JP4454521B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device that drives and controls a synchronous motor such as a brushless motor configured by a rotor with a permanent magnet.

  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 “motor”), an intermittent energization with an energization stop period and an energization angle of less than 180 degrees is performed. A drive system is generally used. 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.

  As another driving method, there is a so-called 180-degree energization driving method in which the motor is driven without providing an energization stop period. A typical example of the 180-degree energization drive method is a sine wave energization drive method.

  As a method for determining energization timing when the 180-degree energization drive method is used in sensorless operation, a three-phase motor coil neutral point and a resistor are connected in parallel with the three-phase coil, and a three-phase motor coil neutral point and resistance are connected. A method of detecting the motor induced voltage by comparing the voltage with the neutral point and determining the energization timing based on the detected motor induced voltage, detecting the motor position by calculating the motor current at high speed and Examples include a method of determining, or a method of determining energization timing based on the phase difference between the motor drive voltage and the motor current.

  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 intermittent energization drive system.

Further, Patent Document 1 discloses a control device that controls driving of the motor by switching between both of these driving methods. The motor control device disclosed in Patent Document 1 includes a motor current flowing through a motor coil, a phase difference between the motor drive voltage output from the inverter circuit and the motor current, a DC current supplied to the inverter circuit, or a converter circuit. A disturbance is detected from the AC voltage supplied to the power source, and when a disturbance is detected, the 180-degree conduction drive system is switched to the intermittent conduction drive system.
JP 2003-111470 A JP-A-8-19263

  However, the motor control device that controls the driving of the motor by switching between the two driving methods disclosed in Patent Document 1 has an advantage that the driving can be continued without stopping even when a disturbance occurs. Reliability in case of gradual change is not considered. That is, in the motor control device disclosed in Patent Document 1, when the load fluctuation changes gently, for example, even if phase difference control feedback is applied, the phase difference between the motor voltage and the motor current becomes the target value. It becomes impossible to control, which may cause a decrease in reliability and instability of the rotation speed of the motor.

  In view of the above problems, the present invention provides a motor control device that can improve reliability and stabilize the rotational speed of a motor by switching between an intermittent energization drive method and a 180-degree energization drive method. Objective.

In order to achieve the above object, a motor control device according to the present invention includes a power supply unit that supplies power to a synchronous motor, and the synchronous motor that is driven by a 180-degree energization drive method that does not provide an energization pause period. 180 degree energization drive means for controlling the power supply means, intermittent energization drive means for controlling the power supply means so as to drive the synchronous motor in an intermittent energization drive system with an energization pause period, and the 180 degree energization a selecting means for selecting one of the driving method and the intermittent conduction drive method, and a load drive state monitoring means for driving condition of the synchronous motor is to monitor whether unstable control, the 180-degree conduction drive method When the synchronous motor is driven, the load driving state monitoring means determines that the driving state of the synchronous motor is unstable and the selection When a predetermined time elapses after the stage switches the drive method from the 180-degree conduction drive method to the intermittent conduction drive method, the selection unit returns the drive method from the intermittent conduction drive method to the 180-degree conduction drive method. When the driving state of the synchronous motor is again determined to be unstable by the load driving state monitoring means, the driving method is switched from the 180-degree energizing driving method to the intermittent energizing driving method, and the switching is performed in a predetermined manner. If it is performed a number of times, the 180-degree energization drive method is not selected until the synchronous motor is stopped once . Note that the drive state of the synchronous motor is unstable control means that the steady-state deviation exceeds a predetermined level when control feedback (for example, phase difference control feedback, rotation control feedback) is applied to the synchronous motor drive. It means that For example, it comprises phase difference detection means for detecting the phase difference between the motor voltage and motor current of the synchronous motor, and the load drive state monitoring means receives the detection result of the phase difference detection means, and the motor voltage of the synchronous motor When the phase difference between the motor and the motor current is larger than a predetermined value during a predetermined period, it may be determined that the driving state of the synchronous motor is unstable in control.

  According to such a configuration, if the driving state of the synchronous motor is determined to be unstable by the load driving state monitoring unit, the driving method is switched from the 180-degree energizing driving method to the intermittent energizing driving method. In the sensorless 180-degree energization drive, even if the control becomes unstable once, the motor drive can be maintained without deteriorating factors such as efficiency, torque fluctuation, vibration, noise, etc., improving reliability and rotating the motor The number can be stabilized.

