KR101366161B1 - Brushless Direct Current Motor Without Position Sensor - Google Patents

Abstract

The present invention relates to a brushless DC motor driving apparatus without a position sensor, and according to an embodiment of the present invention, includes: a driving control unit for outputting a current command value and a voltage command value for driving a brushless DC motor; A current detector which detects the largest current value among the currents of each phase driving the brushless DC motor and outputs the actual current; A counter electromotive force estimator for calculating a counter electromotive force using the voltage command value and the actual current; An electric angle estimating unit for calculating an electric angle and an electric angular velocity using the counter electromotive force; An angular error correction unit outputting an angular error component for reducing the angular error by using the current command value and the actual current; And a motor driver for driving the brushless DC motor according to the electric angle and the angle error component.

Description

Brushless Direct Current Motor Without Position Sensor

The present invention relates to a brushless DC motor operating apparatus without a position sensor, and more particularly, to determine the rotor position of a brushless DC motor in real time without using the rotor position sensor of the motor to control the speed of the motor. It relates to a brushless DC motor driving device.

In accordance with the trend toward miniaturization and lightening of the electronics industry, research has been carried out to eliminate the brushes necessary for DC motors.As a result, instead of removing the brushes, brushless motors supplying the inverted voltage to the DC motors by precisely controlling the supply voltage in circuits. (Brushless Motor) has been developed. In such a brushless motor, accurate positioning of the rotor may be essential for accurate voltage supply.

1 is a timing diagram showing control voltages in six sections according to the shape of the counter electromotive force and the shape of the counter electromotive force of a typical three-phase brushless DC motor.

As shown in Fig. 1, a three-phase brushless DC motor is ideally distributed with a phase difference of 120 degrees in the shape of the counter electromotive force of each phase. Thus, by combining three phases and the shape of back EMF, it can be divided into six sections for each electric wheel. In order to control the brushless DC motor, the switch switching form of the three-phase inverter is controlled according to these six sections. That is, in the drawing of FIG. 1, in phase 1, a phase is non-conducting and controlled by V _cb through which the upper switch of c phase and the lower switch of b phase are conducted. Is controlled by the conduction V _ab . This combination is divided into six sections, one phase is non-conducting, and two phases are connected and controlled. In order to drive the brushless DC motor in a 102-degree conduction method, a position sensor for dividing the six sections is used. In general, three Hall effect sensors are used. However, the use of Hall sensors increases the cost of the drive and is susceptible to humidity, heat, and mechanical shock, which can cause sensor malfunction.

In general, a brushless DC motor driving device without a position sensor finds a zero crossing point (ZCP) of counter electromotive force by measuring a voltage of each phase.

FIG. 2 is a timing diagram illustrating a basic principle of operation of a brushless DC motor without a general position sensor. FIG. 2 shows a counter electromotive force (ε _α ), a phase voltage (V _{α n} ), and a zero crossing point (ZCP) of counter electromotive force, respectively. .

Referring to FIG. 2, when any phase is in a non-conducting period, the counter electromotive force changes from a positive voltage to a negative voltage. At this time, since the potential of the neutral point changes to V _dc / 2 and 0 as the other phase switches ON / OFF, the voltage of the non-conductive phase 7 is expressed as follows.

Where V ₀ represents the non-conductive voltage and е ₀ represents the counter electromotive force.

3 is a graph illustrating a method of estimating a general counter electromotive force ZCP through a phase voltage.

Referring to Fig. 3, it can be seen that the voltage on the non-conduction coincides with the ZCP of the counter electromotive force when passing the V _dc / 2 point. This point is 30 degrees ahead of the transition point that separates the actual section, and is matched with the transition point through the phase delay filter.

It is a commonly used method to determine the switching point using the voltage of each phase in the manner described above.

However, as described above, the method of determining the switching time using the voltage of each phase requires a separate power supply from the comparator to sense the time when the non-conductive voltage becomes V _dc / 2. There is an increasing problem. In addition, since the phase delay filter is used, there is a problem that the position resolution at high speed is reduced. In addition, there is a problem in that noise is vulnerable because the size changes rapidly according to switching when the switching point is determined using the phase voltage.

An object of the present invention for solving the above problems is to provide a brushless DC motor operating apparatus without a position sensor that is robust to noise and disturbance without configuring additional hardware.

