CN104297720A - Target positioning method with assistance of mobile node - Google Patents

Abstract

The invention discloses a target positioning method with the assistance of a mobile node. The mobile node configured with directive antennas and a GPS advances in a network in an obstacle-avoidance mode to traverse the whole network, and during the period, coordinate positions of the mobile node are broadcast periodically. After receiving the coordinates, an unknown node regards the coordinates as virtual beacons, the virtual beacons are virtually projected to a straight line where the head beacon and the tail beacon are located through a virtual projection method, and therefore virtual projection beacons are obtained. Then, a perpendicular foot is solved through an expandable directive antenna positioning method, and perpendicular lines are drawn. After the mobile node enters the communication range of the unknown nodes two or more times, results of two times of entering are drawn randomly, and the intersection point of the two perpendicular lines is solved and serves as coordination positions of the unknown node. A complex distance measurement process is not needed, complex calculation and cooperation of a lot of beacons are not needed either, and the target positioning method is suitable for dynamically evolved event driven scenes and provides supports for target dynamic positioning and event continuous observation.

Description

A kind of mobile node assist under object localization method

Technical field

The present invention relates to a kind of object localization method, especially a kind of be applicable to assist the mobile node of the aspects such as wild animal tracking, emergency management and rescue, dangerous person's recognition and tracking, personal management under object localization method.Belong to radio communication and field of information processing.

Background technology

Target localization has broad application prospects in wild animal tracking, emergency management and rescue, dangerous person's recognition and tracking, personal management etc.

From the need of finding range, target localization can be divided into range finding and non-ranging two large classes.In the localization method of range finding, the method based on RSSI does not consider channel fading, and distance accuracy is not high; And based on the exigent synchronization accuracy of method of time of arrival, so there is people to propose the method for difference time of arrival, but its cost high, need line-of-sight transmission; Also the method for ultra broadband can be utilized to find range, but price is high; And the method for angle measurement needs to measure angle of arrival by aerial array, the problem in sensor bulk, cost and precision etc. can be run on using.

From the need of centralized processing, target localization can be divided into centralized location and the large class of Distributed localization two.Need Centroid in centralized location algorithm, it receives the information that ordinary node sends, and in order to calculate the coordinate of unknown node, therefore needs the energy safeguard of Centroid.And Distributed positioning system does not need center control nodes, it is by the mutual Collaboration computing out position information between unknown node, and the energy distribution of different node is more even.

The localization method that mobile node is assisted is a kind of Distributed localization method, it needs a mobile beacon node to roam at guarded region according to the path of setting in advance, in moving process, periodically send to unknown node the position that signal informs oneself, unknown node calculates oneself position accordingly.This method does not need to dispose a large amount of beaconing nodes in a network, and cost is lower; Mobile node can move according to the path of planning or autonomous selection schemer, uses flexibly.But this method requires that the barrier ability of keeping away of mobile beacon is strong, it is simple to calculate.

Summary of the invention

Technical matters: the object of the invention is for Problems existing in prior art, there is provided a kind of method simple, use flexibly, mobile node that cost is low assist under object localization method, how keep away under barrier advances to solve mobile beacon in complex environment, be problem that unknown node is located.

Technical scheme: mobile node of the present invention assist under object localization method by mobile node location scene in keep away barrier advance, self coordinate of the transmission of period, formed virtual beacon; After unknown node receives the coordinate of virtual beacon, lasting preservation is in the virtual beacon in oneself communication range; Then, the method for virtual projection is utilized to try to achieve the position of virtual projection beacon; Asked the intersection point of two vertical lines of intersection point, as the coordinate position of unknown node; Concrete steps are as follows:

(1) mobile node keeps away barrier advance at the scene, in advance process, periodically send self coordinate, forms virtual beacon;

(2) virtual beacon be in oneself communication range is preserved after unknown node receives virtual beacon;

(3) utilize free routing virtual projection method to carry out virtual projection to virtual beacon, obtain virtual projection beacon, the coordinate figure of solving virtual projection beacon;

(4) utilize expansion directional antenna localization method, solve intersection point and draw vertical line, asking the intersection point of two vertical lines, as the coordinate position of unknown node, realize mobile node assist under target localization.

