CN101599732B - Control method of brushless DC motor (BLDC) position signal phase error based on back EMF zero crossing point reconstruction - Google Patents

Abstract

The invention discloses a control method of brushless D.C. motor (BLDC) position signal phase error based on back EMF zero crossing point reconstruction, belonging to the technical field of the control method of BLDC non-position sensor technology. The method comprises the following steps: respectively collecting three phases of filtered terminal voltage waveforms, the coordinate systems thereof being alfa coordinate system in which vectors of three axels in the alfa coordinate system are used for representing three filtered terminal voltages, calculating the projection of the three vectors of the alfa coordinate system in the belta coordinate system. The degree beta by which the belta coordinate system lags behind the alfa coordinate system is controlled to achieve real-time compensation for the error of position signal phase caused by RC first order low pass filtering, and the zero-crossing points of the three vectors in the belta coordinate system are phase-changing points, thus realizing accurate phase-changing. The invention can avoid being affected by RC filtering under the working condition of broad rotating speed.

Description

The control method of the BLDC position signalling phase error of back-emf zero crossing point reconstruction

Technical field

Invention relates to a kind of control method of BLDC position signalling phase error of back-emf zero crossing point reconstruction, belongs to the technical field of the control method of bldc position-sensor-free technology.

Background technology

At present, sensorless technology is motor and the important research direction that the field of driving recent two decades comes, and has developed the various control technology.In the field of permanent-magnet brushless DC electric machine (bldc) sensorless technology, judge that based on the back-emf zero crossing information position-sensor-free technology of rotor-position is an important part, derive three main directions: 1) terminal voltage method; 2) phase voltage method; 3) triple-frequency harmonics method.These three main directions have two problems that need solution jointly: 1) how to reject the noise that is brought by PWM; 2), obtain commutation accurately constantly how accurately with 30 ° of back-emf zero crossing information phase shifts.Traditional method has added a RC filter at the front end of voltage acquisition when solving these two problems.The RC filter is being undertaken dual task promptly: 1) filtering is by the High-frequency Interference of PWM generation; 2) counter potential waveform that will reject after disturbing postpones 30 °, obtains zero crossing information then and then obtains commutation constantly.Because the cut-off frequency of RC filter can't change with the change of speed, phase shift can't reach accurate 30 ° under the different rotating speeds condition, thereby under wide rotating speed operating condition, needs back-emf is carried out phase-shift compensation on the basis of conventional method.How to carry out phase-shift compensation accurately, and then realize commutation accurately, become the key issue of wide rotating speed operation bldc position-sensor-free technology.

Summary of the invention

The present invention seeks to provides a kind of simple at the defective that prior art exists, practical and can realize under the rotating speed service conditions of broad that permanent-magnet brushless DC electric machine (bldc) the position-sensor-free technology of accurate commutation is the control method of the BLDC position signalling phase error of back-emf zero crossing point reconstruction.

The present invention adopts following technical scheme for achieving the above object:

The control method of the BLDC position signalling phase error of back-emf zero crossing point reconstruction of the present invention is characterized in that comprising the steps:

1) the three-phase input end voltage with permanent-magnet brushless DC electric machine obtains three opposite potential through single order RC low pass filter respectively, wherein three phase terminals voltage is respectively a phase terminal voltage Va, b phase terminal voltage Vb, c phase terminal voltage Vc, and three opposite potential are respectively a opposite potential Ea, b opposite potential Eb, c opposite potential Ec;

2) described three opposite potential of step 1 are obtained digital signal and export microprocessor to through modulate circuit, AD sample circuit successively;

3) the described digital signal of step 2 is passed through the pwm switching signal that microprocessor obtains three-phase full-bridge inverter;

4) pwm switching signal with the described three-phase full-bridge inverter of step 3 passes through the three-phase input end voltage that three-phase full-bridge inverter obtains permanent-magnet brushless DC electric machine.

Advantage of the present invention is as follows: the zero crossing information that 1. can directly reflect opposite potential under motor is not drawn the condition of neutral point.2. different rotating speeds down can be real-time the position signalling phase place that causes by the RC filter of compensation on error.

Description of drawings

Fig. 1 is the system block diagram of permanent-magnet brushless DC electric machine position-sensor-free technology.

Fig. 2 is a coordinate transform schematic diagram of the present invention, solid line is represented the alfa coordinate system, dotted line represents to lag behind the belta coordinate system of alfa coordinate system β (β=π/6-α), Ea, Eb and Ec are that three of 120 ° of mutual deviations are through filtered back-emf vector under the alfa coordinate system, and Ea ', Eb ' and Ec ' are three vectors after coordinate transform reconstruct of 120 ° of mutual deviations under the belta coordinate system.

