KR20100070221A - Aparatus and method for controlling speed of a sensoless bldc motor - Google Patents

Abstract

PURPOSE: An apparatus and a method for controlling speed of a sensor-less bldc motor are provided to reduce an error between a current position and an estimated position. CONSTITUTION: A motor parameter variation unit(150) varies the inductance parameter of a motor according to the size of the detected motor current by detecting the motor current. An estimated current output unit produces an estimated current of the motor based on the varied inductance parameter. A controller(170) controls the speed of the motor based on the estimated current. The motor parameter variation unit reduces one of a q-shaft and a d-shaft inductance according to the increase of a detected motor current.

Description

FIELD AND METHOD FOR CONTROLLING SPEED OF A SENSOLESS BLDC MOTOR

The present invention relates to a method and apparatus for controlling a sensorless BLDC motor, and more particularly, an estimation error of a motor rotor by estimating the rotor of the motor by varying the inductance parameter of the motor according to the magnitude of the current flowing in the motor. It relates to a control method and apparatus of a sensorless BLDC motor to minimize the.

BLDC motors are used in a wide range of fields from home appliances such as refrigerators and air conditioners to information processing equipment such as floppy disk drivers. A separate detection device is installed to detect the rotational speed of the BLDC motor and the position of the rotor. By the way, a BLDC motor in which this detection device is not installed is called a sensorless BLDC motor.

1 is a block diagram showing a configuration of a speed control system of a general sensorless BLDC motor. As shown in Fig. 1, the input is the speed command value We *, and this speed command value We * is compared with the current speed estimation value We ^, and the q-axis current command through the speed controller 11 is obtained. Create a value (iq *).

In addition, by the current controller 12, the q-axis current command value iq * is fed back to the current q-axis current value iq to make the q-axis current command value iq *, and also the q-axis current command value iq *. The current q-axis voltage Vq is fed back so that the current flows to the value iq *, thereby making the q-axis voltage command value Vq *. The q-axis voltage command value Vq * is used by the space vector control unit 13 as a voltage value for making a PWM signal like the d-axis voltage command value Vd *.

Then, the d-axis current command value (id *) is calculated for the operation of the field based on the current speed estimation value (We ^).

At this time, since the control unit 18 can sufficiently produce the q-axis current even if the d-axis current value Id is '0', the control unit 18 generates a command value to maintain the d-axis current at '0'. In this case, d-axis current command value (id *) is generated with a value of '-' so that field weakening operation allows current to flow in d-axis.

Then, in order to control the d-axis current command value id *, the d-axis voltage command value Vd is fed back to generate the d-axis voltage command value Vd *.

Using the d-axis voltage command value (Vd *) generated above and the q-axis voltage command value (Vq *) generated for speed control, a voltage signal in space is constructed to create a PWM signal.

The application of the voltage again changes the magnitude of the current, which is input to the position and back EMF estimation of the change value of the current and the voltage value output through the PWM and used to estimate the position and the back EMF.

In addition, the speed estimator 17 generates the speed estimating value We ^ used for the speed control by using the rotor position and the position estimating value θ ^ calculated by the emf estimator 16.

In estimating the rotor position of the rotor BLDC motor using the senseless algorithm, the voltage applied to the BLDC motor, the current flowing through the BLDC motor, and motor parameters (resistance, Lq, Ld, and counter electromotive force constant) are used. Here, the motor parameter Lq is the q-axis inductance of the motor, and Ld is the d-axis inductance of the motor. Among the motor parameters used in the sensorless control method, the most important parameters are Ld and Lq.

However, the above-described conventional sensorless control method limits the fluctuation of the slope of acceleration / deceleration when the deceleration and acceleration are frequently performed by using the counter electromotive voltage estimation gain and the position estimation gain of the rotor as fixed constant values. This causes a problem in that the position detection error of the rotor becomes large and the motor operates unstable.

In addition, in the above-described conventional sensorless control method, Lq and Ld values were measured using an LCR measuring instrument, and were simply treated as constant values. In practice, however, Ld and Lq are affected by the magnetic flux saturation depending on the magnitude of the current flowing in the motor. Therefore, in the prior art, the senseless algorithm is used without reflecting the change of Ld and Lq according to the current change. In the case of controlling the BLDC motor, the position estimation error becomes large, and the error occurs in the speed control.

