Position estimating device and position estimating method

Abstract

This position estimating device (3) is configured so as to comprise: a distance measurement unit (11) that, on the basis of electromagnetic waves transmitted and received between a plurality of wireless devices (1-1 to 1-5) installed in a vehicle and a terminal (2) carried by a user, measures the distance between a wireless device (1-n (n=1, ..., 5)) and the terminal (2); a distance selection unit (12) that selects a distance that can be used for trilateration of the position of the terminal (2) on the basis of a plurality of distances measured by the distance measurement unit (11); and a position estimating unit (13) that estimates the position of the terminal (2) using the distance selected by the distance selection unit (12).

Description

Position estimation device and position estimation method

[0001] The present disclosure relates to a position estimation device and a position estimation method.

[0002] There is a position estimation device that measures the distance between multiple radios installed in a vehicle and a terminal carried by a user based on electromagnetic waves transmitted and received between each radio and the terminal, and estimates the position of the terminal using the measured distances. For example, Patent Document 1 discloses a position estimation device that includes a technology for preventing degradation of the accuracy of position estimation due to the influence of electromagnetic wave shielding by a human body or the influence of multipath, which causes the distance measurement result to be larger than the actual distance. This technology selects a highly reliable measurement result from multiple distance measurement results based on the reception strength of the electromagnetic waves from each radio, and estimates the position of the terminal using the selected measurement result.

[0003] Japanese Patent Application Laid-Open No. 2023-177066

[0004] In the location estimation device disclosed in Patent Document 1, the antenna of the radio device has directionality, and the received strength of electromagnetic waves can change depending on the direction of the antenna. As a result, it is sometimes impossible to select a measurement result with high reliability from among multiple distance measurement results, which can result in a deterioration in the accuracy of location estimation.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a position estimation device that can prevent deterioration in position estimation accuracy even if the antenna of a radio device has directionality.

[0006] The position estimation device of the present disclosure includes a distance measurement unit that measures the distance between each radio device and a terminal carried by a user based on electromagnetic waves transmitted and received between the multiple radio devices installed in a vehicle and the terminal, a distance selection unit that selects a distance that can be used for trilateration of the terminal's position based on the multiple distances measured by the distance measurement unit, and a position estimation unit that estimates the terminal's position using the distance selected by the distance selection unit.

[0007] According to the present disclosure, even if the antenna of a wireless device has directionality, it is possible to prevent deterioration in the accuracy of position estimation.

[0008] 1 is an explanatory diagram showing wireless devices 1-1 to 1-5 installed in a vehicle to which a position estimation device 3 according to a first embodiment is applied. FIG. 1 is a configuration diagram showing a position estimation device 3 according to the first embodiment. FIG. 2 is a hardware configuration diagram showing the hardware of the position estimation device 3 according to the first embodiment. FIG. 3 is a hardware configuration diagram of a computer in the case where the position estimation device 3 is realized by software, firmware, or the like. FIG. 4 is an explanatory diagram showing UWB wireless communication between a wireless device 1-n (n = 1, ..., 5) and a terminal 2. FIG. 5 is a flowchart showing a position estimation method, which is a processing procedure of the position estimation device 3. FIG. 6 is an explanatory diagram showing transmission and reception of pulse signals between the wireless device 1-n and the terminal 2. FIG. 7 is an explanatory diagram showing transmission and reception of pulse signals between the wireless device 1-n and the terminal 2. FIG. 8 is a configuration diagram showing a position estimation device 3 according to a second embodiment. FIG. 9 is a hardware configuration diagram showing the hardware of the position estimation device 3 according to the second embodiment. FIG. 10 is a configuration diagram showing a position estimation device 3 according to a third embodiment. FIG. 11 is a hardware configuration diagram showing the hardware of the position estimation device 3 according to the third embodiment. FIG. 12 is an explanatory diagram showing distances stored in a queue. FIG. 13 is an explanatory diagram showing completion of a missing value nan using distances stored in a queue.

[0009] In order to explain the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0010] Embodiment 1. FIG. 1 is an explanatory diagram showing radios 1-1 to 1-5 installed in a vehicle to which a position estimation device 3 according to embodiment 1 is applied. In FIG. 1, radios 1-1 to 1-5 are anchors installed in the vehicle. In the example of FIG. 1, radios 1-1 to 1-4 are installed on the body outside the vehicle cabin, and radio 1-5 is installed inside the vehicle cabin. In the example of FIG. 1, five radios 1-1 to 1-5 are installed, but the number of installed radios is not limited to five radios 1-1 to 1-5 as long as two or more radios are installed. Terminal 2 is a mobile terminal such as a smartphone carried by a user, or a tag such as a vehicle remote control carried by a user.

