RFID-based coupler state parameter monitoring system and method thereof

Abstract

The invention discloses a coupler state parameter monitoring system and method based on RFID. The system comprises an information processor, an ultrahigh frequency reader, an ultrahigh frequency antenna, a detected coupler and an ultrahigh frequency passive tag array. An ultrahigh frequency passive tag array is mounted on the outer surface of the coupler; the ultrahigh frequency antenna is installed above the coupler through an antenna support. Detecting and collecting a timestamp and a position at which the RSSI value of a passive tag in the ultrahigh frequency passive tag array reaches the maximum value and phase data of the passive tag through an ultrahigh frequency antenna and an ultrahigh frequency reader; the information processing center calculates the rotating speed and the torsion angle of the coupler based on the timestamp and the position when the passive tag RSSI value reaches the maximum value; and the information processing center calculates the axis track of the coupling based on the phase data of the passive tag. The reliability and the operation efficiency of mechanical equipment are greatly improved, the shutdown and maintenance cost caused by sudden failures is reduced, and the overall economic benefit and the safety level are improved.

Description

Technical Field

[0001] The invention relates to the technical field of RFID non-contact sensing, and is an RFID-based monitoring system for coupling state parameters. Background Art

[0002] Couplings, as key components in mechanical transmission systems, are primarily used to connect two rotating components to transmit torque and power. Couplings are widely used in modern machinery, including but not limited to vehicles, hoists, ships, and rockets. Their primary function is to transmit the output force and torque of the power source to the actuator, ensuring the proper operation of the mechanical system. In practical applications, couplings often face complex operating environments, including high temperatures, high humidity, corrosive media, and frequent load fluctuations. These environmental factors can cause wear, aging, loosening, or even breakage of the coupling, impacting the stability and reliability of the entire mechanical system.

[0003] In order to ensure the healthy operation of the coupling, it is of great significance to dynamically monitor the speed, torsion angle and axis trajectory of the coupling. In general engineering applications, the measurement of the coupling speed can be divided into contact and non-contact types. The most widely used non-contact measurement is to use Hall effect sensors or eddy current sensors to measure the speed by detecting the magnetic field changes or eddy current changes of the coupling. This measurement method does not affect the motion state of the coupling, but is easily interfered by external magnetic fields. Common contact measurements are photoelectric sensors and magnetic induction sensors that measure the speed by installing reflective markers on the coupling. The sensor cost is relatively high. For the measurement of the torsion angle of the coupling, the most common method is to install a torque sensor on the coupling and use the torque generated by the shaft under the action of torque. Small deformations are measured by internal strain gauges to measure torque. This method has high accuracy and reliability, but it is expensive and requires a specific installation location. There are many ways to measure the axis trajectory of the coupling. Laser displacement sensors, eddy current sensors and high-speed camera image processing can all be used to measure the axis trajectory, but laser displacement sensors are expensive and sensitive to factors such as ambient light and reflectivity, requiring a clean and dust-free installation environment. Eddy current sensors can only measure metal surfaces and cannot be used for non-metallic materials. High-speed camera image processing has limited accuracy, and the measurement accuracy is relatively low, requiring complex image processing algorithms and computing resources. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a system and method for monitoring coupling status parameters based on RFID. By arranging and installing multiple passive tag measuring points on the coupling, the installation difficulty and time are reduced. By using the antenna to transmit the passive tag signal, the rotational speed, torsion angle, axis trajectory and other states of the coupling can be monitored, thereby greatly improving the reliability and operating efficiency of mechanical equipment, reducing the downtime and maintenance costs caused by sudden failures, and improving the overall economic benefits and safety level.

[0005] Technical solution: To achieve the above-mentioned purpose, the present invention provides an RFID-based coupling status parameter monitoring system, which includes an information processor, an UHF reader, an UHF antenna, a coupling to be measured and an UHF passive tag array; an UHF passive tag array is installed on the outer surface of the coupling; the UHF antenna is installed above the coupling through an antenna bracket; the UHF reader controls the UHF antenna to transmit a signal to the UHF passive tag array, activating the UHF passive tag array; the UHF antenna receives the carrier signal emitted by the UHF passive tag array and transmits it to the UHF reader for preprocessing; the preprocessed carrier signal is transmitted to the information processor for processing, thereby obtaining the rotational speed, torsion angle and axis trajectory of the coupling.

[0006] Furthermore, the coupling includes an active end and a passive end; the ultra-high frequency passive tag array includes a first passive tag array and a second passive tag array; the passive tags in the first passive tag array are evenly installed on the side surface of the active end parallel to the axis of the coupling, and the passive tags in the second passive tag array are evenly installed on the side surface of the passive end parallel to the axis of the coupling; the passive tags in the first passive tag array correspond one-to-one to the passive tags in the second passive tag array.

