JP7578045B2 - Motor Control Device - Google Patents

Description

This disclosure relates to a motor control device.

A motor control device that controls the drive of a motor has a switching module that generates a three-phase AC voltage (hereinafter sometimes referred to as a "three-phase voltage") that is applied to the motor. The switching module is composed of multiple switching elements. The switching module is sometimes called an inverter.

When vector control is used for the motor control device, the motor control device generates a d-axis current command value and a q-axis current command value so that the motor rotation speed matches the speed command value (target speed), and generates a d-axis voltage command value and a q-axis voltage command value from the d-axis current command value and the q-axis current command value. Furthermore, the motor control device converts the d-axis voltage command value and the q-axis voltage command value into three-phase voltage command values.

PWM (Pulse Width Modulation) is known as a technique for controlling a switching module based on three-phase voltage command values. PWM is a technique for changing the output voltage (i.e., three-phase voltage) of a switching module by adjusting the on/off time of multiple switching elements that make up the switching module. A signal (hereinafter sometimes referred to as a "PWM signal") that controls the on/off of the switching elements is generated based on the result of comparing a carrier signal, which is the carrier wave of the PWM, with a comparison value. By controlling the on/off of the switching elements according to the PWM signal, a three-phase voltage is applied to the motor, controlling the drive of the motor.

There is also known a technology (hereinafter sometimes referred to as the "position sensorless method") that controls the drive of a motor without using a sensor (hereinafter sometimes referred to as the "position sensor") for detecting the rotational position of the motor rotor (hereinafter sometimes referred to as the "rotor position"). In the position sensorless method, the rotor position is estimated without using a position sensor by detecting the three-phase current (hereinafter sometimes referred to as the "motor current") that flows through the motor.

The "single-shunt detection method" is also known as a method for detecting motor current. In the single-shunt detection method, two phases of the motor current are detected based on the bus current flowing between the DC power supply and the switching module that generates the three-phase voltage, and the remaining one phase of current is calculated from the two phases of current using Kirchhoff's law.

Here, a prior art has been proposed in which a first connection line that transmits an amplified voltage obtained by amplifying the voltage generated across a shunt resistor for detecting a bus current to a first A/D converter and a second connection line that transmits an offset voltage generated by an offset voltage generating unit to a second A/D converter are arranged so as to be as equally affected by noise as possible. In this prior art, when noise is superimposed on the first connection line, noise is also superimposed on the second connection line, so that a determination is made as to whether or not a large noise is superimposed on the bus current (hereinafter, sometimes referred to as "noise determination") by determining whether or not the offset voltage is a voltage outside a predetermined range. In addition, in this prior art, when the offset voltage is a voltage outside a predetermined range, it is determined that the influence of noise is large, and the amplified voltage as the bus current detected simultaneously with the offset voltage is discarded, and when the offset voltage is within a predetermined range, a PWM signal is generated based on the bus current detected simultaneously with the offset voltage. In this way, it becomes possible to control the motor using a current value that is less affected by noise (i.e., a current value with high accuracy).

JP 2015-126555 A

In the above prior art, when making a noise judgment, it is necessary to sample the offset voltage at the same time as sampling the amplified voltage, so a separate circuit for acquiring the offset voltage and a second A/D converter for sampling the offset voltage are required. For this reason, in the above prior art, when controlling the motor using a highly accurate current value, the number of parts in the motor control device increases.

Therefore, this disclosure proposes a technology that can control a motor using highly accurate current values while minimizing an increase in the number of parts in a motor control device.

The motor control device of the present disclosure has a switching module, a detection unit, a first calculation unit, a conversion unit, a prediction unit, and a determination unit. The switching module converts a DC voltage supplied from a DC power source into an AC voltage and applies the AC voltage to a motor. The detection unit detects a bus current of the switching module using a resistor connected between the DC power source and the switching module. The first calculation unit calculates a three-phase current of a fixed coordinate in the motor based on the bus current. The conversion unit converts the three-phase current into a two-phase current of a rotating coordinate. The prediction unit calculates a predicted value of the two-phase current. The determination unit determines whether the two-phase current or the predicted value is to be used to control the motor based on the two-phase current and the predicted value. The prediction unit also performs a Fourier transform on the two-phase current or the predicted value that the determination unit has determined to be used for controlling the motor, to separate the determined value into frequency components of multiple orders, and calculates the predicted value by synthesizing the frequency components of multiple orders.

