Location estimation system, information processing device, location estimation method

Abstract

The accuracy of estimating the target's position will be improved by using three communication terminals. [Solution] In the position estimation system, the information processing device uses one of the first communication terminal 100A, second communication terminal 100B, and third communication terminal 100C, which perform multi-carrier transmission, as a reference communication terminal, and estimates a first distance between the reference communication terminal and the target communication terminal 10 based on the communication results between the reference communication terminal and the target communication terminal 10. Based on the first distance, it calculates the second and third distances between each of the other two of the first, second, and third communication terminals and the target communication terminal based on the position coordinates of the target communication terminal at a predetermined time prior, and then estimates the position coordinates of the target communication terminal at a predetermined time prior based on the first, second, and third distances, sequentially executing the process of estimating the position coordinates of the target communication terminal at a predetermined time prior, using each of the first, second, and third communication terminals as a reference communication terminal.

Description

[Technical Field]

[0001] The present invention relates to a position estimation system, an information processing device, and a position estimation method. [Background technology]

[0002] As a technique for estimating location using multiple communication terminals, for example, a technique is known in which wireless communication is performed between a mobile terminal and multiple beacons whose placement information has been registered in advance, the distance between each of the multiple beacons and the mobile terminal is estimated from this communication state, and the location of the mobile terminal is estimated based on the information of these multiple estimated distances and the placement information of each pre-registered beacon, and in the process of estimating the distance or the location, a correction is made according to the characteristics of the beacon (see Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-138262 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, one method for estimating the position of a target object is to estimate the distance from three communication terminals (anchor nodes) to the target object (the target communication terminal) and use the principle of triplicate positioning. However, in this method, when estimating the distance using the power of the received signal from the communication terminal at the target position, there is a problem that the accuracy of distance estimation deteriorates significantly when the power of the received signal fluctuates due to multipath.

[0005] On the other hand, as a method for estimating the position of a target object, for example, a technique is known in which a signal is sent from one of three communication terminals to the target communication terminal, and the target communication terminal sends a signal (RT signal) back to the source communication terminal to measure the distance, and this process is performed sequentially for each source communication terminal to estimate the position of the target communication terminal.

[0006] However, the technique of estimating the position of a target communication terminal using RT signals requires estimating the distance to the target communication terminal for each source communication terminal before estimating the position of the target communication terminal, which takes time. Furthermore, this technique cannot simultaneously estimate the distance for three communication terminals. As a result, this technique has problems such as degraded tracking characteristics when the target object is moving, leading to decreased accuracy and longer processing times.

[0007] This invention addresses the above-mentioned problem as an example and aims to provide a technology that improves the accuracy of estimating the position of a target object using three communication terminals. [Means for solving the problem]

[0008] To achieve the above objective, the position estimation system according to the present invention comprises: a first communication terminal, a second communication terminal, and a third communication terminal that perform multi-carrier transmission; a target communication terminal that can communicate with each of the first, second, and third communication terminals; and an information processing device that estimates the position of the target communication terminal according to the communication results between each of the first, second, and third communication terminals and the target communication terminal, wherein the information processing device uses one of the first, second, and third communication terminals as a reference communication terminal and the reference communication terminal Based on the communication results between the reference communication terminal and the target communication terminal, the first distance between the reference communication terminal and the target communication terminal is estimated. Based on the first distance, the second and third distances between each of the other two of the first, second, and third communication terminals and the target communication terminal are calculated based on the position coordinates of the target communication terminal at a predetermined time prior. Based on the first, second, and third distances, the position coordinates of the target communication terminal at a predetermined time prior are estimated. This process is performed sequentially, with each of the first, second, and third communication terminals being the reference communication terminal. [Effects of the Invention]

[0009] The position estimation system according to the present invention can improve the accuracy of estimating the position of a target object using three communication terminals. [Brief explanation of the drawing]

[0010] [Figure 1] This is a functional block diagram schematically showing the configuration of a position estimation system according to an embodiment of the present invention. [Figure 2] This is a flowchart illustrating the position estimation process of a target communication terminal in the position estimation system according to this embodiment. [Figure 3] This is a schematic diagram illustrating an example of the position estimation process for a target communication terminal at time t+1 using the position estimation system according to this embodiment. [Figure 4]This is a schematic diagram generally showing an example of distance measurement processing between a reference communication terminal and a target communication terminal in the position estimation system according to the present embodiment. [Figure 5] This is a schematic diagram showing an example of an estimation result of the movement path of a target communication terminal in the position estimation system according to the present embodiment. [Figure 6] This is a schematic diagram generally showing an example of the position estimation process of a target communication terminal in Reference Example 1 where distance estimation is simultaneously performed by three communication terminals and the target communication terminal. [Figure 7] This is a schematic diagram generally showing an example of the position estimation process of the target communication terminal at time t + 1 in Reference Example 2 where distance estimation is sequentially performed between each of the three communication terminals and the target communication terminal. [Figure 8] This is a schematic diagram generally showing an example of the position estimation process of the target communication terminal at time t + 2 in Reference Example 2. [Figure 9] This is a schematic diagram generally showing an example of the position estimation process of the target communication terminal at time t + 3 in Reference Example 2.

