JP7447835B2 - motor control device - Google Patents

Description

The present invention relates to a motor control device.

As a conventional motor control device, for example, a technique as described in Patent Document 1 is known. The motor control device described in Patent Document 1 includes a motor including a stator and a rotor having a permanent magnet, a command section that transmits a command signal to the motor, a position estimation section that estimates the initial position of the rotor, Equipped with The position estimating section of this motor control device applies a minute voltage change to the voltage command signal, and estimates the initial position of the stator based on the amount of current change at that time.

Japanese Patent Application Publication No. 2007-60899

By the way, in the above-mentioned conventional technology, since it is necessary to adjust a minute change in voltage from a minute change in current, there is a problem in that the result of position estimation becomes susceptible to the influence of noise. Therefore, it has been desired to improve the estimation accuracy of the position estimation of the motor rotor.

An object of the present invention is to provide a motor control device that can improve the accuracy of estimating the initial position of a motor rotor.

A motor control device according to one aspect of the present invention includes a motor including a stator and a rotor having a permanent magnet, a command section that transmits a command signal to the motor, and a harmonic superimposition section that superimposes harmonics on the command signal. and a position estimation unit that estimates the initial position of the rotor, the position estimation unit performs the first position estimation process in a state in which harmonics are superimposed, and the harmonic superposition unit performs the first position estimation process. The command unit performs energization processing to energize the motor with a d-axis current of a predetermined value based on the result of the first position estimation processing in a state in which harmonics of a higher frequency than the current are superimposed. The position estimating unit performs the second position estimating process when the current applied to the motor satisfies a predetermined condition.

In such a motor control device, the position estimating unit performs a first position estimating process for estimating the initial position of the rotor of the motor, and a second position estimating process. Here, the energization process is performed between the first position estimation process and the second position estimation process. In this energization process, the command unit sets a predetermined value based on the result of the first position estimation process while the harmonic superimposition unit superimposes harmonics with a higher frequency than that during the first position estimation process. Apply d-axis current to the motor. In this case, in the first position estimation process, by suppressing the harmonic frequency, it is possible to estimate the position of the rotor while suppressing the influence of changes in inductance due to current changes. In this way, by knowing the position of the rotor, in the energization process, high frequency harmonics are superimposed on the d-axis, and the d-axis current is applied to the motor, which enables detection for position estimation. The signal can be made louder. Therefore, in the second position estimation, the position estimation section can accurately estimate the initial position of the rotor by using a large detection signal. As described above, the accuracy of estimating the initial position of the motor rotor can be improved.

In the first position estimation process, the position estimation unit performs an initial position assumption process in which the initial position of the rotor is assumed in a state in which harmonics are superimposed, and the magnetic poles of the rotor are determined based on the assumed initial position. A determination process may be performed to determine the position, and a determination process may be performed to determine the initial position in the first position estimation process based on the determination result in the determination process. In this case, in a state where the initial position of the rotor is unknown, the initial position can be estimated while suppressing the harmonic frequency.

In the energization process, the position estimation unit may stop position estimation. In this case, even if a current change occurs due to the energization process, the position estimating section temporarily stops position estimation, thereby suppressing errors in position estimation due to the current change.

According to the present invention, the accuracy of estimating the initial position of the rotor of the motor can be improved.

1 is a schematic configuration diagram showing a motor control device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a specific configuration of a motor. 5 is a flowchart showing a control process when starting a motor by a motor control device according to an embodiment of the present invention. It is a graph showing the transition of the d-axis current and the transition of the estimation result over time.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a motor control device 1 according to an embodiment of the present invention. The motor control device 1 according to the present embodiment is a device that can perform high-performance motor control when starting the motor 2 without using a sensor for detecting the electrical angle position. The motor control device 1 includes a motor 2, a current command section 3 (command section), a voltage command section 4 (command section), a conversion section 5, a detection section 6, a harmonic superposition section 7, and a position estimation section. 8.

