CN101975634A - Engine excitation force measurement method employing window length varying phase difference correction method - Google Patents

Abstract

The invention discloses an engine excitation force measurement method employing a window length varying phase difference correction method. In the method, signal frequency error of an engine excitation frequency interval is solved by utilizing phase difference produced by adding Hanning with different time lengths during signal processing after a vibration acceleration signal on the surface or a suspension point of an engine cylinder is discretely sampled, and the signal frequency error is used for solving actual excitation frequency f, amplitude information and phase information of an engine in a vibration displacement frequency spectrum, so that the vibration displacement vector value in an excitation force measurement formula is accurately obtained and combined with other known engine parameters to calculate the excitation force F (f). The method of the invention can solve the problem that due to the lack of accurate phase information during the engine excitation force measurement, a complex non-linear equation needs to be solved.

Description

Use the engine exciting force measuring method that changes the correction method of window appearance potential difference

Technical field

This aspect relates to power machine and signal Processing field, specifically is a kind of frequency, amplitude, phase method for position of accurate identification of Engine vibration signal, is applied to the identification of engine exciting force.

Background technology

The exciting force of engine mainly is to obtain by the rigid dynamics Model Calculation at present, the excitation that the principal element of considering in calculating is a gas burst power in the cylinder, rotating inertia force and reciprocal inertia force produced.The major defect of this method is need to obtain precise parameters, and the accurate acquisition of some parameter is very difficult, the moment resulting from sidesway that causes as gas burst etc.On the other hand, in actual conditions, engine always links to each other with many annexes, and theoretical calculation formula is not considered the coupling of engine and these annexes usually, this will inevitably cause result of calculation and engineering is actual that certain deviation is arranged, and deviation can be very big in some cases.

In application of practical project, method is by experiment obtained the engine exciting force and is studied by numerous scholars, and this is the problem of typically inverting, and normally adopts the frequency response function matrix method of inverting.But in the vibration control problem of engine, what need is the equivalent force and the equivalent moment at Motor Mass Centre place, owing to can't directly apply excitation at the barycenter place, also the reciprocity method is used in the response that can't directly obtain the barycenter place, therefore can't record transport function, cause the frequency response function matrix method of inverting in the engine exciting force is measured, can't directly use.On the other hand, concerning the exciting force at Motor Mass Centre place was measured, the frequency response function matrix method of inverting was too complicated comparatively speaking.

External scholar J.S.TAO, G.R.LIU and K.Y.LAM etc. has proposed a kind of method (J.S.TAO that measures Motor Mass Centre place exciting force, G.R.LIU and K.Y.LAM is in 2001 articles of delivering on periodical " Journal of Sound and Vibration " " Excitation force identification of an engine with velocity data at mounting points "), point out the amplitude and the phase information of the three-way vibration velocity spectrum at each suspension point place of engine of measuring by extraction, can rebuild the exciting force of engine accurately, the exciting force measure equation

But this method is when extracting phase information, usually can't obtain absolute phase information, therefore proposed only to utilize phase differential to obtain the method for exciting force, and this processing has been introduced and the measurement identical phase variant of counting that suspends, the non-linear overdetermined equation that makes finding the solution of problem become to find the solution a complexity has increased the complicacy of finding the solution.

Summary of the invention

The objective of the invention is defective at existing recognition methods, the engine exciting force measuring method that a kind of application changes the correction method of window appearance potential difference is proposed, solve for want of accurate phase information in the measurement of engine exciting force, and need find the solution the problem of complex nonlinear equation.

The object of the invention is achieved through the following technical solutions:

A kind of application changes the engine exciting force measuring method of window appearance potential difference correction method, comprises the steps:

(1) coordinate system is set up with correlation parameter and is collected: utilize the engine moment inertia experiment table, test out engine quality m, Motor Mass Centre O, with O is that initial point is set up coordinate system O-XYZ, the Y-axis forward points to crankshaft free-end, and Z axle forward is determined the X-axis forward by the right-hand rule straight up; Utilize the engine moment inertia experiment table to test out the moment of inertia J of engine again around the coordinate system X-axis _x, Y-axis moment of inertia J _y, the Z axle moment of inertia J _z, engine is to the product of inertia J of X-axis and Y-axis _Xy, to the inertia J of Y-axis and Z axle _Yz, to the inertia J of Z axle and X-axis _ZxForm the engine quality matrix M;

