JP4363119B2 - Brushless DC motor control method and apparatus - Google Patents

Description

  In order to control a brushless DC motor whose speed is controlled by an inverter, a brushless DC motor control method for obtaining and outputting a current phase command for giving a weak magnetic flux current for reducing a speed electromotive voltage from a rotation speed and a current, and its Relates to the device.

  Conventionally, methods for performing flux-weakening control of a synchronous motor have been proposed (see Patent Document 1, Patent Document 2, and Patent Document 3).

  Patent Document 1 discloses a first phase that is the maximum phase of the weak magnetic flux direction in which the required torque of the synchronous motor can be guaranteed and a maximum phase of the strong field direction in which the required torque of the synchronous motor can be guaranteed. It is described that the phase of the current is controlled to an average value of the first phase and the second phase using the phase of 2.

  Japanese Patent Application Laid-Open No. 2005-228561 describes that flux-weakening control is performed based on the magnitude of a field current obtained by dividing a field magnetic flux unique to a synchronous motor by its inductance.

Patent Document 3 describes that the value of the flux-weakening current is calculated from the maximum voltage that can be applied and the required torque.
JP 2001-86780 A JP 2001-197764 A Japanese Patent Laid-Open No. 7-107772

  In Patent Document 1, the current phase itself is fixed and the average value is used as the current phase to maximize the margin for the error. Therefore, when the error exceeds the margin, the torque is not guaranteed. There is no guarantee that the maximum output of the motor can be achieved.

  In Patent Document 2, the current phase is determined by a mathematical formula, but not only the error due to the variation of the motor constant cannot be eliminated, but the error caused by the encoder attachment error cannot be eliminated.

  In Patent Document 3, the current phase is determined by a mathematical expression, but not only the error due to the variation of the motor constant cannot be eliminated, but also the error caused by the encoder attachment error cannot be eliminated.

  Further explanation will be given.

  In the case of adopting a configuration that provides an incremental encoder without a Z phase, if the current phase command is derived from the current phase table or mathematical formula, the magnetic pole position at the time of start-up can be detected in an area that is operated with high-speed flux-weakening control. If there is an error, the current phase cannot be sufficiently advanced or excessively advanced, so that a desired motor output area cannot be obtained.

  That is, when the flux weakening is insufficient, the duty command (output voltage command) supplied from the current control unit to the inverter unit is saturated, and the difference between the induced voltage of the motor and the inverter output voltage cannot be sufficiently obtained. As a result, the current of the value as commanded cannot be flowed into the motor.

  On the contrary, when the weak magnetic flux is excessive, the duty command supplied from the current control unit to the inverter unit becomes a low value, and in this case, the induced voltage of the motor can be suppressed. Therefore, the motor output torque is reduced because more current than necessary is used.

  In the case of adopting a configuration in which an incremental encoder (or an absolute encoder) having a Z phase is employed, the same inconvenience occurs due to an encoder mounting error.

  When magnetic pole position detection is performed without using a position sensor, the same inconvenience occurs when a magnetic pole position estimation error occurs.

  It may be possible to set a current phase table after creating a current phase map based on actual measurement data based on various parameters such as power supply voltage, rotation speed, and current. However, the amount of data is extremely large and the memory is extremely large. Will be needed. Moreover, when there are many parameters, the number of points actually measured increases, which takes time and effort. Furthermore, if the motor constant fluctuates due to production variations, changes over time, etc., the optimum current phase also fluctuates, resulting in the same inconvenience as described above.

  The present invention has been made in view of the above problems, and provides a brushless DC motor control method and apparatus capable of operating at a desired operating point regardless of the presence or absence of a magnetic pole position detection error or the like. It is intended to provide.

In the brushless DC motor control method according to claim 1, the brushless DC motor is controlled by the inverter.
The necessity of phase correction is determined from the current phase command value and the weak flux control start phase for starting the weak flux control that gives the weak flux current to reduce the speed electromotive force,
In response to determining that phase correction is necessary, determine the correction direction based on the output voltage command,
In this method, a predetermined phase correction value is added to the determined correction direction with respect to the current phase command value to obtain a current phase command.

