A real-time stress monitoring method and system for wind power bolts

Abstract

The present invention relates to stress monitoring, and particularly to a real-time stress monitoring method and system for wind power bolts. The method includes: Step 1, collecting data on the motor spindle speed, the voltage at the motor output end, and the air pressure at multiple positions on the blade surface at a preset frequency; Step 2, obtaining the dynamic total load of the motor based on the collected motor spindle speed, the voltage at the motor output end, and the air pressure; Step 3, distributing the dynamic total load to bolts at different positions through a total load distribution model, that is, mapping the dynamic total load to the stresses of bolts at different positions; Step 4, monitoring the stresses of bolts at different positions to determine whether the bolts are faulty. If so, proceed to Step 5; otherwise, return to Step 1; Step 5, performing bolt replacement processing, analyzing and evaluating the impact of the processed bolts on the stresses of other bolts, and determining the stress safety of other bolts.

Description

Technical Field

[0001] The present invention relates to the technical field of stress monitoring, and particularly to a real-time stress monitoring method and system for wind power bolts. Background Art

[0002] During the operation of a wind turbine, it needs to withstand wind loads, blade centrifugal forces, etc. The randomness of wind loads causes the bolts in the wind turbine to bear periodic tensile and compressive forces (such as periodic vibrations during blade rotation, etc.), that is, the bolts need to bear dynamic loads. The torque of the gearbox and the swing of the blade will generate lateral forces on the bolts, and the friction of the bolt connection surface will cause the bolts to bear a certain shear force. If the bolt connection surface is uneven or there is an installation deviation, it will cause the bolts to be eccentrically loaded. In addition, the tower flange will undergo local bending under strong winds, forcing the bolts to bear bending moments. That is to say, the stress states of bolts at different positions on the wind turbine are the result of the coupling of multiple physical fields. Real-time monitoring of bolt stress is an important means to ensure the safe operation of wind turbine equipment. The existing technical means are mainly divided into direct measurement methods (such as the resistance strain method based on strain gauges and the ultrasonic propagation time method, etc.) and indirect inference methods (such as the method of back-calculating based on pre-tightening force and torque). These two types of methods have defects such as low environmental adaptability, high cost, and poor monitoring accuracy.

[0003] Therefore, through AI technology, combining stress data and the operating state of the wind turbine, monitoring bolt stress and predicting bolt failures through machine learning algorithms has become a development trend. Summary of the Invention

[0004] Based on the operating data of the motor such as the rotational speed of the motor spindle and the output voltage of the motor, and combining with the air pressure received by the blade, the present invention indirectly obtains the dynamic total load; and distributes the dynamic total load to different bolts to obtain the stress data of different bolts, realizing the function of monitoring the stress of bolts.

[0005] The technical solution proposed by the present invention is: a real-time stress monitoring method for wind power bolts, the method comprising:

[0006] Step 1: Collect the rotational speed of the motor spindle, the output voltage of the motor output end, and the air pressure data at multiple positions on the blade surface at a preset frequency;

[0007] Step 2: Obtain the dynamic total load of the motor based on the collected rotational speed of the motor spindle, the output voltage of the motor output end, and the air pressure;

[0008] Step 3: Distribute the dynamic total load to bolts at different positions through a total load distribution model, that is, map the dynamic total load to the stress of bolts at different positions;

[0009] Step 4: Monitor the stress of bolts at different positions, determine whether the bolts are faulty. If so, enter Step 5; otherwise, return to Step 1;

[0010] Step 5: Perform bolt replacement, analyze and evaluate the impact of the treated bolt on the stress of other bolts, and judge the stress safety of other bolts.

[0011] Preferably, obtaining the dynamic total load of the motor based on the collected motor spindle speed, motor output voltage, and air pressure includes the following steps:

[0012] Convert the motor spindle speed to angular velocity , obtain the current corresponding to the motor output voltage , calculate and obtain the electromagnetic torque , where represents the output voltage of the motor;

[0013] Obtain the aerodynamic torque of the motor blade based on the pressure data , where respectively represent the pressure at the blade surface position , the radius of rotation at position , and the wind energy utilization coefficient; represents the total number of positions;

[0014] Calculate the mechanical loss torque compensation , where represents the friction coefficient, represents the cogging torque;

[0015] Then the dynamic total load is ;

[0016] Distributing the dynamic total load to bolts at different positions through the total load distribution model, that is, mapping the dynamic total load to the stress of bolts at different positions, includes:

[0017] Establish a load transfer path to transfer the dynamic total load to each bolt; specifically including:

[0018] Apply a unit force or a unit moment [[ID=5s]] to the blade in sequence, and record the response force or moment of each bolt;

[0019] Calculate the unit axial force distribution coefficient of the bolt based on the response force of each bolt and the applied unit force or moment;

[0020] Use the unit distribution coefficient to construct a dynamic total load distribution matrix ; where represents the row vector of the axial force distribution coefficient; represents the row vector of the bending moment distribution coefficient;

[0021] Build the total load distribution model ; where respectively represent the axial tensile force, shear force and torque assigned to the th bolt; respectively represent the force and torque of the dynamic total load in the axis direction in the global coordinate system.