[0011] Fig. 2 is a configuration diagram showing a position estimation device 3 according to the first embodiment. Fig. 3 is a hardware configuration diagram showing the hardware of the position estimation device 3 according to the first embodiment. The position estimation device 3 shown in Fig. 2 includes a distance measurement unit 11, a distance selection unit 12, and a position estimation unit 13. The distance measurement unit 11 is realized by, for example, a distance measurement circuit 21 shown in Fig. 3. The distance measurement unit 11 calculates the distance L between the wireless device 1-n and the terminal 2 based on electromagnetic waves transmitted and received between the wireless device 1-n (n = 1, ..., 5) and the terminal 2. ｎ The distance measurement unit 11 measures the distance L between the wireless device 1-n and the terminal 2. ｎ The distance selecting unit 12 outputs distance information indicating the distance.

[0012] The distance selection unit 12 is realized by, for example, a distance selection circuit 22 shown in Fig. 3. The distance selection unit 12 acquires distance information from the distance measurement unit 11. The distance selection unit 12 selects a distance L indicated by the distance information. １ ~L ５ Among these, the distance L that can be used for trilateration of the position of the terminal 2 is ＳＥＬ１ , L ＳＥＬ２ The distance selection unit 12 selects the distance L indicated by the distance information. １ ~L ５ Based on the distance information, a distance that can be used for trilateration of the position of the terminal 2 can be selected. １ ~L ５ The distance selection unit 12 may perform processing such as averaging, smoothing, or error correction on the distance L, and select the processed distance as a distance that can be used for trilateration. ＳＥＬ１ , L ＳＥＬ２ 2 outputs selection information indicating the distance L to the position estimation unit 13. For the sake of simplicity, the position estimation device 3 shown in FIG. 2 assumes that the height at which the terminal 2 is present does not change, and estimates the position of the terminal 2 on a two-dimensional plane parallel to the ground. For this reason, the distance selection unit 12 selects two distances L as distances that can be used for trilateration of the position of the terminal 2. ＳＥＬ１ , L ＳＥＬ２ is selected.

[0013] The position estimation unit 13 is realized by, for example, the position estimation circuit 23 shown in Fig. 3. The position estimation unit 13 acquires selection information from the distance selection unit 12. The position estimation unit 13 calculates the distance L indicated by the selection information. ＳＥＬ１ , L ＳＥＬ２ The position of the terminal 2 is estimated using the above information. Information indicating the position estimated by the position estimation unit 13 is output to, for example, a control device of the vehicle. The control device of the vehicle has, for example, a function for preventing relay attacks, and controls the vehicle based on the position of the terminal 2.

[0014] 2, it is assumed that each of the components of the position estimation device 3, that is, the distance measurement unit 11, the distance selection unit 12, and the position estimation unit 13, is realized by dedicated hardware as shown in Fig. 3. That is, it is assumed that the position estimation device 3 is realized by a distance measurement circuit 21, a distance selection circuit 22, and a position estimation circuit 23. Each of the distance measurement circuit 21, the distance selection circuit 22, and the position estimation circuit 23 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0015] The components of the position estimation device 3 are not limited to those realized by dedicated hardware, and the position estimation device 3 may be realized by software, firmware, or a combination of software and firmware. Software or firmware is stored as a program in the memory of a computer. A computer refers to hardware that executes a program, and includes, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor).

[0016] 4 is a hardware configuration diagram of a computer when the position estimation device 3 is realized by software, firmware, etc. When the position estimation device 3 is realized by software, firmware, etc., programs for causing a computer to execute the respective processing procedures of the distance measurement unit 11, the distance selection unit 12, and the position estimation unit 13 are stored in the memory 31. Then, the processor 32 of the computer executes the programs stored in the memory 31.

[0017] 3 shows an example in which each of the components of the position estimation device 3 is realized by dedicated hardware, while Fig. 4 shows an example in which the position estimation device 3 is realized by software, firmware, etc. However, this is merely an example, and some of the components in the position estimation device 3 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0018] Next, the operation of the position estimation device 3 shown in Fig. 2 will be described. As shown in Fig. 5, the wireless devices 1-n (n = 1, ..., 5) and the terminal 2 perform, for example, UWB (Ultra-Wide Band) wireless communication. Fig. 5 is an explanatory diagram showing UWB wireless communication between the wireless devices 1-n (n = 1, ..., 5) and the terminal 2. For example, the terminal 2 transmits a first pulse signal, which is an electromagnetic wave, and the wireless device 1-n receives the first pulse signal and then transmits a second pulse signal, which is an electromagnetic wave, to the terminal 2. Then, after receiving the second pulse signal, the terminal 2 transmits a third pulse signal, which is an electromagnetic wave, and the wireless device 1-n receives the third pulse signal. The time required for each transmission and reception of these pulse signals (hereinafter referred to as "required time T ｎ ") is measured, the required time T ｎ Here, for the sake of simplicity, the delay time from when the wireless device 1-n receives the first pulse signal until when it transmits the second pulse signal to the terminal 2, and the delay time from when the terminal 2 receives the second pulse signal until when it transmits the third pulse signal to the wireless device 1-n will be ignored, and the distance between the wireless device 1-n and the terminal 2 can be calculated based on the required time Tｎ Here, an example is shown in which the wireless device 1-n and the terminal 2 perform UWB wireless communication. However, this is only an example, and the wireless device 1-n and the terminal 2 may perform wireless communication using a short-range wireless communication technology other than UWB wireless communication.

