Method for determining positions of anchors, and position determination system therefor

Abstract

An anchor-tag assembly for estimating the position of a communication entity by using triangulation or trilateration is disclosed. The anchor-tag assembly comprises: an anchor including a first transmission antenna and a first reception antenna; and a tag including a tag modulation unit, a second transmission antenna and a second reception antenna. The tag modulates and transmits a received signal, and the anchor receives a reflected signal that is transmitted by an external communication entity in response to the signal transmitted by the anchor, after the signal transmitted by the anchor is transmitted. The anchor-tag assembly calculates the distance between the anchor-tag assembly and the external communication entity on the basis of the reflected signal.

Description

Method for determining the positions of anchors and a positioning system therefor

[0001] The present invention relates to a technique for determining the spatial coordinates of a communication entity, and more particularly, to a technique for correcting the position of an anchor in a situation where the position information of the anchor may change while already known.

[0002] In radar technology, anchors and tags are concepts primarily used in position tracking systems and play a fundamental role in calculating location.

[0003] A tag is a device attached to the object being tracked. It continuously emits a signal to relay its location to a tracking system. For example, tags can be attached to items, equipment, or people in a warehouse to track their location in real time. Tags are small, battery-powered devices that transmit wireless signals. An anchor receives the signal emitted by the tag and uses it to calculate its location.

[0004] An anchor is a device installed in a fixed location, with multiple anchors deployed in a specific space. These anchors receive signals transmitted from tags and calculate their location using methods such as triangulation or trilateration. Anchors are typically fixed in a location with a power supply, and their locations must be known in advance. Based on this fixed location information, distance data from the tag can be calculated, and by synthesizing the information collected by multiple anchors, the tag's precise location can be estimated.

[0005] According to one embodiment, a tag can transmit a signal to announce its location. Multiple anchors can receive the signal from the tag. Each anchor can calculate the distance to the tag based on the time it takes for the signal transmitted by the tag to reach the anchor. The anchors can exchange distance information with each other, and based on this information, they can use trilateration techniques or other methods to calculate the tag's precise location.

[0006] The accuracy of location tracking may vary depending on the placement and number of anchors and the signal quality of the tags.

[0007] In radar technology, Time of Flight (ToF) is a technology for measuring the distance to an object. It calculates the distance by measuring the round-trip time of a signal (light, sound, radio waves, etc.) that reflects off the object and returns. ToF's operating principle can be explained as follows: A signal (light or radio waves) emitted from a radar system reaches a target object, is reflected by the object, and the reflected signal returns to the radar system. At this time, the time from the signal's emission to its return is measured, and the speed of the signal (the speed of light or radio waves) can be used to calculate the distance to the object.

[0008] Figure 1 illustrates the concept of a triangulation technique using the distance between an anchor and a tag according to the prior art.

[0009] Typically, trilateration techniques utilize the distance between anchors and tags to calculate the relative coordinates of tags by applying trilateration techniques based on the distance between the anchors and tags. To achieve this, it is essential to determine the location of each anchor within the space where the trilateration system, including anchors and tags, is installed.

[0010] Even after an anchor's location has been determined, its physical location can fluctuate due to vibration and motion factors in the installation environment. These fluctuations directly cause errors in distance measurements from the tag, ultimately reducing the accuracy of trilateration- or triangulation-based positioning calculations. Therefore, in actual operating environments, procedures are required to periodically or as needed correct the fluctuating anchor location.

[0011] For example, if a set of anchors is installed inside a factory, mechanical vibration or shock may cause slight displacement of the anchor's fixed position, which may result in a discrepancy with the existing reference coordinates and cause position calculation errors. Alternatively, if a set of anchors is installed on a moving vehicle, the spacing or position of the anchors installed on the vehicle may be displaced by vehicle vibration, causing calculation errors. As another example, if a set of anchors is installed on a high-rise structure, environmental factors such as wind vibration or earthquakes may cause the structure to slightly shake or move, which may cause the positions of the anchors, which are assumed to be fixed, to change, thereby reducing the stability of position measurement. In environments where anchor position changes are possible, it is necessary to apply an anchor position correction algorithm or a re-measurement procedure.

[0012] The present invention aims to provide a technology for correcting the coordinates of anchors to accurate values ​​and measuring the spatial coordinates of tags based on the determined coordinates of anchors.

[0013] According to one aspect of the present invention, in a case where it is necessary to identify the position of an anchor in order to apply position recognition using ToF between an anchor and a tag in a three-dimensional space, in a situation where information about the installation space, such as the location information of the anchor, is unknown or insufficient, a method for finding the position (relative coordinates) of an anchor using an anchor and a tag (or a tag structure including a plurality of tags) may be provided. In this case, an anchor-tag combination in which an anchor and a tag are combined may be used, and each anchor may identify the ToF to a identifiable tag in the vicinity in order to obtain the anchor-tag distance.

[0014] According to one aspect of the present invention, a localization system utilizing ToF can provide a software algorithm that enables automatic measurement of the relative coordinates of an anchor, and anchor and tag hardware for efficient operation of the algorithm. Hereinafter, the localization system may also be referred to as a positioning system in this specification.

[0015] According to one aspect of the present invention, an anchor-tag combination (100) configured to estimate a position of a communication entity may be provided. The anchor-tag combination includes: an anchor (200) including a first transmitting antenna (Tx_A) and a first receiving antenna (Rx_A); and a tag (300) including a tag modulator (301), a second transmitting antenna (Tx_T), and a second receiving antenna (Rx_T). The tag is configured to modulate and transmit a received signal, and the anchor is configured to receive a reflected signal transmitted by an external communication entity in response to the signal transmitted by the anchor after the anchor transmits a signal, and to calculate a ToF between the anchor and the external communication entity based on the reflected signal.

[0016] At this time, the anchor and the calculated ToF can be used to calculate the distance between the anchor and the external communication entity.

[0017] According to another aspect of the present invention, a positioning system may be provided, including a first anchor-tag combination having the same structure as the anchor-tag combination, a second anchor-tag combination, a third anchor-tag combination, an external communication entity, and a computing device. In this case, the mutual distances between three anchors, which are a first anchor constituting the first anchor-tag combination, a second anchor constituting the second anchor-tag combination, and a third anchor constituting the third anchor-tag combination, are known in advance. The computing device is configured to perform a step of determining coordinates of the three anchors and the external communication entity, and estimating the mutual distances between the three anchors based on the determined coordinates; and a step of correcting the determined coordinates of the three anchors and the external communication entity so as to reduce a difference between the known mutual distances and the estimated mutual distances for the three anchors. And the first anchor-tag combination is configured to receive a first reflection signal transmitted by a second tag constituting the second anchor-tag combination in response to the first signal after the first anchor transmits the first signal, and to calculate a twelfth distance, which is a distance between the first anchor-tag combination and the second anchor-tag combination, based on the first reflection signal. And the computing device is configured to execute a step of correcting the previously known mutual distances for the three anchors using the calculated twelfth distance.

[0018] According to another aspect of the present invention, a method for performing position determination in a position determination system including a first anchor-tag combination having the same structure as the anchor-tag combination, a second anchor-tag combination, a third anchor-tag combination, an external communication entity, and a computing device may be provided. In this case, the mutual distances between three anchors, which are a first anchor constituting the first anchor-tag combination, a second anchor constituting the second anchor-tag combination, and a third anchor constituting the third anchor-tag combination, are known in advance. The method includes a step of the computing device determining coordinates of the three anchors and the external communication entity, and estimating the mutual distances between the three anchors based on the determined coordinates; and a step of the computing device correcting the determined coordinates of the three anchors and the external communication entity to reduce a difference between the known mutual distances and the estimated mutual distances with respect to the three anchors. At this time, the first anchor-tag combination is configured to receive a first reflection signal transmitted by a second tag constituting the second anchor-tag combination in response to the first signal after the first anchor transmits the first signal, and to calculate a twelfth distance, which is a distance between the first anchor-tag combination and the second anchor-tag combination, based on the first reflection signal. And the method further includes a step of the computing device correcting the previously known mutual distances for the three anchors using the calculated twelfth distance.

[0019] At this time, in the position determination system and method, the second anchor-tag combination may be configured to receive a second reflection signal transmitted by a first tag constituting the first anchor-tag combination in response to the second signal after the second anchor transmits the second signal, and calculate a twenty-first distance, which is a distance between the second anchor-tag combination and the first anchor-tag combination, based on the second reflection signal. And the first anchor-tag combination may be configured to calculate an AoA of the received first reflection signal. And the second anchor-tag combination may be configured to calculate an AoA of the received second reflection signal. And the correcting step may include a step of the computing device correcting the previously known mutual distance between the first anchor and the second anchor using the AoA of the first reflection signal, the AoA of the second reflection signal, the distance between the first anchor and the first tag, the distance between the second anchor and the second tag, the twelfth distance, and the twenty-first distance.

[0020] At this time, in the position determination system and the method, the estimating step may include: determining initial coordinates of three devices selected from among the three anchors and the external communication entity; and determining initial coordinates of the remaining device based on distances measured between the three devices and the remaining device.

[0021] At this time, in the process of selecting the three devices, among the three anchors and the external communication entities, if the DOP (Dilution Of Precision) value of the triangle formed by the combination is the lowest, if the area of ​​the triangle is large, or if the coordinate instability of the communication entities forming the combination is the lowest, the combination may be preferentially selected.

[0022] At this time, in the position determination system and method, the external communication entity may include a tag that modulates and transmits a signal it has received.

[0023] At this time, in the position determination system and method, the external communication entity may be a fourth anchor-tag combination having the same structure as the anchor-tag combination of the first clause.

[0024] According to another aspect of the present invention, a positioning system may be provided, including a first anchor-tag assembly having the same structure as the anchor-tag assembly, and a second anchor-tag assembly. The first anchor-tag assembly is configured to receive a second tag transmission signal transmitted by a second tag of the second anchor-tag assembly in response to the first anchor transmission signal after the first anchor of the first anchor-tag assembly transmits a first anchor transmission signal, thereby calculating a first ToF between the first anchor and the second tag.

[0025] At this time, the position determination system may further include a computing device configured to communicate with the first anchor-tag combination and the second anchor-tag combination. The computing device may access a memory in which a predetermined inter-anchor distance between the first anchor and the second anchor of the second anchor-tag combination is stored. The computing device may be configured to determine a measured distance between the first anchor and the second anchor based on the first ToF, and perform a predetermined subsequent process when the measured distance is determined to be different from the predetermined inter-anchor distance. The first anchor-tag combination and the second anchor-tag combination may each further include a communication module capable of communicating with the computing device.

[0026] At this time, the computing device may be configured to calculate the measured distance using a distance between the first anchor and the second tag determined based on the first ToF; a first distance given in advance between the first anchor and the first tag of the first anchor-tag combination; a second distance given in advance between the second anchor and the second tag; and a relative orientation difference of the second anchor-tag combination with respect to the first anchor-tag combination.

[0027] At this time, the first anchor-tag combination further includes a first inertial measurement device, the second anchor-tag combination further includes a second inertial measurement device, the first anchor-tag combination is configured to transmit the attitude of the first anchor-tag combination measured by the first inertial measurement device to the computing device, the second anchor-tag combination is configured to transmit the attitude of the second anchor-tag combination measured by the second inertial measurement device to the computing device, and the computing device may be configured to determine the relative attitude using the attitude of the first anchor-tag combination and the attitude of the second anchor-tag combination.

