JP2008172948A - Controller for brushless motors - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller wherein at the time of switching between intermittent energization driving and 180-degree energization driving, it is possible to stabilize the number of motor revolutions and enhance the reliability of driving scheme switching. <P>SOLUTION: The controller includes: a power supply 1 for supplying power to a brushless motor 6; a 180-degree energization drive unit 9 that controls power supply so that the brushless motor is driven by a 180-degree energization driving scheme with no energization pause period provided; an intermittent energization drive unit 8 that controls power supply so that the brushless motor 6 is driven by an intermittent energization driving scheme with an energization pause period provided; and a driving scheme selection unit 10 for selecting either of these schemes. When one driving scheme is switched to another, a number-of-revolutions control PWM duty/modulation factor computation unit 12 and an energization switching control voltage/current phase difference computation and voltage phase computation unit 15 carry out control so that the current phase corresponding to the rotor position of the brushless motor 6 in one driving scheme immediately before switching is equal to the current phase immediately after switching. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor control device that controls and drives a brushless motor constituted by a rotor with a permanent magnet mounted without a position sensor, and more particularly to a control device for a brushless motor that is used by switching a driving method.

  Conventionally, in a sensorless drive system of a motor that controls and drives a motor without using a rotor position sensor that detects the position of the motor rotor, when energizing the motor coil, an energization suspension period of a certain period is provided, An intermittent energization drive is generally performed in which an induced voltage generated in a motor coil due to the rotation of the motor is detected from a motor coil terminal and the energization timing to the motor is determined from the induced voltage. Among such intermittent energization drive controls, so-called 120-degree energization drive with an energization angle of 120 degrees is generally performed.

  As another drive method, there is a so-called 180-degree energization drive including sine wave energization that drives a brushless motor without providing an energization pause period. The 180-degree energization drive, for example, connects a resistance in parallel with the three-phase motor coil neutral point and the three-phase coil, and compares the voltage between the neutral point and the resistance neutral point to determine the motor induced voltage. Detect and drive the motor by determining the energization timing from now on, or drive the motor position by detecting the motor position by calculating the motor current at high speed, or drive the motor drive voltage and motor current There is a method of driving by determining energization timing based on the phase difference between the two.

  In general, it is said that the 180-degree energization drive is a drive system with less torque fluctuation and rotation fluctuation due to the smoothness of the drive waveform than the 120-degree energization drive.

  Further, as a conventional example of a configuration for switching between these two driving methods, there is one disclosed in Patent Document 1. 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. In addition, what is disclosed in Patent Document 2 corrects the drive signal at the time of switching in one drive system and suppresses the drive signal in the other drive system in order to suppress fluctuations in the rotational speed of the motor at the time of switching the drive system. It is characterized by doing.

  Further, in the motor control device using sine wave 180 ° energization in the driving of the synchronous motor, the motor current areas in the two phase periods based on the motor voltage are respectively detected by the motor current detection amplifier, and the two motor current areas are detected. The control microcomputer calculates the ratio of this as phase difference information, controls the motor drive voltage with this phase difference information, and applies a sine wave of a predetermined period to the motor coil, resulting in low noise, low vibration, and high efficiency A device capable of 180 ° driving including sine wave energization for power saving has been proposed (see Patent Document 3).

Japanese Patent Laid-Open No. 10-341594 JP 2003-111469 A JP 2001-112287 A

  However, in the control of the motor, fluctuations in the number of revolutions at the time of switching the driving method and reliability of switching the energizing method are not taken into consideration. The output of the brushless motor changes due to the switching of the driving method, and as a result, the rotational speed fluctuates. In the position sensorless drive, the position detection accuracy is deteriorated in a transient state at the time of drive switching, and in the worst case, there is a possibility of stepping out. In addition, it is possible to suppress the rotational speed fluctuation by correcting the drive signal at the time of switching the drive system, but since the current phase is not taken into account, depending on the driving situation before and after the switching, for example, the load situation and the voltage, the switching is possible. Torque fluctuations occur before and after, resulting in rotational speed fluctuations.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a brushless motor control device capable of stabilizing the rotational speed of the motor and improving the reliability of switching the driving method.