Fig. 3 is the concrete implementing procedure schematic diagram of the present invention.

Fig. 4 is a program flow diagram of the present invention.

Fig. 5 is that the present invention is with a P _N=24W, U _N=24V, n _NTwo pairs of utmost point surface-mount type permanent-magnet brushless DC electric machines of=3000rmp are research object, test.Experimental waveform such as figure five (a) and (b), (c), (d), (e) and (f).(a) E in _a, E _bAnd E _cBe respectively A, B and the waveform of C phase terminal voltage behind low-pass first order filter, E ' _aBe the A opposite potential waveform after the coordinate transform reconstruct.Because DC component of offsetting after the coordinate transform and triple-frequency harmonics, and more than 5 times and 5 times harmonic content seldom, so waveform is near sinusoidal.(b) be the oscillogram of motor during from the 1500rmp raising speed to 3000rmp; (c) be the refinement oscillogram in the 1500rmp scope in the motor boosting velocity procedure; (d) be the refinement oscillogram in the 3000rmp scope in the motor boosting velocity procedure.Can find at 1500rmp in the 3000rmp scope E ' _aZero crossing all with A go up the jumping the edge and jump along overlapping down of hall signal mutually, then rely on E ' _a, E ' _bAnd E ' _cZero crossing information can obtain phase change logic, realize the position-sensor-free technology; (e) for after adopting position-sensor-free technology of the present invention, the A phase current i when motor speed is 1500rmp _aCounter potential waveform E ' after waveform and the A phase reconstruction _aWaveform; (f) for after adopting position-sensor-free technology of the present invention, the A phase current i when motor speed is 3000rmp _aCounter potential waveform E ' after waveform and the A phase reconstruction _aWaveform; Experimental result has confirmed feasibility of the present invention.

Embodiment

Be elaborated below in conjunction with the technical scheme of accompanying drawing to invention:

Adopt the permanent-magnet brushless DC electric machine drive system of this specific implementation method to form as shown in Figure 1.Comprising four parts: 1) with DSP2812 be control control core module; 2) three phase full bridge power model; 3) permanent-magnet brushless DC electric machine body; 4) single order RC low-pass filter circuit module.

With TMS320F2812 is that control control core module mainly contains four work: the 1) collection of back-emf signal; 2) the angle of phase displacement α that caused by the RC low-pass first order filter of real-time calculating; 3) three opposite potential that AD sampling is obtained are carried out coordinate transform, promptly calculate the projection of alfa coordinate system under the belta coordinate system, make belta coordinate system hysteresis alfa coordinate system β (β=π/6-α); 4) draw commutation according to the zero crossing information of following three waveforms of belta coordinate system and provide 6 road pwm signals constantly.The effect of single order RC low-pass filtering module: the High-frequency Interference that filtering is caused by PWM (pulse-width modulation), but simultaneously the counter potential waveform of motor has been caused certain phase shift α, and the different α of rotating speed are also different, and the relation between α and the rotating speed is as follows:

$\mathrm{\α}\left(\mathrm{\ω}\right)={\tan }^{-1}\frac{R_0{R}_1\mathrm{C\ω}}{R_0+R_1}$

ω is the electric angle speed of motor.How to compensate the error on the position signalling phase place of under different rotating speeds, bringing by single order RC low pass filter.

Shown in Fig. 3,4.Concrete implementation step is as follows:

1, gather three phase terminals voltage (i.e. the mid point voltage to earth of three brachium pontis) and bring noise by PWM (pulse-width modulation) through single order RC low pass filter filters out, the selection of RC low pass filter cutoff frequency is according to the frequency of PWM, makes the decay of high-frequency signal amplitude near 0, chooses according to following formula:

$A\left({\mathrm{\ω}}_h\right)=\frac{R_1}{\sqrt{{(R_0+R_1)}^2+\left(R_0{R}_{1}C{\mathrm{\ω}}_h\right)}}$

ω _hBe switching frequency.

2, with filtered three phase terminals voltage through modulate circuit, zoom to DSP2812 acceptable 0 in the scope of 3v, be converted into digital signal through the AD sampling and give DSP2812, on the basis of hardware platform that with DSP2812 is the control core, realize: the 1) calculating of motor electric angle speed by programming; 2) calculate under a certain rotating speed angle of phase displacement α that brings by RC single order low-pass filtering; 3) be illustrated in figure 2 as coordinate transform schematic diagram of the present invention, the projection of alfa coordinate system under the belta coordinate system promptly calculated in coordinate transform; 4) draw phase change logic, provide 6 road pwm switching signals.