(2) obtain the multiple stiffness matrix that suspends: with engine by mount supports at threst stand; Determine engine mounting number h, h=3 or h=3; In the coordinate system O-XYZ of engine, give the label that suspends according to the descending order of directions X, be defined as first suspend, second suspend ... h suspends, and with the elastic body test macro the multiple stiffness characteristics that respectively suspends is tested, and obtains the first multiple rigidity that suspends

The second multiple rigidity that suspends

The multiple rigidity that h suspends

Form the multiple stiffness matrix K that suspends ^*=[K ^* ₁K ^* ₂K ^* _h];

(3) sensor installation: on the different test points of engine cylinder surface or suspension point, L three-dimensional acceleration transducer is installed, L 〉=3, each test point is installed a three-dimensional acceleration transducer; Sensor connects data acquisition unit, and data acquisition unit connects portable computer; In the coordinate system O-XYZ of engine, determine that according to the descending order of directions X the coordinate of three-dimensional acceleration transducer is respectively [x ₁y ₁z ₁], [x ₂y ₂z ₂] ..., [x _Ly _Lz _L];

(4) on threst stand, setting engine moves with operate as normal rotating speed w, after treating that operating mode is stable, the acquisition time in 10s～30s, the vibration acceleration signal X of X-axis forward, Y-axis forward and Z axle forward by data acquisition unit collection and each test point of synchronous recording _1n, X _2nX _LnY _1n, Y _2nY _LnZ _1n, Z _2nZ _LnX wherein _1nBe the vibration acceleration signal sequence with n point of the first test point X-axis forward collection, X _LnBe n the vibration acceleration signal sequence of putting that L test point X-axis forward is gathered, Y _1nBe n the vibration acceleration signal sequence of putting that the first test point Y-axis forward is gathered, X _LnThe vibration acceleration signal sequence of n the point that L test point Y-axis forward is gathered; Z _1nBe n the vibration acceleration signal sequence of putting that the first test point Z axle forward is gathered, Z _LnThe vibration acceleration signal sequence of n the point that L test point Z axle forward is gathered; Sample frequency f _s, sampling number N represents the data point number that discrete series comprises, wherein n=0,1 ..., N-1, require f _s=N=2 ^p, P=9 or 10, frequency resolution Δ f=f _s/ N=1;

(6) according to formula

Measure the engine exciting force, wherein:

Exciting force F (f) be mean engine under humorous excitation frequency f of rotating speed w η, the exciting force F of engine X-axis forward _x(f), around the excitation torque M of X-axis _x(f), the exciting force F of Y direction _y(f), around the excitation torque M of Y-axis _y(f), the exciting force F of Z-direction _z(f), around the excitation torque M of Z axle _z(f);

K ^*＝[K ^* ₁?K ^* ₂…K ^* _h]

$M=\left[\begin{array}{cccccc}m& & & & & \\ & m& & & & \\ & & m& & & \\ & & & J_x& -J_{\mathrm{xy}}& -J_{\mathrm{zx}}\\ & & & -J_{\mathrm{xy}}& J_y& -J_{\mathrm{yz}}\\ & & & {-J}_{\mathrm{zx}}& -J_{\mathrm{yz}}& J_z\end{array}\right]$

$\stackrel{\‾}{E}=\left[\begin{array}{cccccc}1& 0& 0& 0& z_1& -y_1\\ 0& 1& 0& -z_1& 0& x_1\\ 0& 0& 1& y_1& -x_1& 0\\ 1& 0& 0& 0& z_2& -y_2\\ 0& 1& 0& {-z}_2& 0& x_2\\ 0& 0& 1& y_2& -x_2& 0\\ \·& \·& \·& \·& \·& \·\\ \·& \·& \·& \·& \·& \·\\ \·& \·& \·& \·& \·& \·\\ 1& 0& 0& 0& z_3& -y_3\\ 0& 1& 0& {-z}_3& 0& x_3\\ 0& 0& 1& y_3& -x_3& 0\end{array}\right]$

$f=\frac{1}{3L}(f_{1x}+f_{1y}+f_{1z}+f_{2x}+f_{2y}+f_{2z}+\·\·\·+f_{\mathrm{Lx}}+f_{\mathrm{Ly}}+f_{\mathrm{Lz}})$