  The brushless motor control apparatus according to the present invention controls the power supply means so that the brushless motor is driven by a power supply means for supplying power to the brushless motor, and a 180-degree energization drive system without an energization pause period. Energization drive means, intermittent energization drive means for controlling the power supply means so that the brushless motor is driven by an intermittent energization drive system having an energization suspension period, the 180-degree energization drive system, and the intermittent energization drive A selection means for selecting one of the methods, and when switching from one drive method of the 180-degree energization drive method and the intermittent energization drive method to the other drive method, the just before the switch in the one drive method Control that the current phase with respect to the rotor position of the brushless motor is equal to the current phase immediately after switching. It is an butterfly.

  According to the present invention, it is possible to realize a motor control device that can stably switch between the intermittent energization driving method and the 180-degree energization driving method.

  When switching from 180-degree energization drive to intermittent energization drive, the current phase and voltage phase with respect to the rotor position are estimated from the load torque and voltage / current phase difference before switching, respectively, and the estimated current phase and voltage phase are calculated. Used to determine the voltage phase of intermittent energization drive after switching.

  When switching from intermittent energization drive to 180-degree energization drive, the current phase and voltage / current phase difference with respect to the rotor position are estimated from the load torque and voltage phase before switching, and the estimated current phase, voltage / current level are estimated. Using the phase difference, the voltage / current phase difference in the 180-degree energization drive is determined.

  Further, a DC current detecting means for detecting a DC current flowing in the winding of the brushless motor is provided, and a load state of the brushless motor is estimated based on the DC current.

  According to the first and second aspects of the present invention, the fluctuation of the brushless motor output is reduced when switching from the intermittent energization drive to the 180-degree energization drive, and the rotational speed is stabilized and the drive system switching is improved. Can be planned.

  Further, according to the first and third aspects of the invention, the fluctuation of the brushless motor output is reduced when switching from the 180-degree energization drive to the intermittent energization drive, and the rotation speed is stabilized and the drive system switching reliability is improved. Improvements can be made.

  Furthermore, according to the invention described in claim 4, a special load torque detector or the like can be dispensed with, and the cost can be reduced.

  Embodiments of a motor control apparatus according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an embodiment of a motor control device according to the present invention. The hardware electric system portion of the motor control device is shown as a simple circuit diagram, and the software portion that controls the motor control device is shown as a block diagram. 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 unit. The rectifier circuit 3 rectifies the AC voltage into a DC voltage, and the smoothing circuit 4 smoothes the ripple of the DC voltage. Although a full-wave rectifier circuit is shown in FIG. 1, it may be a voltage doubler rectifier circuit. Further, a so-called PAM method, which is a variable power supply method performed in recent years, may be used.

  The rectified DC voltage is supplied to the inverter circuit 5. In the inverter circuit 5, six semiconductor switching elements are connected in a three-phase bridge shape, and the output voltage of the inverter circuit 5 is connected to the three-phase brushless motor 6.

