JP2011185692A - System, method and apparatus for determining abnormal displacement of positioning apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technical solution for determining whether a positioning apparatus is displaced in a space. <P>SOLUTION: There are provided a system, a method and an apparatus for determining whether the positioning apparatus is displaced in the space. There is provided a system, which includes: a tag having the function for generating a ranging signal; the positioning apparatus for obtaining a relative coordinate of a position point at which the tag is positioned relative to the positioning apparatus based on the ranging signal from the tag; and a server for determining whether the positioning apparatus is displaced or not based on the relative coordinate of the position point in the space, a calibration parameter of the positioning apparatus and a reliable absolute coordinate. The embodiment of the invention correctly and comprehensively determines whether the positioning apparatus is displaced in real time. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to the field of positioning, and more particularly to a system, method, and apparatus for determining whether a positioning device has been displaced in space.

  Location information is basic context information that can be used to identify the geographical relationship between the user and the environment, thereby enabling a deeper understanding of the user's behavior. In view of the importance and future of location recognition applications, the design and implementation of systems that provide location information has become popular, especially in systems that are applied to indoor and urban environments. At present, several positioning systems that accurately and in real time track people and objects have been developed, and are used for various purposes in environments such as offices, medical facilities, coal mines, subways, smart buildings, restaurants, and the like.

  Currently, these positioning systems are roughly classified into those using ultrasonic waves and those using ultra-wideband radio. A feature common to these systems is that positioning is performed with an accuracy of one centimeter. Among these positioning devices, in order to monitor the position of an object moving within an area of interest (AOI), the positioning device is placed in the environment of use and then calibrated continuously. There is something you need. Typically, positioning systems that can track the position of moving objects in real time are used to provide location-based services. For example, in an office environment, it is possible to track the positions of terminals and employees by arranging a positioning device. Therefore, a “security management area” can be defined by setting location-based access rules. In other words, access to the database storing the secret information is permitted only within the security management area and prohibited elsewhere. This security management area can be set in one room, a part of the workplace, or even one table.

FIG. 1 is a schematic diagram showing the arrangement and displacement of a positioning system in the prior art. Here, a room is taken as an example. Positioning devices (for example, positioning devices located in <x ₁ , y ₁ , d ₁ > to <x ₆ , y ₆ , d ₆ >) are usually arranged so as to form an array on the ceiling of the room. Since these positioning devices are all calibrated, by monitoring the position of the tag, it is possible to monitor the position and behavior of the person or object that attached the tag. (X _i , y _i ) is the position of the i-th positioning device in the room, and d _i is the distance between the i-th positioning device and the tag.

However, if some of the positioning devices in the positioning system (eg, <x ₆ , y ₆ , d ₆ > shown in FIG. 1) are secretly displaced by an attacker, the calibrated positional parameters of the positioning device are actually May not match the position parameter of the tag so that the entire positioning system cannot accurately determine the tag position. In this case, it becomes impossible to accurately monitor the region of interest. This would create a security pitfall because people without access rights can access computers in the area of interest. This is called a “moving attack”.

  Therefore, there is a need in the positioning field for a technical solution for determining whether a positioning device has been displaced.

  The object of the present invention is to provide a technical solution for determining whether a positioning device in space has been displaced.

  According to one aspect of the invention, a system is provided. The system includes a tag having a function of generating a distance measurement signal, and a positioning device configured to acquire relative coordinates of the position point where the tag is located with respect to the positioning device based on the distance measurement signal from the tag. And a server configured to determine whether the positioning device has been displaced based on the relative coordinates of the position points in space, the calibration parameters of the positioning device, and the trusted absolute coordinates.

  According to another aspect of the invention, a method is provided for determining whether a positioning device has been displaced in space. The method includes receiving a relative coordinate of a position point relative to a positioning device in space, a calibration parameter of the positioning device, and a trusted absolute coordinate at a position point in space; and a relative coordinate, a calibration parameter, and a trusted absolute coordinate And determining whether or not the positioning device has been displaced.

  According to yet another aspect of the invention, an apparatus is provided for determining whether a positioning device has been displaced in space. The apparatus includes a receiving means for receiving relative coordinates of the position point relative to the positioning device in space, a calibration parameter of the positioning device, and a trusted absolute coordinate at the position point in space, and relative coordinates, calibration parameters, and confidence. Determination means for determining whether or not the positioning device is displaced based on the absolute coordinates.

  The effect of the embodiment of the present invention is that it is possible to accurately, comprehensively and in real time determine whether or not the positioning device has been displaced, thereby effectively preventing a potential movement attack.

It is the schematic which showed arrangement | positioning and displacement of the positioning device in a prior art. It is the schematic of the space which used the room as an example of the space where this invention is mounted. 1 is a schematic view of a positioning device according to an embodiment of the present invention. 3 is a three-dimensional schematic diagram of a reference space according to an embodiment of the present invention. FIG. 3 is a simplified two-dimensional schematic diagram of a reference space according to the embodiment of the present invention. FIG. 6 is a schematic diagram illustrating a method of calibrating another positioning device based on one calibrated positioning device, according to one embodiment of the present invention. 1 is a schematic block diagram of a system for determining whether a positioning device has been displaced, according to one embodiment of the present invention. FIG. 4 is a flowchart of a method for determining whether a tag has been displaced, according to one embodiment of the present invention. FIG. 3 is a spatial schematic diagram of a method for determining an offset of a positioning device, according to one embodiment of the present invention. 6 is a flowchart of a method for determining whether a positioning device has been displaced, according to another embodiment of the present invention. FIG. 6 is a schematic diagram illustrating changes in parameters after the positioning device is displaced according to another embodiment of the present invention. FIG. 6 is a spatial schematic diagram of a method for determining whether a positioning device has been displaced using another calibrated positioning device, according to one embodiment of the present invention. FIG. 6 is a block diagram of an apparatus for determining whether a positioning device has been displaced, according to one embodiment of the present invention. It is a block diagram of the judgment means by one Example of this invention. It is a block diagram of the judgment means by the other Example of this invention.

