JPH09247983A - Brushless motor control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue position detection operation by preventing stopping and out-of-step without any interference with rotation control even in case of being unable to detect position of a rotor in a brushless motor. SOLUTION: In carrying out rotation control of a brushless motor 4, the voltage of an armature winding in the motor is compared with reference voltage by a position detection part 10 for attainment of a position detection signal D. The detection signal D is inputted into a control circuit 11 to detect the position of a rotor 4a in the motor, and based on the position detection, current- carrying of the winding voltage of the motor is switched. At this point, the control circuit 11 counts time between position detection intervals. Based on the counted time, the time corresponding to a phase angle 30 is predicted from the position detection and position detection at the predicted time is checked. In case of no position, present current-carrying switching is conducted based on a previous switching time of current-carrying. In case of no position, the control circuit 11 adds the content of position detection register by one. For presence of position detection, the circuit subtracts the content of the register by one. If the content of the register is the prescribed value or more, applied voltage of the motor is decreased to the prescribed value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control technology of a sensorless DC brushless motor (hereinafter referred to as a brushless motor) used in a compressor of an air conditioner, and more particularly, to a position detection of a brushless motor rotor. Both relate to a method of controlling a brushless motor that enables switching of energization of armature winding current and appropriate switching of energization.

[0002]

2. Description of the Related Art In controlling the rotation of a brushless motor of this type, there is a method of utilizing a voltage induced in an armature winding of a brushless motor, for example, without using a Hall element as a means for detecting the position of the rotor. is there. When the position of the rotor is detected by using this induced voltage to switch the energization of the armature winding of the brushless motor, for example, the control device shown in FIG. 6 is required.

In FIG. 6, this control device rectifies and smoothes an AC power supply (commercial 100 V) 1 by a voltage doubler rectifying and smoothing circuit 2, and switches the DC power supply Vdc that has been voltage doubled and smoothed to a plurality of times. Element (transistor) U,
The inverter circuit 3 in which V, W, X, Y and Z are bridge-connected is switched and applied to the armature winding of the three-phase brushless motor 4. The voltage doubler rectifying / smoothing circuit 2 includes a rectifier circuit, a capacitor circuit, and a smoothing capacitor which are already known.

The terminal voltage of the brushless motor 4 (for example, 1
20 degree phase difference voltage; including induced voltage) R, S, T
Is inputted to the position detecting section 5, and the position detecting section 5 delays and smooths the voltage waveforms of the terminal voltages R, S, T by 90 degrees and compares them with the neutral point potential Vn and compares them with the position detecting signal A. ，
B and C are output to the control circuit (microcomputer) 6. Therefore, the position detecting unit 5 includes a differentiating circuit 5a and an integrating circuit 5b, a resistance circuit 5c for obtaining a neutral point potential Vn by combining a 90 degree phase delayed voltage, the 90 degree phase delayed voltage and a neutral point potential. Comparison circuit 5d for comparing with Vn
And

The brushless motor 4 is started and operated synchronously,
After this synchronous operation is performed for a predetermined time, the position detection operation is performed by switching the energization of each armature winding based on the position detection signals A, B and C from the position detection unit 5. Therefore, the control circuit 6 outputs to the drive circuit 7 a drive signal for driving the switching elements (transistors) U, V, W, X, Y, Z of the inverter circuit 3 on and off and a chopping signal for chopping drive.

As shown in FIG. 6, when the above control device is used for controlling the compressor of the air conditioner, the power factor improving reactor 8 is provided between the AC power source 1 and the voltage doubler rectifying and smoothing circuit 2.
Is provided.

In the position detecting operation of the control apparatus having the above-mentioned structure, the position detecting section 5 sets the terminal voltages R, S and T of the armature windings shown in FIGS. , The voltage of this phase delay (FIGS. 7 (d) to (f))
(Shown in FIG. 7) and the neutral point potential Vn are compared, and a position detection signal (shown in FIGS. 7G to 7I) that changes at the intersection is compared.
Outputs A, B and C.

