JPH09312989A - Method and device for controlling brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a shift in a position detecting timing caused by a change in a rotating speed and thereby suppress the deterioration in an operation efficiency of a brushless motor and prevent a locking, etc., of the brushless motor. SOLUTION: A brushless motor 1 is controlled by a method wherein when the excitation of a plurality of stator windings of the brushless motor 1 is switched, a neutral point of the terminal voltage (induced voltage) of each of the stator winding is detected by a position detecting section 3 at a specified phase delayed timing and then the detection result is output as a position detection signal of a rotor 1a and the excitation of the stator windings is switched based on the position detection signal. In this case, the position detection signal is input into a control circuit 5 and then the control circuit 5 estimates the time to a next edge, taking a change in time interval of the detection of an edge of the position detection signal into consideration. According to the estimated time interval, a timing of switching the excitation of the stator windings of the brushless motor is determined. And, a plurality of switching elements of an inverter section 2 are turned on and off based on the determined excitation timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control technique for a DC brushless motor used for a motor of an air conditioner, and more specifically, a method for controlling a brushless motor that enables optimal operation of the brushless motor and a method thereof. It relates to the device.

[0002]

2. Description of the Related Art In controlling the rotation of a DC brushless motor (hereinafter referred to as a brushless motor), for example, in the case of a three-phase brushless motor, a control device shown in FIG. 4 is used.

This control device is provided with a plurality of switching elements (transistors) for switching a power supply Vcc obtained by converting an AC power supply into a direct current by an AC / DC converter and applying it to the stator winding of the brushless motor 1. A bridge connection of an inverter unit 2, a position detection unit 3 for detecting the position of the rotor 1a based on terminal voltages of stator windings of the brushless motor 1 (for example, voltages different in phase by 120 degrees; induced voltage), and a brushless To drive the inverter unit 2 to switch the energization of each stator winding of the motor 1 in a predetermined manner and to switch the energization of each stator winding in a predetermined manner based on the position detection signal from the position detection unit 3. And a control circuit (microcomputer) 4 for outputting the signal of.

In this control device, when the brushless motor 1 is started, the brushless motor 1 is synchronously operated for a predetermined time, but after the elapse of the predetermined time, the brushless motor 1 is detected based on the position detection signal of the rotor 1a of the brushless motor 1. Rotation control (switch to operation by so-called position detection).

In the operation based on the above position detection, the position of the rotor 1a is detected and the energization of each stator winding is switched based on this position detection. The switching timing is an induction generated in each stator winding. Generally, the phase angle is delayed by 30 degrees or 90 degrees from the neutral point of the voltage.

Therefore, the position detecting section 3 is, for example, 1
The terminal voltage of one stator winding is smoothed by the noise absorbing circuit (filter; integrating circuit) 3a, and the phase angle is delayed by 90 degrees (see FIG. 5A). Further, the signal delayed by 90 degrees in phase angle is compared with a predetermined reference voltage (neutral point voltage) in the comparison circuit 3b to obtain a position detection signal (see FIG. 5B). The reference voltage is the resistance circuit 3c and the DC power source Vcc.
Is obtained by partial pressure.

The position detection signal is input to the control circuit 4, and the control circuit 4 measures the edge interval time of the position detection signal, and the average value of the measured interval times, for example, the interval time obtained this time and the previous time. Predict the time from the edge of this position detection signal to the edge of the next position detection signal based on the average value with the obtained interval time, and switch the energization of the three-phase stator winding based on this estimated time. Timing is determined, and the ON / OFF signal is output to each switching element of the inverter unit 2 based on these timings.

The control circuit 4 is, for example, the inverter unit 2
Of the signals for driving the brushless motor 1 are chopped (chopping for PWM control), and the on / off ratio (on time, off time) of this chopping is varied to set the brushless motor 1 to a predetermined rotation speed. To do.

The position detecting section 3 may be provided with circuits for three phases, that is, three position detecting signals may be obtained by the terminal voltage of each stator winding. In this case, the control circuit 4 determines the energization switching timing of each stator winding by the same method as described above, based on the three position detection signals.

