KR20150089374A - Apparatus and method for localization of mobile node - Google Patents

Abstract

The present invention aims to measure a position of nearby anchors having a lower error. According to an embodiment of the present invention, the apparatus for measuring a position comprises: a communication unit for exchanging information for measuring a position from surrounding nodes; a position measuring unit for measuring a position by using the information received from the surrounding nodes; a spreading degree calculating unit for calculating the frequency of renewal of the initial position value to display an accumulated position error; a covariance calculating unit for calculating an error covariance from at least a part of the surrounding nodes; and a control unit for using at least one from the result of calculation by the spreading degree calculating unit and the result of calculation by the covariance calculating unit, selecting at least a part of the surrounding nodes, and measuring the current position by using the information received from the selected nodes.

Description

[0001] APPARATUS AND METHOD FOR LOCALIZATION OF MOBILE NODE [0002]

The present invention is for measuring a position in a mobile node, in particular for measuring a position from adjacent anchors having a lower error.

In general, it is possible to accurately measure the position of a vehicle outdoors using GPS (Global Positioning System) or GNSS (Global Navigation Satellite System), and more accurate trajectory generation is possible by using carrier measurement values. On the other hand, if a TWR (Two Way ranging) measurement based on UWB (Ultra-Wideband) is acquired, highly accurate position measurement is possible. The components of the TWR-based positioning system can be divided into a base station, a tag, and an anchor. Where the base station initializes and configures the network, and sends TWR start and stop commands to the available tags. In this case, when the anchor list is transmitted to the tag, the tag communicates with surrounding anchors based on the tag, and acquires the TWR-based measurement value through communication with each anchor and returns the measured value to the base station.

The difference between a tag and an anchor is that the anchor knows its position, and the tag is a node that computes the position value. Each node can act as an anchor or tag, and the anchor node can move to the shadow area of the GPS to perform mission. An anchor moving to a shaded area of the GPS can be tagged by himself to obtain his position from other anchors. That is, each node can operate as an anchor when it knows its location and as a tag when it does not know its location.

Therefore, when the nodes are moved repeatedly by repeating the tag-anchor conversion, it is possible to continuously enlarge the positioning area according to the location update of the nodes.

In the case where the positioning area is expanded by repeating the tag-anchor conversion (Collaborative Localization), if the continuous positioning is performed by repeating the tag-anchor conversion at the cooperative positioning, the position estimation value Shows a tendency to accumulate every time a tag obtains a position.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a position measuring apparatus and method that can minimize the cumulative error that may occur during cooperative positioning of mobile nodes.

It is another object of the present invention to provide a position measuring apparatus and method that enable a more accurate position to be measured during cooperative positioning of such mobile nodes.

According to an aspect of the present invention, there is provided a position measuring apparatus including a communication unit for exchanging information for position measurement from neighboring nodes, a position measuring unit for measuring a position using information received from the neighboring nodes, A propagation degree calculation unit for calculating the number of times the position value is updated from the initial position value to display the accumulated position error, and a covariance calculation unit for calculating an error covariance from at least one of the neighboring nodes Calculating at least one of neighboring nodes by using at least one of a calculation result of the propagation coefficient calculation unit and a calculation result of the covariance calculation unit and using the information received from the selected nodes to calculate a current position And a control unit for measuring the power supply voltage.

In one embodiment, the initial position value is a position value calculated using a Global Positioning System (GPS) or a Global Navigation Satellite System (GNSS), and the propagation degree is a value obtained by calculating at least one node And the number of times the position value is updated.

In one embodiment of the present invention, the control unit may select only the nodes among the neighboring nodes that know the position value of the neighboring nodes, the nodes having the propagation degree lower than a predetermined level, And the position is measured based on the result of the error covariance calculation and the information received from the selected nodes.

In one embodiment, the control unit generates at least one combination from nodes having a propagation degree of less than a certain level, the combination being at least equal to a minimum number required for position measurement, and calculates the error covariance from each of the generated combinations And the position is measured using the information received from the nodes constituting the combination having the smallest error covariance.

