CN109819396B - Wireless positioning method and system - Google Patents
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- CN109819396B CN109819396B CN201910090393.2A CN201910090393A CN109819396B CN 109819396 B CN109819396 B CN 109819396B CN 201910090393 A CN201910090393 A CN 201910090393A CN 109819396 B CN109819396 B CN 109819396B
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Abstract
The invention discloses a wireless positioning method and a wireless positioning system. The wireless positioning system comprises at least one synchronous base station, a plurality of positioning base stations and at least one positioning label, and further comprises network communication equipment and a computing server, wherein the synchronous base stations can also be used as the positioning base stations at the same time, and the synchronous base stations and the positioning base stations further comprise high-precision clocks. The method comprises the following steps: the synchronous base station sends a synchronous signal at intervals; the positioning base station receives the synchronous signal and uploads the data to the calculation server; the calculation server performs time synchronization on every two positioning base stations; the positioning tag broadcasts a positioning signal once every a period of time; the positioning base station receives the positioning signal and uploads the data to the calculation server; and the calculation server calculates the coordinates of the positioning labels.
Description
Technical Field
The invention relates to the field of sensor measurement, in particular to a wireless positioning method and system.
Background
With the development of emerging fields such as the internet of things and robots, high-precision indoor positioning technology is receiving more and more attention. The traditional indoor positioning accuracy based on technologies such as WiFi and Bluetooth is poor, and generally the positioning accuracy is only a few meters, so that the requirement of high-accuracy positioning cannot be met; the ultrasonic-based positioning technology can achieve higher precision, usually in centimeter level, but is extremely easy to be influenced by environment and shelters, and the practicability is poor.
Ultra Wideband (UWB) has the advantages of low power consumption, high interference immunity, high multipath resistance, etc., and has been widely used in high-precision indoor/outdoor positioning in recent years. The UWB positioning scheme based on TOF (Time of Flight) is used most, and is characterized by simple algorithm and stable positioning accuracy, however, the positioning scheme based on TOF needs bidirectional communication between a label to be positioned and a positioning base station for distance measurement, the occupied Time of a channel is long, and the power consumption is large; the positioning scheme based on AOA (Angle of Arrival) is usually used for local positioning due to higher hardware cost, and is less used for positioning of large area; the positioning scheme based on TDOA (Time Difference of Arrival) does not need bidirectional communication between the labels to be positioned and the positioning base station, the one-Time positioning channel of the positioning scheme has short occupied Time and extremely low power consumption, can realize simultaneous positioning of a large number of positioning labels, and has wide application prospect.
The UWB positioning scheme based on TDOA has a plurality of advantages, the technical problem to be solved is the time synchronization problem among the positioning base stations, and the existing technical scheme comprises wired synchronization and wireless synchronization. The wired synchronization needs a high-precision time synchronization device and strict wiring, and the equipment and construction cost is high; there are fewer existing perfect wireless synchronization schemes.
In addition, in indoor positioning, the existing UWB positioning scheme usually has high requirements on building structures, needs to ensure that the building structures are wide and unobstructed, and is limited in application to the scenes that the building structures are complex, or narrow and long channels, or base stations can only be installed on one side.
Disclosure of Invention
The invention provides a wireless positioning method and a system, which realize a UWB positioning technology based on TDOA, can well solve the problem of time synchronization among base stations and can be applied to various scenes.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a wireless positioning method is applied to a set of wireless positioning system, the wireless positioning system comprises at least one synchronous base station, a plurality of positioning base stations, at least one positioning label, network communication equipment and a calculation server, the synchronous base station can also be used as the positioning base station, the synchronous base station and the positioning base station also comprise high-precision clocks, and the high-precision clocks can achieve picosecond-level time resolution and precision; wherein, the wireless positioning method comprises the following steps:
the synchronous base station sends a synchronous signal once at a certain time interval, the time interval can be a fixed time or a random value within a certain range, preferably tens of milliseconds to several seconds, and the synchronous signal data packet comprises a source base station unique identifier and a synchronous signal packet unique identifier. The base station unique identifier may be a base station ID; the unique identifier of the synchronization signal packet may be a signal packet sequence number, which is referred to as a packet sequence for short.
And the positioning base station receives the synchronous signal of the synchronous base station, acquires a receiving timestamp corresponding to a local high-precision clock, and uploads the receiving timestamp, the source synchronous base station ID, the positioning base station ID and the synchronous signal packet sequence to a computing server through network communication equipment.
