CN102095885B - Vibration measuring method of engine speed by applying four-point energy centrobaric correction method - Google Patents

Abstract

The invention discloses a vibration measuring method of engine speed by applying a four-point energy centrobaric correction method, which comprises the steps of: discrete-sampling a vibration acceleration signal on the surface of an engine block to obtain a time series; obtaining a frequency domain signal X1(f) through fast Fourier transformation of Zn(t); correcting the peak frequency fi of X1(f) by adopting a four-point energy centrobaric correction method, and obtaining a corrected frequency; obtaining a time spectrum signal ZZn(t) through carrying out self-related transformation and fast Fourier transformation on the frequency domain signal X1(f); correcting the time ti corresponding to the peak of ZZn(t) by adopting the four-point energy centrobaric correction method again, and obtaining the corrected time; and finding the accurate 1/2 harmonic frequency value of the rotating speed w of the four stroke engine according to the corrected frequency and time, and calculating the rotating speed w of the engine through a relational expression. The vibration measuring method of engine speed can solve the problem that the rotating speed of the engine cannot be detected when the number of engine blocks cannot be determined; and the method has the advantages of better universality, high noise-proof performance and accurate and reliable result.

Description

Use the vibration measurement method of the engine speed of 4 energy barycenter correction methods

Technical field

This aspect relates to power machine and signal Processing field, particularly relates to the vibration measurement method of the engine speed of using 4 energy barycenter correction methods, is a kind of under the situation of unknown cylinder number, tests out the method for engine speed.

Background technology

Because at present most is being Otto cycle engine with car, for Otto cycle engine, in Otto cycle engine referred to during 720 ° of the crankshaft rotating, engine was accomplished air inlet, igniting, acting, four strokes of exhaust; 1/2 humorous time is the most basic simple harmonic quantity; Can know through the torque analysis to engine simultaneously, be the engine of i for the cylinder number, and its main humorous time is (i * m)/2 (the same, m is any positive integer).Because each humorous time amplitude reduces rapidly with humorous time increase, in the ideal case, is the engine of i for the cylinder number, the amplitude that its i/2 is humorous time maximum (below be referred to as first main humorous time).When engine speed was n (r/min), corresponding commentaries on classics was n/60Hz frequently, established first main humorous the corresponding frequency f ₀, following relation is then arranged:

${\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="HSA00000326885800012.png,HSA00000326885800013.png"\; state="\{\{state\}\}">f</figure-callout>}}_0=\frac{n}{60}\&times;\frac{i}{2}---(2-1)$

At present domesticly relevantly all be based on formula (2-1) based on the speed measuring system that vibrates and method and carry out tachometric survey.Employing formula (2-1) can be tried to achieve the rotating speed of engine in theory very easily through the frequency spectrum of analyzing engine luggine, but when the rotating speed identification of real engine, has following problem: (1) needs the cylinder of known engine to count i, and versatility is poor; (2) when frequency resolution is low, first main humorous f can appear confusing ₀Phenomenon; (3) noiseproof feature of this method is relatively poor, and first main humorous f appears confusing in regular meeting under noise ₀Phenomenon; (4) tachometric survey precision is lower, receives the influence of Fourier transform frequency resolution, has 30 times frequency resolution tachometric survey error.

Summary of the invention

The objective of the invention is defective to the available engine rotating speed measurement method; The measurement of engine rotate speed method of 4 energy barycenter correction methods of a kind of application is proposed; Work as the problem that to foresee engine cylinder number and can not measure engine speed to solve, and test rotating speed versatility is better, noiseproof feature is high, the result is accurately reliable.

