CN103455829A - Method for achieving indoor positioning based on RFID - Google Patents

Abstract

The invention discloses a method for achieving indoor positioning based on RFID. The method for achieving indoor positioning based on RFID comprises the following steps that V readers and m reference labels are arranged in a positioning area, and the reference labels are evenly arranged on a marginal area; the multilateral measurement and positioning method is applied to a non-marginal area, and the LANDMARC positioning method is applied to the marginal area. Compared with the method that the multilateral measurement and positioning method is applied to all positioning areas, the method for achieving indoor positioning based on RFID improves the positioning accuracy of overall positioning areas. Compared with the method that the LANDMARC positioning method is applied to all the positioning areas, the method for achieving indoor positioning based on RFID reduces the number of the used reference labels although the overall positioning accuracy is slightly poorer, therefore, the cost of a positioning system is reduced and the difficulty of the arrangement of the reference labels in a special positioning area is reduced.

Description

A kind of method that realizes indoor positioning based on RFID

Technical field

The present invention relates to a kind of method that realizes indoor positioning based on RFID, be specifically related to a kind of tag location of the RFID for indoor locating system method.

Background technology

Radio frequency discrimination RFID (Radio Frequency Identification) is a kind of non-contacting automatic identification technology, its ultimate principle is to utilize radiofrequency signal and Space Coupling (inductive coupling or electromagnetic coupled) transport property, realizes being identified the automatic identification of object.RFID has the unrivaled advantage of many traditional recognition technologies, as noncontact, non line of sight, distance, contain much information, need not manual intervention, multiple goal identifies etc. simultaneously.

Carry out owing to utilizing RF-wise the purpose that bidirectional communication data exchange reaches identification, do not need to set up Mechanical Contact between recognition system and specific objective, the RFID technology has shown huge development potentiality and application space, is considered to one of the most rising infotech of 21 century.Now, RFID is widely used in warehousing management, industrial automation, animal tracking and management, library management, the various fields such as false proof.Equally, also can utilize the RFID technology to realize indoor positioning.

Location technology is a kind of important and practical technology, and it provides abundant absolute position and the information of relative position for people.Indoor positioning technology commonly used mainly contains infrared ray, bluetooth, ultrasound wave, 802.11, RFID technology.Utilize by infrared ray, ultrasound wave and 802.11 technology and realize that the required system in location is more complicated, cost is also higher; Utilize Bluetooth technology to realize that positioning error is larger.The RFID technology is with its noncontact, non line of sight, cost is low, the positioning precision advantages of higher becomes the indoor positioning technology gradually first-selection.

Received signal strength indicator (Received Signal Strength Indictor, RSSI), the wireless signal strength received while being the rfid interrogator identification label, usually with dBm, measured, it is the messaging parameter of and Range-based, and main flow rfid interrogator in the market all starts to support gradually directly to export the function of RSSI, than other messaging parameter, be more prone to obtain.At present, the indoor orientation method based on the RSSI technology mainly comprises polygon measurement and positioning method and LANDMARC localization method.

Polygon measurement and positioning method: model signal propagation path loss model, then utilize this model to obtain the distance between read write line and label, according to known read write line coordinate, list the positioning equation group, finally use the least square method scheduling algorithm to solve the positioning equation group.The coordinate figure of trying to achieve is the estimated value of label to be positioned.The method solves simply, and calculated amount is little but positioning precision is general.Especially in the zone away from from read write line, due to the indoor environment complexity, range error is generally larger, thereby causes positioning error also larger, sometimes even can't realize location.The present invention has proposed a kind of improved localization method on its basis.

The LANDMARC localization method: it is a kind of indoor positioning algorithm based on active RFID system of classics.Its principle is to adopt fixed reference label auxiliary positioning, the comparison between the signal strength values by label to be positioned and the signal strength values of reference label, and employing " nearest-neighbors " weight thought, calculate the position of label to be positioned.The layout of reference label and quantity have very important impact to the setting accuracy of system.

