Motor control device

Abstract

To provide a control device for controlling operation of an electric motor, which is improved in accuracy of estimating a resistance value of the electric motor.SOLUTION: A resistance value R^ of an electric motor M is estimated in accordance with Expression 1: id(n)-id(n-1)=Ts×{-R^ / Ld×id(n-1)+ω×Lq / Ld×iq(n-1)}, where Ts represents a prescribed time period in a time period during which switching elements of upper arms / lower arms in respective phases of an inverter circuit 2 are all in an on state, id(n) represents a d-axis current Id at time t1 in the prescribed time period Ts, id(n-1) represents a d-axis current Id at time t0 that is prior to the time t1 in the prescribed time period Ts, iq(n-1) represents a q-axis current Iq at the time t0, R^ represents the resistance value of the electric motor M, Ld represents a d-axis inductance Ld of the electric motor M, Lq represents a q-axis inductance Lq of the electric motor M, and ω represents the number of rotations ω^ of a rotor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for controlling the operation of an electric motor. [Background technology]

[0002] There is a control device for a motor that estimates the resistance value of the motor by substituting parameters such as a voltage command value and a current flowing through the motor into a voltage equation that corresponds to a model of the motor.

[0003] However, there is a risk that an error will be included in the voltage command value due to an operational delay of a switching element of an inverter circuit that drives an electric motor.

[0004] Therefore, in the above control device, there is a risk that the accuracy of estimating the resistance value will decrease due to an error contained in the voltage command value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-146155 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object according to one aspect of the present invention is to improve the accuracy of estimating a resistance value of an electric motor in a control device that controls the operation of the electric motor. [Means for solving the problem]

[0007] One embodiment of the present invention provides a motor control device that includes an inverter circuit that rotates a rotor of a motor by turning on and off a number of switching elements, and a control circuit that converts a current flowing through the motor into a d-axis current and a q-axis current, estimates a resistance value of the motor, and turns on and off the multiple switching elements by vector control using at least the d-axis current, the q-axis current, and the resistance value.

[0008] The control circuit estimates the resistance value of the motor using the following equation 1, where Ts is a predetermined period during which all switching elements of the upper arm or lower arm of each phase of the inverter circuit are on, id(n) is the d-axis current at a first time within the predetermined period, id(n-1) is the d-axis current at a second time before the first time within the predetermined period, and iq(n-1) is the q-axis current at the second time. The resistance value of the motor is R^, the d-axis inductance of the motor is Ld, the q-axis inductance of the motor is Lq, and the rotation speed of the rotor is ω.

[0009] id(n)-id(n-1)=Ts×{-R^ / Ld×id(n-1)+ω×Lq / Ld×iq(n-1)} ··· Formula 1

[0010] In this manner, the resistance value is estimated using the d-axis current and the q-axis current during a predetermined period during which all switching elements of the upper arm or lower arm of each phase of the inverter circuit are on. Since the above formula 1 does not include a parameter of the voltage command value, the resistance value can be estimated without being affected by an error contained in the voltage command value due to an operational delay of the switching elements of the inverter circuit. Furthermore, since all terms on the right and left sides of the above formula 1 include parameters of the d-axis current and the q-axis current, respectively, the gain of the amplifier of the current sensor can offset errors contained in the parameters of the d-axis current and the q-axis current, and the resistance value can be estimated without being affected by the errors. Furthermore, since the above formula 1 does not include a parameter of the induced voltage, the resistance value can be estimated without being affected by fluctuations in the induced voltage due to temperature changes. This improves the estimation accuracy of the resistance value of the motor.

[0011] Furthermore, the inverter circuit may be configured to turn on and off the multiple switching elements based on a comparison result between a voltage value of a carrier wave and a voltage command value, and the control circuit may be configured to include a position estimating unit that estimates a position of a rotor of the electric motor using the resistance value, a current converting unit that converts a current flowing through the electric motor into the d-axis current and the q-axis current using the position, a current command value output unit that outputs a d-axis current command value and a q-axis current command value based on a rotation speed difference between a rotation speed of the rotor and a rotation speed command value, a voltage command value calculating unit that calculates a d-axis voltage command value so as to reduce a difference between the d-axis current and the d-axis current command value, and calculates a q-axis voltage command value so as to reduce a difference between the q-axis current and the q-axis current command value, and a voltage command value converting unit that converts the d-axis voltage command value and the q-axis voltage command value to the voltage command value using the position.

