CN115409143A - Speed measuring method of ultrahigh frequency RFID system - Google Patents
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Abstract
The invention relates to a speed measuring method of an ultrahigh frequency RFID system, belonging to the field of radio frequency identification. The RFID identification and reading equipment antenna is arranged beside or right above the channel to be monitored and is made to face the channel to be monitored; collecting the label data and the phase information of an RFID label attached to an object to be tested by using an ultrahigh frequency RFID reader-writer, and recording the label data and the phase information together with timestamp information when the data is collected; sorting the acquired label data information according to labels to obtain the phase and time stamp information of each label; and processing the acquired tag data and the acquired phase information of the RFID tag to obtain the movement speed of the object attached with the RFID tag. The method provided by the invention has the characteristics of small operand, high real-time performance and convenience for integration into the existing ultrahigh frequency RFID system, and has very high practical value in occasions with speed measurement requirements such as electronic identification of motor vehicles, intelligent storage and the like.
Description
Technical Field
The invention belongs to the field of radio frequency identification, and particularly relates to a speed measuring method for an ultrahigh frequency RFID system.
Background
In an application scene of the RFID, a speed measurement requirement sometimes exists, for example, in a dispatching management system of a highway or a parking lot, in order to evaluate a congestion condition of a road, a deployed motor vehicle electronic identification system is required to be capable of acquiring a movement speed of each vehicle; the dispatching system of the intelligent storehouse needs to acquire the motion conditions of the goods attached with the RFID electronic tags and the like carried by the assembly line or the robot through each RFID reading device.
In response to such a need, an RFID identification device capable of measuring doppler shift and a speed calculation method have been developed, but such a scheme is high in cost and complex in method, and is not suitable for being integrated into an RFID application system; and other methods for estimating the speed based on the signal strength and the recognition rate of the RFID tag have the defects of poor precision, high algorithm complexity and poor practicability.
Therefore, an RFID speed measuring method with high precision and low cost is urgent to expand the application scene of RFID. The present invention has been made in light of this real need.
Disclosure of Invention
Technical problem to be solved
The invention aims to solve the technical problem of how to provide a speed measuring method for an ultrahigh frequency RFID system, so as to solve the problems of poor precision, high algorithm complexity and poor practicability of the conventional method.
(II) technical scheme
In order to solve the technical problem, the invention provides a speed measuring method of an ultrahigh frequency RFID system, which comprises the following steps:
s1, equipment deployment: deploying an RFID identification device antenna beside or right above a channel to be monitored and enabling the RFID identification device antenna to be right opposite to the channel to be monitored;
s2, data acquisition: in the monitoring process, the RFID reading equipment identifies the RFID tags in the reading range of the RFID reading equipment and records tag information, the phase of a tag signal and a timestamp of each identification, namely a data combination EPC n ,θ n ,t n ]Wherein n represents a serial number of the data combination ordered according to the acquisition sequence;
s3, data arrangement: for a specific timeThe data combination obtained in the period is sorted according to EPC codes to obtain the phase and time stamp combination [ theta ] of each tag in the RFID reading equipment reading range in the period i ,t i ]；
S4, a speed calculation step: and processing the acquired phase and time stamp information of the RFID tag to obtain the movement speed of the object attached with the RFID tag.
Further, in the step S1, the vertical distance from the RFID antenna to the passageway is h, the distance from the RFID antenna to the RFID tag is S, the distance from the RFID tag to the projection point of the center of the RFID antenna on the passageway is d,
the variation of unit time d is the moving speed of the object we are concerned with, and the phase of the tag response signal is related to d as follows:
where λ is the wavelength of the uhf RFID signal.
Further, the step S4 specifically includes: an edge detection step, an operation condition judgment step and an operation step.
Further, the edge detecting step includes: starting when the RFID tag first enters the reading range, if theta i -θ i-1 If the current value is more than Th, judging that an abrupt rising edge occurs in the RFID label response signal; if theta is greater than theta i -θ i-1 And < Th, judging that the phase of the response signal of the RFID tag has an abrupt falling edge, and counting the detected rising edge as R and the falling edge as N.
Further, the threshold value Th is π/4.