The disclosed technology makes it possible to control a motor using highly accurate current values while minimizing an increase in the number of parts in a motor control device.

FIG. 1 is a diagram illustrating an example of the configuration of a motor control device according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of the configuration of a noise determination unit according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of the operation of the current prediction unit according to the embodiment of the present disclosure.

Below, examples of the present disclosure will be described with reference to the drawings. In the following examples, the same components are given the same reference numerals.

[Example]
<Configuration of the motor control device>
FIG. 1 is a diagram showing an example of the configuration of a motor control device according to an embodiment of the present disclosure. The motor control device 100 shown in FIG. 1 controls the driving of a motor M using a position sensorless method, a one-shunt detection method, and PWM. In FIG. 1, the motor control device 100 includes subtraction units 46, 47, and 52, a d-axis current setting unit 48, a speed control unit 49, a d-axis and q-axis voltage setting unit 45, a dq/3φ conversion unit 43, a PWM unit 41, a switching module 10, a DC power supply E _DC , and a shunt resistor Rs. The motor control device 100 also includes a DC voltage detection unit 31, a current detection unit 21, AD conversion units 71 and 72, a 3φ current calculation unit 61, a DC voltage calculation unit 32, a 3φ/dq conversion unit 42, a position and speed estimation unit 44, a 1/Pn processing unit 51, and a noise determination unit 80.

The subtraction units 46, 47, 52, the d-axis current setting unit 48, the speed control unit 49, the d-axis/q-axis voltage setting unit 45, the dq/3φ conversion unit 43, the PWM unit 41, the DC voltage detection unit 31, the current detection unit 21, the AD conversion units 71, 72, the 3φ current calculation unit 61, the DC voltage calculation unit 32, the 3φ/dq conversion unit 42, the position/speed estimation unit 44, the 1/Pn processing unit 51, and the noise determination unit 80 are realized as hardware, for example, by an MCU (Micro Control Unit).

The switching module 10 also has upper arm switching elements SWup, SWvp, and SWwp, and lower arm switching elements SWun, SWvn, and SWwn.

In the motor control device 100, the d-axis current setting unit 48 outputs a predetermined d-axis current command value id ^* to the subtraction unit 46.

The subtraction unit 46 receives the d-axis current command value id ^* from the d-axis current setting unit 48, and receives the d-axis current id from the noise determination unit 80. The subtraction unit 46 calculates the d-axis current deviation Δid by subtracting the d-axis current id from the d-axis current command value id ^* , and outputs the calculated d-axis current deviation Δid to the d-axis/q-axis voltage setting unit 45.

The speed control unit 49 calculates the q-axis current command value iq ^* so that the speed deviation Δω input from the subtraction unit 52 approaches zero, and outputs the calculated q-axis current command value iq ^* to the subtraction unit 47.

The subtraction unit 47 receives the q-axis current command value iq ^* from the speed control unit 49 and the q-axis current iq from the noise determination unit 80. The subtraction unit 47 calculates the q-axis current deviation Δiq by subtracting the q-axis current iq from the q-axis current command value iq ^*, and outputs the calculated q-axis current deviation Δiq to the d-axis/q-axis voltage setting unit 45.

The d-axis/q-axis voltage setting unit 45 receives the d-axis current deviation Δid from the subtraction unit 46, the q-axis current deviation Δiq from the subtraction unit 47, and the d-axis current id and the q-axis current iq from the noise determination unit 80. The d-axis/q-axis voltage setting unit 45 calculates a d-axis voltage command value Vd ^* and a q-axis voltage command value Vq ^* so that the d-axis current deviation Δid and the q-axis current deviation Δiq approach zero, and outputs the calculated d-axis voltage command value Vd ^* and q-axis voltage command value Vq ^* to the position/speed estimation unit 44 and the dq/3φ conversion unit 43. The d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* also change according to the U-phase current iu, the V-phase current iv, and the W-phase current iw, which are motor currents calculated by the 3φ current calculation unit 61.