  2 and 3, terms used in the embodiments of the present invention will be briefly described.

1. Space “Space” in an embodiment of the present invention means a space in which an object moves, and includes a room, an office, a conference room, and the like. FIG. 2 is a schematic view of the space 10 taking a room as an example. It will be appreciated that embodiments of the present invention are not limited to square rooms as shown in FIG. 2 and may be any shape of room.

2. Spatial feature position point “Spatial feature position point” means a position point for determining a space. For example, in the space 20 which is the room in the example of FIG. Basically, any point in the space can be selected as the spatial feature point as long as it can be used to determine the space. When the room is another polygon such as a hexagon, the vertex of the polygon can be used as the feature position point. If the room has an irregular shape, it can be used as a polygon even if the room has a shape other than the polygon because it fits the polygon using three or more position points on the boundary of the room. .

3. Positioning on one device (POD)
A POD according to an embodiment of the present invention is an apparatus for determining the coordinates of a position point in space. FIG. 3 shows an example of the POD used in the embodiment of the present invention. As shown in FIG. 3, the POD used in the embodiment of the present invention is a sensor array having a plurality of leaf node position points. This sensor array includes at least two leaf node position points. In other words, the POD includes at least two leaf node position point sensors, and one sensor is disposed between the at least two leaf node position point sensors. In general, the more the leaf node position node points, the higher the positioning accuracy. The POD in FIG. 3 has six leaf node position points. In the practical application shown in FIG. 3, the POD 14 is usually disposed on the ceiling of the space 10. The POD 14 can generate a ranging signal toward the position point of the object in the space 10 and can receive the ranging signal from the position point of the object in the space 10.

  In the present invention, only the POD reception function is used. However, the POD can be provided with a calculation function for executing a related calculation based on the received ranging signal. Alternatively, the POD can be wired or wirelessly connected to a remote server or a dedicated computer device, and calculation based on the distance measurement signal can be executed in the remote server or the dedicated computer device.

  Usually, the coordinates of the object position point in the space can be obtained by conventional triangulation or coordinate conversion based on the distance measurement signal received by the POD from the object position point. Since the structure and function of the POD are well known in the art, their details are omitted.

4). Absolute Coordinate System In an embodiment of the present invention, a coordinate system in which a position point in space is used as a coordinate origin is referred to as an “absolute coordinate system”. Any feature position point in space can be used as the origin of the absolute coordinate system. For example, the feature position point 11 is used as the origin of the absolute coordinate system in the space 10 shown in FIG. Of course, those skilled in the art will understand that selecting one feature location point as the origin facilitates the calculation, but is not absolutely necessary. Even when another position point is selected as the coordinate origin, the absolute coordinate system can be obtained by simple coordinate conversion. Since this coordinate transformation is well known to those skilled in the art, its details are omitted.

5. Relative Coordinate System In the embodiment of the present invention, a coordinate system in which POD is used as the origin is referred to as a “relative coordinate system”. The origin of the relative coordinate system is the center point of the POD, and the X-axis direction is the first sensor (not shown) of the POD. The “first sensor” here may be specified at the time of initial configuration during POD manufacturing. When the X axis is designated, a direction perpendicular to the X axis on the POD plane is defined as the Y axis.

  At the time of POD calibration, a depression angle θ may be formed between the relative coordinate system and the absolute coordinate system. In the present invention, this “declining angle” means the mounting angle of the POD in the absolute coordinate system, and corresponds to the POD angle 18 in FIG. Therefore, the position parameter of the position of the POD in the space (corresponding to the POD position 17 in FIG. 2) is constituted by the absolute coordinates in the absolute coordinate system and the attachment angle θ of the POD.

6). Tag In the embodiments of the present invention, “tag” means a tag having a function of generating a ranging signal, and includes an RF tag and the like. By arranging one tag at one position point in the space and receiving a ranging signal emitted from the tag by POD, the relative coordinates or absolute coordinates of the position point can be obtained. There are various types of ranging signals including ultrasonic waves, infrared rays, lasers, RF signals, ultra-wideband pulse signals, Doppler signals, and sound waves. Since a method for determining relative coordinates or absolute coordinates of a position point using a POD and a tag is well known in the art, the details thereof are omitted.

7). Region of Interest (AOI) and AOI Feature Points “Region of Interest” means a geographic space characterized by a user in connection with application specific requirements (eg, security protection, etc.). The region of interest exists in space. For example, in the use of “secure table”, the table is defined as the region of interest. Access to confidential information is permitted only within the region of interest, and access to confidential information is prohibited elsewhere. “AOI feature point” means a position point used for characterizing a region of interest. FIG. 2 shows the region of interest 15 and the AOI feature point 16.

  With reference to the figures, a method for initially calibrating a positioning device according to one embodiment of the present invention will first be described.

  According to one embodiment of the present invention, three spatial feature position points in space (corresponding to the reference spatial feature position points in FIG. 2) are selected to determine the relative coordinates of the three spatial feature position points with respect to the positioning device. Therefore, tags having a function of generating a ranging signal are arranged at these characteristic position points. In order to determine the relative coordinates of the spatial feature location points, individual tags are placed at each spatial feature location point. Alternatively, in order to determine the relative coordinates of these spatial feature position points, one identical tag may be sequentially arranged at the selected spatial feature position points.

  Next, the positioning device is placed in the space. The positioning device may be arranged anywhere in the space. The positioning device can also be arranged on the ceiling in the space. Since this initial location is arbitrary, it may be any location on the ceiling. Next, the positioning device acquires the relative coordinates of these spatial feature position points with respect to the own device based on the distance measurement signal from the tag.

