JP4050489B2 - Motor control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor control method and a control apparatus for driving and controlling a synchronous motor such as a brushless motor constituted by a rotor equipped with a permanent magnet without a position sensor.
[0002]
[Prior art]
Conventionally, in a sensorless operation in which a motor is driven and controlled without using a position sensor that detects a rotor position of a brushless motor (hereinafter referred to as a motor), intermittent energization driving with an energization pause period and an energization angle of less than 180 degrees is performed. Generally done. In this intermittent energization drive system, when the motor coil is energized, an induced voltage generated in the motor coil due to the rotation of the motor during a certain period of energization is detected from the motor coil terminal, and the energization to the motor is detected from this induced voltage. Determine timing. As such an intermittent energization drive method, a so-called 120-degree energization drive with an energization angle of 120 degrees is common.
[0003]
As another driving method, there is a so-called 180-degree energization drive including sinusoidal energization that drives a motor without providing an energization pause period. In the 180-degree conduction drive system, a resistance is connected in parallel with the two-phase motor coil neutral point and the two-phase coil, and the motor induced voltage is detected by comparing the voltage between the neutral point and the resistance neutral point. Then, drive by determining the energization timing to the motor, or drive the motor position by detecting the motor position by calculating the motor current at high speed, or the phase difference between the motor drive voltage and the motor current The energization timing is determined based on the driving.
[0004]
Generally, the 180-degree energization drive system is said to be a drive system with less torque fluctuation and rotation fluctuation because the drive waveform is smoother than the 120-degree energization drive system.
[0005]
Japanese Patent Laid-Open No. 10-341594 discloses a method for controlling the drive of the motor by switching between these two drive systems. In this case, the 180 ° energization drive is performed based on the output of the rotation pulse generating means such as an encoder, and when the output pulse from the rotation pulse generating means cannot be detected, the drive is switched to the 120 ° energization drive.
[0006]
[Problems to be solved by the invention]
However, in the motor control method for switching between the two driving methods, the fluctuation of the rotational speed at the time of switching the driving method and the reliability of the energization switching are not taken into consideration. For example, the output of the motor changes due to the switching of the driving method, and as a result, the rotational speed fluctuates, resulting in noise and vibration. In the sensorless operation, in the transient state at the time of drive switching, the rotor position detection accuracy deteriorates due to the fluctuation of the induced voltage, the energization timing becomes unstable, and in the worst case, there is a possibility that the step-out occurs.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a motor control method and control device that can stabilize the rotational speed of a motor and improve the reliability at the time of switching the drive system when using different drive systems together. And
[0008]
[Means for Solving the Problems]
The problem-solving means according to the present invention includes a 180-degree energization driving method for energizing a motor that drives a load, and an intermittent energization driving method for providing an energization pause period and an energization angle of less than 180 degrees. A control method that controls driving of a motor by selecting one of the driving methods. When switching from one driving method to the other, when switching in one driving method to suppress fluctuations in the motor speed The driving signal is corrected to be a driving signal in the other driving method.
[0009]
That is, when switching from the intermittent energization drive method to the 180-degree energization drive method, the drive signal in the intermittent energization drive method is corrected so as to increase the rotation speed of the motor. At this time, if it is switched without correction, the motor rotation speed will decrease too much, and it will take time for the rotation to stabilize, but this correction will reduce the decrease in the motor rotation speed immediately after switching. The target speed can be reached quickly and stable rotation can be achieved. Further, when switching from the 180-degree energization drive method to the intermittent energization drive method, the drive signal in the 180-degree energization drive method is corrected so as to reduce the rotational speed of the motor.
[0010]
As a specific method for correcting the drive signal, when switching from the intermittent energization drive method to the 180-degree energization drive method, the PWM duty at the time of switching in the intermittent energization drive method is corrected, and the 180-degree energization drive method is used. The modulation rate. In the correction, the PWM duty is multiplied by a predetermined value of 1 or more, and this value is used as the modulation factor of 180 ° energization. Further, when switching from the 180-degree energization drive method to the intermittent energization drive method, the 180-degree energization modulation rate at the time of switching in the 180-degree energization drive method is corrected to obtain the PWM duty in the intermittent energization drive method. The correction is performed by multiplying the modulation factor of 180-degree energization by a predetermined value of 1 or less and setting this value as the PWM duty.
[0011]
The predetermined value is not limited to a unique value and may be changeable. For example, it changes according to the energization angle of intermittent energization drive, changes according to the number of rotations of the motor at the time of switching, changes according to the DC voltage at the time of switching of the inverter circuit that drives the motor, supplied from an AC power source Change according to the AC voltage at the time of switching.
[0012]
When switching from the intermittent energization drive method to the 180-degree energization drive method, the energization phase when starting the 180-degree energization drive is determined according to the energization mode of the intermittent energization drive at the time of switching and the motor rotation speed or the load state of the motor. . By adjusting the energization phase at the time of switching, a stable transition can be made with an accurate energization phase, and the drive system can be switched reliably.