[0012] The control circuit may also be configured to set the resistance value of the motor to a moving average of multiple resistance values ​​obtained by using two adjacent times out of three or more times within the specified period as the first time and the second time.

[0013] This makes it possible to estimate the resistance value of the motor while suppressing the influence of errors contained in each of the multiple resistance values ​​before calculating the average, thereby further improving the accuracy of estimating the resistance value of the motor. Effect of the Invention

[0014] According to the present invention, in a control device that controls the operation of an electric motor, it is possible to improve the accuracy of estimating the resistance value of the electric motor. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a diagram illustrating an example of a control device for an electric motor according to an embodiment. [Diagram 2] FIG. 4 is a diagram for explaining an example of a method for estimating a resistance value of a motor. [Diagram 3] FIG. 10 is a diagram for explaining another example of a method for estimating a resistance value of a motor. [Figure 4] FIG. 4 is a diagram illustrating another example of the control device for the electric motor in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0017] FIG. 1 is a diagram illustrating an example of a control device for an electric motor according to an embodiment.

[0018] 1 controls the operation of an electric motor M mounted on a vehicle such as an electric forklift or a plug-in hybrid vehicle, and includes an inverter circuit 2 and a control circuit 3. The electric motor M is, for example, an embedded magnet motor or a surface magnet motor.

[0019] The inverter circuit 2 drives the motor M with power supplied from a power source P, and includes a capacitor C, switching elements SW1 to SW6 (for example, IGBTs (Insulated Gate Bipolar Transistors)), and current sensors Se1 and Se2. That is, one terminal of the capacitor C is connected to the positive terminal of the power source P and the collector terminals of the switching elements SW1, SW3, and SW5, and the other terminal of the capacitor C is connected to the negative terminal of the power source P and the emitter terminals of the switching elements SW2, SW4, and SW6. A connection point between the emitter terminal of the switching element SW1 and the collector terminal of the switching element SW2 is connected to a U-phase input terminal of the motor M via the current sensor Se1. A connection point between the emitter terminal of the switching element SW3 and the collector terminal of the switching element SW4 is connected to a V-phase input terminal of the motor M via the current sensor Se2. A connection point between the emitter terminal of the switching element SW5 and the collector terminal of the switching element SW6 is connected to a W-phase input terminal of the motor M.

[0020] The capacitor C smoothes the voltage output from the power source P and input to the inverter circuit 2 .

[0021] The switching element SW1 is turned on or off based on a drive signal S1 output from the control circuit 3. The switching element SW2 is turned on or off based on a drive signal S2 output from the control circuit 3. The switching element SW3 is turned on or off based on a drive signal S3 output from the control circuit 3. The switching element SW4 is turned on or off based on a drive signal S4 output from the control circuit 3. The switching element SW5 is turned on or off based on a drive signal S5 output from the control circuit 3. The switching element SW6 is turned on or off based on a drive signal S6 output from the control circuit 3. By turning on or off the switching elements SW1 to SW6, respectively, the DC voltage output from the power source P is converted into three AC voltages whose phases differ from each other by 120 degrees, and these AC voltages are applied to the input terminals of the U phase, V phase, and W phase of the electric motor M, and the rotor of the electric motor M rotates. That is, the inverter circuit 2 rotates the rotor of the electric motor M by turning on and off the switching elements SW1 to SW6.

[0022] The current sensor Se1 is configured with a Hall element, a shunt resistor, etc., and detects a U-phase current Iu flowing through the U-phase of the electric motor M and outputs the detected current to the control circuit 3. In addition, the current sensor Se2 is configured with a Hall element, a shunt resistor, etc., and detects a V-phase current Iv flowing through the V-phase of the electric motor M and outputs the detected current to the control circuit 3.

[0023] The control circuit 3 includes a storage unit 4, a drive circuit 5, and a calculation unit 6.