The position detection signals A, B, C are transmitted to the control circuit 6
When input to the position detection signal A, B,
Based on the timing of C, a drive signal (shown in FIGS. 7 (j) to 7 (o)) for switching the conduction state of each transistor U, V, W, X, Y, Z of the inverter circuit 3 is generated.

Each drive signal causes each transistor U, V,
Since W, X, Y, and Z are driven, the brushless motor 4
The armature winding current of the brushless motor 4
Is controlled to rotate.

The control circuit 6 outputs a chopping signal having a predetermined duty ratio (ON / OFF ratio) to the drive circuit 7 in addition to the drive signal, and the drive circuit 7 outputs the transistor U of the upper arm of the inverter circuit 3. , V, W drive signals are chopped on (shown in FIGS. 7 (j) to 7 (l)). There is also a method of chopping driving the transistors X, Y, Z of the lower arm.

As described above, the energization of each armature winding of the brushless motor 4 is switched based on the position detection signals A, B and C to control the rotation of the brushless motor 4 and the on / off ratio of chopping is changed. Then, the brushless motor 4 is controlled to a predetermined rotation speed.

[0012]

In the brushless motor control method, the position of the rotor 4a is detected using the integrating circuit 5b, and the armature winding winding is detected based on this position detection. Since the timing to switch the power supply is obtained,
The following problems occur.

First, various frequency components are mixed in the voltage waveform induced in the armature winding, and constants cannot be determined for all frequencies due to the characteristics of the integrating circuit (integrating filter) 5b. Therefore, the voltage waveform passing through the integrating circuit includes an unnecessary frequency component, and in particular, the frequency included due to the change in the rotation speed of the brushless motor 4 causes an error in the output delay of 90 degrees, resulting in the position of the rotor 4a. There is an error in detection.

Further, since the integrating circuit 5b is required, not only the cost is inevitably increased, but also the control board is large due to the increase in the number of parts and there is a drawback that a space is taken up.

Further, although the 90 ° delay obtained through the integrating circuit 5b is always constant, the 90 ° delay is not optimum depending on the rotation speed and load condition of the brushless motor 4, that is, the energization that maximizes the efficiency of the brushless motor 4. Since the switching timing varies depending on the number of revolutions and load condition,
It is not possible to switch the energization for maximum efficiency at all times.

Therefore, there is a method of controlling the brushless motor 4 by detecting the position of the rotor 4a without using the integrating circuit 5b. In the case of this control method, the voltage waveform induced in the armature winding is compared with the neutral point potential (reference voltage), and the result of this comparison is input to the control circuit (microcomputer) of the brushless motor 4, It is calculated by a computer to determine the energization switching timing.

More specifically, the terminal voltage waveform (induced voltage waveform) of the direct armature winding and the reference voltage (Vdc / 2)
The position detection signal obtained by comparing and is input to the microcomputer. This microcomputer uses the first change point of the position detection signal after switching the energization as the position detection point of the rotor 4a, and from this position detection point a phase angle of 30 degrees (electrical angle 3
The energization of the armature winding is switched when a time corresponding to (0 degree) has elapsed.

In this way, by using the integrating circuit 5b, 90
Whereas the position detection signal delayed by 90 degrees (energization switching timing at 90 degrees) is obtained, in the method which does not use the integrating circuit 5b, the switching timing is 30 degrees, which is the timing closest to the intersection of the induced voltage and the reference voltage. It becomes possible to switch the energization.

However, in the case where the integration circuit 5b is not used, the change point (detection edge) of the first position detection signal after the energization switching is normal due to the noise due to the back electromotive voltage (spike voltage k) due to the energization switching. It may not be the position detection point. For example, there are cases where the voltage width of the spike voltage k is large and is applied to the position detection point (the intersection of the induced voltage and the reference voltage), and the position detection point cannot be obtained.

As described above, when the spike voltage k is applied to the position detection point and the position detection point of the rotor 4a cannot be obtained, the rotation control of the brushless motor 4 is hindered, and the cause of stoppage and step out occurs. In addition, the position detection operation may not be continued.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to stop the rotation of the brushless motor without any trouble even if the position of the rotor of the brushless motor cannot be detected. It is an object of the present invention to provide a brushless motor control method capable of preventing step-out and continuing position detection operation.

