Method for measuring and calculating rotating speed of fan impeller and displacement of main shaft based on eddy current sensor

Abstract

The invention discloses a method for measuring and calculating the rotating speed of an impeller and the displacement of a main shaft of a fan based on an eddy current sensor, which comprises the following steps of: firstly, mounting a coded disc on the main shaft, and simultaneously measuring the rotating speed of the impeller and the displacement of the main shaft by adopting the eddy current sensor; for the measurement of the rotating speed of the impeller, the eddy current sensor scans the tooth surface and the tooth space of the coded disc, outputs a corresponding analog quantity signal, performs setting processing, calculates the rotating speed of the impeller according to the falling edge interval time of the processed signal, and if the rotating speed of the impeller is lower than a preset value, adopts a frequency method and a periodic method for calculation, otherwise, adopts the frequency method for calculation; for the measurement of the spindle displacement, the eddy current sensor detects the tooth surface of the coded disc, outputs a corresponding analog quantity signal according to the distance between the eddy current sensor and the tooth surface, eliminates abnormal data in the analog quantity signal, carries out mean value processing, and compares the latest calculated mean value with the last calculated mean value to judge the spindle displacement condition. According to the method, the real-time impeller rotating speed and the spindle displacement condition of the fan can be accurately and efficiently measured and calculated.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a method and system for measuring the rotational speed of a wind turbine impeller and the displacement of a main shaft based on an eddy current sensor. Background Art

[0002] With advances in wind power technology and the expansion of the industry, the capacity of wind turbines (also known as wind turbines, wind generator sets, and wind turbine generators) continues to increase. Improving wind turbine power generation efficiency, reducing operation and maintenance costs, and improving the overall economic efficiency of wind farms have become increasingly important. Wind turbines primarily use wind energy to drive their impellers, which are then transmitted to the generator via a gearbox, thereby converting wind energy into mechanical energy and electrical energy. Smart wind power is now a key development direction in the industry, requiring wind turbines to have more robust status detection and fault diagnosis capabilities, enabling intelligent operation and maintenance.

[0003] Impeller speed is crucial for wind turbine control and is typically measured using encoders, speed sensors, proximity switches, and other devices. Encoders offer high precision and can directly and accurately measure impeller speed and position. However, they have high installation requirements, requiring precise coaxial installation with the impeller shaft. Furthermore, encoders are more expensive than other sensors. As wind power grid parity advances, companies are continuously improving their technology and reducing unit costs, making encoders less suitable for cost reduction. The wind turbine's main shaft and bearings bear enormous loads during operation, and their operating status directly impacts turbine reliability. Eddy current sensors can detect parameters such as main shaft displacement, vibration, and speed, enabling timely detection of problems such as shaft imbalance, misalignment, and bearing wear, preventing failures and minimizing power generation losses.

[0004] Existing methods for measuring impeller speed in wind turbines primarily use encoders, proximity switches, eddy current sensors, and other methods, then calculate the impeller speed through algorithmic processing. Neither encoders nor proximity switches can synchronously measure spindle displacement.

[0005] There are some problems with the existing fan impeller speed and main shaft displacement monitoring methods:

[0006] 1. Currently, the most common method is to use devices such as proximity switches or encoders to measure impeller speed. Encoders offer high measurement accuracy, but this solution is costly. A proximity switch requires a code disk mounted on the spindle. When the sensor scans the code disk's tooth tips and tooth gaps, it outputs a corresponding DI signal. The main controller calculates the impeller speed based on the DI signal changes. During this process, sensor accuracy is significantly affected by the environment, requiring complex algorithms to optimize the signal and evaluate the data. Furthermore, factors such as the distance between the interface switch and the code disk must be controlled, making installation complex.

[0007] 2. Wind turbines require two sensors to measure impeller speed and main shaft displacement. This solution is relatively expensive given the drive to reduce costs and increase efficiency. Chinese patent CN221503442U describes a device for detecting main shaft displacement in wind turbines. Displacement sensors are installed at multiple locations on the main bearing, and monitoring values ​​are read using specialized software. This solution, while installing displacement sensors at multiple locations on the main bearing, helps maintenance personnel easily identify wear and facilitates repairs. However, this device also presents a high cost.