Mode for Carrying Out the Invention

[0011] 1. Outline of the Embodiment First, an outline of typical embodiments of the invention disclosed in the present application will be described. In the following description, as an example, reference numerals in the drawings corresponding to the components of the invention are described with parentheses.

[0012] [1] A position estimation system (1) comprising: a first communication terminal (100A), a second communication terminal (100B), and a third communication terminal (100C) that perform multi-carrier transmission; a target communication terminal 10 that can communicate with each of the first, second, and third communication terminals; and an information processing device (500) that estimates the position of the target communication terminal according to the communication results between each of the first, second, and third communication terminals and the target communication terminal, wherein the information processing device uses one of the first, second, and third communication terminals as a reference communication terminal (200) and the reference communication terminal and the A position estimation system that sequentially performs the following processes, using the first, second, and third communication terminals as the reference communication terminal: estimating a first distance between the reference communication terminal and the target communication terminal based on the communication results with the target communication terminal; calculating second and third distances between the target communication terminal and each of the other two of the first, second, and third communication terminals based on the first distance, based on the position coordinates of the target communication terminal at a predetermined time prior; and estimating the position coordinates of the target communication terminal at a predetermined time prior, based on the first, second, and third distances, with each of the first, second, and third communication terminals as the reference communication terminal.

[0013] [2] The position estimation system according to [1], wherein the information processing device performs a process to estimate the movement path of the target communication terminal based on the estimated position coordinates of the target communication terminal.

[0014] [3] The position estimation system according to [2], wherein the information processing device calculates an exponential moving average of the estimated position coordinates of the target communication terminal to estimate the movement path.

[0015] [4] The position estimation system according to [1], wherein the information processing device estimates the first distance by removing the phase difference between each of the plurality of waveforms with different wavelengths included in the communication result between the reference communication terminal and the target communication terminal and the waveform transmitted by the reference communication terminal.

[0016] [5] The position estimation system according to [1], wherein the information processing device estimates the first distance, the second distance, and the third distance after a predetermined time using distance prediction by a Kalman filter based on the first distance, the second distance, and the third distance.

[0017] [6] An information processing device (500) that estimates the position of a target communication terminal (10) according to the communication results between each of a first communication terminal (100A), a second communication terminal (100B), and a third communication terminal (100C) that perform multi-carrier transmission and a target communication terminal (10), wherein the information processing device sequentially performs the following processes, with each of the first, second, and third communication terminals being the reference communication terminal: estimating a first distance between the reference communication terminal and the target communication terminal based on the communication results between the reference communication terminal and the target communication terminal, using one of the first, second, and third communication terminals as the reference communication terminal; calculating second and third distances between each of the other two of the first, second, and third communication terminals and the target communication terminal based on the position coordinates of the target communication terminal at a predetermined time prior to the first distance; and estimating the position coordinates of the target communication terminal at a predetermined time prior to the first, second, and third distances, using each of the first, second, and third communication terminals as the reference communication terminal.

[0018] [7] A method by which an information processing device (500) estimates the position of a target communication terminal (10) in accordance with the communication results between each of the first communication terminal (100A), second communication terminal (100B), and third communication terminal (100C) that perform multi-carrier transmission and the target communication terminal, wherein the information processing device estimates a first distance between the reference communication terminal and the target communication terminal based on the communication results between the reference communication terminal and the target communication terminal, with one of the first communication terminal, the second communication terminal, and the third communication terminal as the reference communication terminal. A position estimation method comprising: calculating the second and third distances between each of the first communication terminal, the second communication terminal, and the other two of the third communication terminals and the target communication terminal based on the first distance, based on the position coordinates of the target communication terminal at a predetermined time prior; and sequentially performing the process of estimating the position coordinates of the target communication terminal at a predetermined time based on the first distance, the second distance, and the third distance, with each of the first communication terminal, the second communication terminal, and the third communication terminal as the reference communication terminal.

[0019] 2. Specific Examples of Embodiments The following describes a position estimation system, information processing device, and position estimation method according to embodiments of the present invention with reference to the drawings.

[0020] Figure 1 is a functional block diagram schematically showing the configuration of the position estimation system 1 according to an embodiment of the present invention. As shown in Figure 1, the position estimation system 1 consists of a target communication terminal 10, a communication terminal 100, and a server 500. In the position estimation system 1, the target communication terminal 10 is a terminal that moves together with the target object whose position is to be estimated. In the position estimation system 1, the communication terminal 100 is a terminal that communicates wirelessly with the target communication terminal 10 and acquires information necessary for estimating the distance to the target communication terminal 10, which is required for the position estimation method.