The motor 2 is an electric motor driven by three-phase AC power. The motor 2 has a stator and a rotor having a permanent magnet, and rotates the rotor. An example of a specific configuration of the motor 2 is shown in FIG. As shown in FIG. 2, it includes U-phase, V-phase, and W-phase stators 22 and a rotor 20. Each stator 22 has an inductance section 23 having a predetermined inductance and a resistance section 24 having a predetermined resistance value. The rotor 20 has permanent magnets 21 . Each stator 22 rotates the rotor 20 by creating a rotating magnetic field around the rotor 20 when an alternating current is passed therethrough. The motor 2 has R (resistance value), L (inductance), and K _E (induced voltage constant) as motor constants.

Here, a rotating coordinate system synchronized with the rotor 20 and a fixed fixed coordinate system are set for the motor 2. In the rotating coordinate system, the main magnetic flux direction (the north pole direction of the permanent magnet 21) is taken as the d-axis, and the q-axis is taken orthogonal to the d-axis. The fixed coordinate system has an α-axis and a β-axis that are orthogonal to each other. Note that the angle formed by the d-axis of the rotating coordinate system with respect to the α-axis of the fixed coordinate system is θ _re .

As shown in FIG. 1, the current command section 3 and the voltage command section 4 function as a command section that transmits a command signal to the motor 2 via the conversion section 5. The current command section 3 receives the rotation speed command, calculates a current command signal corresponding to the rotation speed command, and transmits the current command signal to the voltage command section 4 . The current command unit 3 calculates a current command signal using speed PI control, for example. The current command unit 3 calculates a current command value on the d-axis of the rotating coordinate system (i _d command), and calculates a current command value on the q-axis of the rotating coordinate system (i _q command).

The voltage command section 4 receives the current command signal from the current command section 3, calculates a voltage command signal corresponding to the current command, and transmits the voltage command signal to the conversion section 5. The voltage command unit 4 calculates a voltage command signal using, for example, current PI control. The voltage command unit 4 generates a voltage command value on the d-axis and a voltage command value on _{the d-} axis based on a current command value on the d-axis (i d command) and a current command value on the q-axis (i _q command). The voltages on the q-axis are calculated and converted into voltage command values (V _u command, V _v command, V _w command) for each of the three-phase U-phase, V-phase, and W-phase stator 22.

The converter 5 is a device that applies arbitrary alternating current to the stator 22 of the motor 2. The conversion unit 5 converts the voltage command value from the voltage command unit 4 into a PWM signal. Further, the converter 5 performs a switching operation based on the PWM signal, converts DC power into AC power, and applies a voltage corresponding to the voltage command calculated by the voltage command unit 4 to the motor 2.

The detection unit 6 detects the current flowing through the motor 2. Further, the detection unit 6 transmits the detected current to the voltage command unit 4 and the position estimation unit 8.

The harmonic superimposing section 7 superimposes harmonics on the command signal. The harmonic superimposing section 7 superimposes harmonics on the current command signal of the current command section 3. The harmonic superimposing section 7 superimposes harmonics set at a predetermined frequency and a predetermined current value (amplitude). For example, as shown in FIG. 4, if the harmonic superimposition unit 7 superimposes harmonics on a motor 2 that has been given a command signal to apply a -50A d-axis current, the d-axis The current draws a waveform whose amplitude is based on -50A. How to estimate the initial position of the rotor 20 by superimposing the harmonics in the harmonic superimposing section 7 will be described later.

The position estimation unit 8 estimates the position of the rotor 20 of the motor 2. When the motor 2 is started, it is unclear at what electrical angle position (initial position) the rotor 20 is located in the rotational direction. Estimate 20 initial positions. The position estimating section 8 acquires a command signal for the motor 2 from the voltage command section 4 and a detection result from the detecting section 6, and estimates the initial position of the rotor 20 based on the information.

Here, the basic equation in the rotating coordinate system (dq coordinate system) is shown as equation (1). When this basic formula is transformed into a formula unified by _Lq , it is shown as formula (2). On the other hand, in a rotating coordinate system, a harmonic superimposed current as shown in equation (3) is defined. Since harmonics have a large impedance change due to current, taking into account that L _q is a function of current, e _d and e _q for only the harmonics are calculated as shown in equation (4).