[0028] At this time, the first inertial measurement device and the second inertial measurement device may each be configured with a 3-axis accelerometer, a 3-axis gyroscope, and optionally a 3-axis geomagnetic sensor.

[0029] At this time, the second anchor-tag combination may be configured to receive the first tag transmission signal transmitted by the first tag in response to the second anchor transmission signal after the second anchor transmits the second anchor transmission signal. The first anchor-tag combination and the second anchor-tag combination may each further include a circuit for measuring an AoA of an incident radio wave and an accelerometer for measuring a gravity direction. The first anchor-tag combination may be configured to transmit the first AoA of the second tag transmission signal and the first gravity direction measured by the first anchor-tag combination to the computing device. The second anchor-tag combination may be configured to transmit the second AoA of the first tag transmission signal and the second gravity direction measured by the second anchor-tag combination to the computing device. The computing device may be configured to determine the relative attitude using the first AoA, the second AoA, the first gravity direction, and the second gravity direction.

[0030] At this time, the circuit for measuring the AoA may include a multi-antenna array, an RF receiving circuit, and a signal processing module.

[0031] At this time, the predetermined subsequent processor may be a process that outputs an alarm that the measured distance is different from the pre-given distance between anchors through a user interface of the computing device or transmits the alarm to another computing device.

[0032] At this time, the predetermined subsequent processor may be a process that updates the distance between the anchors given in advance by replacing it with the measured distance.

[0033] At this time, the positioning system may further include a set of external communication entities. At this time, the distance between at least three fixed entities among the set of entities comprising the first anchor, the second anchor, and the set of external communication entities may be fixed to a predetermined value. In addition, the computing device may be configured to perform a step of calculating coordinates of the set of entities based on the measured distances between the entities of the set.

[0034] Additionally, the computing device may be further configured to perform a step of correcting the calculated coordinates of the set of entities to reduce an error between the measured distance between the three fixed entities and the fixed distance between the three fixed entities.

[0035] At this time, the positioning system may further include a third anchor-tag combination having the same structure as the anchor-tag combination of the first clause.

[0036] At this time, the memory stores a pre-given anchor distance between the first anchor, the second anchor, and the third anchor of the third anchor-tag combination, and the three fixed entities may be the first anchor, the second anchor, and the third anchor.

[0037] At this time, the calculating step may include: determining initial coordinates of three reference entities selected from the set of entities; and determining initial coordinates of the remaining other entities based on distances measured between the three reference entities and the remaining other entities.

[0038] At this time, the three selected reference entities may be the first anchor, the second anchor, and the third anchor.

[0039] At this time, some or all of the above set of external communication entities may include a tag that modulates and transmits the signal it receives.

[0040] At this time, some or all of the above set of external communication entities may have the same structure as the anchor-tag combination of the first clause.

[0041] According to another aspect of the present invention, a positioning method may be provided, which is executed in a positioning system comprising three anchor-tag combinations having the same structure as the anchor-tag combinations, a set of external communication entities, and a computing device configured to communicate with at least some of the three anchor-tag combinations and the set of external communication entities. The method comprises the steps of: obtaining, by the computing device, predetermined fixed anchor-to-anchor distances between three anchors included in the three anchor-tag combinations; calculating, by the computing device, coordinates of a set of entities, the set of entities comprising the three anchors and the set of external communication entities, based on measured distances between the entities in the set; and correcting, by the computing device, the calculated coordinates of the set of entities to reduce an error between the measured distances between the three anchors and the fixed distances between the three anchors. At this time, any first anchor-tag combination among the three anchor-tag combinations is configured to receive a second tag transmission signal transmitted by a second tag of any second anchor-tag combination among the three anchor-tag combinations in response to the first anchor transmission signal after the first anchor of the first anchor-tag combination transmits the first anchor transmission signal, thereby calculating a first ToF between the first anchor and the second tag.And the computing device is configured to perform a step of determining a measurement distance between the first anchor and the second anchor of the second anchor-tag combination based on the first ToF, and, if it is determined that the measurement distance is different from a pre-given anchor-to-anchor distance between the anchors, outputting an alarm indicating that the measurement distance is different from the pre-given anchor-to-anchor distance through a user interface of the computing device, or transmitting the alarm to another computing device, or performing a subsequent process of updating the pre-given anchor-to-anchor distance between the anchors by replacing it with the measurement distance.

[0042] According to another aspect of the present invention, a method may be provided for executing a positioning system comprising a first anchor-tag combination having the same structure as the anchor-tag combination, and a second anchor-tag combination. The method includes the steps of: a first anchor of the first anchor-tag combination transmitting a first anchor transmission signal; a step of the first anchor receiving a second tag transmission signal transmitted by a second tag of the second anchor-tag combination in response to the first anchor transmission signal; and a step of the first anchor-tag combination calculating a first ToF between the first anchor and the second tag.

[0043] At this time, the position determination system further includes a computing device configured to communicate with the first anchor-tag combination and the second anchor-tag combination, and the first anchor-tag combination and the second anchor-tag combination each further include a communication module capable of communicating with the computing device, and the computing device can access a memory in which a predetermined inter-anchor distance between the first anchor and the second anchor of the second anchor-tag combination is stored. And the method may further include a step of the computing device determining a measured distance between the first anchor and the second anchor based on the first ToF; and a step of the computing device performing a predetermined subsequent process when it is determined that the measured distance is different from the predetermined inter-anchor distance.

[0044] In order to determine the relative attitude of the second anchor-tag assembly with respect to the first anchor-tag assembly described above, the attitude of each anchor-tag assembly with respect to the ground surface can be determined and utilized. To this end, the anchor-tag assembly of the present invention can calculate the angle at which the device is tilted with respect to the ground surface using an inertial measurement unit (IMU) consisting of a three-axis accelerometer, a three-axis gyroscope, and optionally a three-axis geomagnetic sensor. This method can estimate the tilt angle both when the device is stationary and when it is moving. To this end, the present invention can define two coordinate systems. One is a Earth-based coordinate system, which can be composed of axes for east, north, and upward. The other is a device coordinate system fixed to the device body, which is set as a horizontal axis, a vertical axis, and a forward axis with respect to one side of each anchor-tag assembly. The rotational relationship between these two coordinate systems determines the inclination of the device, and a series of procedures can be used to estimate it.

[0045] Looking at the operating principles of these sensors, a gyroscope measures the device's rotational speed, allowing it to track short-term rotational changes. However, long-term integration can accumulate errors, resulting in drift. An accelerometer measures the acceleration a device experiences, allowing it to estimate the direction of Earth's gravity when stationary. However, when the device moves, gravity and linear acceleration mix, reducing accuracy. A geomagnetic sensor measures the Earth's magnetic field to determine absolute direction, but is vulnerable to environmental metals and electromagnetic interference. Therefore, the strengths of each sensor can be combined.

[0046] During initial startup, the accelerometer can be used to estimate the direction of gravity. This allows the device's initial tilt to be established, and if necessary, the geomagnetic sensor can be used to determine the initial orientation. The device's rotational state can then be predicted based on the gyroscope's output, and any resulting discrepancies can be compensated for by comparing the gravitational vector obtained from the accelerometer.

[0047] This sensor fusion process determines the direction of gravity in the device's coordinate system, allowing the inclination angle of the anchor-tag assembly to be determined. Inclination angles are typically defined as roll and pitch. The absolute orientation angle (yaw) can be compensated for using a geomagnetic sensor if necessary, but this is not essential when only determining the inclination relative to the ground.

[0048] Additionally, by using a geomagnetic sensor, a complete 3D posture including orientation can be estimated depending on the environment.

[0049] To measure the AoA described above, each anchor-tag combination may include a multi-antenna array and wireless receiving circuitry capable of processing the array. Specifically, two or more antenna arrays receive radio waves transmitted from the same signal source at different locations, and based on the resulting phase or time difference, the direction from which the signal came can be estimated. These antenna arrays may be arranged in various geometric configurations, such as linear, circular, or planar.

[0050] The RF reception circuit (RF front-end) connected to each antenna converts the electromagnetic waves input from the antenna into electrical signals and can simultaneously acquire phase and amplitude information for multiple channels. At this time, phase coherence between each channel can be maintained to perform AoA calculations. The received signals are then analyzed by a baseband signal processor or digital signal processor (DSP), calculating the phase difference or arrival time difference between the multiple antenna signals. Based on this, an AoA estimation algorithm, such as MUSIC or ESPRIT, is applied to ultimately calculate the signal's angle of incidence.

[0051] The AoA measured in this way can be used to determine the relative attitude of two anchor-tag combinations. When two anchor-tag combinations transmit and receive signals toward each other and obtain the first and second AoAs, respectively, these two AoA information alone cannot completely determine the rotation between the two device coordinate systems. That is, the relative twist with respect to the line-of-sight (LOS) between the two devices, or in other words, the roll component, remains undetermined. To eliminate this ambiguity, an additional non-collinear reference vector that both devices can commonly recognize is required.

[0052] As additional information for this, gravity vectors obtained from the accelerometers of both devices can be utilized. Each anchor-tag combination can convert the gravity direction extracted from the low-pass filter of the accelerometer into its own local coordinate system and exchange it. This gravity direction, combined with the AoA, can uniquely calculate the rotation between the two coordinate systems. However, when the LOS is nearly parallel to gravity, the sensitivity of the calculation may be reduced, requiring auxiliary information.

[0053] For more accurate measurements, the anchor-tag assembly can utilize an additional geomagnetic sensor. By combining the gravity and magnetic field vectors measured from both anchor-tag assemblies, it is possible to eliminate not only torsion around the LOS axis but also mirror symmetry ambiguities such as left-right reversal.

[0054] According to the present invention, a technology can be provided for correcting the coordinates of anchors to accurate values ​​and measuring the spatial coordinates of tags based on the determined coordinates of anchors.

[0055] Figure 1 is a drawing illustrating a tag location estimation concept using a triangulation technique between an anchor and a tag according to the prior art.

[0056] FIG. 2 is a flowchart illustrating the procedure of an algorithm for calculating coordinates from a distance between points according to one embodiment of the present invention.

[0057] Figure 3 is a flowchart illustrating the procedure of a coordinate calculation algorithm according to another embodiment.

[0058] Figure 4a is a drawing showing an example of setting a coordinate system based on three points with set coordinates.

[0059] Figure 4b is a drawing showing an example of a step after Figure 4a, in which the coordinates of an unset point (PU1) are calculated and updated to PK4.

[0060] FIG. 5 is a flowchart illustrating, step by step, a coordinate calculation and correction procedure performed to determine relative positions between a plurality of entities arranged in space, according to one embodiment of the present invention.

[0061] Figure 6 illustrates examples of the structure of an anchor-tag combination including a transmitting antenna, a receiving antenna, and a backscatter tag.

[0062] Figure 7 illustrates a concept of measuring the bond-bond distance using anchor-tag bonds having the structure presented in (a) of Figure 6.

[0063] FIG. 8A illustrates a concept of correcting the measured assembly-to-assembly distance based on the relative position of the tag with respect to the anchor, in a case where the tag coupled to the anchor is not positioned at the center of the anchor-tag assembly but at the periphery thereof, according to one embodiment of the present invention.

[0064] FIG. 8b illustrates a concept of correcting the measured compound-combination distance according to another embodiment of the present invention.