[0021] The communication terminal 100 is, for example, an electronic device capable of multi-carrier transmission. The communication terminal 100 may be a device used to estimate the position coordinates of the target communication terminal 10 via wireless communication such as a radio beacon, or it may be an electronic device such as a smartphone, tablet terminal, or various types of computers. The communication terminal 100 functions as a first communication terminal, a second communication terminal, and a third communication terminal.

[0022] In this embodiment, the first communication terminal is also referred to as code 100A, the second communication terminal as code 100B, and the third communication terminal as code 100C. In the position estimation system 1, in order to estimate the position coordinates of the target communication terminal 10, at least three communication terminals 100 are required to be in a state where they can communicate with the target communication terminal 10. Furthermore, when performing the process of estimating the position coordinates of the target communication terminal 10, one of the three communication terminals 100 that can communicate with the target communication terminal 10, namely the first communication terminal 100A, the second communication terminal 100B, and the third communication terminal 100C, becomes the reference communication terminal, and the process of estimating the first distance is performed by sequentially changing the reference communication terminal. In other words, first, the first communication terminal 100A acts as the reference communication terminal to estimate the first distance. Then, when estimating the second and third distances, which are the distances between the remaining second and third communication terminals 100B and 100C and the target communication terminal 10, based on the first distance, the process is executed in which the second communication terminal 100B then acts as the reference communication terminal to estimate the first distance, followed by the third communication terminal 100C. Note that the number of communication terminals 100 in the position estimation system 1 may be three or more.

[0023] The target communication terminal 10 can be any electronic device capable of communicating with the communication terminal 100 via wireless communication, such as a smartphone, tablet, or various types of computers. The target communication terminal 10 and the communication terminal 100 may be the same electronic device, or they may be different electronic devices capable of communicating with each other.

[0024] Both the target communication terminal 10 and the communication terminal 100 have control units 11, 110, storage units 12, 120, and communication units 13, 130.

[0025] The control units 11 and 110 are implemented by a computer such as a microcomputer, which is made up of a processor such as an MCU (Micro Control Unit) (not shown) and a memory for calculations such as RAM (Random Access Memory). The MCU is a computing device that realizes various functions as the target communication terminal 10 or communication terminal 100 by executing the calculation processing of a program. The memory is a volatile memory in which the program processed by the MCU is stored. The control units 11 and 110 store the functional programs stored in the storage units 12 and 120 in the memory. The functional programs stored in the storage units are programs for realizing various functions of the target communication terminal 10 or communication terminal 100 in this embodiment. Programs corresponding to the functions to be realized are sequentially stored in the memory and executed sequentially by the MCU. The program is composed of functions and fixed values ​​corresponding to the function. When the program is executed, not only functions but also data, which are fixed values, are required.

[0026] The memory units 12 and 120 store identification information that can uniquely identify each target communication terminal 10 or communication terminal 100 within the position estimation system 1, the position coordinates of each target communication terminal 10 or communication terminal 100 itself, and programs that can be executed by the control units 11 and 110 described above.

[0027] Both communication units 13 and 130 transmit and receive multiple carriers and can communicate with other communication terminals 100 or the target communication terminal 10 by multi-carrier transmission, where each carrier has a different wavelength. The multi-carrier transmission used by the target communication terminal 10 and the communication terminal 100 includes, for example, OFDM (Orthogonal Frequency-Division Multiplexing) such as Wi-Fi and LTE, and frequency-hopping spread spectrum such as Bluetooth®.

[0028] Server 500 is an example of an information processing device. Server 500 can, for example, communicate the communication results between communication terminal 100 and target communication terminal 10 via wireless or wired communication. Server 500 is an example of a computer, such as a PC or server device, realized by a processor (such as an MCU, not shown), a memory for calculations (such as RAM, or Random Access Memory), and a memory unit for storing programs and processing data. The MCU is a calculation unit that realizes various functions of Server 500, as described below, by executing the calculations of programs. Memory is a volatile memory in which programs processed by the MCU are stored. Server 500 stores the functional programs stored in memory. The functional programs stored in memory are programs for realizing various functions of Server 500 in this embodiment. Programs corresponding to the functions to be realized are sequentially stored in memory and executed sequentially by the MCU. Programs consist of functions and fixed values ​​corresponding to the functions. When a program is executed, not only functions but also fixed value data are required.

[0029] The server 500, with the hardware configuration and program described above, comprises functional blocks such as the control unit 501, storage unit 502, and communication unit 503.

[0030] The control unit 501, in cooperation with the MCU and memory, executes a program stored in the storage unit 502, thereby realizing its function as an information processing device in the position estimation system 1 by the server 500, and performing the following processing, and executing the position estimation method for the target communication terminal 10.

[0031] The memory unit 502 is implemented using non-volatile memory such as EEPROM (Electrically Erasable Programmable Read-Only Memory). The memory unit 502 stores functional programs for implementing various functions. The memory unit 502 also stores various processing data used by the server 500, such as information used when estimating the position coordinates of the target communication terminal 10, specifically information on the first distance, second distance, and third distance received from the communication terminal 100, and information on calculation formulas used to estimate the position coordinates of the target communication terminal 10.

