vehicle Hv includes communication devices 1a to 1d and 1p to 1r as communication devices 1, as shown in FIG. Communication devices 1a to 1d are communication devices 1 disposed on the outer surface of vehicle Hv. For example, the communication device 1a is placed at the right corner of the front bumper, and the communication device 1b is placed at the left corner of the front bumper. The communication device 1c is arranged at the right corner of the rear bumper, and the communication device 1d is arranged at the left corner of the rear bumper. Furthermore, the communication devices 1p to 6r are the communication devices 1 placed inside the vehicle interior. The communication device 1p is placed, for example, at the upper end of the windshield or at the center of the ceiling inside the vehicle. The communication device 1q is arranged near the right edge of the ceiling inside the vehicle, and the communication device 1r is arranged near the left edge of the ceiling inside the vehicle. Since each communication device 1 is mounted on a vehicle, it can also be referred to as a vehicle-mounted communication device.

The operation of each communication device 1 is controlled by a smart ECU 2. Each communication device 1 transmits data indicating the reception status of signals from the mobile device 9 to the smart ECU 2. The reception status may include presence or absence of reception, reception strength, measured distance value, and the like. The communication device 1 is primarily a communication device for determining device positions, and is also called an anchor, a reference station, or the like. Each communication device 1 calculates a measured distance value, which is the distance to the mobile device 9, by transmitting and receiving impulse signals to and from the mobile device 9, and outputs it to the smart ECU 2. Details of the communication device 1 will be described separately later.

The smart ECU 2 is an ECU that determines the device position with respect to the vehicle Hv based on the reception status of the signal from the mobile device 9 in each of the plurality of communication devices 1, and performs vehicle control according to the determination result. The device position refers to the position of the mobile device 9. Based on the fact that at least one communication device 1 has received the UWB signal transmitted from the mobile device 9, the smart ECU 2 detects that the mobile device 9 is present within a predetermined range outside the vehicle, and performs device position determination processing. or perform wireless authentication processing. The wireless authentication process may be performed using a challenge-response method, for example. The smart ECU 2 corresponds to a position calculation device.

The smart ECU 2 is realized using a computer. That is, as shown in FIG. 2, the smart ECU 2 includes a processor 21, a memory 22, a storage 23, an input/output circuit 24, and a bus line connecting these components. The processor 21 is an arithmetic core such as a CPU (Central Processing Unit). The memory 22 is a volatile memory such as RAM (Random Access Memory). The storage 23 includes a nonvolatile storage medium such as a flash memory. A control program executed by the processor 21 is stored in the storage 23 . The input/output circuit 24 is a circuit module for communicating with other devices.

The storage 23 stores communication device setting data indicating the mounting position of each communication device 1 in the vehicle Hv. The storage 23 corresponds to a storage device. The mounting position of each communication device 1 can be expressed, for example, as a point on a vehicle coordinate system, which is a two-dimensional coordinate system centered on an arbitrary position on the vehicle Hv and parallel to both the width direction and the longitudinal direction of the vehicle Hv. . The X-axis forming the vehicle coordinate system can be set parallel to the vehicle width direction, and the Y-axis can be set parallel to the vehicle longitudinal direction. As the center of the coordinate system, for example, an arbitrary location such as the center of the vehicle body or the mounting position of the smart ECU 2 can be adopted. The storage 23 corresponds to a storage device.

Various in-vehicle devices can be connected to the smart ECU 2 directly or indirectly. For example, the smart ECU 2 is connected to a door sensor, a start switch, a body ECU, a power supply ECU, etc. via an in-vehicle network so that they can communicate with each other.

The door sensor is a sensor for detecting that the user performs an operation to unlock and lock the door of the vehicle Hv. The door sensor may be a touch sensor or a push switch. The start switch is a push switch used by the user to turn on/off the running power. The body ECU is an ECU that controls the door lock motor and vehicle lighting equipment. The power source ECU is an ECU that controls on/off of a driving power source mounted on the vehicle Hv. Note that the running power source is a power source for driving the vehicle Hv, and when the vehicle Hv is an engine vehicle, it refers to an ignition power source. When the vehicle Hv is an electric vehicle, the driving power source refers to the system main relay.

In addition, the smart ECU 2 may be connected to a BLE communication device for implementing wireless communication (hereinafter referred to as BLE communication) based on the Bluetooth (registered trademark) Low Energy standard. The BLE communication device can function as a means for performing data communication with the mobile device 9. The smart ECU 2 includes a position calculation unit F1 and a vehicle control unit F2 as functional units in which the processor 21 executes a control program stored in the storage 23. Details of the smart ECU 2 including these functional units will be described separately later.

<About mobile device 9>
The mobile device 9 is a portable and general-purpose information processing terminal equipped with a UWB communication function. As the mobile device 9, various communication terminals such as a smartphone, a wearable device, etc. can be employed. Wearable devices are devices that are worn on the user's body and can take various shapes, such as a wristband, a wristwatch, a ring, glasses, and earphones.

The mobile device 9 includes a UWB communication section and a device control section. The UWB communication unit is a communication module for implementing UWB communication. The device control unit is configured as a computer including, for example, a processor, memory, storage, and the like. A device ID is stored in the storage. The device ID is a device identification number and differs for each mobile device 9. As the device ID, for example, a device address or a UUID (Universally Unique Identifier) can be used.

The device control unit performs processing related to data communication with the communication device 1 and the smart ECU 2. A key code used in wireless authentication processing with the smart ECU 2 may be stored in the storage of the mobile device 9. The key code can also be called an encryption key.

