JP2019198148A - Electric motor control device and electric motor control method - Google Patents

Abstract

To provide an electric motor control device and an electric motor control method for enabling stable control of torque and a rotation speed with a simple configuration.SOLUTION: The electric motor control device for controlling an electric motor such that a driving current for the electric motor follows a current command value, includes a sensor magnet that forms a first magnetic field by rotating in association with a rotor of the electric motor, a magnetic sensor that measures a synthetic magnetic field including the first magnetic field and a second magnetic field formed by the driving current, a rotation angle calculation unit that separates the first magnetic field from a measurement value of the synthetic magnetic field, and calculates the rotation angle of the rotor from the separated first magnetic field, a current calculation unit that separates the second magnetic field from the measurement value of the synthetic magnetic field, and calculates a driving current from the second magnetic field, and a current control unit that controls the electric motor on the basis of the rotation angle calculated by the rotation angle calculation unit, the driving current calculated by the current calculation unit, and the current command value.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a motor control device and a motor control method.

  In general, an electric motor using an inverter is feedback controlled to compensate for the influence of disturbance. For this purpose, the electric motor is provided with an ammeter such as a shunt resistor for measuring the drive current and an angle sensor such as a resolver for measuring the rotation angle of the rotor.

  Patent Document 1 describes a feedback control method for a current sensorless motor that is reduced in cost by omitting an ammeter for measuring drive current. The electric motor without a current sensor described in Patent Document 1 includes an arithmetic device that estimates the value of the drive current by calculation based on the voltage command value of the inverter instead of omitting the ammeter.

JP 2006-14431 A

  However, in the electric motor without a current sensor disclosed in Patent Document 1, the estimated value of the driving current deviates from the actual electric current value when the disturbance is large or the driving condition is that the fluctuation of the torque of the electric motor or the fluctuation of the rotation speed is large. Torque ripple occurs in the motor, and the electric power efficiency of the motor decreases. In addition, if the drive current is estimated with high accuracy, the amount of calculation of the arithmetic device increases, and a high-performance arithmetic device is required, which increases the cost of the motor control device.

  Accordingly, an object of the present invention is to provide a motor control device and a motor control method capable of stably controlling torque and rotational speed with a simple configuration.

  According to one aspect of the present invention, there is provided a motor control device that controls an electric motor so that a driving current of the electric motor follows a current command value, wherein the sensor rotates with the rotor of the electric motor to form a first magnetic field. A magnet, a magnetic sensor for measuring a combined magnetic field including a first magnetic field and a second magnetic field formed by a drive current, and a first magnetic field separated from the measured value of the combined magnetic field, and from the separated first magnetic field A rotation angle calculation unit that calculates a rotation angle of the rotor, a current calculation unit that separates the second magnetic field from the measured value of the combined magnetic field, and calculates a drive current from the separated second magnetic field; and a rotation angle calculation unit There is provided a motor control device including a current control unit that controls the motor based on the rotation angle calculated by the above, the drive current calculated by the current calculation unit, and the current command value.

  According to another aspect of the present invention, a combined magnetic field including a sensor magnet that rotates with the rotor of the electric motor to form a first magnetic field, and a second magnetic field that is formed by the first magnetic field and the driving current of the electric motor. And a magnetic sensor for measuring the first magnetic field separated from the measured value of the combined magnetic field in the motor control device that controls the motor so that the drive current follows the current command value. A rotation angle calculation step for calculating the rotation angle of the rotor from the magnetic field of the current, a current calculation step for separating the second magnetic field from the measured value of the combined magnetic field, and calculating a drive current from the separated second magnetic field, and rotation An electric motor control method is provided that includes a current control step for controlling the electric motor based on the rotation angle calculated in the angle calculation step, the drive current calculated in the current calculation step, and the current command value. That.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus and the control method of an electric motor which can control a torque and a rotational speed stably with a simple structure are provided.

It is a figure which shows typically the structure of the electric motor controlled by the control apparatus of the electric motor which concerns on 1st Embodiment. It is a figure which shows the waveform of the time change of the drive current in one period of the rotation angle of a rotor when the number of pole pairs of an electric motor is two. It is a figure which shows the structure of the control apparatus of the electric motor which concerns on 1st Embodiment with an electric motor. It is a figure which shows the example of arrangement | positioning of the magnetic sensor in the control apparatus of the electric motor which concerns on 1st Embodiment. It is a flowchart which shows the control method of the electric motor which concerns on 1st Embodiment. It is a figure which shows the example of arrangement | positioning of the magnetic sensor in the control apparatus of the electric motor which concerns on 2nd Embodiment. It is a figure which shows the example of arrangement | positioning of the magnetic sensor in the control apparatus of the electric motor which concerns on 3rd Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment, In the range which does not deviate from the summary, it can change suitably. In addition, components having the same or corresponding functions in each drawing are denoted by the same reference numerals, and the description thereof may be omitted or simplified.