Described expansion directional antenna localization method step is as follows:

A. twice is got from repeatedly entering virtual projection beacon that unknown node formed to appoint: if straight line enters, be virtual beacon; If curve enters, then it is virtual projection beacon;

B. the intersection point entered each time is solved: if the number of virtual projection beacon is odd number, with middle virtual projection beacon for intersection point draws a vertical line; If the number of virtual projection beacon is even number, then the mean value getting the coordinate of middle two virtual projection beacons is that intersection point draws a vertical line;

C. solve the intersection point of two vertical lines, realize the location of expansion directional antenna.

Described free routing virtual projection method step is as follows:

A. by first virtual beacon with last virtual beacon as end points, draw straight line section as the virtual mobile route of mobile beacon; In formula: j represents the communication range that mobile beacon jth time enters unknown node, represent first virtual beacon stayed after mobile beacon jth time enters unknown node communication range, for its coordinate figure, N _brepresent whole virtual beacon numbers that mobile beacon stays in unknown node communication range; secondary last virtual beacon entering unknown node communication range and stay of mobile beacon jth, for its coordinate figure.

B. except first virtual beacon with last virtual beacon outward, virtual beacon is crossed the boost line that one, each picture is parallel with x-axis, makes these boost lines and virtual mobile route form a series of intersection point, is called the virtual projection beacon of virtual beacon on virtual mobile route, uses virtual projection beacon represent; First virtual projection beacon with last virtual projection beacon be considered as respectively with virtual beacon overlap;

C. virtual projection beacon B is determined _picoordinate figure, work as straight-line segment slope time, coordinate figure is drawn by following formula:

$\left\{\begin{array}{c}{x}_{\mathrm{pi}}^j=\frac{1}{k_j}\·(y_{B_i}^j-y_{B_1}^j)+x_{B_1}^j\\ y_{\mathrm{pi}}^j=y_{B_i}^j\end{array}\right.;$

Otherwise coordinate figure is drawn by following formula:

$\left\{\begin{array}{c}{x}_{\mathrm{pi}}^j=x_{B_i}^j\\ y_{\mathrm{pi}}^j=k_j\·(x_{B_i}^j-x_{B_1}^j)+y_{B_1}^j\end{array}\right.;$

In formula: k _jit is straight-line segment slope, be the coordinate figure of first virtual beacon, the i-th, (i=2 ..., N _b-1) coordinate figure of individual virtual beacon, for virtual projection beacon B _pi, (i=2 ..., N _b-1) coordinate figure.

Beneficial effect: owing to have employed technique scheme, the present invention utilizes the mobile node of outfit 4 directional antennas and GPS to keep away barrier advance in a network, travels through, the coordinate position of the broadcast of period oneself to whole network.It is considered as virtual beacon after receiving these coordinates by unknown node, utilizes the method for virtual projection subsequently by these virtual beacon virtual projections on the straight line at initial and end virtual beacon place, obtains virtual projection beacon.If the number of virtual projection beacon is odd number, with middle virtual projection beacon for intersection point draws a vertical line; If the number of virtual projection beacon is even number, then the mean value getting the coordinate of middle two virtual projection beacons is that intersection point draws a vertical line.After mobile node enters the communication range of unknown node for more than twice, then randomly draw the result entered for twice, ask the intersection point of two vertical lines, as the coordinate position of unknown node.Its method is simple, use is flexible, cost is low, and compared with prior art tool has the following advantages:

(1) do not need complicated ranging process, do not need complicated calculating and the cooperation of a large amount of beacon yet, be suitable for the event-driven scene of dynamic evolution, for target dynamic location and event Continuous Observation provide support;

(2) mobile node can advance according to free routing, and on-the-spot adaptable, mobile node can according to the external environment condition such as barrier, road conditions in advance process, self-adaptative adjustment mobile alignment.