1) rotating speed of motor calculating is identical with traditional method, and establishing two adjacent zero crossing time differences of back-emf is t, and then the electric angle speed of motor is:

$\mathrm{\ω}=\frac{\mathrm{\π}}{t}$

2) calculate the angle of phase displacement α that brings by RC single order low-pass filtering under a certain rotating speed.After the filter hardware design was finished, α was that the monotropic function of ω is as follows:

$\mathrm{\α}\left(\mathrm{\ω}\right)={\tan }^{-1}\frac{R_0{R}_1\mathrm{C\ω}}{R_0+R_1}$

According to following formula, by in the CCS environment, programming, the real-time phase shifting angle α that calculates under a certain rotating speed.

3) coordinate transform.As shown in Figure 2, three mutual deviations under the alfa coordinate system

Vector represent three-phase through filtered terminal voltage respectively, show as and have direct current and be

The back-emf information of biasing, and on phase place, differ α with real back-emf, as previous step result calculated, i.e. E _a, E _bAnd E _cMake belta coordinate system hysteresis alfa coordinate system β by programming, the pass between β and the α is:

$\mathrm{\β}=\frac{\mathrm{\π}}{6}-\mathrm{\α}$

And calculate three vector E under the alfa coordinate system _a, E _bAnd E _cProjection under the belta coordinate system obtains E ' _a, E ' _bAnd E ' _cThree vectors, E _a, E _b, E _cWith E ' _a, E ' _b, E ' _cBetween relation as follows:

$\left\{\begin{array}{c}{E}_a^{\′}=E_a\cos \mathrm{\β}+E_b\cos [\frac{2\mathrm{\π}}{3}-\mathrm{\β}]+E_c\cos [\frac{2\mathrm{\π}}{3}+\mathrm{\β}]\\ E_b^{\′}=E_b\cos \mathrm{\β}+E_c\cos [\frac{2\mathrm{\π}}{3}-\mathrm{\β}]+E_a\cos [\frac{2\mathrm{\π}}{3}+\mathrm{\β}]\\ E_c^{\′}=E_c\cos \mathrm{\β}+E_a\cos [\frac{2\mathrm{\π}}{3}-\mathrm{\β}]+E_b\cos [\frac{2\mathrm{\π}}{3}+\mathrm{\β}]\end{array}\right.$

The operational block diagram of coordinate transform as shown in Figure 3.

4) obtain phase change logic, provide 6 road pwm switching signals.Three vector E ' after the reconstruct _a, E ' _bAnd E ' _cWith three vector E before the reconstruct _a, E _bAnd E _cCompare, the cycle equates, the phase phasic difference $\mathrm{\β}(\mathrm{\β}=\frac{\mathrm{\π}}{6}-\mathrm{\α}),$ And E ' _a, E ' _bAnd E ' _cEliminated and be biased to

DC component, do not have the zero crossing information that has directly reacted opposite potential under the condition that neutral point draws at motor.Three vector E ' after the reconstruct then _a, E ' _bAnd E ' _cZero crossing be desirable commutation constantly constantly, promptly as E ' _a＞0 o'clock shutoff three-phase full-bridge inverter A manages, opens three-phase full-bridge inverter A mutually down and goes up pipe, E ' mutually _aTurn-offed A at＜0 o'clock and manage, open A pipe down mutually on mutually, B, the commutation of C phase and then obtain phase change logic by that analogy, and then provide 6 road pwm switching signals.Realization is based on the position-sensor-free technology of the BLDC position signalling phase error correction of back-emf zero crossing point reconstruction.

With the A opposite potential is example, and B and C opposite potential are analogized as follows according to symmetry:

$E_a^{\′}=\underset{n=1}{\overset{n=\∞}{\mathrm{\Σ}}}{a}_n\left(2\cos \mathrm{\β}\cos \right[\mathrm{n\ωt}]\sin {\left[\frac{\mathrm{n\π}}{3}\right]}^2-\sqrt{3}\sin \mathrm{\β}\sin [\frac{2\mathrm{n\π}}{3}\left]\sin \right[\mathrm{n\ωt}\left]\right)+b_n\left(\sqrt{3}\sin \mathrm{\β}\sin \right[\frac{2\mathrm{n\π}}{3}\left]\cos \right[\mathrm{n\ωt}]+2\cos \mathrm{\β}\sin [\mathrm{n\ωt}\left]\sin {\left[\frac{\mathrm{n\π}}{3}\right]}^2\right)$

