CN102455421A - Sound positioning system and method without time synchronization - Google Patents
Sound positioning system and method without time synchronization Download PDFInfo
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Abstract
The invention discloses a sound positioning system and a sound positioning method without time synchronization, which are designed for solving the problems of dependency of the conventional positioning system on the time synchronization and errors and extra overhead caused by the time synchronization. The sound positioning system comprises a node to be positioned, more than two receivers, a server and a wireless access point (AP), wherein the node to be positioned is used for producing sound source signals to the outside; the more than two receivers are divided into a standard receiver and a beacon receiver and used for recording the sound source signals emitted by the node to be positioned and successive sound source signals emitted to the outside by the standard receiver and outputting the record data after the recording is completed to the server; the server is used for receiving the record data output by each receiver, calculating the position of the node to be positioned according to the record data and displaying the position of the node to be positioned on an interface of the server; and the wireless AP is used for constructing a wireless local area network consisting of the node to be positioned, the receivers and the server. According to the system and the method, the time synchronization in the positioning system is removed, and good positioning precision is obtained.
Description
Technical field
The present invention relates to a kind of wireless sensor network field, relate in particular to the sound positioning system and the method that need not time synchronized in a kind of wireless sensor network.
Background technology
Along with popularizing of wireless mobile apparatus, the application that much is the basis with context aware (context-aware) is arisen at the historic moment.Use in the situation of institute's foundation at these, the position is one of most important factor often, for example: in environmental monitoring, need know the particular location of gathering environmental information; Need know the zone that enemy personnel and equipment move afield; In the management of colliery, need know definite place that accident takes place or the like.In these were used, human observer usually used wireless sensor network to come the monitoring incident.In this case, expect the position that the monitoring incident takes place, at first will know the geographic position of sensor node self.Because sensor network often is arranged in the restricted or dangerous zone, like the nuclear radiation zone, battlefield or remote mountains etc., so people lay sensor node usually at random, and let of the mode co-ordination of these nodes with self-organization.Common example is with aircraft sensor node to be broadcasted sowing in the appointed area.The node of shuffle can't be learnt the position of oneself in advance, therefore must be implemented in lay after location voluntarily.It is known self-position that small number of nodes is arranged in the sensor network at first, and this node is called as beaconing nodes (beacon), and they often carry some specific installation, like GPS etc., is used to learn self-position.For the location of a unknown node, be exactly according to these beaconing nodes, realize according to certain location mechanism.
Up to now, researchers have proposed multiple localization method, these methods roughly can be divided into based on distance with two types of range-independence.The former needs absolute distance or orientation between the measured node, and calculates the position of unknown node according to internodal actual range; The latter need not to obtain internodal absolute distance or orientation, and is to use estimated value.In these two class methods, can reach higher precision, have widely and use based on the method for distance.
Method based on distance comprises based on (Time of Arrival time of arrival; TOA) location; Based on time of arrival poor (Time Difference of Arrival, location TDOA) and based on receiving signal intensity (Received Signal Strength, location RSS).The different range finding means of these method utilizations, wherein TOA and TDOA have better precision.But these two kinds of methods all need be carried out mutual computing to the timestamp on two different nodes (time stamp); Therefore require the clock of each node in the network to keep highly unanimously adopted certain mechanism to make the originally asynchronous consistent process of local clock trend of each node; Be called as time synchronized (time synchronization), this is an indispensable step in TOA and the TDOA method.
For the error that makes time synchronized is littler, expense is lower, and researchers begin from simple method, update the algorithm of time synchronized.Method for synchronous commonly used now has reference-broadcast synchronization (Reference BroadcastSynchronization; RBS); The sensor network time synchronization protocol (Timing-sync Protocol forSensor Networks, TPSN), inundation time synchronization protocol (the Flooding Time SynchronizationProtocol; FTSP) and the gradient time synchronization protocol (the Gradient Time Synchronization Protocol, GTSP) etc.In general, time synchronized is accomplished through a series of message exchange between the beaconing nodes.When a node produces the timestamp of oneself and sends it to another node seeking when synchronous, the transmission bag that carries timestamp tends to before arriving receiving node, meet with and postpones.This delay makes two nodes be difficult to accurately aim at their clock.People such as Fikret once roughly were divided into following components with this delay:
(1) transmitting time.Promptly produce a time of sending bag at transmitting terminal.