[0008] In summary, the existing measurement of fan impeller speed and main shaft displacement is costly, requires two devices to be implemented together, and has weak data processing diversity. There are technical problems such as how to improve the reliability and stability of fan impeller speed measurement, how to judge the main shaft displacement phenomenon based on sensor data, and how to effectively process sensor data to improve confidence and avoid false alarms of fan failures. Summary of the Invention

[0009] The first purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a safe, reliable and highly accurate method for measuring the impeller speed and main shaft displacement of a fan based on an eddy current sensor.

[0010] The second object of the present invention is to provide a system for measuring the speed of the fan impeller and the main shaft displacement based on the eddy current sensor.

[0011] The first object of the present invention is achieved by the following technical solution: a method for measuring the impeller speed and main shaft displacement of a fan based on an eddy current sensor, wherein the method is to first install a code disk on the main shaft, and then use an eddy current sensor to simultaneously measure the impeller speed and main shaft displacement;

[0012] For the measurement of impeller speed, the eddy current sensor sweeps the tooth surface and tooth gap of the code disk, outputs the corresponding analog signal, performs tuning processing on the analog signal, and then calculates the impeller speed according to the falling edge interval time of the tuned signal. If the calculated impeller speed is lower than the preset value, the period method and frequency method are used to obtain the impeller speed, and the average speed value is output as the final impeller speed. Otherwise, the frequency method is used as the basis, that is, the impeller speed calculated by the falling edge interval time is directly output as the final impeller speed. Finally, the final impeller speed is compared with the impeller speed obtained by dividing the generator speed by the gearbox speed ratio. If the deviation exceeds the preset limit, a fault is reported, otherwise it is normal.

[0013] For the measurement of spindle displacement, the eddy current sensor detects the tooth surface of the code disk and outputs the corresponding analog signal according to the distance between itself and the tooth surface, eliminates abnormal data, and performs average processing. The latest calculated average value is compared with the last calculated average value. If the deviation exceeds the preset limit, a spindle displacement fault is reported, otherwise it is normal.

[0014] Furthermore, for the measurement of impeller speed, the analog signal output by the eddy current sensor is close to a square wave waveform. A threshold value is set in the program to convert the analog signal and condition it into a square wave signal. The time point corresponding to the falling edge of the square wave signal is collected, and an array with the same capacity as the number of teeth on the code disk is created to store the time interval data between every two falling edges. According to the first-in-first-out principle of data, each time a new set of time interval data is entered, the earliest set of data is removed. At this time, the sum of the data in the array is exactly the time consumed by the impeller to rotate one circle. The inverse of this time is the impeller speed calculated by the frequency method.

[0015] Furthermore, when the impeller speed is lower than the preset value, the period method and the frequency method are used to jointly calculate the impeller speed. The following is the period method for calculating the impeller speed: First, a time period needs to be set, which is divided into three sections. The first section uses the moment when the speed is lower than the preset value as the timing zero point, the second section uses the time midpoint of the first section as the timing zero point, and the third section uses the time midpoint of the second section as the timing zero point. Then, the number of pulses is read in the corresponding time period segment respectively, and the impeller speed is further calculated based on the ratio of the number of pulses in the time period segment to the number of impeller teeth. That is, the ratios calculated in the three time period segments are averaged as the impeller speed calculated by the period method; finally, the impeller speeds obtained by the frequency method and the period method are averaged as the final impeller speed.

[0016] Furthermore, the method for measuring the fan impeller speed and main shaft displacement based on the eddy current sensor includes the following steps:

[0017] 1) The fan's main control reads the eddy current sensor data and adjusts the data;

[0018] 2) Using the first-in-first-out principle, the impeller rotation time is obtained in real time;

[0019] 3) The time interval data in the array is summed in real time, and the reciprocal of the sum is the impeller speed calculated by the frequency method;

[0020] 4) Taking the impeller speed calculated by the frequency method as the benchmark, when the impeller speed is less than the preset value, three cycle timers are added to calculate the number of pulses in the cycle. The first timer is zeroed when the speed calculated by the frequency method is less than the preset value. The second timer is zeroed at the midpoint of the first timer. The third timer is zeroed at the midpoint of the second timer. Finally, the real-time speed when the impeller speed is less than the preset value is calculated using the average value of the three cycle timers and the frequency method as the final impeller speed.