When the mobile device 9 of this embodiment receives the UWB signal transmitted from the vehicle Hv, it returns a response signal according to the received signal. For example, when the mobile device 9 receives a response request signal from the vehicle Hv, it returns a UWB signal as a response signal to the vehicle Hv. The response request signal is a signal for the vehicle Hv to search for the mobile device 9, and is a type of signal that requests the mobile device 9 to return a response signal. The UWB signals transmitted by the mobile device 9 and the communication device 1 may include a code indicating the source or destination. The source and destination can be expressed by a device ID or the like. As the source information, a device management number may be used instead of the device ID. The device management number is a number that the smart ECU 2 assigns to each mobile device 9.

Note that the mobile device 9 may be a smart key that is a dedicated device as an electronic key for the vehicle Hv. The smart key is a device that is transferred to the owner along with the vehicle Hv when the vehicle Hv is purchased. A smart key can be understood as one of the accessories of the vehicle Hv. Smart keys can take a variety of shapes, such as a flat rectangular parallelepiped, a flat ellipse (so-called fob type), and a card type. A smart key may be called a vehicle portable device, key fob, key card, access key, etc.

<About the configuration of the communication device>
Here, the configuration of each communication device 1 will be explained. Each of the plurality of communication devices 1 includes an antenna 11, a transmitter 12, a receiver 13, and a controller 14, as shown in FIG. The antenna 11 is an antenna element (conductor) for transmitting and receiving UWB signals. The communication device 1 of this embodiment includes a first antenna 11A and a second antenna 11B as the antennas 11. The first antenna 11A is a transmitting antenna 11 and is electrically connected to the transmitter 12. The second antenna 11B is a receiving antenna 11 and is electrically connected to the receiving section 13. Note that the first antenna 11A may be configured as a transmitting/receiving antenna. In that case, the first antenna 11A may also be connected to the receiving section 13. The antenna 11 is configured to be excited in a desired frequency band, such as the fifth channel of UWB.

The transmitter 12 is configured to generate a UWB signal corresponding to the baseband signal input from the smart ECU 2, and radiate this UWB signal as a radio wave from the first antenna 11A. The transmitter 12 includes a circuit that electrically processes the baseband signal, such as a modulation circuit 121. The transmitter 12 outputs an electrical impulse signal corresponding to transmission data to the antenna 11.

The receiving unit 13 is a circuit module that receives the UWB signal transmitted from the mobile device 9 and electrically processes it. The receiving section 13 includes a demodulation circuit 131, a reception strength detection circuit 132, and the like. The reception strength detection circuit 132 sequentially outputs a signal indicating the reception strength to the controller 14. Note that, in order to reduce power consumption, the receiving unit 13 may be configured to start observing the reception strength using the transmission of the impulse signal by the transmitting unit 12 as a trigger.

The controller 14 outputs received data to the smart ECU 2 and outputs transmitted data input from the smart ECU 2 to the transmitter 12. The controller 14 is realized using, for example, an IC (Integrated Circuit).

The controller 14 performs a search process based on instructions from the smart ECU 2. The search process refers to a series of processes including transmitting a UWB signal as a response request signal, waiting to receive a response signal, and reporting a reception result. The report data when a response signal is successfully received may include the device ID of the mobile device 9 that returned the response and a measured distance value, which will be described later. If a response signal is not received even after a predetermined response waiting time has elapsed after transmitting the response request signal, the controller 14 returns a code indicating that the mobile device 9 could not be found to the smart ECU 2 as report data. I can do it. Such report data can be referred to as search result data.

The controller 14 includes a setting storage section 141, a received pulse detection section 142, a distance calculation section 143, a reporting section 144, and a temporary memory 145 as configurations related to the above search processing. The setting storage section 141, the received pulse detection section 142, and the distance calculation section 143 are mainly configured to measure round trip time (RTT). RTT roughly corresponds to the elapsed time from when the transmitter 12 transmits a UWB signal as a response request signal until when the receiver 13 receives a response signal from the mobile device 9. The communication device 1 corresponds to a wireless distance measuring device. The setting storage section 141 corresponds to a model value storage section.

As shown in FIG. 4, RTT is equivalent to the sum of the round trip flight time (Tf x 2), the length of the response request signal (Lrq), and the response processing time (Tn) in the mobile device 9. do. Tf in FIG. 4 indicates the one-way flight time. Lrq in FIG. 4 indicates the length of the response request signal, and Trs indicates the length of the response signal. The response processing time is the time required to generate and output a response signal corresponding to a received signal. The one-way flight time corresponds to the inter-device distance, which is the distance from the communication device 1 to the mobile device 9.

The setting storage unit 141 stores a standard rise time (TRm ) is the registered storage medium. The setting storage section 141 corresponds to a model value storage section. A received pulse is a received signal having an intensity greater than or equal to a predetermined threshold. For example, a series of time-series data of received strength from when the received strength exceeds a predetermined threshold until it falls below the threshold corresponds to a received pulse.

When the received pulse corresponding to the impulse signal transmitted from the mobile device 9 is not interfered with by reflected waves or the like, it takes on an upwardly convex substantially parabolic shape as shown in FIG. 5, and the position of the peak becomes clear. In FIG. 5, Pq indicates the received strength at the peak, τa indicates the time when the rising point was observed, and τpq indicates the time when the peak was observed.

Note that the rising point of the received pulse refers to the point in time when the received intensity reaches a predetermined rising edge determination value (Pth), and in reality, refers to the point in time when the received intensity equal to or higher than the rising edge determination value (Pth) is detected. The rising determination value is a value designed in advance. The rise determination value can be determined by the characteristics of the IC that constitutes the controller 14. The peak of the received pulse corresponds to the maximum value of the received intensity that constitutes one received pulse.

