Motor control device, motor, and motor control method

Abstract

The present invention provides a motor control device, a motor, and a motor control method. The motor control device controls a motor by adjusting three-phase currents including a first-phase current, a second-phase current, and a third-phase current. The motor control device includes a control unit that performs feedback on a control current value obtained from the three-phase currents to control the three-phase currents. The control unit is capable of performing a first feedback control and a second feedback control. In the first feedback control, any one of a first control current value calculated based on the second-phase current and the third-phase current, a second control current value calculated based on the third-phase current and the first-phase current, and a third control current value calculated based on the first-phase current and the second-phase current is used as the control current value for feedback. In the second feedback control, the first control current value, the second control current value, and the third control current value are switched as the control current value for feedback.

Description

Technical Field

[0001] The present invention relates to a motor control device, a motor, a motor control method, and a program. Background Art

[0002] There is known a method of controlling a motor by adjusting three-phase currents supplied to the motor. For example, Patent Document 1 describes a method of controlling a motor by PWM (Pulse Width Modulation) control.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-048249

[0004] In the motor control device as described above, sometimes a control current value is controlled by detecting a phase current generated in PWM control by a detection element such as a shunt resistor. However, if the duty ratio of the pulse wave becomes large, the current detection time of the detection element such as the shunt resistor becomes short, and there is a problem that the current detection accuracy of the detection element is reduced. Therefore, sometimes the control current value cannot be appropriately controlled. As a result, the duty ratio of the pulse wave cannot be increased to a certain level or more, and there is a problem that it is difficult to sufficiently improve the output of the motor. Summary of the Invention

[0005] An object of the present invention is to provide a motor control device, a motor, a motor control method, and a program capable of improving the output of a motor.

[0006] One aspect of the present invention is a motor control device that controls a motor by adjusting three-phase currents including a first-phase current, a second-phase current, and a third-phase current. The motor control device has a control unit that feedback-controls the control current value obtained from the three-phase currents to control the three-phase currents. The control unit can execute a first feedback control and a second feedback control. In the first feedback control, any one of a first control current value calculated from the second-phase current and the third-phase current, a second control current value calculated from the third-phase current and the first-phase current, and a third control current value calculated from the first-phase current and the second-phase current is feedback as the control current value. In the second feedback control, the first control current value, the second control current value, and the third control current value are switched and feedback as the control current value.

[0007] In addition, one aspect of the present invention is a motor having the above-described motor control device.

[0008] In addition, one aspect of the present invention is a motor control method that controls a motor by adjusting three-phase currents including a first-phase current, a second-phase current, and a third-phase current. The motor control method includes performing feedback on a control current value obtained from the three-phase currents to control the three-phase currents. Controlling the three-phase currents includes the following: performing first feedback control in which any one of a first control current value calculated from the second-phase current and the third-phase current, a second control current value calculated from the third-phase current and the first-phase current, and a third control current value calculated from the first-phase current and the second-phase current is used as the control current value for feedback; and performing second feedback control in which the first control current value, the second control current value, and the third control current value are switched as the control current value for feedback.

[0009] According to the present invention, the output of the motor can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 FIG. is a diagram showing the structure of a motor according to a first embodiment of the present invention.

[0011] Figure 2 FIG. is a block diagram showing the structure of a control unit.

[0012] Figure 3 FIG. is a diagram showing a generated control signal.

[0013] Figure 4 FIG. is a flowchart showing the flow of processing executed in a motor control device.

[0014] Figure 5 FIG. is a flowchart showing the processing flow of another determination method.

[0015] Figure 6 FIG. is a diagram showing a method for setting a threshold value of a control signal in a modified example.

[0016] REFERENCE SIGNS LIST

[0017] 1: motor; 20: motor control device; 21: control unit; DR, Du, Dv, Dw: duty ratio; Ic1: first control current value; Ic2: second control current value; Ic3: third control current value; Id, Iq: dq-axis current; Iu: first-phase current; Iv: second-phase current; Iw: third-phase current; TH: threshold value. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] Hereinafter, embodiments of a motor control device, a motor, a motor control method, and a program according to the present invention will be described with reference to the drawings.

[0019] As Figure 1 shown, the motor 1 is, for example, a three-phase brushless motor supplied with three-phase alternating current. The motor 1 has a motor body 2 and a motor control device 20 that controls the motor body 2. The motor body 2 has a rotor and a stator 3 (not shown). The stator 3 has a U-phase coil 3U, a V-phase coil 3V, and a W-phase coil 3W. In the present embodiment, the motor control device 20 controls the motor body 2 by PWM control. As Figure 1 shown, the motor control device 20 has an inverter circuit section 10, a control section 21, and a storage section 22. Although not shown, the motor control device 20 has an acquisition section that acquires various detection values, command values, and the like. The storage section 22 stores data such as detection values, command values, and programs related to control.

