Motor control device

Abstract

To provide a motor control device that is capable of correct rotor position detection by sensorless control without being affected by component variations.SOLUTION: A motor control device comprises: a rotor position detection unit 12 that detects a rotor position from an induction voltage value and a phase current value that are calculated on the basis of an inverter output voltage value calculated from a duty ON time calculated by a PWM signal generation unit; an origin estimation unit 32 that calculates a duty ON time at which the phase current value becomes 0, and estimates an origin from the relationship between the duty ON time and the phase current value; a correction value calculation unit 33 that calculates a correction value for correcting the inverter output value on the basis of the estimated origin; and a rotor position calculation unit that calculates a rotor position on the basis of the induction voltage value and the phase current value that are calculated on the basis of the induction voltage value corrected with the correction value.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Conventionally, permanent magnet synchronous motors, particularly embedded permanent magnet synchronous motors with permanent magnets embedded in the rotor, have been widely used in motors for electric compressors (vehicle air conditioners) that constitute air conditioning devices for electric vehicles such as electric cars. However, a motor control device for controlling the drive of this type of motor is composed of a motor, an inverter, a DC power supply (HV battery), and a control unit (controller) incorporating a microcomputer.

[0003] Further, in the above motor control device, sensorless control for controlling the motor is performed without using a physical position detection sensor by detecting the rotor position from the phase current value detected by a shunt resistor, the inverter output voltage value (three-phase voltage value), and the induced voltage value (value of the counter electromotive force) obtained from the coil resistance (winding resistance) and the phase current value (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The induced voltage value for calculating the rotor position cannot be accurately calculated unless the inverter output voltage value is known precisely. On the other hand, since there is a delay (overshoot) in the rise and fall of the applied voltage (actual inverter output voltage) due to the ON / OFF of the switching elements constituting the inverter, an error occurs between the calculated inverter output voltage value (three-phase voltage value) obtained by multiplying the duty ON time by the HV voltage and the actual inverter output voltage value applied to the motor. Therefore, conventionally, the above error was obtained in advance with a prototype, and the calculated inverter output voltage value was corrected accordingly.

[0006] However, the error between the calculated inverter output voltage value and the actual inverter output voltage value applied to the motor varies due to component variations such as switching elements. As a result, it becomes impossible to correct the calculated inverter output voltage value so that the inverter output voltage value required for calculating the induced voltage value becomes the optimal value (the actual inverter output voltage value applied to the motor), and there was a problem that accurate rotor position detection could not be performed.

[0007] The present invention has been made to solve such conventional technical problems, and provides a motor control device capable of accurately detecting the rotor position by sensorless control without being affected by component variations.

Means for Solving the Problems

[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 by an inverter, and includes a current detection unit that detects the value of the phase current flowing through the motor coil, a PWM signal generation unit that calculates the duty ON time of a plurality of switching elements constituting the inverter, generates a PWM signal from the calculated duty ON time, and outputs the PWM signal to the inverter, an induced voltage value calculated based on the inverter output voltage value obtained from the duty ON time calculated by this PWM signal generation unit, a rotor position detection unit that detects the rotor position based on the phase current value detected by the current detection unit, and an origin estimation unit that obtains the duty ON time when the phase current value becomes 0 from the relationship between the phase current value detected by the current detection unit and the duty ON time calculated by the PWM signal generation unit, and estimates the origin, and includes a correction value calculation unit that calculates a correction value for correcting the inverter output voltage value based on the origin estimated by this origin estimation unit. The rotor position detection unit corrects the inverter output voltage value with the correction value calculated by the correction value calculation unit, and has 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] In the motor control device of the invention according to claim 2, in the above invention, the origin estimation unit estimates the origin for each switching element, the correction value calculation unit calculates a correction value for each switching element, and the rotor position calculation unit adopts each of the calculated correction values for correcting the inverter output voltage value of each switching element.

[0010] In the motor control device of the invention according to claim 3, in the invention according to claim 1, the origin estimation unit estimates the origin for each switching element, the correction value calculation unit calculates a correction value for each switching element, and the rotor position calculation unit adopts the average value of the calculated correction values for correcting the inverter output voltage value of each switching element.

[0011] The motor control device according to the invention of claim 4 is characterized in that, in the invention of claim 2 or claim 3, it includes 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.