  Further, at least one reference value larger than the predetermined value may be provided, and the predetermined period may be changed according to a period in which the phase difference between the motor voltage and the motor current of the synchronous motor is larger than the reference value. Thereby, when the phase difference between the motor voltage and the motor current of the synchronous motor is large, it is possible to reduce the time for the load driving state monitoring means to determine that the driving state of the synchronous motor is unstable in control. .

  According to the present invention, the reliability can be improved and the rotational speed of the motor can be stabilized by switching between the intermittent energization driving method and the 180-degree energization driving method.

  Embodiments of the present invention will be described below with reference to the drawings. An example of the configuration of a motor control device according to the present invention is shown in FIG. A motor control device according to the present invention shown in FIG. 1 includes a converter circuit 2, an inverter circuit 3, a three-phase brushless motor 4 (hereinafter referred to as “motor 4”), a direct current detection amplifier 5, and a control circuit 6. The rotor position detection circuits 17 and 18, the current detection resistor R 1, and the resistors R 2 to R 4 are configured to receive power from the commercial power source 1. If the rotor position detection circuits 17 and 18 are digital rotor position detection circuits, the rotor position detection circuits 17 and 18 may be built in the control circuit 6.

  The converter circuit 2 includes a reactor 2A, a rectifier circuit 2B, and a smoothing capacitor 2C. The converter circuit 2 converts an AC voltage from the commercial power source 1 into a DC voltage and supplies the DC voltage to the inverter circuit 3. An AC voltage from the commercial power source 1 is supplied to the rectifier circuit 2B through the reactor 2A. The reactor 2A is provided to improve the power factor drop in the smoothing capacitor 2C. The rectifier circuit 2B rectifies and outputs the input AC voltage to a DC voltage, and the DC voltage output from the rectifier circuit 2B is smoothed by the smoothing capacitor 2C. In this embodiment, the full-wave rectifier circuit formed by bridge-connecting four diodes is used for the rectifier circuit 2B, but other rectifier circuits such as a voltage doubler rectifier circuit may be used. Further, a so-called PAM (Pulse Amplitude Modulation) method, which is a variable power supply method performed in recent years, may be employed.

  The DC voltage smoothed by the smoothing capacitor 2C is supplied to the inverter circuit 3. The inverter circuit 3 is a circuit in which driving elements which are six semiconductor switching elements are connected in a three-phase bridge shape, and the driving voltage from the inverter circuit 3 is output to the motor 4.

  The converter circuit 2 and the inverter circuit 3 are connected by a positive DC line and a negative DC line, and a current detection resistor R1 is provided on the negative DC line. The direct current detection amplifier 5 detects the direct current flowing from the converter circuit 2 to the inverter circuit 3 based on the voltage generated at both ends of the current detection resistor R1, amplifies the detected direct current, and controls it as a direct current signal. It outputs to the motor current estimation part 11 in the circuit 6.

  The rotor position detection circuit 17 detects the rotor position based on the induced voltage from the motor coil terminal, and the rotor position detection circuit 18 detects the voltage at the neutral point of the three-phase motor coil and the voltage at the neutral point of the resistors R2 to R4. The rotor position is detected based on.

  The control circuit 6 is a circuit for driving and controlling the motor 4 and generally uses a microcomputer or a DSP (Digital Signal Processor). The control circuit 6 includes an intermittent energization drive unit 7, a 180 degree energization drive unit 8, a drive method selection unit 9, a PWM creation unit 10, a motor current estimation unit 11, a phase difference detection unit 12, and a load drive state. A monitoring unit 13, a target phase difference information storage unit 14, an adder 15, and a PI calculation unit 16 are provided, and each process is performed in software according to a program.

  The motor current estimation unit 11 includes a current change calculation unit and a distribution calculation unit. The current change calculation unit obtains a change in the DC current from the DC current signal that is the output of the DC current detection amplifier 5, and the DC current is calculated. The motor current signal is estimated and calculated by distributing the change for each phase by the distribution calculation unit. Here, the current change calculation unit and the distribution calculation unit can be realized using a known technique (for example, see Patent Document 2).

  The phase difference detection unit 12 uses the motor voltage phase information used when the control circuit 6 performs PWM output and the motor current signal estimated by the motor current estimation unit 11 to calculate the motor voltage and the motor current. , And information on the detected phase difference (hereinafter referred to as phase difference information) is output to the load drive state monitoring unit 13 and the adder 15.

  The load drive state monitoring unit 13 determines whether the load can be stably driven using the phase difference information output from the phase difference detection unit 12.

  The target phase difference information storage unit 14 stores information on the phase difference between the target motor voltage and motor current (hereinafter referred to as target phase difference information), and outputs the target phase difference information to the adder 15.