[0022] Preferably, monitoring the stress of bolts at different positions to determine whether the bolts are faulty includes:

[0023] Using the pre-trained regression model LSTM to monitor the bolt stress and determine whether the bolts are faulty;

[0024] The input of the LSTM is the axial tensile force, shear force and torque of different bolts after normalization processing, and the output is the combined stress of different bolts;

[0025] Set the bolt fault threshold to 70% of the maximum yield strength of the bolt;

[0026] If the combined stress is greater than the bolt fault threshold, it is determined that the bolt is faulty and needs to be replaced; otherwise, it does not need to be replaced.

[0027] Preferably, the dynamic total load is distributed to bolts at different positions through the total load distribution model, that is, the dynamic total load is mapped to the stresses of bolts at different positions, and further includes:

[0028] Considering the force transfer between bolts, introduce the coupling matrix Optimize the dynamic total load distribution matrix to obtain the optimized dynamic total load matrix ; where represents the dynamic total load distribution matrix of bolt , and the elements in represent the force transfer coefficient of bolt to bolt ;

[0029] , where represents the local stiffness of bolt , and represents the coupling stiffness of bolts and ;

[0030] Preferably, the dynamic total load is distributed to bolts at different positions through the total load distribution model, that is, the dynamic total load is mapped to the stresses of bolts at different positions, and further includes:

[0031] The dynamic total load is divided into aerodynamic load and mechanical load; the mechanical load includes one or more of gearbox torque, inertial load of rotating components, gravity load, and frictional loss;

[0032] Mechanical load ;

[0033] Set the aerodynamic load distribution matrix, which is calibrated through wind tunnel experiments, specifically including:

[0034] Apply stepped wind speeds in the wind tunnel and measure the strains of each bolt and the aerodynamic load vector in the global coordinate system ;

[0035] Aerodynamic load distribution matrix ;

[0036] Set the mechanical load distribution matrix, which is calibrated through bench tests, specifically including:

[0037] Disconnect the blade and apply stepped torque through the motor;

[0038] Measure the strains of each bolt and the mechanical load vector in the global coordinate system ;

[0039] Mechanical load distribution matrix ;

[0040] Using the aerodynamic load distribution matrix and the aerodynamic load vector in the global coordinate system, calculate the axial tensile force, shear force, and torque of the bolt, and then obtain the combined stress under the aerodynamic load; if the combined stress under the aerodynamic load exceeds the preset aerodynamic load combined stress threshold, it is determined that the bolt stress anomaly is caused by the aerodynamic load;

[0041] Using the mechanical load distribution matrix and the mechanical load vector in the global coordinate system, calculate the axial tensile force, shear force, and torque of the bolt, and then obtain the combined stress under the mechanical load; if the combined stress under the mechanical load exceeds the preset mechanical load combined stress threshold, it is determined that the bolt stress anomaly is caused by the mechanical load.

[0042] Preferably, for monitoring the stresses of bolts at different positions and determining whether the bolts are faulty, it further includes: constructing a state space model, capturing the interaction between the mechanical load and the aerodynamic load through the state space model, and identifying the stress distribution of the bolts, specifically including the following steps:

[0043] Constructing a state space model includes:

[0044] Obtain the deformation of the bolt connection part , that is, the rigidity of the bolt;

[0045] Obtain the vibration velocity of the bolt , and the strain of the bolt ;

[0046] Construct the state vector ;

[0047] State equation ; Among them, respectively represent the state transition matrix, input matrix and observation matrix;

[0048] Input vector , among which, respectively represent the wind speed, the pressure at the th position on the blade surface and the gearbox torque;

[0049] By using the system identification method N4SID, determine the parameters of the matrix ; Through the off-diagonal elements in reflect the dynamic coupling between state vectors; Through the elements in reflect the influence degree of the elements in the input vector on the elements in the state vector;

[0050] Identify the stress distribution of the bolt, including:

[0051] Through the observation matrix, correlate the state vector with the bolt stress; If only the bolt stress is concerned, then , represents the identity matrix;

[0052] Using the model after the system identification method, input the real-time load data to predict the bolt stress:

[0053] , where respectively represent the state vector at the starting moment and the input vector at the moment of;

[0054] Obtain the measured stress of the bolt, calculate the difference between the predicted bolt stress and the measured stress, that is, the stress residual ;

[0055] Calculate the correlation coefficients of the stress residuals of each bolt with the corresponding mechanical load distribution matrix and aerodynamic load distribution matrix, specifically:

[0056] Aerodynamic load correlation coefficient , Mechanical load correlation coefficient ;

[0057] If then it is judged that the bolt failure comes from the aerodynamic load;

[0058] If It is determined that the bolt failure is due to mechanical load;

[0059] Obtain the real-time wind speed data and the air pressure at multiple positions on the blade surface, and determine whether the air pressures match to judge whether the variables related to the aerodynamic load in the input vector are normal; measure the vibration data of the gearbox, extract the spectral data during gear meshing, and detect whether the frequency assignment suddenly increases during gear meshing to judge whether the variables related to the mechanical load in the input vector are normal;

[0060] If the variables related to both the mechanical load and the aerodynamic load are normal, but the residual is continuously abnormal, it is determined that the mechanical load distribution matrix and the aerodynamic load distribution matrix fail, and the mechanical load distribution matrix and the aerodynamic load distribution matrix need to be recalibrated.