[0065] Figures 9a to 9i illustrate various structural forms of the anchor-tag complex.

[0066] FIG. 10 is a diagram illustrating the concept of a distance measurement method according to one embodiment of the present invention, specifically showing the signal propagation path between two anchor-tag combinations and the measurement principle thereof.

[0067] FIG. 11A is a diagram illustrating a concept of measuring the AoA of a signal at an anchor receiving antenna within an anchor-tag combination according to one embodiment of the present invention.

[0068] FIG. 11b is a diagram illustrating a situation in which the AoA of a signal is measured at a tag receiving antenna within an anchor-tag combination according to another embodiment of the present invention.

[0069] FIG. 12a is a conceptual diagram illustrating a method for defining the local coordinate system reference positions of components within an anchor-tag combination according to one embodiment of the present invention.

[0070] FIG. 12b is an extended embodiment of FIG. 12a, illustrating a local coordinate system-based antenna position representation for a tag-only structure.

[0071] Figure 12c shows that the absolute position of the antenna can be quantified based on the local coordinate system even in an anchor-only device.

[0072] FIG. 13 is a conceptual diagram defining a relative positional relationship between a plurality of anchor-tag combinations according to one embodiment of the present invention on a global coordinate system.

[0073] FIG. 14 is a conceptual diagram for explaining a relative position alignment process between a plurality of anchor-tag combinations when information on the relationship between antennas by ToF and AoA is given according to one embodiment of the present invention.

[0074] FIG. 15 is a conceptual diagram illustrating a process of matching relative direction information between two anchor-tag combinations based on AoA constraints, according to one embodiment of the present invention.

[0075] FIG. 16 is a conceptual diagram visually illustrating six degree-of-freedom variables considered for aligning relative positional and orientation relationships between multiple anchor-tag combinations, according to one embodiment of the present invention.

[0076] FIG. 17 is a conceptual diagram illustrating a method of integrating internal components of an anchor-tag combination composed of a plurality of nodes into a single node, designating representative coordinates, and calculating the distance between these representative nodes, according to one embodiment of the present invention.

[0077] FIG. 18 is a conceptual diagram illustrating a case in which only some antennas within each anchor-tag combination are considered to be in the same position and merged according to one embodiment of the present invention.

[0078] FIG. 19 is a conceptual diagram illustrating a case in which all antennas within each anchor-tag combination are merged as a single antenna existing in the same location, according to one embodiment of the present invention.

[0079] Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be implemented in various other forms. The terminology used herein is intended to aid understanding of the embodiments and is not intended to limit the scope of the present invention. Furthermore, the singular forms used below also include the plural forms, unless the context clearly indicates otherwise.

[0080] <Software algorithm for finding the coordinates of nodes>

[0081] According to one embodiment of the present invention, a software algorithm (hereinafter, simply referred to as 'algorithm') may be provided.

[0082] The above algorithm can be defined as a set of steps performed by instruction codes running on a computing device.

[0083] In this specification, the computing device may be a device that calculates the distance, or AoA, from signals measured at an anchor to a tag. In a preferred embodiment, the computing device may be a device included in the anchor, such as a DSP board. Alternatively, in another embodiment, the computing device may be a separate device distinct from the anchor, such as a server that communicates with the anchor in real time via a network. In the following description, AoA may also be referred to as angle of arrival or angle of incidence.

[0084] The above algorithm can calculate the three-dimensional relative coordinates of an anchor through a two-step process of (1) calculating the initial coordinate values ​​of each node representing an anchor and a tag when the anchor-anchor distance, anchor-tag distance, and tag-tag distance are determined, and (2) optimizing by calculating the solution of an optimization problem that minimizes the error between the calculated initial coordinate values ​​and all determined distance information.

[0085] In this specification, the anchor-tag distance and the tag-tag distance may also be referred to as anchor-tag distance values ​​and tag-tag distance values. Additionally, the distance between nodes may also be referred to as inter-node distances or inter-node distance values.

[0086] In order to execute the above algorithm, the anchor-tag distances and tag-tag distances distributed in the target space, which are calculated through measurements or known through prior information, i.e., the 'known node-to-node distances', must be input to the above algorithm.

[0087] Here, points indicating the location of the anchor and points indicating the location of the tag are collectively defined as "nodes" without distinction. At this time, it is not necessary to know the distances between all nodes to execute the algorithm. In other words, even if distance information between some nodes is not secured, such as when securing a straight path is impossible due to an obstacle blocking the field of view or moving beyond the field of view (FoV), the algorithm can still operate normally.

[0088] Embodiments of the above algorithm are described below.

[0089] FIG. 2 is a flowchart illustrating a method executed by an algorithm provided according to one embodiment of the present invention.

[0090] In step (S110), the calculation device can calculate the initial coordinate value of each node using the distance between nodes.

[0091] The above-mentioned computing device may be a computing device including a processor, memory, a communication unit, and a power supply unit. The computing device may be included in the anchor as described above or may be a server.

[0092] Specifically, step (S110) may include a step (S111) of selecting three nodes through an arbitrary criterion and setting a three-dimensional coordinate system by considering a plane formed by the three nodes as an xy plane. At this time, the coordinates of the three nodes may be designated as an origin, a node on the x-axis, and / or a node on the xy plane, respectively. In addition, step (S110) may include a step (S112) of calculating coordinates of points whose coordinates are unknown from nodes whose coordinates are calculated through a trilateration technique after step (S111).

[0093] In a preferred embodiment, the three nodes may be three anchors.

[0094] In step (S120), the above-mentioned calculation device can perform optimization and error correction through a process of calculating a solution to an optimization problem.

[0095] Specifically, step (S120) may include a step (S121) of calculating a solution or approximate solution of an optimization problem that minimizes the difference between the initial coordinate values ​​of all nodes calculated in step (S110) and the 'node-to-node distance' known through the measurement or prior information, and correcting the error.

[0096] FIG. 3 is a flowchart illustrating a method executed by an algorithm provided according to another embodiment of the present invention.

[0097] Figures 4a and 4b illustrate nodes arranged in space and the distances between nodes to help understand the method presented in Figure 3.

[0098] Figure 4a shows a situation where there are three nodes whose coordinates have already been set.

[0099] Figure 4b shows a node (P) whose coordinates have not yet been set in Figure 4a. U1 ) is determined according to the above algorithm, and the node (P) whose coordinates are set K4 ) indicates the updated status.

[0100] The following description is made with reference to FIG. 3, FIG. 4a, and FIG. 4b.

[0101] In step (S210), the calculation device can calculate the initial coordinate value of each node using the distance between nodes.

[0102] Step (S210) may include step (S211) and step (S212) described later.

[0103] In step (S211), three nodes (ex: P) are selected according to certain specific criteria. K1 , P K2 , P K3 ) as the standard for coordinates, and a coordinate system setting step (S211) may be included in which a coordinate system is set by taking the plane formed by the three nodes as the xy plane. At this time, the first node (ex: P) among the three nodes K1 ) as the origin, the second node (ex: P K2 ) is the node above the x-axis, the third node (ex: P K3 ) is treated as a point on the xy plane and its coordinates are set. All three-dimensional coordinates calculated thereafter can be calculated based on this coordinate system.

[0104] In step (S212), nodes (P) whose coordinates have already been set K1 , P K2 , P K2 ) and nodes whose coordinates have not yet been set (P U1 , P U2 , P U3 , P U4 ) using the triangulation technique from the distance values ​​between nodes (P) for which the coordinates are not setU1 , P U2 , P U3 , P U4 ) can set the 3D coordinates.

[0105] For example, the first set of nodes (P) whose coordinates have already been set K1 , P K2 , P K3 ) and nodes whose coordinates have not yet been set (P U1 ) are measured between the first set of distances (d K1,U1 , d K2,U1 , d K3,U1 ), and the nodes of the first set (P K1 , P K2 , P K3 ) using the coordinates of the node (P) whose coordinates have not yet been set U1 ) can determine the three-dimensional coordinates.

[0106] The above step (S212) may be repeated until the coordinates of all nodes are set. In this case, when step (S212) is repeated, the three reference nodes selected as the basis for the trilateration technique in each repetition may be selected by considering spatial diversity to minimize errors.

[0107] For example, when selecting three nodes from among several nodes whose coordinates have already been set, the three nodes that maximize the area of ​​the triangle formed by these nodes can be selected as the three reference nodes. Alternatively, the three reference nodes can be selected in descending order of Dilution of Precision (DOP) for n points whose coordinates have already been set.

[0108] For example, in Fig. 4a, a node (P) whose coordinates have not yet been set U1 ) is determined, this node is a node (P) whose coordinates have already been set as shown in Fig. 4b. K4 ) can be updated. At this time, the node (P) whose coordinates have not yet been set U2) can be considered two methods to determine the coordinates of the first set of nodes (P K1 , P K2 , P K3 ) and nodes whose coordinates have not yet been set (P U2 ) measured between the second set of distances (d K1,U2 , d K2,U2 , d K3,U2 ), and the nodes of the first set (P K1 , P K2 , P K3 ) using the coordinates of the node (P) whose coordinates have not yet been set U2 ) can determine the three-dimensional coordinates of the nodes. Second, the nodes of the second set (P) whose coordinates have already been set K1 , P K2 , P K4 ) and nodes whose coordinates have not yet been set (P U2 ) measured between the third set of distances (d K1,U2 , d K2,U2 , d K4,U2 ), and the nodes of the second set (P K1 , P K2 , P K4 ) using the coordinates of the node (P) whose coordinates have not yet been set U2 ) can determine the three-dimensional coordinates of the nodes (P) of the first set. K1 , P K2 , P K3 ) than the first area (S1) of the triangle defined by the second set of nodes (P K1 , P K2 , P K4 ) is larger, the second method can be selected. Conversely, if the second area (S2) is smaller than the first area (S1), the first method can be selected. Fig. 4b illustrates a case where the second area (S2) is larger than the first area (S1).

[0109] Even if the above step (S212) is repeated, there may be cases where the 3D coordinate values ​​of all nodes cannot be calculated. In this case, since there is insufficient known input information that can be input to the above algorithm, the anchor placement can be modified or the tag structure moved or additionally placed to obtain additional input information that can be input to the above algorithm, and then step (S210) can be executed again.

[0110] If the three-dimensional coordinate values ​​of all nodes are calculated by repeating the above step (S212), the process can proceed to step (S220).

[0111] In step (S220), the computing device can execute optimization and error correction through a process of calculating a solution to an optimization problem.

[0112] The process of calculating the solution to the above optimization problem can be performed using Equations 1, 2, and 3 below.

[0113] [Formula 1]

[0114]

[0115] d in formula 1 ij represents the calculated distance between nodes i and j, and is indicated by a horizontal bar above d ij represents the given distance between nodes i and j.

[0116] Equation 1 represents the loss function for the optimization problem. The loss function represents the MSE (Mean Square Error) loss of the difference between the distance between nodes calculated using the relative coordinates of the set nodes and the distance between nodes known through measurements or prior information.

[0117] [Formula 2]

[0118]

[0119] Equation 2 represents an equation whose solution is the coordinates of the nodes that minimize the loss function. Equation 2 is an equation that calculates the coordinates of the nodes that minimize the MSE loss in Equation 1. Methods such as the least-squares method or gradient descent can be used to find a solution or approximate solution to this equation.

