WO2015002246A1

WO2015002246A1 - Distance estimation system

Info

Publication number: WO2015002246A1
Application number: PCT/JP2014/067687
Authority: WO
Inventors: 康孝西村; 吉原　貴仁
Original assignee: Kddi株式会社
Priority date: 2013-07-04
Filing date: 2014-07-02
Publication date: 2015-01-08
Also published as: JP6033174B2; JP2015014504A

Abstract

This invention provides a distance estimation system whereby increases in error due to the effects of reflected waves or noise can be reduced. A base unit (1P) and a remote unit (1C) use distance-estimation-signal transmission/reception units (3P, 3C) to continuously exchange distance-estimation signals at prescribed intervals and obtain transmission/reception times therefor. A clock-offset computation unit (5) in the base unit (1P) uses said transmission/reception times to compute the offset between clocks in the base unit and the remote unit each time the distance-estimation signals are exchanged. From a history of computed clock offsets, if a determination unit (6) identifies the current clock offset as an off-target value, said determination unit (6) determines that the transmission/reception times need to be corrected, and a correction unit (7) corrects said transmission/reception times. A distance estimation unit (4) computes a distance on the basis of the transmission/reception times, and if a correction was made, the distance estimation unit (4) uses the corrected transmission/reception times.

Description

Distance estimation system

The present invention relates to distance estimation between terminals (master unit and slave unit) using radio signals, and more particularly to a distance estimation system capable of reducing an increase in error in distance estimation due to the influence of reflected waves and noise.

If we know the distance between people, people and things, things and things, various applications can be realized. For example, if the distance between a person and a house door is known, a smart entry that automatically releases and locks the door lock according to the distance can be realized. In addition, when the distance between the parent and the child is known, it is possible to realize lost child prevention such as an alarm notification when both are separated by a certain distance or more.

Conventionally, as a typical method of distance estimation, there is a method of estimating a distance based on received signal strength when radio waves such as radio waves and sound waves are exchanged between terminals. However, since the received signal intensity varies depending on the sensitivity of the wireless device, ambient noise, and shielding, the estimation accuracy is not sufficient.

On the other hand, in the method using the propagation time, the influence of the sensitivity and noise of the wireless device is small, and highly accurate distance estimation is possible. In particular, Non-Patent Document 1 using a sound wave (ultrasonic wave) having a propagation time slower than that of an electromagnetic wave achieves an accuracy of an error number of 10 cm.

Specifically, in Non-Patent Document 1, the distance is estimated by transmitting and receiving sound waves between the parent terminal and the child terminal, and the child terminal notifying the parent terminal of information on the transmission and reception times of the sound waves. FIG. 4 conceptually shows the estimation. A cross-correlation function is used to calculate the reception time. The waveform of the transmitted sound wave is shared between both terminals in advance and a reference signal is generated. The cross-correlation function between the received sound and the reference signal is calculated, and the peak point is determined as the sound wave reception time.

However, in Non-Patent Document 1 related to the prior art, when the cross-correlation function of the reflected wave or noise is larger than the cross-correlation function of the direct wave due to the influence of the reflected wave or noise, the reception time of the sound wave is There was a problem that errors and errors in distance estimation would increase.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a distance estimation system that can reduce an increase in error due to the influence of reflected waves and noise.

In order to achieve the above object, the present invention is a distance estimation system that includes a parent device and a child device, and estimates a distance between the parent device and the child device, both the parent device and the child device, A distance estimation signal is continuously transmitted and received between each time with a predetermined interval between each time, and a distance estimation signal transmission / reception unit for acquiring the transmission / reception time is provided, and the master unit is based on the acquired transmission / reception time, A distance estimation unit that estimates a distance between the parent device and the child device at each time; and a clock deviation calculation unit that calculates a clock deviation between the parent device and the child device at each time based on the acquired transmission / reception time; And a determination unit for determining whether or not the acquired transmission / reception time at each time is a correction target based on the calculated clock deviation history.

