JP2002034277A - Method for controlling brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance operating efficiency in a brushelss motor by, in case of a speed change during one turn, avoiding position detection failure attributed to the speed change. SOLUTION: In this method for controlling brushless motor, the intervals of the position detection of a rotor are clocked and the intervals (sectional period) of the position detection for one turn are stores (step ST1). Out of the intervals for one turn, the period of a prescribed section has a prescribed weight, the average value of the intervals is calculated based on the number of the intervals for one turn and that with the weight added, and the time (sectional period) from the position detection to the next position detection is estimated based on the average value (step ST2). Based on the estimated sectional period, a failure determining period for determining position detection failure and an energization switching period for switching the energization of an armature winding of the brushless motor are calculated (step ST3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control technology for a sensorless brushless DC motor (hereinafter referred to as a brushless motor) used for a motor such as an air conditioner (compressor). The present invention relates to a method for controlling a brushless motor that can accurately determine an abnormality in position detection when there is a change.

[0002]

2. Description of the Related Art To control a brushless motor, for example, a control device shown in FIG. 7 is required. In FIG. 7, an AC power supply 1 is converted into a predetermined DC power supply by an AC / DC conversion circuit 2, and this DC power supply is switched by switching elements Ua, Va, Wa, X, Y, and Z of an inverter circuit 3 to perform a brushless motor. 4 to the armature windings U, V, W
The rotation of the brushless motor 4 is controlled according to the PWM signal.

The position detecting circuit 5 compares an induced voltage waveform (induced voltage waveform generated in a non-energized phase) included in the terminal voltages of the armature windings U, V, W of the brushless motor 4 with a reference value. Then, a half point (so-called zero cross point) of the induced voltage waveform is detected, and a position detection signal inverted at the zero cross point is output to a control circuit (mainly composed of a microcomputer) 6.

The control circuit 6 detects the induced voltage of 1 based on the edge (rising edge or falling edge) of the input position detection signal.
/ 2 points (rotor position detection points) are detected, and a position detection interval (section time) is calculated from the current position detection time and the previous position detection time.

[0005] Then, for example, the section time of one rotation section (12 sections in the case of a three-phase quadrupole) is added and divided by 12, and based on the averaged section time, the electrical angle is 30 degrees or less. Is calculated, and the calculated time is added to the current position detection time to estimate the next energization switching time. When the estimated time comes, a predetermined drive signal is output to the inverter circuit 3 via the drive circuit 7, and the armature winding U,
V, W energization is appropriately switched.

If the above-mentioned position is not detected, not only the energization switching is not performed, but also the brushless motor 4 may cause a failure or breakage. Therefore, for example, an abnormality determination angle (time) is set in advance, and if position detection is not performed even after the abnormality determination time elapses after energization switching, abnormality of the brushless motor 4 is determined and the brushless motor 4 Stop control.

As described above, since the brushless motor 4 is de-energized and the brushless motor 4 is stopped, not only the brushless motor 4 but also the control device can be prevented from being broken or damaged.

[0008]

However, in the above-described method of controlling a brushless motor, when there is a speed fluctuation during one rotation as in a compressor motor of an air conditioner, the averaged section time (predicted section) is used. Time) is far from the actual section time (time until the next position detection) (for example, refer to positions 6 and 12 shown in FIG. 6), which has various adverse effects.

The adverse effect is that the brushless motor 4
In addition to lowering the efficiency, the position detection is not performed within the abnormality determination angle (time) where the section time is large, and an erroneous abnormality determination is made, that is, erroneous control is performed.

The present invention has been made in view of the above problems, and has as its object the purpose of the present invention even when there is a speed fluctuation during one rotation.
An object of the present invention is to provide a brushless motor control method capable of performing optimum motor control without erroneously determining an abnormality by position detection and without reducing motor efficiency.