[0021] 5) The main control compares the final impeller speed with the impeller speed calculated by dividing the generator speed by the gearbox speed ratio. If the deviation between the two exceeds the preset limit γ, a fault is reported.

[0022] Furthermore, in step 1), the main control adjusts the read eddy current sensor data into square wave data according to the set upper and lower threshold values ​​α and β, and outputs it in the form of Bool value.

[0023] Further, in step 2), the eddy current sensor sweeps across the tooth surface to the tooth gap, and a falling edge will appear in the waveform. The main control captures the time corresponding to the falling edge, obtains the time interval data between each two falling edges, and stores them in an array with the same capacity as the number of teeth on the code disk. The sum of the time interval data is exactly the time it takes for the impeller to rotate one circle. The first-in-first-out principle is adopted. Each time a time interval data is entered, the earliest data is discarded, so the impeller rotation time is refreshed to the latest value in real time.

[0024] Furthermore, in step 3), the time interval data in the array is summed in real time, and the reciprocal of the sum is the impeller speed calculated by the frequency method. The calculation formula is as follows:

[0025]

[0026] Where, T k T is the moment when the current master captures the falling edge of the eddy current sensor signal. k-1 The moment before the main controller captures the falling edge of the eddy current sensor signal, n is the number of teeth on the encoder, and r is the impeller speed. When the impeller speed is greater than or equal to the preset value, the frequency method is used for calculation. When the impeller speed is lower than the preset value, the period method and the frequency method are used together to calculate the impeller speed.

[0027] Furthermore, for the measurement of spindle displacement, if the fan has spindle displacement, it will inevitably cause the distance between the code disk tooth surface and the eddy current sensor to be offset, and the output value of the eddy current sensor will change at this time; the fan's main control reads the output value of the eddy current sensor by sampling, reading it once for each set time period, and reading n values ​​each time, where n is the number of code disk teeth, that is, the main control reads the n code disk tooth surface distance data output by the eddy current sensor each time, and calculates the corresponding average value, and then adopts the first-in-first-out principle to continuously update the sampled average value, and compare the latest calculated average value with the previous average value. If the deviation exceeds the preset limit a, a spindle displacement fault is reported.

[0028] Furthermore, the code disc is a square tooth code disc with the same tooth surface and tooth gap size. Starting from the first falling edge, the impeller rotates one circle after the n+1th falling edge, where n is the number of teeth on the code disc.

[0029] The second object of the present invention is achieved by the following technical solution: a system for measuring the fan impeller speed and main shaft displacement based on an eddy current sensor, used to implement the above-mentioned method for measuring the fan impeller speed and main shaft displacement based on an eddy current sensor, comprising:

[0030] The impeller speed measurement module measures the impeller speed based on an eddy current sensor. The eddy current sensor scans the tooth surface and tooth gap of the code disk and outputs a corresponding analog signal. The analog signal is calibrated and then the impeller speed is calculated based on the falling edge interval time of the calibrated signal. If the calculated impeller speed is lower than the preset value, the period method and frequency method are used to obtain the impeller speed, and the average speed value is output as the final impeller speed. Otherwise, the frequency method is used, that is, the impeller speed calculated by the falling edge interval time is directly output as the final impeller speed. Finally, the final impeller speed is compared with the impeller speed obtained by dividing the generator speed by the gearbox speed ratio. If the deviation exceeds the preset limit, a fault is reported, otherwise it is normal.

[0031] The spindle displacement measurement module measures the spindle displacement based on an eddy current sensor. The eddy current sensor detects the tooth surface of the code disk and outputs a corresponding analog signal based on the distance between itself and the tooth surface. Abnormal data is eliminated and averaged. The latest calculated average value is compared with the last calculated average value. If the deviation exceeds the preset limit, a spindle displacement fault is reported, otherwise it is normal.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] 1. Cost reduction and universal applicability: The solution of the present invention only requires one eddy current sensor and a code disk to measure the impeller speed and main shaft displacement of the unit, and this sensor has a better price advantage than the proximity switch sensor.