Further, the operation condition judging step includes: judging whether the obtained rising edge and falling edge conditions meet the operation conditions, wherein the condition 1 is as follows: a certain number of rising edges and the first falling edge are captured, i.e. R >1, n > =1; the condition 2 is: the last rising edge and a certain number of falling edges are captured, i.e., R > =1, n > -1; if one of the condition 1 or the condition 2 is satisfied, performing an operation; if the condition 1 and the condition 2 are both satisfied, performing two operations; if the two conditions are not met, the operation cannot be carried out, the calculation fails, and data are collected for a period of time and then judged.
Further, the operation step includes: for data satisfying the operation condition, the speed calculation is performed according to the following formula:
in the formula, R is the number of detected rising edges, N is the number of detected falling edges, lambda is the wavelength of the ultrahigh frequency RFID signal, h is the distance from the antenna of the RFID reading device to the channel, and t 1 Average of the time stamps of two points of the detected first rising edge, t 2 Average value of two-point time stamps of last detected rising edge, t 3 Mean value of time stamps for two points of the first detected falling edge, t 4 The last detected falling edge is the average of the two point timestamps.
Further, for a tag satisfying one of the condition 1 and the condition 2, the operation result is directly taken as the speed calculation value; for the labels satisfying both conditions 1 and 2, the average value of the results of the two operations is used as the calculated value of the speed.
Further, the method is applied to a dispatching management system of a highway or a parking lot, and the passageway is a road of the highway or the parking lot.
Further, the method is applied to a scheduling system of an intelligent warehouse, and the channel is a production line.
(III) advantageous effects
The invention provides a speed measuring method of an ultrahigh frequency RFID system and discloses a speed measuring method of an ultrahigh frequency RFID system. The method comprises the following steps: and (1) equipment deployment. And arranging an antenna of the RFID identification device beside or over the passageway to be monitored, and enabling the antenna to face the passageway to be monitored. And (2) collecting data. Collecting the label data and the phase information of an RFID label attached to an object to be measured by using an ultrahigh frequency RFID reader-writer, and recording the label data and the phase information together with timestamp information when the data is collected; and (3) data arrangement. And sorting the acquired label data information according to labels to obtain the phase and time stamp information of each label. And (4) calculating the speed. And processing the acquired tag data and the acquired phase information of the RFID tag to obtain the movement speed of the object attached with the RFID tag.
The method provided by the invention has the characteristics of small operand, high real-time performance and convenience for integration into the existing ultrahigh frequency RFID system, and has very high practical value in occasions with speed measurement requirements such as electronic identification of motor vehicles, intelligent storage and the like.
Drawings
FIG. 1 is a schematic view of a speed measurement scenario of an UHF RFID system according to the present invention;
FIG. 2 is a schematic flow chart of the method of the present invention.
Detailed Description
In order to make the objects, contents and advantages of the present invention clearer, the following detailed description of the embodiments of the present invention will be made in conjunction with the accompanying drawings and examples.
The invention discloses a speed measuring method of an ultrahigh frequency RFID system. The method comprises the following steps: and (1) equipment deployment. And arranging an antenna of the RFID identification device beside or above the passageway to be monitored, and enabling the antenna to face the passageway to be monitored. And (2) data acquisition. Collecting the label data and the phase information of an RFID label attached to an object to be tested by using an ultrahigh frequency RFID reader-writer, and recording the label data and the phase information together with timestamp information when the data is collected; and (3) data arrangement. And sorting the acquired label data information according to labels to obtain the phase and time stamp information of each label. And (4) calculating the speed. And processing the acquired tag data and the phase information of the RFID tag to obtain the movement speed of the object attached with the RFID tag.
The method provided by the invention has the characteristics of small operand, high real-time performance and convenience for integration into the existing ultrahigh frequency RFID system, and has very high practical value in occasions with speed measurement requirements such as electronic identification of motor vehicles, intelligent storage and the like.
The invention aims to provide a speed measuring method of an ultrahigh frequency RFID system, which is used for calculating the movement speed of an object attached with an RFID electronic tag.
The method fully utilizes the linear relation between the phase information of the RFID label response signal acquired by the ultrahigh frequency RFID identification and reading equipment and the distance between the RFID label response signal and the antenna of the RFID identification and reading equipment when the RFID label responds, and the periodicity of the phase change of the RFID label response signal, and utilizes the problem that the phase of the RFID label response phase acquired by the RFID identification and reading equipment is 180-degree phase fuzzy, so as to realize the calculation of the motion speed of the object.