An object of the present invention is to detect the current flowing in the motor and vary the inductance of the motor parameters according to the detected current magnitude to further approximate the motor model to the actual motor to estimate the current of the motor, thereby estimating the current and the detected current of the motor. The present invention provides a method and apparatus for controlling a sensorless BLDC motor that accurately estimates a current difference of motor currents and accurately estimates the position of a rotor of the motor.

Another object of the present invention is to control the sensorless BLDC motor for accurately estimating the position of the rotor of the motor by using the estimated position gain and the counter electromotive force estimation gain of the rotor of the motor to vary according to the speed of the motor. A method and apparatus are provided.

In the control method of a sensorless BLDC motor according to an embodiment of the present invention for achieving the above object, in the control method of a permanent magnet type synchronous motor, the motor current is detected and the motor according to the magnitude of the detected motor current Varying the inductance parameters of; Obtaining a current error between an estimated motor current and the detected current based on the variable inductance parameter; Controlling the speed of the motor based on the current error.

The q-axis inductance of the inductance parameter decreases as the magnitude of the detected motor current increases, and the d-axis inductance of the inductance parameter decreases as the magnitude of the detected motor current increases.

Here, the reduction rate of the q-axis inductance according to the increase of the motor current is larger than the decrease flow of the d-axis inductance.

The controlling of the speed of the motor may include: detecting a motor speed and varying an estimated gain varying at least one of a rotor position estimation gain pattern and a counter electromotive force estimation gain according to the detected motor speed; And estimating the position of the rotor using at least one of the variable position estimation gain and the counter electromotive force estimation gain.

The rotor position estimation gain decreases as the rotor speed increases in a region below a constant speed,

The counter electromotive force estimation gain decreases as the speed of the rotor increases in a region below a predetermined speed.

The control device of a sensorless BLDC motor according to an embodiment of the present invention for achieving the above object, in the control device of a permanent magnet synchronous motor, detects a motor current, the motor in accordance with the magnitude of the detected motor current A motor parameter variable unit configured to vary an inductance parameter of the motor; An estimated current calculator configured to calculate an estimated current of the motor based on the variable inductance parameter; And a controller for controlling the speed of the motor based on the estimated current.

The motor parameter variable unit may reduce at least one of a q-axis inductance and a d-axis inductance as the magnitude of the detected motor current increases.

The control unit includes: an estimation gain variable unit configured to vary the position estimation gain and the counter electromotive force estimation gain of the rotor according to the motor speed; And a position estimator for estimating the position of the rotor using the position estimation gain and the counter electromotive force estimation gain.

The estimated gain variable part may have a pattern in which at least one of the position estimation gain and the counter electromotive force estimation gain decreases as the motor speed increases in a region below a predetermined speed.

The control method and apparatus of the sensorless BLDC motor according to an embodiment of the present invention, by using the inductance parameter of the motor to be functionalized to vary depending on the magnitude of the current flowing in the motor, the error between the actual position and the estimated position of the rotor It is effective to operate the motor stably by reducing the

The control method and apparatus for a sensorless BLDC motor according to an embodiment of the present invention, by using the estimated position gain and the counter electromotive force estimation gain of the rotor to be variable depending on the speed of the motor, the actual position and estimation of the rotor By reducing the error between the positions there is an effect to operate the motor stably.

In the following, the position induction of the rotor of the motor is estimated by varying the inductance parameter of the motor according to the current flowing in the motor, and estimating the position of the rotor of the motor by varying the estimated back electromotive force of the motor and the estimated rotor of the motor. An embodiment of a control apparatus and method of a sensorless BLDC motor capable of minimizing errors will be described in detail with reference to FIGS. 2 to 9.

Figure 2 shows a control device of a sensorless BLDC motor that can vary the parameters of the motor model according to the motor current according to an embodiment of the present invention.

Referring to FIG. 2, a control device of a sensorless BLDC motor according to an embodiment of the present invention includes a BLDC motor 100 and a current / voltage which detects a voltage of a DC link terminal and a current flowing through the motor. The detection unit 140, the motor parameter variable unit 150 for varying the inductance parameters Lq and Ld of the motor model, the controller 170 for estimating the rotor position of the motor and the speed of the motor, and the phase of the current. Current phase converter 160 for converting the voltage and speed controller 110 for generating command currents i * q and i * d of the motor according to an error between the estimated speed w ＾ and the command speed w * of the motor. ), And a current controller 120 for converting the command current into command voltages V * q and V * d and outputting the same, and a PWM controller 130 for generating and outputting a space vector voltage according to the command voltage. do.