[0013]
When switching from the 180-degree energization drive method to the intermittent energization drive method, the energization phase of the 180-degree energization drive at the time of switching is determined according to the number of rotations of the motor at the time of switching or the load state of the motor. And the energization mode when starting intermittent energization drive is determined according to the energization phase of 180 degree energization drive at the time of switching. Thus, by determining the energization phase and the energization mode, the phase information is inherited at the time of switching, and a stable transition can be made, and the reliability of the switching control is improved.
[0014]
The load state of the motor is the difference between the PWM duty at the motor speed at the time of switching and the reference PWM duty at the speed, or the modulation rate at the motor speed at the time of switching and the reference modulation rate at the speed. Estimated based on the power consumption calculated from the DC current and DC voltage supplied to the inverter circuit that drives the motor, estimated based on the DC current supplied to the inverter circuit that drives the motor Estimating based on the AC current supplied from the AC power source, estimating based on the power consumption calculated from the AC current and AC voltage supplied from the AC power source, estimating based on the motor current flowing through the motor, etc. Thus, it is determined by any estimation method. Therefore, a new sensor such as a load torque detector can be eliminated, and the cost can be reduced.
[0015]
Then, after switching the driving method, switching of the driving method is prohibited for a predetermined time. As a result, frequent switching of the drive system can be prevented, so that the load on the control device can be reduced, and stress on the inverter circuit, motor, etc. can be reduced.
[0016]
It is assumed that the acceleration / deceleration of the motor is prohibited for a predetermined time after the drive system is switched. Therefore, since it is possible to secure a time until the control after switching is stabilized, acceleration / deceleration control can be resumed smoothly.
[0017]
When the rotational speed of the motor after switching decreases from the rotational speed before switching and does not reach the target rotational speed, the target rotational speed is changed to a low value. Specifically, when the rotational speed immediately after switching decreases compared to the rotational speed immediately before switching and a large deviation occurs from the target rotational speed, the target rotational speed is adjusted to the low rotational speed after switching. Since the maximum rotation speed of the intermittent energization drive method is lower than the maximum rotation speed of the 180 ° energization drive method, the motor rotation speed may decrease when switching from the 180 ° energization drive method to the intermittent energization drive method. The control may become unstable. Therefore, when there is such a risk, the deviation of the rotational speed before and after switching can be reduced by changing the target rotational speed to be low as described above, and the control can be stabilized.
[0018]
It is assumed that the PWM carrier frequency is changed when the driving method is switched. As a result, a drive signal can be output at a PWM carrier frequency suitable for the switched drive system, the motor can be stably rotated, and can be driven with high efficiency and low noise.
[0019]
In this case, when switching from the 180 degree energization drive method to the intermittent energization drive method, the PWM carrier frequency of the intermittent energization drive is set lower than the PWM carrier frequency of the 180 degree energization drive. Thereby, when the position of the rotor of the motor is detected without a sensor, reliable position detection can be performed.
[0020]
After detecting the induced voltage generated in the motor and switching the driving method, when the induced voltage cannot be detected, the energization to the motor is stopped. If the induced voltage cannot be detected, the rotor position cannot be known and appropriate drive control cannot be performed. At this time, by stopping energization of the motor, it is possible to prevent the overcurrent from flowing through the inverter circuit and to protect the circuit components.
[0021]
As a control device for executing the above control method, a 180-degree energization drive unit that energizes 180 degrees with respect to a motor that drives a load, and an intermittent energization drive with an energization pause period provided with an energization angle of less than 180 degrees. The intermittent energization drive means, the selection means for selecting one of the 180-degree energization drive system and the intermittent energization drive system according to the state of the motor or an external command, and switching from one drive system to the other drive system In order to suppress fluctuations in the rotational speed of the motor, there is provided correction means for correcting the drive signal at the time of switching in one drive system to obtain a drive signal in the other drive system.
[0022]
When switching from the intermittent energization drive method to the 180-degree energization drive method, the correction means modulates 180-degree energization in the 180-degree energization drive method by multiplying the PWM duty at the time of switching in the intermittent energization drive method by a predetermined value of 1 or more. When switching from the 180-degree energization drive method to the intermittent energization drive method, the PWM duty in the intermittent energization drive method is a value obtained by multiplying the modulation rate of 180-degree energization at the time of switching in the 180-degree energization drive method by a predetermined value of 1 or less. And
[0023]
Furthermore, after switching the drive system, means for prohibiting the switching of the drive system for a predetermined time, after switching the drive system, for prohibiting the acceleration / deceleration of the motor for a predetermined time, after the switching of the drive system, the induced voltage generated in the motor Means for stopping the energization of the motor when it cannot be detected.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a motor control apparatus according to an embodiment of the present invention. In FIG. 1, an AC voltage from a commercial power source is supplied from an AC power source 1 to a rectifier circuit 3 via a reactor 2. The reactor 2 is inserted as a power factor correction circuit for improving the power factor reduction in the smoothing circuit 4. The rectifier circuit 3 rectifies the AC voltage into a DC voltage, and the smoothing circuit 4 smoothes the ripple of the DC voltage. Here, although a full-wave rectifier circuit is used, a voltage doubler rectifier circuit may be used. Further, a so-called PAM method, which is a variable power supply method performed in recent years, may be used.
