JPH08237988A - Control method for brushless motor - Google Patents

Abstract

PURPOSE: To enhance the operational efficiency by detecting the rotor position accurately at all times regardless of the load in the control.method for brushiess motor. CONSTITUTION: A voltage induced in the armature winding of a brushless motor 3 is compared with a reference voltage at a position detecting section 4 and a rotor position detection signal is delivered to a control circuit 10. A switching element at an inverter section 4 is then turned ON/OFF to switch the armature winding current thus subjecting the switching element at an inverter section 3 to chopping control and performing rotation control and speed control. The control circuit 10 detects the ending timing of spike voltage occurring at the time of switching the armature winding current and calculates the Lime up to time cross point of the induced voltage and the reference voltage. Finally, the current switching timing of armature winding is determined at least based on the time thus calculated and the armature winding current of the brushless motor 3 is switched.

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 for a sensorless DC brushless motor (hereinafter referred to as a brushless motor) used in a compressor of an air conditioner, and more specifically, it optimally switches a winding current of the brushless motor. The present invention relates to a brushless motor control method for improving the operating efficiency of a brushless motor.

[0002]

2. Description of the Related Art In order to control the rotation of a brushless motor of this type, for example, in the case of a three-phase motor, a controller shown in FIG. 8 is required.

In FIG. 8, this control device converts an AC power supply 1 into a DC power in a converter unit 2, and converts the converted DC power supply into switching elements (transistors) U, V ,.
The brushless motor 3 is switched by an inverter unit (inverter means) 4 in which W, X, Y, and Z are bridge-connected.
Supply to.

The terminal voltage of the brushless motor 3 (for example, 1
20 degree phase difference voltage; including induced voltage) R, S, T
Is input to the position detector 5 to detect the position of the rotor 3a. The position detection unit 5 divides the power supply voltage of the inverter unit 4 into halves to generate a reference voltage a, and a terminal voltage (induced voltage) R, S, T of each phase. It comprises comparator circuits 5b, 5c and 5d which compare with a reference voltage and output position detection signals R0, S0 and T0 synchronized with the rotation of the brushless motor 3. In addition, the resistance circuit 5e,
5f and 5g adjust the levels of the terminal voltages R, S and T.

The position detection signals R0, S0, T0 are input to the control circuit 6 to obtain a drive signal for switching the current of each armature winding of the brushless motor 3 to a predetermined value. Also,
The control circuit 6 outputs a chopping signal (PWM signal) for varying the voltage applied to each armature winding and the drive signal to the chopping unit 7.

The chopping unit 7 chops a predetermined drive signal by the drive signal and the chopping signal,
The driver unit 8 drives the transistors U, V, W, X, Y and Z of the inverter unit 4 by the drive signal (including the chopped drive signal) obtained by the chopping unit 7.

In the control device having the above-described structure, when the brushless motor 3 is started, for example, the brushless motor 3 is synchronously operated for a predetermined time, but after the predetermined time has elapsed, the brushless motor 3 is operated based on the position detection signals R0, S0, T0. To drive.

In the operation by the above position detection, the position of the rotor 3a is detected, and the current of each armature winding is switched based on this position detection (intersection point of the induced voltage and the reference voltage a). For that purpose, the position detecting section 5 is, for example, as shown in
The terminal voltage R shown in (a) is compared with the reference voltage a, and the position detection signal R0 that changes at the intersection is output (FIG. 9).
(See (b)). Although not shown, the other position detection signals S0 and T0 are similarly obtained.

The position detection signals R0, S0, T0 are input to the control circuit 6, which detects the intersection (position detection point) between the waveform of the induced voltage section of the terminal voltage and the reference voltage a. The time of one cycle (electrical angle of 360 degrees) is calculated from the position detection points. Then, based on the time of the intersection and the time of one cycle, the electrical angle 60 is calculated from the intersection.
And a drive signal for switching the conduction states of the transistors U, V, W, X, Y, and Z of the inverter unit 4 is generated after ½ of the obtained time has elapsed from the intersections.