[0019] 6 is a flowchart showing a location estimation method, which is a processing procedure of the location estimation device 3. The distance measurement unit 11 measures the distance L between the wireless device 1-n (n=1, . . . , 5) and the terminal 2 based on electromagnetic waves transmitted and received between the wireless device 1-n and the terminal 2. ｎ (Step ST1 in FIG. 6). Specifically, the distance measurement unit 11 measures the required time T ｎ The distance L is calculated from the required time T and the speed of light c as shown in the following equation (1). ｎ The speed of light c is the speed of the pulse signal. ｎ = c × T ｎ　　　　　　 (1) The distance measurement unit 11 measures the distance L between the wireless device 1-n and the terminal 2. ｎ The distance selecting unit 12 outputs distance information indicating the distance.

[0020] The distance selection unit 12 acquires distance information from the distance measurement unit 11. The distance selection unit 12 selects the distance L indicated by the distance information. １ ~L ５ Among these, the distance L that can be used for trilateration of the position of the terminal 2 is ＳＥＬ１ , L ＳＥＬ２ (Step ST2 in FIG. 6). The distance selection unit 12 selects the selected distance L ＳＥＬ１ , L ＳＥＬ２ The distance selection unit 12 outputs selection information indicating the distance L ＳＥＬ１ , L ＳＥＬ２ The selection process will be specifically described below.

[0021] The distance selection unit 12 selects the distance L measured by the distance measurement unit 11. １ ~L ５Specifically, when determining whether or not the distance L1 between the wireless device 1-1 and the terminal 2 among the wireless devices 1-1 to 1-5 is an abnormal value, the distance selection unit 12 determines whether or not the following formula (2) holds for n=1. n ≦D_(n,m)+L ｍ +Th 1　　　　　　 (m≠n) (2) In formula (2), L m is the distance between the terminal 2 and the other wireless devices 1-m (m=2, ..., 5) other than the wireless device 1-1, and is the value output from the distance measurement unit 11. D_(n, m) is the distance between the wireless device 1-1 and the wireless device 1-m (m=2, ..., 5), and D_(1, m) is known. In this case, m=2, ..., 5. Th １ is the first threshold value. １ may be stored in an internal memory of the distance selection unit 12 or may be provided from outside the position estimation device 3.

[0022] When equation (2) holds for m=2, . . . , 5, the distance selection unit 12 determines the distance L between the wireless device 1-1 and the terminal 2 as １ If the formula (2) does not hold for any of m=2, ..., 5, the distance selection unit 12 determines that the distance L between the wireless device 1-1 and the terminal 2 is not an abnormal value. １ The distance selection unit 12 determines that the distance L between the wireless device 1-1 and the terminal 2 is an abnormal value. １ If it is determined that the distance is an abnormal value, the distance L １ Discard the distance L between the wireless device 1-n (n=2, ..., 5) and the terminal 2. ｎ Regarding the distance L １ As in the case of n=1, it is determined whether the distance indicates an abnormal value.

[0023] The distance selection unit 12 selects a distance L that can be used for trilateration from the remaining distances that have not been discarded. ＳＥＬ１ , L ＳＥＬ２ In the example of FIG. 1, the distance L that can be used for trilateration is selected. ＳＥＬ１ Assuming that the distance L between the wireless device 1-1 and the terminal 2 is１ is selected, and L ＳＥＬ２ Assuming that the distance L between the wireless device 1-5 and the terminal 2 is ５ is selected.

[0024] The position estimation unit 13 acquires the selection information from the distance selection unit 12. The position estimation unit 13 determines the distance L indicated by the selection information. ＳＥＬ１ , L ＳＥＬ２ The position of the terminal 2 is estimated using the distance L (step ST3 in FIG. 6). The positions of the wireless devices 1-1 and 1-5 are known to the position estimation unit 13, and the distance between the wireless devices 1-1 and 1-5 is also known to the position estimation unit 13. ＳＥＬ１ , L ＳＥＬ２ The transmitting and receiving directions of the electromagnetic waves transmitted and received by the wireless devices 1-1 and 1-5 when the distance L is measured are also known to the position estimation unit 13. ＳＥＬ１ , L ＳＥＬ２ If the position estimating unit 13 knows the position of the terminal 2 by trilateration, the position estimating unit 13 can estimate the position of the terminal 2 by trilateration.