v _d : d-axis voltage v _q : q-axis voltage p: differential operator L _d : d-axis inductance L _q : q-axis inductance ω _re : rotational angular velocity of the rotor
R: resistance i _d : d-axis current i _q : q-axis current K _e : induced voltage constant



e _d : d-axis extended induced voltage e _q : q-axis extended induced voltage



i _d0 : DC component of d-axis current i _q0 : DC component of q-axis current i _h : Harmonic current ω _h : Angular velocity of harmonic φ: Angle with respect to d-axis



e _dh : d-axis extended induced voltage of harmonic component e _qh : q-axis extended induced voltage of harmonic component A _Lq : Current differential value L of _Lq q0 : DC component of Lq L _d0 : DC component _of Ld

From equation (4), if a harmonic is superimposed on "φ=0", a harmonic voltage will be excited on the q-axis, so by detecting the signal in a fixed coordinate system (αβ coordinate system), The position of the rotor 20 can be estimated. However, since the value of φ is unknown when estimating the initial position, the motor control device 1 estimates the initial position by executing a control process as shown in FIG.

With reference to FIG. 3, a control process performed by the motor control device 1 according to the present embodiment when starting the motor 2 will be described. This control process is a control process performed to estimate the initial position of the rotor 20 without a sensor before starting the motor 2 and actually rotating the rotor 20. Further, in the following description, the explanation will be given with reference to FIG. 4 as appropriate. FIG. 4 is a graph showing changes in the d-axis current and changes in the estimation results over time. The upper graph in FIG. 4 shows the d-axis current, and the lower graph shows the estimation results. In the example shown in FIG. 4, it is assumed that the actual electrical angle of the north pole of the rotor 20 is 300 degrees. Note that the graph of the estimated position is shown as a combination of straight lines, but in reality there may be fluctuations due to fluctuations in the estimation results or deviations in the detected values, but these fluctuations are omitted for ease of understanding. are doing.

As shown in FIG. 3, the motor control device 1 executes a first position estimation process S10, an energization process S20, and a second position estimation process S30.

First, the motor control device 1 executes a first position estimation process S10. The first position estimation process S10 is a process in which the position estimation unit 8 estimates the position of the rotor 20 in a state where harmonics are superimposed. In the first position estimation process S10, the position estimation unit 8 executes an initial position assumption process S40, a determination process S50, and a confirmation process S60.

Here, since the value of φ is unknown at the time of starting the first position estimation process S10, it is not possible to superimpose harmonics based on "φ=0", and harmonics also appear on the d-axis. voltage is excited. Therefore, in the motor 2 whose inductance changes with current changes, as shown in equation (4), when the frequency (i.e., rotational speed ω _h ) is increased, the differential value A of the d-axis inductance at the d-axis extended induced voltage e _dh Since the influence of _Lq becomes large and position estimation may not be performed satisfactorily, the harmonic frequency (ie, rotation speed ω _h ) is kept low.

The motor control device 1 executes initial position assumption processing S40. The initial position assumption process S40 is a process in which the position estimation unit 8 assumes the initial position of the rotor 20 in a state where harmonics are superimposed. In the initial position assumption process S40, the current value commanded by the current command unit 3 is 0A. The harmonic superimposing section 7 superimposes harmonics on the current command signal. The frequency of the harmonics at this time (ie, the rotational speed ω _h ) is suppressed to a low value as described above. Therefore, as shown by "S40" in the upper graph of FIG. 4, the d-axis current changes its amplitude with 0A as a reference. In this state, the position estimation unit 8 assumes where the initial position of the rotor 20 is based on the command signal and the detection result of the detection unit 6. In addition, at the stage of initial position assumption processing S40, since the polarity of the permanent magnet of the rotor 20 is unknown, it is not possible to estimate where the N pole exists between 0 and 360 degrees, It is only possible to estimate whether either the pole or the S pole exists between 0° and 180°. Therefore, when the position estimating unit 8 grasps any position between 0 and 180°, it assumes that the position is the initial position of the north pole. In the graph shown in the lower part of FIG. 4, it is assumed that the position of the north pole is 120°.

Specifically, in the initial position assumption process S40, the harmonic superimposition unit 7 starts harmonic superimposition by setting θ _re =0°. On the other hand, the position estimation unit 8 calculates the extended induced voltages e _α and e _β in the αβ coordinate system, performs detection processing and bandpass filter processing, and calculates tan ⁻¹ (e _α /e _β ) as needed. This allows the initial position of the north pole to be assumed.

