CN105841867A - Measuring method for tooth groove torque of permanent magnet motor - Google Patents

Abstract

The invention discloses a wavelet-signal-analysis-based measuring method for tooth groove torque of a permanent magnet motor. The method comprises: a torque sensor is used for detecting a measured permanent magnet motor; a signal pre-treatment module carries out conditioning on a sensing signal; according to a preset sampling frequency fs and a sampling point number N, a signal acquisition module extracts a torque signal output frequency f of the sensing signal after conditioning, wherein the f meets a formula: f=fs/N, and a torque signal of the measured permanent magnet motor is calculated; a feature extraction module carries out multi-resolution decomposition on the torque signal to obtain a wavelet coefficient of the torque signal and corrects the wavelet coefficient; and wavelet reconstruction is carried out by using the corrected wavelet coefficient, thereby obtaining a tooth groove torque of the measured permanent magnet motor. According to the invention, the method is easy to implement; the measurement difficulty is low; the measurement precision is high, and the cost is low.

Description

The measuring method of cogging torque of permanent magnet motor

Technical field

The present invention relates to the optimum design and control technical field of magneto, particularly relate to a kind of magneto The measuring method of cogging torque.

Background technology

Along with improving constantly of permanent magnetic material performance, magneto is increasingly widely used in high-performance speed With position Mechanical & electrical Transmission Control system, such as fields such as Digit Control Machine Tool, robot, electronic manufacture, elevators.So And, in magneto, permanent magnet and grooved armature iron core interact, and inevitably produce teeth groove Torque, its result causes torque ripple, causes vibration and noise, have impact on the control accuracy of system.

Cogging torque is the distinctive problem of magneto, is the physical quantity relevant to position, complete at motor manufacturing Will not change after one-tenth.Cogging torque is to must take into and solve in high-performance permanent magnet design of electrical motor and manufacture Critical problem.In high performance machine electric servo system, the magneto of bigger cogging torque can not meet The requirement of high performance control.Such as, the Permanent Magnet and Electric in the system such as high speed and super precision Digit Control Machine Tool, industrial robot Machine designs, and its primary demand is exactly Low gullet torque, because too high cogging torque can affect positioning precision. The cogging torque of magneto is measured, current domestic two kinds of methods of usual employing: is lever mensuration.This Kind of method is simple, directly perceived, be easily achieved, but precision is difficult to ensure that, can only react the general letter of cogging torque Breath, cannot use under certainty of measurement requires high occasion.Two is the static measurement using stepper motor, Namely it is conventional to dragging method.Its concrete metering system is: use the stepper motor that a torque pulsation is the least With the reductor of a high speed reducing ratio, by connecting reductor, motor speed to be measured is reduced, turn with rotating speed The torque pulsation in rotating shaft measured by square instrument, is cogging torque.The method requires that torque sensor precision is high, Measuring method is complicated, and instrument cost is high, and test function is single.

Summary of the invention

The technical problem to be solved is to provide a kind of cogging torque of permanent magnet motor being easily achieved Measuring method, the cogging torque reducing magneto is measured the cost of system, is improved its certainty of measurement.

For solving above technical problem, the embodiment of the present invention provides a kind of cogging torque of permanent magnet motor measuring method, Including:

Step 101: tested magneto is detected by torque sensor, exports described torque sensor Transducing signal sends to signal pre-processing module；

Step 102: described transducing signal is nursed one's health by described signal pre-processing module；

Step 103: signal acquisition module is according to sample frequency f preset_sWith sampling number N, extract conditioning After transducing signal in actual measurement torque output frequency value f=f_s/N；

Step 104: described signal acquisition module is according to conversion formula M=A × (f-f₀)/(f_p-f₀), meter Calculate the dtc signal M of described tested magneto；Wherein, A is torque full scale, and f is defeated for actual measurement torque Go out frequency values, f₀For torque offset output frequency values, f_pFor forward Full-span output frequency values；

Step 105: the described dtc signal collected is transmitted to feature extraction mould by described signal acquisition module Block；Described dtc signal includes cogging torque signal；

Step 106: described characteristic extracting module utilizes wavelet transform to differentiate described dtc signal more Rate is decomposed, it is thus achieved that the wavelet coefficient of described dtc signal；

Step 107: described characteristic extracting module is according to the pulsation of the cogging torque signal of described tested magneto Frequency, is modified described wavelet coefficient；

Step 108: described characteristic extracting module uses revised wavelet coefficient to carry out wavelet reconstruction, it is thus achieved that institute State the cogging torque signal of tested magneto.