[0120] [Formula 3]

[0121]

[0122] d in formula 3 ij represents the calculated distance between nodes i and j, and is indicated by a horizontal bar above d ij represents the given distance between nodes i and j.

[0123] Equation 3 is an example of solving an optimization problem using gradient descent. For a natural number N, the gradient descent method in Equation 3 is repeated N times. The natural number N can be set flexibly depending on the performance target. A higher performance target requires a larger value for N. By adjusting the relative coordinates of each node as in Equation 3 during a single application of gradient descent, optimization can proceed in the direction of reducing the loss function in Equation 1.

[0124] The above-described algorithm is expressed for three dimensions, and this algorithm can be modified to target two dimensions.

[0125] FIG. 5 is a flowchart illustrating, step by step, a coordinate calculation and correction procedure performed to determine relative positions between a plurality of entities arranged in space, according to one embodiment of the present invention.

[0126] This drawing includes a series of processes for calculating the coordinates of each entity based on distance information between entities and comparing the calculated coordinates with the actual distance to correct them.

[0127] First, in step (S310), distance information between multiple entities placed in space is acquired. These entities may include various sensors, units, tags, anchors, or other objects capable of wireless communication. The distance information between these entities is measured using methods such as ToF or RSSI (Received Signal Strength Index).

[0128] Next, step (S320) is a coordinate calculation step, and includes sub-step (S321) and sub-step (S322). First, in step (S321), the initial coordinates of three entities selected from among a plurality of entities are determined based on the distances between the three entities. These three entities should generally be arranged in a non-collinear triangle shape, thereby establishing a reference coordinate system. The 'initial coordinates' of the three entities may be referred to as 'estimated coordinates'.

[0129] In the following step (S322), the initial coordinates of the remaining entities are sequentially calculated by applying trilateration or triangulation techniques, utilizing the distances between entities with set initial coordinates and entities whose coordinates are not yet determined. This process is performed repeatedly by inferring the coordinates of other entities based on the initial coordinates. The "initial coordinates" of the remaining entities may be referred to as "estimated coordinates."

[0130] Step (S330) is a coordinate correction step, and first, in step (S331), entities of a first group whose actual (ground truth) distance information is known in advance are selected from among a plurality of entities.

[0131] The following step (S332) is an optimization step for correcting the estimated coordinates based on the previously calculated estimated coordinates to minimize the error between the calculated distance and the actual distance between entities in the first group. This correction process aims to reduce the distortion of the entire coordinate system and obtain more precise relative coordinates. In this optimization process, the estimated coordinates of the remaining entities excluding the first group are also adjusted, and at this time, the condition for minimizing the error between the actual distance and the estimated distance between entities in the first group can be set as a priority optimization criterion. That is, in step (S332), the error can be corrected by calculating a solution or an approximate solution to an optimization problem that minimizes the difference between the initial coordinate values ​​of all calculated nodes and the distance between nodes known through the measurement or transmission information. At this time, the optimization problem can be calculated with the top priority of minimizing the difference between the actual distance between entities in the first group and the estimated distance between entities in the first group. For example, the loss function of the optimization problem may reflect the difference between the actual distance between entities in the first group and the estimated distance between entities in the first group as a high weight.

[0132] Finally, in step (S340), the coordinates of the anchors contained in multiple entities are finally determined using the corrected coordinate information. This can be used as a reference point in subsequent operations, such as position estimation or distance calculation between anchors and tags.

[0133] In a preferred embodiment of the present invention, the anchor described above may be an interrogator. Typically, an interrogator is a device that sends signals to tags, transponders, or sensors in wireless communication, identification, or sensing systems to elicit responses, and then receives and interprets those responses. The interrogator transmits interrogation signals to induce the target device to reflect or transmit information. The interrogator's primary functions are broadly divided into four. First, it acts as a transmitter, transmitting interrogation signals in the form of RF, light, or sound waves to activate or trigger actions on the target device. Second, it acts as a receiver, receiving reflected, modulated, or responded signals from the target device. Third, it demodulates and decodes the received signals through signal processing functions to extract identification information, sensor data, status information, etc. Fourth, it manages communication sessions through control and management functions, and performs tasks such as multiple access, noise removal, and channel allocation. Typical components of an interrogator include a signal generator, a transmit / receive antenna (Tx / Rx), a receiver, a signal processor, and a control unit. The signal generator generates the interrogation signal, and the transmit / receive antennas transmit the signal and receive the response. The receiver receives and amplifies the response signal, and the signal processor performs demodulation, filtering, and data extraction. The control unit manages and synchronizes the protocol and manages multiple targets.

[0134] In a preferred embodiment of the present invention, the interrogator described above may be a device that transmits an interrogation signal in which a unit chirp signal that changes from a first frequency to a second frequency is periodically repeated, and receives and demodulates a signal reflected and modulated from a tag. The transmitter of the interrogator generates an interrogation signal in which the unit chirp signal is continuous and transmits the interrogation signal, and the receiver and demodulator of the interrogator mix the received tag signal and the original interrogation signal to generate an intermediate signal (IF), and then performs a fast Fourier transform (FFT) through filtering to extract the tag signal from frequency components excluding a noise bin. In addition, the interrogator supports distance-based channel allocation with respect to the tag and frequency division multiple access, and has a function of removing clutter noise by separating a noise bin and a tag bin in the frequency domain. To this end, the interrogator first transmits a continuous interrogation signal consisting of a unit chirp signal, and then the tag receives a tag signal that is reflected and modulated by the signal. After that, the original interrogation signal and the tag signal are multiplied in a mixer to generate an intermediate signal (IF), and the signal is converted into FFT to distinguish between noise and valid signals in the frequency domain, and then the signal located in the tag bin is detected to demodulate the data.

[0135] A tag provided according to one embodiment of the present invention is typically a device that receives an interrogation signal transmitted from an interrogator in a wireless communication, identification, or sensing system, modulates or reflects the signal, or transmits a response signal generated by itself to transmit information. Tags are mainly divided into passive and active types. Passive tags do not have their own power supply, operate using electromagnetic energy transmitted from the interrogator, and transmit response signals by reflection or backscatter. On the other hand, active tags are powered by a built-in battery and can actively transmit response signals using their own RF transmitter as needed.

[0136] According to one embodiment of the present invention, the tag can reflect an interrogation signal received from an interrogator by frequency-modulating it using a method such as impedance modulation without its own oscillator. The receiving unit of the tag receives the interrogation signal, the modulating unit of the tag frequency-modulates the interrogation signal according to a given modulation frequency or data, and the transmitting unit of the tag reflects and transmits the modulated signal (tag signal). This device has energy-saving characteristics that enable long-term operation using energy harvesting or a small battery. The tag first receives an interrogation signal in the millimeter wave band from the interrogator, controls an internal modulating unit (e.g., an impedance switch) to modulate the frequency of the signal, and then reflects and transmits the modulated signal through an antenna. At this time, the frequency modulation can use a tag ID, sensor data, or a fixed modulation frequency. Channels are distinguished according to the distance difference between the tag and the interrogator, and thereby multiple tags can communicate simultaneously. According to one embodiment of the present invention, the tag may be a backscatter tag.

[0137] The term "tag" in the present invention may be replaced with the term "transponder." A transponder is a device that receives a signal from an interrogator or other transmitting device, processes it, and then transmits a new signal. Transponders typically perform more complex functions than tags, which simply modulate and reflect the received signal. They can interpret the received signal, generate a response signal containing the necessary information, and then actively transmit it.

[0138] <Structure of an anchor-tag combination for precise measurement of the distance between anchors>

[0139] According to one embodiment of the present invention, to measure precise distances between anchors (i.e., the distance between two anchors), tags may be fixedly coupled to each anchor. Such a combination of anchors and tags may be referred to herein as an anchor-tag combination, or simply a combination. In particular, the distance between a pair of paired anchor-tag combinations may be referred to herein simply as a combination-to-combination distance.

[0140] That is, it is easy to understand that, while the distance between two anchors cannot be measured with just two anchors, and the distance between two tags cannot be measured with just two tags, the distance between them can be measured with just one anchor and one tag. Accordingly, by using a first anchor-tag combination and a second anchor-tag combination in which an anchor and a tag are combined, the distance between two anchors can be measured. For example, it can be understood that the distance between the first anchor in the first anchor-tag combination and the second tag in the second anchor-tag combination can be measured, and the distance between the second anchor in the second anchor-tag combination and the first tag in the first anchor-tag combination can be measured.

[0141] For the above-described algorithm to work effectively, the anchor-to-anchor distance must be accurately measured.

[0142] Figure 6 illustrates examples of the structure of an anchor-tag combination including a transmitting antenna, a receiving antenna, and a backscatter tag.

[0143] As shown in FIG. 6, a transmitting antenna (210), a receiving antenna (220), and a backscatter tag (300) may be provided within the anchor-tag combination (100). Here, the transmitting antenna (210) and the receiving antenna (220) are antennas of the anchor. The backscatter tag (300) may be arranged adjacent to the transmitting antenna (210) and / or the receiving antenna (220). The backscatter tag (300) may include its own transmitting antenna and receiving antenna, which are not illustrated in FIG. 6. However, in FIGS. 9c, 9d, 9e, 9g, 9h, 10, 11a, and 11b described below, the transmitting antenna and the receiving antenna constituting the tag (300) are explicitly illustrated separately from each other.

[0144] Using this structure, the combination-to-combination distance can be approximated as the distance from the anchor of the anchor-tag combination to a tag positioned within the counterpart anchor-tag combination, or as the distance from a tag positioned within the anchor-tag combination to the anchor of the counterpart anchor-tag combination. The distance determined by approximation can be measured by correcting for errors resulting from the structure of the anchor-tag combination presented in Fig. 6.

[0145] The distance between anchors and tags within an anchor-tag assembly is known in advance as a fixed value. Furthermore, the AoA of the radio waves received by the anchors within an assembly can be measured. Therefore, once the assembly-to-assembly distance and AoA are determined, the distances between anchors within each assembly can also be calculated.

[0146] To measure the AoA of a radio wave received by an anchor within a single assembly, the anchor must be equipped with hardware components that satisfy certain conditions. For this purpose, the anchor may include a multi-antenna array. Typically, two or more receiving antennas are arranged at a regular interval (usually less than half a wavelength), and the array configuration can be selected from a Uniform Linear Array (ULA), a Circular Array, or a Two-Dimensional Planar Array. These arrays are designed to measure the phase difference of incoming radio waves. Each antenna may include an RF receiver module that converts high-frequency signals to low frequencies, an independent low-noise amplifier (LNA), mixer, and filter for each receiving path. Additionally, a reference oscillator may be included to synchronize the signals received from each antenna to the same reference clock. In addition, an analog-to-digital converter (ADC) capable of accurately extracting phase information may be equipped for each channel. In addition, a signal processing module (DSP or FPGA-based) that can analyze the phase and amplitude differences of the received signals may be included.