[0010]

However, in the above brushless motor control method, when the rotation speed of the brushless motor 1 changes (for example, shown by the chain double-dashed line in FIG. 3C), the stator winding is wound. Since the line energization switching timing (the timing shown by the broken line in FIG. 3C) is shifted,
There is a problem that the operation efficiency of the brushless motor 1 is inevitably lowered and the brushless motor 1 is locked in the worst case. That is, the edge timing of the predicted next position detection signal is different from the actual position of the rotor 1a.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to suppress the deviation of the energization switching timing with respect to the change of the rotation speed of the brushless motor, and to suppress the deterioration of the operating efficiency. It is an object of the present invention to provide a method of controlling a brushless motor and an apparatus therefor capable of preventing the brushless motor from being locked.

[0012]

In order to achieve the above object, the present invention relates to a terminal voltage (induced voltage) of the stator winding when switching energization of a plurality of stator windings of a brushless motor. A method for controlling a brushless motor, which detects a sex point, sets a timing delayed by a predetermined phase from the neutral point as a position detection signal of a rotor of the brushless motor, and switches energization of the stator winding based on the position detection signal. The interval time between the edge detected previously and the edge detected this time is measured and stored for each edge detection of the position detection signal, while the plurality of interval times already stored and the interval time measured this time are stored. While detecting the change in the interval time based on the time interval, when determining the predicted time from the edge of this position detection signal to the edge of the next position detection signal based on the interval time of this measurement Consideration of change of the interval time, is characterized by obtaining the energization switching timing of the stator winding by the prediction time determined in consideration of the change of the interval time.

According to this, the terminal voltage of the stator winding is passed through the filter to obtain a position detection signal with a phase angle delay of 90 degrees, and the front edge and the current edge are detected every time the edge detection of the position detection signal is detected. Interval time (time between edges) is measured and stored in the memory (or register) of the control circuit. For example, at least the interval time (T
b) and (Tc) are stored.

When the time intervals (Tb) and (Tc) measured last time and the time before last are stored, the measured time interval (Ta) is already stored in the edge detection of the position detection signal this time. The absolute value of the difference (ΔTab) from the interval time (previously measured interval time) (Tb) is calculated, and it is determined whether this absolute value is smaller than a predetermined value.

When the absolute value of the difference (ΔTab) is smaller than the predetermined value, it is determined that the interval time (Ta) measured this time is almost the same as the interval time (Tb) measured last time, that is, the rotation of the brushless motor. Assuming that the speed has not changed, the elapsed point of the interval time (Ta) measured this time is regarded as the edge timing of the next position detection signal. With this timing, the energization switching timing of the plurality of stator windings of the brushless motor can be obtained.

When the absolute value of the difference (ΔTab) is larger than the predetermined value, it is determined that the time (Ta) measured this time is different from the interval time (Tb) measured last time, that is, the rotation speed of the brushless motor changes. The difference (ΔTab) between the current measurement interval time (Ta) and the last measurement interval time (Tb), the difference between the last measurement interval time (Tb) and the pre-previous measurement interval time (Tc) ( It is determined whether or not the absolute value of the difference (ΔTab−ΔTbc) from ΔTbc) is smaller than a predetermined value.

When the absolute value of the difference (ΔTab-ΔTbc) is smaller than a predetermined value, it is assumed that the rotation speed of the brushless motor has not changed so much, and the difference ΔTab is added to the interval time (Ta) of this time measurement. The elapsed point of time is regarded as the edge of the next position detection signal.

When the absolute value of the difference (ΔTab-ΔTbc) is larger than the predetermined value, it is assumed that the rotation speed of the brushless motor is largely changed, and the interval time (Ta) of the present measurement and the interval of the previous measurement are determined. The difference (ΔTab) between the average value ((Ta + Tb) / 2) and the time (Tb),
Average value of (ΔTbc) ((ΔTab + ΔTbc) / 2)
The lapsed point of time obtained by adding is regarded as the edge of the next position detection signal.