[0025]
The rectified DC voltage is supplied to the inverter circuit 5. In the inverter circuit 5, driving elements which are six semiconductor switching elements are connected in a three-phase bridge shape, and the driving voltage from the inverter circuit 5 is output to the three-phase brushless motor 6.
[0026]
A control circuit 7 drives and controls the motor 6 and generally uses a microcomputer or a DSP. 8 is an intermittent energization drive unit that controls the setting of energization timing, the setting of a drive voltage (PWM duty) reference value, etc. in order to drive the motor 6 with an energization angle of less than 180 degrees and provide an energization pause period; Is a 180-degree energization drive unit that controls the setting of energization timing, drive voltage (PWM duty) reference value, etc., in order to drive the motor 6 by 180-degree energization, and 10 is a drive system selection unit that determines the drive system, Reference numeral 11 denotes a PWM creation / each phase distribution unit that creates and outputs a PWM signal for driving each drive element of the inverter circuit 5 for each drive element, and 12 denotes a rotation speed for calculating a PWM duty or a modulation rate when the drive system is switched. It is a control PWM duty / modulation rate calculation unit.
[0027]
The drive method selection unit 10 selects a drive method according to the state of the motor 6 or an external instruction as to whether the motor 6 is intermittently energized or driven 180 degrees. The state of the motor 6 includes the rotational speed, efficiency, load state, disturbance state, and the like. For example, intermittent energization drive at low speed, 180 degree energization drive at high speed, intermittent energization drive at light load, and 180 degree energization drive at high load may be used. In addition, when a disturbance occurs that makes it difficult to continue the 180-degree energization drive, the drive may be switched to the intermittent energization drive. Furthermore, the operator can switch the driving method by an external switch. For example, when driving at night, priority is given to noise reduction, and switching is performed when 180-degree energization driving is desired.
[0028]
In order to improve efficiency, suppress torque fluctuation, vibration, and noise, it is desirable that the 180-degree energization drive has a sine wave shape that can realize a smooth change in the drive waveform. Further, the drive waveform of intermittent energization drive may be any drive waveform as long as the energization angle is less than 180 degrees and an energization stop period is provided in the drive waveform and an induced voltage generated during that period can be detected. For example, 120-degree energization driving is complete two-phase energization, and rectangular wave energization is possible. Therefore, there is an advantage that it is easy to create a drive waveform to be supplied to each phase.
[0029]
The drive waveform in each drive system is shown. FIG. 2 shows a drive waveform of 120-degree rectangular energization as an example of intermittent energization drive, and FIG. 3 shows a drive waveform of sine-wave energization as an example of 180-degree energization drive. FIGS. 2 and 3 are waveform diagrams showing the signals for driving the drive elements of the inverter circuit 5 (PWM creation / output of each phase distribution unit 11) as analog values for each coil terminal, during the actual energization period. The drive waveform is PWM chopped at several to several tens of kHz, and the duty of the PWM drive signal is changed so as to reach the target rotational speed. By changing the duty, the voltage or current applied to the motor 6 is changed, and the rotational speed and torque are controlled.
[0030]
FIG. 4 shows the procedure for controlling the rotational speed of the motor 6 at this time. When 120-degree energization drive, which is an example of intermittent energization drive, is selected, the control circuit 7 receives a command signal for rotating at the target rotation speed N1 in step 1 (abbreviated as S1 in the drawing). , The rotational speed control PWM duty is set. The control circuit 7 drives the inverter circuit 5 with the set rotation speed control PWM duty. In S3, the actual rotational speed N of the motor 6 at that time is detected. In S4, it is determined whether or not the actual rotational speed N matches the target rotational speed N1.
[0031]
If they do not match, it is compared in S5 whether the current actual rotational speed N is smaller or larger than the target rotational speed N1. If the actual rotational speed N is larger than the target rotational speed N1, the rotational speed control PWM duty is decreased in S6. Conversely, if the actual rotational speed N is smaller than the target rotational speed N1, the rotational speed control PWM duty is increased in S7. Is done. By repeating this operation, the rotational speed control PWM duty is adjusted, and rotational speed control for controlling the actual rotational speed of the motor 6 according to the target rotational speed is performed.
[0032]
FIG. 5 shows an inverter drive signal for the U-phase upper arm when 120 energization drive is selected. In the 120-degree energization drive, a PWM duty equal to the rotation speed control PWM duty is output over the entire energization section. Other sections are idle periods.