The position/speed estimator 44 receives the d-axis current id and the q-axis current iq from the noise determiner 80, and receives the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* from the d-axis/q-axis voltage setting unit 45. The position/speed estimator 44 estimates the electrical angular velocity ^ωe of the motor M, and the electrical angle phase θe and the mechanical angle phase θm of the motor M in the rotating coordinates (dq coordinates) based on the d-axis current id, the q-axis current ^iq , the d-axis voltage command value Vd*, and the q-axis voltage command value Vq*. The position/speed estimator 44 outputs the estimated angular velocity ωe to the 1/Pn processor 51, outputs the estimated electrical angle phase θe to the 3φ/dq converter 42 and the dq/3φ converter 43, and outputs the estimated mechanical angle phase θm to the noise determiner 80.

The 1/Pn processing unit 51 converts the electrical angular velocity ωe into the mechanical angular velocity ωm of the rotor of the motor M by dividing the angular velocity ωe by the number of pole pairs of the motor M, and outputs the converted angular velocity ωm to the subtraction unit 52.

The subtraction unit 52 receives the angular velocity ωm from the 1/Pn processing unit 51, and receives a speed command value ωm ^* from outside the motor control device 100 (for example, from a higher-level controller of the motor control device 100). The subtraction unit 52 calculates a speed deviation Δω by subtracting the angular velocity ωm from the speed command value ωm ^* , and outputs the calculated speed deviation Δω to the speed control unit 49.

The dq/3φ converter 43 converts the two-phase d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* in the rotating coordinates into three-phase voltage command values Vu ^* , Vv ^* , Vw ^* in the fixed coordinates (UVW coordinates) using the electrical angle phase θe. The dq/3φ converter 43 outputs the converted voltage command values Vu ^* , Vv ^* , Vw ^* to the PWM unit 41.

The PWM unit 41 receives the voltage command values Vu ^* , Vv ^* , Vw ^* from the dq/3φ conversion unit 43 and receives the DC voltage Vdc from the DC voltage calculation unit 32. A carrier signal, which is a PWM carrier wave, is also input to the PWM unit 41 from outside the motor control device 100 (for example, from a higher-level controller of the motor control device 100). The PWM unit 41 generates three-phase PWM signals Up, Un, Vp, Vn, Wp, Wn based on the voltage command values Vu ^* , Vv ^* , Vw ^* , the DC voltage Vdc, and the carrier signal, and outputs the generated PWM signals Up, Un, Vp, Vn, Wp, Wn to the switching module 10 and the 3φ current calculation unit 61.

The switching module 10 is supplied with a DC voltage from a DC power supply E _DC , and receives PWM signals Up, Un, Vp, Vn, Wp, and Wn from a PWM unit 41. The switching module 10 converts the DC voltage supplied from the DC power supply E _DC into a three-phase AC voltage in accordance with the PWM signals Up to Wn, and applies the converted three-phase AC voltage to a motor M. The motor M is driven by applying the three-phase AC voltage to the motor M. In the switching module 10, the switching elements SWup, SWun, SWvp, SWvn, SWwp, and SWwn are turned on/off in accordance with the PWM signals Up, Un, Vp, Vn, Wp, and Wn, thereby converting the DC voltage into a three-phase voltage. Freewheeling diodes Dup, Dun, Dvp, Dvn, Dwp, and Dwn are connected to both ends of each of the switching elements SWup, SWun, SWvp, SWvn, SWwp, and SWwn.

The current detection unit 21 detects the bus current Is of the switching module 10 by using a shunt resistor Rs connected between the DC power supply E _DC and the switching module 10. The shunt resistor Rs is arranged on an N line _LN which is a DC line between an N-side terminal of the DC power supply E _DC and the switching module 10. The shunt resistor Rs may be arranged on a P line _LP which is a DC line between a P-side terminal of the DC power supply E _DC and the switching module 10. A bus current Is corresponding to a U-phase current, a V-phase current, and a W-phase current which are motor currents and a PWM signal flows through the shunt resistor Rs, and when the bus current Is flows through the shunt resistor Rs, a voltage drop occurs across the shunt resistor Rs. The current detection unit 21 detects the bus current Is flowing through the shunt resistor Rs from the magnitude of this voltage drop and the resistance value of the shunt resistor Rs. Furthermore, the current detection unit 21 calculates an analog voltage VA1 expressed by equation (1) based on the shunt resistance Rs and the bus current Is, and outputs the calculated analog voltage VA1 to the AD conversion unit 72. "k" in equation (1) represents a predetermined amplification factor.
VA1=k×(Rs・Is)…(1)

The AD conversion unit 72 samples the analog voltage VA1 to convert it into a digital voltage value VA2, and outputs the converted digital voltage value VA2 to the 3φ current calculation unit 61.