[0147] Based on this hardware configuration, the method of measuring AoA proceeds as follows, for example. First, when multiple antennas receive the same radio signal at different locations, the phase and time of arrival (ToA) at each antenna change depending on the difference in the path that the radio wave arrives. The signal from each receiving path is digitized through an ADC and then synchronized to a reference clock. The signal processing module calculates the phase difference between each channel using the fast Fourier transform (FFT) or complex signal correlation operation. The phase difference is converted by considering the wavelength of the radio wave and the spacing between the antennas, and the angle of arrival (AoA) of the signal can be calculated from the trigonometric relationship. For example, if the distance between the two antennas is d, the received phase difference is Δφ, and the wavelength of the radio wave is λ, the AoA θ is calculated in the form of θ = arcsin(λ*Δφ, / 2πd). When using a multi-antenna array for more precise measurements, high-resolution algorithms such as MUSIC (Multiple Signal Classification) and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) can be applied to estimate accurate AoA even in noisy environments. Thus, to realize AoA measurement at an anchor within a single assembly, a multi-antenna array, RF receiving circuits for each channel, a high-precision reference clock, an ADC, and a signal processing unit are essential. During the measurement process, the phase difference or arrival time difference can be analyzed to derive the AoA through trigonometric calculations or a high-resolution estimation algorithm.

[0148] Figure 7 illustrates a concept of measuring the bond-bond distance using anchor-tag bonds having the structure presented in (a) of Figure 6.

[0149] The radio waves transmitted by the transmitting antenna (210) of the first anchor-tag assembly (101_1) can be reflected from the backscatter tag (300) of the second anchor-tag assembly (101_2) and reach the receiving antenna (220) of the first anchor-tag assembly (101_1).

[0150] In one embodiment, the real distance (i.e., real unit-unit distance) between the first anchor-tag combination (101_1) and the second anchor-tag combination (101_2) in the example of FIG. 7 may be defined as the distance between the center of the first anchor-tag combination (101_1) and the center of the second anchor-tag combination (101_2). In this case, the first anchor-tag combination (101_1) is located along the first path (P) of the radio wave. T ) and the second path (P R ) may be configured to determine a measured distance (i.e., measured unit-unit distance) between the first anchor-tag assembly (101_1) and the second anchor-tag assembly (101_2) based on the movement time. At this time, there may be an error between the real distance and the measured distance. Therefore, the measured distance may be an approximated value of the real distance. At this time, the error may be corrected by using the arrangement structure of the antennas (210, 220) and the backscatter tag (300) arranged in the first tag assembly (101_1) and the second tag assembly (101_2).

[0151] FIG. 8A illustrates a concept of correcting the measured assembly-to-assembly distance based on the relative position of the tag with respect to the anchor, in a case where the tag coupled to the anchor is not positioned at the center of the anchor-tag assembly but at the periphery thereof, according to one embodiment of the present invention.

[0152] In FIG. 8a and FIG. 8b described below, the bold lines indicate the edges of the anchor-tag combinations (100). The square portion indicated by reference numeral 300 at the bottom of each anchor-tag combination (100) indicates a tag included in the corresponding anchor-tag combination, and the remaining portions indicate the anchors of each anchor-tag combination.

[0153] Hereinafter, for convenience of explanation, “the distance between the center of A and the center of B” is expressed as “the distance between A and B.” Also, “the direction of the center of B with respect to the center of A” is expressed as “the direction of B with respect to A.”

[0154] In one embodiment, the anchor of the first anchor-tag combination (104_1) transmits a signal, the backscatter tag (302) used in the second anchor-tag combination (104_2) emits a signal corresponding to the signal transmitted by the anchor of the first anchor-tag combination (104_1), and the anchor of the first anchor-tag combination (104_1) receives the signal emitted by the backscatter tag (302).

[0155] Hereinafter, for convenience of explanation, the expression that the anchor of the anchor-tag combination (104_1) transmits or receives a signal may be simply expressed as that the anchor-tag combination (104_1) transmits or receives a signal.

[0156] The real distance between the first anchor-tag combination (104_1) and the second anchor-tag combination (104_2) is the distance (d) between the center (110_1) of the first anchor-tag combination (104_1) and the center (110_2) of the second anchor-tag combination (104_2). Ra,a ) can be defined. However, the measured first measurement distance (i.e., the measured unit-unit distance) between the first anchor-tag combination (104_1) and the second anchor-tag combination (104_2) is the first transmission path (P T1 ) and the first nerve pathway (P R1 ) is determined based on.

[0157] At this time, the distance (d) between the center of the second anchor-tag combination (104_2) and the center of the backscatter tag (302) of the second anchor-tag combination (104_2) AT ) is a value known as a pre-designed value. Therefore, the distance (d) AT ) can reduce the error between the above-mentioned true distance and the above-mentioned measured first distance. The result of correcting the above-mentioned error can be referred to as the first corrected distance.

[0158] FIG. 8b illustrates a concept of correcting the measured compound-combination distance according to another embodiment of the present invention.

[0159] The state in which the two anchor-tag combinations (104_1, 140_2) presented in Fig. 8a are arranged is the same as the state in which the two anchor-tag combinations (104_1, 140_2) presented in Fig. 8b are arranged.

[0160] However, FIG. 8a shows a situation in which a signal transmitted by an anchor of a first anchor-tag combination (104_1) is reflected by a tag (302) of a second anchor-tag combination (104_2) and reaches the anchor of the first anchor-tag combination (104_1) again, and in contrast, FIG. 8b shows a situation in which a signal transmitted by an anchor of a second anchor-tag combination (104_2) is reflected by a tag (301) of the first anchor-tag combination (104_1) and reaches the anchor of the second anchor-tag combination (104_2) again.

[0161] The method for correcting the 'measured compound-combination distance' described in Fig. 8a can be equally applied to both the situations of Fig. 8a and Fig. 8b.

[0162] That is, in FIG. 8b, the second anchor-tag combination (104_2) transmits a signal, the backscatter tag (301) used in the first anchor-tag combination (104_1) emits a signal corresponding to the signal transmitted by the second anchor-tag combination (104_2), and the second anchor-tag combination (104_2) receives the signal emitted by the backscatter tag (301).

[0163] The real distance between the first anchor-tag combination (104_1) and the second anchor-tag combination (104_2) is the distance (d) between the center (110_1) of the first anchor-tag combination (104_1) and the center (110_2) of the second anchor-tag combination (104_2). Ra,a ) can be defined. However, the measured second measurement distance (i.e., the measured anchor-anchor distance) between the first anchor-tag combination (104_1) and the second anchor-tag combination (104_2) is defined as the second transmission path (P T2 ) and the second receiving pathway (P R2 ) is determined based on.

[0164] At this time, the distance (d) between the center of the first anchor-tag combination (104_1) and the backscatter tag (301) of the first anchor-tag combination (104_1) AT ) is a value known as a pre-designed value. Therefore, the distance (d) AT ) can reduce the error between the above-mentioned true distance and the measured second distance. The result of correcting the error can be referred to as the second corrected distance.

[0165] That is, in the situation of FIG. 8a, the first anchor (104_1) can correct the measured joint-joint distance that it has measured itself, and in the situation of FIG. 8b, the second anchor (104_2) can correct the measured joint-joint distance that it has measured itself. The distance between the first anchor (104_1) and the second anchor (104_2) can be finally determined by using the first correction distance and the second correction distance together.

[0166] Hereinafter, according to another embodiment of the present invention, a structural embodiment of an anchor-tag combination in which an anchor and a tag are formed as a single combination is described in detail.

[0167] Figures 9a to 9i illustrate various structural forms of the anchor-tag complex.

[0168] FIG. 9A illustrates a structure in which an anchor transmitting antenna (Tx_A) and an anchor receiving antenna (Rx_A) are individually positioned, and a tag (300) is positioned between them. In this case, the anchor transmitting antenna (Tx_A) is positioned in the anchor transmitting antenna area (211), and the anchor receiving antenna (Rx_A) is positioned in the anchor receiving antenna area (221). The tag (300) may be configured as a separate circuit module, and may be positioned adjacent to the anchor, either inside or outside.

[0169] The tag (300) may include a tag modulation unit (301), a transmitting antenna (361), and a receiving antenna (371), as described later in FIG. 9c.

[0170] Fig. 9b has a structure similar to Fig. 9a. However, compared to Fig. 9a, the tag (300) is not located in the center between the anchor transmitting antenna (Tx_A) and the anchor receiving antenna (Rx_A), but is located in the outer area.

[0171] FIG. 9c explicitly shows the positions of the tag transmitting antenna (Tx_T) and the tag receiving antenna (Rx_T) included in the tag (300), and presents the relative positions with respect to the anchor transmitting antenna (Tx_A) and the anchor receiving antenna (Rx_A).

[0172] The tag (300) includes a tag modulation unit (301), a tag transmitting antenna (Tx_T), and a tag receiving antenna (Rx_T).

[0173] The tag transmitting antenna (Tx_T) and the tag receiving antenna (Rx_T) are arranged in the tag transmitting antenna area (371) and the tag receiving antenna area (361), respectively.

[0174] The tag modulation unit (301) can be placed between the anchor transmitting antenna (Tx_A) and the anchor receiving antenna (Rx_A).

[0175] FIG. 9d includes the same components as FIG. 9c, but shows a state in which the tag modulation unit (301) is placed between the tag transmitting antenna (Tx_T) and the tag receiving antenna (Rx_T).

[0176] In FIGS. 9c and 9d, the transmitting antenna areas (211, 361) and the receiving antenna areas (221, 371) are symmetrically arranged left and right or up and down, respectively. This may be a design that minimizes electromagnetic interference and takes spatial balance into account.

[0177] FIG. 9e shows a structure in which the anchor transmitting antenna and receiving antenna are configured as a single integrated transmitting / receiving antenna area (230), and the tag includes its own tag transmitting antenna (Tx_T), tag receiving antenna (Rx_T), and tag modulation unit (301). That is, the anchor has an integrated transmitting / receiving antenna structure, and the tag has a set of antennas configured separately for transmitting and receiving.

[0178] Figure 9f has a structure similar to that of Figure 9e. However, since the transmitting antenna and receiving antenna of the tag are arranged very closely together, the separate transmitting and receiving antennas and the tag modulation unit are not depicted separately in the drawing, but are simply expressed as a tag (300) as a single component.

[0179] FIG. 9g illustrates a structure in which the transmitting antennas (Tx_AT) of the anchor and the tag are integrated into one area (410), and the receiving antennas (Rx_AT) of the anchor and the tag are also integrated into one area (420). In this case, the tag modulation unit (301) exists independently, and the integration of the device can be improved through antenna sharing.

[0180] Figure 9h is similar to Figure 9g, but the placement of the tag modulation unit (301) is different, and the transmission / reception antenna sharing structure is applied in the same way. The above placement may be an example that takes interference minimization or circuit optimization into consideration during PCB design.

[0181] In the examples presented in FIGS. 9a, 9b, and 9f, the transmitting antenna and receiving antenna of the tag are arranged very closely together, so that separate transmitting and receiving antennas and tag modulation units are not shown separately in the drawings, but are simply expressed as a tag (300) as a single component.

[0182] In contrast, FIGS. 9c, 9d, 9e, 9g, and 9h illustrate embodiments in which the tag's transmitting antenna and receiving antenna are designed to be separated by a non-negligible distance, and the tag modulation unit, the tag transmitting antenna, and the tag receiving antenna are depicted as being separated from each other.

[0183] Figure 9i illustrates a structure in which the transmitting and receiving antennas of the anchor and the tag share a single, fully integrated transmitting and receiving antenna area (430). At this time, the tag modulation unit (301) can modulate the phase or amplitude of the communication signal in conjunction with the antenna circuit.

[0184] Through the embodiments illustrated in FIGS. 9A to 9I described above, it can be understood that various design modifications are possible depending on the purpose of configuration flexibility, space optimization, circuit integration, and positioning accuracy supplementation of the anchor-tag combination.

