Motor control device and motor control method

Abstract

To provide a motor control device and a motor control method capable of accurately determining idling of a three-phase motor even when a power supply voltage is high.SOLUTION: A motor control device 100 includes a current detection unit 30 that detects a current input to the motor 101 and a control unit 10 that controls driving of the motor 101. Then, the control unit 10 includes a three-phase to two-phase conversion unit 14 that obtains a q-axis current value Iq by converting the three-phase current input to the motor 101 detected by the current detection unit 30 into two phases, and a determination unit 16 that determines that the motor 101 is idling when the q-axis current value Iq is equal to or less than a preset determination threshold value S.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a motor control device and a motor control method.

Background Art

[0002] Conventionally, an inverter device for driving an electric motor has been known (see, for example, Patent Document 1).

[0003] The inverter device described in Patent Document 1 operates the electric motor at a variable speed. In this inverter device, the motor current is measured by a current detector provided in the DC main circuit section inside the inverter. Then, when the measured motor current has decreased to a preset threshold value (motor no-load current value) and a preset time has elapsed, the no-load operation state (idle state and cut-off operation state) of the electric motor is detected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, in the inverter device described in Patent Document 1, since the motor current is measured by a current detector provided in the DC main circuit section inside the inverter, the power supply current output from the power supply is measured as the motor current. In this case, when controlling the rotation speed of the motor to be constant, the power supply current becomes smaller when the input power supply voltage is large. Therefore, when the power supply voltage is large, the measured current value becomes small, so that even if the motor is not in the no-load operation state, the measured current value falls below the threshold value (motor no-load current value) for determining the no-load operation state. As a result, there is a problem that when the power supply voltage is large, the no-load operation (idle rotation) of the electric motor (three-phase motor) cannot be accurately determined.

[0006] The present invention has been made to solve the above problems, and one object of the present invention is to provide a motor control device and a motor control method capable of accurately determining the idling of a three-phase motor even when the power supply voltage is large.

Means for Solving the Problems

[0007] To achieve the above object, a motor control device according to a first aspect of the present invention is a motor control device that performs vector control of driving a three-phase motor by a d-axis current command and a q-axis current command, and includes a current detection unit that detects a current input to the three-phase motor, and a control unit that controls the driving of the three-phase motor. The control unit includes a three-phase to two-phase conversion unit that obtains a q-axis current value by converting the three-phase current input to the three-phase motor detected by the current detection unit into two phases, and a determination unit that determines that the three-phase motor is idling when the q-axis current value is less than or equal to a preset determination threshold value. The determination unit, when the rotational speed of the three-phase motor is less than a predetermined minimum rotational speed by the q-axis current value Idling of the three-phase motor of Determination is performed without fail, and when the rotational speed is equal to or greater than the minimum rotational speed by the q-axis current value is configured to determine the idling of the three-phase motor. Here, the "idling" mentioned here means driving in a no-load operation state of the three-phase motor.

[0008] In the motor control device according to the first aspect of the present invention, as described above, when the q-axis current value is equal to or less than a preset determination threshold value, it is determined that the three-phase motor is idling. Here, the q-axis current value used for vector control of the drive of the three-phase motor is a current value indicating a vector component in the direction of torque for rotating the three-phase motor among the currents input to the three-phase motor. Since this q-axis current value is not affected by the power supply voltage, the acquired q-axis current value does not decrease even when the power supply voltage is large. Therefore, by determining that the three-phase motor is idling when the q-axis current value is equal to or less than the preset determination threshold value, it is possible to accurately determine the idling of the three-phase motor even when the power supply voltage is large. Further, since it is possible to determine the idling of the three-phase motor based on the q-axis current value calculated when the drive of the three-phase motor is vector-controlled, it is possible to easily determine the idling of the three-phase motor without providing a new configuration. Further, in vector control, the q-axis current value is calculated as a direct current. Therefore, the processing load required for arithmetic processing can be reduced as compared with the case where the idling is determined directly using the alternating current input to the three-phase motor.

[0009] In the motor control device according to the first aspect, preferably, the determination unit is configured to determine that the three-phase motor is idling when the q-axis current value is equal to or less than a determination threshold value set in advance so as to increase in accordance with an increase in the rotation speed of the three-phase motor.

[0010] With this configuration, since the q-axis current value for vector control of the three-phase motor increases in accordance with an increase in the rotation speed of the three-phase motor, the idling of the three-phase motor can be detected more accurately by presetting the determination threshold value for determining idling so as to increase in accordance with an increase in the rotation speed of the three-phase motor.

[0011] In the motor control device according to the first aspect, preferably, the control unit further includes a rotation speed acquisition unit that acquires the rotation speed of the three-phase motor, and the determination unit does not determine the idling of the three-phase motor when the rotation speed acquired by the rotation speed acquisition unit is less than a predetermined minimum rotation speed, and is configured to determine the idling of the three-phase motor when the rotation speed is equal to or higher than the minimum rotation speed.

