CN108761117A - Portable type current detects rotational speed detector - Google Patents
Portable type current detects rotational speed detector Download PDFInfo
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- CN108761117A CN108761117A CN201810846959.5A CN201810846959A CN108761117A CN 108761117 A CN108761117 A CN 108761117A CN 201810846959 A CN201810846959 A CN 201810846959A CN 108761117 A CN108761117 A CN 108761117A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/42—Devices characterised by the use of electric or magnetic means
- G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
- G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
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Abstract
The present invention relates to one kind to be convenient for carrying, small, light-weight, and can apply to the detection rotational speed detector of the portable type current on most of motor.This portable type current detection rotational speed detector is used based on stator current spectrum analysis without sensor rotation speed on-line identification algorithm, it is proposed two kinds of analysis methods based on stator current frequency spectrum and based on stator current squared spectral, after Fast Fourier Transform (FFT), rotor frequency is accurately extracted in its spectrogram, in order to save hardware cost, improve frequency resolution, the Spectrum Correction technology based on multiple modulation ZoomFFT frequency spectrum refinements technology and based on ratio method is respectively adopted, analysis is optimized to original signal spectrum, the experimental results showed that, after this optimization algorithm, the identification precision of rotating speed is set to be increased to 2r/min from 5r/min, close to international most advanced level.
Description
Technical field
The present invention relates to a kind of test equipments, and in particular to a kind of portable type current detection rotational speed detector, for electricity
Machine rotating speed carries out live Efficiency testing.
Background technology
With the continuous aggravation of energy shortage problem and greenhouse effects, clean energy resource is developed and used, energy-saving and emission-reduction have become
Countries in the world focus of attention.It is energy saving just to seem particularly necessary for shortage of resources, populous China.It is middle-size and small-size
Threephase asynchronous is most widely used high energy consumption product, and application range spreads national economy every field, electricity consumption
Account for about the 50% of national total electricity consumption, be even more to account for 2/3 or so, and motor running efficiency is generally relatively low in industrial circle,
Therefore, the operational efficiency for improving motor is of great significance.The reason for causing motor running efficiency relatively low has very much, including
The problem of motor itself, but more important is using problem, such as load factor is relatively low, motor ages.Solve the problems, such as that this has
Many methods such as promote the use of high efficiency motor, replace the apparent relatively low motor of operational efficiency, or carry by control method appropriate
The operational efficiency etc. of high motor.It realizes this target, first has to accurately examine in the case where not interfering motor normal operation
Measure its actual operating efficiency.Traditional detection method based on laboratory environment cannot be directly used to Site Detection, this be because
For no-load test, short-circuit test, stator resistance detection and Rotating speed measring at the scene in the case of be difficult complete.
For large-size machine, often it is furnished with motor status on-line monitoring system, is generally possible to the operational efficiency of detection motor,
For Small And Medium Capacity motor, from a cost perspective, it is not equipped with monitoring system generally.And Small And Medium Capacity motor no matter from quantity also
It is that power consumption is taken temperature, all accounts in the overwhelming majority with motor.On-line monitoring is carried out to all middle and small motors to be nearly impossible,
This work must be completed by field personnel.For this reason, it is necessary to develop suitable for the live efficiency of the low cost of middle small machine
Detection device.And Field Force is it is generally desirable to the operation of detection device is as simple as possible, it is small, light-weight and easy to carry.
Common portable detector is that hand-held is infrared or laser sensor, compared to photoelectric encoder, valence
Lattice are cheap, and need not be mounted on motor, easy to operate, for middle-size and small-size, low-power motor is more practical.However for
Those can not observe that the large-size machine of motor shaft, sensors with auxiliary electrode will be unable to use, and infrared or laser sensor measures
Precision is relatively low, often can not meet high precision measurement system requirements.Discovery is considered, for field portable electromechanical testing system
For system, it is insecure to directly obtain motor speed using sensor, so motor speed of the research without sensor is distinguished online
Know algorithm, is of great significance to obtaining high-precision motor speed result.
Invention content
In order to solve technical problem present in background technology, the present invention provides a kind of lightweight, portable, convenient and practical, and surveys
The high portable type current of accuracy of measurement detects rotational speed detector.
The technical solution adopted by the present invention to solve the technical problems is：
A kind of portable type current detection rotational speed detector, the cover top portion trepanning of the rotational speed detector allow line to pick out, are used for
With tested motor wiring, rotational speed detector is internally provided with processor, and processor detects tested motor by current sensor
Electric current carries out in the filtered device of electric current that current sensor measures after Signal Regulation and filtering in input processor；
Include micro treatment module in the processor, current data acquisition module, electric current number are connected on micro treatment module
According to processing module, spectroscopy processing module, rotating speed processing module, wherein current data acquisition module is connected with current sensor, electricity
The stator rotating speed of tested motor is sent to by micro treatment module in current data processing module by flow data acquisition module, electric current number
The signal after demodulation is sent to by micro treatment module in spectroscopy processing module according to processing module, spectroscopy processing module will be at frequency spectrum
Signal after reason is sent to by micro treatment module in rotating speed processing module, is found rotor frequency and is calculated motor speed.
The case surface offers display screen and a variety of buttons to be controlled.
The processor is ARM microcontroller.
The current sensor is Rogowski coil.
Display module, Keysheet module are additionally provided on the processor.
Signal processing module is additionally provided on the processor, processor is sent to by signal processing module by signal is handled
Control module, control module control tested motor rotation.
This portable type current detection rotational speed detector calculates electricity based on the Speed Identification algorithm of stator current frequency spectrum
Machine rotating speed.
