Motor control device

Abstract

[Problem] To provide a motor control device configured so as to be capable of performing accurate rotor position detection by sensorless control without being affected by variation in components. [Solution] The present invention comprises: a rotor position detection unit 12 that detects a rotor position by means of a phase current value and an induced voltage value calculated on the basis of an inverter output voltage value obtained from a duty ON time calculated by a PWM signal generation unit; a starting point estimation unit 32 that determines a duty ON time at which the phase current value becomes 0 from the relationship of the phase current value to the duty ON time and estimates a starting point; a correction value calculation unit 33 that calculates a correction value for correcting the inverter output voltage value on the basis of the estimated starting point; and a rotor position calculation unit that calculates the rotor position on the basis of the phase current value and an induced voltage value calculated on the basis of the result of correcting the inverter output voltage value by the correction value.

Description

Motor control device

[0001] The present invention relates to a motor control device that detects the rotor position of a permanent magnet synchronous motor through sensorless control and drives the motor using an inverter.

[0002] Conventionally, permanent magnet synchronous motors, particularly interior permanent magnet synchronous motors with permanent magnets embedded in the rotor, have been widely used as motors for electric compressors that make up air conditioners (vehicle air conditioners) for electrically powered vehicles such as electric automobiles. However, the motor control device that controls the drive of this type of motor comprises a motor, an inverter, a DC power supply (HV battery), and a control unit (controller) with a built-in microcomputer.

[0003] Furthermore, in the motor control device, the rotor position is detected from the phase current values ​​detected by the shunt resistors, the inverter output voltage values ​​(three-phase voltage values), and the induced voltage values ​​(back electromotive force voltage values) calculated from the coil resistances (winding resistances), and sensorless control is performed to control the motor without using a physical position detection sensor (see, for example, Patent Document 1).

[0004] Patent No. 5838032

[0005] The induced voltage value used to calculate the rotor position cannot be calculated accurately unless the inverter output voltage value is accurately known. Meanwhile, delays (roundings) occur in the rise and fall of the applied voltage (actual inverter output voltage) due to the ON / OFF switching of the switching elements that make up the inverter, resulting in an error between the calculated inverter output voltage value (three-phase voltage value) obtained by multiplying the duty ON time and the HV voltage and the inverter output voltage value actually applied to the motor. Therefore, in the past, this error was determined in advance using a prototype, and the calculated inverter output voltage value was corrected.

[0006] However, the error between the calculated inverter output voltage value and the inverter output voltage value actually applied to the motor varies depending on the variations in components such as switching elements. This makes it impossible to correct the calculated inverter output voltage value so that the inverter output voltage value required to calculate the induced voltage value becomes the optimal value (the inverter output voltage value actually applied to the motor), resulting in the problem of being unable to accurately detect the rotor position.

[0007] The present invention has been made to solve the above-mentioned conventional technical problems, and provides a motor control device that is capable of performing accurate rotor position detection through sensorless control, without being affected by component variations.

[0008] The motor control device of the present invention detects the rotor position of a permanent magnet synchronous motor by sensorless control and drives the motor using an inverter, and includes a current detection unit that detects the phase current values ​​flowing through the motor coils, a PWM signal generation unit that calculates the duty ON times of multiple switching elements that make up the inverter, generates a PWM signal from the calculated duty ON times, and outputs the PWM signal to the inverter, and a rotor control unit that detects the rotor position using an induced voltage value calculated based on the inverter output voltage value found from the duty ON times calculated by the PWM signal generation unit and the phase current values ​​detected by the current detection unit. an origin estimation unit that estimates an origin by determining the duty ON time at which the phase current value becomes 0 from the relationship between the duty ON time calculated by the PWM signal generation unit and the phase current value detected by the current detection unit; and a correction value calculation unit that calculates a correction value for correcting the inverter output voltage value based on the origin estimated by the origin estimation unit, wherein the rotor position detection unit corrects the inverter output voltage value using the correction value calculated by the correction value calculation unit, and includes a rotor position calculation unit that calculates the rotor position based on the induced voltage value calculated based on the corrected inverter output voltage value and the phase current value.

[0009] A motor control device according to a second aspect of the present invention is characterized in that in the above invention, the origin estimating unit estimates an origin for each switching element, the correction value calculating unit calculates a correction value for each switching element, and the rotor position calculating unit employs each calculated correction value for correcting the inverter output voltage value of each switching element.

[0010] The motor control device of the invention of claim 3 is characterized in that in the invention of claim 1, the origin estimating unit estimates an origin for each switching element, the correction value calculating unit calculates a correction value for each switching element, and the rotor position calculating unit uses an average value of the calculated correction values ​​to correct the inverter output voltage value of each switching element.