  In the present invention, in order to simplify the configuration of the motor control device and reduce the cost, an ammeter for measuring the drive current flowing through the motor, and an angle sensor for measuring the rotation angle of the rotor of the motor, Are integrated into one magnetic sensor. This magnetic sensor measures a combined magnetic field including a first magnetic field formed by a sensor magnet that rotates together with a rotor of an electric motor and a second magnetic field formed by a driving current of the electric motor. Then, the motor control device of the present invention separates the first magnetic field and the second magnetic field from the measured combined magnetic field, and then calculates the rotation angle of the rotor from the separated first magnetic field. The drive current is calculated from the second magnetic field.

  According to the motor control apparatus of the present invention, the configuration of the motor control apparatus can be simplified by omitting the ammeter for measuring the drive current and its wiring. Further, unlike a motor without a current sensor, both the drive current of the motor and the rotation angle of the rotor are fed back, so that the torque and rotation speed of the motor are stabilized.

[First Embodiment]
FIG. 1A is a diagram schematically illustrating an example of the structure of the electric motor 1 when the number of pole pairs is one. FIG. 1B is a diagram schematically showing an example of the structure of the electric motor 1 when the number of pole pairs is two. The electric motor 1 includes a stator 11 and a rotor 12.

  The stator 11 is a fixed non-rotating portion of the electric motor 1 and typically has a cylindrical shape having a space inside. A plurality of windings 13 through which three-phase AC drive currents iu, iv, and iw flow are fixed to the inner wall of the stator 11.

  In the electric motor 1, an αβ coordinate system fixed to the stator 11 is set as a first coordinate system. The α axis and β axis are set on a plane orthogonal to the central axis of the stator 11, and the origin of the αβ coordinate system is set on the central axis of the cylindrical stator 11. In the electric motor 1 having one pole pair shown in FIG. 1A, the α axis and the β axis are set to be orthogonal to each other. In the electric motor 1 having two pole pairs shown in FIG. The α axis and the β axis are set to intersect each other at an angle of 45 ° (= 90 ° / number of pole pairs). The α axis of the αβ coordinate system is set in the direction in which the winding 13 through which the drive current iu flows is arranged. In other words, the winding 13 through which the drive current iu flows is arranged on the α axis of the αβ coordinate system. The windings 13 through which the drive currents iv and iw flow are arranged in directions rotated by + 120 ° and −120 ° with respect to the α axis, respectively.

The waveform of the time change of the drive currents iu, iv, iw of the three-phase alternating current flowing in the winding 13 is expressed by the following equation (1). Here, i0 is the absolute value of the amplitude of the drive currents iu, iv, iw, and θ is the phase angle calculated by multiplying the angular velocity ω of the drive currents iu, iv, iw by time t.
iu = i0 × sin θ,
iv = i0 × sin (θ− (2/3) π),
iw = i0 × sin (θ + (2/3) π) (1)

  The three-phase AC drive currents iu, iv, iw satisfy iu + iv + iw = 0. Therefore, one phase of the drive currents iu, iv, and iw in the above equation (1) can be derived from the other two phases. When the drive currents iu, iv, and iw represented by the above equation (1) are passed through the winding 13, a magnetic field B2 that rotates in time with the origin in the αβ coordinate system as the rotation center is formed inside the stator 11. Is done.

  On the other hand, the rotor 12 typically has a cylindrical shape and is rotatably supported inside the stator 11. The rotation axis of the cylindrical rotor 12 coincides with the central axis of the cylindrical stator 11. The rotor 12 has a permanent magnet, and the rotor 12 rotates in the stator 11 according to the change of the magnetic field B2. As a result, torque T is generated in the stator 11.

  At this time, it occurs in the stator 11 when the direction connecting the N pole and S pole of the permanent magnet of the rotor 12 is controlled to be orthogonal to the direction of the magnetic field B2 formed by the drive currents iu, iv, iw. Torque T to be maximized. A sensor magnet 14 for measuring the rotation angle θm of the rotor 12 with respect to the stator 11 is fixed to the rotation shaft of the rotor 12.