[0012] The motor control device according to the invention of claim 5 is characterized in that, in the invention of claim 1, the inverter is composed of three upper arm switching elements and three lower arm switching elements, and the origin estimation unit maintains two lower arm switching elements in the ON state and changes the duty ON time of one upper arm switching element in the direction of increasing it. When this is done, the slope is obtained from the region where the relationship between the changed duty ON time and the phase current value approximates a linear function, and the duty ON time at which the phase current value becomes 0 on the straight line of the slope is taken as the origin.

[0013] The motor control device according to the invention of claim 6 is characterized in that, in the invention of claim 1, the inverter is composed of three upper arm switching elements and three lower arm switching elements, and the origin estimation unit maintains two upper arm switching elements in the ON state and changes the duty ON time of one lower arm switching element in the direction of increasing it. When this is done, the slope is obtained from the region where the relationship between the changed duty ON time and the phase current value approximates a linear function, and the duty ON time at which the phase current value becomes 0 on the straight line of the slope is taken as the origin.

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

[0015] The motor control device according to the invention of claim 8 is characterized in that, in the invention of claim 1, it includes a failure determination unit that determines that the inverter has failed when the correction value calculated by the correction value calculation unit is outside a predetermined specified range.

Advantages of the Invention

[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 by an inverter, a current detection unit that detects the value of the phase current flowing through the motor coil, a duty ON time of a plurality of switching elements constituting the inverter is calculated, a PWM signal generation unit that generates a PWM signal from the calculated duty ON time and outputs the PWM signal to the inverter, an induced voltage value calculated based on the inverter output voltage value obtained from the duty ON time calculated by this PWM signal generation unit, and a rotor position detection unit that detects the rotor position based on the phase current value detected by the current detection unit, and an origin estimation unit that obtains the duty ON time when the phase current value becomes 0 from the relationship between the phase current value detected by the current detection unit and the duty ON time calculated by the PWM signal generation unit and estimates the origin, and a correction value calculation unit that calculates a correction value for correcting the inverter output voltage value based on the origin estimated by this origin estimation unit are provided. The rotor position detection unit corrects the inverter output voltage value with the correction value calculated by the correction value calculation unit, and has 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. Therefore, the error between the calculated inverter output voltage value due to component variations and the actual inverter output voltage value applied to the motor can be appropriately corrected, and the rotor position detection performance can be improved.

[0017] As a result, particularly the operation range in the low speed region is expanded, and sensorless control of a high-efficiency permanent magnet synchronous motor over the entire range can be realized. In addition, since the inverter output voltage value is corrected by the control unit, it is possible to reduce the setting work of the correction value using a prototype that was necessary in the past, and it is also possible to contribute to the improvement of productivity.

[0018] In this case, like the invention of claim 2, the origin estimation unit may estimate the origin for each switching element, the correction value calculation unit may calculate the correction value for each switching element, and the rotor position calculation unit may adopt each calculated correction value for the correction of the inverter output voltage value of each switching element respectively. Also, like the invention of claim 3, a value obtained by averaging each calculated correction value may be adopted for the correction of the inverter output voltage value of each switching element.

[0019] Also, like the invention of claim 4, by providing a rotor moving unit that moves the rotor to the energization phase of the switching element for which the origin estimation unit estimates the origin and the correction value calculation unit calculates the correction value, the influence due to the rotation of the rotor can be eliminated.

[0020] Also, like the invention of claim 5, when the inverter is composed of three upper arm switching elements and three lower arm switching elements, and correction of the inverter output voltage value for the upper arm switching element is performed, the origin estimation unit maintains two lower arm switching elements in the ON state and changes the duty ON time of one upper arm switching element in the direction of increasing it. When the relationship between the changed duty ON time and the phase current value approximates a linear function, the slope is obtained from the region where they approximate the linear function, and the duty ON time at which the phase current value becomes 0 on the straight line of the slope is set as the origin, so that an appropriate origin can be set.

[0021] On the other hand, when correction of the inverter output voltage for the lower arm switching element is performed, like the invention of claim 6, the origin estimation unit maintains two upper arm switching elements in the ON state and changes the duty ON time of one lower arm switching element in the direction of increasing it. When the relationship between the changed duty ON time and the phase current value approximates a linear function, the slope is obtained from the region where they approximate the linear function, and the duty ON time at which the phase current value becomes 0 on the straight line of the slope may be set as the origin.