[0011] The motor control device of the invention of claim 4 is characterized in that the motor control device of the invention of claim 2 or 3 further includes a rotor moving unit that moves the rotor to the conduction phase of the switching element for which the origin estimating unit estimates the origin and the correction value calculating unit calculates the correction value.

[0012] A motor control device according to a fifth aspect of the present invention is characterized in that, in the first aspect of the present invention, the inverter is made up of three upper arm switching elements and three lower arm switching elements, and the origin estimator determines a slope from a region where the relationship between the changed duty ON time and the phase current value approximates a linear function when the two lower arm switching elements are maintained in an ON state and the duty ON time of one upper arm switching element is changed in a direction to increase it, and sets the duty ON time on the line of the slope where the phase current value becomes 0 as the origin.

[0013] A motor control device according to a sixth aspect of the present invention is characterized in that, in the first aspect of the present invention, the inverter is made up of three upper arm switching elements and three lower arm switching elements, and the origin estimator determines a slope from a region where the relationship between the changed duty ON time and the phase current value approximates a linear function when the two upper arm switching elements are maintained in an ON state and the duty ON time of the one lower arm switching element is changed in a direction to increase it, and sets the duty ON time on the line of the slope at which the phase current value becomes 0 as the origin.

[0014] The motor control device of the invention of claim 7 is characterized in that in the invention of claim 5 or claim 6, the correction value calculation unit, when changing the duty ON time, sets the time when the duty ON time is 0 as the starting point, and calculates the correction value from the difference between the starting point and the origin.

[0015] The motor control device of the invention of claim 8 is characterized in that it is provided with a failure judgment unit that judges that there is a failure in the inverter if the correction value calculated by the correction value calculation unit is outside a predetermined specified range in the invention of claim 1.

[0016] According to the present invention, in a motor control device that detects the rotor position of a permanent magnet synchronous motor by sensorless control and drives the motor with an inverter, the motor control device includes a current detection unit that detects the value of a phase current flowing through the coil of the motor, a PWM signal generation unit that calculates the duty ON time of a plurality of switching elements that make up the inverter and generates a PWM signal from the calculated duty ON time and outputs it to the inverter, a rotor position detection unit that detects the rotor position from an induced voltage value calculated based on the inverter output voltage value found from the duty ON time calculated by the PWM signal generation unit and the phase current value detected by the current detection unit, and a current detection unit that detects the rotor position from the duty ON time calculated by the PWM signal generation unit. The rotor position detection unit is configured to include an origin estimating unit that estimates an origin by finding a duty-on time at which the phase current value becomes zero from the relationship between the phase current values ​​estimated by the origin estimating unit, and a correction value calculating unit that calculates a correction value for correcting the inverter output voltage value based on the origin estimated by the origin estimating unit, and the rotor position detection unit corrects the inverter output voltage value using the correction value calculated by the correction value calculating unit, and calculates the rotor position based on the induced voltage value calculated based on the corrected inverter output voltage value and the phase current value, so that it is possible to appropriately correct the error between the calculated inverter output voltage value and the inverter output voltage value actually applied to the motor, which is caused by component variations, and improve rotor position detection performance.

[0017] This expands the operating range, especially in the low-speed range, and enables highly efficient sensorless control of the permanent magnet synchronous motor across the entire range. In addition, because the inverter output voltage value is corrected by the control unit, it is possible to eliminate the work of setting correction values ​​using prototypes, which was previously required, and this can also contribute to improving productivity.

[0018] In this case, as in the invention of claim 2, the origin estimating unit may estimate an origin for each switching element, the correction value calculating unit may calculate a correction value for each switching element, and the rotor position calculating unit may employ each calculated correction value for correcting the inverter output voltage value of each switching element, or as in the invention of claim 3, an average value of the calculated correction values ​​may be employed for correcting the inverter output voltage value of each switching element.

[0019] Furthermore, as in the invention of claim 4, by providing a rotor moving unit that moves the rotor to the conduction phase of the switching element for which the origin estimation unit estimates the origin and the correction value calculation unit calculates the correction value, it becomes possible to eliminate the influence of rotor rotation.

[0020] Furthermore, in the case where the inverter is composed of three upper arm switching elements and three lower arm switching elements as in the invention of claim 5, and the inverter output voltage value for the upper arm switching elements is corrected, when the origin estimator maintains the two lower arm switching elements in the ON state and changes the duty ON time of one upper arm switching element in a direction to increase it, it is possible to determine the slope from the region where the relationship between the changed duty ON time and the phase current value approximates a linear function, and to set the duty ON time on the straight line of the slope where the phase current value becomes 0 as the origin, thereby making it possible to set an appropriate origin.