[0033]
FIG. 6 shows the procedure for controlling the rotational speed of the motor 6 when the 180-degree energization drive is selected. When a command signal for rotating at the target rotation speed N1 is given in S8, the control circuit 7 sets the rotation speed control modulation rate in step S9. The control circuit 7 drives the inverter circuit 5 with the set rotation speed control modulation rate. In S10, the actual rotational speed N of the motor 6 at that time is detected. In S11, it is determined whether or not the actual rotational speed N matches the target rotational speed N1.
[0034]
If they do not match, it is compared in S12 whether the current actual rotational speed N is smaller or larger than the target rotational speed N1. If the actual rotational speed N is greater than the target rotational speed N1, the rotational speed control modulation factor is decreased in S13. Conversely, if the actual rotational speed N is less than the target rotational speed N1, the rotational speed control modulation factor is increased in S14. Is done. By repeating this operation, the rotational speed control modulation rate is adjusted, and rotational speed control is performed to control the actual rotational speed of the motor 6 according to the target rotational speed.
[0035]
FIG. 7 shows an inverter drive signal for the U-phase upper arm when 180-degree energization drive is selected. In the 180-degree energization drive, PWM duty calculated using the rotation speed control modulation rate is output so that the motor current waveform becomes sinusoidal according to the energization phase.
[0036]
Here, when the drive method is switched from 120-degree energization drive, which is an example of intermittent energization drive, to 180-degree energization drive, the rotation speed control PWM duty in intermittent drive is directly used as the rotation speed control modulation rate of 180-degree energization drive. Can be considered. Note that the PWM duty and the modulation factor are the same dimension.
[0037]
However, in this method, an imbalance occurs between the current motor 6 state such as the rotation speed and motor torque and the inverter output, and as shown by the broken line in FIG. However, it may take some time for the actual rotational speed and the target rotational speed to coincide. Further, if the rotational speed fluctuation is large, the position detection accuracy is deteriorated, and in the worst case, there is a possibility of stepping out.
[0038]
Therefore, when switching from intermittent energization drive to 180-degree energization drive, the rotational speed control PWM duty of intermittent energization drive is not directly used as the rotation speed control modulation rate of 180-degree energization, but the rotational speed control PWM duty / modulation rate calculation The unit 12 calculates a value obtained by multiplying the PWM duty of the intermittent energization drive output from the intermittent energization drive unit 8 by a predetermined value α, and the value corrected in this way is used as a modulation factor of 180 ° energization drive. Output to the drive unit 9. The 180-degree energization drive unit 9 generates an energization voltage corresponding to the energization timing based on this modulation factor and outputs it to the PWM creation / each phase distribution unit 11. The PWM creation / each phase distribution unit 11 creates a PWM signal for each drive element, outputs the PWM signal to the inverter circuit 5, and the motor 6 is rotationally driven.
[0039]
In FIG. 8, as indicated by the solid line, the number of rotations after switching increases compared to the case where no correction is performed, fluctuations in the number of rotations are reduced, and stable switching of the driving method is possible. Note that the predetermined value α is a value set in advance by experiment or simulation so that the fluctuation of the rotational speed at the time of switching the driving method becomes small.
[0040]
Next, when switching from the 180-degree energization drive to the 120-degree energization drive that is an example of the intermittent energization drive, a method is considered in which the rotation speed control modulation rate of the 180-degree energization drive is directly used as the rotation speed control PWM duty of the intermittent energization drive. . However, even with this method, an imbalance occurs between the current motor state such as the rotational speed and the motor torque and the inverter output, and the rotational speed fluctuation occurs as shown by the broken line in FIG. It may take some time for the target rotational speed to match. Further, if the rotational speed fluctuation is large, the position detection accuracy is deteriorated, and in the worst case, there is a possibility of stepping out.
[0041]
Therefore, at the time of switching from 180 degree energization drive to intermittent energization drive, the rotation speed control modulation rate of 180 degree energization drive is not directly used as the rotation speed control PWM duty of intermittent drive, but the rotation speed control PWM duty / modulation rate calculation The unit 12 calculates a value obtained by multiplying the modulation factor of the 180-degree energization drive by the predetermined value β, and outputs the corrected value as the PWM duty of the intermittent energization drive. The motor 6 is rotationally driven by the drive signal output from the control circuit 7 based on the PWM duty.
[0042]
In FIG. 9, as indicated by the solid line, the number of rotations after switching is reduced and fluctuations in the number of rotations are reduced as compared with the case where no correction is performed, and switching of a stable driving method is possible. Note that the predetermined value β is a value set in advance by experiment or simulation so that the fluctuation in the number of revolutions at the time of switching the driving method becomes small.
[0043]
For the predetermined values α and β, α is 1 or more and β is 1 or less. Further, the predetermined values α and β may be values according to the state of the motor 6 instead of constant values. As a result, fine drive control can be performed, the rotational speed fluctuation can be further reduced, and the rotational speed can be further stabilized. That is, a value corresponding to any of the energization angle of the intermittent energization drive, the rotation speed of the motor 6 at the time of switching, the DC voltage at the time of switching supplied to the inverter circuit 5, and the AC voltage at the time of switching supplied from the AC power supply 1. And
[0044]
For example, as shown in FIG. 10, the predetermined values α and β set in advance according to the energization angle of the intermittent energization drive are stored as ROM data of the control circuit 7. When the driving method is switched, the energization angle of the intermittent energization drive is detected from the intermittent energization drive unit 8 and the predetermined values α and β corresponding to the energization angle are read.
