KR20060068845A - Apparatus for estimating rotor position of three phase brushless dc motor without position sensors - Google Patents

Abstract

The output voltage of the voltage divider is integrated into the low pass filter and the phase delay in the low pass filter is compensated for so that the phase is delayed by exactly 90 °.

The counter electromotive force generated by the three-phase current output from the inverter section and flowing through the a-phase, b-phase and c-phase coils wound on the stator of the 3-phase BLDC motor is distributed to the voltage divider, and converted from the analog / digital converter to the digital voltage. After integrating with the digital low pass filter, the phase delay compensator compensates for the phase that is not delayed exactly 90 ° in the digital low pass filter, and delays the phase by 90 °. By outputting the position estimation signal of the rotor, it is possible to drive the three-phase BLDC motor stably by accurately controlling the switching operation of the inverter according to the position of the rotor, and improve the driving efficiency.

BLDC motor, rotor position, low pass filter, phase delay compensator, integrator

Description

Apparatus for estimating rotor position of three phase Brushless DC motor without position sensors}

1 is a block diagram showing an example of a conventional rotor position estimation device.

Figure 2 is a block diagram showing another example of a conventional rotor position estimation device.

Figure 3 is a block diagram showing the configuration of the rotor position estimation device of the present invention.

Explanation of symbols on the main parts of the drawings

300: inverter 310: three-phase BLDC motor

320: voltage divider 330: analog-to-digital converter

340: digital low pass filter 350: phase delay compensator

360: comparator

The present invention does not use expensive position control signal generators such as encoders to position the rotor of a brushless three-phase DC motor (hereinafter, abbreviated as 'three-phase BLDC motor'). The present invention relates to a rotor position estimator for a three-phase BLDC motor without a position sensor for accurately estimating.

In general, three-phase BLDC motor is developed to maintain the characteristics of three-phase DC motor while removing the brush that acts as a commutator in a conventional three-phase DC motor, a rotor made of permanent magnets, and three A coil, that is, a stator in which a, b and c phase coils are wound.

The three-phase BLDC motor supplies three-phase currents to the a-phase, b-phase, and c-phase coils wound on the stator, and the a-phase, b-phase, and c-phase coils respectively generate magnetic fields according to the supplied three-phase currents. To rotate the rotor made of permanent magnets.

At this time, in order to accurately control the rotational speed of the rotor of the BLDC motor, it is necessary to accurately estimate the position of the rotor. That is, the BLDC motor is configured to selectively switch the switching elements of the inverter unit for estimating the position of the rotor and for switching the direction of the current flowing to the a-phase, b-phase and c-phase coils wound on the stator according to the estimated rotor position. The rotational speed of the rotor is controlled by adjusting the on and off points.

1 is a block diagram showing an example of a conventional rotor position estimation apparatus. As shown therein, the counter electromotive force Va, Vb, Vc generated by the current flowing through the a-phase, b-phase, and c-phase coils output from the inverter unit 100 and wound around the stator of the three-phase BLDC motor 110 is obtained. A voltage divider 120 for distributing, an integrator 130, 130a, 130b for integrating respective counter electromotive forces Va, Vb, and Vc distributed by the voltage divider 120, and the integrators 130, 130a, and 130b, respectively. ) Is compared with the ground voltage, and zero crossings are detected and comparators 140, 140a and 140b are generated to generate the rotor position estimation signal.

An example of the conventional rotor position estimator configured as described above outputs a three-phase current while the switching elements of the inverter unit 100 are selectively turned on and off according to a switching control signal, and the output three-phase current is a three-phase BLDC. The rotor is rotated by being supplied to the a-phase, b-phase and c-phase coils wound on the stator of the motor 110.

As the three-phase coil flows into the three-phase current, the counter electromotive force Va, Vb, Vc is generated, and the generated counter electromotive force Va, Vb, Vc is distributed in the voltage divider 120 and output. The counter electromotive force Va, Vb, Vc output from the 120 is integrated in the integrators 130, 130a, and 130b, respectively, and the phase is delayed. Here, the integrators 130, 130a, and 130b are pure integrators that delay the phases of the counter electromotive forces Va, Vb, and Vc by 90 ° using, for example, operational amplifiers.

Output signals of the integrators 130, 130a, and 130b are respectively applied to the non-inverting input terminals (+) of the comparators 140, 140a and 140b, and to the inverting input terminals (-) of the comparators 140, 140a and 140b. As the ground voltage is applied, the comparators 140, 140a, and 140b compare the output voltages of the integrators 130, 130a, and 130b with the ground voltages, respectively, and detect zero crossing of the output voltages of the integrators 130, 130a, and 130b. Output pulse signal.

The pulse signals output by the comparators 140, 140a, and 140b are signals for estimating the position of the rotor of the three-phase BLDC motor 110, and a gate driving signal is generated according to the output signals of the comparators 140, 140a and 140b. In addition, a gate driving signal for switching the switching elements of the inverter unit 100 is generated.