[0061] Preferably, when performing the bolt replacement process, analyze and evaluate the influence of the treated bolt on the stress of other bolts, including:

[0062] Obtain the bolt data after the fault recovery, including the new pre-tightening force and the new stiffness of the bolt;

[0063] The new stiffness of the bolt ; where respectively represent the new pre-tightening force and the bolt elongation;

[0064] Update the bolt For the bolt coupling coefficient, and obtain the new coupling coefficient matrix ; where represents the bolt before replacement axial stiffness;

[0065] Obtain the historical pre-tightening force of the failed bolt from the database , update the dynamic total load distribution matrix, and obtain the updated dynamic total load distribution matrix ;

[0066] Using and calculate the new axial tensile force, shear force and torque, and then obtain the new stress matrix ;

[0067] Calculate and obtain the tensile stress [[ID=�3]], shear stress and bending stress ; where represents the distance from the neutral axis of the bolt cross-section to the outermost edge. If the cross-section of the bolt is circular, then , represents the diameter of the cross-section;

[0068] The combined stress is ;

[0069] Synthetic stress change rate , if , then it is determined to update the bolt affects the stress safety of other bolts.

[0070] Preferably, the bolt replacement treatment is carried out, and the influence of the treated bolt on the stress of other bolts is analyzed and evaluated, and further includes:

[0071] Consider the influence of the installation of the new bolt on the local contact pressure distribution, the influence of the pre-tightening force of the new bolt on the structural deformation of its contact part, and the change of the friction coefficient under dynamic load, specifically:

[0072] Measure the axial stiffness of the bolt through a hydraulic tensioner of ;

[0073] Measure the contact pressure distribution of the bolt connection surface through an ultrasonic detector and calculate the friction coefficient ;

[0074] Monitor the pre-tightening force attenuation ratio of adjacent bolts through distributed strain gauges ;

[0075] Correct the coupling coefficient to obtain a new corrected coupling coefficient , where represents the bolt belongs to the adjacent bolt set ; respectively represent the friction coefficients of the bolt before and after replacement ;

[0076] Apply a stepped load to the bolt and record the measured strain response;

[0077] Construct a nonlinear regression model , where represents the measured strain response, that is, the measured stress matrix , represents the stepped load vector; represents the coefficient matrix; , ;

[0078] Output the predicted through the nonlinear regression model, and combine to calculate and obtain the corresponding tensile stress, shear stress and bending stress, and then obtain the corresponding synthetic stress change rate to judge the influence of the installation of the new bolt on the stress safety of other bolts.

[0079] The present invention also provides a computer-readable storage medium storing a computer program which, when executed by a processor, implements the real-time stress monitoring method for wind power bolts as described above.

[0080] Advantages of the present invention:

[0081] 1. In the present invention, by collecting the rotational speed of the wind turbine, the air pressures at different positions on the blade surface, and the voltage data at the output end, associating these data with bolts at different positions, calculating the forces and torques transmitted to the bolts through a load distribution model, and predicting the stress of the bolts based on the forces and torques. By analyzing the stress residuals between the measured stress and the predicted stress, it is determined whether the bolt is faulty.

[0082] 2. In the present invention, based on the rotational speed of the wind turbine, the air pressures at different positions on the blade surface, and the voltage data at the output end, a dynamic total load is obtained, and the dynamic total load is divided into a mechanical load (which can be applied to the monitoring of bolts in the gearbox) and an aerodynamic load (which can be used for the stress monitoring of bolts at the blade root). And by calculating the correlation coefficients between the stress residuals of each bolt and the mechanical load and aerodynamic load distribution matrices, it is determined whether the source of the bolt fault is the aerodynamic load or the mechanical load. Description of the Drawings

[0083] Figure 1 is a flowchart of a real-time stress monitoring method for wind power bolts according to the present invention. Detailed Embodiments

[0084] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments in the following description are only examples, and those skilled in the art can think of other obvious deformations. The basic principles defined in the following description can be applied to other implementation schemes, deformation schemes, improvement schemes, equivalent schemes, and other technical schemes that do not depart from the spirit and scope of the present invention.

[0085] It can be understood that the term "one" should be understood as "at least one" or "one or more". That is, in one embodiment, the number of an element can be one, while in other embodiments, the number of the element can be multiple. The term "one" cannot be understood as a limitation on the number.