Further, the dq coordinate system that rotates together with the rotor 12 is set as the second coordinate system in the electric motor 1. The d axis and the q axis are set on a plane orthogonal to the rotation axis of the rotor 12, and the origin of the dq coordinate system is set on the rotation axis of the rotor 12. In the motor 1 with the number of pole pairs shown in FIG. 1A, the d axis and the q axis are set to be orthogonal to each other, and in the motor 1 with the number of pole pairs shown in FIG. The d-axis and the q-axis are set to intersect each other at an angle of 45 ° (= 90 ° / number of pole pairs). The dq coordinate system is a coordinate system rotated by the rotation angle θm of the rotor 12 with respect to the αβ coordinate system. The d axis of the dq coordinate system is set, for example, in a direction perpendicular to the direction connecting one N pole and one S pole of the permanent magnet of the rotor 12. Coordinate conversion from αβ coordinates (xα, xβ) to dq coordinates (xd, xq) is expressed by the following equation (2) using the rotation angle θm of the rotor 12.
xd = xα × cos θm + xβ × sin θm,
xq = −xα × sin θm + xβ × cos θm (2)

  Here, the rotor 12 of the motor 1 having the number of pole pairs of 2 shown in FIG. 1B has two pairs of N and S poles of permanent magnets, and the stator 11 Two pairs of windings 13 through which drive currents iu, iv, and iw flow are provided. For this reason, in the electric motor 1 shown in FIG. 1B, the phase angle θ of the drive currents iu, iv, iw changes by two cycles while the rotation angle θm of the rotor 12 makes one rotation. Thus, in the electric motor 1 having two or more pole pairs, the rotation angle θm of the rotor 12 and the phase angle θ of the drive currents iu, iv, and iw do not match.

  FIG. 2 is a diagram showing the time-varying waveforms of the drive currents iu, iv, iw in one cycle of the rotation angle θm of the rotor 12 when the number of pole pairs of the electric motor 1 is two. Waveforms 201, 202, and 203 shown in FIG. 2 indicate temporal changes in the drive currents iu, iv, and iw, respectively. The horizontal axis in FIG. 2 indicates the rotation angle θm of the rotor 12, and the vertical axis in FIG. 2 indicates the magnitudes of the drive currents iu, iv, iw. As shown in FIG. 2, in the electric motor 1 having two pole pairs, the phase angle θ of the drive currents iu, iv, and iw changes by two cycles while the rotation angle θm of the rotor 12 makes one rotation.

More generally, in the electric motor 1 having the number of pole pairs of N2, the phase angle θ of the drive currents iu, iv, and iw changes by N2 periods while the rotation angle θm of the rotor 12 rotates once. The rotation angle θm of the rotor 12 is called a mechanical angle, and the phase angle θ of the drive currents iu, iv, iw is called an electrical angle. The relationship between the rotation angle θm (mechanical angle) of the rotor 12 of the electric motor 1 and the phase angle θ (electrical angle) of the drive currents iu, iv, iw is expressed by the following equation (3).
Phase angle θ of drive current = number of pole pairs N2 × rotation angle θm of rotor (3)

  FIG. 3 is a diagram illustrating the configuration of the control device for the electric motor 1 according to the first embodiment together with the electric motor 1. The electric motor 1 is feedback-controlled by the control device of the electric motor 1 of the present embodiment so that the driving currents iu, iv, iw follow the current command values id *, iq *.

  The control device for the electric motor 1 according to the present embodiment includes a current command value calculation unit 2, a current control unit 3, an electric motor drive unit 4, and a current measurement unit 5. Note that the components realized as an integrated circuit below may be integrated into one or a plurality of integrated circuits, or realized by executing a program stored in advance in a storage unit by one or a plurality of processors. May be.

  The current command value calculation unit 2 is realized as an integrated circuit, and a current command value id required for causing the electric motor 1 to generate a torque T corresponding to the torque command value T * according to the torque command value T * input from the outside. * And iq * are calculated and output. Here, the symbol “*” of the current command values id * and iq * indicates a command value. Specifically, the current command value calculation unit 2 refers to a table that defines the relationship between the torque command value T * and the current command values id * and iq * stored in advance in the storage unit, for example. Current command values id * and iq * corresponding to T * are set.

  In general, the current command values id * and iq * which are command values are expressed not in the uvw coordinate system that needs to handle alternating current but in the dq coordinate system that does not need to handle alternating current in order to reduce the calculation load. At this time, the torque T of the electric motor 1 is basically controlled by the current command value iq *. The current command value id * may be fixed to zero, or may be non-zero for higher efficiency or higher rotation. However, the current command values id * and iq * can be expressed in an arbitrary coordinate system and are not limited to the dq coordinate system.