For Otto cycle engine, 1/2 humorous time is the most basic simple harmonic quantity, as if 1/2 humorous time that can identify engine, under the prerequisite of unknown engine cylinder number, also can obtain the rotating speed of engine rapidly.In the real engine torsional vibration of shafting; Except that the driving torque that inertial load produced of gas load that bears above analysis and moving component; Also bearing some other disturbance torque; So in real engine torsional vibration of shafting signal, 1/2 humorous time might not be all high-visible, but frequency interval one is decided to be 1/2 humorous time.So when the amplitude spectrum that to engine shaft is torsion vibration signal carries out autocorrelation analysis; Frequency interval is that 1/2 humorous time relevant nature has determined the humorous inferior amplitude of 1/2 base to improve greatly; The amplitude that in like manner is spaced apart 1,1.5,2 etc. humorous times also can become obviously outstanding, and promptly each humorous composition is arranged in the autocorrelation function of vibration signal amplitude spectrum by the interval of humorous time of 1/2 base.When this signal was carried out Fourier transform again, the amplitude that 1/2 base is humorous time will become the maximum amplitude that is only second to zero-frequency humorous time.Autocorrelation analysis has tangible noise reduction effect to the random noise of sneaking in measuring in addition, and this also helps to extract the base of 1/2 in the engine luggine signal humorous time.Because the Changing Pattern that is contained in the engine luggine signal that the acceleration transducer of cylinder body top records is consistent with the Changing Pattern that acts on the driving torque that engine shaft fastens, so can extract 1/2 basic humorous inferior frequency through analyzing the vibration signal that records on the cylinder body.

Because time domain is blocked and the frequency domain discretize; Block so long as not signal being carried out the complete cycle time domain; Harmonic signal carries out the resulting frequency of DFT, amplitude and phase place and all has error; Therefore, receive the influence of Fourier transform frequency resolution in the measurement of rotating speed, have 30 times frequency resolution tachometric survey error.For improving the precision of measurement of engine rotate speed, adopt 4 high energy barycenter correction methods of noiseproof feature that the engine of being tried to achieve is changeed and frequently proofread and correct, through calculating the higher engine speed of precision.

The object of the invention realizes through following technical scheme:

Use the vibration measurement method of the engine speed of 4 energy barycenter correction methods, it is characterized in that comprising the steps:

(1) coordinate system is set up: setting up coordinate system O-XYZ, is initial point O with engine and variator tie point, and Y axle forward points to crankshaft front end, and Z axle forward is confirmed X axle forward by the right-hand rule straight up;

(2) sensor installation: more smooth and sensor easy arrangement point place in the engine cylinder surface, 1 unidirectional acceleration transducer is installed, measurement direction be Z to; Sensor connects data acquisition unit, and data acquisition unit connects portable computer;

(3) on the threst stand or on the real vehicle, make engine with operate as normal rotating speed w operation, it is in 10s～20s that the data acquisition unit acquisition time is set, SF is f _s, sampling number N representes the data point number that discrete series comprises, and requires f _s=N=2 ^p, P=9,10 or 11, frequency resolution Δ f=f _s/ N=1, sampling time interval Δ t=1/f _sThrough the vibration acceleration signal of data acquisition unit collection and synchronous recording test point, and obtain time signal Z after the automatic average processing _n(t), Z _n(t) the vibration acceleration signal sequence of n point of table Z direction test point collection; Wherein n=0,1, Λ, N-1; T=n* Δ t;

(4) to burst Z _n(t), add Hanning window according to formula (1-1) The conversion of N point quick Fourier, obtain amplitude spectrum X ₁(f), real part spectrum R ₁(f), imaginary part spectrum I ₁(f), phase spectrum Φ ₁(f);

$\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{Z}_n\left(t\right)[0.5-0.5\cos \left(\frac{2\mathrm{\&pi;n}}{N}\right)]e^{-j\frac{2\mathrm{\&pi;}}{N}\mathrm{fn}}=R_1\left(f\right)+j{I}_1\left(f\right)=X_1\left(f\right)e^{j{\mathrm{\&Phi;}}_1\left(f\right)}$ $f=\mathrm{0,1},\mathrm{\&Lambda;},\frac{N}{2}-1---(1-1)$

Wherein $Z_n\left(t\right)=Z_n(n*\mathrm{\&Delta;\; t})=Z_n(n*\frac{1}{f_s}),$ J representes imaginary part.