[0007] Furthermore, the first passive tag array includes an a1 tag, an a2 tag, an a3 tag, and an a4 tag; the second passive tag array includes a b1 tag, a b2 tag, a b3 tag, and a b4 tag; the line connecting the a1 tag and the a3 tag is perpendicular to the line connecting the a2 tag and the a4 tag; the line connecting the b1 tag and the b3 tag is perpendicular to the line connecting the b2 tag and the b4 tag.

[0008] Furthermore, the a1 tag, a2 tag, a3 tag and a4 tag correspond to the b1 tag, b2 tag, b3 tag and b4 tag respectively; in the initial state, the line connecting the a1 tag and the a3 tag is parallel to the line connecting the b1 tag and the b3 tag; the line connecting the a2 tag and the a4 tag is parallel to the line connecting the b2 tag and the b4 tag.

[0009] Furthermore, the coupling speed monitoring method comprises the following steps:

[0010] S1-1, selecting any passive tag in the first passive tag array as a speed monitoring passive tag;

[0011] S1-2. The RSSI value of the speed monitoring passive tag is collected through the UHF reader and UHF antenna. The data contains the collection timestamp. The RSSI value collected at this time is compared with the RSSI value collected previously.

[0012] S1-3, when the RSSI value changes from gradually increasing to decreasing for the first time, it is determined that the RSSI value at this time is the maximum RSSI value of the speed monitoring passive tag. At this time, the speed monitoring passive tag is facing the UHF antenna;

[0013] S1-4. Subtract the timestamp of the maximum RSSI value of the speed monitoring passive tag at this time from the timestamp of the previous speed monitoring passive tag at the initial position to obtain the time difference; based on the time difference and the radius of the active end of the coupling, calculate the speed of the coupling; and realize the monitoring of the speed of the coupling.

[0014] Furthermore, the method for monitoring the coupling torsion angle comprises the following steps:

[0015] S2-1, arbitrarily selecting two corresponding passive tags from the first passive tag array and the second passive tag array as the first angle passive tag and the second angle passive tag for monitoring the torsion angle;

[0016] S2-2. Use the UHF reader and UHF antenna to collect the RSSI values ​​of the first-angle passive tag and the second-angle passive tag. The data contains the timestamp of the collection. Compare the RSSI value collected at this time with the RSSI value collected previously to determine the maximum RSSI value of the first-angle passive tag and the second-angle passive tag.

[0017] S2-3. In the initial state, the timestamp when the RSSI value of the first-angle passive tag reaches its maximum value is equal to the timestamp when the RSSI value of the second-angle passive tag reaches its maximum value; when it is detected that the RSSI values ​​of the first-angle passive tag and the second-angle passive tag reach their maximum values ​​at different times, it is determined that the active end and the driven end are twisted;

[0018] S2-4. Subtract the timestamp when the RSSI value of the passive tag at the first angle reaches its maximum value from the timestamp when the RSSI value of the passive tag at the second angle reaches its maximum value to obtain a time difference;

[0019] S2-5. Calculate the torsion angle based on the time difference and the rotational speed of the coupling, and calculate the torsion angles generated by the two corresponding passive tags at the other three locations respectively; perform interpolation simulation on the torsion angles of the other locations on the coupling based on the torsion angles of the four locations to monitor the torsion angle of the coupling.

[0020] Furthermore, the method for monitoring the axis trajectory of the coupling comprises the following steps:

[0021] S3-1. Select any two orthogonal passive tags in the second passive tag array, that is, two adjacent passive tags on the driven end, as the first axis tag and the second axis tag for monitoring the axis trajectory;

[0022] S3-2, collecting phase data of the first axis tag and the second axis tag, and determining whether the phase data of the passive tag needs to balance the periodic changes caused by the phase jump, and if so, proceeding to the next step;

[0023] S3-3. Obtain the distances from the center of the UHF antenna to the first axis tag and the second axis tag based on the phase data of the first axis tag and the second axis tag.

[0024] S3-4. Subtract the timestamp of the passive tag's phase data from the timestamp of the passive tag at its initial position to obtain a difference, and calculate the rotation angles of the first axis tag and the second axis tag using the difference and the speed of the coupling at this time.

[0025] S3-5. Measure the distance between the center of the UHF antenna and the center of the coupling. Based on the results of S3-3 and S3-4 and the geometric relationship, calculate the distance from the center of the coupling to the first axis tag and the second axis tag. The difference between the distance from the center of the coupling to the first axis tag and the distance from the center of the coupling to the second axis tag and the radius of the coupling is the amplitude of the passive tag.