[0086] Embodiment 1:

[0087] Referring to Figure 1 , the technical solution provided by the present invention is: a real-time stress monitoring method for wind power bolts, including the following steps:

[0088] Step 1: Collect the rotational speed of the motor main shaft, the voltage at the motor output end, and the air pressure data at multiple positions on the blade surface at a preset frequency;

[0089] Step 2. Obtain the dynamic total load of the motor based on the collected motor spindle speed, motor output voltage, and air pressure, including:

[0090] Step 2.1. Convert the motor spindle speed to angular velocity , obtain the current corresponding to the motor output voltage , calculate and obtain the electromagnetic torque , where represents the output voltage of the motor;

[0091] Step 2.2. Obtain the aerodynamic torque of the motor blades based on the pressure data , where respectively represent the pressure at the blade surface position , the turning radius at position , and the wind energy utilization coefficient; represents the total number of positions;

[0092] Step 2.3. Calculate the mechanical loss torque compensation , where represents the friction coefficient, represents the cogging torque;

[0093] Then the dynamic total load is ;

[0094] Step 3. Allocate the dynamic total load to the bolts at different positions through the total load distribution model, that is, map the dynamic total load to the stresses of the bolts at different positions, including the following steps:

[0095] Establish a load transfer path to transfer the dynamic total load to each bolt, specifically including:

[0096] Apply a unit force or a unit moment to the blade in sequence, and record the response force or moment of each bolt;

[0097] Based on the response force of each bolt and the applied unit force or moment, calculate the unit axial force distribution coefficient of the bolt;

[0098] Construct a dynamic total load distribution matrix using the unit distribution coefficient ; where represents the row vector of the axial force distribution coefficient; represents the row vector of the bending moment distribution coefficient;

[0099] Construct the total load distribution model ; where respectively represent the distribution to the The axial tensile force, shear force and torque of a bolt; respectively represent the dynamic total load in the global coordinate system acting as the force and torque in the

[0100] Step 4: Monitor the stress of bolts at different positions, and determine whether the bolts are faulty. If so, go to Step 5; otherwise, return to Step 1. Specifically:

[0101] Use the pre-trained regression model LSTM to monitor the bolt stress and determine whether the bolts are faulty;

[0102] The input of the LSTM is the axial tensile force, shear force and torque of different bolts after normalization processing, and the output is the combined stress of different bolts;

[0103] Set the bolt fault threshold to 70% of the maximum yield strength of the bolt;

[0104] If the combined stress is greater than the bolt fault threshold, it is determined that the bolt is faulty and needs to be replaced; otherwise, it does not need to be replaced.

[0105] For example, by measurement, we obtain KN, the torque in the KNm;

[0106] Obtain the dynamic total load distribution matrix through experimental calibration:

[0107] ;

[0108] ;

[0109] Then, the tensile stress MPa (taking M36 bolt as an example, the effective cross-sectional area , the moment of inertia of the bolt cross-section , the yield strength MPa).

[0110] The shear stress MPa;

[0111] The bending stress MPa;

[0112] The combined stress MPa;

[0113] Set the safety threshold to 900×0.7 = 630 MPa. Since 28 MPa is less than 630 MPa, it is determined that the bolt stress is normal, the bolt is safe, and it does not need to be replaced.

[0114] Step 5: Perform bolt replacement and analyze and evaluate the impact of the treated bolt on the stress of other bolts to determine the stress safety of other bolts, including the following steps:

[0115] Obtain the bolt data after fault recovery, including the new pre-tightening force and new stiffness of the bolt;

[0116] The new stiffness of the bolt ; where respectively represent the new pre-tightening force and bolt elongation;

[0117] Update the bolt For the bolt coupling coefficient to obtain a new coupling coefficient matrix ; where represents the bolt before replacement axial stiffness;

[0118] Obtain the historical pre-tightening force of the failed bolt from the database , update the dynamic total load distribution matrix to obtain the updated dynamic total load distribution matrix ;

[0119] Use and to calculate the new axial tensile force, shear force and torque, and then obtain a new stress matrix ;

[0120] Use the stress matrix to calculate and obtain the tensile stress , shear stress and bending stress ; where represents the distance from the neutral axis of the bolt cross-section to the outermost edge. If the cross-section of the bolt is circular, then , represents the diameter of the cross-section;

[0121] The combined stress is ;

[0122] The combined stress change rate , if , then it is determined that the updated bolt affects the stress safety of other bolts.

[0123] Example 2:

[0124] When distributing the total load to bolts at different positions, the mutual influence between bolts needs to be considered. And when replacing new bolts, the impact of the new bolt replacement on other bolts also needs to be considered. For this reason, the following scheme is further proposed on the basis of Example 1:

[0125] Considering the force transfer between bolts, a coupling matrix is introduced Optimize the dynamic total load distribution matrix to obtain the optimized dynamic total load matrix ; where represents the dynamic total load distribution matrix of bolt , and the elements in represent the force transfer coefficient of bolt to bolt ;

[0126] , where represents the local stiffness of bolt , and represents the coupling stiffness of bolts and ;

[0127] Considering the influence of the installation of new bolts on the local contact pressure distribution, the influence of the pre-tightening force of new bolts on the structural deformation of their contact parts, and the change of the friction coefficient under dynamic loads, specifically:

[0128] Measure the axial stiffness of bolt through a hydraulic tensioner;

[0129] Measure the contact pressure distribution of the bolt connection surface through an ultrasonic detector and calculate the friction coefficient ;

[0130] Monitor the pre-tightening force attenuation ratio of adjacent bolts through distributed strain gauges ;

[0131] Correct the coupling coefficient to obtain the corrected new coupling coefficient , where represents that bolt belongs to the adjacent bolt set ; respectively represent the friction coefficients of bolts before and after replacement;

[0132] Apply a stepped load to bolt and record the measured strain response;

[0133] Construct a nonlinear regression model , where represents the measured strain response, that is, the measured stress matrix , represents the stepped load vector; represents the coefficient matrix; , ;

[0134] Output the prediction through the non - linear regression model and combine with to calculate and obtain the corresponding tensile stress, shear stress and bending stress, and further obtain the corresponding synthetic stress change rate to judge the impact of the installation of the new bolt on the stress safety of other bolts.

