A fastener loosening monitoring system and method based on rotation angle measurement

Abstract

The present application relates to the technical field of fastening bolt state monitoring, and specifically discloses a fastening bolt loosening monitoring system and method based on rotation angle measurement. The monitoring system comprises one or two sets of paired angle sensors and a data processing device; the one or two sets of paired angle sensors are arranged at the screw rod and / or the nut of the measured fastening bolt, and the paired angle sensors are used to measure the relative rotation angle of the screw rod / nut of the measured fastening bolt; the data processing device is connected with each set of paired angle sensors; the data processing device obtains the reference angle data of the measured fastening bolt under the set fastening condition and the real-time angle data of the measured fastening bolt within the monitoring period through the corresponding paired angle sensors, and the difference between the real-time angle data and the reference angle data, combined with the set early warning threshold, forms the monitoring result. The present application can realize all-weather, high-precision and high-reliability online monitoring of the measured fastening bolt.

Description

Technical Field

[0001] This invention relates to the field of fastener condition monitoring technology, specifically a fastener loosening monitoring system and method based on rotation angle measurement. Background Technology

[0002] Bolts, as connecting structures between adjacent components in assembled structures, play a vital role in securing and bearing loads. They are widely used in various assembled equipment, including large outdoor equipment such as wind turbines. In wind turbines, multiple bolts are typically densely arranged in a circumferential pattern at intervals on the tower, blades, hub, and main shaft.

[0003] To maintain the operational stability and safety of assembled equipment, it is necessary to regularly check the looseness of fastening bolts. For example, in the operation and maintenance of wind turbines, it is necessary to regularly check the looseness of the fastening bolts at the flanges between tower sections. This is because, due to the technical requirements for elevation, the tower of a wind turbine is usually assembled axially from multiple tower sections using high-strength bolts. Due to the special operating environment of wind turbines, under the influence of long-term alternating loads, wind-induced vibrations, and environmental corrosion, the fastening bolts of the tower sections are prone to loss of preload and loosening. In severe cases, this can lead to tower structural instability and catastrophic accidents.

[0004] Currently, the detection of loose bolts on wind turbine towers mainly relies on regular manual inspections or random checks with torque wrenches. This method has significant time lag, cannot achieve real-time online monitoring, and is inefficient. Furthermore, the unique outdoor and high-altitude environment makes the detection process cumbersome and technically challenging. Summary of the Invention

[0005] The technical objective of this invention is to provide a fastening bolt loosening monitoring system based on rotation angle measurement technology, which is capable of all-weather, high-precision, and highly reliable online monitoring, and a monitoring method based on this monitoring system, taking into account the special characteristics of the service and maintenance of the fastening bolts, especially those on wind turbines, and the shortcomings of existing technologies.

[0006] The technical objective of this invention is achieved through the following technical solution: a fastening bolt loosening monitoring system based on rotation angle measurement, wherein the monitoring system includes one or two sets of paired angle sensors and data processing equipment; One or two sets of paired angle sensors are arranged at the screw and / or nut of the fastening bolt being measured; The same set of paired angle sensors includes a first angle sensor and a second angle sensor. The first angle sensor is arranged on the fastening bolt being measured, and the second angle sensor is arranged on the fixed structure next to the fastening bolt being measured, adjacent to the first angle sensor and arranged in pairs. The paired angle sensors are used to measure the relative rotation angle of the screw / nut of the fastening bolt being measured. The data processing device is connected to each pair of angle sensors. The data processing device acquires the reference angle data of the tested fastening bolt under set fastening conditions through the corresponding paired angle sensor, and acquires the real-time angle data of the tested fastening bolt within the monitoring period. The monitoring result is formed by the difference between the real-time angle data and the reference angle data, combined with the set warning threshold.

[0007] As one of the preferred technical solutions, the data processing device calculates the axial preload loss / torque loss of the measured fastening bolt based on the difference between the real-time angle data and the reference angle data. The axial preload loss / torque loss of the tested fastening bolt is obtained and combined with the set warning threshold to form the monitoring result.

