CN112903271A - Non-contact asynchronous vibration parameter identification method for rotor blade - Google Patents
Non-contact asynchronous vibration parameter identification method for rotor blade Download PDFInfo
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Abstract
The application belongs to the technical field of rotor blade non-contact asynchronous vibration parameter identification, and particularly relates to a rotor blade non-contact asynchronous vibration parameter identification method, which comprises the following steps: extraction of fs、{yj(n)}、θjWherein f issFor the rotation frequency, { yj(n) is the vibration displacement sequence for the jth sensor undersampling a single rotor blade, θjIs the physical included angle between the jth sensor and the jth-1 sensor if fsAt selected { yj(n) the rotation time is changed, or yj(n) in the effective spectrum
If it is not a single frequency component, then f is updateds、{yj(n)}、θj(ii) a Calculating to obtain delta f, wherein the delta f is difference frequency; f is calculated, where f is the frequency of the rotor blade vibration.
Description
Technical Field
The application belongs to the technical field of rotor blade non-contact asynchronous vibration parameter identification, and particularly relates to a rotor blade non-contact asynchronous vibration parameter identification method.
Background
Many aircraft faults are caused by engine faults, many engine faults are related to fracture failure of rotor blades, many fracture failure of rotor blades are caused by high-cycle fatigue caused by resonance, and in order to avoid resonance in actual working conditions, the natural frequency of the rotor blades is increased through design.
The vibration frequency of the rotor blade is composed of one or more components which are not integral multiples of the rotation frequency, the vibration mode is asynchronous vibration, and at present, the vibration information of the rotor blade is mainly obtained by a contact type strain gauge measuring method or a non-contact type measuring method in the actual working condition and component performance test of the whole machine.
The contact type strain gauge measuring method is high in sampling frequency and capable of obtaining accurate blade vibration information, but the method is large in modification of an engine structure, the performance of the engine is affected by partial modification structures, the service life is short, the blade vibration information cannot be obtained completely by the aid of related sensors and lead wires of the sensors, the service life of the sensors is short, the blade vibration information cannot be obtained effectively for a long time, the sensors can only be used as special tests, and the test cost is high.
The non-contact measuring method is simple in test structure modification, small in influence on the performance of the engine, and capable of working for a long time to obtain data of the engine blade under the real working condition.
The non-contact measurement method is a test technology for obtaining the displacement of the rotor blade by calculation through comparing the recorded arrival time of the rotor blade with a rotating speed signal, and is essentially to perform discontinuous measurement on the relative displacement of the tip of the blade, restore the relative displacement into an original vibration process of the blade according to a measured value, and analyze the parameters of the whole vibration process of the blade.
Under the conditions that the engine is in a stable rotating speed step and the rotor blade vibrates at a single asynchronous vibration frequency, the vibration equation of the blade tip of the rotor blade relative to the rotor can be written as follows:
wherein the content of the first and second substances,
y is the vibration displacement of a single rotor blade, A is the maximum vibration amplitude of the rotor blade relative to the equilibrium position, f is the frequency of the rotor blade vibration, fsIs the rotational frequency of the blade, omega is the rate of change of phase of the rotor blade, omegasThe angular velocity of the rotor blade, dc, is the deviation of the theoretical position of the rotor blade tip due to assembly errors,
is the initial phase of vibration of the rotor blade.