(5) amplitude spectrum X ₁(f) the highest spectral line peak value X in ₁(f _i), corresponding frequency is f _i, substitution formula (1-2) is obtained power spectral value G (f _i); In like manner obtain frequency f _i-1 with corresponding power spectral value G (f _i-1), frequency f _i+ 1 with corresponding power spectral value G (f _i+ 1); Compare f then _iThe amplitude X of the correspondence of ± 2 these two spectral lines ₁(f _i+ 2) and X ₁(f _i-2), get both amplitude the greater frequency value corresponding and be defined as f _Max, corresponding power spectral value G (f _Max);

$G\left(f\right)=\frac{{\sin }^2\left(\mathrm{\&pi;f}\right)}{4{\mathrm{\&pi;}}^2{\left(f\right)}^2{[1-{\left(f\right)}^2]}^2}---(1-2)$

(6) four energy barycenter methods are meant for frequency f to be corrected _i, utilize frequency f _iPower spectral value G (f with correspondence _i), f _iAdjacent frequency f _i-1 with power spectral value G (f _i-1), f _i+ 1 with corresponding power spectral value G (f _i+ 1), f _MaxWith corresponding power spectral value G (f _Max), totally four frequency and corresponding power spectral value are come emending frequency f _iComputing method.To frequency f _iAdopt 4 energy barycenter correction methods (k=-1,0,1 and f _Max), substitution formula (1-3) obtains f _iFrequency values after the correction

$f_i^{*}=\frac{\underset{k=-1}{\overset{1}{\mathrm{\&Sigma;}}}(f_i+k)G(f_i+k)+f_{\mathrm{Max}}G\left(f_{\mathrm{Max}}\right)}{\underset{k=-1}{\overset{1}{\mathrm{\&Sigma;}}}G(f_i+k)+f_{\mathrm{Max}}G\left(f_{\mathrm{Max}}\right)}$ K round numbers (1-3)

(7) to amplitude spectrum X ₁(f) carry out auto-correlation according to formula (1-4) and calculate, obtain the autocorrelation function R of new frequency variable f ' _Xx(f ');

$R_{\mathrm{xx}}\left(f^{\&prime;}\right)=\frac{1}{\frac{N}{2}-1-f^{\&prime;}}\underset{f=1}{\overset{\frac{N}{2}-1-f^{\&prime;}}{\mathrm{\&Sigma;}}}{X}_1\left(f\right)X_1(f+f^{\&prime;})f^{\&prime;}=\mathrm{0,1},L,\frac{N}{2}-2---(1-4)$

(8) to autocorrelation function R _Xx(f '), (1-5) carries out according to formula

The Fast Fourier Transform (FFT) of point obtains time series ZZ _n(t);

${\mathrm{ZZ}}_n\left(t\right)=\underset{f^{\&prime;}=0}{\overset{\frac{N}{2}-1}{\mathrm{\&Sigma;}}}{Z}_n\left(f^{\&prime;}\right)e^{-j\frac{2\mathrm{\&pi;}}{N}{\mathrm{tf}}^{\&prime;}}$ $t=\mathrm{0,1}*\mathrm{\&Delta;t},\mathrm{\&Lambda;},(\frac{N}{2}-1)*\mathrm{\&Delta;t}---(1-5)$

(9) the time spectrum signal ZZ to obtaining _n(t), ZZ _n(t) the highest spectral line peak value ZZ in _n(t _i), time corresponding is t _i, substitution formula (1-2) is obtained power spectral value G (t _i); In like manner obtain time t _i-Δ t and corresponding power spectral value G (t _i-Δ t), time t _i+ Δ t and corresponding power spectral value G (t _i+ Δ t); Compare t then _iThe amplitude ZZ of the correspondence of these two spectral lines of ± 2* Δ t _n(t _i-2* Δ t) and ZZ _n(t _i+ 2* Δ t), get both amplitude the greater frequency value corresponding and be defined as t _Max, corresponding power spectral value G (t _Max); To time t _iAdopt 4 energy barycenter correction methods once more, substitution formula (1-6) obtains t _iValue after the correction