After receiving the data uploaded by the positioning base stations, the computing server performs time synchronization on every two positioning base stations, and the time synchronization method comprises the following steps:
for two positioning base stations, finding out two groups of synchronous signal packets with the same sequence from the synchronous signals received by the base stations, and calculating the clock frequency ratio of the two base stations by using corresponding time stamps, for example, the time stamps of the base station 1 receiving the synchronous signal 1 and the synchronous signal 2 are T11 and T12, the time stamps of the base station 2 receiving the synchronous signals 1 and 2 are T21 and T22, and the clock frequency ratio of the base station 1 and the base station 2 is
k12＝(T11–T12)/(T21–T22)；
Then, one group of synchronization signals and the coordinates of the base stations are utilized to determine the clock values of the two base stations at a certain time, if the synchronization signal 1 comes from the synchronization base station 3, the distance d31 from the synchronization base station 3 to the positioning base station 1 and the distance d32 from the synchronization base station 2 can be calculated, at the time when the base station 1 receives the synchronization signal 1, the clock value of the base station 1 is T11, and the clock value of the base station 2 is T11
T12 ═ T12- (d 32-d 31)/c, c is the speed of light;
the time when the base station 1 receives the synchronization signal 1 is used as the common starting time of the base stations 1 and 2, and at this time, the clock value of the base station 1 is T11, and the clock value of the base station 2 is T12'.
Finally, a clock conversion equation from the positioning base station 2 to the positioning base station 1 can be obtained:
t2’＝T11+k12·(t2-T12’)
that is, when the clock value of the positioning base station 2 is t2, the clock value of the corresponding positioning base station 1 is t 2'.
In turn, the clock transfer equation for positioning base station 1 to positioning base station 2 is:
t1’＝T12’+(t1–T11)/k12
that is, when the clock value of the positioning base station 1 is t1, the clock value of the corresponding positioning base station 2 is t 1'.
And when a new synchronous signal is received, updating the clock conversion equation of every two base stations.
The positioning tag broadcasts a positioning signal once every a period of time, and the positioning signal data packet comprises a unique positioning tag Identifier (ID) and a unique data packet identifier (packet sequence).
And the positioning base station receives the positioning signal of the positioning label, acquires the receiving timestamp, and uploads the receiving timestamp, the positioning label ID, the positioning signal packet sequence and the positioning base station ID to the calculation server.
The calculation server can calculate the distance difference between the positioning tag and the two base stations by utilizing the clock conversion equation of any two base stations and the positioning tag positioning signal receiving time stamp. For example, the timestamps of a certain positioning signal received by the positioning tags by the base stations 1 and 2 are t1 and t2, the clock t2 of the base station 2 is converted to the base station 1, and the corresponding clock value on the base station 1 is:
t2’＝T11+k12·(t2-T12’)
the location tag now has a difference in distance to base stations 1 and 2 of
r12＝c·(t1–t2’)
Similarly, the distance differences r13, r14, r15 … between the positioning tag and the other base station can be calculated, and these values are called distance difference measurement values, and the base station 1 is called a reference base station.
Assuming that the coordinates of the positioning tag are (x, y,0), the coordinates of the base station i are (xi, yi, zi), and the distance difference between the positioning tag and the reference base station 1 and other positioning base stations i is r1, i, there is an equation:
and solving the equation set to obtain the coordinates (x, y) of the positioning label, wherein the solving method is related to the installation mode of the positioning base station.
When the positioning base station is installed, according to the characteristics of a building, four optional installation modes are provided: two-dimensional square placement, one-dimensional straight line side by side placement, long channel two-end placement, and small-space single base station placement.
The two-dimensional square arrangement means that base stations can be spliced and arranged in a square or rectangular manner in a large site or indoors, at least four base stations are needed, and two-dimensional positioning of the positioning labels is realized.
The one-dimensional straight lines are arranged side by side, namely, base stations can be arranged only on one side due to site installation and power supply limitation in a stadium, a parking lot and the like, the one-dimensional straight lines can be arranged side by side, two-dimensional positioning of one side of each straight line is achieved, and the number of the base stations needs to be positioned at least.
The two ends of the long channel are placed at narrow places such as corridors and mines but long places, the two ends of the base stations can be placed to realize positioning between the two base stations, and at least two base stations are needed.
The small-space single base station is placed in a small room or a narrow space, two-dimensional positioning of the positioning tags is not needed, whether the positioning tags are located in the small room or the narrow space or not is only needed to be detected, whether the positioning tags are located in the small room or the narrow space or not can be detected by independently placing the single base station, and at least one base station is needed.
For two-dimensional square placement, at least 3 distance difference values of at least 4 positioning base stations are utilized, the equation set is reduced into a nonlinear equation and at least two linear equations, and the linear equation set is solved by adopting a weighted least square method, so that the two-dimensional coordinate of the positioning label can be calculated.
Preferably, when there are at least 3 distance difference values of at least 4 positioning base stations, the linear equation set is solved to obtain an initial value of the positioning tag coordinate, the initial value is used as an initial point, a taylor convergence method is used for at least 3 nonlinear equations before cancellation, the positioning tag coordinate is further optimized, and higher solving accuracy is obtained.
And for the one-dimensional straight lines which are arranged side by side, at least two linear equations can be obtained by utilizing at least two distance differences of at least 3 positioning base stations, and the two-dimensional coordinates of the positioning labels are calculated by adopting a weighted least square method for solving.
And for the placement of the two ends of the long channel, calculating the position of the positioning label in the channel by using at least 1 distance difference value of at least two positioning base stations.
For the arrangement of a single base station in a small space, a base station synchronization result and an equation do not need to be solved, and only whether the positioning label is in the space is judged and the coordinate of the positioning base station is output.