A non-contact measurement method is implemented based on a non-contact measurement system, the principle is shown in figure 1, a rotor blade tip timing sensor is installed in the direction perpendicular to a reflecting surface of a rotor blade of an engine case, when the rotor blade tip sweeps across the sensor, pulses are generated, the time of each rotor blade pulse reaching the sensor can be recorded, a rotating speed sensor is installed on an engine shaft, one pulse can be output every one circle, the reaching time of the rotating speed pulse can be recorded, the time sequence of signals collected by the sensor is shown in figure 2, when the rotor blade vibrates, the position of the blade tip can generate vibration displacement, as shown in figure 3, for the given number N of the rotor bladesbThe rotor blade system with the blade tip position diameter D and the rotating speed omega can obtain a rotating speed cycle as follows: t2 pi/ω;
when the rotor blade does not vibrate, the rotor blade passes through oneThe time of each cascade spacing is: t isb＝T/Nb；
When the rotor blade vibrates, the rotor blade sweeps over a blade row pitch T assuming an amplitude Δ A of the rotor blade at a rotational speed ωaAnd the theoretical to sweep time TbOccurrence of a deviation Δ T ═ Ta-Tb；
Because the amplitude Δ a of the rotor blade is much smaller than the circumferential perimeter of the engine case, the corresponding relationship between the amplitude of the rotor blade and the time deviation is as follows: y ═ Δ a ≈ ω R Δ t;
the distribution of the sensors on the engine case is shown in FIG. 4, and the physical angle distribution of each sensor on the engine case is [ theta ]1,θ1+θ2,θ1+θ2+θ3...(θ1+θ2+θ3...+θi)]The physical included angle between the jth sensor and the jth-1 sensor along the rotation direction is thetajAccording to the test principle, at a constant speed, each sensor rotates at a speed frequency fsSampling rotor blade vibration, wherein the jth sensor can obtain an undersampled single rotor blade vibration displacement sequence { y }for a single rotor bladej(n), where n represents the nth sample time, there are:
wherein T is a sampling period; v (t) is a noise signal; Δ f is a low-frequency aliasing signal of the rotor blade vibration frequency in a sampling frequency band, namely a vibration difference frequency; m is an integer part of the ratio of the vibration frequency to the sampling frequency, and is a calculation operator; Δ m is the fractional part of the ratio of the vibration frequency to the sampling frequency.
In the non-contact measurement method implemented based on the non-contact measurement system, full phase fourier transform (AFFT) is performed on data of different sensors to obtain phases corresponding to difference frequency and difference frequency, phase difference values between different sensors are calculated by traversing estimated frequencies of rotor blade vibration, and the vibration frequency of the rotary blade vibration is determined by finding the minimum value of the difference between the measured phase difference value and the theoretical difference value, and the process is as shown in fig. 5:
extraction of { yj(n)}、θjFull phase Fourier transform { yj(n) obtaining Δ f,
Application of
Searching m for minimum, and judging the difference degree between the frequency generated by m and the real frequency by an error operator E (m);
f ═ Δ f + m × f is obtaineds。
The non-contact measurement method implemented based on the non-contact measurement system has the following defects:
1) the rotor blade can be better suitable for single-frequency vibration, and error identification information can be obtained when the rotor blade is suitable for multi-frequency composite vibration;
2) the full-phase FFT method is a whole-segment data analysis method, and can directly give out a single difference frequency delta f and a corresponding phase thereof
In practice, a lot of interference signals are often generated around the frequency, the method is easy to select noise frequency as a main frequency and extract an error phase, the difference frequency and the corresponding phase in subsequent calculation are used for calculating a judgment calculation operator m, when the selection of the error frequency and phase information for fitting calculation is selected, the subsequent calculation result is in error, an error frequency parameter identification result is given, and the test success rate is low.
3) The phase angle is to be adjusted
And regulating to [0,2 pi ]), the calculation can carry out data estimation in the integrated calculation process, certain data authenticity is lost, the calculation is easy to distort, and the calculation precision of subsequent calculation E (m) is influenced.
The present application has been made in view of the above-mentioned technical drawbacks.
It should be noted that the above background disclosure is only for the purpose of assisting understanding of the inventive concept and technical solutions of the present invention, and does not necessarily belong to the prior art of the present patent application, and the above background disclosure should not be used for evaluating the novelty and inventive step of the present application without explicit evidence to suggest that the above content is already disclosed at the filing date of the present patent application.