$t_i^{*}=\frac{\underset{k=-1}{\overset{1}{\mathrm{\&Sigma;}}}(t_i+k*\mathrm{\&Delta;\; t})G(t_i+k*\mathrm{\&Delta;\; t})+t_{\mathrm{Max}}G\left(t_{\mathrm{Max}}\right)}{\underset{k=-1}{\overset{1}{\mathrm{\&Sigma;}}}G(t_i+k*\mathrm{\&Delta;\; t})+G\left(t_{\mathrm{Max}}\right)}$ K round numbers (1-6)

(10) for Otto cycle engine; 1/2 humorous time is the most basic simple harmonic quantity, if can identify 1/2 humorous vibration frequency

of the rotating speed w of engine then also can obtain engine rapidly under the prerequisite of unknown engine cylinder number rotating speed.But real engine vibration; Except that the inertial excitation moment of bearing gas load and moving component; Also bearing other disturbance torques; So in the actual vibration signal; 1/2 humorous vibration frequency

is difficult to confirm occurrence, but frequency interval one is decided to be 1/2 humorous time.Therefore through amplitude spectrum X to vibration signal ₁(f) carry out autocorrelation analysis and obtain autocorrelation function R _Xx(f '); Frequency interval is that 1/2 humorous time relevant nature has determined the humorous inferior amplitude of 1/2 base to improve greatly; The amplitude that in like manner is spaced apart 1,1.5,2 etc. humorous times also can become obviously outstanding, and promptly each humorous composition is by interval R in the autocorrelation function of vibration signal amplitude spectrum of humorous time of 1/2 base _Xx(f ') arranges.To this signal R _XxWhen (f ') carried out Fourier transform again, signal obtained time series ZZ from frequency domain to time domain _n(t) in, this moment 1/2, base was humorous time

Time corresponding t after the Fourier transform _iThe amplitude of (in the Fourier transform, there are reciprocal relation in corresponding frequency and time) will become maximal value ZZ _n(t _i).Through maximizing ZZ _n(t _i) can find out time t _iBecause through behind the auto-correlation computation, time t _iNumerical value have slight error, so time

Right

The round number obtains whole humorous the L of frequency, obtains

1/2 humorous frequency value corresponding of rotating speed w Obtain engine speed

For realizing that further the object of the invention, described crankshaft front end are the end that bent axle connects belt pulley.

Described operate as normal rotating speed w is preferably 750r/min to 8000r/min.

With respect to prior art, the present invention has following advantage

The objective of the invention is defective, propose the measurement of engine rotate speed method of 4 energy barycenter correction methods of a kind of application, have following advantage to the available engine rotating speed measurement method:

(1) can solve the problem that to measure engine speed when engine cylinder number being foreseen, so versatility is better;

(2) through autocorrelation analysis and 4 energy barycenter correction methods to signal, the noiseproof feature of signal improves, and greatly reduces the revolution speed calculating mistake that the frequency identification error causes;

(3) through 4 energy barycenter correction methods, improve the tachometric survey precision, reduced the low tachometric survey error that causes of frequency resolution.

Description of drawings

Fig. 1 is amplitude spectrum X ₁(f) with the frequency after proofreading and correct

Change curve;

Fig. 2 is autocorrelation function R _Xx(f ') curve;

Fig. 3 is time series ZZ _n(t) with after proofreading and correct Change curve.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is further described, but embodiment of the present invention does not limit to so.