  The current control unit 3 is realized as an integrated circuit, and includes current command values id * and iq * output from the current command value calculation unit 2 and current measurement values id and iq output from a current measurement unit 5 described later. The electric motor 1 is controlled via the subsequent electric motor drive unit 4 so that the deviation is reduced. For this purpose, the current control unit 3 calculates voltage command values vd * and vq * necessary for flowing the drive currents iu, iv and iw corresponding to the current command values id * and iq * to the electric motor 1.

  The motor drive unit 4 generates a three-phase AC voltage corresponding to the voltage command values vd * and vq * output from the current control unit 3, and applies the three-phase AC voltage to the motor 1 to drive the motor 1. . FIG. 3 shows an example of the motor drive unit 4 when the motor 1 is driven by a three-phase AC voltage obtained by pulse width modulation (PWM) of the DC voltage E. The electric motor drive unit 4 shown in FIG. 3 includes a dq / uvw conversion unit 41, a modulation unit 42, and an inverter 43.

The dq / uvw conversion unit 41 is realized as an integrated circuit, receives the rotation angle θm of the rotor 12 from the rotation angle calculation unit 53 of the current measurement unit 5 described later, and drives the drive currents iu, iv, The phase angle θ of iw is calculated. Alternatively, the dq / uvw conversion unit 41 may receive the phase angle θ of the drive currents iu, iv, iw from the rotation angle calculation unit 53. Then, the dq / uvw conversion unit 41 converts the voltage command values vd * and vq * expressed in the dq coordinate system into the command values vu * of the three-phase AC voltage expressed in the uvw coordinate system according to the following equation (4). , Vv *, vw *. In the following formula (4), the symbol “*” indicating the command value is omitted.
vu = √ (2/3) {vd × cos θ−vq × sin θ},
vv = √ (2/3) {vd × cos (θ-2π / 3) −vq × sin (θ-2π / 3)},
vw = √ (2/3) {vd × cos (θ + 2π / 3) −vq × sin (θ + 2π / 3)} (4)

  The modulation unit 42 is realized as an integrated circuit, performs switching control on the DC voltage E supplied to the inverter 43 in the subsequent stage, and has a duty ratio corresponding to the command values vu *, vv *, and vw * of the three-phase AC voltage. Three-phase pulse voltages are generated respectively. The inverter 43 outputs a three-phase pulse voltage having a duty ratio corresponding to the command values vu *, vv *, and vw * of the three-phase AC voltage to the electric motor 1. As a result, drive currents iu, iv, and iw flow through the electric motor 1, and torque T is generated in the electric motor 1.

  The current measuring unit 5 measures the drive currents iu, iv, iw of the electric motor 1 and the rotation angle θm of the rotor 12. Then, the current measuring unit 5 calculates the phase angle θ of the drive currents iu, iv, iw according to the above equation (3), and the dq coordinates rotated by the rotation angle θm with respect to the αβ coordinate system based on these values. The measured current values id and iq expressed in the system are calculated and output to the current control unit 3. The current measurement unit 5 of the present embodiment shown in FIG. 3 includes a magnetic sensor 51, a current calculation unit 52, a rotation angle calculation unit 53, and an αβ / dq conversion unit 54. Hereinafter, the current measurement unit 5 of the present embodiment will be described in detail with reference to FIGS. 3 and 4.

  FIG. 4 is a diagram illustrating an arrangement example of the magnetic sensor 51 in the control device for the electric motor 1 according to the first embodiment. As described above, the sensor magnet 14 for measuring the rotation angle θm of the rotor 12 with respect to the stator 11 is fixed to the rotating shaft of the rotor 12. The number of pole pairs N2 of the rotor 12 shown in FIG. 4 is 2, and the number of pole pairs N1 of the sensor magnet 14 is 1. In the present embodiment, the number of pole pairs N2 of the rotor 12 is made larger than the number of pole pairs N1 of the sensor magnet 14.

  The magnetic sensor 51 of the present embodiment is fixed to the stator 11 of the electric motor 1 so as to face the sensor magnet 14 on the extension of the rotating shaft of the rotor 12 of the electric motor 1. At the position where the magnetic sensor 51 is disposed, the first magnetic field B1 formed by the sensor magnet 14 and the second magnetic field B2 formed by the drive currents iu, iv, iw are superposed. The magnetic sensor 51 measures the combined magnetic field B including the first magnetic field B1 and the second magnetic field B2. As the magnetic sensor 51, for example, a Hall sensor can be used. The synthesized magnetic field B measured by the magnetic sensor 51 includes, for example, a magnetic field formed by a permanent magnet of the rotor 12 in addition to the first magnetic field B1 and the second magnetic field B2.

