JP7444001B2 - motor control device - Google Patents

Description

The present invention relates to a motor control device.

As a motor control device, at the control timing, the motor drive control is temporarily stopped, the peak value of the induced voltage applied to the motor is obtained as an induced voltage constant, and the temperature of the motor is estimated from the obtained induced voltage constant. Some devices control the drive of the motor by adjusting the torque command value of the motor according to the estimated temperature. A related technique is Patent Document 1.

However, in the above control device, the motor drive control is stopped from the control timing until the induced voltage reaches its peak value, so if the stop period is relatively long, the motor control amount will be large when the motor drive control is restarted. There is a concern that the controllability of the motor will deteriorate. For example, when the motor control amount increases when motor drive control is restarted, there is a risk that an overcurrent may flow through the motor, forcibly stopping the motor drive, or causing the entire motor control system to pulsate.

JP2017-108568A

An object of one aspect of the present invention is to suppress deterioration in controllability of the motor when calculating an induced voltage constant of the motor in a motor control device.

A motor control device according to one embodiment of the present invention includes a control unit that controls the drive of the motor based on the rotational speed of the motor and an induced voltage constant, and a control unit that controls the drive of the motor by stopping the drive control of the motor. The induced voltage constant is calculated by converting the voltage applied to each phase of the motor into a d-axis voltage and a q-axis voltage while cutting off the current flowing to each phase of the motor, and calculating the induced voltage constant from the q-axis voltage and the rotation speed. and a voltage constant calculation section.

As a result, the induced voltage constant can be calculated without waiting until the motor's induced voltage reaches its peak value, so it is possible to prevent the motor control amount from increasing when motor drive control is resumed. Deterioration of controllability can be suppressed.

Further, if the rotation speed is not stable when the drive control of the motor is stopped, the induced voltage constant calculation unit restarts the drive control of the motor, and restarts the drive control of the motor. Therefore, if the rotation speed becomes stable, the drive control of the motor is stopped again, and if the rotation speed is stable when the drive control of the motor is stopped again, the induced voltage constant is It may be configured to calculate.

As a result, the calculation accuracy of the induced voltage constant can be improved, and by controlling the drive of the motor using the induced voltage constant, it is possible to further suppress a decrease in the controllability of the motor.

Further, the induced voltage constant calculation unit may be configured to calculate the induced voltage constant when the drive of the motor is controlled by field weakening control before the drive control of the motor is stopped, and when the drive control of the motor is stopped. If the position of the rotor is outside the region where the induced voltage cannot be obtained, the induced voltage constant may be calculated.

As a result, the calculation accuracy of the induced voltage constant can be improved, and by controlling the drive of the motor using the induced voltage constant, it is possible to further suppress a decrease in the controllability of the motor.

Further, the induced voltage constant calculation unit may be configured to calculate the induced voltage constant based on the d-axis voltage, the q-axis voltage, and the rotation speed.

As a result, the calculation accuracy of the induced voltage constant can be improved, and by controlling the drive of the motor using the induced voltage constant, it is possible to further suppress a decrease in the controllability of the motor.

Further, the control section may be configured to include a temperature estimating section that estimates the temperature of the motor based on the induced voltage constant.

This makes it possible to determine an appropriate torque command value that corresponds to the motor temperature, and by controlling the drive of the motor using that torque command value, it is possible to further prevent a decrease in motor controllability. .

Further, a motor control device according to one embodiment of the present invention includes a drive circuit that outputs a drive signal according to a comparison result between a voltage command value obtained from the rotation speed of the motor and a voltage value of a carrier wave; and an inverter circuit that converts input DC power into AC power to drive the motor by turning on and off switching elements in response to a drive signal, and the control unit controls the current flowing through the motor and the voltage command. The rotation speed estimating unit may be configured to estimate the rotation speed based on the induced voltage constant and the induced voltage constant.

According to the present invention, in a motor control device, it is possible to suppress a decrease in controllability of the motor when calculating an induced voltage constant of the motor.

FIG. 1 is a diagram showing an example of a motor control device according to an embodiment. 5 is a flowchart showing the operation of an induced voltage constant calculating section in the first embodiment. It is a flowchart which shows the operation of the induced voltage constant calculation part in 2nd Example. It is a flow chart which shows operation of an induced voltage constant calculation part in a 3rd example. It is a figure showing an example of induced voltage. It is a flowchart which shows the operation of the induced voltage constant calculation part in 4th Example. It is a figure showing an example of induced voltage. It is a figure which shows the modification of the control device of the motor of embodiment.

Embodiments will be described in detail based on the drawings.

FIG. 1 is a diagram showing an example of a motor control device according to an embodiment.