Further, since the PWM control system is adopted, the control circuit 6 uses the transistors U, V, W of the upper arm of the inverter unit 4 and the transistor X, of the lower arm of the inverter unit 4.
A chopping signal for chopping a predetermined portion of the Y and Z drive signals at a predetermined duty ratio (ON / OFF ratio) is output to the chopping unit 7.

As described above, the armature winding current of the brushless motor 3 is switched by the chopped drive signal (see FIGS. 9C to 9H), and the brushless motor 3 is rotationally controlled. Further, the applied voltage of the brushless motor 3 is changed by changing the on / off ratio of the chopping signal (see FIG. 9 (j)), and the brushless motor 3 is controlled to a predetermined rotation speed.

[0012]

In the above brushless motor control method, the armature winding current is calculated based on the intersection (position detection point) between the induced voltage generated in the armature winding and the reference voltage a. Switch.

When the armature winding current is switched in this way, as shown in FIG. 9A, the spike voltage b is always generated when the armature winding current is switched, and the load is heavy. As the spike voltage (width) increases, the spike voltage b reaches a delicate position near the intersection of the induced voltage and the reference voltage a, and in the worst case, the spike voltage b
May cross the intersection.

When the spike voltage b is applied to the position detection point,
The position detection point is delayed by one cycle of the chopping signal (an error occurs in position detection), and in the worst case, the position detection point cannot be obtained up to the next intersection of the induced voltage and the reference voltage a (a large error in position detection). Occurs).

If an error occurs in the position detection, the current switching timing of the armature winding of the brushless motor 3 is deviated, and thus the voltage (terminal voltage) of the armature winding changes from the end of the spike voltage b. An error occurs between the time to the zero cross point (the intersection of the induced voltage and the reference voltage a) and the time from this zero cross point to the current zero cross point of the armature winding shown in FIG. 9 (i). It is said that if this error occurs, the operating efficiency of the brushless motor 3 is reduced.

Further, if a large error occurs in the position detection, not only the above-mentioned drawbacks but also the vibration and noise of the brushless motor 3 increase, and in the worst case, step-out stop, damage of the brushless motor 3, and damage of control parts may occur. There is.

The present invention has been made in view of the above problems, and an object thereof is to always be able to accurately detect the position of the rotor regardless of the weight of the load, and to improve the operating efficiency. It is also an object of the present invention to provide a control method for a brushless motor, which is capable of reducing the vibration and noise and preventing damage to the motor and parts.

[0018]

In order to achieve the above object, the present invention has inverter means in which switching elements are bridge-connected to drive a brushless motor, which is generated in an armature winding of the brushless motor. The position of the rotor of the brushless motor is detected by comparing the induced voltage with the reference voltage, and the switching element of the inverter means is turned on and off based on the detected position, thereby the armature winding of the brushless motor. In the method of controlling the brushless motor, the current is switched to rotate the brushless motor, and the speed is controlled by chopping the switching element of the inverter means.
The end timing of the spike voltage generated at the time of switching the armature winding current is detected, the time from the end timing of the spike voltage to the intersection of the induced voltage and the reference voltage is calculated, and based on the calculated time. The gist is that the current switching timing of the armature winding is obtained and the current of the armature winding of the brushless motor is switched at the obtained timing.

Further, according to the present invention, the end timing of the spike voltage generated when the armature winding current is switched is detected, and the intersection point (position detection point) of the induced voltage and the reference voltage is detected from the end timing of the spike voltage. Up to the position detection point, the time for one cycle is calculated between the position detection points, and the current switching timing of the armature winding is obtained based on the calculated time. The armature winding current of the braless motor is switched so that the time from the detection point to the switching of the shortest armature winding current becomes equal.

Further, according to the present invention, the brushless motor is a three-phase motor, the end timing of the spike voltage generated in the armature winding of the brushless motor is detected, and the induced voltage is detected from the end timing of the spike voltage. The time to the intersection (position detection point) with the reference voltage is calculated, the current switching timing of the three-phase armature winding of the brushless motor is obtained based on the calculated time, and the obtained timing is obtained. The current of the armature winding of the braless motor is switched.

