CN1198381C - Rotor position detecting method of brushless DC motor having no sensor - Google Patents

Abstract

The present invention relates to a rotor position detecting method for a brushless DC motor without a sensor. The method has the detecting steps: in the first step: judging whether a user selects a position information repairing mode; in the second step: if the position information repairing mode is not selected, estimating the position of a main rotor to drive the motor by using the current and the voltage of an A phase, a B phase and a C phase; in the third step: if the position information repairing mode is the judged result in the first step, detecting the phase voltage of the A phase, the B phase and the C phase after the phase current of the A phase, the B phase and the C phase is cut off; in the fourth step: calculating the back electromotive force of the A phase, the B phase and the C phase through the phase voltage of the A phase, the B phase and the C phase detected in the third step. The steps can detect the position information of the rotor, and the method also comprises an initializing step of a rotor position signal. The present invention has the advantage of stable driving of the brushless DC motor.

Description

Brshless DC motor does not have the rotor position detecting method of transducer

Technical field

What the present invention relates to is about the DC motor rotor location detection method, particularly be the rotor position detecting method that brshless DC motor does not have transducer.

Background technology

Describe relevant prior art with reference to the accompanying drawings in detail.

The drive circuit of the existing brushless electric machine of Fig. 1.As shown in the figure, the drive circuit of brushless electric machine is: capacitor C 1, C2 series connection, this series capacitance are to make the AC power after the rectification can be steadily; Frequency converter converts the direct voltage of above-mentioned capacitor C 1, C2 to three-phase alternating voltage according to the control signal of microcomputer; Motor drives by the three-phase alternating voltage of frequency converter; The microcomputer utilization is applied to the position that voltage and current on the motor detects rotor, and microcomputer is controlled the driving of frequency converter according to the position of detected rotor then.

Fig. 2 is the schematic diagram that the control device structure of the no transducer of brshless DC motor connects.The control device of the no transducer of general as shown in the figure brshless DC motor has following structure: comparator 1 compares the signal of desirable motor speed of user and current motor speed, then the corresponding with it comparison signal of output; According to the comparison signal of comparator 1 output, speed control 2 output speed control signals; The speed control signal of speed control 2 and motor rotor position signal are input on the voltage instruction generator 3,3 generations of voltage instruction generator and speed control signal and the corresponding voltage instruction of motor rotor position signal; According to the voltage instruction that voltage generator produces, frequency converter 4 converts direct voltage to three-phase alternating voltage; Current/voltage detector 6 detects each phase voltage of frequency converter 4 outputs, detects direct voltage Vdc by series resistance Rdc simultaneously; Speed/positional calculation portion receives from the current/voltage detection signal of above-mentioned current/voltage detector output, then the current/voltage detection signal is performed calculations, and the motor rotor position signal that output is corresponding is with it also exported the rate signal when front motor simultaneously.

The course of work to the control device of the no transducer of existing brshless DC motor with said structure describes below.

At first, 1 pair of desirable motor speed of user of comparator and present speed signal compare, then the corresponding with it comparison signal of output.According to the comparison signal of comparator 1 output, the corresponding with it speed control signal of speed control 2 outputs that is to say that if current motor speed is littler than the desirable motor speed of user then output increases the speed control signal of motor speed; If current motor speed is bigger than the desirable motor speed of user, then output reduces the speed control signal of motor speed.

The motor rotor position signal of the speed control signal of above-mentioned speed control 2 and speed/positional calculation portion 7 is input on the voltage instruction generator 3,3 generations of voltage instruction generator and speed control signal and the corresponding voltage instruction of motor rotor position signal.The voltage instruction that voltage generator produces is applied on each switching device of frequency converter 4, so frequency converter 4 converts direct voltage Vdc to three-phase alternating voltage.So motor 5 drives by the three-phase alternating voltage of frequency converter 4 outputs.

Current/voltage detector 6 detects each phase voltage of frequency converter 4 outputs, detects above-mentioned direct voltage Vdc by series resistance Rdc simultaneously, that is to say as shown in Figure 3, the DC series electric current by the resistance detection of contacting.

Speed/positional calculation this moment portion receives from the current/voltage detection signal of current/voltage detector 6 outputs, then above-mentioned current/voltage detection signal is performed calculations, the motor rotor position signal that output is corresponding with it, also output outputs to voltage instruction generator 3 and comparator 1 with the motor rotor position signal with when the rate signal of front motor respectively when the rate signal of front motor simultaneously.

The speed and the positions of motor are calculated by wherein above-mentioned speed/positional calculation portion 7 by following mathematical expression.