A control device 1 shown in FIG. 1 is, for example, a control device for driving a motor M (permanent magnet synchronous motor, etc.) mounted on a vehicle (an electric forklift, a plug-in hybrid vehicle, etc.), and is connected to an inverter circuit 2. , and a control circuit 3. The motor M has an electrical angle detection unit Sp (resolver) that detects the position θ of the rotor (rotor) (the phase from the reference position of the rotor to the current position) and outputs the detected position θ to the control circuit 3. etc.). Further, voltage dividing resistors R1 and R2 connected in series are connected between the U-phase input terminal of the motor M and the ground (the negative terminal of the power supply P). Furthermore, voltage dividing resistors R3 and R4, which are connected in series with each other, are connected between the V-phase input terminal of the motor M and the ground. Further, voltage dividing resistors R5 and R6 connected in series are connected between the W-phase input terminal of the motor M and the ground.

The inverter circuit 2 converts DC power supplied from the power supply P into AC power to drive the motor M, and includes a capacitor C and switching elements SW1 to SW6 (IGBT (Insulated Gate Bipolar Transistor), etc.). , current sensors Si1 and Si2. That is, one end of the capacitor C is connected to the positive terminal of the power supply P and the collector terminals of the switching elements SW1, SW3, and SW5, and the other end of the capacitor C is connected to the negative terminal of the power supply P and each of the switching elements SW2, SW4, and SW6. Connected to the emitter terminal. A connection point between the emitter terminal of switching element SW1 and the collector terminal of switching element SW2 is connected to the U-phase input terminal of motor M via current sensor Si1. A connection point between the emitter terminal of switching element SW3 and the collector terminal of switching element SW4 is connected to the V-phase input terminal of motor M via current sensor Si2. A connection point between the emitter terminal of switching element SW5 and the collector terminal of switching element SW6 is connected to the W-phase input terminal of motor M.

Capacitor C smoothes the voltage output from power supply P to inverter circuit 2 .

The switching element SW1 is turned on when the drive signal S1 output from the control circuit 3 is at a high level, and is turned off when the drive signal S1 is at a low level. The switching element SW2 is turned on when the drive signal S2 output from the control circuit 3 is at a high level, and is turned off when the drive signal S2 is at a low level. The switching element SW3 is turned on when the drive signal S3 output from the control circuit 3 is at a high level, and is turned off when the drive signal S3 is at a low level. The switching element SW4 is turned on when the drive signal S4 output from the control circuit 3 is at a high level, and is turned off when the drive signal S4 is at a low level. The switching element SW5 is turned on when the drive signal S5 output from the control circuit 3 is at a high level, and is turned off when the drive signal S5 is at a low level. The switching element SW6 is turned on when the drive signal S6 output from the control circuit 3 is at a high level, and is turned off when the drive signal S6 is at a low level.

By repeatedly turning on and off the switching elements SW1 to SW6, the DC voltage output from the power supply P is converted into AC voltages Vu, Vv, and Vw whose phases differ by 120 degrees from each other. Then, AC voltage Vu is applied to the U-phase input terminal of motor M, AC voltage Vv is applied to the V-phase input terminal of motor M, and AC voltage Vw is applied to the W-phase input terminal of motor M. By being applied, alternating currents Iu, Iv, and Iw whose phases differ by 120 degrees from each other flow through the motor M, and the rotor of the motor M rotates.

The current sensor Si1 includes a Hall element, a shunt resistor, and the like, and detects the alternating current Iu flowing in the U phase of the motor M, and outputs the detected alternating current Iu to the control circuit 3. Further, the current sensor Si2 includes a Hall element, a shunt resistor, and the like, and detects the alternating current Iv flowing in the V phase of the motor M, and outputs the detected alternating current Iv to the control circuit 3.

The control circuit 3 includes a storage section 4, a drive circuit 5, and a calculation section 6.

The storage unit 4 is composed of a RAM (Random Access Memory), a ROM (Read Only Memory), or the like.

The drive circuit 5 is constituted by an IC (Integrated Circuit), etc., and combines the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* output from the calculation unit 6 with the carrier wave voltage. The driving signals S1 to S6 corresponding to the comparison results are output to the respective gate terminals of the switching elements SW1 to SW6. Note that the carrier wave may be a triangular wave, a sawtooth wave, a reverse sawtooth wave, or the like.

For example, when the U-phase voltage command value Vu* is equal to or higher than the carrier wave voltage value, the drive circuit 5 outputs the high-level drive signal S1 and the low-level drive signal S2, and the U-phase voltage command value Vu When * is smaller than the voltage value of the carrier wave, a low-level drive signal S1 and a high-level drive signal S2 are output. Further, when the V-phase voltage command value Vv* is equal to or higher than the voltage value of the carrier wave, the drive circuit 5 outputs the high-level drive signal S3 and the low-level drive signal S4, and outputs the V-phase voltage command value Vv When * is smaller than the voltage value of the carrier wave, a low level drive signal S3 is outputted, and a high level drive signal S4 is outputted. Further, when the W-phase voltage command value Vw* is equal to or higher than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S5 and a low-level drive signal S6, When * is smaller than the voltage value of the carrier wave, a low level drive signal S5 is outputted, and a high level drive signal S6 is outputted.