[0135] Example 3:

[0136] When distributing the dynamic total load to bolts at different positions through the total load distribution model, the technical solution given in Example 1 is to distribute the load as a whole without considering the separate distribution of mechanical load and pneumatic load in the total load. Therefore, on the basis of Example 1, we further improve the total load distribution method and propose the following technical solution:

[0137] Divide the dynamic total load into pneumatic load and mechanical load; the mechanical load includes one or more of gearbox torque, inertial load of rotating components, gravity load and friction loss;

[0138] Mechanical load ;

[0139] Set up a pneumatic load distribution matrix, which is calibrated through wind tunnel experiments, specifically including:

[0140] Apply stepped wind speeds in the wind tunnel and measure the strains of each bolt and the pneumatic load vector in the global coordinate system ;

[0141] Pneumatic load distribution matrix ;

[0142] Set up a mechanical load distribution matrix, which is calibrated through bench tests, specifically including:

[0143] Disconnect the blade and apply stepped torque through the motor;

[0144] Measure the strains of each bolt and the mechanical load vector in the global coordinate system ;

[0145] Mechanical load distribution matrix ;

[0146] Use the pneumatic load distribution matrix and the pneumatic load vector in the global coordinate system to calculate the axial tensile force, shear force and torque of the bolt, and further obtain the synthetic stress under the pneumatic load; if the synthetic stress under the pneumatic load exceeds the preset pneumatic load synthetic stress threshold, it is judged that the abnormal bolt stress is caused by the pneumatic load;

[0147] Using the mechanical load distribution matrix and the mechanical load vector in the global coordinate system, calculate the axial tensile force, shear force and torque of the bolt, and then obtain the combined stress under the mechanical load; if the combined stress under the mechanical load exceeds the preset mechanical load combined stress threshold, it is determined that the abnormal bolt stress is caused by the mechanical load.

[0148] For example, in this embodiment, through measurement, it is obtained that: the wind speed is 12 m / s, the motor spindle speed is 15 rpm, the output terminal voltage is 690 V, and the current is 200 A. ; the blade length is 40 m.

[0149] Then the aerodynamic load is:

[0150] KNm;

[0151] Wherein, respectively represent air density, wind speed, wind energy utilization coefficient, blade swept area and angular velocity;

[0152] Electromagnetic torque KNm;

[0153] Mechanical loss KNm;

[0154] Mechanical load KNm;

[0155] The bolt load distribution is the mechanical load distribution and the aerodynamic load distribution: and ;

[0156] By calculating the strain of the corresponding bolt under the aerodynamic load, if the corresponding strain exceeds the preset aerodynamic strain threshold, it is determined that the bolt failure is caused by the aerodynamic load;

[0157] By calculating the strain of the corresponding bolt under the mechanical load, if the corresponding strain exceeds the preset mechanical strain threshold, it is determined that the bolt failure is caused by the mechanical load;

[0158] Since the aerodynamic load is a periodic alternating force generated by the wind acting on the blade, it is easy to cause bolt fatigue failure; the mechanical load includes gearbox torque, inertial force and friction loss, etc., which are easy to cause bolt overload or looseness;

[0159] Therefore, by separating the load distribution and monitoring the corresponding stress, it is helpful to judge the type of bolt failure that will occur.

[0160] Example 4:

[0161] In Embodiment 3, we propose a technical solution for separately allocating the total load. Based on this technical solution, when judging bolt failures and identifying bolt stress distributions, it is necessary to consider the interaction between mechanical loads and pneumatic loads. Therefore, we propose the following solution:

[0162] Construct a state space model to capture the interaction between mechanical loads and pneumatic loads through the state space model and identify the stress distribution of bolts. The specific steps are as follows:

[0163] Construct a state space model, including:

[0164] Obtain the deformation of the bolt connection part , that is, the rigidity of the bolt;

[0165] Obtain the bolt vibration velocity , and the strain of the bolt ;

[0166] Construct a state vector ;

[0167] State equation ; where respectively represent the state transition matrix, input matrix, and observation matrix;

[0168] Input vector , where respectively represent the wind speed, the pressure at the th position on the blade surface, and the gearbox torque;

[0169] By using the system identification method N4SID, determine the parameters of the matrix ; through the off-diagonal elements in reflect the dynamic coupling between state vectors; through the elements in reflect the degree of influence of the elements in the input vector on the elements in the state vector.