Accompanying drawing explanation

Fig. 1 (a) is the antenna configuration schematic diagram of mobile beacon of the present invention;

Fig. 1 (b) is that mobile node of the present invention moves schematic diagram according to any slope straight line path;

Fig. 2 is expansion directional antenna of the present invention location schematic diagram;

Fig. 3 (a) is that mobile beacon of the present invention moves schematic diagram according to curved path;

Fig. 3 (b) be the present invention by virtual beacon " projection " to the schematic diagram on straight line;

Fig. 4 is the target localization process flow diagram that mobile node of the present invention assists down based on directed electric wire;

Fig. 5 is disaster relief wireless sensor network model schematic of the present invention.

Embodiment

Below in conjunction with accompanying drawing, one embodiment of the present of invention are further described:

Mobile node of the present invention assist under object localization method, use one network area movement, the equipment that can communicate with unknown node as mobile node, the such as small-sized disaster relief aircraft of a Disaster Relief Robot or low latitude.The energy of mobile node is unrestricted, to ensure fully to travel through network according to the path of planning.Mobile node has stronger computing power, and is equipped with GPS module, to ensure that mobile node can the actual position of real-time perception oneself.Mobile node in a network movement time, the coordinate position of periodically broadcast oneself, each position is called a virtual beacon; After unknown node receives the coordinate of virtual beacon, lasting preservation is in the virtual beacon in oneself communication range; Then, the method for virtual projection is utilized to try to achieve the position of virtual projection beacon; Asked the intersection point of two vertical lines of intersection point, as the coordinate position of unknown node; Concrete steps are as follows:

(1) mobile node keeps away barrier advance at the scene, in advance process, periodically send self coordinate, forms virtual beacon;

(2) virtual beacon be in oneself communication range is preserved after unknown node receives virtual beacon;

(3) utilize free routing virtual projection method to carry out virtual projection to virtual beacon, obtain virtual projection beacon, the coordinate figure of solving virtual projection beacon; Described free routing virtual projection method step is as follows:

A. by first virtual beacon with last virtual beacon as end points, draw straight line section as the virtual mobile route of mobile beacon; In formula: j represents the communication range that mobile beacon jth time enters unknown node, represent first virtual beacon stayed after mobile beacon jth time enters unknown node communication range, for its coordinate figure, N _brepresent whole virtual beacon numbers that mobile beacon stays in unknown node communication range; secondary last virtual beacon entering unknown node communication range and stay of mobile beacon jth, for its coordinate figure;

B. except first virtual beacon with last virtual beacon outward, virtual beacon is crossed the boost line that one, each picture is parallel with x-axis, makes these boost lines and virtual mobile route form a series of intersection point, is called the virtual projection beacon of virtual beacon on virtual mobile route, uses virtual projection beacon represent; First virtual projection beacon with last virtual projection beacon be considered as respectively with virtual beacon overlap;

C. virtual projection beacon B is determined _picoordinate figure, work as straight-line segment slope time, coordinate figure is drawn by following formula:

$\left\{\begin{array}{c}{x}_{\mathrm{pi}}^j=\frac{1}{k_j}\·(y_{B_i}^j-y_{B_1}^j)+x_{B_1}^j\\ y_{\mathrm{pi}}^j=y_{B_i}^j\end{array}\right.;$

Work as straight-line segment slope time, coordinate figure is drawn by following formula:

$\left\{\begin{array}{c}{x}_{\mathrm{pi}}^j=x_{B_i}^j\\ y_{\mathrm{pi}}^j=k_j\·(x_{B_i}^j-x_{B_1}^j)+y_{B_1}^j\end{array}\right.;$

In formula: k _jit is straight-line segment slope, be the coordinate figure of first virtual beacon, the i-th, (i=2 ..., N _b-1) coordinate figure of individual virtual beacon, for virtual projection beacon B _pi, (i=2 ..., N _b-1) coordinate figure;

(4) utilize expansion directional antenna localization method, solve intersection point and draw vertical line, asking the intersection point of two vertical lines, as the coordinate position of unknown node, realize mobile node assist under target localization.