Tests have confirmed that the observed value of rise time (TRo) is approximately constant in an ideal environment. The ideal environment refers to an environment where there is nothing between the communication device 1 and the mobile device 9, and where there is no interference such as reflected waves. For example, an environment in which nothing is placed other than the communication device 1 and the mobile device 9 in an anechoic chamber corresponds to an ideal environment. The ideal environment can also be described as free space. Reflected wave interference refers to a phenomenon in which a reflected wave is combined (superimposed) with a direct wave, resulting in an apparent received pulse having a longer width than its original pulse width. The case where the direct wave is being interfered with by the reflected wave can be understood as the case where the reflected wave is coupled to the rear side of the direct wave.

Standard rise times are designed based on test results in ideal environments. As the standard rise time, the average value or median value of a plurality of measurement results can be adopted. Here, as an example, the standard rise time is set to 1.5 nanoseconds. Of course, the standard rise time may vary depending on the rise determination value, transmission power, reception sensitivity, and other setting values. The standard startup time may be set to 1.0 nanoseconds, 1.2 nanoseconds, or 1.6 nanoseconds in consideration of various setting values. Note that the model value is a value registered in advance, and can also be called a sample value or a standard value. The setting storage unit 141 is realized using a nonvolatile memory such as a flash memory or a ROM (Read Only Memory).

The received pulse detection unit 142 detects received pulses and acquires pulse information accompanying the received pulses based on time-series data (histogram) of received intensity. The pulse information includes at least the rise detection time (Ta).

As shown in FIG. 6, the rise detection time (Ta) is the elapsed time from when the transmitter 12 transmits the impulse signal until the reception strength first exceeds the rise determination value. Note that for a predetermined period of time immediately after the transmitter 12 transmits the impulse signal, the transmitter 13 can observe the transmitter signal itself rather than the response signal from the mobile device 9 . A dead period, which is a period during which reception pulses are not detected, may be set in the receiving section 13. The length of the dead period corresponds to the length of the UWB signal output from the transmitter 12. Of course, the dead period may not be provided. The controller 14 may be configured to extract only the received signal component by subtracting the received strength component corresponding to the transmitted signal from the time-series data of the received strength.

Such a rise detection time (Ta) may correspond to the time until the reception strength exceeds a predetermined rise determination value for the first time after the transmitter 12 completes transmission of the UWB signal. The rise detection time can be measured based on the time when the transmitter 12 transmits the fast pulse. A fast pulse is an impulse signal located at the head of a plurality of impulse signals that constitute transmission/reception data.

The rise detection time (Ta) can be measured based on the peak position of the transmission fast pulse. The transmission fast pulse refers to a fast pulse of a response request signal (that is, a transmission signal) transmitted by the transmitter 12. The controller 14 may specify the transmission timing (peak position) of the fast pulse by the transmitter 12 based on the notification from the transmitter 12, or may specify the voltage level of the signal line from the transmitter 12 to the first antenna 11A. It may be identified by monitoring. Further, the controller 14 may identify the peak of the transmission fast pulse based on time-series data of the reception strength.

The received pulse detection unit 142 may be configured to detect peak intensity, peak detection time, rise time, fall time, pulse width, etc. in addition to the rise detection time. Peak strength refers to the received strength at the peak of the received pulse. The peak detection time is the time from when the impulse signal is transmitted until the peak of the received pulse is observed. The peak detection time can match the RTT in ideal circumstances. Similarly to the rise detection time, the peak detection time is also measured based on the peak position of the transmission fast pulse.

Rise time is the time from the rise point to the peak. The rise time corresponds to the value obtained by subtracting the rise detection time from the peak detection time. Falling time refers to the time from the peak to the falling point. The falling point refers to the point at which the reception strength falls below the rising determination value for the first time after the peak.

Such a received pulse detection unit 142 can be understood as a configuration that extracts a feature amount of a received pulse. The received pulse detector 142 can measure the rise detection time and the like by counting clock signals input from a clock oscillator (not shown).

Note that the rise detection time and the peak detection time (hereinafter referred to as rise time, etc.) can be measured using, for example, a timer that is triggered by the transmission of a fast pulse. Of course, the received pulse detection unit 142 records the clock count value at the time when the fast pulse is transmitted as the transmission time (τs), and based on the difference from the time when the rising point or peak is detected, The rising detection time and the like may also be calculated. For example, the received pulse detection unit 142 calculates the rise detection time (Ta) by subtracting the transmission time (τs) of the impulse signal from the rise detection time (τa), which is the time when the rise point is detected. You may do so.

The distance calculation unit 143 is configured to calculate a distance value based on the rise detection time (Ta) acquired by the reception pulse detection unit 142 and the standard rise time (TRm) stored in the setting storage unit 141. be. For example, the distance calculation unit 143 calculates the distance measurement value by regarding the value obtained by adding the standard rise time (TRm) registered in the setting storage unit 141 to the observed rise detection time (Ta) as the RTT.

This configuration corresponds to a configuration in which the time point when the standard rise time (TRm) is added to the observed rise detection time (Ta) is regarded as the arrival time of the peak of the received pulse corresponding to the direct wave. In the present disclosure, a point that is behind the observed (detected) rising point by a standard rising time on the time axis is also referred to as a standard peak position. In the present disclosure, the value obtained by adding the standard rise time (TRm) to the observed rise detection time (Ta) is also referred to as model-based RTT.