  The magnetic sensor 51 measures the x component and the y component of the combined magnetic field B in an xy orthogonal coordinate system set on a plane orthogonal to the central axis of the stator 11. In such a magnetic sensor 51, for example, a first magnetic sensor capable of measuring a magnetic field component in the x-axis direction and a second magnetic sensor capable of measuring a magnetic field component in the y-axis direction are arranged so as to overlap each other. Is realized. Alternatively, a single magnetic sensor capable of biaxial measurement may be used as the magnetic sensor 51.

  As described above, in the electric motor 1 having the number of pole pairs of N2, the phase angle θ of the drive currents iu, iv, and iw changes by N2 periods while the rotation angle θm of the rotor 12 rotates once. Therefore, the frequency f2 of the second magnetic field B2 is N2 times the frequency f1 of the first magnetic field B1. Therefore, the current measurement unit 5 of the present embodiment uses the difference between the frequency f1 of the first magnetic field B1 and the frequency f2 of the second magnetic field B2 to change the first magnetic field B1 and the first magnetic field B1 from the combined magnetic field B. The two magnetic fields B2 are separated.

Specifically, the current calculation unit 52 includes a high-pass filter for separating the second magnetic field B2 formed by the drive currents iu, iv, and iw from the measured value of the combined magnetic field B. The cut-off frequency fc of the high pass filter is set so as to satisfy the following expression (5).
f1 <fc <f2 (5)

  The high-pass filter may be an analog filter that passes a signal component having a cutoff frequency fc of the measurement value of the combined magnetic field B or higher, and digitally separates a signal component having a cutoff frequency fc of the measurement value of the combined magnetic field B or not. It may be a digital filter.

  However, in order to vary the cut-off frequency fc of the high-pass filter in accordance with the change in the rotation speed of the electric motor 1, the high-pass filter is preferably a digital filter. The digital filter is realized by, for example, a fast Fourier transform (FFT). In this case, the current calculation unit 52 includes an analog / digital conversion unit for digitizing the measurement value of the combined magnetic field B in addition to the digital filter.

  Specifically, the current calculation unit 52 first performs analog-digital conversion on the measured value of the combined magnetic field B. Next, the current calculation unit 52 performs a fast Fourier transform on the digitized measurement value of the synthesized magnetic field B, removes frequency components below the cutoff frequency fc of the synthesized magnetic field B, and then performs an inverse fast Fourier transform. Do. Thereby, the second magnetic field B2 formed by the drive currents iu, iv, iw is separated from the measured value of the combined magnetic field B.

The current calculation unit 52 is realized as an integrated circuit, and calculates the measured values iα and iβ in the αβ coordinate system of the drive currents iu, iv, and iw from the values of the second magnetic field B2 separated by the high-pass filter (6) ). Here, B2x and B2y are the x component and the y component of the second magnetic field B2 expressed in the xy orthogonal coordinate system, respectively. The coefficients K _αx , K _αy , K _βx , and K _βy are proportional constants determined from the shape of the winding 13 and the relative arrangement of the winding 13 and the magnetic sensor 51, and are determined by measurement in advance. The For example, in a configuration having dedicated windings for measuring three-phase AC drive currents iu, iv, and iw as in a third embodiment to be described later, the direction of the α axis and the direction of the β axis are respectively set to the x axis. And the direction of the y-axis. In this case, these coefficients are K _αx = K _βy = K and K _αy = K _βx = 0, where the coefficient K is the gain of the magnetic sensor 51.
iα = K _αx · B2x + K _αy · B2y
_{iβ = K βx · B2x + K} βy · B2y (6)

  Similarly, the rotation angle calculation unit 53 has a low-pass filter for separating the first magnetic field B1 formed by the sensor magnet 14 from the measured value of the combined magnetic field B. The low-pass filter passes a signal component that is equal to or lower than the cut-off frequency fc of the measurement value of the combined magnetic field B, and the cut-off frequency fc of the low-pass filter is set to satisfy the above equation (5). Note that the frequency of the high-pass filter included in the current calculation unit 52 and the cutoff frequency of the low-pass filter included in the rotation angle calculation unit 53 may be different. The low pass filter of the rotation angle calculation unit 53 is realized in the same manner as the high pass filter of the current calculation unit 52. Thereby, the first magnetic field B1 formed by the sensor magnet 14 is separated from the measured value of the combined magnetic field B.