[0012] Here, when the rotation speed of the three-phase motor is low, the difference between the q-axis current value acquired in a state where there is a load (normal state) on the three-phase motor and the q-axis current value acquired in a state where the three-phase motor is idling becomes small. Therefore, when the rotation speed of the three-phase motor is low, it is considered difficult to determine the idling of the three-phase motor based on a preset determination threshold value. In consideration of this, in the present invention, the determination unit does not determine the idling of the three-phase motor when the rotation speed acquired by the rotation speed acquisition unit is less than a predetermined minimum rotation speed, and determines the idling of the three-phase motor when the rotation speed is equal to or higher than the minimum rotation speed. With this configuration, when the rotation speed of the three-phase motor is low, the idling of the three-phase motor is not determined, so that it is possible to suppress misjudgment of the idling of the three-phase motor.

[0013] Further, a motor control method according to a second aspect of the present invention is a motor control method for vector-controlling the drive of a three-phase motor by a d-axis current command and a q-axis current command, including a step of detecting a current input to the three-phase motor, a step of acquiring a q-axis current value by converting three-phase currents input to the three-phase motor into two phases, and a step of determining that the three-phase motor is idling when the q-axis current value is equal to or less than a preset determination threshold value. The step of determining that the three-phase motor is idling does not perform the determination when the rotation speed of the three-phase motor is less than a predetermined minimum rotation speed, and by the q-axis current value Idling of the three-phase motor of Determination is performed instead, when the rotation speed is equal to or higher than the minimum rotation speed by the q-axis current value includes a step of determining the idling of the three-phase motor.

[0014] In the motor control method according to the second aspect of the present invention, as described above, when the q-axis current value is equal to or less than a preset determination threshold value, it is determined that the three-phase motor is idling. Here, the q-axis current value used for vector control of the drive of the three-phase motor is a current value indicating the vector component in the torque direction for rotating the three-phase motor among the currents input to the three-phase motor. Since this q-axis current value is not affected by the power supply voltage, the acquired q-axis current value does not decrease even when the power supply voltage is large. Therefore, by determining that the three-phase motor is idling when the q-axis current value is equal to or less than a preset determination threshold value, it is possible to provide a motor control method capable of accurately determining the idling of the three-phase motor even when the power supply voltage is large. Further, since the idling of the three-phase motor can be determined based on the q-axis current value calculated when the drive of the three-phase motor is vector-controlled, it is possible to provide a motor control method capable of easily determining the idling of the three-phase motor without providing a new configuration. Further, in vector control, the q-axis current value is calculated as a direct current. Therefore, it is possible to provide a motor control method capable of reducing the processing load required for arithmetic processing as compared with the case where the idling is determined directly using the alternating current input to the three-phase motor.

[0015] In the motor control method according to the second aspect described above, preferably, the step of determining that the three-phase motor is idling includes a step of determining that the three-phase motor is idling when the q-axis current value is equal to or less than a determination threshold value set in advance so as to increase in accordance with an increase in the rotational speed of the three-phase motor.

[0016] With this configuration, since the q-axis current value for vector control of the three-phase motor increases in accordance with an increase in the rotational speed of the three-phase motor, by presetting the determination threshold value for determining idling so as to increase in accordance with an increase in the rotational speed of the three-phase motor, it is possible to provide a motor control method capable of more accurately detecting the idling of the three-phase motor.

[0017] In addition, in the motor control device according to the first aspect, the following configuration is also conceivable.

[0018] (Additional Clause 1) That is, the determination unit is configured to determine that the three-phase motor connected to the pump is idling.

[0019] With this configuration, by determining whether the q-axis current value of the three-phase motor connected to the pump is less than or equal to a preset determination threshold value, it is possible to easily determine whether the pump is idling. Therefore, it is possible to easily determine whether the liquid discharge or suction by the pump is being performed normally.

[0020] (Additional Clause 2) In the motor control device that determines that the three-phase motor is idling based on a preset determination threshold value that increases as the rotational speed of the three-phase motor increases, the determination unit is configured to determine that the three-phase motor is idling when the q-axis current value is less than or equal to the determination threshold value based on a preset determination threshold value that increases in proportion to the increase in the rotational speed.

[0021] With this configuration, since the determination threshold value is set to increase in proportion to the rotational speed, it is possible to obtain the determination threshold value at the current rotational speed without performing complex arithmetic processing. Therefore, it is possible to more easily execute the arithmetic processing for performing the idling determination using the determination threshold value.