[0045]
As shown in FIG. 11, the predetermined values α and β set in advance according to the rotation speed of the motor 6 are stored as ROM data of the control circuit 7. At the time of switching the driving method, the rotation speed of the motor 6 is detected by a known rotation speed detection means, and predetermined values α and β corresponding to the rotation speed are read out.
[0046]
Further, as shown in FIG. 12, DC voltage detecting means 13 for detecting the DC voltage of the inverter circuit 5 is provided, and the DC voltage is input to the control circuit 7. Then, as shown in FIG. 13, the predetermined values α and β corresponding to the DC voltage are stored in advance as ROM data of the control circuit 7. At the time of switching the drive system, the control circuit 7 reads predetermined values α and β corresponding to the DC voltage based on the DC voltage input from the DC voltage detection means 13.
[0047]
Further, as shown in FIG. 14, AC voltage detection means 14 for detecting an AC voltage applied to the rectifier circuit 3 in the previous stage of the inverter circuit 5 is provided, and the AC voltage is input to the control circuit 7. Then, as shown in FIG. 15, the predetermined values α and β corresponding to the AC voltage are stored in advance as ROM data of the control circuit 7. At the time of switching the driving method, the control circuit 7 reads predetermined values α and β corresponding to the AC voltage based on the AC voltage input from the AC voltage detection means 14.
[0048]
In the above embodiment, a control method for further improving the stability of rotation and the reliability of control will be described below. The intermittent energization drive is a method in which the energization mode is sequentially switched to 0, 1,..., 5, 0. FIG. 16 shows an example of the energization mode in the 120-degree energization drive.
[0049]
Then, when switching from intermittent energization drive to 180-degree energization drive, the current energization phase is calculated from the energization mode at the time of switching, and 180-degree energization drive is performed. For example, at the switching timing from the energization mode 1 to the energization mode 2 in the 120-degree energization drive, when switching from the energization mode 1 of the 120-degree energization drive to the sine wave waveform of the 180-degree energization drive, the phase angle is 120 degrees. The sine wave data is set using this phase angle of 120 degrees. However, instead of using this value as it is, the rotational speed variation can be made smaller by adjusting the phase angle according to the rotational speed. For example, 5 degrees is added to 125 degrees in the low speed range, and 5 degrees is subtracted to 115 degrees in the high speed range. Thus, when the energization phase at the time of drive switching is determined according to the rotation speed of the motor 6, the rotation speed of the motor 6 is stabilized and the reliability of switching the driving method is improved.
[0050]
The motor current waveform at the time of switching from the 120-degree energization drive to the 180-degree energization drive at this time is shown in FIG. At the time of switching the drive method, by determining the energization phase to start the 180 degree energization drive according to the energization mode and the rotation speed of the 120 degree energization drive at the time of switching, the phase information is inherited from the 120 degree energization drive, and the accurate energization phase It turns out that it shifts stably. Further, instead of adjusting the energization phase for starting the 180-degree energization drive according to the rotational speed, the energization phase may be adjusted according to the load state of the motor 6.
[0051]
Further, at the time of switching from the 180-degree energization drive to the 120-degree energization drive, the energization mode of the 120-degree energization drive after switching is determined according to the energization phase of the 180-degree energization drive at the time of switching. In other words, the energization phase of the 180-degree energization drive to be switched is determined according to the energization mode of the 120-degree energization drive after the drive method is switched.
[0052]
For example, if the 120-degree energization drive after switching the drive method starts from the energization mode 1, the energization phase of the 180-degree energization drive at the time of switching may be a period from 60 degrees to 120 degrees, but the low rotation speed It is determined according to the rotational speed such as 90 degrees in the range and 80 degrees in the high rotational speed area. As a result, the reliability of switching the driving method is improved.
[0053]
The motor current waveform at the time of switching from the 180 ° energization drive to the 120 ° energization drive at this time is shown in FIG. At the time of switching the drive method, the phase information is inherited from the 180-degree energization drive by determining the energization phase of the 180-degree energization drive to be switched according to the number of rotations of the motor 6, and the stable transition can be made with an accurate energization phase. I understand. Further, instead of determining the energization phase of the 180-degree energization drive that switches the driving method according to the rotational speed, it may be determined according to the load state of the motor 6.
[0054]
The magnitude of the load on the motor 6 is: (1) the amount of increase in the rotational speed control PWM duty, that is, the rotational speed control PWM duty value at a certain rotational speed and the rotational speed control PWM duty value at the same rotational speed at the reference load. (2) Increase amount of the rotational speed control modulation rate, that is, the difference between the rotational speed control modulation rate value at a certain rotational speed and the rotational speed control modulation rate value at the same rotational speed at the reference load, (3) It can be estimated from any one of DC current, (4) AC current, (5) motor current, and (6) power consumption.