[0185] Additionally, each structure can be considered as an independent node, either at an antenna region (hereinafter referred to as 'antenna') or at a specific location on an anchor-tag combination, when applied to a coordinate determination algorithm.

[0186] Fig. 10 is a diagram illustrating the concept of a distance measurement method according to one embodiment of the present invention, specifically showing the signal propagation path and the measurement principle between two anchor-tag combinations (108[1], 108[2]). Each anchor-tag combination has a structure including an anchor transmitting antenna (211; Tx_A), an anchor receiving antenna (221; Rx_A), a tag receiving antenna (320; Rx_T), a tag transmitting antenna (310; Tx_T), and a tag modulation unit (301).

[0187] Anchor-tag combination (108[1]) and anchor-tag combination (108[2]) each represent different instances of the anchor-tag combination illustrated in FIG. 14d.

[0188] In this drawing, a signal is emitted from an anchor transmitting antenna (211; Tx_A) included in an anchor-tag assembly 108[2]. This signal propagates through space and reaches a tag receiving antenna (320; Rx_T) of an opposite assembly, the anchor-tag assembly 108[1]. The received signal passes through a tag modulation unit (301), is modulated in a predetermined manner, and then is re-radiated through a tag transmitting antenna (310; Tx_T) located in the same assembly.

[0189] The retransmitted signal is then returned to the anchor-tag combination 108[2] that initially transmitted the signal, and reception is performed at the anchor receiving antenna (221; Rx_A) of the combination. The round-trip path of the signal formed through this entire process can be converted into a total distance by measuring the Time-of-Flight (TOF) time from the transmitting point to the receiving point.

[0190] What is important in this embodiment is that the signal path is configured in the order of 'Tx_A(211) → Rx_T(371) → Tx_T(361) → Rx_A(221)'. The total time measured through this path can be multiplied by the signal propagation speed to calculate the total distance value, which is used to numerically express the connectivity between two anchor-tag combinations. In addition, such distance measurement can be usefully used as a constraint for an algorithm that corrects or initializes the relative positions between combinations.

[0191] Additionally, each anchor-tag combination (108[1], 108[2]) shown in the embodiment of FIG. 10 can be interpreted as being expanded or reduced to a simple tag or a single anchor depending on the system configuration. For example, if the function of the anchor in the anchor-tag combination (108[1]) is disabled, the function of the anchor-tag combination (108[1]) can be limited to simply the function of a tag. Conversely, if the function of the tag in the anchor-tag combination (108[1]) is disabled, the function of the anchor-tag combination (108[1]) can be limited to simply the function of an anchor.

[0192] FIG. 11A is a diagram illustrating a concept of measuring the AoA of a signal at an anchor receiving antenna (221) within an anchor-tag assembly (108[2]) according to one embodiment of the present invention. This diagram includes incident direction vector information when a unidirectional signal propagates from one assembly to another during a communication process between two anchor-tag assembly (108[1], 108[2]).

[0193] Specifically, the anchor-tag assembly (108[1]) located at the top functions as a transmitting entity, and radio waves are radiated through the tag transmitting antenna (310; Tx_T) of the assembly. The radiated signal reaches the anchor-tag assembly 108[2] located at the bottom, and is received by the anchor receiving antenna (221; Rx_A) therein.

[0194] The received radio wave contains not only the strength of the received signal (RSSI), but also information about the AoA of the radio wave, which is the direction of arrival of the signal, expressed as a unit vector 71 = (ν x , ν y , ν z ) can be expressed as. The vector is defined as a vector having a directionality that matches the directionality of the incident signal, and is measured based on the local coordinate system of the combination (108[2]).

[0195] As shown in Fig. 11a, by quantitatively expressing the direction of arrival of a signal and utilizing this as a constraint of a position matching algorithm, it can be used to calculate the relative direction or rotation matrix (R, ψ, θ, φ) between anchor-tag combinations. In particular, since the component receiving the signal in Fig. 16a is the receiving antenna of the anchor, it can be effectively applied to environments with high directional accuracy of the receiving position (such as when a directional receiving antenna is built-in).

[0196] FIG. 11b is a diagram illustrating a situation in which the AoA of a signal is measured at a tag receiving antenna (371) within an anchor-tag combination (108[2]) according to another embodiment of the present invention. This diagram also has a similar structure to FIG. 11a, but differs in that the subject measuring the AOA is a tag.

[0197] In Fig. 11b, the anchor-tag combination (108[1]) located at the top functions as a signal transmitter, and in this case, a signal is radiated from the anchor's transmitting antenna (211; Tx_A). This radio wave reaches the combination 108[2] at the bottom and is received via the tag receiving antenna (320; Rx_T) therein.

[0198] At this time, the incident direction of the received signal is vector 72 = (ν′ x , ν′ y , ν′ z) can be expressed as, and this vector is defined as a unit direction vector based on the local coordinate system of the assembly (108[2]). The AoA vector matches the arrival direction of the received electromagnetic wave, and based on this, the relative position and rotation angle with respect to the external assembly can be estimated.

[0199] Figure 11b demonstrates that AoA information can be obtained even at the tag level, particularly when backscatter tags or active tags incorporate AoA sensors. This vector information, along with distance information, can be used as constraints for algorithms (e.g., nonlinear optimization, gradient descent) to precisely estimate the relative position between antennas.

[0200] The method presented in Figures 11a and 11b allows for selective placement of AoA measurement locations depending on the type of receiving antenna (anchor or tag), thereby enabling acquisition of directional information between multiple anchor-tag combinations. This overcomes the limitations of simple distance-based trilateration methods and achieves high-dimensional positioning accuracy (improved DOP).

[0201] By expressing AoA information in the form of a unit vector, it can be directly utilized in Jacobian calculations or direction cosine matrices in terms of algorithms, which is advantageous in improving the position estimation accuracy of the entire system.

[0202]

[0203] FIG. 12a is a conceptual diagram illustrating a method for defining the local coordinate system reference positions of components within an anchor-tag combination (100) according to one embodiment of the present invention.

[0204] This drawing mathematically defines the spatial positions of multiple antennas, including a transmitting antenna and a receiving antenna, contained within the assembly. These spatial positions can be used as coordinate base values ​​for subsequent transformation into a global coordinate system or in the connectivity inference process.

[0205] In the illustrated example, the interior of the assembly (100) includes a total of four representative points (antennas). The local coordinates of the anchor transmitting antenna point (P211) are set to (a₁, b₁, 0). The local coordinates of the anchor receiving antenna point (P221) are (a₂, b₂, 0). The local coordinates of the tag receiving antenna point (P371) are (a₃, b₃, 0). The local coordinates of the tag transmitting antenna point (P361) are (a₄, b₄, 0).

[0206] All of the above coordinates are placed on a single plane (e.g., the plane where z = 0 in three-dimensional space), which reflects that the structure of the assembly is hardware installed on a single substrate or plane.

[0207] The local coordinate system sets the origin at the lower left corner of the assembly, and the local x-axis, local y-axis, and local z-axis are defined based on this. This coordinate system functions as a reference frame expressing relative positions within the assembly, and can be transformed into the global coordinate system for connectivity alignment with external assembly.

[0208] In particular, the following objectives can be achieved with the coordinates defined in Fig. 12a.

[0209] First, by numerically expressing the positional information of each antenna within the assembly (100), the antennas can be used as input values ​​for a coordinate matching algorithm when communicating with an external assembly or exchanging distance / direction information.

[0210] Second, the local coordinates of each antenna are then converted into a rotation matrix (R, e.g., pitch, yaw, roll) and a translation vector (t x , t y , t z ) can be converted to global coordinates.

[0211] Third, the distance between antennas (d ij), AoA(ν), rotation information (θ, ψ, φ), etc. are given, the antenna position based on the local coordinate system is used as an essential reference point in calculating the degree of freedom.

[0212] Fig. 12b is an extended embodiment of Fig. 12a, and is a drawing illustrating a local coordinate system-based antenna position representation for a tag (300)-only structure. In this embodiment, a tag transmitting antenna point (P361) and a tag receiving antenna point (P371) are arranged in the local x-axis and y-axis directions, and their respective coordinates are expressed as (a₄, b₄, 0) and (a₃, b₃, 0). In this way, by setting a local coordinate system even in a tag-only device, the relative positions between multiple units or antennas can be defined and compared in a unified manner.

[0213] The structure of Figure 12b will be used as the basis for consistently mapping location information into a global coordinate system when the tag communicates with other anchor-tag combinations in the future. In particular, this coordinate information can be used in the linear transformation process essential for interpreting AoA, distance (ToF), and direction information.

[0214] Fig. 12c is a diagram illustrating an example of antenna arrangement on a local coordinate system for an anchor-only configuration (200). The antennas P211 and P221 expressed in this embodiment correspond to the anchor transmitting antenna point and the anchor receiving antenna point, respectively, and the coordinates of the corresponding antennas are defined as (a₁, b₁, 0) and (a₂, b₂, 0), respectively.

[0215] Figure 12c shows that the absolute position of the antenna can be quantified based on the local coordinate system even in an anchor-only device. These coordinate settings are then converted to the global coordinate system or used as reference coordinates when analyzing connectivity with other devices. In particular, the rotation matrix and translation transformation (t) can be performed using coordinate information defined on the same plane. x , t y , tz ) enables global position alignment.

[0216] FIG. 13 is a conceptual diagram defining the relative positional relationship between a plurality of anchor-tag combinations according to one embodiment of the present invention on a global coordinate system. Specifically, the diagram illustrates how, when two anchor-tag combinations (108 [1], 108 [2]) are arranged in an arbitrary space, the coordinates of their respective constituent antennas are expressed based on the global coordinate system, and how a base frame for coordinate alignment can be established.

[0217] The anchor-tag assembly (108[2]) positioned at the bottom is set as the reference frame of the global coordinate system in this embodiment. That is, the local coordinate system of the assembly (108[2]) is considered to be identical to the global coordinate system, and thus, all antennas of the assembly can be defined as static positions on the z = 0 plane. The global coordinates of the four points (antennas) included in this assembly are P5=(a5, b5, 0), P6=(a6, b6, 0), P7=(a7, b7, 0), and P8=(a8, b8, 0).

[0218] On the other hand, the assembly (108[1]) placed on top is a device having a separate local coordinate system, and has coordinates transformed on the global coordinate system, and the global coordinates of the following four points (antennas) are P1=(x₁, y₁, z₁), P2=(x₂, y₂, z₂), P3=(x₃, y₃, z₃), P4=(x₄, y₄, z₄).

[0219] Each antenna (P1~P4) of the assembly (108[1]) has a position (q₁~q₄ = (a₁, b₁, 0)~(a₄, b₄, 0)) defined in the local coordinate system of the assembly, and these are mapped to positions (P1~P4) in the global coordinate system through rotation (R) and translation (t) operations. It is expressed mathematically as in Equation 4.

[0220] [Formula 4]

[0221] pi = R · q i + t (i = 1, 2, 3, 4)

[0222] Here, t = (t x , t y , t z ) represents a translation vector where the local coordinate system origin of the combination (108[1]) is located in the global coordinate system.

[0223] Here, R is a rotation matrix of the assembly (108[1]), which includes three-axis rotations corresponding to Pitch(θ), Yaw(φ), and Roll(ψ), and can be given as in Equation 5.