In addition, the method may further include selecting a plurality of nodes of the neighboring nodes that know their position values, and generating at least one combination including at least a part of the selected nodes Selecting at least one of the at least one combination and generating a position measurement model from the nodes constituting the selected combination; calculating an error covariance from the generated position measurement model; Selecting a combination with the smallest position error using the error covariance, and measuring the position using the position measurement related information received from the nodes included in the combination with the smallest position error .

In one embodiment, the step of selecting a plurality of nodes among the neighboring nodes comprises the steps of: confirming, from each of the neighboring nodes, the propagation degree indicating the number of times the position value has been updated from the initial position value; And selecting only the nodes having the propagation degree lower than a predetermined level among the surrounding nodes.

In one embodiment, the initial position value is a value calculated using a global positioning system (GPS) or a global navigation satellite system (GNSS) And the number of times the position value is updated from the value.

In one embodiment, the generating of the at least one combinations is a step of generating at least one combination constituted by a minimum number of nodes required for position measurement among the selected nodes.

The apparatus for measuring a position of a mobile node according to an embodiment of the present invention minimizes an error by allowing a position to be measured from a combination of anchors having a minimum error so that a more accurate position can be measured, There is an effect to be able to.

1 is a block diagram showing the configuration of a position measuring apparatus according to an embodiment of the present invention.
2 is a conceptual diagram for explaining a method for minimizing an accumulated error using a propagation diagram in a position measuring apparatus according to an embodiment of the present invention.
Figs. 3A and 3B are conceptual diagrams showing an example of setting the propagation degree described in Fig. 2. Fig.
4 is a conceptual diagram for explaining a method of minimizing an accumulated error by calculating a positioning covariance in a position measuring apparatus according to an embodiment of the present invention.
Figs. 5A and 5B are conceptual diagrams for explaining an estimated position error that may occur when a position is measured from an adjacent anchor. Fig.
FIG. 6 is a conceptual diagram for explaining a case where anchors are selected based on the propagation degree described in FIG. 2 when selecting anchors in the method described in FIG.

It is noted that the technical terms used herein are used only to describe specific embodiments and are not intended to limit the invention. Also, the singular forms "as used herein include plural referents unless the context clearly dictates otherwise. In this specification, "comprises" Or "include." Should not be construed to encompass the various components or steps described in the specification, and some of the components or portions may not be included, or may include additional components or steps And the like.

Further, in the description of the technology disclosed in this specification, a detailed description of related arts will be omitted if it is determined that the gist of the technology disclosed in this specification may be obscured.

Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings. In the following description, the TWR-based positioning system will be described as an example. Accordingly, 'tag' used herein is a mobile node that does not know its location, and refers to a node to measure a position. An 'anchor' measures its own position, It is assumed that it refers to a mobile node. In the following description, it is assumed that the anchor and the tag can be switched to each other through the cooperative positioning.

In order to facilitate a complete understanding of the present invention, a basic principle of the present invention will be described. In the present invention, a location quality indicator (LQI) is introduced to measure its fixed position value through GPS or GNSS Set the propagation diagram of the nodes to 0, set the worst propagation diagram of the mobile node (anchor) used at the collaborative positioning to n, and set the propagation diagram of the mobile node designated by the tag to perform cooperative positioning to n +1. Then, a predetermined number or more of anchors may be selected based on the propagation degree, and the position may be measured.

Alternatively, the position measuring apparatus according to the embodiment of the present invention may calculate the positioning covariance (the covariance of the error included in the measurement position) from surrounding anchors that can be used for measuring the current position, The position may be measured from a certain number or more of the anchors selected based on the positioning covariance value.

Alternatively, the position measuring apparatus according to the embodiment of the present invention may select a certain number of anchors that can generate the smallest cumulative error using both the propagation degree and the positioning covariance, and measure the position from the selected anchors have.

1 is a block diagram showing the configuration of a position measuring apparatus according to an embodiment of the present invention.

1, the apparatus for measuring a position of a mobile node according to an embodiment of the present invention includes a communication unit 106, a covariance calculation unit 108, a propagation calculation unit 110, a memory 104, (112), and a control unit (100). And may further include a display unit 102. [ However, the components shown in FIG. 1 are not essential, and may have more or fewer components.

Hereinafter, the components will be described in order.