[0022]

In order to achieve the above-mentioned object, the present invention, when controlling the rotation of a brushless motor, detects the position obtained by comparing the voltage of the armature winding of the brushless motor with a reference voltage. A brushless motor control method for detecting the position of the rotor of the brushless motor by a signal, and switching the energization of the winding voltage of the brushless motor based on the position detection. The time is counted, and at least the time after the next position detection is predicted based on the measured time, and when there is no position detection at the predicted time, the current switching is performed based on the previous power switching time. It is characterized by doing so.

Further, the brushless motor control method of the present invention measures the time of the position detection interval, predicts at least the next position detection time based on the measured time, and detects the position at the predicted time. When there is no detection, the current energization switching is performed based on the previous energization switching time, while when the position is detected, the content of the position detection register is incremented, and when there is no position detection, the content of the position detection register is detected. Decrement
When the content of the position detection register is equal to or more than a predetermined value at the predicted time, the applied voltage of the brushless motor is lowered by a predetermined value.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS. FIG.
6, the same parts as those in FIG. 6 and corresponding parts are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 1, a control device to which this brushless motor control method is applied is a terminal voltage (including induced voltage) R of an armature winding of a brushless motor 4 and a reference voltage V.
dc is compared with the position detection unit 10, and the result is output to the control circuit 11 as a position detection signal D. Control circuit 11
Detects the position of the rotor 4a from the first change point of the position detection signal after switching the energization, measures the time of this position detection interval, and based on the position detection time and the time of the position detection interval. Then, the energization switching timing is calculated, and a drive signal for driving the transistor of the inverter circuit 3 is output according to the calculated energization switching timing.

The position detecting circuit 10 compares the reference voltage generating circuit 10a for generating the reference voltage Vdc / 2 with the DC power supply Vdc of the inverter circuit 3 being 1/2, and the reference voltage and the terminal voltage R of the brushless motor 4. And a comparison circuit 10b for outputting the position detection signal D.

The control circuit 11 temporarily stores the calculated energization switching timing (energization switching time). On the other hand, when the current position cannot be detected by a predetermined time (predicted time), the control circuit 11 already stores the energization switching timing. Then, the energization of the armature winding current of the brushless motor 4 is switched. When the position is not detected at the predicted time, the content of the position detection register is incremented, and when the position is detected, the content of the position detection register is decremented by, and the content of the position detection register is a predetermined value or more. In that case, the applied voltage of the brushless motor 4 is lowered by a predetermined value. The control unit 11 has the function of the control circuit 6 shown in FIG.

Next, the operation of the control device will be described in detail with reference to the time chart of FIG. 2 and the flow charts of FIGS. 3 to 5. First, the rotation control of the brushless motor 3 enters the position detection operation mode. It is assumed that

In this case, the position detecting section 10 compares the terminal voltage R of the brushless motor 4 (see FIG. 2A) with the reference voltage Vdc / 2 from the reference voltage generating circuit 10a.
0b is compared, and a position detection signal D that changes at the intersection of the comparison results is output (see FIG. 2B).

Then, the control circuit 11 detects the position of the rotor 4a at the first change point (edge) of the position detection signal after switching the energization (after the spike voltage k), and determines the position detection interval time. And the phase angles of 30 degrees, 90 degrees, and 150 degrees are calculated. The energization switching timing (time) is calculated based on this calculated time, and energization of the armature winding current of the brushless motor 4 is switched at this calculated time.

Therefore, as shown in FIGS. 2 (c) to 2 (h), the transistors U, V, W, and
A drive signal is output to drive X, Y, and Z, and a chopping signal and a switching signal are output to chop a predetermined section of the drive signal.

At this time, the control circuit 11 measures the time T1 between position detections (one cycle) for each position detection, and
The next position detection point time is calculated based on this time T1, and a predetermined time (predicted time) T corresponding to a phase angle of 30 degrees is calculated from the next position detection point. The predetermined time T may be between the next position detection time and the time corresponding to the phase angle 30.

