KR100612042B1 - Initial electric angle position estimation method and starting method of rotor of brushless DC motor without position sensor - Google Patents

Abstract

The present invention is driven by a space voltage vector output by a three-phase inverter of a pulse width modulation method, and is used to estimate and start an initial electric angle position of a rotor of a brushless DC motor (BLDC motor) without a position sensor. It is about.

The method of estimating the initial electric angle of the rotor according to the present invention estimates that the d-axis of the rotor is located in the section of the space voltage vector representing the smallest inductance, and then rotates the space in the space voltage vector section representing the largest inductance. Estimating that the q-axis of the former is located. Therefore, the position of the d-axis can be estimated within the -30 degree electric angle range or the +30 degree electric angle range with respect to the space voltage vector. For motors with reversed inductance characteristics, the case relations are reversed when comparing inductances.

In addition, in the BLDC motor starting method according to the present invention, after comparing the inductance of each of the two spatial voltage vectors used in the synthesis, the magnitude relationship is changed, or the inductance for the spatial voltage vector having a large application time shows the maximum value. Assuming that the rotor has moved 30 degrees at the time of decreasing, a voltage is applied to the estimated q-axis of the rotor. Therefore, the maximum torque can be generated by tracking the position of the rotor in units of 30 degrees.

Description

Estimation Method of Initial Position of Rotor and Starting Method of Brushless DC Motor without Position Sensor for Rotor of Brushless DC Motor without Position Sensor

1 is a structure of a BLDC motor.

2A is a BLDC motor model.

2B is a two pole equivalent model of a BLDC motor.

3 is a model equivalent to the form that the rotor is a BLDC electric motor inside.

4 is an equivalent circuit of a BLDC motor.

5 is a diagram illustrating a relationship between a reference coordinate system and a synchronous coordinate system.

6A and 6B are a d-axis equivalent circuit and a q-axis equivalent circuit on a synchronous coordinate system of a BLDC motor, respectively.

7 is an equivalent circuit of a BLDC motor in which the magnetic component of the rotor is ignored.

8 is an equivalent circuit of a BLDC motor when the space voltage vector V1 is applied.

9 is a space vector voltage output by the three-phase inverter.

10 is a theoretical value of the time of the DC power supply current for inductance measurement.

11 is a result of measuring the magnitude of the DC power current according to the position of the rotor.

12 is a result of measuring the size of the inductance according to the position of the rotor.

13 is an area where the rotor d-axis is assumed to be located when I1> I4 (that is, when L1 <L4).

14A and 14B are detailed positions of the d-axis of the rotor when I2> I6 (that is, when L2 <L6) and when I2 <I6 (that is, when L2> L6).

15 is a flowchart of a rotor estimation process according to the present invention.

16 is a rise time measurement for inductance measurement.

17 is a current rising waveform having different time constants.

18 is a starting process and an applied voltage angle according to the position of the rotor.

19 is a spatial voltage vector and DC power side current waveform used for synthesis within a PWM period.

20 is a block diagram of an experiment apparatus.

21 is a spindle motor for HDD disk rotation used in the experiment.

22 is a DC power supply current waveform in the initial angle position estimation process.

23 is a time point of sampling current for inductance measurement.

24 shows the actual electric angle of the rotor and the electric angle estimated according to the invention.

25 is the error between the actual electrical angle and the estimated electrical angle of the rotor.

Fig. 26 is the number of application of the synthesized voltage during the estimation process.

Fig. 27 shows the estimated and actual angles of the rotor when starting from stop to 600 rpm by the starting method according to the present invention.

Fig. 28 is a control characteristic when a disturbance occurs in the middle of starting by a conventional starting method;

29 is a control characteristic when a disturbance occurs in the middle of starting by the starting method of the present invention.

30 is a flow chart of a BLDC motor starting method according to the present invention.

The present invention is driven by a space voltage vector output by a three-phase inverter of a pulse width modulation method, and is used to estimate and start an initial electric angle position of a rotor of a brushless DC motor (BLDC motor) without a position sensor. It is about.

In general, the characteristics of an induction motor (IM) are governed by the slip frequency corresponding to the difference between the frequency of the voltage applied to the motor and the frequency at which the actual motor rotates. The slip frequency is related to the motor constant and current. Therefore, in the induction motor, information about the speed and slip frequency of the rotor is more important than the actual position information of the rotor.

On the other hand, in the case of brushless DC motors (hereinafter referred to as "BLDC motors"), the magnetic flux is supplied from the permanent magnet attached to the rotor, so that the absolute position of the rotor is generated to generate the maximum torque. You must know exactly This is because the maximum torque is generated when the control angle is synchronized to the absolute position of the magnetic flux supplied by the rotor.

In order to obtain absolute position information of the rotor, a position sensor such as a resolver, an absolute encoder, or a Hall effect sensor should be attached to the rotor.

The resolver or absolute encoder has the advantage of continuously detecting the position of the rotor, but the disadvantage is that the price is very high, which greatly increases the price of the entire system. Therefore, these position sensors are widely used in the field requiring high precision and stability, and the flux sensor is mainly used in the general BLDC motor system. The magnetic flux sensor is a sensor based on the Hall effect that generates a voltage proportional to the magnetic flux density. The magnetic flux sensor is attached to the stator at an electric angle of 120 degrees to directly measure the magnetic flux of the rotor.

When using a resolver, an absolute encoder, a magnetic flux sensor, or the like, the absolute position of the rotor magnetic flux can be determined relatively accurately. However, using these position sensors presents the following problems:

First, cost increases significantly. In general, small home appliance systems are sensitive to rising prices, and the cost of an electric motor system is not a big part of the overall system. However, because flux and position sensors are quite expensive, the use of flux and position sensors results in a significant increase in the price of the overall system.

Second, the size and weight are increased in mechanical terms. In the case of a small mobile home appliance, its portability is subject to size and weight constraints. However, the flux and position sensors are generally attached to the stator side, thus increasing the overall size and weight.

Third, there is a risk of malfunction in terms of reliability. Since the position and flux sensors are a sensing system attached to the stator side, they are easily damaged by mechanical shock. In addition, there is a risk of malfunction and failure due to factors such as electrical noise, vibration, temperature and environment. Thus, the use of flux and position sensors can degrade the reliability of the overall system.

As such, the BLDC motor has many advantages in terms of cost and control as the motor itself, but has a big disadvantage of detecting the absolute position of the rotor and using magnetic flux and position sensors for this purpose.

In recent years, in order to overcome these disadvantages, researches on a driving method without using a position and magnetic flux sensor have been actively conducted. Such a driving method is commonly referred to as a sensorless driving method.

Various methods are used for the sensorless driving method. The method of identifying the rotor position (zero-crossing method) from the point of time when the sign of the counter electromotive force changes is easy to implement, so it is mainly used in BLDC motor system. Since the BLDC motor has a magnet attached to the surface of the rotor, when the rotor rotates at high speed, the position information of the rotor can be obtained by using back electromotive force information according to the position of the rotor.