The calculation section 6 is composed of a microcomputer or the like, and includes a rotation speed calculation section 7, a subtraction section 8, a temperature estimation section 9, a torque control section 10, a torque/current command value conversion section 11, and a coordinate conversion section 12. , a subtraction section 13 , a subtraction section 14 , a current control section 15 , a coordinate conversion section 16 , and an induced voltage constant calculation section 17 . For example, by executing the program stored in the storage unit 4 by the microcomputer, the rotation speed calculation unit 7, the subtraction unit 8, the temperature estimation unit 9, the torque control unit 10, the torque/current command value conversion unit 11, the coordinate A conversion section 12, a subtraction section 13, a subtraction section 14, a current control section 15, a coordinate conversion section 16, and an induced voltage constant calculation section 17 are configured.

The rotation speed calculation unit 7 calculates the rotation speed ω of the motor M using the position θ detected by the electrical angle detection unit Sp. For example, the rotation speed calculation unit 7 calculates the rotation speed ω by dividing the position θ by a predetermined time (such as the clock cycle of the calculation unit 6).

The subtraction unit 8 calculates the rotation speed difference Δω between the rotation speed command value ω* input from the outside and the rotation speed ω output from the rotation speed calculation unit 7.

The temperature estimation unit 9 estimates the temperature T of the motor M based on the induced voltage constant Ψa output from the induced voltage constant calculation unit 17. For example, the temperature estimation unit 9 refers to information stored in the storage unit 4 in which the induced voltage constant of the motor M and the temperature of the motor M are associated with each other, and outputs the output from the induced voltage constant calculation unit 17. The temperature corresponding to the induced voltage constant Ψa corresponding to the induced voltage constant Ψa is output as the temperature T. Note that the induced voltage constant Ψa is a value corresponding to the peak value of the induced voltage applied to any phase of the motor M after the current flowing to any phase of the motor M is cut off.

The torque control unit 10 outputs a torque command value T* using the rotational speed difference Δω output from the subtraction unit 8 and the temperature T output from the temperature estimation unit 9. For example, the torque control unit 10 refers to information stored in the storage unit 4 in which the rotation speed of the motor M and the torque of the motor M are associated with each other, and determines the rotation speed corresponding to the rotation speed difference Δω. The torque corresponding to is set as the torque command value T*. Further, when the temperature T output from the temperature estimating unit 9 is equal to or higher than the temperature threshold Tth, the torque control unit 10 reduces the torque command value T* by a predetermined value and outputs the torque command value T*, so that the temperature T is smaller than the temperature threshold Tth. In this case, the torque command value T* is output as is. Note that the temperature threshold Tth is the maximum value of the temperature T in a state where the permanent magnet provided in the rotor of the motor M is not demagnetized.

The torque/current command value conversion unit 11 converts the torque command value T* output from the torque control unit 10 into a d-axis current command value Id* and a q-axis current command value Iq*. For example, the torque/current command value conversion unit 11 converts information stored in the storage unit 4 that associates the torque of the motor M with the d-axis current command value Id* and the q-axis current command value Iq*. With reference to this, a d-axis current command value Id* and a q-axis current command value Iq* corresponding to the torque corresponding to the torque command value T* are output.

The coordinate conversion unit 12 determines the alternating current Iw flowing in the W phase of the motor M using the alternating current Iu detected by the current sensor Si1 and the alternating current Iv detected by the current sensor Si2. Note that the currents detected by the current sensors Si1 and Si2 are not limited to the combination of alternating currents Iu and Iv, but may be a combination of alternating currents Iv and Iw or a combination of alternating currents Iu and Iw. When alternating currents Iv and Iw are detected by current sensors Si1 and Si2, coordinate conversion unit 12 uses alternating currents Iv and Iw to obtain alternating current Iu. Furthermore, when the current sensors Si1 and Si2 detect the alternating currents Iu and Iw, the coordinate conversion unit 12 uses the alternating currents Iu and Iw to obtain the alternating current Iv.

Further, the coordinate conversion unit 12 uses the position θ detected by the electrical angle detection unit Sp to convert the alternating currents Iu, Iv, and Iw into d-axis current Id (current component for controlling the back electromotive force) and q-axis Convert to current Iq (current component for controlling torque). For example, the coordinate conversion unit 12 converts alternating currents Iu, Iv, and Iw into a d-axis current Id and a q-axis current Iq using a conversion matrix C1 shown in Equation 1 below. Note that when the drive control of the motor M is resumed after the drive control of the motor M is temporarily stopped, noise included in the position θ detected by the electrical angle detection unit Sp and alternating current when converting from an analog value to a digital value are There is a possibility that the controllability of the motor M may deteriorate due to an increase in the control amount of the motor M (rotational speed difference Δω, etc.) due to the quantization error included in Iu and Iv.