The method comprises the following steps:
s1, equipment deployment: and arranging an RFID reading device antenna beside or over the channel to be monitored and enabling the RFID reading device antenna to be opposite to the channel to be monitored.
S2, data acquisition: in the monitoring process, the RFID identification device identifies RFID tags in the identification range of the RFID identification device and records tag information, the phase of tag signals and time stamps of each identification, namely data combination EPC n ,θ n ,t n ]And n represents a serial number of the data combination ordered according to the acquisition sequence.
S3, data arrangement: the data combination acquired in a specific time period is sorted according to EPC codes to obtain the phase and time stamp combination [ theta ] of each tag in the RFID reading equipment reading range in the time period i ,t i ]。
S4, a speed calculation step: and processing the collected phase and time stamp information of the RFID tag to obtain the movement speed of the object attached with the RFID tag.
Starting when the RFID label enters the recognition range for the first time by utilizing the relation between the signal phase of the RFID label and the distance s from the RFID label to the antenna, if theta is larger than the distance of the RFID label, the distance is smaller than the distance of the RFID label to the antenna i -θ i-1 If the signal is more than Th, judging that a sudden rising edge of the RFID label response signal occurs; if theta is greater than theta i -θ i-1 And < Th, the RFID label response signal phase is judged to have a sudden falling edge, and the threshold Th can be selected to be pi/4. Counting the detected rising edge as R, counting the detected falling edge as N, and recording the time average value of the two phase time combinations of the detected first rising edge as t 1 Two phases of the last detected rising edgeThe time average in the time combination is denoted as t 2 The time average of the two phase time combinations of the first detected falling edge is denoted t 3 Finally, the time average of the two phase time combinations in which the falling edge is detected is recorded as t 4 . The time when the RFID-tagged object is first detected to have a phase rising edge is approximately t 1 The time for the object to reach the position opposite to the antenna is approximately (t) 3 +t 2 ) And/2, the time taken for the object to move from the first detected phase rising edge to the opposite antenna is as follows:
t＝(t 3 +t 2 )/2-t 1
s when the object is detected for the first time as a phase rising edge is approximately lambda (R-1) + h, lambda is the wavelength of the UHF RFID signal, and corresponding d is approximately:
the speed of the object motion can be approximated by:
similarly, the motion speed of the object can be calculated by using the data collected in the process that the object gradually gets away from the RFID antenna:
on the premise that the collected data is sufficient, the calculation can be carried out twice, and the object motion speed v can be respectively obtained 1 And v 2 Can be adjusted v to improve accuracy 1 And v 2 If the acquired data is insufficient and only one speed value can be calculated, taking the speed value as a calculation result, otherwise, failing to measure the speed.
Example 1:
the invention utilizes the characteristic that the phase responded by the RFID label has linear relation with the distance between the RFID label and the RFID antenna, and fully considers the problem of edge jump phenomenon caused by the periodicity of phase change in the phase acquisition process of the RFID label response signal in practical application and phase ambiguity caused by the principle that the RFID reading equipment solves the phase.
The flow chart of the method is shown in figure 2.
Device deployment step S1: and deploying the antenna of the RFID identification device beside or right above the channel to be monitored and enabling the antenna to be opposite to the channel to be monitored. Wherein the vertical distance from the RFID antenna to the channel is h, the distance from the RFID antenna to the RFID tag is s, the distance from the RFID tag to the projection point of the center of the RFID antenna on the channel is d,
the amount of change per unit time d is the speed of movement of the object we are interested in. The phase of the tag response signal is related to d by:
where λ is the wavelength of the uhf RFID signal.
A data acquisition step S2: the RFID identification device records the collected data information of each RFID label, the phase information of the signal and the time stamp information [ EPC ] of the identification time n ,θ n ,t n ]。
A data arrangement step S3: the information is sorted according to tag EPC data and is sequenced according to the time sequence to obtain the combination [ theta ] of the phase and the time stamp of each tag i ,t i ]。
Speed calculation step S4: the speed calculation step comprises three substeps of an edge detection step, an operation condition judgment step and an operation step.