$\stackrel{\‾}{S}\left(f\right)={\left[\begin{array}{cccccccc}{\mathrm{dX}}_1& d{Y}_1& {\mathrm{dZ}}_1& {\mathrm{dX}}_2& {\mathrm{dY}}_2& {\mathrm{dZ}}_2\·\·\·{\mathrm{dX}}_L& {\mathrm{dY}}_L& {\mathrm{dZ}}_L\end{array}\right]}^T$

Representing matrix

Transposition;

Humorous excitation frequency f of η and its corresponding transposed matrix

Determine by the following method:

Humorous the η that selects the engine exciting force to analyze, η=0.5,1,1.5,2,2.5 or 3; Behind humorous time of the η of designated analysis engine speed w, carry out following computing:

Vibration acceleration signal sequence X to the first test point X-axis forward collection with n point _1n, add Hanning window (Hanning) w (t) 0≤t≤T of time length T=1, carry out N point quick Fourier conversion (FFT) according to formula (1-1), obtain amplitude spectrum X ₁(f); To X _1nAdd time length

Hanning window (Hanning) w (t) 0≤t≤T carries out N/2 point quick Fourier conversion (FFT) according to formula (1-2), obtains amplitude spectrum X ₂(f);

$X_1\left(f\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}{x}_n[0.5-0.5\cos \left(\frac{2\mathrm{\πn}}{N}\right){]e}^{-j\frac{2\mathrm{\π}}{N}\mathrm{fn}}=R_1\left(f\right)+{\mathrm{jI}}_1\left(f\right)=y_1\left(f\right)e^{j{\mathrm{\Φ}}_1\left(f\right)}$ $f=\mathrm{0,1},\·\·\·,\frac{N}{2}-1---(1-1)$

$X_2\left(f\right)=\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{x}_n[0.5-0.5\cos \left(\frac{4\mathrm{\πn}}{N}\right){]e}^{-j\frac{4\mathrm{\π}}{N}\mathrm{fn}}=R_2\left(f\right)+{\mathrm{jI}}_2\left(f\right)=y_2\left(f\right)e^{j{\mathrm{\Φ}}_2\left(f\right)}$ $f=\mathrm{0,1},2\·\·\·,\frac{N}{4}-1---(1-2)$

According to engine speed w, determine emending frequency interval [f ₁, f ₂], wherein

Round numbers; Round numbers;

At emending frequency interval [f ₁, f ₂] in, X ₁(f) peak-peak respective frequencies f _i, f _iReal part is R ₁(f _i), imaginary part is I ₁(f _i), phase place is Φ ₁(f _i), amplitude is y ₁(f _i); X ₂(f) peak-peak frequency f _j, phase place is Φ ₂(f _j); If emending frequency interval [f ₁, f ₂] interior peak-peak actual frequency is f ₀, f ₀Corresponding true phase place

True amplitude A ₀(f ₀); If f _iFrequency error be

f _iWith actual frequency f ₀Difference

For people's formula (1-3), obtain frequency error

$\▿f=-2{[\mathrm{\Φ}}_1\left(f_i\right)-{\mathrm{\Φ}}_2\left(f_j\right)-\frac{\mathrm{\π}(2f_i-f_j)}{2}]/\mathrm{\π}---(1-3)$

Calculate actual frequency f ₀

Calculate true phase place

The spectral function of Hanning window (Hanning)

Calculate amplitude A after the correction according to formula (1-6) ₀(f ₀), form actual frequency f ₀Acceleration with correspondence

To sequence X _2nX _LnY _1n, Y _2nY _LnZ _1n, Z _2nZ _LnWith the vibration acceleration signal sequence X _1nCarry out same processing, obtain the humorous inferior excitation frequency f of engine speed w η respectively _2xF _Lxf _1y, f _2yF _Lyf _1z, f _2zF _Lz

(1≤H≤L), the engine excitation frequency that records its directions X is f for any sensor H in L the sensor test point _Hx, corresponding acceleration is The engine excitation frequency that records the Y direction is f _Hy, corresponding acceleration is

The engine excitation frequency that records the Z direction is f _Hz, corresponding acceleration is

The directions X displacement of sensor H is dX _H, the displacement of Y direction is dY _H, the displacement of Z direction is dZ _H,

Obtain the transposed matrix of sensor H thus:

The excitation frequency of L sensor

And corresponding transposed matrix

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

Described engine is defined as suspension point with the contact point that suspends that supports it.

Described operate as normal rotating speed w is preferably 750r/min to 5500r/min; Described operating mode is stable to be meant that the engine speed fluctuation is in 20r/min.

