CN102761964A - Underground personnel positioning method based on ZigBee - Google Patents

Abstract

The invention discloses a method for locating underground personnel based on ZigBee. A plurality of base stations are arranged in the roadway, and the base stations include a plurality of master base stations and a plurality of slave base stations. The master base station and the slave base stations are arranged at intervals; In the communication mode, multiple positioning targets communicate with the master base station or slave base station based on ZigBee in a time-division multiplexing manner; according to the distance h ₁ , the area between two adjacent base stations is divided into a near base station area and a far base station area. When the positioning target is in When the base station area is near, the RSSI positioning method is used for positioning; when the positioning target is in the far base station area, the VT positioning method is used for positioning. The underground personnel positioning method based on ZigBee has high positioning accuracy and large positioning range.

Description

Method for underground personnel positioning based on ZigBee

technical field

The present invention relates to a ZigBee-based underground personnel positioning method, in particular to a method for the signal strength is easily affected by the environment and the positioning accuracy is difficult to improve, and the positioning distance of the base station based on the RSSI positioning algorithm is much smaller than its communication distance. A scheme for underground personnel positioning based on ZigBee.

Background technique

The precise positioning of underground personnel can provide support for strengthening mine supervision, and can also provide important help for mine disaster rescue, which is an important guarantee for mine safety production. Positioning algorithms can be divided into two categories: non-ranging-based positioning algorithms and ranging-based positioning algorithms. Positioning algorithms based on non-ranging include: centroid method, DV-Hop algorithm, etc. These methods require a dense wireless sensor network to achieve high positioning accuracy, and the cost of improving positioning accuracy is high, and the narrow underground environment It is also not suitable to use this kind of positioning algorithm; positioning algorithms based on distance measurement include: TOA (Time of Arrival), TDOA (Time Difference of Arrival), AOA (Angle of Arrival), RSSI positioning method, etc. Fast, TOA and TDOA require high-precision clocks, and AOA requires specialized direction-finding equipment. Therefore, TOA, TDOA, and AOA positioning algorithms have high requirements for hardware, and large-scale applications require high equipment investment costs. RSSI positioning algorithms are due to signal strength. The value RSSI, that is, the received power P _R can be directly obtained from the device-related registers, which has low requirements on the device, is easy to implement, and has a low cost, so it has a good application prospect.

However, because the signal strength of the wireless signal is easily affected by many environmental factors such as multipath effect, metal reflection, humidity, etc., it is difficult to improve the positioning accuracy of the positioning algorithm based on RSSI, and the effective positioning distance is much smaller than its communication distance. At present, the positioning algorithms based on RSSI mainly include signal attenuation model method and signal fingerprint method. The former is based on the signal attenuation curve of the IEEE802.15.4 standard, and then establishes parameters according to the actual environment to establish a mathematical relationship model between signal strength and distance, and then uses this model for ranging and positioning. This method has a higher accuracy in short distances. However, as the distance increases, the positioning accuracy will decrease significantly after the signal attenuation is not obvious; the latter adopts the method of establishing the RSSI fingerprint database in a specific environment, and then compares the collected received power data _PR with the The fingerprint database is matched for positioning. Although the positioning accuracy of this method is relatively guaranteed, it has poor adaptability and adaptability to the environment.

The positioning based on Zigbee technology usually adopts the RSSI positioning algorithm, that is, according to the exponential attenuation relationship between the signal strength of electromagnetic wave transmission and the transmission distance, the transmission distance is determined by measuring the signal strength for positioning. At a short distance, the transmitted signal strength attenuates quickly, the transmission distance is not sensitive to the interference of the transmitted signal strength, and the positioning accuracy is high. In the long distance, the transmitted signal strength attenuates slowly, and the transmission distance is more sensitive to the interference of the transmitted signal strength, and the positioning accuracy cannot be guaranteed under the influence of interference.

Contents of the invention

The technical problem to be solved by the present invention is to provide a ZigBee-based underground personnel positioning method, which has high positioning accuracy and a large positioning range.