However, the method using the back electromotive force cannot obtain the position information of the rotor when the rotor is stopped or rotating at a low speed. Therefore, it is necessary to drive from a standstill to a constant speed (that is, a speed at which the counter electromotive force becomes large enough) in a special way. In general motor systems such as spindle motors that do not control instantaneous torque from zero speed to low speed, the open loop method is used to accelerate the rotor by applying voltage in a predetermined voltage form without using position information. have.

However, recent BLDC motors for home appliances have tended to become low voltage and high speed, and accordingly, the strength of magnets has gradually decreased. Therefore, the magnitude of back EMF induced at the same speed gradually decreases, and the speed range in which the open loop start method should be used increases. However, in the case of an open loop start, it is vulnerable to disturbance, so that a case of synchronous outage occurs due to a small disturbance during start up. In addition, since the electrical and mechanical parameters of the motor must be accurately known and a voltage profile must be made, the system is sensitive to the parameters of the system.

Therefore, there is a need for a starting method that can grasp the instantaneous position of the rotor and apply voltage in synchronization with the position of the rotor, which is robust to the motor constants.

In addition, when the initial position of the rotor is not known, a case in which the rotor temporarily rotates in the opposite direction at the time of initial start may occur. In addition, there is a possibility that starting fails because the required torque at the time of initial starting cannot be maximized. Therefore, it is possible to prevent the reverse rotation of the rotor by knowing the initial position correctly, to obtain the maximum initial starting torque. Therefore, it is necessary to accurately estimate the initial position.

Among the known rotor estimation methods, a method using the saturation phenomenon of the stator core by the magnet of the rotor is mainly used. In this method, six voltage vectors of a three-phase inverter are sequentially applied, the vector having the smallest inductance is found, and the d-axis of the rotor is estimated at the 60 degree position near the vector. However, since this method estimates in 60 degree units, the estimation performance is poor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is to accurately detect and start the initial position of the rotor in a sensorless BLDC motor without a position and magnetic flux sensor.

The sensorless start according to the present invention can accurately estimate the initial position of the rotor at standstill without using the position and magnetic flux sensors, and can accelerate from zero speed to a measurable speed by increasing the counter electromotive force to some extent. .

Accordingly, an object of the present invention is to provide a method for accurately determining the initial position of a rotor of a BLDC motor. It is also an object of the present invention to provide a method of accurately locating a rotor in a BLDC motor and then starting the BLDC motor without a sensor in a low speed region.

The present invention is driven by a spatial voltage vector output by a three-phase inverter of the pulse width modulation method, and the initial electric angle position estimation method and starting method of the rotor of the brushless DC motor (BLDC motor) without the position sensor It is about.

The method of estimating the initial electric angle of the rotor according to the present invention estimates that the d-axis of the rotor is located in the section of the space voltage vector representing the smallest inductance, and then rotates the space in the space voltage vector section representing the largest inductance. Estimating that the q-axis of the former is located. Therefore, the position of the d-axis can be estimated in units of 30 degrees within the -30 degree electrical angle range or the +30 degree electrical angle range with respect to the space voltage vector.

More specifically, the present invention is driven by the space voltage vector output from the three-phase inverter of the pulse width modulation method, the initial electric angle position estimation method of the rotor of the brushless DC motor (BLDC motor) without the position sensor and brush As

(A) obtaining an inductance L1 by applying a space voltage vector V1 having an electric angle of 0 degrees to the stator in the fixed coordinate system;

(B) obtaining an inductance L4 by applying a spatial voltage vector V4 having an electric angle of 180 degrees to the stator in the fixed coordinate system;

Comparing the magnitudes of the inductances L1 and L4 and selecting a space voltage vector representing a small inductance value among the space voltage vectors V1 and V4 as a reference space voltage vector Vk;

(D) obtaining an inductance Lk + 1 by applying a spatial voltage vector Vk + 1 positioned at an electrical angle of +60 degrees with respect to the selected reference spatial voltage vector Vk;

(E) obtaining an inductance Lk-1 by applying a spatial voltage vector Vk-1 located at an electrical angle of −60 degrees with respect to the selected reference spatial voltage vector Vk;

Inductance Lk of the reference spatial voltage vector Vk obtained in step (a) or step (b), and the smallest inductance of the three inductances of inductance Lk + 1 and Lk-1 obtained in steps (d) and (e) (F) estimating that the d-axis of the rotor is located in a section of the spatial voltage vector representing (i.e., an electric angle range of -30 degrees to +30 degrees with respect to the direction of the spatial voltage vector); And

(G) estimating that the q-axis of the rotor is located in the space voltage vector section representing the largest inductance among the three inductances compared in the step (f).

Thus, by estimating the position of the rotor's q-axis in step (g), an electric angle range of -30 degrees with respect to the direction of the spatial voltage vector where the d-axis of the rotor represents the smallest inductance of the three inductances or It can be estimated more precisely by being in the electric angle range of +30 degrees.

On the other hand, as a result of comparing the inductance L1 and L4 in the step (c), when the difference is less than a predetermined value (for example, less than 10%, or less than 5% of the value of the inductance L1 or L4), The initial electric angle position estimation method of the rotor of the BLDC motor according to,

Obtaining a inductance L2 by applying a spatial voltage vector V2 having an electric angle of 60 degrees to the stator in the fixed coordinate system (a2);

(B2) obtaining an inductance L5 by applying a space voltage vector V5 having an electric angle of 240 degrees to the stator in the fixed coordinate system;

Comparing the magnitudes of the inductances L2 and L5 and selecting a space voltage vector representing a small inductance value among the space voltage vectors V2 and V5 as a reference space voltage vector Vk;

Obtaining an inductance Lk + 1 by applying a spatial voltage vector Vk + 1 positioned at an electrical angle of +60 degrees with respect to the selected reference spatial voltage vector Vk (d2);

The inductance Lk of the reference spatial voltage vector Vk obtained in the step (a2) or step (b2), the inductance Lk + 1 obtained in the step (d2), and the electric angle -60 degrees with respect to the selected reference spatial voltage vector Vk. Inductance Lk-1 obtained when the space voltage vector Vk-1 is applied, where inductance Lk-1 is one of the three inductances of L1 and L4 obtained in step (a) and step (b). (E2) estimating that the d-axis of the rotor is located in a section of a space voltage vector representing a small inductance; And

And estimating that the q-axis of the rotor is located in the space voltage vector section representing the largest inductance among the three inductances compared in the step (e2).

By the same principle, instead of applying the spatial voltage vectors V2 and V5 in steps (a2) and (b2) above, the spatial voltage vector V6 having an electrical angle of -60 degrees and the spatial voltage vector having an electrical angle of 120 degrees in a fixed coordinate system. Inductance can be compared by applying V3 to the stator.

By the same principle, for motors with inverse inductance characteristics, the magnitude of inductance is reversed. That is, after estimating that the d-axis of the rotor is located in the section of the spatial voltage vector representing the largest inductance, the q-axis of the rotor may be estimated in the spatial voltage vector section representing the smallest inductance.