The distance value calculated by the distance calculation unit 143 is a parameter indicating the distance from the communication device 1 to the mobile device 9. The distance calculation unit 143 calculates the round trip flight time by subtracting the estimated value of the non-propagation element from the calculated RTT. Note that the non-propagation element is a delay element that is not related to the propagation time (flight time) of radio waves in space, and refers to the delay time derived from internal processing/circuit characteristics of the communication device or mobile device 9. . Non-propagation elements can include the length of the response request signal (Lrq) in addition to the response processing time (Tn). The non-propagation elements may also include the reaction delay time of the circuit that constitutes the receiving section 13. Non-propagating elements can also be called subtraction elements or correction elements.

For example, the distance calculation unit 143 calculates the round-trip flight time by subtracting the expected response processing time (Tn) and the design value (Lrq) of the length of the response request signal as non-propagation elements from the model-based RTT. do. The distance calculation unit 143 then uses the value obtained by dividing the round trip flight time by 2 and multiplying the flight speed of the radio wave as the distance measurement value. Of course, the calculation formula for calculating the measured distance value from the RTT is not limited to the above example. The calculation formula can be changed as appropriate.

In this embodiment, the measured distance value is expressed in the distance dimension, but in other embodiments, the measured distance value may be a parameter in the time dimension. For example, the measured distance value may be the time of flight (ToF) for one way or round trip. The measured distance value can also be called a ToF-related value.

The reporting unit 144 is configured to report the measured distance value to the smart ECU 2 in association with the device ID indicating the transmission source of the response signal as search result data. The distance measurement information for each transmission source transmitted by the reporting unit 144 is used for position calculation of the mobile device 9 by the smart ECU 2. Temporary memory 145 is volatile memory such as RAM. The temporary memory 145 temporarily stores data input from the receiving unit 13, values of calculation processes, calculation results, and the like. For example, the controller 14 associates the observed value of the reception strength input from the receiving unit 13 with impression time information, such as a count value of a timer, and stores it in the temporary memory 145.

<About search processing>
Here, the search process performed by each communication device 1 will be explained using the flowchart shown in FIG. The search process may be performed periodically based on a request from the smart ECU 2, for example, when the vehicle Hv is parked. The search process includes steps S11 to S17, as an example. Each step is mainly executed by the communication device 1, for example, the controller 14. Each step may be performed in order according to the direction of the arrow shown in FIG.

Step S11 is a step in which the controller 14 causes the first antenna 11A to transmit a UWB signal as a response request signal. The received pulse detection unit 142 starts a timer for specifying the rise detection time and the like in conjunction with the transmission of the impulse signal.

Step S12 is a step in which the controller 14 determines whether a response signal from the mobile device 9 has been received based on the input data from the receiving unit 13. If the controller 14 is able to receive the response signal (S12 YES), the controller 14 stores the source information (device ID) included in the received data as communication partner information in a memory or the like, and executes the processes from step S14 onwards. On the other hand, if the response signal is not received even after the predetermined waiting time has elapsed after transmitting the response request signal (NO in step S12), a non-response report is performed in step S13. The non-response report refers to a process of transmitting a code indicating that the mobile device 9 could not be found to the smart ECU 2 as search result data.

Step S14 is a step in which the received pulse detection unit 142 detects a rising point based on time-series data of the received intensity after the impulse signal is transmitted, and obtains a rising detection time (Ta). Step S15 is a step in which a value obtained by adding the standard rise time to the rise detection time obtained in step S14 is calculated as RTT.

Step S16 is a step in which the distance calculation unit 143 calculates a measured distance value based on the RTT calculated in step S15. Assuming that the measured distance value is D, the estimated value of the non-propagation element is γ, and the propagation speed of the radio wave is C, the distance calculation unit 143 calculates the measured distance value using, for example, the following equation (1).

D=(RTT-γ)×C/2...(1)
Here, since the measured distance value is a one-way distance, (RTT-γ)×C is divided by 2, but the present invention is not limited to this. In a configuration in which the round-trip distance is treated as a distance measurement value, the process of dividing by 2 can be omitted. Note that if the transmission time of the impulse signal is τs, and the time when the rising point is detected is τa, then Ta=τa−τs, so the above RTT has the relationship of (τa−τs)+TRm.

If there are no/very small non-propagating elements, γ may be set to 0 or a few nanoseconds. The case where there is no non-propagation element/very small means, for example, when the communication device and the mobile device 9 are configured to measure distance by transmitting and receiving a single impulse signal, or when the non-propagation element is configured to measure distance by transmitting and receiving a single impulse signal, or when there is no reflection like in radar. For example, it may be used to measure the distance to a reflective object.

Step S17 is a step of transmitting the distance measurement value calculated by the above processing to the smart ECU 2 together with the device ID indicating the transmission source of the response signal.

<About the functions of smart ECU2>
The smart ECU 2 detects unlocking operations, locking operations, etc. based on various data/signals input from sensors, ECUs, switches, etc. mounted on the vehicle Hv. The unlocking operation is a user operation for unlocking the vehicle Hv. The locking operation is an operation for locking the vehicle Hv. The smart ECU 2 can detect a touch operation on the door sensor as an unlocking/locking operation. The smart ECU 2 may determine that a locking operation or an unlocking operation has been performed when it is detected that the user's foot is placed over an infrared sensor that forms a detection area under the door.

The smart ECU 2 causes each communication device 1 to perform a search process intermittently while the driving power source is off. In response to a user operation on the vehicle Hv (for example, an unlocking operation), the smart ECU 2 may cause the communication device 1 to perform a search process according to the operation content. The smart ECU 2 executes a process of acquiring data indicating the communication status with the mobile device 9 and received data from the communication device 1 and storing the data in the memory. The data indicating the communication status includes search result data.