[0026] S3-6. Combine and analyze the amplitude of the first axis label and the amplitude of the second axis label to obtain the axis trajectory of the coupling, thereby monitoring the axis trajectory of the coupling.

[0027] Furthermore, in S1-4, the speed n of the coupling is calculated:

[0028] n=2π·R / (t M′ -t M )

[0029] Where R is the radius of the coupling, t M′ This is the timestamp when the RSSI value of the speed monitoring passive tag is the maximum value. M The passive tag for speed monitoring is located directly below the UHF antenna, which is the timestamp of the initial position.

[0030] Beneficial effects: The present invention provides a system and method for monitoring coupling status parameters based on RFID. Compared with traditional speed sensors and torque sensors, ultra-high frequency passive anti-metal flexible passive tags are light in weight and small in size, have little impact on the coupling, do not affect the normal working state of the coupling, have low monitoring costs, and have small restrictions on tag installation space. Under conditions of limited space, the layout is simple and convenient. The flexible tag adapts to different surface shapes and can be directly pasted on the metal surface. The radio frequency signal is transmitted wirelessly without the need to introduce additional leads. An ultra-high frequency passive anti-metal flexible tag array is used and arranged and installed at a specific position of the coupling. The RSSI value and phase parameters of the tag are integrated to realize monitoring of three different physical quantities of the coupling: speed monitoring, torsion angle monitoring and axis trajectory. Compared with traditional monitoring methods, the structure and cost of the sensor and measurement system are greatly reduced, and the monitoring cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the logic block diagram of the RFID-based monitoring system for coupling status parameters;

[0032] Figure 2 It is a structural diagram of the coupling;

[0033] Figure 3 Schematic diagram of the UHF passive tag array on the coupling;

[0034] Figure 4 The diagram of calculation structure of coupling speed monitoring method is shown in FIG.

[0035] Figure 5 The diagram of the calculation structure of the monitoring method for the coupling torsion angle is shown;

[0036] Figure 6 Schematic diagram of the calculation structure of the coupling axis trajectory monitoring method. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings.

[0038] like Figure 1As shown, a monitoring system for coupling state parameters based on RFID includes an information processor 1, an UHF reader 2, an UHF antenna 3, a coupling 4 to be measured and an UHF passive tag array 5; the information processor 1 is bidirectionally connected to one end of the UHF reader 2, and the other end of the UHF reader 2 is bidirectionally connected to the UHF antenna 3. An UHF passive tag array 5 is installed on the outer surface of the coupling 4, and the UHF passive tag array 5 is evenly arranged on the outer surface of the coupling 4, corresponding to the upper and lower surfaces; the UHF reader 2 controls the UHF antenna 3 to transmit a signal to the UHF passive tag array 5, activating the UHF passive tag array 5; the UHF antenna 3 receives the carrier signal emitted by the UHF passive tag array 5 and transmits it to the UHF reader 2 for preprocessing; the preprocessed carrier signal is transmitted to the information processor 1 for processing, thereby obtaining the rotational speed, torsion angle and axis trajectory of the coupling 4. The information processor 1 is a high-performance computer, which uses a network interface or serial interface to connect the information processor 1 to the UHF reader 2 for data transmission. The network port or serial data port at one end of the UHF reader 2 is connected to the information processor 1, and the antenna port of the UHF reader 2 at the other end and the UHF antenna 3 transmit UHF electromagnetic wave data through a radio frequency feeder. The coupling 4 is a key part of the entire transmission system.

[0039] The UHF antenna 3 and the UHF reader 2 detect and collect the timestamp and position when the RSSI value of the passive tag in the UHF passive tag array 5 reaches the maximum value, as well as the phase data of the passive tag; the information processing center 1 calculates the rotational speed and torsion angle of the coupling based on the timestamp and position when the RSSI value of the passive tag reaches the maximum value; the information processing center 1 calculates the axis trajectory of the coupling based on the phase data of the passive tag.

[0040] RFID-based passive sensing technology utilizes the backscattering of ultra-high frequency (UHF) electromagnetic waves to transmit parameters containing external information collected by the tag to a reader / writer via an UHF antenna, completing the information collection. UHF tags are compact, low-cost, and occupy minimal space, allowing for quick and easy installation in complex working environments. Multiple measurement points can be deployed simultaneously in confined spaces and on irregular surfaces to collect external information. RFID passive tag monitoring technology can capture coupling operating status data, promptly identifying potential faults and anomalies, allowing preventive measures to be taken and reducing the economic and human losses caused by coupling failures.