Here, the parameter variable unit 150 varies the inductance parameters Lq and Ld of the motor in inverse proportion to the magnitude of the three-phase current of the motor 100 output from the current / voltage detector. The controller 170 estimates an estimated rotor position θ ＾ and an estimated speed w ＾ based on the variable inductances Lq and Ld and the detected motor applied voltage. The speed controller 110 obtains an error between the estimated motor speed w \ and the command speed w * and generates command currents i * q and i * d of the motor on the synchronous coordinates according to the error.

This embodiment relates to control of a sensorless BLDC motor of a 180 ° energization method. 3 illustrates a synchronous rotation coordinate system and a synchronous rotation estimation coordinate system of a rotor to which a control method of a sensorless BLDC motor according to the present invention is applied. Referring to FIG. 3, in the 180 ° sinusoidal sensorless control algorithm, a dq-axis actual rotation coordinate system including a d-axis, which is a position in the magnetic flux direction of the rotor, and a q-axis traveling 90 ° in the rotational direction from the d-axis, and control. Axis deviation (Δθ) between the virtual rotor position (γ) axis of the image and the γ-δ axis consisting of the δ axis which is advanced by 90 ° in the rotational direction from the γ axis is determined, and the Δθ is controlled to zero.

When the detected current and the estimated current of the motor are obtained as described above, the position (θ) of the rotor can be obtained, and the position error of the rotor is obtained by integrating the angular velocity (ω) of the rotor. The angular velocity omega of the rotor to be zero is obtained, and the motor is controlled based on the omega.

In more detail, when the control algorithm of the sensorless BLDC motor to which the present invention is applied is represented by a synchronous rotation coordinate system, Equation 1 below.

[Equation 1]

Where R is the phase resistance of the motor and Wm is the speed of the rotor.

       Ld: d-axis inductance of the motor Lq: q-axis inductance of the motor

At this time, the dq axis is the synchronous rotational coordinate system of the rotor, Vd, Id, Vq, Iq is the value of the voltage and current of the d-axis and q-axis respectively on the synchronous rotational coordinate system of the rotor, e is the counter electromotive force generated while the rotor rotates to be.

And it is assumed that the estimated rotor position is the γ-δ axis located at a position different from the actual synchronous rotation coordinate system, and if it is assumed that Δθ is sufficiently small, it is expressed as Equation 2 below.

&Quot; (2) "

Where Vγ, Vδ, iγ, and iδ are values of voltage and current on the γ-δ axis, and Δθ is an angular error with the γ-δ axis, which is the position coordinate system of the rotor.

Here, it is assumed that the position of the rotor estimated by the controller 170 is different from the actual synchronous rotational coordinate system, that is, the γ-δ axis having an error of Δθ with the dq axis of the actual synchronous rotational coordinate system. At this time, it is assumed that Δθ is sufficiently small to control the position of the rotor of the motor.

In the case of calculating the above Equations 1 and 2, the estimation of the position of the rotor uses a fast DSP. In this case, the equations in n and (n-1) steps are summarized as Equation 3 below. .

&Quot; (3) "

Where iγ (n) is the current on the γ-axis measured in n steps,

        iδ (n) is the current on the δ axis measured in n steps

iγ _M (n) is the current on the γ-axis predicted by the output of the (n-1) step

iδ _M (n) is the current on the δ axis predicted by the output of the (n-1) step

Here, if the assumption that DELTA θ is sufficiently small is applied to Equation 3 above, the error current of the detected current and estimated current in Equation 3 below (predicted current) is given by Equation 3 below. It can be approximated as shown in 4.

&Quot; (4) "

If Equation 4 is rearranged into an equation for calculating the counter electromotive force and the position of the rotor again, Equation 5 below.

[Equation 5]

In Equation 5, Ke is the counter electromotive voltage estimation gain and Kθ is the rotor position estimation gain. Thus, the motor is driven by estimating the position of the rotor using the estimation error of the current.

When estimating the rotor position of the rotor BLDC motor using the senseless algorithm, the voltage applied to the BLDC motor, the current flowing through the BLDC motor, and the motor parameters (resistance, Lq, Ld, and counter electromotive force constant) are used. Here, the motor parameter Lq is the q-axis inductance of the motor, and Ld is the d-axis inductance of the motor. Among the motor parameters used in the sensorless control method, the most important parameters are Ld and Lq.