The position calculation unit F1 included in the smart ECU 2 is configured to calculate the position coordinates of the target device with respect to the vehicle Hv by combining the measured distance values of the plurality of communication devices 1 and the mounting position of each communication device 1 in the vehicle Hv. . The calculation process is performed using a method similar to three-point positioning in the technical fields of GNSS (Global Navigation Satellite System) and position estimation. Three-point positioning can also include multi-point positioning in which positioning is performed using three or more reference points. In the present disclosure, a process of determining device position coordinates using distance measurement values from a plurality of anchors, such as three-point positioning, is also referred to as a coordinate calculation process. The device position coordinates may be expressed in a two-dimensional vehicle coordinate system or the like. The device position coordinates may be expressed in a three-dimensional coordinate system.

Note that three-point positioning conceptually corresponds to calculating the coordinates of the intersection of three ranging circles. The ranging circle is a circle whose center is the installation position of the communication device 1 and whose radius is the observed ranging value. Since the installation position of the communication device 1 in the vehicle Hv is known, if the distances from three or more communication devices 1 to the mobile device 9 can be obtained, the position coordinates of the mobile device 9 (device position coordinates) can be obtained by solving simultaneous equations. can be identified. Note that since each distance measurement value includes an error, three or more distance measurement circles may not intersect at exactly one point. The coordinate calculation process, which is the process of calculating device position coordinates, is the process of calculating the point where the total value of distances from multiple ranging circles is the minimum in a local area where the intersections of multiple ranging circles are concentrated. You can.

Further, the vehicle control unit F2 included in the smart ECU 2 is configured to perform control/processing according to the device position in cooperation with other ECUs in response to user operations on the vehicle Hv. For example, if it is determined that the mobile device 9 is present near the door and the door sensor is detected to have been touched by the user, the vehicle control unit F2 performs processing for locking or unlocking the door. do. Further, when it is determined that the mobile device 9 is present in the vehicle interior and the start switch is detected to have been pressed by the user, the vehicle control unit F2 cooperates with the power supply ECU to turn off the driving power. Switch on.

<About the issues and effects that this embodiment attempts to solve>
When the direct wave is not interfered with by the reflected wave, the peak and hence the RTT can be measured with relatively high accuracy as shown in FIG. On the other hand, if the direct wave is interfered with by the reflected wave, a peak may be detected behind the true peak position (Pq1) (Pq2), as shown in FIG. Naturally, in a configuration in which the distance is calculated based on the peak position, if the peak position is erroneously detected, the distance measurement error may increase. Further, since the interior of the vehicle/near the vehicle is a multipath environment, the reflected waves themselves may be multiple-coupled as shown in FIG. In such a case, the distance measurement error may further increase. In FIG. 8, the broken line represents the direct wave, the two-dot chain line represents the reflected wave, and the solid line represents the outline of the received pulse.

In response to such issues, the developers of the present disclosure repeatedly analyzed the received waveform when there was no interference from reflected waves, and found that the time from rise to peak (that is, rise time) is approximately constant. We obtained such knowledge. This tendency indicates the tendency of direct waves, so even if there is interference from reflected waves, the peak position corresponding to the direct wave will be the position where the rise time has elapsed from the rising point. We can expect that.

The present disclosure has been created based on the above findings and ideas, and in one embodiment, the controller 14 is configured to set a predetermined standard rise time from the rise point without being caught by the peak position of the actual waveform. The point at which the distance is behind is regarded as the peak. That is, the controller 14 calculates the distance value using the time obtained by adding the standard rise time to the rise detection time as the RTT.

According to the configuration of this embodiment, in which the distance value is calculated by regarding the point behind the rise point by the standard rise time as the peak position, even if the direct wave is interfered with by the reflected wave, However, it is possible to suppress an increase in distance measurement errors due to reflected waves. Furthermore, it is possible to ensure distance measurement accuracy in a multipath environment such as inside a vehicle or near a vehicle.

<Modification (1)>
In an actual communication environment, the receiving unit 13 can receive various noises. Depending on the setting of the rise determination value, instantaneous noise may be erroneously detected as a rise point. Of course, if the rise determination value is set large (high), it is possible to reduce the possibility of erroneously detecting noise as a rise point, but this makes it difficult to detect a true direct wave. This is because the level of the direct wave may be a small value depending on the propagation environment.

On the other hand, noise that exceeds the rise determination value is often instantaneous. Based on such circumstances, the controller 14 may be configured to detect a rising point or peak using a moving average value of the received intensity. The moving average value of reception strength refers to the average value of the most recent past N observed values of reception strength. N can be 4, 8, 10, etc. The moving average values for each time are arranged in chronological order and stored in the temporary memory 145.

When detecting a rising point or the like using a moving average, the controller 14 can perform a search process according to the flowchart shown in FIG. 10 . Step S21 shown in FIG. 10 is a step of transmitting a UWB signal including at least one impulse as a response request signal. Step S22 is a step of sequentially calculating a moving average value of the reception strength. Note that the steps from step S22 onwards correspond to the processing when the response signal is successfully received. If the response signal cannot be received, the controller 14 can perform the same process as step S13. Although FIG. 10 does not illustrate the step of determining whether or not a response signal has been received, the determination itself may be performed in the same manner as in the embodiment.