Beneficial effects of the present invention：
This patent rotational speed detector is convenient for carrying, small, light-weight, and can be applied on most of motor, this
Portable type current detects rotational speed detector when detecting the rotating speed of motor, first passes through touchless Rogowski coil and measures tested electricity
The electric current of machine obtains stator current original signal, then carries out solution for the current to it by being sent to after filter process in processor
Tune, spectrum analysis, frequency spectrum refinement, Spectrum Correction, frequency search finally accurately calculate the rotating speed of motor, and the rotating speed obtained misses
Difference is smaller, and precision is higher.
In addition the identification algorithm that this portable type current detection rotational speed detector uses has the following advantages：
(1) this portable type current detects rotational speed detector using no sensor rotation speed on-line identification method, instead of original
The effect of speed probe obtains the rotary speed parameter calculated needed for electric efficiency.
(2) it uses based on stator current spectrum analysis without sensor rotation speed on-line identification algorithm, proposes to be based on stator
Current spectrum and two kinds of analysis methods based on stator current squared spectral, after Fast Fourier Transform (FFT), in its spectrogram
In accurately extract rotor frequency.In order to save hardware cost, improve frequency resolution, it has been respectively adopted and has been based on multiple modulation
ZoomFFT frequency spectrum refinements technology and Spectrum Correction technology based on ratio method optimize analysis, experimental result to original signal spectrum
Show, using after this optimization algorithm, the identification precision of rotating speed to be made to be increased to 2r/min from 5r/min, first intake close to the world
It is flat.
Description of the drawings
Present invention will be further explained below with reference to the attached drawings and examples.
Fig. 1 is the shape assumption diagram of portable type current detection rotational speed detector of the present invention.
Fig. 2 is the schematic diagram of portable type current detection rotational speed detector of the present invention.
Fig. 3 is the internal module schematic diagram of processor in Fig. 2.
Fig. 4 is Speed Identification algorithm flow chart used by portable type current detection rotational speed detector of the present invention.
Fig. 5 is the Butterworth LPF width phase-frequency characteristic curve graph of low-pass filter in the present invention.
Fig. 6 is the flow chart that multiple modulation refines spectral analysis method in stator current spectrum analysis of the present invention.
Fig. 7 be stator current spectrum analysis of the present invention in multiple modulation refinement spectral analysis method in each frequency content of signal more
Close original signal spectrum and the zoom FFT simulation result diagram based on Zoom FFT.
Fig. 8 be stator current spectrum analysis of the present invention in multiple modulation refinement spectral analysis method in each frequency content of signal apart
Original signal spectrum farther out and the zoom FFT simulation result diagram based on Zoom FFT.
Fig. 9 is that the present invention is based on the hanning window function spectrograms when Spectrum Correction of ratio method.
Figure 10 is that the present invention is based on the relational graphs of frequency and amplitude rectification when the Spectrum Correction of ratio method.
Figure 11 is the spectrum analysis knot before and after the hanning window Spectrum Corrections that each frequency content of signal of the present invention is closer to
Fruit is schemed.
Figure 12 is the spectrum analysis knot before and after each frequency content of signal of the present invention hanning window Spectrum Corrections apart from each other
Fruit is schemed.
Figure 13 is the motor actual speed curve graph acquired by motor measurement module when in-circuit emulation of the present invention.
Figure 14 is that the present invention is based on the motor speed on-line identification algorithms of rotor frequency to the analysis result figure of stator current.
Figure 15 is that the present invention is based on the schematic diagrams of the rotating speed of the method on-line identification motor of stator current spectrum analysis.
In figure：Processor 1, micro treatment module 1.1, current data acquisition module 1.2, current data processing module 1.3, frequency
Compose processing module 1.4, rotating speed processing module 1.5, current sensor 2, filter 3, display module 4, Keysheet module 5, at signal
Manage module 6, control module 7, tested motor 8.
Specific implementation mode
Below in conjunction with attached drawing, the present invention is described in further detail.
The present invention relates to a kind of portable type currents to detect rotational speed detector, and referring to Fig. 1, this portable type current detects rotating speed
The cover top portion trepanning of tester allows line to pick out, for and tested motor wiring, case surface offer display screen and a variety of
Button is controlled.
This portable type current detection rotational speed detector is internally provided with microcontroller, and tested electricity is acquired by current sensor
The stator current of machine, and electric current demodulation, spectrum analysis, frequency spectrum refinement, Spectrum Correction are carried out to it by ARM microcontroller, most
The rotating speed of motor is accurately calculated eventually.
Referring to Fig. 2, this portable type current detection rotational speed detector mainly contains processor 1, which is that ARM is micro-
Controller, inside have the function of electric current JieDuHuaYu II Decoction spectrum analysis, frequency spectrum refinement, Spectrum Correction, frequency search and rotating speed calculating etc..
Processor 1 detects the electric current of tested motor 8 by current sensor 2, and tested motor 8 is the most widely used
Ac three-phase asynchronous motor, the current sensor 2 are Rogowski coil, and Rogowski coil is also known as current measurement coil, measuring principle
Based on Faraday's electromagnetic induction law, output signal is the differential of Current versus time, then passes through an integrating circuit
True current signal is restored, its advantage is that being free of magnetic material, no hysteresis effect, phase error is almost nil, and no saturation is existing
As measurement range has wide measurement range, high certainty of measurement, response from number peace to hundreds of peaces, compared to traditional current transformer
Fireballing advantage is suitable for the occasion high to current precision.