[0041] like Figure 1-3As shown, the UHF antenna 3 is mounted above the coupling 4 via an antenna bracket. The UHF antenna 3 is mounted on the antenna bracket, which is located above the coupling 4 being measured. The coupling 4 includes an active end 41 and a passive end 42, both of which are key components in the transmission system. The active end 41 and the passive end 42 have complex surface structures, and there is limited space available for installing traditional sensors. During normal operation, the active end 41 and the passive end 42 experience a large rotational distance of torsion, and traditional measurement tools such as strain gauges cannot meet the requirements for measuring the torsion angle of the coupling 4. The UHF passive tag array 5 includes a first passive tag array and a second passive tag array. The passive tags in the first passive tag array are evenly mounted on the side surface of the active end 41 parallel to the axis of the coupling 4, and the passive tags in the second passive tag array are evenly mounted on the side surface of the passive end 42 parallel to the axis of the coupling 4. The passive tags in the first passive tag array correspond one-to-one with the passive tags in the second passive tag array. A passive tag array consisting of four orthogonal passive tags is arranged at each of the active end 41 and the driven end 42 of the coupling 4 to measure the rotational speed, torsion angle and axis trajectory of the coupling 4 .

[0042] like Figure 2-3 As shown, the passive tags in the first passive tag array and the second passive tag array are both metal-resistant flexible passive tags, which are suitable for conditions of narrow installation space, and the tag characteristics meet the requirements of complex metal surface installation; the first passive tag array includes a1 tag 51, a2 tag 52, a3 tag 53 and a4 tag 54; the second passive tag array includes b1 tag 55, b2 tag 56, b3 tag 57 and b4 tag 58; the a1 tag 51, a2 tag 52, a3 tag 53 and a4 tag 54 are arrayed on the side surface of the active end 41, and the b1 tag 55, b2 tag 56, b3 tag 57 and b4 tag 58 are arrayed on the side surface of the driven end 41; the line connecting the a1 tag 51 and the a3 tag 53 is perpendicular to the line connecting the a2 tag 52 and the a4 tag 54; the line connecting the b1 tag 55 and the b3 tag 56 is perpendicular to the line connecting the b2 tag 57 and the b4 tag 58.

[0043] like Figure 3 As shown, the a1 tag 51, a2 tag 52, a3 tag 53 and a4 tag 54 correspond to the b1 tag 55, b2 tag 56, b3 tag 57 and b4 tag 58 respectively; in the initial state, the line connecting the a1 tag 51 and the a3 tag 53 is parallel to the line connecting the b1 tag 55 and the b3 tag 56; the line connecting the a2 tag 52 and the a4 tag 54 is parallel to the line connecting the b2 tag 57 and the b4 tag 58.

[0044] like Figure 4As shown, a working method of a coupling state parameter monitoring system based on RFID, the coupling 4 rotation speed monitoring method includes the following steps:

[0045] S1-1, selecting any one of the passive tags in the first passive tag array as a rotation speed monitoring passive tag, for example, any one of the a1 tag 51, the a2 tag 52, the a3 tag 53, and the a4 tag 54;

[0046] S1-2. The RSSI value of the speed monitoring passive tag is collected through the UHF reader 2 and the UHF antenna 3. The data contains the timestamp of the collection. The RSSI value collected at this time is compared with the RSSI value collected previously.

[0047] S1-3, when the RSSI value changes from gradually increasing to decreasing for the first time, it is determined that the RSSI value at this time is the maximum RSSI value of the speed monitoring passive tag, and at this time the speed monitoring passive tag is facing the UHF antenna 3;

[0048] S1-4. Subtract the timestamp of the maximum RSSI value of the speed monitoring passive tag at this time from the timestamp of the previous speed monitoring passive tag at the initial position to obtain the time difference; based on the time difference and the radius of the active end 41 of the coupling 4, calculate the speed of the coupling 4; and realize the monitoring of the speed of the coupling 4.

[0049] The RFID radio frequency tag collects information in a random manner, and the data contains a timestamp of the collection; when the RSSI value of the speed monitoring passive tag is maximum, the speed monitoring passive tag is facing the UHF antenna 3, and the straight-line distance between the speed monitoring passive tag and the UHF antenna 3 is the shortest, the speed monitoring passive tag is located at the top of the coupling 4, and the energy received from the UHF antenna 3 reaches a maximum; the speed monitoring passive tag starts to rotate from the position facing the UHF antenna 3, gradually rotates to the bottom of the coupling 4, and the straight-line distance between the speed monitoring passive tag and the UHF antenna 3 is the longest; thereafter, as the coupling 4 rotates, the RSSI value of the speed monitoring passive tag gradually increases. At this time, the RSSI value collected each time by the speed monitoring passive tag is compared with the previous RSSI value. If the RSSI value decreases for the first time, it is judged that the RSSI value this time is the maximum value of the RSSI value of the speed monitoring passive tag, that is, the speed monitoring passive tag is now in a position facing the UHF antenna 3.