(2) entry time.Before transmission encapsulates transmission, in medium access control (Medium Access Control, MAC) time of sublayer stop.
(3) travel-time.Send bag from leaving transmitting terminal to the time of arriving at receiving end.
(4) time of reception.After receiving bag, receiving end also need be through the process of a decoding, and gives the more upper strata of network with decoded data transmission.
Some synchronized algorithms can remove one or two delay wherein, but can not all delays all be eliminated.Even there is a kind of method can eliminate all delays, because the existence of clock drift (clock skew and drifting), time synchronized still needs repeatedly to be carried out, and has so just increased the expense of system greatly.
It is thus clear that; Time synchronized has been introduced extra communication overhead; Expended the originally limited energy of sensor node, and the time error that stays is enough to bring very big distance error to the positioning system of using high speed signal (like radiofrequency signal), thereby bearing accuracy significantly reduced.
Summary of the invention
To existing positioning system time synchronized exist is relied on, and time synchronized itself can be brought the problem of sum of errors overhead, the present invention proposes a kind ofly, but need not the sound positioning system and the method for time synchronized based on TDOA.
For achieving the above object, the sound positioning system that need not time synchronized according to the invention comprises:
Node to be positioned externally sends sound-source signal;
Plural receiver is divided into two kinds of benchmark receiver and beacon receivers, record the follow-up sound-source signal that sound-source signal that said node to be positioned sends and said benchmark receiver externally send, and the recording data that will record after the end is exported to server;
Server receives the recording data of each receiver output, and goes out the position of node to be positioned and it is presented on the server interface according to this recording data computation; And,
Wireless aps makes up said node to be positioned, the WLAN that receiver and server are formed.
Especially, said receiver is by loudspeaker, and microphone and wireless connector constitute.
Especially, described server comprises communication and transceive data module and data processing and computing module; Wherein,
Said communication and transceive data module are used for to the receiver sending controling instruction, and the recording data that receive each receiver output;
Said data processing and computing module are used to analyze the recording data that are sent to server, through correlation computations with get peak value calculate TDOA and final positioning result.
The sound localization method that need not time synchronized according to the invention may further comprise the steps:
(1) receiver recording beginning, node t to be positioned externally sends sound-source signal constantly;
(2) benchmark receiver t ' externally sends follow-up sound-source signal constantly;
(3) behind the End of Tape, receiver sends to server with the recording data of sound-source signal of recording and follow-up sound-source signal composition;
(4) after server receives the recording data, to its positioning result that carries out data processing and calculate node to be positioned.
Wherein, step (4) comprises following step:
4.1 after server receives the recording data, find out sound-source signal corresponding sampling points i when arriving receiver, and follow-up sound-source signal corresponding sampling points j when arriving receiver, and calculate the TD2S value of this receiver based on the method for sampled point counting;
4.2, remove TD2S value singularly based on the method for majority decision;
4.3 calculate the TDOA value according to the TD2S value;
4.4 calculate the positioning result of node to be positioned by the TDOA value.
Further, the performing step of the method for the decision of the majority described in the step 4.2 is following:
4.2.1 establishing receiver A and receiver B has all recorded node t to be positioned and externally sends sound-source signal constantly and externally send follow-up sound-source signal with the benchmark receiver t ' moment;
4.2.2 calculate the TD2S value of receiver A and receiver B respectively, and set up the TD2S value relational expression of receiver A and receiver B:
|Δ
TD|＝|TD2S
A-TD2S
B|≤2d
AB/V；
4.2.3 the ultimate range of establishing between each receiver is D, then has | Δ
TD|≤2D/V;
4.2.4 the TD2S value of all receivers is formed a S set;
4.2.5 it all is correct supposing the TD2S value of most of receiver, and the element in the S set is divided into following three types:
One type: any two element a in such, b all has | a-b|＜2D/V.
Two types: any element d in such in class of any element c and (1) all has | c-d|＞2D/V.
Three types: other elements;
Be exceptional value 4.2.6 establish two dvielements.