Preferably, described signal pre-processing module includes: the voltage follower, the signal that are sequentially connected with amplify electricity Road, wave filter and shaping circuit；Described step 102 specifically includes:

Step 201: the magnitude of voltage of described transducing signal is adjusted by described voltage follower, so that described electricity The output voltage of pressure follower matches with input voltage；

Step 202: the transducing signal that described voltage follower is exported by described signal amplification circuit is amplified；

Step 203: the interference signal in the transducing signal after amplification process is filtered by described wave filter；

Step 204: filtered transducing signal is shaped as rectangular pulse signal by described shaping circuit, and provides To data collecting card.

Preferred embodiment central in one, described wave filter is the second order active using hardware circuit to realize Low pass filter.

In the middle of another preferred embodiment, described wave filter uses the mode of software filtering to sensing letter Number it is filtered.

Preferably, described step 106 specifically includes:

Step 601: after described characteristic extracting module treats that the sample rate of described dtc signal meets sampling thheorem, The total frequency band occupied by the signal collected is defined as SPACE V₀, described total frequency band is 0～f_s/2；Through a fraction Xie Hou, by V₀It is divided into low frequency subspace V₁With high frequency subspace W₁；, described V₁Frequency band be 0～f_s/ 4, Described W₁Frequency band is f_s/ 4～f_s/2；

Step 602: after two grades are decomposed, by described V₁It is decomposed into low frequency subspace V₂With high frequency subspace W₂, described V₂Frequency band be 0～f_s/ 8, described W₂Frequency band be f_s/ 8～f_s/4；And so on, by frequency Uniformly subdivision is: V₀=V₁⊕W₁, V₁=V₂⊕W₂..., V_j-1=V_j⊕W_j, therefore:

V₀=W₁⊕W₂⊕W₃......W_j⊕V_j

Wherein, each W_jIt is reflection V_j-1The high frequency subspace of spacing wave details, V_jIt is reflection V_j-1Spacing wave The low frequency subspace of details, W_jFor V_jAt V_j-1The orthogonal complement space；

Step 603: by multiresolution analysis and orthogonal space resolution theory,Wherein J is Arbitrarily yardstick, by signal x (t) ∈ L²(R) at space L²(R) upper launch, obtain following expression:

Wherein, Double-scaling equation is:

Ifd_j+1,n=< f_j,ψ_j+1,n>, and then decompose and obtain wavelet coefficient and be:

$c_{j+1,k}=\underset{n}{\&Sigma;}h(n-2k)c_{j,n}$

$d_{j+1,k}=\underset{n}{\&Sigma;}g(n-2k)d_{j,n}$

Wherein, k=0,1,2 ... n-1, represent translation position；The j frequency range to induction signal；c_j+1,k, d_j+1,kFor Described wavelet coefficient；H (k) is low pass filter sampling response；G (k) is high-pass filter sampling response； For scaling function；ψ_j,kT () is wavelet function.

Preferably, described step 107 comprises the following steps:

Step 701: according to rotating speed v and teeth groove quantity Z of described tested magneto, calculate described tested Cogging torque ripple frequency f of magneto_c=v × Z/60；

Step 702: according to described dtc signal output frequency f and described cogging torque ripple frequency f_c, select Small echo；And determine number of plies n of wavelet decomposition, wherein n > 0；

Step 703: described dtc signal is carried out 1 wavelet transform arriving n-layer, decomposes and obtain each layer Wavelet coefficient；

Step 704: retain and described cogging torque ripple frequency f_cThe component of corresponding wavelet coefficient, and will The component zero setting of the wavelet coefficient that remaining frequency range is corresponding, it is thus achieved that revised wavelet coefficient.