The technical solution of the invention is as follows:

An underground personnel positioning scheme based on ZigBee. Multiple base stations are set in the roadway. The base stations include multiple master base stations and multiple slave base stations. The master base station and slave base stations are set at intervals; Multiple positioning targets communicate with the master base station or slave base station based on ZigBee by means of time division multiplexing;

According to the distance h _1, the area between two adjacent base stations is divided into the near base station area and the far base station area, that is, when the distance between the positioning target and the nearest base station is less than h ₁ , it indicates that the positioning target is in the near base station area; otherwise, the positioning target is in the far base station area. Base station area; [distance _h1 is determined by the nature of RSSI positioning, if the distance _h1 is far away, the positioning accuracy will be worse, in the example of the present invention, _h1 is 10m]

When the positioning target is in the near base station area, the RSSI positioning method is used for positioning;

When the positioning target is in the far base station area, the V-T positioning method is used for positioning.

其中P_R0是相对发射基站参考距离的接收功率，u为衰减系数；【参考距离d₀=1米，衰减系数u是通过在矿井巷道采集到的数据通过一元线性回归的方法获取】The RSSI positioning method is: the distance between the positioning target and the nearest base station

Among them, P _R0 is the received power relative to the reference distance of the transmitting base station, and u is the attenuation coefficient; [the reference distance d ₀ =1 meter, the attenuation coefficient u is obtained by the method of unary linear regression from the data collected in the mine roadway]

$\stackrel{\‾}{P_R}\frac{1}{k}\underset{i=1}{\overset{k}{\mathrm{\Σ}}}{P}_R\left(i\right),$ P _R (i)∈[μ-0.84σ,μ+0.84σ];

是P_R的平均值，k是n个P_R值中落入[μ-0.84σ,μ+0.84σ]的值的个数，均值 $\mathrm{\μ}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{P}_R\left(i\right),$ 标准差 $\mathrm{\σ}=\sqrt{\frac{1}{n-1}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(P_R\left(i\right)-\mathrm{\μ})}^2};$ in,

is the average value of P _R , k is the number of n values of P _R that fall into [μ-0.84σ, μ+0.84σ], and the mean $\mathrm{\μ}=\frac{1}{\mathrm{no}}\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\Σ}}}{P}_R\left(i\right),$ standard deviation $\mathrm{\σ}=\sqrt{\frac{1}{\mathrm{no}-1}\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\Σ}}}{(P_R\left(i\right)-\mathrm{\μ})}^2};$

The method of obtaining P _R (i) is as follows:

The host computer connected to the current base station—denoted as base station X—caches n received power values P _R [i] data of a positioning target. If m received powers P _R are greater than the threshold value P _RT , it indicates that the positioning target is at In the area near the base station, the n _PR [i] data are effective data, wherein, n is the number of received power data received by the same target node at the same base station in a continuous time; [n is considered by the real-time nature of data, and in the present invention , set n=10, m is an empirical threshold, the present invention sets n=7, P _RT is the received power value from base station X to its border near the base station, when h ₁ =10 meters, the measured received power P _RT =- 62.02dBm;] base station X [refers to the current base station, that is, obtains the base station corresponding to _PR (i)] the signal strengths of the base stations on the adjacent two sides to the target node are respectively: P _Rl , P _Rr , determined by the value of P _Rl , P _Rr The size of determines which side of the base station the positioning target is on.

3. the underground personnel locating scheme based on ZigBee according to claim 2, it is characterized in that, VT locating method is based on d=vt+h ₁ location, and d is the distance of locating target and base station X, and v is that locating target is near The average speed in the base station area; base station X [refers to the current base station, that is, obtains the base station corresponding to _PR (i)] The signal strengths of the base stations on the adjacent two sides to the target node are respectively: P _Rl , P _Rr , determined by P _Rl , The value of P _Rr determines which side of the base station the positioning target is on.

