CN104793183A - Intersection point judgment based trilateral locating method - Google Patents

Abstract

The invention provides an intersection point judgment based trilateral locating method. The method specifically includes: selecting three reference nodes; arranging a circle for each reference node and calculating an intersection point between any two optional cycles among the three cycles; selecting one intersection point from the intersection points of every two intersection cycles as a vertex of a triangle according to the selection criterion that when two intersection points exist between the two circles, the intersection point closest to the circumference of the third cycle is the vertex of the triangle; taking the triangle center of gravity formed by the three vertexes as the location estimation value of a tag node; calculating location estimation values of reference node combinations; calculating the average value of all tag node location estimation values and taking the average value as the final location of the tag node to realize location of the tag node. The third cycle is taken as the reference, two interaction points between the two cycles are selected, better fault tolerance of the triangle can be determined, the center of gravity of the triangle is closer to the tag node, and the selection method is simple in calculation and easy to implement.

Description

A kind of three limit localization methods judged based on intersection point

Technical field

The invention belongs to sensor node to label node field of locating technology, be specifically related to a kind of three limit localization methods judged based on intersection point, the method can be applied to industry, agricultural, military affairs, business and indoor positioning field.

Background technology

In recent years, along with popularizing of Internet of Things concept, wireless sensor network (Wireless sensor network, WSN) and the location technology of the facing area such as WLAN (wireless local area network) (Wireless Local Network, WLAN) more and more paid close attention to by the researcher in the fields such as industry, agricultural, military affairs, business.The target of WSN wirelessly makes dispersion and independently sensor node is interconnected, composition distributed wireless sensor network, thus process for the environmental information of Real-time Collection, to realize the mutual of user and environment.In environmental information, the very important point is exactly spatial positional information, location-based estimation, and namely location technology is applied to real-life every aspect, as hospital patient wireless supervisory control system, museum's intelligent guidance system etc.In addition, indoor positioning technologies also has very vast potential for future development, wireless family automatic network (the Wireless HomeAutomation Networks of current proposition, WHANs) be exactly the special wireless sensor network correlation technique provided for Smart Home, the technology of existing Zigbee, Z-wave, INSTEON, Wavenis and IP based on IEEE 802.15.4 related protocol standard all provides technical support around related hardware standard and agreement.

Ultra broadband (Ultra wideband, UWB) technology, after within 2006, formally being have passed by US Federal Communication Committee and using it for civilian proposal, is applied to wireless sensor network positioning field greatly.It avoids unlimited segmentation frequency spectrum run into technical bottleneck impassable in physics realization by replacing carrying out splitting signal from wave band or frequency from time upper splitting signal.Ultra broadband frequency of operation is 3.1 ~ 10.6GHz, system bandwidth and the ratio of system centre frequency be greater than 20% or system bandwidth be at least 500MHz, compared with the unlimited electrical resistivity survey examining system of tradition, without the need to carrier signal, directly can produce burst pulse de-energisation antenna.Super-broadband tech has low-power consumption, antijamming capability is strong, insensitive to fading channel, good concealment, penetration capacity are strong, positioning precision is high feature.In recent years, subnanosecond level Ultra-short pulse is utilized to do the large great development of closely placement technology, as UWB Precise Position System, the LocalSense wireless location system of Tsing-Hua University's research and development and the iLocate of Tang En Science and Technology Ltd. that MultispectralSolutions company and facilities engineering service centre of USN develop jointly ^tMsystem.

Whether measure the distance of actual node according to position fixing process, location algorithm is divided into: based on range finding (range-based) location algorithm and the location algorithm without the need to find range (range-free).Based on location algorithm by point-to-point distance or angle information between measured node, the algorithm for estimating such as trilateration (trilateration), triangulation (triangulation) or maximal possibility estimation are used to reduce range error to the impact of location survey; Location can be realized according to information such as network connectivties without the need to location algorithm.Compared to without the need to location algorithm, be easier to hardware implementing based on location algorithm, and be used widely.

Commonly use ranging technology based on ranging localization algorithm and have TOA, TDOA, TOF and AOA etc.TOA (Time of Arrival) algorithm needs nodal exactness ground time synchronized, cannot be used for loose couplings positioning system; TDOA (Time difference of Arrival) Technology Restriction is in ultrasonic propagation distance finite sum NLOS problem to the propagation effect of the signals such as ultrasound wave, and the usual propagation distance of ultrasound wave is 6-9 rice; AOA (Angle ofArrival) is also affected by the external environment, and needs additional hardware, and hardware size and power consumption possibly cannot be used for sensor node; TOF (Time of Flight) technology refer to by measure single node the signal of target sent and time of reception poor, calculate the distance with target.This algorithm without the need to exact time synchronization, and realizes simple, and consume hardware resource less, be applicable to the sensor network of energy priority, the present invention adopts TOF technology to find range.