Preferably, described small echo is the western small echo of many shellfishes.

Preferably, described step 108 comprises the following steps:

Step 801: utilize the multi-resolution characteristics of small echo, searches the frequency corresponding to cogging torque ripple frequency section Segment signal；

Step 802: order remaining frequency band signals in addition to the frequency band signals of described correspondence is zero, and process obtains new Wavelet coefficient；

Step 803: utilize described wavelet coefficient that signal is reconstructed by below equation:

$c_{j,k}=\underset{n}{\&Sigma;}{c}_{j+1,k}h(n-2k)+\underset{n}{\&Sigma;}{d}_{j+1,k}g(n-2k)$

Wherein, c_j,kFor cogging torque signal, the signal that reconstruct obtains is cogging torque signal.

The technical scheme that the embodiment of the present invention provides, it provides the benefit that can be to general conventional torque sensor Transducing signal process, utilize signal acquisition module and data collecting card to extract turning of tested magneto Square signal, and according to the multi-resolution characteristics of wavelet decomposition, use characteristic extracting module and Industry Control to calculate DAS in machine carries out wavelet decomposition to dtc signal, and extraction turns with the teeth groove in dtc signal The wavelet coefficient that square ripple frequency matches carries out wavelet reconstruction, and the final teeth groove obtaining tested magneto turns Square signal, certainty of measurement is high and is easily achieved, and dtc signal and the industry that can be exported by data collecting card are controlled The cogging torque signal of computer export processed exports in display and shows, measures more directly perceived and can be real Time reflected measurement signal parameter situation.

Accompanying drawing explanation

Fig. 1 is that an embodiment flow process of a kind of cogging torque of permanent magnet motor measuring method that the present invention provides is shown It is intended to；

Fig. 2 is that a kind of of step S102 shown in Fig. 1 can the schematic flow sheet of implementation；

Fig. 3 is that a kind of of step S106 shown in Fig. 1 can the schematic flow sheet of implementation；

Fig. 4 is that a kind of of step S107 shown in Fig. 1 can the schematic flow sheet of implementation；

Fig. 5 is the system test platform structural representation that the present invention provides；

Fig. 6 is a kind of hardware circuit connection figure of signal pre-processing module；

Fig. 7 is motor cogging torque oscillogram.

Detailed description of the invention

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clearly Chu, it is fully described by.

See Fig. 1, be an embodiment of the measuring method of a kind of cogging torque of permanent magnet motor that the present invention provides Schematic flow sheet.

In the present embodiment, by utilize torque sensor, signal pre-processing module, signal acquisition module with The measurement apparatus of characteristic extracting module, industrial control computer composition, described cogging torque of permanent magnet motor Measuring method, comprises the following steps S101～step S108:

Step S101: torque sensor detects the torque of tested magneto, is exported by described torque sensor Transducing signal send to signal pre-processing module.

Step S102: described transducing signal is nursed one's health by described signal pre-processing module.Specifically, its letter Number conditioning process includes that signal is followed, signal amplifies, signal filtering and signal shaping, its pretreatment or conditioning Purpose be so that the signal of signal pre-processing module output meets the input signal of next stage processing module Requirement.

In a kind of attainable mode, signal pre-processing module is made up of hardware circuit.

Referring to Fig. 2, it is that a kind of of step S102 shown in Fig. 1 can the schematic flow sheet of implementation.

Voltage follower that shown signal pre-processing module includes being sequentially connected with, signal amplification circuit, filtering Device and shaping circuit.

The most described step S102, specifically includes step S201～step S204:

Step S201: the magnitude of voltage of described transducing signal is adjusted by described voltage follower, so that described The output voltage of voltage follower matches with input voltage.Voltage follower is so that output voltage and input The circuit that voltage is identical, is characterized in that input impedance is high, output impedance is low, thus voltage follower can conduct The buffer stage of front stage circuits and late-class circuit and isolation level, thus improve the load capacity of circuit.