[0024] The storage unit 4 is configured with a RAM (Random Access Memory) or a ROM (Read Only Memory), etc.

[0025] The drive circuit 5 is composed of an IC (Integrated Circuit) or the like, and compares the voltage value of a carrier wave (such as a triangular wave, a sawtooth wave, or an inverse sawtooth wave) with the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* output from the calculation unit 6, and outputs drive signals S1 to S6 according to the comparison results to the gate terminals of the switching elements SW1 to SW6, respectively.

[0026] For example, when the U-phase voltage command value Vu* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S1 and a low-level drive signal S2, and when the U-phase voltage command value Vu* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S1 and a high-level drive signal S2. When the V-phase voltage command value Vv* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S3 and a low-level drive signal S4, and when the V-phase voltage command value Vv* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S3 and a high-level drive signal S4. When the W-phase voltage command value Vw* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S5 and a low-level drive signal S6, and when the W-phase voltage command value Vw* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S5 and a high-level drive signal S6.

[0027] The calculation unit 6 is configured by a microcomputer or the like, and includes a current conversion unit 7, a resistance estimation unit 8, a temperature estimation unit 9, a position estimation unit 10, a subtraction unit 11, a torque command value calculation unit 12, a current command value output unit 13, a subtraction unit 14, a subtraction unit 15, a voltage command value calculation unit 16, and a voltage command value conversion unit 17. For example, the microcomputer executes a program stored in the storage unit 4, whereby the current conversion unit 7, the resistance estimation unit 8, the temperature estimation unit 9, the position estimation unit 10, the subtraction unit 11, the torque command value calculation unit 12, the current command value output unit 13, the subtraction unit 14, the subtraction unit 15, the voltage command value calculation unit 16, and the voltage command value conversion unit 17 are configured.

[0028] The current converter 7 determines a W-phase current Iw flowing through the W-phase of the electric motor M, using the U-phase current Iu detected by the current sensor Se1 and the V-phase current Iv detected by the current sensor Se2.

[0029] In addition, the current conversion unit 7 converts the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw into a d-axis current Id (a current component for generating a weakened field in the motor M) and a q-axis current Iq (a current component for generating torque in the motor M) using the rotor position θ^ (phase angle) of the motor M estimated by the position estimation unit 10.

[0030] For example, the current converter 7 converts the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw into a d-axis current Id and a q-axis current Iq using a conversion matrix C1 shown in the following equation 2.

[0031]

number

[0032] The currents detected by the current sensors Se1 and Se2 are not limited to the combination of the U-phase current Iu and the V-phase current Iv, but may be the combination of the V-phase current Iv and the W-phase current Iw, or the combination of the U-phase current Iu and the W-phase current Iw. When the V-phase current Iv and the W-phase current Iw are detected by the current sensors Se1 and Se2, the current converter 7 determines the U-phase current Iu using the V-phase current Iv and the W-phase current Iw. When the U-phase current Iu and the W-phase current Iw are detected by the current sensors Se1 and Se2, the current converter 7 determines the V-phase current Iv using the U-phase current Iu and the W-phase current Iw.

[0033] In addition, if the inverter circuit 2 further includes, in addition to the current sensors Se1 and Se2, a current sensor Se3 that detects the current flowing through the W phase of the motor M, the current conversion unit 7 may be configured to convert the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current sensors Se1 to Se3 into the d-axis current Id and the q-axis current Iq using the position θ^ estimated by the position estimation unit 10.