Further, when the inverter circuit 2 further includes a current sensor Si3 that detects the alternating current Iw flowing in the W phase of the motor M in addition to the current sensors Si1 and Si2, the coordinate conversion section 12 detects the The alternating currents Iu, Iv, and Iw detected by the current sensors Si1 to Si3 may be converted into the d-axis current Id and the q-axis current Iq using the position θ.

The subtraction unit 13 calculates a current difference ΔId between the d-axis current command value Id* output from the torque/current command value conversion unit 11 and the d-axis current Id output from the coordinate conversion unit 12.

The subtraction unit 14 calculates a current difference ΔIq between the q-axis current command value Iq* output from the torque/current command value conversion unit 11 and the q-axis current Iq output from the coordinate conversion unit 12.

The current control unit 15 determines the d-axis voltage command value Vd* and the q-axis voltage command value by PI (Proportional Integral) control using the current difference ΔId output from the subtraction unit 13 and the current difference ΔIq output from the subtraction unit 14. Calculate Vq*. For example, the current control unit 15 calculates the d-axis voltage command value Vd* using Equation 2 below, and calculates the q-axis voltage command value Vq* using Equation 3 below. Note that Kp is the constant of the proportional term of PI control, Ki is the constant of the integral term of PI control, Lq is the q-axis inductance of the coil that makes up motor M, and Ld is the d-axis inductance of the coil that makes up motor M. Let ω be the rotational speed output from the rotational speed calculation unit 7, and Ψa be the induced voltage constant output from the induced voltage constant calculation unit 17.

d-axis voltage command value Vd* = Kp x current difference ΔId + Ki x ∫ (current difference ΔId) - ωLqIq...Formula 2
Q-axis voltage command value Vq*=Kp×current difference ΔIq+Ki×∫ (current difference ΔIq)+ωLdId+ωΨa...Formula 3

That is, the current control unit 15 calculates the d-axis voltage command value Vd* so that the current difference ΔId between the d-axis current Id and the d-axis current command value Id* becomes small, and also calculates the d-axis voltage command value Vd* between the q-axis current Iq and the q-axis current command The q-axis voltage command value Vq* is calculated so that the current difference ΔIq with the value Iq* becomes small.

The coordinate conversion unit 16 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into the U-phase voltage command value Vu* and the V-phase voltage command using the position θ detected by the electrical angle detection unit Sp. It is converted into a value Vv* and a W-phase voltage command value Vw*. For example, the coordinate conversion unit 16 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into the U-phase voltage command value Vu* and the V-phase voltage command value using the transformation matrix C2 shown in equation 4 below. Vv* and W-phase voltage command value Vw*.

Note that the rotation speed calculation section 7, the subtraction section 8, the temperature estimation section 9, the torque control section 10, the torque/current command value conversion section 11, the coordinate conversion section 12, the subtraction section 13, the subtraction section 14, the current control section 15, and It is assumed that the coordinate transformation section 16 constitutes a control section. That is, the control unit controls the drive of the motor M based on the rotation speed ω of the motor M and the induced voltage constant Ψa.

The induced voltage constant calculation unit 17 calculates the induced voltage applied to each phase of the motor M when the alternating currents Iu, Iv, and Iw flowing through each phase of the motor M are cut off by stopping the drive control of the motor M. The voltages Vu, Vv, and Vw are converted into a d-axis voltage Vd and a q-axis voltage Vq, and an induced voltage constant Ψa is calculated from at least the q-axis voltage Vq and the rotation speed ω. Note that cutting off the alternating currents Iu, Iv, Iw means a state in which the alternating currents Iu, Iv, Iw are reduced after the drive control of the motor M is stopped. For example, this is a state in which the values of alternating currents Iu, Iv, and Iw have decreased to almost zero.

<First example>
FIG. 2 is a diagram showing an example of the operation of the induced voltage constant calculating section 17 in the first embodiment.