[0022] (Additional Clause 3) In a motor control device that determines that a three-phase motor is idling based on a determination threshold value preset to increase as the rotational speed of the three-phase motor increases, the control unit further includes a rotational speed acquisition unit that acquires the rotational speed of the three-phase motor. The three-phase to two-phase conversion unit is configured to acquire a d-axis current value in addition to a q-axis current value by converting the three-phase current input to the three-phase motor into two phases. The rotational speed acquisition unit is configured to estimate the rotational speed of the three-phase motor based on the d-axis control voltage calculated based on the d-axis current command, the q-axis control voltage calculated based on the q-axis current command, the q-axis current value, and the d-axis current value.

[0023] With this configuration, it is possible to estimate the rotational speed of the three-phase motor using the acquired d-axis control voltage, q-axis control voltage, q-axis current value, and d-axis current value without providing an angle sensor or the like. Therefore, it is possible to suppress the complication of the device configuration for measuring the rotational speed of the three-phase motor. As a result, even when determining idling, it is possible to compare the determination threshold value and the q-axis current value based on the estimated rotational speed, so that idling can be accurately determined without complicating the device configuration.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Best Mode for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0026] With reference to FIGS. 1 to 4, the configuration of the motor control device 100 according to the present embodiment will be described. The motor control device 100 is configured to control a motor 101 (an example of a "three-phase motor" in the claims) by vector control.

[0027] (Configuration of the motor) First, with reference to FIG. 1, the motor 101 controlled by the motor control device 100 will be described. The motor 101 is a sensorless brushless motor. Also, the motor 101 is provided with a permanent magnet (not shown). And the motor 101 is, for example, an IPM motor (Interior Permanent Magnet Motor) in which a permanent magnet is embedded in a rotor, or an SPM motor (Surface Permanent Magnet Motor) in which a permanent magnet is arranged on the surface of the rotor.

[0028] Also, the motor 101 is connected to a pump 102. The pump 102 is an electric water pump. The pump 102 is mounted on a vehicle 110 such as an automobile. And the pump 102 supplies coolant to the engine 103 of the vehicle 110. That is, the motor 101 operates the pump 102 to supply coolant. Also, the motor control device 100 controls the rotational speed (number of revolutions) of the motor 101 based on a speed command ω ref (see FIG. 2).

[0029] The vehicle control device 104 is a microcomputer (microcontroller) including, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), and a storage unit such as a flash memory. The vehicle control device 104 changes the flow rate of the coolant supplied to the engine 103 based on the rotational speed, temperature, etc. of the engine 103. Specifically, the vehicle control device 104 changes the flow rate of the coolant by controlling the rotational speed of the motor 101 that operates the pump 102. Specifically, the vehicle control device 104 outputs a speed command ω ref to the motor control device 100 in order to control the rotational speed of the motor 101.

[0030] (Configuration of the motor control device) Next, with reference to FIGS. 2 to 4, the configuration of the motor control device 100 will be described.

[0031] As shown in FIG. 2, the motor control device 100 includes a control unit 10, an inverter unit 20, and a current detection unit 30.

[0032] The inverter unit 20 converts the DC power input from a battery (not shown) or the like into AC power. Then, the inverter unit 20 outputs the converted AC power to the motor 101. Specifically, based on the control signal from the control unit 10, the gate signal from a driver unit (not shown) is input to the gate terminal of the switching element included in the inverter unit 20. The inverter unit 20 outputs three-phase AC power corresponding to the control signal to the motor 101 by controlling the switching operation of the switching element based on the input gate signal. Further, the inverter unit 20 includes, for example, a three-phase two-level inverter circuit having six switching elements. And the six switching elements are, for example, IGBTs (Insulated Gate Bipolar Transistors).

[0033] The current detection unit 30 detects the current of the AC power output from the inverter unit 20 and input to the motor 101. Specifically, the current detection unit 30 detects each of the currents of the three-phase AC power input to the motor 101. Then, the current detection unit 30 outputs the U-phase current value I u , V-phase current value I v , and W-phase current value I w as detection results to the three-phase to two-phase conversion unit 14 (described later) of the control unit 10. The current detection unit 30 includes, for example, a current transformer that detects current. The current detection unit 30 also includes an amplifier that amplifies the acquired signal and an AD converter that converts the acquired signal into a digital signal.

[0034] The control unit 10 is a microcomputer including, for example, a CPU, a RAM, and a storage unit such as a flash memory. The control unit 10 executes the control of each part of the motor control device 100. And the control unit 10 controls the driving of the motor 101. Specifically, the control unit 10 controls the switching operation of the switching elements included in the inverter unit 20 to control the AC power output to the motor 101.