[0034] The resistance estimation unit 8 estimates the resistance value (resistance component) R^ of the electric motor M by using the following formula 1. Note that Ts is a predetermined period of the period T0 in which the upper arm switching elements SW1, SW3, and SW5 of each phase of the inverter circuit 2 or the lower arm switching elements SW2, SW4, and SW6 are all on, and is set to a period in which at least the d-axis voltage command value Vd* becomes zero, as shown in FIG. 2(a), for example. The predetermined period Ts is set to a period equal to or shorter than the period T0. Note that in the example shown in FIG. 2 and the example shown in FIG. 4 described later, the predetermined period Ts is set to the same period as the period T0. Also, id(n) and id(n-1) are d-axis currents Id output from the current conversion unit 7, and, for example, as shown in FIG. 2(b), id(n) is set to the d-axis current Id at time t1 (first time) within the predetermined period Ts, and id(n-1) is set to the d-axis current Id at time t0 (second time) prior to time t1 within the period Ts. In FIG. 2, time t1 is the timing immediately before the d-axis voltage command value Vd* changes from zero to a negative value, but may be set to any time within the period Ts. Also, time t0 is the timing immediately after the d-axis voltage command value Vd* changes from a negative value to zero, but may be set to any time before time t1 within the predetermined period Ts. Also, iq(n-1) is the q-axis current Iq output from the current conversion unit 7, and is, for example, the q-axis current Iq at time t0 as shown in FIG. 2(c). Also, R^ is the resistance value of the motor M, and ω is the rotor rotation speed (angular velocity) ω^ estimated by the position estimation unit 10. Also, Ld is the d-axis inductance of the motor M, and Lq is the q-axis inductance of the motor M. Also, the d-axis inductance Ld and the q-axis inductance Lq are assumed not to vary with the temperature change of the motor M.

[0035] id(n)-id(n-1)=Ts×{-R^ / Ld×id(n-1)+ω×Lq / Ld×iq(n-1)} ··· Formula 1

[0036] The above formula 1 is derived through the following process.

[0037] First, a voltage equation corresponding to the model of the motor M is given by the following formula 3. Vd is the d-axis voltage command value Vs* calculated by the voltage command value calculation unit 16, and Vq is the q-axis voltage command value Vq* calculated by the voltage command value calculation unit 16. R^ is the resistance value of the motor M, p is the differential operator, Ld is the d-axis inductance of the motor M, Lq is the q-axis inductance of the motor M, and ω is the rotation speed ω^ estimated by the position estimation unit 10. id is the d-axis current Id output from the current conversion unit 7, and iq is the q-axis current Iq output from the current conversion unit 7. L is the inductance of the motor M, and Ψa is the induced voltage of the motor M.

[0038]

number

[0039] Next, the above formula 3 is transformed into the following formula 4 by time differentiation over a predetermined period Ts.

[0040]

number

[0041] Then, the above equation 1 is obtained by converting the equation shown in the following equation 5 related to the d-axis current Id in the above equation 4 into a difference equation. Note that the equation related to the q-axis current Iq in the above equation 4 is not used because it includes the induced voltage Ψa that varies with temperature change.

[0042]

number

[0043] In this manner, the resistance value R^ is estimated using the d-axis current Id and the q-axis current Iq during a predetermined period Ts (i.e., at least a period during which the d-axis voltage command value Vd* is zero) in the period T0 during which the upper arm switching elements SW1, SW3, and SW5 of each phase of the inverter circuit 2 or the lower arm switching elements SW2, SW4, and SW6 are all on. Since the above formula 1 does not include parameters of the d-axis voltage command value Vd* and the q-axis voltage command value Vq*, the resistance value R^ can be estimated without being affected by errors included in the d-axis voltage command value Vd* and the q-axis voltage command value Vq* due to operation delays of the switching elements SW1 to SW6 of the inverter circuit 2. In addition, since all terms on the right and left sides of the above formula 1 include parameters of the d-axis current Id and the q-axis current Iq, the gains of the amplifiers of the current sensors Se1 and Se2 can offset errors included in the parameters of the d-axis current Id and the q-axis current Iq, and the resistance value R^ can be estimated without being affected by these errors. In addition, since the above formula 1 does not include a parameter for the induced voltage Ψa, the resistance value R^ can be estimated without being affected by fluctuations in the induced voltage Ψa that accompany temperature changes. This improves the accuracy of estimating the resistance value R^ of the motor M.

[0044] For example, the resistance estimation unit 8 estimates the resistance value R^ using system identification. That is, when the left side of the above formula 1 is Q, the right side of the above formula 1 is Q^, γ is the identification gain, and R^ is the resistance value of the electric motor M, the resistance estimation unit 8 repeats the calculation of the following formula 6 to determine R^ when the difference between Q and Q^ becomes zero as the resistance value R^ of the electric motor M.