The communication unit 106 may include one or more modules that enable wireless communication with the nodes around the position measuring device. The communication unit 106 may request at least one neighboring node for information necessary for calculating its own position, or may transmit at least one neighboring node its current position value or the neighboring node needs to calculate the position Information can be transmitted. Or a position value measured from GPS or GNSS.

The position measuring unit 112 may obtain the current position from the at least one neighboring node through the communication unit 106 using the information for the received position measurement (for example, a position measurement value for each surrounding node) . The position measuring unit 112 may calculate at least one position measurement value from a predetermined number or more of peripheral nodes and may generate a measurement model based on the calculated position measurement values.

In the present invention, the positioning covariance when performing positioning using a mobile node that calculates its position through GPS or GNSS is derived. For this, the covariance calculation unit 108 may obtain an error covariance of the noise (error) included in the calculated position measurement value from the measurement model. The covariance calculation unit 108 analyzes the correlation from the errors included in the at least one position measurement values, and calculates a covariance according to the correlation. The residual position can be calculated from the at least one position measurement value using the calculated error covariance. Here, 'residual position' refers to the amount of change in the existing position, and refers to the difference between the existing position measurement value and the newly measured position measurement value. The covariance calculation unit 108 may calculate the covariance positioning covariance based on the residual position and the change amount of the measured position value.

The propagation factor calculation unit 110 sets the propagation degree to 0 if the position measuring apparatus according to the embodiment of the present invention measures its position through GPS or GNSS. However, when the position measuring apparatus according to the embodiment of the present invention measures its position using the position measurement values calculated by the neighboring nodes, the position measurement value is set to a larger value than the propagation degree set in the node transmitting the position measurement value Set the propagation diagram.

For example, if the position measurement is received from a node having the propagation power of '1', the propagation factor calculation unit 110 of the position measuring apparatus according to the embodiment of the present invention calculates the propagation factor The degree can be set to 1 + 1, i.e., 2. This means "position value measured using the position measurement value calculated from the node having the propagation degree of 1 ", and the position value measured through GPS or GNSS at the beginning, that is, The position measurement value may be propagated to a position measuring device according to an embodiment of the present invention via a node having a propagation degree of '1'.

In the following description of the present invention, it is assumed that a specific node receives a position value and measures its own position value to 'update' the position value. Accordingly, the 'propagation degree' Quot; updated " by at least one node from the position value. Therefore, in the above example, the node having the propagation degree of '1' updates the initial position value once, that is, at least one node calculates the position value with the initial position value as the reference position value, Quot; 2 " may be a position value calculated by using the position value calculated based on the initial position value as the reference position value again. Here, the 'reference position value' means a previously calculated position measurement value of the anchor node around the tag node for measuring the position of the tag node itself.

In this way, the LQI (Location Quality Indicator) is used to display the degree of propagation of the first measured position value by increasing the propagation degree one by one when another node measures the position value using the nodes for which the position value is measured will be. That is, the propagation degree represents the number of times the position value has been updated from at least one of the nodes from the initial position value. Since the error is included every time the position value is calculated from the node, the propagation degree is accumulated every time the position value is updated To display the error.

Therefore, the higher the propagation degree, the earlier the position value calculated by GPS or GNSS reflects the position value measured by more nodes, which may mean that there are many errors included. The propagation factor calculation unit 110 may display a qualitative characteristic of the cumulative error included in the currently measured position value, by setting the propagation degree.

Meanwhile, the control unit 100 may measure a position value having a minimum error using at least one of the propagation degree calculated by the propagation degree calculation unit 110 or the cooperative positioning covariance calculated by the covariance calculation unit 108 . For example, since the controller 100 has propagated through more nodes as the propagation degree is higher, it can be considered that errors can be accumulated more.

That is, the controller 100 may select only the ones having the propagation degree lower than a predetermined level among the at least one nearby anchor that can be used for measuring the current position, and may use the selected position to measure the position . Alternatively, the control unit 100 may allow the position to be measured using the at least one neighboring anchor that the cooperative positioning covariance calculated through the covariance calculation unit 108 can have the minimum value (optimization using error covariance).