Three limit localization methods are the processes by the absolute of the distance determination impact point between measuring target point and three known coordinate points or relative position.As shown in Figure 1-2, conventional at present method is least-squares estimation and the method based on geometric center of gravity.Thought based on least-squares estimation makes the Combined estimator mean square deviation of position minimum, by its local derviation, determines the estimated value of target, but in actual location, owing to there is error to set a distance, three circles really can not be allowed to meet at a bit, therefore there is larger error in some cases.Method based on geometric center of gravity refers to the intersection point intersected between two by solving three circles, builds a geometry polygon to its line, then asks the polygonal geometric center of gravity of its geometry to be object space coordinate estimated value.The method can reduce the error because dysmetria causes, and realizes simple, is easy to calculate.But, because the two circle intersection points chosen are probably too wide in the gap with impact point, thus increase error.To this problem, the present invention proposes the solution of intersection point decision algorithm.

In sum, location subject matter is still based on existing hardware basis at present, realizes the location algorithm of cheap high-precision low-power consumption.

Summary of the invention

In view of this, the problem that the present invention is directed to is that the factor such as multipath transmisstion, sighting distance being limited to signal causes dysmetria and the two circle intersection points that bring are probably too wide in the gap with impact point, thus utilize traditional three limit localization methods to bring larger positioning error, to such an extent as to positioning precision demand in actual life cannot be met; The present invention proposes a kind of three limit localization methods judged based on intersection point, the method is in the process determining two circle intersection points, have employed intersection point decision criteria, utilize this criterion can choose from the intersection point close to target, this criterion is simple to operate, being easy to realize, when not causing computation burden, the object improving positioning precision can being reached very well.

Realize technical scheme of the present invention as follows:

Based on the three limit localization methods that intersection point judges, detailed process is:

(1) from N number of anchor node of spatial arrangement, 3 are selected as reference node;

(2) for each reference mode, with its present position for the center of circle, with the distance between itself and the label node of required location for radius establishes circle; Calculate the intersection point between any two circles in 3 circles;

(3) from the intersection point of each crossing two circle, an intersection point is selected as vertex of a triangle, selected criteria is: when only there is an intersection point between two circles, using this intersection point as vertex of a triangle, when between two circles, intersection point exists two, judge from the nearest intersection point of the circumference of the 3rd circle as a leg-of-mutton summit;

(4) triangle core that three summits will determined by step (three) are formed is as the location estimation value of label node;

(5) reselect 3 anchor nodes as with reference to node, calculate the location estimation value of label node according to the mode of step (two)-(four), till the array configuration of all reference modes is all traversed;

(6) calculate the average of all label node location estimation values, and it can be used as the final position of label node, realize the location of label node.

Beneficial effect

Method provided by the invention, with the 3rd circle for reference, by choosing two intersection points between two circles, make the triangle determined have better fault-tolerance, triangle core closer to label node, thus can improve the estimated accuracy of coordinates of targets, this choosing method calculates simple, is easy to realize.

Accompanying drawing explanation

Fig. 1 is ideally three limit localization method schematic diagram.

Fig. 2 is the three limit localization method schematic diagram based on gravity model appoach.

Fig. 3 is the process flow diagram that the present invention is based on the three limit localization methods that intersection point judges.

Fig. 4 is anchor node and label node schematic layout pattern.

Fig. 5 is the three limit localization methods that propose of the present invention and the three traditional limit localization methods positioning result at different anchor node number.

Fig. 6 is the three limit localization methods that propose of the present invention and penetrates the positioning error of three limit localization methods at different anchor node number based on barycenter.

Embodiment

Below in conjunction with instantiation, the present invention is described in detail.

When label node (target) positioning function starts, label node outwards sends request; The anchor node of spatial arrangement receives from after label node request, sends ultra-wideband impulse signal immediately to label node; After label node receives the ultra-wideband impulse signal from anchor node, immediately this ultra-wideband impulse signal is returned to anchor node; Anchor node calculates the flight time ToF of signal, thus calculates the distance d with label node _i, and be stored in hardware register; Anchor node will distribute to self ID i, distance d _iwith positional information (x _i, y _i) (i=1,2 ...) send to gateway; The information that gateway will receive, the three limit localization methods adopting the present invention to propose calculate the position of label node, and detailed process is, as shown in Figure 3:

(1) select from N number of anchor node information of spatial arrangement wherein 3 anchor nodes as with reference to node.