For example, as shown in FIG. 2, if the current position detection is point a, a predetermined time T at point c is calculated (the time corresponding to a phase angle of 30 degrees is predicted from the next position detection). . In calculating the predetermined time T, the time of the speed variation α (degree) of the brushless motor 4 may be taken into consideration.
Also, (the time of the previous 30-degree energization switching) + (180
(Time corresponding to the degree), the predetermined time T may be calculated, and the time of the speed variation α (degree) may be added to the calculated time.

At the predetermined time T, it is judged whether or not the position is detected. When the position is detected, the routine shown in FIG. 3 is executed, while the routine shown in FIG. If not, the brushless motor 4 is added by adding a predetermined time to the previous energization switching time.
While the energization of the armature winding current is switched, the routine shown in FIG. 4 is executed.

In the routine shown in FIG. 3, since the position is first detected, the internal position detection flag is set (step ST1), and the content of the internal position detection register (rotation speed without position detection) is 1 or more. Or not (step ST2).

When the content of the position detection register is 1 or more, that is, the position detection is not performed several times,
If the position is detected this time, steps ST2 to ST3
Proceed to and set the contents of the position detection register to a specified value (for example, 1)
Decrease.

When the content of the position detection register is not 1 or more, that is, when the position has been detected so far, the routine is ended.

On the other hand, when it is determined that the position is not detected, the energization switching of the phase angle 30 is immediately performed because the predetermined time T corresponds to the phase angle of 30 degrees.
The subsequent energization switching of the phase angles of 90 degrees and 150 degrees is set to be performed 180 degrees after the previous energization switching time. That is, the phase angles of 90 degrees and 150
The time corresponding to the degree is set in the internal timer. In addition,
If the predetermined time (predicted time) is not the time corresponding to the phase angle of 30 degrees, the time corresponding to the phase angle of 30 degrees may be set in the internal timer.

For example, as shown by the broken line in FIG.
When the spike voltage k is applied to the point b and the position is not detected, the energization is switched based on the previous energization switching time (previous data), that is, the brushless motor 4
Is performed like a synchronous operation. When position detection is not continuous, energization is switched based on the previous energization switching time.

As a result, even if the position cannot be detected, the rotation control can be prevented, stoppage and step-out can be prevented, and the position detection operation can be continued.

Since no position is detected at the predetermined time T, the routine shown in FIG. 4 is executed. First, the content of the position detection register is increased by a predetermined value (for example, 1) (step ST10), and it is determined whether or not the content of the position detection register becomes a predetermined value (for example, 3) or more (step ST11).

When the position detection is above the predetermined value, the content of the position detection register is returned to 3 (step ST
12) And, since there is a possibility that the position cannot be detected thereafter, chopping is turned off or turned off to reduce the voltage applied to the brushless motor 4 by a predetermined value (step ST13). If the position detection is not more than the predetermined value, the above process is not necessary and the routine is ended.

For example, as shown by the broken line in FIG. 3, when the spike voltage k is large and the position detection (broken line arrow b in the same figure) is applied, the applied voltage of the brushless motor 4 is lowered and the spike voltage k is changed to the position. It is possible to prevent detection.

Therefore, the energization can be switched again on the basis of the normal position detection, and the optimum rotation control can be performed. Naturally, the position detection operation can be optimally continued without the stop and the step-out. .

By the way, when it is determined that the position has been detected, the routine shown in FIG. 5 is executed at every predetermined time T. First, when the position detection flag is set, that is, when the position can be detected,
From step ST20 to ST21, the energization switching process with the phase angle of 30 degrees is immediately performed. That is, the predetermined time T
Corresponds to the energization switching timing of the phase angle of 30 degrees. If the predetermined time T is not the time corresponding to the phase angle 30, the time corresponding to the phase angle 30 is also set in the internal timer as described above.

Then, the time corresponding to the phase angle of 90 degrees is set in the internal timer (step ST22). For example, T90 = (previous 90-degree energization switching time) +
The time corresponding to the phase angle of 90 degrees is calculated using the formula (time corresponding to 180 degrees).

Then, the time corresponding to the phase angle of 150 degrees is set in the internal timer (step ST23). For example, T150 = (the time of the previous 150-degree energization switching)
+ (Time corresponding to 180 degrees) phase angle 15
Calculate the time corresponding to 0 degrees.