[0008] Furthermore, the data processing device calculates the axial preload loss of the measured fastening bolt according to the following relationship: =( ); In the formula, ΔF represents the axial preload loss of the measured fastening bolt; K represents the torsional stiffness of the bolt being tested; Δθ represents the difference between the real-time angle of the measured fastening bolt and the reference angle; L represents the effective length of the bolt being measured.

[0009] Furthermore, the data processing device calculates the torque loss of the measured fastening bolt according to the following formula: ΔT = C * Δθ;

[0010] In the formula, ΔT represents the torque loss of the measured fastening bolt; C represents the rotation angle-torque coefficient of the fastening bolt being measured; Δθ represents the difference between the real-time angle of the measured fastening bolt and the reference angle.

[0011] As one of the preferred technical solutions, the data processing device is equipped with an angle measurement module, a feature database, a calculation and processing module, and an early warning analysis module. The angle measurement module acquires the reference angle data of the fastened bolt under set fastening conditions through the corresponding paired angle sensor, and acquires the real-time angle data of the fastened bolt within the monitoring period. The feature database is used to store the feature parameter data of the fastening bolt being measured, as well as the reference angle data and real-time angle data acquired by the angle measurement module. The calculation and processing module uses the data stored in the feature database to calculate the current rotation angle and axial preload / torque loss of the measured fastening bolt, and generates real-time monitoring results. The early warning analysis module generates early warning information on the loosening status of the tested fastening bolt by combining the real-time monitoring results output by the calculation and processing module with the set early warning threshold.

[0012] Furthermore, the data processing equipment of the monitoring system consists of an edge computer and a remote host computer connected by a signal; The angle measurement module, feature database, and calculation processing module are deployed within the edge computer. The early warning analysis module is deployed in the remote host computer.

[0013] As one of the preferred technical solutions, the monitoring system is used to monitor the status of fastening bolts arranged at at least one location of the wind turbine, including the tower, blades, hub, and main shaft. The fastening bolts at the corresponding locations of the wind turbine generators are multiple bolts arranged at circumferential intervals, and the monitoring system is arranged at least at the corresponding fastening bolt locations in different circumferential directions.

[0014] As one of the preferred technical solutions, the first angle sensor of the paired angle sensor is a magnetic code disk; The second angle sensor of the paired angle sensor is a magnetic encoder reading head.

[0015] A method for monitoring the loosening of fastening bolts based on rotation angle measurement, the monitoring method being based on the aforementioned monitoring system; The monitoring method includes the following processes: S1. Arrange a first angle sensor at the screw and / or nut of the selected fastening bolt to be measured, and arrange a second angle sensor at the fixed structure on the side corresponding to the arrangement position of the first angle sensor, so that a pairing relationship is established between the one-to-one second angle sensor and the first angle sensor. The angle measurement actions of each pair of angle sensors on the same fastening bolt and each pair of angle sensors on different fastening bolts are independent of each other; Acquire the characteristic parameter data of the fastening bolt under test and store it in the data processing equipment; Set early warning thresholds in data processing equipment; S2. When the measured fastening bolt reaches the set fastening condition, the same set of paired angle sensors are matched by the data processing equipment to obtain the reference angle data. Store the obtained reference angle data; S3. According to the set acquisition cycle and / or operating conditions, acquire real-time angle data of the same set of paired angle sensors through data processing equipment; S4. Calculate the difference between the real-time angle data of S3 and the reference angle data of S2; S5. Using the difference from S4 and the established calculation relationship, obtain the axial preload loss / torque loss of the tested fastening bolt; S6. The obtained axial preload loss / torque loss of the tested fastening bolt is compared with the warning threshold set in S1, and the corresponding fastening bolt loosening status warning information is generated according to the set comparison logic.