[mathematical expression 1]

$K_E{\mathrm{\ω}}_r\mathrm{SIN}{\mathrm{\θ}}_r=V_a-{\mathrm{Ri}}_a-\frac{{\mathrm{di}}_a}{\mathrm{dt}}\left(L_s{i}_a\right)$

$K_E{\mathrm{\ω}}_r\mathrm{SIN}({\mathrm{\θ}}_r+120)=V_b-{\mathrm{Ri}}_b-\frac{{\mathrm{di}}_b}{\mathrm{dt}}\left(L_s{i}_b\right)$

$K_E{\mathrm{\ω}}_r\mathrm{SIN}({\mathrm{\θ}}_r+240)=V_c-{\mathrm{Ri}}_c-\frac{{\mathrm{di}}_c}{\mathrm{dt}}\left(L_s{i}_c\right)$

R wherein: resistance θ _r: motor rotor position

L _s: induction coefficient i _a, i _b, i _c: phase current

V _a, V _b, V _c: phase voltage

Carry out above-mentioned work then repeatedly, the driving of motor 5 is controlled.

But when adopting the brshless DC motor with said structure not have the sensor drive washing machine, the position that utilizes phase current and phase voltage to detect rotor drives motor.In these cases, if causing motor to take off groove, the error of position signalling change conference just is difficult to return to normal condition.

Summary of the invention

The objective of the invention is to overcome above-mentioned technology and supply, provide a kind of and calculate back electromotive force by cut off phase current in the motor-driven process, the brshless DC motor that accurately calculates the position signalling of rotor does not have the rotor position detecting method of transducer:

The present invention solves the problems of the technologies described above the technical scheme that is adopted: the present invention is the rotor position detecting method that a kind of brshless DC motor does not have transducer, and this detection method is to utilize the voltage and current on this motor to calculate rotor-position, and it is as follows to detect step:

First step: judge whether the user has selected positional information revisal pattern; Second step: if not positional information revisal pattern, then utilize ' electric current of A, B, C ' phase and voltage, the position of calculating main rotor drives motor; Third step: in the judged result of first step, if positional information revisal pattern is then cut off and ' after the phase current of A, B, C ' phase, detected ' the phase voltage of A, B, C ' phase; The 4th step: by above-mentioned third step detected ' the phase voltage Va of A, B, C ' phase, Vb, Vc, calculate ' back electromotive force Emfa, the Emfb of A, B, C ' phase, Emfc, this formula of mathematical is as follows:

Va-Vb＝Emfa-Emfb

Vb-Vc＝Emfb-Emfc

Vc-Va＝Emfc-Emfa

The 5th step: calculate the positional information of rotor, this formula of mathematical is as follows:

Wherein Emfd is the magnetic flux back electromotive force; Emfq is the back electromotive force of moment of torsion.

The invention has the beneficial effects as follows: this law is bright to be that phase current calculates back electromotive force by cutting off arbitrarily in the motor-driven process, and the position signalling by the accurate initialization rotor of back electromotive force that calculates more stably drives brshless DC motor.

Description of drawings

Fig. 1 is the drive circuit of existing brushless electric machine;

Fig. 2 is the schematic diagram that the control device structure of the no transducer of existing brshless DC motor connects;

Fig. 3 adopts series resistance to detect the circuit diagram of phase current on the basis of Fig. 2;

Fig. 4 is a workflow diagram of the present invention;

Fig. 5 is the oscillogram of each phase voltage of the present invention when not applying electric current;

Fig. 6 is the oscillogram of each the phase voltage back electromotive force of the present invention when not applying electric current;

Fig. 7 is the figure that concerns between each phase voltage of the present invention and the back electromotive force.

Embodiment

With reference to the accompanying drawings embodiments of the invention are elaborated.

The present invention is the rotor position detecting method that brshless DC motor does not have transducer.This method is identical with the device of employed device and prior art shown in Figure 2.Fig. 4 is a workflow diagram of the present invention.As shown in Figure 4, the brshless DC motor of the present invention rotor position detecting method that do not have a transducer comprises the steps: first step: judge whether the user has selected positional information revisal pattern; Second step: if not positional information revisal pattern, then utilize ' electric current of A, B, C ' phase and voltage, the position of calculating main rotor drives motor; Third step: if positional information revisal pattern is then cut off and ' after the phase current of A, B, C ' phase, detected ' the phase voltage of A, B, C ' phase; The 4th step: by third step detected ' phase voltage of A, B, C ' phase, the calculating ' back electromotive force of A, B, C ' phase.By the 4th step calculate ' back electromotive force of A, B, C ' phase, detectable rotor position information also comprise the initialization step of rotor-position signal.

The implementation that brshless DC motor of the present invention is not had a rotor position detecting method of transducer is elaborated below:

At first, 1 pair of desirable motor speed of user of comparator and present speed signal compare, then the corresponding with it comparison signal of output.According to the comparison signal of comparator 1 output, the corresponding with it speed control signal of speed control 2 outputs that is to say that if current motor speed is littler than the desirable motor speed of user then output increases the speed control signal of motor speed; If current motor speed is bigger than the desirable motor speed of user, then output reduces the speed control signal of motor speed.

