Detailed Description
So that those skilled in the art can better understand and practice the present patent, a detailed description of embodiments of the application will be presented with reference to the drawings.
Please refer to fig. 1, a hydropower station oil gas pressure system fault prediction method integrating sensing data and a knowledge graph is characterized by comprising the following steps:
step 1, multi-mode data acquisition and preprocessing;
step 2, feature extraction and cross-modal correlation analysis;
Step 3, knowledge graph construction and dynamic updating;
Step 4, fusing a physical mechanism model and a data driving model;
step 5, constructing a fault mode library and reasoning knowledge;
step 6, training and optimizing the multi-mode prediction model;
and 7, generating fault early warning and maintenance strategies.
The invention improves the dynamic property of generalization of the failure prediction of the hydro-pneumatic pressure system of the hydropower station.
The embodiment of the invention is described in detail as follows:
step 1: the multi-mode data acquisition and preprocessing, namely sensing state data of the multi-mode data in real time through vibration, liquid level and pressure sensors arranged on an oil gas pressure oil tank, eliminating fluctuation and noise of the sensed data, and smoothing the sensed data by adopting a filtering algorithm, wherein the specific substeps are as follows:
Step 1-1, installing vibration sensors at the joints of a bearing seat of a pressure oil tank, a gear box shell and a sealing element, monitoring the vibration frequency of equipment in real time, adopting a magnetic oil particle sensor to detect the concentration of metal particles, adopting a spectrum analyzer to detect the index and the liquid level of oil oxidation products, acquiring the pressure at the oil pump outlet, the top of the oil tank and the joint of the sealing element, adopting an infrared thermal imager to monitor the temperature distribution of the surface of the oil tank, synchronizing the data of the multiple sensors to a centralized monitoring center through an industrial Ethernet (such as Profinet) or an OPC UA protocol, and sampling each sensor by 1KHz, wherein the numerical record is as the following formula:
,
Wherein the method comprises the steps of Is a time domain sensing signal (which can be a vibration signal, a pressure signal and an oil index),For the amplitude of the i-th sensor,For the sampling frequency of the i-th sensor,For the phase value used for calibration for the ith sensor.
Step 1-2, carrying out N layers of discrete wavelet decomposition on the sensing signal to obtain corresponding detail coefficients and approximation coefficients, wherein the detail coefficients and approximation coefficients are shown in the formula:
,
Wherein the method comprises the steps of Coefficients for the N-th layer wavelet decomposition, i.e., associated low frequency components; and the detail coefficient of the k layer corresponds to high-frequency components with different scales.
The decomposition coefficients are processed according to soft threshold values:
,
,
c is the original coefficient (e.g And),As a result of the threshold value being set,The standard deviation of noise, M is the signal length;
reconstructing a sensing signal, wherein the signal strength after noise elimination is as follows:
,
Step 1-3, performing Z-score standardization (the mean value is 0 and the standard deviation is 1) on sensing data of an oil gas pressure system so as to ensure that the data of different sensors are in the same dimension, wherein the method is shown as follows, and adopting a3 sigma principle to reject abnormal values (such as points exceeding the mean value plus or minus 3 times of the standard deviation) in the data of the pressure sensors:
Wherein the method comprises the steps of AndThe mean and variance, respectively.
The step 2 of feature extraction and cross-modal correlation analysis is to extract time domain features, frequency domain features and operation related features of mechanical abrasion and vibration of an oil gas pressure system reflected by a sensing signal so as to realize cross-modal alignment of a multi-source sensor and better serve early fault detection, and specifically comprises the following sub-steps:
Extracting and calculating time domain characteristics of each sensing signal of the oil gas pressure system, wherein the time domain characteristics comprise root mean square value (RMS), peak-to-peak value (PPV) and Kurtosis (Kurtosis) characteristics, and the time domain characteristics are used for detecting bearing wear or gear cracks;
the root mean square value is calculated as follows to measure the energy intensity and vibration intensity of the signal:
,
The method comprises the steps that (1) the ith sampling point of a signal x is obtained, and N is the total number of sampling points used for calculating the signal;
the peak-to-peak calculation formula is as follows to measure the dynamic range and impact characteristics of the signal, especially abnormal characteristics:
,
The kurtosis characteristic calculation formula is as follows to reflect the signal spike characteristics:
,
as has been shown in the foregoing, AndThe mean and variance of the signal, respectively.
And 2-2, extracting main frequency components by adopting Fast Fourier Transform (FFT), and detecting early faults such as crack resonance and the like by combining envelope analysis, wherein the early faults are shown in the formula:
,
Wherein the method comprises the steps of For the frequency signal, f is the frequency variable, N is the nth frequency cost, and N is the total frequency component.
And 2-3, extracting oil related characteristics including temperature difference between the surface of an oil tank and the ambient temperature, acid value and moisture content characteristics of oil spectrum analysis and metal particle concentration characteristics.