Progress Signal Regulation and input after filtering in the filtered device 3 of motor stator electric current that current sensor 2 measures
It manages in device 1.
Include micro treatment module 1.1 referring to Fig. 3 and Fig. 4, in the processor 1, electric current is connected on micro treatment module 1.1
Data acquisition module 1.2, current data processing module 1.3, spectroscopy processing module 1.4, rotating speed processing module 1.5, wherein electric current
Data acquisition module 1.2 is connected with current sensor 2, obtains the stator rotating speed of tested motor 8, current data acquisition module 1.2
The stator rotating speed of tested motor 8 is sent to by micro treatment module 1.1 in current data processing module 1.3, by current data
It manages module 1.3 to demodulate electric current, the signal after demodulation is sent to frequency by current data processing module 1.3 by micro treatment module 1.1
It composes in processing module 1.4, spectrum analysis, frequency spectrum refinement, Spectrum Correction is carried out to signal by spectroscopy processing module 1.4, at frequency spectrum
Signal after correction is sent to by reason module 1.4 by micro treatment module 1.1 to be found rotor frequency in rotating speed processing module 1.5 and counts
Motor speed is calculated, the motor speed precision obtained in this way is higher.
Processor 1 carries out electric current demodulation, spectrum analysis, frequency spectrum refinement, Spectrum Correction, frequency search to it, final accurate
Calculate the rotating speed of motor.
Display module 4, Keysheet module 5 and signal processing module 6 are additionally provided on the processor 1, processor 1 can will be counted
The motor speed adjusted value of calculating is sent to control module 7 by signal processing module 6, and control module 7 and 8 phase of tested motor
Even, the rotating speed of tested motor 8 can be controlled.
Modules wherein in processor 1 can calculate motor speed by the Speed Identification algorithm of optimization,
The motor revolution error obtained is smaller, and precision is higher.
The Speed Identification algorithm is Speed Identification algorithm based on stator current frequency spectrum or is based on stator current squared spectral
Speed Identification algorithm, by Fourier analysis it is found that any periodic signal can regard as different amplitudes, different frequency sine
The superposition of wave has the sinusoidal signal of a certain frequency spectrum in periodic signal, can find in its frequency spectrum its corresponding frequency at
Point.
After being passed through balanced three-phase current in stator winding, due to electromagnetic induction scene, change will produce rotating excitation field, i.e.,
" electric magnetisation " process.At the same time, closed rotor winding coil is under the action of the rotating excitation field that stator winding generates, cutting
Magnetic induction line generates induced electromotive force and induced current in the windings, i.e. " magnetic life electricity " process.Electrical conductor is in magnetic field by electricity
The effect of magnetic force and rotate, simultaneously because electromagnetic induction phenomenon, after electrification rotor windings equally will produce changing magnetic field, it is fixed
Sub- winding induces corresponding induced current under the action of rotor Induced magnetic field, this induced current is related with rotor speed, because
This can calculate motor speed by detecting this current component.Principle flow chart is as shown in figure 15.
1) stator current demodulates
1. the Speed Identification algorithm based on stator current frequency spectrum：
Motor stator electric current is generally acquired by current sensor.A phase in three-phase current is only needed in the algorithm i.e.
It can.The demodulation of stator current is the core of the algorithm.According to Fourier analysis it is found that any one periodic signal can
It is decomposed into the sinusoidal signal of different frequency ingredient, therefore collected stator current can be demodulated, the stator current is obtained
Frequency constituent, so as to extract the rotor frequency of needs.
Stator current can be expressed as：
I (t)=[k1+k2cos(2πf2t)+k3cos(2πf3t)+...+kn cos(2πfnt)]cos(2πf1t) 3.1
Wherein, knAnd fnThe respectively amplitude and frequency of nth harmonic.K1=50Hz is the frequency of communication power supply.
Motor stator electric current can also be expressed as：
I (t)=m (t) cos (2 π f1t) 3.2
Wherein enable
M (t)=k1+k2cos(2πf2t)+k3cos(2πf3t)+...+kn cos(2πfnt) 3.3
M (t) is the amplitude of stator current.
Then a square processing is carried out to stator current, obtained
In view of the signal frequency ingredient in signal m (t) is both less than f1, it is possible to allow stator current to pass through low-pass filtering
Device thus obtains m (t) signals from stator current, and the cutoff frequency of the general low-pass filter is less than 2f1.Then right
Extraction of square root processing is carried out by the signal of low-pass filter, to realize the demodulation to stator current.It extracts square root in order to prevent
Distorted signals afterwards generally carries out direct current biasing to stator current first before demodulation.
After low-pass filter of the signal that formula 3.4 is indicated by above-mentioned design, just m (t) signal extractions are come out, it will be low
Signal after pass filter carries out evolution processing, can obtain the stator current signal for being eventually used for spectrum analysis, such as following formula.
I (t)=0.707m (t) 3.5
2. the Speed Identification algorithm based on stator current squared spectral：
The algorithm includes mainly phase current acquisition, phase current analysis, spectrum analysis three parts.Wherein first and Part III
It is identical as first method, second part-phase current analysis is mainly introduced herein.
In view of the asynchronous machine of an ideal operating conditions, phase current expression formula is：
I (t)=Imax cos(ωt) 3.6
Wherein ImaxIt is the amplitude of phase current.
So the expression formula of phase current square is：
Its frequency is analyzed it is recognised that first can be there are one DC component, in addition there are one 2f in meetingsFrequency content.