4. the underground personnel positioning scheme based on ZigBee according to claim 3, is characterized in that, the calculation method of average speed is: when judging that a locating target enters near base station area, start timing it; when judging that this locating target When walking out of the area near the base station, stop timing it, and read the timing time t ₁ ; calculate the average moving speed of the positioning target: v=2h ₁ /t ₁ . [In special cases, if the positioning target enters from the base station, 2h1 here is replaced by h1. 】

As shown in Figure 1, the range within h ₁ meter from base stations A and B is set as their near base station area, and the range outside h ₁ meter is set as far base station area. For the convenience of the following description, it is assumed that the positioning target moves from base station A to base station B. In the area near the base station, the RSSI positioning algorithm is used, and the host computer timed the movement of the underground personnel in the area near the base station. Assume that the timing time of the distance h ₁ from the base station A to the right boundary of the area near the base station A is t ₁ , therefore, the obtained The average moving speed of underground personnel v=2h ₁ /t ₁ ; in the far base station area, the host computer re-times the personnel from the right boundary of the area near the base station A, and estimates the distance from the base station in the roadway far base station area from the timing time t The distance of A is as follows:

d=vt+h ₁ ;

Therefore, the above formula can be used to calculate the distance between the positioning target and the base station in the far base station area, and thus determine the precise position of the person in the far base station area. The flowchart of the algorithm is shown in Figure 4.

Algorithm steps:

Step 1: Initialization. According to experience, it is necessary to set a default speed V _def of underground personnel and a distance h ₁ meter from base station A to the right boundary of the near base station area, which requires a minimum time T _min and a maximum time T _max . If the required time t ₁ within h ₁ meter is greater than the maximum time T _max , the person is working in this area without moving forward; if the required time t ₁ within h ₁ meter is less than the shortest time T _min , it may be the system Fault. In the above two cases, the system will default the personnel speed V _def ;

Step2: Determine that the positioning target has entered the near base station area, and start timing;

Step3: Judging that the positioning target has left the area near the base station, the timing ends;

Step4: Judging the time T _min <t ₁ <T _max required for personnel h ₁ meter, if so, obtain the average speed v according to the distance of h ₁ meter and the required time; otherwise, the average speed of underground personnel movement is the default speed V _def ;

Step5: According to the average movement speed of Step4, estimate the real-time position of the far base station area of the roadway where the person is located;

Step6: Determine whether the personnel is underground, if so, turn to Step2; otherwise, end the cycle.

ZigBee communication scheme, the communication scheme aims to eliminate the signal interference between base stations and nodes, and ensure the positioning accuracy. The scheme divides the positioning base station into: the master station, the slave base station, and the positioning target constitute the ZigBee positioning communication system. The difference between the master base station and the slave base station is that the master base station can actively send a positioning request, and the slave base station only receives a positioning response.

The ZigBee communication system base station layout is shown in Figure 1. On the mine roadway, the master and slave base stations are arranged alternately. The positioning base station and the positioning target adopt a time-division multiplexing question-and-answer communication method: the main base station sends out positioning requests in sequence according to the positioning target ID number, and the positioning target responds to the positioning request by broadcasting after receiving the positioning request, and then the master and slave base stations sequentially pass through the RS485 bus Upload the received target positioning information to the host computer, and the host computer locates and displays the positioning target according to the information. The data flow diagram of the ZigBee communication system and the working sequence diagram of the main base station are shown in Figure 2 and Figure 3 respectively.

Beneficial effect:

The ZigBee-based underground personnel positioning method of the present invention, based on ZigBee technology, regards a certain section of the mine roadway as a straight line or a segmented straight line, and divides the area between the two base stations of the roadway into two areas: a near base station area and a far base station area. district. For example, the base station of two ZigBee modules in the mine roadway is the master base station A and the slave base station B respectively, with a distance of 60 meters, where h ₁ =10 meters, as shown in Figure 1. The results show that the maximum absolute error of the measurement in the near base station area is 3 meters, and the maximum absolute error of the simulation in the far base station area is 5 meters. Compared with the RFID-based underground positioning system commonly used in mines at present, the present invention can realize accurate positioning of underground personnel, and can reduce system cost.

