JP2001268969A - Controlling method for brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress load pulsation in a brushless motor and fluctuation in load pulsation due to rotational fluctuation. SOLUTION: A basic correction voltage pattern is provided to suppress load pulsation in the brushless motor. Using this basic correction voltage pattern, the applied voltage of the brushless motor is corrected, and one revolution of the brushless motor is divided into m blocks 0,..., and m-1 in terms of mechanical angle. The load pulsation in each block is detected at block time t10,..., and t1m-1, and the block time for L revolutions is detected. The block time mean values α10,..., and am-1 for L revolutions are calculated for the respective blocks, and the mean value β of these block time mean values α0,..., and am-1 is calculated. The difference between each block time mean value α0,..., or am-1 and the mean value β is calculated, and the basic correction voltage pattern is adjusted so that each block time mean value α0,..., or am-1 approaches the mean value β to obtain a new basic correction voltage pattern.

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 brushless motor used for a motor such as an air conditioner (compressor), and more particularly, to suppressing load pulsation during one rotation and reducing vibration and noise. The present invention relates to a method for controlling a brushless motor.

[0002]

2. Description of the Related Art As a control method of a brushless motor,
Since the torque and the armature winding current are in a proportional relationship,
There is a method using a method in which a current of an armature winding is detected and this current is fed back to perform torque control. In this torque control, real-time control can be performed, but a current sensor is required to detect the current of the armature winding.

On the other hand, there is a control method in which torque control is performed for each time (section time) of a position detection interval based on a rotor position detection signal. In this case, a voltage pattern may be empirically determined in advance according to the usage state of the brushless motor, and this voltage pattern may be added to the applied voltage for each section time, so that components such as a current sensor are not required.

A control device for controlling the brushless motor includes, for example, as shown in FIG.
/ DC converter 2 converts the DC power into a predetermined DC power, and this DC power is used as the switching elements Ua, Va,
Switching is performed at Wa, X, Y, and Z, and is supplied to armature windings U, V, and W of the brushless motor (DCM) 4.

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, and W of the brushless motor 4 with a reference value. To detect a half point of the induced voltage waveform.
A position detection signal including the / 2 point is output to a control circuit (mainly composed of a microcomputer) 6.

[0006] The control circuit 6 detects the induced voltage 1 by the edge (rising edge, falling edge) of the input position detection signal.
/ 2 points (rotor position detection points) are detected, and a position detection interval is calculated based on the current position detection time and the previous position detection time.

For example, a time corresponding to a value equal to or less than 30 degrees of the electrical angle is calculated from the past position detection intervals, and the calculated time is added to the current position detection time to estimate the next energization switching time. Then, when the estimated time comes, in order to switch the energization, a predetermined drive signal is output to the inverter circuit 3 via the drive circuit 7, and the energization of the armature windings U, V, W is appropriately switched.

When the load pulsates, the speed of the brushless motor 4 fluctuates during one rotation.
As a result, mechanical vibration is generated in the brushless motor 4 and noise is generated. For example, in a compressor or the like, there is a periodic rotation fluctuation during one rotation due to a refrigerant discharge and compression cycle, and the rotation fluctuation includes a rotation error due to a position detection error and a torque ripple. When such rotation fluctuations are considered as load pulsations, the energization switching is deviated from the optimal timing due to these load pulsations, which may cause the above-described vibration and noise.

Therefore, as described above, the voltage pattern obtained in advance according to the pulsation of the load is stored in the internal memory, each section is detected by the position detection signal, and the applied voltage is determined based on the voltage pattern for each section. to correct.

The voltage pattern is, for example, the amount of increase / decrease in the ON width of the PWM on / off ratio when the brushless motor 4 is controlled by the PWM control method. Therefore, the applied voltage of the brushless motor 4 increases and decreases according to the pulsation of the load.
The pulsation of the load is canceled, and the vibration and noise of the brushless motor 4 can be suppressed.

[0011]

However, in the above-described brushless motor control method, since the voltage pattern for canceling the load pulsation is fixed to one, a change in load condition and the like and a speed fluctuation (speed change) are required. ), It is difficult to determine one optimal voltage pattern. Further, torque control for correcting the applied voltage based on the voltage pattern becomes positive feedback, causing vibration, and it is difficult to suppress vibration and noise.