Described expansion alignment antenna localization method step is as follows:

A. twice is got from repeatedly entering virtual projection beacon that unknown node formed to appoint: if straight line enters, be virtual beacon; If curve enters, then it is virtual projection beacon;

B. the intersection point entered each time is solved: if the number of virtual projection beacon is odd number, with middle virtual projection beacon for intersection point draws a vertical line; If the number of virtual projection beacon is even number, then the mean value getting the coordinate of middle two virtual projection beacons is that intersection point draws a vertical line;

C. solve the intersection point of two vertical lines, realize expansion directional antenna location.

Embodiment 1,

1. classical directional antenna localization method

In classical directional antenna localization method, mobile node is equipped with 4 directional antenna D ₁, D ₂, D ₃, D ₄, see Fig. 1 (a).Each directional antenna with compass so that the moment allow antenna D ₁, D ₃with x-axis keeping parallelism, antenna D ₂, D ₄parallel with y-axis.Mobile beacon moves with chessboard path, and when it moves along y direction time, unknown node chooses the y value of intermediate value as self from the multiple virtual beacon y values received.When mobile beacon moves along X direction time, similar method is adopted to ask for x value.Be expressed as follows with mathematic(al) representation:

Wherein, the coordinate that (x, y) is unknown node, the coordinate that (x', y') is virtual beacon, N _x, N _ybe respectively mobile beacon at transverse shifting with when vertically moving, by the number of the virtual beacon that unknown node receives.

2. expand directional antenna localization method

Classical directional antenna localization method requires that mobile beacon must move according to chessboard path, namely mobile beacon or transverse shifting, or vertically moves, thus ensures the validity of formula (1).But mobile beacon cannot ensure laterally or longitudinally necessarily having feasible mobile route, therefore classical directional antenna location is expanded to the situation of mobile beacon according to the rectilinear movement of any slope, see Fig. 1 (b).Here N is used _brepresent the virtual beacon quantity in unknown node overlay area.

In classical directional antenna localization method, mobile beacon at least needs the communication entering unknown node for twice: one time horizontal direction enters, in order to solve the horizontal ordinate of unknown node; Another time vertical direction enters, in order to solve the ordinate of unknown node.Extended method also needs at least to enter twice, is respectively used to solve horizontal ordinate and ordinate.After mobile beacon enters the communication range of unknown node, first virtual beacon that unknown node listens to is mobile beacon sends to last virtual beacon of unknown node to be before leaving the communication range of unknown node (N _bvirtual beacon quantity in unknown node overlay area), j here represents that mobile beacon jth time enters the communication range of unknown node.

As shown in Figure 2, from the mobile route Path that jth time enters _jon get a some C _j.Make i-th virtual beacon B _icoordinate be c _jcoordinate be:

Cross C _jdraw one and Path _jvertical straight line VLine _j, so VLine _i, VLine _j(i ≠ j) is (here with the VLine in Fig. 2 ₁, VLine ₂for example) two vertical lines will intersect at a point, and this intersection point is the estimated position of unknown node.Can find out, classical directional antenna localization method is the special case of this method.

At mobile route Path _jon get first virtual beacon with last virtual beacon obtain the equation of mobile route:

$y=\frac{y_{B_{\mathrm{NB}}}^j-y_{B_1}^j}{x_{B_{\mathrm{NB}}}^j-x_{B_1}^j}\·(x-x_{B_1}^j)+y_{B_1}^j---\left(3\right)$

Wherein, (when or time can directly solve by classical directional antenna localization method);

By C _jcoordinate substitute into above formula, obtain VLine finally _jequation is:

$y=-\frac{1}{k_j}\·x+\frac{1}{k_j}{x}_C^j+y_C^j$

Wherein, $k_j=\frac{y_{B_{\mathrm{NB}}}^j-y_{B_1}^j}{x_{B_{\mathrm{NB}}}^j-x_{B_1}^j}.$

$\begin{array}{c}x=\frac{k_i{k}_j}{k_i-k_j}(X_C^j-X_C^i)\\ y=\frac{k_j}{k_j-k_i}(X_C^j-X_C^i)+X_C^i\end{array}---\left(4\right)$

Wherein, k _jfor straight-line segment when mobile beacon jth time to enter unknown node communication range slope, for the intersection point coordinate of trying to achieve when jth time enters, k _iit is straight-line segment when entering for i-th time slope, the intersection point coordinate of trying to achieve when being and entering for i-th time.