First, when the induced voltage constant calculation timing comes, the induced voltage constant calculation unit 17 stops the drive control of the motor M (step S11), and then acquires the voltages Vu, Vv, and Vw (step S12). For example, the induced voltage constant calculation unit 17 sends an instruction to stop the drive control of the motor M to the current control unit 15 or the coordinate conversion unit 16 when the induced voltage constant calculation timing comes. When the current control unit 15 receives an instruction to stop the drive control of the motor M, the current control unit 15 forcibly sets the d-axis voltage command value Vd* and the q-axis voltage command value Vq* to zero. Alternatively, upon receiving an instruction to stop the drive control of the motor M, the coordinate conversion unit 16 forces the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw*, respectively. set to zero. Then, each of the drive signals S1 to S6 becomes a low level, and each of the switching elements SW1 to SW6 is turned off at all times, cutting off the current flowing through each phase of the motor M. Then, the induced voltage constant calculation unit 17 calculates the voltage Vu applied to the U phase of the motor M based on the voltage applied to the connection point of the voltage dividing resistors R1 and R2 and the resistance values of the voltage dividing resistors R1 and R2. Further, the induced voltage constant calculation unit 17 calculates the voltage Vv applied to the V phase of the motor M from the voltage applied to the connection point of the voltage dividing resistors R3 and R4 and the resistance values of the voltage dividing resistors R3 and R4. Further, the induced voltage constant calculation unit 17 calculates the voltage Vw based on the voltage applied to the connection point of the voltage dividing resistors R5 and R6 and the resistance values of the voltage dividing resistors R5 and R6. Note that a voltage sensor may be provided for each phase of the motor M instead of the voltage dividing resistors R1 to R6. When configured in this way, the induced voltage constant calculation unit 17 acquires the voltage Vu with the voltage sensor provided on the U phase of the motor M, acquires the voltage Vv with the voltage sensor provided on the V phase of the motor M, and The voltage Vw is acquired by a voltage sensor provided on the W phase of M.

Next, the induced voltage constant calculation unit 17 converts the voltages Vu, Vv, and Vw into a d-axis voltage Vd and a q-axis voltage Vq (step S13). For example, the induced voltage constant calculation unit 17 converts the voltages Vu, Vv, and Vw into a d-axis voltage Vd and a q-axis voltage Vq using the conversion matrix C1 shown in Equation 1 above.

Next, the induced voltage constant calculation unit 17 calculates the induced voltage constant Ψa based on the q-axis voltage Vq and the rotation speed ω (step S14). For example, the induced voltage constant calculation unit 17 calculates the induced voltage constant Ψa by calculating the induced voltage constant Ψa=q-axis voltage Vq/rotation speed ω. Note that the d-axis voltage Vd and the q-axis voltage Vq are determined by the following equation 5, R is a resistance component of a coil constituting the motor M, and p is a differential operator. Thereby, by substituting zero for the d-axis current Id and the q-axis current Iq in Equation 5 below, it is possible to obtain the induced voltage constant Ψa=q-axis voltage Vq/rotation speed ω.

Then, the induced voltage constant calculation unit 17 restarts the drive control of the motor M, and ends the calculation process of the induced voltage constant Ψa (step S15). For example, the induced voltage constant calculation unit 17 sends an instruction to restart the drive control of the motor M to the current control unit 15 or the coordinate conversion unit 16. Upon receiving the instruction to restart the drive control of the motor M, the current control unit 15 sets the d-axis voltage command value Vd* and the q-axis voltage command value Vq obtained by PI control using the current difference ΔId and the current difference ΔIq. Output *. Alternatively, upon receiving an instruction to restart drive control of the motor M, the coordinate conversion unit 16 converts the U-phase voltage command values Vu*, V converted from the d-axis voltage command value Vd* and the q-axis voltage command value Vq*. A phase voltage command value Vv* and a W-phase voltage command value Vw* are output.

Note that the induced voltage constant calculation unit 17 may be configured to calculate a plurality of induced voltage constants and output the average value of the induced voltage constants as the induced voltage constant Ψa. Thereby, the calculation accuracy of the induced voltage constant Ψa can be improved.

According to the first embodiment, the induced voltage constant Ψa can be calculated at an arbitrary induced voltage constant calculation timing without waiting until the induced voltage of the motor M reaches its peak value, so that the drive control of the motor M can be restarted. At times, the control amount of the motor M can be prevented from increasing, and the controllability of the motor M can be prevented from deteriorating.

<Second example>
FIG. 3 is a diagram showing an example of the operation of the induced voltage constant calculating section 17 in the second embodiment. Note that steps S11 to S13 and S15 shown in FIG. 3 are the same as steps S11 to S13 and S15 shown in FIG. 2, so a description thereof will be omitted.

After converting the voltages Vu, Vv, and Vw into the d-axis voltage Vd and the q-axis voltage Vq (step S13), the induced voltage constant calculation unit 17 calculates the induced voltage based on the d-axis voltage Vd, the q-axis voltage Vq, and the rotation speed ω. A constant Ψa is calculated (step S14'). For example, the induced voltage constant calculation unit 17 calculates the induced voltage constant Ψa by calculating the following equation 6. Note that |Vdq| is a value equivalent to the product of the peak value of the induced voltage applied to any phase of motor M after current stops flowing to any phase of motor M, and (3/2) ^1/2 . , shall be determined by the following equation 7. In addition, the d-axis voltage Vd and the q-axis voltage Vq are determined by the following equation 8, and Δθ is determined by the offset error of the electrical angle detection unit Sp and the quantization error when converting the position θ from an analog value to a digital value. Let it be the error included in θ. That is, the induced voltage constant calculation unit 17 calculates the induced voltage constant Ψa by dividing the value of the root of the sum of the square of the d-axis voltage Vd and the square of the q-axis voltage Vq by the rotational speed ω.