According to the present invention, it is possible to automatically determine whether the transmission / reception time used for the current distance estimation is to be corrected by comparing the history of the clock deviation with the clock deviation when attempting to estimate the current distance. Here, since it is possible to obtain information with a high possibility that the accuracy of the transmission / reception time itself is low at the times determined to be correction targets, an increase in error due to the influence of reflected waves and noise is taken into consideration in advance. Can be avoided, and the influence can be reduced.

It is a functional block diagram of the main | base station and the subunit | mobile_unit which comprise the distance estimation system based on one Embodiment. It is a figure which shows the example of the process sequence between the main | base station and the subunit | mobile_unit in this invention. It is a figure for demonstrating typically the time of each transmission / reception of the distance estimation signal transmitted / received between a main | base station and a subunit | mobile_unit. It is a figure which shows the distance estimation in a nonpatent literature 1 notionally.

FIG. 1 is a functional block diagram of a parent device and a child device constituting a distance estimation system according to an embodiment of the present invention. The distance estimation system 100 includes a parent device 1P and a child device 1C. Master unit 1P includes a control signal transmission / reception unit 2P and a distance estimation signal transmission / reception unit 3P, and slave unit 1C includes a control signal transmission / reception unit 2C and a distance estimation signal transmission / reception unit 3C. Here, the control signal transmission / reception units 2P and 2C and the distance estimation signal transmission / reception units 3P and 3C to which the same names and corresponding symbols are attached respectively have the same function and / or functions corresponding to each other as described below.

The control signal transmission / reception units 2P and 2C transmit and receive various control signals between the master unit 1P and the slave unit 1C. By transmitting and receiving the control signal, various setting information used in the present invention is shared between the master unit 1P and the slave unit 1C, and various processes performed between the master unit 1P and the slave unit 1C are executed. Timing adjustments are made.

Communication media for control signals include Bluetooth (registered trademark), Wi-Fi (registered trademark), sound wave / ultrasound, 2G / 3G / LTE / WiMax (registered trademark), etc., directly between master unit 1P and slave unit 1C Anything that communicates or via a base station can be used. Here, the type of communication media used for each type of control signal may be different.

The distance estimation signal transmitting / receiving unit 3P, 3C performs transmission / reception of a distance estimation signal for estimating the distance between the two

units

1P, 1C between the master unit 1P and the slave unit 1C, and the time at which the transmission / reception is performed. Record (transmission / reception time).

The distance estimation signal is a pulse-shaped radio signal whose component frequency is set by the control signal, and is also transmitted i times (i = 1, 2, 3, ...) by the control signal T (i) Is set, and transmission / reception is continuously performed between the parent device 1P and the child device 1C.

As the communication medium for the distance estimation signal, Bluetooth (registered trademark), Wi-Fi (registered trademark), sound waves / ultrasonic waves, or the like that can communicate directly between the parent device and the child device can be used.

Furthermore, the distance estimation signal transmission / reception unit 3C on the side of the slave unit 1C notifies the distance estimation signal transmission / reception unit 3P on the side of the base unit 1P of the transmission / reception time information recorded in the slave unit 1C. For the notification of the transmission / reception time, a signal separate from the distance estimation signal may be used, or a communication medium similar to the control signal may be used.

On the other hand, as shown in FIG. 1, base unit 1P further includes a distance estimation unit 4, a clock shift calculation unit 5, a clock shift history recording unit 51, a determination unit 6, a correction unit 7, and a transmission / reception time recording unit 8. The outline of each part is as follows.

The distance estimation unit 4 transmits the transmission / reception time in the parent device 1P itself acquired by the distance estimation signal transmission / reception unit 3P and the transmission / reception time in the child device 1C acquired by the distance estimation signal transmission / reception unit 3C (to the parent device 1P side) And the distance D (i between the parent device 1P and the child device 1C when the i-th distance estimation signal is transmitted / received based on (the “time of transmission / reception at the i-th time”) ).