Alternatively, the control unit 100 may measure the position using both the propagation degree and the cooperative positioning covariance result. That is, the controller 100 may select only the surrounding anchors having a propagation below a certain level to further reduce the calculation amount, and determine at least one combination that can be generated from the selected anchors. Then, the control unit 100 can calculate the cooperative positioning covariance for each determined combination, and can select the combination having the calculated cooperative positioning covariance as the minimum value. The controller 100 may calculate the position measurement value (the optimization of the position measurement value) having the minimum accumulated error by measuring the position from the selected combination of anchors.

The operation of the controller 100 will be described in detail with reference to FIGS. 2, 4 and 6.

Meanwhile, the memory 104 may store a program for the operation of the control unit 100, and may temporarily store input / output data (for example, a calculated covariance value or propagation diagram).

The display unit 102 displays information on anchors around the position measuring apparatus according to the embodiment of the present invention and a plurality of combinations that can be generated by at least a part of the anchors, And a covariance result value calculated from the covariance matrix.

According to the above description, the controller 100 of the position measuring apparatus according to the embodiment of the present invention calculates an optimized position measurement value (a position measurement value with the minimum accumulated error) using at least one of the propagation map and the cooperative positioning covariance It can be calculated.

FIG. 2 is a view for explaining a method for minimizing the cumulative error using only the propagation angle in the position measuring apparatus according to the embodiment of the present invention. 3A and 3B are conceptual diagrams illustrating an example of setting the propagation diagram described with reference to FIG.

Referring to FIG. 2, the controller 100 of the position measuring apparatus according to the embodiment of the present invention selects nodes that are determined as 'anchors' among surrounding nodes when the position measurement is started (S200). That is, the control unit 100 can search for the node where its own position measurement value is calculated in its vicinity, and select the nodes.

Then, the controller 100 can extract only the selected anchors whose propagation degrees are less than a predetermined level (S202). Here, the propagation degree is for indicating the degree of propagation of the position value measured first as described above. That is, the higher the propagation degree, the earlier the position value calculated by GPS or GNSS reflects the position value measured by the more nodes, which means that there are many errors.

This propagation degree can be determined according to the propagation degree of the surrounding anchor used at the time of the position measurement. For example, as shown in FIG. 3A, when the propagation degree of the surrounding anchors 302, 304, 306, and 308 transmitting the position measurement value is '0', the control unit 100 determines The propagation degree of the position measuring apparatus 300 can be set to '1'. This is because the position is measured using the position measurement of the anchors having the propagation degree of '0'.

However, if the propagation degree of any one of the surrounding anchors used for measuring the position is not '0', the propagation degree of the position measuring apparatus according to the embodiment of the present invention may not be '1'. FIG. 3B shows this example.

Referring to FIG. 3B, an anchor 352, 354 having a propagation degree of '0' and an anchor 356 having a propagation degree of '0' are used in FIG. (350) measures the position. In this case, the controller 100 can set the propagation degree of the position measuring apparatus 350 according to the embodiment of the present invention according to the propagation degree of the anchor 356 having a larger propagation degree, that is, the anchor 356.

Therefore, as shown in FIG. 3B, when the position is measured using the position measurement value calculated by the anchor 356 having the propagation degree of '1', the controller 100 determines that the propagation degree of the anchor 356 is '1' , It is possible to set its propagation degree to '2'.

On the other hand, when extracting the anchors, the controller 100 may preferentially extract a predetermined number of anchors having the minimum propagation degree. For example, the controller 100 may extract a predetermined number of anchors having a propagation degree of '0'. Alternatively, when the predetermined level is '0', the control unit 100 may determine that the anchor where the propagation degree is '0' among surrounding anchors, that is, the accurate position is measured by GPS or GNSS around the anchor, Only the extracted nodes may be extracted.

Then, the controller 100 receives the position measurement value from the currently extracted anchors, and can measure the position using the received value (S204). Accordingly, the controller 100 selects only the anchors whose propagation degrees are less than or equal to a certain level, and therefore, only the anchors whose cumulative errors are below a certain level can be used for the position measurement. Thus, an optimized position measurement value with a minimized cumulative error can be obtained. Then, the controller 100 can calculate its own propagation degree based on the propagation degree of the currently extracted anchors.