[0021] On the other hand, when correcting the inverter output voltage for the lower arm switching elements, as in the invention of claim 6, when the origin estimator maintains the two upper arm switching elements in the ON state and changes the duty ON time of one lower arm switching element in a direction to increase it, it is preferable to obtain a slope from a region where the relationship between the changed duty ON time and the phase current value approximates a linear function, and to set the duty ON time where the phase current value becomes 0 on the straight line of the slope as the origin.

[0022] As in the seventh aspect of the invention, the correction value calculation unit, when changing the duty ON time, sets the start point when the duty ON time is 0, and calculates the correction value from the difference between this start point and the origin.This makes it possible to accurately correct the calculated inverter output voltage value that arises from delays in the rise and fall of the applied voltage (actual inverter output voltage value) due to the ON / OFF switching of the switching elements, and to accurately detect the rotor position.

[0023] Furthermore, as in the invention of claim 8, by providing a failure judgment unit that judges that there is an inverter failure if the correction value calculated by the correction value calculation unit is outside a predetermined specified range, it becomes possible to quickly judge component failure and improve reliability.

[0024] It is an electric circuit diagram of a motor control device of an embodiment to which the present invention is applied. It is a functional block diagram of a control unit of the motor control device of Figure 1. It is a functional block diagram of a rotor position direction unit of the control unit of Figure 2. It is a flowchart explaining the correction operation of the inverter output voltage value of the motor control device of claim 1. It is an electric circuit diagram explaining the correction operation of the inverter output voltage value of the upper arm switching element of the U phase. It is a diagram explaining an example of the relationship between duty ON time and phase current value.

[0025] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. (1) Configuration of Motor Control Device 1 The motor control device 1 of the embodiment drives a permanent magnet synchronous motor 2 (hereinafter simply referred to as a motor) built into, for example, an electric compressor of a vehicle air conditioner (not shown), and is composed of a control unit 3, an inverter 4, an HV battery (HV DC power supply) 6, and an LV battery (LV DC power supply) 7. The HV battery 6 is a DC power supply for driving the motor 2 and the traction motor of the electric vehicle, and the LV battery 7 is a DC power supply for the control unit 3.

[0026] The motor 2 of the embodiment, which is the object of control by the motor control device 1, is a three-phase brushless DC motor, and has a stator 10 (FIG. 2) including three-phase coils (windings) 5u, 5v, and 5w, and a rotor 15 (FIG. 2) with built-in permanent magnets that rotates inside this stator 10.

[0027] (2) Configuration of control unit 3 The control unit 3 is composed of a microcomputer and peripheral electric circuits, and as shown in the functional block diagram of FIG. 2, has a PWM signal generation unit 11, a rotor position detection unit 12, a rotation speed detection unit 13, a target current phase setting unit 14, an adder 16, a voltage peak value detection unit 18, a voltage phase detection unit 19, and a phase voltage setting unit 21, and drives the motor 2 based on a drive command from the vehicle's host ECU 22 (FIG. 1).

[0028] (3) Configuration of Inverter 4 Inverter 4 of the embodiment is composed of three upper arm switching elements (U-phase upper arm switching element 24A, V-phase upper arm switching element 24B, and W-phase upper arm switching element 24C), all of which are IGBTs, and three lower arm switching elements (U-phase lower arm switching element 24D, V-phase lower arm switching element 24E, and W-phase lower arm switching element 24F), with U-phase upper arm switching element 24A and lower arm switching element 24D connected in series, V-phase upper arm switching element 24B and lower arm switching element 24E connected in series, and W-phase upper arm switching element 24C and lower arm switching element 24F connected in series.

[0029] The collectors of each of the upper arm switching elements 24A to 24C are connected to the positive bus 26 of the HV battery 6, and the emitters of each of the lower arm switching elements 24D to 24F are connected to the negative bus 27. The connection point between the upper arm switching element 24A and the lower arm switching element 24D of the U phase is connected to the U phase coil 5u of the motor 2, the connection point between the upper arm switching element 24B and the lower arm switching element 24E of the V phase is connected to the V phase coil 5v of the motor 2, and the connection point between the upper arm switching element 24C and the lower arm switching element 24F of the W phase is connected to the W phase coil 5w of the motor 2.

[0030] The gates of the switching elements 24A to 24F and the secondary output terminal of the HV battery 6 are connected to the PWM signal generating unit 11 of the control unit 3. A flywheel diode is connected in anti-parallel to each of the switching elements 24A to 24F.

[0031] A shunt resistor 31 constituting a current detection unit is connected to the negative bus 27 between the inverter 4 and the HV battery 6. The inverter 4 derives the U-phase current Iu, V-phase current Iv, and W-phase current Iw from the voltage generated by the shunt current flowing through the shunt resistor 31, and sends these values ​​to the rotor position detection unit 12 of the control unit 3.