[0050] like Figure 4As shown, the rotation center of the coupling 4 is set to O, the center of the UHF antenna 3 is set to O′, and the initial position M of the speed monitoring passive tag on the active end 41 is located below the UHF antenna 3; during the rotation of the coupling 4, the distance between the speed monitoring passive tag and the UHF antenna 3 first decreases and then increases, and the collected RSSI value also decreases and then increases accordingly; the RSSI value collected at this time is compared with the RSSI value collected last time. When the RSSI value gradually increases, the RSSI value is detected to decrease for the first time. At this time, the RSSI value is the maximum value, and the speed monitoring passive tag rotates one circle and is located at the position M′ facing the UHF antenna. Based on the timestamp t obtained at the speed monitoring passive tag at this time M′ and the timestamp t of the initial position M Calculate the speed n of the coupling;

[0051] n=2π·R / (t M′ -t M )

[0052] Where R is the radius of the coupling 4, t M′ This is the timestamp when the RSSI value of the speed monitoring passive tag is the maximum value. M The timestamp of the speed monitoring passive tag being located directly below the UHF antenna 3, that is, the initial position.

[0053] like Figure 5 As shown, the method for monitoring the torsion angle of the coupling 4 includes the following steps:

[0054] S2-1. Arbitrarily select two corresponding passive tags from the first passive tag array and the second passive tag array as the first angle passive tag and the second angle passive tag for monitoring the torsion angle; for example, the a1 tag 51 corresponds to the b1 tag, the a2 tag 52 corresponds to the b2 tag, the a3 tag 53 corresponds to the b3 tag, and the a4 tag 54 corresponds to the b4 tag.

[0055] S2-2. Collect the RSSI values ​​of the first-angle passive tag and the second-angle passive tag using the UHF reader 2 and the UHF antenna 3. The data contains the timestamp of the collection. Compare the RSSI value collected at this time with the RSSI value collected previously to determine the maximum RSSI value of the first-angle passive tag and the second-angle passive tag.

[0056] S2-3. In the initial state, the timestamp when the RSSI value of the first angle passive tag reaches its maximum value is equal to the timestamp when the RSSI value of the second angle passive tag reaches its maximum value; when it is detected that the RSSI values ​​of the first angle passive tag and the second angle passive tag reach their maximum values ​​at different times, it is determined that the active end 41 and the driven end 42 are twisted;

[0057] S2-4. Subtract the timestamp when the RSSI value of the passive tag at the first angle reaches its maximum value from the timestamp when the RSSI value of the passive tag at the second angle reaches its maximum value to obtain a time difference;

[0058] S2-5. Calculate the torsion angle based on the time difference and the rotational speed of the coupling 4, and calculate the torsion angles generated by the two corresponding passive tags at the four locations respectively; perform interpolation simulation on the torsion angles of other locations on the coupling 4 based on the torsion angles of the four locations to monitor the torsion angle of the coupling 4.

[0059] When either the passive tag on the active end 41 or the passive tag on the driven end 42 is facing the UHF antenna 3, the energy of the receiving antenna is maximized, i.e., the RSSI value reaches its maximum. During the rotation of the coupling 4, the active end 41 and the driven end 42 experience relative twisting, and the passive tags in the first passive tag array and the corresponding passive tags in the second passive tag array experience corresponding offsets, deviating from the same vertical line. Therefore, when twisting occurs, the passive tag on the active end 41 and the corresponding passive tag on the driven end do not reach the maximum RSSI value at the same time when the coupling 4 is operating. The twisting angles of the four groups of tags corresponding to the two passive tags at the active end 41 and the driven end 42 on the coupling 4 are calculated, and the twisting angles of other parts of the coupling 4 that are not equipped with passive tags are interpolated and simulated based on the twisting angles of the four groups of tags to monitor the twisting angle of the coupling 4.

[0060] like Figure 5 As shown, after the coupling 4 has been running for a period of time, the active end 41 and the driven end 42 are relatively twisted. The radius of the driven end 42 is OA', the speed of the coupling 4 is n, and the rotation direction remains unchanged. Assuming that the position of the passive tag at the active end of the coupling remains unchanged at P, and the position of the passive tag at the driven end is twisted from A to A', the UHF reader 2 measures that the RSSI value of the passive tag at position P reaches the maximum value at the time t1, and the RSSI value of the passive tag at position A' reaches the maximum value at the time t2. Then the torsion angle θ of the measured coupling 4 is:

[0061] θ=n·(t2-t1) / OA′

[0062] Similarly, the torsion angles of the other three groups of tags on the coupling 4 can be measured, and interpolation simulation can be performed to obtain the torsion angle of the entire coupling, thereby realizing the function of coupling torsion angle monitoring.