Meanwhile, FIG. 4 is a conceptual diagram for explaining a method for minimizing an accumulated error by calculating a positioning covariance in the position measuring apparatus according to the embodiment of the present invention. 5A and 5B are conceptual diagrams for explaining an estimated position error that may occur when a position is measured from an adjacent anchor.

Referring to FIG. 4, the controller 100 of the position measuring apparatus according to an embodiment of the present invention, when the position measurement is started, determines whether or not an 'anchor' (S400). Then, the controller 100 determines at least one combination that can be generated from the selected anchors (S402). Here, the combination is for the controller 100 to measure its position from the selected anchors, and may be composed of a minimum number of nodes necessary for position calculation. For example, if there are five anchors in the position measuring apparatus according to the embodiment of the present invention, and the minimum number required for position calculation is three, the controller 100 sets the five nodes to 3 And combinations of three, four, and five different nodes, respectively.

If the combinations are generated in step S402, the controller 100 may select any one of the combinations and generate a position measurement model by estimating positions from the anchors constituting the combination (S404).

FIG. 5A shows an example showing such a positioning scenario.

번째 앵커가 GPS 또는 GNSS로 구한 3차원위치 측정값에서 오차 벡터

가 존재할 때 오차 공분산

이며, 이는 3차원 공간에서 타원체 모양으로 나타내어질 수 있다. For example,

The second anchor calculates the error vector in the three-dimensional position measurement value obtained by GPS or GNSS

When there is an error covariance

, Which can be expressed in an ellipsoid shape in a three-dimensional space.

At this time, it is assumed that one node, which is unknown to the position as shown in FIG. 5A, acquires TWR measurements with three or more anchors that know its position value. At this time, the propagation of the positioning error corresponds to the covariance, and the propagation amount corresponds to the error covariance projected with the viewing angle vector.

와 위치 오차 벡터

와 내적으로 수식화할 수 있다. FIG. 5B is a schematic representation of TWR estimates for modeling the effect of this positioning error propagation on TWR estimates. The node designated by the tag generates the node and TWR estimate specified by the anchor. The TWR estimate can be expressed as the sum of the distance between the actual antennas and the measurement noise. However, each node specified as an anchor may be different from the expected position and actual position of the antenna, and this amount may appear as an actual estimated position error. In this case,

And the position error vector

And can be formulated internally.

는 태그로 지정된 노드에서 거리 추정을 수행하고자 하는

번째 앵커 방향을 가리키는 단위 벡터이다. 이를 수식으로 나타내면 하기 수학식 1과 같다. Here,

To perform distance estimation at the node designated by the tag

Lt; RTI ID = 0.0 > anchor < / RTI > This can be expressed by the following equation (1).

는 태그로 지정된 노드의 미지의 위치이며,

는 앵커로 지정된

번째 앵커의 위치 측정값이며,

의 값을 가진다. 이 때 태그로 지정된 노드와 앵커로 지정된

번째 앵커의 앵커의 협업 측위 TWR 추정치는 하기 수학식 2와 같이 나타낼 수 있다. From here

Is the unknown location of the node specified by the tag,

Is specified as an anchor

Th anchor,

Lt; / RTI > At this point, the node specified with the tag and the anchor specified

The TWR estimate of the cooperative positioning of the anchor of the second anchor can be expressed by Equation (2) below.

는 분산이

인 측정치 잡음이다. here

Is distributed

Is the measured noise.

) 공분산을 구하는 과정은 하기 수학식 3과 같다. The controller 100 may calculate the error covariance included in the measured value model using the measured value model in step S406, as shown in Equation 2, in step S404. Here, the error in the measurement model

) The process of obtaining the covariance is shown in Equation 3 below.

Using the equation derived from Equation (3), the TWR measurement covariance matrix can be summarized as Equation (4).

The TWR measurement covariance matrix shown in equation (4) can be the cooperative positioning TWR measurement of the present invention. When the cooperative positioning TWR measurement value is calculated, the controller 100 can calculate the residual position of the position estimate that may occur at the time of the position measurement, as shown in Equation (5) (S408).