[0035] Specifically, the control unit 10 generates a PWM signal (Pulse Width Modulation signal) for controlling the switching operation of the switching elements included in the inverter unit 20 based on the U-phase voltage V u , V-phase voltage V v , and W-phase voltage V w calculated by the two-phase to three-phase conversion unit 13 (described later). Then, the control unit 10 outputs the generated PWM signal as a control signal to a driver unit (not shown) to control the switching operation of the switching elements of the inverter unit 20. That is, the control unit 10 controls the switching operation of the switching elements of the inverter unit 20 by generating a PWM signal so as to output three-phase AC power corresponding to the calculated U-phase voltage V u , V-phase voltage V v , and W-phase voltage V w .

[0036] <Configuration of Control Unit> The motor control device 100 according to the present embodiment is configured to perform vector control based on the d-axis current command I dref and the q-axis current command I qref . In vector control, the three-phase current (U-phase current value I u , V-phase current value I v , and W-phase current value I w ) of the motor 101 is coordinate-transformed into vector components in the d-axis direction, which is the direction of the magnetic field generated by the permanent magnet, and the q-axis direction, which is the direction of torque orthogonal to the d-axis, so that feedback control is executed. And the control unit 10 is configured to acquire the speed command ω ref from the vehicle control device 104, and drive the motor 101 at the rotational speed corresponding to the acquired speed command ω ref .

[0037] Specifically, the control unit 10 includes a speed control unit 11, a current control unit 12, a two-phase to three-phase conversion unit 13, a three-phase to two-phase conversion unit 14, a rotational speed acquisition unit 15, and a determination unit 16. The speed control unit 11, the current control unit 12, the two-phase to three-phase conversion unit 13, the three-phase to two-phase conversion unit 14, the rotational speed acquisition unit 1$, and the determination unit 16 are configured as functional configurations (function blocks) in the control unit 10. That is, the control unit 10 is configured to execute the functions of each function block by a program stored in a storage unit such as the flash memory of the control unit 10 being executed by a CPU (processor). Note that these function blocks may be configured as processing circuits (hardware) that execute respective processes.

[0038] The speed command ω ref from the vehicle control device 104 is input to the speed control unit 11. Also, the speed estimated value ω calculated by the rotational speed acquisition unit 15 described later is input to the speed control unit 11. Then, the speed control unit 11 calculates the q-axis current command I ref based on the input speed command ω qref and the speed estimated value ω.

[0039] The current control unit 12 receives the d-axis current command I dref . The d-axis current command I dref is calculated, for example, so that the torque of the motor 101 is maximized based on the speed estimated value ω obtained by the rotation speed acquisition unit 15 described later and the q-axis current command I qref calculated by the speed control unit 11. Note that the d-axis current command I dref may be set to 0. Further, the current control unit 12 receives the q-axis current command I qref calculated by the speed control unit 11. Also, the current control unit 12 receives the d-axis current value I d and the q-axis current value I q calculated by the three-phase to two-phase conversion unit 14 described later. Then, based on the d-axis current command I dref and the q-axis current command I qref , and the d-axis current value I d and the q-axis current value I q , the current control unit 12 calculates the d-axis control voltage V dctrl and the q-axis control voltage V qctrl . Specifically, the current control unit 12 executes feedback control based on the d-axis current command I dref which is the command value and the d-axis current value I d which is the measured value, to calculate the d-axis control voltage V dctrl . Also, the current control unit 12 executes feedback control based on the q-axis current command I qref which is the command value and the q-axis current value I q which is the measured value, to calculate the q-axis control voltage V qctrl .

[0040] The two-phase to three-phase conversion unit 13 receives the d-axis control voltage V dctrl and the q-axis control voltage V qctrl calculated by the current control unit 12. Then, the two-phase to three-phase conversion unit 13 performs an inverse Park transformation and an inverse Clarke transformation on the input d-axis control voltage V dctrl and the q-axis control voltage V qctrl to obtain the U-phase voltage V u, the V-phase voltage V v , the W-phase voltage V w is calculated. Note that the two-phase to three-phase conversion unit 13 performs an inverse Park transformation using the rotation angle obtained from the rotation speed acquisition unit 15 described later.

[0041] The three-phase to two-phase conversion unit 14 receives the U-phase current value I indicating the three-phase (U-phase, V-phase, and W-phase) currents detected by the current detection unit 30 u , the V-phase current value I v , and the W-phase current value I w . Then, the three-phase to two-phase conversion unit 14 converts the three-phase currents input to the motor 101 into two phases to obtain the d-axis current value I d and the q-axis current value I q . Specifically, the three-phase to two-phase conversion unit 14 performs a Clarke transformation and a Park transformation on the input U-phase current value I u , the V-phase current value I v , and the W-phase current value I w to calculate the d-axis current value I d and the q-axis current value I q . Note that the three-phase to two-phase conversion unit 14 performs a Park transformation using the rotation angle obtained from the rotation speed acquisition unit 15 described later.