[0063] The axis trajectory of the coupling 4 is a synthesis of two orthogonal displacement parameters, that is, two perpendicular displacement parameters; therefore, the tag array for measuring the axis trajectory is four b1 tags 55, b2 tags 56, b3 tags 57 and b4 tags 58 evenly installed on the driven end 42 of the coupling; the UHF antenna 3 has a poor receiving ability for non-linear electromagnetic waves. During the vibration process, there are only two orthogonal passive tags on the side facing the UHF antenna 3. The phase data collected by the two orthogonal passive tags are used as component parameters of the axis trajectory. During the rotation of the two orthogonal passive tags, the distance between the passive tag and the UHF antenna exceeds the distance of the UHF antenna wavelength, and the phase data generates a step from 0 to 2π or 2π to 0. Each phase jump indicates that the distance from the UHF antenna 3 to the passive tag increases by one wavelength. According to the difference between two consecutive phase values, it is judged whether it is necessary to balance the periodic phase changes caused by the phase jump by adding or subtracting 2π. The sampling of passive tags by the UHF reader 2 is random. The two orthogonal tags facing the UHF antenna 3 cannot collect phase data at the same time. The continuity of the phase data cannot meet the needs of monitoring the axis trajectory of the coupling 4. Therefore, the collected phase data is simulated and interpolated with a certain accuracy so that the two orthogonal tags can collect phase data approximately at the same time.

[0064] like Figure 6 As shown, the method for monitoring the axis trajectory of the coupling 4 includes the following steps:

[0065] S3-1. Select any two orthogonal passive tags in the second passive tag array, that is, two adjacent passive tags on the driven end 42, as the first axis tag and the second axis tag for monitoring the axis trajectory; select two orthogonal passive tags, that is, two adjacent passive tags at the driven end 42, and the line connecting the two adjacent passive tags and the center of the coupling 4 is perpendicular to each other; generally along the opposite direction of the rotation direction, the first passive tag is the first axis tag, and the second passive tag is the second axis tag.

[0066] S3-2, collecting phase data of the first axis tag and the second axis tag, and determining whether the phase data of the passive tag needs to balance the periodic changes caused by the phase jump. In S3-2, determining whether the phase data of the first axis tag and the second axis tag need to balance the periodic changes caused by the phase jump by adding or subtracting 2π, and if so, executing the next step;

[0067] S3-3. Obtain the distances from the center of the UHF antenna 3 to the first axis tag and the second axis tag based on the phase data of the first axis tag and the second axis tag.

[0068] S3-4. Subtract the timestamp of the passive tag phase data from the timestamp of the passive tag at the initial position to obtain a difference, and calculate the rotation angles of the first axis tag and the second axis tag based on the difference and the rotation speed of the coupling 4 at this time;

[0069] S3-5. Measure the distance between the center of the UHF antenna 3 and the center of the coupling 4. Based on the results of S3-3 and S3-4 and the geometric relationship, calculate the distance from the center of the coupling 4 to the first axis tag and the second axis tag. The difference between the distance from the center of the coupling 4 to the first axis tag and the distance from the center of the coupling 4 to the second axis tag and the radius of the coupling 4 is the amplitude of the passive tag.

[0070] S3-6. Analyze the amplitude of the first axis tag and the amplitude of the second axis tag together to obtain the axis trajectory of the coupling 4, thereby monitoring the axis trajectory of the coupling 4.

[0071] In S3-4, the timestamp of the passive tag phase data is subtracted from the timestamp of the passive tag at the initial position to obtain the difference; the initial position of the first axis tag is located directly below the ultra-high frequency antenna 3, and the line connecting the initial position of the second axis tag and the center of the coupling 4 is perpendicular to the line connecting the initial position of the first axis tag and the center of the coupling 4, and the initial position of the first axis tag is in the opposite direction of the rotation direction of the coupling 4.