[0025] Here, the position estimation unit 13 estimates the distance L ＳＥＬ１ , L ＳＥＬ２ The position estimation unit 13 estimates the position of the terminal 2 using the distance L ＳＥＬ１ , L ＳＥＬ２ Instead, the distance L measured by the distance measuring unit 11 ｎ (n=1, ..., 5) to estimate the position of the terminal 2. Specifically, the position estimation unit 13 may estimate the position (x, y, z) of the terminal 2 by performing, for example, a nonlinear least squares method as shown in the following equation (3) as the optimization calculation. At this time, the position estimation unit 13 estimates the distance L ＳＥＬ１ , L ＳＥＬ２ The area where the terminal 2 may be present may be estimated based on the above, and any position within the area may be used as an initial value to perform optimization calculations. The area where the terminal 2 may be present may be, for example, a distance L from the wireless device 1-1. ＳＥＬ１ and is within a distance L from the wireless device 1-5. ＳＥＬ２ The distance range can be limited to include

[0026] In formula (3), (x ｎ , y ｎ , z ｎ ) is the position of wireless device 1-n (n = 1, ..., 5). Assuming that the height at which terminal 2 is present does not change, the position of terminal 2 may be estimated on a two-dimensional plane parallel to the ground. In other words, the position estimation unit 13 may fix the z-coordinate value z of terminal 2 to a predetermined value and calculate the position (x, y, z) of terminal 2 on the xy plane.

[0027] In the above-described first embodiment, the position estimation device 3 is configured to include a distance measurement unit 11 that measures the distance between a wireless device 1-n (n = 1, ..., 5) and a terminal 2 based on electromagnetic waves transmitted and received between a plurality of wireless devices 1-1 to 1-5 installed in a vehicle and a terminal 2 carried by a user, a distance selection unit 12 that selects a distance that can be used for trilateration of the position of the terminal 2 based on the plurality of distances measured by the distance measurement unit 11, and a position estimation unit 13 that estimates the position of the terminal 2 using the distance selected by the distance selection unit 12. Therefore, the position estimation device 3 can prevent deterioration in the accuracy of position estimation even if the antenna of the wireless device 1-n has directionality.

[0028] In the first embodiment, the position estimation device 3 is configured so that the distance selection unit 12 discards distances that show abnormal values ​​from among the multiple distances measured by the distance measurement unit 11, and selects distances that can be used for trilateration based on the remaining distances. Therefore, the position estimation device 3 can exclude distances that show abnormal values ​​due to the influence of electromagnetic wave shielding by a human body or the influence of multipath, and as a result, it is possible to prevent deterioration of the position estimation accuracy.

[0029] In the first embodiment, the position estimation device 3 is configured so that, if the distance between a certain wireless device among the multiple wireless devices 1-1 to 1-5 and the terminal 2 is equal to or greater than the sum of the distance between the certain wireless device and another wireless device and the first threshold value, the distance selection unit 12 discards the distance between the certain wireless device and the terminal 2 as a distance indicating an abnormal value. Therefore, the position estimation device 3 can easily discard distances indicating abnormal values.

[0030] In the position estimation device 3 shown in FIG. 2, the delay time required for the wireless device 1-n to receive the first pulse signal and transmit the second pulse signal to the terminal 2 is ignored, and the delay time required for the terminal 2 to receive the second pulse signal and transmit the third pulse signal to the wireless device 1-n is ignored. ｎ However, this is only an example, and the wireless device 1-n may calculate the required time T ｎ may be calculated.

[0031] For example, using the DS-TWR (Double-Sided Two-Way Ranging) method, the required time T ｎ When calculating the time difference (τ), terminal 2 transmits a first pulse signal, and after wireless device 1-n receives the first pulse signal, it transmits a second pulse signal to terminal 2. Then, after terminal 2 receives the second pulse signal, it transmits a third pulse signal, and wireless device 1-n receives the third pulse signal.

[0032] At this time, as shown in FIG. 7, the terminal 2 receives the second pulse signal after a time T ｒｏｕｎｄ１ and the time T from the reception time of the second pulse signal to the transmission time of the third pulse signal. ｒｅｐｌｙ２ The terminal 2 performs UWB wireless communication or other communication and measures the time T ｒｏｕｎｄ１ and time T ｒｅｐｌｙ２ The wireless device 1-n transmits information indicating the time T from the time of receiving the first pulse signal to the time of transmitting the second pulse signal. ｒｅｐｌｙ１ and the time T from the transmission time of the second pulse signal to the reception time of the third pulse signal. ｒｏｕｎｄ２ 7 is an explanatory diagram showing transmission and reception of pulse signals between the wireless device 1-n and the terminal 2. The wireless device 1-n measures the time T ｒｏｕｎｄ１ and time T ｒｏｕｎｄ２ and time T ｒｅｐｌｙ１ and time T ｒｅｐｌｙ２ Using the above, the required time T ｎ In FIG. ｐｒｏｐis the propagation time required from when the communication partner transmits a pulse signal until when the communication partner receives the pulse signal. ｎ Is T ｐｒｏｐ is.

[0033]

[0034] For example, using the SS-TWR (Single-Sided Two-Way Ranging) method, the required time T ｎ When calculating the time difference (τ), the terminal 2 transmits a first pulse signal, and the wireless device 1-n receives the first pulse signal. After receiving the first pulse signal, the wireless device 1-n transmits a second pulse signal, and the terminal 2 receives the second pulse signal.