[0032] (4) Operation of control unit 3 and inverter 4 The PWM signal generation unit 11 of the control unit 3 calculates the duty ON time Dt (the time during which the switching element is ON during one carrier period) of each of the switching elements 24A to 24F of the U, V and W phases based on the HV voltage value Vh of the HV battery 6 and the U-phase voltage command value Vut, V-phase voltage command value Vvt, and W-phase voltage command value Vwt set by the phase voltage setting unit 21, and generates a PWM signal (output duty ratio) from this duty ON time Dt for turning each of the switching elements 24A to 24F ON / OFF and outputs the PWM signal to the inverter 4.

[0033] The PWM signal generating unit 11 calculates the duty ON time Dt for each of the switching elements 24A to 24F, resulting in six calculated duty ON times Dt. Each of the switching elements 24A to 24F of the inverter 4 is turned ON / OFF in a predetermined pattern by the PWM signal from the PWM signal generating unit 11, and the U-phase inverter output voltage Vur, V-phase inverter output voltage Vvr, and W-phase inverter output voltage Vwr based on this ON / OFF pattern are applied to the coils 5u to 5w of the U, V, and W phases of the motor 2. These Vur, Vvr, and Vwr are the inverter output voltage values ​​actually applied to the motor 2.

[0034] Furthermore, the PWM signal generating unit 11 calculates the U-phase inverter output voltage value Vu, the V-phase inverter output voltage Vv, and the W-phase inverter output voltage Vw (three-phase voltage values) from the duty ON time Dt of the switching elements 24A to 24F of each of the U, V, and W phases and the HV voltage value Vh of the HV battery 6 using the following formula (I), and outputs these to the rotor position detecting unit 12: Vuvw=Dt×Vh (I) These Vu, Vv, and Vw are the calculated inverter output voltage values. Furthermore, the PWM signal generating unit 11 also outputs the duty ON time Dt of each of the switching elements 24A to 24F to the rotor position detecting unit 12.

[0035] In calculating the inverter output voltages Vu, Vv, and Vw, when the phase current flows into the motor 2, the inverter output voltage changes depending on whether the upper arm switching element is turned on or off, so the duty ON time Dt of the upper arm switching element is used. When the phase current flows out of the motor 2, the inverter output voltage changes depending on whether the lower arm switching element is turned on or off, so the duty ON time Dt of the lower arm switching element is used.

[0036] Rotor position detection unit 12 derives a phase current peak value Ip (current phase) and rotor position θm using the U-phase current value Iu, V-phase current value Iv, and W-phase current value Iw sent from inverter 4, and sends the phase current peak value Ip to target current phase setting unit 14, while sending the rotor position θm to rotation speed detection unit 13. Rotor position detection unit 12 also derives and outputs a d-axis current Id from the phase current values.

[0037] The rotor position θm is calculated based on the induced voltage E and the phase current values ​​Iu, Iv, and Iw, and the induced voltage E is calculated using the following formula (II): E=Vuvw-R×Iuvw (II) where Vuvw is the calculated inverter output voltage values ​​Vu, Vv, and Vw sent from the PWM signal generating unit 11, and R is the resistance value of the coils 5u to 5w of each phase of the motor 2.

[0038] This rotor position θm enables sensorless control that does not rely on a physical position detection sensor, but as mentioned above, errors occur due to component characteristics between the calculated inverter output voltage values ​​Vu, Vv, Vw and the inverter output voltage values ​​Vur, Vvr, Vwr that are actually applied to the motor 2, and since these errors also vary depending on the component, they are corrected by the rotor position detection unit 12. The correction operation of the inverter output voltage values ​​Vu, Vv, Vw by the rotor position detection unit 12 will be described in detail later.

[0039] Rotation speed detection unit 13 uses rotor position θm sent from rotor position detection unit 12 to find rotor position change amount Δθm by subtracting rotor position θm-1 from the rotor position θm in the previous calculation cycle, and then applies a predetermined filter to this rotor position change amount Δθm to calculate rotation speed ω of motor 2, which is sent to adder 16. Then, rotation speed ω found by rotation speed detection unit 13 is fed back via adder 16 to target rotation speed ωt of motor 2 instructed to control unit 3, and rotation speed difference Δω is calculated by processing such as P control or PI control, and this is sent to voltage peak value detection unit 18.

[0040] The voltage peak value detection unit 18 uses the calculated rotation speed difference Δω to detect the applied voltage peak value Vp of the voltage to be applied to the motor 2 through processing such as P control or PI control, and sends this to the phase voltage setting unit 21.