[0032] The communication unit 503 can communicate with external devices, i.e., multiple communication terminals 100, for example, by wireless or wired communication via a communication interface (not shown). The communication unit 503 may also be able to communicate with the target communication terminal 10.

[0033] The server 500 may also be equipped with an operation unit and a display unit, which are input interfaces for the user to operate the server 500 and output interfaces for the user to perceive the operating status of the server 500.

[0034] Examples of hardware configurations for implementing the control unit include various touch panels, keyboards, numeric keypads, buttons, etc. However, the hardware configuration for implementing the control unit is not limited to the examples described above; it only needs to have the functionality to receive input from the user to operate the server 500. The control unit may, for example, accept operations via commands from various communication interfaces via the communication unit 503, or it may accept operations via voice command input.

[0035] The hardware configuration for the display unit is a display device equipped with a functional unit for the user to perceive the operating status of the server 500, such as an LCD (Liquid Crystal Display) or an organic EL. If the operation unit and display unit are, for example, a touch panel, then the operation unit function and the display unit function are integrated. Furthermore, the server 500 may not have some of the functions of an operation unit or display unit. Also, the server 500 is not limited to having an operation unit and display unit; for example, the operation unit and display unit functions of the server 500 may be realized from other information processing terminals such as a communication terminal 100, a smartphone, or a tablet terminal.

[0036] Next, we will describe the specific processing of the method for estimating the position of the target communication terminal 10, which is performed by the server 500 in the position estimation system 1.

[0037] Figure 2 is a flowchart illustrating the position estimation process of the target communication terminal 10 in the position estimation system 1. Figure 3 is a schematic diagram illustrating an example of the position estimation process of the target communication terminal 10 at time t+1 by the position estimation system 1.

[0038] As shown in Figures 2 and 3, in the position estimation system 1, the server 500 (see Figure 1) estimates a first distance between the reference communication terminal and the target communication terminal 10 at any given time t, using one of the first communication terminal 100A, the second communication terminal 100B, and the third communication terminal 100C, for example, the first communication terminal 100A as the reference communication terminal, based on the communication results between this reference communication terminal and the target communication terminal 10 (step S101). Based on the first distance (and on the fact that it is different from the first communication terminal 100A), the server 500 estimates the other two of the first communication terminal 100A, the second communication terminal 100B, and the third communication terminal 100C, in Figure 3, the second distance between the second communication terminal 100B and the target communication terminal 10, and the third distance between the third communication terminal 100C and the target communication terminal 10, respectively, based on the position coordinates of the target communication terminal 10 at a predetermined time t-1 (step S102). The server 500 predicts the first distance, second distance, and third distance at time t+1, which is a predetermined time after the first distance, second distance, and third distance, based on the first distance, second distance, and third distance (step S103), and estimates the position coordinates of the target communication terminal 10 at time t+1 (step S104).

[0039] The server 500 sequentially executes the processes described in steps S101 to S104 above, using the second communication terminal 100B and the third communication terminal 100C as reference communication terminals, in addition to the first communication terminal 100A. That is, at time t+1, the server 500 estimates the first distance using the second communication terminal 100B as the reference communication terminal, and based on that first distance (and based on the fact that it is different from the second communication terminal 100B), it calculates, for example, the second distance between the first communication terminal 100A and the target communication terminal 10, and the third distance between the third communication terminal 100C and the target communication terminal 10, based on the position coordinates of the target communication terminal 10 at time t a predetermined time earlier, and predicts the first distance, second distance, and third distance at time t+2 a predetermined time later, based on the first distance, second distance, and third distance, and estimates the position coordinates of the target communication terminal 10 at time t+2. Subsequently, at time t+2, server 500 estimates a first distance using the third communication terminal 100C as the reference communication terminal, and based on this first distance (and based on the fact that it is different from the third communication terminal 100C), calculates, for example, a second distance between the first communication terminal 100A and the target communication terminal 10, and a third distance between the second communication terminal 100B and the target communication terminal 10, based on the position coordinates of the target communication terminal 10 at time t+1, a predetermined time earlier. Based on the first, second, and third distances, server 500 predicts the first, second, and third distances at time t+3, a predetermined time later, and estimates the position coordinates of the target communication terminal 10 at time t+3.

[0040] The server 500 calculates an exponential moving average of the position coordinates of the target communication terminal 10 estimated as described above (step S105). The server 500 then performs a process to estimate the movement path of the target communication terminal 10 based on the position coordinates of the target communication terminal 10 estimated as described above (step S106).

[0041] The details of the method for estimating the position of the target communication terminal 10 in the above-described position estimation system 1 will now be explained.

[0042] In the position estimation system 1, when the server 500 performs the position estimation process and the movement path estimation process of the target communication terminal 10, each of the first communication terminal 100A, the second communication terminal 100B, and the third communication terminal 100C is used as a communication terminal (reference communication terminal) serving as a reference for distance estimation.