[0045] R^=γ×∫(QQ^)dt ···Equation 6

[0046] The resistance value R^ may be estimated by calculating the following equation 7 obtained by modifying the above equation 1 with respect to R^, and the method for estimating the resistance value R^ is not particularly limited.

[0047] R^=ω×Lq×iq(n-1) / id(n-1)-Ld / id(n-1)×{(id(n)-id(n-1)) / Ts}...Equation 7

[0048] 1 estimates the temperature T^ of the electric motor M using the resistance value R^ estimated by the resistance estimation unit 8. The method of estimating the temperature T^ is not particularly limited, and the temperature T^ may be calculated by a calculation using the resistance value R^ and a coefficient, or may be calculated by referring to information in which the temperature and the resistance value of the electric motor M are associated with each other and is stored in advance in the storage unit 4. The temperature T^ estimated by the temperature estimation unit 9 may be used to correct various command values ​​that vary with temperature changes, such as a torque command value T* described later.

[0049] The position estimation unit 10 estimates the rotation speed ω^ and the position θ^.

[0050] For example, the position estimation unit 10 estimates ω as the rotation speed ω^ by substituting the d-axis current Id and q-axis current Iq output from the current conversion unit 7, the d-axis voltage command value Vd* and q-axis voltage command value Vq* calculated by the voltage command value calculation unit 16, and the resistance value R^ estimated by the resistance estimation unit 8 into the voltage equation shown in the above formula 3. Furthermore, the position estimation unit 10 estimates a result of multiplying the rotation speed ω^ by a unit time (for example, the clock period of the calculation unit 6) as the position θ^.

[0051] The position estimator 10 may be configured to obtain an extended induced voltage excited by superimposing a high-frequency voltage on the d-axis voltage command value Vd* calculated by the voltage command value calculator 16, using a resistance value R^ or the like, and to estimate the rotor position θ^ from the phase of the extended induced voltage. When configured in this way, the position estimator 10 estimates the result of dividing the position θ^ by a unit time (for example, the clock period of the calculator 6) as the rotation speed ω^.

[0052] The subtraction unit 11 calculates the rotation speed difference Δω between the rotation speed command value ω* input from the outside and the rotation speed ω^ estimated by the position estimation unit 10 .

[0053] The torque command value calculation unit 12 calculates the torque command value T* by using the rotation speed difference Δω output from the subtraction unit 11. For example, the torque command value calculation unit 12 refers to information (not shown) stored in the storage unit 4 in which the rotation speed of the rotor of the electric motor M and the torque of the electric motor M are associated with each other, and determines the torque corresponding to the rotation speed equivalent to the rotation speed difference Δω as the torque command value T*. Note that the torque command value calculation unit 12 may increase the torque command value T* as the temperature T^ estimated by the temperature estimation unit 9 increases. This makes it difficult for a current to flow through the electric motor M as the temperature T^ increases, and it is possible to suppress a decrease in the torque generated in the electric motor M due to a decrease in the magnetic field strength of the permanent magnet as the temperature T^ increases.

[0054] The current command value output unit 13 outputs a d-axis current command value Id* and a q-axis current command value Iq* using the torque command value T*. For example, the current command value output unit 13 refers to information (not shown) stored in the storage unit 4, in which the torque of the electric motor M is associated with the d-axis current command value Id* and the q-axis current command value Iq*, to determine the d-axis current command value Id* and the q-axis current command value Iq* corresponding to the torque command value T*.

[0055] That is, the current command value output unit 13 outputs a d-axis current command value Id* and a q-axis current command value Iq* based on the rotation speed difference Δω between the rotor rotation speed ω^ and the rotation speed command value ω*.

[0056] The subtraction unit 14 calculates the difference ΔId between the d-axis current command value Id* output from the current command value output unit 13 and the d-axis current Id output from the current conversion unit 7 .

[0057] The subtraction unit 15 calculates the difference ΔIq between the q-axis current command value Iq* output from the current command value output unit 13 and the q-axis current Iq output from the current conversion unit 7 .