In this way, a change in the rotation speed of the brushless motor is detected, and the predicted time of the edge timing of the next position detection signal is corrected by this change. For example, when the rotation speed changes greatly, the position detection signal of this time is changed. The prediction time from the edge to the edge of the next position detection signal (position detection timing) is shortened.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention controls a brushless motor that detects the position of the rotor of a DC brushless motor and predicts the edge (energization switching timing) of the next position detection signal for each edge detection of this position detection signal. Focusing on the fact that the change in the rotation speed of the brushless motor is reflected in the interval time between the edges of the position detection signal in the method and the device, the interval time from the previous edge to the current edge is detected for each edge detection. While measuring and storing, the change in the interval time (change in the rotation speed of the brushless motor) is detected based on the already obtained multiple interval times and the interval time of this measurement, and the interval time obtained this time is also detected. Then, when predicting the time from the edge of the position detection signal this time to the next edge, the change in the interval time is taken into consideration, and the change in the interval time is taken into consideration. Boss was so as to obtain the energization switching timings of a plurality of stator windings of the brushless motor by prediction interval time.

Therefore, the controller of the brushless motor of the present invention has, for example, the configuration shown in FIG. In addition,
In the figure, the same parts as those in FIG.

According to this, the control device detects the edge of the position detection signal from the position detection unit 3, and measures and stores the edge interval (time from the previous edge to the current edge) for each edge detection. On the other hand, the interval time of this measurement,
Detect the change in the interval time based on the interval time of the previous measurement or the interval time of the previous measurement, and use the above interval when predicting the interval time to the edge of the next position detection signal based on the interval time obtained this time. A control circuit (microcomputer) 5 is provided that obtains the energization switching timing of the plurality of stator windings of the brushless motor 1 based on the predicted interval time determined by taking into account the change in time. The control circuit 5 also has the function of the control circuit 4 shown in FIG.

Next, the operation of the controller will be described in detail with reference to the time chart of FIG. 2 and the flowchart of FIG. 3. First, for example, when the three-phase brushless motor 1 is started, the brushless motor 1 is In order to perform the synchronous operation, the control device 5 outputs a signal for turning on and off the six switching elements of the inverter unit 2 in a predetermined manner, and chops one signal for driving the switching element of the upper arm or the lower arm, for example (( Chopping for PWM control).

Then, the brushless motor 1 is gradually accelerated from a low frequency, and the synchronous operation is executed until the position detection signal can be output from the position detection section 3. Since the control during the synchronous operation is already known, detailed description thereof will be omitted.

When the brushless motor 1 is rotationally controlled for a predetermined time by the synchronous operation, the position detecting section 3 smoothes the terminal voltage of one stator winding by a noise absorbing circuit (filter; integrating circuit) 3a as in the conventional case. , And the phase angle is delayed by 90 degrees (shown in FIG. The signal delayed by 90 degrees in phase angle is compared with a predetermined reference voltage (neutral point voltage) in the comparison circuit 3b to obtain a position detection signal (shown in FIG. 7B).

The position detection signal is input to the control circuit 5. When the control circuit 5 detects an edge (for example, a rising edge) of the input position detection signal, steps ST1 to S
Proceeding to T2, the time Ta (shown in FIG. 2) from the edge (falling edge) of the previous position detection signal to this edge is measured using an internal timer, and this interval time Ta is stored in the internal memory (or Register; storage means) 5
Temporarily store in a. Further, the memory 5a stores the interval time Tb calculated previously (shown in FIG. 2) and the interval time Tc calculated two times before (shown in FIG. 2) shown in FIG. The interval time of is stored.

Subsequently, the difference ΔTab (a positive or negative value) between the interval time Ta obtained this time and the interval time Tb obtained last time.
And the difference ΔTab is temporarily stored in the internal memory (or register) 5a (step S
T3). In the previous time, the difference ΔTbc (a positive or negative value) between the interval time Tb and the interval time Tc is calculated, and this difference ΔTbc is temporarily stored in the internal memory 5a.