[0043] As shown in FIG. 3, in step S101, in the position estimation system 1, an RT (Round Trip) signal, which is a beacon signal, is transmitted from this reference communication terminal to the target communication terminal 10. The target communication terminal 10 returns the received RT signal to the reference communication terminal that is the transmission source.

[0044] The server 500 obtains the distance between this reference communication terminal and the target communication terminal 10, that is, the first distance d1, with each of the first communication terminal 100A, the second communication terminal 100B, and the third communication terminal 100C as the reference communication terminal. For example, the server 500 obtains the first distance d1 by the Multi-Carrier Phase Difference (MCPD) method that estimates the distance by obtaining the phase difference between the signal transmitted by the reference communication terminal and the signal received by the reference communication terminal from the target communication terminal 10.

[0045] FIG. 4 is a schematic diagram schematically showing an example of the distance measurement process between the reference communication terminal 200 and the target communication terminal 10 in the position estimation system 1. As shown in FIG. 4, the waveform of the signal A transmitted from the reference communication terminal 200 to the target communication terminal 10 can be expressed as cos(2πft + θ c t + θ A -2πf c τ). When the target communication terminal 10 receives this signal A, the phase B of the signal is θ A -2πf c τ - θ B is.

[0046] The waveform of the signal C transmitted from the target communication terminal 10 to the reference communication terminal 200 can be expressed as cos(2πft + θ c t + θ B -2πf c τ). When the target communication terminal 10 receives this signal C, the phase D of the signal C is θ B-2πf c τ-θ A That is the case.

[0047] The first communication terminal 100A, the second communication terminal 100B, and the third communication terminal 100C, which serve as the reference communication terminal 200, and the target communication terminal 10 all perform multi-carrier transmission, transmitting multiple signals with different wavelengths. Therefore, in order to measure the distance between the reference communication terminal 200 and the target communication terminal 10, the wavelength f described above is used. c For waveforms of multiple different wavelengths, for example, wavelength f1 and wavelength f2, the phase difference between wavelength f1 and wavelength f2 can be obtained from the following equations (1) and (2), which are the sum of phase B and phase D.

[0048] θ1 = θ A -2πf1τ-θ B +θ B -2πf1τ-θ A =-2πf1(2τ)···(1)

[0049] θ² = θ A -2πf2τ-θ B +θ B -2πf2τ-θ A =-2πf2(2τ)···(2)

[0050] From equations (1) and (2) above, the first distance d1 can be calculated from equation (3) below. In equation (3), c is the speed of light.

[0051] TIFF2026046497000002.tif21169

[0052] In step S102, the server 500 estimates the second distance d2 between the second communication terminal 100B and the target communication terminal 10 and the third distance d3 between the third communication terminal 100C and the target communication terminal 10, respectively, based on the position coordinates of the target communication terminal 10 at time t-1, a predetermined time prior, based on the first distance d1 (which is different from the first communication terminal 100A).

[0053] Distance measurement using the actual propagation signal, such as the MCPD method described above, can be performed by one-to-one communication between the reference communication terminal 200 and the target communication terminal 10. In other words, the second distance d2 and the third distance d3, which are the distances between communication terminals other than the reference communication terminal 200 and the target communication terminal 10, cannot be measured simultaneously with the first distance d1 using the actual propagation signal. Therefore, in step S102 of the position estimation system 1, the second distance d2 and the third distance d3 are calculated by the following process.

[0054] Let j be the index of the reference communication terminal 200 from which the first distance d1 was determined in step S101, and the distance estimated by actual propagation measurement at the reference communication terminal j Let's use TIFF2026046497000003.tif12169.

[0055] For communication terminals 100 other than the reference communication terminal j, the estimated position coordinates of the target communication terminal 10 are Let's use TIFF2026046497000004.tif11168.

[0056] The distance between communication terminals 100 other than the reference communication terminal j and the target communication terminal 10 is calculated using the following formula (4). TIFF2026046497000005.tif13169

[0057] By rearranging equation (4), the measured distance at time t (first distance d1) and the coordinate distance to the estimated position (second distance d2 and third distance d3), obtained in steps S101 and S102, are combined into ψ i When written in terms of (t), it can be obtained by the following equation (5). TIFF2026046497000006.tif20169

[0058] In step S103, the server 500 predicts the first distance d1, second distance d2, and third distance d3 at time t+1, which is a predetermined time after a certain period of time, using distance prediction by a Kalman filter, for example, based on the first distance d1, second distance d2, and third distance d3 obtained in the processing up to step S102.