  According to the brushless DC motor control method of claim 2, in response to the determination that the phase correction is necessary, the output voltage command and the specified value determined before saturation when increasing the output voltage to be saturated. This is a method for determining the correction direction based on the magnitude of.

  The brushless DC motor control method according to claim 3 causes the phase correction value to be increased or decreased until it is determined that the phase correction is unnecessary, and a predetermined phase correction is performed in the determined correction direction with respect to the current phase command value. This is a method of adding values to obtain a current phase command.

  The brushless DC motor control method according to claim 4 is a method of adopting a value having hysteresis before and after the specified value determined before saturation instead of the specified value determined before saturation.

  The brushless DC motor control method of claim 5 is a method of adopting a dead zone provided before and after the specified value determined before saturation instead of the specified value determined before saturation.

The brushless DC motor control device according to claim 6 controls the brushless DC motor by an inverter,
Necessity determining means for determining whether or not phase correction is necessary from a current phase command value and a weakening magnetic flux control start phase for starting a weakening magnetic flux control that gives a weakening magnetic flux current to reduce the speed electromotive force;
In response to determining that the phase correction is necessary, a correction direction determination unit that determines a correction direction based on the output voltage command;
Current phase command generating means for adding a predetermined phase correction value in the determined correction direction to the current phase command value to obtain a current phase command.

  The brushless DC motor control device according to claim 7 saturates when the correction direction determination means increases the output voltage command and the output voltage to saturate in response to determining that phase correction is necessary. What determines a correction direction based on the magnitude with respect to the predetermined value defined previously is employ | adopted.

  The brushless DC motor control device according to claim 8 is configured to cause the current phase command generation means to increase or decrease a phase correction value until it is determined that phase correction is unnecessary, and the determination is made with respect to the current phase command value. In this case, a current phase command is added by adding a predetermined phase correction value in the correction direction.

  The brushless DC motor control device according to claim 9 uses a value having hysteresis before and after the specified value determined before saturation instead of the specified value determined before saturation. It is adopted as a means.

  The brushless DC motor control device according to claim 10 employs a dead zone region provided before and after the specified value determined before saturation instead of the specified value determined before saturation as the correction direction determination means. Adopted.

In the brushless DC motor control method according to claim 11, a current phase command value for providing an optimum weakening magnetic flux current for reducing the speed electromotive force is obtained by correcting the motor rotational speed and the motor current obtained from the actual power supply voltage and the motor rotational speed. From
This is a method for determining whether or not phase correction is necessary from the obtained current phase command value and the weak magnetic flux control start phase for starting the weak magnetic flux control for giving the weak magnetic flux current to reduce the speed electromotive force.

  The brushless DC motor control device according to claim 12 uses a corrected motor rotational speed and a motor current obtained from an actual power supply voltage and a motor rotational speed as a current phase command value for providing an optimum weakening magnetic flux current for reducing the speed electromotive force. Current phase command value calculating means obtained from the above, and as the necessity determining means, a weakening magnetic flux control start phase for starting a weakening magnetic flux control for giving a weakening magnetic flux current to reduce the speed electromotive force and the obtained current phase command value From this, it is determined whether or not phase correction is necessary.

  The invention of claim 1 enables operation at a desired operating point regardless of the presence or absence of errors in magnetic pole position detection, encoder mounting errors, power supply voltage fluctuations, and motor device constant errors caused by production variations. There is a unique effect of being able to.

  The invention of claim 2 has the same effect as that of claim 1.

  The invention of claim 3 has the same effect as that of claim 1.

  The invention of claim 4 has the same effect as that of claim 2.

  The invention of claim 5 has the same effect as that of claim 2.

  The invention of claim 6 enables operation at a desired operating point regardless of the presence or absence of errors in magnetic pole position detection, encoder installation errors, power supply voltage fluctuations, and motor device constants due to production variations. There is a unique effect of being able to.

  The invention of claim 7 has the same effect as that of claim 6.

  The invention of claim 8 has the same effect as that of claim 6.

  The invention of claim 9 has the same effect as that of claim 7.

  The invention of claim 10 has the same effect as that of claim 7.