[0016] Furthermore, in S1 or S6, the warning threshold is set as a warning level and an alarm level; The warning level is defined as a value of ≥10% and <20% of the initial axial preload / torque. When the warning level is triggered, it is determined that the tested fastening bolt "shows obvious looseness" and the monitoring frequency is increased. The alarm level is ≥20% of the initial axial preload / torque. When the alarm level is triggered, it is determined that the tested fastening bolt "has a safety hazard" and an emergency alarm message is generated.

[0017] The beneficial technical effects of this invention are as follows: The above-mentioned technical measures address the unique characteristics of the service and maintenance of fastening bolts, especially those on wind turbines. Based on the rotation angle measurement technology between paired angle sensors, the invention collects and calibrates the initial relative angle of the fastening bolt under test (i.e., obtains reference angle data). During the service life of the fastening bolt, the real-time rotation angle is dynamically collected. Monitoring results are generated by analyzing and comparing the real-time angle data with the reference angle data. In particular, the axial preload loss / torque loss of the fastening bolt under test is calculated based on the difference between the real-time angle data and the reference angle data. The axial preload loss / torque loss of the fastening bolt under test is then compared with a set warning threshold to generate different levels of monitoring results. This enables all-weather, high-precision, and highly reliable online monitoring of the fastening bolt under test, effectively replacing traditional manual inspection methods and eliminating their technical drawbacks.

[0018] More specifically, the above-mentioned technical measures have the following main technical advantages: 1. Excellent real-time performance and continuity; The paired angle sensors arranged on the fastened bolts and the side fixed structures under test can realize 24-hour uninterrupted detection, with fast response speed. They can capture the changes in the state of fastened bolts under various working conditions (such as extreme working conditions such as strong winds), and achieve the real-time and timely monitoring effect of timely detection of early loosening and prevention of problems. 2. Achieve quantitative evaluation; The difference between the real-time angle data measured by the paired angle sensor and the reference angle data is calculated. The difference is combined with the set calculation relationship to obtain the axial preload loss / torque loss of the tested fastening bolt. The axial preload loss / torque loss of the tested fastening bolt is directly compared with the set warning threshold, so that the monitoring results are accurate and reliable, which is better than the simple "loose / tight" qualitative judgment. 3. High precision and high sensitivity; The paired angle sensor consists of a magnetic code disk and a magnetic encoder reading head. It has high measurement resolution and can detect angle changes corresponding to displacements at the micrometer or even nanometer level, with extremely high sensitivity. 4. Easy to implement and low cost; The arrangement structure of paired angle sensors in the working environment is relatively simple, easy to install and implement, and is particularly suitable for working scenarios with a large number of fastening bolts, such as wind turbines, with low overall cost. 5. Strong anti-interference ability; Paired angle sensors directly measure mechanical displacement, thus being far less affected by environmental noise and temperature fluctuations than detection technologies such as acoustic emission and ultrasound, and have strong anti-interference capabilities. Attached Figure Description

[0019] Figure 1 This is an architecture diagram of the monitoring system of the present invention.

[0020] Figure 2 for Figure 1 A schematic diagram of the mating relationship between the paired angle sensor and the fastening bolt being measured.

[0021] Figure 3 This is a process flow diagram of the monitoring method of the present invention.

[0022] The symbols in the diagram have the following meanings: 1—the bolt being measured; 2—the first angle sensor; 3—the second angle sensor; 4—the edge computer; 41—the angle measurement module; 42—the feature database; 43—the calculation and processing module; 5—the host computer; 51—the early warning analysis module. Detailed Implementation

[0023] This invention relates to the field of fastener condition monitoring technology, particularly to the field of fastener condition monitoring technology for fasteners connected at any point in a wind turbine, such as the tower, blades, hub, or main shaft. Specifically, it is a fastener loosening monitoring system based on rotation angle measurement, and a monitoring method based on this system. The technical solution of this invention will be clearly and thoroughly explained below with reference to several embodiments, each of which can be referred to in conjunction with the accompanying drawings of this specification. Figure 1 , Figure 2 and Figure 3 The technical solution of this invention will be clearly and thoroughly explained.