Disclosure of Invention
The present application is directed to a method for identifying non-contact asynchronous vibration parameters of a rotor blade, which is applicable to a constant rotation speed situation, so as to overcome or alleviate at least one of the technical disadvantages of the known prior art.
The technical scheme of the application is as follows:
a non-contact asynchronous vibration parameter identification method for a rotor blade comprises the following steps:
extraction of fs、{yj(n)}、θjWherein f issIs the rotation frequency, and is also the sampling frequency yj(n) is the vibration displacement sequence for the jth sensor undersampling a single rotor blade, θjIs the physical included angle between the jth sensor and the jth-1 sensor if fsAt selected { yj(n) the rotation time is changed, or yj(n) in the effective spectrum
If it is not a single frequency component, then f is updateds、{yj(n)}、θj；
Calculating to obtain delta f, wherein the delta f is difference frequency;
f is calculated, where f is the frequency of the rotor blade vibration.
According to at least one embodiment of the present application, in the method for identifying non-contact asynchronous vibration parameters of a rotor blade, the calculating step obtains Δ f, specifically:
for { yj(n) performing recursive least square identification calculation to obtain a parameter matrix theta, and if elements in the theta are not converged to a fixed value, updating fs、{yj(n)}、θjAnd Δ f is recalculated.
According to at least one embodiment of the present application, in the above-mentioned method for identifying parameters of non-contact asynchronous vibration of a rotor blade,
wherein the content of the first and second substances,
Δ f is the difference frequency;
Δfjthe difference frequency corresponding to the jth sensor;
i is the number of sensors.
According to at least one embodiment of the present application, the method for identifying non-contact asynchronous vibration parameters of a rotor blade further includes:
construction of a parameter matrix by Δ f
Δ fk is a difference frequency corresponding to the kth sensor;
t is time;
k is 1, 2, …, N, N is selected from { y }j(n) }.
According to at least one embodiment of the present application, in the method for identifying non-contact asynchronous vibration parameters of a rotor blade, the calculating step includes:
using thetajAnd (5) calculating a difference operator S (m) by the elements, searching the minimum value, and further calculating to obtain f.
The application has at least the following beneficial technical effects:
providing a non-contact asynchronous vibration parameter identification method for a rotor blade, which uses fsAt selected { yj(n) whether or not a change has occurred in the revolution time，{yj(n) in the effective spectrum
Whether or not a single frequency component is taken as yj(n)}、θjThe use conditions of (2) can be well suitable for various situations.
In addition, the rotor blade non-contact asynchronous vibration parameter identification method is used for judging the effectiveness of the delta f based on a recursive least square identification algorithm, and the validity of the result can be ensured by applying the method when the delta f is judged to be effective.
Drawings
FIG. 1 is a schematic diagram of a non-contact measurement system of a non-contact measurement method;
FIG. 2 is a timing diagram of a non-contact measurement method and a non-contact measurement system sensor signal acquisition;
FIG. 3 is a schematic illustration of a tip position vibro-displacement of a rotor blade as it vibrates;
FIG. 4 is a schematic illustration of the distribution of sensors on the engine case;
FIG. 5 is a flow chart of a prior art method for non-contact asynchronous vibration parameter identification of a rotor blade;
FIG. 6 is a schematic diagram of a single aliasing frequency of a single vibration frequency of a rotor blade at a corresponding frequency band provided by an embodiment of the present application.
FIG. 7 is a flow chart of a method for non-contact asynchronous vibration parameter identification of a rotor blade according to an embodiment of the present application;
for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; further, the drawings are for illustrative purposes, and terms describing positional relationships are limited to illustrative illustrations only and are not to be construed as limiting the patent.
Detailed Description
In order to make the technical solutions and advantages of the present application clearer, the technical solutions of the present application will be further clearly and completely described in the following detailed description with reference to the accompanying drawings, and it should be understood that the specific embodiments described herein are only some of the embodiments of the present application, and are only used for explaining the present application, but not limiting the present application. It should be noted that, for convenience of description, only the parts related to the present application are shown in the drawings, other related parts may refer to general designs, and the embodiments and technical features in the embodiments in the present application may be combined with each other to obtain a new embodiment without conflict.