[0072] like Figure 6 As shown, the axis trajectory of the coupling is the composite of displacements in two orthogonal directions. Four orthogonal passive tags are installed at positions A, B, C, and D around the driven shaft 42 of the coupling. The tag array is judged during rotation, and the two tags facing the UHF antenna serve as orthogonal tags for monitoring the axis trajectory of the coupling. In the hardware settings of the UHF reader 2, the electromagnetic wave transmission frequency is set to f and the propagation speed of the electromagnetic wave in the air is set to v. Then, the wavelength λ of the UHF electromagnetic wave is:

[0073]

[0074] The phase of the orthogonal passive tags in the rotation process is unwrapped to eliminate the influence of phase jump. At the same time, the distance O′E′ between the UHF antenna 3 and the passive tag is calculated based on the relationship between wavelength and phase, and the phase φ = 2π / wavelength λ. Due to the limitations of the sampling frequency and random sampling method of the UHF reader 2, the phase data is interpolated and expanded to expand the data volume, which not only meets the conditions for axis trajectory measurement, but also regards the expanded data as simultaneously sampled data to reduce errors. Taking the static positions E and F and dynamic positions E′ and F′ of two orthogonal passive tags on the coupling 4 as an example, the distance OO′ between the coupling center O and the center O′ of the UHF antenna 3 and the coupling radius OE can be obtained by measurement, and the coupling speed n can be obtained from the passive tag at the active end. Then the angle α between the radius OE and OO′ is:

[0075] α=n·(t E′ -t A ) / OA′

[0076] Where, t E′ is the timestamp when the passive tag rotates to position E′, t A is the timestamp of the passive tag's initial A position, and OA' is the radius of the driven end. Similarly, the angle between OF and OD is calculated using the formula. Based on the known geometric relationships: OO' distance, O'E' distance, the angle α between OE' and OO', and the specific position E' of the passive tag, the distance OE' can be calculated using trigonometric functions. The difference EE' between OE' and the coupling radius OE is the amplitude of the passive tag being measured, i.e., the coupling offset distance component. Similarly, the offset distance FF' of the other passive tag can be calculated. By comprehensively analyzing the offset distances of the two orthogonal passive tags, the coupling's axis motion trajectory can be synthesized, enabling coupling axis trajectory monitoring.

[0077] The collected data are interpolated and expanded by combining data processing and signal analysis methods, and the RSSI and phase information including the speed, torsion angle and axis trajectory of the coupling are untangled and calculated, which effectively improves the accuracy of tag array monitoring.

[0078] The above is only a description of the preferred embodiment of the present invention. Ordinary technicians in this technical field can make several modifications and optimizations based on the above disclosure without departing from the above basic principles. These improvements and optimizations should be regarded as the scope of protection understood by the present invention.

Claims

1. A coupling status parameter monitoring system based on RFID, characterized in that: The invention comprises an information processor (1), an ultra-high frequency reader (2), an ultra-high frequency antenna (3), a coupling (4) to be tested and an ultra-high frequency passive tag array (5); the ultra-high frequency passive tag array (5) is installed on the outer surface of the coupling (4); the ultra-high frequency antenna (3) is installed above the coupling (4) through an antenna bracket; the ultra-high frequency reader (2) controls the ultra-high frequency antenna (3) to transmit a signal to the ultra-high frequency passive tag array (5) to activate the ultra-high frequency passive tag array (5); the ultra-high frequency antenna (3) receives the carrier signal emitted by the ultra-high frequency passive tag array (5) and transmits it to the ultra-high frequency reader (2) for preprocessing; the preprocessed carrier signal is transmitted to the information processor (1) for processing, thereby obtaining the rotation speed, torsion angle and axis trajectory of the coupling (4).

2. The RFID-based coupling state parameter monitoring system according to claim 1, characterized in that: The coupling (4) comprises an active end (41) and a passive end (42); the ultra-high frequency passive tag array (5) comprises a first passive tag array and a second passive tag array; the passive tags in the first passive tag array are evenly mounted on a side surface of the active end (41) parallel to the axis of the coupling (4), and the passive tags in the second passive tag array are evenly mounted on a side surface of the passive end (42) parallel to the axis of the coupling (4); the passive tags in the first passive tag array correspond one-to-one to the passive tags in the second passive tag array.

3. The RFID-based coupling state parameter monitoring system according to claim 2, characterized in that: The first passive tag array includes an a1 tag (51), an a2 tag (52), an a3 tag (53) and an a4 tag (54); the second passive tag array includes a b1 tag (55), a b2 tag (56), a b3 tag (57) and a b4 tag (58); the line connecting the a1 tag (51) and the a3 tag (53) is perpendicular to the line connecting the a2 tag (52) and the a4 tag (54); the line connecting the b1 tag (55) and the b3 tag (56) is perpendicular to the line connecting the b2 tag (57) and the b4 tag (58).

4. The RFID-based coupling state parameter monitoring system according to claim 3 is characterized in that: The a1 tag (51), a2 tag (52), a3 tag (53) and a4 tag (54) correspond to the b1 tag (55), b2 tag (56), b3 tag (57) and b4 tag (58) respectively; in an initial state, the line connecting the a1 tag (51) and the a3 tag (53) is parallel to the line connecting the b1 tag (55) and the b3 tag (56); the line connecting the a2 tag (52) and the a4 tag (54) is parallel to the line connecting the b2 tag (57) and the b4 tag (58).