Further, step 4.3 is concrete realizes as follows:
4.3.1 if C is the benchmark receiver, D is the beacon receiver, then sound-source signal S is respectively at t
C1And t
D1Arrive C and D, C is at t
C3Constantly send follow-up sound-source signal S ' from loudspeaker, S ' is respectively at t then
C4And t
D3Constantly arrive C and D, draw:
TD2S
C＝t
C4-t
C1，TD2S
D＝t
D3-t
D1
TDOA value between C and the D has:
TDOA
CD＝t
C1-t
D1＝d
CD/V-TD2S
D+TD2S
C-d
CC/V
Wherein, d
CDAnd d
CCTo the distance between the microphone of C, V is the aerial velocity of propagation of sound: V=331.3+0.6*theta under this scene to the loudspeaker of representing C respectively to the loudspeaker of distance between the microphone of D and C, and wherein theta is the temperature under this scene;
4.3.2 if C, D all is not the benchmark receiver, then the TDOA value between C and the D has: TDOA
CD=TDOA
CE-TDOA
DE, wherein, TDOA
CEBe TDOA value between C and the benchmark receiver E, its computing method are with step 4.3.1, TDOA
DEBe TDOA value between D and the benchmark receiver E, its computing method are with step 4.3.1.
Sound positioning system that nothing according to the invention takes time and method have following some beneficial effect:
One, need not time synchronized.The present invention has fundamentally changed the TDOA scheme through removing this necessary step in other TDOA methods, and has avoided the error that is much caused by time synchronized.
Two, high position precision.Under the prerequisite that adopts the 44.1kHz SF, the present invention can obtain the time precision of 0.023ms, under this time precision, can obtain very high bearing accuracy.According to the experimental result in the 3D zone of a 9m*9m*4m, system can obtain the precision of 10～20cm, and this can satisfy the demand of extensive application.
Three, the present invention can be deployed in commercial ready-made (Commercial off-the-shelf, COTS) on the equipment, like mobile phone, PDA, MP3 player etc.This makes that system of the present invention is more easy-to-use, and lower deployment cost is lower, is easy to promote.
Description of drawings
Fig. 1 is the structural representation that need not the sound positioning system of time synchronized according to the invention;
Fig. 2 is the typical time series synoptic diagram of two node A and B;
Fig. 3 is that a typical signal is asked relevant synoptic diagram as a result;
Fig. 4 is the figure that lays of each node of many environmental experiments of the present invention 2D scene;
Fig. 5 is the figure that lays of each node of many environmental experiments of the present invention 3D scene;
Fig. 6 is the perspective view of each node of 3D scene on the xy plane;
Fig. 7 is the perspective view of each node of 3D scene on the yz plane;
Fig. 8 is the abnormity point quantity synoptic diagram of experimental result in the 2D scene of the present invention;
Fig. 9 is the abnormity point quantity synoptic diagram of experimental result in the 3D scene of the present invention;
Figure 10 is the cumulative distribution figure of the positioning error of experimental result in the 2D scene of the present invention;
Figure 11 is the cumulative distribution figure of the positioning error of experimental result in the 3D scene of the present invention;
Embodiment
Do detailed description below in conjunction with the Figure of description specific embodiments of the invention.
Basic system architecture of the present invention is as shown in Figure 1, and the hardware that mainly comprises has: a node to be positioned, wireless aps 2, one notebooks 3 and several receivers 1 as server.Wherein, described several receiver 1 is divided into beacon receiver and benchmark receiver.Said benchmark receiver and said beacon receiver are deployed in known allocation really.The position of said node to be positioned waits to ask.The principle of work of each parts of sound positioning system that need not time synchronized according to the invention is following:
Node to be positioned externally sends sound-source signal;
Receiver is divided into two kinds of benchmark receiver and beacon receivers, record the follow-up sound-source signal that sound-source signal that said node to be positioned sends and said benchmark receiver externally send, and the recording data that will record after the end is exported to server;
Server receives the recording data of said beacon receiver output, and goes out the position of node to be positioned and it is presented on the server interface according to this recording data computation;
Wireless aps makes up said node to be positioned, benchmark receiver, the WLAN that beacon receiver and server constitute.