The above object is, according to an embodiment of the present invention, a drive control unit for outputting a current command value and a voltage command value for driving a brushless DC motor; A current detector which detects the largest current value among the currents of each phase driving the brushless DC motor and outputs the actual current; A counter electromotive force estimator for calculating a counter electromotive force using the voltage command value and the actual current; An electric angle estimating unit for calculating an electric angle and an electric angular velocity using the counter electromotive force; An angular error correction unit outputting an angular error component for reducing the angular error by using the current command value and the actual current; And a motor driver for driving the brushless DC motor according to the electric angle and the angle error component.

Preferably, the drive control unit, a first comparator for comparing the control speed input by the user to drive the brushless DC motor and the actual speed of the brushless DC motor according to each other, and processing in the first comparator A speed controller for outputting a current command value for controlling the electric angular velocity of the brushless DC motor according to a predetermined value, a second comparator for comparing the current command value output from the actual current with the speed controller, and in the second comparator And a current controller for outputting a voltage command value for driving the brushless DC motor according to the processed value.

Preferably, the counter electromotive force estimator includes a DC current estimator for outputting an estimated DC current using the voltage command value, a comparator for comparing the estimated DC current with the actual current, and a counter electromotive force according to a value processed by the comparator. And a back electromotive force estimator for estimating.

를 사용하여 역기전력의 크기를 산출하며, 이때

는 실제전류,

는 추정전류,

는 고정자 인덕턴스,

는 추정 역기전력,

는 실제 역기전력인 것을 특징으로 한다.Here, the counter electromotive force estimator is based on an error between the estimated DC current and the actual current.

Calculate the magnitude of back EMF using

Is the actual current,

Is the estimated current,

Stator inductance,

Is the estimated back EMF,

Is characterized by the actual counter electromotive force.

Preferably, the electric angle estimating unit includes an electric angle estimator for calculating an electric angle using the counter electromotive force, and an electric angular velocity estimator for calculating an actual electric angular velocity using the electric angle.

Preferably, the angle error correction unit, a comparator for comparing the current command value and the actual current, an error polarity converter for converting the polarity of the value processed by the comparator differently and outputs, and the output signal of the error polarity converter And an angular error corrector for outputting an angular error component for reducing the angular error.

Here, the angle error corrector is divided into 30 degrees of the electric angle based on the error of the current command value and the actual current divided by 30 degrees whether the position of the estimated rotor ahead of the actual rotor position through the distorted current It is characterized by outputting the angular error component by proportionally integrating the value output through the error polarity converter.

Preferably, the motor driving unit, a switching time discriminator for determining a time to switch to any one of a plurality of phases for driving the brushless DC motor according to the electric angle and the angle error component, and the voltage command value and A PWM circuit for outputting a pulse-shaped control signal for controlling the rotation angle and speed of the brushless DC motor according to the phase switching time of the switching time discriminator, and a three-phase DC voltage according to the control signal of the PWM circuit. It characterized in that it comprises a drive inverter for driving the brushless DC motor by varying the AC voltage.

According to the present invention configured and functioning as described above, the following effects are obtained.

First, since there is no separate hardware to determine the conversion time, there is an effect that can reduce the volume and cost.

Second, since the position is estimated using only the phase current without using the phase voltage, the controllable speed range is wide and it has the effect of being robust against noise.

Third, there is an effect that can drive the motor without constraints such as resolution degradation at high speed due to the phase delay filter, the use of the center point.

Fourth, since the electric angle can be calculated in real time and has a closed loop type control circuit, there is an effect of improving control characteristics.