[0022] Then, like the invention of claim 7, when the correction value calculation unit changes the duty ON time, starting from the point where the duty ON time is 0, the correction value is calculated from the difference between the starting point and the origin, so that the rise and fall delays of the applied voltage (actual inverter output voltage value) due to the ON / OFF of the switching element can be accurately corrected, and accurate rotor position detection can be performed.

[0023] Furthermore, like the invention of claim 8, by providing a failure determination unit that determines a failure of the inverter when the correction value calculated by the correction value calculation unit is outside a predetermined specified range, component failures can be quickly determined and reliability can be improved.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (1) Configuration of the motor control device 1 The motor control device 1 of the embodiment drives a permanent magnet synchronous motor 2 (hereinafter simply referred to as the motor) incorporated in, 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, an LV battery (LV DC power supply) 7, and the like. The HV battery 6 is a DC power supply for driving the motor 2 and the motor for driving a 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 control target of 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, 5w, and a permanent magnet built-in rotor 15 (Fig. 2) that rotates inside the stator 10.

[0027] (2) Configuration of the control unit 3 The control unit 3 is composed of a microcomputer and peripheral electric circuits. As shown in the functional block of Fig. 2, it 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 instruction from a host ECU 22 (Fig. 1) of the vehicle.

[0028] (3) Configuration of the inverter 4 The inverters 4 of the embodiments are all composed of three upper arm switching elements (the upper arm switching element 24A of the U phase, the upper arm switching element 24B of the V phase, and the upper arm switching element 24C of the W phase) made of IGBTs, and three lower arm switching elements (the lower arm switching element 24D of the U phase, the lower arm switching element 24E of the V phase, and the lower arm switching element 24F of the W phase). The upper arm switching element 24A and the lower arm switching element 24D of the U phase are connected in series, the upper arm switching element 24B and the lower arm switching element 24E of the V phase are connected in series, and the upper arm switching element 24C and the lower arm switching element 24F of the W phase are connected in series.

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

[0030] Also, the gates of the switching elements 24A to 24F and the secondary output terminals of the HV battery 6 are respectively connected to the PWM signal generation unit 11 of the control unit 3. Incidentally, freewheeling diodes are respectively connected in anti-parallel to the switching elements 24A to 24F.

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

[0032] (4) Operations of the control unit 3 and the 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 in one carrier period) of the switching elements 24A to 24F of each 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, the V-phase voltage command value Vvt, and the W-phase voltage command value Vwt set by the phase voltage setting unit 21. From this duty ON time Dt, a PWM signal (output duty ratio) for turning ON / OFF the switching elements 24A to 24F is generated and output to the inverter 4.

[0033] The PWM signal generation unit 11 calculates the duty ON time Dt for each of the switching elements 24A to 24F. Therefore, six duty ON times Dt will be calculated. 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 generation unit 11. Based on this ON / OFF pattern, the inverter output voltage Vur of the U phase, the inverter output voltage Vvr of the V phase, and the inverter output voltage Vwr of the W phase are applied to the coils 5u to 5w of each phase of the motor 2. These Vur, Vvr, and Vwr are the inverter output voltage values actually applied to the motor 2.

[0034] Also, the PWM signal generation unit 11 calculates the inverter output voltage value Vu of the U phase, the inverter output voltage Vv of the V phase, and the inverter output voltage Vw (three-phase voltage values) of the W phase 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 according to the following mathematical formula (I), and outputs them to the rotor position detection unit 12. Vuvw = Dt × Vh ···(I) These Vu, Vv, and Vw are the calculated inverter output voltage values. Further, the PWM signal generation unit 11 also outputs each duty ON time Dt of the switching elements 24A to 24F to the rotor position detection unit 12.

[0035] In addition, in the calculation of the above inverter output voltages Vu, Vv, and Vw, when the phase current flows into the motor 2, the inverter output voltage changes due to the ON / OFF of the switching element of the upper arm. Therefore, the duty ON time Dt of the switching element of the upper arm is adopted. When the phase current flows out of the motor 2, the inverter output voltage changes due to the ON / OFF of the switching element of the lower arm. Therefore, the duty ON time Dt of the switching element of the lower arm is adopted.