Wherein, described receiver all has the basic hardware of a cover, comprises loudspeaker, microphone, wireless connector (like bluetooth or WiFi).These receivers have constituted a LAN through wireless aps and said server.
The flow process of system works is roughly: receiver recording beginning=＞node sounding to be positioned=＞benchmark receiver sounding=＞the receiver End of Tape=＞receiver with recording file send to server=＞the server process data, draw the positioning result of node to be positioned.
The concrete steps of the sound localization method that need not time synchronized according to the invention are following:
Behind step 3, the End of Tape, the receiver data of will recording send to server;
After step 4, server receive recording file, it is handled and calculates the positioning result of node to be positioned.
After 4.1 server receives the recording data; Find out sound-source signal corresponding sampling points i when arriving the beacon receiver based on the method for sampled point counting; And follow-up sound-source signal corresponding sampling points j when arriving the beacon receiver, and calculate the TD2S value of this beacon receiver.
Fig. 2 is the typical time series (node refers to benchmark receiver or beacon receiver, down together) of two node A and B.Among the figure, use t respectively
A1And t
B1Represent sound source S to arrive the time of the microphone of A and B.If the clock of two nodes is in full accord, so t
B1-t
A1It is exactly the TDOA value of A and B.If but only did this simple calculations, must need step through clock synchronization.
The present invention adopts TD2S to represent that a node plays and receives elapsed time till the S ' from receiving S.Concerning each node, calculate this value and all only involve the clock of self, and do not need to carry out synchronously with other node.According to the TD2S value of each node and the coordinate of anchor node (being the beacon receiver), can calculate the TDOA between any two nodes.
But, voice signal from arrive microphone to by node detection to still needing a period of time.In this case, t
B2-t
A2The TDOA value that the system that is only is calculated, and t
B2-t
A2And t
B1-t
A1Normally unequal.In order to eliminate this uncertainty, the present invention has used the method for sampled point counting.Because when S and S ' arrival node; Node is in recording state all the time, and with a definite recording frequency f voice signal is sampled, so; If can find corresponding sampling points i when S arrives node in this section sampled data; And S ' corresponding sampling points j when arriving node, just can draw the TD2S value of this node, i.e. TD2S=(j-i)/f.Obviously, the SF of equipment can have influence on the precision of TD2S, and SF is high more, and time precision is just high more.The sampled voice frequency that the present invention adopts is 44.1kHz, and the equipment of most of COTS can both reach this frequency.
So, how to find out S and S ' corresponding sampling points respectively exactly? Here, the present invention has adopted traditional relevant (correlating) method of asking.This method is only effective to the signal that can carry out mathematical description in advance.Therefore, in experimentation, consider the autocorrelation performance requirement of signal, having adopted frequency range is 2～6kHz, length be the Linear chirp signal of 50ms as S, and S ' is set at identical with it.In the ideal case, correlated results is as shown in Figure 3, and what previous peak was corresponding is the moment that S arrives, the arrival of the back corresponding S ' in a peak.But in practical application, because multipath effect (multi-path) and other factors that reflection causes, two tops can not be represented S and S ' respectively.Therefore, the present invention changes into and gets the long ω of being before the top getting the top
0Moving window in the earliest peak, ω
0It is an empirical parameter.Can judge whether a point can be can be regarded as the peak from setting threshold on height and the average gradient.
4.2, remove TD2S value singularly based on the method for majority decision;
Through step 4.1, drawn the TD2S value, but the recording of node often is unsettled, sound source and internodal obstacle or background noise all possibly cause defective recording result.The TD2S value that is obtained by this recording file is exactly an exceptional value (outlier).
Because time of sending of S all is unknown with sending the place, therefore be difficult to provide in advance a TD2S should scope.The present invention has provided the method for most decisions, judges that which value is an exceptional value.