However, the above-described conventional rotor position estimator integrates the back EMF Va, Vb, Vc output from the voltage divider 120 into the integrators 130, 130a, 130b, and delays the phase by 90 °. Drift due to the characteristics of the DC offset of the amplifier and saturation problems of the integrators 130, 130a, and 130b occur.

Therefore, most drives that drive three-phase BLDC motors do not use integrators 130, 130a, 130b that delay the phase by an exact 90 °, and as shown in FIG. 2, low pass filters 200, 200a, 200b. Integrating the counter electromotive force Va, Vb, Vc output from the voltage divider 120 using.

However, integrating the back EMF Va, Vb, Vc using the low pass filters 200, 200a, 200b reduces the drift as the poles of the low pass filters 200, 200a, 200b move away from the origin. The delay is not exactly 90 ° and the gain is lowered.

This phenomenon occurs more severely toward the low speed region where the cutoff frequency of the low pass filters 200, 200a, and 200b is low, and the phase delay is not exactly 90 °, so that the switching sequence of the inverter unit 100 is not accurate. Therefore, there was a problem that can not drive the three-phase BLDC motor efficiently.

It is therefore an object of the present invention to provide a rotor position estimation apparatus for a three-phase BLDC motor without a position sensor capable of accurately estimating the rotor position of a three-phase BLDC motor without using a position sensor.                         

Another object of the present invention is to integrate the output voltage of the voltage divider into the low pass filter, the rotor position of the three-phase BLDC motor without position sensor to compensate for the phase delay in the low pass filter so that the phase is delayed by exactly 90 ° The present invention provides an estimation apparatus.

The rotor position estimation device for a three-phase BLDC motor without a position sensor of the present invention having the above object includes a voltage divider for distributing a counter electromotive force generated according to a three-phase current output from an inverter unit and flowing to a three-phase BLDC motor. An analog / digital converter for converting each counter electromotive force distributed by a divider into a digital voltage, a digital low pass filter for digitally integrating the output voltage of the analog / digital converter, and a phase of an output signal of the digital low pass filter. Comprising a phase delay compensator for compensating the phase delay by 90 °, and a comparator for outputting the output voltage of the phase delay compensator as a position estimation signal of the rotor of the three-phase BLDC motor compared to the ground voltage.

이고, 상기 위상지연 보상기의 위상지연보상계수는

인 것을 특징으로 한다.The integral value of the digital low pass filter is

The phase delay compensation coefficient of the phase delay compensator

It is characterized by that.

는 디지털 저역통과필터로 입력되는 역기전력이고,

는 디지털 저역통과필터에서 출력되는 역기전력이며,

는

이며,

는 디지털 저역통과필터의 극(pole)이며,

는 위상이다.here,

Is the back EMF input to the digital low pass filter,

Is the back EMF output from the digital low pass filter,

Is

Is,

Is the pole of the digital lowpass filter,

Is phase.

Hereinafter, a rotor position estimation apparatus for a three-phase BLDC motor without a position sensor according to the present invention will be described in detail with reference to the accompanying drawings of FIG. 3.

3 is a block diagram showing the configuration of the rotor position estimation device of the present invention. As shown therein, the back EMF (Va1, Vb1, Vc1) that is generated in accordance with the three-phase current output from the inverter unit 300 and flowing to the a-phase, b-phase and c-phase coil of the three-phase BLDC motor 310 A voltage divider 320 and an analog-to-digital converter 330 for converting each of the counter electromotive forces Va2, Vb2, and Vc2 distributed by the voltage divider 320 into digital voltages Va3, Vb3, and Vc3, respectively, and the analog The digital low pass filter 340 for digitally integrating the output voltage of the digital converter 330 and the phase delay compensator 350 for compensating the phase of the output signal of the digital low pass filter 340 to be delayed by 90 °. And a comparator 360 for outputting the output voltage of the phase delay compensator 350 as a position estimation signal of the rotor of the three-phase BLDC motor 310 by comparing the output voltage with the ground voltage.

The rotor position estimating apparatus of the present invention configured as described above outputs three-phase current while the switching elements of the inverter unit 300 are selectively turned on and off according to the switching control signal, and the output three-phase current is a three-phase BLDC motor ( The rotor is rotated by being supplied to the a-phase, b-phase and c-phase coils wound on the stator of 310.

After the three-phase current flows to the a-phase, b-phase and c-phase coils, the counter electromotive force Va1, Vb1, Vc1 is generated, and the generated counter electromotive force Va1, Vb1, Vc1 is distributed in the voltage divider 320. The analog / digital converter 330 converts the digital back electromotive force Va2, Vb2, and Vc3 into outputs.

The counter electromotive force Va2, Vb2, Vc3 output from the analog-to-digital converter 330 is integrated in the digital low pass filter 340, and the phase is delayed to less than 90 °, and the output voltage of the digital low pass filter 340 is reduced. Va3, Vb3, Vc3) is compensated for the phase delay in the phase delay compensator 350 so that the phase is delayed by exactly 90 degrees.

