JP2000050676A - Motor control equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technique which can detect position of a rotor without using positioning sensors. SOLUTION: Motor control equipment is provided with a filter part 22, and a current sensor part 28 which are connected with the same phase from among three-phase AC voltages U, V and W. The filter part 22 detects a current value when an induced electromotive force at rotation of a rotor does not exist, from the internal impedance of a motor 3 and a voltage value and outputs the current value to an operating part 23, as a signal. The current sensor part 28 measures a current, which actually flows in the phase with which the filter part 22 is connected and outputs the current to the operating part 23, as a signal. The operating part 23 operates and processes (subtraction) the two inputted signals, eliminates a current value corresponding to the internal impedance of the motor 3, extracts induced current components due to rotation of the rotor, and detects the angular velocity of the rotor. Since the position of the rotor is detected from the angular velocity, a three-phase AC voltage control part 21 can so control a voltage that the most suitable electromagnetic force is applied to the rotor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for controlling a brushless motor, and more particularly to a technique for detecting a speed of a rotor of a brushless motor.

[0002]

2. Description of the Related Art Conventionally, a three-phase brushless motor has been
It is widely used in place of motors using brushes and commutators because of the lack of mechanical wear and sparks.

[0003] In a three-phase brushless motor, it is fundamental to supply a current so as to have the same phase as the induced voltage of the winding. Therefore, a control device for controlling the three-phase brushless motor needs information on the position of the rotor.

[0004] There are two types of typical energizing systems for a three-phase brushless motor, a 120 ° square wave energizing system and a sine wave energizing system.

In the 120 ° square wave energization method, as shown in FIG. 5, the energization period per phase is 240 °, and a period t ₁ during which voltage is applied to the U phase and the V phase among the three phases. During this time, no voltage is applied to the remaining W phase. Therefore, during the period t ₁ , the current flowing between the U phase and the V phase
By measuring the voltage induced in the winding connected to the W phase, the speed and position of the rotor can be determined. In the following periods t ₂ and t ₃ , the speed and position of the rotor during the entire period can be obtained by measuring the voltage induced in the W phase and the U phase.

As described above, in the above-described 120 ° square wave conduction method, the unused portion of the winding can be used for the current sensor, so that the position and speed of the rotor can be relatively easily obtained.

However, when switching three-phase voltages, torque ripple is likely to occur, which causes vibration and noise, and is not suitable for high-end applications such as machine tools and servomotors.

[0008] In contrast to a system in which a voltage is applied intermittently such as a 120 ° square wave conduction system, in a system in which a voltage is applied continuously such as a sine wave conduction system, a current flows continuously in each phase. , It is possible to eliminate torque ripple,
Since there are no unused windings, the windings cannot be used in place of the sensors.

Therefore, when a three-phase AC voltage is applied and operation is performed without causing torque ripple, it is necessary to provide a positioning sensor such as a Hall element or a rotary encoder, which is an obstacle to miniaturization and cost reduction. I was

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages of the prior art, and has as its object to provide a technique capable of detecting the position of a rotor without using a positioning sensor. Is to do.

[0011]

According to a first aspect of the present invention, there is provided a motor control apparatus comprising: a three-phase AC voltage control unit for generating a three-phase AC voltage to be supplied to a three-phase brushless motor; A filter section for calculating a current flowing through the three-phase brushless motor from a voltage output from the three-phase AC voltage control section; a current sensor section detecting the current flowing through the three-phase brushless motor; A calculation unit for calculating an induced current component due to an induced electromotive force of the three-phase brushless motor from the calculated current value and the detected current value output from the current sensor unit; and a calculation unit for the rotor of the three-phase brushless motor from the induced current component. A detection unit for calculating an angular velocity, wherein the three-phase AC voltage control unit controls a three-phase AC voltage supplied to the three-phase brushless motor according to the angular velocity.

According to a second aspect of the present invention, there is provided the motor control device according to the first aspect, wherein the three-phase AC voltage control unit includes a voltage supplied to the three-phase brushless motor and the voltage corresponding to the voltage. The phase difference between the current flowing through the three-phase brushless motor is obtained, the angular position of the rotor of the three-phase brushless motor is obtained from the phase difference and the angular velocity, and the three-phase AC voltage is controlled according to the angular position. .