Step S202: the transducing signal that described voltage follower is exported by described signal amplification circuit is carried out rationally Amplify.In the present embodiment, the purpose being amplified transducing signal is to adopt for the ease of late-class circuit signal The process of collection module, to obtain the highest precision.When being embodied as, to biography near signal source amplitude Sense signal is amplified, and the destruction of noise will reduce.Preferably, the amplitude that transducing signal amplifies is with letter The maximum input range of number acquisition module is as the criterion.

Step S203: the interference signal in the transducing signal after amplification process is filtered by described wave filter. When being embodied as, there is the High-frequency Interference of the electrical equipments such as motor due to measure field, when measured signal is the most weak, Will cover by disturbed signal (noise etc.), cause the data collected to there is error.According to torque sensing Device output signal characteristics, can design hardware circuit and realize second order active low pass filter, filter in transducing signal Unwanted composition or noise.

Alternatively, in the present embodiment, it is possible to use the mode of software filtering, the sensing letter that will collect Number utilize LabVIEW (Laboratory Virtual Instrument Engineering Workbench) software, I.e. laboratory virtual instrument Engineering Task platform, transducing signal is filtered by filtration module therein.

Step S204: filtered transducing signal is shaped as rectangular pulse signal by described shaping circuit.Specifically During enforcement, the transducing signal after torque sensor and filter process is often sawtooth waveforms or off-gauge side Ripple, after the transducing signal of this waveform is delivered to signal acquisition module, the dtc signal output frequency collected The data such as rate will form error.Therefore, before transducing signal is carried out dtc signal collection, need to set Meter shaping circuit carries out shaping to transducing signal.

Step S103: signal acquisition module is according to sample frequency f preset_sWith sampling number N, extract tune Actual measurement torque output frequency value f in transducing signal after reason, wherein f=f_s/N.Specifically, signals collecting Module is realized by data collecting card, it is preferable that described data collecting card chooses NI (National Instruments) i.e. the PCI-6251 multifunctional data acquisition card of National Instruments realizes.

Specifically, when actual measurement torque output frequency value f is extracted, according to default sample frequency f_sWith Sampling number N, i.e. can obtain the sampling time T=N/f to dtc signal_s, i.e. gather in time interval T Obtain a torque value, therefore, the output frequency f=1/T of dtc signal.

In the present embodiment, it is contemplated that follow-up time dtc signal is analyzed, count if sample frequency can not be sampled Divide exactly, it will cause energy leakage, amplitude distortion.Therefore, sampling number and sample frequency ratio are the most pre- It is set to integer.Such as, during measuring, when sample frequency f of data collecting card_sFor 1.25MHz (megahertz Time hereby), can set sampling number as 1250 points, being calculated the sampling period is 1ms (millisecond).The most every 1ms Transmitting a torque value, it is 1000Hz (hertz) that correspondence obtains the output frequency of torque value.Magneto rotating speed It is adjusted to 10 revs/min.Then the motor required time that turns around is 6 seconds.The torque value that this period collects Number is 6000.When being embodied as, can be by the Wave data of dtc signal that collects with electrical form Form preserves the appointment position to host hard drive.

When being embodied as, PCI-6251 multifunctional data acquisition card both can also may be used in the way of using simulation input In the way of using counter, dtc signal is acquired.When using the mode of simulation input, by torque The pulse signal of sensor output collects computer by analog channel；By arranging hits and sampling frequency Rate, comprises several pulse periods in making the sampling time, will by data collecting card analog signal input channel After pulse signal completely gathers into, utilize the extraction sub-VI of single-frequency information inside LabVIEW to obtain and turn The output frequency of square signal.When the mode using counter measures, setting measurement frequency range is Big value and minimum of a value, utilize survey engineering function to carry out frequency calculating, and multiple frequency values are measured in circulation every time, And using the mean value of multiple frequencies that records as collecting desired signal.

Step S104: described signal acquisition module is according to conversion formula M=A × (f-f₀)/(f_p-f₀), Calculate the dtc signal M of described tested magneto.Wherein, A is torque full scale, f₀For torque zero point Output frequency value, f_pFor forward Full-span output frequency values.In the present embodiment, described torque letter M ＞ 0 Time, for forward torque output valve；During dtc signal M ＜ 0, for opposing torque output valve.

