CN106644050B - The method of the fundamental vibration frequency of object is measured in the case where Frequency spectrum quality is good - Google Patents
The method of the fundamental vibration frequency of object is measured in the case where Frequency spectrum quality is good Download PDFInfo
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- CN106644050B CN106644050B CN201610938567.2A CN201610938567A CN106644050B CN 106644050 B CN106644050 B CN 106644050B CN 201610938567 A CN201610938567 A CN 201610938567A CN 106644050 B CN106644050 B CN 106644050B
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- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H17/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves, not provided for in the preceding groups
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Abstract
The present invention relates to the methods for the fundamental vibration frequency that object is measured in the case where Frequency spectrum quality is good.Method includes the following steps: wherein r is between 10 times to 50 times of the fundamental vibration frequency of the object using sensor with the physical quantity of sample frequency r measurement object；Fast Fourier Transform (FFT) (FFT) is done to the physical quantity, obtains FFT power spectrum, wherein FFT operation points N is not less than 4096；FFT power spectrum is pre-processed, the peak power spectrum in FFT power spectrum is obtained；And frequency matching method is used, obtain the candidate fundamental vibration frequency f of the object2.The present invention can be in the case where Frequency spectrum quality be good with the fundamental vibration frequency of degree of precision automatic measurement object, without manual identified fundamental frequency.
Description
Technical field
The present invention relates to Digital Signal Processings, and in particular to the vibration of object is measured in the case where Frequency spectrum quality is good
The method of fundamental frequency.
Background technique
Fundamental vibration frequency is an important physical parameter of various objects, is able to reflect the physics shape of object or physical structure
State and characteristic.Structural health detection, object flaw detection etc. are widely used in the measurement of fundamental vibration frequency.Measure the vibration base of object
The usual method of frequency is, first using sensor with the physical quantity of certain sample frequency measurement object (such as acceleration, speed
Or displacement etc.), Fast Fourier Transform (FFT) (FFT) then is done to the physical quantity measured and obtains FFT power spectrum, finally from FFT
Manual identified goes out the fundamental vibration frequency of object in power spectrum.The mode of this manual identified fundamental vibration frequency is more troublesome, dependent on a
The experience of people, and result is often not accurate enough.
Summary of the invention
To solve the above-mentioned problems, the present invention provides one kind and automatically and can compare in the case where Frequency spectrum quality is good
The method for accurately measuring the fundamental vibration frequency of object.
According to the present invention, a kind of method for the fundamental vibration frequency measuring object in the case where Frequency spectrum quality is good includes following step
It is rapid:
Using sensor with the physical quantity of sample frequency r measurement object, wherein r is arrived in 10 times of fundamental vibration frequency of the object
Between 50 times；
Fast Fourier Transform (FFT) (FFT) is done to the physical quantity, obtains FFT power spectrum, wherein FFT operation points N is not less than
4096；
FFT power spectrum is pre-processed, the peak power spectrum in FFT power spectrum is obtained；And
For cyclic variable u=1, each value of 2 ..., p, the peak work in FFT power spectrum that wherein p is
The quantity of peak value in rate spectrum executes a wheel circulate operation, unless exiting circulation in advance under the following conditions: looking in the following manner
The maximum u frequency point n of amplitude in peak power spectrum in FFT power spectrum out1,n2,…,nu, this u frequency point is made the difference two-by-two, is obtained
It arrivesA frequency point, by thisA frequency point is together with u original frequency point n1,n2,…,nuAltogetherA frequency point from
It is small to sort to big, the frequency point m after being sortedi, whereinFrom m1After beginning stepping through these sequences
Frequency point, for each frequency point m of traversali, calculate matching degreeWherein, j=1,2 ..., u, wherein W
ForImmediate integer, and corresponding matching value y is seti,j, wherein j=1,2 ..., u, if Yi,jGreater than predetermined matching threshold
Value σ, wherein 0 < σ≤0.1, then yi,j=0, otherwise yi,j=1, then calculate fundamental frequency similarityIf ziLess than pre-
Determine similarity threshold R, wherein 0.5 < R < 1, then continue to traverse, otherwise stop traversal, and exit circulation in advance, determines current traversal
Frequency point miFor candidate fundamental vibration frequency point x2, pass through operationAnd obtain the candidate fundamental vibration frequency f of the object2。
The present invention can in the case where Frequency spectrum quality is good with the fundamental vibration frequency of degree of precision automatic measurement object, without
Want manual identified fundamental frequency.
Detailed description of the invention
Fig. 1 is the process of the method for the fundamental vibration frequency according to the present invention that object is measured in the case where Frequency spectrum quality is good
Figure.
Specific embodiment
The vibration base according to the present invention that object is measured in the case where Frequency spectrum quality is good is described in detail below with reference to Fig. 1
Each step of the method for frequency.
As shown in Figure 1, in step S1, using sensor with the physical quantity of sample frequency r measurement object (such as acceleration,
Speed or displacement etc.), wherein r is between 10 times to 50 times of the fundamental vibration frequency of the object.In step S2, which is done
Fast Fourier Transform (FFT) (FFT), obtains FFT power spectrum, wherein FFT operation points N is not less than 4096.Here, in order to guarantee this
The accuracy of the measurement method of invention is defined the value range of sample frequency r and FFT operation points N.