In the BLDC motor starting method according to the present invention, the inductance of each of the two spatial voltage vectors used in the synthesis is compared, and the point of magnitude changes or the inductance of the spatial voltage vector having a large electric angle is shown as the maximum value. Assuming that the rotor has moved 30 degrees at the time of decreasing, a voltage is applied to the estimated q-axis of the rotor. Therefore, the maximum torque can be generated by tracking the position of the rotor in units of 30 degrees.

More specifically, the present invention is a drive method of a BLDC motor without a position sensor and a brush driven by a space voltage vector output by a pulse width modulation three-phase inverter,

(A) estimating initial electric angles of the d-axis and q-axis of the rotor according to the above-described method;

(B) synthesizing two spatial voltage vectors Vn and Vn + 1 adjacent to the electrical angle of the estimated q-axis with the average voltage angle of the region where the estimated q-axis exists and applying them to the stator;

If the d-axis of the rotor is present at 0 degrees to 30 degrees, 60 degrees to 90 degrees, 120 degrees to 150 degrees, 180 degrees to 210 degrees, 240 degrees to 270 degrees, or 300 degrees to 330 degrees, (C) monitoring the inductance Ln + 1 for the large electric angle of the space voltage vector Vn + 1 of the two space voltage vectors Vn and Vn + 1 used;

(D) estimating that the rotor has moved 30 degrees from the time when the inductance Ln + 1 for the space voltage vector Vn + 1 decreases after indicating the maximum value;

If the d-axis of the rotor is present at 30 degrees to 60 degrees, 90 degrees to 120 degrees, 150 degrees to 180 degrees, 210 degrees to 240 degrees, 270 degrees to 300 degrees, or 330 degrees to 360 degrees, (E) comparing the inductances Ln and Ln + 1 for each of the two spatial voltage vectors Vn and Vn + 1 used;

(F) estimating that the rotor has moved 30 degrees from the time when the magnitude relationship between the inductance Ln and Ln + 1 is changed; And

Thereafter, the step (b) to step (f) it comprises the step (g) to repeat.

In the present invention, the process of measuring the inductance by applying the space voltage vector to the stator, instead of obtaining the inductance value itself, after applying the space voltage vector, the current value of the stator after a predetermined time elapsed do or; After applying the space voltage vector, it is preferable to measure the time required until the current value of the stator reaches a predetermined value and compare the measured current value or the required time with an inductance value.

At this time, the measured current value and inductance are in inverse relationship, and the required time and inductance are in proportion. Therefore, the larger the measured current value, the smaller the inductance value, and the shorter the time required for the current value to reach a predetermined value, the smaller the inductance value.

Hereinafter, mathematical modeling of the BLDC motor used in the present invention will be described.

Basically, the equivalent model of the sine wave type counter electromotive force is the same as that of the surface mounted permanent magnet synchronous motor. In addition, the permanent magnet synchronous motor is basically the same as the conventional synchronous motor provided with the field winding, except that the magnetic flux is supplied from the permanent magnet.

Therefore, mathematical modeling of the BLDC motor can be obtained by the same method as that of analyzing a synchronous motor having a field winding. Thus, P.C. Krause, "Analysis of Electric Machinery," from McGraw-Hill Book Company, 1987. and W. Based on the equivalent circuit presented in Leonard, "Control of Electrical Drives," from Springer-Verlag, 1985.], the concept of the reference coordinate system is introduced to analyze the BLDC motor.

First, in order to facilitate the interpretation of BLDC motors, the circuit equations of the motors are derived in this specification on the basis of several assumptions:

1) BLDC motor is a rotating field type, the three-phase winding of the stator has a spatially symmetrical distribution, the impedance of each winding is also three-phase symmetrical;

2) the length and width of the pores are constant, and the flux linking the pores takes the form of a spatially perfect sinusoid;

3) the magnetization properties of the iron core are linear and there is no loss due to hysteresis and eddy currents;

4) The rotor is a permanent magnet and maintains a constant magnetic flux, and there is no auxiliary winding for maneuvering.

1 illustrates an example of a BLDC motor to which a driving method according to the present invention is applied. The motor has eight magnetic poles and twelve slots, in which the rotor is external. A schematic model of the motor and a model assumed to be two poles are shown in FIGS. 2A and 2B, respectively.

3 is an equivalent model of the motor shown in FIGS. 1, 2A, and 2B in the form of an electric motor having a rotor therein. The stator consists of three-phase Y-connected windings, which are electrically spaced 120 degrees apart from each other. The equivalent resistance of each stator is R _S , wound by the equivalent number of windings N _S. The stator windings are typically connected to the output terminals of a pulse width modulated three-phase inverter to supply power.

The windings of the stator in Figure 3 are shown in A, B and C phases, respectively. In order to indicate the direction of the linkage magnetic flux, the concept of the direct-axis (d-axis) and the horizontal-axis (Quadrature-axis, q-axis) was introduced and represented by d and q, respectively. At this time, the direction of the linear axis is the direction of the magnetic flux supplied from the permanent magnet, and corresponds to the direction indicated by the north pole of the magnet. The abscissa refers to the direction electrically 90 degrees away from the linear axis. In the present specification, the horizontal axis defines a direction 90 degrees away from the counterclockwise direction with respect to the linear axis. In addition, when the motor rotates in the counterclockwise direction was defined as positive (+) direction rotation.

In FIG. 3, currents flowing on the stator windings A, B, and C were defined _as i _as , i _bs, and i _cs , respectively. The motor is assumed to be cylindrical symmetric. Since the voltage, current, and magnetic flux on the stator side always exist on the same plane, these physical quantities are all treated as vectors.

In addition, assuming that the magnetomotive force of the permanent magnet is induced by a constant current source, the BLDC motor can be represented by an equivalent circuit as shown in FIG. Based on the equivalent circuit of FIG. 4, the voltages of each phase of the stator are represented by v _as , v _bs, and v _cs , respectively, and the total fluxes that link each phase of the stator are λ _as , λ _bs and λ _cs The stator side voltage equation of the permanent magnet motor can be expressed as Equation 1 below:

[Equation 1]

Where p represents the derivative operator over time, ie d / dt.

On the other hand, since the rotor side is made of a permanent magnet having a constant magnetic flux, there is no need to analyze separately.

When the mutual inductance between the stator winding and the virtual winding of the rotor is represented by L _M , the linkage magnetic flux may be expressed by Equation 2 below.

[Equation 2]

λ _abcs = L _S i _abcs + L _M I _F

In the above formula,

λ _abcs is the vector representation of the linkage flux of the stator,

i _abcs is the vector of stator current

L _S is the vector representation of the inductance of the stator winding,

L _M is a vector representation of the mutual inductance between the rotor and stator windings.

Respective equations 3 to 6 are defined as follows:

[Equation 3]

[Equation 4]

[Equation 5]

[Equation 6]

Where L _ls is the leakage inductance of the stator winding and L _A is the self inductance of the stator winding.

In general, as a reference coordinate system mainly used to solve the complexity of the time-varying differential equations in the voltage equation of an AC motor and to analyze the transient state, a stationary reference frame and a synchronous speed based on the stator side are used. There is a synchronous reference frame that rotates.