[0058] The voltage command value calculation unit 16 calculates the d-axis voltage command value Vd* and the q-axis voltage command value Vq* by PI control using the difference ΔId output from the subtraction unit 14 and the difference ΔIq output from the subtraction unit 15. For example, the voltage command value calculation unit 16 calculates the d-axis voltage command value Vd* by calculating the following formula 8, and calculates the q-axis voltage command value Vq* by calculating the following formula 9. Note that Kp is a constant of the proportional term of the PI control, Ki is a constant of the integral term of the PI control, Lq is the q-axis inductance of the motor M, Ld is the d-axis inductance of the motor M, ω is the rotation speed ω^ estimated by the position estimation unit 10, and Ψa is the induced voltage.

[0059] d-axis voltage command value Vd* = Kp × difference ΔId + ∫(Ki × difference ΔId) - ωLqIq Equation 8

[0060] q-axis voltage command value Vq* = Kp × difference ΔIq + ∫(Ki × difference ΔIq) + ωLdId + ωΨa Equation 9

[0061] That is, the voltage command value calculation unit 16 calculates the d-axis voltage command value Vd* so that the difference ΔId between the d-axis current Id and the d-axis current command value Id* is small, and calculates the q-axis voltage command value Vq* so that the difference ΔIq between the q-axis current Iq and the q-axis current command value Iq* is small.

[0062] The voltage command value conversion unit 17 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into a U-phase voltage command value Vu*, a V-phase voltage command value Vv*, and a W-phase voltage command value Vw* using the position θ^ estimated by the position estimation unit 10. For example, the voltage command value conversion unit 17 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* using a conversion matrix C2 shown in the following equation 10.

[0063]

number

[0064] That is, the control circuit 3 converts the U-phase current Iu, V-phase current Iv, and W-phase current Iw flowing through the motor M into a d-axis current Id and a q-axis current Iq, estimates the resistance value R^ of the motor M, and turns the switching elements SW1 to SW6 on and off by vector control using at least the d-axis current Id and the q-axis current Iq, and the resistance value R^.

[0065] In this way, according to the control device 1 for the electric motor M of the embodiment, it is possible to accurately estimate the resistance value R^ of the electric motor M while the electric motor M is being driven.

[0066] Furthermore, according to the control device 1 for the electric motor M of the embodiment, the resistance value R^ of the electric motor M can be accurately estimated, thereby improving the estimation accuracy of the temperature T^ of the electric motor M estimated using the resistance value R^.

[0067] In addition, in the control device 1 for the electric motor M of the embodiment, since the temperature T^ of the electric motor M can be estimated, there is no need to provide a temperature sensor for detecting the temperature of the electric motor M, and therefore the control device 1 can be made smaller.

[0068] The present invention is not limited to the above-described embodiment, and various improvements and modifications are possible without departing from the gist of the present invention.

[0069] <Variation 1> Fig. 3 is a diagram showing another example of the motor control device according to the embodiment, in which the same components as those shown in Fig. 1 are given the same reference numerals and the description thereof will be omitted.

[0070] The control device 1 shown in FIG. 3 differs from the control device 1 shown in FIG. 1 in that it includes a position detection unit Sp (such as a resolver) that detects the rotor position θ^ (phase angle) of the electric motor M and outputs the detected position θ^ to the control circuit 3, and that it includes a rotation speed calculation unit 18 instead of the position estimation unit 10 of the calculation unit 6.

[0071] The rotation speed calculation unit 18 calculates the rotation speed ω^ using the position θ^ detected by the position detection unit Sp. For example, the rotation speed calculation unit 18 obtains the rotation speed ω^ by dividing the position θ^ by a predetermined time (for example, the clock period of the calculation unit 6).

[0072] In the control device 1 configured in this manner, since the resistance value R^ is estimated by the resistance estimating unit 8, the resistance value R^ of the motor M can be estimated with high accuracy while the motor M is being driven.

[0073] <Variation 2> The resistance estimation unit 8 (control circuit 3) may be configured to set the moving average of multiple resistance values ​​obtained by setting two adjacent times, t1 and t0, among three or more times within a predetermined period Ts as the resistance value R^ of the electric motor M.

