JP2009250627A - Sensor position locating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that large-size and expensive sensors have been required in the case that GPS is built in sensors to determine the positions of sensors of known positions and the problem that surveys on positions and their input in sensors have required time and labor in the case that positions determined through the use of position survey instruments such as GPS are required to be previously input in sensors since at least three sensors of known positions are initially required to determine the self-positions of all the sensors constituting a sensor network in a sensor position locating method by a conventional technique. <P>SOLUTION: Two sensors of known positions are installed in the outermost circumference of a sensor installation region when sensors are to be installed. The self-positions of sensors of unknown positions are determined on the basis of values of measured distances between the two sensors of known positions and the sensors of unknown positions. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention uses two reference sensors whose positions are known in advance in a sensor network in which a plurality of sensors constitute a network by wireless communication, and a plurality of sensors installed based on distance information from these two reference sensors The present invention relates to a sensor position locating method for locating each sensor position.

  A sensor network in which a plurality of sensors constitutes a network by wireless communication. The position of each sensor can be determined by GPS or other equipment without performing position surveys one by one. Application to surrounding intruder security is considered.

  Conventionally, when determining the self-position of each sensor, the position of each sensor is calculated based on the distance between each sensor and a sensor having three or more known positions. If there are three or more sensors whose positions are already known in the sensor network, the self-position can be determined from the distance to these sensors, and the sensor whose self-position is determined becomes a sensor whose new position is known. By repeating this, all the sensors in the sensor network are finally sensors whose positions are known (see, for example, Patent Document 1).

JP 2006-234425 A

In the sensor position locating method according to the prior art, in order to determine the self-position of all the sensors constituting the sensor network, a sensor having at least three known positions is required first. It is necessary to determine the position of the sensor whose position is already known by incorporating the GPS in the sensor, or to input the position obtained in advance using a position surveying instrument such as GPS to the sensor.
However, in the former case, there is a problem that the sensor is large and expensive, and in the latter case, it takes time to measure the position and input it to the sensor.

  The present invention has been made to solve the above-described problems, and provides a method for locating the position of a sensor while reducing the number of sensors whose positions that are first required are known. Objective.

  The sensor position locating method according to the present invention uses two reference sensors of a first reference sensor and a second reference sensor whose positions are known in advance in a sensor network in which a plurality of sensors constitute a network by wireless communication. A sensor position locating method for locating a sensor position of a target third sensor based on distance information between two reference sensors, wherein the first reference sensor and the second sensor are connected to the sensor. Installing on the outer periphery of the network; the position of the first reference sensor; the position of the second reference sensor; the distance between the first reference sensor and the third sensor; Calculating a plurality of positions of the third sensor based on a distance between a second reference sensor and the third sensor; and, among the calculated positions, the sensor network. Extracting position on the inside of the outer periphery of the click, the steps of the extracted location is determined to be the position of the third sensor, and a.

  According to the present invention, the position of the sensor can be determined in a state in which the number of sensors whose positions that are first required in the position determination of the sensor are known is reduced.

Embodiment 1 FIG.
FIG. 1 and FIG. 2 are diagrams for explaining a sensor position locating method according to this embodiment. 1 is a first sensor with a known position, 2 is a second sensor with a known position, and 3a to 3j are self-positions. A plurality of sensors 10 for calculating the number 10 are management devices that manage and control the network. Reference numeral 100 denotes an outer peripheral line connecting the first sensor 1 and the second sensor whose positions are known in advance, and the sensors 3a to 3j are installed in one of the areas with the outer peripheral line 100 as a boundary. The first sensor 1, the second sensor 2, and the sensors 3a to 3j are given IDs in advance and can be identified by the IDs.
In the example shown in FIG. 1, the sensors 3 a to 3 j are installed in an area opposite to the area where the management apparatus 10 is located with the outer peripheral line 100 as a boundary. If the area on which the management device 10 is located with the outer peripheral line 100 as a boundary is outside, the sensors 3 a to 3 j are not installed outside the outer peripheral line 100. Thus, the 1st sensor 1 and the 2nd sensor 2 are installed in the position used as the outermost periphery of the sensor network which consists of the 1st sensor 1, the 2nd sensor 2, and the sensors 3a-3j.
In the present embodiment, it is assumed that the first sensor 1 and the second sensor 2 whose positions are known are installed on the outermost periphery of the sensor network, and management is performed on the inner side (that is, with the outer periphery line 100 as a boundary). The case where the position of each sensor of the sensors 3a to 3j in the area opposite to the apparatus 10 is determined will be described.
The first sensor is an example of a first reference sensor, and the second sensor is an example of a second reference sensor.

