CN106895971B - A kind of method for measuring slender axles rotor internal damping - Google Patents

A kind of method for measuring slender axles rotor internal damping Download PDF

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CN106895971B
CN106895971B CN201710235214.0A CN201710235214A CN106895971B CN 106895971 B CN106895971 B CN 106895971B CN 201710235214 A CN201710235214 A CN 201710235214A CN 106895971 B CN106895971 B CN 106895971B
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CN106895971A (en
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郑世强
陈诚
刘刚
韩邦成
王灿
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Beihang University
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Beihang University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M13/00—Testing of machine parts

Abstract

The present invention relates to a kind of method for measuring slender axles rotor internal damping, slender axles rotor static horizontal is placed on testing stand, vibration acceleration sensor is mounted on rotor surface, hammer horizontal positioned static rotor, vibration signal is measured by vibration acceleration sensor, signal after filtering, after amplification, then rotor mode amplitude is obtained after being handled by oscillograph, then can accurately measure out rotor internal damping by specific algorithm.This method is simple to operate, easily realizes, provides great convenience to measurement slender axles rotor internal damping, and improve the precision and efficiency of measurement rotor internal damping.

Description

A kind of method for measuring slender axles rotor internal damping
Technical field
The present invention relates in a kind of method for measuring rotor internal damping, more particularly to a kind of accurate measurement slender axles rotor The method of damping.
Background technology
Magnetic suspension motor technology reaches its maturity, and its application is also more and more extensive, such as the magnetcisuspension in aerospace field Suspension flywheel, magnetic suspension control torque gyroscope, high-energy-density motor in the industrial production, the magnetic suspension in clean energy resource field Air compressor, molecular pump etc..Magnetic suspension motor can have high rotating speed, contactless, nothing to rub extensively using it is primarily due to Wipe, the advantages that service life is long, key technology is to employ slender axles control supporting rotor high speed steady running.Thus slender axles Rotor is particularly important in the entire system, and the accurate parameters for measuring rotor are critically important, for the stabilization of whole system Property, security and economy all produce significant impact.
At present, rotor internal damping is measured, mainly there is half-power bandwidth method, amendment half-power bandwidth method and mode fitting Method.Because half-power bandwidth method and amendment half-power bandwidth method are carried out in frequency domain, it is necessary to carry out FFT, energy leakage without Method avoids, and causes the precision for influenceing measurement rotor internal damping.Mode fitting process needs good condition of work simultaneously, for example encourages Sufficient condition, good signal to noise ratio, enough frequency resolutions, also, mode fitting process performance difficulty, have very high to equipment It is required that.
The content of the invention
The technology of the present invention solves problem：Overcome the deficiencies in the prior art, using vibration acceleration sensor, then pass through The analyzing and processing of oscillograph, improves the precision and efficiency of measurement slender axles rotor internal damping, and reduces method implementation Difficulty.
The present invention technical solution be：A kind of method for measuring slender axles rotor internal damping, comprises the following steps：
(a) the slender axles rotor that quiescent levels are placed is hammered, is mounted on the vibration acceleration sensor detection of rotor surface To vibration signal, collection vibration acceleration sensor output signal XOUTAnd YOUT, the signal of collection is respectively by LPF electricity Amplifying circuit, output voltage U are accessed with differential form behind roadOUT。XOUTAnd YOUTFor the primary signal of vibrating sensor collection, UOUT For the voltage signal of output, directly it is connected into oscillograph.