[0024] It should be noted that the accompanying drawings of this invention are schematic, and unnecessary details have been simplified to clarify the technical objectives of this invention, so as to avoid obscuring the technical solutions contributed by this invention to the prior art. Furthermore, the terms "approximately" or "basically" used below to refer to quantities or fit relationships mean that reasonable assembly and processing errors are allowed in the industry, and do not literally describe absolute quantities or fit relationships. Example 1

[0025] See Figure 1 and Figure 2 As shown, the present invention is a monitoring system for the status of fastening bolts on wind turbine towers. It is based on rotation angle measurement technology and includes paired angle sensors arranged at the large end of the fastening bolt 1 being measured, an edge computer 4, a remote host computer 5 (wind farm monitoring system SCADA), and a mobile terminal for operation and maintenance personnel.

[0026] Specifically, since there are several fastening bolts at the flange of the wind turbine tower section, which are arranged in a dense and spaced manner in the circumferential direction, online monitoring of each bolt would result in a dense sensor arrangement and increased cost. Therefore, one bolt is selected as the object to be measured in the four directions of east, south, west and north in the circumferential direction.

[0027] For the measured bolt 1, a pair of angle sensors are arranged at its large end to measure the rotation angle. These paired angle sensors include a first angle sensor 2 and a second angle sensor 3. The first angle sensor 2 uses a magnetic encoder disk structure, and the second angle sensor 3 uses a magnetic encoder reading head. The first angle sensor 2 is located on the large end face of the bolt 1, and the second angle sensor 3 is located on a fixed structure beside the large end of the bolt 1—for example, a flange or tower as a fixed carrier. This arrangement creates a close proximity relationship between the second angle sensor 3 and the first angle sensor 2 with a small gap, and the paired angle sensors are used to measure the relative rotation angle of the bolt 1.

[0028] The paired angle sensors on the measured fastening bolt 1 are connected to the edge computer 4, which serves as a data processing device. This connection ensures that the edge computer 4 can acquire the measurement data from the paired angle sensors in real time. The paired angle sensors on each of the circumferentially measured fastening bolts 1 at the tower flange are also connected to the edge computer 4, and the measurement actions of each pair of paired angle sensors are independent. The edge computer 4, as the data processing device, is also connected to the remote host computer 5. This connection ensures high-speed interaction between the edge computer 4 and the remote host computer 5, such as through a fiber optic network.

[0029] The aforementioned edge computer 4 is housed within the control cabinet at the base of the tower. Edge computer 4 is equipped with a Linux system, running analysis programs written in Python (OpenCV, Scikit-learn) and C++. Edge computer 4 also houses an angle measurement module 41, a feature database 42, and a calculation and processing module 43. Angle measurement data collected by paired angle sensors from each group is transmitted to edge computer 4. Specifically: The angle measurement module 41 acquires the reference angle data of the current fastening bolt 1 under the set fastening conditions through the corresponding paired angle sensor, and acquires the real-time angle data of the current fastening bolt 1 within the monitoring period (e.g., every 6 hours under normal conditions, every 1 hour under abnormal conditions, and real-time acquisition after the event in case of working conditions such as strong winds). The feature database 42 is used to store the feature parameter data of the fastened bolt 1 under test (including the effective length L of the screw, the torque stiffness K of the screw, etc.), as well as the reference angle data and real-time angle data acquired by the angle measurement module 41. The calculation and processing module 43 uses the data stored in the feature database to calculate the current rotation angle and axial preload loss of the measured fastening bolt 1, and generates real-time monitoring results.

[0030] The aforementioned remote host computer 5 is equipped with an early warning analysis module 51. This early warning analysis module 51 uses the real-time monitoring results output by the calculation and processing module 43, combined with the set early warning threshold, to generate early warning information on the loosening status of the tested fastening bolt 1.

[0031] The mobile terminals of maintenance personnel, such as mobile phones, are connected to the aforementioned remote host computer 5, which pushes information in real time according to the early warning monitoring results.