Use the vibration measurement method of the engine speed of 4 energy barycenter correction methods, comprise the steps:

(1) adopt acceleration transducer to obtain vibration acceleration signal from engine cylinder cover (or cylinder body);

(2) carry out FFT, obtain frequency spectrum;

(3) adopt 4 energy barycenter methods of discrete spectrum to carry out frequency correction to the spectrum of the maximum in frequency spectrum peak;

(4) amplitude spectrum is carried out autocorrelation analysis, make each humorous composition in the autocorrelation function of vibration signal amplitude spectrum, arrange, improve the signal to noise ratio (S/N ratio) of vibration signal simultaneously by the humorous inferior interval of 1/2 base;

(5) autocorrelation spectrum is carried out FFT once more, the composition that further outstanding 1/2 base is humorous time; Adopt 4 energy barycenter methods of discrete spectrum to proofread and correct, obtain the approximate value of 1/2 humorous secondary frequencies obtaining the humorous inferior composition of 1/2 base;

(6) the 3rd step of 1/2 humorous time frequency information evaluation algorithm of utilizing for the 5th step obtained is proofreaied and correct the corresponding engine in the spectrum peak that obtains humorous time;

(7) precise rotation after obtaining proofreading and correct.

Below in conjunction with embodiment the present invention is done further description, need to prove, embodiment does not constitute the qualification that the present invention is required protection domain.

Embodiment 1---engine bench test

The confirmatory experiment that carries out rotating speed identification at engine pedestal, rotating speed that records through this method of testing and German AVL TT&C system record the result and compare checking.

(1) coordinate system is set up: tested engine is the four-stroke-cycle BBG of unknown cylinder number, sets up coordinate system O-XYZ, is initial point O with engine and variator tie point, and Y axle forward points to crankshaft front end, and Z axle forward is confirmed X axle forward by the right-hand rule straight up;

(2) sensor installation: the PCB acceleration transducer is installed at the engine cylinder-body place of having an even surface, measurement direction be Z to; Sensor connects Miller shellfish nurse (BBM) MKII signal picker, and data acquisition unit connects portable computer;

(3) on threst stand, make engine with operate as normal rotating speed w=1500rpm operation, this rotating speed Germany AVL TT&C system records, and it is 20s that the data collector is provided with acquisition time, SF f _sWith sampling number N be f _s=N=2 ¹¹=2048, frequency resolution Δ f=f _s/ N=1, sampling time interval Δ t=1/f _s=1/2048; Through the vibration acceleration signal of data acquisition unit collection and synchronous recording test point, and obtain time signal Z after the automatic average processing _n(t), wherein n=0,1, Λ, 2047; T=n* Δ t;

(4) to burst Z _n(t), add 2048 point quick Fourier conversion of Hanning window, obtain amplitude spectrum X according to formula (1-1) ₁(f) as shown in Figure 1, this Fig. 1 curve representation in the 0-1400HZ frequency, amplitude spectrum X ₁(f) with the variation of frequency; To amplitude spectrum X ₁(f) the highest spectral line peak value X in ₁(f _i) corresponding frequency is f _i=50HZ, f _i-1=49HZ, f _i+ 1=51HZ, f _ibig amplitude person f in ± 2 _Max=48HZ, substitution formula (1-2) is obtained power spectrum G (50), G (49), G (51) and G (48) respectively, and substitution formula (1-3) adopts 4 energy barycenter correction methods, the frequency values after obtaining proofreading and correct $f_i^{*}=50.011\mathrm{HZ}$

(5) to amplitude spectrum X ₁(f) carry out auto-correlation according to formula (1-4) and calculate, obtain the autocorrelation function R of new frequency variable f ' _Xx(f ') is as shown in Figure 2; The figure shows autocorrelation function R _Xx(f ') is with new frequency variable f ' variation diagram.

(6) to autocorrelation function R _Xx(f '), (1-5) carries out according to formula The Fast Fourier Transform (FFT) of point obtains time series ZZ _n(t) change curve of t is as shown in Figure 3 in time; To ZZ _n(t) the highest spectral line peak value time corresponding is t in _i=0.07987s, t-Δ t=0.07938s, t+ Δ t=0.08036s, the ZZ that t ± 2 Δ t are corresponding _n(t) amplitude higher value t _Max=0.07889, substitution formula (1-2) is obtained power spectrum G (0.07987), G (0.07938), G (0.08036) and G (0.07889) respectively, and substitution formula (1-3) adopts 4 energy barycenter correction methods, the value after obtaining proofreading and correct As shown in Figure 3;