  As the control circuit 7 for driving and controlling the brushless motor 6, a microcomputer or a DSP (Digital Signal Processor) is generally used. In order to set the brushless motor 6 to intermittent energization drive with an energization stop period of less than 180 degrees, an intermittent energization drive unit 8 is provided for performing control such as energization timing setting and drive voltage (PWM duty) reference value setting. It has been. Further, in order to drive the brushless motor 6 180 degrees energized, a 180 degree energization drive unit 9 is provided for performing control such as setting of energization timing and setting of a drive voltage (PWM duty) reference value. Further, a driving method selection unit 10 that determines a driving method is provided. The PWM creation / each phase distribution unit 11 creates and outputs a PWM signal for driving each motor drive element of the inverter circuit 5 for each drive element. A rotation speed control PWM duty / modulation rate calculator 12 is provided for switching the drive system. If the rotor position detection circuit 13 is a digital rotor position detection circuit, the rotor position detection circuit 13 may be built in the control circuit 7. Energization switching control / Voltage / current phase difference calculation / potential phase difference calculation unit (hereinafter abbreviated as “switching control / calculation unit”) 15 estimates the current phase at the time of switching the driving method and sets the voltage / current phase difference or voltage phase. Further, a correction coefficient for the rotational speed control PWM duty is set. Further, the DC current is measured by the DC current detecting means 14 and the shunt resistor 16, the DC current is detected, and the load torque is estimated.

  Whether the brushless motor 6 is driven intermittently or driven 180 degrees is selected and driven by the drive system selection unit 10 according to the state of the brushless motor or an external instruction.

  The operating state of the brushless motor is the rotational speed, efficiency, load state, disturbance state, etc., and may be intermittent energization drive at low speed, 180 degree energization drive at high speed, or intermittent energization drive at high load, high load Then, 180-degree energization drive may be used. In addition, there is a method of switching to intermittent energization drive at the time of disturbance input that makes it difficult to continue the 180-degree energization drive. Furthermore, it is conceivable that the operator switches the driving method using an external switch.

  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.

  The drive waveform for intermittent energization drive may be any drive waveform as long as the energization stop period is provided in the drive waveform with an energization angle of less than 180 degrees and an induced voltage generated during that period can be detected. The energization drive is complete two-phase energization, and rectangular wave energization is possible. Therefore, there is an advantage that a drive waveform supplied to each phase can be easily created.

  The drive waveforms of each phase are shown in the figure as each energization waveform. 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.

  FIG. 2 and FIG. 3 are waveform diagrams showing the state of energization of the signal (PWM creation / output of each phase distribution unit 11) for driving the drive element of the inverter circuit 2 as an analog value for each coil terminal. The drive waveform during the energization period 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 brushless motor 6 is changed, and the rotation speed and torque can be controlled.

  FIG. 4 is a flowchart showing the rotational speed control of the brushless motor 6 when the 120-degree energization drive which is an example of the intermittent energization drive is selected in the control circuit shown in FIG.

  When the control circuit 7 is given a command signal for rotation at the target rotation speed N1 in step (abbreviated as S in the figure and the following description) S1, a rotation speed control PWM duty is set in S2. The control circuit 7 drives the inverter with the rotational speed control PWM duty, and the actual rotational speed N of the brushless motor 6 at that time is detected in S3. In S4, it is determined whether or not the actual rotational speed N matches the target rotational speed N1, and if not, it is compared in S5 whether the current actual rotational speed N is smaller or larger than the target rotational speed N1. The 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. The By repeating this operation, the rotational speed control PWM duty is adjusted, and rotational speed control is performed to control the actual rotational speed N of the brushless motor 6 to be equal to the target rotational speed N1.

  FIG. 5 is an inverter drive signal for the U-phase upper arm when 120 energization drive is selected in the control circuit shown in FIG. In the 120-degree energization drive, a PWM duty equal to the rotation speed control PWM duty is output over the entire energization section.

  FIG. 6 is a flowchart showing the rotational speed control of the brushless motor 6 when the 180 ° energization drive is selected in the control circuit shown in FIG.

  When a command signal for rotating the control circuit 7 at the target rotational speed N1 is given in S8, the rotational speed control modulation rate is set in S9. The control circuit 7 drives the inverter with the rotational speed control modulation rate, and the actual rotational speed N of the brushless motor 6 at that time is detected in S10. In S11, it is determined whether or not the actual rotational speed N matches the target rotational speed N1, and if not, it is compared in S12 whether the current actual rotational speed N is less than or greater than the target rotational speed N1. The 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 smaller than the target rotational speed N1, the rotational speed control modulation factor is increased in S14. The By repeating this operation, the rotational speed control modulation rate is adjusted, and rotational speed control is performed to control the actual rotational speed N of the brushless motor 6 to coincide with the target rotational speed N1.