[0036] The rotor position detector 12 uses the phase current values of the U-phase current value Iu, V-phase current value Iv, and W-phase current value Iw sent from the inverter 4 to derive the phase current peak value Ip (current phase) and the rotor position θm. The phase current peak value Ip is sent to the target current phase setting unit 14, and the rotor position θm is sent to the rotation speed detector 13. Further, the rotor position detector 12 derives and outputs the d-axis current Id from the phase current values.

[0037] The above rotor position θm is calculated based on the induced voltage E and the phase current values Iu, Iv, and Iw. The induced voltage E is calculated by the following mathematical formula (II). E = Vuvw - R × Iuvw ···(II) Here, Vuvw is the calculated inverter output voltage values Vu, Vv, and Vw sent from the PWM signal generator 11 described above, and R is the resistance value of each phase coil 5u to 5w of the motor 2.

[0038] With this rotor position θm, sensorless control without a physical position detection sensor becomes possible. However, there is an error due to component characteristics between the calculated inverter output voltage values Vu, Vv, and Vw and the actual inverter output voltage values Vur, Vvr, and Vwr applied to the motor 2. Also, since this error varies depending on the components, the rotor position detector 12 corrects this. The correction operation of the inverter output voltage values Vu, Vv, and Vw by the rotor position detector 12 will be described in detail later.

[0039] The rotation speed detector 13 uses the rotor position θm sent from the rotor position detector 12 to subtract the rotor position θm-1 one operation cycle before from the rotor position θm to obtain the rotor position change amount Δθm. A predetermined filter is applied to this rotor position change amount Δθm to calculate the rotation speed ω of the motor 2, and this is sent to the adder 16. Then, the rotation speed ω obtained by the rotation speed detector 13 is fed back to the target rotation speed ωt of the motor 2 instructed to the control unit 3 through the adder 16, and the rotation speed difference Δω is calculated by processes such as P control and PI control, and this is sent to the voltage peak value detector 18.

[0040] The peak voltage detection unit 18 detects the peak value Vp of the voltage applied to the motor 2 through processes such as P control or PI control using the obtained rotational speed difference Δω, 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 generated torque of the motor 2 with respect to the phase current becomes maximum by current vector control, for example, called maximum torque / current control. Specifically, the target d-axis current Idt is set using the peak value Ip of the phase current 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 detects the applied voltage phase θv (target voltage phase) of the voltage applied to the motor 2 using the target d-axis current Idt set by the target current phase setting unit 14, and sends this to the phase voltage setting unit 21.

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

[0044] The PWM signal generation unit 11 supplies sinusoidal current (180-degree conduction) to the coils 5u to 5w of each phase of the motor 2 via the inverter 4 based on the ON / OFF pattern of the PWM signal for the applied set voltage set by the phase voltage setting unit 21, and thus operates the motor 2 at a desired rotational speed.

[0045] (5) Correction operation of the inverter output voltage value by the rotor position detection unit 12 Next, with reference to FIGS. 3 to 6, the correction operation of the above-described inverter output voltage values Vu, Vv, Vw (calculated inverter output voltage values) by the rotor position detection unit 12 will be described in detail. The rotor position detection unit 12 of the embodiment has a configuration including an origin estimation unit 32, a correction value calculation unit 33, a rotor position calculation unit 34, a rotor movement unit 36, and a failure determination unit 37, as shown in the functional block diagram of FIG. 3.

[0046] Next, the correction operation will be described with reference to the flowchart of FIG. 4. For example, when the upper ECU 22 starts the motor 2 (electric compressor) (at the first start or each time it starts), the control unit 3 is sent a correction instruction for the inverter output voltage values Vu, Vv, Vw. When the rotor position detection unit 12 constituting the control unit 3 receives this correction instruction for the inverter output voltage values Vu, Vv, Vw in step S1 of FIG. 4, in step S2, the rotor movement unit 36 moves the rotor 15 of the motor 2 to the conduction phase of the switching element 24A that is first to be corrected. Actually, the rotor movement unit 36 outputs a movement request signal to the PWM signal generation unit 11, and the inverter 4 conducts a predetermined energization to the coils 5u to 5w of the motor 2 to move the rotor 15 and fix it to the conduction 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, and changes and outputs the duty ON time Dt of the switching element 24A in the direction of increasing from 0 in several steps. At this time, only the switching element 24A of the upper arm is turned ON, and the other switching elements 24B and 24C are 100% OFF. Also, for the lower arm, the switching element 24D is 100% OFF, and the switching elements 24E and 24F are 100% ON.