[0034] 2. High Accuracy and Reliability: The present invention adjusts the analog (AI) signal transmitted to the main control by the eddy current sensor through the tooth surface and tooth gap of the code disk. The time interval is calculated based on the falling edge signal, and the code disk sweep time is counted on a first-in-first-out basis to calculate the impeller speed. This can make the calculated impeller speed smoother, avoid the significant impact of individual defects on the calculated speed, and has higher reliability and accuracy. In addition, the spindle displacement is determined by comparing the average value of the sensor and code disk tooth surface with previous data, which can reduce the influence of other factors such as the environment on the results.

[0035] 3. Intelligence and safety: With the intelligent development of wind turbines and the impact of cost reduction trends, the safety of wind turbines is monitored from multiple aspects and directions, and the impeller speed and main shaft displacement of the wind turbine are monitored. At the same time, the impeller speed can be verified with the impeller speed converted by the main control (the main control synchronously collects the generator speed measured on the converter side, which can be further converted according to the gearbox speed ratio, specifically the generator speed divided by the gearbox speed ratio). This improves the safety of the wind turbine and is also a reflection of the intelligence of the wind turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Flowchart of the method of the present invention.

[0037] Figure 2 This is an architectural diagram of the system of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0039] Example 1

[0040] like Figure 1 As shown, this embodiment discloses a method for measuring the impeller speed and main shaft displacement of a fan based on an eddy current sensor. The method is to first install a code disk on the main shaft, and then use an eddy current sensor to simultaneously measure the impeller speed and main shaft displacement, as follows:

[0041] For the measurement of impeller speed, the eddy current sensor sweeps across the tooth surface and tooth gap of the encoder and outputs the corresponding analog signal. The analog signal is close to a square wave waveform and needs to be adjusted. The main control of the fan sets the thresholds α and β for the upper and lower limits of the waveform, adjusts it into square wave data, and outputs it in the form of Bool quantity. The eddy current sensor sweeps across the tooth surface to the tooth gap, and the waveform will have a falling edge. The main control captures the time corresponding to the falling edge moment, calculates the time interval between each two falling edges, and stores them in an array with a capacity of 20 in sequence. The encoder used by the fan is a 20-tooth square tooth encoder. The tooth surface and tooth gap are the same size. Starting from the first falling edge, after the 21st falling edge, the impeller has just rotated one circle. When the impeller speed is high, the time difference (i.e., time interval data) is recorded by the frequency method, so that the impeller speed can be calculated. Therefore, an array with a capacity of 20 is used to store the time interval data between each two falling edges. The first-in-first-out method is used. Each time a new set of time interval data is entered, the earliest set of data is removed, thereby completing the continuous transformation calculation of the speed. At this time, the sum of the array data is exactly the time consumed by the impeller to rotate one circle. The reciprocal of this time is the impeller speed calculated by the frequency method. The calculation formula is as follows:

[0042]

[0043] Where, T k T is the moment when the current master captures the falling edge of the eddy current sensor signal. k-1 It is the moment before the main controller captures the falling edge of the eddy current sensor signal, n is the number of teeth on the encoder, and r is the impeller speed.