When estimating the distance D (i), based on the determination by the determination unit 6 described later, as the series of transmission / reception times in the parent device 1P and the child device 1C used for estimation, the acquired value as it is Either (the i-th transmission / reception time) or a value obtained by correcting the acquired value as it is by the correction unit 7 is used. Details of the distance estimation will be described later.

The clock deviation calculation unit 5 calculates a deviation t_dif (i) between the clock in the master unit 1P and the clock in the slave unit 1C when the i-th distance estimation signal is transmitted / received based on the i-th transmission / reception time. . Details of the calculation will be described later.

The clock shift history recording unit 51 records the clock shift t_dif (i) calculated for each i times by the clock shift calculation unit 5 and holds it as a history. The stored history is referred to by the determination unit 6.

The determination unit 6 refers to the clock deviation history t_dif (i) recorded in the time i recorded in the clock deviation history recording unit 51, and whether the transmission / reception time at the i-th time is a target to be corrected with low accuracy. Judge whether or not. Details of the determination will be described later.

When the determination unit 6 determines that the i-th transmission / reception time is to be corrected, the correction unit 7 corrects the i-th transmission / reception time. Details thereof will be described later.

The transmission / reception time recording unit 8 records the transmission / reception time at the i-th time as a history over each i-th (i = 1, 2, 3, ...), and the record for each part of the main unit 1P, Use as a reference if necessary. In FIG. 1, the flow arrows provided for the reference are not drawn for the sake of simplicity.

FIG. 2 is a diagram showing an example of each step in the processing procedure between the master unit 1P and the slave unit 1C when performing distance estimation with correction according to the present invention. Details of the processing of each unit in FIG. 1 will be described while explaining the processing procedure.

In step S01, a communication channel is established between the

parent devices

1P and 1C via the control signal transmission / reception units 2P and 2C. In step S02, a signal to start processing for a series of distance estimations continued over i each time is transmitted from the parent device 1P to the child device 1C through the control signal transmission / reception units 2P and 2C. .

In FIG. 2, (1) shows the first time of the series of processing (when i = 1), and (i) shows the general i-th time of the series of processing. Since each process is basically the same, the general i-th process of (i) will be described below. Each process is repeated with a predetermined interval T (i) as described above.

In step SPC [i] 0, distance estimation signal transmission / reception unit 3P of base unit 1P transmits i-th distance estimation signal P_i, and distance estimation signal transmission / reception unit 3C of handset 1C performs i-th distance estimation signal Send C_i. Further, in step SPC [i] 0, with each transmission, the distance estimation signal transmitting / receiving unit 3P of the parent device 1P acquires the transmission time T _{P_S} (i) of the P_i transmitted by itself and transmitted by the child device 1C. Obtain the reception time T _{P_R} (i) of C_i. Similarly, the distance estimation signal transmitting / receiving unit 3C of the slave unit 1C acquires the transmission time T _{C_S} (i) of _{C_i} transmitted by itself and acquires the reception time T _{C_R} (i) of P_i transmitted by the master unit 1P. .

FIG. 3 is a diagram for schematically explaining the above-described series of transmission / reception times in step SPC [i]. (1) is a time-series viewpoint, and (2) is a device-like transmission / reception. From this point of view, the series of times are shown. (2) is a transmission unit 3PS (speaker if the signal is a sound wave) and a reception unit 3PM (a microphone if the signal is a sound wave) included in the distance estimation signal transmission / reception unit 3P, and a transmission included in the distance estimation signal transmission / reception unit 3C. A unit 3CS and a receiving unit 3CM are shown.

The transmission unit 3PS transmits the signal P_i, and the reception time at the reception unit 3PM at the “self” 3P of the transmitted P_i is the “transmission” time T _{P_S} (i), and the other party of the transmitted P_i The reception time at the reception unit 3CM at 3C is the reception time T _{C_R} (i).

Similarly, the transmission unit 3CS transmits a signal C_i, and the reception time at the reception unit 3CM at the “self” 3C of the transmitted _{C_i} is the “transmission” time T _{C_S} (i), and the transmitted C_i The reception time at the receiving unit 3PM at the other party 3P is the reception time T _{P_R} (i).