Referring to FIG. 4, the controller 170 for controlling the BLDC motor using a sensorless control algorithm in which the above-described inductance parameter is changed according to the detection current will be described in more detail.

The controller 170 calculates a current estimator 171 for estimating the current of the motor using a parameter of the motor including the Lq of the motor varied according to the motor current, and calculates a current error between the motor current and the estimated current. A comparator 172, a rotor position estimator 173 for estimating the position of the rotor of the motor based on the current error, and a speed estimation gain Ke and the rotor position estimation based on the speed of the motor. An estimated gain variable unit 174 for varying a gain Kθ and a motor speed estimator 175 for estimating a speed of a motor according to the variable estimated gain and the estimated rotor position.

That is, the parameter variable unit 150 varies the inductance parameter of the motor according to the magnitude of the detected motor current, and the current estimator 171 calculates the estimated current of the motor based on the variable inductance parameter. Finally, the controller 170 controls the rotation speed of the motor based on the estimated current.

In more detail, the parameter variable unit 150 decreases at least one of the q-axis inductance and the d-axis inductance as the magnitude of the detected motor current increases. As the motor current increases, the q-axis inductance and d-axis inductance gradually decrease.

Here, as the motor current increases, since the q-axis inductance is dominantly reduced compared to the d-axis inductance, the d-axis inductance is assumed to be a constant, even if only the q-axis inductance is varied, the object of the present invention Can be achieved.

In addition, the controller 170 may further include an estimation gain variable unit 174 that varies the position estimation gain and the counter electromotive force estimation gain of the rotor according to the motor speed. In this case, the rotor position estimator 173 can estimate the position of the rotor using the position estimation gain and the counter electromotive force estimation gain.

The estimated gain variable unit 174 decreases at least one of the position estimation gain and the counter electromotive force estimation gain as the motor speed increases in a region below a predetermined speed.

FIG. 5 is a flowchart illustrating a control method of a control method of a sensorless BLDC motor capable of varying parameters of a motor model according to an embodiment of the present invention, and FIG. Detailed flowchart is shown.

5 and 6, in a method of controlling a sensorless BLDC motor according to an embodiment of the present invention, detecting a motor current and varying an inductance parameter of the motor according to the magnitude of the detected motor current ( S10, S20); Comparing the estimated motor current with the detected current based on the variable inductance parameter to obtain an error current (S30 and S40); Controlling the speed of the motor based on the error current (S60).

In the step S20 of varying the parameter, the q-axis inductance of the inductance parameter decreases as the magnitude of the detected motor current increases, and the d-axis inductance of the inductance parameter also corresponds to the detected motor current. It decreases as size increases.

Based on the variable inductance parameter, the current error between the detected current flowing through the motor and the estimated current according to the parameter of the motor is obtained. (S30, S40) Also, by detecting the motor speed, estimating the rotor position and the counter electromotive force of the motor. It is also possible to control the position of the rotor of the motor more precisely by varying the estimated gain.

That is, when the rotor position and the counter electromotive force gain of the motor are used as constants, an error occurs because the rotor position and the counter electromotive force gain of the motor are changed according to the speed of the motor in the actual motor. Therefore, the speed of the motor is detected and the estimated gain of the rotor position and the counter electromotive force estimation gain of the motor are varied according to the detected speed of the motor.

In the controlling of the speed of the motor (S60), it is possible to first perform the step (S50) of varying the estimated gain.

The step of varying the estimated gain (S50) detects the motor speed and varies the position estimation gain Ke of the rotor according to the detected motor speed. (S41, S42) Then, the back EMF estimation gain is varied (S43). ). The position of the rotor is estimated using at least one of the variable position estimation gain and the counter electromotive force estimation gain (S44).

The rotor position estimation gain has a pattern that decreases as the rotor speed increases in a region below a constant speed, and the counter electromotive force estimate gain also decreases as the rotor speed increases in a region below a constant speed. Has a pattern.

As shown in FIG. 7, the pattern of the back EMF estimation gain detects the magnitude of the motor speed, selects the back EMF estimation pattern according to the magnitude of the motor speed, and, from the pattern of the selected back EMF estimation gain, The position of the rotor is estimated by determining the estimated back electromotive force of the rotor according to the electron speed.