는 위치 변화의 분포를 말하는 것이며,

는 잔여 위치, 즉 기존 위치에서의 현재 변화량을 말하는 것이다. Here,

Is a distribution of positional changes,

Quot; refers to the remaining position, i.e., the current amount of change in the existing position.

의 공분산 결과로부터 산출될 수 있다. When the residual position estimate is calculated as described above, the controller 100 calculates the cooperative positioning covariance from the calculated residual position estimate (S410). For example, the cooperative positioning covariance may be a distribution of positional changes,

Lt; / RTI >

의 측위 공분산을 가지고 있는 태그로 지정된 노드가 첫 번째 앵커로 지정되었으며, 새로운 태그로 지정된 노드가 측위를 시작하는 경우의 TWR 측정치 공분산은 하기 수학식 7과 같이 산출될 수 있다. If the cooperative position estimation is performed using the TWR estimate

The TWR measurement covariance when the node designated by the tag having the positioning covariance is designated as the first anchor and the node designated by the new tag starts positioning can be calculated as shown in Equation (7).

로 계산이 가능하다. Therefore, the cooperative positioning covariance can be expressed by Equation (6)

Can be calculated.

If the cooperative positioning covariance according to the combination of the currently selected anchors is calculated in step S410, the control unit 100 determines whether the positioning covariance for all the generated combinations is calculated (S412). If it is determined in step S412 that the cooperative positioning covariances for all combinations are not calculated, the controller 100 selects another combination (S416). In step S404, the controller 100 proceeds to step S410 to calculate the cooperative positioning covariance of the anchor nodes constituting the currently selected combination.

However, if it is determined in step S412 that the covariance positioning covariance for each of all the combinations generated in step S402 has been calculated, the controller 100 determines the combination anchors having the minimum value among the currently calculated cooperative positioning covariance values Select. Then, the position is measured using the selected anchors. That is, the controller 100 selects only the anchors constituting the combination having the minimum cooperative positioning covariance, and measures the position of the selected anchors from the position values of the selected anchors, thereby obtaining a position measurement result in which the cumulative error is minimized .

As shown in FIG. 2, the control unit 100 may use only the propagation degree of the surrounding anchor nodes, or use the covariance calculation unit 108, as shown in FIG. 4, to determine the cooperative positioning position covariance, The cumulative error can be minimized by measuring the position of the user.

However, these two methods have different advantages and disadvantages. For example, as shown in the following table, there is a problem that the method using the propagation diagram has merits of simple calculation, but it can not confirm how the error actually occurs (quantitative characteristic) since only qualitative characteristics can be confirmed. The method of using the covariance of the error calculated using the covariance calculation unit 108 is advantageous in that it can measure the amount of error actually generated, but the problem that the calculation amount is large is required to calculate the covariance for all possible combinations have.

On the other hand, two different methods can be used to complement each other. For example, the method using the propagation diagram may be used to reduce the calculation amount in a method using the covariance of the error.

FIG. 6 is a view for explaining all of the above two methods. In the method described in FIG. 5, in the case of selecting the anchors, in the case of using the covariance of the error by selecting the anchors based on the propagation diagram shown in FIG. 2 To reduce the amount of computation.

Referring to FIG. 6, when the position measurement is started, the controller 100 can select the anchors among neighboring nodes and confirm the propagation diagram of the selected anchors (S600). Then, the controller 100 can select only the anchors whose propagation calculations are less than a predetermined level among the selected anchors (S602).

That is, when selecting anchors around the anchors, the controller 100 may select only those whose propagation angles are below a certain level so that the anchors whose positioning errors are above a certain level can be excluded from the objects for calculating the covariance have. This is because, when the position value is calculated from the anchors having the positioning error of a certain level or more, there is a high possibility that the positioning error of the certain level or higher is reflected as it is.

Accordingly, if only the anchors having the propagation degree lower than a certain level are selected through the steps S600 and S602, the controller 100 can generate the possible combinations using only the anchors having the smallest positioning error in the vicinity thereof. Accordingly, the number of combinations that can be generated is greatly reduced, and the number of times of calculating the covariance can also be greatly reduced, so that the amount of calculation can also be greatly reduced.