Step S105: the described dtc signal collected is sent to feature extraction by described signal acquisition module Module；Described dtc signal includes cogging torque signal.

Step S106: described characteristic extracting module utilizes wavelet transform that described dtc signal is carried out many points Resolution is decomposed, it is thus achieved that the wavelet coefficient of described dtc signal.When being embodied as, can be by LabVIEW Calling MATLAB (Matrix Laboratory) software work platform, is mixed by programming realization wavelet transformation The algorithm of characteristic signal, carries out wavelet decomposition to dtc signal, it is thus achieved that the wavelet coefficient of dtc signal.

MATLAB is a kind of height for algorithm development, data visualization, data analysis and numerical computations Level technology computational language and interactive environment.

Referring to Fig. 3, it is that dtc signal is differentiated by the wavelet transform that utilizes that the embodiment of the present invention provides more Rate analyze a kind of can the flow chart of steps of implementation.

When being embodied as, when utilizing wavelet transform that dtc signal is carried out multiresolution analysis, it is concrete Decomposable process is:

Step S601: after described characteristic extracting module treats that described dtc signal sample rate meets sampling thheorem, The total frequency band occupied by the signal collected is (if frequency band is 0～f_s/ 2) it is defined as SPACE V₀, after level of decomposition V₀It is divided into two sub spaces: low frequency subspace V₁(frequency band is 0～f_s/ 4) and high frequency subspace W₁(frequently Band is f_s/ 4～f_s/2)。

Step S602: V after two grades are decomposed₁It is broken down into again the V of low frequency₂(frequency band is 0～f_s/ 8) and high Frequently subspace W₂(frequency band is f_s/ 8～f_s/ 4), and so on.The subdivision of this frequency subspace is as follows:

V₀=V₁⊕W₁, V₁=V₂⊕W₂..., V_j-1=V_j⊕W_j, therefore:

V₀=W₁⊕W₂⊕W₃......W_j⊕V_j (1)

Step S603: by multiresolution analysis and orthogonal space resolution theory,Wherein J appoints Meaning yardstick, by signal x (t) ∈ L²(R) at space L²(R) upper launch, obtain following expression:

Wherein, Double-scaling equation is:

Ifd_j+1,n=< f_j,ψ_j+1,n> and then decompose the wavelet coefficient obtained For:

$c_{j+1,k}=\underset{n}{\&Sigma;}h(n-2k)c_{j,n}---\left(5\right)$

$d_{j+1,k}=\underset{n}{\&Sigma;}g(n-2k)d_{j,n}---\left(6\right)$

Wherein, k=0,1,2 ... n-1, represent translation position, only need in limited range value；J is to induction signal Frequency range；c_j+1,k, d_j+1,kFor described wavelet coefficient；H (k) is low pass filter sampling response；G (k) is High-pass filter sampling response；For scaling function；ψ_j,kT () is wavelet function.

The multiresolution analysis of wavelet transform, the mixed signal formed by various different frequencies is (such as torque Signal) it is decomposed into the signal of different frequency range, signal is had by frequency band disposal ability.

Step S107: described characteristic extracting module according to the cogging torque signal of described tested magneto Ripple frequency, is modified described wavelet coefficient.When being embodied as, by equation (5) and equation (6) Calculating after, obtain dtc signal wavelet coefficient；Pulsation further according to the cogging torque signal in dtc signal Frequency, extracts the wavelet coefficient matched in the wavelet coefficient of dtc signal with cogging torque signal ripple frequency Component, and other wavelet coefficient component zero setting, to revise wavelet coefficient.

Referring to Fig. 4, it is that a kind of of step S107 shown in Fig. 1 can the schematic flow sheet of implementation.

Specifically, described step S107 comprises the following steps S701～step S704:

Step S701: according to rotating speed v and teeth groove quantity Z of described tested magneto, calculate described quilt Survey cogging torque ripple frequency f of magneto_c=v*Z/60.