[0042] The rotation speed acquisition unit 15 acquires the rotation speed of the motor 101. In this embodiment, the rotation speed acquisition unit 15 estimates the rotation speed of the motor 101 by calculating the speed estimation value ω. That is, the rotation speed acquisition unit 15 acquires the calculated speed estimation value ω as the rotation speed of the motor 101. Specifically, the rotation speed acquisition unit 15 acquires the d-axis current value I d and the q-axis current value I q acquired by the three-phase to two-phase conversion unit 14. Also, the rotation speed acquisition unit 15 acquires the d-axis control voltage V dctrl and the q-axis control voltage V qctrl calculated by the current control unit 12. Then, the rotation speed acquisition unit 15 combines the acquired d-axis current value I d and the q-axis current value I q with the d-axis control voltage V dctrl and the q-axis control voltage V qctrlBased on this, the estimated speed ω is calculated. Also, the rotation speed acquisition unit 15 calculates the rotation angle of the motor 101 for inverse Park transformation by the two-phase to three-phase conversion unit 13. Further, the rotation speed acquisition unit 15 calculates the rotation angle of the motor 101 for Park transformation by the three-phase to two-phase conversion unit 14.

[0043] 〈Idle determination〉 And in this embodiment, the motor control device 100 is configured to determine the idling (no-load operation) of the motor 101 by the determination unit 16. That is, the motor control device 100 detects a shortage of the coolant inside the pump 102 (being in an idling state) due to liquid leakage or evaporation of the coolant.

[0044] As shown in FIG. 2, the determination unit 16 acquires the q-axis current value I q acquired by the three-phase to two-phase conversion unit 14. Also, the determination unit 16 acquires the estimated speed ω acquired by the rotation speed acquisition unit 15. And in this embodiment, the determination unit 16 determines that the motor 101 is idling when the q-axis current value I q acquired by the three-phase to two-phase conversion unit 14 is equal to or less than a preset determination threshold S (see FIG. 3).

[0045] As shown in FIG. 3, in this embodiment, the determination threshold S is preset to increase in accordance with the increase in the rotation speed of the motor 101. Specifically, the determination threshold S is preset to increase in proportion to the increase in the rotation speed. Also, the determination threshold S is prestored in the storage unit of the control unit 10. The determination unit 16 determines that the motor 101 is idling when the acquired q-axis current value I q is equal to or less than the determination threshold S at the rotation speed corresponding to the acquired estimated speed ω.

[0046] Note that the solid line L1 in FIG. 3 is the q-axis current value I of the motor 101 in a normal state that is not an idling state (no-load operation state) q (q-axis current value I qAn example of the relationship between the absolute value of ) and the rotational speed (estimated speed ω) is shown. The solid line L2 in FIG. 3 represents the q-axis current value I of the motor 101 in the idling state q (absolute value of the q-axis current value I q and the rotational speed (estimated speed ω). When the motor 101 is in a normal state, the acquired q-axis current value I q (absolute value of the q-axis current value I q ) is greater than the determination threshold value S. On the other hand, when the motor 101 is in an idling state, the acquired q-axis current value I q (absolute value of the q-axis current value I q ) is greater than the determination threshold value S.

[0047] 〈Idling non-detection region〉 Also, in the present embodiment, the determination unit 16 (control unit 10) does not determine the idling of the motor 101 when the rotational speed (estimated speed ω) acquired by the rotational speed acquisition unit 15 is less than a predetermined minimum rotational speed ω1, and determines the idling of the motor 101 when the rotational speed (estimated speed ω) is equal to or greater than the minimum rotational speed ω1. Specifically, the control unit 10 stores a preset minimum rotational speed ω1. The minimum rotational speed ω1 is determined based on, for example, the rotational speed (estimated speed ω) at which the difference between the q-axis current value I q in the normal state and the q-axis current value I q in the idling state is smaller than a predetermined magnitude. For example, when the rotational speed of the motor 101 is configured to be controllable in the range of 0 rpm (revolutions per minute) or more and 6000 rpm or less, 2000 rpm is set as the minimum rotational speed ω1.

[0048] 〈Fail control〉 As shown in FIG. 4, when it is determined that the motor 101 is idling, the control unit 10 executes fail control to intermittently drive the motor 101. That is, when it is determined that the motor 101 is idling, the control unit 10 is configured to control the inverter unit 20 so as to alternately repeat driving and stopping of the motor 101.

[0049] For example, when the determination unit 16 determines wheel spin at time point T1 in FIG. 4, the control unit 10 controls the inverter unit 20 to repeat driving and stopping the motor 101 at a predetermined interval (for example, 1 second). In this case, the motor 101 is stopped during the one second from time point T1 to time point T2 in FIG. 4. Then, the motor 101 is driven during the one second from time point T2 to time point T3. Similar operations are repeated at time points T4, T5, T6, ··· after time point T3. The control unit 10 is configured to execute the above-described fail control during the period in which the determination unit 16 has obtained the determination of wheel spin.