In FIG. 3, when the axis coinciding with the A phase of the stator is defined as the d ^s axis, and the direction perpendicular to the axis is defined as the q ^s axis, this coordinate system is called a stationary coordinate system because it is independent of the position of the rotor.

In the synchronous motor, since the rotor is rotating at the synchronous speed, if the magnetic flux direction of the rotor is defined by the d ^r axis and the direction perpendicular to this axis is defined by the q ^r axis, the coordinate system rotates in synchronization with the rotor. Therefore, it is called a synchronous coordinate system synchronized with the rotor.

5 shows the relationship between the axes of the stationary coordinate system and the axes of the synchronous coordinate system. In the figure, θ ^r is the angle (electric angle) between the magnetic axis and the rotor generated by the a-phase winding at a given point in time.

If the physical quantity of three phases is added instantaneously, if the value is 0, there is no image content. Therefore, the physical quantity of three phases can be expressed by the physical quantity of two phases on the d-q axis | shaft of FIG. This is expressed as a determinant form as shown in Equations 7 and 8 below:

[Equation 7]

[Equation 8]

In the above formula,

f ^s _d and f ^s _q are physical quantities on the d ^s and q ^s axes, respectively,

f _a , f _b and f _c are physical quantities on the a, b and c axes, respectively.

In order to represent the voltage equation of Equation 1 as a voltage equation in a stationary coordinate system, it is represented by a vector, and Substituting Equation 2 above gives Equation 9.

[Equation 9]

v _abcs = R _s i _abcs + p (L _S i _abcs + L _M I _F )

In the above formula, v _abcs = [v _as v _bs v _cs ] ^T.

By multiplying and converting the transformation matrix to the static coordinate system represented by Equation 7 and the voltage equation of Equation 9, the voltage equation in the static coordinate system as shown in Equations 10 and 11 can be obtained:

[Equation 10]

[Equation 11]

Where

v ^s _ds and v ^s _qs are the dq-axis voltages in the static coordinate system of the stator, respectively,

로 정의되는 BLDC 전동기 고정자의 상 인덕턴스(phase inductance)이며,L _s is

Phase inductance of a BLDC motor stator defined by

K _e is the back emf constant as K _e = L _m I _F.

In the synchronous coordinate system, the coordinate axis rotates at the synchronous speed. The voltage and current vectors of the stator rotating at the synchronous speed become constant values in the synchronous coordinate system. Therefore, it is advantageous in terms of control to use a synchronous coordinate system as compared to using a static coordinate system.

Converting the physical quantity of the still coordinate system to the physical quantity of the synchronous coordinate system or converting the physical quantity of the synchronous coordinate system to the physical quantity of the static coordinate system is expressed in a matrix form as follows:

[Equation 12]

[Equation 13]

In the above formula,

f ^r _d and f ^r _q each represent a physical quantity on a synchronous coordinate system,

f ^s _d and f ^s _q represent the physical quantities on the stationary coordinate system, respectively.

By multiplying the voltage equation in the static coordinate system of Equation 10 or Equation 11 by the transformation matrix of Equation 12, the voltage equation in the synchronous coordinate system of the BLDC motor can be expressed as follows:

[Equation 14]

[Equation 15]

In the above formula, v ^r _ds and v ^r _qs are stator side dq axis voltages on the synchronous coordinate system, respectively.

In addition, when there are no images, a matrix for converting a physical quantity of three phases into a physical quantity on a synchronous coordinate system and a matrix for inverse transform can be expressed as follows.

[Equation 16]

[Equation 17]

6A and 6B show a d-axis equivalent circuit and a q-axis equivalent circuit on a synchronous coordinate system of a BLDC motor based on Equation 14 or 15, respectively.

6A and 6B, λ ^r _ds and λ ^r _{qs, which} are linkage fluxes of the synchronous coordinate system dq-axis, are represented by Equation 18:

Equation 18

The torque type of BLDC motor can be obtained from the motor output. The instantaneous input P _in due to three-phase phase voltage and phase current is:

[19]

P _in = v _as i _as + v _bs i _bs + v _cs i _cs

When the three-phase phase voltage and the phase current of Equation 19 are converted to the voltage and current of the synchronous coordinate system using Equation 17, the instantaneous input is as shown in Equation 20:

[Equation 20]

Again, converting the voltages of Equation 20 into equations using the constants of the current and the motor using Equation 14, the instantaneous input is given by Equation 21:

[Equation 21]

In the above formula, the first term on the right side represents copper loss, the second term represents magnetic field energy conversion rate, and the third term represents mechanical energy output.

Thus, the mechanical output P _out of the motor is:

[Equation 22]

On the other hand, the output of the motor is expressed by the torque and the speed of the motor rotor as follows:

[Equation 23]

P _out = ω _rm T _e

In addition, the relationship between the electrical angular velocity and the mechanical angular velocity is as follows:

[Equation 24]

Where P is the number of poles of the motor.

Therefore, the motor output torque is as follows:

[Equation 25]

Where K _T is the torque constant.

From Equation 25, the torque of the motor is entirely proportional to the q-axis current, it can be seen that the current of the d-axis component does not affect the torque at all.

The mechanical motion equation of the motor is:

[Equation 26]

In the above formula,

T _L is the load torque,

J is the moment of inertia

B is a friction coefficient.

The counter electromotive force, which is the rate of change of the rotor flux of the motor at standstill or in the low speed region, is almost negligible compared to the DC supply voltage. Therefore, in the electric motor model of FIG. 4, portions representing the counter electromotive force by the rotor may be omitted. 7 is an equivalent circuit in which back electromotive force by the rotor is omitted in FIG. 4. At this time, the motor is seen as a three-phase symmetric load consisting of R and L.

Hereinafter, a method of estimating the initial angle of the rotor according to the present invention will be described in detail. However, the present invention is not limited by the following examples.

As described above, the motor in the low speed region can be modeled as an R-L load in which three phases are balanced. In practice, however, the magnetic flux generated by the magnet of the rotor passes through the stator core, causing partial saturation of the core. Due to this saturation phenomenon, when a voltage is applied to the stator windings, the rate of change of the increasing current, that is, the inductance of the stator circuit, changes according to the position of the rotor magnet.

The change of inductance according to the position of the rotor of the motor was confirmed by experiment. When the voltage V1 of the three-phase inverter space vector voltage is applied to the test target motor for a time T = 25 ms, the motor may be represented by an equivalent circuit as shown in FIG. 8. 9 shows the three-phase inverter space vector voltage.

In the equivalent circuit, the current value obtained by sampling the DC power supply current at t = T is defined as I1. The DC power supply current i (t) is represented by Equation 27, and can be represented by a graph as shown in FIG.

[Equation 27]

In the above formula,

R is a parallel composite resistance of a phase resistance and b and c phase resistance,

V is the DC supply voltage.

The result of measuring the current i (t) according to the position of the rotor is shown in FIG. 11.

Further, the inductance obtained from Equation 27 is as follows:

[Equation 28]

Thus, converting the current value of FIG. 11 into inductance, an inverted graph can be obtained as shown in FIG. As can be seen from Figure 12, the inductance of the stator windings varies by more than about 15% depending on the position of the rotor magnetic flux. Therefore, the d-axis position of the rotor can be estimated using the change of inductance.