Suppose that sound source M has sent the S signal constantly at t, datum node N has constantly sent S ' signal at t ', and node A and B have write down this twice sounding.The TD2S of A and B satisfies following relation so:
|Δ
TD|＝|TD2S
A-TD2S
B|
＝|((t’+d
AN/v)-(t+d
AM/v))-((t’+d
BN/v)-(t+d
BM/v))|
＝|(d
AN-d
BN)-(d
AM-d
BM)|/v
≤|d
AN-d
BN|/v+|d
AM-d
BM|/v
≤2d
AB/v
Suppose that D is the ultimate range between all nodes, to any a pair of node, has so | Δ
TD|≤2D/V.So, if the TD2S of all nodes is formed a S set, and there is not exceptional value in the set, the greatest member in the set and the difference of least member will be not more than 2D/V.
The value mistake of small number of nodes if the TD2S value of most of node is all correct, the element among the S can be divided into following three types so:
(1) any two element a in such, b all has | a-b|＜2D/V.
(2) any element d in the class of any element c and (1) in such all has | a-b|＞2D/V.
(3) other elements.
In this case, can think that (2) dvielement all is an exceptional value, and only use (1) dvielement to carry out next step computing.This mode classification is not the hypothesis of exceptional value based on most of TD2S, and this hypothesis very approximates to the facts.In experiment, this classification and to remove the method performance of exceptional value very good.
4.3 calculate the TDOA value of two nodes according to the TD2S value;
Draw the TDOA value that normal TD2S value (being that error is not enough so that it becomes each node TD2S value of exceptional value) further draws any two nodes based on step 4.2.Fig. 2 is the typical time series of two node A and B in the system, and wherein A is a datum node.In the drawings, S is respectively at t
A1And t
B1Arrive A and B, A is at t
A3Constantly send S ' from loudspeaker, S ' is respectively at t then
A4And t
B3Constantly arrive the microphone place of A and B.Significantly, TD2S
A=t
A4-t
A1, TD2S
B=t
B3-t
B1To the TDOA value between A and the B, use following method to try to achieve:
TDOA
AB＝t
B1-t
A1
＝(t
B3-t
A3)-(t
B3-t
B1)+(t
A3-t
A1)
＝(t
B3-t
A3)-(t
B3-t
B1)+(t
A4-t
A1)-(t
A4-t
A3)
＝d
AB/V-(t
B3-t
B1)+(t
A4-t
A1)-d
AA/V
＝d
AB/V-TD2S
B+TD2S
A-d
AA/V
Wherein, d
ABAnd d
AAThe loudspeaker of representing A respectively to the loudspeaker of distance between the microphone of B and A to the distance between the microphone of A.Because the position of A and B all is fixing measurable, so these two values all are constant; Two TD2S values can draw with above-mentioned method; V is the aerial velocity of propagation of sound under this scene, can calculate it through formula V=331.3+0.6*theta, and wherein theta is the temperature under this scene.So just on each asynchronous node, drawn the TDOA value.
If two nodes of A and B are not datum nodes, their TDOA value can draw through simple calculations, and formula is: TDOA
AB=TDOA
AC-TDOA
BC, wherein, TDOA
ACBe the TDOA value between A and the datum node C, TDOA
BCBe the TDOA value between B and the datum node C.
4.4 calculate the positioning result of node to be positioned by the TDOA value;
Utilization TDOA is worth the position, generally speaking is a process of separating Nonlinear System of Equations.Corresponding method has many kinds, like the method for directly solving an equation, and the method for utilization Taylor formula, the method for dividing and ruling etc.The present invention has chosen a kind of algorithm that Chan proposes through the analysis to these algorithms, and it has obtained balance preferably on degree of accuracy and computational complexity.These algorithms generally require node to have 4 at least.
The algorithm of Chan at first draws an initial solution with the method that is similar to the Taylor expansion; Ask the covariance matrix of error vector then; And with this matrix initial solution is done further to revise, draw net result, through theoretical analysis; Though this method has only carried out once revising, have and the suitable precision of Taylor method of deploying of iteration repeatedly.And it can also take different modification methods in the zone near beaconing nodes respectively with the zone away from beaconing nodes according to the difference in sound source zone of living in, makes the result more accurate, and application scenarios is more extensive.
Through above step, the present invention is just set out by the recording data of several nodes, has finally calculated the position of sound source, i.e. the position of node to be positioned.