[0020] The inverter circuit section 10 is controlled by the control section 21 to generate a control current for driving the motor body 2. In the present embodiment, the control current generated by the inverter circuit section 10 is an alternating current, which is a three-phase current including a first-phase current, a second-phase current, and a third-phase current. The inverter circuit section 10 generates, for example, three-phase control signals including a U-phase signal, a V-phase signal, and a W-phase signal. Each generated signal is an alternating current signal. As Figure 1 shown, the inverter circuit section 10 has a switching section 11 that generates three-phase control signals. In the present embodiment, the switching section 11 includes three switching sections 12, 13, and 14. Since each of the switching sections 12, 13, and 14 has the same structure, the switching section 11 is denoted without particularly distinguishing the switching sections 12, 13, and 14.

[0021] The three-phase control signals generated by the inverter circuit section 10 are input to the motor body 2, and the motor body 2 is driven. In addition, the inverter circuit section 10 has a shunt resistor 15. In the present embodiment, the shunt resistor 15 includes three shunt resistors 16, 17, and 18. Since each of the shunt resistors 16, 17, and 18 has the same structure, the shunt resistor 15 is denoted without particularly distinguishing the shunt resistors 16, 17, and 18.

[0022] Each switching section 11 has, for example, two switching elements connected in series between the power supply line V and the GND line G to generate an alternating current signal for driving the motor body 2.

[0023] The switching unit 12 generates a U-phase signal in the three-phase AC signal. The switching unit 12 supplies the generated U-phase signal as a drive signal to the motor body 2. The switching unit 12 includes a high-side switching element 12A and a low-side switching element 12B connected in series with the switching element 12A. The upstream side of the switching element 12A is connected to the power supply line V. The downstream side of the switching element 12B is connected to the GND line G via a shunt resistor 16 connected in series. The U-phase coil 3U of the motor body 2 is electrically connected between the switching element 12A and the switching element 12B.

[0024] The switching element 12A and the switching element 12B are constituted by, for example, an IGBT (Insulated Gate Bipolar Transistor) with a FWD (Free Wheeling Diode), a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or a power transistor. A control signal (gate voltage) output from the control unit 21 is input to the gate terminals of the switching elements 12A and 12B respectively. The high-side gate voltage (Vg_UH) of the U-phase is input to the switching element 12A. The low-side gate voltage (Vg_UL) of the U-phase is input to the switching element 12B. When a gate voltage equal to or higher than a specified threshold value is input to each of the switching elements 12A and 12B, each of the switching elements 12A and 12B becomes an on state.

[0025] The switching elements 12A and 12B respectively switch between the on state and the off state by controlling the gate voltage input from the control unit 21, and perform switching control. The U-phase signal generated by the switching control is output from the node 12C between the switching element 12A and the switching element 12B. The U-phase signal is a pulse signal whose duty ratio is adjusted according to the output. When the U-phase signal is input to the U-phase coil 3U of the motor body 2, a sine-wave current flows through the U-phase coil 3U.

[0026] The switching unit 13 generates a V-phase signal in the three-phase AC signal. The switching unit 13 supplies the generated V-phase signal as a drive signal to the stator 3. The switching unit 13 has the same structure as the switching unit 12. The switching unit 13 includes a high-side switching element 13A, a low-side switching element 13B, and a shunt resistor 17. The V-phase of the stator 3 is connected between the switching element 13A and the switching element 13B.

[0027] The high-side gate voltage (Vg_VH) of the V-phase is input to the switching element 13A, and it becomes an on state. The low-side gate voltage (Vg_VL) of the V-phase is input to the switching element 13B, and it becomes an on state.

[0028] A V-phase signal generated by switching control is output from the node 13C between the switching elements 13A and 13B. When the V-phase signal is input to the V-phase coil 3V of the stator 3, a sinusoidal current flows through the V-phase coil 3V.

[0029] The switching unit 14 generates a W-phase signal in the three-phase AC signal. The switching unit 14 has the same structure as the switching units 12 and 13. The switching unit 14 supplies the generated W-phase signal as a drive signal to the stator 3. The switching unit 14 includes a high-side switching element 14A, a low-side switching element 14B, and a shunt resistor 18. The connection between the switching element 14A and the switching element 14B is made to the W-phase of the stator 3.

[0030] The high-side gate voltage (Vg_WH) of the W-phase is input to the switching element 14A, making it in the on state. The low-side gate voltage (Vg_WL) of the W-phase is input to the switching element 14B, making it in the on state.

[0031] A W-phase signal generated by switching control is output from the node 14C between the switching elements 14A and 14B. When the W-phase signal is input to the W-phase coil 3W of the stator 3, a sinusoidal current flows through the W-phase coil 3W.

[0032] When driving the high-side switching elements 12A, 13A, and 14A described above, current does not flow simultaneously through the low-side switching elements 12B, 13B, and 14B and the shunt resistor 15.