[0041] The target current phase setting unit 14 sets the target current phase so that the torque generated by the motor 2 relative to the phase current is maximized by current vector control, for example, called maximum torque / current control. Specifically, the target d-axis current Idt is set using the phase current peak value Ip detected by the rotor position detection unit 12 and a previously prepared data table, and this is sent to the voltage phase detection unit 19.

[0042] The voltage phase detection unit 19 uses the target d-axis current Idt set by the target current phase setting unit 14 to detect the applied voltage phase θv (target voltage phase) of the voltage to be applied to the motor 2, and sends this to the phase voltage setting unit 21.

[0043] The phase voltage setting unit 21 uses the applied voltage peak value Vp detected by the voltage peak value detection unit 18 and the applied voltage phase θv detected by the voltage phase detection unit 19 to set the above-mentioned U-phase voltage command value Vut, V-phase voltage command value Vvt, and W-phase voltage command value Vwt, which are applied set voltages to be applied to the coils 5u to 5w of each of the UVW phases of the motor 2, and sends these to the PWM signal generation unit 11.

[0044] The PWM signal generating unit 11 applies a set voltage set by the phase voltage setting unit 21 to the coils 5u to 5w of each of the UVW phases of the motor 2 via the inverter 4 in a sinusoidal wave manner (180-degree energization) based on the ON / OFF pattern of the PWM signal, thereby operating the motor 2 at the desired rotation speed.

[0045] (5) Correction Operation of Inverter Output Voltage Values ​​by Rotor Position Detection Unit 12 Next, the correction operation of the above-mentioned inverter output voltage values ​​Vu, Vv, Vw (calculated inverter output voltage values) by rotor position detection unit 12 will be described in detail with reference to Figures 3 to 6. As shown in the functional block diagram of Figure 3, rotor position detection unit 12 in this embodiment is configured to include an origin estimation unit 32, a correction value calculation unit 33, a rotor position calculation unit 34, a rotor movement unit 36, and a fault determination unit 37.

[0046] Next, the correction operation will be described with reference to the flowchart of FIG. 4. For example, the host ECU 22 sends a correction instruction for the inverter output voltage values ​​Vu, Vv, and Vw to the control unit 3 when the motor 2 (electric compressor) is started (either at the initial start or each time the motor is started). When the rotor position detection unit 12 constituting the control unit 3 receives the correction instruction for the inverter output voltage values ​​Vu, Vv, and Vw in step S1 of FIG. 4, the rotor movement unit 36 ​​moves the rotor 15 of the motor 2 to the energization phase of the switching element 24A that is the first target of correction in step S2. In practice, the rotor movement unit 36 ​​outputs a movement request signal to the PWM signal generation unit 11, and the inverter 4 energizes the coils 5u to 5w of the motor 2 as specified, moving the rotor 15 and fixing it in the energization phase of the switching element 24A.

[0047] Next, in step S3, the origin estimation unit 32 outputs a duty ON time output request signal for the switching element 24A to the PWM signal generation unit 11, causing the duty ON time Dt of the switching element 24A to be changed in several increments from 0 and output. At this time, in the upper arm, only the switching element 24A is turned ON, and the other switching elements 24B and 24C are turned 100% OFF. In addition, in the lower arm, the switching element 24D is turned 100% OFF, and the switching elements 24E and 24F are turned 100% ON.

[0048] The current paths through the inverter 4 and motor 2 at this time are indicated by bold arrows in Figure 5. The duty ON time Dt is output a predetermined number of times by repeating steps S4 and S3, and is changed so that it gradually increases each time. In practice, each duty ON time Dt is output for a fixed period of time each time, and the phase current value at each duty ON time Dt is input to the origin estimation unit 32.

[0049] When the duty ON time Dt has been output a predetermined number of times, the process proceeds to step S5, where correction values ​​for the inverter output voltages Vu, Vv, and Vw are calculated. At this time, the origin estimator 32 estimates a predetermined origin Dt1 using the method shown in FIG. 6. Even if the duty ON time Dt is increased from 0, the increase in the phase current value is delayed due to the component characteristics of the switching element 24A. As shown by the solid line in FIG. 6, the phase current value initially increases gradually, and then gradually increases linearly. In this linear region, the relationship between the duty ON time Dt and the phase current value approximates a linear function.

[0050] Therefore, the origin estimator 32 finds the slope from the region that approximates this linear function, and sets the duty-on time Dt, on the straight line of this slope (shown by the dashed line in FIG. 6 ), where the phase current value is 0, as the origin Dt1. The origin Dt1 estimated by the origin estimator 32 is sent to the correction value calculator 33.