Summary of the invention

The objective of the invention is to solve the problem that in polygon measurement and positioning method, the fringe region positioning error greatly even can't be located.Adopt the principle of reference label by using for reference the LANDMARC localization method, in location, fringe region is arranged equally distributed reference label, and adopt the LANDMARC localization method at the fringe region of arranging reference label, and still adopt polygon measurement and positioning method at non-fringe region.

Purpose of the present invention is achieved through the following technical solutions:

Realize the method for indoor positioning based on RFID, comprise the steps:

Step (1): all read write lines and label (comprising reference label and label to be positioned) position is all in the rectangular coordinate system first quartile and set initial point and coordinate axis, arrange v read write line, a m reference label at locating area, reference label evenly is placed on the marginal portion of locating area, v=3,4 or 5;

Step (2): by v read write line, respectively m reference label and label to be positioned are gathered to RSSI;

Step (3): according to indoor environment, set up the signal propagation path loss model, the RSSI of the label to be positioned received according to read write line, calculate label to be positioned to the distance between each read write line, and to go out label to be positioned according to this Distance Judgment be to be also non-fringe region in fringe region;

Step (4): if label to be positioned in non-fringe region, adopts polygon measurement and positioning method; If label to be positioned, in fringe region, adopts the LANDMARC localization method;

Step (5): the positioning result calculated is presented on positioning map.

The accompanying drawing explanation:

Fig. 1 is the read write line placed in indoor environment of the present invention and the layout structure schematic diagram of label (comprising reference label and label to be positioned).

Fig. 2 is localization method process flowchart of the present invention.

Embodiment:

For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, embodiment of the present invention is described further in detail.But the scope of protection of present invention is not limited to the scope that embodiment is explained.

Shown in Figure 1, locating area is 20 meters * 20 meters, and 4 read write lines are arranged on 4 angles, and 68 reference label are evenly arranged edge region, and the spacing between reference label is 2 meters.Locating area has two labels to be positioned, a label edge region to be positioned, and another is at non-fringe region.

Treat positioning label and carry out location estimation, concrete steps have:

Step (1): all read write lines and label (comprising reference label and label to be positioned) position is all in the rectangular coordinate system first quartile and set initial point and coordinate axis, and the coordinate of read write line is respectively A (0,0), B (0,20), C (20,0), D (20,20);

Step (2): first by 4 read write lines, treat respectively positioning label and gathered its received signal strength value $\stackrel{\&RightArrow;}{S}=\{S_1,{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="DEST\_PATH\_HSB00001108226500011.png"\; state="\{\{state\}\}">S</figure-callout>}}_2,S_3,S_4\};$

Step (3): utilize signal propagation path loss model formula

obtain 4 read write lines to the distance between label to be positioned

judgement relation with 20.6 meters.If

rice, judge that label to be positioned is in fringe region, uses the LANDMARC localization method; If

rice, judge that label to be positioned is in non-fringe region, uses polygon measurement and positioning method.Wherein, the implication of 20.6 meters is that in fringe region the maximal value in the distance between any one o'clock and 4 read write lines is all than 20.6 meters these values greatly.

Step (4): during in fringe region, use the LANDMARC localization method when label to be positioned, it carries out following steps:

Step (a): first by 4 read write lines, respectively 68 reference label are gathered to the received signal strength value

$\stackrel{\&RightArrow;}{{\mathrm{\&theta;}}_1}=\{{\mathrm{\&theta;}}_{\mathrm{1,1}},{\mathrm{\&theta;}}_{\mathrm{2,1}},{\mathrm{\&theta;}}_{\mathrm{3,1}},{\mathrm{\&theta;}}_{\mathrm{4,1}}\},$

$\stackrel{\&RightArrow;}{{\mathrm{\&theta;}}_2}=\{{\mathrm{\&theta;}}_{1,2},{\mathrm{\&theta;}}_{2,2},{\mathrm{\&theta;}}_{3,2},{\mathrm{\&theta;}}_{4,2}\},$