Therefore, as described in parentheses in (2), the transmission time T _{P_S} (i) and the reception time T _{P_R} (i) are the _{values of} the watch that manages the reception recording (recording if the signal is a sound wave) in the receiving unit 3PM. It is acquired as the time, that is, as the time of the clock of the parent device 1P. Similarly, the reception time T _{C_R} (i) and the transmission time T _{C_S} (i) are acquired as the clock time for managing reception records in the reception unit 3CM, that is, as the clock time of the slave unit 1C.

In addition, in order to acquire each transmission / reception time as described above from the reception record in the reception units 3PM and 3CM, it is necessary to detect the waveform of the corresponding sound wave from the reception record. The detection may be performed as follows.

That is, a cross-correlation function is used to acquire each transmission / reception time. Specifically, using the control signals transmitted and received by the control signal transmitting / receiving units 2P and 2C, the waveform of the distance estimation signal is shared in advance, and the transmission units 3PS and 3CS transmit the reference signal sharing the waveform. To do. Receiving units 3PM and 3CM calculate a cross-correlation function between a series of signals and a reference signal in reception recording, and determine peak times as transmission / reception times.

Returning to FIG. 2, when the transmission / reception of step SPC [i] 0 as described above is completed, the distance estimation signal transmission / reception unit 3P receives the transmission / reception interval acquired by itself in step SP [i] 1 on the base unit 1P side. T _P (i) can be calculated as follows. Similarly, at step SC [i] 1 in the slave unit 1C side, the distance estimation signal transmitting and receiving part 3C has a calculated ready as follows its acquired apart T _C (i) of the transmission and reception . Each of these may actually calculate each interval.
T _P (i) = T _{P_R} (i) -T _{P_S} (i)
T _C (i) = T _{C_R} (i) -T _{C_S} (i)

In step SC [i] 2, slave unit 1C notifies base unit 1P of reception time T _{C_R} (i) and transmission time T _{C_S} (i) that it acquired in step SPC [i] 0. In step SP [i] 2, base unit 1P acquires the notified times. As described above, the notification is performed via the distance estimation signal transmitting / receiving units 3P and 3C. At this time, a signal for information notification that is separate from the distance estimation signal may be used.

In step SP [i] 3, the master unit 1P, a series of transmission and reception time that it has acquired (acquired T _{P_r} the base unit 1P (i) and T _{P_S} (i), the slave unit 1C obtains the master unit notified T _{C_R} the 1P (i) and T _{C_S} (i)) is, whether it should be corrected, it is determined at decision section 6.

In step SP [i] 3, first, the clock deviation calculation unit 5 performs the following series of processes in order to make the determination. As a first process, a clock deviation t_dif (i) between the parent device 1P and the child device 1C at the i-th transmission time (referred to as “this time”) is calculated based on the series of transmission / reception times. As a second process, the history t_dif (j) (j = 1, which is already calculated and recorded in the clock deviation history recording unit 51 in the past j (j = 1, 2, 今回 ..., i-1) before i this time. , 2, ..., i-1) is compared with the “normal value” t_dif of the clock deviation obtained from this time and the current value t_dif (i) to determine whether or not these values are close to each other.

When the determination unit 6 determines that the values are close in the second process, the determination unit 6 determines that the series of transmission / reception times acquired by the determination unit 6 need not be corrected. If it is determined, it is determined that the series of transmission / reception times acquired by itself should be corrected. Hereinafter, details of the first and second processes by the clock deviation calculation unit 5 and the determination process by the determination unit 6 will be described.

As a premise, when performing the processing of i this time, the past transmission / reception times of the master unit 1P and the _slave unit 1C (T _{P_S} (j), T _{P_R} (j), T _{C_S} (j), T _{C_R} (j)) (j = 1, 2,..., i−1) is held in the transmission / reception time recording unit 8 of the base unit 1P as described above. The held information can be referred to as appropriate by each unit of base unit 1P.