[0035] At this time, as shown in FIG. 8, the terminal 2 receives the second pulse signal after a time T ｒｏｕｎｄ The terminal 2 performs UWB wireless communication or other communication and measures the time T ｒｏｕｎｄ The wireless device 1-n transmits information indicating the time T from the time of receiving the first pulse signal to the time of transmitting the second pulse signal. ｒｅｐｌｙ 8 is an explanatory diagram showing transmission and reception of pulse signals between the wireless device 1-n and the terminal 2. The wireless device 1-n measures the time T ｒｏｕｎｄ and time T ｒｅｐｌｙ Using the above, the required time T ｎ In FIG. ｐｒｏｐ is the propagation time required from when the communication partner transmits a pulse signal until when the communication partner receives the pulse signal. ｐｒｏｐ = (T ｒｏｕｎｄ -T ｒｅｐｌｙ ) / 2 (5) At this time, T ｎ Is T ｐｒｏｐ is.

[0036] In the second embodiment, the distance measurement unit 14 measures the distance L between the wireless device 1-n (n=1, . . . , 5) and the terminal 2. ｎ is repeatedly measured, and the distance L between the wireless device 1-n and the terminal 2 is calculated. ｎThe position estimation device 3 including the pre-processing unit 15 for calculating the smoothed value of is now described.

[0037] Fig. 9 is a configuration diagram showing a position estimation device 3 according to embodiment 2. Fig. 10 is a hardware configuration diagram showing hardware of the position estimation device 3 according to embodiment 2. The position estimation device 3 shown in Fig. 9 includes a distance measurement unit 14, a preprocessing unit 15, a distance selection unit 16, and a position estimation unit 17.

[0038] The distance measurement unit 14 is realized by, for example, a distance measurement circuit 24 shown in Fig. 10. The distance measurement unit 14 calculates the distance L between the wireless device 1-n (n = 1, ..., 5) and the terminal 2 based on the electromagnetic waves transmitted and received between the wireless device 1-n and the terminal 2. ｎ The distance measurement unit 14 repeatedly measures the distance L between the wireless device 1-n and the terminal 2. ｎ The distance information indicating the distance is repeatedly output to the pre-processing unit 15.

[0039] The preprocessing unit 15 is realized by, for example, a preprocessing circuit 25 shown in Fig. 10. The preprocessing unit 15 repeatedly acquires distance information from the distance measuring unit 14. The preprocessing unit 15 calculates the distance L between the wireless device 1-n (n = 1, ..., 5) and the terminal 2, which is repeatedly measured by the distance measuring unit 14. ｎ Smoothed value S ｎ The preprocessing unit 15 calculates the smoothed value S ｎ is output to the distance selection unit 16.

[0040] The distance selector 16 is realized by, for example, a distance selector circuit 26 shown in Fig. 10. The distance selector 16 receives the smoothed value S ｎ The distance selection unit 16 obtains the smoothed value S １ ~S ５ Among these, a smoothed value S that can be used for trilateration of the position of the terminal 2 is ＳＥＬ１ , S ＳＥＬ２ The distance selector 16 selects the selected smoothed value S ＳＥＬ１ , S ＳＥＬ２ The position estimation unit 17 outputs selection information indicating the above to the position estimation unit 17.

[0041] The position estimation unit 17 is realized by, for example, a position estimation circuit 27 shown in Fig. 10. The position estimation unit 17 acquires selection information from the distance selection unit 16. The position estimation unit 17 calculates the smoothed value S ＳＥＬ１ , S ＳＥＬ２ The position estimation unit 17 estimates the position of the terminal 2. Information indicating the position estimated by the position estimation unit 17 is output to, for example, a control device of the vehicle.

[0042] 9, it is assumed that each of the components of the position estimation device 3, namely, the distance measurement unit 14, preprocessing unit 15, distance selection unit 16, and position estimation unit 17, is realized by dedicated hardware as shown in Fig. 10. That is, it is assumed that the position estimation device 3 is realized by a distance measurement circuit 24, preprocessing circuit 25, distance selection circuit 26, and position estimation circuit 27. Each of the distance measurement unit 14, preprocessing circuit 15, distance selection unit 16, and position estimation unit 17 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0043] The components of the position estimation device 3 are not limited to those realized by dedicated hardware, and the position estimation device 3 may be realized by software, firmware, or a combination of software and firmware. When the position estimation device 3 is realized by software, firmware, or the like, a program for causing a computer to execute the respective processing procedures of the distance measurement unit 14, preprocessing unit 15, distance selection unit 16, and position estimation unit 17 is stored in memory 31 shown in Fig. 4. Then, a processor 32 shown in Fig. 4 executes the program stored in memory 31.