If it is considered that rotor is eccentric, in this case, the expression formula of stator current square is：
Wherein ImaxIt is the amplitude of phase current, IlsbIt is the amplitude of phase current lower sideband component, IlsbIt is phase current upper sideband point
The amplitude of amount.Can find out from expression formula, electric current square frequency spectrum include a flip-flop, 2fsFrequency content, two
Sideband 2fs-frAnd 2fs+frAnd additional frequency content fr, 2fr, 2fs-2frAnd 2fs+2fr.So by stator current
Square carry out spectrum analysis, f can be accurately extracted from frequency spectrumrFrequency content, i.e. rotor frequency turn to pick out motor
Speed.
2) low pass filter design
Due to needing to carry out low-pass filtering to signal before obtaining last signal, filtering technique is most base in signal processing
This is also most important technology, can extract useful signal component from complicated signal by means of filtering, filter useless
Ingredient.Filter is the signal processing apparatus for having corresponding transmission characteristic, and classification is as follows：
(1) low-pass filter, high-pass filter, bandpass filter and bandstop filter can be divided into according to range；
(2) IIR and FIR filter can be divided by time domain specification；
(3) analog filter and digital filter can be divided by signal type.
Consider this patent demand, a kind of Butterworth LPF is designed using Matlab, its main feature is that having
The amplitude versus frequency characte of maximally-flat in passband, and increase smooth monotonic with frequency and decline；Order is higher, and characteristic is closer to rectangle, mistake
It is narrower to spend bandwidth.
The amplitude square function of Butterworth LPF is：
Wherein, ωcFor the cutoff frequency of filter, N is the exponent number of filter.In formula, N is integer, referred to as filter system
Number, N is bigger, and the approximation of passband and stopband is better, and intermediate zone is also steeper.
The function that Butterworth LPF is provided in Matlab Matlab DSPToolBoxes is as follows
[n, wn]=buttord (wp, ws, rp, rs)；
[b, a]=butter (n, wn)；
Wherein, n is filter order, and wn is system filter cutoff frequency, and b, a are the filter coefficient of design.Wp is
Normalize cut-off frequecy of passband；Ws is normalization stopband cutoff frequency；Rp is maximum ripple decaying in passband；Rs be stopband in most
Small decaying.
The frequency of supply f of China's three-phase electricity1=50Hz, so the cut-off frequecy of passband of low-pass filter is set as 100Hz,
Stopband cutoff frequency is set as 200Hz, the Butterworth LPF width phase-frequency characteristic curve such as Fig. 5 institutes designed in this patent
Show.
3) spectrum analysis technique based on stator current
1. the spectrum analysis based on Fast Fourier Transform (FFT) (FFT)
The signal obtained after filtering is carried out Fast Fourier Transform (FFT) (FFT) must in the spectrogram to obtain its spectrogram
Surely include required rotor frequency ingredient.
Fourier transformation is that the signal of a certain mechanical periodicity is expressed as to the linear combination of countless sinusoidal (or cosine) signals,
Signal can be transformed from the time domain in frequency domain, so as to find the feature that can't see in time domain.In different research fields,
Fourier transformation has different forms, is broadly divided into continuous fourier transform and discrete Fourier transform.
In time domain and frequency domain all it is discrete form when discrete Fourier transform (DFT) carries out Fourier transformation, in shape
In formula, the sequence of Fourier transformation both ends time domain and frequency domain is time-limited, in transformation, needs signal carrying out periodic extension
It is converted again at periodic signal.
Under normal conditions, when carrying out Fourier transformation to finite length sequence in time domain with butterfly computation, often calculation amount
It is very big, generally it is difficult real-time process problem.Nineteen sixty-five, Cooley and Turkey be odd, even according to discrete Fourier transform, it is empty,
The characteristics such as real, improve conventional discrete Fourier Transform Algorithm, it is proposed that calculate the efficient, quick of discrete Fourier transform
Algorithm, i.e. Fast Fourier Transform (FFT) (FFT) calculate time for greatly reducing multiplication when discrete Fourier transform using this algorithm
Number, reduces several orders of magnitude, and the points of Fourier transformation are more by the operand of DFT, and FFT is compared in DFT calculation amounts
That reduces is more notable.According to being decomposed to sequence and the difference of choosing method produces a variety of fft algorithms, be broadly divided into base 2DIT and
Two kinds of base 2DIF.Due to the small remarkable advantage of Fast Fourier Transform (FFT) calculation amount, it is made to be widely used in field of signal processing, then
It can realize that the real-time processing of signal, Digital Signal Processing go out also with fast fourier transform algorithm by hardware
Now also rapidly develop, play the role of to the development of Digital Signal Processing it is vital, improve arithmetic speed and
Reduce hardware cost.For example, time-devision system in the analysis of noise signal, communication system and frequency division system (TDM/FDM) are converted,
Filtering Analysis, the spectrum analysis of signal are carried out in frequency domain, the fields such as extraction useful signal, the resolution ratio for improving signal will use
FFT。
When carrying out frequency analysis with Fast Fourier Transform (FFT), only in the case where meeting synchronized sampling and complete cycle truncation condition
It can accurately just obtain the harmonic parameters such as the frequency, amplitude and phase of signal, but be difficult often to meet in the actual environment
Condition is stated, therefore carry out FFT to signal to have spectral leakage and fence effect, seriously affects the precision of signal analysis, it is difficult
To meet actual needs.Since but spectral leakage can not avoid, it is necessary to design the frequency spectrum that different window functions reduces signal
Leakage.In order to reduce frequency analysis time-frequency spectrum leakage influence, carry out Fast Fourier Transform (FFT) before make signal be multiplied by one it is specific
Window function, generate so as to reduce due to signal cutout and be put into secondary lobe component, reduce spectral leakage, but be added window
Function can reduce the precision of main lobe frequency, subsequently also need to take measures to be made up.Common window function mainly has rectangular window, the Chinese
Peaceful window (hanning), hamming window (hanming), Blackman windows etc., different window function spectral characteristics is different, to reducing frequency
The influence for composing leakage is also different [55,56].It is Hanning window and rectangular window to use in practical applications at most.In this patent
Using Hanning window (hanning).