The motor control device 1 executes determination processing S50. The determination process S50 is a process in which the position estimation unit 8 determines the magnetic poles of the rotor 20 based on the assumed initial position. In the determination process S50, the harmonic superimposition unit 7 applies positive and negative voltage pulses to the d-axis based on the assumed initial position. Then, the position estimation unit 8 determines the polarity of the permanent magnet 21 at the assumed initial position by observing the change in the d-axis current caused by the voltage pulse. Specifically, assuming that the -90° position is the d-axis, positive and negative voltage pulses are applied to the d-axis. The one with the smaller d-axis current is the north pole, but in the lower graph of FIG. 4, the d-axis current fluctuates slightly toward the negative side. Therefore, the position estimation unit 8 determines that the magnetic pole located at the 120° position is the S pole.

The motor control device 1 executes confirmation processing S60. The determination process S60 is a process in which the position estimation unit 8 determines the initial position in the first position estimation process S10 based on the determination result in the determination process S50. In confirmation processing S60, the position estimating unit 8 adds 180° to the assumed initial position of the north pole to be 120°, and estimates that 300° is the initial position of the north pole (see the lower part of FIG. 4). (S50 to S60 of the graph). Then, the harmonic superimposing section 7 superimposes harmonics using the estimated N pole, that is, the d-axis (φ=0) as a reference. Thereby, the estimated d-axis position can be converged and the initial position can be determined. With the above, the first position estimation process S10 is completed. In the first position estimation process S10, the position of the rotor 20 is estimated while keeping the harmonic frequency low. In subsequent processing, the frequency of the harmonics is increased to perform position estimation with higher accuracy.

Next, the motor control device 1 executes energization processing S20. In the energization process S20, the current command unit 3 performs energization based on the result of the first position estimation process S10 while the harmonic superimposition unit 7 superimposes harmonics with a higher frequency than that in the first position estimation process S10. , is a process in which a d-axis current of a predetermined value is applied to the motor 2. The predetermined value of the d-axis current is a current value when the motor 2 is normally stopped, that is, in a state where the rotor 20 can be rotated immediately upon receiving a rotation speed command. In the upper graph of FIG. 4, the predetermined value of the d-axis current is set to -50A, but is not particularly limited. Note that because high-frequency harmonics are superimposed on the current command, the d-axis current at "S20" and "S30" in the upper graph of FIG. 4 is higher than at "S40" and "S60". It oscillates with a period of -50A as a reference. Note that the harmonic frequency in the energization process S20 may be set to 1.5 to 3.0 times the frequency in the first estimation process S10.

Here, when a predetermined value of d-axis current is applied to the motor 2, a current change occurs, for example, as indicated by "B" in the upper graph of FIG. If the position estimation unit 8 continues the position estimation process in this state, an error will occur in the position estimation result. Therefore, in the energization process S20, the position estimating unit 8 stops estimating the position. Therefore, in the section indicated by "T" in the lower graph of FIG. 4, data updating due to position estimation processing is temporarily stopped. Therefore, in the interval "T", the estimation result of the position estimation in "S60" is maintained.

Next, the motor control device 1 executes a second position estimation process S30. The second position estimation process S30 is a process in which the position estimation unit 8 performs position estimation when the current flowing to the motor 2 satisfies a predetermined condition. The position estimation unit 8 restarts the stopped position estimation at the timing when the current flowing through the motor 2 reaches a predetermined value according to the current command signal and the state becomes stable. The position estimation unit 8 adjusts the timing for restarting position estimation by comparing the current command signal and the detection result by the detection unit 6. Specifically, in the upper graph of FIG. 4, the position estimation unit 8 has started the second position estimation process S30. When the second position estimation process S30 ends, the control process shown in FIG. 3 ends.

Next, the functions and effects of the motor control device 1 according to this embodiment will be explained.