Described engine moment inertia experiment table preferably adopts three string pendulum method of testing experiment tablees.

The present invention only needs the value by conversion η, η=0.5,1,1.5,2,2.5,3 to the exciting force test of different humorous the η of engine; Calculate different frequency refinement interval [f ₁, f ₂], recalculate this excitation frequency f and corresponding transposed matrix of humorous time

Solve humorous the exciting force F of η (f) of engine speed w.

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

The present invention is by after sampling to the vibration displacement signal discrete on engine cylinder surface or the suspension point, the phase differential that adds the Hanning window (Hanning) of different time length and produce, utilize precise frequency, amplitude and the phase information of each response point vibration signal of this phase difference correction, thereby improve the measuring accuracy of exciting force.The present invention is in conjunction with J.S.TAO, the exciting force measure equation that G.R.LIU and K.Y.LAM proposes

Middle K ^*, M,

Method for solving proposes to use the correction method of change window appearance potential difference and accurately extracts transposed matrix

In frequency, amplitude and phase information, improved and utilized the phase differential method to calculate Method, avoided finding the solution of problem having been become the non-linear overdetermined equation of finding the solution a complexity because of utilizing the phase differential method, improved and found the solution

Precision and efficient, and improved the simplicity that F (f) finds the solution.

Embodiment:

The invention will be further described below in conjunction with embodiment, need to prove, embodiment does not constitute the qualification to the claimed scope of the present invention.

Embodiment 1

(1) utilize three-way pendulum engine rotary inertia experimental bench to test out: certain 1.8L in-line four cylinder engine quality m, Motor Mass Centre O is that initial point is set up coordinate system O-XYZ with barycenter O; And then test out the moment of inertia J of engine around the coordinate system X-axis _x, Y-axis moment of inertia J _y, the Z axle moment of inertia J _z, engine is to the product of inertia J of X-axis and Y-axis _Xy, to the inertia J of Y-axis and Z axle _Yz, to the inertia J of Z axle and X-axis _Zx, form the engine quality matrix M;

$M=\left[\begin{array}{cccccc}m& & & & & \\ & m& & & & \\ & & m& & & \\ & & & J_x& -J_{\mathrm{xy}}& -J_{\mathrm{zx}}\\ & & & -J_{\mathrm{xy}}& J_y& -J_{\mathrm{yz}}\\ & & & {-J}_{\mathrm{zx}}& -J_{\mathrm{yz}}& J_z\end{array}\right]=\left[\begin{array}{cccccc}80\mathrm{kg}& & & & & \\ & 80\mathrm{kg}& & & & \\ & & 80\mathrm{kg}& & & \\ & & & {7.5\mathrm{kgm}}^2& {1.5\mathrm{kgm}}^2& -0.5\mathrm{kg}{m}^2\\ & & & {1.5\mathrm{kgm}}^2& 3.5{\mathrm{kgm}}^2& 1\mathrm{kg}{m}^2\\ & & & -0.5\mathrm{kg}{m}^2& {1\mathrm{kgm}}^2& {6\mathrm{kgm}}^2\end{array}\right]$

(2) determine engine mounting number h, h=3; In the coordinate system O-XYZ of engine, give the label that suspends according to the descending order of directions X, be defined as and suspend 1, suspend 2 ... the h that suspends adopts German MTS831 type elastic body test system and test to go out the multiple rigidity that respectively suspends, and forms the multiple stiffness matrix K that suspends ^*=[k ^* ₁K ^* ₂K ^* ₃]=[be N/m (70000+7000j) N/m (80000+8000j) N/m (75000+7500j)];

(3) 1.8L in-line four cylinder engine is installed on the German FEV threst stand, adopts CPB three-dimensional acceleration transducer, number L=3 is arranged in the suspension point place.Measure the coordinate of 3 sensor test points by three-coordinates measuring machine, form the test point coordinate matrix