[0170] For example, in the real-time stress monitoring of the bolt group of an onshore wind turbine gearbox, the state vector includes the vibration displacement, velocity of the gearbox, and the stress of the bolts ;

[0171] The input vector includes the wind speed and the gearbox torque, and outputs the stress data of each bolt in the bolt group;

[0172] Collect 10 groups of working condition data and identify using the N4SID method to obtain:

[0173] ,[[ID=NSID=64]] ;

[0174] Through the matrix It shows that the wind speed (pneumatic) has a greater impact on State 1 (vibration displacement), and the gearbox torque (mechanical) has a greater impact on State 2 (speed). The coupling term indicates that the speed change affects the displacement, and then through it affects the stress of the bolt. Thus, it reflects the influence of the pneumatic load on the mechanical load state and the influence on the stress after coupling.

[0175] Identify the stress distribution of the bolt, including:

[0176] Associate the state vector with the bolt stress through the observation matrix; if only the bolt stress is concerned, then ;

[0177] Use the model after the system identification method, input the real-time load data to predict the bolt stress:

[0178] , where respectively represent the state vector at the starting moment and the input vector at the moment of

[0179] Obtain the measured stress of the bolt, calculate the difference between the predicted bolt stress and the measured stress, that is, the stress residual ;

[0180] Calculate the correlation coefficients between the stress residuals of each bolt and the corresponding mechanical load distribution matrix and pneumatic load distribution matrix, specifically:

[0181] Pneumatic load correlation coefficient Mechanical load correlation coefficient ;

[0182] If then it is judged that the bolt failure comes from the pneumatic load;

[0183] If then it is judged that the bolt failure comes from the mechanical load;

[0184] Obtain the real-time wind speed data and the air pressure at multiple positions on the blade surface, judge whether the air pressure matches, so as to judge whether the variables related to the pneumatic load in the input vector are normal; measure the gearbox vibration data, extract the spectrum data when the gears are meshing, and detect whether the frequency assignment increases suddenly when the gears are meshing, so as to judge whether the variables related to the mechanical load in the input vector are normal;

[0185] If the variables related to both the mechanical load and the pneumatic load are normal, but the residuals are continuously abnormal, then it is judged that the mechanical load distribution matrix and the pneumatic load distribution matrix fail, and the mechanical load distribution matrix and the pneumatic load distribution matrix need to be recalibrated.

[0186] The present invention also provides a real-time stress monitoring system for a wind power bolt, comprising: a measurement module, a monitoring module and a communication module. Among them, the measurement module is used to collect the rotational speed of the motor main shaft, the air pressure at multiple positions on the blade surface, as well as the motor output voltage and current. The monitoring module is used to analyze and process the data input by the measurement module, monitor the stress of different screws, judge whether different bolts are faulty, and output the judgment result. The communication module is used to connect to the upper computer and transmit the judgment result to the upper computer; the system is used to execute the above-mentioned real-time stress monitoring method for a wind power bolt. Specifically, the measurement module includes a rotational speed sensor, a plurality of pressure sensors and a voltage transformer, and the monitoring module includes a processor and a memory connected to the processor.

[0187] The present invention also provides a computer-readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the above-mentioned real-time stress monitoring method for a wind power bolt.

[0188] Embodiments disclosed by the present invention. The processes described above with reference to the flowcharts can be implemented as computer software programs. Embodiments disclosed by the present invention include a computer program product, which includes a computer program carried on a computer-readable medium. The computer program contains program codes for performing the methods shown in the flowcharts. In such an embodiment, the computer program can be downloaded and installed from a network through a communication part, and / or installed from a removable medium. When the computer program is executed by a central processing unit (CPU), the above-mentioned functions defined in the methods of the present invention are performed. It should be noted that the computer-readable medium in the present invention can be a computer-readable signal medium, a computer-readable storage medium, or any combination of the two. A computer-readable storage medium can, for example, but not be limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples of a computer-readable storage medium can include, but not be limited to: an electrical connection with one or more wire segments, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present invention, a computer-readable storage medium can be any tangible medium that contains or stores a program, and this program can be used by or combined with an instruction execution system, apparatus, or device. In the present invention, a computer-readable signal medium can include a data signal propagated in a baseband or as part of a carrier wave, in which computer-readable program codes are carried. Such a propagated data signal can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. A computer-readable signal medium can also be any computer-readable medium other than a computer-readable storage medium, and this computer-readable medium can send, propagate, or transmit a program for use by or combined with an instruction execution system, apparatus, or device. The program codes contained on the computer-readable medium can be transmitted by any appropriate medium, including but not limited to: wireless segments, wire segments, optical cables, RF, etc., or any suitable combination of the above.

[0189] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagram may represent a module, a segment of a program, or a part of code, which contains one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than that marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, as well as combinations of blocks in the block diagram and / or flowchart, may be implemented by a dedicated hardware-based system that performs the specified functions or operations, or may be implemented by a combination of dedicated hardware and computer instructions.

[0190] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functions and structural principles of the present invention have been demonstrated and illustrated in the embodiments. Without departing from the said principles, any changes or modifications may be made to the embodiments of the present invention.