[0051] The correction value calculation unit 33 calculates a correction value Vuhosa of the inverter output voltage value Vu for the switching element 24A based on the origin Dt1 estimated by the origin estimation unit 32. Note that this correction value Vuhosa is a correction value when the U-phase current Iu flows into the motor 2. In practice, when the PWM signal generation unit 11 changes the duty-on time Dt, the correction value calculation unit 33 sets the time when the duty-on time Dt is 0 as a start point Dt0, calculates a correction voltage value from the difference (Dt1-Dt0) between this start point Dt0 and the origin Dt1, and sets this correction voltage value as the correction value Vuhosa.

[0052] Next, in step S6, the failure determination unit 37 determines whether the calculated correction value Vuhosa is outside a specified range. If it is outside the specified range, the process proceeds to step S9, where it is determined that the switching element 24A is faulty. If it is determined that the switching element 24A is faulty, the control unit 3 outputs a predetermined failure alarm using an alarm device (display, etc.) not shown.

[0053] On the other hand, if it is within the specified range in step S6, the process proceeds to step S7 to determine whether or not calculation of the correction values ​​for the switching elements 24A to 24F of all phases UVW has been completed. If not, the process returns to step S2 and repeats the above.

[0054] After the calculation of the correction value Vuhosa for the U-phase upper arm switching element 24A is completed, the correction value Vvhosb for the V-phase upper arm switching element 24B is calculated. This correction value Vvhosb is the correction value for the inverter output voltage value Vv when the V-phase current Iv flows into the motor 2. In this case, the movement of the rotor 15 and the calculation method are the same as those described above, but in this case, only the upper arm switching element 24B is turned ON, and the other switching elements 24A and 24C are turned 100% OFF. In addition, in the lower arm, switching element 24E is turned 100% OFF, and switching elements 24D and 24F are turned 100% ON.

[0055] After the calculation of the correction value Vvhosb for the V-phase upper arm switching element 24B is completed, the correction value Vwhosc for the W-phase upper arm switching element 24C is calculated. This correction value Vwhosc is the correction value for the inverter output voltage value Vw when the W-phase current Iw flows into the motor 2. In this case, the movement of the rotor 15 and the calculation method are the same as those described above, except that in this case, only the upper arm switching element 24C is turned ON, and the other switching elements 24A and 24B are turned 100% OFF. In addition, in the lower arm, switching element 24F is turned 100% OFF, and switching elements 24D and 24E are turned 100% ON.

[0056] After the calculation of the correction value Vwhosc for the W-phase upper arm switching element 24C is completed, the correction value Vuhosd for the U-phase lower arm switching element 24D is calculated. This correction value Vuhosd is the correction value for the inverter output voltage value Vu when the U-phase current Iu flows out from the motor 2. In this case, the movement of the rotor 15 and the calculation method are the same as those described above, but in this case, only the lower arm switching element 24D is turned ON, and the other switching elements 24E and 24F are turned 100% OFF. In addition, in the upper arm, the switching element 24A is turned 100% OFF, and the switching elements 24B and 24C are turned 100% ON.

[0057] After the calculation of the correction value Vuhosd for the U-phase lower arm switching element 24D is completed, the correction value Vvhose for the V-phase lower arm switching element 24E is calculated. This correction value Vvhose is the correction value for the inverter output voltage value Vv when the V-phase current Iv flows out from the motor 2. In this case, the movement of the rotor 15 and the calculation method are the same as those described above, but in this case, only the lower arm switching element 24E is turned ON, and the other switching elements 24D and 24F are turned 100% OFF. In addition, in the upper arm, the switching element 24B is turned 100% OFF, and the switching elements 24A and 24C are turned 100% ON.

[0058] After the calculation of the correction value Vvhose for the V-phase lower arm switching element 24E is completed, the correction value Vwhosf for the W-phase lower arm switching element 24F is calculated. This correction value Vwhosf is the correction value for the inverter output voltage value Vw when the W-phase current Iw flows out from the motor 2. In this case, the movement of the rotor 15 and the calculation method are the same as those described above, but in this case, only the lower arm switching element 24F is turned ON, and the other switching elements 24D and 24E are turned 100% OFF. In addition, in the upper arm, switching element 24C is turned 100% OFF, and switching elements 24A and 24B are turned 100% ON.

[0059] When the calculation of the correction values ​​for switching elements 24A to 24F of all phases has been completed in this manner, the process proceeds to step S8. In step S8, rotor position calculation unit 34 employs the correction values ​​Vuhosa, Vuhosd, Vvhosb, Vvhose, Vwhosc, and Vwhosf calculated by correction value calculation unit 33 as described above, and corrects the calculated inverter output voltage values ​​Vu, Vv, and Vw sent from PWM signal generation unit 11, respectively, using the respective correction values.