[0032] See Figure 3As shown, based on the above monitoring system, the present invention monitors the loosening status of fastening bolts on the wind turbine tower according to the following monitoring method, specifically including the following processes: S1. At the large end of the selected bolt 1 to be measured, a first angle sensor 2 is arranged, and a second angle sensor 3 is arranged on the side fixing structure corresponding to the arrangement position of the first angle sensor 2, so that the one-to-one correspondence between the second angle sensor 3 and the first angle sensor 2 establishes a pairing relationship. The angle measurement actions of each pair of paired angle sensors on the different fastening bolts 1 being measured in the circumferential direction of the tower flange are independent of each other; Acquire the characteristic parameter data of the tested fastening bolt 1 and store it in the edge computer 4; A warning threshold is set within the remote host computer 5. This warning threshold is configured with a warning level and an alarm level; wherein: The warning level is defined as a value ≥10% and <20% of the initial axial preload, that is, the range of 10% to 20% of the initial axial preload, but excluding 20%. The alarm level is ≥20% of the initial axial preload; S2. When the measured fastening bolt 1 reaches the set tightening condition (i.e., the condition of reaching the design torque tightening condition), the edge computer 4 performs matching processing on the angle measurement relationship of the same set of paired angle sensors and obtains the reference angle data. ; The obtained reference angle data storage; S3. According to the set acquisition cycle and / or operating conditions, acquire real-time angle data from the same set of paired angle sensors via the edge computer 4. ; S4. Calculate the real-time angle data of S3. , and the reference angle data of S2 The difference between ; The specific calculation process satisfies the following relationship: = - ; To eliminate noise interference, digital signal processing algorithms such as moving average filtering can be used; S5. The difference from S4 The axial preload loss of the measured fastening bolt is obtained by using the calculation relationship set below. The calculation of the axial preload loss of the tested fastening bolt 1 satisfies the following relationship: =( ); In the formula, ΔF represents the axial preload loss of the measured fastening bolt; K represents the torsional stiffness of the bolt being tested; Δθ represents the difference between the real-time angle of the measured fastening bolt and the reference angle; L represents the effective length of the fastening bolt being measured; S6. The obtained axial preload loss of the tested fastening bolt 1. The warning information is compared with the warning threshold set in S1, and the corresponding loosening status warning information of the fastening bolt is generated according to the set comparison logic. Specifically, when When the warning level is triggered, it is determined that the tested fastening bolt "shows obvious looseness" and the monitoring frequency is increased; when When the alarm level is triggered, it is determined that the tested fastening bolt "has a safety hazard" and an emergency alarm message is generated.

[0033] Based on the monitoring process described above, the emergency alarm information generated in S6 should include the location of the loose bolt, its rotation angle, and the loss of axial preload. The report includes diagnostic information such as the warning level. This report will then be sent to relevant personnel via audio-visual aids, platform messages, and SMS. Example 2

[0034] See Figure 1 and Figure 2 As shown, the present invention is a monitoring system for the status of fastening bolts on wind turbine towers. It is based on rotation angle measurement technology and includes paired angle sensors arranged at the large end of the fastening bolt 1 being measured, an edge computer 4, a remote host computer 5 (wind farm monitoring system SCADA), and a mobile terminal for operation and maintenance personnel.

[0035] Specifically, since there are several fastening bolts at the flange of the wind turbine tower section, which are arranged in a dense and spaced manner in the circumferential direction, online monitoring of each bolt would result in a dense sensor arrangement and increased cost. Therefore, one bolt is selected as the object to be measured in the four directions of east, south, west and north in the circumferential direction.

[0036] For the measured bolt 1, a pair of angle sensors are arranged at its large end to measure the rotation angle. These paired angle sensors include a first angle sensor 2 and a second angle sensor 3. The first angle sensor 2 uses a magnetic encoder disk structure, and the second angle sensor 3 uses a magnetic encoder reading head. The first angle sensor 2 is located on the large end face of the bolt 1, and the second angle sensor 3 is located on a fixed structure beside the large end of the bolt 1—for example, a flange or tower as a fixed carrier. This arrangement creates a close proximity relationship between the second angle sensor 3 and the first angle sensor 2 with a small gap, and the paired angle sensors are used to measure the relative rotation angle of the bolt 1.