[0021]

According to the above means, when the induced voltage is rising when the position detection signal is obtained by comparing the induced voltage generated in the armature winding of the brushless motor with the reference voltage, the armature winding current is switched. The end of the spike voltage is detected by the first falling edge of the position detection signal later. Then, the intersection (position detection point) of the induced voltage and the reference voltage is detected by the first rising edge of the position detection signal.

Based on the difference between the time tb at the position detection point and the time ta at the end of the spike voltage, the current switching timing of the next armature winding can be obtained.

For example, when using only the terminal voltage (induced voltage) of one-phase armature winding among the three-phase brushless motor armature windings, in order to switch the current of each phase armature winding, t (30) = tb + (tb-ta), t (90) = tb + T × 60/360 + (tb-ta) and t (150) = tb + T × 120/360 + (tb-ta) The current switching time is calculated.
In addition, T is the time of one cycle (electrical angle of 360 degrees).

Alternatively, when the terminal voltage (induced voltage) of the armature winding of the three-phase brushless motor is used, the time when (tb-ta) elapses from the time tb of the position detection point of each armature winding. Current switching timing.

In this way, when the current switching timing of the armature winding is obtained, since the end point of the spike voltage is taken into consideration, the spike voltage will not be applied to the intersection of the induced voltage and the reference voltage.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described in detail below with reference to FIGS. In the figure, the same parts as those in FIG. 8 are designated by the same reference numerals, and duplicate description will be omitted.

In FIG. 1, the control device to which the method for controlling a brushless motor of the present invention is applied is the first for obtaining a predetermined time by the edge of the position detection signal from the position detection section 5.
Timer 10a, a spike detector 10b that detects the end time of the spike voltage b based on its position detection signal, and the armature of the brushless motor 3 based on the predetermined time obtained by the first timer 10a and the end time of the spike voltage. An arithmetic unit 10 that calculates chopping information (PWM on / off ratio information) for setting the brushless motor 3 at a predetermined rotation speed while calculating the time for switching the winding current.
c, a second timer 10 for measuring the calculated time
d, a drive signal switching unit 10e that outputs a drive signal for driving the inverter unit 2 to the chopping circuit 7 in order to switch the armature winding current at this clocked time, and the applied voltage of the brushless motor 3 is changed by the chopping information. The control circuit 10 includes an applied voltage output unit 10f that outputs a chopping signal (PWM signal) for performing the operation to the chopping unit 7. The control circuit 10 has the same function as 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 7. First, the brushless motor 3 enters the position detection operation mode. I shall.

At this time, the position detecting section 5 compares the induced voltage of the terminal voltage R (see FIG. 2A) with the reference voltage a from the reference voltage generating circuit 5a in the comparison circuit 5b. The position detection signal R0 is output (shown in FIG. 2 (d)).

Then, the spike detector 1 of the control circuit 10
0b detects the end point of the spike voltage b generated by the current switching of the armature winding (step ST1).
In this case, when the induced voltage rises, the calculation unit 10c
Is the time ta (FIG. 2) at the end of the spike voltage b based on the time of the first timer 10a (for example, the first falling edge of the position detection signal R0 after the spike voltage b).
(See (a)) is calculated and stored in the internal memory.

When the induced voltage generated after the switching of the armature winding current falls, for example, the time ta of the first rising edge of the position detection signal R0 after the spike voltage b is calculated and stored.

Subsequently, the arithmetic unit 10c operates the first timer 10
The time tb at the position detection point of the rotor 3a (the intersection of the induced voltage and the reference voltage a) is detected based on the time of a (FIG. 2).
(Shown in (a)). For example, the time tb of the first rising edge of the position detection signal R0 after the end of the spike voltage b is calculated and stored in the internal memory (step ST2).
When the induced voltage generated after the switching of the armature winding current is falling, for example, the time t of the first rising edge of the position detection signal R0 after the end of the spike voltage b.
Calculate b.

The arithmetic unit 10c has a first timer 10a.
The time between the position detection points (time of one cycle of the rotor 3a) T is calculated based on the time of (step ST3). In this case, the rising edge times Tb and Td of the position detection signal R0 after the end of the spike voltage are obtained by the first timer 10a, and one cycle time T (= Tb-Td is obtained by the time Td two times before this time and the time Tb this time. ) Is calculated.