[0033] The shunt resistor 15 is a resistance element that can detect the current flowing through the switching unit 11 by measuring the voltage between terminals. The shunt resistor 15 can detect the current value flowing through the low-side switching elements 12B, 13B, and 14B that are in the on state when the high-side switching elements 12A, 13A, and 14A are in the off state. That is, based on the shunt resistor 15, the current values flowing through the switching elements 12B, 13B, and 14B can be detected when detecting the off state in one cycle of the pulse wave that is the control signal.

[0034] The shunt resistor 16 is arranged, for example, between the switching unit 12 and the GND line G. The shunt resistor 16 is arranged between the switching unit 12 and the GND line and can detect the U-phase voltage. The first-phase current of the U-phase can be calculated based on the detected value of the voltage obtained from the shunt resistor 16. A node 12D serving as a detection terminal is arranged between the switching unit 12 and the shunt resistor 16.

[0035] The shunt resistor 17 is arranged, for example, between the switching unit 13 and the GND line G. The shunt resistor 17 is arranged between the switching unit 13 and the GND line, and can detect the voltage of the V phase. The second-phase current of the V phase can be calculated based on the detected value of the voltage obtained from the shunt resistor 17. A node 13D serving as a detection terminal is arranged between the switching unit 13 and the shunt resistor 17.

[0036] The shunt resistor 18 is arranged, for example, between the switching unit 14 and the GND line G. The shunt resistor 18 is arranged between the switching unit 14 and the GND line, and can detect the voltage of the W phase. The third-phase current of the W phase can be calculated based on the detected value of the voltage obtained from the shunt resistor 18. A node 14D serving as a detection terminal is arranged between the switching unit 14 and the shunt resistor 18.

[0037] As Figure 2 shown, the control unit 21 calculates a target current based on, for example, the commanded motor torque Tm and the motor electrical angle θm of the motor body 2 output from a control device (not shown) on the vehicle side, and controls the switching unit 11 to perform feedback control on the torque generated by the motor body 2. The motor control device 20 outputs a control current value (control signal) that causes the switching unit 11 to operate in the feedback control.

[0038] The control unit 21 adjusts, for example, the three-phase currents including the first-phase current Iu supplied to the U-phase coil 3U, the second-phase current Iv supplied to the V-phase coil 3V, and the third-phase current Iw supplied to the W-phase coil 3W, and performs feedback on the control current value obtained from the three-phase currents to control the motor 1.

[0039] As Figure 2 shown, the control unit 21 includes, for example, a target current calculation unit 21A, a three-phase two-axis conversion unit 21B, a PI control unit 21C, a two-axis three-phase conversion unit 21D, a PWM controller 21F, and a pre-driver 21G. In Figure 2 this, a value with an asterisk added to the calculated value represents a target value. The target current calculation unit 21A calculates the target current value of each phase current based on the commanded motor torque Tm as a command value. In the present embodiment, the target current value is calculated as the dq-axis current value described later. The PWM controller 21F generates a pre-driver drive signal for each phase to maintain the motor torque at a desired target value, and outputs it to the pre-driver 21G. The pre-driver 21G generates a driver drive signal for each phase by performing a prescribed signal process on the pre-driver drive signal for each phase input from the PWM controller 21F, and outputs it to the switching unit 11.

[0040] The three-phase two-axis conversion unit 21B receives the values of the first-phase current Iu, the second-phase current Iv, and the third-phase current Iw of the three phases obtained from the shunt resistor 15, and the motor electrical angle θm of the motor body 2. The three-phase two-axis conversion unit 21B calculates the value of the d-axis current Id obtained by converting the three-phase current through two axes, namely the d-axis in the motor body 2 and the q-axis in the motor body 2, and the value of the q-axis current Iq as the control current values. The d-axis in the motor body 2 is the axis in the direction of the magnetic flux formed by the magnetic poles of the magnets provided on the rotor. The q-axis in the motor body 2 is the axis in a direction perpendicular to the d-axis. In the following description, the d-axis current Id and the q-axis current Iq are collectively referred to as the dq-axis currents Id, Iq. Specifically, in the present embodiment, the three-phase two-axis conversion unit 21B applies the condition that the sum of the three-phase currents is zero, uses two of the three-phase currents and the motor electrical angle θm, and calculates the values of the dq-axis currents as the control current values based on any of the following equations (1) to (3).

[0041]

[0042]

[0043]

[0044] Among them,

[0045] Iu / Iv / Iw U / V / W phase current Id_vw / Iq_vw d / q axis current (V, W phases) Id_wu / Iq_wu d / q axis current (W, U phases) Id_uv / Iq_uv d / q axis current (U, V phases) <![CDATA[θ m > Motor electrical angle <![CDATA[C 32 > Three-phase two-axis conversion coefficient 。

[0046] The above equation (1) is an equation for calculating the first control current value Ic1. The first control current value Ic1 is the value of the dq-axis current calculated from the second-phase current Iv and the third-phase current Iw. The above equation (2) is an equation for calculating the second control current value Ic2. The second control current value Ic2 is the value of the dq-axis current calculated from the third-phase current Iw and the first-phase current Iu. The above equation (3) is an equation for calculating the third control current value Ic3. The third control current value Ic3 is the value of the dq-axis current calculated from the first-phase current Iu and the second-phase current Iv.