  For example, the positioning device determines the relative coordinates of the three sensors using the central point of the device itself as the coordinate origin. Next, the three sensors acquire the distances from the sensors to the respective spatial feature position points based on the distance measurement signals from the tags arranged at the spatial feature position points. And finally, based on the distance from each spatial feature position point to each sensor and the relative coordinates of each sensor, each space for the positioning device using a conventional triangulation algorithm (eg, least mean square error algorithm) The relative coordinates of the feature position point are acquired. A method for obtaining the relative coordinates of each spatial feature position point with respect to the positioning device using a conventional triangulation algorithm is well known in the art, and the details thereof are omitted.

  Thereafter, the relevant calculation automatically determines the position parameters of the positioning device in space, thereby automatically calibrating the positioning device. This will be described in detail below. Alternatively, the position parameter includes the absolute coordinates (x, y, z) of the positioning device in the space and the mounting angle. In the present invention, the position parameter of the calibrated positioning device is referred to as “positioning device calibration parameter”.

  Here, with reference to FIG. 4 and FIG. 5, a method for determining the position parameter of the positioning device in the space based on the relative coordinates of the acquired three reference space feature position points in the rectangular room will be described.

As shown in FIG. 4, the relative coordinates of the three reference space feature position points on the ground surface are (x ₁ , y ₁ , z ₁ ), (x ₂ , y ₂ , z ₂ ), (x ₃ , y ₃ , z ₃ ). These relative coordinates are determined using a positioning device and a tag. The feature position point (x ₁ , y ₁ , z ₁ ) is defined as the origin of the absolute coordinate system (0, 0, 0) in the reference space. The length (l), width (w), and height (h) of the room, the absolute coordinates (x, y, z) of the positioning device, and the mounting angle θ of the POD are unknown.

First, the z-coordinate of the positioning device (that is, the height (h) of the positioning device) is determined. Since the ceiling is generally parallel to the ground surface, the height of the positioning device is h, ie z = h = z ₁ = z ₂ = z ₃ . However, the z coordinate is determined as z = h = (z ₁ + z ₂ + z ₃ ) / 3 in consideration of the possibility of an error due to unevenness of the ground surface.

  After z is determined, the other two unknown values in the two-dimensional space need to be resolved.

  FIG. 5 illustrates unknown values (eg, room length (l), width (w), and height (h), absolute coordinates of POD (x, y), and mounting angle) in a two-dimensional space according to the present invention. It is the schematic which shows the calculation method of (theta etc.).

  As shown in FIG. 5, in the present invention, the coordinate system indicated by a solid line is an absolute coordinate system, and the coordinate system indicated by a dotted line is a relative coordinate system having a positioning device as an origin. The depression angle formed by the two coordinate systems (that is, the attachment angle of the positioning device) is θ.

According to FIG. 5, equation group (1) is obtained by conventional coordinate transformation.
x ₁ sin (θ) −y ₁ cos (θ) + y = 0
x ₂ cos (θ) −y ₂ sin (θ) + x = l
x ₂ sin (θ) −y ₂ cos (θ) + y = w (1)
x ₃ cos (θ) −y ₃ sin (θ) + x = l
x ₃ sin (θ) −y ₃ cos (θ) + y = 0
(X ₁ −x ₃ ) ² + (y ₁ −y ₃ ) ² = l ²
(X ₂ −x ₃ ) ² + (y ₂ −y ₃ ) ² = w ²

  Those skilled in the art understand that the more reference space feature position points, the greater the number of equations (ie, the number of rows in the coefficient matrix) that make up equation group (1). I will. Since this is well known to those skilled in the art, details are omitted.

ｘ＝（ｘ_１ ^２＋ｙ_１ ^２−ｘ_１ｘ_３−ｙ_１ｙ_３）／ｌ （４）
ｙ＝ｘ_３ ^２＋ｙ_３ ^２−ｘ_２ｘ_３−ｙ_２ｙ_３）／ｗ （５）

The absolute coordinates (x, y) and angle θ of the positioning device and the length l and width w of the reference space are derived by solving equation group (1). This calculation process is as follows.

x = (x ₁ ² + y ₁ ² −x ₁ x ₃ −y ₁ y ₃ ) / l (4)
y = x ₃ ² + y ₃ ² -x ₂ x ₃ -y ₂ y ₃ ) / w (5)

  Thereby, the size of the reference space and the position parameters of the positioning device in the reference space (absolute coordinates (x, y, z) of the positioning device, mounting angle θ, etc.) are obtained, and the purpose is to acquire the calibration parameters of the positioning device. Thus, the determination of the size of the space and the calibration of the positioning device are automatically completed.

  After calibration, the positioning device can directly obtain the absolute coordinates of any point in space using existing triangulation algorithms. Further, the positioning device can obtain the absolute coordinates of an arbitrary point in the space by converting the relative coordinates to the absolute coordinates. That is, the relative coordinates of the position point in the space with respect to the positioning device are acquired, and then the absolute coordinates of the position point are acquired by conventional coordinate conversion.

  In the above example, the calibration process of the positioning device according to the invention when three spatial feature position points have been selected has been described. However, the present invention is not limited to implementations using three spatial feature position points, and in some implementations it is possible to perform calibration of the positioning device using only one or two spatial feature position points. For example, when the positioning device is arranged on the ceiling of the room, the X axis (direction of the first sensor) of the relative coordinate system of the own device is parallel to the X axis of the absolute coordinate system of the space. In this case, the attachment angle θ of the positioning device is actually zero. At this point, one corner of the room is determined as the origin of the absolute coordinate system (ie, the absolute coordinates of this corner) as (0, 0, 0). The relative coordinates of this corner with respect to the positioning device can be obtained by the positioning device. As described above, the Z coordinate of the positioning device is equal to the Z coordinate value of the relative coordinates with respect to the corner positioning device. In the two-dimensional plane, the absolute X coordinate and absolute Y coordinate of the positioning device are obtained by normal coordinate system translational transformation based on the relative coordinates and absolute coordinates of the corners. Since this conversion is well known in the art, its details are omitted.