[0011]

In order to achieve the above object, the present invention detects the position of a rotor of a brushless motor, and determines the time from the current position detection to the next position detection based on the position detection interval. (Section time) is predicted, and based on the predicted section time, energization of the armature winding of the brushless motor is switched, and a position detection abnormality is determined. At the same time as measuring the detection interval, storing a position detection interval (section time) for at least one rotation, and assigning a predetermined weight to a predetermined section time in the section time for one rotation,
The average value of the section based on the number of sections for one rotation and the number of sections weighted is calculated, and this average value is predicted as the time from the current position detection to the next position detection (section time). The present invention is characterized in that the energization of the armature winding of the brushless motor is switched based on the predicted section time, and a position detection abnormality is determined.

The present invention detects the position of the rotor of a three-phase four-pole brushless motor used for a compressor motor of an air conditioner, and determines the time (section) from the current position detection to the next position detection based on the position detection interval. Time), and based on the predicted section time, a method of controlling the brushless motor to switch the energization of the armature winding of the brushless motor and determine the position detection abnormality. The interval is counted and one rotation is required.
The position detection interval (section time) of two sections is stored, and this 12
Among the section times of the section, a predetermined weight is assigned to the section time that is at least a multiple of 6, and an average value of the section is calculated based on the section time of the 12 sections and the section time obtained by adding the weight. Predict the time (section time) from the current position detection to the next position detection, switch the energization of the armature winding of the brushless motor based on the predicted section time, and determine the position detection abnormality It is characterized by doing.

An interval between the actual position detection (section time) and the predicted section time is also assigned to the section close to the current position detection of the brushless motor by weighting or by speed fluctuation during one rotation of the brushless motor. It is advisable to assign the weights to sections that are significantly different. This makes it possible to adapt even when the speed fluctuation during one rotation differs according to the load of the motor.

Instead of assigning weights to sections that are multiples of six, the weights may be assigned to sections that are multiples of two. Thereby, finer weighting can be applied to the speed fluctuation during one rotation. Also, depending on the speed fluctuation, the predicted section time may be made closer to the actual section time.

[0015]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described in detail with reference to FIG. In FIG. 2,
The same parts as those in FIG. 7 are denoted by the same reference numerals, and redundant description will be omitted.

In FIGS. 2 and 5, the control device to which the brushless motor control method of the present invention is applied includes a section time of at least a multiple of 6 or a multiple of 2 in the section time of one rotation (12 sections). Weighting the section time of
The section time (t1,..., T12) for one rotation is added, and the added value is added to the weighted section time (for example, 8 · t2, 8 · t6, 8 · t12), and the weight is added. A predetermined number (12 + 24 = 3) taking into account the number of sections
6), a control circuit (microcomputer) 10 for calculating an average value and estimating the average value as a time (section time t) from the current position detection to the next position detection. Note that the control circuit 10 also has the function of the control circuit 6 shown in FIG.

Next, the operation of the control device having the above configuration will be described with reference to the flowcharts of FIGS. 1, 3 and 4, the schematic diagram of FIG. 5, and the graph of FIG. First, the control circuit 1
0 indicates that the rotation speed of the brushless motor 4 is set to the target rotation speed by PWM control. Further, the control circuit 10
While the position of the rotor is detected and the energization of the brushless motor 4 is switched, the subroutine of FIGS. 1, 3 and 4 is executed.

In FIG. 1, when the time from the current position detection to the next position detection is predicted every time the position is detected, the position detection interval (section time) is determined by the position detection signal from the position detection circuit 5. In addition to the calculation, the section time is stored for one rotation (for example, for 12 sections shown in FIG. 5) (step ST1).

Subsequently, of the twelve sections, the section time t2,
While t6 and t12 are weighted by a predetermined value (for example, 8), each section time t1,... t12 is added, and the weighted section times 8.t2, 8.t6,8.t1 are added to this added value.
In addition, 2 is added, and the addition result is divided by 36 to calculate a section time (predicted section time) t until the next position detection (step ST2). The reason why the section time t2 is also weighted is that it is effective when the brushless motor 4 is accelerated or decelerated, for example.