[0224] [Formula 5]

[0225]

[0226] This structure is the basic structure for relative position alignment between anchor-tag combinations. In other words, it is the basic structure for the process of accurately aligning the positions and directions of multiple combinations based on a unified reference (global coordinate system). Here, in a state where there are no distance or direction constraints, there are a total of six degrees of freedom (DOF). The DOF is composed of three elements of R (ψ, θ, φ) and three elements of t (t x , t y , t z ) and once these values ​​are determined, the overall antenna position of the assembly (108[1]) is uniquely determined.

[0227] FIG. 13 can be used to explain how the above six DOFs are gradually removed and ultimately the absolute positions between antennas can be determined when constraints such as distance information (ToF), AoA information, and attitude information (fixed IMU-based ψ, θ, φ, etc.) presented in FIGS. 14 to 16 are given.

[0228] As shown in Fig. 13, in a system including multiple anchor-tag combinations, the relative positional relationship can be mathematically formalized by setting the coordinate system of one combination as the reference coordinate system, and then the overall antenna positions can be aligned based on distance and direction information.

[0229] FIG. 14 is a conceptual diagram illustrating a relative position matching process between a plurality of anchor-tag assemblies when information on the relationship between antennas by ToF and AoA is given according to an embodiment of the present invention. Specifically, this diagram visually illustrates, based on the structure described in FIG. 18, how distance information contributes to connectivity determination or degree of freedom reduction when the distance values ​​between some pairs of antennas existing between two anchor-tag assemblies (108 [1], 108 [2]) are pre-measured or given as constraints secured by the system.

[0230] In Fig. 14, the anchor-tag assembly (108[1]) arranged at the top includes four antennas (P1, P2, P3, P4), which are located at positions (x₁, y₁, z₁) to (x₄, y₄, z₄) on the global coordinate system, respectively. The assembly (108[2]) at the bottom is a reference assembly that coincides with the reference frame of the global coordinate system, and the antennas (P5 to P8) are located on the planes (a5, b5, 0) to (a8, b8, 0), respectively.

[0231] In Fig. 14, the distance between antenna (P3) and antenna (P5) is d53, the distance between antenna (P4) and antenna (P6) is d46, and the internal distance between antenna (P3) and antenna (P4) is d34.

[0232] These distance equations are the six degree-of-freedom variables (t) required to determine the position of the anchor-tag assembly (108[1]). x , t y , t z, ψ, θ, φ) serve to constrain some of them. For example, each additional distance constraint reduces the number of degrees of freedom that can control the possible combinations of locations in space. In Fig. 14, since one independent distance constraint is given, one degree of freedom can be reduced.

[0233] Thus, when the distance values ​​between multiple antennas are known, they can be used as numerical constraints to calculate the positions and orientations of unaligned assemblies within the system. Furthermore, the distance information allows for the estimation of a rotation matrix (R) and a translation vector (t) based on the relationships between position vectors. This distance information can be used to narrow the initial position estimation range during the numerical process of aligning the relative coordinates of multiple nodes with respect to the global coordinate system.

[0234] FIG. 15 is a conceptual diagram illustrating a process for matching relative direction information between two anchor-tag combinations based on AoA constraints, according to one embodiment of the present invention. This diagram visually illustrates a method of using a unit vector (direction vector) representing the direction in which a signal arrives as a constraint to address the problem of insufficient relative direction information, which may be insufficient with distance information between combinations alone.

[0235] An anchor-tag combination (108[1]) is positioned at the top of the drawing, and an anchor-tag combination (108[2]) set as a reference combination is positioned at the bottom. At this time, the local coordinate system of the combination (108[2]) is set to the global coordinate system, and serves as a reference frame for overall relative position alignment.

[0236] A signal transmitted from the assembly (108[2]) propagates through space and reaches a specific antenna (e.g., P2) of the assembly (108[1]). At this time, a receiving antenna (e.g., an anchor receiving antenna or a tag receiving antenna) included in the assembly (108[1]) can measure the AoA of the arriving electromagnetic wave. The measured AoA is usually expressed as direction information in the form of a unit vector, which is defined as in Equation 6 based on the local coordinate system of the assembly (108[1]):

[0237] [Formula 6]

[0238]

[0239] When the direction component of the unit vector representing AoA is expressed in the local coordinate system as above, Equation 7 can be obtained to convert the direction component of the local coordinate system to the global coordinate system (through the rotation matrix R) through the corresponding constraint.

[0240] [Formula 7]

[0241]

[0242] The direction of AoA can be expressed in ways other than the above equation. If the equation is added as a constraint, the dimensions that t_x, t_y, t_z, ψ, θ, and φ can have are reduced by 2, and the DOF of the relative positions between nodes is reduced by 2.

[0243] By expressing AoA in the form of a direction vector in this way and using it as a constraint linking it to R, it can be used to determine t_x, t_y, t_z, ψ, θ, and φ.

[0244] The AoA information, which is an additional constraint means in addition to the distance constraint, provides a stronger spatial constraint than a single distance value and can serve as a reference for the direction of the receiving antenna. Furthermore, in the global coordinate matching problem, a single AoA constraint can typically reduce two degrees of freedom (DOF), and when only one component in either the horizontal or vertical direction is given, it has the effect of reducing one DOF. Furthermore, in cases where distance information alone cannot determine the position (e.g., in a rotational axis-symmetric situation), AoA information can narrow the solution space and reduce ambiguity in the calculated position matching by providing additional directional information.

[0245] FIG. 16 is a conceptual diagram visually illustrating six degrees of freedom (DOF), namely translational and rotational variables, considered for aligning relative positional and orientational relationships between multiple anchor-tag combinations according to one embodiment of the present invention. In particular, this diagram illustrates the mathematical structure of positional and attitude transformations of one combination when the coordinate system of another combination is considered a fixed global coordinate system, and explains the process by which these variables are gradually fixed according to constraints (distance, AoA, attitude, etc.).

[0246] Specifically, the drawing illustrates an anchor-tag combination (108[1]) located at the top and a reference combination (108[2]) located at the bottom. The combination (108[2]) is set as a reference frame of the global coordinate system, and thus its own coordinate system is considered as a static reference without rotation or translation. On the other hand, the combination (108[1]) is defined based on a separate local coordinate system, and a total of six transformation variables are required to align this coordinate system with the global coordinate system. These variables are translation variables t x , t y , t z, and rotation variables ψ (Yaw), θ (Pitch), and φ (Roll). The translational variables are translation vectors in which the origin of the local coordinate system is located on the global coordinate system, and the rotational variables are three-axis rotation angles for aligning the local coordinate system to the global coordinate system.

[0247] Using these six variables, the local coordinates q of each antenna within the assembly (108[1]) i = (a i , b i , 0) to the global coordinate system coordinate p i = (x i , y i , z i ) can be converted to .

[0248] As illustrated in Figure 16, the relative positioning problem between multiple assemblies essentially has six degrees of freedom, which represents the initial state without any constraints. As sensor-based constraints such as AoA, range (ToF), and IMU-based attitude information (ψ, θ, φ fixed) are added, these six degrees of freedom are removed one by one, and in the process of reducing the number of DOFs, connectivity becomes fully computable. It can be understood that the position and orientation of each assembly can be aligned using the same principle in a complex positioning system that includes three or more anchor-tag assemblies.

[0249] When the pitch / yaw / roll information (in the example, pitch / yaw / roll relative to the anchor-tag combination (108[1])) relative to the global coordinate system of the anchor-tag combination (108[2]) is added, the values ​​of ψ, θ, and φ are fixed, resulting in t x , t y , t z , ψ, θ, φ can have a dimension that is reduced by 1 for each of pitch / yaw / roll. The DOF of the relative position between antennas is reduced by 1.

[0250] When the above-described formulas are added as constraints, the DOF is reduced as described above, but when the information provided by the newly given formula overlaps with the constraints given previously, the amount of reduction in DOF may be less than that or may be 0.

[0251] By adding constraints that reduce the DOF, the DOF of the relative position between the anchor-tag combinations can be reduced, and the connectivity between antennas can be calculated through the process of finding the solution to the unknown.

[0252] As an example of how to determine the DOF reduced by constraints, there is a method of calculating the Jacobian matrix of equations and then calculating the Rank of the Jacobian matrix. At this time, the degree of freedom of the relative position between anchor-tag combinations is the value obtained by subtracting the Rank from the initial degree of freedom (6 in this example). If an equation is added but the Rank of the Jacobian matrix does not increase, the added equation does not provide new information as an existing constraint.

[0253] As in the example introduced above, when antennas are given, the distance between antennas can be additionally calculated through constraints that are given in advance or obtained through measurements in cases where the connectivity between antennas is not given, and the connectivity between antennas can be calculated by reducing the DOF in the same way for three or more anchor-tag combinations. This method for calculating the distance between antennas is generally applicable not only to anchor-tag combinations and anchor-tag combinations, but also between anchor-tag combinations / anchors / tags. In this way, relative position matching regarding the distance and direction between anchor-tag combinations can be performed from constraints on the positional relationship between antennas, and this can be used to calculate the positional relationship between nodes in the future.

[0254] <Modeling of the Reduced Degree of Freedom Between Anchor-Tag Combinations Based on the Antenna Integration Assumption>

[0255] FIG. 17 is a conceptual diagram illustrating a method for designating representative coordinates and calculating distances between representative nodes by integrating internal components of an anchor-tag assembly composed of multiple nodes into a single node, according to one embodiment of the present invention. This illustrates that even if multiple transmitting antennas, receiving antennas, and tag antennas are physically present within the assembly, the coordinate matching algorithm can be simplified by designating a single node representing them from the perspective of position calculation or connectivity determination.

[0256] The drawing illustrates two anchor-tag assemblies (108[1], 108[2]). Each assembly internally includes multiple antennas (P1 to P8, etc.), but in this embodiment, all antennas inside each assembly are modeled as a single representative node. For example, in the assemblies (108[1]), a single node P9 representing internal antennas (e.g., transmitting antenna, receiving antenna, tag transmitting / receiving antenna) is located at coordinates (a9, b9, 0). Similarly, in the assemblies (108[2]), an identically integrated representative node P10 is located at coordinates (a 10 , b 10 , 0) is located.

[0257] The distance between these integrated representative nodes (P9, P10) is d 910 , which can be calculated according to the general Euclidean distance formula.

[0258] This method performs distance matching based on only one representative coordinate instead of considering all individual antenna locations within each assembly, so the complexity of the relative coordinate calculation algorithm can be significantly reduced, and the effect of averaging the effects of noise or installation errors can also be expected.

[0259] That is, according to one embodiment of the present invention, even if there are multiple antennas, the relative coordinate calculation algorithm can be simply implemented by considering them as one virtual node. In addition, when each combination is expressed as a single node, the relative position of the combination is expressed as a translation vector (t x , t y , t z ) is defined only by the degree of freedom of the entire system, which is reduced from the typical 6 to 3. This distance information between representative nodes (d 910 ) can be obtained through measurement using the ToF (Time of Flight) method or through a reference value determined in advance at the design stage, and can be used as an input constraint in the relative coordinate calculation algorithm.

[0260] According to the method of Fig. 17, the complexity of the relative coordinate calculation algorithm can be reduced by designating one node representing the positions of the antennas within the anchor-tag complex after a rigorous calculation process without approximation.