The process of estimating the d-axis position of the rotor according to the invention is as follows:

1) First, V1 and V4 of the six spatial voltage vectors (see FIG. 9) output by the three-phase inverter are applied. At this time, the currents raised after the predetermined time T are defined as I1 and I4. According to Equation 28, the magnitude relationship between I1 and I4 is opposite to the magnitude relationship between the inductance in the V1 direction and the inductance in the V4 direction. That is, when the inductance in the V1 direction is smaller than the inductance in the V4 direction, I1 is larger than I4. At this time, as shown in Fig. 13, the d-axis of the rotor is located in the right half plane of the stator reference coordinate system.

2) Thereafter, the remaining two voltage vectors present in the 180-degree range (ie, the electric angle of −90 degrees to +90 degrees) in which the d-axis of the rotor is estimated to be applied are sequentially applied, and the inductance at that time is applied. Measure For example, when it is assumed that the rotor d-axis is located in the right half plane as shown in FIG. 13, voltages in the V2 and V6 vector directions are sequentially applied, and the rising currents I2 and I6 are measured after a predetermined time. do.

3) By comparing the magnitude relationship of the inductances in the three voltage vectors, the direction of the voltage vector having the smallest inductance is the d-axis direction. Therefore, the d-axis of the rotor is assumed to be in the range of -30 degrees to +30 degrees with respect to the voltage vector direction. Then, as illustrated in FIGS. 14A and 14B, the q-axis of the rotor is estimated by comparing the inductances in the two voltage vector directions except for the voltage vector having the smallest inductance.

   For example, as shown in FIG. 14A, when the inductance in the V1 direction is the smallest and the inductance in the V6 direction is larger than the inductance in the V2 direction, the q-axis of the rotor is in the vicinity of the V6 voltage vector direction (ie, electric angle −90). It can be estimated to be located in the (degree to -30 degrees range). Therefore, it can be estimated that the d-axis position of the rotor is in the range of +30 degrees with respect to the V1 direction, and the average position is +15 degrees. In this way, the d-axis position of the rotor can be estimated in units of 30 degrees.

   Conversely, if the inductance in the V2 direction is greater than the inductance in the V6 direction, it can be estimated that the q-axis of the rotor is located near the V2 voltage vector direction (that is, in the electric angle range of +30 degrees to +90 degrees). Therefore, it can be assumed that the d-axis position of the rotor is in the range of -30 degrees with respect to the V1 direction, and the average position is -15 degrees.

4) After determining the direction closest to the d-axis and the direction closest to the q-axis in the order of 1), 2) and 3), 12 regions (30 degrees) where the d-axis of the rotor can be finally located Unit) can be determined.

However, in the process 1), when the V1 voltage vector and the V4 voltage vector are in the directions near the q-axis and -q-axis, the difference in inductance in the two directions is very small, so that it is difficult to accurately determine them. Thus, when the two inductances measured in step 1) are less than or equal to a predetermined value (e.g., the difference is 10% or less, preferably 5% or less with respect to the measured inductance), the V2 voltage vector and the V5 voltage vector Based on the above, the process 2) and the process 3) are repeated again. In the case of estimating in this way, the probability of wrong estimation is greatly reduced.

15 is a flowchart of an estimating process according to the present invention.

First, as in step 1), spatial voltage vectors V1 and V6 are sequentially applied to the stator to obtain inductances L1 and L6 (S100 and S200).

Then, as in the process 2), when L1 is smaller than L6 (S400), since the d-axis of the rotor is located in the right plane of the stator reference coordinate system (S510), by applying V2 and V6 in turn to each inductance It obtains (S520, S530).

Thereafter, as in step 3), the d-axis is estimated by comparing the L1, L2, and L6 (S540). In addition, the q-axis is estimated by comparing the inductances of the remaining two voltage vectors (S900).

However, as a result of the comparison in step S400, when L6 is smaller than L1 (S400), since the d-axis of the rotor is located in the left half plane of the stator reference coordinate system (S610), V3 and V5 are sequentially applied to each other. To obtain the inductance of (S620, S630). Then, the d-axis is estimated by comparing the L4, L3 and L5 (S640). In addition, the q-axis is estimated by comparing the inductances of the remaining two voltage vectors (S900).

On the other hand, when the two inductance measured in the step (S100, S200) is 5% or less (S300), V2 and V5 are sequentially applied to the stator to obtain the inductance L2 and L5 (S310, S320). Then, if L2 is smaller than L5 (S450), it is assumed that the d-axis of the rotor is within V2 in the stator reference coordinate system (i.e., in the range of -90 degrees to +90 degrees relative to V2) ( S710). After that, the inductance is obtained by applying V3 (S720). Thereafter, the process of estimating the d-axis by comparing the L2, L3, and L1 (S730) and estimating the q-axis by comparing the inductances of the remaining two voltage vectors (S900) is the same.

In addition, when L5 is smaller than L2 (S450), it is assumed that the d-axis of the rotor includes V5 in the stator reference coordinate system (that is, within a range of -90 degrees to +90 degrees with respect to V5) ( S810). Thereafter, V6 is applied to obtain an inductance (S820). Thereafter, the process of estimating the d-axis by comparing the L5, L6 and L4 (S830), and estimating the q-axis by comparing the inductance of the remaining two voltage vectors (S900).

During the d-axis estimation process according to the present invention, a total of four or five voltage vectors are applied. Compared to the conventional estimation method for determining the initial position in units of 60 degrees by applying a voltage six times, in the present invention, the initial position is determined in units of 30 degrees while reducing the number of times of voltage application. It can be seen that can be estimated.

Hereinafter, an embodiment of the method for estimating the initial position angle of the rotor according to the present invention will be described.

When the DC voltage is applied to the motor as shown in Fig. 8, the current measured by the current sensor on the DC voltage source side rises with a unique time constant. At this time, there are two ways to simply measure the inductance.

The first method is a method of measuring a current value after a predetermined time, as shown in FIG. According to Equation 28, inductance can be obtained from the measured current value.

The second method is a method of measuring the time to reach a predetermined current value as shown in FIG. If the time taken to reach the arbitrarily set current I _SET is T1, the inductance can be obtained from Equation 29:

[Equation 29]

In the present invention, the absolute magnitude of the inductance is not measured, but only the relative magnitude is considered, so any method can be used. In this embodiment, the first method is used.

In general, the difference in inductance value in BLDC motors is very small. In addition, the smaller the strength of the magnet, the smaller the inductance value. If the difference between the current samples for measuring the inductance is very small, it is very difficult to determine the magnitude relationship of the inductance. Therefore, the time at which the difference between the largest current samples can be obtained is selected, and the magnitude relationship of the inductance can be determined most accurately when the current is measured after that time has elapsed.