[0059] For the process of estimating the first distance to the target communication terminal 10 using the i-th (i=1,2,3) communication terminal as the reference communication terminal, the state estimate consisting of the estimated distance from the i-th communication terminal to the target communication terminal 10 (first distance d1) at time t-1 and the estimated distance change rate is given by equation (6). TIFF2026046497000007.tif11169

[0060] Furthermore, the estimated predicted state at time t, when position estimation is performed, is given by equation (7). TIFF2026046497000008.tif11169

[0061] In equation (7), A is the state transition matrix from the state at time t-1 to time t, as shown in equation (8). TIFF2026046497000009.tif16169

[0062] In equation (6), dt represents the time interval during which position estimation is performed. Furthermore, the posterior covariance matrix P at time t-1 is also expressed. i Using (t-1), we calculate the prior covariance matrix (uncertainty of the estimate) at time t shown in equation (9) below. TIFF2026046497000010.tif10169

[0063] In equation (9), b is the system noise vector, TIFF2026046497000011.tif10169 is a system noise dispersion.

[0064] The Kalman gain is calculated using the following equation (10).

[0065] TIFF2026046497000012.tif21146

[0066] In equation (10), TIFF2026046497000013.tif11161 is the observed noise.

[0067] Based on the above, the state estimate, which consists of the estimated distance (first distance d1) from the i-th communication terminal to the target communication terminal 10 at time t and the estimated distance change rate, is updated from the state estimate at time t-1 shown in equation (6) to equation (11). TIFF2026046497000014.tif11169

[0068] Furthermore, the posterior covariance matrix shown in equation (9) is updated to the following equation (12). TIFF2026046497000015.tif9169

[0069] In equation (12), I is a 2x2 identity matrix. Equation (12) is used for position estimation at the next time t+1.

[0070] The predicted distance at time t is obtained from the estimated value of the predicted state using the observation vector c =

[0010] T Using this method, we obtain the following equation (13). TIFF2026046497000016.tif12169

[0071] From equation (13), the distance between the position coordinates (x,y) of the target communication terminal 10 and the position coordinates (x1,y1) of the first communication terminal 100A is obtained as shown in equation (14). TIFF2026046497000017.tif11169

[0072] Similarly, the second distance between the position coordinates (x,y) of the target communication terminal 10 and the position coordinates (x2,y2) of the second communication terminal 100B is given by equation (15). TIFF2026046497000018.tif11169

[0073] Furthermore, the third distance between the position coordinates (x,y) of the target communication terminal 10 and the position coordinates (x3,y3) of the third communication terminal 100C is given by equation (16). TIFF2026046497000019.tif13169

[0074] In step S104, which estimates the position coordinates of the target communication terminal 10 at time t+1, when estimating the first distance between the reference communication terminal and the target communication terminal 10 at time t+1, the system of equations for the position coordinates of the target communication terminal 10 to be determined from equations (13) to (16) is as shown in equation (17). TIFF2026046497000020.tif16169

[0075] The value of C in equation (17) is shown in equation (18). TIFF2026046497000021.tif15169

[0076] Furthermore, q(t) in equation (17) is shown in equation (19). TIFF2026046497000022.tif16169

[0077] Solving equation (17) yields equation (20). TIFF2026046497000023.tif18169

[0078] Server 500 can estimate the real-time position coordinates of the target communication terminal 10 at time t+1 using equation (20).

[0079] In steps S105 and S106, the server 500 applies an exponential moving average to the estimated position coordinates of the target communication terminal 10 obtained up to step S104 in order to estimate the movement path of the target communication terminal 10, thereby suppressing outliers or overshoots.

[0080] Movement path position coordinates TIFF2026046497000024.tif8169 can be expressed as shown in equation (21).

[0081] TIFF2026046497000025.tif18168

[0082] In equation (21), γ P This is the moving average (time constant). Server 500 can estimate the movement path of the target communication terminal 10 using equation (21).

[0083] Figure 5 is a schematic diagram showing an example of the estimation result of the movement path of the target communication terminal 10 by the position estimation system 1. In Figure 5, for example, the results of assuming the actual movement path and the movement path estimated by the position estimation system 1 when a customer moves a shopping cart in a store such as a supermarket. In Figure 5, the dashed line shows the actual movement path, and the solid line shows the estimated movement path. Also in Figure 5, the movement speed of the target communication terminal 10 is assumed to be 0.5 m / s, the time interval for position estimation processing is 0.5 s, and the time interval for the estimation processing of the first distance d1 by the first communication terminal 100A, the second communication terminal 100B, and the third communication terminal 100C is assumed to be 1.5 s.

[0084] As shown in Figure 5, the difference between the actual movement path of the target communication terminal 10 and the estimated movement path is small. Therefore, it can be seen that the position estimation system 1 can estimate the position of the target object using three communication terminals.

[0085] Figure 6 is a schematic diagram illustrating an example of the position estimation process for a target communication terminal in Reference Example 1, where distance estimation is performed simultaneously by three communication terminals and the target communication terminal. In Reference Example 1, a beacon signal is emitted from the target communication terminal 20, and the beacon signal is simultaneously received by the three communication terminals 300. The distance is estimated from the power of the received signals, and the position is estimated by tripoint positioning.

[0086] However, distance estimation based on the power of the received signal of a beacon signal emitted from a target communication terminal 20, as in Reference Example 1, had the problem that the accuracy of distance estimation deteriorated significantly due to fluctuations in received power caused by multipath.