[0044] During the process of wind turbine blade retraction and shutdown, when the impeller speed is low, the pulse refresh is slow, which will cause the above calculated value to take a long time to become 0. Therefore, a limit is set. When the impeller speed is lower than 1rpm, the impeller speed is calculated by the periodic method and the frequency method. The following is the periodic method for calculating the impeller speed: First, set the time period to 3s, which is divided into three sections. The first section uses the moment when the impeller speed is lower than 1rpm as the timing zero point, the second section uses the midpoint of the first section as the timing zero point, and the third section uses the midpoint of the second section as the timing zero point. Then, read the number of pulses in the corresponding time period respectively. The impeller speed can be further calculated based on the ratio of the number of pulses in the time period to the number of impeller teeth. That is, the ratios calculated in the three time periods are averaged as the impeller speed calculated by the periodic method; finally, the impeller speeds obtained by the frequency method and the periodic method are averaged as the final impeller speed. In practical applications, the impeller speed calculated by the frequency method is used as a benchmark. When the impeller speed is less than 1rpm, three cycle timers are added to calculate the number of pulses in the cycle. The cycle is 3s. The first timer uses the moment when the speed is less than 1rpm calculated by the frequency method as the zero point. The second timer uses the midpoint of the first timer as the zero point. The third timer uses the midpoint of the second timer as the zero point. Finally, the real-time speed when the impeller speed is less than 1rpm is calculated by using these three cycle timers and the frequency method to obtain the average value as the final impeller speed.

[0045] The wind turbine's main control unit simultaneously collects the generator speed measured on the converter side and further converts it into the impeller speed based on the gearbox speed ratio (i.e., generator speed divided by the gearbox speed ratio). This speed is then compared with the final impeller speed calculated above. If the deviation between the two exceeds the preset limit γ, a fault is reported; otherwise, the situation is normal. Furthermore, if a sudden deviation in the calculated final impeller speed is detected, the main control unit will assess this. If this phenomenon occurs twice within 30 minutes, the main control unit will prompt on-site maintenance colleagues to check the eddy current sensor and encoder, thereby improving the wind turbine's fault monitoring capabilities.

[0046] When measuring spindle displacement, if the fan experiences spindle displacement, the distance between the encoder tooth surface and the eddy current sensor will inevitably shift, causing the output value of the eddy current sensor to change. The fan's main control reads the output value of the eddy current sensor through sampling, reading it once every half an hour, reading 20 values ​​each time, calculating the 20 encoder tooth surface distance data output by the eddy current sensor, and finding the corresponding average value. A total of 10 such average values ​​are stored. The first-in-first-out principle is also used to continuously update the average value of these 10 samples, and the newly calculated average value is compared with the previous average value. If the deviation exceeds the preset limit a, a spindle displacement fault is reported.

[0047] Example 2

[0048] This embodiment discloses a system for measuring the fan impeller speed and main shaft displacement based on an eddy current sensor, which is used to implement the method for measuring the fan impeller speed and main shaft displacement based on an eddy current sensor described in Example 1. Figure 2 As shown, it includes the following functional modules:

[0049] The impeller speed measurement module measures the impeller speed based on an eddy current sensor. The eddy current sensor scans the tooth surface and tooth gap of the code disk and outputs a corresponding analog signal. The analog signal is calibrated and then the impeller speed is calculated based on the falling edge interval time of the calibrated signal. If the calculated impeller speed is lower than the preset value, the period method and frequency method are used to obtain the impeller speed, and the average speed value is output as the final impeller speed. Otherwise, the frequency method is used, that is, the impeller speed calculated by the falling edge interval time is directly output as the final impeller speed. Finally, the final impeller speed is compared with the impeller speed obtained by dividing the generator speed by the gearbox speed ratio. If the deviation exceeds the preset limit, a fault is reported, otherwise it is normal.

[0050] The spindle displacement measurement module measures the spindle displacement based on an eddy current sensor. The eddy current sensor detects the tooth surface of the code disk and outputs a corresponding analog signal based on the distance between itself and the tooth surface. Abnormal data is eliminated and averaged. The latest calculated average value is compared with the last calculated average value. If the deviation exceeds the preset limit, a spindle displacement fault is reported, otherwise it is normal.

[0051] Example 3

[0052] This embodiment discloses a storage medium storing a program. When the program is executed by a processor, the method described in Example 1 for measuring the fan impeller speed and main shaft displacement based on an eddy current sensor is implemented.

[0053] The storage medium in this embodiment can be a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), a USB flash drive, a mobile hard disk, or the like.

[0054] Example 4

[0055] This embodiment discloses a computing device, including a processor and a memory for storing a program executable by the processor. When the processor executes the program stored in the memory, the method of measuring the fan impeller speed and main shaft displacement based on the eddy current sensor described in Example 1 is implemented.