In the first process, the clock shift calculation unit 5 calculates the clock shift t_dif (i) of the current i by the following equation.
t_dif (i) = ((T _{P_S} (i) + T _{P_R} (i))-(T _{C_S} (i) + T _{C_R} (i))) / 2

The principle that the clock deviation can be calculated by the above formula is the same as that of NTP (Network Time Protocol) widely used for time synchronization on the Internet, and the explanation is omitted. NTP is disclosed in Non-Patent Document 2 below.

[Non-Patent Document 2] Network Time Protocol (IETF RFC 1305)
http://www.ietf.org/rfc/rfc1305.txt

The above first processing has been carried out in the past before i this time, and a series of clock deviation histories has been obtained. In the present invention, in particular, the second process is performed using the history from the following viewpoints.

That is, the clocks of the master unit 1P and the slave unit 1C shift with time due to the difference in clock source, but in a short period such as a period in which distance estimation is repeatedly performed, it can be considered that the change of the clock shift is extremely small. Therefore, ideally, the clock deviation t_dif (i) is expected to be a substantially constant value. On the other hand, due to the influence of reflected waves and noise, if at least one of the transmission / reception times acquired by the master unit 1P and the slave unit 1C includes an error in the current i, the clock deviation t_dif (i) of the current i is This value is somewhat different from the normally calculated value t_dif.

In the second process, based on the above viewpoint, it is determined whether or not the clock deviation t_dif (i) in the current i-th distance estimation is different from the original normal clock deviation t_dif by a predetermined threshold th or more. The determination unit 6 determines whether or not to correct according to the determination. Therefore, when the following equation is established, the current time i deviation t_dif (i) is an outlier, and it is determined that the transmission / reception time needs to be corrected. On the other hand, if it does not hold, it is determined that the correction is unnecessary.
| t_dif-t_dif (i) |> th

Here, the threshold value th is given in advance as a parameter that depends on the required accuracy for distance estimation in the distance estimation unit 4. For example, when the distance estimation signal is a sound wave and the required accuracy is 30 cm, the threshold th is about 1 [ms].

The original normal clock deviation t_dif is calculated from the past history t_dif (j) (j = i-m,..., I-2, i-1) over a predetermined period of clock deviation. m is a parameter indicating the number of past information to be used. For example, an average value or median value of the past m clock deviations t_dif (j) may be used as the actual clock deviation t_dif.

When using the above-mentioned past history, the distribution of the clock deviation value t_dif (j) in the past history may be obtained, and those determined to be outliers may be excluded. The determination of the threshold th may also serve as a determination as to whether or not to exclude from the history after i this time.

As described above, when it is determined whether or not the correction should be made in step SP [i] 3, in step SP [i] 4, the distance estimation unit 4 uses the estimation method according to the determination to cause the distance estimation unit 4 to perform the parent device 1P and the child device 1C. And estimate the distance D (i) at this time i. Hereinafter, a case where correction is not performed and a case where correction is performed will be described.

(If not corrected)
The distance estimation unit 4 calculates the distance D (i) by the following equation.
D (i) = ((T _{P_R} (i)-T _{P_S} (i))-(T _{C_S} (i)-T _{C_R} (i)) / 2 * c

In the above equation, c is the speed of the distance estimation signal (the speed of sound if sound waves). Further, since the principle of calculating the distance by the above formula is well known, the description thereof will be omitted, but the influence of the clock deviation is removed by using the four times by the principle. In Non-Patent Document 1, the distance is calculated based on the principle.

(When correcting)
First, the correction unit 7 performs propagation times t _P (i) and t _C (i) of the signals P_i and C_i transmitted from the parent device 1P and the child device 1C in the form in which the transmission / reception time is corrected by the following equation: Calculate
t _P (i) = T _{C_R} (i)-T _{P_S} (i) + t_dif
t _C (i) = T _{P_R} (i)-T _{C_S} (i)-t_dif

In the above equation, t_dif is the original normal clock deviation obtained in step SP [i] 3 described above. Here, unlike (when not corrected), only two times are used instead of four times, so the clock deviation t_dif is adjusted as shown in the above equation in order to eliminate the influence of the error caused by the clock deviation t_dif. ing.