(7) according in the Fourier transform; There are reciprocal relation in corresponding frequency and time; Promptly

therefore

round number obtain L=4, can obtain

(8) obtain the rotating speed of engine

When the multiple relation of engine speed w and humorous f existence 60 of engine, promptly when rotating speed was w (r/min), corresponding engine changeed first humorous f frequently ₁=w/60Hz, second humorous f ₂=w/30Hz, 1/2 humorous time is first humorous time 1/2 times, therefore is

For verifying the validity of this algorithm; In whole test, use the general measurement of rotating speed equipment of automobile industry---German AVL TT&C system simultaneously; Carry out tachometric survey, listed German AVL TT&C system in the table 1 and recorded rotating speed result and the contrast of this method test method results:

Table 1 engine pedestal experiment tachometer value contrast (rpm)

Embodiment 1 records contrast verification as a result through rotating speed and the German AVL TT&C system that this method of testing records; Explained that the present invention can solve when foreseeing engine cylinder number; And can not measure the problem of engine speed, and test rotating speed versatility is better, noiseproof feature is high, the result is accurately reliable.

Claims (3)

1. use the vibration measurement method of the engine speed of 4 energy barycenter correction methods, it is characterized in that comprising the steps:

(1) coordinate system is set up: setting up coordinate system O-XYZ, is initial point O with engine and variator tie point, and Y axle forward points to crankshaft front end, and Z axle forward is confirmed X axle forward by the right-hand rule straight up;

(2) sensor installation: 1 unidirectional acceleration transducer is installed at the engine cylinder-body place of having an even surface, measurement direction be Z to; Sensor connects data acquisition unit, and data acquisition unit connects portable computer;

(3) on the threst stand or on the real vehicle, make engine with operate as normal rotating speed w operation, it is in 10s～20s that the data acquisition unit acquisition time is set, SF is f _s, sampling number N representes the data point number that discrete series comprises, and requires f _s=N=2 ^p, P=9,10 or 11, frequency resolution Δ f=f _s/ N=1, sampling time interval Δ t=1/f _sThrough the vibration acceleration signal of data acquisition unit collection and synchronous recording test point, and obtain time signal Z after the automatic average processing _n(t), Z _n(t) the vibration acceleration signal sequence of n point of table Z direction test point collection; Wherein n=0,1, Λ, N-1; T=n* Δ t;

(4) to burst Z _n(t), add Hanning window according to formula (1-1) The conversion of N point quick Fourier, obtain amplitude spectrum X ₁(f), real part spectrum R ₁(f), imaginary part spectrum I ₁(f), phase spectrum Φ ₁(f);

$\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{Z}_n\left(t\right)[0.5-0.5\cos \left(\frac{2\mathrm{\&pi;n}}{N}\right)]e^{-j\frac{2\mathrm{\&pi;}}{N}\mathrm{fn}}=R_1\left(f\right)+j{I}_1\left(f\right)=X_1\left(f\right)e^{j{\mathrm{\&Phi;}}_1\left(f\right)}$ $f=\mathrm{0,1},\mathrm{\&Lambda;},\frac{N}{2}-1$

$(1-1)$

Wherein $Z_n\left(t\right)=Z_n(n*\mathrm{\&Delta;\; t})=Z_n(n*\frac{1}{f_s})$

(5) amplitude spectrum X ₁(f) the highest spectral line peak value X in ₁(f _i), corresponding frequency is f _i, substitution formula (1-2) is obtained power spectral value G (f _i); In like manner obtain frequency f _i-1 with corresponding power spectral value G (f _i-1), frequency f _i+ 1 with corresponding power spectral value G (f _i+ 1); Compare f then _iThe amplitude X of the correspondence of ± 2 these two spectral lines ₁(f _i+ 2) and X ₁(f _i-2), get both amplitude the greater frequency value corresponding and be defined as f _Max, corresponding power spectral value G (f _Max);