Subsequently, it is judged whether or not the absolute value of the difference ΔTab obtained this time is smaller than the predetermined value k1, and when the change of the interval time is small, the process proceeds from step ST4 to ST5, and from the edge of the position detection signal of this time to the next. The time Tf until the edge (falling edge) of the position detection signal of
To decide. That is, it can be predicted that the rotation speed of the brushless motor 1 has not changed and the next position timing of the rotor 1a does not change from the interval time Ta obtained this time.

Next, it is determined that the time when the determined interval time Ta has passed is the edge of the next position detection signal of the rotor 1a, and the plural stator windings of the brushless motor 1 are determined based on the determined timing. Get the power switch timing of
A signal for turning on and off each switching element of the inverter unit 2 is output at these energization switching timings (step ST6). At this time, as before,
For example, one of the signals for driving the upper arm or the lower arm of the inverter unit 2 is chopped at a predetermined ON / OFF ratio.

By the way, when the absolute value of the difference ΔTab obtained this time is larger than the predetermined value k1, that is, when the change of the interval time is large, the process proceeds from step ST4 to ST7, and the difference ΔTab obtained this time and the difference ΔTbc obtained last time are compared. Difference (ΔTab-
It is determined whether or not the absolute value of ΔTbc) is smaller than the predetermined value k2.

When the absolute value of the difference (ΔTab-ΔTbc) is smaller than the predetermined value k2, it is determined that the rotation speed of the brushless motor 1 has not changed so much, and the next position detection is performed from the edge of the current position detection signal. The time Tf to the signal edge (falling edge) is the interval time T obtained this time
The value is determined by adding the difference ΔTab to a.

Then, the above determined time (Ta + ΔT
ab) is determined to be the edge of the next position detection signal of the rotor 1a, and in the same manner as above, the energization switching timing of the plurality of stator windings of the brushless motor 1 is obtained based on the determined timing. Each switching element of the inverter unit 2 is turned on according to these energization switching timings.
Output a signal for driving off (step ST
6).

When the absolute value of the difference (ΔTab-ΔTbc) is larger than the predetermined value k2, it is determined that the rotation speed of the brushless motor 1 is largely changed, and the next position from the edge of the current position detection signal is determined. The interval time Ta obtained this time is the time Tf until the edge (falling edge) of the detection signal
And the average value of the previously obtained interval time Tb (Ta + Tb)
The average value of the difference ΔTab and the difference ΔTbc (ΔTab +
The value is determined by adding ΔTbc) / 2.

Then, the above determined time (Ta + T
b) / 2 + (ΔTab + ΔTbc) / 2 is determined to be the edge of the next position detection signal of the rotor 1a, and the plural stator windings of the brushless motor 1 are determined based on the determined timing in the same manner as above. A signal for driving each switching element of the inverter unit 2 to turn on and off is output in accordance with the energization switching timing of (step ST6).

Thus, when predicting the edge of the next position detection signal (timing corresponding to the energization switching timing) for each edge detection of the input position detection signal, the interval time from the previous edge to the current edge is measured. While remembering
A change in the interval time (corresponding to the rotation speed of the brushless motor 1) is detected based on the interval time Ta obtained this time, the interval time Tb obtained last time, and the interval time Tc obtained two times before, and this interval time (rotation speed ), The time Tf from the edge of the current position detection signal to the edge of the next position detection signal is predicted.

Specifically, for example, when the rotational speed is slightly increased as shown by the chain double-dashed line in FIG. 3 (c), the time Tf to the edge of the next position detection signal is corrected to a small value. The edge time Tf of the position detection signal becomes the same as the actual position timing of the rotor 1a (timing shown by the solid line in FIG. 7C), that is, the predicted edge timing of the next position detection signal is the actual rotor. It will be adjusted to the position timing of 1a.

As a result, it is possible to quickly switch the energization of the stator winding at the actual position timing of the rotor 1a in response to changes in the rotation speed of the brushless motor 1.
That is, the deviation of the predicted position detection timing with respect to the actual position of the rotor 1a can be suppressed to an extremely small value, and the operation efficiency of the brushless motor 1 can be prevented from decreasing, and the brushless motor can be prevented from being locked. .