Description of drawings

Figure 1 is a schematic diagram of mine roadway and base station layout;

Fig. 2 is a ZigBee positioning system data flow diagram;

Figure 3 is a working sequence diagram of the main base station;

Fig. 4 is the flow chart of V-T algorithm;

Fig. 5 is an overall flow chart of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with accompanying drawing and specific embodiment:

Example 1:

1. Base station layout and communication with ZigBee positioning system

In the system, the master base station, the slave base station and the node as the positioning target all use ZigBee technology to communicate. Since there are many positioning base stations and positioning targets in the underground personnel positioning system, and the RSSI-based positioning method is adopted, the base station and the base station, the base station and the base station are excluded. The primary task is to realize the normal communication of the ZigBee positioning system under the condition of positioning target, positioning target and positioning target signal interference.

In order to prevent a positioning target from receiving multiple positioning requests at the same time, the positioning base station is divided into the master base station and the slave base station, and the master and slave base stations are arranged at intervals in the roadway, as shown in Figure 1, the master base station and the slave base station The difference between the slave base stations is that the master base station can send positioning requests and also receive positioning responses, while the slave base stations can only receive positioning responses.

The data flow diagram of the ZigBee positioning system is shown in Figure 2, and the main base station is the core of the ZigBee communication system. The primary base station sends positioning requests sequentially according to the positioning target ID numbers, and the positioning request data packet includes: the positioning target ID and the base station ID. After receiving the positioning request, the positioning target node checks whether the received positioning target ID is consistent with its own ID. If the positioning target ID is consistent with its own ID, it will respond to the positioning request to the master base station and the slave base station by broadcasting. The response data packet includes: target ID, the master base station and the slave base station receive the response data packet, and extract the received power value P _R and the corresponding positioning target node ID, master base station ID or slave base station ID constitute a new sending data packet, and then the master base station and the slave base station upload the sending data packet to the host computer sequentially through the RS485 bus, and the host computer according to the information Measure the distance of the positioning target node, and convert the target node into coordinates based on the known base station position for graphical display on the host computer. If the positioning target ID is inconsistent with its own ID, it does not respond and waits for the next positioning request.

The difference between broadcast communication and point-to-point communication in the present invention: the sending data packet of the point-to-point communication sending device (the sending device can be a host station or a target node) includes: a source ID number and a destination ID number. However, the sending data packet of the sending device in the broadcast communication mode (the sending device can only be the target node) only includes: the source ID number, not the destination ID number.

The working sequence of the main base station is shown in Figure 3. The main base station has n working sequences, and the positioning operation of a positioning target is completed in each sequence; each working sequence has 4 time slots: request, wait, receive, upload, If the positioning target does not respond, the receiving and uploading time slots will be skipped directly to speed up the system positioning scanning frequency.

In order to determine the location area where the positioning target is located so as to determine the positioning algorithm, the host computer caches n pieces of received power data P _R [n] of the same target node uploaded by a certain base station in the host computer, and then the host computer caches the n pieces of cached power data P R [n] The received power data P _R [n] is compared with the set threshold P _RT . Among them, P _RT is set according to the specific environment of the mine roadway, that is, the received power value measured at the border of the base station. In the present invention, we experimented in a mine roadway and set the distance from the base station to the border of the base station to be 10 meters, namely h ₁ =10 meters. Thus the measured threshold P _RT = -62.02dBm. If there are more than m (m<n) P _R values greater than the threshold P _RT , it is judged that the target is in the near base station area, and the RSSI positioning algorithm is used for the near base station area; otherwise, it is judged as the far base station area, and the VT positioning method for the far base station area is used .