[0261] Figure 18 is a conceptual diagram illustrating a case in which only some antennas within each anchor-tag combination are considered to be in the same location and merged according to one embodiment of the present invention. This illustrates a method for partially reducing the degrees of freedom (DOF) of the positioning algorithm by considering the locations of some antennas to be identical, without performing complete antenna integration.

[0262] As shown in the drawing, an anchor-tag combination (108[1]) is positioned at the top, and an anchor-tag combination (108[2]) is positioned at the bottom. Each combination is represented as containing only two nodes.

[0263] In the anchor-tag combination (108[1]), the coordinates (a₁, b₁, 0) of the antenna (P1) and the coordinates (a₂, b₂, 0) of the antenna (P2) are defined.

[0264] In the anchor-tag combination (108[2]), the coordinates (a3, b3, 0) of the antenna (P3) and the coordinates (a4, b4, 0) of the antenna (P4) are defined.

[0265] In this example, although multiple transmit / receive antennas and tag antennas actually exist within each assembly, some of them are merged and represented as a single antenna. For example, the anchor's transmit and receive antennas are maintained as separate antennas (P1, P2), while the tag's transmit and receive antennas are either merged into one of these or omitted, modeled as just two antennas.

[0266] This type of antenna merging method can be called partial node unification, and as a result, the degrees of freedom for relative positioning start from 5DOF, which is reduced from the full 6DOF. That is, translation (t x , t y , t z ) and two axes of rotation (e.g., Yaw, Pitch) can be freely changed, but one axis of rotation (e.g., Roll) is implicitly considered fixed.

[0267] In this way, system analysis is possible even without merging all antennas. By assuming only some antennas are in the same location, the computational burden is reduced while maintaining the required positional accuracy. Furthermore, it is understandable that the user can selectively remove all six DOFs, depending on the environment and measurement possibilities, rather than fixing all six. Furthermore, even when integrating the coordinates of some antennas, accurate positioning can be calculated while reducing the DOF by adding various constraints, such as distance (ToF), AoA, and attitude sensor (IMU).

[0268] According to the method of Fig. 18, since the approximation of the positions of antennas within the anchor-tag complex is performed, and as a result, the number of nodes is also reduced, the complexity of the position matching algorithm that reduces the DOF and the complexity of the relative coordinate calculation algorithm can both be reduced.

[0269] Figure 19 is a conceptual diagram illustrating a case in which all antennas within each anchor-tag combination are merged as a single antenna located at the same location, according to one embodiment of the present invention. This allows for a complete simplification of the complex hardware structure, consisting of multiple transmitting antennas, receiving antennas, tag antennas, etc., from a mathematical modeling perspective, abstracting each combination into a single point.

[0270] The drawing shows two anchor-tag assemblies (108[1], 108[2]), each represented by only one antenna. The coordinates of a single antenna (P1) of the assemblies (108[1]) are (a₁, b₁, 0). The coordinates of a single antenna (P2) of the assemblies (108[2]) are (a₂, b₂, 0).

[0271] This simplified model assumes and calculates that the transmitting antenna, receiving antenna, and tag transmitting and receiving antennas within the assembly are in the same location, even though they may actually be located in different locations. In other words, each assembly is treated as having only one location, like a point.

[0272] As a result, the degree of freedom of the position alignment algorithm can be minimized. In a general 6DOF (3-axis translation + 3-axis rotation) model, the rotation (roll, pitch, yaw) of the assembly must be considered, but in a single antenna model such as Fig. 24, the concept of rotation does not exist, so the translation (t) x , t y , t z ) can be interpreted as a 3DOF model that only considers the 3D object.

[0273] The model of Fig. 19 is useful in environments where the actual positional error of the hardware is negligible, the number of sensors or resolution is limited, direction alignment is difficult or unnecessary, tags or anchors are fixed structures and rotation is limited, and real-time processing systems where mathematical computational costs must be minimized.

[0274] The connectivity between two single antennas can be calculated based on the actual distance between antennas (P1) and (P2), and the measured Time of Flight (ToF) or reference distance information can be used as a constraint. With just this distance value, the translational vector (t x , t y , t z ) can be removed, and complete position estimation becomes possible when multiple distance measurements are provided.

[0275] The example in Fig. 19 is an example explaining a method for analyzing the shortest path of a position matching problem, and is a model that can improve the effectiveness of system implementation in an environment where high-precision position calculation is not required.

[0276] By utilizing the embodiments of the present invention described above, those skilled in the art will be able to easily implement various changes and modifications without departing from the essential characteristics of the present invention. The content of each claim may be combined with other claims that are not in a citation relationship within the scope of this specification, as long as it is understood.

Claims

1. An anchor-tag combination (100) configured to estimate the location of a communication entity, An anchor (200) including a first transmitting antenna (Tx_A) and a first receiving antenna (Rx_A); and A tag (300) including a tag modulation unit (301), a second transmitting antenna (Tx_T), and a second receiving antenna (Rx_T); Includes, The above tag is configured to modulate and transmit a received signal, The above anchor is configured to receive a reflected signal transmitted by an external communication entity in response to the signal transmitted by the anchor after the anchor transmits a signal. Based on the above reflected signal, the ToF between the anchor and the external communication entity is calculated, Anchor-tag combination.

2. In paragraph 1, The anchor is characterized in that the calculated ToF is used to calculate the distance between the anchor and the external communication entity. Anchor-tag combination.

3. A positioning method executed in a positioning system including three anchor-tag combinations having the same structure as the anchor-tag combination of paragraph 1, a set of external communication entities, and a computing device configured to communicate with at least some of the three anchor-tag combinations and the set of external communication entities, The computing device obtains a fixed distance between three anchors included in the three anchor-tag combinations; and A step in which the computing device calculates coordinates of a set of entities, the set of entities comprising the three anchors and the set of external communication entities, based on measured distances between the entities of the set; Includes, Any first anchor-tag combination among the three anchor-tag combinations is configured to receive a second tag transmission signal transmitted by a second tag of any second anchor-tag combination among the three anchor-tag combinations in response to the first anchor transmission signal after the first anchor of the first anchor-tag combination transmits the first anchor transmission signal, thereby calculating a first ToF between the first anchor and the second tag. The computing device is configured to perform a step of determining a measurement distance between the first anchor and the second anchor of the second anchor-tag combination based on the first ToF, and, if it is determined that the measurement distance is different from a pre-given anchor-to-anchor distance between the anchors, outputting an alarm indicating that the measurement distance is different from the pre-given anchor-to-anchor distance through a user interface of the computing device, or transmitting the alarm to another computing device, or performing a subsequent process of updating the pre-given anchor-to-anchor distance between the anchors by replacing it with the measurement distance. Positioning system.

4. A positioning system comprising a first anchor-tag combination having the same structure as the anchor-tag combination of paragraph 1, and a second anchor-tag combination, The first anchor-tag combination is configured to receive a second tag transmission signal transmitted by a second tag of the second anchor-tag combination in response to the first anchor transmission signal after the first anchor of the first anchor-tag combination transmits a first anchor transmission signal, thereby calculating a first ToF between the first anchor and the second tag. Positioning system.

5. In paragraph 4, Further comprising a computing device configured to communicate with the first anchor-tag combination and the second anchor-tag combination, The computing device is configured to determine a measurement distance between the first anchor and the second anchor of the second anchor-tag combination based on the first ToF, The computing device measures the distance, The distance between the first anchor and the second tag determined based on the first ToF; a second pre-given distance between the second anchor and the second tag; and The relative orientation difference of the second anchor-tag combination with respect to the first anchor-tag combination; It is designed to be produced using, Positioning system.

6. In paragraph 5, The second anchor-tag combination is configured to receive a first tag transmission signal transmitted by the first tag in response to the second anchor transmission signal after the second anchor transmits a second anchor transmission signal. The first anchor-tag combination and the second anchor-tag combination each further include a circuit for measuring the AoA of an incident radio wave and an accelerometer for measuring the direction of gravity, The first anchor-tag combination is configured to transmit the first AoA of the second tag transmission signal and the first gravity direction measured by the first anchor-tag combination to the computing device, The second anchor-tag combination is configured to transmit the second AoA of the first tag transmission signal and the second gravity direction measured by the second anchor-tag combination to the computing device, The computing device is configured to determine the relative attitude using the first AoA, the second AoA, the first gravity direction, and the second gravity direction. Positioning system.

7. In paragraph 4, Further comprising a computing device configured to communicate with the first anchor-tag combination and the second anchor-tag combination, The computing device can access a memory in which a pre-given inter-anchor distance between the first anchor and the second anchor of the second anchor-tag combination is stored, The computing device is configured to determine a measurement distance between the first anchor and the second anchor based on the first ToF, and perform a predetermined subsequent process when the measurement distance is determined to be different from the distance between the anchors given in advance. The first anchor-tag combination and the second anchor-tag combination each further include a communication module capable of communicating with the computing device. Positioning system.

8. In paragraph 7, The above-described subsequent process is a process of outputting an alarm through a user interface of the computing device or transmitting the alarm to another computing device that the measured distance is different from the pre-given distance between anchors. Positioning system.

9. In paragraph 7, The above-described subsequent process is a process of updating the distance between the anchors given in advance by replacing it with the measured distance. Positioning system.

10. In paragraph 7, Includes one more set of external communication entities, The distance between at least three fixed entities among a set of entities comprising the first anchor, the second anchor, and the set of external communication entities is fixed to a pre-given value, The computing device is configured to perform a step of calculating coordinates of the set of entities based on measured distances between the set of entities; Positioning system.

11. In paragraph 10, The above positioning system further includes a third anchor-tag combination having the same structure as the anchor-tag combination of the first clause, In the above memory, a pre-given anchor distance between the first anchor, the second anchor, and the third anchor of the third anchor-tag combination is stored, wherein the three fixed entities are characterized by being the first anchor, the second anchor, and the third anchor; Positioning system.

12. In paragraph 10, The above calculating steps are: A step of determining the initial coordinates of three reference entities selected from the above set of entities; and A step of determining the initial coordinates of the remaining other entities based on the measured distances between the three reference entities and the remaining other entities; including, Positioning system.

13. In paragraph 12, The above positioning system further includes a third anchor-tag combination having the same structure as the anchor-tag combination of the first clause, wherein the three selected reference entities are characterized in that they are the first anchor, the second anchor, and the third anchor of the third anchor-tag combination. Positioning system.

14. A method for executing a positioning system including a first anchor-tag combination having the same structure as the anchor-tag combination of paragraph 1 and a second anchor-tag combination, A step in which the first anchor of the first anchor-tag combination transmits a first anchor transmission signal; A step in which the first anchor receives a second tag transmission signal transmitted by the second tag of the second anchor-tag combination in response to the first anchor transmission signal; and A step in which the first anchor-tag combination calculates a first ToF between the first anchor and the second tag; including, method.

15. In paragraph 14, The positioning system further comprises a computing device configured to communicate with the first anchor-tag combination and the second anchor-tag combination, The first anchor-tag combination and the second anchor-tag combination each further include a communication module capable of communicating with the computing device, The computing device can access a memory in which a pre-given inter-anchor distance between the first anchor and the second anchor of the second anchor-tag combination is stored, The computing device determines a measurement distance between the first anchor and the second anchor based on the first ToF; and A step of performing a predetermined follow-up process when the computing device determines that the measured distance is different from the pre-given distance between anchors; including more, method.

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