[0055]
Therefore, as load state estimating means, (1) means for calculating the increase amount of the PWM duty, (2) means for calculating the increase amount of the modulation factor, (3) means for detecting the DC current supplied to the inverter circuit 5 (4) Means for detecting the AC current supplied from the AC power source 1, (5) Means for detecting the current flowing through the motor coil, (6) Detecting the DC current and DC voltage supplied to the inverter circuit 5 Any of the means for calculating the power consumption from these may be used.
[0056]
Similarly, another control method will be described. If the drive system is frequently switched, the load on the control circuit 7 becomes large, and the stress on the inverter circuit 5, the motor 6 and the like becomes excessive. Therefore, the control circuit 7 has means for prohibiting the switching of the driving system for a predetermined time after the switching of the driving system.
[0057]
Thus, once the drive system is switched, the drive system is maintained for a predetermined time, and the drive system can be switched again after the predetermined time has elapsed. Therefore, frequent switching of the drive system can be suppressed, the overload of the control circuit 7 can be prevented, the stress applied to the inverter circuit 5, the motor 6 and the like can be reduced, and the life can be extended and the reliability can be improved.
[0058]
Further, if the drive method is switched in a transient state where acceleration or deceleration is being performed toward the target rotational speed and acceleration or deceleration is continued even after the switching, control stability may deteriorate. Therefore, the control circuit 7 has means for prohibiting acceleration / deceleration of the motor 6 for a predetermined time after switching of the drive system.
[0059]
After switching the driving method, the motor 6 is driven at the rotation speed at the time of switching for a predetermined time, and is accelerated / decelerated after the predetermined time has elapsed. In this way, by waiting for the control after switching to stabilize and restarting acceleration or deceleration, the load on the control circuit 7 is reduced, and the control reliability can be improved.
[0060]
Similarly, another control method will be described. Since the intermittent energization drive has an energization prohibition period, the maximum input to the motor 6 is smaller than the 180 degree energization drive without the energization prohibition period, and the maximum rotational speed is also lower than the 180 degree energization drive. Therefore, when switching from 180-degree energization drive to intermittent energization drive at a rotation speed equal to or higher than the maximum rotation speed of intermittent energization drive, the actual rotation speed after switching decreases to the maximum rotation speed of intermittent energization drive. The discrepancy with the number of revolutions will increase. Therefore, the control circuit 7 sets the target rotation when the rotation speed of the motor 6 after the switching is lower than the rotation speed before the switching and does not reach the target rotation speed when switching from the 180-degree energization drive to the intermittent energization drive. Means to change the number low.
[0061]
When the actual rotational speed of the motor 6 immediately after switching from the 180-degree energization drive to the intermittent energization drive decreases compared to the actual rotational speed immediately before the switching, and a deviation of more than a predetermined value from the target rotational speed occurs, the target rotational speed is temporarily set. Change to the actual rotation speed after transition to intermittent energization drive. As a result, there is no difference between the target rotational speed and the actual rotational speed, fluctuations in the rotational speed are quickly settled, and control is stabilized. Note that when the decrease in the actual rotational speed of the motor 6 after switching is smaller than a predetermined value, the target rotational speed is not changed.
[0062]
In consideration of the efficiency and noise of the motor 6, the optimum PWM carrier frequency in 180-degree energization driving may be different from the optimum PWM carrier frequency in intermittent energization driving. Therefore, the control circuit 7 has means for changing the PWM carrier frequency at the time of switching the driving method. As a result, regardless of which drive method is selected, the optimum carrier frequency according to the drive method after switching is obtained, and the motor 6 can be driven with high efficiency and low noise.
[0063]
Here, the load driven by the motor 6 is a compressor such as an air conditioner or a refrigerator. Since such a motor 6 is a synchronous motor unlike an induction motor, it is necessary to accurately detect the rotor position and output a drive voltage waveform signal from the inverter circuit 5 in accordance with the position state. However, since the inside of the compressor is high temperature and high pressure, and a sensor cannot be built in, a sensorless position detection circuit that detects the rotor position by detecting the induced voltage generated in the motor coil as the magnet rotor rotates is used. ing.
[0064]
The sensorless position detection circuit is roughly divided into two methods, an analog method and a digital method. In the analog method, an analog filter circuit consisting of a capacitor and a resistor is inserted into the position detection input section that inputs the motor terminal voltage waveform, and the waveform is shaped into a sine wave and input to the comparator, compared with the virtual neutral point potential, A position detection signal is generated. Because of this filter circuit, the detected voltage waveform is 90 degrees out of phase with the actual induced voltage waveform.
[0065]
In the digital method, the induced voltage waveform of the motor 6 is input to the comparator as a pulse-shaped waveform that is PWM-switched, and compared with a reference voltage that is ½ of the DC voltage to generate a position detection signal.