  The invention of claim 11 can achieve optimum phase control even when the power supply voltage fluctuates, can always operate at the optimum operating point, and prevents step-out stop due to phase shift. In addition, the same effects as in any one of claims 1 to 5 can be obtained.

  The invention of claim 12 can achieve the optimum phase control even when the power supply voltage fluctuates, can always perform the operation at the optimum operation point, and prevents the step-out stop due to the phase shift. In addition, the same effects as in any one of claims 6 to 10 can be obtained.

  Embodiments of a brushless DC motor control method and apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic view showing an embodiment of a brushless DC motor control device of the present invention.

  The brushless DC motor control device includes a converter unit 12 that outputs an AC voltage from an AC power source, an inverter unit 11 that outputs an AC voltage from an input DC voltage and supplies the AC voltage to the brushless DC motor 1, and the brushless DC motor 1. And have. Then, a pulse signal is output from the encoder 2 connected to the brushless DC motor 1, and the current speed is detected based on, for example, the pulse interval in the speed detection unit 3 that receives the pulse signal. Reference numeral 12a denotes a smoothing capacitor.

  Further, a speed controller 4 that outputs a current command by performing a speed control calculation with the speed command and the current speed as inputs, and a current control that outputs a current voltage and a current phase command by inputting the current command and the current phase command to output an output voltage duty 5, a current phase map unit 6 that holds a current phase map created in advance and outputs a map current phase according to the current command and the current speed, and determines whether or not the weakening magnetic flux control is required by using the map current phase as an input A weak magnetic flux determination unit 7, a phase correction direction determination unit 9 that determines the direction of phase correction based on the magnitude of the output voltage duty as an input and a predetermined value that is determined just before saturation, and a result of determining whether or not a weak magnetic flux control is necessary In addition, the phase correction direction judgment result is input, the phase correction amount is increased or decreased until the target output voltage duty is reached, and finally the phase correction amount is output. A correction controller 8, and an adder 10 which outputs as a current phase command adds the map current phase and the phase correction amount.

  Therefore, for the flux-weakening control, the map current phase and the phase correction amount can be added to obtain an appropriate current phase command, resulting in magnetic pole position detection error, encoder installation error, power supply voltage fluctuation, and production variation. Regardless of whether or not there is an error in the motor device constant, it is possible to operate at a desired operating point.

  FIG. 2 is a block diagram illustrating another configuration example of the current phase map unit 6, the magnetic flux weakening determination unit 7, the phase correction controller 8, the phase correction direction determination unit 9, and the adder 10.

  The apparatus in FIG. 2 receives the map current phase as input, determines the magnitude of the magnetic flux control start phase βy depending on the motor attribute, and outputs a first control signal (correction operation mode signal) corresponding to the determination result. The magnetic flux determination unit 7 receives a duty filter value obtained by outputting the output voltage duty through the filter 9a, determines the magnitude of the two reference duties dutyH and dutyL, and outputs a second control signal (correction direction signal) corresponding to the determination result. The phase correction direction determination unit 9 to output, the weak magnetic flux control necessity determination result and the phase correction direction determination result are input, the phase correction amount is increased or decreased until the target output voltage duty is reached, and finally the phase correction amount is determined. A phase correction controller 8 for outputting, and an adder 10 for adding the map current phase and the phase correction amount and outputting the result as a current phase command.

  The weak flux determination unit 7 determines whether or not the current brushless DC motor operating state requires weak flux control depending on whether or not the map current phase is larger than the weak flux control start phase βy. When necessary, a correction operation mode signal is output to instruct to operate as the phase correction mode, and to instruct to operate as the phase map mode when the flux-weakening control is unnecessary.

  When operating in the phase correction mode, the desired motor output area may not be obtained unless the brushless DC motor is operating in the optimum phase. Therefore, it is necessary to perform phase correction control so that the brushless DC motor always operates at the optimum phase. Therefore, the phase correction direction determination unit 9 monitors the output voltage duty.

  And when the output voltage duty is smaller than the reference duty dutyL, since the inverter output voltage has a margin because it operates on the leading side from the optimum phase, the flux current flows more weakly than necessary. It is necessary to perform phase correction toward the delay side.