[0060] For example, in the examples of Figures 5 and 6, if the difference in duty ON time calculated from the origin Dt1 - the start point Dt0 is +0.5 μs, the voltage value equivalent to this +0.5 μs is set as the correction value Vuhosa, and a correction is performed by adding this correction value Vuhosa to the inverter output voltage value Vu.

[0061] In this correction, as described above, the correction values ​​Vuhosa, Vuhosd, Vvhosb, Vvhose, Vwhosc, and Vwhosf may be used to correct the inverter output voltage values ​​Vu, Vv, and Vw, respectively, or their average values ​​may be used to correct the inverter output voltage values ​​Vu, Vv, and Vw.

[0062] Then, the induced voltage E is calculated using the corrected inverter output voltage values ​​Vu, Vv, and Vw according to the aforementioned equation (II), and the rotor position θm is calculated using this induced voltage E and the respective phase currents Iu, Iv, and Iw.

[0063] It is believed that delays in the rise and fall of the inverter output voltages Vur, Vvr, and Vwr actually applied to the motor 2 are caused by delays in changes in phase current values ​​due to the component characteristics of each of the switching elements 24A to 24F, as described above, so by calculating a correction value from the difference (Dt1-Dt0) between the start point Dt0 and the origin Dt1 and correcting the calculated inverter output voltages Vu, Vv, and Vw, as described above, the calculated inverter output voltages Vu, Vv, and Vw sent to the rotor position detection unit 12 can be made to match or approach the inverter output voltages Vur, Vvr, and Vwr actually applied to the motor 2. This makes it possible to accurately calculate the rotor position θm.

[0064] As described above in detail, according to the present invention, the errors between the calculated inverter output voltage values ​​Vu, Vv, Vw and the inverter output voltage values ​​Vur, Vvr, Vwr actually applied to the motor 2, which are caused by variations in components, can be appropriately corrected using the correction values ​​Vuhosa, Vuhosd, Vvhosb, Vvhose, Vwhosc, Vwhosf, thereby improving rotor position detection performance. This expands the operating range, particularly in the low speed range, and makes it possible to achieve highly efficient sensorless control of the permanent magnet synchronous motor 2 over the entire speed range.

[0065] Furthermore, according to the present invention, the control unit 3 corrects the inverter output voltage values ​​Vu, Vv, and Vw, which makes it possible to reduce the work of setting correction values ​​using prototypes, which was previously required, and also contributes to improving productivity.

[0066] In addition, in the embodiment, the origin estimation unit 32 estimates the origin, and the correction value calculation unit 33 is provided with a rotor movement unit 36 ​​that moves the rotor 15 to the conduction phase of the switching elements 24A to 24F for which the correction value is calculated, so that it is possible to eliminate the influence of the rotation of the rotor 15.

[0067] Furthermore, in the embodiment, when correcting the inverter output voltage value for the upper arm switching elements 24A to 24C, the origin estimation unit 32 maintains the two lower arm switching elements in the ON state and changes the duty ON time Dt of one upper arm switching element in the direction of increasing it.The origin estimation unit 32 then determines the slope from the region where the relationship between the changed duty ON time Dt and the phase current value approximates a linear function, and sets the duty ON time Dt where the phase current value is 0 on the straight line of the slope as the origin Dt1, thereby making it possible to set an appropriate origin Dt1.

[0068] On the other hand, when correcting the inverter output voltage for the lower arm switching elements 24D to 24F, the origin estimation unit 32 maintains the two upper arm switching elements in the ON state and changes the duty ON time Dt of one lower arm switching element in a direction to increase it.The origin estimation unit 32 then determines the slope from the region where the relationship between the changed duty ON time Dt and the phase current value approximates a linear function, and sets the duty ON time Dt where the phase current value is 0 on the straight line of the slope as the origin Dt1, thereby making it possible to set an appropriate origin Dt1.

[0069] In the embodiment, when the duty ON time Dt is changed, the correction value calculation unit 33 sets the time when the duty ON time Dt is 0 as the starting point Dt0, and calculates the correction values ​​Vuhosa, Vuhosd, Vvhosb, Vvhose, Vwhosc, and Vwhosf from the difference (Dt1-Dt0) between the starting point Dt0 and the origin Dt1. This makes it possible to accurately correct the calculated inverter output voltage values ​​Vu, Vv, and Vw that arise from delays in the rise and fall of the applied voltages (actual inverter output voltage values ​​Vur, Vvr, and Vwr) due to the ON / OFF switching of the switching elements 24A to 24F, and to accurately detect the rotor position.