And 2-4, analyzing the relation between the vibration signal and the concentration of oil particles by adopting a Pearson correlation coefficient, and constructing a coupling relation between the concentration of metal particles existing in oil pump abrasion and vibration spectrum deviation for the follow-up knowledge graph, wherein the coupling relation is specifically shown as a formula:
,
r is a correlation coefficient, xi and yi are values of two sensors or modalities respectively, AndRespectively the average of n samples.
Step 3, knowledge graph construction and dynamic updating, wherein the step is to construct a fault-related knowledge graph according to the working mechanism of the oil gas pressure system, provide a more definite entity relationship and an association mapping relationship between performance and faults, and dynamically update in time, and specifically comprises the following sub-steps:
Step 3-1, extracting equipment entities (such as an oil gas pressure tank, an oil pump, a sealing element and a bearing) and fault types (such as seal failure, bearing abrasion and oil pump cavitation) by adopting a named entity method:
,
Wherein the method comprises the steps of As an entity type (e.g. "device"),As an attribute (such as "pressure"),Is an attribute value (e.g., "1.5 MPa").
And 3-2, extracting monitoring relations and causal relations between equipment entity faults and perceived data features according to the working mechanism specification, wherein the monitoring relations (such as { "oil liquid sensor", "monitoring", "oil liquid particle concentration" }) and causal relations (such as { "seal wear", "causal", "oil liquid leakage" } and { "oil liquid leakage", "causal", "pressure fluctuation" }).
Step 3-3, extracting equipment faults, associated indexes and causal relations from a working mechanism specification and technical analysis maintenance manual by adopting a large language model or a natural language processing tool, constructing a related knowledge graph, and carrying out characterization modeling on entity relations by adopting a graph neural network:
,
Wherein the method comprises the steps of A vector is embedded for a layer i node,In order to be a contiguous matrix,In order for the weight matrix to be learnable,To activate the function.
And 3-4, updating a knowledge graph (such as abrasion of a sealing element when the concentration of oil particles is more than 13) according to the monitoring attribute indexes and fault phenomena in the real-time operation process, wherein the method specifically comprises the following steps:
,
Wherein the method comprises the steps of For newly added entities or attributes (such as "oil pump", "particle concentration"),Is a new relationship (such as connection, cause and effect).
And 4, fusing a physical model with a data model, further constructing a physical mechanism model by utilizing the knowledge graph generated in the step 3, fusing a data-driven prediction model, simulating oil flow and a pressure model of an oil-gas pressure system to eliminate noise influence, and simultaneously predicting outlet pressure fluctuation of an oil pump better to accurately predict faults of the oil-gas system, wherein the method specifically comprises the following sub-steps:
Step 4-1, establishing an oil fluid density, speed and pressure correlation model by adopting a fluid dynamics model, and predicting the pressure fluctuation of an oil gas pressure tank port:
,
Wherein the method comprises the steps of In order to achieve a fluid density,Is the fluid velocity,Is pressure (pressure),Is of dynamic viscosity,Is an external force.
Step 4-2, calculating the oil tank surface temperature distribution by using a Fourier heat conduction equation (∂ T/∂ T=alpha (∂ 2T/∂ x 2)), and predicting the heat aging rate of the sealing element by combining the heat boundary conditions (such as the convective heat transfer coefficient h=10W/m 2K).
Step 4-3, partitioning the sensing signal data according to 1024 points, and extracting a time sequence dependency relationship by adopting a transducer model so as to be used for predicting the residual service life of bearing abrasion:
,
, respectively input data, query, key, value matrix.
And 4-4, carrying out weighted fusion on the data obtained by the physical model and the predicted value of the data model so as to reduce the influence of data noise on the predicted result:
,
such as oil and gas port pressure physical model Simulating and calculating the obtained value for the dynamics model obtained in the step 4-1,And (3) obtaining a predicted value obtained in the step (4-3), wherein alpha is a model weight and can be taken as 0.6.
Step 5, constructing a fault mode library and knowledge reasoning, wherein the step extracts a fault mode based on the steps and the historical data, and builds a related network model for fault classification and causal reasoning, and the method specifically comprises the following substeps:
and 5.1, constructing a fault mode library based on historical fault cases, and classifying the fault modes into mechanical faults and oil faults, wherein the mechanical faults comprise bearing wear, gear breakage and seal aging, the oil faults comprise emulsification, oxidization and water exceeding, and the corresponding parameter characteristics of the fault modes are as follows:
,
Wherein the method comprises the steps of Based on the pattern library, the k-th fault characteristic (such as 'oil pressure abnormality') is used for classifying historical fault data through a machine learning method such as random forest and the like, and a new fault pattern (such as 'oil pump cavitation') is automatically supplemented.