  It will be appreciated that according to the present invention, the more spatial feature position points selected, the greater the number of equations obtained by coordinate transformation, and the more accurate positioning device position parameters are determined.

  Also, while the above has described a calibration process for a positioning device in a square room, it will also be appreciated that the embodiments described above are not limited to square rooms. If the space is irregularly shaped, it can be adapted to a polygon using three or more points on the boundary of the space, so even a irregularly shaped space is treated like a polygonal space. be able to.

  According to another embodiment of the present invention, when a plurality of PODs are arranged in a space, one POD can be calibrated by the above method and then another POD can be calibrated. In order to simplify the description, the calibrated POD is referred to as “first positioning device (POD1)”, and the POD to be calibrated is referred to as “second positioning device (POD2)”.

  FIG. 6 is a schematic diagram illustrating a method of calibrating a second positioning device (POD2) based on a calibrated first positioning device (POD1) according to another embodiment of the present invention.

  6 is calibrated according to equation group (1). According to the present embodiment, in order to calibrate POD2, first the cover areas of POD1 and POD2 are determined. At this time, it is necessary to determine so that there is a portion where the cover area of POD1 and the cover area of POD2 overlap. is there. As shown in FIG. 6, the cover area of POD1 is referred to as “first cover area”, that of POD2 is referred to as “second cover area”, and the cover areas of POD1 and POD2 partially overlap. The overlapping coverage area can be determined by various methods. For example, if POD1 is 3 meters high and the radius of its cover area is 4 meters, POD2 can be placed at a distance of about 6 meters. Further, when it is desired to know whether or not a certain position is in the overlapping cover area, it can be determined by whether or not both POD1 and POD2 can detect the tag at that position.

Subsequently, in order to calibrate the POD 2, the absolute coordinates (x ₂₀ , y ₂₀ , z ₂₀ ) of the POD 2 in the room and the angle θ ₂₀ of the POD 2 are calculated. Specifically, two position points (referred to as “overlapping cover area position points” for convenience of explanation) are selected within the overlapping cover area, and distance measurement signals (referred to as “overlapping cover area distance measurement signals” for the same reason). ) Is placed at each position point (for the same reason, “overlapping cover area tag”). In this way, the POD 1 first acquires the relative coordinates of these two overlapping cover area position points in its own coordinate system, and then, by coordinate conversion, the absolute coordinates (x ₁₁ , y) of these two overlapping cover area position points. ₁₁ , z ₁₁ ) and (x ₁₂ , y ₁₂ , z ₁₂ ) are acquired. Needless to say, POD 1 can directly acquire the absolute coordinates of these two overlapping cover region position points by an existing triangulation algorithm. Since a method for acquiring the absolute coordinates of a target object (for example, a position point in space) by a calibrated positioning device is well known in the art, its details are omitted.

At the same time, POD2 can obtain the relative coordinates of these two overlapping cover region position points, for example, shown as (x ₂₁ , y ₂₁ , z ₂₁ ) and (x ₂₂ , y ₂₂ , z ₂₂ ) in the own coordinate system. it can. Since POD1 has already been calibrated, the absolute coordinates of these two overlapping cover area position points are known. Since POD2 is also arranged on the ceiling in this example, the absolute coordinate of POD2 is z ₂₀ = h = (z1 + z2 + z3) / 3. As a result, the calculation of the coordinates (x ₂₀ , y ₂₀ , z ₂₀ ) of the POD 2 and the angle θ ₂₀ is simplified and can be executed with two-dimensional coordinates.

The absolute coordinates of POD2 in the reference space can be calculated by conventional coordinate transformation using the following equation group.

From equation group (7), the following matrix computation is derived.

By solving this matrix, the following is obtained as the absolute coordinates and the angle theta ₂₀ of POD2.

である。 here,

It is.

  In this way, the absolute coordinates and angle of the POD 2 to be calibrated are determined, and the calibration parameters can be obtained by calibrating the POD 2.

  Note that more than two overlapping cover area position points can be selected. This increases the number of rows of the coefficient matrix described above, but the calculation process is the same as the calculation process described above. Increasing the number of overlapping cover area position points to be selected improves positioning accuracy.

  Furthermore, the coverage area can be increased if more PODs are progressively calibrated based on the calibrated PODs using the method described above. Details are omitted here. In the above description, the case where the two overlapping cover region position points in the above-described embodiment are selected and the calibration process of the positioning device according to the embodiment of the present invention is executed has been described. However, the embodiment of the present invention has two overlapping covers. It is not limited to the region position point. In some implementations, it is possible to perform calibration of the positioning device using only one overlapping cover area position point. For example, when the first positioning device is already calibrated and the second positioning device is to be calibrated, the X axis of the second positioning device can be set parallel to the X axis of the first positioning device. In this case, the mounting angle of the second positioning device is the same as the known mounting angle of the first positioning device. At this point, the absolute coordinates of the overlapping cover region position point are obtained by the calibrated first positioning device, and the relative coordinates of the position point with respect to the second positioning device are obtained by the second positioning device. Thereafter, the absolute coordinates of the second positioning device can be obtained by normal coordinate transformation.

  If it is an engineer familiar with the said technique, while acquiring the knowledge of concepts, such as "relative coordinate", "absolute coordinate", "coordinate transformation", from the description performed with reference to FIGS. It will be appreciated how to calibrate one or more calibration devices to obtain calibration parameters.

  The following describes a method for determining whether a calibrated positioning device has been displaced in space, according to one embodiment of the present invention. FIG. 7 is a schematic diagram of a system 100 for determining whether a calibrated positioning device has been displaced in space, according to one embodiment of the present invention.