(b) oscillograph is by voltage signal UOUTHandled, be processed into using the cycle as TdCosine signal, can measure remaining The peak value of string signal, and modal frequency ωnDirectly it can be read by oscillograph, because the signal unit after oscillograph processing is DBV, i.e., voltage signal is converted into dB signal, thus, read i-th of cycle maximum mode amplitude U of oscillographdB_iCorrespondingly Time TiAnd i+1 cycle maximum mode amplitude UdB_i+1With corresponding time Ti+1, determine i-th of cycle maximum mode amplitude UdB_iWith i+1 cycle maximum mode amplitude UdB_i+1The absolute value of difference be Δ UdB, and be shown below：
ΔUdB=| UdB_i-UdB_i+1|
Wherein i=1,2,3 ... ..., N, N are oscillograph sampling number, i-th of cycle maximum original mode amplitude Ui, i.e., Do not entered the maximum voltage peak value in i-th of cycle of oscillograph processing, can be represented by the formula：
20lgUi=UdB_i
Wherein i+1 cycle maximum original mode amplitude Ui+1, i.e., do not entered the i+1 cycle of oscillograph processing Maximum voltage peak value, can be represented by the formula：
20lgUi+1=UdB_i+1
Wherein：TdFor the time difference between two peak values, i.e. in the cosine signal cycle, can be represented by the formula：
Td=Ti+1-Ti
(c) the Δ U measureddB=| UdB_i-UdB_i+1| pass through following algorithmic formula, it is as follows can directly to obtain internal damping formula：
Rotor impulse response is as follows：
Wherein：A is impulse response amplitude；ζ is rotor internal damping；ωnFor modal frequency；tiFor the time；θ is impulse response Phase angle.
I-th of cycle maximum original mode amplitude Ui, it is shown below：
I+1 cycle maximum original mode amplitude Ui+1, it is shown below：
By UiAnd Ui+1Compared to can obtain：
Both sides, which are taken the logarithm, to be obtained：
Abbreviation above formula can obtain：
I.e.：
X in the step (a)OUTAnd YOUTFor raw voltage values, signal is gone by that can be realized after filter circuit Tooth pitch and noise attenuation, noise floor density is reduced by filtering, improve measurement accuracy, the present invention uses vibration acceleration to sense Device model ADXL203, the representative value of its output signal bandwidth is 2.5kHz, and signal is filtered, and can effectively prevent frequency Rate aliasing.ADXL203 can change filter capacitor C according to being actually needed2To set output signal bandwidth, signal bandwidth is smaller, Noise is smaller, thus precision is higher.
U in the step (b)OUTFor modulate circuit output valve, oscillograph is to UOUTSynthesis processing is carried out, can obtain with week Phase is TdCan the original mode amplitude U of maximum measured directlyi, and on the basis of original value, follow-up measurement for convenience Calculate, by raw voltage values UiIt is converted into the value U in units of decibel for being easy to measurementdB_i。
The present invention principle be：Vibration acceleration sensor ADXL203 outputs are continuous signal, can react thin with gamut The amplitude response of long-shaft rotor, circuit realiration removes tooth pitch and noise attenuation to two axis signals of output after filtering respectively, so subtracts Few noise floor density, improves measurement accuracy, and two groups of signals access amplifying circuit in a differential manner, are amplified to signal and are beneficial to Oscillograph Treatment Analysis scope, oscillograph is by signal UOUTHandled, the cosine signal formed in units of decibel, by showing Ripple device direct measurement draws the difference absolute value delta U of adjacent peakdBAnd cycle Td, the Δ U that measuresdBAnd TdAlgorithm public affairs can be brought directly to In formula, slender axles rotor internal damping ζ is finally drawn.
The present invention compared with prior art the advantages of be：
(1) method for the measurement slender axles rotor internal damping that the present invention proposes, it is simple to operate, it is easy to accomplish, it is applicable In most of occasions, modulate circuit can flexible modulation output area, improve the precision of vibration acceleration sensor signal condition And efficiency.
(2) the method applied in the present invention only needs just to can accurately measure rotor internal damping by oscillograph, without a large amount of Work, workload are small.
Brief description of the drawings
Fig. 1 is present system flow chart；
Fig. 2 is slender axles rotor and vibration acceleration sensor position relationship schematic diagram；
Fig. 3 is system organization connection figure；
Fig. 4 is T1Oscillograph work sheet under moment；
Fig. 5 is T2Oscillograph work sheet under moment；
Fig. 6 is vibration acceleration sensor modulate circuit figure.