Preferably, the distance difference values are used as many as possible, and the more the distance difference values are, the higher the solving precision is.
Preferably, if it cannot be known in advance which positioning base stations can receive a certain positioning signal of a certain positioning tag, and can successfully upload corresponding data to the calculation server, in order to ensure that the distance difference as much as possible is obtained, after the calculation server receives the first positioning data of a certain packet of the certain positioning tag, the coordinates of the positioning tag are solved after a delay time, where the delay time is determined by network delay, generally 50 milliseconds to 500 milliseconds, so as to ensure that the positioning base stations which can receive the positioning signal as much as possible successfully upload the positioning data to the calculation server.
Preferably, in order to filter abnormal data, the base station clock ratio k12 calculated each time is judged, and if k12 exceeds the possible maximum frequency offset of the high-precision clock, the abnormal data is judged; if the clock oscillator frequency offset is + -10 ppm, k12 should be greater than 0.99998 and less than 1.00002.
Preferably, in order to filter abnormal data, the coordinates of the positioning tag are solved each time, the distance difference between the positioning tag and the reference base station and between the positioning tag and each other base station is inversely calculated by using the coordinates and is compared with the distance difference measured value, and if the difference between the distance difference measured value and the distance difference measured value exceeds a certain threshold value, the data is judged to be abnormal; the threshold value can be three times of standard deviation of the error of the measured distance difference value, and the standard deviation of the error of the measured distance difference value can be obtained through statistics.
Preferably, when the difference between the back-calculated range difference and the range difference measurement value exceeds a threshold value and the data is judged to be abnormal, only three optimal range difference measurement values are screened and reserved, and other range difference measurement values are discarded, so that normal measurement values are possibly reserved, and accurate positioning tag coordinates are solved; three distance measurement values which make the determinant of the coefficient matrix of the linear equation set as large as possible are taken as the retained optimal values.
Preferably, a chain time synchronization method is adopted to realize time synchronization of any two base stations, for example, base stations 1 and 2 can be directly synchronized, and base stations 2 and 3 can be directly synchronized, but base stations 1 and 3 cannot be directly synchronized, so that base stations 1 and 3 can realize chain synchronization through relay of base station 2; and the shortest chain synchronization of any two base stations is realized by adopting a graph theory algorithm, so that the accumulated error is minimum.
Preferably, in order to synchronize any two base stations by the chain time synchronization method, when the base stations are installed, it is ensured that at least one positioning base station capable of communicating together exists in two adjacent synchronization base stations, and if the positioning base station 1 can receive the signal of the synchronization base station 1 and the positioning base station 2 can receive the signal of the synchronization base station 2, at least the positioning base station 3 can receive the signals of the synchronization base stations 1 and 2, so that the chain time synchronization method can be adopted to synchronize the positioning base stations 1 and 3.
Preferably, median filtering or Kalman filtering is performed on the solved positioning tag coordinates, or Kalman filtering is performed after the median filtering.
Optionally, the synchronization base station may be simultaneously used as a positioning base station, when a certain base station is simultaneously used as the synchronization base station and the positioning base station, a sending timestamp for sending the synchronization signal needs to be obtained, the timestamp is used as a receiving timestamp for the base station to receive the synchronization signal, and the receiving timestamp, the source synchronization base station ID, the local positioning base station ID, and the synchronization signal packet sequence are uploaded to the computing server through the network communication device, where the source synchronization base station ID and the local positioning base station ID are the same value.
In addition, the invention also provides a set of wireless positioning system, which comprises at least one synchronous base station, a plurality of positioning base stations and at least one positioning label, and also comprises network communication equipment and a computing server, wherein the synchronous base station can also be used as the positioning base station, and the synchronous base station and the positioning base station also comprise high-precision clocks.
The synchronous base station is used for broadcasting a synchronous signal to the positioning base station.
The positioning base station is used for receiving a positioning signal of the positioning label and also receiving a synchronous signal of the synchronous base station; the positioning base station is communicated with the computing server through a wireless or wired network and uploads synchronous data and positioning tag positioning data.
The network communication device can be a wireless router, a wired switch, a POE switch and the like.
And the calculation server receives and processes the data uploaded by the positioning base station, and comprises calculating a base station clock conversion equation, calculating a distance difference, calculating a positioning label coordinate and filtering abnormal data.
The technical scheme provided by the invention has the following beneficial effects:
the method and the system provided by the invention can well solve the problem of time synchronization between base stations in the UWB positioning based on TDOA, and the wireless time synchronization method is used, so that the equipment and construction cost is low; the method and the system can solve the problem of large-scale base station time synchronization, have good expansibility and low installation requirement on the base station; the method and the system can be applied to scenes with complex building structures, and base stations can be installed on one side; the method and the system can realize high-precision positioning, and the positioning precision can reach centimeter level; the method and the system can realize large-scale positioning of the positioning labels, and can position hundreds to thousands of positioning labels; the requirement of low power consumption of the positioning tag can be met, and the endurance time of the positioning tag can reach several months to one year.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The present invention will be described in detail below with reference to the accompanying drawings so that the above advantages of the present invention will be more apparent. Wherein the content of the first and second substances,
FIG. 1 is a schematic diagram of a wireless location system according to the present invention;
fig. 2 is a flow chart of the wireless positioning method of the present invention.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
Additionally, the steps illustrated in the flow charts of the figures may be performed in a computer system such as a set of computer-executable instructions and, although a logical order is illustrated in the flow charts, in some cases, the steps illustrated or described may be performed in an order different than here.