Step S702: according to described dtc signal output frequency f and described cogging torque ripple frequency f_c, select Small echo；And determine number of plies n of wavelet decomposition, wherein n ＞ 0.

In this embodiment, it is preferred that, described small echo is the western small echo of many shellfishes (Daubechies Wavelet).Many The western small echo of shellfish is also referred to as DB small echo, and it is to have the small echo that the compactly support of high vanishing moment is orthogonal, in the pressure of signal Contracting, denoising and Singularity Detection aspect play an important role.

Specifically, in cogging torque ripple frequency f_cAfter acquisition, number of plies n of wavelet decomposition small echo is carried out Can be determined after choosing.One signal length is that the signal of m at most can be analyzed to n=log₂M layer, often One layer all has corresponding frequency range.When being embodied as, each band limits can be obtained by calculating, further according to Cogging torque ripple frequency finds out its place frequency range, so that it is determined that required number of plies n decomposed of wavelet transformation.

Step S703: described dtc signal is carried out 1 wavelet transform arriving n-layer, decomposes and obtain each layer Wavelet coefficient.

Step S704: retain and described cogging torque ripple frequency f_cThe component of corresponding wavelet coefficient, and By the component zero setting of wavelet coefficient corresponding for remaining frequency range, it is thus achieved that revised wavelet coefficient.

Further, the measuring method of described cogging torque of permanent magnet motor also includes step S108: described feature Extraction module uses revised wavelet coefficient to carry out wavelet reconstruction, it is thus achieved that the teeth groove of described tested magneto Dtc signal.

In a kind of attainable mode, described step S108 specifically includes following steps S801～S803:

Step S801: utilize the multi-resolution characteristics of small echo, finds corresponding to cogging torque ripple frequency section Frequency band signals.

Step S802: order remaining frequency band signals in addition to the frequency band signals of described correspondence is zero, processes and obtains newly Wavelet coefficient, the signal that obtains of reconstruct is cogging torque signal.

Step S803: utilize described wavelet coefficient that signal is reconstructed by below equation:

$c_{j,k}=\underset{n}{\&Sigma;}{c}_{j+1,k}h(n-2k)+\underset{n}{\&Sigma;}{d}_{j+1,k}g(n-2k)---\left(7\right)$

Wavelet reconstruction process is the inverse operation of decomposable process, and the signal that reconstruct obtains is cogging torque signal.

As it is shown in figure 5, be the validity of the magnetic groove torque measuring method that checking the present embodiment proposes further, this Embodiment constructs the permagnetic synchronous motor system test platform with LabVIEW as upper computer software, Qi Zhongzhu Partly to have: magnetic powder brake, JN338 digital-type intelligent torque rotary speed sensor, NI PCI-6251 data Capture card, SCB-68 terminal box, Guangzhou Numerical Control Equipment Co., Ltd GSK SJT series magneto with And supporting DAH01 series of servo driver, wherein the parameter of JN338 torque rotary speed sensor is: torque Range 30N.m, the number of teeth 60 tooth, the degree of accuracy 0.5 grade, the linearity≤0.5%F S；The Permanent Magnet and Electric of measurand Machine parameter is: rated power 1.5kW, rated speed 2500r/min, nominal torque 6N.m, teeth groove number 60.

After the software and hardware part of experiment porch designs, carry out magneto magnetic groove torque measurement experiment.Profit With JN338 torque sensor, tested magneto is detected, and utilize Signal Pretreatment mould shown in Fig. 6 Surveyed transducing signal is nursed one's health by block.According to default sample frequency f_sWith sampling number N, extract conditioning After the dtc signal output frequency f=f of transducing signal_s/ N, and calculate the torque letter of described tested magneto Number.According to formula, dtc signal is carried out Multiresolution Decomposition, calculates the wavelet coefficient of surveyed dtc signal, And described wavelet coefficient is modified, then revised wavelet coefficient is carried out wavelet reconstruction, it is thus achieved that institute State the cogging torque signal of tested magneto.