[0047] The first control current value Ic1, the second control current value Ic2, and the third control current value Ic3 are current values that are theoretically all the same. However, in practice, the first-phase current Iu, the second-phase current Iv, and the third-phase current Iw each have deviations, so the control current values calculated from different two-phase currents have deviations. In the present embodiment, the three-phase two-axis conversion unit 21B calculates the deviations of the respective control current values, that is, the values of the respective dq-axis currents, as the offset correction values Owu, Ouv according to the following equations (4) and (5).

[0048]

[0049]

[0050] Among them,

[0051] Id_wu_ofs / Iq_wu_ofs d / q axis current correction value (W, U phases) Id_uv_ofs / Iq_uv_ofs d / q axis current correction value (U, V phases) 。

[0052] The offset correction value Owu is the difference obtained by subtracting the first control current value Ic1 from the second control current value Ic2. Therefore, by subtracting the offset correction value Owu from the second control current value Ic2, the second control current value Ic2 can be corrected to the same value as the first control current value Ic1. The offset correction value Ouv is the difference obtained by subtracting the first control current value Ic1 from the third control current value Ic3. Therefore, by subtracting the offset correction value Ouv from the third control current value Ic3, the third control current value Ic3 can be corrected to the same value as the first control current value Ic1.

[0053] The target current value calculated in the target current calculation unit 21A and the control current value calculated in the three-phase two-axis conversion unit 21B, that is, the values of the dq-axis currents Id and Iq, are input to the PI control unit 21C. The PI control unit 21C performs the following PI control on the target current value: feedback is performed on the control current value calculated in the three-phase two-axis conversion unit 21B, that is, the values of the dq-axis currents Id and Iq. In the PI control unit 21C, any one of the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3 is used as the control current value to be feedback. The PI control unit 21C calculates the dq-axis command voltages Vd and Vq according to the PI control.

[0054] The dq-axis command voltages Vd and Vq calculated in the PI control unit 21C and the motor electrical angle θm are input to the two-axis three-phase conversion unit 21D. The two-axis three-phase conversion unit 21D calculates the three-phase command voltages Vu, Vv, and Vw according to the dq-axis command voltages Vd and Vq and the motor electrical angle θm. The three-phase command voltages Vu, Vv, and Vw are input to the inverter circuit unit 10. By the command voltages Vu, Vv, and Vw input to the inverter circuit unit 10, each switching unit 11 of the inverter circuit unit 10 is controlled to adjust the three-phase current supplied to the motor main body 2.

[0055] Hereinafter, the control method of the control unit 21 will be described. The control unit 21 can execute the first feedback control and the second feedback control in the PI control unit 21C.

[0056] The first feedback control is a feedback control that uses any one of the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3 as the control current value for feedback. In the first feedback control of the present embodiment, the control unit 21 uses the first control current value Ic1 as the control current value for feedback. In the first feedback control, the control unit 21 does not use the other control current values, that is, the second control current value Ic2 and the third control current value Ic3, as the control current value for feedback. In the present embodiment, the control unit 21 performs the first feedback control when the duty ratios of the pulse waves respectively generated for the first-phase current Iu, the second-phase current Iv, and the third-phase current Iw all vary within a range below a specified threshold TH.

[0057] In the present embodiment, during the execution of the first feedback control, the control unit 21 calculates the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3, and obtains the differences between the respective control current values. Specifically, during the execution of the first feedback control, the control unit 21 obtains the offset correction values Ouv and Owu as the differences between the respective control current values, for example, using the above-described equations (4) and (5).

[0058] The second feedback control is a feedback control that switches the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3 as the control current value for feedback. In the present embodiment, the control unit 21 performs the second feedback control when at least one of the duty ratios DR of the pulse waves respectively generated for the first-phase current Iu, the second-phase current Iv, and the third-phase current Iw varies within a range including a value greater than the threshold TH.

[0059] In Figure 3 shows an example of the relationship between the duty ratios Du, Dv, Dw of the pulse waves respectively generated for the first-phase current Iu, the second-phase current Iv, and the third-phase current Iw and time t. The duty ratio Du is the duty ratio DR of the pulse wave for generating the first-phase current Iu. The duty ratio Dv is the duty ratio DR of the pulse wave for generating the second-phase current Iv. The duty ratio Dw is the duty ratio DR of the pulse wave for generating the third-phase current Iw. The variations of the respective duty ratios Du, Dv, Dw with respect to time t form the same waveform as the variations of the values of the respective phase currents with respect to time t. The waveforms of the respective duty ratios Du, Dv, Dw are, for example, sine waves with mutually staggered phases. The waveforms of the respective duty ratios Du, Dv, Dw may also be three-phase waveforms with mutually staggered phases subjected to neutral point modulation. Figure 3 The example of

[0060] In Figure 3In the example, the specified threshold value TH is the higher value among the values of the duty ratio DR at the point where the waveforms of two duty ratios DR among the respective duty ratios Du, Dv, and Dw intersect. Therefore, at any time t, the number of duty ratios DR greater than the threshold value TH among the respective duty ratios Du, Dv, and Dw is one or less. Figure 3 The example shows the case where the respective duty ratios Du, Dv, and Dw change to the maximum value, i.e., 100%. Therefore, regardless of how the change ranges of the respective duty ratios Du, Dv, and Dw change, the number of duty ratios DR greater than the threshold value TH among the respective duty ratios Du, Dv, and Dw is only one or less at each time t. In Figure 3 the example, the threshold value TH is 75%.