Embodiment
As shown in Fig. 1,2,3,4,5,6, specific method of the invention is as follows：
(a) as shown in Fig. 2, Fig. 3, Fig. 6, Fig. 2 is that vibration acceleration sensor is mounted on rotor surface schematic diagram, and Fig. 3 is Connection figure between system organization connection figure, i.e. sensor, modulate circuit and oscillograph, Fig. 6 adjust for vibration acceleration sensor Manage circuit diagram, including filter circuit and differential amplifier circuit two parts.The slender axles rotor that quiescent levels are placed is hammered, is mounted on The vibration acceleration sensor of rotor surface detects vibration signal, vibration acceleration sensor output signal XOUTAnd YOUTRespectively Low-pass filter circuit is accessed, uses vibration acceleration sensor model ADXL203, the representative value of its output signal bandwidth is 2.5kHz, signal is filtered, can effectively prevent frequency alias.ADXL203 can change filtered electrical according to being actually needed Hold C2To set output signal bandwidth, the relation of filter capacitor and signal bandwidth is shown below：
Wherein F represents bandwidth value, RFILTRepresent ADXL203 internal nominal resistance, C2Represent C2Capacitance.
In order that a width of 1kHz of ADXL203 output signal bands, it is known that ADXL203 internal nominal resistance RFILTFor 16K Ω, We are by electric capacity C2Size determine in 0.01 μ F.ADXL203 typical output valve is 0.15V, thus will be respectively to two letters Number access amplifying circuit makes envelope eapsulotomy, magnification ratio 4.XOUTAnd YOUTAfter filtering after amplifying circuit, then with differential form Access ratio is 5 amplifying circuit, and differential form can improve the precision of whole system, finally by reasonable arrange parameter, can be incited somebody to action Output signal UOUTIt is transferred in the range of 0~3V, to facilitate oscillograph to read and analyze and process.
(b) as shown in Figure 4, Figure 5, figure is oscillograph by voltage signal U in Fig. 6OUTHandled, be processed into cosine signal, The peak value of cosine signal, and modal frequency ω can be measurednDirectly it can be read by oscillograph, because after oscillograph processing Signal unit is dBV, i.e., voltage signal is converted into dB signal.Thus, read i-th of cycle maximum mode amplitude of oscillograph UdB_iWith corresponding time TiAnd i+1 cycle maximum mode amplitude UdB_i+1With corresponding time Ti+1.As shown in Figure 4 and Figure 5, We take the 1st and the 2nd cycle, read the 1st cycle maximum mode amplitude U of oscillographdB_1With corresponding time T1And the 2nd Individual cycle maximum mode amplitude UdB_2With corresponding time T2, determine the 1st cycle maximum mode amplitude UdB_1With the 2nd cycle most Big mode amplitude UdB_2The absolute value of difference be Δ UdB, and be shown below：
ΔUdB=| UdB_1-UdB_2|
Wherein the 1st cycle maximum original mode amplitude U1, i.e., do not entered the maximum electric of the 1st cycle that oscillograph is handled Voltage crest value, can be represented by the formula：
20lgU1=UdB_1
Wherein the 2nd cycle maximum original mode amplitude U2, i.e., do not entered the maximum electric of the 2nd cycle that oscillograph is handled Voltage crest value, can be represented by the formula：
20lgU2=UdB_2
Wherein TdFor the time difference between two peak values, i.e. in the cosine signal cycle, can be represented by the formula：
Td=T2-T1
U is thus understood by Fig. 4 and Fig. 5dB_1、UdB_2、T1、T2And ωnRespectively 13.8dB V, 25.1dB V, 10ms, 110ms and 818Hz.
(c) the Δ U measureddB=| UdB_1-UdB_2| pass through following algorithmic formula, it is as follows can directly to obtain internal damping formula：
1st cycle maximum original mode amplitude U1, it is shown below：
Wherein A is impulse response amplitude；ζ is rotor internal damping；ωnFor modal frequency.
2nd cycle maximum original mode amplitude U2, it is shown below：
Wherein A is impulse response amplitude；ζ is rotor internal damping；ωnFor modal frequency.