  As shown in FIG. 7, the system 100 has a function of generating a ranging signal, and the tag is arranged based on the tag 110 arranged at one position point in the space and the ranging signal from the tag. A positioning device 120 arranged in space, configured to obtain relative coordinates of the position point with respect to its own device, a relative coordinate of the position point in space, a trusted absolute coordinate of the position point in space, and And a server 130 configured to determine whether the positioning device 120 has been displaced based on calibration parameters of the positioning device 120.

  The positioning device 120 can be pre-calibrated using the method described above for obtaining the calibration parameters of the positioning device 120 in advance. Of course, other methods known in the art may be used to pre-calibrate the positioning device 120 (ie, obtain calibration parameters for the positioning device 120). Calibration parameters can also be stored in advance.

  The “reliable absolute coordinate” in the embodiment of the present invention means a reliable absolute coordinate of the position point in the space. The trusted absolute coordinates of the position point can be obtained, for example, using a positioning device that has been calibrated and determined not to be displaced.

  Next, a method for determining whether the positioning device 120 has been displaced according to an embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 8, in step S210, the relative coordinates of the position point with respect to the positioning device 120 in the space are received, and in step S220, based on the relative coordinates of the positioning device 120 and the calibration parameters, the position point in the space. In step S230, whether or not the positioning device 120 has been displaced is determined based on the trusted absolute coordinates and the calculated absolute coordinates.

  Here, a specific mounting process of steps S210 to S230 will be described.

  In step S210, one position point in the space is selected, and one tag is placed at that position point. The trusted absolute coordinates of the position point have already been acquired and stored. When it is necessary to check whether or not the positioning device 120 has been displaced, the positioning device 120 first receives a tag ranging signal and obtains the relative coordinates of the position point relative to the positioning device 120 from the ranging signal. To do.

  This position point can be arbitrarily selected. According to a preferred embodiment of the present invention, as the position point, a position in the space, for example, a corner of a room that facilitates calculation is selected.

  Alternatively, the tag can be hidden (referred to herein as a “hidden tag”) to prevent an attacker's malicious behavior. Here, “hide” means to embed a tag in a wall or randomly place a tag at a position point in the space. For example, if the positioning device 120 has been calibrated, several position points in space can be randomly selected and the positioning device 120 can calculate and store the trusted absolute coordinates of these position points. If it is suspected that the positioning device 120 has been displaced, the tag can be placed once again at the first position point and it can be determined whether the positioning device 120 has been displaced according to the embodiment shown in FIG. The advantage of such a design is that the feature location points are chosen randomly, so that the attacker cannot know where the location point was originally selected and cannot damage the hidden tag. is there. In addition to those skilled in the art in connection with the foregoing description, the term “hide” includes not only visual hiding but also any means to prevent an attacker from knowing the location of the tag. It is.

  Of course, placing the tag is just one example, and the invention is not so limited, so any of the known methods, including manual measurements, can be used.

  Subsequently, in step 220, the absolute coordinates of the position point in the space are calculated based on the acquired relative coordinates of the positioning device 120 and based on the calibration parameters of the positioning device 120. Next, an absolute coordinate calculation process will be described with reference to FIG.

It is assumed that, for example, the calibration parameters of the POD in the space of the positioning device 120 are (x _P , y _P , z _P , θ _P ). Here, (x _P , y _P , z _P ) is an absolute coordinate of the center point of the POD in the reference space, and θ _P is the calibrated POD angle described above. These parameters can be obtained by equations (4) to (6).

As shown in FIG. 9, four hidden tags are arranged in the reference space, and the absolute coordinates calculated first are (x ₁ , y ₁ , z ₁ ) to (x ₄ , y ₄ , z ₄ ), respectively. Suppose there is. These four coordinates can be stored as trusted absolute coordinates. For convenience of explanation, these coordinates are referred to as “calibrated coordinates”.

If it is suspected that the positioning device has been displaced, the absolute coordinates of the hidden tag (herein referred to as “suspicious absolute coordinates (x _i ′, y _i ′)”) are calculated by the following set of equations: The

Where (x _ri ′, y _ri ′) is the current relative coordinates of the hidden tag with respect to the positioning device detected by the positioning device, r means “relative”, and i is the index of the hidden tag N means the number of hidden tags. In practice, the solution of equation (10) is similar to the solution of equation (7).

  Note that the z-coordinate calculation is omitted because the positioning device can directly detect the z-coordinate.

Since the solution of equation (10) is implemented with reference to the calibration coordinates (x _P , y _P , z _P ) of the positioning device 120, the tag is not displaced and the positioning device 120 is displaced The suspicious absolute coordinates of the acquired tag do not match the trusted absolute coordinates originally stored. Conversely, if the positioning device 120 is not displaced, the suspicious absolute coordinate coincides with the initially stored trusted absolute coordinate.

After the suspicious absolute coordinates (x _i ', y _i ') of the hidden tag are obtained, various means can be used to determine whether the positioning device has been displaced.

  For example, statistics are taken on the error between the acquired absolute coordinate and the trusted absolute coordinate, and if the error exceeds a predetermined threshold value, it can be determined that the positioning device has been displaced.

As the criterion of “error” here, many can be used. Calculate the mean of the difference between the obtained suspicious absolute coordinates and the trusted absolute coordinates, the mean square error (MSE: Mean Square Error) between the suspicious absolute coordinates and the trusted absolute coordinates, or the covariance between them be able to. For example, the process of calculating the MSE is expressed as equation (11).

  Here, Equation (11) represents only two dimensions, because the height of the positioning device rarely changes, and therefore the calculation of the z coordinate is omitted. Needless to say, it is easy for those skilled in the art to extend equation (11) to three dimensions.

  Further, the threshold value is selected according to use conditions. If the threshold value is decreased, the sensitivity is increased, but even a minor interference is interpreted as a displacement of the positioning device. Conversely, if the threshold value is increased, the sensitivity decreases, but there is a possibility that a potential mobile attack may be missed.