In sum, sound positioning system and the method that need not time synchronized according to the invention mainly used following technology:
(1) dual signal perception.During system start-up, several clock different received devices are recorded the follow-up signal S ' that sound-source signal S and benchmark receiver send.
(2) sampled point counting.After recording end, the sampled point number on each receiver of system statistics between these two signals, thus it is poor to draw the time of reception of these two signals on each receiver.Through further analysis and calculating, it is poor to obtain the time of reception of source signal on different receivers, just can use the principle calculating location of TDOA then.Because signal sampling generally can reach higher frequency, so the calculating of mistiming can reach higher precision.The system of adding has avoided the error of time synchronized, so the location of native system can be compared precisely.
Below in conjunction with a specific embodiment sound positioning system and the method that need not time synchronized of the present invention explained further.
One, builds experimental system
Present embodiment has used 8 mobile phones, and wherein 6 Dopod mobile phones are beacon receivers, is used for recording; A SonyEricsson mobile phone is used as node to be positioned; An O2 XDA mobile phone is as the benchmark receiver.With these 8 mobile phones, a PC and an AP (Access Point) are connected in the star network, and AP all sends to the recording data that mobile phone write down on the PC as the center of network, and is dealt with and calculated by PC, finally draws position result.
In the experimental system that present embodiment makes up, why used beaconing nodes more than 4, the one, because can guarantee when abnormity point occurs that so available TD2S value is still above 4; The 2nd, because more node also can improve locating accuracy.
Two, the software that runs locator routine
The system software of present embodiment is divided into the software that is deployed on the server and is deployed in the software two parts on the receiver.The software that is deployed on the server mainly plays system's control and deal with data, and the software that is deployed on the receiver mainly plays control recording and sounding.The both comprises communication module and is used for sending each other and receiving instruction.
Software on the server is divided into two separate modules again: communication and transceive data module and data processing and computing module.Said communication and transceive data module are used for to each receiver sending controling instruction, and the recording data that receive each receiver; Said data processing and computing module are used to analyze the recording data that are sent to server, and through relevant, the calculating of getting peak value obtains TDOA and net result.
The communication module that is deployed in the software and services device on the mobile phone realizes by Visual C++ programming, the computing module of server then realized by Matlab, and generated the com component that can be called by communication module.
In the position fixing process of one whole, at first will be with each receiver, AP and server PC are connected in the network, the intercommunication between the assurance equipment; Then the user by server issues positioning command, and system automatically performs the recording of all receivers, and the work of the sounding of sound source and recording data transmission all is sent to server until all recording data; At last, the server calls computing module in conjunction with the coordinate information of each receiver, is analyzed all recording files, finally calculates sound source position and it is presented on the server interface.Next, just can begin to have located next time.
Three, many environmental experiments
In the concrete steps of introducing,,, still there are some factors can influence locating accuracy in the above like the fluctuation of the velocity of sound etc. except some negligible factors.This mainly comprises:
(1) signal to noise ratio (S/N ratio) of signal (Signal to Noise Ratio, SNR)
In experiment, neighbourhood noise always can go on record.If the energy of transmission signals too a little less than, perhaps the frequency of noise approaches the frequency of transmission signals, will make system be difficult to find the due in of transmission signals.
(2) multipath effect
Because the existence of sound reflection, same voice signal possibly arrive same receiver several times through different paths.More reasonably choose first peak as the method for time of arrival though adopted in the experiment, still mistake possibly occur.
(3) solve an equation
When the error of TDOA hour, the method for Chan can obtain higher precision.But along with the increase of error, the performance of this method also worse and worse.In the experiment, the error of most of TDOA can both remain on below the 0.4ms, and the method for Chan can obtain result preferably in this case.But still little a part of error is arranged is bigger, and therefore at this moment this method will great errors.
According to top analysis to source of error, in the 2D and 3D scene of running experiment, the system that again present embodiment is made up is in three kinds of different environment and experimentizes.These three kinds of environment are respectively:
(1) quiet environment of open air.
(2) noisy environment of open air.The position that is provided with is the same with (1), has just placed the loudspeaker of a playing back music aside.
(3) indoor quiet environment.An open hall, size is about 9m*9m*4m, and environment is comparatively quiet.