3. free routing virtual projection method

Under complex scene, barrier is numerous, and advancing in the substantially unlikely path according to straight line of mobile node, but is keeping away curve in barrier process, forms the curve movement path as shown in Fig. 3 (a).Obviously, no matter such curved path, be classical directional antenna object localization method or extended method, all cannot complete location;

With first virtual beacon in Fig. 3 (a) last virtual beacon for end points, draw straight line section in the drawings be called the virtual mobile route VPath of mobile beacon; Subsequently, remove in mistake overlay area with outside virtual beacon the boost line that one, each picture is parallel with x-axis, these boost lines and virtual mobile route form a series of intersection point, are called the virtual projection beacon of virtual beacon on virtual mobile route, use represent, as shown in Fig. 3 (b); Obviously, can be considered as respectively with overlap.

As can be seen from Fig. 3 (b), only virtual projection beacon need be determined coordinate figure, namely available expansion localization method is located unknown node.

Consider mistake in virtual projection boost line according to the relation (Fig. 3 b) of virtual projection beacon and virtual beacon, known so straight line equation be:

$y=y_{B_i}^j---\left(5\right)$

This straight line with straight line intersection point, be namely virtual projection beacon due to virtual beacon with coordinate all known, therefore equation can represent with formula (3).

Combinatorial formula (5) and formula (3), draw virtual projection beacon B _picoordinate be:

$\left\{\begin{array}{c}{x}_{\mathrm{pi}}^j=\frac{1}{k_j}\·(y_{B_i}^j-y_{B_1}^j)+x_{B_1}^j\\ y_{\mathrm{pi}}^j=y_{B_i}^j\end{array}\right.---\left(6\right)$

Work as B _pi, (i=1 ..., N _b) coordinate all try to achieve after, the coordinate of unknown node can be solved according to the method for expansion directional antenna location.

Said method is according to the method virtual projection parallel with x-axis, is suitable for straight line slope | k _j|>= ¹scene.When | k _j| < ¹time, more suitable according to the method virtual projection parallel with y-axis, to prevent virtual projection beacon to be compressed on a shorter straight-line segment, virtual projection beacon B now _picoordinate be:

$\left\{\begin{array}{c}{x}_{\mathrm{pi}}^j=x_{B_i}^j\\ y_{\mathrm{pi}}^j=k_j\&CenterDot;(x_{B_i}^j-x_{B_1}^j)+y_{B_1}^j\end{array}\right.\text{---}\left(7\right)$

In formula (5), (6), (7): k _jit is straight-line segment slope, be the coordinate figure of first virtual beacon, the i-th, (i=2 ..., N _b-1) coordinate figure of individual virtual beacon, for virtual projection beacon B _pi,(i=2 ..., N _b-1) coordinate figure.

4. mobile node assists down the target localization based on directional antenna

Directional antenna is utilized to carry out the complete algorithm of target localization as follows:

(1) utilize the mobile node of outfit 4 directional antennas and GPS to keep away barrier in a network to advance, whole network is traveled through, the coordinate position of the broadcast of period oneself, form virtual beacon;

(2) unknown node Node _xreceive a virtual beacon B ₁afterwards, lasting preservation is in the virtual beacon B in oneself communication range _i;

(3) basis calculated line slope, if | kj|>=1, utilizes formula (6) to calculate virtual projection beacon B _picoordinate if | k _j| < 1, then use formula (7) to calculate;

(4) appoint the virtual projection beacon getting two virtual projection paths, such as i-th and jth bar, substitute into formula (2) respectively, try to achieve the intersection point of vertical line in two virtual projection paths with

(5) by k _i, k _j, substitute into formula (4), try to achieve the coordinate of unknown node.