[0048] The energization paths of the inverter 4 and the motor 2 at this time are shown by thick solid arrows in Fig. 5. The output of the duty ON time Dt is performed a predetermined number of times by repeating steps S4 and S3, and is changed to gradually increase for each number of times. Actually, each duty ON time Dt is output at regular intervals each time, and the phase current value at each duty ON time Dt is input to the origin estimation unit 32.

[0049] When the output of the duty ON time Dt has been completed for a predetermined number of times, the process proceeds to step S5 to calculate correction values for the inverter output voltage values Vu, Vv, and Vw. At this time, the origin estimation unit 32 estimates a predetermined origin Dt1 by the method shown in Fig. 6. Here, even if the duty ON time Dt is increased from 0, due to the component characteristics of the switching element 24A, the increase in the phase current value is delayed, and as shown by the solid line in Fig. 6, it first gradually increases and then eventually has a characteristic of increasing 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 estimation unit 32 obtains the slope from the region that approximates this linear function, and on the straight line of this slope (shown by the broken line in Fig. 6), the duty ON time Dt at which the phase current value becomes 0 is set as the origin Dt1. The origin Dt1 estimated by this estimated origin estimation unit 32 is sent to the correction value calculation unit 33.

[0051] Based on the origin Dt1 estimated by the origin estimation unit 32, the correction value calculation unit 33 calculates a correction value Vuhosa for the inverter output voltage value Vu with respect to the switching element 24A. Incidentally, this correction value Vuhosa is the correction value when the U-phase current Iu flows into the motor 2. Actually, 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 the starting point Dt0, obtains a voltage value for correction from the value of the difference (Dt1 - Dt0) between this starting point Dt0 and the origin Dt1, and sets this voltage value for correction as the correction value Vuhosa.

[0052] Next, in step S6, the failure determination unit 37 determines whether or not the calculated correction value Vuhosa is outside the specified range. If it is outside the specified range, the process proceeds to step S9, and it is determined that the switching element 24A has failed. When the switching element 24A is determined to have failed, the control unit 3 outputs a predetermined failure warning by an alarm device (such as a display) not shown in the figure.

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

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

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

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

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

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

[0059] When the calculation of the correction values for all the switching elements 24A to 24F of the entire phase is completed in this way, the process proceeds to step S8. In step S8, the rotor position calculation unit 34 adopts the correction values Vuhosa, Vuhosd, Vvhosb, Vvhose, Vwhosc, and Vwhosf calculated by the correction value calculation unit 33 as described above, and corrects the calculated inverter output voltage values Vu, Vv, and Vw sent from the PWM signal generation unit 11 with each correction value respectively.

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

[0061] In addition, in this correction, each of the correction values Vuhosa, Vuhosd, Vvhosb, Vvhose, Vwhosc, and Vwhosf may be adopted for the correction of the inverter output voltage values Vu, Vv, and Vw as described above, or the average value thereof may be adopted for the correction of each of the inverter output voltage values Vu, Vv, and Vw.

[0062] Then, the induced voltage E is calculated by the above-described formula (II) using the corrected inverter output voltage values Vu, Vv, and Vw, and the rotor position θm described above is calculated using this induced voltage E and each phase current Iu, Iv, and Iw.

[0063] The rise and fall delays of the inverter output voltages Vur, Vvr, and Vwr actually applied to the motor 2 are considered to be caused by the delay in the change of the phase current value due to the component characteristics of each of the switching elements 24A to 24F described above. Therefore, as described above, by obtaining a correction value from the value of the difference (Dt1 - Dt0) between the starting point Dt0 and the origin Dt1 and correcting the calculated inverter output voltages Vu, Vv, and Vw, the calculated inverter output voltages Vu, Vv, and Vw sent to the rotor position detection unit 12 can be made to match, or be brought closer to, the inverter output voltages Vur, Vvr, and Vwr actually applied to the motor 2. As a result, the rotor position θm can be accurately calculated.

[0064] As described in detail above, according to the present invention, the errors between the calculated inverter output voltage values Vu, Vv, and Vw due to component variations and the inverter output voltage values Vur, Vvr, and Vwr actually applied to the motor 2 are appropriately corrected by the correction values Vuhosa, Vuhosd, Vvhosb, Vvhose, Vwhosc, and Vwhosf, and the rotor position detection performance can be improved. As a result, in particular, the operating range in the low-speed region is expanded, and sensorless control of the high-efficiency permanent magnet synchronous motor 2 over the entire range can be realized.