In step S3, FFT power spectrum is pre-processed, obtains the peak power spectrum in FFT power spectrum.The master of step S3
Syllabus is to find peak value outstanding in FFT power spectrum.Under normal conditions, the fundamental vibration frequency of object or its higher hamonic wave can be
Peak position in FFT power spectrum.
It will be appreciated by those skilled in the art that step S3 can be realized in several ways.For example, step S3 can include:
Scanning FFT power spectrum is not dealt with if the frequency point scanned is maximum point, otherwise direct zero setting, thus scanning through
The peak power spectrum in FFT power spectrum is obtained after finishing.
Alternatively, step S3 can include:
Sliding average processing is carried out to FFT power spectrum, obtains FFT smooth power spectrum, wherein sliding average processing is taken
Window width is 5~20 frequency points, so as to significantly reduce the influence of interference peak in FFT power spectrum；
By the 1st point of FFT smooth power spectrum to the direct zero setting of M-1 point (since the peak value of low-frequency range in frequency spectrum can reduce
The accuracy of fundamental vibration frequency measurement, in this way processing can exclude the influence of the peak value of low-frequency range), wherein M isBetween it is whole
Number (a lesser integer is generally taken, such as)；
From M point to N spot scan FFT smooth power spectrum, retain all maximum points in FFT smooth power spectrum,
His non-maximum point whole zero setting；
Again from the 1st point to all non-zero points in N spot scan FFT smooth power spectrum, FFT function is obtained in the following manner
Peak power spectrum in rate spectrum: setting kth point as the non-zero points of Current Scan, and k-1 point is the non-zero points of upper one scanning, and k+1 is
The non-zero points of next scanning, if the amplitude of kth point be greater than -1 point of kth+1 point of amplitude and kth amplitude or kth point with most
The distance of nearly non-zero points is not less than predetermined distance threshold D, and wherein D isBetween integer (generally take one it is close with M
Integer), then it is not processed and continues to scan on+1 point of kth, otherwise (purpose handled in this way is removal in FFT function by the zero setting of kth point
Rate spectrum in distance very close to two peak values in amplitude smaller, this is because two very close to peak value will affect vibration base
The accuracy of frequency measurement).
The candidate fundamental vibration frequency f of the object is obtained using frequency matching method in step S42.Specifically, for circulation
Each value of variable u=1,2 ..., p, wherein p is in the peak power spectrum in the FFT power spectrum that step S3 is obtained
The quantity of peak value executes a wheel circulate operation, unless exiting circulation in advance under the following conditions: finding out FFT function in the following manner
The maximum u frequency point n of amplitude in peak power spectrum in rate spectrum1,n2,…,nu, this u frequency point is made the difference two-by-two, is obtainedA frequency point, by thisA frequency point is together with u original frequency point n1,n2,…,nuAltogetherA frequency point is from small
Frequency point m to big sequence, after being sortedi, whereinFrom m1Frequency after beginning stepping through these sequences
Point, for each frequency point m of traversali, calculate matching degreeWherein, j=1,2 ..., u, wherein W beImmediate integer, and corresponding matching value y is seti,j, wherein j=1,2 ..., u, if Yi,jGreater than predefined matching threshold
σ, wherein 0 < σ≤0.1 (σ generally take one close to 0 number, such as 0.01), then yi,j=0, otherwise yi,j=1, then calculate base
Frequency similarityIf ziLess than predetermined similarity threshold R, wherein 0.5 < R < 1 (R generally take one close to 1 number,
Such as 0.75), then continue to traverse, otherwise stop traversal, and exit circulation in advance, determine the frequency point m currently traversediFor candidate's vibration
Dynamic fundamental frequency x2, pass through operationAnd obtain the candidate fundamental vibration frequency f of the object2。
It optionally, can after step s4, using window weight in order to improve the accuracy of measurement method of the invention
Method obtains the candidate fundamental vibration frequency f of the object1, and more candidate fundamental vibration frequency f1With candidate fundamental vibration frequency f2To determine candidate vibration
Dynamic fundamental frequency f1Or f2For the fundamental vibration frequency (step S5) of the object.
Specifically, step S5 can include:
For frequency pointEach value, wherein M beBetween integer (one
As take a lesser integer, such as), it obtains assessing parameter E accordingly in the following mannerx: in xth point, 2x point,
3x point ..., thePoint place (i.e. frequency point x and its each harmonic at), it is maximum value 1 that a kind of center is arranged centered on frequency point
And edge is the window (such as rectangular window, quarter window, Cosine Window etc.) of minimum value 0, the width of the window isBetween
Integer (a lesser integer is generally taken, such as)；By in the FFT power spectrum that step S3 is obtained peak power spectrum with
The window is multiplied, and obtains FFT window weight power spectrum；By the non-zero amplitude-value in FFT window weight power spectrum it is cumulative after divided byObtain assessment parameter Ex；
It findsIn maximum value Exmax, by ExmaxCorresponding frequency point is as candidate
Fundamental vibration frequency point x1, and pass through operationAnd obtain the candidate fundamental vibration frequency f of the object1；
Compare candidate fundamental vibration frequency f1With candidate fundamental vibration frequency f2If meetingWherein V isIt is closest
Integer, it is determined that candidate fundamental vibration frequency f2For the fundamental vibration frequency of the object, candidate fundamental vibration frequency f is otherwise determined1For the object
Fundamental vibration frequency.