Edge detection substep S41: the method based on threshold judgment is adopted to judge the sudden change situation of the phase of the RFID label response signal in the motion process, and specifically comprises the following steps: starting when the RFID tag first enters the reading range, if theta i -θ i-1 If the signal is more than Th, judging that a sudden rising edge of the RFID label response signal occurs; if theta is greater than theta i -θ i-1 And if the threshold value is less than Th, the RFID tag response signal phase is judged to have an abrupt falling edge, and the threshold value Th can be selected to be pi/4. The detected rising edge is counted as R and the falling edge is counted as N.
Operation condition determination substep S42: judging whether the obtained rising edge and falling edge conditions meet the operation conditions, specifically: a certain number of rising edges and the first falling edge are captured (condition 1), i.e., R >1, n > =1; the last rising edge and a certain number of falling edges are captured (condition 2), i.e. R > =1, n >, 1. If one of the conditions 1 or 2 is satisfied, an operation can be performed once; if both the condition 1 and the condition 2 are satisfied, two operations can be performed; if the two conditions are not met, the operation cannot be carried out, and if the calculation fails, data can be collected for a period of time and then judged.
The operator step S43: for data satisfying the operation condition, the velocity calculation can be performed according to the following formula:
in the formula, R is the number of detected rising edges, N is the number of detected falling edges, lambda is the wavelength of the ultrahigh frequency RFID signal, h is the distance from the antenna of the RFID reading device to the channel, and t 1 Average of the time stamps of two points of the detected first rising edge, t 2 Average value of two-point time stamps of last detected rising edge, t 3 Is the mean value of the time stamps of two points of the first detected falling edge, t 4 To finally detectAlong the average of the two point timestamps. For a tag satisfying one of condition 1 and condition 2, the operation result is directly taken as a speed calculation value; for the labels satisfying both the condition 1 and the condition 2, the average value of the results of the two operations is taken as the calculated value of the speed.
Further, the method is applied to a dispatching management system of a highway or a parking lot, and the passageway is a road of the highway or the parking lot.
Further, the method is applied to a scheduling system of an intelligent warehouse, and the channel is a production line.
Example 2:
a method for measuring speed of an ultrahigh frequency RFID system comprises the following steps:
(1) A device deployment step: and deploying the antenna of the RFID identification device beside or right above the channel to be monitored and enabling the antenna to be opposite to the channel to be monitored.
(2) A data acquisition step: the RFID identification device records the collected data information of each RFID label, the phase information of the signal and the time stamp information [ EPC ] of the identification time n ,θ n ,t n ]。
(3) Data arrangement: EPC obtained from data acquisition step n ,θ n ,t n ]Sorting according to EPC codes of the tags to obtain phase information and time stamp combination [ theta ] of each tag i ,t i ]。
(4) And a speed calculation step, which specifically comprises an edge detection step, an operation condition judgment step and an operation step.
Further, in the velocity calculating step, the edge detecting method includes:
judging the sudden change situation of the phase information of the RFID label in motion by adopting a threshold-based judging method, if theta is larger than the threshold value i -θ i-1 If the signal is more than Th, judging that a sudden rising edge of the RFID label response signal occurs; if theta is greater than theta i -θ i-1 And if the threshold value is less than Th, the falling edge of a sudden change of the phase of the response signal of the RFID tag is judged, and the threshold value Th measured by the actual measurement is selected to be pi/4. The detected rising edge is counted as R and the falling edge is counted as N.
Further, in the speed calculating step, the operation condition judging method includes:
the method is adopted to carry out two preconditions of speed calculation: a certain number of rising edges and the first falling edge are captured (condition 1), i.e. R >1, n > =1; the last rising edge and a certain number of falling edges are captured (condition 2), i.e. R > =1, n >, 1. And judging whether the collected information of the specific label meets the two conditions.
Further, in the speed calculation step, the operation method includes:
the RFID tag movement speed is calculated as follows:
in the formula, R is the number of detected rising edges, N is the number of detected falling edges, lambda is the wavelength of the ultrahigh frequency RFID signal, h is the distance from the antenna of the RFID identification and reading equipment to the channel, and t 1 Average of the time stamps of two points of the detected first rising edge, t 2 Average value of two time stamps of the last detected rising edge, t 3 Is the mean value of the time stamps of two points of the first detected falling edge, t 4 The last detected falling edge is the average of the two point timestamps. For a tag satisfying one of condition 1 and condition 2, the operation result is directly taken as a speed calculation value; for the labels satisfying both conditions 1 and 2, the average value of the results of the two operations is used as the calculated value of the speed.