Claims

1. A real-time stress monitoring method for wind power bolts, characterized in that, The method includes: Step 1: Collect data on the motor spindle speed, the voltage at the motor output end, and the air pressure at multiple positions on the blade surface at a preset frequency; Step 2: Obtain the dynamic total load of the motor based on the collected motor spindle speed, the voltage at the motor output end, and the air pressure; Step 3: Allocate the dynamic total load to bolts at different positions through a total load distribution model, that is, map the dynamic total load to the stresses of bolts at different positions; including: Establish a load transfer path to transfer the dynamic total load to each bolt; specifically including: Apply unit forces to the blade successively or unit torques and record the response forces or torques ; Calculate the unit axial force distribution coefficient of the bolt based on the response force of each bolt and the applied unit force or moment; Construct a dynamic total load distribution matrix using the unit distribution coefficient ; among which, represents the row vector of axial force distribution coefficient; represents the row vector of bending moment distribution coefficient; Build the total load distribution model ; where respectively represent the axial tensile force, shear force and torque assigned to the th bolt; respectively represent the force and torque of the dynamic total load in the axis direction in the global coordinate system; Considering the force transfer between bolts, a coupling matrix is introduced Optimize the dynamic total load distribution matrix to obtain the optimized dynamic total load matrix ; where represents the dynamic total load distribution matrix of bolt , and the elements in represent the force transfer coefficients of bolt to bolt ; , where represents the local stiffness of the bolt , represents the coupling stiffness of the bolt and . Step 4: Monitor the stresses of bolts at different positions to determine whether the bolts are faulty. If so, enter Step 5; otherwise, return to Step 1; Step 5: Perform bolt replacement processing, analyze and evaluate the impact of the processed bolts on the stresses of other bolts, and determine the stress safety of other bolts.

2. The real-time stress monitoring method for a wind power bolt according to claim 1, wherein The obtaining of the dynamic total load of the motor based on the collected motor spindle speed, the voltage at the motor output end, and the air pressure includes the following steps: Convert the rotational speed of the motor spindle to angular velocity , obtain the current corresponding to the voltage at the output end of the motor , calculate and obtain the electromagnetic torque , where represents the output voltage of the motor; Obtaining the Aerodynamic Torque of Motor Blades Based on Pressure Data , where respectively represent the pressure at the blade surface position , the rotational radius at position , and the wind energy utilization coefficient; represents the total number of positions; Calculating mechanical loss torque compensation , where represents the friction coefficient, represents the cogging torque; Then the dynamic total load is .

3. A real-time stress monitoring method for a wind power bolt according to claim 2, characterized in that, The monitoring of the stresses of bolts at different positions to determine whether the bolts are faulty includes: Use a pre-trained regression model LSTM to monitor the bolt stresses and determine whether the bolts are faulty; The input of the LSTM is the axial tensile force, shear force, and torque of different bolts after normalization processing, and the output is the combined stress of different bolts; Set the bolt failure threshold to 70% of the maximum yield strength of the bolt; If the combined stress is greater than the bolt failure threshold, it is determined that the bolt is faulty and needs to be replaced; otherwise, replacement is not required.

4. A real-time stress monitoring method for a wind power bolt according to claim 3, characterized in that, The allocation of the dynamic total load to bolts at different positions through a total load distribution model, that is, mapping the dynamic total load to the stresses of bolts at different positions, further includes: Divide the dynamic total load into aerodynamic load and mechanical load; the mechanical load includes one or more of gearbox torque, inertial load of rotating components, gravity load, and friction loss; Mechanical load ; Set an aerodynamic load distribution matrix, which is calibrated through a wind tunnel experiment, specifically including: Apply a stepped wind speed in the wind tunnel and measure the strain of each bolt and the aerodynamic load vector in the global coordinate system ; Aerodynamic load distribution matrix ; Set a mechanical load distribution matrix, which is calibrated through a bench test, specifically including: Disconnect the blade and apply a stepped torque through the motor; Measure the strain of each bolt and the mechanical load vector in the global coordinate system ; Mechanical load distribution matrix ; Use the aerodynamic load distribution matrix and the aerodynamic load vector in the global coordinate system to calculate the axial tensile force, shear force, and torque of the bolt, and then obtain the combined stress under the aerodynamic load; if the combined stress under the aerodynamic load exceeds the preset aerodynamic load combined stress threshold, it is determined that the bolt stress anomaly is caused by the aerodynamic load; Use the mechanical load distribution matrix and the mechanical load vector in the global coordinate system to calculate the axial tensile force, shear force, and torque of the bolt, and then obtain the combined stress under the mechanical load; if the combined stress under the mechanical load exceeds the preset mechanical load combined stress threshold, it is determined that the bolt stress anomaly is caused by the mechanical load.