Here in order to represent that for simplicity use " Normal " respectively, " Noisy " and " Inside " refers to (1), (2) and (3) these three kinds of environment.The purpose that these three kinds of experimental situations are set is: attempt to disclose the influence of single disturbing factor to experimental result.Under every kind of experimental situation, sound source cloth is placed on 16 different points, and on each point, repeats to do 10 samplings.Therefore, 2 scenes just have 960 groups of recording results in 3 kinds of environment.
In 2D and the 3D scene, under various environment, it all is duplicate that node lays.The node of 2D scene lays as shown in Figure 4, and the laying like Fig. 5 of each node of 3D scene is shown in 6 and 7.Wherein, the position that the different node to be positioned of ■ representative sends sound source, ● represent the position of receiver.Because laying of receiver be symmetrical, sound source position only need take 1/4 space and get final product.
Four, experimental result
1, abnormity point number
If the beaconing nodes number of exceptional value surpasses 2 under the 3D scene, under the 2D scene, surpass 3, will draw a positioning result that misses by a mile.Such result has greatly increased the average error of positioning result, valueless basically, and is easy to make a distinction with other results.
Therefore, when the average error of compute location, can earlier these abnormal resultses be removed, calculate residue result's average then.But, be the stability of research system, the number of present embodiment meeting records abnormal positioning result.
Fig. 8,9 shown respectively under the 2D scene with the 3D scene under the unusual quantity of positioning result in whole experiment.As can be seen from the figure, the abnormal results of the experiment gained under the 2D scene is wanted much less than under the 3D scene, and this explains that more redundant node can increase the stability of system.
2, positioning error
Figure 10,11 have described the accumulative total density profile (cumulative density function) of positioning error under 2D and 3D scene respectively.Wherein, 4 is " Normal " environment, and 5 is " Noisy " environment, and 6 is " Inside " environment.Table 1, table 2 have write down the average and some threshold values of positioning error.Can find out that from chart the average error of locating in the 3D scene is 10～20cm, and the average error of 2D is 10～21cm.This explains that system of the present invention can both obtain precision preferably under various environment.
Table 1 2D positioning error
| Index (cm) | Normal | Noisy | Inside |
| Average error | 20.0 | 20.3 | 13.7 |
| 50% error | 12.7 | 18.8 | 10.9 |
| 90% error | 38.1 | 33.7 | 29.9 |
| Standard deviation | 12.8 | 10.9 | 12.1 |
| The abnormity point ratio | 1.25％ | 5％ | 0.6％ |
Table 2 3D positioning error
| Index (cm) | Normal | Noisy | Inside |
| Average error | 14.7 | 14.4 | 15.2 |
| 50% error | 13.7 | 13.8 | 12.8 |
| 90% error | 22.8 | 21.9 | 28.2 |
| Standard deviation | 6.2 | 7.4 | 9.9 |
| The abnormity point ratio | 2.5％ | 5％ | 12.5％ |
From above-mentioned table, observe, the result who under outdoor quiet environment, locatees is not necessarily best.Though can find out that by Fig. 8 and Fig. 9 noise and multipath effect have increased the number of abnormity point, they significantly do not change total average error.This explains that also system of the present invention has stronger antijamming capability.
In sum, sound positioning system and the method that need not time synchronized according to the invention through removing time synchronized, fundamentally changed the scheme of TDOA; Technology through dual signal perception and sampled point counting has obtained high orientation precision.Experiment shows, the experiment of in the 3D zone of a 9m*9m*4m, being done can obtain the mean accuracy of 10～20cm.Experimental facilities adopts commercial mobile phone, cost is decreased and system deployment is more prone to.
More than; Be merely preferred embodiment of the present invention, but protection scope of the present invention is not limited thereto, any technician who is familiar with the present technique field is in the technical scope that the present invention discloses; The variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain that claim was defined.
Claims (7)
1. a sound positioning system that need not time synchronized is characterized in that, comprising:
Node to be positioned externally sends sound-source signal;
Plural receiver is divided into two kinds of benchmark receiver and beacon receivers, record the follow-up sound-source signal that sound-source signal that said node to be positioned sends and said benchmark receiver externally send, and the recording data that will record after the end is exported to server;
Server receives the recording data of each receiver output, and goes out the position of node to be positioned and it is presented on the server interface according to this recording data computation; And,
Wireless aps makes up said node to be positioned, the WLAN that receiver and server are formed.