[0070] Furthermore, in the embodiment, a failure determination unit 37 is provided which determines that there is a failure in the inverter 4 if the correction values ​​Vuhosa, Vuhosd, Vvhosb, Vvhose, Vwhosc, and Vwhosf calculated by the correction value calculation unit 33 are outside a predetermined specified range, so that it is possible to quickly determine failure in components such as switching elements and improve reliability.

[0071] In the embodiment, the rotor position detection unit 12 is provided with the origin estimation unit 32, rotor movement unit 36, correction value calculation unit 33, and failure determination unit 37, but the present invention is not limited to this, and units other than the rotor position calculation unit 34 may be provided in, for example, the PWM signal generation unit 11.

[0072] In addition, in the embodiment, the present invention is applied to a motor control device 1 that drives and controls the motor 2 of an electric compressor of a vehicle air conditioning system, but the present invention is not limited to this and is also effective for driving and controlling the motors of various devices that perform sensorless control.

[0073] REFERENCE SIGNS LIST 1 Motor control device 2 Motor 3 Control unit 4 Inverter 5 Coil 6 HV battery 7 LV battery 10 Stator 11 PWM signal generation unit 12 Rotor position detection unit 15 Rotor 21 Phase voltage setting unit 24A to 24F Switching elements 31 Shunt resistor (current detection unit) 32 Origin estimation unit 33 Correction value calculation unit 34 Rotor position calculation unit 36 ​​Rotor movement unit 37 Fault determination unit

Claims

1. A motor control device that detects the rotor position of a permanent magnet synchronous motor by sensorless control and drives the motor by an inverter, comprising: a current detection unit that detects phase current values ​​flowing through a coil of the motor; a PWM signal generation unit that calculates a duty ON time of a plurality of switching elements that constitute the inverter, generates a PWM signal from the calculated duty ON time, and outputs the PWM signal to the inverter; a rotor position detection unit that detects the rotor position from an induced voltage value calculated based on an inverter output voltage value obtained from the duty ON time calculated by the PWM signal generation unit and the phase current value detected by the current detection unit; an origin estimation unit that estimates an origin by determining the duty ON time at which the phase current value becomes zero from the relationship between the duty ON time calculated by the PWM signal generation unit and the phase current value detected by the current detection unit; and a correction value calculation unit that calculates a correction value for correcting the inverter output voltage value based on the origin estimated by the origin estimation unit, a rotor position calculation unit that corrects the inverter output voltage value by the correction value calculated by the correction value calculation unit, and calculates the rotor position based on the induced voltage value calculated on the basis of the corrected inverter output voltage value and the phase current value.

2. The motor control device according to claim 1, characterized in that the origin estimation unit estimates the origin for each of the switching elements, the correction value calculation unit calculates the correction value for each of the switching elements, and the rotor position calculation unit employs each of the calculated correction values ​​for correcting the inverter output voltage value of each of the switching elements.

3. The motor control device according to claim 1, characterized in that the origin estimation unit estimates the origin for each of the switching elements, the correction value calculation unit calculates the correction value for each of the switching elements, and the rotor position calculation unit adopts an average value of the calculated correction values ​​for correcting the inverter output voltage value of each of the switching elements.

4. A motor control device as described in claim 2 or 3, characterized in that the origin estimation unit estimates the origin and the correction value calculation unit is further provided with a rotor movement unit that moves the rotor to the current-carrying phase of the switching element for which the correction value is calculated.

5. The motor control device according to claim 1, wherein the inverter is composed of three upper arm switching elements and three lower arm switching elements, and the origin estimator determines a slope from a region where the relationship between the changed duty ON time and the phase current value approximates a linear function when two of the lower arm switching elements are maintained in an ON state and the duty ON time of one of the upper arm switching elements is changed in a direction to increase, and sets the duty ON time at which the phase current value becomes 0 on a straight line of the slope as the origin.

6. The motor control device according to claim 1, wherein the inverter is composed of three upper arm switching elements and three lower arm switching elements, and the origin estimator determines a slope from a region where the relationship between the changed duty ON time and the phase current value approximates a linear function when the two upper arm switching elements are maintained in an ON state and the duty ON time of one lower arm switching element is changed in a direction to increase the duty ON time, and sets the duty ON time at which the phase current value becomes 0 on a straight line of the slope as the origin.

7. A motor control device as described in claim 5 or 6, characterized in that the correction value calculation unit, when changing the duty ON time, sets the time when the duty ON time is 0 as a starting point, and calculates the correction value from the difference between the starting point and the origin.

8. The motor control device according to claim 1, further comprising a failure determination unit which determines that the inverter is faulty if the correction value calculated by the correction value calculation unit is outside a predetermined specified range.

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