5. A real-time stress monitoring method for a wind power bolt according to claim 4, characterized in that The monitoring of the stresses of bolts at different positions to determine whether the bolts are faulty further includes: Construct a state space model to capture the interaction between the mechanical load and the aerodynamic load through the state space model and identify the stress distribution of the bolt, specifically including the following steps: Construct a state space model, including: Obtain the deformation amount of the bolt connection part , that is, the rigidity of the bolt; Obtain the vibration velocity of the bolt , and the strain of the bolt ; Construct a state vector ; State equation ; wherein represent the state transition matrix, the input matrix, and the observation matrix, respectively; Input vector , where respectively represent wind speed, pressure at the th position on the blade surface, and gearbox torque; Determine the parameters of matrix by using the system identification method N4SID; the off-diagonal elements in reflect the dynamic coupling between state vectors; the elements in reflect the influence degree of the elements in the input vector on the elements in the state vector; Identify the stress distribution of bolts, including: Associate the state vector with the bolt stress through the observation matrix; if only the bolt stress is of concern, then , represents the identity matrix; Using the model after system identification method, input real-time load data to predict bolt stress: , where respectively represent the state vector at the starting moment and the input vector at the moment; Obtain the measured stress of the bolt and calculate the difference between the predicted bolt stress and the measured stress, that is, the stress residual ; Calculate the correlation coefficients between the stress residuals of each bolt and the corresponding mechanical load distribution matrix and aerodynamic load distribution matrix, specifically: Aerodynamic load correlation coefficient , Mechanical load correlation coefficient ; If it is determined that the bolt failure is due to pneumatic load; If it is determined that the failure of the bolt is due to mechanical load; Obtain real-time wind speed data and air pressures at multiple positions on the blade surface, and determine whether the air pressures match to judge whether the variables related to aerodynamic loads in the input vector are normal; measure the vibration data of the gearbox, extract the spectral data during gear meshing, and detect whether the frequency assignment suddenly increases during gear meshing to judge whether the variables related to mechanical loads in the input vector are normal; If the variables related to both mechanical loads and aerodynamic loads are normal, but the residuals remain abnormal, then judge that the mechanical load distribution matrix and the aerodynamic load distribution matrix fail, and it is necessary to recalibrate the mechanical load distribution matrix and the aerodynamic load distribution matrix.

6. A real-time stress monitoring method for a wind power bolt according to claim 5, characterized in that, Perform bolt replacement processing, and analyze and evaluate the influence of the processed bolts on the stresses of other bolts, including: Obtain the bolt data after fault recovery, including the new pre-tightening force and new stiffness of the bolts; New stiffness of the bolt ; wherein respectively represent the new pre-tightening force and the bolt elongation; Updated bolt For the bolt The coupling coefficient is obtained to get a new coupling coefficient matrix ; among which represents the bolt before replacement Axial stiffness Obtain the historical pre-tightening force of the faulty bolt from the database , update the dynamic total load distribution matrix to obtain the updated dynamic total load distribution matrix ; Utilize and to calculate the new axial tensile force, shear force and torque, and further obtain the new stress matrix ; Calculating and obtaining tensile stress using the stress matrix , shear stress and bending stress ; among them, represents the distance from the neutral axis of the bolt cross-section to the outermost edge. If the cross-section of the bolt is circular, then , represents the diameter of the cross-section; The combined stress is ; Synthetic stress change rate If , then it is determined to update the bolt affects the stress safety of other bolts.

7. A real-time stress monitoring method for a wind power bolt according to claim 6, characterized in that Perform bolt replacement processing, and analyze and evaluate the influence of the processed bolts on the stresses of other bolts, further including: Consider the influence of the installation of the new bolt on the local contact pressure distribution, the influence of the pre-tightening force of the new bolt on the structural deformation of its contact part, and the change of the friction coefficient under dynamic loads, specifically: Measuring the axial stiffness of bolts by hydraulic tensioners ; ; Measure the contact pressure distribution of the bolt connection surface with an ultrasonic detector and calculate the friction coefficient ; Monitoring the pre-tightening force attenuation ratio of adjacent bolts through distributed strain gauges ; Modify the coupling coefficient to obtain a new modified coupling coefficient , where represents a bolt belongs to the set of adjacent bolts ; respectively represent the friction coefficients of the bolts before and after replacement ; For the bolt Apply a stepped load and record the measured strain response; Construct a non - linear regression model , where represents the measured strain response, that is, the measured stress matrix , represents the step load vector; represents the coefficient matrix; , ; Output the prediction through the non-linear regression model , combined with calculate and obtain the corresponding tensile stress, shear stress and bending stress, and then obtain the corresponding composite stress change rate to judge the impact of the installation of the new bolt on the stress safety of other bolts.

8. A real-time stress monitoring system for wind power bolts, including: A measurement module for collecting the rotational speed of the motor main shaft, the air pressures at multiple positions on the blade surface, and the motor output voltage and current; A monitoring module for analyzing and processing the data input by the measurement module, monitoring the stresses of different screws, judging whether different bolts are faulty, and outputting a judgment result; A communication module for connecting to a host computer and transmitting the judgment result to the host computer; It is characterized in that the system is used to execute a real-time stress monitoring method for wind power bolts described in any one of claims 1-7 above.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, and the computer program is executed by a processor to implement a real-time stress monitoring method for wind power bolts described in any one of claims 1-7 above.

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