1 is a timing diagram showing a control voltage of six sections according to the shape of the back electromotive force and the shape of the back electromotive force of a typical three-phase brushless DC motor.
Figure 2 is a timing diagram showing the basic principle of the operation of a brushless DC motor without a general position sensor.
3 is a graph for explaining a method of estimating a general counter electromotive force ZCP through a phase voltage.
Figure 4 is a block diagram showing the configuration of a brushless DC motor driving apparatus without a position sensor according to an embodiment of the present invention.
5 is a graph for explaining the determination of the position signal for the drive of the brushless DC motor driving apparatus without a position sensor according to an embodiment of the present invention at each switching point of 60 degrees.
6 is a graph for explaining a case where a PWM pulse is applied at a position where the estimated rotor position is ahead of the actual rotor position according to an embodiment of the present invention.
7 is a graph for explaining a case where a PWM pulse is applied at a position in which the estimated rotor position is behind the actual rotor position according to an embodiment of the present invention.
8 is a graph illustrating a distorted current when a PWM pulse is applied at a position where the estimated rotor position is ahead of the actual rotor position according to an embodiment of the present invention.
9 is a graph for explaining a distorted current when applying a PWM pulse at a position where the estimated rotor position is behind the actual rotor position according to an embodiment of the present invention.
10 is a graph for explaining that the polarity is switched every 30 degree intervals in order to determine the case where the estimated rotor position is ahead or behind the actual rotor position according to an embodiment of the present invention.
11 is a graph for explaining that an electric angle error exists after estimating an electric angular velocity of a rotor according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 4 is a block diagram showing the configuration of a brushless DC motor driving apparatus without a position sensor according to an embodiment of the present invention.

In the brushless DC motor driving apparatus without a position sensor according to an exemplary embodiment of the present invention, as shown in FIG. 4, the drive control unit 10 outputs a current command value and a voltage command value for driving the brushless DC motor 1. And a current detector 20 which detects the largest current value among the currents of each phase driving the brushless DC motor 1 and outputs the actual current, and calculates a counter electromotive force using the voltage command value and the actual current. A back electromotive force estimator 30, an electric angle estimator 40 for calculating an electric angle and an electric angular velocity using the back electromotive force, and an angular error component for reducing an angular error using the current command value and the actual current An angle error correction unit 50, and a motor driving unit 60 for driving the brushless DC motor 1 in accordance with the electrical angle and the angle error component.

)와 이에 따른 상기 브러시리스 직류모터(1)의 실제속도(

)를 서로 비교하는 제1비교기(12)와, 상기 제1비교기(12)에서 처리된 값에 따라 상기 브러시리스 직류모터(1)의 전기각속도(

)를 제어하기 위한 전류지령치(i^* _dc)를 출력하는 속도제어기(14)와, 상기 실제전류(i_dc)와 상기 속도제어기(14)에서 출력되는 전류지령치를 비교하는 제2비교기(16)와, 상기 제2비교기(16)에서 처리된 값에 따라 상기 브러시리스 직류모터(1)의 구동을 위한 전압지령치(v^* _dc)를 출력하는 전류제어기(18)로 구성된다.The drive controller 10 may control a speed input by a user to drive the brushless DC motor 1.

) And thus the actual speed of the brushless DC motor 1

) And the electric angular velocity of the brushless DC motor 1 according to the value processed by the first comparator 12 and the first comparator 12

Speed controller 14 for outputting a current command value (i ^* _dc ) for controlling (), and a second comparator 16 for comparing the current command value output from the actual current (i _dc ) and the speed controller (14). And a current controller 18 for outputting a voltage command value v ^* _dc for driving the brushless DC motor 1 according to the value processed by the second comparator 16.

)를 출력하는 직류전류 추정기(32)와, 상기 추정 직류전류와 상기 실제전류를 비교하는 비교기(34)와, 상기 비교기(34)에서 처리된 값에 따라 역기전력을 추정하는 역기전력 추정기(36)로 구성된다. The counter electromotive force estimating unit 30 uses the voltage command value to estimate an estimated direct current (

) Is a DC current estimator 32 for outputting the?, A comparator 34 for comparing the estimated DC current with the actual current, and a back EMF estimator 36 for estimating back EMF based on the value processed by the comparator 34; It is composed.

의 고정자 전압 방정식을 이용한다. 이때, v^* _dc는 전압지령치이고,

는 고정자 저항이고,

는 고정자 인덕턴스이고,

는 계산된 역기전력의 크기이다.Here, the method of calculating the estimated DC current using the voltage command value is the following equation

Use the stator voltage equation of. Where v ^* _dc is the voltage command value,

Is a stator resistance,

Is the stator inductance,

Is the magnitude of the calculated back EMF.

를 사용하여 역기전력의 크기를 산출하며, 이때

는 실제전류,

는 추정전류,

는 고정자 인덕턴스,

는 추정 역기전력,

는 실제 역기전력이다.And based on the error of the estimated DC current and the actual current

Calculate the magnitude of back EMF using

Is the actual current,

Is the estimated current,

Stator inductance,

Is the estimated back EMF,

Is the actual counter electromotive force.