The rotation angle calculation unit 53 is realized as an integrated circuit, calculates the rotation angle θm of the rotor 12 from the value of the first magnetic field B1 separated by the low-pass filter, according to the following equation (7), and dq / uvw conversion To the unit 41 and an αβ / dq converter 54 described later. Here, B1x and B1y are an x component and a y component of the first magnetic field B1, respectively. The rotation angle calculation unit 53 calculates the phase angle θ of the drive currents iu, iv, and iw from the rotation angle θm of the rotor 12 according to the above equation (3) instead of outputting the rotation angle θm of the rotor 12. Then, the phase angle θ may be output.
tan θm = B1y / B1x (7)

The αβ / dq conversion unit 54 is realized as an integrated circuit, receives the rotation angle θm of the rotor 12 from the rotation angle calculation unit 53 of the current measurement unit 5, and calculates the drive currents iu, iv, iw according to the above equation (3). The phase angle θ is calculated. Alternatively, the αβ / dq conversion unit 54 may receive the phase angle θ of the drive currents iu, iv, iw from the rotation angle calculation unit 53. The αβ / dq converter 54 is expressed in the dq coordinate system based on the measured values iα and iβ of the drive current calculated by the current calculator 52 and the phase angle θ of the drive currents iu, iv and iw. The measured current values id and iq are calculated according to the following equation (8).
id = iα × cos θ + iβ × sin θ
iq = −iα × sin θ + iβ × cos θ (8)

  According to the control device for the electric motor 1 of the present invention, the configuration of the control device for the electric motor 1 can be simplified by omitting the ammeter and the wiring for measuring the drive currents iu, iv, and iw. . Further, unlike the current sensorless motor, both the drive currents iu, iv, iw of the motor 1 and the rotation angle θm of the rotor 12 are fed back, so that the torque and the rotation speed of the motor 1 are stabilized.

  FIG. 5 is a flowchart illustrating a method for controlling the electric motor 1 according to the first embodiment. The control device for the electric motor 1 of the present embodiment performs the following steps S1 to S6 with predetermined control so that the driving currents iu, iv, and iw of the electric motor 1 follow the current command values id * and iq *. Feedback control is repeated in a cycle. This feedback control is processed by the above-described integrated circuit or processor included in the control device of the electric motor 1 of the present embodiment.

  In step S1, the magnetic sensor 51 measures the combined magnetic field B including the first magnetic field B1 formed by the sensor magnet 14 and the second magnetic field B2 formed by the drive currents iu, iv, iw.

  In step S2, the current calculation unit 52 separates the second magnetic field B2 from the combined magnetic field B measured by the magnetic sensor 51, and αβ of the drive currents iu, iv, iw from the separated value of the second magnetic field B2. The measurement values iα and iβ in the coordinate system are calculated. In step S3, the rotation angle calculation unit 53 separates the first magnetic field B1 from the combined magnetic field B measured by the magnetic sensor 51, and calculates the rotation angle θm of the rotor 12 from the separated value of the first magnetic field B1. calculate.

  In step S4, the αβ / dq conversion unit 54 determines the dq coordinates based on the measured values iα and iβ of the drive current calculated by the current calculation unit 52 and the rotation angle θm calculated by the rotation angle calculation unit 53. The current measurement values id and iq expressed in the system are calculated.

  In step S5, the current control unit 3 reduces the deviation between the current command values id * and iq * output from the current command value calculation unit 2 and the current measurement values id and iq output from the current measurement unit 5. In addition, the electric motor 1 is controlled via the electric motor drive unit 4. For this purpose, the current control unit 3 calculates voltage command values vd * and vq * necessary for flowing the drive currents iu, iv and iw corresponding to the current command values id * and iq * to the electric motor 1.

  In step S <b> 6, the electric motor drive unit 4 drives the electric motor 1 by applying a three-phase AC voltage corresponding to the voltage command values vd * and vq * calculated by the current control unit 3 to the electric motor 1. As a result, drive currents iu, iv, and iw flow through the electric motor 1, and torque T is generated in the electric motor 1.

  As described above, the motor control device according to the present embodiment includes the magnetic sensor that measures the combined magnetic field including the first magnetic field formed by the sensor magnet and the second magnetic field formed by the drive current. Then, the motor control device according to the present embodiment separates the first magnetic field and the second magnetic field from the measured value of the combined magnetic field, calculates the rotation angle of the rotor from the separated first magnetic field, and separates the rotor. A drive current is calculated from the second magnetic field.

  According to such a configuration, a motor control device and a motor control method capable of stably controlling torque and rotational speed with a simple configuration are provided.