In addition, unless otherwise defined, technical or scientific terms used in the description of the present application shall have the ordinary meaning as understood by one of ordinary skill in the art to which the present application belongs. The terms "upper", "lower", "left", "right", "center", "vertical", "horizontal", "inner", "outer", and the like used in the description of the present application, which indicate orientations, are used only to indicate relative directions or positional relationships, and do not imply that the devices or elements must have a specific orientation, be constructed and operated in a specific orientation, and when the absolute position of the object to be described is changed, the relative positional relationships may be changed accordingly, and thus, should not be construed as limiting the present application. The use of "first," "second," "third," and the like in the description of the present application is for descriptive purposes only to distinguish between different components and is not to be construed as indicating or implying relative importance. The use of the terms "a," "an," or "the" and similar referents in the context of describing the application is not to be construed as an absolute limitation on the number, but rather as the presence of at least one. The use of the terms "comprising" or "including" and the like in the description of the present application is intended to indicate that the element or item preceding the term covers the element or item listed after the term and its equivalents, without excluding other elements or items.
Further, it is noted that, unless expressly stated or limited otherwise, the terms "mounted," "connected," and the like are used in the description of the invention in a generic sense, e.g., connected as either a fixed connection or a removable connection or integrally connected; can be mechanically or electrically connected; they may be directly connected or indirectly connected through an intermediate medium, or they may be connected through the inside of two elements, and those skilled in the art can understand their specific meaning in this application according to the specific situation.
The present application is described in further detail below with reference to fig. 1 to 7.
Step one, obtaining f from a non-contact measurement systems、{yj(n)}、θjAnd judging whether:
determination of applicable conditions:
(1)、fsat selected { yj(n) whether the rotation time is kept constant;
(2)、{yj(n) performing a Fast Fourier Transform (FFT) on the data sequence at the effective frequency spectrum
Whether the frequency component is single or not is judged.
For the jth sensor, y with the length of N is acquiredj(N) performing an FFT on
The frequency band results in a single aliasing frequency, i.e. the difference frequency Δ f, of the rotor blade single vibration frequency f in this frequency band, as shown in fig. 7.
It is determined whether the difference frequency Δ f is a single peak, and it cannot be applied when the difference frequency Δ f is not a single peak, and when the difference frequency Δ f is a single peak, it indicates that the rotor blade is vibrating at a single asynchronous vibration frequency.
Selecting different sensor data to judge, and respectively calculating to obtain delta f of the sensor No. jjThen the difference frequency Δ f is:
carrying out equivalent deformation on the collected blade vibration equation:
the rotor blade vibrations may be divided into groups of linear elementsA matrix of complex theta parameters, formed by non-linear elements
Calculating a matrix and a noise vector, wherein for a single sensor, the amplitude and the initial phase of the rotor blade are unique, and the sampling time point of delta f is the same as the sampling point value of the real frequency, so that the amplitude and the initial phase of the rotor blade can be constructed by delta f
Parameter matrix:
the process of step one can be expressed as follows:
step 1: extracting f from a non-contact measurement systems、{yj(n)}、θj；
Step 2: determination fsIf the change is not applicable within the acquisition time, if the change is not applicable, the next step is carried out;
step 3: selecting length N yj(n) } and its frequency of use fsFor { yj(n) performing FFT to determine whether a single difference frequency, which is not applicable if it is, is a single difference frequency record Δ fjCarrying out the next step;
step 4: using difference frequency deltaf of different sensorsjCalculating a corrected difference frequency delta f value;
step 5: construction of a calculation parameter matrix using Δ f
In the first step, when the vibration condition of the rotor blade is not changed, the larger the value selected by N is, the higher the frequency resolution is, and the more accurate the obtained difference frequency Δ f is.