FIG. 2 is a diagram showing an example of the configuration of the first sensor 1. The first sensor 1 includes a wireless communication unit 31, a target detection unit 32, a self-positioning unit 33, and a communication partner search unit 34.
The target detection means 32 is composed of an IR sensor, a vibration sensor, or the like, and generates a detection signal by detecting, for example, the approach of an intruder by temperature change or ground vibration.
The self-positioning means 33 can obtain the position information of the first sensor 1 by being constituted by GPS, but it may separately input the position information measured using GPS or other surveying means. In this case, there is an effect that the cost and power consumption can be reduced as compared with the case where GPS is used for the first sensor 1.
The communication partner searching means 34 is for transmitting and receiving radio waves between the surrounding sensors 3 and the wireless communication means 9 to identify the surrounding sensors 3 that can communicate with each other, and to acquire distance information between the communicable sensors 3. . Each sensor is previously given an ID for identifying an individual sensor, and the communication partner searching means 7 can identify a surrounding sensor 1 that can communicate with the ID.
The wireless communication unit 31 configures an ad hoc network by communicating with each other, and transmits distance information between the communicable sensor 3 and the sensor 3 to the management device 10.
The first sensor 1 has a built-in clock function in order to record the acquired information and the time of the processing status.
Although the configuration example of the first sensor 1 is shown in FIG. 3, the second sensor 2 has the same configuration as that in FIG.
Further, the sensors 3a to 3j are different from the configuration of the first sensor 1 in that there is no self-position locating means 13, and the description thereof is omitted here.

Here, an example of a method for calculating the distance by the first sensor 1 communicating with the surrounding sensors 3a will be described. The principle is that a predetermined processing time is subtracted from the time difference between the transmission time transmitted to the communication partner and the reception time of the reply signal returned from the communication partner, and the time after the subtraction is divided by the radio wave speed. However, in a communication method using wireless communication, the distance may vary depending on the degree of communication congestion, the spatial noise level, the temperature condition, and the load condition of the calculation unit. For this reason, in Patent Document 1, time synchronization is performed in consideration of the time required for propagation of the synchronization signal. That is, in a wireless network system in which a plurality of devices communicate with each other by wireless communication, the following procedure is performed in order to synchronize the time ticked by the clock built in each device with the reference time.
Procedure 1: A device serving as a time reference (management device) periodically transmits a time synchronization signal.
Procedure 2: In each device subject to time synchronization, the arrival time of the radio signal when the signal of procedure 1 is received is read from the internal clock of the device and transmitted to the common server.
Procedure 3: In the common server, the time information received in Step 2 from each device subject to time synchronization and the transmission time of Procedure 1 to the radio propagation time obtained by dividing the distance between the sender and receiver in Procedure 1 by the radio propagation speed The difference from the reference time of each device to be synchronized with time is calculated from the difference between the times obtained by adding.

By calculating the distance based on the propagation time of the radio wave propagating between the sensors in this way, the first sensor 1 communicates with the surrounding sensor 3a, so that the first sensor 1 and the sensor 3a communicate with each other. It is possible to calculate an accurate distance between the two.

The wireless communication unit 31 of the first sensor 1 transmits the ID of the communicable sensor 3 a and the distance information between the sensor 3 a and the first sensor 1 to the management device 10. Note that the wireless communication means 31 of the first sensor 1 may be the ID of the sensor, the sensor, and the first sensor 1 if there is a sensor (for example, sensor 3d or sensor 3c) other than the sensor 3a. Is also transmitted to the management device 10.
Similarly, the wireless communication means 31 of the second sensor 2 transmits to the management device 10 the communicable sensor 3a and the distance information between the sensor 3a and the second sensor 2. Further, the wireless communication means 31 of the second sensor 2 may include the ID of the sensor, the sensor, and the first sensor if there is a sensor (for example, the sensor 3a or the sensor 3b) other than the sensor 3a. 1 is also transmitted to the management apparatus 10.