For example, if there are five anchor nodes in the vicinity of the position measuring apparatus according to the embodiment of the present invention, up to nine combinations can be generated assuming that the anchors necessary for position measurement are at least three. And in this case all the error covariances of each of the nine combinations must be calculated. However, if it is assumed in step 600 and step 602 that only nodes having a propagation degree of 1 or less are selected, and that the number of nodes having a propagation degree of 1 or less among the five neighboring nodes is four, Only four nodes having a propagation degree of 1 or less are selected, so that combinations that can be generated can be three. Accordingly, the control unit 100 can calculate the error covariance only for the three combinations, respectively, so that the calculation amount can be greatly reduced.

Therefore, when only an anchor having a certain level of propagation is selected and the position is measured by selecting a combination having the smallest accumulated error, there is no need to perform unnecessary calculation, The quantitative comparison of the covariance provides the advantage of being able to measure the position with the smallest error. Accordingly, in the cooperative positioning method in which the anchor and the nodes repeat the tag-to-anchor conversion and enlarge the positioning area, the error accumulated according to the tag-to-anchor conversion can be minimized.

That is, the position measuring apparatus according to the embodiment of the present invention may operate as a tag and perform an operation according to the above-described operation before its position is measured. Then, after the position is measured, the sensor can operate as an anchor and transmit its calculated position information to another tag serving as a tag. Therefore, when the tag node minimizes the position error as shown in the present invention, it is possible to reduce the cumulative error of the overall cooperative positioning system and consequently to optimize the cooperative positioning system.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the essential characteristics thereof. Therefore, the embodiments disclosed in the present invention are not intended to limit the scope of the present invention but to limit the scope of the technical idea of the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

100: control unit 102:
104: memory 106:
108: Covariance calculation unit 110: Propagation calculation unit
112:

Claims (8)

A communication unit for exchanging information for position measurement from neighboring nodes;
A position measuring unit for measuring a position using information received from the neighboring nodes;
A propagation factor calculation unit for calculating a number of times the position value is updated from the initial position value to display a cumulative position error;
A covariance calculation unit for calculating an error covariance from at least some of the neighboring nodes; And
And a control unit for selecting at least a part of neighboring nodes by using at least one of the calculation result of the propagation coefficient calculation unit or the calculation result of the covariance calculation unit and measuring the current position by using the information received from the selected nodes The position measuring apparatus comprising:
The method according to claim 1,
The initial position value may be calculated by:
Is a position value calculated using a Global Positioning System (GPS) or a Global Navigation Satellite System (GNSS)
The above-
And the number of times at least one node updates the position value from the initial position value.
The apparatus of claim 1,
Selecting only the nodes among the neighboring nodes having at least a certain level of the propagation degree among the neighboring nodes,
Wherein at least some of the selected nodes are selected based on the result of the error covariance calculation and the position is measured using information received from the selected nodes.
The apparatus of claim 3,
Generating at least one combination consisting of a minimum number of nodes necessary for position measurement from nodes having the propagation degree lower than a certain level,
Calculates the error covariance from each of the generated combinations, and measures the position using information received from the nodes constituting the combination having the smallest error covariance.
Selecting a plurality of nodes of the neighboring nodes that know their position value;
Generating at least one combination of at least some of the selected nodes;
Selecting any one of the at least one combination and generating a position measurement model from the nodes constituting the selected combination;
Calculating an error covariance from the generated position measurement model;
Selecting a combination having a minimum position error using the calculated error covariance; And
And measuring the position using the position measurement related information received from the nodes included in the combination having the minimum position error.
6. The method of claim 5, wherein selecting a plurality of nodes among neighboring nodes comprises:
Confirming a propagation degree indicating the number of times the position value is updated from the initial position value, from each of the neighboring nodes; And
Further comprising the step of selecting only those nodes among said neighboring nodes whose propagation degree is below a predetermined level.
6. The method of claim 5,
The initial position value may be calculated by:
A value calculated using a Global Positioning System (GPS) or a Global Navigation Satellite System (GNSS)
The above-
Wherein the number of times the position value has been updated by the at least one node from the initial position value is displayed in order to display the cumulative position error.
6. The method of claim 5, wherein generating the at least one combinations comprises:
And generating at least one combination of the selected nodes that is at least equal to a minimum number required for position measurement.

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