  The adder 15 subtracts the phase difference value of the phase difference information output from the phase difference detection unit 12 from the target phase difference value of the target phase difference information output from the target phase difference information storage unit 14 to obtain a target position. An error amount between the phase difference and the detected phase difference is obtained, and the error amount is output to the PI calculation unit 16.

  The PI calculation unit 16 performs a predetermined amplification on the error amount by P control to calculate a proportional error amount, integrates the error amount by I control, amplifies the integrated value, and calculates an integration error amount The proportional error amount and the integral error amount are added to obtain a drive voltage (PWM duty) reference value.

  The intermittent energization drive unit 7 sets the energization timing based on the rotor position detection signal output from the position detection circuit 17 in order to drive the motor 4 by the intermittent energization drive method in which the energization angle is less than 180 degrees and the energization stop period is provided. Then, control such as setting of a drive voltage (PWM duty) reference value based on an error between the target rotation speed and the actual rotation speed of the motor 4 is performed. As a result, the motor 4 can be driven and controlled at a desired rotational speed.

  The 180 degree energization drive unit 8 sets the energization timing based on the rotor position detection signal output from the position detection circuit 18 and drives output from the PI calculation unit 16 in order to drive the motor 4 by the 180 degree energization drive method. Control such as setting of a drive voltage (PWM duty) reference value using a voltage (PWM duty) reference value is performed. Therefore, when the motor 4 is driven by the 180-degree energization drive method, the magnitude of the drive voltage (the duty width of the PWM duty) is determined by the phase difference control feedback for controlling the phase difference between the motor voltage and the motor current to be constant. It is determined. Thereby, drive control of the motor 4 can be performed with a desired phase difference.

  The drive method selection unit 9 selects a drive method and operates the intermittent energization drive unit 7 or the 180-degree energization drive unit 8. The PWM creation unit 10 creates a PWM drive signal for driving each drive element of the inverter circuit 3 based on the output of the intermittent energization drive unit 7 or the 180-degree energization drive unit 8 for each drive element. Output.

  In addition, when the PWM creation unit 10 creates a PWM drive signal based on the output of the 180-degree conduction drive unit 8, the PWM creation unit 10 is based on the sine wave data obtained from the rotational speed command value input separately and the output of the 180-degree conduction drive unit 8. To create a PWM drive signal. As a result, the motor 4 can be driven and controlled at a desired rotational speed.

  The drive method selection unit 9 selects either the intermittent energization drive method or the 180-degree energization drive method according to the state of the motor 4 and the output of the load drive state monitoring unit 13. Here, the state of the motor 4 refers to the rotational speed, efficiency, load state, disturbance state, and the like. For example, when the rotation speed of the motor 4 is low, the intermittent drive method is selected by the drive method selection unit 9, and when the rotation number of the motor 4 is high, the 180 ° drive method is selected by the drive method selection unit 9. It may be. When a disturbance that makes it difficult to continue the 180 ° energization drive occurs, the drive method selection unit 9 selects the intermittent energization drive method. Further, an external switch for giving an external instruction is provided to the driving method selection unit 9 so that the driving method selection unit 9 can select either the intermittent energization driving method or the 180-degree energization driving method according to the external instruction. Also good. As a result, the driving method can be switched by the operator operating the external switch. For example, when driving at night, the motor 4 is driven by the 180-degree energization drive method with an emphasis on noise reduction, and the operator causes the drive method selection unit 9 to select the 180-degree energization drive method by operating an external switch. Can do.

  In order to suppress torque fluctuation, vibration, noise, and improve efficiency, it is desirable to use 180-degree energization drive and sinusoidal energization that can realize a smooth change in the drive waveform. The drive waveform for intermittent energization driving 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 in the energization stop 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 supplied to each phase.

  Next, a driving waveform in the intermittent energization driving method and a driving waveform in the 180 degree energization driving method will be described. FIG. 2 shows a drive waveform in a rectangular wave 120-degree conduction drive method that is an example of the intermittent conduction drive method, and FIG. 3 shows a drive waveform in a sine wave conduction drive method that is an example of the 180-degree conduction drive method. 2 and 3 are waveform diagrams showing PWM drive signals for driving the drive elements of the inverter circuit 3 (output signals of the PWM creation unit 10) 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 of the PWM drive signal, the voltage or current applied to the motor 4 is changed, and the rotation speed and torque are controlled.