  On the other hand, when the output voltage duty is larger than the reference duty dutyH, the inverter output voltage is saturated because it operates on the delay side from the optimum phase. Therefore, it is necessary to perform phase correction toward the advance side.

  When the output voltage duty is between both reference duties dutyH and dutyL, the brushless DC motor is operated with the output voltage duty set in that section by stopping the increase / decrease of the phase correction amount. That is, if the brushless DC motor is operated in a state where the output voltage duty is between both reference duties dutyH and dutyL, the current phase command is in the optimum phase (the inverter output voltage is just before saturation). That is, there is a dead zone between the two reference duties dutyH and dutyL.

  Then, the phase correction amount is set by the phase correction controller 8 according to the correction operation mode determined by the magnetic flux weakening determination unit 7 and the correction direction determined by the phase correction direction determination unit 9.

  When operating in the phase correction mode, according to the correction direction, the predetermined phase amount is increased with respect to the current phase correction during advance correction, and the predetermined phase amount is decreased with respect to the current phase correction during delay correction. .

  When the phase correction mode is switched to the phase map mode, the map current phase is adopted as the current phase command, so the phase correction amount needs to be set to zero. However, in this case, the current phase command may change suddenly.

  Therefore, at the time of such mode switching, it is preferable to gradually change the phase correction amount toward 0, and the possibility that the current phase command changes suddenly can be eliminated.

  Further description will be given with reference to FIGS.

  If the current phase is not sufficiently advanced due to a magnetic pole position detection error or an equipment constant error caused by production variations, the speed is increased from point A in FIG. The induced voltage of the DC motor increases, and the output voltage duty is saturated at point B in FIG. The relationship between the output voltage duty and the current at that time is as shown in FIG. As can be seen from FIG. 4, since the output voltage duty is saturated before correction, no more current can be flowed in. If the speed is further increased, the output torque decreases and the limit speed (point C in FIG. 3). To see). However, the current can be increased by performing phase correction so that the output voltage duty is not saturated. Therefore, by repeating the phase correction so that the output voltage duty is always close to saturation, the speed can be increased to point D in FIG. 3 which is the maximum output area.

  If the current phase is advanced too much, the induced voltage of the brushless DC motor can be suppressed by increasing the speed from the point A in FIG. 3, but since the flux current is weakened more than necessary, the current flows as shown in FIG. The current limit is reached at point B. The relationship between the output voltage duty and the current at that time is as shown in FIG. As can be seen from FIG. 5, since the current has reached the limit before correction, the output torque decreases at a speed higher than that and reaches the limit speed (see point C in FIG. 3). However, by performing phase correction in the direction of saturation of the output voltage duty, it is possible to increase the speed because there is a margin in current. Therefore, by repeating the phase correction so that the output voltage duty is always close to saturation, the speed can be increased to point D in FIG. 3 which is the maximum output area.

  Similarly, when the power supply voltage fluctuates, it is possible to operate in the maximum output area possible with the fluctuating power supply voltage.

  As a result, it is possible to output the maximum torque in this state while maintaining the follow-up performance of the current phase command with high response by the phase map. In the operation area where the flux-weakening control is required, the current value for outputting the required torque can be reduced by this control, so that the operation is performed at the current phase close to the maximum efficiency point. Become.

  In the above embodiment, since the current phase map using the rotation speed and the motor current as parameters is used, it is possible to reduce the number of current phase maps that need to be prepared without requiring parameters such as the power supply voltage. it can. As a result, the memory capacity can be reduced, and the effort for creating the current phase map can be reduced.

  In addition, the dead zone can be omitted, and hysteresis can be provided before and after the specified value instead of providing the dead zone.

  Furthermore, instead of the value immediately before the saturation, a value that is somewhat before the saturation can be adopted.

  FIG. 6 is a schematic view showing another embodiment of the brushless DC motor control device of the present invention.

  This brushless DC motor control device is different from the brushless DC motor control device of FIG. 1 in that a voltage detector 13 that detects the voltage of the DC portion of the inverter unit 11 and an output from the speed detector 3 using the detected voltage. Only the point that further includes a speed corrector 14 that corrects the current speed to be output, outputs a corrected speed (corrected rotation speed), and supplies the corrected speed to the current phase map 6.