The method provided by the invention has the characteristics of small operand, high real-time performance and convenience for integration into the conventional ultrahigh frequency RFID system, and has very high practical value in occasions with speed measurement requirements, such as electronic identification, intelligent storage and the like of the motor vehicle.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A method for measuring speed of an ultrahigh frequency RFID system is characterized by comprising the following steps:
s1, equipment deployment: deploying an RFID identification device antenna beside or right above a channel to be monitored and enabling the RFID identification device antenna to be right opposite to the channel to be monitored;
s2, data acquisition: in the monitoring process, the RFID identification device identifies RFID tags in the identification range of the RFID identification device and records tag information, the phase of tag signals and time stamps of each identification, namely data combination EPC n ,θ n ,t n ]Wherein n represents a serial number of the data combination sorted according to the acquisition sequence;
s3, data arrangement: the data combination acquired in a specific time period is sorted according to EPC codes to obtain the phase and time stamp combination [ theta ] of each tag in the RFID reading equipment reading range in the time period i ,t i ]；
S4, a speed calculation step: and processing the acquired phase and time stamp information of the RFID tag to obtain the movement speed of the object attached with the RFID tag.
2. The UHF RFID system speed measurement method of claim 1, wherein in step S1, the vertical distance from the RFID antenna to the channel is h, the distance from the RFID antenna to the RFID tag is S, the distance from the RFID tag to the projection point of the center of the RFID antenna on the channel is d,
the variation of d per unit time is the moving speed of the object we are concerned with, and the phase of the tag response signal is related to d as follows:
where λ is the wavelength of the uhf RFID signal.
3. The method for measuring speed of an ultrahigh frequency RFID system according to claim 1 or 2, wherein the step S4 specifically comprises: an edge detection step, an operation condition judgment step and an operation step.
4. The uhf RFID system velocimetry method of claim 3, wherein the edge detection step comprises: starting when the RFID tag first enters the reading range, if theta i -θ i-1 If the current value is more than Th, judging that an abrupt rising edge occurs in the RFID label response signal; if theta is greater than theta i -θ i-1 And < Th, judging that the phase of the response signal of the RFID tag has an abrupt falling edge, and counting the detected rising edge as R and the falling edge as N.
5. The method according to claim 4, wherein the threshold Th is pi/4.
6. The UHF RFID system velocimetry method of claim 4 or 5, wherein said operation condition determining step comprises: judging whether the obtained rising edge and falling edge conditions meet the operation conditions, wherein the condition 1 is as follows: a certain number of rising edges and the first falling edge are captured, i.e. R >1, n > =1; the condition 2 is: the last rising edge and a certain number of falling edges are captured, i.e., R > =1, n > -1; if one of the condition 1 or the condition 2 is satisfied, performing an operation; if the condition 1 and the condition 2 are both satisfied, performing two operations; if the two conditions are not met, the operation cannot be carried out, the calculation fails, and data are collected for a period of time and then judged.
7. The uhf RFID system velocimetry method of claim 6, wherein said computing step comprises: for data satisfying the operation condition, the speed calculation is performed according to the following formula:
wherein R is the number of detected rising edges, NIn order to detect the number of falling edges, lambda is the wavelength of the ultrahigh frequency RFID signal, h is the distance from the antenna of the RFID reading device to the channel, and t 1 Average of the time stamps of two points of the detected first rising edge, t 2 Average value of two time stamps of the last detected rising edge, t 3 Is the mean value of the time stamps of two points of the first detected falling edge, t 4 The last detected falling edge is the average of the two point timestamps.
8. The uhf RFID system velocity measurement method of claim 7, wherein for a tag satisfying one of condition 1 and condition 2, the operation result is directly used as a velocity calculation value; for the labels satisfying both the condition 1 and the condition 2, the average value of the results of the two operations is taken as the calculated value of the speed.
9. The uhf RFID system velocimetry method of claim 1, wherein the method is applied to a dispatching management system of a highway or a parking lot, and the channel is a road of the highway or the parking lot.
10. The UHF RFID system speed measurement method of claim 1, wherein the method is applied to a dispatching system of an intelligent warehouse, and the channel is a pipeline.
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