[0066]
However, when the PWM waveform is turned off as in intermittent energization driving, the induced voltage waveform does not appear when the PWM waveform is turned off. Therefore, processing is performed by the microcomputer in the control circuit 7 so that the position can be detected from the induced voltage waveform only when the PWM waveform is turned on. . Based on the generated position detection signal, the timing for outputting the actual PWM waveform is determined, and advance angle (field weakening) control is performed. Advance angle control enables high-efficiency operation and expansion of high-speed ranges. In addition, since there is no filter circuit, detection accuracy is high, there is no phase delay, and advance (field weakening) control becomes easy. In addition, position detection is possible even at low speeds where the induced voltage is low, and operation is possible from a low rotational speed during startup. As a result, the starting current can be reduced, damage to the transistors of the inverter circuit 5 due to overcurrent can be prevented, and reliability can be improved.
[0067]
Although the digital method has many advantages over the analog method, the digital method has a disadvantage that position detection can be performed only when the PWM waveform is on. Also, the ON time of the PWM waveform changes if the carrier frequency changes even if the PWM duty is the same, and becomes longer as the carrier frequency is lower.
[0068]
Therefore, in order to secure the minimum on-time of the PWM waveform capable of position detection in consideration of the signal transmission delay time, the position detection processing time in the microcomputer, etc., the control circuit 7 uses the PWM carrier frequency of 180 ° energization drive. Compared to the above, there is means for setting the PWM carrier frequency of intermittent energization drive low.
[0069]
Although the PWM carrier frequency is changed according to the drive method after switching, the carrier frequency of intermittent energization drive is set low particularly when the drive method is switched from 180-degree energization drive to intermittent energization drive. Then, the ON time of the PWM waveform becomes longer, and the time for which position detection is possible becomes longer. Therefore, when a digital position detection circuit is used, reliability of position detection can be ensured.
[0070]
In the intermittent energization drive method, the energized phase is switched by detecting the induced voltage generated in the motor coil. When switching from the 180-degree energization drive to the intermittent energization drive, a certain amount of time elapses after the switching. However, when the induced voltage cannot be detected, the rotor position with respect to the energization mode of the intermittent energization drive is considered to be greatly deviated. In the worst case, there is a possibility that the motor 6 is locked, an excessive current flows through the drive element of the inverter circuit 5, and the drive element is destroyed. Therefore, the control circuit 7 has means for stopping energization of the motor 6 when the induced voltage cannot be detected even after a predetermined time has elapsed after switching the energization method.
[0071]
If the induced voltage cannot be detected, the position cannot be detected and normal drive control of the motor 6 cannot be performed. In such a case, the energization of the motor 6 is stopped, so that an excessive current does not flow through the inverter circuit 5, damage to driving elements such as transistors can be prevented, and reliability of driving control can be improved. it can.
[0072]
In addition, this invention is not limited to the said embodiment, Of course, many corrections and changes can be added to the said embodiment within the scope of the present invention. Each of the above-described control methods may be used alone or may be further improved by performing a combination of arbitrary control methods. Also, as the intermittent energization drive method, energization drive with an energization angle other than 120 degrees may be adopted to switch the drive method between the plurality of intermittent energization drive methods and the 180 degree energization drive method.
[0073]
【The invention's effect】
As is apparent from the above description, according to the present invention, when switching the driving method between the intermittent energization driving and the 180-degree energization driving, the PWM duty or the modulation factor that is a drive signal output to the inverter circuit is adjusted. As a result, fluctuations in the motor output can be kept small, and the motor rotation can be stabilized and the reliability of the switching control can be improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a motor control device according to an embodiment of the present invention.
FIG. 2 is a diagram showing a drive waveform of intermittent energization drive
FIG. 3 is a diagram showing a drive waveform of 180-degree energization drive
FIG. 4 is a flowchart showing the rotational speed control of intermittent energization drive.
FIG. 5 is a diagram showing an inverter drive signal of a U-phase upper arm for intermittent energization drive
FIG. 6 is a flowchart showing the rotational speed control of the 180-degree energization drive.
FIG. 7 is a diagram showing an inverter drive signal of a U-phase upper arm that is driven at 180 degrees.
FIG. 8 is a diagram showing how the rotational speed fluctuates when switching from intermittent drive to 180-degree drive
FIG. 9 is a diagram showing how the rotational speed fluctuates when switching from 180-degree energization drive to intermittent energization drive.
FIG. 10 is a diagram illustrating an example of PWM duty with respect to a conduction angle and predetermined values α and β for correcting a modulation rate.
FIG. 11 is a diagram showing an example of PWM duty with respect to the rotational speed and predetermined values α and β for correcting the modulation rate.
FIG. 12 is a configuration diagram of another embodiment of a motor control device.
FIG. 13 is a diagram illustrating an example of PWM duty with respect to a DC voltage and predetermined values α and β for correcting a modulation rate.