Note that the induced voltage constant calculation unit 17 may be configured to calculate a plurality of induced voltage constants and output the average value of the induced voltage constants as the induced voltage constant Ψa. Thereby, the calculation accuracy of the induced voltage constant Ψa can be improved.

According to the second embodiment, as in the first embodiment, the induced voltage constant Ψa can be calculated without waiting until the induced voltage of the motor M reaches its peak value. It is possible to suppress the control amount of the motor M from increasing, and it is possible to suppress a decrease in the controllability of the motor M.

Further, according to the second embodiment, since the calculation accuracy of the induced voltage constant Ψa can be improved, the drive controllability of the motor M is reduced by controlling the drive of the motor M using the induced voltage constant Ψa. This can be further suppressed.

<Third Example>
FIG. 4 is a diagram showing an example of the operation of the induced voltage constant calculating section 17 in the third embodiment. Note that steps S11 to S15 shown in FIG. 4 are the same as steps S11 to S15 shown in FIG. 2, and therefore the description thereof will be omitted.

At the induced voltage constant calculation timing, the induced voltage constant calculation unit 17 stops the drive control of the motor M (step S11), and then determines whether the rotation speed ω is stable (S16). For example, if the magnitude of the fluctuation in the rotational speed ω is greater than or equal to the threshold th1, the induced voltage constant calculation unit 17 determines that the rotational speed ω is not stable, and the magnitude of the fluctuation in the rotational speed ω is less than the threshold th1. If it is small, it is determined that the rotational speed ω is stable. Alternatively, if the magnitude of variation in the torque command value T* output from the torque control unit 10 is greater than or equal to the threshold th2, the induced voltage constant calculation unit 17 determines that the rotational speed ω is not stable, and the torque command If the magnitude of the variation in the value T* is smaller than the threshold th2, it is determined that the rotation speed ω is stable. Alternatively, the induced voltage constant calculation unit 17 determines that the rotation speed ω is not stable when the magnitude of voltage fluctuation of any phase of the motor M is equal to or greater than the threshold th3, and the induced voltage constant calculation unit 17 determines that the rotation speed ω is not stable. If the magnitude of the voltage fluctuation is smaller than the threshold th3, it is determined that the rotation speed ω is stable.

Next, when the induced voltage constant calculation unit 17 determines that the rotation speed ω is not stable (step S16: No), the rotation speed ω is stabilized after restarting drive control of the motor M (step S17). It is repeatedly determined whether or not the rotation speed ω is stable until the rotation speed ω is stable (step S18: No). If it is determined that the rotation speed ω is stable (step S18: Yes), the process returns to step S11 and the motor M is Stop drive control.

When the induced voltage constant calculation unit 17 determines that the rotational speed ω is stable (step S16: Yes), it performs the processes of steps S12 to S15.

That is, if the rotation speed ω becomes unstable due to variations in the load (torque) of the motor M, as shown in FIG. 5(a), when the drive control of the motor M is stopped (position θ1), the motor M Since the amplitude value of the induced voltage applied to any phase changes, the calculation accuracy of the induced voltage constant Ψa decreases. Therefore, in the third embodiment, when the rotation speed ω is fluctuating, as shown in FIG. By stabilizing the rotational speed ω close to ω*, the amplitude value of the induced voltage is stabilized. As a result, in the third embodiment, when the drive control of the motor M is stopped again (position θ3), the induced voltage constant Ψa can be calculated by stabilizing the amplitude value of the induced voltage. The accuracy of calculation can be improved. That is, if the rotation speed ω is not stable when the drive control of the motor M is stopped, the induced voltage constant calculation unit 17 restarts the drive control of the motor M; Therefore, if the rotation speed ω becomes stable, the drive control of the motor M is stopped again, and if the rotation speed ω is stable when the drive control of the motor M is stopped again, the induced voltage constant Ψa is calculate.

Note that the induced voltage constant calculation unit 17 may be configured to calculate a plurality of induced voltage constants and output the average value of the induced voltage constants as the induced voltage constant Ψa. Thereby, the calculation accuracy of the induced voltage constant Ψa can be improved.

Further, step S14 shown in FIG. 4 may be replaced with step S14' shown in FIG. 3.

According to the third embodiment, as in the first embodiment, the induced voltage constant Ψa can be calculated without waiting until the induced voltage of the motor M reaches its peak value. It is possible to suppress the control amount of the motor M from increasing, and it is possible to suppress a decrease in the controllability of the motor M.

Further, according to the third embodiment, since the calculation accuracy of the induced voltage constant Ψa can be improved, the drive controllability of the motor M is reduced by controlling the drive of the motor M using the induced voltage constant Ψa. This can be further suppressed.