$\stackrel{\‾}{E}=\left[\begin{array}{cccccc}1& 0& 0& 0& z_1& -y_1\\ 0& 1& 0& {-z}_1& 0& x_1\\ 0& 0& 1& y_1& -x_1& 0\\ 1& 0& 0& 0& z_2& -y_2\\ 0& 1& 0& -z_2& 0& x_2\\ 0& 0& 1& y_2& -x_2& 0\\ 1& 0& 0& 0& z_3& -y_3\\ 0& 1& 0& -z_3& 0& x_3\\ 0& 0& 1& y_3& -x_3& 0\end{array}\right]=\left[\begin{array}{cccccc}1& 0& 0& 0& 0.1& -0.3\\ 0& 1& 0& -0.1& 0& 0\\ 0& 0& 1& 0.3& 0& 0\\ 1& 0& 0& 0& -0.2& 0.2\\ 0& 1& 0& 0.2& 0& 0.12\\ 0& 0& 1& -0.2& 0.12& 0\\ 1& 0& 0& 0& -0.2& 0.2\\ 0& 1& 0& 0.2& 0& 0.12\\ 0& 0& 1& -0.2& -0.12& 0\end{array}\right]$

(4) input of CPB three-dimensional acceleration transducer is the data acquisition system (DAS) of German Miller shellfish nurse (BBM) testing apparatus, and data acquisition signal input portable computer is by the PAK test analysis software of installing on the portable computer, real-time monitored and tracer signal;

(5) on threst stand, set engine with certain operate as normal rotating speed w=1815rpm operation, treat the stable back of operating mode (being that the fluctuation of speed is in 20r/min), the beginning image data, the data acquisition system (DAS) of German Miller shellfish nurse (BBM) testing apparatus imported signal by CPB three-dimensional acceleration transducer, by PAK test analysis software, real-time monitored and the tracer signal of installing on the portable computer.Acquisition time length is 30s; Sample frequency f _s=512, sampling number N=512, then frequency resolution Δ f=f _s/ N=1, the vibration acceleration signal X of X-axis forward, Y-axis forward and Z axle forward by data acquisition unit collection and each test point of synchronous recording _1n, X _2n, X _3nY _1n, Y _2n, Y _3nZ _1n, Z _2n, Z _3nWherein n=0,1 ..., N-1; To vibration acceleration signal X _1n, X _2n, X _3nY _1n, Y _2n, Y _3nZ _1n, Z _2n, Z _3nCarry out the conversion of N=512 point fast Fourier.

According to engine speed w=1815rpm, determine frequency separation [f ₁, f ₂], the refinement interval of 0.5 humorous excitation frequency f of engine speed w is f ₁=10HZ and f ₂=20HZ; 1 humorous time refinement interval is f ₁=25HZ and f ₂=35HZ; 1.5 humorous time refinement interval is f ₁=40HZ and f ₂=50HZ; 2 humorous times refinement interval is f ₁=55HZ and f ₂=65HZ; 2.5 humorous time refinement interval is f ₁=71HZ and f ₂=81HZ; 3 humorous times refinement interval is f ₁=86HZ and f ₂=96HZ; To each frequency separation [f ₁, f ₂], to use to change window appearance potential difference method, concrete steps are carried out according to formula (1-1) to (1-7).

3), only list 1 humorous time and 2 humorous times the excitation frequency f of engine speed w here, the 1 humorous secondary frequencies interval [f of engine speed w owing to the length relation ₁, f ₂]=[25,35], use to change window appearance potential difference method, obtain 3 sensor correspondences the excitation frequency f and the acceleration of test point separately As shown in table 1; The 2 humorous secondary frequencies interval [f of engine speed w ₁, f ₂]=[55,65], use to change window appearance potential difference method, obtain 3 sensor correspondences the excitation frequency f and the acceleration of test point separately

As shown in table 2;

1 humorous secondary frequencies and the acceleration of table 1 engine speed w

2 humorous secondary frequencies and the accelerations of table 2 engine speed w

Obtain thus: when

The time,

Transposed matrix Wherein:

$\left[\begin{array}{ccc}{\mathrm{dX}}_1& d{Y}_1& {\mathrm{dZ}}_1\end{array}\right]=\left[\begin{array}{ccc}\frac{-1}{2\mathrm{\π}*30.25}0.174e^{-179.37j}& \frac{-1}{2\mathrm{\π}*30.25}0.0491e^{179.42j}& \frac{-1}{2\mathrm{\π}*30.25}0.4436e^{0.48j}\end{array}\right]$

$\left[\begin{array}{ccc}{\mathrm{dX}}_2& d{Y}_2& {\mathrm{dZ}}_2\end{array}\right]=\left[\begin{array}{ccc}\frac{-1}{2\mathrm{\π}*30.25}0.0518e^{1.81j}& \frac{-1}{2\mathrm{\π}*30.25}0.1887e^{1.08j}& \frac{-1}{2\mathrm{\π}*30.25}0.0417e^{-176.19j}\end{array}\right]$