The 3φ current calculation unit 61 calculates the motor current using a single shunt detection method. The 3φ current calculation unit 61 calculates the motor currents U-phase current iu, V-phase current iv, and W-phase current iw based on the resistance value of the shunt resistor Rs, the amplification factor k, the digital voltage value VA2, and the PWM signals Up to Wn, and outputs the calculated motor currents iu, iv, and iw to the 3φ/dq conversion unit 42.

The 3φ/dq conversion unit 42 converts the motor currents iu, iv, and iw, which indicate the three-phase current vector of the fixed coordinate system, into d-axis current and q-axis current, which indicate the two-phase current vector of the rotating coordinate system, using the electrical angle phase θe input from the position and speed estimation unit 44. Hereinafter, the d-axis current after conversion by the 3φ/dq conversion unit 42 may be referred to as the "detected d-axis current," and the q-axis current after conversion by the 3φ/dq conversion unit 42 may be referred to as the "detected q-axis current." The 3φ/dq conversion unit 42 outputs the detected d-axis current id_det and the detected q-axis current iq_det to the noise determination unit 80.

The noise determination unit 80 receives the detected d-axis current id_det and the detected q-axis current iq_det from the 3φ/dq conversion unit 42, and the mechanical angle phase θm from the position/speed estimation unit 44. The noise determination unit 80 performs noise determination, and based on the result of the noise determination, determines the d-axis current id to be output to the position/speed estimation unit 44, the d-axis/q-axis voltage setting unit 45, and the subtraction unit 46, and the q-axis current iq to be output to the position/speed estimation unit 44, the d-axis/q-axis voltage setting unit 45, and the subtraction unit 47. Details of the noise determination unit 80 will be described later.

The DC voltage detection unit 31 detects a bus voltage between the P line _LP and the N line _LN , and outputs the detected analog bus voltage VB1 to the AD conversion unit 71.

The AD conversion unit 71 samples the analog bus voltage VB1 to convert it into a digital bus voltage value VB2, and outputs the converted digital bus voltage value VB2 to the DC voltage calculation unit 32.

The DC voltage calculation unit 32 calculates the DC voltage Vdc from the digital bus voltage value VB2 and outputs the calculated DC voltage Vdc to the PWM unit 41.

<Configuration of Noise Determination Unit>
2 is a diagram showing an example of the configuration of a noise determination unit according to an embodiment of the present disclosure. In FIG. 2, the noise determination unit 80 includes a current prediction unit 81, a difference calculation unit 82, and a current determination unit 83. The current prediction unit 81 receives the d-axis current id and the q-axis current iq determined by the current determination unit 83 as described below, and also receives the mechanical angle phase θm from the position/speed estimation unit 44. The difference calculation unit 82 and the current determination unit 83 receive the detected d-axis current id_det and the detected q-axis current iq_det from the 3φ/dq conversion unit 42.

The current prediction unit 81 calculates a predicted d-axis current id_pre, which is a predicted value of the d-axis current, and a predicted q-axis current iq_pre, which is a predicted value of the q-axis current, using the d-axis current id determined by the current determination unit 83 at each control timing and input from the current determination unit 83, the q-axis current iq determined by the current determination unit 83 at each control timing and input from the current determination unit 83, and the mechanical angle phase θm input from the position/speed estimation unit 44. The current prediction unit 81 outputs the calculated predicted d-axis current id_pre and predicted q-axis current iq_pre to the difference calculation unit 82 and the current determination unit 83. Details of the current prediction unit 81 will be described later.