[0065] Also, according to the present invention, since the control unit 3 corrects the inverter output voltage values Vu, Vv, and Vw, it is possible to reduce the setting work of the correction values using prototype products, which was necessary in the past, and it can contribute to an improvement in productivity.

[0066] Also, in the embodiment, since the origin estimation unit 32 estimates the origin and the rotor moving unit 36 that moves the rotor 15 to the energization phases of the switching elements 24A to 24F for which the correction value calculation unit 33 calculates the correction values is provided, the influence due to the rotation of the rotor 15 can be eliminated.

[0067] Also, 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 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. When the relationship between the changed duty ON time Dt and the phase current value approximates a linear function, the slope is obtained from the region where the approximation holds. The duty ON time Dt at which the phase current value becomes 0 on the straight line of the slope is set as the origin Dt1. Thus, an appropriate origin Dt1 can be set.

[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 also maintains two upper arm switching elements in the ON state and changes the duty ON time Dt of one lower arm switching element in the direction of increasing it. When the relationship between the changed duty ON time Dt and the phase current value approximates a linear function, the slope is obtained from the region where the approximation holds. The duty ON time Dt at which the phase current value becomes 0 on the straight line of the slope is set as the origin Dt1. Thus, an appropriate origin Dt1 can be set.

[0069] And in the embodiment, when the correction value calculation unit 33 changes the duty ON time Dt, the start point Dt0 is set when the duty ON time Dt is 0. The correction values Vuhosa, Vuhosd, Vvhosb, Vvhose, Vwhosc, and Vwhosf are calculated from the difference (Dt1 - Dt0) between the start point Dt0 and the origin Dt1. Thus, the correction of the calculated inverter output voltage values Vu, Vv, and Vw caused by the rise and fall delays of the applied voltages (actual inverter output voltage values Vur, Vvr, Vwr) due to the ON / OFF of the switching elements 24A to 24F can be accurately performed, and accurate rotor position detection can be achieved.

[0070] Furthermore, in the embodiment, a failure determination unit 37 is provided to determine a failure of the inverter 4 when the correction values Vuhosa, Vuhosd, Vvhosb, Vvhose, Vwhosc, and Vwhosf calculated by the correction value calculation unit 33 are outside a predetermined specified range. Therefore, component failures such as switching elements can be quickly determined, enhancing reliability.

[0071] Note that in the embodiment, an origin estimation unit 32, a rotor movement unit 36, a correction value calculation unit 33, and a failure determination unit 37 are provided in the rotor position detection unit 12. However, it is not limited thereto, and other components except the rotor position calculation unit 34 may be provided in, for example, the PWM signal generation unit 11.

[0072] Also, in the embodiment, the present invention is applied to the motor control device 1 that drives and controls the motor 2 of the electric compressor of the vehicle air conditioner. However, it is not limited thereto, and the present invention is effective for driving and controlling motors of various devices that perform sensorless control.

Explanation of Reference Numerals

[0073] 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~24F Switching element 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 Failure determination unit

Claims

1. In 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, a current detection unit that detects the value of the 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 constituting 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 based on the induced voltage value calculated based on the 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 obtains the duty ON time at which the phase current value becomes 0 from the relationship between the phase current value detected by the current detection unit with respect to the duty ON time calculated by the PWM signal generation unit, and estimates the origin; comprising 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 with the correction value calculated by the correction value calculation unit, and has 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. The motor control device is characterized by this.

2. 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. The motor control device according to claim 1 is characterized by this.

3. 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, for correcting the inverter output voltage value of each of the switching elements, a value obtained by averaging each of the calculated correction values. The motor control device according to claim 1 is characterized by this.

4. The motor control device according to claim 2 or claim 3, further comprising a rotor moving unit that moves the rotor to the energization phase of the switching element for which the origin estimation unit estimates the origin and the correction value calculation unit calculates the correction value.

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

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

7. The correction value calculation unit, When changing the duty ON time, starting from the time when the duty ON time is 0, the correction value is calculated from the difference between the starting point and the origin. The motor control device according to claim 5 or claim 6.

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

Images