By U1And U2Compared to can obtain：
Both sides, which are taken the logarithm, to be obtained：
Abbreviation above formula can obtain：
I.e.：
By UdB_1=13.8dBV, UdB_2=25.1dBV, T1=10ms, T2=110ms and ωn=818Hz is brought into respectively Above formula, obtain ζ=0.016062417.
The present invention can be as a kind of general measurement slender axles rotor internal damping method, and modulate circuit can be more accurately real Existing proportion adjustment output signal, it is simple to operate, easily realize, improve the precision and effect of vibration acceleration sensor signal condition Rate, algorithm is efficiently convenient, improves the efficiency of calculating.
Non-elaborated part of the present invention belongs to techniques well known.

Claims (4)

  1. A kind of 1. method for measuring slender axles rotor internal damping, it is characterised in that：It is achieved by the steps of：
    (a) the slender axles rotor that quiescent levels are placed is hammered, the vibration acceleration sensor for being mounted on rotor surface is detected and shaken Dynamic signal, collection vibration acceleration sensor output signal XOUTAnd YOUT, the signal of collection is respectively after low-pass filter circuit Amplifying circuit, output voltage U are accessed with differential formOUT, XOUTAnd YOUTFor the primary signal of vibrating sensor collection, UOUTTo be defeated The voltage signal gone out, is directly connected into oscillograph；
    (b) oscillograph is by voltage signal UOUTHandled, be processed into using the cycle as TdCosine signal, cosine signal can be measured Peak value, and modal frequency ωnDirectly it can be read by oscillograph, because the signal unit after oscillograph processing is dBV, i.e., Voltage signal is converted into dB signal, thus, read i-th of cycle maximum mode amplitude U of oscillographdB_iWith corresponding time Ti And i+1 cycle maximum mode amplitude UdB_i+1With corresponding time Ti+1, determine i-th of cycle maximum mode amplitude UdB_iWith I+1 cycle maximum mode amplitude UdB_i+1The absolute value of difference be Δ UdB, and be shown below：
    ΔUdB=| UdB_i-UdB_i+1|
    Wherein i=1,2,3 ... ..., N, N are oscillograph sampling number, i-th of cycle maximum original mode amplitude Ui, i.e., do not entered The maximum voltage peak value in i-th of cycle of oscillograph processing, can be represented by the formula：
    20lgUi=UdB_i
    Wherein i+1 cycle maximum original mode amplitude Ui+1, i.e., do not entered oscillograph processing the i+1 cycle maximum Voltage peak, it can be represented by the formula：
    20lgUi+1=UdB_i+1
    Wherein：TdFor the time difference between two peak values, i.e. in the cosine signal cycle, can be represented by the formula：
    Td=Ti+1-Ti
    (c) the Δ U measureddB=| UdB_i-UdB_i+1| pass through following algorithmic formula, can directly obtain internal damping, rotor impulse response It is as follows：
    <mrow> <mi>S</mi> <mrow> <mo>(</mo> <msub> <mi>t</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mo>=</mo> <msup> <mi>Ae</mi> <mrow> <mo>-</mo> <msub> <mi>&amp;zeta;&amp;omega;</mi> <mi>n</mi> </msub> <mi>t</mi> </mrow> </msup> <mi>s</mi> <mi>i</mi> <mi>n</mi> <mrow> <mo>(</mo> <msub> <mi>&amp;omega;</mi> <mi>d</mi> </msub> <msub> <mi>t</mi> <mi>i</mi> </msub> <mo>+</mo> <mi>&amp;theta;</mi> <mo>)</mo> </mrow> </mrow>
    Wherein：A is impulse response amplitude；ζ is rotor internal damping；ωnFor modal frequency；tiFor the time；θ is the phase of impulse response Parallactic angle；