First passing through servo-driver setting and making motor speed perseverance is 10r/min, soft at LabVIEW host computer The sample frequency of PCI-6251 data collecting card is set in part 600KHz, and gathering counts is set to 600, according to Formula f=f_s/ N, calculating actual measurement torque output frequency is 1000Hz, through overfrequency and torque reduction formula M=A × (f-f₀)/(f_p-f₀) calculate the dtc signal of described tested magneto.

Then carry out utilizing wavelet transform that described torque is believed according to surveyed dtc signal according to step S106 Number carry out Multiresolution Decomposition and obtain the wavelet coefficient of dtc signal, and by step S107 to obtained wavelet systems Number is modified, and is reconstructed wavelet coefficient after revising finally by step S108, obtains cogging torque letter Number, waveform is as shown in Figure 7.

The measuring method of a kind of cogging torque of permanent magnet motor that the embodiment of the present invention provides, can be to general precision The transducing signal of torque sensor processes, it is not necessary to expensive high accuracy torque sensor of arranging in pairs or groups makes With, utilize signal acquisition module or data collecting card to extract the faint dtc signal in transducing signal, and according to The multi-resolution characteristics of wavelet decomposition, carries out wavelet decomposition through MATLAB platform to dtc signal, and extracts The wavelet coefficient matched with the cogging torque ripple frequency in dtc signal carries out wavelet reconstruction, finally obtains The cogging torque signal of tested magneto, certainty of measurement is high and is easily achieved.

The above is the preferred embodiment of the present invention, it is noted that for the common skill of the art For art personnel, under the premise without departing from the principles of the invention, it is also possible to make some improvements and modifications, this A little improvements and modifications are also considered as protection scope of the present invention.

Claims (8)

1. the measuring method of a cogging torque of permanent magnet motor, it is characterised in that comprise the following steps:

Step 101: tested magneto is detected by torque sensor, exports described torque sensor Transducing signal sends to signal pre-processing module；

Step 102: described transducing signal is nursed one's health by described signal pre-processing module；

Step 103: signal acquisition module is according to sample frequency f preset_sWith sampling number N, extract conditioning After transducing signal in actual measurement torque output frequency value f=f_s/N；

Step 104: described signal acquisition module is according to conversion formula M=A × (f-f₀)/(f_p-f₀), meter Calculate the dtc signal M of described tested magneto；Wherein, A is torque full scale, and f is defeated for actual measurement torque Go out frequency values, f₀For torque offset output frequency values, f_pFor forward Full-span output frequency values；

Step 105: the described dtc signal collected is transmitted to feature extraction mould by described signal acquisition module Block；Described dtc signal includes cogging torque signal；

Step 106: described characteristic extracting module utilizes wavelet transform to differentiate described dtc signal more Rate is decomposed, it is thus achieved that the wavelet coefficient of described dtc signal；

Step 107: described characteristic extracting module is according to the pulsation of the cogging torque signal of described tested magneto Frequency, is modified described wavelet coefficient；

Step 108: described characteristic extracting module uses revised wavelet coefficient to carry out wavelet reconstruction, it is thus achieved that institute State the cogging torque signal of tested magneto.

2. the measuring method of cogging torque of permanent magnet motor as claimed in claim 1, it is characterised in that described Signal pre-processing module includes: voltage follower, signal amplification circuit, wave filter and the shaping being sequentially connected with Circuit；Described step 102 specifically includes:

Step 201: the magnitude of voltage of described transducing signal is adjusted by described voltage follower, so that described electricity The output voltage of pressure follower matches with input voltage；

Step 202: the transducing signal that described voltage follower is exported by described signal amplification circuit is amplified；

Step 203: the interference signal in the transducing signal after amplification process is filtered by described wave filter；

Step 204: filtered transducing signal is shaped as rectangular pulse signal by described shaping circuit, and provides To data collecting card.

3. the measuring method of cogging torque of permanent magnet motor as claimed in claim 2, it is characterised in that described Wave filter is the second order active low pass filter using hardware circuit to realize.