The foregoing describe the embodiment of the present invention, above description is merely exemplary, and not restrictive.Based on above stating
Bright, those skilled in the art are readily apparent that various modifications and change to the embodiment of the present invention, these modifications and change
More it is within.
Claims (4)
1. a kind of method for the fundamental vibration frequency for measuring object in the case where Frequency spectrum quality is good, comprising the following steps:
Using sensor with the physical quantity of sample frequency r measurement object, wherein 10 times to 50 times of fundamental vibration frequency in the object of r
Between；
Fast Fourier Transform (FFT) FFT is done to the physical quantity, obtains FFT power spectrum, wherein FFT operation points N is not less than 4096；
FFT power spectrum is pre-processed, the peak power spectrum in FFT power spectrum is obtained；And
For cyclic variable u=1, each value of 2 ..., p, the peak power spectrum in the FFT power spectrum that wherein p is
In peak value quantity, in the following manner execute one wheel circulate operation, unless exiting circulation in advance under the following conditions: finding out
The maximum u frequency point n of amplitude in peak power spectrum in FFT power spectrum1,n2,…,nu, this u frequency point is made the difference two-by-two, is obtainedA frequency point, by thisA frequency point is together with u original frequency point n1,n2,…,nuAltogetherA frequency point is from small
Frequency point m to big sequence, after being sortedi, whereinFrom m1Frequency after beginning stepping through these sequences
Point, for each frequency point m of traversali, calculate matching degreeWherein, j=1,2 ..., u, wherein W beImmediate integer, and corresponding matching value y is seti,j, wherein j=1,2 ..., u, if Yi,jGreater than predefined matching threshold
σ, wherein 0 < σ≤0.1, then yi,j=0, otherwise yi,j=1, then calculate fundamental frequency similarityIf ziLess than predetermined
Otherwise similarity threshold R stops traversal, and exit circulation in advance wherein 0.5 < R < 1, then continue to traverse, what determination currently traversed
Frequency point miFor candidate fundamental vibration frequency point x2, pass through operationAnd obtain the candidate fundamental vibration frequency f of the object2。
2. the method according to claim 1, wherein carrying out pretreated step to FFT power spectrum includes: scanning FFT power spectrum,
If the frequency point scanned is maximum point, do not deal with, otherwise direct zero setting.
3. the method according to claim 1, wherein carrying out pretreated step to FFT power spectrum includes:
Sliding average processing is carried out to FFT power spectrum, obtains FFT smooth power spectrum, wherein sliding average handles taken window
Width is 5~20 frequency points；
By the 1st point of FFT smooth power spectrum to the direct zero setting of M-1 point, wherein M isBetween integer；
From M point to N spot scan FFT smooth power spectrum, retain all maximum points in FFT smooth power spectrum, other are non-
Maximum point whole zero setting；
Again from the 1st point to all non-zero points in N spot scan FFT smooth power spectrum, FFT power spectrum is obtained in the following manner
In peak power spectrum: set kth point as the non-zero points of Current Scan, k-1 point is the non-zero points of upper one scanning, and k+1 is next
The non-zero points of a scanning, if the amplitude of kth point be greater than+1 point of amplitude and kth of -1 point of kth amplitude or kth point with it is nearest non-
The distance of zero point is not less than predetermined distance threshold D, and wherein D isBetween integer, then be not processed and continue to scan on
K+1 point, otherwise by kth point zero setting.
4. according to the method described in claim 3, further comprising the steps of:
For frequency pointEach value, wherein M beBetween integer, by with lower section
Formula obtains assessing parameter E accordinglyx: in xth point, 2x point, 3x point ...,At point, it is arranged centered on frequency point
A kind of center is maximum value 1 and edge is the window of minimum value 0, and the width of the window isBetween integer；By FFT function
Peak power spectrum in rate spectrum is multiplied with the window, obtains FFT window weight power spectrum；It will be in FFT window weight power spectrum
After non-zero amplitude-value is cumulative divided byObtain assessment parameter Ex；
It findsIn maximum value Exmax, by ExmaxCorresponding frequency point is as candidate vibration
Fundamental frequency x1, and pass through operationAnd obtain the candidate fundamental vibration frequency f of the object1；
Compare candidate fundamental vibration frequency f1With candidate fundamental vibration frequency f2If meetingWherein V isIt is immediate whole
Number, it is determined that candidate fundamental vibration frequency f2For the fundamental vibration frequency of the object, candidate fundamental vibration frequency f is otherwise determined1For the vibration of the object
Fundamental frequency.
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