  FIG. 7 is a schematic diagram for explaining an example of a main part of the brushless DC motor control device of FIG.

  In the speed corrector 14, the detected voltage (DC voltage) and the detected rotational speed are input, for example, the detected voltage (DC voltage) of the DC voltage at the time of creating the current phase map with respect to the detected rotational speed. ) And a correction speed (correction speed) is output. Then, by supplying the corrected rotational speed and the current command to the current phase map 6, the current phase corresponding to the corrected rotational speed and the current command is output as the map current phase.

  By supplying this map current phase and output voltage duty to a phase corrector (phase correction controller, phase correction direction determination unit, and weakening magnetic flux determination unit) 8 ′, a phase correction amount is calculated and output.

  Then, the current phase command can be calculated and output by adding the map current phase and the phase correction amount.

  However, when an AC voltage (AC voltage) can be detected, the AC voltage at the time of current phase map creation is detected instead of the ratio of the DC voltage at the time of current phase map creation to the detected voltage (DC voltage). The ratio to the other voltage (AC voltage) can be employed.

  FIG. 8 is a schematic diagram for explaining the variation of the map current phase when the power supply voltage varies.

  When the power supply voltage is the reference voltage V0, the correction rotation speed is w0 and the map current phase is β0.

  When the power supply voltage is V1 lower than the reference voltage V0, the rotational speed is corrected to make the corrected rotational speed w1 (w0 <w1), and the map current phase is advanced to β1 (β0 <β1).

  Conversely, when the power supply voltage is V2 higher than the reference voltage V0, the rotational speed is corrected to make the corrected rotational speed w2 (w2 <w0), and the map current phase is delayed to β2 (β2 <β0). .

  However, this map current phase is not always the optimum current phase due to differences in motors. Specifically, for example, as shown in FIG. 9, the optimum current phase βop (β1 <βop) is given.

  Therefore, the speed corrector 14 outputs a map current phase that is as close to the optimum current phase as possible in consideration of the fact that the optimum current phase also fluctuates due to fluctuations in the power supply voltage.

  Further, the current phase map 6 to which the speed corrector 14 is added plays a role of feedforward, thereby enabling a high response of the current phase that can withstand fluctuations in the power supply voltage. Further, the phase corrector 8 ' Make fine adjustments to the phase. As a result, current phase control can be performed so that the motor always operates at an optimal current phase.

  In other words, it is possible to achieve an improvement in responsiveness with respect to the current phase advance when the power supply voltage fluctuates due to feedforward, and in combination with the phase corrector 8 ′, reliable and quick to the optimum current phase is achieved. Convergence can be achieved.

  FIG. 10 is a schematic diagram for explaining the current phase correction operation. (A) shows an example of the change in the map current phase before and after the start of the weak flux control, (B) shows an example of the change in the map current phase after the start of the weak flux control, and (C) shows the start of the weak flux control. (D) shows an example of the fluctuation of the current phase command (map current phase + phase correction quantity) after the start of the flux-weakening control.

  As can be seen from FIG. 10, the map current phase is shifted from the optimum current phase. However, the current phase command can be set to the optimum current phase by adding the phase correction amount to the map current phase.

  In this case, the detection speed is corrected in accordance with the fluctuation of the power supply voltage, and the map current phase is read from the current phase map 6, so that the optimum current phase is set to be higher than the map current phase read without correcting the detection speed. Even when the difference is small and a high response is required, the flux-weakening control can be performed without causing instability of control (in the worst case, step-out stop).

It is the schematic which shows one Embodiment of the brushless DC motor control apparatus of this invention. It is a block diagram which shows the other example of a structure of the electric current phase map part of FIG. 1, a weakening magnetic flux determination part, a phase correction controller, a phase correction direction determination part, and an adder. It is a figure explaining the change of a motor output area and an operating point. FIG. 4 is a diagram showing a relationship between output voltage duty and current when the current phase is too late at point B in FIG. 3. FIG. 4 is a diagram showing a relationship between output voltage duty and current when the current phase is excessively advanced at point B in FIG. 3. It is the schematic which shows other embodiment of the brushless DC motor control apparatus of this invention. It is the schematic for demonstrating an example of the principal part of the brushless DC motor control apparatus of FIG. It is the schematic explaining the fluctuation | variation of the map current phase when a power supply voltage fluctuates. It is a figure explaining the shift | offset | difference of the map current phase based on correction | amendment rotation speed, and an optimal current phase. It is the schematic explaining current phase correction operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brushless DC motor 7 Weak magnetic flux determination part 8 Phase correction controller 9 Phase correction direction determination part 10 Adder 11 Inverter part 13 Voltage detector 14 Speed corrector 8 'Phase corrector