Then, the position detection flag is cleared and the routine ends. Even if the position detection flag is not set in step ST20,
The position detection flag is cleared and the routine ends.

As described above, when the position of the rotor 4a cannot be detected, the current energization switching time (phase angle 30 °, 90 ° and 1) is based on the previous energization switching time.
Since 50 degrees) is obtained, stoppage and step-out can be prevented and the position detection operation can be continued without impeding the rotation control of the brushless motor 4.

On the other hand, when the position is not detected, the routine shown in FIG. 4 is executed so that the spike voltage k does not reach the position detection point (the intersection of the induced voltage and the reference voltage Vdc). The position detection and the optimum rotation control can be performed, and naturally, the position detection operation can be optimally continued without any stop or step out.

[0051]

As described above, according to claim 1 of the brushless motor control method of the present invention, the position of the rotor is detected, and the armature winding of the brushless motor is detected based on this position detection. When switching the energization of the current, the time after the next position detection is predicted, and when there is no position detection at this predicted time, the current is energized based on the previous energization switching time. Even if the detection is not performed, it is possible to switch the energization of the brushless motor, thereby preventing the rotation control from being interrupted, preventing the stop and step-out, and continuing the position detection operation. effective.

According to a second aspect of the present invention, in addition to the first aspect, the content of the position detection register is incremented when the position is not detected, and the content of the position detection register is decremented when the position is detected. When the content of the position detection register is equal to or more than the predetermined value, the applied voltage of the brushless motor 4 is lowered by the predetermined value. Therefore, in addition to the same effect as in claim 1, regular position detection and optimum rotation control are possible. The advantage is that the position detection operation can be optimally continued.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a control device to which an embodiment of the present invention is applied, to which a control method of a brushless motor is applied.

FIG. 2 is a schematic time chart diagram for explaining the operation of the controller for the brushless motor shown in FIG.

3 is a schematic flowchart for explaining the operation of the brushless motor control device shown in FIG. 1. FIG.

FIG. 4 is a schematic flowchart for explaining the operation of the brushless motor control device shown in FIG. 1.

FIG. 5 is a schematic flowchart for explaining the operation of the brushless motor control device shown in FIG.

FIG. 6 is a schematic block diagram of a conventional control device for a brushless motor.

FIG. 7 is a schematic time chart diagram for explaining the operation of the brushless motor control device shown in FIG. 6.

[Explanation of symbols]

1 AC power supply 2 Double voltage rectifier circuit 3 Inverter circuit 4 Brushless motor (sensorless DC brushless motor) 4a Rotor (of brushless motor 4) 6,11 Control circuit (microcomputer) 10 Position detection unit 10a Reference voltage generation circuit 10b Comparison circuit D Position detection signal k Spike voltage R Armature winding terminal voltage Vdc Reference voltage

Claims (2)

[Claims] 1. When controlling the rotation of a brushless motor, the position of the rotor of the brushless motor is detected by a position detection signal obtained by comparing a voltage of an armature winding of the brushless motor with a reference voltage, A method of controlling a brushless motor that switches energization of a winding voltage of the brushless motor based on position detection, wherein the time of the position detection interval is measured, and at least the next position is determined based on the measured time. A method for controlling a brushless motor, characterized in that a time after detection is predicted, and when there is no position detection at the predicted time, current energization switching is performed based on a previous energization switching time. 2. When controlling the rotation of the brushless motor, the position of the rotor of the brushless motor is detected by a position detection signal obtained by comparing the voltage of the armature winding of the brushless motor with a reference voltage, A method of controlling a brushless motor that switches energization of a winding voltage of the brushless motor based on position detection, wherein the time of the position detection interval is measured, and at least the next position is determined based on the measured time. While predicting the detection time, when there is no position detection at the predicted time, while performing the current energization switching based on the previous energization switching time, when there is the position detection, increment the contents of the position detection register, When there is no position detection, the contents of the position detection register are decremented, and the contents of the position detection register at the predicted time. The method of the brushless motor, characterized in that as lower a predetermined value the voltage applied the brushless motor when a predetermined value or more.