Subsequently, based on the calculated section time t, a time (angle) until the next energization switching is calculated, and an abnormality determination time (angle) for position detection is calculated (step ST3). Are stored until the next position detection. Note that the energization switching time is determined to be an ideal timing in the motor, and the abnormality determination time takes into account the section time t. That is, it is preferable to determine the time slightly longer than the section time t.

In FIG. 3, it is determined whether or not the next position detection cannot be performed even if the calculated abnormality determination time has elapsed (step ST20). If the position is detected before the abnormality determination time elapses, the abnormality determination routine ends, and the energization switching routine shown in FIG. 4 starts. However, if the next position detection is not performed before the abnormality determination time elapses, the process proceeds from step ST20 to ST21, where it is determined that an abnormality has occurred in the brushless motor 4 or the like, and the brushless motor 4 Stop control.

As shown in FIG. 6, the ratio between the actual section and the section time calculated by the above-described method (see the solid line in FIG. 6) and the section time calculated by the conventional method (see the dashed line in FIG. 6) is clear. As if, in sections 6 and 12,
The predicted section time according to the present invention is close to the actual section time.

In this case, the conventional method is a method of estimating the section time by averaging the section times t1,..., T12 of the 12 sections. The horizontal axis in FIG. 6 indicates the position of the rotor, but the number of positions is different from the section time.

Therefore, when there is a speed change during one rotation as in a compressor, the speed does not depend on the speed change.
The time until the next position detection (predicted section time) becomes closer to the actual section time.

Further, since the abnormality determination time is calculated based on the predicted section time t close to the actual section time,
The abnormality determination is accurate, the air conditioner can be continuously operated without stopping the brushless motor 4 by mistake, and a comfortable environment can be maintained.

As shown in FIG. 4, during the period from the current position detection to the next position detection, when the calculated energization switching time elapses from the current position detection, that is, the energization switching time is set to the current position detection time. When the time added to the detection time elapses, the process proceeds from step ST30 to ST31, and the energization of the brushless motor 4 is switched as in the related art.

As described above, since the energization switching time is based on the section time used for calculating the abnormality determination time, even when there is a speed fluctuation during one rotation, the speed fluctuation is obtained as in the case of the abnormality determination. Power supply is switched at an optimal timing as the brushless motor 4 of the compressor, and the brushless motor 4 can be controlled with high efficiency.

In the above-described embodiment, a case has been described in which a section of a multiple of 6 is weighted. However, a section of a multiple of 2 is weighted, or a section of a multiple of 2 and 6
A weight may be assigned to a section obtained by combining a section with a multiple of. In addition, when there is a predetermined section, that is, a section in which the predicted section time is greatly different from the actual section time in accordance with the speed fluctuation during one rotation of the brushless motor 4,
To make the predicted section time closer to the actual section time,
The predetermined section may be weighted.

Further, when the brushless motor 4 is accelerated or decelerated, weighting may be applied only to a section near the current position detection (recent section). This is because the predicted section is significantly different from the actual section time during acceleration or deceleration. Furthermore, the weight may be a value corresponding to the difference between the predicted section time and the actual section, and for example, the larger the difference, the larger the weight value may be.

[0030]

As described above, according to the present invention,
The following effects are obtained. According to the brushless motor control method of the present invention, when estimating the rotor position detection interval in order to obtain the energization switching time and the position detection abnormality determination time, a predetermined interval time of a rotation period is set to a predetermined interval time. , The average value of the section time is calculated from the number of sections for one rotation and the number of sections with the weight, and this average value is calculated as the time from the current position detection to the next position detection (section time). ), If there is a speed change during one rotation, if a predetermined section time is weighted in accordance with the speed change, the predicted section time until the next position detection becomes closer to the actual section time. In addition, since the abnormality determination based on the position detection is accurately performed, there is an effect that optimal motor control can be performed without lowering the efficiency of the motor.