$\stackrel{\&RightArrow;}{{\mathrm{\&theta;}}_3}=\{{\mathrm{\&theta;}}_{1,3},{\mathrm{\&theta;}}_{2,3},{\mathrm{\&theta;}}_{3,3},{\mathrm{\&theta;}}_{4,3}\},$

…，

$\stackrel{\&RightArrow;}{{\mathrm{\&theta;}}_{68}}=\{{\mathrm{\&theta;}}_{1,68},{\mathrm{\&theta;}}_{2,68},{\mathrm{\&theta;}}_{3,68},{\mathrm{\&theta;}}_{4,68}\};$

In formula, θ _{i, m}mean the received signal strength value that i read write line gathers m reference label, i=1,2,3,4; M=1,2 ..., 68.

Step (b): by first reference label signal intensity received

with label signal intensity to be positioned

calculate the Euclidean distance of first reference label and label to be positioned according to the Euclidean distance formula

Step (c): repeating step (b) obtains the Euclidean distance E of all 68 reference label and label to be positioned _m, (m=1,2, L, 68);

Step (d): 68 reference label that step (c) is obtained and the Euclidean distance E of label to be positioned _msort from small to large;

Step (e): select 4 Euclidean distances minimum in step (d) and be worth corresponding 4 reference label; Described 4 reference label are 4 nearest neighbour's labels of distance label to be positioned;

Step (f): according to these 4 position coordinateses that neighbour's label is known, calculate the estimated position of label to be positioned.When the Euclidean distance of certain reference label and label to be positioned is less, think that this reference label and label to be positioned are nearer.The coordinate (x, y) of label to be positioned can be tried to achieve by following formula:

$(x,y)=\underset{k=1}{\overset{4}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_k\&CenterDot;(x_k,y_k)$

In formula, ω _kit is the weight (k=1,2,3,4) of k the reference label nearest with tag distances to be positioned.ω _krule of thumb formula obtains:

${\mathrm{\&omega;}}_k=\frac{1/{{\mathrm{<figure-callout\; id="2"\; label="E\; k"\; filenames="DEST\_PATH\_HSB00001108226500011.png"\; state="\{\{state\}\}">E</figure-callout>}}_k}^2}{\underset{k=1}{\overset{4}{\mathrm{\&Sigma;}}}(1/{E_k}^2)}$

Use polygon measurement and positioning method when label to be positioned during in non-fringe region, it carries out following steps:

Step (a): according to known coordinate and 4 read write lines obtaining and the distance of label to be positioned of read write line

list the positioning equation group:

$\left\{\begin{array}{c}{(x-x_1)}^2+{(y-y_1)}^2={L_1}^2\\ {(x-x_2)}^2+{(y-y_2)}^2={L_2}^2\\ {(x-x_3)}^2+{(y-y_3)}^2={L_3}^2\\ {(x-x_4)}^2+{(y-y_4)}^2{{=\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="DEST\_PATH\_HSB00001108226500011.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}^2\end{array}\right.$

In formula, (x, y) is the estimated coordinates of label to be positioned; (x ₁, y ₁), (x ₂, y ₂), (x ₃, y ₃), (x ₄, y ₄) be respectively the coordinate of read write line A, B, C, D.

Step (b): front 3 equations of system of equations are deducted respectively to the 4th equation, thereby reach the linearizing purpose of quadratic equation, obtain following system of equations:

$\left\{\begin{array}{c}2(x_4-x_1)x+2(y_4-y_1)y={L_1}^2-{{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="DEST\_PATH\_HSB00001108226500011.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}^2-({x_1}^2+{y_1}^2)+({x_4}^2+{y_4}^2)\\ 2(x_4-x_2)x+2(y_4-y_2)y={{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="DEST\_PATH\_HSB00001108226500011.png"\; state="\{\{state\}\}">L</figure-callout>}}_2}^2-{{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="DEST\_PATH\_HSB00001108226500011.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}^2-({x_2}^2+{y_2}^2)+({x_4}^2+{y_4}^2)\\ 2(x_4-x_3)x+2(y_4-y_3)y={L_3}^2-{L_4}^2-({x_3}^2+{y_3}^2)+({x_4}^2+{y_4}^2)\end{array}\right.$