[0056] The computing device described in this embodiment may be a desktop computer, a laptop computer, a smart phone, a PDA handheld terminal, a tablet computer, a programmable logic controller (PLC), or other terminal devices with a processor function.

[0057] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for measuring the fan impeller speed and main shaft displacement based on an eddy current sensor, characterized in that: The method is to first install the code disc on the main shaft, and then use an eddy current sensor to simultaneously measure the impeller speed and main shaft displacement; For the measurement of impeller speed, the eddy current sensor sweeps the tooth surface and tooth gap of the code disk, outputs the corresponding analog signal, performs tuning processing on the analog signal, and then calculates the impeller speed according to the falling edge interval time of the tuned signal. If the calculated impeller speed is lower than the preset value, the period method and frequency method are used to obtain the impeller speed, and the average speed value is output as the final impeller speed. Otherwise, the frequency method is used as the basis, that is, the impeller speed calculated by the falling edge interval time is directly output as the final impeller speed. Finally, the final impeller speed is compared with the impeller speed obtained by dividing the generator speed by the gearbox speed ratio. If the deviation exceeds the preset limit, a fault is reported, otherwise it is normal. For the measurement of spindle displacement, the eddy current sensor detects the tooth surface of the code disk and outputs the corresponding analog signal according to the distance between itself and the tooth surface, eliminates abnormal data, and performs average processing. The latest calculated average value is compared with the last calculated average value. If the deviation exceeds the preset limit, a spindle displacement fault is reported, otherwise it is normal.

2. The method for measuring the fan impeller speed and main shaft displacement based on the eddy current sensor according to claim 1, characterized in that: For the measurement of impeller speed, the analog signal output by the eddy current sensor is close to a square wave waveform. The threshold value is set in the program to convert the analog signal and condition it into a square wave signal. The time point corresponding to the falling edge of the square wave signal is collected, and an array with the same capacity as the number of teeth on the code disk is created to store the time interval data between every two falling edges. According to the first-in-first-out principle of data, each time a new set of time interval data is entered, the earliest set of data is removed. At this time, the sum of the data in the array is exactly the time consumed by the impeller to rotate one circle. The inverse of this time is the impeller speed calculated by the frequency method.

3. The method for measuring the fan impeller speed and main shaft displacement based on the eddy current sensor according to claim 2, characterized in that: When the impeller speed is lower than the preset value, the impeller speed is calculated together by the period method and the frequency method. The following is the period method for calculating the impeller speed: First, the time period needs to be set, which is divided into three sections. The first section uses the moment when the speed is lower than the preset value as the timing zero point, the second section uses the time midpoint of the first section as the timing zero point, and the third section uses the time midpoint of the second section as the timing zero point. Then, the number of pulses is read in the corresponding time period segment respectively, and the impeller speed is further calculated based on the ratio of the number of pulses in the time period segment to the number of impeller teeth. That is, the ratios calculated in the three time period segments are averaged as the impeller speed calculated by the period method; finally, the impeller speeds obtained by the frequency method and the period method are averaged as the final impeller speed.

4. The method for measuring the fan impeller speed and main shaft displacement based on the eddy current sensor according to claim 3, characterized in that: The following steps are involved: 1) The fan's main control reads the eddy current sensor data and adjusts the data; 2) Using the first-in-first-out principle, the impeller rotation time is obtained in real time; 3) The time interval data in the array is summed in real time, and the reciprocal of the sum is the impeller speed calculated by the frequency method; 4) Taking the impeller speed calculated by the frequency method as the benchmark, when the impeller speed is less than the preset value, three cycle timers are added to calculate the number of pulses in the cycle. The first timer is zeroed when the speed calculated by the frequency method is less than the preset value. The second timer is zeroed at the midpoint of the first timer. The third timer is zeroed at the midpoint of the second timer. Finally, the real-time speed when the impeller speed is less than the preset value is calculated using the average value of the three cycle timers and the frequency method as the final impeller speed. 5) The main control compares the final impeller speed with the impeller speed calculated by dividing the generator speed by the gearbox speed ratio. If the deviation between the two exceeds the preset limit γ, a fault is reported.