[0050] Here, in the pump 102 for supplying the coolant, a wheel spin phenomenon called air biting may occur when a part of the coolant contains air (gas). The control unit 10 is configured to eliminate the wheel spin due to air biting by repeating driving and stopping of the motor 101 as in the above-described fail control. Note that when the wheel spin is no longer detected due to elimination of air biting or the like in a state where the determination unit 16 has detected wheel spin, the control unit 10 ends the fail control and drives the motor 101 normally again.

[0051] Further, when the control unit 10 determines that the motor 101 is in wheel spin, it outputs information indicating wheel spin to the vehicle control device 104. The vehicle control device 104 displays, on a display device (not shown), a display indicating the wheel spin (wheel spin of the pump 102) of the motor 101 based on the information indicating wheel spin from the control unit 10. Further, the vehicle control device 104 may output a command to stop driving the motor 101 or may continue the fail control based on the information indicating wheel spin from the control unit 10.

[0052] (Motor control method according to this embodiment) Hereinafter, with reference to FIG. 5, the control process of the motor control method in the determination of wheel spin by the control unit 10 will be described. The motor control method according to this embodiment controls the driving of the motor 101 with a d-axis current command I dref and a q-axis current command I qrefIt is a motor control method for vector control.

[0053] First, in step S1, the current input to the motor 101 is detected. Specifically, the U-phase current value I of the motor 101 detected by the current detection unit 30 u , V-phase current value I v , and W-phase current value I w are obtained.

[0054] Next, in step S2, the three-phase currents (U-phase current value I u , V-phase current value I v , and W-phase current value I w ) input to the motor 101 are converted into two phases, and the d-axis current value I d and q-axis current value I q are obtained. Specifically, the Clark transformation and Park transformation are performed on the obtained U-phase current value I u , V-phase current value I v , and W-phase current value I w by the three-phase to two-phase conversion unit 14, and the d-axis current value I d and q-axis current value I q are calculated.

[0055] Next, in step S3, the rotational speed of the motor 101 is obtained. Specifically, based on the obtained d-axis current value I d and q-axis current value I q , and the d-axis control voltage V dctrl and q-axis control voltage V qctrl , the speed estimated value ω is calculated by the rotational speed acquisition unit 15.

[0056] Next, in step S4, it is determined whether the calculated speed estimated value ω is equal to or greater than a preset minimum rotational speed ω1. If it is determined that the speed estimated value ω is equal to or greater than the minimum rotational speed ω1, the process proceeds to step S5. If it is not determined that the speed estimated value ω is equal to or greater than the minimum rotational speed ω1, the no-load determination is not performed and the process returns to step S1.

[0057] In step S5, the q-axis current value I calculated in step S2 is q is equal to or less than a predetermined threshold S. Specifically, the threshold S is set in advance so as to increase in accordance with an increase in the rotation speed (estimated speed value ω) of the motor 101. Then, the acquired q-axis current value I q It is determined whether the absolute value of is equal to or less than the determination threshold S for the acquired speed estimate ω. q If it is determined that the q-axis current value I is equal to or less than the determination threshold value S, it is determined that the motor 101 is rotating freely, and the process proceeds to step S6. q If it is not determined that is equal to or smaller than the determination threshold value S, the process returns to step S1.

[0058] In step S6, based on the determination that the motor 101 is idling, a fail control is executed in which the motor 101 is repeatedly driven and stopped. If it is determined that the motor 101 is idling, the fail control is continued. If it is no longer determined that the motor 101 is idling, the fail control is terminated.

[0059] The above control process is executed continuously from the time when the driving of the motor 101 is started until the time when the driving is ended.

[0060] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0061] In this embodiment, as described above, the q-axis current value I q is equal to or less than a predetermined threshold S, the motor 101 (three-phase motor) is determined to be idling. Here, the q-axis current value I q is a current value that indicates a vector component in the direction of the torque for rotating the motor 101, among the currents input to the motor 101. This q-axis current value I q is not affected by the power supply voltage, so even when the power supply voltage is large, the acquired q-axis current value I qwill not decrease. Therefore, when the q-axis current value I q is less than or equal to a preset determination threshold value S, it is determined that the motor 101 is idling. Thus, even when the power supply voltage is high, it is possible to accurately determine the idling of the motor 101. Further, when the motor 101 is driven by vector control, the q-axis current value I q can be used to determine the idling of the motor 101. Therefore, it is possible to easily determine the idling of the motor 101 without providing a new configuration. Also, in vector control, the q-axis current value I q is calculated as a direct current. Therefore, compared with the case where the idling determination is performed directly using the alternating current input to the motor 101, the processing load required for the arithmetic processing can be reduced.