4. the measuring method of cogging torque of permanent magnet motor as claimed in claim 2, it is characterised in that described Wave filter uses the mode of software filtering to be filtered transducing signal.

5. the measuring method of cogging torque of permanent magnet motor as claimed in claim 1, it is characterised in that described Step 106 specifically includes:

Step 601: after described characteristic extracting module treats that the sample rate of described dtc signal meets sampling thheorem, The total frequency band occupied by the signal collected is defined as SPACE V₀, described total frequency band is 0～f_s/2；Through a fraction Xie Hou, by V₀It is divided into low frequency subspace V₁With high frequency subspace W₁；, described V₁Frequency band be 0～f_s/ 4, Described W₁Frequency band is f_s/ 4～f_s/2；

Step 602: after two grades are decomposed, by described V₁It is decomposed into low frequency subspace V₂With high frequency subspace W₂, described V₂Frequency band be 0～f_s/ 8, described W₂Frequency band be f_s/ 8～f_s/4；And so on, by frequency Uniformly subdivision is: V₀=V₁⊕W₁, V₁=V₂⊕W₂..., V_j-1=V_j⊕W_j, therefore:

V₀=W₁⊕W₂⊕W₃......W_j⊕V_j

Wherein, each W_jIt is reflection V_j-1The high frequency subspace of spacing wave details, V_jIt is reflection V_j-1Spacing wave The low frequency subspace of details, W_jFor V_jAt V_j-1The orthogonal complement space；

Step 603: by multiresolution analysis and orthogonal space resolution theory,Wherein J is Arbitrarily yardstick, by signal x (t) ∈ L²(R) at space L²(R) upper launch, obtain following expression:

Wherein, Double-scaling equation is:

Ifd_{J+1, n}=< f_j, ψ_{J+1, n}> and then decompose and obtain wavelet coefficient and be:

$c_{j+1,k}=\underset{n}{\&Sigma;}h(n-2k)c_{j,n}$

$d_{j+1,k}=\underset{n}{\&Sigma;}g(n-2k)d_{j,n}$

Wherein, k=0,1,2 ... n-1, represent translation position；The j frequency range to induction signal；c_j+1,k, d_j+1,kFor Described wavelet coefficient；H (k) is low pass filter sampling response；G (k) is high-pass filter sampling response； For scaling function；ψ_j,kT () is wavelet function.

6. the measuring method of cogging torque of permanent magnet motor as claimed in claim 1, it is characterised in that described Step 107 comprises the following steps:

Step 701: according to rotating speed v and teeth groove quantity Z of described tested magneto, calculate described tested Cogging torque ripple frequency f of magneto_c=v × Z/60；

Step 702: according to described dtc signal output frequency f and described cogging torque ripple frequency f_c, select Small echo；And determine number of plies n of wavelet decomposition, wherein n > 0；

Step 703: described dtc signal is carried out 1 wavelet transform arriving n-layer, decomposes and obtain each layer Wavelet coefficient；

Step 704: retain and described cogging torque ripple frequency f_cThe component of corresponding wavelet coefficient, and will The component zero setting of the wavelet coefficient that remaining frequency range is corresponding, it is thus achieved that revised wavelet coefficient.

7. the measuring method of cogging torque of permanent magnet motor as claimed in claim 6, it is characterised in that described Small echo is the western small echo of many shellfishes.

8. the measuring method of cogging torque of permanent magnet motor as claimed in claim 1, it is characterised in that described Step 108 comprises the following steps:

Step 801: utilize the multi-resolution characteristics of small echo, searches the frequency corresponding to cogging torque ripple frequency section Segment signal；

Step 802: order remaining frequency band signals in addition to the frequency band signals of described correspondence is zero, and process obtains new Wavelet coefficient；

Step 803: utilize described wavelet coefficient that signal is reconstructed by below equation:

$c_{j,k}=\underset{n}{\&Sigma;}{c}_{j+1,k}h(n-2k)+\underset{n}{\&Sigma;}{d}_{j+1,k}g(n-2k)$

Wherein, c_j,kFor cogging torque signal, the signal that reconstruct obtains is cogging torque signal.