Subsequently, the timing t for switching the next armature winding current based on the times ta and tb.
Calculate (30). In this case, t (30) = tb +
From the time t (30), so-called time tb, the time corresponding to the electrical angle of 30 degrees is calculated by the equation (tb-ta).

Then, the time t (30) is calculated by the arithmetic unit 10.
It is set in the compare register A of the second timer 10d (hereinafter referred to as a free-running timer) preset in c (step ST4). After that, the position detection signal R
It is determined whether or not the edge detection of 0 is a rising edge (step ST5), the flag is set when operating at the rising edge of the position detection signal R0 (step ST6), and operation is performed at the falling edge of the position detection signal R0. Flag is cleared while (step ST
7).

After setting or clearing this flag, the interrupt processing shown in FIG. 4 is executed. In this case, when the value of the compare register A and the value of the free running timer match, the t (30) interrupt routine shown in FIG. 4 is executed.

When the above flag is set,
From step ST20 to ST21, the inverter unit 4
The signal for driving the transistor W is turned off, and the signal for turning on the signal driving the transistor U is output to the drive signal switching unit 10e. At the same time, the inverter unit 4
In order to chop the signals for driving the transistors X, Y, Z forming the lower arm, chopping information and a control signal for switching from the upper arm to the lower arm chopping are output to the applied voltage output unit 10f.

Then, the drive signal switching unit 10e outputs a predetermined drive signal to the chopping unit 7, and the applied voltage output unit 10
f outputs a predetermined chopping signal to the chopping unit 7 (step ST22). As a result, the inverter unit 2
2 are driven according to FIGS. 2 (e) to 2 (j).

On the other hand, when the flag is cleared, the process proceeds from step ST20 to ST23, the signal for driving the transistor Z of the inverter section 4 is turned off, and the signal for driving the transistor X is turned on. At the same time, the lower arm is switched to the upper arm chopping so as to chop the signals for driving the transistors U, V, W forming the upper arm of the inverter unit 4 (step ST24).

When the interrupt process is completed, the process returns to the main routine. In the main routine, since the time t (90) at which the armature winding current is switched after the above t (30), that is, the time corresponding to the electrical angle 90 degrees is calculated from the time tb, t (90) = tb + T × 90. / 360 + (tb
-Ta) is used (step ST9). The time t (90) thus calculated is set in the compare register B (step ST10).

After that, when the value of the compare register B and the value of the free running timer match, the (90) interrupt routine is executed. When the flag is set, the process proceeds from step ST30 to ST31 to turn off the signal for driving the transistor Y of the inverter unit 4 (shown in FIG. 2 (i)) and turn on the signal for driving the transistor Z. (Shown in FIG. 2 (j)). At the same time, a control signal for switching from the lower arm to the upper arm chopping is applied to the applied voltage output unit 10f so that the signals for driving the transistors U, V, W forming the upper arm of the inverter unit 4 are chopped. Is output (step ST32).

On the other hand, when the flag is cleared, the process proceeds from step ST30 to ST33, the signal for driving the transistor V of the inverter section 4 is turned off, and the signal for driving the transistor W is turned on. At the same time, the upper arm is switched to the lower arm so as to chop the signals for driving the transistors X, Y and Z forming the lower arm of the inverter unit 4 (step ST34).

When the interrupt process is completed, the process returns to the main routine. In the main routine, since the time t (150) at which the armature winding current is switched after the above t (90), that is, the time corresponding to the electrical angle of 150 degrees is calculated from the so-called time Tb, t (150) = tb + T × 120 / 360
The expression + (tb-ta) is used (step ST1
1). The time t (90) thus calculated is set in the compare register C (step ST12).

After that, when the value of the compare register C and the value of the free running timer match, t shown in FIG.
(150) The interrupt routine is executed. When the above flag is set, steps ST40 to ST40
Proceeding to step 41, the signal driving the transistor U of the inverter unit 4 is turned off (shown in FIG. 2 (e)), and the signal driving the transistor V is turned on (FIG. 2 (f)).
Shown in). At the same time, a control signal for switching from the upper arm to the lower arm chopping is applied to the applied voltage output unit 10f so that the signals for driving the transistors X, Y, Z forming the lower arm of the inverter unit 4 are chopped. Is output (step ST42).