The invention provides a wireless positioning method and system, which realize UWB positioning based on TDOA, a specific embodiment is shown as a block diagram of a wireless positioning system in figure 1, and the system of the specific embodiment comprises:
positioning the label; a synchronous base station and a positioning base station; a computing server (PC); the POE switch or the wireless router is used for establishing Ethernet transmission data between the base station and the positioning server; in addition, a user interface is also provided.
The positioning tags automatically and periodically broadcast positioning signals, the base station receives and uploads positioning data to the computing server, the computing server calculates and obtains state information such as coordinates and electric quantity of each positioning tag, the positioning tag information is stored in the database, and the user interface displays the state information such as the positions of the positioning tags.
The specific implementation method of the embodiment comprises the following steps:
the synchronous base stations send synchronous signals once at intervals, and the interval time is a fixed value of hundreds of milliseconds plus a random value of 0 to tens of milliseconds, so that the signals transmitted by the synchronous base stations are prevented from continuously colliding with one another; the synchronization signal data packet contains a source base station unique Identification (ID) and a synchronization signal packet unique identification (packet sequence).
And the positioning base station receives the synchronous signal of the synchronous base station, acquires a receiving time stamp, and transmits the receiving time stamp, the source synchronous base station ID, the local positioning base station ID and the synchronous signal packet sequence to the calculation server through the Ethernet.
The calculation server receives the synchronous data and stores the synchronous data into the data queue, meanwhile, checks whether the data in the data queue is expired or not, and deletes the expired data, wherein the data in dozens of seconds is usually reserved.
In this embodiment, the synchronization base station is simultaneously used as the positioning base station, so that after the synchronization base station transmits the synchronization signal, the transmission timestamp is acquired, and the transmission timestamp, the synchronization base station ID, and the synchronization signal packet sequence are uploaded to the computing server through the network device.
After receiving the data uploaded by the positioning base stations, the computing server performs time synchronization on every two positioning base stations, and the time synchronization method comprises the following steps:
for two positioning base stations, finding out two groups of synchronous signal packets with the same sequence from the synchronous signals received by the base stations, and calculating the clock frequency ratio of the two base stations by using corresponding time stamps, for example, the time stamps of the base station 1 receiving the synchronous signal 1 and the synchronous signal 2 are T11 and T12, the time stamps of the base station 2 receiving the synchronous signals 1 and 2 are T21 and T22, and the clock frequency ratio of the base station 1 and the base station 2 is
k12＝(T11–T12)/(T21–T22)；
Then, one group of synchronization signals and the coordinates of the base stations are utilized to determine the clock values of the two base stations at a certain time, if the synchronization signal 1 comes from the synchronization base station 3, the distance d31 from the synchronization base station 3 to the positioning base station 1 and the distance d32 from the synchronization base station 2 can be calculated, at the time when the base station 1 receives the synchronization signal 1, the clock value of the base station 1 is T11, and the clock value of the base station 2 is T11
T12 ═ T12- (d 32-d 31)/c, and c is the speed of light
The time when the base station 1 receives the synchronization signal 1 is used as the common starting time of the base stations 1 and 2, and at this time, the clock value of the base station 1 is T11, and the clock value of the base station 2 is T12'.
Finally, a clock conversion equation from the positioning base station 2 to the positioning base station 1 can be obtained:
t2’＝T11+k12·(t2-T12’)
that is, when the clock value of the positioning base station 2 is t2, the clock value of the corresponding positioning base station 1 is t 2'.
In turn, the clock transfer equation for positioning base station 1 to positioning base station 2 is:
t1’＝T12’+(t1–T11)/k12
that is, when the clock value of the positioning base station 1 is t1, the clock value of the corresponding positioning base station 2 is t 1'.
And when a new synchronous signal is received, updating the clock conversion equation of every two base stations. For example, when the base station 1 receives a synchronization signal with the packet sequence 1 of the synchronization base station 1, it goes through all the positioning base stations, finds out all the positioning base stations that have received the synchronization signal according to the synchronization base station ID and the packet sequence, and if the positioning base stations 2 and 3 are found, updates the clock conversion equations between the base stations 1 and 2 and between the base stations 1 and 3.
In order to filter abnormal data, after the clock frequency ratio is calculated each time, since the maximum frequency deviation of the clock crystal oscillator used in the embodiment is ± 10ppm, whether the clock frequency ratio is between 0.99998 and 1.00002 is judged, and if not, the result is not updated.
In addition, the positioning tag broadcasts a positioning signal once every a period of time, and the positioning signal data packet comprises a unique positioning tag Identification (ID) and a unique data packet identification (packet sequence).