[0061] In the present embodiment, the control unit 21 calculates a control current value based on the phase current values of two phases in which the duty ratio DR in the three-phase current is equal to or less than the threshold value TH in the second feedback control. That is, in the second feedback control, when the duty ratio Du is greater than the threshold value TH and the duty ratios Dv and Dw are equal to or less than the threshold value TH, the control unit 21 calculates a first control current value Ic1 based on the second phase current Iv and the third phase current Iw. In the second feedback control, when the duty ratio Dv is greater than the threshold value TH and the duty ratios Dw and Du are equal to or less than the threshold value TH, the control unit 21 calculates a second control current value Ic2 based on the third phase current Iw and the first phase current Iu. In the second feedback control, when the duty ratio Dw is greater than the threshold value TH and the duty ratios Du and Dv are equal to or less than the threshold value TH, the control unit 21 calculates a third control current value Ic3 based on the first phase current Iu and the second phase current Iv.

[0062] In the second feedback control, the control unit 21 switches the feedback control current value according to the change in the duty ratio DR of each pulse wave that generates the first phase current Iu, the second phase current Iv, and the third phase current Iw. In the second feedback control of the present embodiment, the switching of the control current value is performed when the respective duty ratios Du, Dv, and Dw that change with time t exceed the threshold value TH.

[0063] That is, for example, in the second feedback control, when the duty ratio Dw exceeds the threshold TH in a state where the first control current value Ic1 is used as the control current value for feedback, the control unit 21 switches the control current value from the first control current value Ic1 to the third control current value Ic3. In the second feedback control, when the duty ratio Dv exceeds the threshold TH in a state where the third control current value Ic3 is used as the control current value for feedback, the control unit 21 switches the control current value from the third control current value Ic3 to the second control current value Ic2. In the second feedback control, when the duty ratio Du exceeds the threshold TH in a state where the second control current value Ic2 is used as the control current value for feedback, the control unit 21 switches the control current value from the second control current value Ic2 to the first control current value Ic1.

[0064] In the present embodiment, the control unit 21 corrects the control current value based on the difference between the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3 in the second feedback control. Specifically, in the second feedback control, the control unit 21 uses the offset correction values Ouv and Owu to correct the two control current values that are not used in the first feedback control among the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3 to the value of the one control current value used in the first feedback control. That is, when calculating the second control current value Ic2 in the second feedback control, the control unit 21 uses the value obtained by subtracting the offset correction value Owu from the calculated second control current value Ic2 as the control current value. When calculating the third control current value Ic3 in the second feedback control, the control unit 21 uses the value obtained by subtracting the offset correction value Ouv from the calculated third control current value Ic3 as the control current value. The correction of the control current value using the offset correction values Ouv and Owu is performed, for example, in the three-phase two-axis conversion unit 21B.

[0065] The control unit 21, for example, by following Figure 4 the flowchart shown, can execute each feedback control corresponding to the changes in the above-described duty ratios Du, Dv, and Dw. As Figure 4 shown, first, the control unit 21 determines whether the duty ratio Du is greater than the threshold TH (step S100). When the duty ratio Du is greater than the threshold TH (step S100: Yes), the control unit 21 sets the control current value for feedback control to the first control current value Ic1 (step S102). When the duty ratio Du is less than or equal to the threshold TH (step S100: No), the control unit 21 determines whether the duty ratio Dv is greater than the threshold TH (step S104).

[0066] When the duty ratio Dv is greater than the threshold TH (step S104: Yes), the control unit 21 sets the control current value for feedback control to the second control current value Ic2 (step S106). When the duty ratio Dv is less than or equal to the threshold TH (step S104: No), the control unit 21 determines whether the duty ratio Dw is greater than the threshold TH (step S108).

[0067] When the duty ratio Dw is greater than the threshold TH (step S108: Yes), the control unit 21 sets the control current value for feedback control to the third control current value Ic3 (step S110). When the duty ratio Dw is less than or equal to the threshold TH (step S108: No), the control unit 21 sets the control current value for feedback control to the first control current value Ic1 (step S112).

[0068] By repeatedly performing the above steps S100 to S112, the control unit 21 can execute the first feedback control and the second feedback control according to the magnitudes of the respective duty ratios Du, Dv, and Dw. In the present embodiment, the case of executing step S112 is the case of executing the first feedback control. The case where steps S102, S106, and S110 are periodically switched and executed is the case of executing the second feedback control.