The distance estimation unit 4 estimates the corrected distance D (i) using the propagation times t _P (i) and t _C (i) as in the following (Procedure 1) to (Procedure 3). To do.

(step 1)
The distances D _P (i) and D _C (i) when the propagation times t _P (i) and t _C (i) are used are calculated by the following equations. The distances correspond to the signals P_i and C_i, respectively. Here, c is the speed of the distance estimation signal as described above.
D _P (i) = T _P (i) * c
D _C (i) = T _C (i) * c

(Step 2)
The calculated distance is compared with the latest estimated distance D (i-1) in the past to confirm whether it is an outlier. The confirmation may be performed by confirming whether the following (Expression 1) and (Expression 2) are satisfied. Here, Vth is a threshold value indicating the maximum value of the relative speed between the parent device 1P and the child device 1C, and a predetermined value corresponding to a specific application to which the distance estimation system 100 is applied may be given in advance. By using (Expression 1) and (Expression 2), it is possible to eliminate an abnormal distance that is difficult to occur in practice. T (i) is an interval when the transmission / reception / distance estimation is repeated as shown in FIG. 2, and is an interval between the current i-th time and the immediately preceding i-1th time.
| D (i-1) -D _P (i) | <T (i) * Vth (Equation 1)
| D (i-1) -D _C (i) | <T (i) * Vth (Formula 2)

The past estimated distance D (i-1) may be recorded as additional information by the transmission / reception time recording unit 8 or the like.

(Procedure 3)
The distance estimation unit 4 obtains the corrected distance D (i) according to the following case classifications 1 to 3.

(Case 1)
If both (Equation 1) and (Equation 2) are satisfied, the propagation time is long and easily erroneous due to the influence of the reflected wave, so the smaller of D _P (i) and D _C (i) is the estimated distance D (i) And

(Case 2)
When only one of (Equation 1) and (Equation 2) is satisfied, the distance (D _P (i) or D _C (i)) that satisfies is assumed to be the estimated distance D (i). In this case, the time acquired for the unsatisfied signal P_i or C_i is not used because it is likely to be erroneous due to the influence of reflected waves or the like. That is, the selection is performed from the two signals P_i or C_i.

(Case 3)
If both (Equation 1) and (Equation 2) are not satisfied, both are likely to be wrong. In this case, the result of the estimated distance D (i) may be an estimation failure, or the past estimated distance D (ik) may be substituted. In the case of substituting, it is sufficient to use the latest past ik in which the distance is estimated based on the determination not to be corrected among the past d.

Hereinafter, supplementary items in the present invention will be described.

(Supplement 1) As shown in FIG. 2, the interval T (i) for each transmission of the distance estimation signal i and the distance estimation associated therewith as shown in FIG. Thus, by sharing the master unit 1P and the slave unit 1C, the time zone during which the distance estimation signal will be received can be roughly predicted with a predetermined accuracy. Therefore, the above-described reference signal may be detected only in the time period.

Alternatively, the interval T (i) is grasped only in the master unit 1P, and the slave unit 1C that has received a predetermined reference signal from the master unit 1P immediately transmits the reference signal to the master 1P side. Good. (1) of FIG. 3 is an example of a time series possible with such a configuration.

In general, it is not necessary to determine which of the parent device 1P and the child device 1C transmits the reference signal first every i times. In the example of (1) of FIG. 3, the _context of T _{P_S} (i) and T _{P_R} (i) and the context of T _{C_R} (i) and T _{C_S} (i) may be reversed. The parent device 1P and the child device 1C only need to be able to identify that the reference signal received from the counterpart side corresponds to the i-th time. The identification can be performed by the presetting by the control signal.