$\left[\begin{array}{ccc}{\mathrm{dX}}_3& d{Y}_3& {\mathrm{dZ}}_3\end{array}\right]=\left[\begin{array}{ccc}\frac{-1}{2\mathrm{\π}*30.25}0.0518e^{1.81j}& \frac{-1}{2\mathrm{\π}*30.25}0.4715e^{0.56j}& \frac{-1}{2\mathrm{\π}*30.25}0.3353e^{-176.7j}\end{array}\right]$

When

The time,

Transposed matrix

Wherein:

$\left[\begin{array}{ccc}{\mathrm{dX}}_1& d{Y}_1& {\mathrm{dZ}}_1\end{array}\right]=\left[\begin{array}{ccc}\frac{-1}{2\mathrm{\π}*60.5}0.2061e^{0.17j}& \frac{-1}{2\mathrm{\π}*60.5}0.1592e^{0.25j}& \frac{-1}{2\mathrm{\π}*60.5}1.1794e^{0.06j}\end{array}\right]$

$\left[\begin{array}{ccc}{\mathrm{dX}}_2& d{Y}_2& {\mathrm{dZ}}_2\end{array}\right]=\left[\begin{array}{ccc}\frac{-1}{2\mathrm{\π}*60.5}1.7755e^{-179.79j}& \frac{-1}{2\mathrm{\π}*60.5}0.3839e^{-179.93j}& \frac{-1}{2\mathrm{\π}*60.5}2.877{1e}^{0.12j}\end{array}\right]$

$\left[\begin{array}{ccc}{\mathrm{dX}}_3& d{Y}_3& {\mathrm{dZ}}_3\end{array}\right]=\left[\begin{array}{ccc}\frac{-1}{2\mathrm{\π}*60.5}1.7755e^{-179.79j}& \frac{-1}{2\mathrm{\π}*60.5}0.5075e^{-0.15j}& \frac{-1}{2\mathrm{\π}*60.5}0.1938e^{-179.53j}\end{array}\right]$

(7) fundamental formular of measuring according to the engine exciting force Wherein:

For the mass matrix M among the people (1), the multiple stiffness matrix K that suspends in (2) ^*, the measuring point coordinates matrix in (3)

When asking 1 humorous exciting force of engine speed w, for people f=30.25HZ and

1 humorous exciting force obtaining engine start machine rotating speed w is as shown in table 3; When asking 2 humorous exciting forces of engine speed w, for people f=60.5HZ and

2 humorous exciting forces obtaining engine start machine rotating speed w are as shown in table 4;

1 humorous exciting force of table 3 engine speed w

2 humorous exciting forces of table 4 engine speed w

Embodiment 1 has illustrated that the present invention is by after sampling to the vibration displacement signal discrete on engine cylinder surface or the suspension point, the phase differential that adds the Hanning window (Hanning) of different time length and produce, utilize precise frequency, amplitude and the phase information of each response point vibration signal of this phase difference correction, thereby improve the measuring accuracy of exciting force.

Claims (5)

1. use the engine exciting force measuring method that changes the correction method of window appearance potential difference, it is characterized in that comprising the steps:

(1) coordinate system is set up with correlation parameter and is collected: utilize the engine moment inertia experiment table, test out engine quality m, Motor Mass Centre O, with O is that initial point is set up coordinate system O-XYZ, the Y-axis forward points to crankshaft free-end, and Z axle forward is determined the X-axis forward by the right-hand rule straight up; Utilize the engine moment inertia experiment table to test out the moment of inertia J of engine again around the coordinate system X-axis _x, Y-axis moment of inertia J _y, the Z axle moment of inertia J _z, engine is to the product of inertia J of X-axis and Y-axis _Xy, to the inertia J of Y-axis and Z axle _Yz, to the inertia J of Z axle and X-axis _Zx, form the engine quality matrix M;

(2) obtain the multiple stiffness matrix that suspends: with engine by mount supports at threst stand; Determine engine mounting number h, h=3 or h=3; In the coordinate system O-XYZ of engine, give the label that suspends according to the descending order of directions X, be defined as first suspend, second suspend ... h suspends, and with the elastic body test macro the multiple stiffness characteristics that respectively suspends is tested, and obtains the first multiple rigidity that suspends

The second multiple rigidity that suspends

The multiple rigidity that h suspends

Form the multiple stiffness matrix K that suspends ^*=[K ^* ₁K ^* ₂K ^* _h];