[0062] Also, in the present embodiment, as described above, the determination unit 16 is based on a preset determination threshold value S that increases as the rotation speed (speed estimated value ω) of the motor 101 (three-phase motor) increases. When the q-axis current value I q is less than or equal to the determination threshold value S, it is configured to determine that the motor 101 is idling. Thereby, since the q-axis current value I q for vector control of the motor 101 increases as the rotation speed of the motor 101 increases, by presetting the determination threshold value S for determining idling so as to increase as the rotation speed of the motor 101 increases, it is possible to more accurately detect the idling of the motor 101.

[0063] Also, in the present embodiment, as described above, the control unit 10 includes a rotation speed acquisition unit 15 that acquires the rotation speed of the motor 101 (three-phase motor). Then, the determination unit 16 does not determine the idling of the motor 101 when the rotation speed (speed estimated value ω) acquired by the rotation speed acquisition unit 15 is less than a predetermined minimum rotation speed ω1, and determines the idling of the motor 101 when the speed estimated value ω is greater than or equal to the minimum rotation speed ω1. Here, when the rotation speed of the motor 101 is low, the q-axis current value I qand the q-axis current value I obtained when the motor 101 is idling q The difference from becomes small. Therefore, when the rotational speed of the motor 101 is low, it is considered difficult to determine the idling of the motor 101 based on a preset determination threshold value S. In consideration of this, in the present embodiment, the determination unit 16 does not determine the idling of the motor 101 when the rotational speed (speed estimated value ω) obtained by the rotational speed acquisition unit 15 is less than a predetermined minimum rotational speed ω1, and determines the idling of the motor 101 when the rotational speed is equal to or higher than the minimum rotational speed ω1. With this configuration, when the rotational speed of the motor 101 is low, the idling of the motor 101 is not determined, so that it is possible to suppress misjudgment of the idling of the motor 101.

[0064] (Effect of the motor control method according to the present embodiment) In the motor control method of the present embodiment, the following effects can be obtained.

[0065] In the motor control method of the present embodiment, by configuring as described above, when the q-axis current value I q is equal to or less than a preset determination threshold value S, it is determined that the motor 101 (three-phase motor) is idling. Here, the q-axis current value I q used for vector control of the drive of the motor 101 is a current value indicating the vector component in the direction of the torque for rotating the motor 101 among the currents input to the motor 101. Since this q-axis current value I q is not affected by the power supply voltage, even when the power supply voltage is large, the obtained q-axis current value I q does not become small. Therefore, by determining that the motor 101 is idling when the q-axis current value I q is equal to or less than a preset determination threshold value S, it is possible to provide a motor control method capable of accurately determining the idling of the motor 101 even when the power supply voltage is large. Also, the q-axis current value I qSince it is possible to determine the idling of the motor 101 based on this, it is possible to provide a motor control method capable of easily determining the idling of the motor 101 without providing a new configuration. Also, in vector control, the q-axis current value I q is calculated as a direct current. Therefore, it is possible to provide a motor control method capable of reducing the processing load required for arithmetic processing as compared with the case of directly using the alternating current input to the motor 101 for determining idling.

[0066] Also, in the motor control method of the present embodiment, as described above, in step S5 of determining that the motor 101 (three-phase motor) is idling, based on a determination threshold value S preset so as to increase in accordance with an increase in the rotation speed (speed estimated value ω) of the motor 101, when the q-axis current value I q is less than or equal to the determination threshold value S, it is determined that the motor 101 is idling. Thereby, since the q-axis current value I q for vector control of the motor 101 increases in accordance with an increase in the rotation speed of the motor 101, it is possible to provide a motor control method capable of more accurately detecting the idling of the motor 101 by presetting the determination threshold value S for determining idling so as to increase in accordance with an increase in the rotation speed of the motor 101.

[0067] [Modification Example] The above-described embodiment disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the description of the above embodiment but by the claims, and further includes all changes (modification examples) within the meaning and scope equivalent to the claims.

[0068] For example, in the above embodiment, an example was shown in which the current detection unit 30 uses a current transformer between the inverter unit 20 and the motor 101 to detect the current input to each of the three phases (U-phase, V-phase, and W-phase) of the motor 101. However, the present invention is not limited to this. In the present invention, like the current detection unit 230 according to the modified example shown in FIG. 6, at each negative side of each of the three switching elements on the lower arm side among the six switching elements included in the inverter unit 220, the current input to the motor 101 from each of the provided terminals P1, terminal P2, and terminal P3 may be detected. In this case, the current detection unit 230 includes, for example, an amplifier (operational amplifier).