  In addition to the aforementioned criteria, other parameters can also be used as criteria. Alternatively, the average value can be used as a criterion. As an example, there is a method of summing and averaging the difference between the suspicious absolute coordinate and the reliable absolute coordinate for a plurality of position points. Furthermore, the weight can be used for judgment. In this case, the weighting target can be a specific parameter such as an x coordinate or a specific positioning device. For example, if there are multiple positioning devices, a large weight is assigned to some specific positioning devices. Then, even if these positioning devices are slightly displaced, a significant influence occurs in MSE and other criteria. Therefore, the determination of whether or not these specific positioning devices are displaced is more sensitive than others.

  In the above, the present invention has been described only with respect to several kinds of judgment criteria. However, the present invention is not limited to these judgment criteria, and any method known in the art that can reflect data fluctuation can be used.

  According to another embodiment of the invention, it is possible to determine whether the positioning device has been displaced by calculating the offset of the positioning device. In the following, referring to FIG. 10, a method for determining whether the positioning device 120 has been displaced according to another embodiment of the present invention will be described.

  As shown in FIG. 10, in step S310, the relative coordinates of the position point in the space with respect to the positioning device are received. In step S320, the absolute absolute coordinates of the position point and the calibration parameters of the positioning device are received. In step S330, a positioning device offset is calculated based on the relative coordinates, the trusted absolute coordinates, and the positioning device calibration parameters. In step S340, if the offset exceeds a predetermined threshold value, it is determined that the positioning device has been displaced. Next, the mounting process of steps S310 to S340 will be described in detail with reference to FIG. 11 and FIG.

As shown in FIG. 11, it is necessary to understand that if a positioning device such as POD is displaced, the initial calibration parameters such as coordinates and angles may also change. In this figure, the initial calibrated position parameters of the _{POD (x P, y P,} z P, θ P) and to the position parameters _{(x P} + △ _{x P} after the _{change, y P + △ y P,} z _P + △ _{z P,} is set to θ _P + △ θ _P). The offset _{(△ x P, △ y P} , △ z P, △ θ P) is calculated, and whether the positioning device is displaced is determined.

Although calculation of Again △ z _P is omitted, it goes without saying it can be extended to three dimensions the computation by a person skilled in the art.

  If there are three unknown values, at least three equations are needed to solve these three unknown values. Since one position point involves two equations, at least two position points are required to determine the offset of the positioning device.

N position points (eg, N hidden tags) are selected and the initial absolute coordinates (ie, trusted absolute coordinates) of these position points are (x ₁ , y ₁ ), (x ₂ , y ₂ ). ,. . . Let it be expressed as (x _N , y _N ). If it is suspected that the positioning device has been displaced, the relative coordinates (x _r1 , y _r1 ), (x _r2 , y _r2 ),. . (X _rN , y _rN ) is obtained using this positioning device.

Then, by the coordinate transformation, the position offset parameters of the positioning device _{(△ x P, △ y P} , △ z P, △ θ P) is calculated. The equation group (12) represents this specific calculation process.

The equation group (12) is composed of 2N equations in total. Therefore, if N is 2, the offset _{(△ x P, △ y P} , △ θ P) is solved.

  Similarly, in one embodiment of the present invention, an error such as MSE can be used as a criterion, and it is determined whether the positioning device has been displaced by comparing the offset to a specific threshold. If the offset is above this particular threshold, it is determined that the positioning device has been displaced.

  It should be understood that if it is determined that there is no change in the mounting angle of the positioning device when the positioning device is displaced, the offset of the positioning device can be determined at only one position point.

  The “reliable absolute coordinate” in the above description is a reliable absolute coordinate of at least one position point stored in advance. According to another embodiment of the present invention, the trusted absolute coordinates can be obtained by other positioning devices that are determined not to be displaced and that have overlapping coverage areas with the positioning device 120. Thus, the system of FIG. 7 can include other positioning devices that have been calibrated and determined not to be displaced.

  According to this embodiment of the present invention, the position point is in the overlapping area of the positioning device 120 and the other positioning device, and it is determined that the other positioning device is calibrated and not displaced. The trusted absolute coordinates of the position point can be obtained by the other positioning device.

  Hereinafter, a specific implementation of this embodiment will be described with reference to FIG.

  As shown in FIG. 12, it is assumed that there are two positioning devices (in this example, POD1 and POD2) that share an overlapping cover area, and it is determined that POD1 has been calibrated and not displaced. Since POD1 has already been calibrated, the absolute coordinates of any position point within the cover area of the apparatus itself can be obtained directly or indirectly by coordinate transformation, and this absolute coordinate is a trusted absolute coordinate.

  In order to determine whether POD2 has been displaced, first a position point in the overlapping cover area of POD1 and POD2 is selected. Then, POD1 acquires the absolute coordinates of the position point as trusted absolute coordinates, and POD2 acquires the relative coordinates of the position point with respect to its own device. Thus, whether the POD2 has been displaced is determined by using the method shown in FIGS. 8 and 10 and the absolute coordinates specified by the POD1, the relative coordinates of the position point with respect to the POD2, and the calibration parameters of the POD2 acquired in advance. It becomes possible to determine based on the above.

  It is desirable to determine whether or not the POD 2 has been displaced by selecting a plurality of position points within the overlapping cover area. Thereby, the accuracy of determination is improved.

  There are various methods for selecting a plurality of position points. For example, a plurality of tags are simultaneously arranged in the overlapping cover region so that POD1 and POD2 can receive the coordinates of the characteristic position points represented by these tags. In this embodiment of the present invention, it is desirable to be able to use mobile tags (tags that can move within overlapping coverage areas) to achieve this goal. In this case, while the mobile tag moves, it is possible to acquire a data set that reflects the feature position point that the mobile tag has passed.