And 5.2, carrying out probability prediction reasoning on the oil gas faults according to attribute characteristics by adopting a Monte Carlo simulation method based on a fault mode library:
,
Wherein the method comprises the steps of The posterior probability after the occurrence of the feature, such as carrying out Monte Carlo simulation on the oil tank temperature field for a plurality of times, predicts the probability (such as 95%) that the thermal stress of the sealing element exceeds a critical value (> 150 MPa%), and triggers maintenance early warning.
And 5.3, performing causal reasoning by adopting a Bayesian network, and determining the occurrence probability of related faults according to attribute indexes, such as a formula:
,
If the probability of the oil particle concentration >12 is 0.8 and the vibration spectrum deviation >20% is approximately 0.7, the probability of bearing wear is calculated (p=0.92).
And 6, training and optimizing the multi-mode prediction model, wherein the step is to train and verify the end-to-end model related to the step, design a loss function aiming at the training result of the model so as to balance minimum mean square error and cross entropy, optimize and adjust training learning rate aiming at data characteristics, and verify the result, and specifically comprises the following sub-steps.
Step 6-1, taking a weighted index as a loss function, and balancing a minimum Mean Square Error (MSE) and a cross entropy (CrossEntropy), optimizing the prediction accuracy of a physical model through the MSE, and meeting the probability prediction accuracy of fault type identification through CrossEntropy:
,
Wherein the method comprises the steps of Weights are the penalty functions.
Step 6-2, adjusting the learning rate of a transducer prediction model by using Bayesian optimization, adding an L2 regularization (lambda=0.01) and an early-stop mechanism (patience =10) in model training to prevent overfitting, and simultaneously adopting an Adam optimizer to perform gradient descent optimization training, wherein the following formula is as follows:
,
Wherein the method comprises the steps of AndModel parameters and learning rates, respectively.
And 6-3, adopting 5-fold cross validation to ensure the generalization capability of the model under different working conditions (such as high load and low load), and evaluating the accuracy, F1 fraction and recall rate of the model.
Step 7, generating fault early warning and maintenance strategies, wherein the step adopts a Z-score to calculate a threshold according to historical data, and generates corresponding maintenance actions according to different fault probabilities so as to determine immediate shutdown checking or regular maintenance, and the method specifically comprises the following steps of:
step 7-1, calculating and setting a fault early warning threshold value from historical data by adopting a Z-score:
,
if the short-term trend threshold of the oil particle concentration is EMA+3σ (e.g. 150 μm) using exponential moving average calculation, early warning is started.
And 7-2, generating maintenance suggestions according to the fault probability, such as high-probability immediate stop check (when the probability of the oxidation degree of oil liquid >8 exceeds 0.8, immediate stop maintenance and oil liquid replacement), and low-probability periodic maintenance (such as RUL >200 hours and periodic maintenance every 150 hours):
。
the invention has the following main beneficial technical effects:
1. the accuracy of fault prediction is improved, namely hidden correlations among different sensor data and knowledge graph information are revealed through cross-modal correlation analysis, and early and weak fault characteristics are captured.
2. The fault root analysis capability is improved, namely, when potential faults are predicted, possible fault components, failure modes and propagation paths thereof can be quickly traced through the topological structure of the knowledge graph and rich associated information, so that the problem core can be accurately positioned.
3. The comprehensive perception and cognition capability is enhanced, namely, through fusing multi-mode perception data (such as sensor data of vibration, temperature, pressure and the like) and a knowledge graph (comprising structural knowledge of equipment structure, historical faults, maintenance records, expert rules and the like), the system state is more comprehensively and deeply understood, and the limitation of a single data source or model is broken through.
4. The decision support capability is enhanced, namely the fault early warning and maintenance strategy generation part not only predicts the fault probability, but also fuses the associated information (such as spare part condition, maintenance cost, influence range and best maintenance practice) provided by the knowledge graph to generate more intelligent and operable maintenance proposal and coping strategies, so as to assist operation and maintenance personnel to make optimal decisions and reduce unplanned downtime.
5. The interpretation and the credibility of the model are improved, namely the knowledge graph is used as a background knowledge base, interpretation and support of a semantic layer are provided for the prediction result of the data driving model, and the credibility and the user acceptance of the model result are enhanced.
6. The method forms a complete intelligent analysis and prediction closed loop from data acquisition, processing, analysis and model construction to final early warning and decision support, and remarkably improves the intelligent level and efficiency of operation and maintenance of key equipment (oil gas pressure system) of the hydropower station.
The above-described embodiments are only preferred embodiments of the present invention, and should not be construed as limiting the present invention. The protection scope of the present invention is defined by the claims, and the protection scope includes equivalent alternatives to the technical features of the claims. I.e., equivalent replacement modifications within the scope of this invention are also within the scope of the invention.