That is, since the pulsation shape of the load differs due to a change in load conditions and the like and a speed fluctuation, the rotation of the brushless motor 4 fluctuates, and this rotation fluctuation adds to the load pulsation. Further, since the load pulsation is not limited to one shape, a plurality of voltage patterns may be prepared in response to the fluctuation of the load pulsation. However, the voltage pattern is enormous, and the memory capacity is enormous. Which is not very realistic.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to appropriately suppress pulsation even by a change in load pulsation and to enable stable rotation control by suppressing rotation fluctuation. It is another object of the present invention to provide a brushless motor control method capable of suppressing vibration and noise.

[0014]

In order to achieve the above object, the present invention detects a position of a rotor of a brushless motor, and based on the detected position, energizes an armature winding of the brushless motor. A brushless motor control method for controlling the rotation of the brushless motor, the brushless motor having one basic correction voltage pattern for suppressing load pulsation of the brushless motor, and applying the applied voltage of the brushless motor using the basic correction voltage pattern. On the other hand, one rotation of the brushless motor is equally divided into a plurality of sections by a mechanical angle, the load pulsation of each section is detected at the same section time, and the section time of each section is obtained for a plurality of rotations. Each time, the basic correction voltage pattern is adjusted so that the section time average value approaches the average value of the section time average value for one rotation, and the adjusted base The voltage applied to the brushless motor is corrected by the correction voltage pattern, while suppressing the load pulse, and characterized in that so as to suppress the fluctuation of the load pulse according to the rotation fluctuation of the brushless motor.

A method for controlling a brushless motor according to the present invention comprises:
In order to suppress the load pulsation of the brushless motor, one rotation of the brushless motor is equally divided into a plurality of sections by a mechanical angle, and one basic correction voltage pattern for correcting the applied voltage of the brushless motor for each section is defined as While correcting the applied voltage of the brushless motor using the basic correction voltage pattern, measuring the time of each section, calculating the section time average value for a plurality of rotations for each section, The average value is calculated by adding the section time average value and dividing it by the number of divisions, and adjusting the basic correction voltage pattern according to the difference between each section time average value and the average value. The voltage applied to the brushless motor is corrected using the correction voltage pattern to suppress the load pulsation of the brushless motor and to suppress the fluctuation of the load pulsation. It has been characterized by.

The basic correction voltage pattern is preferably stored in advance as an initial value and updated each time the adjustment is performed. Thus, in the torque control for suppressing the load pulsation, the convergence of the control is performed in a short time, and the torque control does not hunt.

The amount by which the basic correction voltage pattern is adjusted is a difference between the average value of each section time and the average value. In a section where the average value of the section time is larger than the average value, the difference is expressed by the basic correction voltage pattern. , The voltage applied to the brushless motor is increased, and in a section where the average value of the section time is smaller than the average value, the difference may be subtracted from the basic correction voltage pattern to reduce the applied voltage of the brushless motor. As a result, the basic correction voltage pattern becomes optimal according to the shape of the load pulsation that is actually occurring, and a basic correction voltage pattern that suppresses load pulsations of various shapes can be obtained.

[0018]

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. 5 are denoted by the same reference numerals, and redundant description will be omitted.

As shown in FIG. 1, in the method of controlling a brushless motor according to the present invention, times t10,..., T1m- in a section (0 to m-1) in which one rotation is divided into m (positive integers).
1 and the section time average value α0 (= (t1) for a plurality of rotations (L (positive integer) rotations) for each section.
0 + ... + t1m-1) / L),..., Α1m-1 (= tL
0 + ... + tLm-1) / L) to calculate the average value β of these section time average values α0,..., Α1m-1, and calculate the section time average values α0,. Is adjusted to increase or decrease the basic correction voltage pattern in accordance with the difference between the two, and a new basic correction voltage pattern is obtained.

For this reason, as shown in FIG. 2, the control device to which the brushless motor control method is applied is configured such that one rotation is performed for m sections (for example, in the case of a three-phase four-pole motor, 12 sections), and the time (section time) of each section is obtained by counting 12 times. This is obtained for L rotations, and the section time is added for each section.
Each of the added section times is divided by L to calculate twelve section time average values α0,..., Α11.