)을 산출하는 전기각 추정기(42)와, 상기 전기각을 이용하여 실제 전기각속도(

)를 산출하는 전기각속도 추정기(44)로 구성된다.The electric angle estimating unit 40 uses the counter electromotive force to generate an electric angle (

An electrical angle estimator 42 for calculating the electrical angle velocity

It is composed of an electric angular velocity estimator 44 that calculates ().

의 적분기를 사용한다. 이때

은 추정 역기전력이고,

은 전기각 변화량(전기각 속도)이고, K_E는 역기전력 상수이고, T는 샘플링 주기와 같다.Here, the method of calculating the actual electric angular velocity using the electric angle is the following equation

Use the integrator of. At this time

Is the estimated back EMF,

Is the electric angle change (electric angle speed), K _E is the counter electromotive force constant, and T is equal to the sampling period.

)을 출력하는 각오차 보정기(56)로 구성된다.The angle error correction unit 50 includes a comparator 52 for comparing the current command value with the actual current, and an error polarity converter 54 for converting and outputting the polarities of the values processed by the comparator 52 differently. Angular error component for reducing the angular error according to the output signal of the error polarity converter 54

) Is composed of an angular error corrector 56.

)보다 추정각(

)이 앞선 경우와 실제각이 추정각보다 뒤진 경우 모두 상기 비교기(52)의 출력 극성이 같고, 상기 각오차 보정기(56)는 이를 구분하지 못하기 때문에 오차극성 변환기(54)를 통해 극성을 다르게 하여 출력한다.Where the actual angle (

Estimated angle ()

), The output polarity of the comparator 52 is the same, and if the actual angle is behind the estimated angle, and the error correction device 56 does not distinguish it, the polarity of the polarity is changed by the error polarity converter 54. To print.

Accordingly, the angle error corrector 56 determines whether the case is ahead or behind the actual rotor position through the distorted current by dividing the electric angle 360 degrees based on the error between the current command value and the actual current. The angular error component is output by proportionally integrating the value output through the error polarity converter 54.

The motor driving unit 60 includes a switching time discriminator 62 for determining a time point for switching to any one of a plurality of phases driving the brushless DC motor 1 according to the electric angle and the angle error component. And a PWM circuit 64 for outputting a pulse-shaped control signal for controlling the rotation angle and speed of the brushless DC motor 1 according to the voltage command value and the phase switching time of the switching time discriminator 62. And a drive inverter 66 which drives the brushless DC motor 1 by varying the DC voltage into a three-phase AC voltage according to the control signal of the PWM circuit 64.

FIG. 5 is a graph for explaining determining a position signal for driving a brushless DC motor driving apparatus without a position sensor according to an exemplary embodiment of the present invention as a switching point every 60 degrees.

Referring to FIG. 5, the brushless DC motor is controlled by conducting a corresponding phase for a section in which the counter electromotive force has a trapezoidal shape and the counter electromotive force is flat. That is, in general brushless DC motors, since the stator has a three-phase Y connection, the change in the counter electromotive force of one phase affects the currents of both phases.

FIG. 6 is a graph illustrating a case where a PWM pulse is applied at a position where the estimated rotor position is ahead of the actual rotor position according to an embodiment of the present invention, and FIG. 7 is an estimation circuit according to an embodiment of the present invention. 8 is a graph illustrating a case where a PWM pulse is applied at a position where the former position is behind the actual rotor position, and FIG. 8 is a position where the estimated rotor position is earlier than the actual rotor position according to an embodiment of the present invention. Figure 9 is a graph illustrating a distorted current when applying a PWM pulse, Figure 9 is a distortion when applying a PWM pulse at a position that the position of the estimated rotor behind the actual rotor in accordance with an embodiment of the present invention 10 is a graph illustrating a current, and FIG. 10 is a diagram illustrating a case in which the estimated rotor position according to an embodiment of the present invention is located before or after the actual rotor position. A graph for explaining a conversion for each interval the polarity, 11 is a graph for explaining that the electric angle error exists, since an estimate of the electrical angular speed of the rotor according to an embodiment of the invention.