Step two, calculating theta based on a Recursive Least Square (RLS) method and judging element convergence:
calculating the data length N of the jth sensor by applying a recursive least square identification calculation methodj(n) }, performing recursive least square identification calculationCorresponding parameter matrix thetajThe specific process is as follows:
{k＝1,2,…,N}，
is a parameter estimate calculated after iterating N steps, wherein:
decision parameter matrix thetajIf the calculated parameter in (1) is converged to a fixed value, when the element in the parameter matrix theta is not converged, the difference frequency delta f selected by the user is proved to have a larger error with the true value, the calculated parameter matrix theta cannot be applied, the step one is returned to for recalculation, when the element in the parameter matrix theta is converged to the fixed value, the calculation result is shown to be effective, and the parameter matrix theta of the sensor No. j is respectively recordedj。
The process of step two can be expressed as follows:
step 1: selecting y of length Mj(M)；
Step 2: let k equal to 1;
P0＝106；133-dimensional column vectors whose representative elements are all 1;
step 3: using the output from step one
Judging that k is equal to M and is not equal to the next step;
step 4: calculate P (k), K (k).
Step 5: updating a parameter estimation vector
Step 6: k equals k +1, and returns to Step 2.
Step 7: determination
Whether the middle element is converged or not is judged, and the convergence records the parameter matrix theta of the jth sensorj(k) If not, returning to the step I to correct the difference frequency delta f.
Due to the frequency resolution, the difference frequency delta f is different from the true value necessarily, when the data is selected too long, the difference is amplified, so that the identification parameters are not converged, the data in the second step can be part of the data section in the first step, and M is less than or equal to N, so that the calculation success rate can be effectively improved.
Step three, utilizing thetajElement calculation difference operator s (m) and finding its minimum value to confirm f:
from the equation of blade vibration, in a parameter matrix
Then there are parameters A, dc in the rotor blade vibration equation:
the vibration phase collected by the jth sensor has
Use of
For calculation, the tangent value corresponds to the angle in a one-to-one manner, and the tangent value calculation process can eliminate the influence of the amplitude A on the calculation.
Analysis of vibration signals collected by the (j-1) th sensor
Analysis of the jth sensor, due to its relative jth-1 sensorHysteresis on engine case thetajThe physical included angle, the sampling vibration information of the jth sensor deduced by the fixed rotating speed is:
from the frequency aliasing equation Δ f ═ f-mfsI, |, can be:
thereby simplifying to be known
Δm、θjAnd obtaining the value of m.
The phase difference of vibration between adjacent sensors is
According to the trigonometric function relationship, the following can be obtained:
construction of a judgment operator S+(m)、S-(m)：
Because the vibration frequency of the rotor blade is in a certain range, the value m is a positive integer with an upper limit, different S (m) can be obtained by traversing the value m, when the value m is a true value and the front sign of the delta m is correct, the S (m) is minimum, the value m and the front sign of the delta m can be determined, and the vibration frequency f of the rotor blade is as follows:
the blade vibration equation can be written as:
the process of step three can be expressed as follows:
step 1: calculated by different sensors
Calculating to obtain parameters A and dc in a vibration equation;
step 2: calculating the measured phase of the jth sensor
Corresponding to
Step 3: selecting the jth and j-1 sensors, and correspondingly calculating a judgment operator S+(m)、S-(m) a value;
step 4: search for a judgment operator S+(m)、S-(m) obtaining corresponding m and a difference frequency symbol;
step 5: the rotor blade vibration frequency f is calculated as A, f, dc.
The application discloses rotor blade non-contact asynchronous vibration parameter identification method, theoretical minimum only need two sensors that distribute circumferentially, when minimum and time minimums are close, should select more sensor data and verify each other, and theoretical i sensor can select
The more sensors, the more accurate the result of mutual authentication.