In the motor control device 1, the position estimation unit 8 performs a first position estimation process S10 for estimating the initial position of the rotor 20 of the motor 2, and a second position estimation process S30. Here, an energization process S20 is performed between the first position estimation process S10 and the second position estimation process S30. In this energization process S20, the current command unit 3, based on the result of the first position estimation process S10, with the harmonic superimposing unit 7 superimposing harmonics of a higher frequency than that in the first position estimation process S10. Then, a predetermined value of d-axis current is applied to the motor. In this case, in the first position estimation process S10, by suppressing the harmonic frequency, the position of the rotor 20 can be estimated while suppressing the influence of changes in inductance due to current changes. In this way, by knowing the position of the rotor 20, in the energization process S20, high frequency harmonics are superimposed on the d-axis and the d-axis current is energized to the motor 2 to estimate the position. The detection signal for this purpose can be increased. That is, by supplying the d-axis current, the position of the rotor 20 can be fixed, and the detection signal can be increased by high-frequency harmonics. Therefore, in the second position estimation process S30, the position estimation unit 8 can accurately estimate the initial position of the rotor 20 by using a large detection signal. As described above, the accuracy of estimating the initial position of the rotor 20 of the motor 2 can be improved. In addition, since the detection signal for position estimation is large, the position estimation unit 8 can perform stable position estimation even when the current changes when the motor 2 starts rotating, and suppresses step-out etc. A reliable start can be performed in this condition.

More specifically, in the second position estimation, since the harmonic frequency (i.e. rotation speed ω _h ) is set high, the q-axis extension induced by the harmonic component is The voltage (e _qh ) increases. Therefore, the position estimating unit 8 can perform more reliable position estimation against disturbances caused by detection processing, processing delays of bandpass filters, and the like. Furthermore, when the rotation of the motor 2 starts, a current corresponding to the rotational speed is applied, and the q-axis inductance increases due to the large harmonic component of the q-axis extended induced voltage (e _qh ) even with respect to the current change. Since the influence of the current differential value (A _Lq :) of (L _q ) and the direct current component (i _q0 ) of the q-axis current is reduced, it is possible to stably start the rotation of the motor 2.

In the first position estimation process S10, the position estimation unit 8 performs an initial position assumption process S40 in which the initial position of the rotor 20 is assumed in a state in which harmonics are superimposed, and based on the assumed initial position, the A determination process S50 may be performed to determine the magnetic pole of the child 20, and a determination process S60 may be performed to determine the initial position in the first position estimation process S10 based on the determination result in the determination process S50. In this case, in a state where the initial position of the rotor 20 is unknown, the initial position can be estimated while suppressing the harmonic frequency.

In the energization process S20, the position estimation unit 8 may stop position estimation. In this case, even if a current change occurs in the energization process S20, the position estimation unit 8 temporarily stops position estimation, thereby suppressing errors in position estimation caused by the current change.

The invention is not limited to the embodiments described above.

For example, in the first position estimation process S10, processes S40 to S60 are adopted, but the present invention is not limited to these methods. That is, other known initial position estimation methods may be applied to the first position estimation process S10.

Furthermore, in the energization process S20, the position estimation unit 8 does not necessarily have to stop position estimation.

Further, the overall configuration of the motor control device 1 shown in FIG. 1 and the configuration of the motor 2 shown in FIG. 2 are merely examples, and can be modified as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1... Motor control device, 2... Motor, 3... Current command part (command part), 4... Voltage command part (command part), 7... Harmonic superposition part, 8... Position estimation part, 20... Rotor, 21... Permanent magnet, 22...Stator.

Claims (3)

a motor comprising a stator and a rotor having a permanent magnet;
a command section that transmits a command signal to the motor;
a harmonic superimposition unit that superimposes harmonics on the command signal;
a position estimation unit that estimates an initial position of the rotor;
The position estimation unit performs a first position estimation process in a state in which the harmonics are superimposed,
With the harmonic superimposing unit superimposing harmonics of a higher frequency than during the first position estimation process, the command unit may set d to a predetermined value based on the result of the first position estimation process. Performing energization processing to energize the motor with shaft current,
The position estimating unit is a motor control device that performs a second position estimating process when a current flowing through the motor satisfies a predetermined condition. In the first position estimation process, the position estimation unit:
performing an initial position assumption process of assuming the initial position of the rotor in a state in which the harmonics are superimposed;
Performing a determination process to determine the magnetic poles of the rotor based on the assumed initial position,
The motor control device according to claim 1, wherein a determination process is performed to determine the initial position in the first position estimation process based on a determination result in the determination process. The motor control device according to claim 1 or 2, wherein in the energization process, the position estimating section stops estimating the position.

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