[0074] For example, as shown in FIG. 4, an arbitrary time within a predetermined period Ts is denoted as t α At time t α Let t be the time before β At time t β Let t be the time before γ At time t α The d-axis current corresponding to α At time t β The d-axis current corresponding to β At time t γ The d-axis current corresponding to γ At time t β The q-axis current corresponding to β At time t γ The q-axis current corresponding to γ Let us assume the case where:

[0075] First, the resistance estimation unit 8 calculates the resistance between two adjacent times t β and time t γ By setting the time to t1 and the time to t0, the d-axis current id β is id(n), and the d-axis current id γ is id(n-1), and the q-axis current iq γ Let iq(n-1) be the resistance value R^ using the above formula 1.βγ Estimate.

[0076] Next, the resistance estimation unit 8 calculates the resistance between two adjacent times t α and time t β By setting the time to t1 and the time to t0, the d-axis current id α is id(n), and the d-axis current id β is id(n-1), and the q-axis current iq β Let iq(n-1) be the resistance value R^ using the above formula 1. αβ Estimate.

[0077] Then, the resistance estimation unit 8 calculates the resistance value R^ βγ and resistance value R^ αβ The sum of these two values ​​divided by 2 is the resistance value R^.

[0078] This allows multiple resistance values ​​R^ (resistance value R^ βγ and resistance value R^ αβ ) can be suppressed to estimate the resistance value R^ of the motor M, thereby further improving the estimation accuracy of the resistance value R^ of the motor M. [Explanation of symbols]

[0079] 1 Control device 2. Inverter circuit 3 Control Circuit 4 Storage section 5 Drive circuit 6 Arithmetic section 7 Current conversion section 8 Resistance estimation section 9 Temperature estimation section 10 Position estimation part 11 Subtraction section 12 Torque command value calculation section 13 Current command value output section 14 Subtraction section 15 Subtraction section 16 Voltage command value calculation section 17 Voltage command value converter 18 Rotational speed calculation section P power supply C Capacitor Se1 Current Sensor Se2 Current Sensor Sp position detector

Claims

1. an inverter circuit that rotates a rotor of an electric motor by turning on and off a plurality of switching elements; a control circuit that converts a current flowing through the electric motor into a d-axis current and a q-axis current, estimates a resistance value of the electric motor, and turns on and off the plurality of switching elements by vector control using at least the d-axis current, the q-axis current, and the resistance value; Equipped with The control circuit estimates the resistance value of the motor using the following formula 1, where Ts is a predetermined period during which all switching elements of the upper arm or lower arm of each phase of the inverter circuit are on, id(n) is the d-axis current at a first time within the predetermined period, id(n-1) is the d-axis current at a second time prior to the first time within the predetermined period, and iq(n-1) is the q-axis current at the second time. The resistance value of the motor is R^, the d-axis inductance of the motor is Ld, the q-axis inductance of the motor is Lq, and the rotation speed of the rotor is ω. id(n)-id(n-1)=Ts×{-R^ / Ld×id(n-1)+ω×Lq / Ld×iq(n-1)}...Formula 1 A control device for an electric motor.

2. The motor control device according to claim 1, the inverter circuit turns on and off the plurality of switching elements according to a comparison result between a voltage value of a carrier wave and a voltage command value; The control circuit includes: a position estimating unit that estimates a position of a rotor of the electric motor using the resistance value; a current converter for converting a current flowing through the electric motor into the d-axis current and the q-axis current using the position; a current command value output unit that outputs a d-axis current command value and a q-axis current command value according to a difference between a rotation speed of the rotor and a rotation speed command value; a voltage command value calculation unit that calculates a d-axis voltage command value so as to reduce a difference between the d-axis current and the d-axis current command value, and calculates a q-axis voltage command value so as to reduce a difference between the q-axis current and the q-axis current command value; a voltage command value conversion unit that converts the d-axis voltage command value and the q-axis voltage command value into the voltage command value using the position; A control device for an electric motor comprising:

3. The motor control device according to claim 1 or 2, The control circuit determines a moving average of a plurality of resistance values ​​obtained by setting two adjacent times among the three or more times within the predetermined period as the first time and the second time, as the resistance value of the electric motor. A control device for an electric motor.

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