As shown in FIG. 17, when the current rises with different time constants, it means that inductances are different from each other. Each of the currents i ₁ (t) and i ₂ (t) can be represented as follows:

Equation 30

The difference in current i _diff (t) is as follows:

Equation 31

To find the time T at which i _diff (t) becomes maximum, the derivative with respect to time is:

Equation 32

T obtained from Equation 32 is as follows:

[Equation 33]

Assume that τ _{1 ≒} τ ₂ , τ ₂ = τ ₁ + Δ (Δ ≒ 0). Thus, the point T at which i _diff (t) is maximized is:

[Equation 34]

Therefore, it is preferable to determine the current sampling time t by the value of the intermediate value of τ corresponding to the rotor position of the target motor, that is, the (maximum value of tau + the minimum value of tau) / 2. In practice, however, when voltage is applied for a time of 1τ, the magnitude of the current is significantly increased, so that the electric motor can rotate. Therefore, the sampling time T is determined as the smaller value between the maximum time that the rotor does not rotate due to the static friction force and the median value of the measured time constant.

Hereinafter, a method of starting a BLDC motor according to the present invention will be described in detail. However, the present invention is not limited by the following examples.

As can be seen from Equation 25, the torque is generated only by the rotor q-axis current. Therefore, in order to obtain the maximum torque during the starting process, it is necessary to increase the q-axis current by applying a voltage as close to the q-axis as possible.

The initial position of the rotor may be estimated using the above-described method of estimating the initial angle of the rotor within the range of 30 degrees. 18 shows the applied voltage angle according to the position of the rotor. In this figure, the solid line represents the actual rotor axis, and the dotted line represents the estimated axis.

When the d-axis of the rotor is located between 330 degrees and 0 degrees as shown in Fig. 18A, the d-axis position of the rotor is estimated at 345 degrees, and the q-axis at this time is located at 75 degrees. Therefore, when the V2 voltage, the V3 voltage, and the zero voltage are combined and the average voltage angle is applied at 75 degrees, the voltage closest to the q-axis is applied. As a result, the rotor generates the largest torque per unit current and rotates counterclockwise.

Then, when the d-axis of the rotor passes 0 degrees as shown in (b), since the inductance is the largest in the q-axis of the rotor, the inductance at V3 becomes larger than the inductance at V2. Therefore, it is possible to continuously compare the inductance at V2 and the inductance at V3, and determine that the rotor d-axis passes zero degrees at the time when the magnitude relationship changes.

If it is determined that the d-axis of the rotor has passed 0 degrees, the rotor has moved to the next area. Therefore, as in (c), it can be estimated that the q-axis of the rotor also moves to the next region and is located at 105 degrees. Similarly, when the voltages V2, V3, and zero voltage are combined and applied at an average voltage angle of 105 degrees, the average voltage is applied closest to the q-axis while the rotor is located in this region.

From this point on, only the inductance in the V3 direction is measured. As shown in (e), when the d-axis of the rotor is located at 30 degrees, the inductance has a maximum value because the V3 direction is the q-axis direction. As the rotor rotates further, the d-axis exceeds 30 degrees, the inductance in the V3 direction decreases. Therefore, when the inductance in the V3 direction becomes maximum, it is determined that the rotor passes 30 degrees.

At the same time, the estimated position of the rotor is moved to the next area as in (f). The position of the q-axis also moves by 30 degrees to 135 degrees. The V3 voltage, the V4 voltage, and the zero voltage are synthesized, and a voltage is applied in the direction of the voltage angle of 135 degrees.

By repeating this process, the position of the rotor can be estimated throughout the electric angle 360 degrees, and voltage can be applied to the q-axis position within an error range of ± 15 degrees.

30 is a flowchart of the BLDC motor starting method as described above.

First, an initial electric angle of the d-axis and the q-axis of the rotor is estimated according to the rotor initial electric angle estimation method as described above (S10).

Then, the d-axis position of the rotor is determined (S15).

Thereafter, two spatial voltage vectors Vn and Vn + 1 adjacent to the electric angles of the estimated q-axis are synthesized and applied to the stator at the average voltage angle of the region where the estimated q-axis exists.

Subsequently, as a result of the determination in step S25, the d-axis electric angle of the rotor is 0 degrees to 30 degrees, 60 degrees to 90 degrees, 120 degrees to 150 degrees, 180 degrees to 210 degrees, 240 degrees to 270 degrees, Alternatively, when present at 300 to 330 degrees, the inductance Ln + 1 of the large spatial voltage vector Vn + 1 of the two spatial voltage vectors Vn and Vn + 1 used in the synthesis is measured (S35). Monitor (S60).

Subsequently, it is estimated that the rotor has moved 30 degrees from the time when the inductance Ln + 1 for the space voltage vector Vn + 1 decreases after indicating the maximum value (S70).

Thereafter, the process returns to step S15 to determine the d-axis position of the rotor again. In addition, since the rotor has moved 30 degrees, the composite voltage of the space voltage vector is increased by 30 degrees and applied (S25).

In this case, the d-axis electric angle of the rotor is present at 30 degrees to 60 degrees, 90 degrees to 120 degrees, 150 degrees to 180 degrees, 210 degrees to 240 degrees, 270 degrees to 300 degrees, or 330 degrees to 360 degrees. . In this case, the inductance Ln and Ln + 1 for each of the two spatial voltage vectors Vn and Vn + 1 used in the synthesis are measured (S30) and compared (S40).

From the time point when the magnitude relationship between the inductance Ln and Ln + 1 is changed, it is estimated that the rotor has moved 30 degrees (S15).

Thereafter, the process returns to the step S15 again, and the steps S15 to S70 are repeated.

As such, after estimating the initial electric angle of the rotor, whether the magnitude of the inductance changes with respect to two spatial voltage vectors of adjacent inductances is changed (S40) or the inductance for the spatial voltage vector having a larger electric angle shows the maximum peak. By monitoring whether or not (S60), it is possible to find out the rotation of the rotor in units of 30 degrees.

Hereinafter, an embodiment of the BLDC motor starting method according to the present invention will be described.

In order to implement the above-described starting method, three voltages of two voltage vectors and zero vectors are always output within one switching period, and the inductance is continuously measured when one or two vectors are applied. shall. The inductance measuring method can use the above-mentioned method as it is. Therefore, it can be implemented by only one or two current sampling in one switching period.

FIG. 19 illustrates a current waveform and an inductance measuring method in a switching period in the situation of FIG. 18A. The voltage angle in this case is 75 degrees. Since the time when the voltage vector V2 is applied is longer, the time is defined as T _long , the time when the voltage vector V3 is applied is defined as T _short , the time when the zero vector is applied is defined as T _zero , and the entire switching period If we define T _s , each time is

[Equation 35]

[Equation 36]

[Equation 37]

In the above formula,

T _s is a period,

| V | is the magnitude of the voltage vector applied in one period.

Hereinafter, an experimental example for confirming the effects of the initial angle estimation method and the motor starting method of the rotor according to the present invention.

In the case of a small low-cost electric motor system, since there are generally many systems in which only one current sensor is used instead of two or more current sensors, only one DC power supply current sensor is used in this embodiment.

20 is a configuration diagram of an experimental apparatus used in the present experimental example.