Next, the management apparatus 10 stores the ID of the communicable sensor transmitted from the first sensor 1 and the distance information between the sensor and the first sensor 1 in the storage unit.
Similarly, the management apparatus 10 stores the ID of the communicable sensor transmitted from the second sensor 2 and the distance information between the sensor and the second sensor 2 in the storage unit.
The calculation unit of the management apparatus 10 extracts one sensor that can communicate in common with the first sensor 1 and the second sensor 2 and determines the position of this sensor (here, referred to as sensor 3a).

Here, R1 is a distance between the first sensor 1 and the sensor 3a, and R2 is a distance between the second sensor 2 and the sensor 3a.
Since the position (X1, Y1) of the first sensor 1 and the position (X2, Y2) of the second sensor 2 are known, the calculation unit of the management device 10 performs the position (X1, Y2) of the first sensor 1. The position of the sensor 3a can be calculated based on Y1), the position (X2, Y2) of the second sensor 2, and R1 and R2.
However, since there are two sensors whose positions are known, the dummy sensor 4 shown in FIG. 3 is obtained on the side opposite to the sensor 3a.
Here, by installing the first sensor 1 and the second sensor 2 on the outermost periphery of the sensor network, the dummy sensor 4 outside the outermost periphery can be determined to be false and can be removed. Thereby, the two positions of the first sensor 1 and the second sensor 2 are known, and the position of the sensor 3a can be determined correctly.
As described above, in this embodiment, it is a premise that the sensors 3a to 3j are installed inside the outer peripheral line 100, and the management apparatus 10 performs a calculation process so as to locate each sensor position based on the premise. It is assumed that it is set.

  If the position of the sensor 3a is determined, three sensors whose positions are known together with the first sensor 1 and the second sensor 2 can be formed. Henceforth, from the distance from the sensor whose three or more positions are known, Similar to the technique, the positions of all the sensors 3 are finally determined.

FIG. 4 summarizes a flow chart of the sensor position locating method according to the present embodiment described so far.
First, the first sensor 1 and the second sensor 2 are installed on the outermost periphery of the sensor network (step 01). The management apparatus 10 acquires information of the sensor 3 (a communicable sensor ID and a distance from a communicable sensor ID) (step 02). Next, the management apparatus 10 calculates the position of the sensor 3 based on the distance information between the first sensor 1 and the second sensor 2 whose positions are known (step 03). The management device 10 extracts a position in a predetermined area with the outer peripheral line 100 as a boundary from the obtained positions of the plurality of sensors 3 (step 04). The management apparatus 10 determines the position extracted in step 04 as the position of the sensor 3 (step 05). Since the number of sensors whose positions are known becomes three in step 05, the positions of the other sensors 3 are calculated using the first sensor, the second sensor, and the sensor obtained in step 05 (step 05). 06).

  As described above, according to the conventional technology, the number of sensors whose positions required at least three at first are known can be reduced to two, so the number of large and expensive sensors with built-in GPS can be reduced to two. effective. In addition, even if the position obtained using a position surveying instrument such as GPS is input to the sensor, there is an effect of saving one time.

Embodiment 2. FIG.
FIG. 5 is an explanatory diagram of the sensor position locating method according to the present embodiment. There is an error in the position and distance measurement value of a sensor whose position is known, and a circle whose radius is a distance measurement value from a sensor whose position is known is 1 It shows a situation where dots do not intersect.

  1 is a first sensor having a known position, 2 is a second sensor having a known position, 5 is a third sensor having a known position, and 6 is to be located around the position of the first sensor 1 A first circle whose radius is the distance R1 between the sensor and the first sensor 1, and 7 is a distance between the sensor to be located and the second sensor 2 centered on the position of the second sensor 2. A second circle whose radius is the value R2, and 8 is a third circle whose radius is a distance measurement value R3 between the sensor to be located around the position of the third sensor 5 and the third sensor 5. 19 is a first straight line connecting two intersections of the first circle 6 and the second circle 7, 20 is a second straight line connecting two intersections of the first circle 6 and the third circle 8, and 21 is This is a third straight line connecting two intersections of the second circle 7 and the third circle 8.

In the sensor position locating method of the present embodiment, the position of the intersection of the first straight line 9 and the second straight line 10 (Xa, Ya), the position of the intersection of the first straight line 9 and the third straight line 11 ( Xb, Yb) and the position of the intersection of the second straight line 10 and the third straight line 11 (Xc, Yc), the position of the sensor to be located is averaged over the three intersections ((Xa + Xb + Xc) / 3, (Ya + Yb + Yc) / 3). Accordingly, there is an effect that the self position can be uniquely determined even when there is an error in the position of the sensor whose position is known and the distance measurement value.