$G\left(f\right)=\frac{{\sin }^2\left(\mathrm{\&pi;f}\right)}{4{\mathrm{\&pi;}}^2{\left(f\right)}^2{[1-{\left(f\right)}^2]}^2}---(1-2)$

(6) to frequency f _iAdopt 4 energy barycenter correction methods, substitution formula (1-3) obtains f _iFrequency values after the correction

$f_i^{*}=\frac{\underset{k=-1}{\overset{1}{\mathrm{\&Sigma;}}}(f_i+k)G(f_i+k)+f_{\mathrm{Max}}G\left(f_{\mathrm{Max}}\right)}{\underset{k=-1}{\overset{1}{\mathrm{\&Sigma;}}}G(f_i+k)+f_{\mathrm{Max}}G\left(f_{\mathrm{Max}}\right)}$ K round numbers (1-3)

(7) to amplitude spectrum X ₁(f) carry out auto-correlation according to formula (1-4) and calculate, obtain the autocorrelation function R of new frequency variable f ' _Xx(f ');

$R_{\mathrm{xx}}\left(f^{\&prime;}\right)=\frac{1}{\frac{N}{2}-1-f^{\&prime;}}\underset{f=1}{\overset{\frac{N}{2}-1-f^{\&prime;}}{\mathrm{\&Sigma;}}}{X}_1\left(f\right)X_1(f+f^{\&prime;})f^{\&prime;}=\mathrm{0,1},L,\frac{N}{2}-2---(1-4)$

(8) to autocorrelation function R _Xx(f '), (1-5) carries out according to formula

The Fast Fourier Transform (FFT) of point obtains time spectrum burst ZZ _n(t);

${\mathrm{ZZ}}_n\left(t\right)=\underset{f^{\&prime;}=0}{\overset{\frac{N}{2}-1}{\mathrm{\&Sigma;}}}{Z}_n\left(f^{\&prime;}\right)e^{-j\frac{2\mathrm{\&pi;}}{N}{\mathrm{tf}}^{\&prime;}}$ $t=\mathrm{0,1}*\mathrm{\&Delta;t},\mathrm{\&Lambda;},(\frac{N}{2}-1)*\mathrm{\&Delta;t}---(1-5)$

(9) the time spectrum burst ZZ to obtaining _n(t), with ZZ _n(t) the highest spectral line peak value ZZ in _n(t _i) time corresponding t _iSubstitution formula (1-2) is obtained power spectral value G (t _i); In like manner obtain time t _i-Δ t and corresponding power spectral value G (t _i-Δ t), time t _i+ Δ t and corresponding power spectral value G (t _i+ Δ t); Compare t then _iThe amplitude ZZ of the correspondence of these two spectral lines of ± 2* Δ t _n(t _i-2* Δ t) and ZZ _n(t _i+ 2* Δ t), get both amplitude the greater frequency value corresponding and be defined as t _Max, corresponding power spectral value G (t _Max); To time t _iAdopt 4 energy barycenter correction methods once more, substitution formula (1-6) obtains t _iTime after the correction

$t_i^{*}=\frac{\underset{k=-1}{\overset{1}{\mathrm{\&Sigma;}}}(t_i+k*\mathrm{\&Delta;\; t})G(t_i+k*\mathrm{\&Delta;\; t})+t_{\mathrm{Max}}G\left(t_{\mathrm{Max}}\right)}{\underset{k=-1}{\overset{1}{\mathrm{\&Sigma;}}}G(t_i+k*\mathrm{\&Delta;\; t})+G\left(t_{\mathrm{Max}}\right)}$ K round numbers (1-6)

(10) time

obtains L to

round number, and 1/2 humorous the frequency value corresponding

that obtains

rotating speed w obtains engine speed

2. the vibration measurement method of the engine speed of 4 energy barycenter correction methods of application according to claim 1 is characterized in that: described crankshaft front end is the end that bent axle connects belt pulley.

3. the vibration measurement method of the engine speed of 4 energy barycenter correction methods of application according to claim 1 is characterized in that: described operate as normal rotating speed w is 750r/min to 8000r/min.

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