And the positioning base station receives the positioning signal of the positioning label, acquires the receiving timestamp, and uploads the receiving timestamp, the positioning label ID, the positioning signal packet sequence and the positioning base station ID to the calculation server.
The calculation server can calculate the distance difference between the positioning tag and the two base stations by utilizing the clock conversion equation of any two base stations and the positioning tag positioning signal receiving time stamp. For example, the timestamps of a certain positioning signal received by the positioning tags by the base stations 1 and 2 are t1 and t2, the clock t2 of the base station 2 is converted to the base station 1, and the corresponding clock value on the base station 1 is:
t2’＝T11+k12·(t2-T12’)
the location tag now has a difference in distance to base stations 1 and 2 of
r12＝c·(t1–t2’)
Similarly, the distance differences r13, r14, r15 … between the positioning tag and the other base station can be calculated, and these values are called distance difference measurement values, and the base station 1 is called a reference base station.
In order to obtain distance difference measurement values as much as possible, the calculation server does not immediately calculate the distance difference after receiving the positioning tag positioning data, the calculation server checks data in the positioning tag positioning data queue at certain intervals, if the distance of the uploading moment of the positioning data of at least one positioning tag i packet sequence j is found to be larger than a certain time value at the present moment, the positioning data of all the positioning tag i packet sequences j are found, all the corresponding distance differences are calculated, and the data are deleted from the queue; the time value is determined by the network delay, and the larger the network delay, the larger the value should be, and is usually set to be between 20 ms and 500 ms.
The clock transfer equations for two base stations sometimes cannot be calculated from the synchronization data. For example, the positioning base stations 1, 2 are in the communication range of the synchronous base station 1, but not in the communication range of the synchronous base station 2; the positioning base stations 3, 4 are in the communication range of the synchronous base station 2 but not in the communication range of the synchronous base station 1. At this time, the positioning base station 1 cannot perform time synchronization with 3 or 4.
In order to solve the problem, a chain time synchronization method is adopted to realize the time synchronization of any two base stations. In order to synchronize any two base stations by the chain time synchronization method, the base stations are installed to ensure that at least one positioning base station capable of communicating together exists between two adjacent synchronous base stations.
For the above example, the position of the synchronization base station 1 is adjusted so that the synchronization base station 1 can communicate with the positioning base stations 1, 2 and 3, and at this time, the positioning base stations 1 and 4 cannot directly synchronize time, and they can be synchronized by using a chain time synchronization method, which includes the following steps:
firstly, calculating a clock conversion equation of the positioning base stations 1 to 3;
then calculating a clock conversion equation of the positioning base stations 3 to 4;
and finally, substituting the clock conversion equations of the positioning base stations 1 to 3 into the clock conversion equations of the base stations 3 to 4 to obtain the clock conversion equations of the base stations 1 to 4 and further obtain the clock conversion equations of the base stations 4 to 1.
Further, when the positioning base stations 5 and 4 can be synchronized, the clock transfer equations of the base stations 1 to 4 are substituted into the clock transfer equations of the base stations 4 to 5 in the same way to obtain the clock transfer equations of the base stations 1 and 5, thereby realizing the chain-type synchronous positioning of the base stations 1 and 5.
Further, a graph theory algorithm is adopted to search the chain synchronous shortest path of any two base stations, so that the accumulated error is minimum. For example, the shortest chain synchronization path of base stations 1 to 5 is base stations 1 to 3, 3 to 4, and 4 to 5, and further, base stations 1 to 2, 2 to 3, 3 to 4, and 4 to 5 can synchronize base stations 1 and 5, but this is not the shortest path.
Assuming that the coordinates of the positioning tag are (x, y,0), the coordinates of the base station i are (xi, yi, zi), and the distance difference between the positioning tag and the reference base station 1 and other positioning base stations i is r1, i, there is an equation:
and solving the equation set to obtain the coordinates (x, y) of the positioning label, wherein the solving method is related to the installation mode of the positioning base station.
In addition, as shown in the block diagram of the wireless positioning system in fig. 1, there are four different installation methods for the positioning base station according to the characteristics of the building: two-dimensional square placement, one-dimensional straight line side by side placement, long channel two-end placement, and small-space single base station placement.
The two-dimensional square arrangement means that base stations can be spliced and arranged in a square or rectangular manner in a large site or indoors, at least four base stations are needed, and two-dimensional positioning of the positioning labels is realized.
The one-dimensional straight lines are arranged side by side, namely, base stations can be arranged only on one side due to site installation and power supply limitation in a stadium, a parking lot and the like, the one-dimensional straight lines can be arranged side by side, two-dimensional positioning of one side of each straight line is achieved, and the number of the base stations needs to be positioned at least.
The two ends of the long channel are placed at narrow places such as corridors and mines but long places, the two ends of the base stations can be placed to realize positioning between the two base stations, and at least two base stations are needed.
The small-space single base station is placed in a small room or a narrow space, two-dimensional positioning of the positioning tags is not needed, whether the positioning tags are located in the small room or the narrow space or not is only needed to be detected, whether the positioning tags are located in the small room or the narrow space or not can be detected by independently placing the single base station, and at least one base station is needed.