[0038]

As described above, according to the present invention, the position detection timing of the rotor can be promptly obtained with respect to the change in the rotation speed of the brushless motor, that is, the energization with respect to the change in the rotation speed can be performed. It is possible to suppress the shift of the switching timing, suppress the deterioration of the operating efficiency of the brushless motor, and prevent the brushless motor from being locked, which is a useful effect.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a brushless motor control device according to an embodiment of the present invention.

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

FIG. 3 is a schematic flowchart illustrating the operation of the controller for the brushless motor shown in FIG.

FIG. 4 is a schematic block diagram of a conventional brushless motor control device.

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

[Explanation of symbols]

 1 Brushless Motor (DC Brushless Motor) 1a Rotor (of Brushless Motor 1) 2 Inverter Section 3 Position Detection Section 3a Noise Absorption Circuit (Filter; Integrating Circuit) 3b Comparison Circuit 3c Resistance Circuit 4, 5 Control Circuit (Microcomputer) 5a Storage means (memory or register)

Claims (3)

[Claims] 1. When switching the energization of a plurality of stator windings of a brushless motor, a neutral point of a terminal voltage (induced voltage) of the stator winding is detected, and a timing delayed from the neutral point by a predetermined phase. Is a position detection signal of the rotor of the brushless motor, and a method of controlling the brushless motor that switches the energization of the stator winding based on the position detection signal, the previous detection for each edge detection of the position detection signal. The interval time between the edge and the edge detected this time is measured and stored, while the change in interval time is detected based on the already stored interval times and the interval time measured this time, while the interval measured this time Taking into account the change in the interval time and the change in the interval time when determining the predicted time from the edge of the current position detection signal to the edge of the next position detection signal based on time A method for controlling a brushless motor, wherein the energization switching timing of the stator winding is obtained based on the predicted time determined by the above. 2. When switching the energization of a plurality of stator windings of a brushless motor, a neutral point of a terminal voltage (induced voltage) of the stator winding is detected, and a timing delayed from the neutral point by a predetermined phase. Is a control method of a brushless motor that switches the energization of the stator winding as a position detection signal of the rotor of the brushless motor, wherein the edge of the previous detection and the edge of the current detection are detected for each edge detection of the position detection signal. In addition to measuring and storing the interval time, at least the interval time obtained in the previous time and the time before the last time is stored, and the interval time obtained this time at the time of detecting the edge of the position detection signal and the time before the previous time and the time before the last time already obtained While detecting the change in the interval time based on the interval time, based on the interval time obtained this time, the edge of the current position detection signal from the edge of the next position detection signal is detected. The change in the interval time is taken into consideration when determining the predicted time until the start time, and the energization switching timing of the stator winding is obtained based on the predicted time determined in consideration of the change in the interval time. Brushless motor control method. 3. A DC power source is applied to a brushless motor by switching it with an inverter means, and when the energization of a plurality of stator windings of the brushless motor is switched, a terminal voltage (induced voltage) of the stator winding is applied. A controller for a brushless motor that detects the neutral point of the brushless motor and switches the energization of the stator winding by using a timing delayed by a predetermined phase from the neutral point as a position detection signal of the rotor of the brushless motor, Of the stator windings, a terminal voltage of one stator winding is passed through a filter to obtain a voltage waveform with a predetermined phase delay, and the obtained voltage waveform is compared with a predetermined reference voltage to determine the neutral point. Position detecting means for detecting and outputting as a position detecting signal of the rotor at the timing of the neutral point;
The position detection signal is input to detect the edge of the same position detection signal, the interval time between the edge of the previous detection and the edge of the current detection is measured every time the edge is detected, and the time is stored in the storage means. The interval time of the previous time is stored in the storage means, and the change of the interval time is detected based on the interval time obtained this time and the interval time of the previous time and the previous time already obtained, while the interval time obtained this time is also detected. And when the prediction time from the edge of the current position detection signal to the edge of the next position detection signal is determined, the change in the interval time is taken into consideration, and the change in the interval time is taken into consideration. A controller for a brushless motor, comprising: a control unit that outputs a signal for driving the inverter unit at an energization switching timing of the stator winding.