The difference calculation unit 82 calculates a difference id_dif between the detected d-axis current id_det and the predicted d-axis current id_pre (hereinafter sometimes referred to as the “d-axis difference”) and a difference iq_dif between the detected q-axis current iq_det and the predicted q-axis current iq_pre (hereinafter sometimes referred to as the “q-axis difference”) according to equations (2.1) and (2.2). The difference calculation unit 82 outputs the calculated d-axis difference id_dif and q-axis difference iq_dif to the current determination unit 83.
id_dif=id_det-id_pre...(2.1)
iq_dif=iq_det−iq_pre…(2.2)

The d-axis difference id_dif and the q-axis difference iq_dif are the differences between the detected values and the predicted values of the d-axis current and the q-axis current. If the detected values and the predicted values differ greatly, it is possible that noise is superimposed on the detected values of the d-axis current and the q-axis current. In addition, the d-axis difference id_dif and the q-axis difference iq_dif may become positive or negative depending on the superimposed noise. The current determination unit 83 performs noise determination by comparing the d-axis difference id_dif and the q-axis difference iq_dif with a predetermined threshold value TH1, which is a negative value, and a predetermined second threshold value TH2, which is a positive value, to determine the d-axis current id and the q-axis current iq at the current control timing.

The first threshold value TH1 is set to a negative value smaller than the bottom values of the steady d-axis difference id_dif and q-axis difference iq_dif when no noise is superimposed on the detected d-axis current id_det and the detected q-axis current iq_det, or when the noise superimposed on the detected d-axis current id_det and the detected q-axis current iq_det is small. For example, the bottom values of the steady d-axis difference id_dif and q-axis difference iq_dif can be obtained in advance by testing. When the bottom values of the steady d-axis difference id_dif and q-axis difference iq_dif are -0.8 [A], the first threshold value TH1 is set to a negative value smaller than the bottom values, for example, -1 [A].

Similarly, the second threshold value TH2 is set to a positive value larger than the peak values of the steady d-axis difference id_dif and q-axis difference iq_dif when no noise is superimposed on the detected d-axis current id_det and the detected q-axis current iq_det, or when the noise superimposed on the detected d-axis current id_det and the detected q-axis current iq_det is small. For example, the peak values of the steady d-axis difference id_dif and q-axis difference iq_dif can be obtained in advance by testing. When the peak values of the steady d-axis difference id_dif and q-axis difference iq_dif are 0.8 [A], the second threshold value TH2 is set to a positive value larger than the peak values, for example 1 [A].

When the d-axis difference id_dif is greater than or equal to the first threshold TH1 and less than the second threshold TH2, the current determination unit 83 determines that no noise is superimposed on the detected d-axis current id_det or that the noise superimposed on the detected d-axis current id_det is small, and determines the detected d-axis current id_det as the d-axis current id to be used for controlling the motor M at the current control timing, and outputs the detected d-axis current id_det of the detected d-axis current id_det and the predicted d-axis current id_pre to the position/speed estimation unit 44, the d-axis/q-axis voltage setting unit 45, the subtraction unit 46, and the current prediction unit 81. On the other hand, when the d-axis difference id_dif is less than the first threshold TH1 or equal to or greater than the second threshold TH2, the current determination unit 83 determines that the noise superimposed on the detected d-axis current id_det is large, determines the predicted d-axis current id_pre as the d-axis current id to be used for controlling the motor M at the current control timing, and outputs the predicted d-axis current id_pre of the detected d-axis current id_det and the predicted d-axis current id_pre to the position/speed estimation unit 44, the d-axis and q-axis voltage setting unit 45, the subtraction unit 46, and the current prediction unit 81.