[Second Embodiment]
FIG. 6 is a diagram illustrating an arrangement example of the magnetic sensor 51 in the control device for the electric motor 1 according to the second embodiment. The magnetic sensor 51 of this embodiment is arrange | positioned between the sensor magnet 14 and the rotor 12, as FIG. 6 shows. Since the other points are the same as those in the first embodiment, differences from the first embodiment will be described below.

  The magnetic sensor 51 of the present invention functions as an ammeter for measuring drive currents iu, iv, iw flowing through the electric motor 1 and as an angle sensor for measuring the rotation angle θm of the rotor 12 of the electric motor 1. Has both functions. Accordingly, the magnetic sensor 51 is disposed at a position where the strength of the first magnetic field B1 formed by the sensor magnet 14 and the strength of the second magnetic field B2 formed by the drive currents iu, iv, iw are both increased. Is preferred.

  Therefore, the magnetic sensor 51 of the present embodiment is disposed between the sensor magnet 14 and the rotor 12 as shown in FIG. Since the magnetic sensor 51 arranged in this manner is close to the sensor magnet 14 that forms the first magnetic field B1 and close to the winding 13 that forms the second magnetic field B2, the first magnetic field B1 and the second magnetic field 51 are arranged. Both of the magnetic fields B2 can be measured with high accuracy.

  Moreover, the magnetic sensor 51 of this embodiment is arrange | positioned in the position away from on the rotating shaft of the rotor 12, as FIG. 6 shows. When the number of pole pairs N2 of the electric motor 1 is 2 or more, the second magnetic field B2 formed by the plurality of windings 13 cancels each other in the vicinity of the rotation axis of the rotor 12 and becomes weak. Therefore, by disposing the magnetic sensor 51 away from the rotation axis of the rotor 12, the strength of the second magnetic field B2 at the position where the magnetic sensor 51 is disposed increases.

  As described above, the magnetic sensor 51 of this embodiment is disposed between the sensor magnet 14 and the rotor 12. As a result, a motor control device and a motor control method capable of more stably controlling torque and rotational speed with a simple configuration are provided.

[Third Embodiment]
FIG. 7 is a diagram illustrating an arrangement example of the magnetic sensor 51 in the control device for the electric motor 1 according to the third embodiment. The current measuring unit 5 of the present embodiment has a dedicated winding 15 for measuring three-phase AC drive currents iu, iv, and iw separately from the winding 13 of the electric motor 1 for driving the rotor 12 to rotate. have. Since the other points are the same as those in the first embodiment, differences from the first embodiment will be described below.

  The drive currents iu, iv, iw that flow through the winding 15 shown in FIG. 7 are the same as the drive currents iu, iv, iw that flow through the winding 13, or the drive currents iu, iv, iw are divided. It is taken out. The number of turns of the winding 15 is less than the number of turns of the winding 13 so that the winding 15 does not affect the operation of the electric motor 1. On the other hand, by arranging the winding 15 in the vicinity of the sensor magnet 14, both the strength of the first magnetic field B1 and the strength of the second magnetic field B2 at the position where the magnetic sensor 51 is disposed are increased. Yes. Also with such a configuration of the current measurement unit 5, the magnetic sensor 51 can accurately measure both the first magnetic field B1 and the second magnetic field B2.

  As described above, the current measurement unit 5 of the present embodiment has a winding for measuring the drive current. As a result, a motor control device and a motor control method capable of more stably controlling torque and rotational speed with a simple configuration are provided.

[Other Embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in the computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  Further, the above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

  In the above-described embodiment, a method for separating the first magnetic field B1 and the second magnetic field B2 from the combined magnetic field B by using the difference between the frequency f1 of the first magnetic field B1 and the frequency f2 of the second magnetic field B2. Although described, the present invention is not limited to such an embodiment.

  For example, in the present invention, the strength of the first magnetic field B <b> 1 formed by the sensor magnet 14 is constant regardless of the torque T of the electric motor 1. Accordingly, the magnetic field component whose strength changes when the torque T of the motor 1 is changed is separated as the second magnetic field B2, and the magnetic field component whose strength does not change even when the torque T of the motor 1 is changed is first. It is also possible to separate them as the magnetic field B1.

  In the present invention, the ratio f1 / f2 between the frequency f1 of the first magnetic field B1 and the frequency f2 of the second magnetic field B2 is a ratio N1 / N2 of the number of pole pairs N1 of the sensor magnet 14 and the number of pole pairs N2 of the motor 1. equal. Such a feature can also be used to separate the first magnetic field B1 and the second magnetic field B2 from the combined magnetic field B.