The electric motor used in the experiment is a spindle motor for rotating a disk of a hard disk drive (HDD) for a desktop PC as shown in FIG. 21. The spindle motor is driven using a MOSFET three-phase inverter using SMPS of 12V voltage as the DC power source. For gating and control of the inverter, a TMS320VC33 DSP control board with fast digital signal processing is used.

One sensing resistor on the DC power supply side was used to measure the current flowing into the DC power supply. The voltage across the sense resistor is amplified by a voltage amplifier with a voltage gain of 15.28 (V / V) and then converted into a digital signal through an A / D converter on the control board. An encoder for measuring the actual rotation angle of the motor is connected to the motor shaft, and the position pulse signal of the rotor is transmitted to the control board.

The spindle motor was experimented by applying the rotor initial angle estimation method and the motor starting method according to the present invention. Even when voltage is applied for initial angle estimation, the maximum voltage application time at which the rotor is stopped is 100 ms. The average value of the motor time constant is 155 ms. Therefore, a voltage was applied for 100 mA and the current was sampled at the time when 100 mA passed. Since the voltage vector is applied at intervals of 1 ms and a total of 4 or 5 voltages are applied, the total time required for the initial angle estimation process is within about 5 ms. DC power supply side current waveforms during the initial angle estimation process are shown in FIGS. 22 and 23.

After applying the V1 voltage vector to the stator to align the rotor in the V1 voltage vector direction, that is, the a-phase direction, the rotor position at that time was defined as 0 degrees. Since the 8-pole motor has a 90 degree mechanical angle and an 360 degree electrical angle, the initial angle estimation method according to the present invention was used while rotating the rotor in 3 degree increments from 1 degree to 88 degrees. The results of five replicate experiments are shown in FIG. 24.

25 shows the error between the actual angle and the estimated angle, and FIG. 26 shows the total number of times the voltage vector is applied. 15 degrees out of 30 actual angles from 1 degree to 88 degrees fail in initial 180 degree discrimination, and it can be seen that voltage was applied once more and sampled. If the initial 180 degree determination is successful, a total of four voltage vectors are applied, and if a failure is unsuccessful, a total of five voltage vectors are applied. Therefore, it can be seen that the voltage is applied and sampled the current 4.5 times over the entire angular range.

As expected, it can be seen from FIG. 25 that the actual angle is estimated within a ± 15 degree error range.

As described above, starting experiments were performed using the starting method according to the present invention starting from a point 90 degrees counterclockwise from the estimated initial rotor position.

In equations (35) to (37), Ts = 300 mV, and the magnitude of the voltage vector applied within one period | V | = 1 / 4Vdc = 3V.

FIG. 27 compares the estimated position of the rotor with the actual rotor angle measured using a 1000ppr encoder attached to the rotor while starting up from 600 rpm. From the figure, it can be seen that the estimated angle has an error of at most [pi] / 4 to estimate the actual angle.

FIG. 28 illustrates an actual angle and an input voltage angle when a disturbance occurs while starting a motor by applying a predetermined magnitude and frequency according to a conventional starting method. The applied voltage is a 3-V symmetric sinusoidal pie of 3 V, similar to the above experiment for the starting method of the present invention, and the frequency was linearly increased to 50 Hz / sec in consideration of the inertia and friction of the rotor.

In order to artificially cause disturbance, the rotor was held by hand for a time in the dotted line of the drawing to stop and then released. When disturbance occurs, it can be seen from the figure that the rotor fails to start due to synchronous outage.

29 is an electric angle and an estimated angle waveform when a disturbance occurs during the startup according to the startup method of the present invention. Unlike FIG. 28, which shows the waveform shown in the case of using the conventional starting method, even if a disturbance that causes the rotor to stop occurs, the position of the actual rotor is still estimated, and the normal starting again after the disturbance is removed. You can see that it starts.

The initial position angle estimation method of the rotor according to the present invention estimates the initial position of the rotor so that the small BLDC motor can be effectively started without the position and magnetic flux sensors.

In addition, the motor starting method according to the present invention estimates the position of the rotor from the initial position estimated by the estimation method to a speed at which the magnitude of the counter electromotive force is sufficiently increased so as to start the motor with a high starting torque without the risk of synchronous outage. Maneuver

In the present invention, using the magnetic saturation of the stator core by the permanent magnet of the rotor, it is confirmed that the inductance of the stator varies depending on the position, and by using this phenomenon, not only at standstill but also to a low speed section that can ignore the counter electromotive force. It was confirmed through experiments that the location of the former can be determined.

Since the method according to the invention determines the position only by the magnitude relationship of the stator inductance, the sensorless drive algorithm is not affected by the electrical and mechanical constants of the motor. In addition, since a separate voltage is not applied to determine the position of the rotor, it is more efficient than the conventional methods including the high frequency injection method, the implementation is simple, and the estimation performance can be obtained in units of 30 degrees. Also, there is no risk of synchronous outage.

Claims (17)