[0069] In addition, the control unit 21 can also execute each feedback control corresponding to the changes in the duty ratios Du, Dv, and Dw as described above, for example, by controlling according to the flowchart shown Figure 5 . In the example of Figure 5 , the control unit 21 determines whether the change ranges of the duty ratios Du, Dv, and Dw of the pulses generating the first-phase current Iu, the second-phase current Iv, and the third-phase current Iw are within the range below the threshold TH (step S200).

[0070] When the change ranges of the duty ratios Du, Dv, and Dw are within the range below the threshold TH (step S200: Yes), the control unit 21 executes the first feedback control (step S202). On the other hand, when the change ranges of the duty ratios Du, Dv, and Dw are not within the range below the threshold TH (step S200: No), the control unit 21 executes the second feedback control (step S204).

[0071] As described above, the motor control method for controlling the motor 1 of the present embodiment is a motor control method for adjusting three-phase currents including the first-phase current Iu, the second-phase current Iv, and the third-phase current Iw, and includes controlling the three-phase currents by feeding back a control current value obtained from the three-phase currents. Controlling the three-phase currents in the motor control method includes performing a first feedback control, in which any one of a first control current value Ic1 calculated from the second-phase current Iv and the third-phase current Iw, a second control current value Ic2 calculated from the third-phase current Iw and the first-phase current Iu, and a third control current value Ic3 calculated from the first-phase current Iu and the second-phase current Iv is fed back as the control current value. In the motor control method, controlling the three-phase currents includes performing a second feedback control, in which the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3 are switched and fed back as the control current value.

[0072] In the above processing, in the motor control device 20 that controls the motor 1, the program adjusts three-phase currents including the first-phase current Iu, the second-phase current Iv, and the third-phase current Iw, and performs processing related to the motor control method. The program causes the motor control device 20 to control the three-phase currents by feeding back a control current value obtained from the three-phase currents.

[0073] When controlling the above three-phase currents, the program causes the motor control device 20 to perform a first feedback control, in which any one of a first control current value Ic1 calculated from the second-phase current Iv and the third-phase current Iw, a second control current value Ic2 calculated from the third-phase current Iw and the first-phase current Iu, and a third control current value Ic3 calculated from the first-phase current Iu and the second-phase current Iv is fed back as the control current value.

[0074] When controlling the above three-phase currents, the program causes the motor control device 20 to perform a second feedback control, in which the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3 are switched and fed back as the control current value.

[0075] As described above, according to the motor control device 20, the control unit 21 can perform the second feedback control in which the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3 are switched as the control current value for feedback. Therefore, even when the duty ratios Du, Dv, and Dw change to a range where the current value cannot be appropriately detected by the shunt resistor 15 or the like, when detecting the control current value, two phase currents whose duty ratios Du, Dv, and Dw become values where the current value can be appropriately detected can be selected, and the control current value can be calculated based on the two phase currents. Thus, for example, even when the duty ratios Du, Dv, and Dw change in a range including relatively large values such as 90% or more and 100% or less, the control current value can be calculated with high accuracy, and the motor 1 can be appropriately controlled. The range of this threshold is set within a range where it is difficult to accurately detect the three-phase current in the inverter circuit unit 10. Therefore, it varies depending on the structure of the inverter circuit unit 10 and the like. By appropriately determining the threshold according to the respective characteristics of the inverter circuit unit 10, the switching of the feedback control can be appropriately performed for each inverter circuit unit 10. Therefore, the duty ratios Du, Dv, and Dw of the pulse wave generating the three-phase current supplied to the motor 1 can be increased, and the output of the motor 1 can be improved. In addition, without changing the structure of the existing motor 1, by changing the program for the motor control device 20 to execute processing, the output of the motor 1 can be improved.

[0076] In addition, according to the present embodiment, the control unit 21 performs the first feedback control when the duty ratios Du, Dv, and Dw of the pulse waves respectively generating the first phase current Iu, the second phase current Iv, and the third phase current Iw all change within a range below the specified threshold TH, and performs the second feedback control when at least one of the duty ratios Du, Dv, and Dw of the pulse waves respectively generating the first phase current Iu, the second phase current Iv, and the third phase current Iw changes within a range including a value larger than the threshold TH. Therefore, for example, by setting the threshold TH to the maximum value of the duty ratio DR at which the current value can be appropriately detected, when the duty ratios Du, Dv, and Dw change to values where the current value cannot be appropriately detected, the second feedback control can be executed to appropriately switch the control current value for feedback. In addition, when the duty ratios Du, Dv, and Dw do not change to values where the current value cannot be appropriately detected, the first feedback control that does not change the control current value is executed, so that the control load of the control unit 21 can be reduced.

[0077] In addition, according to the present embodiment, the control current value is the value of the dq-axis current obtained by converting the three-phase current through two axes, namely, the d-axis and the q-axis perpendicular to the d-axis. Therefore, by calculating the control current value, the rotational position of the rotor in the motor body 2 can be easily grasped. Thus, the motor 1 can be efficiently controlled using the control current value.