Step S23 is a step of detecting a rising point based on the time series data of the moving average value and obtaining the corresponding rising detection time (Ta). Steps S24 to S26 are a group of steps in which a measured distance value is calculated using the rise detection time acquired in step S23 and is reported to the smart ECU 2. The specific contents of steps S24 to S26 can be the same as steps S15 to S17.

Note that since a moving average value is used, the timing at which the rising point is detected may be delayed from the timing at which the reception strength actually rises. In particular, as the value of N increases, the detection time of the rising point or peak may be delayed. Under such circumstances, the standard rise time when using the moving average may be set shorter by a predetermined amount (for example, 1 nanosecond) than when using the raw value of the reception strength. The standard rise time when using a moving average may also be determined by testing or simulation.

According to the configuration in which the rising point is identified using a moving average, it is possible to reduce the possibility that noise will be perceived as the rising point of a fast pulse. Even in scenes where received pulses of direct waves tend to be buried in noise, the possibility of detecting received pulses corresponding to direct waves can be increased. In other words, it is possible to improve the detection accuracy of the rising point of the direct wave.

<Modification (3)>
In the above, a configuration has been described in which the distance measurement value is calculated by regarding the value obtained by adding the standard rise time to the rise detection time as the peak detection time (in other words, RTT), but the usage of various parameters is not limited to this. The controller 14 may be configured to once calculate the distance value using the observed peak detection time, and then correct the distance value using the difference between the observed value of the rise time and the standard rise time. good.

For example, the controller 14 may perform the search process according to the procedure shown in FIG. Steps S31 to S32 shown in FIG. 11 are similar to steps S21 to S22 described above. Step S33 specifies the rise detection time (Ta) and the peak detection time (Tpq) based on the time series data of the moving average value of the reception strength stored in the temporary memory 145.

In step S34, a temporary distance measurement value is calculated by regarding the peak detection time specified in step S33 as RTT. The peak detection time specified in step S33 corresponds to the peak of the received pulse indicated by the time series data of the moving average value, that is, the peak that is actually observed. In this disclosure, calculating a distance value using information on peaks that are actually observed in this manner is also referred to as distance calculation based on observed peaks. On the other hand, a method of calculating a distance value by regarding the time obtained by adding the standard rise time to the rise detection time as RTT is referred to as corrected peak-based distance calculation.

In step S35, the provisional distance measurement value calculated in step S34 is corrected based on the rise time difference. The rise time difference here is the difference between the observed rise time (TRo) and the standard rise time (TRm). The observed rise time (TRo) corresponds to the value obtained by subtracting the rise detection time (Ta) from the peak detection time (Tpq) specified in step S33.

The correction amount based on the rise time difference may be registered in advance in the controller 14 in the form of a map, table, program function, or the like. For example, the distance calculation unit 143 calculates based on CA=δTR×C/2, where δTR is the rise time difference, CA is the correction amount, and C is the propagation speed of the radio wave. Step S36 is a step of transmitting the measured distance value to the smart ECU 2.

Such a distance calculation unit 143 corresponds to a configuration that calculates a temporary measured distance value based on the observed peak and then corrects the measured distance value using the rise time difference. That is, the distance calculation unit 143 calculates the measured distance value using the following equation (2).

D=(Tpq-γ)×C/2-δTR×C/2 (2)
The first term of the above equation (2) is the observed peak-based distance measurement value calculated in step S34, and the second term corresponds to the correction amount (CA). Note that when formula (2) is transformed based on the relationships Tpq=Ta+TRo and δTR=TRo-TRm, it is finally found to be equivalent to formula (1).

D=(Tpq-γ)×C/2-δTR×C/2
= {(Ta+TRo)-γ}/2×C-(TRo-TRm)×C/2
= (Ta+TRo-γ-TRo+TRm)×C/2
=(Ta+TRm-γ)×C/2
As explained above, correcting the measured distance value using the rise time difference indirectly corresponds to correcting the peak position to a position that is behind the rise point on the time axis by the standard rise time. The calculation method (calculation procedure) also produces the same effects as the embodiment described above.

Note that this modification was created based on the knowledge obtained through various tests that the longer the observed value of the rise time, the greater the distance measurement error. FIG. 12 is a diagram showing the relationship between observed values of rise time and distance measurement errors obtained through tests. As shown in FIG. 12, it can be seen that there is a relationship in which the distance measurement error increases in proportion to the rise time. According to the configuration of this modification, the larger the rise time difference, the larger the correction amount of the measured distance value, so it may be possible to reduce the difference between the calculated distance value and the actual distance between devices.

<Modification (4)>
The controller 14 may be configured to employ distance calculation based on a corrected peak as a method of calculating the measured distance value when the degree of peak deviation is greater than or equal to a predetermined value. The peak deviation degree is the difference between the observed peak detection time and the model-based RTT obtained by adding the standard rise time to the rise detection time Ta. The peak deviation degree corresponds to the rise time difference.

For example, the controller 14 may perform the search process according to the procedure shown in FIG. Steps S41 to S43 shown in FIG. 13 are similar to steps S31 to S33 described above.

Step S44 is a step of determining whether the peak deviation degree is less than a predetermined switching threshold. Step S44 may be a step of determining whether the rise time difference is less than a switching threshold. This is because the rise time difference and the peak deviation degree are substantially equivalent. The switching threshold may be set to, for example, 0.5 nanoseconds, 1.0 nanoseconds, 2.0 nanoseconds, or the like.