According to a third aspect of the present invention, there is provided the motor control device according to the first or second aspect, wherein the filter unit is configured to perform the operation based on the three-phase AC voltage and the internal impedance of the three-phase brushless motor. Calculate the current flowing through the three-phase brushless motor.

According to a fourth aspect of the present invention, there is provided the motor control device according to the first, second, or third aspect, wherein the filter unit includes a three-phase AC voltage output from the three-phase AC voltage control unit. The one-phase current is calculated from the one-phase voltage therein, and the current sensor unit detects the same one-phase current as the filter unit.

The present invention is configured as described above, and includes a filter unit, a current sensor unit, a calculation unit, a detection unit, and a three-phase AC voltage control unit. The filter unit and the current sensor unit are connected to at least one phase of the three-phase AC voltage, and the filter unit is configured so that, based on the internal impedance and the voltage value of the motor, there is no electromotive force induced by the rotor. Is obtained, and the value is output to the calculation unit.
The current sensor section measures the current actually flowing in the phase to which the filter section is connected, and outputs the measured current to the calculation section.

The arithmetic unit performs arithmetic processing (subtraction) on the two input signals, erases a current value according to the internal impedance of the motor, and extracts an induced current component due to rotation of the rotor.

By measuring the period of the induced current component, the angular velocity of the rotor can be determined, and the position of the rotor can be determined from the angular velocity, and the voltage is controlled so that an appropriate force is applied to the rotor. it can.

If the position of the rotor is known, the three-phase AC voltage control unit can control the voltage value and apply an optimal electromagnetic force to the rotor.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device according to the present invention will be described together with a control method according to the present invention. Referring to FIG. 1, reference numeral 3 denotes a three-phase brushless motor, which is controlled by a motor control device 2 which is an example of the present invention.

The motor control device 2 has a three-phase AC voltage control unit 21, a filter unit 22, a calculation unit 23, a detection unit 24, a driver unit 26, and a current sensor unit 28.

The three-phase AC voltage control section 21 includes a driver section 2
6, the driver unit 26 supplies a three-phase sine wave having the same waveform as the input signal to the motor 3, and a current sensor is provided between the driver unit 26 and the motor 3. The part 28 is inserted.

The current sensor section 28 is actually the driver section 2
6 is configured to measure the current supplied from the controller 6 and output the measured current to the calculator 23. Here, of the three-phase AC power supply lines (U-phase, W-phase, V-phase) from the driver unit 26, the current sensor unit 28 is inserted only into the U-phase.

The three-phase AC voltage control section 21 and the driver section 26
Are input to the calculation unit 38 via the filter unit 22. Here, it is assumed that the filter unit 22 is connected to the U phase. The filter unit 22 obtains a current flowing in the U-phase of the motor 3 based on the U-phase voltage based on the U-phase voltage.

Therefore, the arithmetic unit 23 includes the filter unit 22
The estimated value (calculated value) of the current flowing in the U-phase of the motor 3 is input from the, and the value of the current actually flowing in the U-phase from the current sensor unit 28 is input.

FIG. 2 shows a conceptual diagram of the motor 3. In general,
As shown in FIG. 2, the motor 3 has windings arranged around a rotor 33 having a magnet. The electrical equivalent circuit of the winding can be represented by a series connection circuit of inductance components 31 _{1 to} 31 ₃ and resistance components 32 _{1 to} 32 ₃ . An induced electromotive force is induced.

Thus, the inductance components 31 ₁ to 31 ₁
In a circuit in which 31 ₃ and the resistance components 32 _{1 to} 32 ₃ are connected in series, the phase of the flowing current is delayed with respect to the applied voltage.

It is assumed that a sine wave voltage is applied to the motor 3 from the three-phase AC voltage control unit 21. When the electrical angle of the U-phase sine wave voltage Vu is represented by ω × t, Vu = V × sin (ω × t) (1)

Generally, the internal temperature of the motor 3 differs between the state before operation and the state during operation. As a result, the magnitude of the inductance components 31 _{1 to} 31 ₃ and the resistance component 32
The size of _{1-32 3} is changed.