  In the present invention, the greater the difference between the frequency f1 of the first magnetic field B1 and the frequency f2 of the second magnetic field B2, the easier it is to separate the first magnetic field B1 and the second magnetic field B2 from the combined magnetic field B. . Therefore, the present invention is preferably applied to the electric motor 1 in which the difference between the number of pole pairs N2 of the electric motor 1 and the number of pole pairs N1 of the sensor magnet 14 is large.

  In the present invention, the first magnetic field B1 and the second magnetic field B2 are separated from the combined magnetic field B as the temporal change in the frequency f1 of the first magnetic field B1 and the frequency f2 of the second magnetic field B2 is smaller. It becomes easy. Therefore, the present invention can be applied to the electric motor 1 in which the temporal change in the rotational speed of the rotor 12 is small compared to the change in the drive currents iu, iv, iw, such as a large moment of inertia of the rotor 12. preferable.

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Current command value calculation part 3 Current control part 4 Electric motor drive part 5 Current measurement part 11 Stator 12 Rotor 13 Winding 14 Sensor magnet 15 Winding 41 uvw conversion part 42 Modulation part 43 Inverter 51 Magnetic sensor 52 Current calculation Unit 53 rotation angle calculation unit 54 dq conversion unit B composite magnetic field B1 first magnetic field B2 second magnetic field

Claims (6)

A motor control device that controls the motor so that the drive current of the motor follows the current command value,
A sensor magnet that rotates with the rotor of the electric motor to form a first magnetic field;
A magnetic sensor for measuring a combined magnetic field including the first magnetic field and the second magnetic field formed by the driving current;
A rotation angle calculation unit that separates the first magnetic field from the measurement value of the combined magnetic field, and calculates a rotation angle of the rotor from the separated first magnetic field;
A current calculation unit that separates the second magnetic field from the measured value of the combined magnetic field and calculates the drive current from the separated second magnetic field;
A current control unit that controls the electric motor based on the rotation angle calculated by the rotation angle calculation unit, the drive current calculated by the current calculation unit, and the current command value;
An electric motor control device. The rotation angle calculation unit and the current calculation unit are configured to calculate the first magnetic field and the second magnetic field from the measured value of the combined magnetic field based on a difference between the frequency of the first magnetic field and the frequency of the second magnetic field. Isolate the magnetic field,
The motor control device according to claim 1. The number of pole pairs of the rotor is larger than the number of pole pairs of the sensor magnet,
The rotation angle calculation unit has a low-pass filter that separates the first magnetic field from the measured value of the combined magnetic field,
The current calculation unit includes a high-pass filter that separates the second magnetic field from the measured value of the combined magnetic field,
The cutoff frequency of the low-pass filter and the cutoff frequency of the high-pass filter are larger than the frequency of the first magnetic field and smaller than the frequency of the second magnetic field,
The motor control device according to claim 2. The magnetic sensor measures a first axial component and a second axial component of the composite magnetic field expressed in an orthogonal coordinate system set on a stator, respectively, and orthogonal to each other;
The rotation angle calculation unit calculates the rotation angle of the rotor based on a ratio of the first axial component and the second axial component of the first magnetic field,
The current calculation unit includes a first axial component of the drive current represented by a first coordinate system set in a stator based on the first axial component of the second magnetic field. And calculating a second axial component of the drive current represented in the first coordinate system based on the second axial component of the second magnetic field,
The current control unit controls the electric motor so that a deviation between the driving current and the current command value represented by the second coordinate system rotating at the rotation angle with respect to the first coordinate system is small. To
The motor control device according to any one of claims 1 to 3. The magnetic sensor is disposed between the sensor magnet and the rotor.
The motor control device according to any one of claims 1 to 4. A sensor magnet that rotates with the rotor of the electric motor to form a first magnetic field;
A magnetic sensor for measuring a combined magnetic field including the first magnetic field and a second magnetic field formed by a driving current of the electric motor;
An electric motor control device for controlling the electric motor so that the drive current follows a current command value,
A rotation angle calculating step of separating the first magnetic field from the measured value of the combined magnetic field and calculating a rotation angle of the rotor from the separated first magnetic field;
A current calculation step of separating the second magnetic field from the measured value of the combined magnetic field and calculating the drive current from the separated second magnetic field;
A current control step for controlling an electric motor based on the rotation angle calculated in the rotation angle calculation step, the drive current calculated in the current calculation step, and the current command value;
A method for controlling an electric motor.