Here, FIG. 4 shows waveforms of the U-phase voltage V _U and the U-phase current I _U of the motor 4 when the load drive state becomes unstable during the 180-degree energization drive. Since sensorless 180-degree energization driving is generally complicated and difficult to control, once control becomes unstable, it becomes difficult to return to stable control, and driving continues in the unstable state shown in FIG. Probability is high. And if it continues to drive in the unstable state shown in FIG. 4, various factors such as efficiency, torque fluctuation, vibration, and noise will deteriorate.

Therefore, in the motor control device according to the present invention shown in FIG. 1, a load drive state monitoring unit 13 is provided. The load drive state monitoring unit 13 uses the phase difference information output from the phase difference detection unit 12 to monitor whether the load (motor 4) can be stably driven. Judged as unstable control. As shown in FIG. 5, the phase difference detection unit 12 measures the phase difference between the motor voltage and the motor current for each cycle of the motor current. In FIG. 5, P1 indicates a period of 180 ° energization drive, P2 indicates a period of intermittent energization drive, V _U indicates a U-phase voltage of the motor 4, I _U indicates a U-phase current of the motor 4, and LV1 Indicates the first unstable state determination phase difference level, and LV2 indicates the second unstable state determination phase difference level. The drive method selection unit 9 switches between the 180-degree energization drive method and the intermittent energization drive method based on the determination result of the load drive state monitoring unit 13. That is, when the load drive state monitoring unit 13 determines that the load drive state is unstable in control based on the phase difference measured by the phase difference detection unit 12, the load state is quickly controlled in the drive method selection unit 9. A signal to that effect is sent, and upon receiving this signal, the drive method selection unit 9 switches the drive method from the 180-degree conduction drive method to the intermittent conduction drive method.

  The drive method selection unit 9 receives a signal from the load drive state monitoring unit 13 that the load state is unstable and switches the drive method from the 180-degree conduction drive method to the intermittent conduction drive method. The 180-degree energization drive method is not selected until the motor 4 stops. In order to realize such an operation, although not shown in FIG. 1, the drive system selection unit 9 inputs the output of the rotor position detection circuit 17 and determines the actual rotational speed of the motor 4 in the intermittent energization drive system. I have confirmed.

  However, when the motor 4 is rarely stopped when the motor 4 is started, the drive method selection unit 9 receives a signal from the load drive state monitoring unit 13 that the load state is unstable and is 180 degrees. When a predetermined time elapses after the drive system is switched from the energization drive system to the intermittent energization drive system, the intermittent energization drive system is returned to the 180-degree energization drive system, and the load state is again unstable from the load drive state monitoring unit 13. When a signal to that effect is received, the drive system is switched from the 180-degree energization drive system to the intermittent energization drive system, and the switching from the 180-degree energization drive system to the intermittent energization drive system due to unstable control of the load state is performed a predetermined number of times. If it is performed (for example, 5 times), it is desirable not to select the 180-degree energization drive method until the motor 4 is stopped once.

  A specific example of the load drive state determination performed by the load drive state monitoring unit 13 will be described with reference to the flowchart of FIG.

  When the phase difference information output from the phase difference detection unit 12 is input, the load drive state monitoring unit 13 starts the operation of the flowchart illustrated in FIG. Since the phase difference detection unit 12 measures the phase difference between the motor voltage and the motor current every cycle of the motor current, the operation of the flowchart shown in FIG. 6 is started every cycle of the motor current.

  In step S10, the load drive state monitoring unit 13 determines whether the phase difference of the phase difference information output from the phase difference detection unit 12 is greater than the first unstable state determination phase difference level LV1.

  If the phase difference of the phase difference information output from the phase difference detector 12 is greater than the first unstable state determination phase difference level LV1 (YES in step S10), the process proceeds to step S30. On the other hand, if the phase difference of the phase difference information output from the phase difference detection unit 12 is not greater than the first unstable state determination phase difference level LV1 (NO in step S10), the load drive state monitoring unit 13 It is determined whether the phase difference of the phase difference information output from the detection unit 12 is greater than the second unstable state determination phase difference level LV2 (step S20). The second unstable state determination phase difference level LV2 is larger than the first unstable state determination phase difference level LV1.

  If the phase difference of the phase difference information output from the phase difference detector 12 is larger than the second unstable state determination phase difference level LV2 (YES in step S20), the process proceeds to step S40. On the other hand, if the phase difference of the phase difference information output from the phase difference detection unit 12 is not greater than the second unstable state determination phase difference level LV2 (NO in step S20), the process proceeds to step S50.

  In step S50, the load drive state monitoring unit 13 clears the unstable state determination counter CN that is a built-in counter, and then ends the flow operation.