Whole algorithmic procedure such as Fig. 3 (a) is that mobile beacon of the present invention moves schematic diagram according to curved path;

Fig. 3 (b) be the present invention by virtual beacon " projection " to the schematic diagram on straight line;

Shown in Fig. 4.

As shown in Figure 5, field rescue scene after occurring for serious disasters and accidents: send helicopter in disaster generating region, give treatment to district's plan favored area temporarily, and may rescue around route between these two regions sows wireless sensor network node, these nodes and treat rescue personnel be all need location unknown node.

Dispose emergency communication command car in interim treatment district, it builds communications platform for on-the-spot with the external world on the other hand on the one hand as the temporary scheduling command centre at whole disaster relief scene.It is very necessary for building Emer-gency Communication for disaster area and extraneous communication, because under disaster scenarios it, neighbouring mobile base station generally by serious damage, causes mobile communications network to be paralysed; Although or do not damaged, disaster has a large amount of librarian use mobile network after occurring, thus causes mobile network's heavy congestion.

The small-sized disaster relief aircraft of a Disaster Relief Robot or low latitude is used to move in network area, i.e. mobile node.The energy of mobile node is unrestricted, to ensure fully to travel through network according to the path of planning.Mobile node has stronger computing power, and is equipped with GPS module, to ensure that Disaster Relief Robot can the actual position of real-time perception oneself.Mobile node in a network movement time, the coordinate position of periodically broadcast oneself, each position is called a virtual beacon.

Mobile node forms the curve movement path as shown in Fig. 3 (a) in moving process.In accordance with the following steps destination node is positioned subsequently:

1. utilize free routing virtual projection method, by virtual beacon virtual projection on virtual mobile route, and the coordinate of solving virtual projection beacon:

(1) first virtual beacon last virtual beacon for end points, draw straight line section be called the virtual mobile route of mobile beacon.

(2) remove in mistake overlay area with outside virtual beacon the boost line that one, each picture is parallel with x-axis, these boost lines and virtual mobile route form a series of intersection point, are called the virtual projection beacon of virtual beacon on virtual mobile route, use represent. be considered as respectively with overlap;

(3) B is determined _picoordinate figure, work as straight-line segment slope time, coordinate figure is drawn by following formula:

$\left\{\begin{array}{c}{x}_{\mathrm{pi}}^j=\frac{1}{k_j}\&CenterDot;(y_{B_i}^j-y_{B_1}^j)+x_{B_1}^j\\ y_{\mathrm{pi}}^j=y_{B_i}^j\end{array}\right.$

Otherwise drawn by following formula:

$\left\{\begin{array}{c}{x}_{\mathrm{pi}}^j=x_{B_i}^j\\ y_{\mathrm{pi}}^j=k_j\&CenterDot;(x_{B_i}^j-x_{B_1}^j)+y_{B_1}^j\end{array}\right.$

In formula: k _jit is straight-line segment slope, be the coordinate figure of first virtual beacon, the i-th, (i=2 ..., N _b-1) coordinate figure of individual virtual beacon, for virtual projection beacon B _pi, (i=2 ..., N _b-1) coordinate figure;

2. utilize expansion directional antenna localization method, solve the coordinate of unknown node:

(1) twice is got from repeatedly entering virtual projection beacon that unknown node formed to appoint: if straight line enters, be virtual beacon; If curve enters, then it is virtual projection beacon;

(2) intersection point entered each time is solved: if the number of virtual projection beacon is odd number, with middle virtual projection beacon for intersection point draws a vertical line; If the number of virtual projection beacon is even number, then the mean value getting the coordinate of middle two virtual projection beacons is that intersection point draws a vertical line.Intersection point coordinate is:

(3) coordinate of intersection point as unknown node of two vertical lines is solved:

$\begin{array}{c}x=\frac{k_i{k}_j}{k_i-k_j}(X_C^j-X_C^i)\\ y=\frac{k_j}{k_j-k_i}(X_C^j-X_C^i)+X_C^i\end{array}$

Wherein, k _jfor straight-line segment when mobile beacon jth time to enter unknown node communication range slope, for the intersection point coordinate of trying to achieve when jth time enters, k _iit is straight-line segment when entering for i-th time slope, the intersection point coordinate of trying to achieve when being and entering for i-th time.