2. according to the said sound positioning system that need not time synchronized of claim 1, it is characterized in that said receiver is by loudspeaker, microphone and wireless connector constitute.
3. according to the said sound positioning system that need not time synchronized of claim 1, it is characterized in that described server comprises communication and transceive data module and data processing and computing module; Wherein,
Said communication and transceive data module are used for to the receiver sending controling instruction, and the recording data that receive each receiver output;
Said data processing and computing module are used to analyze the recording data that are sent to server, through correlation computations with get peak value calculate TDOA and final positioning result.
4. a sound localization method that need not time synchronized is characterized in that, may further comprise the steps:
(1) receiver recording beginning, node t to be positioned externally sends sound-source signal constantly;
(2) benchmark receiver t ' externally sends follow-up sound-source signal constantly;
(3) behind the End of Tape, receiver sends to server with the recording data of sound-source signal of recording and follow-up sound-source signal composition;
(4) after server receives the recording data, to its positioning result that carries out data processing and calculate node to be positioned.
5. according to the said sound localization method that need not time synchronized of claim 4, it is characterized in that wherein, step (4) comprises following step:
4.1 after server receives the recording data, find out sound-source signal corresponding sampling points i when arriving receiver, and follow-up sound-source signal corresponding sampling points j when arriving receiver, and calculate the TD2S value of this receiver based on the method for sampled point counting;
4.2, remove TD2S value singularly based on the method for majority decision;
4.3 calculate the TDOA value according to the TD2S value;
4.4 calculate the positioning result of node to be positioned by the TDOA value.
6. according to the said sound localization method that need not time synchronized of claim 4, it is characterized in that the performing step of the method for the majority decision described in the step 4.2 is following:
4.2.1 establishing receiver A and receiver B has all recorded node t to be positioned and externally sends sound-source signal constantly and externally send follow-up sound-source signal with the benchmark receiver t ' moment;
4.2.2 calculate the TD2S value of receiver A and receiver B respectively, and set up the TD2S value relational expression of receiver A and receiver B:
|Δ
TD|＝|TD2S
A-TD2S
B|≤2d
AB/V；
4.2.3 suppose that the ultimate range between each receiver is D, then have | Δ
TD|≤2D/V;
4.2.4 the TD2S value of all receivers is formed a S set;
4.2.5 it all is correct supposing the TD2S value of most of receiver, and the element in the S set is divided into following three types:
One type: any two element a in such, b all has | a-b|＜2D/V;
Two types: any element d in such in class of any element c and (1) all has | c-d|＞2D/V;
Three types: other elements;
Be exceptional value 4.2.6 establish two dvielements.
7. according to the said sound localization method that need not time synchronized of claim 4, it is characterized in that step 4.3 is concrete to be realized as follows:
4.3.1 if C is the benchmark receiver, D is the beacon receiver, then sound-source signal S is respectively at t
C1And t
D1Arrive C and D, C is at t
C3Constantly send follow-up sound-source signal S ' from loudspeaker, S ' is respectively at t then
C4And t
D3Constantly arrive C and D, draw:
TD2S
C＝t
C4-t
C1，TD2S
D＝t
D3-t
D1
TDOA value between C and the D has:
TDOA
CD＝t
C1-t
D1＝d
CD/V-TD2S
D+TD2S
C-d
CC/V
Wherein, d
CDAnd d
CCTo the distance between the microphone of C, V is the aerial velocity of propagation of sound: V=331.3+0.6*theta under this scene to the loudspeaker of representing C respectively to the loudspeaker of distance between the microphone of D and C, and wherein theta is the temperature under this scene;
4.3.2 if C, D all is not the benchmark receiver, then the TDOA value between C and the D has: TDOA
CD=TDOA
CE-TDOA
DE, wherein, TDOA
CEBe TDOA value between C and the benchmark receiver E, its computing method are with step 4.3.1, TDOA
DEBe TDOA value between D and the benchmark receiver E, its computing method are with step 4.3.1.
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