The counter electromotive force integrated while the phase is delayed by exactly 90 ° in the digital low pass filter 340 and the phase delay compensator 350 is input to the comparator 360 to detect the ground level, compare and zero crossing, and detect the zero crossing. Is output as a rotor position estimation signal of the three-phase BLDC motor 310.

Here, the operation of integrating the phases of the back EMF Va2, Vb2, Vc2 by exactly 90 ° in the digital low pass filter 340 and the phase delay compensator 350 will be described.

)로 적분할 경우에 드리프트 및 적분기의 포화가 발생하므로 본 발명에서는 역기전력(Va)을 디지털 저역통과필터(340)가 다음의 수학식 1과 같이 적분하게 된다.Back EMF (Va2) is pure integrator (

In the present invention, since the drift and the saturation of the integrator occur, the digital low pass filter 340 integrates the back electromotive force Va as shown in Equation 1 below.

는 디지털 저역통과필터로 입력되는 역기전력이고,

는 디지털 저역통과필터에서 출력되는 역기전력이며,

는

이며,

는 디지털 저역통과필터의 극(pole)이다.here,

Is the back EMF input to the digital low pass filter,

Is the back EMF output from the digital low pass filter,

Is

Is,

Is the pole of the digital lowpass filter.

및 이득

은 각각 다음의 수학식 2 및 수학식 3과 같다.Phase in Equation 1

And gain

Are as Equations 2 and 3, respectively.

는 추정된 동기 각속도이다.here,

Is the estimated synchronous angular velocity.

에 위상지연 보상기(350)가 수학식 4와 같이 위상지연 보상계수

를 곱하여 위상지연이 정확히 90°가 되도록 보상한다.In the present invention, the integral voltage output from the low pass filter 340 as shown in Equation 1

The phase delay compensator 350 has a phase delay compensation coefficient as shown in Equation 4.

Multiply by to compensate for a phase delay of exactly 90 °.

이고,

및

이다.Where the phase delay compensation coefficient

ego,

And

to be.

를 적분할 경우에 디지털 저역통과필터(340)의 큰 시정수에 의해서 발생하는 드리프트 문제를 해결하기 위해서는 차단주파수가 커야 되나, 차단주파수가 클 경우에 위상을 저속 영역에서의 위상지연의 정확도가 떨어지는 문제가 발생한다.Reverse electromotive force into which the digital low pass filter 340 is input in the present invention

In order to solve the drift problem caused by the large time constant of the digital low pass filter 340, the cutoff frequency should be large. A problem arises.

가 저속영역에서는 작은 값이고, 3상 BLDC 모터의 회전자의 회전속도가 증가함에 따라 증가하도록 다음의 수학식 5와 같이 주파수의 함수로 설정하였다.Therefore, in the present invention, the pole of the digital low pass filter 340

Is a small value in the low speed region, and is set as a function of frequency so as to increase as the rotation speed of the rotor of the three-phase BLDC motor increases.

는 상수이다.here,

Is a constant.

In this way, the final output voltage passing through the digital low pass filter 340 and the phase delay compensator 350 is expressed by Equation 6 below.

On the other hand, while the present invention has been shown and described with respect to specific preferred embodiments, various modifications and changes of the present invention without departing from the spirit or field of the invention provided by the claims below It can be easily understood by those skilled in the art. That is, the above description is based on the counter electromotive force Va of the a phase generated by the three-phase BLDC motor. In the present invention, the same applies to the counter electromotive force Vb of the b phase and the counter electromotive force Vc of the c phase.

 As described above, the present invention estimates the position of the rotor of a three-phase BLDC motor without using a position sensor, and integrates the back electromotive force of the three-phase BLDC motor with a low pass filter, and compensates the phase delay with a phase delay compensator. By accurately delaying the phase by 90 °, the position of the rotor can be accurately estimated, and the switching operation of the inverter can be accurately controlled according to the estimated position of the rotor to stably drive the three-phase BLDC motor. Can be improved.

Claims (3)

A voltage divider for distributing back EMF generated according to the three-phase current output from the inverter unit and flowing to the three-phase BLDC motor; An analog / digital converter for converting each counter electromotive force distributed by the voltage divider into a digital voltage; A digital low pass filter for digitally integrating the output voltage of the analog / digital converter; A phase delay compensator for compensating the phase of the output signal of the digital low pass filter to delay the phase by 90 °; And Rotor position estimation device for a three-phase brushless DC motor without a position sensor comprising a comparator for outputting the output voltage of the phase delay compensator compared to the ground voltage as a position estimation signal of the rotor of the three-phase BLDC motor. 2. The system of claim 1, wherein the integral value of the digital low pass filter is selected from the group consisting of: a; Rotor position estimation device for a three-phase brushless DC motor without a position sensor, characterized in that the following equation (1). Equation 1

here,

Is the back EMF input to the digital low pass filter,

Is the back EMF output from the digital low pass filter,

Is

Is,

Is the pole of the digital lowpass filter. The method of claim 1 or 2, wherein the phase delay compensation coefficient of the phase delay compensator is;

Rotor position estimation device for a three-phase brushless DC motor without a position sensor. here,

Is phase.

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