5. The working method of the coupling state parameter monitoring system based on RFID according to claim 3 is characterized in that: The method for monitoring the rotation speed of the coupling (4) comprises the following steps: S1-1, selecting any passive tag in the first passive tag array as a rotation speed monitoring passive tag; S1-2, collecting the RSSI value of the speed monitoring passive tag through the UHF reader (2) and the UHF antenna (3), the data contains the timestamp of the collection, and the RSSI value collected at this time is compared with the RSSI value collected last time; S1-3, when the RSSI value changes from gradually increasing to decreasing for the first time, it is determined that the RSSI value at this time is the maximum value of the RSSI value of the speed monitoring passive tag, and at this time the speed monitoring passive tag is facing the UHF antenna (3); S1-4, subtract the timestamp of the maximum RSSI value of the speed monitoring passive tag at this time from the timestamp of the previous speed monitoring passive tag at the initial position to obtain a time difference; based on the time difference and the radius of the active end (41) of the coupling (4), calculate the speed of the coupling (4); and monitor the speed of the coupling (4).

6. The working method of the coupling state parameter monitoring system based on RFID according to claim 4 is characterized in that: The method for monitoring the torsion angle of the coupling (4) comprises the following steps: S2-1, arbitrarily selecting two corresponding passive tags from the first passive tag array and the second passive tag array as the first angle passive tag and the second angle passive tag for monitoring the torsion angle; S2-2, collecting RSSI values ​​of the first angle passive tag and the second angle passive tag through the UHF reader (2) and the UHF antenna (3), the data containing the timestamp of the collection, comparing the RSSI value collected at this time with the RSSI value collected last time, and determining the maximum value of the RSSI values ​​of the first angle passive tag and the second angle passive tag; S2-3, in the initial state, the timestamp when the RSSI value of the first angle passive tag reaches the maximum value is equal to the timestamp when the RSSI value of the second angle passive tag reaches the maximum value; when it is monitored that the times when the RSSI values ​​of the first angle passive tag and the second angle passive tag reach the maximum value are not at the same time, it is determined that the active end (41) and the driven end (42) are twisted; S2-4, subtract the timestamp when the RSSI value of the passive tag at the first angle is the maximum value from the timestamp when the RSSI value of the passive tag at the second angle is the maximum value to obtain a time difference; S2-5. Calculate the torsion angle according to the time difference and the rotation speed of the coupling (4), and calculate the torsion angles generated by two corresponding passive tags at the other three parts respectively; perform interpolation simulation on the torsion angles of other parts on the coupling (4) according to the torsion angles of the four parts, so as to monitor the torsion angle of the coupling (4).

7. The working method of the coupling state parameter monitoring system based on RFID according to claim 4 is characterized in that: The method for monitoring the axis trajectory of the coupling (4) comprises the following steps: S3-1, selecting any two orthogonal passive tags in the second passive tag array, that is, two adjacent passive tags on the driven end (42), as the first axis tag and the second axis tag for monitoring the axis track; S3-2, collecting the phase data of the first axis tag and the second axis tag, and determining whether the phase data of the passive tag needs to balance the periodic change caused by the phase jump, and if so, executing the next step; S3-3, according to the phase data of the first axis tag and the second axis tag, obtain the distance from the center of the UHF antenna (3) to the first axis tag and the second axis tag at this time; S3-4, subtract the timestamp of the passive tag phase data at this time from the timestamp of the passive tag at the initial position to obtain a difference, and calculate the rotation angle of the first axis tag and the second axis tag by using the difference and the rotation speed of the coupling (4) at this time; S3-5, measure the distance between the center of the UHF antenna (3) and the center of the coupling (4), and according to the results and geometric relationship of S3-3 and S3-4, obtain the distance from the center of the coupling (4) to the first axis label and the second axis label, the distance from the center of the coupling (4) to the first axis label and the difference between the distance from the center of the coupling (4) to the second axis label and the radius of the coupling (4), which is the amplitude of the passive tag; S3-6. Combine and analyze the amplitude of the first axis label and the amplitude of the second axis label to obtain the axis trajectory of the coupling (4) and monitor the axis trajectory of the coupling (4).

8. The working method of the coupling state parameter monitoring system based on RFID according to claim 5, characterized in that: In S1-4, the rotation speed n of the coupling (4) is calculated: n=2π·R / (t M′ -t M ) Where R is the radius of the coupling (4), t M′ This is the timestamp when the RSSI value of the speed monitoring passive tag is the maximum value. M The speed monitoring passive tag is located directly below the UHF antenna (3), which is the timestamp of the initial position.

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