<Fourth Example>
FIG. 6 is a diagram showing an example of the operation of the induced voltage constant calculating section 17 in the fourth embodiment. Note that steps S11 to S15 shown in FIG. 6 are the same as steps S11 to S15 shown in FIG. 2, so the explanation thereof will be omitted.

The induced voltage constant calculation unit 17 stops the drive control of the motor M by field weakening control after stopping the drive control of the motor M at the induced voltage constant calculation timing (step S11) and before stopping the drive control of the motor M. It is determined whether or not it has been controlled (S19). For example, if the d-axis current command value Id* output from the torque/current command value converter 11 is a negative value before stopping the drive control of the motor M, the induced voltage constant calculation unit 17 performs field weakening control. If the d-axis current command value Id* is zero, it is determined that the drive of the motor M was not controlled by field weakening control.

Next, when the induced voltage constant calculation unit 17 determines that the drive of the motor M is not controlled by the field weakening control (step S19: No), it performs the processes of steps S12 to S15.

On the other hand, when the induced voltage constant calculation unit 17 determines that the drive of the motor M is controlled by field weakening control (step S19: Yes), it acquires the position θ of the rotor of the motor M (step S20).

In addition, the induced voltage constant calculation unit 17 calculates a region (where the voltages Vu, Vv, and Vw are fixed to the voltage of the power supply P and the induced voltage cannot be correctly acquired among all the positions θ when the rotor rotates once). Hereinafter, the area in which induced voltage cannot be obtained is determined (step S21). For example, the induced voltage constant calculation unit 17 calculates the area where the induced voltage cannot be obtained from the d-axis current command value Id* and the q-axis current command value Iq* output from the torque/current command value conversion unit 11. Note that the order of steps S20 and S21 may be interchanged.

Then, when the induced voltage constant calculation unit 17 determines that the position θ is outside the region where induced voltage cannot be acquired, that is, when it determines that the position θ is within the region where the induced voltage can be correctly acquired (step S22 :Yes), the processes of steps S12 to S15 are performed. For example, in step S12, the induced voltage constant calculation unit 17 calculates that voltage Vu=peak value of induced voltage×sin(θ-π/2), voltage Vv=peak value of induced voltage×sin(θ-π/2-2π /3) and voltage Vw=peak value of induced voltage×sin(θ−π/2−4π/3), the voltages Vu, Vv, and Vw are determined.

That is, if the drive of the motor M is not controlled by field weakening control before the drive control of the motor M is stopped, the peak of the induced voltage applied to any phase of the motor M as shown in FIG. 7(a) Since the value does not exceed the voltage Vp at the positive terminal and the voltage Vn at the negative terminal of the power supply P, the induced voltage constant calculation unit 17 can correctly obtain the induced voltage at any position θ. On the other hand, if the drive of the motor M is controlled by field weakening control before the drive control of the motor M is stopped, as shown in FIG. 7(b), the peak value of the induced voltage applied to any phase of the motor M Since the vicinity is fixed to the voltage Vp and the voltage Vn, the induced voltage constant calculation unit 17 cannot correctly acquire the induced voltage near the peak value (the induced voltage in the region where induced voltage cannot be obtained). Therefore, in the fourth embodiment, when the drive of the motor M is controlled by field weakening control before the drive control of the motor M is stopped, only when the position θ is outside the region where the induced voltage cannot be obtained, that is, the induced The induced voltage constant Ψa is calculated only when the voltage can be acquired correctly. Thereby, the calculation accuracy of the induced voltage constant Ψa can be improved.

Note that the induced voltage constant calculation unit 17 may be configured to calculate a plurality of induced voltage constants and output the average value of the induced voltage constants as the induced voltage constant Ψa. Thereby, the calculation accuracy of the induced voltage constant Ψa can be improved.

Further, step S14 shown in FIG. 6 may be replaced with step S14' shown in FIG. 3.

According to the fourth embodiment, as in the first embodiment, the induced voltage constant Ψa can be calculated without waiting until the induced voltage of the motor M reaches its peak value. It is possible to suppress the control amount of the motor M from increasing, and it is possible to suppress a decrease in the controllability of the motor M.

Further, according to the fourth embodiment, since the calculation accuracy of the induced voltage constant Ψa can be improved, the drive controllability of the motor M is reduced by controlling the drive of the motor M using the induced voltage constant Ψa. This can be further suppressed.

Note that the present invention is not limited to the above-described embodiments, and various improvements and changes can be made without departing from the gist of the present invention.

<Modified example>
FIG. 8 is a diagram showing a modification of the control device 1 for the motor M according to the embodiment. In FIG. 8, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and their explanations will be omitted.

The control device 1 shown in FIG. 8 differs from the control device 1 shown in FIG. 18. For example, the rotation speed estimating section 18 is configured by a microcomputer executing a program stored in the storage section 4.