[0087] Figure 7 is a schematic diagram illustrating an example of the target communication terminal position estimation process at time t+1 in Reference Example 2, where distance estimation is performed sequentially using each of the three communication terminals and the target communication terminal. Figure 8 is a schematic diagram illustrating an example of the target communication terminal position estimation process at time t+2 in Reference Example 2. Figure 9 is a schematic diagram illustrating an example of the target communication terminal position estimation process at time t+3 in Reference Example 2.

[0088] As shown in Figures 7 to 9, the MCPD method, which is also used in position estimation system 1, is a method of receiving signals with multiple waveforms transmitted via multicarrier and estimating distance from the phases of the received signals with multiple waveforms. In the case of the MCPD method, the first arriving wave corresponds to the distance to be estimated, so delayed waves are a factor in degrading the estimation accuracy. However, by using high-resolution multipath separation techniques such as the MUSIC algorithm, which is also used in position estimation system 1, high accuracy in distance estimation can be obtained.

[0089] However, in order to eliminate the influence of the local oscillator phase components of the transmitted wave and the received wave, frequency synchronization between the transmitter and receiver is established, followed by the transmission of a one-to-one bidirectional signal, i.e., an RT signal. Furthermore, in the case of a specification that randomly switches between many narrowband signals within a specified frequency band, it was necessary to transmit the aforementioned RT signal to the target communication terminal 30 in order to accurately estimate the distance. Therefore, measuring the phase of all narrowband signals within the specified band required time corresponding to the number of bands. Also, when attempting to estimate the distance between each of the three communication terminals 100 and the target communication terminal 30, it was not possible to perform the three distance estimation processes simultaneously. For example, as shown in Figures 7 to 9, it was necessary to perform distance estimation for each different communication terminal 100 with a time stagger relative to the target communication terminal 30. Consequently, in the case of Reference Example 2, a problem arose in that the tracking characteristics of the position estimation process deteriorated when the target communication terminal 30 moved.

[0090] On the other hand, in the position estimation system 1 described above, when the server 500 estimates the position of a target communication terminal based on the communication results between each of the multiple communication terminals 100 and the target communication terminal 10, it uses one of the multiple communication terminals 100 as a reference communication terminal 200 and estimates a first distance d1 between the reference communication terminal and the target communication terminal 10, as shown in step S101 of Figure 2. Next, as shown in step S102 of Figure 2, the server 500 calculates the second distance d2 and third distance d3 between each of the multiple communication terminals 100 (excluding the reference communication terminal 200) and the target communication terminal 10 based on the first distance d1, using the position coordinates of the target communication terminal 10 at time t-1, a predetermined time prior. Then, as shown in step S103 of Figure 2, the server 500 sequentially performs a process to estimate the position coordinates of the target communication terminal 10 at time t+1, a predetermined time later, based on the first distance d1, the second distance d2, and the third distance d3, using each of the multiple communication terminals 100 as the reference communication terminal 200.

[0091] The server 500 can then perform a process to estimate the movement path of the target communication terminal 10 based on the estimated position coordinates of the target communication terminal 10.

[0092] The server 500 can estimate the travel path by calculating the exponential moving average of the estimated position coordinates of the target communication terminal 10.

[0093] The server 500 can estimate the first distance by removing the phase difference between each of the multiple waveforms with different wavelengths included in the communication result between the reference communication terminal and the target communication terminal 10 and the waveform transmitted by the reference communication terminal.

[0094] Server 500 can estimate the first, second, and third distances at time t+1, which is a predetermined time after a period of time, using distance prediction by a Kalman filter, based on the first distance d1, second distance d2, and third distance d3.

[0095] By performing the processing as described above, the position estimation system 1 calculates the second and third distances between the other two communication terminals 100 and the target communication terminal 10, respectively, based on the position coordinates of the target communication terminal 10 at time t-1, which is a predetermined time earlier, under the condition that distance estimation by measuring the propagation of the actual signal, i.e., estimation of the first distance d1, can be performed only between one of the multiple communication terminals 100 and the target communication terminal 10. By performing this processing, the position estimation system 1 obtains the estimated distance to the target communication terminal 10 at the same time (for example, time t) for all communication terminals 100, and based on these estimated distances, it can perform distance prediction toward the next control time and perform position estimation by three-point positioning at the next control time.

[0096] Furthermore, in the position estimation system 1, the communication terminal 100 that estimates the first distance d1 is sequentially changed (rotated) as described above, for example, first communication terminal 100A, second communication terminal 100B, third communication terminal 100C, first communication terminal 100A..., and the parameters stored in the memory unit 502 used for distance prediction are updated. In addition, in the position estimation system 1, the performance of position estimation and path estimation (tracking) of the target communication terminal 10 can be maintained by sequentially changing the multiple communication terminals 100 that estimate the first distance d1 to the target communication terminal 10.

[0097] Therefore, the position estimation method performed by the server 500 using the position estimation system 1 can improve the accuracy of estimating the position of a target object using three communication terminals.