In addition, when the q-axis difference iq_dif is greater than or equal to the first threshold value TH1 and less than the second threshold value TH2, the current determination unit 83 determines that no noise is superimposed on the detected q-axis current iq_det or that the noise superimposed on the detected q-axis current iq_det is small, and determines the detected q-axis current iq_det as the q-axis current iq to be used for controlling the motor M at the current control timing, and outputs the detected q-axis current iq_det, of the detected q-axis current iq_det and the predicted q-axis current iq_pre, to the position/speed estimation unit 44, the d-axis and q-axis voltage setting unit 45, the subtraction unit 47, and the current prediction unit 81. On the other hand, when the q-axis difference iq_dif is less than the first threshold value TH1 or greater than or equal to the second threshold value TH2, the current determination unit 83 determines that the noise superimposed on the detected q-axis current iq_det is large, determines the predicted q-axis current iq_pre as the q-axis current iq to be used for controlling the motor M at the current control timing, and outputs the predicted q-axis current iq_pre of the detected q-axis current iq_det and the predicted q-axis current iq_pre to the position/speed estimation unit 44, the d-axis and q-axis voltage setting unit 45, the subtraction unit 47, and the current prediction unit 81.

<Operation of current prediction unit>
3 is a diagram for explaining an example of the operation of the current prediction unit of the embodiment of the present disclosure. Hereinafter, the d-axis current and the q-axis current may be collectively referred to as "two-phase currents." In addition, below, the two-phase current predicted by the current prediction unit 81 based on the sampled two-phase currents may be referred to as "predicted current."

The current prediction unit 81 performs a Fourier transform on the d-axis current id determined by the current determination unit 83 and input from the current determination unit 83 at each control timing in an integral interval in which the mechanical angle phase θm varies from 0 to 2π. That is, the current prediction unit 81 separates the d-axis current id into frequency components of multiple orders by calculating a d-axis Fourier cosine coefficient an_d and a d-axis Fourier sine coefficient bn_d according to equations (3.2) and (3.3). Then, the current prediction unit 81 calculates a predicted d-axis current id_pre by combining the frequency components of multiple orders of the d-axis current id according to equation (3.1). Here, a ₀ /2 in equation (3.1) is the average value of the d-axis current id.

Similarly, the current prediction unit 81 performs a Fourier transform on the q-axis current iq determined by the current determination unit 83 and input from the current determination unit 83 at each control timing in an integral interval in which the mechanical angle phase θm changes from 0 to 2π. That is, the current prediction unit 81 separates the q-axis current iq into frequency components of multiple orders by calculating a q-axis Fourier cosine coefficient an_q and a q-axis Fourier sine coefficient bn_q according to the formulas (4.2) and (4.3). Then, the current prediction unit 81 calculates a predicted q-axis current iq_pre by combining the frequency components of multiple orders of the q-axis current iq according to the formula (4.1). Here, a ₀ /2 in the formula (4.1) is the average value of the q-axis current iq.

In equations (3.1) to (4.3), n is the order, and 1, 2, 3, 4, ... are substituted for n. In other words, the current prediction unit 81 separates the d-axis current id and the q-axis current iq into frequency components of n orders in equations (3.2), (3.3), (4.2), and (4.3).

Here, it is preferable that n is as large as possible. In other words, when the current prediction unit 81 performs a Fourier transform on the d-axis current id and the q-axis current iq, it is preferable to separate the d-axis current id and the q-axis current iq into components of as high order as possible. The number of orders that can be separated is determined based on the processing capacity of the current prediction unit 81, the time allowed for processing by the current prediction unit 81, etc.

Here, for example, if the predicted current is calculated by directly copying the two-phase current, it is necessary to store the two-phase current data in memory at the sampling period. For example, to calculate the predicted current for one period, it is necessary to store in memory "two-phase current period/sampling period [pieces]" data for each of the d-axis current id and q-axis current iq. For this reason, if the period of the two-phase current is long, a large memory area will be used to calculate the predicted current. For example, if the two-phase current with a period of 200 ms is sampled at a period of 0.125 ms, the total number of data for the d-axis current id and q-axis current iq will be 3,200.

On the other hand, when the predicted current is calculated using the Fourier transform as described above, it is possible to calculate the predicted current by integrating the data of each order after separation into the same memory area for each order, regardless of the length of the period of the two-phase current. In other words, all that is required is a memory area for calculating the d-axis Fourier cosine coefficient an_d, the d-axis Fourier sine coefficient bn_d, the q-axis Fourier cosine coefficient an_q, and the q-axis Fourier sine coefficient bn_q obtained for each order, and the number of data stored in the memory is "the number of orders x 4 [pieces]". For example, if the number of orders is 30, the number of data will be 120. Therefore, by calculating the predicted current using the Fourier transform, the memory area used to calculate the predicted current can be reduced.