Here, each POD has a tuple [pod _ID , rpos, t] of the mobile tag related to its own device (pod _ID is an index of the POD, rpos is an index of the mobile tag) when the mobile tag moves within the overlapping cover area. It is assumed that the relative position with respect to the POD and t is the current time) can be acquired. As time goes on, this sequence of tuples becomes [pod ₁ , rpos ₁₁ , t ₁ ], [pod ₂ , rpos ₂₁ , t ₁ ], [pod ₁ , rpos ₁₂ , t ₂ ], [pod ₂ , rpos ₂₂ , t ₂ ],. . . [Pod ₁ , rpos _1k , t _k ] and [pod ₂ , rpos _2k , t _k ]. Here, k represents the number of time position points, and the tuple [pod ₁ , rpos _1k , t _k ] represents the relative position rpos _1k with respect to the POD ₁ of the mobile tag at the time t _k , and similarly the tuple [pod ₂ , rpos _2k , t _k ] represents the relative position rpos _2k of the mobile tag with respect to POD2 at time t _k . A total of 2k tuples can be acquired for each sequence. Further, since it is determined that POD1 is not displaced, the position of the mobile tag specified by the tuple corresponding to POD1 is true.

Here, the relative coordinates of the mobile tag with respect to the j-th POD at time t are (x _jrt ', y _jrt '). “R” means “relative”. Then, the absolute coordinates (x _jt ', y _jt ') of the mobile tag can be obtained for each POD by the equation group (13).

Here, (x _Pj , y _Pj , θ _Pj ) is an initial position parameter of the calibrated j-th POD, and can be stored in advance. The calculation of the z coordinate is omitted here, but it goes without saying that those skilled in the art can easily extend this calculation to three dimensions if necessary.

Next, the trusted absolute coordinate of the position point calculated by the trusted POD1 is expressed as (x _1t , y _1t ), and the suspicious absolute coordinate of the corresponding feature position point calculated by POD2 is (x _2t ′, y _2t ′). The mean square error (MSE) between them is then calculated by equation (14), which determines whether POD2 has been displaced.

  After it is determined that POD2 is safe, POD3, POD4 (not shown), etc. are sequentially determined until all PODs are determined.

  Also, if there are multiple PODs, the suspicious POD displacement offset can be determined using the method shown in equation group (12). In this case, the coordinates of the required position point are provided by the mobile tag. Details are omitted here.

  According to another embodiment of the invention, an alarm is issued to the user when a displacement of the positioning device is detected. Alarm methods include, but are not limited to, alarm sounds and flashing alarm signals. In addition, the display displays the exact position parameters of the various positioning devices to the user in graphics or tabular form, so that the user can determine whether the positioning device has been displaced based on these positional parameters. You can also

  According to yet another embodiment of the present invention, the method shown in FIG. 8 and the method shown in FIG. 10 are combined. In this case, it is first determined whether or not the positioning device has been displaced according to the method of FIG. When the positioning device is displaced, the offset of the positioning device in the space is determined according to the method of FIG. The positioning device is recalibrated based on the acquired offset, if necessary.

  According to yet another aspect of the present invention, as shown in FIG. 13, an apparatus 400 is provided for determining whether a positioning device has been displaced in space. The apparatus 400 includes receiving means 410 for receiving the relative coordinates of the position point relative to the positioning device in space, the calibration parameters of the positioning device, and the trusted absolute coordinates of the position point in space, and the relative coordinates, calibration parameters, and And determining means 420 for determining whether or not the positioning device has been displaced based on the trusted absolute coordinates.

  In one specific example, as shown in FIG. 14, the determination means 420 includes an absolute coordinate calculation means 510 for calculating the absolute coordinates of the position point in the space based on the calibration parameters and the relative coordinates, and the calculated absolute Error statistics means 520 for calculating an error between coordinates and trusted absolute coordinates, and determination means 530 for determining that the positioning device is displaced when the error exceeds a predetermined threshold value. Can do.

  As shown in FIG. 15, in another embodiment, the determining means includes an offset calculating means 610 for calculating an offset of the positioning device based on relative coordinates, calibration parameters, and trusted absolute coordinates, and the offset is predetermined. And a determination means 620 for determining that the positioning device has been displaced when the threshold value is exceeded.

  According to still another embodiment of the present invention, the specific example shown in FIG. 14 can be combined with the specific example shown in FIG. In this case, it is first determined whether or not the positioning device has been displaced according to the specific example of FIG. When the positioning device is displaced, the offset of the positioning device in the space is determined according to the specific example of FIG. The positioning device is recalibrated based on the acquired offset, if necessary.

  In one specific example of this embodiment, the position point is a fixed point whose absolute coordinates are determined in advance, and a tag having a function of generating a distance measurement signal is disposed at the position point, and the distance measurement signal from the tag is Based on this, the relative coordinates are obtained by the positioning device. Tags may be hidden.

  According to a specific example of this embodiment, the position point is randomly located in the overlapping cover area between the positioning device and another positioning device that has been determined to be calibrated and not displaced. A tag having a function of generating a distance measurement signal is arranged, relative coordinates are acquired by a positioning device based on the distance measurement signal from the tag, and absolute reliability is obtained by the other positioning device based on the distance measurement signal from the tag. The coordinates are obtained. The tag may be movable within the overlapping cover area.

  According to still another embodiment of the present invention, the embodiment shown in FIG. 14 can be combined with the embodiment shown in FIG. In this case, it is first determined whether or not the positioning device has been displaced according to the specific example of FIG. When the positioning device is displaced, the offset of the positioning device in the space is determined according to the specific example of FIG. The positioning device is recalibrated based on the acquired offset, if necessary.

  It should be noted that the device 400 can be embedded in the positioning device or can be connected to a remote server or server of the positioning device via a communication link. The apparatus 400 can further be implemented as hardware, software, firmware, or a combination thereof.