  FIG. 7 shows an inverter drive signal for the U-phase upper arm when 180-degree energization drive is selected in the control circuit shown in FIG. In 180-degree energization driving, PWM duty calculated using the rotation speed control modulation factor is output so that the motor current waveform becomes a sine wave shape according to the energization phase if the density is equalized.

  FIG. 8 is a diagram showing how the rotational speed fluctuates when switching from intermittent energization drive to 180-degree energization drive. At the time of switching from intermittent energization drive to 180-degree energization drive, there can be considered a method in which the rotation speed control PWM duty of intermittent energization drive is used as it is as the rotation speed control modulation rate of 180-degree energization drive. There may be an imbalance between the current motor operating state such as torque and the inverter output, a rotational speed fluctuation occurs, and it may take time for the actual rotational speed and the target rotational speed to coincide. In addition, 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.

  In intermittent energization driving, the rotor position is detected by detecting the induced voltage during the energization stop period, and the voltage phase is controlled with respect to the rotor position. For example, in 120-degree energization as an example of intermittent energization drive, the non-energized section has an electrical angle of 60 degrees, and the induced voltage is detected during that period. After the induction voltage is detected, energization is started for the detected phase by an electrical angle of 120 degrees. At this time, for example, when energization is started at the same time as the induced voltage is detected, the voltage phase is advanced by 30 degrees with respect to the induced voltage phase. Therefore, in intermittent energization driving, the voltage phase is controlled with respect to the induced voltage phase (rotor position), and the current phase is not controlled. On the other hand, it is possible to estimate the current phase from the load torque and the voltage phase with respect to the rotor position from the motor parameters such as the winding resistance of the motor and the linkage flux by simulation.

  Further, in the sensorless 180-degree energization drive, since there is no energization stop period, the position detection of the rotor cannot be performed directly. In Patent Literature 1, the AC current detection values are integrated for each phase period of two AC voltages to obtain an AC current signal area, and the area ratio of both AC current signal areas is detected as AC voltage / current phase difference information.

  For example, as shown in FIG. 10, the phase difference between the voltage phase and the current phase is detected by the method according to Patent Document 1 and controlled to a certain target value. Therefore, the current phase is not directly controlled with respect to the rotor position in the 180 ° energization drive by the voltage / current phase difference control. On the other hand, it is possible to estimate the current phase from the load torque and the voltage-current phase difference from the motor parameters such as the winding resistance of the motor and the linkage flux by simulation.

  In the present invention, by controlling so that the current phase during the 180-degree energization drive with the voltage / current phase difference and the current phase during the intermittent energization drive are the same before and after switching, torque fluctuation before and after switching is minimized, It is characterized by minimizing rotational speed fluctuations and rotor vibration.

  Further, DC current detection means for detecting a DC current flowing in the inverter unit that drives the brushless motor is provided, and a load state of the brushless motor can be estimated based on the DC current.