Claims (3)

1. mobile node assist under an object localization method, it is characterized in that: by mobile node location scene in keep away barrier advance, self coordinate of the transmission of period, formed virtual beacon; After unknown node receives the coordinate of virtual beacon, lasting preservation is in the virtual beacon in oneself communication range; Then, the method for virtual projection is utilized to try to achieve the position of virtual projection beacon; Asked the intersection point of two vertical lines of intersection point, as the coordinate position of unknown node; Concrete steps are as follows:

(1) mobile node keeps away barrier advance at the scene, in advance process, periodically send self coordinate, forms virtual beacon;

(2) virtual beacon be in oneself communication range is preserved after unknown node receives virtual beacon;

(3) utilize free routing virtual projection method to carry out virtual projection to virtual beacon, obtain virtual projection beacon, the coordinate figure of solving virtual projection beacon;

(4) utilize expansion directional antenna localization method, solve intersection point and draw vertical line, asking the intersection point of two vertical lines, as the coordinate position of unknown node, realize mobile node assist under target localization.

2. mobile node according to claim 1 assist under object localization method, it is characterized in that: described expansion directional antenna localization method step is as follows:

A. twice is got from repeatedly entering virtual projection beacon that unknown node formed to appoint: if straight line enters, be virtual beacon; If curve enters, then it is virtual projection beacon;

B. the intersection point entered each time is solved: if the number of virtual projection beacon is odd number, with middle virtual projection beacon for intersection point draws a vertical line; If the number of virtual projection beacon is even number, then the coordinate mean value getting middle two virtual projection beacons is that intersection point draws a vertical line;

C. solve the intersection point of two vertical lines, realize the location of expansion directional antenna.

3. mobile node according to claim 1 assist under object localization method, it is characterized in that: described free routing virtual projection method step is as follows:

A. by first virtual beacon with last virtual beacon as end points, draw straight line section as the virtual mobile route of mobile beacon; In formula: j represents the communication range that mobile beacon jth time enters unknown node, represent first virtual beacon stayed after mobile beacon jth time enters unknown node communication range, for its coordinate figure, N _brepresent whole virtual beacon numbers that mobile beacon stays in unknown node communication range, secondary last virtual beacon entering unknown node communication range and stay of mobile beacon jth, for its coordinate figure;

B. except first virtual beacon with last virtual beacon outward, virtual beacon is crossed the boost line that one, each picture is parallel with x-axis, makes these boost lines and virtual mobile route form a series of intersection point, is called the virtual projection beacon of virtual beacon on virtual mobile route, uses virtual projection beacon represent; First virtual projection beacon with last virtual projection beacon, be considered as respectively with virtual beacon overlap;

C. virtual projection beacon B is determined _picoordinate figure, work as straight-line segment slope time, coordinate figure is drawn by following formula:

$\left\{\begin{array}{c}{x}_{\mathrm{pi}}^j=\frac{1}{k_j}\&CenterDot;\left(y_{B_i}^j{-y}_{B_1}^j\right)+x_{B_1}^j\\ y_{\mathrm{pi}}^j=y_{B_i}^j\end{array}\right.;$

Otherwise coordinate figure is drawn by following formula:

$\left\{\begin{array}{c}{x}_{\mathrm{pi}}^j=x_{B_i}^j\\ y_{\mathrm{pi}}^j=k_j\&CenterDot;(x_{B_i}^j-x_{B_1}^j)+y_{B_1}^j\end{array}\right.;$

In formula: k _jit is straight-line segment slope, be the coordinate figure of first virtual beacon, the i-th, (i=2 ..., N _b-1) coordinate figure of individual virtual beacon, for virtual projection beacon B _pi, (i=2 ..., N _b-1) coordinate figure.