The rotation speed estimation unit 18 receives the d-axis current Id and the q-axis current Iq output from the coordinate conversion unit 12, and the d-axis voltage command value Vd* and the q-axis voltage command value Vq* output from the current control unit 15. The rotation speed ω and position θ are estimated using . For example, the rotation speed estimation unit 18 calculates the rotation speed ω using the voltage equation shown in Equation 5 above, and calculates the position θ by multiplying the calculated rotation speed ω by a predetermined time (such as the clock cycle of the calculation unit 6). demand. Note that Ψa is the induced voltage constant output from the induced voltage constant calculating section 17.

The induced voltage constant calculation unit 17 calculates the induced voltage constant Ψa according to the first to fourth embodiments described above. Note that the induced voltage constant calculation section 17 uses the rotation speed ω output from the rotation speed estimation section 18 when calculating the induced voltage constant Ψa. Further, a rotation speed calculation section 18, a subtraction section 8, a temperature estimation section 9, a torque control section 10, a torque/current command value conversion section 11, a coordinate conversion section 12, a subtraction section 13, a subtraction section 14, a current control section 15, and It is assumed that the coordinate transformation section 16 constitutes a control section.

Even with this configuration, the induced voltage constant Ψa can be calculated without waiting until the induced voltage of the motor M reaches its peak value, so the control amount of the motor M increases when drive control of the motor M is restarted. Therefore, it is possible to suppress the controllability of the motor M from deteriorating.

Furthermore, since the control device 1 of the embodiment can relatively shorten the period in which the drive control of the motor M is stopped when calculating the induced voltage constant Ψa, the control device 1 shown in FIG. The error included in the rotation speed ω when estimating the number ω is relatively large, and the control amount of the motor M (rotation speed difference Δω, etc.) tends to become large when the drive control of the motor M is temporarily stopped and restarted. It is particularly effective against

1 Control device 2 Inverter circuit 3 Control circuit 4 Storage section 5 Drive circuit 6 Arithmetic section 7 Rotational speed calculation section 8 Subtraction section 9 Temperature estimation section 10 Torque control section 11 Torque/current command value conversion section 12 Coordinate conversion section 13 Subtraction section 14 Subtraction unit 15 Current control unit 16 Coordinate conversion unit 17 Induced voltage constant calculation unit 18 Rotation speed estimation unit

Claims (6)

a control unit that controls driving of the motor based on the rotation speed of the motor and an induced voltage constant;
When the current flowing through each phase of the motor is cut off by stopping the drive control of the motor, the voltage applied to each phase of the motor is converted into a d-axis voltage and a q-axis voltage, and the q-axis voltage and an induced voltage constant calculation unit that calculates the induced voltage constant based on the rotation speed;
Equipped with
The induced voltage constant calculation unit restarts the drive control of the motor if the rotation speed is not stable when the drive control of the motor is stopped;
If the rotation speed is stabilized by restarting the drive control of the motor, stopping the drive control of the motor again;
A motor control device that calculates the induced voltage constant if the rotational speed is stable when drive control of the motor is stopped again . The motor control device according to claim 1,
The induced voltage constant calculation unit is configured to determine whether the rotor of the motor is controlled when the drive control of the motor is controlled by field weakening control before the drive control of the motor is stopped, and when the drive control of the motor is stopped. A motor control device characterized in that the induced voltage constant is calculated when the position of is outside a region where induced voltage cannot be obtained. The motor control device according to claim 1 or 2 ,
The motor control device, wherein the induced voltage constant calculation unit calculates the induced voltage constant based on the d-axis voltage, the q-axis voltage, and the rotation speed. The motor control device according to any one of claims 1 to 3 ,
A motor control device, wherein the control unit includes a temperature estimation unit that estimates the temperature of the motor based on the induced voltage constant. The motor control device according to any one of claims 1 to 4 ,
a drive circuit that outputs a drive signal according to a comparison result between a voltage command value determined by the rotation speed of the motor and a voltage value of a carrier wave;
an inverter circuit that converts input DC power into AC power to drive the motor by turning on and off a switching element according to the drive signal;
Equipped with
The control device for a motor is characterized in that the control unit includes a rotation speed estimation unit that estimates the rotation speed based on the current flowing through the motor, the voltage command value, and the induced voltage constant. The motor control device according to claim 1,
The induced voltage constant calculation section includes:
If the magnitude of the fluctuation in the rotational speed is greater than or equal to a first threshold value, if the magnitude of fluctuation in the torque command value of the motor is greater than or equal to a second threshold value, or if the magnitude of fluctuation in the voltage of any phase of the motor is If the magnitude is greater than or equal to a third threshold, it is determined that the rotation speed is not stable;
If the magnitude of the variation in the rotational speed is smaller than the first threshold value, if the magnitude of the variation in the torque command value is smaller than the second threshold value, or if the magnitude of the variation in the voltage of the arbitrary phase is smaller than the first threshold value, If it is smaller than the third threshold, it is determined that the rotation speed is stable.
A motor control device characterized by:

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