    I-th of cycle maximum original mode amplitude Ui, it is shown below：
    <mrow> <msub> <mi>U</mi> <mi>i</mi> </msub> <mo>=</mo> <msup> <mi>Ae</mi> <mrow> <mo>-</mo> <msub> <mi>&amp;zeta;&amp;omega;</mi> <mi>n</mi> </msub> <msub> <mi>T</mi> <mi>i</mi> </msub> </mrow> </msup> </mrow>
    I+1 cycle maximum original mode amplitude Ui+1, it is shown below：
    <mrow> <msub> <mi>U</mi> <mrow> <mi>i</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> <mo>=</mo> <msup> <mi>Ae</mi> <mrow> <mo>-</mo> <msub> <mi>&amp;zeta;&amp;omega;</mi> <mi>n</mi> </msub> <msub> <mi>T</mi> <mrow> <mi>i</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> </mrow> </msup> </mrow>
    By UiAnd Ui+1Compared to can obtain：
    <mrow> <mfrac> <msub> <mi>U</mi> <mi>i</mi> </msub> <msub> <mi>U</mi> <mrow> <mi>i</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> </mfrac> <mo>=</mo> <msup> <mi>e</mi> <mrow> <msub> <mi>&amp;zeta;&amp;omega;</mi> <mi>n</mi> </msub> <msub> <mi>T</mi> <mi>d</mi> </msub> </mrow> </msup> </mrow>
    Both sides, which are taken the logarithm, to be obtained：
    <mrow> <msub> <mi>&amp;zeta;&amp;omega;</mi> <mi>n</mi> </msub> <msub> <mi>T</mi> <mi>d</mi> </msub> <mo>=</mo> <mi>ln</mi> <mrow> <mo>(</mo> <mfrac> <msub> <mi>U</mi> <mi>i</mi> </msub> <msub> <mi>U</mi> <mrow> <mi>i</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> </mfrac> <mo>)</mo> </mrow> <mo>=</mo> <mi>ln</mi> <mi> </mi> <msub> <mi>U</mi> <mi>i</mi> </msub> <mo>-</mo> <mi>ln</mi> <mi> </mi> <msub> <mi>U</mi> <mrow> <mi>i</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> </mrow>
    Abbreviation above formula can obtain：
    <mrow> <msub> <mi>&amp;zeta;&amp;omega;</mi> <mi>n</mi> </msub> <msub> <mi>T</mi> <mi>d</mi> </msub> <mo>=</mo> <mfrac> <mrow> <msub> <mi>&amp;Delta;U</mi> <mrow> <mi>d</mi> <mi>B</mi> </mrow> </msub> </mrow> <mn>20</mn> </mfrac> <mi>l</mi> <mi>n</mi> <mn>10</mn> </mrow>
    I.e.：
    <mrow> <mi>&amp;zeta;</mi> <mo>=</mo> <mfrac> <mrow> <msub> <mi>&amp;Delta;U</mi> <mrow> <mi>d</mi> <mi>B</mi> </mrow> </msub> </mrow> <mrow> <mn>20</mn> <msub> <mi>&amp;omega;</mi> <mi>n</mi> </msub> <msub> <mi>T</mi> <mi>d</mi> </msub> </mrow> </mfrac> <mi>l</mi> <mi>n</mi> <mn>10.</mn> </mrow>
  2. 2. the method for measurement slender axles rotor internal damping according to claim 1, it is characterised in that：In the step (a) XOUTAnd YOUTFor raw voltage values, tooth pitch and noise attenuation are gone to signal by that can be realized after filter circuit, pass through filter Ripple reduces noise floor density, improves measurement accuracy.
  3. 3. the method for measurement slender axles rotor internal damping according to claim 1, it is characterised in that：The vibration acceleration Sensor model number is ADXL203, and the representative value of its output signal bandwidth is 2.5kHz, and signal is filtered, can effectively be prevented Only frequency alias.
  4. 4. the method for measurement slender axles rotor internal damping according to claim 1, it is characterised in that：In the step (b) UOUTFor modulate circuit output valve, oscillograph is to UOUTSynthesis processing is carried out, can obtain using the cycle as TdCan be measured directly Maximum original mode amplitude Ui, and on the basis of original value, in order to facilitate follow-up survey calculation, by raw voltage values Ui It is converted into the value U in units of decibel for being easy to measurementdB_i。
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