  The method and apparatus of the present invention can be implemented as hardware, software, firmware, or a combination thereof. The hardware part can be implemented using dedicated logic, and the software part can be stored in a memory and executed by a suitable instruction execution system such as a microprocessor, personal computer (PC), mainframe or the like.

  Although the specification of the present invention has been presented above for purposes of illustration and description, it is not intended to be exhaustive of the invention and the invention is not limited to the disclosed form. Many modifications and variations will be apparent to practitioners skilled in the art.

  Thus, the above examples more clearly illustrate the principles and practical applications of the present invention, and all changes and modifications made without departing from the spirit of the present invention are defined in the appended claims. It has been selected and described so that it can be understood by those skilled in the art that it is included in the protection scope of the present invention.

DESCRIPTION OF SYMBOLS 100: System 110: Tag 120: Positioning device 130: Server 400: Device 410: Receiving means 420: Determination means 510: Absolute coordinate calculation means 520: Error statistics means 530: Determination means 610: Offset calculation means 620: Determination means

Claims (21)

A tag having a function of emitting a ranging signal;
A positioning device configured to acquire relative coordinates of a position point where the tag is located with respect to the positioning device based on a distance measurement signal from the tag;
A server configured to determine whether the positioning device has been displaced based on relative coordinates of position points in space, calibration parameters of the positioning device, and trusted absolute coordinates. . The server is
Calculating the absolute coordinates of the position point in the space based on the relative coordinates and calibration parameters;
Taking statistics of the error between the calculated absolute coordinates and the trusted absolute coordinates,
The system of claim 1, wherein the system is configured to determine that the positioning device has been displaced if the error exceeds a predetermined threshold. The server is
Calculating an offset of the positioning device in the space based on the relative coordinates, the calibration parameters and the trusted absolute coordinates;
The system according to claim 1 or 2, wherein the system is configured to determine that the positioning device has been displaced if the offset exceeds a predetermined threshold.   The system of claim 3, wherein the positioning device is recalibrated based on the offset.   The system of claim 1, wherein the calibration parameters include calibrated absolute coordinates and calibrated mounting angles of the positioning device in the space.   The system according to claim 1, wherein the position point is a fixed point whose absolute coordinates are determined in advance. With other positioning devices that have been calibrated and determined not to be displaced,
The position points are randomly arranged in an overlapping cover area between the positioning device and the other positioning device;
The system according to claim 1, wherein the trusted absolute coordinate is obtained by the other positioning device based on a ranging signal from the tag. A method for determining whether a positioning device has been displaced in space, comprising:
Receiving relative coordinates of the position point relative to the positioning device in space, calibration parameters of the positioning device, and trusted absolute coordinates at the position point in space;
Determining whether the positioning device has been displaced based on relative coordinates, calibration parameters, and trusted absolute coordinates. Determining whether the positioning device has been displaced;
Calculating absolute coordinates of the position point in the space based on the calibration parameters and the relative coordinates;
Taking statistics of the error between the calculated absolute coordinates and the trusted absolute coordinates;
6. The method of claim 5, comprising determining that the positioning device has been displaced if the error exceeds a predetermined threshold. Determining whether the positioning device has been displaced;
Calculating an offset of the positioning device in the space based on the relative coordinates, the calibration parameters and the trusted absolute coordinates;
10. A method according to claim 8 or claim 9, comprising determining that the positioning device has been displaced if the offset exceeds a predetermined threshold.   The method of claim 10, wherein the positioning device is recalibrated based on the offset.   9. The method of claim 8, wherein the calibration parameters include calibrated absolute coordinates and calibrated mounting angles of the positioning device within the space.   9. The method according to claim 8, wherein the position point is a fixed point whose absolute coordinates are determined in advance. A tag having a function of emitting a ranging signal is disposed at the position point,
The method according to claim 13, wherein the relative coordinates are obtained by the positioning device based on a ranging signal from the tag. The position points are randomly placed in an overlapping coverage area between the positioning device and another positioning device that has been determined to be calibrated and not displaced;
A tag having a function of emitting a ranging signal is disposed at the position point,
The relative coordinates are acquired by the positioning device based on a ranging signal from the tag,
9. The method of claim 8, wherein the trusted absolute coordinates are obtained by the other positioning device based on a ranging signal from the tag. A device for determining whether the positioning device has been displaced in space,
Receiving means for receiving relative coordinates of the position point relative to the positioning device in space, calibration parameters of the positioning device, and trusted absolute coordinates at the position point in space;
A determination means for determining whether the positioning device has been displaced based on the relative coordinates, the calibration parameters and the trusted absolute coordinates. The determination means is
Absolute coordinate calculation means for calculating absolute coordinates of the position point in the space based on the calibration parameter and the relative coordinates;
An error statistic means for taking statistics of an error between the calculated absolute coordinate and the trusted absolute coordinate;
17. The apparatus according to claim 16, further comprising first determination means for determining that the positioning device has been displaced when the error exceeds a predetermined threshold value. The determination means is
Offset calculating means for calculating an offset of the positioning device in the space based on the relative coordinates, the calibration parameters and the trusted absolute coordinates;
The apparatus according to claim 16, further comprising: a second determination unit that determines that the positioning device has been displaced when the offset exceeds a predetermined threshold value.   The apparatus of claim 18, wherein the positioning device is recalibrated based on the offset. The position point is a fixed point whose absolute coordinates are predetermined;
A tag having a function of emitting a ranging signal is disposed at the position point,
The apparatus according to claim 16, wherein the relative coordinates are acquired by the positioning device based on a ranging signal from the tag. The position points are randomly placed in an overlapping coverage area between the positioning device and another positioning device that has been determined to be calibrated and not displaced;
A tag having a function of emitting a ranging signal is disposed at the position point,
The relative coordinates are acquired by the positioning device based on a ranging signal from the tag,
The apparatus of claim 16, wherein the trusted absolute coordinates are obtained by the other positioning device based on a ranging signal from the tag.

Images