The frequency spectrum of Hanning window can be regarded as being formed by the spectral overlay of three rectangular windows, and the amplitude of the first secondary lobe is main
The 0.027% of valve amplitude, so as to eliminate High-frequency Interference, has the function that reinforcement main lobe so secondary lobe can cancel out each other,
Effectively inhibit spectral leakage.Comparison Hanning window and rectangular window frequency spectrum it can be found that the main lobe of Hanning window widen, amplitude reduce,
Secondary lobe is substantially reduced, and the rate of decay is also very fast, and from the point of view of reducing spectral leakage, Hanning window is better than rectangular window, but due to master
Valve is widened, and spectral resolution reduces accordingly.
2. the frequency spectrum refinement based on multiple modulation ZoomFFT
Under normal conditions, the frequency spectrum analysis method of mainstream is to carry out Fast Fourier Transform (FFT) on computers, but sometimes
We can encounter the signal of Frequency spectrum ratio comparatively dense, and often be only concerned some very narrow frequency range, and it is desirable that in this frequency range
Frequency resolution is very high.Frequency resolution refers to the minimum interval between discernmible two frequency spectrums in frequency spectrum, i.e.,
Δ f=fs/N 3.10
Wherein fs is sample frequency, and N counts for Fourier transformation.As can be seen from the above equation, it can be improved there are two types of method
Frequency resolution：
(1) sample frequency fs is reduced, too low sample frequency cannot reflect true signal, original signal is caused to be distorted；
(2) increase Fourier transformation points N, it is contemplated that the butterfly computation used when Fourier transformation, calculating can be made by increasing transformation points
It measures exponentially to increase, hardware cost can be significantly greatly increased in this way.
Therefore above two method is in practice and undesirable, in order to solve this problem, has scholar to propose frequency
The theory of refinement is composed, i.e., to a certain frequency range partial enlargement being concerned about in frequency spectrum, increases the spectral density in this frequency range, realizes frequency spectrum
The purpose of refinement.Frequency spectrum refinement technology rapidly develops in recent years, and common method mainly has：Zoom FFT based on multiple modulation,
[57-61] such as Yip-ZOOM transformation, Chirp-Z transformation, divides wherein the ZoomFFT methods based on multiple modulation have compared to other methods
The advantage for analysing precision, computational efficiency aspect, frequency resolution etc., is widely applied.
Multiple modulation refines spectral analysis method and uses：Shift frequency (multiple modulation)-low-pass digital filter-double sampling-FFT and spectrum
Analysis-frequency adjusts such a process, and principle process is as shown in Figure 6.
If analog signal x (t), after A/D is sampled, its discrete-time series x0 (n) is obtained, (n=0,1..., N-1), fs
For the sample frequency of analog signal, fe is the centre frequency of frequency band to be refined, and D is refinement multiple, and N is Fast Fourier Transform (FFT) point
Number.X0 (k) is the discrete spectrum sequence of output.Specifically it is broadly divided into the following steps：
1. multiple modulation shift frequency
Multiple modulation shift frequency refers to frequency domain coordinates to the left or moves right so that the starting point for the frequency range being refined is located at co-ordinate zero point
Position.The discrete Fourier transform of discrete signal x0 (n) is
Assuming that needing to refine the range of frequency range to be f1~f2, then centre frequency fe is
X0 (n) is multiplied byMultiple modulation is carried out, multiple modulation frequency-shift signaling x (n) is obtained
F in formulas=N Δs f is sample frequency, and Δ f is frequency resolution, L0=fe/ Δ f is the center displacement of frequency, that is,
Serial numbers of the centre frequency fe in frequency spectrum, so fe=L0Δf。
Known according to the property of discrete Fourier transform, the discrete spectrum X0 (k) of the discrete spectrum X (k) and x0 (n) of x (n) are full
Foot formula
X (k)=X0(k+L0) 3.14
It can be obtained from above formula, multiple modulation makes the centre frequency fe in former x0 (n) move on to the zero of x (n), that is, X0 (k) frequency spectrums
In the L0 articles spectral line move on to the zeros of X (k) frequency spectrums.Then, resampling is carried out to original discrete signal, sample frequency is made to reduce
It is refinement multiple to fs '=fs/D, wherein D.For prevent refinement after frequency spectrum there is aliasing, need before sampling into
Row low-pass filtering treatment.
2. digital low-pass filtering
In order to ensure that aliasing does not occur for the frequency spectrum after resampling, need to carry out anti-aliasing filter, if refinement multiple is D, then
The cutoff frequency of low-pass filter should meet fc≤fs/2D.
3. resampling
After multiple modulation shift frequency and low-pass filtering, the frequency range of analysis narrows original signal, when with lower sample frequency
Fs '=fs/D resamplings acquires a point per D point, obtains new discrete signal.
4. plural number FFT
New discrete signal is handled by zero padding and ensures that former Fourier analysis points N is constant, carries out FFT, obtain its from
Frequency spectrum is dissipated, frequency resolution is
Δ f'=fs'/N=fs/ DN=Δs f/D 3.15
Therefore frequency resolution improves D times before more refining.