[0078] Further, according to the present embodiment, in the second feedback control, the control unit 21 calculates a control current value based on the phase current values of two phases in which the duty ratios Du, Dv, and Dw in the three-phase current are less than or equal to the threshold TH. Therefore, any of the phase current values of the two phases can be appropriately detected, and the control current value can be appropriately calculated based on the phase current values of the two phases.

[0079] Further, according to the present embodiment, in the second feedback control, the control unit 21 corrects the control current value based on the differences between the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3. Therefore, when switching the control current value among the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3, it is possible to suppress the control current value from becoming discontinuous. Specifically, in the present embodiment, the second control current value Ic2 and the third control current value Ic3 are corrected to the first control current value Ic1 by the offset correction values Ouv and Owu. Therefore, even when switching the control current value in the second feedback control, the control current value can be continuously changed in the same manner as the first control current value in the first feedback control. Therefore, the motor 1 can be more appropriately controlled using the control current value.

[0080] Further, according to the present embodiment, during the execution of the first feedback control, the control unit 21 calculates the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3, and obtains the differences between the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3. That is, when the change ranges of the duty ratios Du, Dv, and Dw are within the ranges where any of the first-phase current Iu, the second-phase current Iv, and the third-phase current Iw can be appropriately detected, the first control current value Ic1, the second control current value Ic2, and the third control current value Ic3 can be detected with high precision, and the deviations of the respective control current values can be obtained with high precision. Thus, when executing the second feedback control, by using the differences obtained in the first feedback control, the control current value can be appropriately corrected. Therefore, it is possible to further suppress the control current value from becoming discontinuous and to more appropriately control the motor 1.

[0081] [Modification Example]

[0082] In the above embodiment, the threshold TH is a value in which the number of duty ratios Du, Dv, and Dw greater than the threshold TH at any time t is one or less, but it is not limited thereto. The threshold TH may also be Figure 6 a value as shown in the example. In Figure 6In the example, the threshold TH becomes a value smaller than the larger one of the duty ratio DR values at the intersection points of the waveforms of two of the duty ratios Du, Dv, Dw and larger than the smaller one of the duty ratio DR values at the intersection points of the waveforms of the two duty ratios DR. In Figure 6 the example, the threshold TH is 60%.

[0083] In Figure 6 such a case, at a certain time t, two of the duty ratios Du, Dv, Dw, namely the duty ratio DR, are larger than the threshold TH. As an example, in Figure 6 the period PH shown, the duty ratio Dv and the duty ratio Dw are larger than the threshold TH. During the period PH, the duty ratio Du is smaller than the threshold TH. Thus, when there are two duty ratios DR larger than the threshold TH, the control unit 21 calculates the control current value based on the phase current value of one phase where the duty ratio DR is below the threshold TH and the phase current value of one phase where the duty ratio DR is larger than the threshold TH in the three-phase current in the second feedback control. For example, during the period PH, the control unit 21 calculates the second control current value Ic2 based on the third-phase current Iw whose duty ratio DR becomes the duty ratio Dw and the first-phase current Iu whose duty ratio DR becomes the duty ratio Du. Even in such a case, if the maximum value of the duty ratio Dw within the period PH can appropriately detect the current value through a shunt resistor 15 or the like, the second control current value Ic2 can also be calculated with high precision.

[0084] As Figure 6 shown in the modification example, by setting the threshold TH to a value smaller than the maximum duty ratio DR at which the current value can be appropriately detected through a shunt resistor 15 or the like, the second feedback control can be executed at a moment when the duty ratio DR is large to a certain extent. Thereby, even when errors occur in the duty ratios Du, Dv, Dw, it is easy to prevent the value of the duty ratio DR used in the calculation of the control current value from becoming a value at which the current value cannot be appropriately detected.

[0085] As Figure 6 shown, the control unit 21 in the motor control device 20 of the modification example also calculates the control current value based on the phase current values of the other two phases at the timing when the phase current value of one phase in the three-phase current changes from below the threshold to greater than the threshold TH in the second feedback control. The motor control device 20 of the modification example also switches between the first feedback control and the second feedback control and executes them when there are two phases with a duty ratio above the threshold.

[0086] All or part of each structural element of the above-described control unit 21 is implemented, for example, by a processor such as a CPU executing a program (software) stored in the storage unit 22. In addition, part or all of the functions of these structural elements can be implemented by hardware (including a circuitry unit: circuitry) such as an LSI, an ASIC, an FPGA, or a GPU, or can be implemented by the cooperation of software and hardware.

[0087] The program can be pre-stored in a storage device such as an HDD or a flash memory, or can be stored in a detachable storage medium such as a DVD or a CD-ROM, and the installation is achieved by mounting the storage medium in a drive device. The storage unit 22 is implemented by a storage medium such as a RAM, a ROM, an HDD, or a flash memory, for example.