Then, the motor rotor position signal of the speed control signal of above-mentioned speed control 2 and speed/positional calculation portion 7 is input on the voltage instruction generator 3,3 generations of voltage instruction generator and speed control signal and the corresponding voltage instruction of motor rotor position signal.The voltage instruction that voltage generator produces is applied on each switching device of above-mentioned frequency converter 4, and frequency converter 4 converts direct voltage Vdc to three-phase alternating voltage.Motor 5 drives by the three-phase alternating voltage of frequency converter 4 outputs.

The phase voltage of each phase that current/voltage detector 6 detects above-mentioned frequency converter 4 outputs is different with prior art, and the switching device of closing each phase detects phase voltage after cutting off electric current.

Speed/positional calculation this moment portion receives from the current/voltage detection signal of current/voltage detector 6 outputs, the current/voltage detection signal is performed calculations, the motor rotor position signal that output is corresponding with it, also output outputs to voltage instruction generator 3 and comparator 1 with the motor rotor position signal with when the rate signal of front motor respectively then when the rate signal of front motor simultaneously.

That is to say, after closing all switching devices of frequency converter 4 and cutting off electric current, current/voltage detector 6 detect as shown in Figure 5 ' phase voltage of A, B, C ' phase, and with above-mentioned ' phase voltage of A, B, C ' phase imposes on speed/positional calculation portion 7.By current/voltage detector 6 output ' phase voltage of A, B, C ' phase, speed/positional calculation portion 7 calculates as shown in Figure 6 that ' back electromotive force of A, B, C ' phase is then by ' back electromotive force of A, B, C ' phase detects rotor position information.The aforementioned calculation process is expressed as follows with mathematical expression.

Fig. 7 is the graph of a relation between each phase voltage and the back electromotive force.Above-mentioned relation is represented then can release following mathematical expression with vector expression.

[mathematical expression 2]

Va-Vb＝Emfa-Emfb

Vb-Vc＝Emfb-Emfc

Vc-Va＝Emfc-Emfa

At this moment owing to Emfd=Emfa, so magnetic flux back electromotive force (Emfd) equals 1/3 (1Va-Vb-Vc).Wherein the back electromotive force of moment of torsion (Emfq) is $\sqrt{3}/2S(\mathrm{Vb}-\mathrm{Vc})$

The mathematical expression of position signalling shown in Figure 7 is as follows:

[mathematical expression 3]

The user sets device according to certain hour revisal at interval for, converts positional information revisal pattern to through behind the certain hour, then cuts off ' behind the electric current of A, B, C ' phase, detecting ' the phase voltage of A, B, C ' phase.

Close all switching devices of frequency converter, cut off each phase current after, detect ' the phase voltage of A, B, C ' phase.

Utilize that above-mentioned ' phase voltage calculation of A, B, C ' phase goes out the ' back electromotive force of A, B, C ' phase.

' back electromotive force of A, B, C ' phase detects the positional information of rotor, and it is benchmark initialization rotor-position signal that above rheme is put detection information in utilization then.

In sum, the present invention is the positional information initialization rotor-position signal that detects rotor by the following method: cut off ' after the phase current of A, B, C ' phase detects phase voltage, utilize that above-mentioned ' phase voltage calculation of A, B, C ' phase goes out the back electromotive force of each phase, then by ' back electromotive force of A, B, C ' phase detects the positional information of rotor, the initialization rotor-position signal.

Claims (2)

1. a brshless DC motor does not have the rotor position detecting method of transducer, it is characterized in that this detection method is to utilize the voltage and current on this motor to calculate rotor-position, and it is as follows to detect step:

First step: judge whether the user has selected positional information revisal pattern;

Second step: if not positional information revisal pattern, then utilize ' electric current of A, B, C ' phase and voltage, the position of calculating main rotor drives motor;

Third step: in the judged result of first step, if positional information revisal pattern is then cut off and ' after the phase current of A, B, C ' phase, detected ' the phase voltage Va of A, B, C ' phase, Vb, Vc;

The 4th step: by above-mentioned third step detected ' the phase voltage Va of A, B, C ' phase, Vb, Vc, calculate ' back electromotive force Emfa, the Emfb of A, B, C ' phase, Emfc, this formula of mathematical is as follows:

Va-Vb＝Emfa-Emfb

Vb-Vc＝Emfb-Emfc

Vc-Va＝Emfc-Emfa

The 5th step: calculate the positional information of rotor, this formula of mathematical is as follows:

Wherein Emfd is the magnetic flux back electromotive force; Emfq is the back electromotive force of moment of torsion.

2. according to the method described in the claim 1, it is characterized in that Overall Steps detects in finishing claim 1 after, detectable rotor position information also comprises the initialization step of rotor-position signal.

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