[0098] Furthermore, those skilled in the art may modify the present invention as appropriate in accordance with prior art knowledge. Such modifications, insofar as they still possess the configuration of the present invention, are of course included within the scope of the present invention.

[0099] For example, in position estimation system 1, an example was described in which the information processing device that performs the position estimation method is a server 500, but the present invention is not limited to this. The information processing device that performs the position estimation method may be an information processing device other than the server 500, and the information processing device and the communication terminal 100 may be a single device.

[0100] For example, in position estimation system 1, the first distance d1 is not limited to being estimated by the MCPD method, but can also be estimated by other methods, such as the Multiple Signal Classification (MUSIC) method.

[0101] For example, in position estimation system 1, in step S103, server 500 predicts the first, second, and third distances at time t+1, which is a predetermined time after a certain period of time, based on the first, second, and third distances, for example, using distance prediction by a Kalman filter. However, it is not limited to this, and other methods such as LMS (Least Mean Square), RMS (Root Mean Square), and particle filters can also be used. [Explanation of symbols]

[0102] 1…Position estimation system, 10, 20, 30…Target communication terminals, 11…Control unit, 12…Storage unit, 13…Communication unit, 100…Communication terminal, 100A…First communication terminal, 100B…Second communication terminal, 100C…Third communication terminal, 110…Control unit, 120…Storage unit, 130…Communication unit, 200…Reference communication terminal, 500…Information processing device, 501…Control unit, 502…Storage unit, 503…Communication unit

Claims

1. A first communication terminal, a second communication terminal, and a third communication terminal that perform multi-carrier transmission, A target communication terminal capable of communicating with each of the first communication terminal, the second communication terminal, and the third communication terminal, An information processing device that estimates the position of the target communication terminal according to the communication results between each of the first communication terminal, the second communication terminal, and the third communication terminal and the target communication terminal, A position estimation system equipped with, The aforementioned information processing device is Using one of the first, second, and third communication terminals as the reference communication terminal, the first distance between the reference communication terminal and the target communication terminal is estimated based on the communication results between the reference communication terminal and the target communication terminal. Based on the first distance, the second and third distances between each of the first communication terminal, the second communication terminal, and the other two of the third communication terminals and the target communication terminal are calculated based on the position coordinates of the target communication terminal at a predetermined time prior. Based on the first distance, the second distance, and the third distance, the process of estimating the position coordinates of the target communication terminal after a predetermined time is performed sequentially using the first communication terminal, the second communication terminal, and the third communication terminal as the reference communication terminal. Location estimation system.

2. The aforementioned information processing device is The process of estimating the movement path of the target communication terminal is executed based on the estimated position coordinates of the target communication terminal. The position estimation system according to claim 1.

3. The aforementioned information processing device is The exponential moving average of the estimated position coordinates of the target communication terminal is calculated to estimate the movement path. The position estimation system according to claim 2.

4. The aforementioned information processing device is For each of the multiple waveforms with different wavelengths included in the communication result between the reference communication terminal and the target communication terminal, the phase difference between each waveform and the waveform transmitted by the reference communication terminal is removed to estimate the first distance. The position estimation system according to claim 1.

5. The information processing device estimates the first distance, the second distance, and the third distance after a predetermined time using distance prediction by a Kalman filter, based on the first distance, the second distance, and the third distance. The position estimation system according to claim 1.

6. This information processing device estimates the position of a target communication terminal based on the communication results between each of the first, second, and third communication terminals, which perform multi-carrier transmission, and the target communication terminal that can communicate with them. The aforementioned information processing device is Using one of the first, second, and third communication terminals as the reference communication terminal, the first distance between the reference communication terminal and the target communication terminal is estimated based on the communication results between the reference communication terminal and the target communication terminal. Based on the first distance, the second and third distances between each of the first communication terminal, the second communication terminal, and the other two of the third communication terminals and the target communication terminal are estimated. Based on the first distance, the second distance, and the third distance, the process of estimating the position coordinates of the target communication terminal after a predetermined time is performed sequentially using the first communication terminal, the second communication terminal, and the third communication terminal as the reference communication terminal. Information processing device.

7. This method involves an information processing device estimating the location of a target communication terminal based on the communication results between each of the first, second, and third communication terminals, which perform multi-carrier transmission, and the target communication terminal that can communicate with them. The aforementioned information processing device Using one of the first, second, and third communication terminals as the reference communication terminal, the first distance between the reference communication terminal and the target communication terminal is estimated based on the communication results between the reference communication terminal and the target communication terminal. Based on the first distance, the second and third distances between each of the first communication terminal, the second communication terminal, and the other two of the third communication terminals and the target communication terminal are estimated. Based on the first distance, the second distance, and the third distance, the process of estimating the position coordinates of the target communication terminal after a predetermined time is performed sequentially using the first communication terminal, the second communication terminal, and the third communication terminal as the reference communication terminal. Location estimation method.

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