[0069] Further, in the above embodiment, an example was shown in which the determination threshold value S is preset so as to increase in accordance with an increase in the rotational speed (speed estimated value ω). However, the present invention is not limited to this. For example, the determination threshold value S may be set to a constant value regardless of the rotational speed (speed estimated value ω) of the motor 101.

[0070] Further, in the above embodiment, an example was shown in which when the rotational speed (speed estimated value ω) is less than the predetermined minimum rotational speed ω1, the idling of the motor 101 is not determined. However, the present invention is not limited to this. For example, without setting the minimum rotational speed ω1, it may be configured to execute the determination of idling in all of the operable speed ranges.

[0071] Further, in the above embodiment, an example was shown in which the motor 101 is a sensorless brushless motor. However, the present invention is not limited to this. For example, by providing an angle sensor such as a hall element in the motor 101, the rotational speed or rotational angle of the motor 101 may be detected. In that case, the rotational speed acquisition unit 15 (control unit 10) is configured to acquire the rotational speed and rotational angle detected by the angle sensor without estimating the rotational speed.

[0072] In the above-described embodiment, an example is shown in which the motor 101 is mounted on the vehicle 110 and configured to operate the pump 102 that supplies the coolant to the engine 103. However, the present invention is not limited to this. For example, a pump that supplies the coolant to a power supply device such as a battery instead of the engine 103 may be operated. Further, the motor may be provided in a shift device of the vehicle and configured to drive a shift member.

[0073] Also, in the above-described embodiment, an example is shown in which the control unit 10 controls the drive of the motor 101 based on the speed command ω from the vehicle control device 104 different from the control unit 10 that controls the drive of the motor 101. However, the present invention is not limited to this. For example, the control unit 10 that controls the drive of the motor 101 may be configured to acquire the speed command ω. ref Also, in the above-described embodiment, an example is shown in which the control unit 10 controls the drive of the motor 101 based on the speed command ω from the vehicle control device 104 different from the control unit 10 that controls the drive of the motor 101. However, the present invention is not limited to this. For example, the control unit 10 that controls the drive of the motor 101 may be configured to acquire the speed command ω. ref to be obtained.

Explanation of Reference Numerals

[0074] 10 Control unit 14 Three-phase to two-phase conversion unit 15 Rotational speed acquisition unit 16 Determination unit 30, 230 Current detection unit 100 Motor control device 101 Motor (three-phase motor) 102 Pump

Claims

1. A motor control device that performs vector control of a three-phase motor using a d-axis current command and a q-axis current command, a current detection unit that detects a current input to the three-phase motor; a control unit that controls the driving of the three-phase motor, The control unit a three-phase to two-phase conversion unit that converts the three-phase current input to the three-phase motor, detected by the current detection unit, into two phases to obtain a q-axis current value; a determination unit that determines that the three-phase motor is running idle when the q-axis current value is equal to or less than a predetermined determination threshold value, the determination unit is configured not to determine whether the three-phase motor is spinning freely based on the q-axis current value when the rotation speed of the three-phase motor is less than a predetermined minimum rotation speed, but to determine whether the three-phase motor is spinning freely based on the q-axis current value when the rotation speed is equal to or greater than the minimum rotation speed.

2. 2. The motor control device according to claim 1, wherein the determination unit is configured to determine that the three-phase motor is idling when the q-axis current value is equal to or less than the determination threshold, the determination threshold being preset to increase as the rotation speed of the three-phase motor increases.

3. the control unit further includes a rotation speed acquisition unit that acquires the rotation speed of the three-phase motor, 3. The motor control device according to claim 2, wherein the determination unit is configured not to determine that the three-phase motor is spinning when the rotational speed acquired by the rotational speed acquisition unit is less than the minimum rotational speed, but to determine that the three-phase motor is spinning when the rotational speed is equal to or greater than the minimum rotational speed.

4. A motor control method for vector-controlling a three-phase motor using a d-axis current command and a q-axis current command, comprising: detecting a current input to the three-phase motor; obtaining a q-axis current value by converting a three-phase current input to the three-phase motor into a two-phase current; determining that the three-phase motor is running idle when the q-axis current value is equal to or less than a predetermined determination threshold value; The step of determining that the three-phase motor is idling includes a step of determining idling of the three-phase motor based on the q-axis current value when the rotational speed of the three-phase motor is equal to or higher than the minimum rotational speed, without determining idling of the three-phase motor based on the q-axis current value when the rotational speed of the three-phase motor is less than a predetermined minimum rotational speed. A motor control method.

5. The step of determining that the three-phase motor is idling includes a step of determining that the three-phase motor is idling when the q-axis current value is equal to or less than the determination threshold value set in advance so as to increase in accordance with an increase in the rotational speed of the three-phase motor. The motor control method according to claim 4.

Images