Step (c): definition

$Q=\left[\begin{array}{cc}2(x_4-x_1)& 2(y_4-y_1)\\ 2(x_4-x_2)& 2(y_4-y_2)\\ 2(x_4-x_3)& 2(y_4-y_3)\end{array}\right]$

$b=\left[\begin{array}{c}{L_1}^2-{{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="DEST\_PATH\_HSB00001108226500011.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}^2-({x_1}^2+{y_1}^2)+({x_4}^2+{y_4}^2)\\ {{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="DEST\_PATH\_HSB00001108226500011.png"\; state="\{\{state\}\}">L</figure-callout>}}_2}^2-{L_4}^2-({x_2}^2+{y_2}^2)+({x_4}^2+{y_4}^2)\\ {L_3}^2-{{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="DEST\_PATH\_HSB00001108226500011.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}^2-({x_3}^2+{y_3}^2)+({x_4}^2+{y_4}^2)\end{array}\right]$

Step (d): the formula in step (b) can be written as:

Solve and can obtain by least square method (LS):

Vector in element be the tag coordinate to be positioned (x, y) calculated.

Step (5): the positioning result calculated is presented on positioning map.

It will be appreciated by those skilled in the art that accompanying drawing is the schematic diagram of a preferential embodiment, the invention described above embodiment sequence number, just to describing, does not represent the quality of embodiment.

The foregoing is only preferred embodiment of the present invention, in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (4)

1. a method that realizes indoor positioning based on RFID is characterized in that comprising the following steps:

Step (1): all read write lines and label (comprising reference label and label to be positioned) position is all in the rectangular coordinate system first quartile and set initial point and coordinate axis, arrange v read write line, a m reference label at locating area, reference label evenly is placed on the marginal portion of locating area, v=3,4 or 5;

Step (2): by v read write line, respectively m reference label and label to be positioned are gathered to its received signal strength;

Step (3): according to indoor environment, set up the signal propagation path loss model.The signal intensity of the label to be positioned received according to read write line, calculate label to be positioned to the distance between each read write line, and to go out label to be positioned according to this Distance Judgment be to be also non-fringe region in fringe region;

Step (4): if label to be positioned in non-fringe region, adopts polygon measurement and positioning method; If label to be positioned, in fringe region, adopts the LANDMARC localization method;

Step (5): the positioning result calculated is presented on positioning map.

2. according to the described method of right 1, it is characterized in that described step (3) signal propagation path loss model generally defers to following formula:

$P_r\left(d\right)=P_r\left(d_0\right)-10\mathrm{nlg}\left(\frac{d}{d_0}\right)+X_{\mathrm{\&delta;}}$

In formula, P _r(d) mean the signal strength values that read write line receives at distance label position d place, unit is dBm; d ₀be reference distance, general value is 1 meter; N is path loss index, means the speed that path loss increases with distance, and it mainly is subject to the impact of surrounding environment and buildings, and span is generally 2～4; X _δthat average is 0, the random numbers of Gaussian distribution are that standard deviation is δ, the span of δ is generally 4～10.

3. according to the described method of right 1, it is characterized in that the polygon measurement and positioning method of described step (4) is at first according to the signal propagation path loss model, to obtain label to be positioned to the distance between each read write line, then set up the positioning equation group, finally use the least square method scheduling algorithm to solve the positioning equation group.

4. according to the described method of right 1, it is characterized in that described step (4) LANDMARC localization method is a kind of indoor positioning algorithm based on active RFID system of classics.Its principle is to adopt fixed reference label auxiliary positioning, the comparison between the signal strength values by label to be positioned and the signal strength values of reference label, and employing " nearest-neighbors " weight thought, calculate the position of label to be positioned.

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