2. RSSI positioning algorithm in the near base station area

If it is judged that the target is in the area near the base station, use the RSSI positioning algorithm in the area near the base station to locate it. First, use the Gaussian filter model to filter the n pieces of _PR data in the buffer, and then use the RSSI ranging model to calculate the distance between the positioning target and the base station. distance. The whole process is completed on the upper computer, and the specific steps are as follows:

1) Calculate the mean μ and standard deviation σ of the cached data P _R [n];

average $\mathrm{\&mu;}=\frac{1}{\mathrm{no}}\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\&Sigma;}}}{P}_R\left(i\right),$ standard deviation $\mathrm{\&sigma;}=\sqrt{\frac{1}{\mathrm{no}-1}\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\&Sigma;}}}{(P_R\left(i\right)-\mathrm{\&mu;})}^2}.$

2) Calculate the high probability occurrence interval of _PR [μ-0.84σ, μ+0.84σ], and filter out all _PR values falling into this interval from _PR [n] _PR [k], 0<k ≤n;

3) Calculate the geometric mean of P _R [k]

代入公式

求出目标距离该基站的距离d，其中P_R0是参考距离d₀=1米时的接收功率，衰减系数u是在矿井巷道采集到的数据，并由这些数据通过一元线性回归的方法获取；4) Will

Into the formula

Find the distance d between the target and the base station, where P _R0 is the received power when the reference distance d ₀ =1 meter, and the attenuation coefficient u is the data collected in the mine roadway, and these data are obtained by the method of unary linear regression;

5) According to the received power of the target node received by the base stations on the adjacent two sides of the base station, and the strength of the above two received powers, determine which side of the base station the target node is on. For example: the power of the target node received by the adjacent base stations on the left and right is respectively P _Rl and P _Rr , if P _Rl >P _Rr , the target node is on the left side of the base station, otherwise, the target node is on the right side of the base station.

6) According to the distance measurement results and the known base station coordinates, the position of the target node is converted into coordinates for graphical display on the host computer.

In addition, the average movement speed of the positioning target should be estimated in the near base station area. The specific steps are as follows:

1) When it is judged that a positioning target enters the near base station area, start timing it;

2) When it is judged that the positioning target is out of the near base station area, stop timing it and read the timing time t ₁ ;

3) Calculate the average moving speed of the positioning target: v=2h ₁ /t ₁ , where h ₁ is the distance to the corresponding base station near the boundary of the base station, that is, the radius of the area near the base station.

3. V-T positioning method in the far base station area

The far base station area estimates the distance between the current distance of the positioning target and the positioning base station according to the average moving speed v of the positioning target estimated by the near base station area and the time length t of the target entering the far base station area. The whole process is completed in the upper computer, and the specific steps are as follows:

1) When it is judged that a positioning target enters the remote base station area, start timing it;

2) Read the estimated average moving speed v of the target near the base station area;

3) Read the current timing t;

4) Use the formula d=vt+h ₁ to calculate the distance d between the target and the base station, where h ₁ is the distance from the border of the base station to the corresponding base station, that is, the radius of the area near the base station;

5) According to the receiving power of the target node received by the base station on the adjacent two sides of the base station, judge which side of the base station the target node is on based on the strength of the above two receiving powers, such as: the left and right adjacent base stations receive the target node The node powers are P _Rl and P _Rr respectively, if P _Rl >P _Rr , then the target node is on the left side of the base station, otherwise, the target node is on the right side of the base station;

6) According to the distance measurement results and the known base station coordinates, the position of the target node is converted into coordinates for graphical display on the host computer.

4. System implementation description: The flow chart of the implementation is shown in Figure 5.

Implementation steps:

1) System initialization, according to the ID of the target node, set the ID range that the main base station will broadcast in turn. Since the experiment uses 10 target nodes, the ID number range (1000, 1009). Therefore, in the present invention, the range of IDs that the main base station will broadcast in turn is (1000, 1009).

2) The main base station initiates positioning requests sequentially according to the ID range, and the data packet includes: the main base station's own ID and the target node ID.

3) The target node judges whether it is its own ID. If so, the target node broadcasts a positioning data packet to the master base station and the slave base station; otherwise, it waits for the next positioning request.

4) The master base station and the slave base station receive the data packet broadcast by the target node, and the data packet includes: the target node ID and the received power value P _R .