The twelve section time average values α0, α0,
, .Alpha.11 are added and divided by 12 to calculate the average value .beta., While the section time average values .alpha.0,.
If the difference between the average and the average β is in the positive direction, the internal memory 10a
A predetermined value is added to the basic correction voltage pattern, and if the difference is in the negative direction, the basic correction voltage pattern is reduced by a predetermined value to adjust the basic correction voltage pattern. Control circuit (microcomputer) 1 for correcting and controlling the applied voltage 4
0 is provided. Note that the control circuit 10 also has the function of the control circuit 6 shown in FIG.

The basic correction voltage pattern is a voltage pattern for canceling load pulsation as in the conventional example. The basic correction voltage pattern may be, for example, a voltage pattern that cancels pulsation at a low load in the case of a compressor.

Specifically, as shown by the curve in FIG. 3, it is assumed that load pulsation of the brushless motor 4 exists, and a basic correction voltage for correcting the applied voltage of the brushless motor 4 so as to cancel the load pulsation. A pattern is obtained (see FIG. 4). In FIGS. 3 and 4, numbers 0 to 11 indicate sections in which one rotation is equally divided into 12 sections in mechanical angles based on the position detection signal as described above.

In this case, as shown in FIG. 4, the average value of the section load pulsation is compared with the average value of the load pulsation of one rotation, and the average value of the section load pulsation is calculated from the average value of the load pulsation of one rotation. In a large section, a reference correction voltage pattern for increasing the applied voltage is obtained so that the load pulsation approaches the average value of the load pulsation of one rotation. In a section in which the average value of the section load pulsation is smaller than the average value of the load pulsation of one rotation, a reference correction voltage pattern for reducing the applied voltage is obtained so that the load pulsation approaches the average value of the load pulsation of one rotation.

In a section where the average value of the section load pulsation is the same as the average value of the load pulsation of one rotation, a reference correction voltage pattern in which the applied voltage remains unchanged is obtained. The reference correction voltage pattern obtained in this manner is shown in FIG. 4, and when the brushless motor 4 is controlled by the PWM control method as in the related art, the ON width increase / decrease amount of the PWM ON / OFF ratio is used.

Next, the operation of the control device having the above configuration will be described. First, the control circuit 10 controls the brushless motor 4 as in the prior art.
It is assumed that the number of rotations is the target number of rotations. At this time, the control circuit 10 performs the torque control for canceling the load pulsation using the basic correction voltage pattern of the internal memory 10a as in the related art.

When the brushless motor 4 rotates L, as described above, the section time average α
, Α11, the average value β of the section time average values α1,..., Α12 is calculated, and the difference between the section time average values α0,. . That is, as is apparent from FIG. 3, since the section time varies depending on the load pulsation, the load pulsation is reflected in the section time, and the section with a large load has a long time, and the section with a small load has a time. Becomes shorter.

If the difference is in the positive direction, a predetermined value is added to the basic correction voltage pattern in that section to obtain a new basic correction voltage pattern. If the difference is in the negative direction, the basic correction voltage pattern in that section is obtained. A new basic correction voltage pattern is obtained by subtracting a predetermined value from the correction voltage pattern. If the difference is zero, the basic voltage pattern in that section remains unchanged.

Thus, a new basic correction voltage pattern obtained by adjusting the basic correction voltage pattern of the internal memory 10a is obtained. The adjusted basic correction voltage pattern may be stored in the internal memory 10a, that is, the basic correction voltage pattern may be updated.

The voltage applied to the brushless motor 4 is corrected based on the adjusted reference correction voltage pattern.
Therefore, the pulsation shape of the load differs due to a change in the load condition or the like and the speed fluctuation, and the rotation of the brushless motor 4 fluctuates. Will be corrected. That is, since the torque control is appropriately performed, the load pulsation is suppressed, and the vibration and noise can be reduced.

As the predetermined value for adjusting the reference correction voltage pattern, a value corresponding to the difference between the section time average values α0,..., Α11 and the average value β is used, or the value of the difference is used as it is. You may. In addition, assuming that the reference correction voltage pattern initially stored in the internal memory 10a is used as an initial value and the initial value is updated with the reference correction voltage pattern adjusted every L rotations as described above, load pulsation can be obtained. Can be converged in a short time, so that hunting does not occur in the torque control.