(3) sensor installation: on the different test points of engine cylinder surface or suspension point, L three-dimensional acceleration transducer is installed, L 〉=3, each test point is installed a three-dimensional acceleration transducer; Sensor connects data acquisition unit, and data acquisition unit connects portable computer; In the coordinate system O-XYZ of engine, determine that according to the descending order of directions X the coordinate of three-dimensional acceleration transducer is respectively [x ₁y ₁z ₁], [x ₂y ₂z ₂] ..., [x _Ly _Lz _L];

(4) on threst stand, setting engine moves with operate as normal rotating speed w, after treating that operating mode is stable, the acquisition time in 10s～30s, the vibration acceleration signal X of X-axis forward, Y-axis forward and Z axle forward by data acquisition unit collection and each test point of synchronous recording _1n, X _2nX _LnY _1n, Y _2nY _LnZ _1n, Z _2nZ _LnX wherein _1nBe the vibration acceleration signal sequence with n point of the first test point X-axis forward collection, X _LnBe n the vibration acceleration signal sequence of putting that L test point X-axis forward is gathered, Y _1nBe n the vibration acceleration signal sequence of putting that the first test point Y-axis forward is gathered, X _LnThe vibration acceleration signal sequence of n the point that L test point Y-axis forward is gathered; Z _1nBe n the vibration acceleration signal sequence of putting that the first test point Z axle forward is gathered, Z _LnThe vibration acceleration signal sequence of n the point that L test point Z axle forward is gathered; Sample frequency f _s, sampling number N represents the data point number that discrete series comprises, wherein n=0,1 ..., N-1, require f _s=N=2 ^p, P=9 or 10, frequency resolution Δ f=f _s/ N=1;

(5) according to formula

Measure the engine exciting force, wherein: Exciting force F (f) be mean engine under humorous excitation frequency f of rotating speed w η, the exciting force F of engine X-axis forward _x(f), around the excitation torque M of X-axis _x(f), the exciting force F of Y direction _y(f), around the excitation torque M of Y-axis _y(f), the exciting force F of Z-direction _z(f), around the excitation torque M of Z axle _z(f);

K ^*＝[K ^* ₁?K ^* ₂?…K ^* _h]

$M=\left[\begin{array}{cccccc}m& & & & & \\ & m& & & & \\ & & m& & & \\ & & & J_x& -J_{\mathrm{xy}}& -J_{\mathrm{zx}}\\ & & & -J_{\mathrm{xy}}& J_y& -J_{\mathrm{yz}}\\ & & & {-J}_{\mathrm{zx}}& -J_{\mathrm{yz}}& J_z\end{array}\right]$

$\stackrel{\‾}{E}=\left[\begin{array}{cccccc}1& 0& 0& 0& z_1& -y_1\\ 0& 1& 0& -z_1& 0& x_1\\ 0& 0& 1& y_1& -x_1& 0\\ 1& 0& 0& 0& z_2& -y_2\\ 0& 1& 0& {-z}_2& 0& x_2\\ 0& 0& 1& y_2& -x_2& 0\\ \·& \·& \·& \·& \·& \·\\ \·& \·& \·& \·& \·& \·\\ \·& \·& \·& \·& \·& \·\\ 1& 0& 0& 0& z_3& -y_3\\ 0& 1& 0& {-z}_3& 0& x_3\\ 0& 0& 1& y_3& -x_3& 0\end{array}\right]$

$f=\frac{1}{3L}(f_{1x}+f_{1y}+f_{1z}+f_{2x}+f_{2y}+f_{2z}+\·\·\·+f_{\mathrm{Lx}}+f_{\mathrm{Ly}}+f_{\mathrm{Lz}})$

$\stackrel{\‾}{S}\left(f\right)={\left[\begin{array}{cccccccc}{\mathrm{dX}}_1& d{Y}_1& {\mathrm{dZ}}_1& {\mathrm{dX}}_2& {\mathrm{dY}}_2& {\mathrm{dZ}}_2\·\·\·{\mathrm{dX}}_L& {\mathrm{dY}}_L& {\mathrm{dZ}}_L\end{array}\right]}^T$

Representing matrix

Transposition;

Humorous excitation frequency f of η and its corresponding transposed matrix

Determine by the following method:

Humorous the η that selects the engine exciting force to analyze, η=0.5,1,1.5,2,2.5 or 3; Behind humorous time of the η of designated analysis engine speed w, carry out following computing:

Vibration acceleration signal sequence X to the first test point X-axis forward collection with n point _1n, add Hanning window w (t) 0≤t≤T of time length T=1, carry out the conversion of N point quick Fourier according to formula (1-1), obtain amplitude spectrum X ₁(f); To X _1nAdd time length

Hanning window w (t) 0≤t≤T carries out N/2 point quick Fourier conversion (FFT) according to formula (1-2), obtains amplitude spectrum X ₂(f);

$X_1\left(f\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}{x}_n[0.5-0.5\cos \left(\frac{2\mathrm{\πn}}{N}\right){]e}^{-j\frac{2\mathrm{\π}}{N}\mathrm{fn}}=R_1\left(f\right)+{\mathrm{jI}}_1\left(f\right)=y_1\left(f\right)e^{j{\mathrm{\Φ}}_1\left(f\right)}$ $f=\mathrm{0,1},\·\·\·,\frac{N}{2}-1---(1-1)$

$X_2\left(f\right)=\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{x}_n[0.5-0.5\cos \left(\frac{4\mathrm{\πn}}{N}\right){]e}^{-j\frac{4\mathrm{\π}}{N}\mathrm{fn}}=R_2\left(f\right)+{\mathrm{jI}}_2\left(f\right)=y_2\left(f\right)e^{j{\mathrm{\Φ}}_2\left(f\right)}$ $f=\mathrm{0,1},2\·\·\·,\frac{N}{4}-1---(1-2)$

According to engine speed w, determine emending frequency interval [f ₁, f ₂], wherein

Round numbers;

Round numbers;

At emending frequency interval [f ₁, f ₂] in, X ₁(f) peak-peak respective frequencies f _i, f _iReal part is R ₁(f _i), imaginary part is I ₁(f _i), phase place is Φ ₁(f _i), amplitude is y ₁(f _i); X ₂(f) peak-peak frequency f _j, phase place is Φ ₂(f _j); If emending frequency interval [f ₁, f ₂] interior peak-peak actual frequency is f ₀, f ₀Corresponding true phase place

True amplitude A ₀(f ₀); If f _iFrequency error be

f _iWith actual frequency f ₀Difference

For people's formula (1-3), obtain frequency error

$\▿f=-2{[\mathrm{\Φ}}_1\left(f_i\right)-{\mathrm{\Φ}}_2\left(f_j\right)-\frac{\mathrm{\π}(2f_i-f_j)}{2}]/\mathrm{\π}---(1-3)$

Calculate actual frequency f ₀

Calculate true phase place

The spectral function of Hanning window

Calculate amplitude A after the correction according to formula (1-6) ₀(f ₀), form actual frequency f ₀Acceleration with correspondence

To sequence X _2nX _LnY _1n, Y _2nY _LnZ _1n, Z _2nZ _LnWith the vibration acceleration signal sequence X _1nCarry out same processing, obtain the humorous inferior excitation frequency f of engine speed w η respectively _2xF _Lxf _1y, f _2yF _Lyf _1z, f _2zF _Lz

(1≤H≤L), the engine excitation frequency that records its directions X is f for any sensor H in L the sensor test point _Hx, corresponding acceleration is

The engine excitation frequency that records the Y direction is f _Hy, corresponding acceleration is

The engine excitation frequency that records the Z direction is f _Hz, corresponding acceleration is

The directions X displacement of sensor H is dX _H, the displacement of Y direction is dY _H, the displacement of Z direction is dZ _H, obtain the transposed matrix of sensor H thus:

The excitation frequency of L sensor

And corresponding transposed matrix

2. application according to claim 1 changes the engine exciting force measuring method of window appearance potential difference correction method, it is characterized in that: described crankshaft free-end is the end that bent axle connects belt pulley.

3. application according to claim 1 changes the engine exciting force measuring method of window appearance potential difference correction method, it is characterized in that: described engine is defined as suspension point with the contact point that suspends that supports it.

4. application according to claim 1 changes the engine exciting force measuring method of window appearance potential difference correction method, and it is characterized in that: described operate as normal rotating speed w is 750r/min to 5500r/min; Described operating mode is stable to be meant that the engine speed fluctuation is in 20r/min.

5. application according to claim 1 changes the engine exciting force measuring method of window appearance potential difference correction method, and it is characterized in that: described engine moment inertia experiment table adopts three string pendulum method of testing experiment tablees.