On the other hand, when the flag is cleared, the process proceeds from step ST40 to ST43, the signal for driving the transistor X of the inverter section 4 is turned off, and the signal for driving the transistor Y is turned on. At the same time, the lower arm is switched to the upper arm so as to chop the signals for driving the transistors U, V, W constituting the upper arm of the inverter unit 4 (step ST44).

When the interrupt process is completed, the process returns to the main routine. In the main routine, the edge detection time of the previous position detection signal R0 is written in the memory that stores the edge detection time td (= Td) of the position detection signal R0 two times before (step ST13).

Further, the edge time tb of the position detection signal R0 of this time is written in the memory storing the edge time tc of the position detection signal R0 of the previous time (step ST14). That is, in order to detect the edge of the next position detection signal R0, the memory for time tb is secured.

Further, the memory that stores the edge time ta of the position detection signal R0 of this time, that is, the ending point of the spike voltage b of this time is cleared (step ST15).
That is, in order to detect the end time of the next spike voltage b, the memory for time ta is secured.

When the end point of the spike voltage b (the rising edge of the input position detection signal R0) is detected,
The main routine is executed again. That is, the induced voltage is lowered, and the rising edge of the input position detection signal R0 is the end point of the spike voltage b.

Thus, for example, when the induced voltage is rising, the end time ta of the spike voltage b (the first falling edge time of the position detection signal R0) ta and the position detection signal R0.
Difference from the first rising edge time tb (tb-t
a) is calculated, and the first rising edge time tb of the current position detection signal R0 is added to this calculation result to calculate the switching timing of the armature winding current.

Similarly, at times t (90) and t (150), 60/360 (or 120/360).
To the value obtained by multiplying the period T by (tb-t
a) is added, and the first rising edge time tb of the position detection signal R0 is added to this calculation result to calculate the switching timing of the armature winding current.

Therefore, even if the weight of the load increases and the spike voltage (width) b increases, the spike voltage b does not reach a delicate position near the intersection of the induced voltage and the reference voltage a, and Also, the spike voltage b is not applied to the intersection of the induced voltage and the reference voltage a, in other words, the intersection (the position detection point) of the induced voltage and the reference voltage a can always be detected accurately.

As a result, the time from the end of the spike voltage b to the zero cross point of the voltage (terminal voltage) of the armature winding (the intersection of the induced voltage and the reference voltage a; see FIG. 2A), The error between the zero cross point and the time from the current zero cross point of the armature winding (see FIG. 2C) becomes small, and it is possible to suppress a decrease in the operating efficiency of the brushless motor 3. Further, it is possible to suppress uneven rotation of the brushless motor 3, vibration and noise, and to prevent step-out and circuit damage.

In the above embodiment, the switching timing of each armature winding current is obtained based on the one-phase position detection signal R0. However, each switching timing is obtained based on the three-phase position detection signal. The timing of switching the armature winding current may be obtained.

In this case, the number of circuits shown by the broken line in FIG. 1 increases. Briefly explaining with reference to the time chart of FIG. 7, when the induced voltage is rising, the end time ta of the spike voltage b is detected, and for example, the first falling edge of the position detection signal R0 (or S0 or T0) is detected. It is obtained at the time ta (step ST50).

Then, the time tb at the intersection (position detection point) of the induced voltage and the reference voltage a is detected, and for example, the first rising edge time tb of the position detection signal R0 (or S0 or T0) is detected (step ST51).

Subsequently, tb-ta =
Calculate tθ, add this calculated value tθ to time tb, and set it in the compare register (step ST5).
2).

Subsequently, the time when the time tθ has elapsed is set as the current switching timing of the armature winding, and the armature winding current is switched (step ST53).

As described above, since the current of the armature winding is switched in consideration of the end point of the spike voltage b,
The same effect as in the previous embodiment can be obtained.