5. shift frequency
It not is actual frequency spectrum through the frequency spectrum that the above process obtains, it is also necessary to move at actual frequency, i.e.,
It realizes in the case where ensureing that Fourier transformation analysis points are constant by above-mentioned 5 steps and is analysed to frequency
The frequency resolution of section improves D times.
From the analysis above, we can see that although under conditions of Fourier transformation points are certain, it can be by phase by ZoomFFT algorithms
The frequency resolution of frequency range is answered to improve D times, but this method is to carry out ZoomFFT on the basis of sacrificing data length
When transformation, the original signal data point needed to the Fourier transformation of N points should be DN, if directly carrying out DN to original signal data point
The Fast Fourier Transform (FFT) of point can equally reach the frequency resolution of ZoomFFT algorithms satisfaction.Thus, ZoomFFT is not
Have and fundamentally solve the problems, such as frequency resolution, can only be reached with less Fourier transformation points originally needed it is huge
The frequency resolution that Fourier transformation points could be realized greatly, due to increasing the calculation amount for converting points meeting Fourier transformation into finger
Number increases, this can undoubtedly greatly increase requirement and the cost of hardware, typically worthless.It is realized by ZoomFFT algorithms
Under the requirement for meeting assigned frequency resolution ratio, requirement and the cost of hardware are reduced, is to be worth extensive in today of the marketization
Application.
6. ZoomFFT frequency spectrum refinement algorithm simulatings
This trifle emulates the frequency spectrum refinement method based on multiple modulation described above, using two different signals
Type, one is each frequency contents to be closer to, and another kind is that each frequency content is apart from each other, verifies the validity of the algorithm.
If an analog current signal expression formula is
I=sin (2 π 9.1t)+sin (2 π 9.2t)+sin (2 π 9.5t) 3.17
Then its original signal spectrum and zoom FFT simulation result based on Zoom FFT are as shown in Figure 7.
If another analog signal is：
I=4cos (2 π/6 π 91.356t+)+3cos (2 π/9 π 101.232t+2)+cos (2 π
113.565·t+4π/3) 3.18
Its original signal spectrum and based on after Zoom FFT refinement frequency spectrum is as shown in Figure 8.
It is found by comparison diagram 7 and Fig. 8, the frequency spectrum refinement method based on Zoom FFT that this patent proposes, which can reach, to be carried
The requirement of high frequency resolution may be implemented to distinguish different frequency contents, and each frequency content in signal is closer,
The effect of frequency spectrum refinement is better, and more preferably for weaker signal component thinning effect.
(3) Spectrum Correction based on ratio method
Usual discrete spectrum can only be analyzed on limited sample length, this will result in spectral leakage, cause through too fast
All there is larger error in the frequency spectrum obtained after fast Fourier transformation, in frequency, amplitude and phase although being added before transformation
Window function can inhibit spectral leakage, but for some to the exigent occasion of these harmonic parameters, and only windowed function obtains
The precision that arrives or far from enough.In addition in modern digital signal processing, the frequency spectrum obtained by FFT or DFT is all discrete
Spectral line obtains frequency spectrum systematic sampling usually after the frequency spectrum process of convolution of the frequency spectrum and window function of echo signal.If
The frequency of echo signal is just on a certain spectral line, and frequency, amplitude and the phase at this moment obtained is all accurate.But often
Under normal circumstances, the frequency of echo signal is not on spectral line, but between two spectral lines, and corresponding spectral line does not exist at this time
On the A of main lobe center, frequency, amplitude and the phase reacted by this two peak value spectral lines are inaccurate.
The application of spectrum analysis technique of this phenomenon strong influence, therefore multi-expert all carries out discrete spectrum both at home and abroad
The research of alignment technique improves identification precision to reduce the identification error of harmonic parameters.
The discrete spectrum correcting theory of unifrequency ingredient or multi-frequency twocomponent signal apart from each other is mainly wrapped at present
It includes：Energy barycenter correction method, ratiometric correction method, FFT+DFT continuous refinements analysis Fourier's method of changing and phase difference method [62-
71].These four methods respectively have advantage and disadvantage, are also all used in Practical Project.Wherein ratiometric correction method is being used
When hanning windows, correction accuracy is very high, and frequency correction error is less than 0.0001 frequency resolution, and amplitude error is less than ten
A ten thousandth, phase difference are less than 1 degree.Since this patent is very high to the required precision of frequency in rotating speed recognizer, so
Hanning windows are added to be corrected the discrete stator current frequency spectrum obtained after FFT using ratiometric correction method, accurately to be turned
Sub- frequency.
Frequency correction is exactly accurately to find out the abscissa at main lobe center.If the frequency spectrum function of window function is f (x), f (x) phases
It is symmetrical for Y-axis, as shown in Figure 9.
Known by Fig. 9, y=f (x), y1=f (x+1), now needs to solve x by y and y1, that is, frequency spectrum correction amount is Δ x
=-x.Now construct a function V
That is V is to be determined by the ratio for being divided into the two of 1 points of ordinate between abscissa and the function of x, can solve its anti-letter
Several
X=g (v) 3.20
It willIt substitutes into, obtains
So Δ x=-x can be solved, this method is known as ratiometric correction method.
Known by Figure 10, in the calculating of actual discrete frequency spectrum, the actual frequency of signal is located at the x0 of main lobe center, yk in figure,
Yk+1 is two adjacent spectral lines of discrete spectrum main lobe center both sides, is enabledX=g (v) is substituted into, then frequency spectrum correction amount is
Δ K=-x.