Claims (12)

A brushless DC motor control method for controlling a brushless DC motor (1) by an inverter (11),
The necessity of phase correction is determined from the current phase command value and the weak flux control start phase for starting the weak flux control that gives the weak flux current to reduce the speed electromotive force,
In response to determining that phase correction is necessary, determine the correction direction based on the output voltage command,
A brushless DC motor control method comprising: adding a predetermined phase correction value in the determined correction direction to the current phase command value to obtain a current phase command. In response to the determination that the phase correction is necessary, the correction direction is determined based on the magnitude of the output voltage command and a predetermined value determined before saturation when the output voltage is increased to be saturated. The brushless DC motor control method according to claim 1. A phase correction value is increased or decreased until it is determined that phase correction is unnecessary, and a predetermined phase correction value is added to the determined correction direction with respect to the current phase command value to obtain a current phase command. Item 2. The brushless DC motor control method according to Item 1. The brushless DC motor control method according to claim 2, wherein a value having hysteresis before and after the specified value determined before saturation is adopted instead of the specified value determined before saturation. The brushless DC motor control method according to claim 2, wherein a dead zone region provided before and after the specified value determined before saturation is adopted instead of the specified value determined before saturation. A brushless DC motor control device for controlling a brushless DC motor (1) by an inverter (11),
Necessity determining means (7) for determining whether or not phase correction is necessary from a current phase command value and a weakening magnetic flux control start phase for starting a weakening magnetic flux control for giving a weakening magnetic flux current to reduce the speed electromotive force;
In response to the determination that phase correction is necessary, correction direction determination means (9) for determining a correction direction based on the output voltage command;
A brushless DC motor control device comprising: current phase command generation means (10) for adding a predetermined phase correction value in the determined correction direction to the current phase command value to obtain a current phase command. . In response to the determination that the phase correction is necessary, the correction direction determination means (9) outputs an output voltage command and a specified value determined before saturation when increasing the output voltage to be saturated. The brushless DC motor control device according to claim 6, wherein the correction direction is determined based on the magnitude of. The current phase command generation means (10) increases or decreases a phase correction value until it is determined that phase correction is unnecessary, and a predetermined phase correction is performed in the determined correction direction with respect to the current phase command value. The brushless DC motor control device according to claim 6, wherein the values are added to obtain a current phase command. The correction direction determination means (9) employs a value having hysteresis before and after the specified value determined before saturation instead of the specified value determined before saturation. Brushless DC motor control device. The brushless DC according to claim 7, wherein the correction direction determination means (9) employs a dead zone provided before and after the specified value determined before saturation, instead of the specified value determined before saturation. Motor control device. Obtain the current phase command value that gives the optimal flux-weakening current that reduces the speed electromotive force from the corrected motor speed and motor current obtained from the actual power supply voltage and motor speed,
6. The necessity of phase correction is determined based on the obtained current phase command value and a weak magnetic flux control start phase for starting a weak magnetic flux control for applying a weak magnetic flux current to reduce the speed electromotive force. The brushless DC motor control method described in 1. Current phase command value calculation means (6) for obtaining a current phase command value for giving an optimum weakening magnetic flux current for reducing the speed electromotive force from the corrected motor rotational speed and the motor current obtained from the actual power supply voltage and the motor rotational speed. (13) (14) further included,
The necessity determination means (7) determines whether or not phase correction is necessary from the obtained current phase command value and the weakening magnetic flux control starting phase for starting the weakening magnetic flux control for applying the weakening magnetic flux current so as to reduce the speed electromotive force. The brushless DC motor control device according to any one of claims 6 to 10, wherein the brushless DC motor control device is one.

Images