In this case, the EMF gain gain pattern is such that the magnitude of the EMF gain is smaller as the load is larger, and the reason why the magnitude of the estimated gain is smaller as the load is larger is that the greater the load, the smaller the change in the rotational speed of the motor at the same current. to be.

In addition, as shown in FIG. 8, the rotor position estimation gain has a pattern that decreases as the speed of the rotor increases in a region below a constant speed.

In the above, the position of the rotor is detected by determining the counter electromotive force estimation gain and the rotor position estimation gain according to the speed of the motor, but the position of the rotor may be detected by determining only the counter electromotive force estimation gain according to the speed of the motor. Also, the position of the rotor may be detected by determining only the position estimation gain of the rotor according to the speed of the motor.

FIG. 9 illustrates Lq and Ld of parameters of a motor model that vary according to a motor current applied in a control device and method of a sensorless BLDC motor according to an embodiment of the present invention.

Specific embodiments or examples made in the detailed description of the present invention are intended to clarify the technical contents of the present invention to the extent that they should not be construed as limited to these specific embodiments and should not be construed in consultation. Many changes are possible within the scope of.

1 is a block diagram showing a driving system of a general sensorless BLDC motor.

Figure 2 shows a block diagram of a control device of a sensorless BLDC motor that can vary the parameters of the motor model according to the motor current according to an embodiment of the present invention.

3 illustrates a synchronous rotation coordinate system and a synchronous rotation estimation coordinate system of a rotor to which a control method of a sensorless BLDC motor according to the present invention is applied.

4 is a detailed block diagram of the motor parameter variable unit and the control unit of FIG. 2.

5 is a flowchart illustrating a control method of a sensorless BLDC motor capable of varying parameters of a motor model according to a motor current according to an embodiment of the present invention.

FIG. 6 is a detailed flowchart of the variable gain estimation step of FIG. 5.

FIG. 7 illustrates a back EMF gain gain pattern applied to a control apparatus and method of a sensorless BLDC motor according to an embodiment of the present invention.

FIG. 8 illustrates a position estimation gain pattern of a rotor applied to a control device and method of a sensorless BLDC motor according to an embodiment of the present invention.

FIG. 9 illustrates Lq and Ld of parameters of a motor model that vary according to a motor current applied in a control device and method of a sensorless BLDC motor according to an embodiment of the present invention.

Claims (10)

In the control method of a permanent magnet synchronous motor, Detecting a motor current and varying inductance parameters of the motor according to the magnitude of the detected motor current; Obtaining an error current by comparing an estimated motor current and the detected current based on the variable inductance parameter; Controlling the speed of the motor based on the error current. The method of claim 1, The q-axis inductance of the inductance parameter is reduced as the magnitude of the detected motor current increases. The method of claim 2, D-axis inductance of the inductance parameter is reduced as the magnitude of the detected motor current increases. The method of claim 1, wherein controlling the speed of the motor comprises: An estimation gain variable step of detecting a motor speed and varying at least one of a position estimation gain and a counter electromotive force estimation gain of the rotor according to the detected motor speed; And estimating a position of the rotor using at least one of the variable position estimation gain and the counter electromotive force estimation gain. The method of claim 4, wherein The position estimation gain of the rotor, the control method of the sensorless BLDC motor, characterized in that it has a pattern that decreases as the speed of the motor increases in the region below a certain speed. The method of claim 5, The counter electromotive force estimation gain has a pattern that decreases as the speed of the motor increases in a region below a predetermined speed. In the control device of a permanent magnet synchronous motor, A motor parameter variable unit configured to detect a motor current and vary an inductance parameter of the motor according to the detected magnitude of the motor current; An estimated current calculator configured to calculate an estimated current of the motor based on the variable inductance parameter; And a controller for controlling the speed of the motor based on the estimated current. The method of claim 7, wherein And the motor parameter variable unit reduces at least one of a q-axis inductance and a d-axis inductance as the magnitude of the detected motor current increases. The method of claim 7, wherein the control unit, An estimation gain variable for varying the position estimation gain and the counter electromotive force estimation gain of the rotor according to the motor speed; And a position estimator for estimating the position of the rotor using the position estimation gain and the counter electromotive force estimation gain. The method of claim 9, The control unit of the sensorless BLDC motor, characterized in that the estimated gain variable portion has a pattern for reducing at least one of the position estimation gain and the counter electromotive force estimation gain as the motor speed increases in a region below a predetermined speed.

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