The brushless DC motor is controlled by conducting a phase corresponding to a flat section with a counter electromotive force having a trapezoidal shape, but if the conductive phase is conducted as shown in FIGS. appear. At this time, if the front angle is distorted as shown in FIG. 8, the estimated angle is ahead of the actual angle as shown in FIG. 10, and if the rear side is distorted as shown in FIG. Each error component is output. Therefore, it is determined whether the estimated angle is earlier or later than the actual angle, and the angular error component is output by proportionally integrating the error component. Here, the reason for using the angular error correction method even after the speed estimation is that the angular velocity of the rotor is accurately estimated as shown in Fig. 11, but since the angular error may exist, the angular error components may be combined to determine the trapezoidal counter electromotive force of the brushless DC motor. The PWM pulse can be applied to the flat section.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the claims that follow may be better understood. The embodiments described above are susceptible to various modifications and changes within the technical scope of the present invention by those skilled in the art. These various modifications and changes are also within the scope of the technical idea of the present invention, and will be included in the claims of the present invention described below.

1: brushless DC motor 10: drive control unit
12: first comparator 14: speed controller
16: second comparator 18: current controller
20: current detector 30: counter electromotive force estimator
32: DC current estimator 34: comparator
36: back EMF estimator 40: electrical angle estimator
42: electric angle estimator 44: electric angular velocity estimator
50: error correction unit 52: comparator
54: Error Polarity Transducer 56: Error Compensator
60: motor drive part 62: switching time discriminator
64: PWM circuit 66: drive inverter

Claims (8)

A drive controller for outputting a current command value and a voltage command value for driving the brushless DC motor;
A current detector which detects the largest current value among the currents of each phase driving the brushless DC motor and outputs the actual current;
A counter electromotive force estimator for calculating a counter electromotive force using the voltage command value and the actual current;
An electric angle estimating unit configured to calculate an electric angle and an electric angular velocity using the counter electromotive force;
An angular error correction unit outputting an angular error component for reducing the angular error by using the current command value and the actual current; And
And a motor driver for driving the brushless DC motor according to the electric angle and the angle error component. The method of claim 1,
The drive control unit may include:
A first comparator for comparing a control speed input by a user to drive the brushless DC motor and thus an actual speed of the brushless DC motor;
A speed controller for outputting a current command value for controlling the electric angular speed of the brushless DC motor according to the value processed by the first comparator;
A second comparator for comparing the actual current with a current command value output from the speed controller;
And a current controller for outputting a voltage command value for driving the brushless DC motor according to the value processed by the second comparator. The method of claim 1,
The back EMF estimator,
A direct current estimator for outputting an estimated direct current using the voltage command value;
A comparator for comparing the estimated direct current with the actual current;
And a back electromotive force estimator for estimating back electromotive force according to the value processed by the comparator. The method of claim 3,
The back EMF estimator,
Based on the error between the estimated DC current and the actual current

To calculate the magnitude of back EMF,
here

Is the actual current,

Is the estimated current,

Stator inductance,

Is the estimated back EMF,

Brushless DC motor driving device, characterized in that the actual back EMF. The method of claim 1,
The electrical angle estimator,
An electric angle estimator for calculating an electric angle using the counter electromotive force;
Brushless DC motor operating apparatus without a position sensor, characterized in that it comprises an electric angular velocity estimator for calculating the actual electric angular velocity using the electric angle. The method of claim 1,
The angle error correction unit,
A comparator for comparing the current command value with the actual current;
An error polarity converter for converting and outputting different polarities of the values processed by the comparator;
And a angular error compensator for outputting an angular error component for reducing angular error according to the output signal of the error polarity converter. The method according to claim 6,
The angular error corrector,
Based on the error between the current command value and the actual current, the electric angle 360 degrees is divided by 30 degrees to determine whether the estimated rotor position is ahead or behind the actual rotor position through the distorted current, and the error polarity converter. Brushless DC motor operation apparatus without a position sensor, characterized in that for outputting the angular error component by proportionally integrating the value output through. The method of claim 1,
The motor drive unit includes:
A switching time discriminator for determining a time point for switching to any one of a plurality of phases driving the brushless DC motor according to the electric angle and the angle error component;
A PWM circuit for outputting a pulse-shaped control signal for controlling the rotation angle and speed of the brushless DC motor according to the voltage command value and the phase switching time of the switching time discriminator;
And a drive inverter for driving the brushless DC motor by varying the DC voltage into a three-phase AC voltage according to the control signal of the PWM circuit.

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