FIG. 14 is a configuration diagram of another embodiment of a motor control device.
FIG. 15 is a diagram illustrating an example of PWM duty with respect to an AC voltage and predetermined values α and β for correcting a modulation rate.
FIG. 16 is a diagram showing an energization mode of 120-degree energization drive.
FIG. 17 is a diagram showing a motor current waveform when switching from intermittent energization drive to 180-degree energization drive.
FIG. 18 is a diagram showing a light shape of a motor current at the time of switching from 180 degree energization driving to intermittent energization driving.
[Explanation of symbols]
1 AC power supply
2 reactors
3 Rectifier circuit
4 Smoothing circuit
5 Inverter circuit
6 3-phase brushless motor
7 Control circuit
8 Intermittent drive unit
9 180 degree conduction drive
10 Drive system selector
1l PWM generator / each phase distributor
12 Speed control PWM duty / modulation rate calculation unit
13 DC voltage detection means
14 AC voltage detection means

Claims (18)

  For the motor that drives the load, either a 180-degree energization drive system that performs 180-degree energization drive or an intermittent energization drive system that provides an energization stop period and an energization angle of less than 180 degrees is selected. A motor control method for driving and controlling the motor, when switching from one drive system to the other drive system while maintaining the target rotational speed, when switching from the intermittent energization drive system to the 180 degree energization drive system, When the drive signal in the intermittent energization drive method is corrected so as to increase the frequency, and when switching from the 180-degree energization drive method to the intermittent energization drive method, the drive signal in the 180-degree energization drive method is corrected so as to reduce the rotational speed of the motor. A motor control method.   For the motor that drives the load, either a 180-degree energization drive system that performs 180-degree energization drive or an intermittent energization drive system that provides an energization stop period and an energization angle of less than 180 degrees is selected. A control method for driving and controlling the motor, and when switching from the intermittent energization drive method to the 180-degree energization drive method while maintaining the target rotation number, in order to suppress fluctuations in the motor rotation number, A motor control method, wherein the PWM duty is corrected to obtain a modulation rate of 180 ° energization in the 180 ° energization drive method. 3. The motor control method according to claim 2 , wherein the correction is performed by setting a value obtained by multiplying the PWM duty by a predetermined value of 1 or more as a modulation factor of 180-degree energization.   For the motor that drives the load, either a 180-degree energization drive system that performs 180-degree energization drive or an intermittent energization drive system that provides an energization stop period and an energization angle of less than 180 degrees is selected. This is a control method for driving and controlling the motor, and when switching from the 180-degree energization drive system to the intermittent energization drive system while maintaining the target rotation speed, when switching in the 180-degree energization drive system to suppress fluctuations in the motor rotation speed. A motor control method characterized in that the PWM duty in the intermittent energization drive system is corrected by correcting the modulation factor of 180 degree energization.   5. The motor control method according to claim 4, wherein the correction is performed by setting a PWM duty as a value obtained by multiplying a modulation factor of 180-degree energization by a predetermined value of 1 or less. 6. The motor control method according to claim 3, wherein the predetermined value in the correction is changed according to the energization angle of the intermittent energization drive. 6. The motor control method according to claim 3, wherein the predetermined value in the correction is changed according to the number of rotations of the motor at the time of switching. 6. The motor control method according to claim 3, wherein the predetermined value in the correction is changed according to the DC voltage at the time of switching of the inverter circuit that drives the motor. 6. The motor control method according to claim 3, wherein the predetermined value in the correction is changed according to an AC voltage at the time of switching supplied from an AC power source. 3. The motor control method according to claim 2, wherein the energization phase when starting the 180-degree energization drive is determined according to the energization mode of the intermittent energization drive at the time of switching and the rotational speed of the motor or the load state of the motor. 5. The motor control method according to claim 4, wherein the energization phase of the 180-degree energization drive at the time of switching is determined according to the rotational speed of the motor at the time of switching or the load state of the motor. 5. The motor control method according to claim 4, wherein the energization mode for starting the intermittent energization drive is determined according to the energization phase of the 180-degree energization drive at the time of switching. After switching of the drive system, the motor control method according to any one of claims 1 to 5, characterized in that prohibiting switching of only driving method given time. After switching of the drive system, the motor control method according to any one of claims 1 to 5, characterized in that prohibiting acceleration and deceleration of the motor for a predetermined time. Rotational speed of the motor after the switching is reduced than the rotational speed of the front switching, when not reached the target speed, the motor according to claim 1, 4 or 5, wherein altering a low target rotation speed Control method. When switching drive system, the motor control method according to any one of claims 1 to 5, characterized in that changing the PWM carrier frequency. 17. The motor control method according to claim 16 , wherein the PWM carrier frequency for intermittent energization drive is set lower than the PWM carrier frequency for 180 degree energization drive. By detecting the induced voltage generated in the motor, after the switching of the drive system, when it can not detect the induced voltage, a motor control method according to claim 1, 4 or 5, wherein stopping the power supply to the motor .

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