5) The master base station and the slave base station will receive the target data packet, and then add the base station ID, target node ID, and received power value P _R to the base station's sending data packet, and then upload it to the host computer through the RS485 bus.

6) The host computer caches n pieces of received power value _PR [n] data, and judges which area the target node is in. If there are m received powers P _R greater than the threshold P _RT , it indicates that the target node is in the area near the base station. Therefore, the RSSI algorithm is used to calculate the distance d from the base station, and at the same time, the signals from the base stations on both sides of the base station to the target node are transmitted. Intensity: P _Rl , P _Rr , which side of the base station is judged by the value of P _Rl , P _Rr ; otherwise, the target node uses the VT positioning algorithm in the far base station area to calculate the distance d from the base station, and also through the above method Determine which side of the base station the target node is on.

7) Convert to coordinates for graphical display.

Claims (4)

1. A ZigBee-based underground personnel positioning scheme is characterized in that a plurality of base stations are arranged in the roadway, and the base station includes a plurality of master base stations and a plurality of slave base stations, and the master base station and the slave base stations are arranged at intervals; the master base station and the positioning target Question-and-answer communication is adopted, and multiple positioning targets adopt time-division multiplexing to communicate with the master base station or slave base station based on ZigBee; According to the distance h _1, the area between two adjacent base stations is divided into the near base station area and the far base station area, that is, when the distance between the positioning target and the nearest base station is less than h ₁ , it indicates that the positioning target is in the near base station area; otherwise, the positioning target is in the far base station area. base station area; When the positioning target is in the near base station area, the RSSI positioning method is used for positioning; When the positioning target is in the far base station area, the V-T positioning method is used for positioning. 2. the underground personnel positioning scheme based on ZigBee according to claim 1, is characterized in that, described RSSI positioning method is: the distance between positioning target and the nearest base station Among them, P _R0 is the received power relative to the reference distance of the transmitting base station, and u is the attenuation coefficient; $\stackrel{\&OverBar;}{P_R}\frac{1}{k}\underset{i=1}{\overset{k}{\mathrm{\&Sigma;}}}{P}_R\left(i\right),$ P _R (i)∈[μ-0.84σ,μ+0.84σ]; in,

is the average value of P _R , k is the number of n values of P _R that fall into [μ-0.84σ, μ+0.84σ], and the mean $\mathrm{\&mu;}=\frac{1}{\mathrm{no}}\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\&Sigma;}}}{P}_R\left(i\right),$ standard deviation $\mathrm{\&sigma;}=\sqrt{\frac{1}{\mathrm{no}-1}\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\&Sigma;}}}{(P_R\left(i\right)-\mathrm{\&mu;})}^2};$ The method of obtaining P _R (i) is as follows: The host computer connected to the current base station as base station X-communication caches n received power values P _R [i] data of a positioning target. If there are m received power values P _R greater than the threshold value P _RT , it indicates that the positioning target is near In the base station area, the n _PR [i] data are valid data, where n is the number of received power data of the same target node received by the same base station in continuous time; The signal strengths of the base stations on both sides adjacent to the base station X to the target node are: P _Rl , P _Rr , which side of the base station the positioning target is based on the values of P _Rl and P _Rr . 3. the underground personnel locating scheme based on ZigBee according to claim 2, it is characterized in that, VT locating method is based on d=vt+h ₁ location, and d is the distance of locating target and base station X, and v is that locating target is near The average speed in the area of the base station; the signal strengths of the base stations on both sides adjacent to the base station X to the target node are: P _Rl , P _Rr , which side of the base station the positioning target is determined by the values of P _Rl and P _Rr . 4. the underground personnel positioning scheme based on ZigBee according to claim 3, is characterized in that, the calculation method of average speed is: when judging that a locating target enters near base station area, start timing it; when judging that this locating target When walking out of the area near the base station, stop timing it, and read the timing time t ₁ ; calculate the average moving speed of the positioning target: v=2h ₁ /t ₁ .

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