FIG. 11 is an energization control flowchart when switching from intermittent energization drive to 180-degree energization drive. The current phase with respect to the rotor position at the time of intermittent energization driving is estimated in advance by simulation from the load torque estimated from the DC current flowing through the inverter unit and the voltage phase with respect to the rotor position, and further the voltage / current is calculated from the estimated current phase. The voltage / current phase difference in the 180 ° energization driving with the phase difference is calculated. That is, a map as shown in FIG. 13 showing the relationship among load torque, voltage phase, and voltage / current phase difference during intermittent energization drive is prepared in advance. In the control circuit 7, when a switching command from the intermittent energization drive to the voltage / current phase difference 180 degree energization drive is set from the drive method selection unit 10, the map is obtained from the load torque and voltage phase in S11 in the energization switching control unit 15. To calculate the voltage / current phase difference. In S12, the voltage / current phase difference is set to a target value of the voltage / current phase difference in the energized driving of the switched voltage / current phase difference of 180 degrees. Therefore, since the fluctuation of the current phase before and after the energization switching becomes small, the torque fluctuation becomes small, the rotation speed fluctuation and the current amplitude fluctuation also become small, and it becomes possible to switch the driving method stably. Further, since the voltage application amount of the 180 / energized voltage / current phase difference and the intermittent energization drive are different at the same PWM duty, in order to correct the voltage application amount accompanying the energization switching, the rotation speed at the time of switching the driving method shown in FIG. In the control PWM duty / modulation rate calculation unit 12, the value obtained by multiplying the PWM duty of the intermittent energization drive by a predetermined value α in S13 is used as the modulation rate of the voltage / current phase difference of 180 ° energization drive, and then the intermittent energization drive is started in S14. When switching to 180 / energization driving of voltage / current phase difference, as shown in the case of “with multiplication of predetermined value α” in FIG. 8, the rotational speed fluctuation becomes small, and a more stable driving system can be switched.
Further, the predetermined value α is adjusted in advance through experiments and simulations so that the rotational speed fluctuation at the time of switching the driving method becomes small.

  Next, switching from 180 degree energization driving to intermittent energization driving will be described. FIG. 9 is a diagram showing how the rotational speed fluctuates when switching from the 180-degree energization drive to the intermittent energization drive 120-degree energization. At the time of switching from 180 degree energization drive to intermittent energization drive, there can be considered a method in which the rotation speed control modulation rate of 180 degree energization is directly used as the rotation speed control PWM duty of intermittent energization drive. Thus, an imbalance may occur between the current motor operating state and the inverter output, and a rotational speed fluctuation may occur, and it may take time until the actual rotational speed and the target rotational speed match. In addition, 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. In the 180 degree voltage / current phase difference energization, the voltage / current phase difference is controlled by the rotational speed control PWM duty / modulation rate.

  FIG. 12 is a control flowchart at the time of switching from voltage / current phase difference 180-degree energization drive to intermittent energization drive. Voltage / current phase difference is estimated in advance from the voltage / current phase difference and the load torque estimated from the DC current flowing through the inverter unit during the 180-degree energization drive, and further from the estimated current phase during the intermittent energization drive. Is calculated. That is, as shown in FIG. 14, the relationship between the load torque, the voltage / current phase difference, and the voltage phase at the time of 180 / energization driving of the voltage / current phase is prepared in advance as a map. In the control circuit 7, when a switching command from the voltage / current phase difference 180 degree energization drive to the intermittent energization drive is set from the drive method selection unit 10, the energization switching control unit 15 determines the load torque, the voltage / current phase difference in S21. From the map, the voltage phase is calculated. In S22, the voltage phase is set to the target value of the voltage phase in the intermittent energization drive after switching. In intermittent energization drive, by detecting the induced voltage phase of the non-energized phase by the rotor position detection circuit 13, it is possible to control the voltage phase with respect to the rotor position so that the detected value matches the target value. is there.

  Therefore, by controlling the voltage phase as the voltage phase in the intermittent energization drive after switching, the variation in the current phase before and after the energization switching is reduced, so that the torque variation is reduced, and the rotation speed variation and current amplitude variation are also reduced. It is possible to switch the driving method stably. Further, since the voltage application amount of the intermittent energization driving and the voltage / current phase difference 180 degree energization driving is different at the same PWM duty, the number of rotations at the time of switching the driving method shown in FIG. In the control PWM duty / modulation rate calculation unit 12, a value obtained by multiplying the PWM duty of intermittent energization driving by a predetermined value β is set as a modulation rate of voltage / current phase difference 180 degrees energization drive, and then the voltage / current phase difference 180 is determined in S24. When switching from the normal energization drive to the intermittent energization drive, as shown in the case of “with multiplication of the predetermined value β” in FIG. 9, the rotational speed fluctuation becomes small, and the drive system can be switched more stably. .