  Further, when the circles have no intersection, for example, as shown in FIG. 6, when the second circle 7 and the third circle 8 do not intersect and the third straight line 11 does not exist, the first straight line 9 and The intersection (Xa, Ya) of the second straight line 10 is determined as the position of the sensor to be located. Accordingly, there is an effect that the self-position can be determined even when the position of the sensor whose position is known and the distance measurement value have an error.

  In the above, the case where the self-position is determined using a sensor having three known positions has been described. In this case, as the number of circles increases, the number of straight lines connecting the intersections between the circles increases, and the number of intersections between the straight lines also increases accordingly. Therefore, the positions of the average intersections also increase. As the positions of the intersections to be averaged increase, random error components among the position errors and distance measurement errors of sensors with known positions are averaged, and there is an effect of improving the positioning accuracy.

Embodiment 3 FIG.
In the sensor position locating method according to the present embodiment, each sensor is provided with means for measuring received radio wave intensity, and three or more sensors having known positions used for self-localization are selected in descending order of received radio wave intensity. Is.

  Since the transmission radio wave intensity of each sensor constituting the sensor network is equal, the communication state between the sensor whose position should be determined and the sensor whose position is known can be considered better as the reception radio wave intensity is higher. That is, since the influence of the attenuation of the radio wave due to the obstacle is small, the accuracy of the distance measurement value obtained by the transmission / reception of the radio wave is increased, and the accuracy of the position determination is improved.

It is a figure explaining the sensor location method of Embodiment 1 of this invention. It is a structural example of the 1st sensor of Embodiment 1 of this invention. It is a figure explaining the sensor location method of Embodiment 1 of this invention. It is a flowchart of the sensor position locating method of Embodiment 1 of this invention. It is a figure explaining the sensor position locating method of Embodiment 2 of this invention. It is a figure explaining the sensor position location method in case the circles of Embodiment 2 of this invention do not have an intersection.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 1st sensor, 2nd sensor, 3a-3j sensor, 4 dummy sensor, 5 3rd sensor whose position is known, 6 1st circle, 7 2nd circle, 8 3rd circle, 10 Management device 19, 20, 21 straight line, 31 wireless communication means, 32 target detection means, 33 self-localization means, 34 communication partner search means, 100 outer peripheral line,

Claims (3)

In a sensor network in which a plurality of sensors constitute a network by wireless communication, distance information between the two reference sensors using two reference sensors of a first reference sensor and a second reference sensor whose positions are known in advance. Is a sensor position locating method for locating the sensor position of the target third sensor,
Installing the first reference sensor and the second sensor on an outer periphery of the sensor network;
The position of the first reference sensor, the position of the second reference sensor, the distance between the first reference sensor and the third sensor, the second reference sensor and the third reference sensor. Calculating a plurality of positions of the third sensor based on the distance to the sensor;
Extracting a position inside the outer circumference of the sensor network among the plurality of calculated positions;
Determining that the extracted position is the position of the third sensor;
A sensor location method characterized by comprising: Between the position of the first reference sensor, the position of the second reference sensor, the position of the third sensor, and the fourth sensor that newly positions the first reference sensor. Based on the distance, the distance between the second reference sensor and the fourth sensor, and the distance between the third sensor and the fourth sensor, the position of the fourth sensor is determined. A step of locating;
The sensor position locating method according to claim 1, further comprising: A first circle centered on the position of the first reference sensor and a radius between the first reference sensor and the fourth sensor, and a center of the position of the second reference sensor. A second circle whose radius is the distance between the second reference sensor and the fourth sensor; and the third reference sensor and the fourth sensor centered on the position of the third reference sensor; Determining a third circle with a radius between
A first straight line connecting the intersection of the first circle and the second circle, a second straight line connecting the intersection of the first circle and the third circle, the second circle and the second Obtaining a third straight line connecting the intersections of the three circles;
The position of the intersection of the first straight line and the second straight line (Xa, Ya), the position of the intersection of the first straight line and the third straight line (Xb, Yb), and the second Calculating the position of the fourth sensor by ((Xa + Xb + Xc) / 3, (Ya + Yb + Yc) / 3) using the position (Xc, Yc) of the intersection of the straight line and the third straight line;
The sensor position locating method according to claim 2, comprising:

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