[0037] The paired angle sensors on the measured fastening bolt 1 are connected to the edge computer 4, which serves as a data processing device. This connection ensures that the edge computer 4 can acquire the measurement data from the paired angle sensors in real time. The paired angle sensors on each of the circumferentially measured fastening bolts 1 at the tower flange are also connected to the edge computer 4, and the measurement actions of each pair of paired angle sensors are independent. The edge computer 4, as the data processing device, is also connected to the remote host computer 5. This connection ensures high-speed interaction between the edge computer 4 and the remote host computer 5, such as through a fiber optic network.

[0038] The aforementioned edge computer 4 is housed within the control cabinet at the base of the tower. Edge computer 4 is equipped with a Linux system, running analysis programs written in Python (OpenCV, Scikit-learn) and C++. Edge computer 4 also houses an angle measurement module 41, a feature database 42, and a calculation and processing module 43. Angle measurement data collected by paired angle sensors from each group is transmitted to edge computer 4. Specifically: The angle measurement module 41 acquires the reference angle data of the current fastening bolt 1 under the set fastening conditions through the corresponding paired angle sensor, and acquires the real-time angle data of the current fastening bolt 1 within the monitoring period (e.g., every 6 hours under normal conditions, every 1 hour under abnormal conditions, and real-time acquisition after the event in case of working conditions such as strong winds). The feature database 42 is used to store the feature parameter data of the fastened bolt 1 under test (including the effective length L of the screw, the torque stiffness K of the screw, etc.), as well as the reference angle data and real-time angle data acquired by the angle measurement module 41. The calculation and processing module 43 uses the data stored in the feature database to calculate the current rotation angle and axial preload loss of the tested fastening bolt 1, generating real-time monitoring results. The aforementioned remote host computer 5 is equipped with an early warning analysis module 51. This early warning analysis module 51 uses the real-time monitoring results output by the calculation and processing module 43, combined with a set early warning threshold, to generate corresponding early warning information about the loosening status of the tested fastening bolt 1.

[0039] The mobile terminals of maintenance personnel, such as mobile phones, are connected to the aforementioned remote host computer 5, which pushes information in real time according to the early warning monitoring results.

[0040] See Figure 3 As shown, based on the above monitoring system, the present invention monitors the loosening status of fastening bolts on the wind turbine tower according to the following monitoring method, specifically including the following processes: S1. At the large end of the selected bolt 1 to be measured, a first angle sensor 2 is arranged, and a second angle sensor 3 is arranged on the side fixing structure corresponding to the arrangement position of the first angle sensor 2, so that the one-to-one correspondence between the second angle sensor 3 and the first angle sensor 2 establishes a pairing relationship. The angle measurement actions of each pair of paired angle sensors on the different fastening bolts 1 being measured in the circumferential direction of the tower flange are independent of each other; Acquire the characteristic parameter data of the tested fastening bolt 1 and store it in the edge computer 4; A warning threshold is set within the remote host computer 5. This warning threshold is configured with a warning level and an alarm level; wherein: The warning level is defined as a value ≥10% and <20% of the initial axial preload, that is, the range of 10% to 20% of the initial axial preload, but excluding 20%. The alarm level is ≥20% of the initial axial preload; S2. When the measured fastening bolt 1 reaches the set tightening condition (i.e., the condition of reaching the design torque tightening condition), the edge computer 4 performs matching processing on the angle measurement relationship of the same set of paired angle sensors and obtains the reference angle data. ; The obtained reference angle data storage; S3. According to the set acquisition cycle and / or operating conditions, acquire real-time angle data from the same set of paired angle sensors via the edge computer 4. ; S4. Calculate the real-time angle data of S3. , and the reference angle data of S2 The difference between ; The specific calculation process satisfies the following relationship: = - ; To eliminate noise interference, digital signal processing algorithms such as moving average filtering can be used; S5. The difference from S4 The torque loss of the fastened bolt under test is obtained by using the calculation relationship set below. The calculation of the torque loss of the tested fastening bolt 1 satisfies the following relationship: ΔT = C * Δθ;

[0041] In the formula, ΔT represents the torque loss of the measured fastening bolt; C represents the rotation angle-torque coefficient of the fastening bolt being measured; where C=E*d*k, E is the torque coefficient, d is the nominal diameter of the bolt, and k is the angle-force coefficient of the bolt. Δθ represents the difference between the real-time angle of the measured fastening bolt and the reference angle.