[0060]

As described above, according to the brushless motor control method of the present invention, the brushless motor is
When the rotation is controlled by the WM control method, the end point of the spike voltage generated by the current switching of the armature winding is detected, and at least the end point of the spike voltage and the intersection of the induced voltage and the reference voltage (position detection point). Since the armature winding current switching timing is obtained based on the time in), even if the spike voltage changes due to load fluctuations, the spike voltage does not reach the position detection point. Regardless of the situation, the position of the rotor can always be detected accurately, which in turn can improve operating efficiency, reduce vibration and noise, and prevent damage to motors and parts. There is an effect.

[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 and to which a brushless motor control method is applied.

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 an operation of the brushless motor control device shown in FIG.

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

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

6 is a schematic flowchart illustrating the operation of the brushless motor control device shown in FIG. 1. FIG.

FIG. 7 is a schematic flow chart illustrating another embodiment of the present invention.

FIG. 8 is a schematic block diagram of a conventional brushless motor control device.

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

[Explanation of symbols]

1 AC power supply (commercial) 2 Converter part 3 Brushless motor (sensorless DC brushless motor) 3a Rotor 4 Inverter part (inverter means) 5 Position detection part 5a Reference voltage generation circuit 5b, 5c, 5d Comparison circuit 6, 10 Control circuit 10a 1st timer 10b Spike detection part 10c Calculation part 10d 2nd timer 10e Drive signal switching part 10f Applied voltage output part R, S, T Terminal voltage R0, S0, T0 of armature winding Position detection signal U, V , W switching element (upper arm transistor) X, Y, Z switching element (lower arm transistor)

Claims (3)

[Claims] 1. A brushless motor having an inverter means in which a switching element is bridge-connected to drive the brushless motor, and comparing an induced voltage generated in an armature winding of the brushless motor with a reference voltage to rotate the brushless motor. The position of the child is detected, and the switching element of the inverter means is turned on and off based on the detected position, thereby switching the armature winding current of the brushless motor to rotate the brushless motor and the inverter means. In a method for controlling a brushless motor that performs speed control by chopping control of the switching element of, the end timing of the spike voltage generated at the time of switching the armature winding current is detected, and the induced voltage is changed from the end timing of the spike voltage. Calculate the time to the intersection with the reference voltage and reduce A brushless motor, wherein a current switching timing of the armature winding is obtained based on the calculated time, and the current of the armature winding of the brushless motor is switched at the obtained timing. Control method. 2. A brushless motor is provided with inverter means in which switching elements are bridge-connected to drive the brushless motor, and the induced voltage generated in the armature winding of the brushless motor is compared with a reference voltage to rotate the brushless motor. The position of the child is detected, and the switching element of the inverter means is turned on and off based on the detected position, thereby switching the armature winding current of the brushless motor to rotate the brushless motor and the inverter means. In a control method of a brushless motor for performing speed control by chopping control of the switching element of, the end timing of the spike voltage generated when switching the armature winding current is detected, and the induced voltage is changed from the end timing of the spike voltage. Calculate the time to the intersection (position detection point) with the reference voltage At the same time, one cycle time is calculated between the position detections, and the current switching timing of the armature winding is obtained based on the calculated time. From the calculated time and the position detection point, A brushless motor control method characterized in that the armature winding current of the braless motor is switched so that the time until switching of the shortest armature winding current becomes equal. 3. A brushless motor having inverter means in which switching elements are bridge-connected to drive a three-phase brushless motor, and the induced voltage generated in an armature winding of the brushless motor is compared with a reference voltage. Detecting the position of the rotor of the motor, by turning on and off the switching element of the inverter means based on the detected position, while switching the armature winding current of the brushless motor to rotate the brushless motor, In a method of controlling a brushless motor that performs speed control by chopping control a switching element of the inverter means, detecting an end timing of a spike voltage generated in an armature winding of the brushless motor, and detecting the end timing of the spike voltage from the end timing of the spike voltage. Up to the intersection of the induced voltage and the reference voltage (position detection point) And the current switching timing of the three-phase armature winding of the brushless motor is obtained based on the calculated time, and the current of the armature winding of the braless motor is calculated at the obtained timing. A control method for a brushless motor, characterized by being switched.