5. The method for measuring the fan impeller speed and main shaft displacement based on the eddy current sensor according to claim 4, characterized in that: In step 1), the main control adjusts the read eddy current sensor data into square wave data according to the set upper and lower threshold values ​​α and β, and outputs it in the form of Bool value.

6. The method for measuring the fan impeller speed and main shaft displacement based on the eddy current sensor according to claim 5, characterized in that: In step 2), the eddy current sensor sweeps across the tooth surface to the tooth gap, and a falling edge will appear in the waveform. The main control captures the time corresponding to the falling edge, obtains the time interval data between each two falling edges, and stores them in an array with the same capacity as the number of teeth on the code disk. The sum of the time interval data is exactly the time it takes for the impeller to rotate one circle. The first-in-first-out principle is adopted, and each time a time interval data is entered, the earliest data is discarded, so the impeller rotation time is refreshed to the latest value in real time.

7. The method for measuring the fan impeller speed and main shaft displacement based on the eddy current sensor according to claim 6, characterized in that: In step 3), the time interval data in the array is summed in real time. The reciprocal of the sum is the impeller speed calculated by the frequency method. The calculation formula is as follows: Where, T k T is the moment when the current master captures the falling edge of the eddy current sensor signal. k-1 The moment before the main controller captures the falling edge of the eddy current sensor signal, n is the number of teeth on the encoder, and r is the impeller speed. When the impeller speed is greater than or equal to the preset value, the frequency method is used for calculation. When the impeller speed is lower than the preset value, the period method and the frequency method are used together to calculate the impeller speed.

8. The method for measuring the fan impeller speed and main shaft displacement based on the eddy current sensor according to claim 1, characterized in that: For the measurement of spindle displacement, if the fan has spindle displacement, it will inevitably cause the distance between the code disk tooth surface and the eddy current sensor to be offset, and the output value of the eddy current sensor will change at this time; the fan's main control reads the output value of the eddy current sensor through sampling, reading it once for each set time period, and reading n values ​​each time, where n is the number of code disk teeth, that is, the main control reads the n code disk tooth surface distance data output by the eddy current sensor each time, and calculates the corresponding average value, and then adopts the first-in-first-out principle to continuously update the sampled average value, and compare the latest calculated average value with the previous average value. If the deviation exceeds the preset limit a, a spindle displacement fault is reported.

9. The method for measuring the fan impeller speed and main shaft displacement based on an eddy current sensor according to any one of claims 1 to 8, characterized in that: The code disc is a square tooth code disc with the same tooth surface and tooth gap size. Starting from the first falling edge, the impeller rotates one circle after the n+1th falling edge, where n is the number of teeth on the code disc.

10. A system for measuring the fan impeller speed and main shaft displacement based on eddy current sensors, characterized in that: The method for calculating the fan impeller speed and main shaft displacement based on an eddy current sensor according to any one of claims 1 to 9 comprises: The impeller speed measurement module measures the impeller speed based on an eddy current sensor. The eddy current sensor scans the tooth surface and tooth gap of the code disk and outputs a corresponding analog signal. The analog signal is calibrated and then the impeller speed is calculated based on the falling edge interval time of the calibrated signal. If the calculated impeller speed is lower than the preset value, the period method and frequency method are used to obtain the impeller speed, and the average speed value is output as the final impeller speed. Otherwise, the frequency method is used, that is, the impeller speed calculated by the falling edge interval time is directly output as the final impeller speed. Finally, the final impeller speed is compared with the impeller speed obtained by dividing the generator speed by the gearbox speed ratio. If the deviation exceeds the preset limit, a fault is reported, otherwise it is normal. The spindle displacement measurement module measures the spindle displacement based on an eddy current sensor. The eddy current sensor detects the tooth surface of the code disk and outputs a corresponding analog signal based on the distance between itself and the tooth surface. Abnormal data is eliminated and averaged. The latest calculated average value is compared with the last calculated average value. If the deviation exceeds the preset limit, a spindle displacement fault is reported, otherwise it is normal.

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