If corrected with spectral line yk-1, yk, then enableSubstitute into x=g (v), this time-frequency spectrum correction amount K=-x-1
Finally correction frequency is
Wherein, K is discrete spectral line serial number (0~N/2-1), and N is Fourier transformation analysis points, and fs is signal sampling frequencies
But for different window functions, entirely different frequency correction function is had, this patent, which is mainly studied, is added the Chinese
Frequency correction effect when peaceful window.
The function expression of Hanning window is:
Its frequency spectrum function expression formula is
WhereinFor Di Liheli cores, Hanning window is corresponded to as a=0.5, when a=0.54 pairs
It should be in hamming window.Three phase differences are in bracketUsing the sum of this three modular functions as the modular function of W (ω), then can obtain
The main lobe function of Hanning window is
It enablesThen formula 3.25 is reduced to
3.26 substitution formula 3.19 of formula can be obtained
Work as a=0.5, when c → ∞, formula 3.24 can be reduced to
The inverse function for solving F (x), obtains
Here it is frequency correction function when addition Hanning window, substitution formula can find out correction frequency.
(4) Spectrum Correction algorithm simulating
The Spectrum Correction algorithm based on ratio method is emulated in this section, is compared by different emulation signals,
Verify the precision and validity of the algorithm.
1. carrying out Spectrum Correction, the front and back result of spectrum analysis such as Figure 11 institutes of correction to signal determined by formula 3.18
Show.
2. increasing the spacing of each spectrum component, if analog signal is
I=4cos (2 π/6 π 81.356t+)+3cos (2 π/9 π 101.232t+2)+cos (2 π
153.565·t+4π/3) 3.30
It is as shown in figure 12 that it corrects front and back result of spectrum analysis.
By the Spectrum Correction result of comparison diagram 11 and Figure 12 it is found that the dense degree of each frequency content influences frequency correction
Precision, each ingredient spacing is bigger, and frequency correction accuracy is higher, so the frequency correcting algorithm based on ratio method is suitable for unifrequency
In the correction of signal or multifrequency signal apart from each other, it is contemplated that need the rotor frequency ingredient extracted and power supply in this patent
Frequency is apart from each other, therefore can accurately obtain rotor frequency using this correcting algorithm.
(5) rotor frequency search and rotating speed calculate
It is exactly that rotor frequency is extracted in frequency spectrum after obtaining current spectrum, the step of most critical.It is special by the machinery of motor
Linearity curve is analyzed it is found that motor general work is in rated condition and hereinafter, so when the minimum value of rotor frequency is by rated speed
Rotor frequency determine, maximum value be rotating excitation field frequency, frequency search region is to be searched between minimum value and maximum value
The frequency corresponding to maximum amplitude in region is rotor frequency.
Wherein p is the number of pole-pairs of motor, and nR is Rated motor rotating speed.
Therefore rotor frequency is between flow and fupp.
After obtaining rotor frequency fr, the rotating speed n of motor can be easily obtained
N=fr×60 3.32
Speed Identification algorithm in-circuit emulation
In order to verify the rotating speed on-line identification algorithm of this patent proposition, establish based on the asynchronous of Matlab/Simulink
Simulation model of motor.The parameter of electric machine used in simulation model is as shown in table 1.
Table 1 emulates the parameter of electric machine
Simulation model, motor are powered using the AC power of 220V, and the motor in Simulink is utilized when operation to measure mould
Block acquires the rotating speed and stator current information of motor, is used for subsequent analysis.
Since the asynchronous machine dynamic model provided in Matlab/Simulink analogue systems is ideal model, motor fortune
The ingredient of power supply dominant frequency (50Hz) is contained only when row in stator current i.e.
ia=Imsin(ωt) 3.33
There is no the ingredients such as the rotor frequency generated under nonideality, eccentric frequency, so being acquired in Simulink
Original signal of stator current when can not be emulated as this algorithm performance, therefore in order to assess the motor studied in this patent
The performance in motor even running of rotating speed on-line identification algorithm needs to be artificially generated a kind of comprising dominant frequency (50Hz), rotor
The simulated machine stator current signal of frequency (in view of the rotating speed of motor is 1450rpm) and bilateral eccentricity component (3Hz)
[72], as shown in formula 3.31.
ia=io+0.1·sin(2π·24.2·t)+0.1·sin(2π·47·t+π/3)+0.1·sin(2π·53·
t) 3.34
Wherein, ia is actual stator electric current, and i0 is ideal stator current.
The motor actual speed such as Figure 13 acquired by motor measurement module shows, it can be seen that motor is starting 0.5s
After reach steady operational status.
The motor speed on-line identification algorithm based on rotor frequency proposed using this patent is to the analysis knot of stator current
Fruit such as Figure 14 shows.
From the analysis result of Figure 14 it is found that in the frequency spectrum of model stator circuit current, accurately known using this patent algorithm
Do not go out rotor frequency, size fr=24.151Hz, error analysis are as shown in table 2.
2 Speed Identification Algorithm Error of table is analyzed
As can be known from Table 2, in this emulation emulation experiment, the practical measurement rotating speed of motor is 1450r/min, passes through rotating speed
The rotor frequency that on-line identification algorithm obtains is 24.151Hz, and it is 1449.1r/min, the error with actual speed to be converted into rotating speed
For 0.9r/min, it is less than 1r/min, simulation result shows that the Speed Identification algorithm reliability that this patent proposes is very high.