If the degree of peak deviation is equal to or greater than the switching threshold, the distance calculation unit 143 performs distance calculation processing on a corrected peak basis in step S45. The contents of step S45 may be steps S34 to S35. On the other hand, if the peak deviation degree is less than the switching threshold, the distance calculation unit 143 performs distance calculation processing on an observed peak basis as step S46. That is, step S46 corresponds to a step that performs the same process as step S34. Step S47 is a step of transmitting the distance measurement value calculated in step S45 or S46 to the smart ECU 2 together with the device ID indicating the communication partner.

In the above configuration, the distance calculation method based on the corrected peak is not always applied. The distance calculation unit 143 of this modification calculates the distance value based on the observed peak when the position of the observed peak substantially matches the standard peak position based on the rising point and standard rise time. Further, when the peak deviation degree/rise time difference is equal to or greater than the switching threshold, it is assumed that the reflected wave is strongly influenced, and the distance measurement value is calculated on a corrected peak basis. According to the configuration, it is possible to reduce the possibility that the measured distance value is calculated to be longer than the actual distance between devices.

In addition, in the corrected peak-based distance calculation method, if the detection of the rising point is delayed within the range of the switching threshold, the estimated position of the peak will also shift backward, so the measured distance value may be less than the actual distance between devices. can also be long. According to the distance calculation based on the observation peak, it may be possible to suppress an increase in distance error due to a delay in detecting the rising point.

The peak detection time actually observed corresponds to the first peak time. Further, the time obtained by adding the standard rise time to the observed rise detection time, that is, the model-based RTT, corresponds to the second peak time. Calculating the distance value based on the observed peak means calculating the distance value using the first peak time, and calculating the distance value based on the corrected peak means calculating the distance value using the second peak time. Each corresponds to calculating .

<Modification (5)>
It is also assumed that the communication device 1 communicates with the mobile device 9 by sequentially switching/using a plurality of channels having different frequency bands. Since the circuit characteristics may differ depending on the frequency, it is also assumed that the standard rise time differs depending on the channel. Under such circumstances, the standard rise time for each frequency band (channel) used for communication with the mobile device 9 may be registered in the setting storage unit 141. The distance calculation unit 143 may calculate the measured distance value using a standard rise time depending on the channel used for communication with the mobile device 9.

<Modification (6)>
The controller 14 may include a reliability evaluation section 146 as shown in FIG. The reliability evaluation unit 146 is configured to calculate the reliability of the measured distance value based on the rise time difference. A large rise time difference indicates that the signal is strongly influenced by reflected waves. Therefore, the reliability evaluation unit 146 sets the reliability to a smaller value as the rise time difference is larger. The reliability determined by the reliability evaluation unit 146 can be transmitted to the smart ECU 2 together with the measured distance value.

According to such a configuration, the smart ECU 2 can identify the communication device 1 with low reliability, in other words, the communication device 1 that is strongly affected by reflected waves. Further, the coordinate calculation process can be performed by preferentially using the communication device 1 that has relatively high reliability. As a result, it may be possible to improve the calculation accuracy of device position coordinates.

<Modification (7)>
A part or all of the transmitter 12 and the receiver 13 may be built into an IC as the controller 14. That is, the communication device 1 may be realized using one antenna 11 and one dedicated IC having various circuit functions. Further, each communication device 1 may have only one antenna 11, or may have three or more antennas 11. The controller 14 may be configured to use one antenna 11 for both signal transmission and reception using a switch or the like.

Further, some of the functions provided in the controller 14, such as the setting storage section 141 and the received pulse detection section 142, may be provided in the receiving section 13. The functional arrangement within the communication device 1 can be changed as appropriate. Furthermore, some of the functions provided by the controller 14 may be provided by the smart ECU 2. For example, the smart ECU 2 may have arithmetic functions for calculating RTT and distance measurement values.

<Modification (8)>
The arrangement of the communication device 1 described in the embodiment is an example and can be changed as appropriate. For example, the communication device 1 may be arranged at the center of the front end, the right door handle, the left door handle, and the center of the rear end. Further, the communication device 1 may be arranged at the front end and the rear end of the vehicle interior ceiling, in other words, at the upper end of the windshield and the upper end of the rear window. For example, when the trunk is provided independently from the cabin, such as in a sedan type, the communication device 1 may be placed in the trunk.

<Modified example (9)>
In the above configuration, a mode has been described in which the rise time and the like are measured based on the peak position of the transmission fast pulse, but the starting points of various times are not limited to this. The controller 14 may measure the rise detection time and the like based on the rise point instead of the peak of the transmission fast pulse. Further, the rise detection time and the like may be measured based on the peak/rise point of the transmission end pulse. The transmission end pulse refers to an impulse signal located at the end of the plurality of impulse signals that constitute the response request signal transmitted by the transmitter 12.

<Modification (10)>
The communication method between the communication device 1 and the mobile device 9 is not limited to UWB-IR, and may be Bluetooth (registered trademark), Wi-Fi (registered trademark), EnOcean (registered trademark), Zigbee (registered trademark), etc. You can. Various communication methods can be used between the communication device 1 and the mobile device 9. Various standards such as IEEE802.11n and IEEE802.11ax can be adopted as Wi-Fi standards.

<Applicable subjects of this disclosure>
The present disclosure is applicable to vehicles with various uses, such as owner cars and shared cars. The present disclosure may be applied to company cars owned by corporate organizations and official cars owned by public institutions. Vehicle Hv can be used by multiple users. Further, the present disclosure is applicable to various vehicles that run on roads. That is, the present disclosure can be installed in various vehicles that can run on roads, such as four-wheeled vehicles, two-wheeled vehicles, and three-wheeled vehicles. Motorized bicycles can also be included in two-wheeled vehicles. The present disclosure is applicable to various vehicles such as electric vehicles and engine vehicles. The concept of electric vehicles includes not only electric vehicles but also hybrid vehicles and fuel cell vehicles.