[0042] S6. The torque loss ΔT of the measured fastening bolt 1 is compared with the warning threshold set in S1, and the corresponding fastening bolt loosening state warning information is generated according to the set comparison logic. Specifically, when ΔT triggers the warning level, it is determined that the tested fastening bolt "shows obvious looseness", and the monitoring frequency is increased; When ΔT triggers the alarm level, it is determined that the tested fastening bolt "has a safety hazard" and an emergency alarm message is generated.

[0043] Based on the monitoring process described above, the emergency alarm information generated in S6 should include a diagnostic report on the location of the loose bolt, its rotation angle, torque loss ΔT, and warning level. This report should then be sent to relevant personnel via audio-visual means, platform messages, and SMS. Example 3

[0044] The rest of the content of this embodiment is the same as that of embodiment 1 or embodiment 2, except that: The paired angle sensors on the fastening bolt being tested consist of two sets that operate independently. One set is located at the large end of the screw to monitor the circumferential rotational loosening of the screw, while the other set is located at the nut to monitor the circumferential rotational loosening of the nut.

[0045] The above embodiments are only used to illustrate the present invention and are not intended to limit it.

Claims

1. A fastening bolt loosening monitoring system based on rotation angle measurement, characterized in that: The monitoring system includes one or two sets of paired angle sensors and data processing equipment; One or two sets of paired angle sensors are arranged at the screw and / or nut of the fastening bolt (1) being measured; The same set of paired angle sensors includes a first angle sensor (2) and a second angle sensor (3). The first angle sensor (2) is arranged on the fastening bolt (1) to be measured, and the second angle sensor (3) is arranged on the fixing structure next to the fastening bolt (1), adjacent to the first angle sensor (2) and arranged in pairs. The paired angle sensors are used to measure the relative rotation angle of the screw / nut of the fastening bolt (1) to be measured. The data processing device is connected to each pair of angle sensors. The data processing device acquires the reference angle data of the tested fastening bolt (1) under the set fastening conditions through the corresponding paired angle sensor, and acquires the real-time angle data of the tested fastening bolt (1) within the monitoring period. The monitoring result is formed by the difference between the real-time angle data and the reference angle data and the set warning threshold.

2. The fastening bolt loosening monitoring system based on rotation angle measurement according to claim 1, characterized in that: The data processing device calculates the axial preload loss / torque loss of the measured fastening bolt (1) based on the difference between the real-time angle data and the reference angle data. The axial preload loss / torque loss of the tested fastening bolt (1) is obtained and combined with the set warning threshold to form the monitoring result.

3. The fastening bolt loosening monitoring system based on rotation angle measurement according to claim 2, characterized in that: The data processing equipment calculates the axial preload loss of the measured fastening bolt (1) according to the following relationship: =( )； In the formula, ΔF represents the axial preload loss of the measured fastening bolt; K represents the torsional stiffness of the bolt being tested; Δθ represents the difference between the real-time angle of the measured fastening bolt and the reference angle; L represents the effective length of the bolt being measured.

4. The fastening bolt loosening monitoring system based on rotation angle measurement according to claim 2, characterized in that: The data processing device calculates the torque loss of the measured fastening bolt (1) according to the following relationship: ΔT = C * Δθ; In the formula, ΔT represents the torque loss of the measured fastening bolt; C represents the rotation angle-torque coefficient of the fastening bolt being measured; Δθ represents the difference between the real-time angle of the measured fastening bolt and the reference angle.