  Further, the predetermined value β is adjusted in advance by experiments and simulations so that the fluctuation in the rotational speed at the time of switching the driving method becomes small.

  Further, in the method based on detecting the induced voltage of the phase in the non-energized section by the position sensorless intermittent energization drive, the advance angle of the voltage phase with respect to the rotor position is limited. For example, in sensorless 120-degree energization, the advance angle of the voltage phase is up to 30 degrees with respect to the induced voltage phase.

Configuration diagram showing an embodiment of the present invention Drive waveform of rectangular wave 120 degree energization as an example of intermittent energization drive Driving waveform of sinusoidal energization as an example of 180 degree energization driving Flow chart showing rotation speed control of 120-degree energization drive Inverter drive signal for U-phase upper arm with 120-degree conduction drive Flow chart showing rotation speed control of 180-degree energization drive Inverter drive signal for U-phase upper arm with 180 degree drive The figure which showed the mode of the rotation speed fluctuation | variation at the time of switching from a 180 degree | times energization drive to an intermittent energization drive. The figure which showed the mode of the rotation speed fluctuation | variation at the time of switching from intermittent energization drive to 180 degree energization drive. Voltage / current phase difference Voltage / current phase difference in 180 degree conduction drive Control flowchart for switching from intermittent energization drive to 180 degree energization drive Control flowchart for switching from 180-degree energization drive to intermittent energization drive Map data of voltage phase, load torque and voltage / current phase difference Map data of voltage / current phase difference, load torque and voltage phase

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power source from commercial power supply 2 Power factor improvement circuit 3 Rectifier circuit that converts AC to DC 4 Smoothing circuit that smoothes DC voltage ripple 5 Inverter circuit 6 Three-phase brushless motor 7 Control circuit 8 Intermittent drive unit 9 180 degrees Energization drive unit 10 Drive system selection unit 11 PWM creation unit / each phase distribution unit 12 Rotational speed control PWM duty / modulation rate calculation unit 13 Rotor position detection circuit 14 DC current detection means 15 Energization switching control / voltage / current phase difference calculation / Voltage phase calculator 16 Shunt resistance

Claims (4)

  A power supply means for supplying power to the brushless motor, a 180-degree energization drive means for controlling the power supply means so that the brushless motor is driven in a 180-degree energization drive system without providing an energization pause period, and an energization pause period An intermittent energization drive means for controlling the power supply means so that the brushless motor is driven by an intermittent energization drive system, and a selection means for selecting one of the 180-degree energization drive system and the intermittent energization drive system And the current phase with respect to the rotor position of the brushless motor immediately before switching in the one driving method when switching from one driving method to the other driving method of the 180-degree energizing driving method and the intermittent energizing driving method. A brushless motor control device, wherein the current phase immediately after switching is controlled to be equal.   In the motor control device, when switching from the 180-degree energization drive to the intermittent energization drive, the current phase and the voltage phase with respect to the rotor position are respectively estimated from the load torque and the voltage / current phase difference before the switching, 2. The brushless motor control device according to claim 1, wherein the voltage phase of the intermittent energization drive after switching is determined using the estimated current phase and voltage phase.   In the motor control device, when switching from the intermittent energization drive to the 180-degree energization drive, the current phase and the voltage / current phase difference with respect to the rotor position are estimated and estimated from the load torque and voltage phase before switching. 2. The brushless motor control device according to claim 1, wherein the voltage / current phase difference in the 180-degree conduction drive is determined using a current phase and a voltage / current phase difference.   4. The brushless motor according to claim 2, further comprising: a DC current detection unit configured to detect a DC current flowing through the winding of the brushless motor, and estimating a load state of the brushless motor based on the DC current. Control device.

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