In the rotor blade non-contact asynchronous vibration parameter identification method disclosed by the application, a { y } is givenj(n)}、θjThe application condition and the use criterion thereof are applicable when the difference frequency only has a single peak value in the sampling frequency spectrum and the interference noise signal at the periphery of the single peak value is lower.
In the non-contact asynchronous vibration parameter identification method for the rotor blade, a difference frequency and phase information calculation method based on a recursive least square identification algorithm is provided, and whether the calculated difference frequency and phase data are effective or not is judged by observing whether the calculated parameters are converged or not. The judgment method is used for judging whether the calculated difference frequency and the phase thereof are true or not, judging whether the calculation result is valid or not by taking whether the observed calculation parameters are converged or not as the basis, if the calculation parameters are converged, the calculation is correct, the calculation can be applied to the next calculation, if the calculated parameters are not converged, the difference frequency information is wrong, the difference frequency correction is recalculated, the recursive least square identification algorithm is re-introduced until the convergence, the wrong calculation information is avoided, and the recursive least square identification algorithm has certain influence on parameter identification by noise reduction.
In addition, in the rotor blade non-contact asynchronous vibration parameter identification method disclosed by the application, the phase tangent value obtained by direct calculation is substituted into the calculation in the phase calculation to replace a calculation scheme of converting a trigonometric function into an angle and normalizing to [0,2 pi ] for calculation, so that the calculation efficiency and the calculation precision can be effectively improved.
Having thus described the present application in connection with the preferred embodiments illustrated in the accompanying drawings, it will be understood by those skilled in the art that the scope of the present application is not limited to those specific embodiments, and that equivalent modifications or substitutions of related technical features may be made by those skilled in the art without departing from the principle of the present application, and those modifications or substitutions will fall within the scope of the present application.
Claims (5)
1. A non-contact asynchronous vibration parameter identification method for a rotor blade is characterized by comprising the following steps:
extraction of fs、{yj(n)}、θjWherein f issFor the rotation frequency, { yj(n) is the vibration displacement sequence for the jth sensor undersampling a single rotor blade, θjIs the physical included angle between the jth sensor and the jth-1 sensor if fsAt selected { yj(n) the rotation time is changed, or yj(n) in the effective spectrum
If it is not a single frequency component, then f is updateds、{yj(n)}、θj；
Calculating to obtain delta f, wherein the delta f is difference frequency;
f is calculated, where f is the frequency of the rotor blade vibration.
2. The method for rotor blade non-contact asynchronous vibration parameter identification as claimed in claim 1,
the calculating obtains Δ f, specifically:
for { yj(n) performing recursive least square identification calculation to obtain a parameter matrix theta, and if elements in the theta are not converged to a fixed value, updating fs、{yj(n)}、θjAnd Δ f is recalculated.
3. The method of claim 1, wherein the rotor blade is characterized in that,
Δ f is the difference frequency;
Δfjthe difference frequency corresponding to the jth sensor;
i is the number of sensors.
4. The method of claim 1, wherein the rotor blade is characterized in that,
further comprising:
construction of a parameter matrix by Δ f
Δ fk is a difference frequency corresponding to the kth sensor;
t is time;
k is 1, 2, …, N, N is selected from { y }j(n) }.
5. The method of claim 1, wherein the rotor blade is characterized in that,
the f obtained by the calculation is specifically as follows:
using thetajAnd (5) calculating a difference operator S (m) by the elements, searching the minimum value, and further calculating to obtain f.
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| CN114812794A (en) * | 2022-01-12 | 2022-07-29 | 天津大学 | Method for correcting blade tip timing parameter identification error caused by frequency sweep rate |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114812794A (en) * | 2022-01-12 | 2022-07-29 | 天津大学 | Method for correcting blade tip timing parameter identification error caused by frequency sweep rate |
| CN114812794B (en) * | 2022-01-12 | 2024-03-22 | 天津大学 | Blade tip timing parameter identification error correction method caused by sweep rate |
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