[0044] 10 shows an example in which each of the components of the position estimation device 3 is realized by dedicated hardware, while Fig. 4 shows an example in which the position estimation device 3 is realized by software, firmware, etc. However, this is merely an example, and some of the components in the position estimation device 3 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0045] Next, the operation of the position estimation device 3 shown in Fig. 9 will be described. The distance measurement unit 14 measures the distance L between the wireless device 1-n (n = 1, ..., 5) and the terminal 2 based on electromagnetic waves transmitted and received between the wireless device 1-n and the terminal 2. ｎ Specifically, the distance measurement unit 14 repeatedly measures the required time T ｎ The distance L is calculated from the required time T and the speed of light c as shown in equation (1). ｎ Here, for convenience of explanation, the distance measurement unit 14 calculates the distance L ｎ is calculated M times, where M is an integer equal to or greater than 2. The distance measurement unit 14 calculates the distance L between the wireless device 1-n and the terminal 2. ｎ The distance information indicating the distance M is output to the pre-processing unit 15 M times.

[0046] The preprocessing unit 15 receives the distance L between the wireless device 1-n and the terminal 2 from the distance measuring unit 14. ｎ The pre-processing unit 15 acquires distance information indicating, for example, M distances L ｎ Among them, the distances showing abnormal values ​​are discarded, and the remaining smoothed values ​​S ｎ The process of discarding the distance indicating an abnormal value is the same as the process of discarding the distance by the distance selector 12 shown in FIG. 2. The preprocessor 15 calculates the smoothed value S ｎ is output to the distance selection unit 16.

[0047] The distance selector 16 receives the smoothed value S ｎ The distance selection unit 16 obtains the smoothed value S １ ~S ５ Among these, a smoothed value S that can be used for trilateration of the position of the terminal 2 is ＳＥＬ１ , S ＳＥＬ２ The distance selector 16 selects the selected smoothed value S ＳＥＬ１ , S ＳＥＬ２ The position estimation unit 17 outputs selection information indicating the above to the position estimation unit 17.

[0048] The position estimation unit 17 acquires the selection information from the distance selection unit 16. The position estimation unit 17 calculates the smoothed value S ＳＥＬ１ , S ＳＥＬ２For example, the positions of the wireless devices 1-1 and 1-5 are known to the position estimation unit 17, and the distance between the wireless devices 1-1 and 1-5 is also known to the position estimation unit 17. ＳＥＬ１ , S ＳＥＬ２ The transmission and reception directions of the electromagnetic waves transmitted and received by the wireless devices 1-1 and 1-5 when the distances related to the smoothed value S ＳＥＬ１ , S ＳＥＬ２ If the position estimating unit 17 knows the position of the terminal 2 by trilateration, the position estimating unit 17 can estimate the position of the terminal 2 by trilateration.

[0049] In the second embodiment described above, the position estimation device 3 shown in FIG. 9 is configured so that the distance measurement unit 14 repeatedly measures the distance between the wireless device 1-n (n = 1, ..., 5) and the terminal 2, and the preprocessing unit 15 calculates a smoothed value of the distance between the wireless device 1-n and the terminal 2 repeatedly measured by the distance measurement unit 14. The position estimation device 3 shown in FIG. 9 is also configured so that the distance selection unit 16 selects a smoothed value that can be used for trilateration of the position of the terminal 2 from among the multiple smoothed values ​​calculated by the preprocessing unit 15, and the position estimation unit 17 estimates the position of the terminal 2 using the smoothed value selected by the distance selection unit 16. Therefore, like the position estimation device 3 shown in FIG. 1, the position estimation device 3 shown in FIG. 9 can prevent deterioration in the position estimation accuracy even if the antenna of the wireless device 1-n has directionality, and can also improve the position estimation accuracy more than the position estimation device 3 shown in FIG. 1.

[0050] In the second embodiment, the position estimation device 3 shown in Fig. 9 is configured so that the preprocessing unit 15 discards any distances that show abnormal values ​​among the distances between the wireless devices 1-n (n = 1, ..., 5) and the terminal 2 that are repeatedly measured by the distance measurement unit 14, and calculates a smoothed value for the remaining distances. Therefore, the position estimation device 3 shown in Fig. 9 can estimate the position with higher accuracy than the position estimation device 3 shown in Fig. 1.

[0051] Third Embodiment In a third embodiment, a position estimation device 3 will be described in which the preprocessing unit 18 complements missing values ​​resulting from measurement failures when the distance measurement unit 14 repeatedly measures the distance or missing values ​​resulting from discarded distances, using the remaining distances that are not discarded.

[0052] Fig. 11 is a configuration diagram showing a position estimation device 3 according to embodiment 3. In Fig. 11, the same reference numerals as in Fig. 9 indicate the same or corresponding parts, and detailed description thereof will be omitted. Fig. 12 is a hardware configuration diagram showing the hardware of the position estimation device 3 according to embodiment 3. In Fig. 12, the same reference numerals as in Fig. 10 indicate the same or corresponding parts, and detailed description thereof will be omitted. The position estimation device 3 shown in Fig. 11 includes a distance measurement unit 14, a preprocessing unit 18, a distance selection unit 16, and a position estimation unit 17.