The method for controlling a brushless motor according to the present invention comprises:
When the brushless motor is a three-phase / four-pole compressor motor, when estimating the rotor position detection interval in order to obtain the energization switching time and the position detection abnormality determination time, the section time for one rotation (12 sections) Among them, a predetermined weight is assigned to an interval time that is a multiple of at least 6, and an average value of the intervals is calculated based on the interval times of the 12 intervals and the interval times assigned with the weights, and this average value is used as the current position detection value. From the time until the next position detection (section time), if at least the section times of the sections 6 and 12 are weighted in accordance with the speed fluctuation during one rotation of the compressor, the prediction until the next position detection is performed. The section time becomes closer to the actual section time, and in addition to the effects described above, the operation efficiency of the air conditioner including the compressor can be improved. Also in this case,
Since it is only necessary to store the section time of 12 sections, the storage capacity can be reduced, and since it can be realized by software, there is an effect that the cost is not burdened.

[Brief description of the drawings]

FIG. 1 is a schematic flowchart illustrating a method for controlling a brushless motor according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram for explaining a control device to which the brushless motor control method of the present invention is applied.

FIG. 3 is a schematic flowchart for explaining the operation of the control device shown in FIG. 2;

FIG. 4 is a schematic flowchart for explaining the operation of the control device shown in FIG. 2;

FIG. 5 is a schematic diagram for explaining the operation of the control device shown in FIG. 2;

FIG. 6 is a schematic graph for explaining the operation of the control device shown in FIG. 2;

FIG. 7 is a schematic block diagram for explaining a conventional brushless motor control device.

[Explanation of symbols]

3 Inverter circuit 4 Brushless motor (Sensorless DC brushless motor) 5 Position detection circuit 6, 10 Control circuit (microcomputer) t1, ..., t12, t Section time

Claims (4)

[Claims] 1. A position of a rotor of a brushless motor is detected, and a time (section time) from a current position detection to a next position detection is predicted based on the position detection interval.
A brushless motor control method for switching energization of the armature winding of the brushless motor based on the predicted section time, and determining a position detection abnormality, wherein at least the time of the position detection is measured, A position detection interval (section time) for one rotation is stored, a predetermined weight is assigned to a predetermined section time in the section time for one rotation, the number of sections for one rotation and a section obtained by adding the weight. Calculates the average value of the section by the number, predicts the average value as the time (section time) from the current position detection to the next position detection, and based on the predicted section time, the armature of the brushless motor. A method for controlling a brushless motor, characterized in that energization of a winding is switched and a position detection abnormality is determined. 2. The position of a rotor of a three-phase four-pole brushless motor used for a compressor motor of an air conditioner is detected, and the time from the current position detection to the next position detection (interval time) is determined based on the position detection interval. ), And controlling the energization of the armature winding of the brushless motor based on the predicted section time and determining a position detection abnormality. And stores the position detection intervals (section times) of 12 sections corresponding to one rotation, and assigns a predetermined weight to a section time that is a multiple of at least 6 among the section times of the 12 sections. The average value of the section is calculated from the section time of the section and the section time obtained by weighting the section, and the average value is predicted as the time from the current position detection to the next position detection (section time). A method for controlling a brushless motor, characterized in that energization of an armature winding of the brushless motor is switched based on a predicted section time, and a position detection abnormality is determined. 3. An actual position detection interval (section time) and a predicted section time are also given to the section close to the current position detection of the brushless motor by weighting or by a speed change during one rotation of the brushless motor. 3. The method according to claim 1, wherein the weight is assigned to a section in which the weight of the brushless motor is significantly different from the weight of the brushless motor. 4. 4. The control method for a brushless motor according to claim 2, wherein instead of assigning the weight to an interval of a multiple of 6, the weight is assigned to an interval of a multiple of 2.