A method of estimating the initial electric angle position of a rotor of a brushless DC motor, which is driven by a spatial voltage vector output by a pulse width modulated three-phase inverter, (A) obtaining an inductance L1 by applying a space voltage vector V1 having an electric angle of 0 degrees to the stator in the fixed coordinate system; (B) obtaining an inductance L4 by applying a spatial voltage vector V4 having an electric angle of 180 degrees to the stator in the fixed coordinate system; Comparing the magnitudes of the inductances L1 and L4 and selecting a space voltage vector representing a small inductance value among the space voltage vectors V1 and V4 as a reference space voltage vector Vk; (D) obtaining an inductance Lk + 1 by applying a spatial voltage vector Vk + 1 positioned at an electrical angle of +60 degrees with respect to the selected reference spatial voltage vector Vk; (E) obtaining an inductance Lk-1 by applying a spatial voltage vector Vk-1 located at an electrical angle of −60 degrees with respect to the selected reference spatial voltage vector Vk; Inductance Lk of the reference spatial voltage vector Vk obtained in step (a) or step (b), and the smallest inductance of the three inductances of inductance Lk + 1 and Lk-1 obtained in steps (d) and (e) Estimating that the d-axis of the rotor is located in a section of the space voltage vector representing f; And (G) estimating that the q-axis of the rotor is located in the space voltage vector section representing the largest inductance among the three inductances compared in the step (f). Initial electric angle position estimation method. The method of claim 1, wherein the vector direction of the space voltage vector V1 coincides with the d axis in the fixed coordinate system. The interval of the spatial voltage vector in which the d axis of the rotor is estimated to be located in step (f) is -30 degrees with respect to the direction of the spatial voltage vector representing the smallest inductance among the three inductances. Initial electric angle position estimation method of the rotor of the BLDC motor, characterized in that the electric angle range of ~ +30 degrees. 4. The method of claim 3, wherein in step (g), by estimating the position of the q-axis of the rotor, the electric current of -30 degrees with respect to the direction of the spatial voltage vector, where the d-axis of the rotor represents the smallest inductance of the three inductances. And (h) estimating that it is located in an angular range or an electric angular range of +30 degrees. The method of claim 1, wherein when the inductance L1 and L4 are compared in the step (c), the difference is less than or equal to a predetermined value. Obtaining a inductance L2 by applying a spatial voltage vector V2 having an electric angle of 60 degrees to the stator in the fixed coordinate system (a2); (B2) obtaining an inductance L5 by applying a space voltage vector V5 having an electric angle of 240 degrees to the stator in the fixed coordinate system; Comparing the magnitudes of the inductances L2 and L5 and selecting a space voltage vector representing a small inductance value among the space voltage vectors V2 and V5 as a reference space voltage vector Vk; Obtaining an inductance Lk + 1 by applying a spatial voltage vector Vk + 1 positioned at an electrical angle of +60 degrees with respect to the selected reference spatial voltage vector Vk (d2); The inductance Lk of the reference spatial voltage vector Vk obtained in the step (a2) or step (b2), the inductance Lk + 1 obtained in the step (d2), and the electric angle -60 degrees with respect to the selected reference spatial voltage vector Vk. Inductance Lk-1 obtained when the space voltage vector Vk-1 is applied, where inductance Lk-1 is one of the three inductances of L1 and L4 obtained in step (a) and step (b). (E2) estimating that the d-axis of the rotor is located in a section of a space voltage vector representing a small inductance; And A step (f2) of estimating that the q-axis of the rotor is located in the space voltage vector section representing the largest inductance among the three inductances compared in the step (e2). Initial electric angle position estimation method. 6. The initial electric power of the rotor of the BLDC motor according to claim 5, wherein when the difference between the inductance L1 and L4 is 5% or less of the value of the inductance L1 or L4, steps (a2) to (f2) are performed. Angular position estimation method. The interval of the spatial voltage vector in which the d-axis of the rotor is located in step (e2) is -30 degrees with respect to the direction of the spatial voltage vector representing the smallest inductance among the three inductances. Initial electric angle position estimation method of the rotor of the BLDC motor, characterized in that the electric angle range of ~ +30 degrees. 8. The method of claim 7, wherein by estimating the position of the q-axis of the rotor in step (f2), the d-axis of the rotor is -30 degrees relative to the direction of the spatial voltage vector representing the smallest inductance of the three inductances. (G2) further comprising estimating the angular range or an electric angle range of +30 degrees. The method of claim 1, wherein when the inductance L1 and L4 are compared in the step (c), the difference is less than or equal to a predetermined value. Obtaining a inductance L6 by applying a spatial voltage vector V6 having an electric angle of 300 degrees to the stator in the fixed coordinate system (a3); (B3) obtaining an inductance L3 by applying a spatial voltage vector V3 having an electric angle of 120 degrees to the stator in the fixed coordinate system; Comparing the magnitudes of the inductances L6 and L3 to select a spatial voltage vector representing a small inductance value among the spatial voltage vectors V6 and V3 as a reference spatial voltage vector Vk; Obtaining an inductance Lk-1 by applying a spatial voltage vector Vk-1 located at an electrical angle of −60 degrees with respect to the selected reference spatial voltage vector Vk (d3); Inductance Lk of the reference space voltage vector Vk obtained in the step (a3) or step (b3), inductance Lk-1 obtained in the step (d3), and the electric angle +60 degrees relative to the selected reference space voltage vector Vk Among the three inductances of inductance Lk + 1 obtained when the space voltage vector Vk + 1 is applied (wherein the inductance Lk + 1 is any one of L1 and L4 obtained in step (a) and step (b)). (E3) estimating that the d-axis of the rotor is located in the interval of the spatial voltage vector representing the smallest inductance; And A step (f3) of estimating that the q-axis of the rotor is located in the spatial voltage vector section representing the largest inductance among the three inductances compared in the step (e3). Initial electric angle position estimation method. 10. The initial electricity of the rotor of the BLDC motor according to claim 9, wherein if the difference between the inductance L1 and L4 is 5% or less of the value of the inductance L1 or L4, steps (a3) to (f3) are performed. Angular position estimation method. 10. The method of claim 9, wherein the interval of the spatial voltage vector in which the d-axis of the rotor is estimated in step (e3) is -30 degrees with respect to the direction of the spatial voltage vector representing the smallest inductance among the three inductances. Initial electric angle position estimation method of the rotor of the BLDC motor, characterized in that the electric angle range of ~ +30 degrees. 12. The method of claim 11, wherein by estimating the position of the q-axis of the rotor in step f3, the electric power of -30 degrees with respect to the direction of the spatial voltage vector where the d-axis of the rotor represents the smallest inductance of the three inductances. (G3) further comprising estimating that it is located in an angle range or an electric angle range of +30 degrees. The process of any one of claims 1 to 12, wherein the process of applying the spatial voltage vector to the stator to obtain an inductance, After applying the spatial voltage vector, measuring a current value of a stator when a predetermined time has elapsed; After applying the space voltage vector, by measuring the time required until the current value of the stator reaches a predetermined value, And using the measured current value or the required time as an inductance value. The initial time of the rotor of the BLDC motor according to claim 13, wherein the time for measuring a current value flowing through the stator is a smaller value between a maximum time at which the rotor does not rotate due to the static friction force and a median value of the measured time constant. Electric angle position estimation method. The method of claim 13, wherein the comparing the inductance values with each other comprises comparing the measured current value or the required time with each other. As a method of starting a BLDC motor without a position sensor and a brush, which is driven by a space voltage vector output by a pulse width modulated three-phase inverter, (A) estimating initial electric angles of the d-axis and q-axis of the rotor by the method according to any one of claims 3, 8 and 12; (B) synthesizing two spatial voltage vectors Vn and Vn + 1 adjacent to the electrical angle of the estimated q-axis with the average voltage angle of the region where the estimated q-axis exists and applying them to the stator; If the d-axis of the rotor is present at 0 degrees to 30 degrees, 60 degrees to 90 degrees, 120 degrees to 150 degrees, 180 degrees to 210 degrees, 240 degrees to 270 degrees, or 300 degrees to 330 degrees, (C) monitoring the inductance Ln + 1 for the large electric angle of the space voltage vector Vn + 1 of the two space voltage vectors Vn and Vn + 1 used; (D) estimating that the rotor has moved 30 degrees from the time when the inductance Ln + 1 for the space voltage vector Vn + 1 decreases after indicating the maximum value; If the d-axis of the rotor is present at 30 degrees to 60 degrees, 90 degrees to 120 degrees, 150 degrees to 180 degrees, 210 degrees to 240 degrees, 270 degrees to 300 degrees, or 330 degrees to 360 degrees, (E) comparing the inductances Ln and Ln + 1 for each of the two spatial voltage vectors Vn and Vn + 1 used; (F) estimating that the rotor has moved 30 degrees from the time when the magnitude relationship between the inductance Ln and Ln + 1 is changed; And Thereafter, step (b) to repeat the step (b) to (f) comprises the step of starting a BLDC motor. The method of claim 16, wherein the measuring and comparing or monitoring the inductance by applying the space voltage vector to the stator comprises: After applying the spatial voltage vector, measuring a current value of a stator when a predetermined time has elapsed; After applying the space voltage vector, by measuring the time required until the current value of the stator reaches a predetermined value, And comparing or monitoring the measured current value or time required as an inductance value.

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