Inductance components 31 _{1 to} 31 ₃ before operation
Size of L _1, the magnitude of the resistance components _{321 to} 323 and the R _1, also code omega ₁ c, assuming that defined by _{ω 1 c = L 1 / R} 1 ... (2), When a sine wave voltage having an angular velocity ω is supplied and when no induced electromotive force is generated by the rotor 33, the phase delay φ ₁ c of the flowing current is expressed by the following equation. φ ₁ c = tan ⁻¹ (ω / ω ₁ c) (3) FIG. 3 shows the relationship between the lag phase φ ₁ c and the U-phase sine wave voltage Vu.

The magnitude L _{1 of} the inductance component and the magnitude R ₁ of the resistance component can be measured. The filter unit 22 of the motor control device 3 has a transfer function F (s) of F (s) = 1. / (SL ₁ + R ₁ ) (4)

[0031] Here, transfer the function puts the Gf the gain of F (s), when the sinusoidal voltage Vu is input to the filter unit 22, the following (5) indicating the current in consideration of the phase delay .phi.1 _c formula The signal iu is generated and output to the calculation unit 23. iu = V × Gf × sin (ω × t−φ ₁ c) (5)

The signal iu has no current induced by the rotor 33, the magnitude of the sine wave voltage Vu, the inductance components 31 _{1 to} 31 ₃ and the resistance component 32 ₁ before operation.
To 32 ₃ indicates the magnitude L _1, a current value obtained from R _1.

However, in the motor 3, the windings 3 of each phase
1 _{1-31 3,} when the rotor 33 is rotated, receiving the induced electromotive force corresponding to the magnitude of the angular velocity omega. Since an induced current is caused to flow by the electromotive force, the current Iu actually flowing in the U phase has a different phase and magnitude from the signal iu of the expression (5) output from the filter unit 22.

When the magnitude of the inductance components 31 _{1 to} 31 ₃ of the winding when the motor 3 is operating is represented by L ₂ , and the magnitude of the resistance components 32 _{1 to} 32 ₃ is represented by R ₂ , the transmission of the motor 3 The function M (s) is represented by the following equation. M (s) = 1 / (sL ₂ + R ₂ ) (11)

Inductance component 31 during operation₁~ 31_Three
Size L_Two, Resistance component 32₁~ 32 _ThreeSize R_TwoAgainst
Phase delay φ_Twoc is represented by the following equation. ω_Twoc = L_Two/ R_Two … (12) φ_Twoc = tan^-1(ω / ω_Twoc)… (13)

When Ke is an induced voltage constant and the rotor 33 is rotating at an angular velocity ω, the following equation is applied to the U phase: e = ω × Ke × sin (ω × t−φ ₂ c) (14) ) Is superimposed.

Therefore, when the gain of M (s) is set to Gm,
The current Iu flowing in the U phase is represented by the following equation. The Iu = V × Gm × sin ( ω × t-φ 2 c) -ω × Ke × sin (ω × t-φ 2 c) ... (15) calculating unit 23 is expressed by equation (5) Signal and the above (1)
The signal represented by the expression (5) is input, and J = iu-Iu (16) is obtained.

[0038] Here, ignoring the variation factors such as temperature, the size R ₁ size L ₁ and a resistance component _{321 to} 323 of the inductance components 31 ₁ to 31 ₃ of the time of stopping the motor 3, during operation of the size L _2, it is assumed and R ₂ are equal, because the _{φ 1 c = φ 2 c (} = φc) Gf = Gm (= G), the signal J by the calculation unit 23 outputs the, J = iu −Iu = V × G × sin (ω × t−φc) −V × G × sin (ω × t−φc) −ω × Ke × sin (ω × t−φc) = ω × Ke × sin (ω × t−φc) (19)

The signal J given by the above equation (19) indicates the magnitude of the induced current flowing when the rotor 33 rotates at the angular velocity ω. Further, since the signal J is a sine wave and varies in magnitude depending on the time t, the detecting unit 24 measures the signal input from the calculating unit 23 for a predetermined time to obtain the period T of the variation. , The value of ω can be obtained from the following equation. ω = 2π / T

The value of the angular velocity ω obtained by the detector 24 is output to the three-phase AC voltage controller 21. Three-phase AC voltage controller 2
1 is the input angular velocity ω and the three-phase AC voltage control unit 21
From the phase (time t) of the three-phase AC voltage output to the driver unit 26, the position (angular position) φx of the rotor 33 can be obtained by φx = φc + ω × t.