(2) for each reference mode, with its present position for the center of circle, with the distance between itself and label node for radius establishes circle; Calculate the intersection point between any two circles in 3 circles; Detailed process is:

If 3 distances between reference mode and label node are d _i, the position of 3 reference modes is (x _i, y _i), i=1,2,3; Suppose that label node coordinate is (x _t, y _t), then meet following equation.

(x _i-x _t) ²+(y _i-y _t) ²＝d _i ²

The equation of simultaneous wherein two reference mode correspondences (such as 1,2), by solving equation group, obtains the intersection point (x of these two node corresponding circles ₁₂, y ₁₂) and (x ₁₂', y ₁₂').

(3) from the intersection point of each crossing two circle, an intersection point is selected as vertex of a triangle, selected criteria is: when only there is an intersection point between two circles, using this intersection point as vertex of a triangle, when between two circles, intersection point exists two, judge from the nearest intersection point of the circumference of the 3rd circle as a leg-of-mutton summit;

Such as, between first circle and second circle, there are two intersection point (x ₁₂, y ₁₂) and (x ₁₂', y ₁₂') time, now calculate the distance between two intersection points and the 3rd the round heart respectively with then the 3rd radius of a circle d is utilized ₃poor with calculated distance, the distance between two intersection points and the 3rd round week can be obtained, as follows:

${(d_3-\sqrt{{(x_{12}-x_3)}^2+{(y_{12}-y_3)}^2})}^2<{(d_3-\sqrt{{({x_{12}}^{\&prime;}-x_3)}^2+{({y_{12}}^{\&prime;}-y_3)}^2})}^2$

If is less than is set up, then this time point (x is described ₁₂, y ₁₂) from the 3rd circle circumference more close to, therefore choose (x ₁₂, y ₁₂) be vertex of a triangle (x based on gravity model appoach _oi, y _oi), otherwise, then choose (x ₁₂', y ₁₂') be (x _oi, y _oi).

(4) leg-of-mutton three summit (x must be determined by step 3 _oi, y _oi).Obtaining according to gravity model appoach selects anchor node ID to be C ₁, C ₂, C ₃time label node coordinate location estimation value

(5) reselect 3 nodes as with reference to node, calculate the location estimation value of label node according to the mode of step (two)-(four), until the array configuration of planting reference mode is all traversed, and now obtains plant label node location estimation value

(6) calculate the average of all label node location estimation values, and it can be used as the final position of label node, realize the location of label node; I.e. label node coordinate position for ${\hat{y}}_{t1}=\frac{1}{C_N^3}{\mathrm{\&Sigma;}}_{i=1}^{C_N^3}{\hat{y}}_{\mathrm{ti}}.$

Cite an actual example below said method is described.

As shown in Figure 4, the plane of 25m*25m places six anchor nodes, and its coordinate is respectively (0,0), (0,14.9), (7.76,14.9), (7.76,0), (5,5), (12,6).Label node is positioned at (5.6,12.8), as shown in table 1.The three limit localization methods that we utilize the present invention to propose respectively and traditional three limit localization methods based on center of gravity carry out UWB location to label node choosing in different anchor node situation, as shown in table 2.Relatively these two kinds of algorithms, positioning result and positioning precision as shown in Figure 5 and Figure 6, wherein positioning precision square error $e_{\mathrm{MSE}}=$ $\frac{1}{N}\sqrt{{\mathrm{\&Sigma;}}_{i=1}^N({(x-\hat{x})}^2+{(x-\hat{y})}^2)}$ Represent.

Table 1 wireless sensor network node layout (unit: rice)

Table 2 effectiveness comparison (unit: rice)

In sum, these are only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (1)

1., based on the three limit localization methods that intersection point judges, it is characterized in that, detailed process is:

(1) from N number of anchor node of spatial arrangement, 3 are selected as reference node;

(2) for each reference mode, with its present position for the center of circle, with the distance between itself and the label node of required location for radius establishes circle; Calculate the intersection point between any two circles in 3 circles;

(3) from the intersection point of each crossing two circle, an intersection point is selected as vertex of a triangle, selected criteria is: when only there is an intersection point between two circles, using this intersection point as vertex of a triangle, when between two circles, intersection point exists two, judge from the nearest intersection point of the circumference of the 3rd circle as a leg-of-mutton summit;

(4) triangle core that three summits will determined by step (three) are formed is as the location estimation value of label node;

(5) reselect 3 anchor nodes as with reference to node, calculate the location estimation value of label node according to the mode of step (two)-(four), till the array configuration of all reference modes is all traversed;

(6) calculate the average of all label node location estimation values, and it can be used as the final position of label node, realize the location of label node.