(Supplement 2) When the determination unit 6 determines the necessity of correction at the i-th time, the distance estimation signal is output at the next i + 1-th time or the i + k-th time after the predetermined number k (k> 0) times. You may make it change the setting of the distance estimation signal which the transmission / reception parts 2P and 2C transmit. For example, the intensity may be decreased by a predetermined ratio to reduce the influence of the reflected wave, and similarly, the constituent frequencies may be switched in a predetermined pattern. The transmission interval T (i) may be narrowed by a predetermined rate.

The change of the setting may be shared by the master unit 1P and the slave unit 1C by the control signal. After the setting change, when it is continuously determined that correction is unnecessary for a predetermined number of times, the original setting may be restored.

(Supplement 3) In order for the determination unit 6 to determine the necessity of correction, it is necessary to obtain a normal clock deviation t_dif. Therefore, it is necessary to accumulate the clock deviation t_dif (i) of each time i by the clock deviation calculation unit 5 over a predetermined number N and analyze the distribution. The distance D (i) may be provisionally calculated by a method in which the distance estimation unit 4 does not perform correction until reaching N times. For example, in FIG. 1, since i = 1, which is the first time, correction determination cannot be made, the step corresponding to step SPC [i] 3 is omitted.

Or, in exactly the same way, the provisionally calculated period is a preparation period for calculating the normal value of the clock deviation t_dif (i), and after the preparation period ends, the distance D (i) is officially calculated. You may make it ask.

(Supplement 4) The distance estimation system 100 of the present invention may include only the determination unit 6 among the determination unit 6 and the correction unit 7. In this case, when the determination unit 6 determines the necessity for correction, the distance estimation unit 4 performs distance estimation by a normal method without correction, and adds information indicating that the estimated distance is low in reliability. Alternatively, the distance estimation result itself may be discarded.

100 ... Distance estimation system, 1P ... Base unit, 1C ... Slave unit, 2P, 2C ... Control signal transmission / reception unit, 3P, 3C ... Distance estimation signal transmission / reception unit, 4 ... Distance estimation unit, 5 ... Clock deviation calculation unit, 51 ... Clock deviation history recording unit, 6 ... judgment unit, 7 ... correction unit, 8 ... transmission / reception time recording unit

Claims

A distance estimation system that includes a parent device and a child device and estimates a distance between the parent device and the child device,
Both the master unit and the slave unit are
A distance estimation signal transmission / reception unit that continuously transmits and receives a distance estimation signal with each other with a predetermined interval between each time, and acquires the transmission / reception time,
The master unit is
Based on the acquired transmission / reception time, a distance estimation unit that estimates the distance between the parent device and the child device at each time;
Based on the acquired transmission / reception time, a clock deviation calculation unit that calculates a clock deviation between the parent device and the child device at each time;
A distance estimation system, comprising: a determination unit configured to determine whether or not the acquired transmission / reception time at each time is a correction target based on the calculated clock shift history.
The determination unit determines, based on the calculated history of clock deviation, that the calculated clock deviation belongs to a deviation value in the history and is the correction target. The distance estimation system according to claim 1.
The base unit further includes a correction unit that corrects the acquired transmission / reception time at a time when the base unit is determined to be the correction target,
The distance estimating unit estimates a distance between the parent device and the child device based on the corrected transmission / reception time at a time when the distance is determined to be the correction target. Or the distance estimation system of 2.
The determination unit determines that the calculated clock shift belongs to a shift value in the history based on the calculated clock shift history, and determines that the correction target is the correction target.
The correction unit, based on the acquired transmission / reception time, out of the distance estimation signals transmitted and received with each other, the first propagation time in the first distance estimation signal transmitted from the base unit to the slave unit, and Calculating the second propagation time in the second distance estimation signal transmitted from the slave unit to the master unit,
The distance estimation unit calculates a first propagation distance and a second propagation distance from the first propagation time and the second propagation time, respectively, and compares each distance with the estimated distance in the latest past. 4. The distance estimation system according to claim 3, wherein any one of the distances is determined as a distance estimated for the current time.
The distance estimation unit compares the distances with the estimated distances in the latest past, and if both of the differences are larger than a predetermined threshold, the distance estimation at this time is not performed. The distance estimation system according to claim 4.