[0032]

As described above, according to the present invention,
The following effects are obtained. The brushless motor control method according to the present invention has one basic correction voltage pattern for suppressing load pulsation of the brushless motor, and corrects the applied voltage of the brushless motor by using the basic correction voltage pattern. One rotation is equally divided into a plurality of sections by a mechanical angle, the load pulsation of each section is detected by the section time, and the section time average value of each section for the plurality of rotations is equal to one.
Since the basic correction voltage pattern is adjusted so as to approach the averaged value of the rotation section time average value, even if there is one basic correction voltage pattern, the adjusted basic correction voltage pattern actually occurs. The effect is that the pulsation can be controlled appropriately by the change of the load pulsation, the rotation fluctuation can be suppressed, the stable rotation control can be performed, and the vibration and noise can be suppressed. There is.

The control method of the brushless motor of the present invention is as follows.
In order to suppress the load pulsation of the brushless motor, one rotation of the brushless motor is equally divided into a plurality of sections by a mechanical angle, and each section has one basic correction voltage pattern for correcting the applied voltage of the brushless motor. While the applied voltage of the brushless motor is corrected using the basic correction voltage pattern, the time of each section is measured, and the section time average is calculated for a plurality of rotations in each section, and the section time average is calculated. Since the basic correction voltage pattern is adjusted according to the difference from the average value of the section time average value, since the section time reflects the current load pulsation,
As described above, the adjusted basic correction voltage pattern corresponds to the load pulsation that is actually occurring, and not only has the same effect as described above, but also can be realized by software by a microcomputer of the control means of the brushless motor. it can.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an embodiment of the present invention and illustrating the operation of a method for controlling a brushless motor.

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 diagram of a load pulsation curve for explaining the operation of the control device shown in FIG. 1;

FIG. 4 is a schematic diagram of a reference correction voltage pattern for explaining the operation of the control device shown in FIG. 1;

FIG. 5 is a schematic block diagram for explaining a conventional brushless motor control device.

[Explanation of symbols]

Reference Signs List 3 inverter circuit 4 brushless motor (sensorless DC brushless motor) 5 position detection circuit 6, 10 control circuit (microcomputer) 10a internal memory L rotation m division number t section time α section time average value (about L rotation) β average value (Average of the average of the section times for one rotation)

Claims (4)

[Claims] 1. A brushless motor control method comprising: detecting a position of a rotor of a brushless motor, switching energization of an armature winding of the brushless motor based on the detected position, and controlling rotation of the brushless motor. Has one basic correction voltage pattern for suppressing the load pulsation of the brushless motor, and corrects the applied voltage of the brushless motor by using the basic correction voltage pattern. It is equally divided into sections, the load pulsation of each section is detected at the same section time, the section time of each section is obtained for a plurality of rotations, and the section time average value for each section is the section time average of the same rotation. The basic correction voltage pattern is adjusted so as to approach the average value of the brushless motor. And controlling the load pulsation and suppressing the fluctuation of the load pulsation due to the rotation fluctuation of the brushless motor. 2. A brushless motor control method comprising: detecting a position of a rotor of a brushless motor, switching energization of an armature winding of the brushless motor based on the detected position, and controlling rotation of the brushless motor. One basic correction voltage pattern for equally dividing one rotation of the brushless motor into a plurality of sections by a mechanical angle and correcting an applied voltage of the brushless motor for each section in order to suppress load pulsation of the brushless motor. While correcting the applied voltage of the brushless motor using the basic correction voltage pattern, while measuring the time of each section, calculating a section time average value for a plurality of rotations for each section, The section time average value is added, the result is divided by the number of divisions to calculate an average value, and the basic value is calculated according to the difference between each section time average value and the average value. A brushless motor that adjusts a correction voltage pattern, corrects an applied voltage of the brushless motor using the adjusted reference correction voltage pattern, suppresses load pulsation of the brushless motor, and suppresses fluctuation of the load pulsation. Control method. 3. The brushless motor control method according to claim 1, wherein the basic correction voltage pattern is stored in advance as an initial value and updated each time the adjustment is performed. 4. The amount by which the basic correction voltage pattern is adjusted is a difference between the average value of each section time and the average value. In a section where the average value of the section time is larger than the average value, the difference is corrected by the basic correction voltage. The voltage applied to the brushless motor is increased by adding the voltage to the voltage pattern, and in a section in which the section average time is smaller than the average value, the difference is subtracted from the basic correction voltage pattern to reduce the applied voltage to the brushless motor. 4. The method for controlling a brushless motor according to claim 2, wherein