[0053] The preprocessing unit 18 is realized by, for example, the preprocessing circuit 28 shown in FIG. 12. The preprocessing unit 18 repeatedly acquires distance information from the distance measurement unit 14. Similar to the distance selection unit 12 shown in FIG. 2, the preprocessing unit 18 determines whether the distance indicated by the distance information is an abnormal value, and discards the distance if it determines that the distance indicates an abnormal value. The preprocessing unit 18 complements missing values ​​resulting from measurement failures when the distance measurement unit 14 repeatedly measures the distance, or missing values ​​resulting from discarded distances, using the remaining distances that were not discarded. The preprocessing unit 18 calculates a smoothed value of the remaining distances that were not discarded and the complemented distances. The preprocessing unit 18 outputs the smoothed value related to the wireless device 1-n to the distance selection unit 16.

[0054] 11, it is assumed that each of the components of the position estimation device 3, namely, the distance measurement unit 14, preprocessing unit 18, distance selection unit 16, and position estimation unit 17, is realized by dedicated hardware as shown in Fig. 12. That is, it is assumed that the position estimation device 3 is realized by a distance measurement circuit 24, preprocessing circuit 28, distance selection circuit 26, and position estimation circuit 27. Each of the distance measurement unit 14, preprocessing circuit 18, distance selection unit 16, and position estimation unit 17 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0055] The components of the position estimation device 3 are not limited to those realized by dedicated hardware, and the position estimation device 3 may be realized by software, firmware, or a combination of software and firmware. When the position estimation device 3 is realized by software, firmware, or the like, a program for causing a computer to execute the respective processing procedures of the distance measurement unit 14, preprocessing unit 18, distance selection unit 16, and position estimation unit 17 is stored in memory 31 shown in Fig. 4. Then, a processor 32 shown in Fig. 4 executes the program stored in memory 31.

[0056] 12 shows an example in which each of the components of the position estimation device 3 is realized by dedicated hardware, while Fig. 4 shows an example in which the position estimation device 3 is realized by software, firmware, etc. However, this is merely an example, and some of the components in the position estimation device 3 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0057] Next, the operation of the position estimation device 3 shown in Fig. 11 will be described. However, apart from the pre-processing unit 18, the position estimation device 3 is the same as that shown in Fig. 9. Therefore, only the operation of the pre-processing unit 18 will be described here.

[0058] The preprocessing unit 18 repeatedly acquires distance information from the distance measurement unit 14. Similar to the distance selection unit 12 shown in FIG. 2 , the preprocessing unit 18 determines whether the distance indicated by the distance information is an abnormal value, and discards the distance if it determines that the distance indicates an abnormal value. As shown in FIG. 13 , the preprocessing unit 18 stores the remaining distances that are not discarded in a queue. FIG. 13 is an explanatory diagram showing distances stored in the queue. In FIG. 13 , nan indicates a missing value resulting from a measurement failure when the distance measurement unit 14 measures the distance, or a missing value resulting from the discarding of the distance. FIG. 13 shows an example in which the preprocessing unit 18 acquires four pieces of distance information from the distance measurement unit 14. However, this is merely an example, and the preprocessing unit 18 may acquire three or fewer pieces of distance information from the distance measurement unit 14, or may acquire five or more pieces of distance information.

[0059] As shown in Fig. 14, the pre-processing unit 18 complements the missing value nan using the distance that remains without being discarded. That is, the pre-processing unit 18 complements the missing value nan using the distance stored in the queue. The process of complementing the missing value nan itself is a known technique, so a detailed description will be omitted. Fig. 14 is an explanatory diagram showing the complementation of the missing value nan using the distance stored in the queue. Completion of the missing value nan may be performed using an average value obtained by averaging multiple distances related to the wireless device 1-n that are repeatedly acquired. Furthermore, the missing value nan may be complemented using distance information acquired immediately before or after the missing value nan. The pre-processing unit 18 calculates a smoothed value S between the distance that remains without being discarded and the complemented distance. ｎ The preprocessing unit 18 calculates the smoothed value S ｎ is output to the distance selection unit 16.

[0060] In the third embodiment described above, the position estimation device 3 shown in Fig. 11 is configured so that the preprocessing unit 18 complements missing values ​​resulting from measurement failures when the distance measurement unit 14 repeatedly measures the distance or missing values ​​resulting from discarded distances using the remaining distances that have not been discarded, and calculates a smoothed value of the remaining distances that have not been discarded and the complemented distances. Therefore, the position estimation device 3 shown in Fig. 11 can improve the position estimation accuracy compared to the position estimation device 3 shown in Fig. 9.

[0061] In the first embodiment, the position estimation unit 13 estimates the distance L ＳＥＬ１ , L ＳＥＬ２ In the second embodiment, the position estimation unit 17 estimates the position of the terminal 2 using the smoothed value S ＳＥＬ１ , S ＳＥＬ２ The position estimation unit 13 may estimate the position of the terminal 2 using the distance selected by the distance selection unit 12, each time a distance is selected by the distance selection unit 12, using the selected distance and calculate an average value of the multiple estimated positions. The position estimation unit 13 may estimate the position of the terminal 2 using the selected distance and calculate a smoothed value of the multiple estimated positions. The position estimation unit 17 may estimate the position of the terminal 2 using the selected smoothed value and calculate an average value of the multiple estimated positions, each time a smoothed value is selected by the distance selection unit 16, each time a smoothed value is selected by the distance selection unit 16, using the selected smoothed value and calculate a smoothed value of the multiple estimated positions. In this case, the position estimation units 13 and 17 may discard the estimated position if the difference between the estimated position and the smoothed value is equal to or greater than a second threshold. Furthermore, the position estimation units 13 and 17 may complement the discarded position using the multiple estimated positions. The process of complementing the discarded positions is a known technique, and therefore a detailed description thereof will be omitted.