  In step S30, the load drive state monitoring unit 13 increments the unstable state determination counter CN, and then proceeds to step S60.

  In step S40, the load drive state monitoring unit 13 increments the unstable state determination counter CN, and then proceeds to step S60. In step S40, since the phase difference is large, the increment value is doubled in step S30. Thereby, when the phase difference is large, it is possible to reduce the time for determining that the load state is unstable in control.

  In step S60, the load drive state monitoring unit 13 determines whether or not the unstable state determination counter CN is larger than the counter value corresponding to the predetermined time T. The counter value corresponding to the predetermined time T is a multiplication value of the predetermined time T and the frequency f of the motor current. Since the operation of the flowchart shown in FIG. 6 is started every cycle of the motor current, the load driving state monitoring unit 13 measures the start interval of the flowchart shown in FIG. Can be sought.

  If the unstable state determination counter CN is not greater than the counter value corresponding to the predetermined time T (NO in step S60), the flow operation is terminated as it is. On the other hand, if the unstable state determination counter CN is greater than the counter value corresponding to the predetermined time T (YES in step S60), the load drive state monitoring unit 13 indicates that the load state is unstable in the drive system selection unit 9. (Step S70), the unstable state determination counter CN is cleared (step S80), and then the flow operation is terminated.

  As described above, in the motor control device according to the present invention shown in FIG. 1, when the load state is determined to be unstable in control, the drive system is switched from the 180-degree energization drive system to the intermittent energization drive system. Even if the control becomes unstable once in driving, it is possible to maintain the motor driving without deteriorating efficiency, torque fluctuation, vibration, noise, and other factors, improving reliability and stabilizing the rotation speed of the motor. Can be planned.

These are figures which show the example of 1 structure of the motor control apparatus which concerns on this invention. These are figures which show the drive waveform in a rectangular wave 120 degree | times energization drive system. These are figures which show the drive waveform in a sine wave energization drive system. These are figures which show a motor voltage waveform and a motor current waveform when a load drive state becomes unstable control during 180 degree | times energization drive. These are figures which show a motor voltage waveform, a motor current waveform, and the phase difference of a motor voltage and a motor current. These are the flowcharts which show the specific example of load drive state determination.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial power supply 2 Converter circuit 3 Inverter circuit 4 Three-phase brushless motor 5 DC current detection amplifier 6 Control circuit 7 Intermittent energization drive part 8 180 degree energization drive part 9 Drive system selection part 10 PWM preparation part 11 Motor current estimation part 12 Phase difference Detection unit 13 Load drive state monitoring unit 14 Target phase difference information storage unit 15 Adder 16 PI calculation unit 17, 18 Rotor position detection circuit R1 Current detection resistor R2 to R4 Resistance

Claims (3)

Power supply means for supplying power to the synchronous motor;
180 degree energization drive means for controlling the power supply means so that the synchronous motor is driven by a 180 degree energization drive method without providing an energization pause period;
Intermittent energization drive means for controlling the power supply means so that the synchronous motor is driven by an intermittent energization drive method in which an energization suspension period is provided;
Selection means for selecting one of the 180-degree energization driving method and the intermittent energization driving method;
Load driving state monitoring means for monitoring whether the driving state of the synchronous motor is unstable in control,
When the synchronous motor is driven by the 180-degree energization drive method,
The load driving state monitoring means determines that the driving state of the synchronous motor is unstable, and a predetermined time after the selection means switches the driving method from the 180-degree energization driving method to the intermittent energization driving method. When the time has elapsed, the selection unit returns the driving method from the intermittent energization driving method to the 180-degree energization driving method, and the driving state of the synchronous motor is again determined to be unstable by the load driving state monitoring unit. Switching the drive method from the 180-degree energization drive method to the intermittent energization drive method, and if the switching is performed a predetermined number of times, the 180-degree energization drive method is not selected until the synchronous motor is stopped once. Motor control device. Phase difference detecting means for detecting a phase difference between the motor voltage and the motor current of the synchronous motor,
When the load driving state monitoring means receives the detection result of the phase difference detecting means and the phase difference between the motor voltage and the motor current of the synchronous motor is larger than a predetermined value during a predetermined period, the driving state of the synchronous motor is The motor control device according to claim 1, wherein the motor control device determines that the control is unstable.   3. The motor control according to claim 2, wherein at least one reference value greater than the predetermined value is provided, and the predetermined period is changed according to a period in which a phase difference between a motor voltage and a motor current of the synchronous motor is greater than the reference value. apparatus.

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