For two-dimensional square placement, at least 3 distance difference values of at least 4 positioning base stations are utilized, the equation set is reduced into a nonlinear equation and at least two linear equations, and the linear equation set is solved by adopting a weighted least square method, so that the two-dimensional coordinate of the positioning label can be calculated.
For example, the distance differences r12, r13, and r14 between the positioning base station 1 and the base stations 2, 3, and 4 are calculated, a nonlinear equation set formed by three nonlinear equations can be established, and the nonlinear equation set is subtracted to obtain a linear equation set formed by two linear equations:
i＝3,4
kx, Ky and Kb are known quantities, and two unknown quantities x and y can be solved by utilizing the linear equation system.
The coordinates (x, y) of the positioning label can be calculated by solving the linear equation set by adopting a weighted least square method, wherein the measured value r1,iHas a covariance matrix of
The distance difference standard deviation is obtained, the diagonal element of the matrix is 1, and other elements are 0.5, and the value of the matrix does not influence the solving result of the weighted least square method, because 1 is taken to facilitate calculation.
Preferably, when there are at least 3 distance difference values of at least 4 positioning base stations, the linear equation set is solved to obtain an initial value of the positioning tag coordinate, the initial value is used as an initial point, a taylor convergence method is used for at least 3 nonlinear equations before cancellation, the positioning tag coordinate is further optimized, and higher solving accuracy is obtained.
And for the one-dimensional straight lines which are arranged side by side, at least two linear equations can be obtained by utilizing at least two distance differences of at least 3 positioning base stations, and the two-dimensional coordinates of the positioning labels are calculated by adopting a weighted least square method for solving.
For example, the positioning base stations 1, 2, and 3 are placed on the same straight line, and their coordinates have the following relationships:
yi＝a·xi+b,i＝1,2,3
the distance difference r12, r13 between the base station 1 and the base stations 2, 3 can obtain an equation system consisting of two linear equations:
wherein K1,KiIn known amounts, (x + a. y) and r1Two free unknowns, r1Indicating the distance of the positioning tag from the base station 1
Solving the linear equation set by using a weighted least square method to obtain (x + a.y) and r1And (x, y) can be calculated.
For the placement of the two ends of the long channel, the position coordinates of the positioning label in the channel are easily calculated by using at least 1 distance difference value of at least two positioning base stations, namely the distance difference from the positioning label to the two ends.
For the arrangement of a single base station in a small space, a base station synchronization result and an equation do not need to be solved, and only whether the positioning label is in the space is judged and the coordinate of the positioning base station is output.
After the coordinates of the positioning tag are solved, the coordinates are used for reversely calculating the distance difference between the positioning tag and the reference base station and other base stations, the distance difference is compared with the distance difference measured value, and if the difference between the distance difference measured value and the distance difference measured value exceeds a certain threshold value, the data are judged to be abnormal; the threshold may be three times the standard deviation of the range difference measurements, which may be statistically derived, and the standard deviation of the range difference measurements based on UWB measurements is typically within 6 centimeters.
When the difference between the back-calculated range difference and the range difference measurement value exceeds a threshold value and the data is judged to be abnormal, three optimal range difference measurement values are screened out, other range difference measurement values are discarded, the three range measurement values enabling the coefficient matrix determinant of the linear equation set to be as large as possible are taken as the reserved optimal values, all abnormal measurement values are possibly removed, and therefore accurate positioning label coordinates are successfully solved.
And further, performing median filtering on the solved positioning tag coordinates, performing Kalman filtering, and finally outputting stable and high-precision positioning tag coordinates.
The present invention is not limited to the above-described embodiments.
It should be noted that for simplicity of description, the above method embodiments are described as a series of acts or combination of acts, but those skilled in the art will recognize that the present application is not limited by the order of acts described, as some steps may occur in other orders or concurrently depending on the application. Further, those skilled in the art should also appreciate that the embodiments described in the specification are preferred embodiments and that the acts and modules referred to are not necessarily required in this application.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects.
Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (13)
1. A wireless positioning method is applied to a set of wireless positioning system, the wireless positioning system comprises at least one synchronous base station, a plurality of positioning base stations and at least one positioning label, and also comprises network communication equipment and a calculation server, the synchronous base station can also be used as the positioning base station, the synchronous base station and the positioning base station also comprise high-precision clocks, and the method is characterized by comprising the following steps:
the synchronous base station sends a synchronous signal at intervals;
the positioning base station receives the synchronous signal and uploads the data to the calculation server;
the calculation server performs time synchronization on every two positioning base stations;
the positioning tag broadcasts a positioning signal once every a period of time;
the positioning base station receives the positioning signal and uploads the data to the calculation server;
the calculation server calculates the coordinates of the positioning labels;
the time synchronization method for the two base stations comprises the following steps:
finding out two groups of synchronous signal packets with the same sequence from the synchronous signals received by the two base stations;
calculating the clock frequency ratio of the two base stations by using the corresponding time stamps;
wherein, the timestamps of the base station 1 receiving the synchronization signals 1 and 2 are T11 and T12, and the timestamps of the base station 2 receiving the synchronization signals 1 and 2 are T21 and T22, then the clock frequency ratio of the base station 1 and the base station 2 is k12 = (T11-T12)/(T21-T22);
determining the clock values of two base stations at a certain time by using one group of synchronous signals and the coordinates of the base stations, comprising the following steps: the synchronous base station 3 transmits a synchronous signal 1, calculates the distance d31 from the synchronous base station 3 to the positioning base station 1 and the distance d32 from the positioning base station 2, and takes the time when the synchronous base station 1 receives the synchronous signal 1 as the common starting time of the two base stations, wherein the clock value of the base station 1 is T11, and the clock value of the base station 2 is:
t12' = T12- (d 32-d 31)/c, c is the speed of light;
finally, a clock conversion equation from the positioning base station 2 to the positioning base station 1 can be obtained:
t2 ’ = T11 + k12·(t2 - T12 ’)；
in turn, the clock transfer equation for positioning base station 1 to positioning base station 2 is:
t1 ’ = T12 ’ + (t1 – T11) / k12；
when a new synchronous signal is received, updating the clock conversion equation of every two base stations;
the method for calculating the coordinates of the positioning tag comprises the following steps:
calculating the distance difference between the positioning tag and the two base stations by using a clock conversion equation of the two positioning base stations and a positioning tag positioning signal receiving timestamp, wherein the method comprises the following steps:
the time stamps of a positioning signal of the positioning tags received by the base station 1 and the base station 2 are t1 and t2, and the distance difference between the positioning tags and the base stations 1 and 2 is
Similarly, the distance differences r13, r14, r15 … between the positioning tag and the base station 1 and other base stations can be calculated, these values are called distance difference measurement values, and the base station 1 is called a reference base station;
and establishing an equation set according to the relation between the coordinates of the positioning tag and the coordinates and the distance difference of the positioning base station, and solving the equation set to obtain the coordinates (x, y) of the positioning tag.
2. The wireless positioning method of claim 1, wherein the time interval for the synchronization base station to transmit the synchronization signal may be a fixed time or a random value within a certain range;
the synchronous signal data packet comprises a source base station unique identifier and a synchronous signal packet unique identifier;
the base station unique identifier may be a base station ID, and the signal packet unique identifier may be a packet sequence;
and the positioning base station acquires a receiving time stamp after receiving the synchronous signal of the synchronous base station, and uploads the receiving time stamp, the source synchronous base station ID, the positioning base station ID and the synchronous signal packet sequence to a computing server through network communication equipment.
3. The wireless positioning method of claim 1, wherein the positioning tag positioning signal data packet comprises a positioning tag unique identifier ID, a data packet unique identifier;
and after receiving the positioning signal of the positioning label, the positioning base station acquires a receiving timestamp and uploads the receiving timestamp, the positioning label ID, the positioning signal packet sequence and the positioning base station ID to the calculation server.
4. The wireless positioning method according to claim 1, wherein the method for solving the positioning tag comprises, when the positioning base station is placed in a two-dimensional square, the method comprising:
obtaining at least two linear equations by using at least 3 distance difference values of at least 4 positioning base stations, solving the linear equation set by using a weighted least square method, and calculating to obtain a two-dimensional coordinate of the positioning label;
the two-dimensional square arrangement means that base stations are arranged in a square or rectangular spliced mode in a large site or indoors, at least four base stations are needed, and two-dimensional positioning of the positioning labels is achieved.
5. The wireless positioning method of claim 4, wherein the method for solving the coordinates of the positioning tag further comprises using a linear system of equations to obtain an initial value of the coordinates of the positioning tag, and using the initial value as an initial point to optimize the coordinates of the positioning tag by using a Taylor convergence method for at least three non-linear equations.
6. The method according to claim 1, wherein the method for solving the coordinates of the positioning tags comprises the steps of obtaining at least two linear equations by using at least two distance differences of at least 3 positioning base stations when the positioning base stations are placed side by side in one-dimensional straight lines, and calculating the two-dimensional coordinates of the positioning tags by adopting a weighted least square method for solution;
the one-dimensional straight lines are arranged side by side, namely, base stations can be arranged only on one side due to site installation and power supply limitation in a stadium, a parking lot and the like, the one-dimensional straight lines can be arranged side by side, two-dimensional positioning of one side of each straight line is achieved, and the number of the base stations needs to be positioned at least.
7. The wireless positioning method according to claim 1, wherein the method for solving the coordinates of the positioning tag comprises the steps of calculating the position coordinates of the positioning tag in the channel by using at least 1 distance difference value of at least two positioning base stations when the positioning base stations are placed at two ends of the long channel;
the two ends of the long channel are placed at narrow places such as corridors and mines but long places, the two ends of the base stations can be placed to realize positioning between the two base stations, and at least two base stations are needed.