Further, the target is not limited to the mobile device 9, but may be a reflective object such as a metal plate or a human body. The target is not limited to one that re-radiates an impulse signal corresponding to the received signal based on receiving the impulse signal transmitted from the communication device 1. The communication device 1 may be configured to calculate the distance to the reflecting object based on the time it takes to receive the impulse signal reflected by the reflecting object.

<Additional remarks>
The various flowcharts shown in the present disclosure are all examples, and the number of steps constituting the flowcharts and the order of execution of processes can be changed as appropriate. Additionally, the devices, systems, and techniques described in the present disclosure may be implemented by a dedicated computer comprising the processor 21, which is programmed to perform one or more functions embodied by a computer program. You can. The apparatus and techniques described in this disclosure may be implemented using dedicated hardware logic circuits. The apparatus and techniques described in this disclosure may be implemented by one or more special purpose computers configured by a combination of a processor 21 executing a computer program and one or more hardware logic circuits. The controller 14 may be implemented using a CPU, MPU, GPU, DFP (Data Flow Processor), or the like. Some or all of the functions provided by the controller 14/smart ECU 2 may be realized using an SoC (System-on-Chip), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array). . Further, the computer program may be stored as instructions executed by a computer in a computer-readable non-transitive tangible storage medium.

1 Communication device (wireless ranging device), 2 Smart ECU (position calculation device), 9 Mobile device (target), 11 Antenna, 12 Transmission section, 13 Receiving section, 23 Storage (memory device), 132 Intensity detection circuit, 14 Controller, 141 Setting storage unit (model value storage unit), 142 Received pulse detection unit, 143 Distance calculation unit, 144 Report unit, 145 Temporary memory, 146 Reliability evaluation unit, F1 Position calculation unit

Claims (9)

a transmitter (12) that transmits an impulse signal in a predetermined frequency band;
a receiving unit (13) that detects the reception strength of radio waves in the frequency band;
a received pulse detection unit (142) that detects a rising point of a received pulse based on time series data of the received intensity detected by the receiving unit;
a model value storage unit (141) in which a model value of the time from the rising point to the peak of the received pulse is registered in advance;
a distance calculation unit (143) that calculates a distance value indicating the distance to the target using the rise detection time, which is the time from when the impulse signal is transmitted until the rise point is detected, and the model value; A wireless ranging device. The wireless ranging device according to claim 1,
The distance calculation unit is
Calculating the time obtained by adding the model value to the rise detection time as the round trip time of the impulse signal,
A wireless ranging device that calculates the distance value based on the round trip time. The wireless ranging device according to claim 1 or 2, configured to be able to transmit and receive the impulse signals in a plurality of frequency bands,
The model value for each frequency band is registered in the model value storage unit,
The distance calculation unit is a wireless ranging device that switches the model value used to calculate the distance value according to the frequency band of the received impulse signal. The wireless ranging device according to claim 1,
The received pulse detection section detects a peak of the received pulse,
The distance calculation unit is
Calculating the distance value using a peak detection time, which is the time from when the impulse signal is transmitted until when the peak is detected, as a round trip time;
A wireless ranging device that corrects the distance measurement value based on a rise time difference that is the difference between the model value and the observed rise time that is the time from the rise point detected by the received pulse detection unit to the peak. The wireless ranging device according to claim 1 or 2,
The received pulse detection section detects a peak of the received pulse,
The distance calculation unit calculates a first peak time, which is a time from when the impulse signal is transmitted until the peak is detected, and a second peak time, which is obtained by adding the model value to the rise detection time. If the difference is greater than or equal to a predetermined value, the distance measurement value is calculated using the second peak time;
A wireless ranging device configured to calculate the distance value using the first peak time when a difference between the first peak time and the second peak time is less than the predetermined value. The wireless ranging device according to claim 1 or 2,
The received pulse detection unit is a wireless ranging device configured to detect the rising point using a moving average value of received intensity. The wireless ranging device according to claim 1 or 2,
The received pulse detection section detects a peak of the received pulse,
a reliability evaluation unit (146) that evaluates the reliability of the measured distance value based on a rise time difference that is the difference between the observed rise time that is the time from the observed rise point to the peak; and the rise time difference that is the difference between the model value; ) A wireless ranging device. The wireless ranging device according to claim 1 or 2, which is used in connection with a position calculation device (2) that calculates the position coordinates of a target,
A wireless ranging device including a reporting unit (144) that reports the measured distance value to the position calculating device. A position determination system including a plurality of wireless ranging devices (1) and a position calculation device (2),
Each of the plurality of wireless ranging devices includes:
a transmitter (12) that transmits an impulse signal in a predetermined frequency band;
a receiving unit (13) that detects the reception strength of radio waves in the frequency band;
a received pulse detection unit (142) that detects a rising point of a received pulse based on time series data of the received intensity detected by the receiving unit;
a model value storage unit (141) in which a model value of the time from the rising point to the peak of the received pulse is registered in advance;
a distance calculation unit (143) that calculates a distance value indicating the distance to the target using the rise detection time, which is the time from when the impulse signal is transmitted until the rise point is detected, and the model value;
a reporting unit (144) that transmits the distance value calculated by the distance calculation unit to the position calculation device,
The position calculation device includes:
a storage device (23) in which data indicating the installation positions of the plurality of wireless ranging devices is registered;
a position determination unit (F1) that calculates the position coordinates of the target based on the data stored in the storage device and the distance measurement values received from the plurality of wireless distance measurement devices; system.

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