The situation that can obtain its each harmonic is as follows:

$\left\{\begin{array}{c}{E}_a^{\′}\left(0\right)=0\\ E_a^{\′}\left(1\right)=\frac{3}{2}\left(a_1\cos \right[\stackrel{`}{\mathrm{\β}}+\mathrm{\ωt}]+b_1\sin [\mathrm{\β}+\mathrm{\ωt}\left]\right)\\ E_a^{\′}\left(3n\right)=0\\ ......\end{array}\right.,$ Wherein n is a natural number

Can find out 1 from following formula) DC component in the filtered terminal voltage is disallowable, do not draw the zero crossing information that can directly reflect opposite potential under the condition of neutral point at motor, and this is one of them advantage.2) the 3n subharmonic is disallowable, causes the waveform conversion to some extent of coordinate transform front and back, but does not influence the zero crossing information of waveform.3) first-harmonic β before the back-emf first-harmonic retardation change after the changes in coordinates is because the phase place of counter potential waveform is identical with the cycle and the phase place of this back-emf first-harmonic with the cycle, so the zero crossing of first-harmonic is the zero crossing of counter potential waveform.Then the zero crossing of waveform is desirable commutation point after the changes in coordinates.The present invention is with a P _N=24W, U _N=24V, n _NTwo pairs of utmost point surface-mount type permanent-magnet brushless DC electric machines of=3000RMP are research object, are the control core with TMS320F2812, test.Experimental result is seen Fig. 5.

Above content is the detailed explanation in conjunction with concrete a kind of mode, can not assert that concrete enforcement of the present invention is confined to this.For the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to the definite scope of patent protection of claim that the present invention submits to.

Claims (2)

1. the control method of the BLDC position signalling phase error of a back-emf zero crossing point reconstruction is characterized in that comprising the steps:

1) the three-phase input end voltage with permanent-magnet brushless DC electric machine obtains the three-phase counter potential waveform through single order RC low pass filter respectively, wherein three phase terminals voltage is respectively a phase terminal voltage Va, b phase terminal voltage Vb, c phase terminal voltage Vc, and three opposite potential are respectively a opposite potential Ea, b opposite potential Eb, c opposite potential Ec;

2) described three opposite potential of step 1 are obtained digital signal and export microprocessor to through modulate circuit, AD sample circuit successively;

3) the described digital signal of step 2 is passed through the pwm switching signal that microprocessor obtains three-phase full-bridge inverter;

4) pwm switching signal with the described three-phase full-bridge inverter of step 3 passes through the three-phase input end voltage that three-phase full-bridge inverter obtains permanent-magnet brushless DC electric machine;

Obtaining of the pwm switching signal of the described three-phase full-bridge inverter of step 3) comprises the steps:

1. adopt the time difference t of two adjacent zero crossings of three opposite potential to obtain the electric angle speed of permanent-magnet brushless DC electric machine:

2. adopt step 1. the electric angle speed omega of described permanent-magnet brushless DC electric machine obtain the phase shifting angle of permanent-magnet brushless DC electric machine:

And then the angle beta of belta coordinate system hysteresis alfa coordinate system is:

3. adopt the angle beta of the 2. described belta coordinate system of step hysteresis alfa coordinate system to obtain the three opposite potential projection under the belta coordinate system respectively under the alfa coordinate system:

E wherein _a' be the A phasor1 after the reconstruct, E _b' be the B phasor1 after the reconstruct, E _c' be the C phasor1 after the reconstruct;

4. obtain phase change logic:

Three vector E after the 3. described three opposite potential reconstruct of step _a', E _b' and E _c' zero crossing be commutation constantly constantly, the three-phase phase change logic is formed in described commutation constantly;

5. the PWM module in the 4. described phase change logic process of the step microprocessor is obtained the pwm switching signal of three-phase full-bridge inverter, wherein R ₀Be the input resistance of single order RC low pass filter, R ₁Be the output resistance in parallel of single order RC low pass filter, C is the output capacitance in parallel of single order RC low pass filter.

2. the control method of the BLDC position signalling phase error of back-emf zero crossing point reconstruction according to claim 1 is characterized in that the cut-off frequency of described single order RC low pass filter is chosen as follows:

ω wherein _hBe the switching frequency of the pwm switching signal of the described three-phase full-bridge inverter of step 3, R ₀Be the input resistance of single order RC low pass filter, R ₁Be the output resistance in parallel of single order RC low pass filter, C is the output capacitance in parallel of single order RC low pass filter.

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