The above explains the examples.

As described above, the motor control device (motor control device 100 of the embodiment) of the present disclosure has a switching module (switching module 10 of the embodiment), a detection unit (current detection unit 21 of the embodiment), a first calculation unit (3φ current calculation unit 61 of the embodiment), a conversion unit (3φ/dq conversion unit 42 of the embodiment), a prediction unit (current prediction unit 81 of the embodiment), and a determination unit (current determination unit 83 of the embodiment). The switching module converts a DC voltage supplied from a DC power source into an AC voltage and applies the AC voltage to a motor (motor M of the embodiment). The detection unit detects the bus current of the switching module using a resistor (shunt resistor Rs of the embodiment) connected between the DC power source and the switching module. The first calculation unit calculates the three-phase current of the fixed coordinate in the motor based on the bus current. The conversion unit converts the three-phase current of the fixed coordinate into two-phase current of the rotating coordinate (detected d-axis current id_det, detected q-axis current iq_det of the embodiment). The prediction unit calculates predicted values of the two-phase currents (predicted d-axis current id_pre, predicted q-axis current iq_pre in the embodiment). The determination unit determines whether the two-phase currents or the predicted values are to be used for motor control based on the two-phase currents of the rotating coordinates and the predicted values of the two-phase currents. The prediction unit also performs a Fourier transform on the two-phase currents or the determined values (d-axis current id, q-axis current iq in the embodiment) that the determination unit has determined to be used for motor control, thereby separating the determined values into frequency components of multiple orders, and calculates the predicted values by combining the frequency components of multiple orders.

For example, the motor control device of the present disclosure has a second calculation unit (difference calculation unit 82 in the embodiment) that calculates the difference between the two-phase currents and the predicted value (d-axis difference id_dif and q-axis difference iq_dif in the embodiment). The decision unit decides to use the two-phase currents to control the motor when the difference is equal to or greater than a first threshold (first threshold TH1 in the embodiment) and less than a second threshold (second threshold TH2 in the embodiment), and decides to use the predicted value to control the motor when the difference is less than the first threshold or equal to or greater than the second threshold.

In this way, when controlling a motor using a highly accurate current value, the offset voltage required by the above-mentioned prior art is no longer necessary, and therefore a circuit for acquiring the offset voltage and an A/D converter for sampling the offset voltage are no longer necessary. Therefore, it is possible to control a motor using a highly accurate current value while suppressing an increase in the number of parts in a motor control device. In addition, because an A/D converter for sampling the offset voltage is no longer necessary, the A/D converter used to sample the offset voltage can be used for another purpose.

REFERENCE SIGNS LIST 100 Motor control device 10 Switching module 21 Current detection section 42 3φ/dq conversion section 61 3φ current calculation section 80 Noise determination section 81 Current prediction section 82 Difference calculation section 83 Current determination section

Claims (1)

a switching module that converts a DC voltage supplied from a DC power source into an AC voltage and applies the AC voltage to a motor;
a detection unit that detects a bus current of the switching module using a resistor connected between the DC power source and the switching module;
a first calculation unit that calculates three-phase currents of a fixed coordinate system in the motor based on the bus currents;
A conversion unit for converting the three-phase current into a two-phase current in a rotating coordinate system;
A prediction unit that calculates a predicted value of the two-phase current;
a determination unit that determines whether the two-phase currents or the predicted value is to be used for control of the motor based on the two-phase currents and the predicted value,
the prediction unit performs a Fourier transform on the two-phase currents determined by the determination unit to be used for control of the motor or a determined value that is the predicted value, thereby separating the determined value into frequency components of a plurality of orders, and calculates the predicted value by synthesizing the frequency components of the plurality of orders;
A second calculation unit calculates a difference between the two-phase currents and the predicted values,
the determination unit determines that the two-phase currents are to be used for control of the motor when the difference is equal to or greater than a negative first predetermined value that is smaller than a bottom value of the steady difference and is less than a positive second predetermined value that is larger than a peak value of the steady difference, and determines that the predicted value is to be used for control of the motor when the difference is less than the first predetermined value or equal to or greater than the second predetermined value.
Motor control device.

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