[0062] In addition, the present disclosure allows for free combination of the respective embodiments, modification of any of the components of the respective embodiments, or omission of any of the components of the respective embodiments.

[0063] The position estimation device according to the present disclosure can prevent deterioration in position estimation accuracy even if the antenna of a wireless device has directionality, and is suitable for use in position estimation devices and the like.

[0064] 1-1 to 1-5 Radio, 2 Terminal, 3 Position estimation device, 11 Distance measurement unit, 12 Distance selection unit, 13 Position estimation unit, 14 Distance measurement unit, 15 Pre-processing unit, 16 Distance selection unit, 17 Position estimation unit, 18 Pre-processing unit, 21 Distance measurement circuit, 22 Distance selection circuit, 23 Position estimation circuit, 24 Distance measurement circuit, 25 Pre-processing circuit, 26 Distance selection circuit, 27 Position estimation circuit, 28 Pre-processing circuit, 31 Memory, 32 Processor.

Claims

1. A position estimation device comprising: a distance measurement unit that measures the distance between each of multiple radios installed in a vehicle and a terminal carried by a user based on electromagnetic waves transmitted and received between the radios; a distance selection unit that selects a distance that can be used for trilateration of the terminal's position based on the multiple distances measured by the distance measurement unit; and a position estimation unit that estimates the terminal's position using the distance selected by the distance selection unit.

2. The position estimation device described in claim 1, characterized in that the distance selection unit discards distances that show abnormal values ​​from among the multiple distances measured by the distance measurement unit, and selects distances that can be used for the trilateration based on the distances that remain.

3. The position estimation device described in claim 2, characterized in that if the distance between a certain radio among the plurality of radios and the terminal is equal to or greater than the sum of the distance between the certain radio and other radios and a first threshold value, the distance between the certain radio and the terminal is discarded as an abnormal value.

4. The position estimation device described in claim 1, characterized in that the ranging unit repeatedly measures the distance between each radio and the terminal, and is equipped with a pre-processing unit that calculates a smoothed value of the distance between each radio and the terminal repeatedly measured by the ranging unit, the distance selection unit selects a smoothed value that can be used for trilateration of the position of the terminal from the multiple smoothed values ​​calculated by the pre-processing unit, and the position estimation unit estimates the position of the terminal using the smoothed value selected by the distance selection unit.

5. The position estimation device described in claim 4, characterized in that the pre-processing unit discards distances that show abnormal values ​​among the distances between each radio and the terminal repeatedly measured by the ranging unit, and calculates smoothed values ​​of the remaining distances.

6. The position estimation device described in claim 5, characterized in that the pre-processing unit complements missing values ​​due to measurement failures when the distance is repeatedly measured by the distance measurement unit, or missing values ​​due to discarded distances, using the distances that remain undiscarded, and calculates a smoothed value of the remaining distances that remain undiscarded and the complemented distances.

7. A position estimation device as claimed in any one of claims 1 to 3, characterized in that the position estimation unit estimates the position of the terminal by performing an optimization calculation using multiple distances measured by the ranging unit instead of the distance selected by the distance selection unit.

8. The position estimation device according to claim 7, characterized in that the position estimation unit estimates an area in which the terminal may be located based on the distance selected by the distance selection unit, and performs the optimization calculation using any position within the area as an initial value.

9. A position estimation device as described in any one of claims 1 to 3, characterized in that the position estimation unit estimates the position of the terminal using the distance selected by the distance selection unit each time the distance is selected, and calculates the average value of the multiple estimated positions.

10. A position estimation device as described in any one of claims 1 to 3, characterized in that the position estimation unit estimates the position of the terminal using the distance each time the distance selection unit selects the distance, calculates a smoothed value of the estimated positions, and if the difference between the position estimated using the distance and the smoothed value is equal to or greater than a second threshold, discards the position estimated using the distance.

11. The position estimation device according to claim 10, wherein the position estimation unit complements the discarded position using the plurality of estimated positions.

12. A position estimation device according to any one of claims 1 to 11, characterized in that the position estimation unit estimates the position of the terminal on a two-dimensional plane parallel to the ground.

13. A position estimation method in which a distance measurement unit measures the distance between each of multiple radios installed in a vehicle and a terminal carried by a user based on electromagnetic waves transmitted and received between the radios, a distance selection unit selects a distance that can be used for trilateration of the terminal's position based on the multiple distances measured by the distance measurement unit, and a position estimation unit estimates the position of the terminal using the distance selected by the distance selection unit.

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