[0088] As described above, one embodiment of the present invention has been described, but the present invention is not limited to the above-described one embodiment, and can be appropriately changed within the scope not departing from its gist. For example, it is illustrated that the motor control device 20 uses dq-axis currents as control current values, but the control current values can also use three-phase current values.

Claims

1. A motor control device that controls a motor by adjusting three-phase currents including a first-phase current, a second-phase current, and a third-phase current, wherein, the motor control device has a control unit that controls the three-phase currents by feeding back a control current value obtained from the three-phase currents, the control unit is capable of performing a first feedback control and a second feedback control, in the first feedback control, any one of a first control current value calculated based on the second-phase current and the third-phase current, a second control current value calculated based on the third-phase current and the first-phase current, and a third control current value calculated based on the first-phase current and the second-phase current is fed back as the control current value, in the second feedback control, the first control current value, the second control current value, and the third control current value are switched and fed back as the control current value, the control unit corrects the control current value based on the difference between the first control current value, the second control current value, and the third control current value in the second feedback control.

2. The motor control device according to claim 1, wherein, the control unit performs the first feedback control when the duty ratios of the pulse waves respectively generating the first-phase current, the second-phase current, and the third-phase current vary within a range where they are all below a specified threshold value, the second feedback control is performed when at least one of the duty ratios of the pulse waves respectively generating the first-phase current, the second-phase current, and the third-phase current varies within a range including a value larger than the threshold value.

3. The motor control device according to claim 1 or 2, wherein, the control current value is a dq-axis current value obtained by converting the three-phase currents through two axes, namely a d-axis and a q-axis perpendicular to the d-axis.

4. The motor control device according to claim 1 or 2, wherein, the control unit calculates the first control current value, the second control current value, and the third control current value and obtains the difference during the process of performing the first feedback control.

5. A motor having the motor control device according to claim 1 or 2.

6. A motor control device that controls a motor by adjusting three-phase currents including a first-phase current, a second-phase current, and a third-phase current, wherein, the motor control device has a control unit that controls the three-phase currents by feeding back a control current value obtained from the three-phase currents, the control unit is capable of performing a first feedback control and a second feedback control, in the first feedback control, any one of a first control current value calculated based on the second-phase current and the third-phase current, a second control current value calculated based on the third-phase current and the first-phase current, and a third control current value calculated based on the first-phase current and the second-phase current is fed back as the control current value, In the second feedback control, the first control current value, the second control current value, and the third control current value are switched as the control current value for feedback. The control unit executes the first feedback control when the duty ratios of the pulse waves respectively generating the first-phase current, the second-phase current, and the third-phase current all vary within a range below a specified threshold value. The second feedback control is executed when at least one of the duty ratios of the pulse waves respectively generating the first-phase current, the second-phase current, and the third-phase current varies within a range including a value larger than the threshold value. In the second feedback control, the control unit calculates the control current value based on the phase current values of two phases among the three-phase currents whose duty ratios are below the threshold value.

7. A motor having the motor control device according to claim 6.

8. A motor control device that controls a motor by adjusting three-phase currents including a first-phase current, a second-phase current, and a third-phase current, wherein: The motor control device has a control unit that performs feedback on a control current value obtained from the three-phase currents to control the three-phase currents. The control unit is capable of executing a first feedback control and a second feedback control. In the first feedback control, any one of a first control current value calculated based on the second-phase current and the third-phase current, a second control current value calculated based on the third-phase current and the first-phase current, and a third control current value calculated based on the first-phase current and the second-phase current is used as the control current value for feedback. In the second feedback control, the first control current value, the second control current value, and the third control current value are switched as the control current value for feedback. The control unit executes the first feedback control when the duty ratios of the pulse waves respectively generating the first-phase current, the second-phase current, and the third-phase current all vary within a range below a specified threshold value. The second feedback control is executed when at least one of the duty ratios of the pulse waves respectively generating the first-phase current, the second-phase current, and the third-phase current varies within a range including a value larger than the threshold value. In the second feedback control, when two of the duty ratios vary within a range including a value larger than the threshold value, the control unit calculates the control current value based on the phase current value of one phase among the three-phase currents whose duty ratio is below the threshold value and the phase current value of one phase whose duty ratio is greater than the threshold value.

9. A motor having the motor control device according to claim 8.

10. A motor control method that controls a motor by adjusting three-phase currents including a first-phase current, a second-phase current, and a third-phase current, wherein: The motor control method includes performing feedback on a control current value obtained from the three-phase currents to control the three-phase currents. Controlling the three-phase currents includes the following: Execute the first feedback control, in which any one of a first control current value calculated based on the second-phase current and the third-phase current, a second control current value calculated based on the third-phase current and the first-phase current, and a third control current value calculated based on the first-phase current and the second-phase current is used as the control current value for feedback; And Execute the second feedback control, in which the first control current value, the second control current value, and the third control current value are switched as the control current value for feedback, In the second feedback control, the control current value is corrected based on the difference between the first control current value, the second control current value, and the third control current value.

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