8. The wireless positioning method according to claim 1, wherein the method for solving the coordinates of the positioning tag comprises the steps of judging whether the positioning tag is in the space or not when the positioning base station is placed in a small-space single base station, and outputting the coordinates of the positioning base station;
the small-space single base station is placed in a small room or a narrow space, two-dimensional positioning of the positioning tags is not needed, whether the positioning tags are located in the small room or the narrow space or not is only needed to be detected, whether the positioning tags are located in the small room or the narrow space or not can be detected by independently placing the single base station, and at least one base station is needed.
9. The wireless positioning method of claim 1, wherein if it is not known in advance which positioning base stations can receive a positioning signal of a positioning tag and successfully upload the corresponding data to the calculation server, the calculation server delays to solve the positioning tag coordinates after receiving a first positioning data of a packet of the positioning tag, and the delay time is determined by a network delay.
10. The wireless positioning method of claim 1, wherein, for filtering abnormal data, each time the coordinates of the positioning tag are solved, the coordinates are used to calculate the distance difference between the positioning tag and the reference base station and each other base station, and the distance difference is compared with the measured distance difference value, if the distance difference value exceeds a certain threshold, the data is determined to be abnormal; the threshold value is determined by the standard deviation of the measured distance difference value, and the standard deviation of the measured distance difference value is obtained through statistics;
or when the difference between the reversely calculated range difference and the range difference measurement value exceeds a threshold value, and the data is judged to be abnormal, only three optimal range difference measurement values are screened and reserved, other range difference measurement values are discarded, so that the normal measurement values are possibly reserved, and accurate positioning label coordinates are solved; three distance measurement values which make the determinant of the coefficient matrix of the linear equation set as large as possible are taken as the retained optimal values.
11. The wireless positioning method of claim 1, wherein the time synchronization method for positioning base stations further comprises using a chain time synchronization method to achieve time synchronization between any two base stations, and using a graph theory algorithm to achieve the shortest chain synchronization between any two base stations, so as to minimize the accumulated error; when the base station is installed, at least one positioning base station capable of communicating together exists in two adjacent synchronous base stations.
12. The wireless positioning method according to claim 1, wherein the median filtering or the kalman filtering is performed on the solved positioning tag coordinates, or the median filtering and then the kalman filtering is performed.
13. A set of wireless positioning system is characterized in that the wireless positioning system comprises at least one synchronous base station, a plurality of positioning base stations, at least one positioning label, network communication equipment and a calculation server, wherein the synchronous base station can also be used as the positioning base station, the synchronous base station and the positioning base station also comprise high-precision clocks, and the synchronous base station sends a synchronous signal at intervals;
the positioning base station receives the synchronous signal and uploads the data to the calculation server;
the calculation server performs time synchronization on every two positioning base stations;
the positioning tag broadcasts a positioning signal once every a period of time;
the positioning base station receives the positioning signal and uploads the data to the calculation server;
the calculation server calculates the coordinates of the positioning labels;
the time synchronization method for the two base stations comprises the following steps:
finding out two groups of synchronous signal packets with the same sequence from the synchronous signals received by the two base stations;
calculating the clock frequency ratio of the two base stations by using the corresponding time stamps;
wherein, the timestamps of the base station 1 receiving the synchronization signals 1 and 2 are T11 and T12, and the timestamps of the base station 2 receiving the synchronization signals 1 and 2 are T21 and T22, then the clock frequency ratio of the base station 1 and the base station 2 is k12 = (T11-T12)/(T21-T22);
determining the clock values of two base stations at a certain time by using one group of synchronous signals and the coordinates of the base stations, comprising the following steps: the synchronous base station 3 transmits a synchronous signal 1, calculates the distance d31 from the synchronous base station 3 to the positioning base station 1 and the distance d32 from the positioning base station 2, and takes the time when the synchronous base station 1 receives the synchronous signal 1 as the common starting time of the two base stations, wherein the clock value of the base station 1 is T11, and the clock value of the base station 2 is:
t12' = T12- (d 32-d 31)/c, c is the speed of light;
finally, a clock conversion equation from the positioning base station 2 to the positioning base station 1 can be obtained:
t2 ’ = T11 + k12·(t2 - T12 ’)；
in turn, the clock transfer equation for positioning base station 1 to positioning base station 2 is:
t1 ’ = T12 ’ + (t1 – T11) / k12；
when a new synchronous signal is received, updating the clock conversion equation of every two base stations;
the method for calculating the coordinates of the positioning tag comprises the following steps:
calculating the distance difference between the positioning tag and the two base stations by using a clock conversion equation of the two positioning base stations and a positioning tag positioning signal receiving timestamp, wherein the method comprises the following steps:
the time stamps of a positioning signal of the positioning tags received by the base station 1 and the base station 2 are t1 and t2, and the distance difference between the positioning tags and the base stations 1 and 2 is
Similarly, the distance differences r13, r14, r15 … between the positioning tag and the base station 1 and other base stations can be calculated, these values are called distance difference measurement values, and the base station 1 is called a reference base station;
and establishing an equation set according to the relation between the coordinates of the positioning tag and the coordinates and the distance difference of the positioning base station, and solving the equation set to obtain the coordinates (x, y) of the positioning tag.
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