5. The fastening bolt loosening monitoring system based on rotation angle measurement according to any one of claims 1 to 4, characterized in that: The data processing device is equipped with an angle measurement module (41), a feature database (42), a calculation and processing module (43), and an early warning analysis module (51). The angle measurement module (41) acquires the reference angle data of the fastening bolt (1) under the set fastening conditions through the corresponding paired angle sensor, and acquires the real-time angle data of the fastening bolt (1) within the monitoring period. The feature database (42) is used to store the feature parameter data of the fastening bolt (1) being measured, as well as the reference angle data and real-time angle data acquired by the angle measurement module (41). The calculation and processing module (43) uses the data stored in the feature database to calculate the current rotation angle and axial preload loss / torque loss of the measured fastening bolt (1) and generate real-time monitoring results. The early warning analysis module (51) generates early warning information on the loosening status of the measured fastening bolt (1) by combining the real-time monitoring results output by the calculation and processing module (43) with the set early warning threshold.

6. The fastening bolt loosening monitoring system based on rotation angle measurement according to claim 5, characterized in that: The data processing equipment of the monitoring system consists of an edge computer (4) and a remote host computer (5) connected by a signal; The angle measurement module (41), feature database (42), and calculation processing module (43) are deployed within the edge computer (4); The early warning analysis module (51) is deployed in the remote host computer (5).

7. The fastening bolt loosening monitoring system based on rotation angle measurement according to claim 6, characterized in that: The monitoring system is used to monitor the status of fastening bolts at at least one location of the wind turbine, including the tower, blades, hub, and main shaft. The fastening bolts at the corresponding locations of the wind turbine generators are multiple bolts arranged at circumferential intervals, and the monitoring system is arranged at least at the corresponding fastening bolt locations in different circumferential directions.

8. The fastening bolt loosening monitoring system based on rotation angle measurement according to claim 1, characterized in that: The first angle sensor (2) of the paired angle sensor is a magnetic encoder disk; The second angle sensor (3) of the paired angle sensor is a magnetic encoder reading head.

9. A method for monitoring the loosening of fastening bolts based on rotation angle measurement, characterized in that: The monitoring method is based on the monitoring system according to any one of claims 1 to 8; The monitoring method includes the following processes: S1. Arrange a first angle sensor at the screw and / or nut of the selected fastening bolt to be measured, and arrange a second angle sensor at the fixed structure on the side corresponding to the arrangement position of the first angle sensor, so that a pairing relationship is established between the one-to-one second angle sensor and the first angle sensor. The angle measurement actions of each pair of angle sensors on the same fastening bolt and each pair of angle sensors on different fastening bolts are independent of each other; Acquire the characteristic parameter data of the fastening bolt under test and store it in the data processing equipment; Set early warning thresholds in data processing equipment; S2. When the measured fastening bolt reaches the set fastening condition, the same set of paired angle sensors are matched by the data processing equipment to obtain the reference angle data. Store the obtained reference angle data; S3. According to the set acquisition cycle and / or operating conditions, acquire real-time angle data of the same set of paired angle sensors through data processing equipment; S4. Calculate the difference between the real-time angle data of S3 and the reference angle data of S2; S5. Using the difference from S4 and the established calculation relationship, obtain the axial preload loss / torque loss of the tested fastening bolt; S6. The obtained axial preload loss / torque loss of the tested fastening bolt is compared with the warning threshold set in S1, and the corresponding fastening bolt loosening status warning information is generated according to the set comparison logic.

10. The method for monitoring loosening of fastening bolts based on rotation angle measurement according to claim 9, characterized in that, In S1 or S6, the warning threshold is set to a warning level and an alarm level; The warning level is defined as a value of ≥10% and <20% of the initial axial preload / torque. When the warning level is triggered, it is determined that the tested fastener "has become significantly loose", and the monitoring frequency is increased. The alarm level is ≥20% of the initial axial preload / torque. When the alarm level is triggered, it is determined that the tested fastening bolt "has a safety hazard" and an emergency alarm message is generated.

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