When the position φx of the rotor 33 is known, the magnitude of the three-phase AC voltage can be controlled so that an optimal electromagnetic force is applied to the rotor 33. For example, control can be performed such that the direction of the rotor 33 and the direction of the magnetic flux formed by the current flowing through the windings 31 _{1 to} 31 ₃ always have a predetermined angle (for example, as is well known, the winding 31 ₁ -31 ₃ flux direction obtained by synthesizing the magnetic flux generated is, the longitudinal direction of the rotor can be controlled to be 90 °.).

Inductance component 3 when motor 3 stops
1 _{1-31 3} between the size L _1, the size R ₁ of the resistance component _{321 to} 323, by beforehand measuring the filter unit 22
Can be set to that value.

Inductance components 31 _{1 to} 31 ₃ during operation
And the size L _2, the size R ₂ of the resistive component _{321 to} 323 is
It depends on the operating state.

FIG. 4 shows an inductance component 31 before operation.
₁~ 31_ThreeAnd the resistance component 32₁~ 32_ThreeSize L₁, R
₁Is the size L during operation_Two, R_Two1.25 times (L₁= 1.
25 × L _Two, R₁= 1.25 × R_Two) Using the motor 3
Assuming that the size before operation and that during operation are equal, the angular velocity ω
This is the example obtained. Actual angular velocity value is 19.8190r
whereas the detected angular velocity was 19.809
It is 0 rps, and the measurement can be performed with high accuracy.

As described above, the present invention does not use a differentiating circuit or a high-pass filter, and the transfer function F (s) has the characteristics of a low-pass filter. Can be measured well.

The case where the U-phase voltage and current are detected has been described above. However, the present invention is not limited to this, and a V-phase or W-phase may be used. In addition, not only one phase, but also two-phase or three-phase voltage and current are detected at the same time,
It is also possible to more accurately determine the angular position of the rotor 33.

[0047]

Since the rotor can be positioned without using a sensor such as a Hall element, a low-cost motor control device can be obtained. Since it is strong against noise, it is easy to use and has high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a motor control device of the present invention.

FIG. 2 is a conceptual diagram for explaining an internal structure of a motor.

FIG. 3 is a diagram for explaining a phase difference between a U-phase voltage and a current obtained from the voltage value;

FIG. 4 is a graph showing a measurement example.

FIG. 5 is a timing chart for explaining a square wave energization method.

[Explanation of symbols]

 2 ... Motor control device 21 ... Three-phase AC voltage control unit 22 ... Filter unit 23 ... Calculation unit 28 ... Current sensor unit ω ... Rotator angular velocity φx ... Rotator position J ... Induction current component

Claims (4)

[Claims] 1. A three-phase AC voltage controller for generating a three-phase AC voltage to be supplied to a three-phase brushless motor, and calculating a current flowing through the three-phase brushless motor from a voltage output from the three-phase AC voltage controller. A filter section, a current sensor section for detecting a current flowing through the three-phase brushless motor, and a three-phase brushless motor based on a calculated current value output from the filter section and a detected current value output from the current sensor section. A calculating unit for calculating an induced current component due to the induced electromotive force, and a detecting unit for calculating an angular velocity of a rotor of the three-phase brushless motor from the induced current component, wherein the three-phase AC voltage control unit determines the angular velocity. A motor control device for controlling a three-phase AC voltage to be supplied to the three-phase brushless motor in response. 2. The three-phase AC voltage control section determines a phase difference between a voltage supplied to the three-phase brushless motor and a current flowing through the three-phase brushless motor according to the voltage, and determines the phase difference and the angular velocity. The motor control device according to claim 1, wherein an angular position of a rotor of the three-phase brushless motor is obtained from the above, and the three-phase AC voltage is controlled according to the angular position. 3. The motor control device according to claim 1, wherein the filter section calculates a current flowing through the three-phase brushless motor based on the three-phase AC voltage and an internal impedance of the three-phase brushless motor. 4. The filter section calculates a one-phase current from a one-phase voltage among the three-phase AC voltages output from the three-phase AC voltage control section. 4. The motor control device according to claim 1, wherein the same one-phase current is detected.