Therefore, the motor speed accuracy obtained by the on-line identification method of above-mentioned optimization is high, and error is smaller.
It is enlightenment with above-mentioned desirable embodiment according to the present invention, through the above description, relevant staff is complete
Various changes and amendments can be carried out without departing from the scope of the technological thought of the present invention' entirely.The technology of this invention
Property range is not limited to the contents of the specification, it is necessary to determine its technical scope according to right.
Claims (7)
1. a kind of portable type current detects rotational speed detector, it is characterised in that：The cover top portion trepanning of the rotational speed detector allows line
It picks out, is used for and tested motor (8) wiring, rotational speed detector are internally provided with processor (1), processor (1) passes through current sense
Device (2) detects the electric current of tested motor (8), and signal tune is carried out in the filtered device of electric current (3) that current sensor (2) measures
After section and filtering in input processor (1)；
Include micro treatment module (1.1) in the processor (1), current data acquisition mould is connected on micro treatment module (1.1)
Block (1.2), current data processing module (1.3), spectroscopy processing module (1.4), rotating speed processing module (1.5), wherein electric current number
It is connected with current sensor (2) according to acquisition module (1.2), current data acquisition module (1.2) turns the stator of tested motor (8)
Speed is sent to by micro treatment module (1.1) in current data processing module (1.3), and current data processing module (1.3) will demodulate
Signal afterwards is sent to by micro treatment module (1.1) in spectroscopy processing module (1.4), and spectroscopy processing module (1.4) will be at frequency spectrum
Signal after reason is sent to by micro treatment module (1.1) in rotating speed processing module (1.5), is found rotor frequency and is calculated motor
Rotating speed.
2. a kind of portable type current according to claim 1 detects rotational speed detector, it is characterised in that：The case surface
Display screen and a variety of buttons are offered to be controlled.
3. a kind of portable type current according to claim 1 detects rotational speed detector, it is characterised in that：The processor
(1) it is ARM microcontroller.
4. a kind of portable type current according to claim 1 detects rotational speed detector, it is characterised in that：The current sense
Device (2) is Rogowski coil.
5. a kind of portable type current according to claim 1 detects rotational speed detector, it is characterised in that：The processor
(1) display module (4), Keysheet module (5) are additionally provided on.
6. a kind of portable type current according to claim 1 detects rotational speed detector, it is characterised in that：The processor
(1) signal processing module (6) is additionally provided on, processor (1) is sent to control mould by signal processing module (6) by signal is handled
Block (7), control module (7) control tested motor (8) and rotate.
7. a kind of Speed Identification algorithm of portable type current detection rotational speed detector according to claim 1, feature exist
In：The Speed Identification algorithm is the Speed Identification algorithm of the Speed Identification algorithm based on stator current frequency spectrum, Speed Identification algorithm
The step of be：
1) stator current demodulates
Stator current is expressed as：
I (t)=[k1+k2cos(2πf2t)+k3cos(2πf3t)+...+kncos(2πfnt)]cos(2πf1t) 3.1
Motor stator electric current can also be expressed as：
I (t)=m (t) cos (2 π f1t)--------------------------------3.2
Wherein enable
M (t)=k1+k2cos(2πf2t)+k3cos(2πf3t)+...+kncos(2πfnt)----------------3.3
A square processing is carried out to stator current, is obtained
The signal that formula 3.4 is indicated by low-pass filter after, just m (t) signal extractions are come out, by the letter after low-pass filtering
Number carry out evolution processing, obtain the stator current signal for being eventually used for spectrum analysis：
I (t)=0.707m (t) --- --- --- --- --- --- --- --- --- --- -- 3.5
2) spectrum analysis technique based on stator current
It is used based on multiple modulation refinement spectral analysis method：Shift frequency-low-pass digital filter-double sampling-FFT and spectrum analysis-frequency
Rate adjusts；
Y=f (x), y1=f (x+1) construct a function V
Solve its inverse function
X=g (v) --- --- --- --- --- --- --- --- --- --- -- 3.20
It willIt substitutes into, obtains
Δ x=-x can be solved；
It enablesX=g (v) is substituted into, then frequency spectrum correction amount is Δ K=-x；
It enablesX=g (v), this time-frequency spectrum correction amount K=-x-1 are substituted into, correction frequency is：
Frequency correction when Hanning window is added, the function expression of Hanning window is:
Its frequency spectrum function expression formula is：
Using the sum of this three modular functions as the modular function of W (ω), then the main lobe function that can obtain Hanning window is：
It enablesThen formula 3.25 is reduced to
3.26 substitution formula 3.19 of formula can be obtained
Work as a=0.5, when c → ∞, formula 3.24 can be reduced to
The inverse function for solving F (x), obtains correction of a final proof frequency：
3) rotor frequency search and rotating speed calculate
The frequency corresponding to maximum amplitude in region of search is rotor frequency：
Rotor frequency is between flowWith fuppBetween, obtain rotor frequency frLater, the rotating speed n of motor is obtained：
N=fr×60------------------------------------------------3.32
To show that the rotating speed n of motor, the rotating speed n of motor are then forwarded to control module (7), the tested electricity of control module (7) control
Machine (8).
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| CN115586345A (en) * | 2022-12-09 | 2023-01-10 | 深圳市双合电气股份有限公司 | Motor self-adaptive rotating speed estimation method and system based on stator current |
| CN116203419A (en) * | 2023-05-05 | 2023-06-02 | 江苏省特种设备安全监督检验研究院 | Motor energy efficiency detecting system based on multi-force field coupling action algorithm |
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