JP4147826B2 - Brushless motor drive control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drive control device for a brushless motor having a plurality of excitation phases, and more particularly to a drive control device for a brushless motor that reduces torque ripple while realizing a high rotational speed in a low torque load region.
[0002]
[Prior art]
A brushless motor used as a drive source for a power steering device of an automobile is a motor having three or more excitation phases, and the drive is performed by a rectangular wave excitation current.
[0003]
For example, in the case of a five-phase brushless motor, the motor drive circuit has five phases (hereinafter referred to as “a” phase to “phase”) arranged so as to surround the outer peripheral surface of the rotor of the motor by an electrical angle of 72 degrees. The excitation coils a to e) (referred to as “e phase”) are excited by a rectangular wave current by sequentially switching the coils one by one by a four-phase excitation method in which four phases are excited simultaneously under the control of a control circuit such as a microcomputer. Thus, the rotor is driven to rotate. In this four-phase excitation method, the motor current flows in four of the five phases, but in order to flow the current in a balanced manner, the resistances of the respective excitation coils are all made equal. Yes.
[0004]
Such a motor drive circuit is usually composed of ten field effect transistors (FETs). These 10 transistors are formed by connecting two corresponding transistors in series to form five series transistor circuits, each being connected between the positive and negative terminals of the power source, and the two transistors of each series transistor circuit. By connecting the connecting portions to the outer ends of the five exciting coils a to e that are star-connected in a Y shape, they are connected to the motor coil circuit.
[0005]
The direction and length of the excitation current (rectangular wave) supplied from the motor drive circuit to each excitation coil are as shown in FIG. 7, for example, with respect to the value of the rotation angle (electrical angle) of the rotor. That is, the rotor is continuously rotated by switching the excitation coil one phase at a time every 36 degrees in electrical angle and exciting one phase coil for 144 degrees in electrical angle. In FIG. 7, when the electrical angle is θ, 0 ° ≦ θ <36 °, 36 ° ≦ θ <72 °, 72 ° ≦ θ <108 °, 108 ° ≦ θ <144 °, 144 ° ≦ θ < 180 °, 180 ° ≦ θ <216 °, 216 ° ≦ θ <252 °, 252 ° ≦ θ <288 °, 288 ° ≦ θ <324 °, 324 ° ≦ θ <360 ° (1),・ ・ ・ ・, (10)
[0006]
In this example, the a-phase current flows in the + direction in the sections (1) and (2), 0 in the section (3), in the-direction in the sections (4) to (7), and in the section (8). 0, it flows in the + direction again in the section (1) through the sections (9) to (10). The b-phase current flows in the + direction in the sections (1) to (4), 0 in the section (5), in the-direction in the sections (6) to (9), 0 in the section (10), and again Flows in the + direction in section (1). c-phase current flows in the-direction in section (1), 0 in section (2), + direction in sections (3)-(6), 0 in section (7), and sections (8)-( After 10), it flows again in the minus direction in section (1). The d-phase current flows in the-direction in the sections (1) to (3), 0 in the section (4), in the + direction in the sections (5) to (8), 0 in the section (9), and the section Flows again in the negative direction from (10). The e-phase current is 0 in the section (1), flows in the-direction in the sections (2) to (5), 0 in the section (6), flows in the + direction in the sections (7) to (10), and again in the section It becomes 0 in (1). Therefore, two of the five exciting coils are switched in the opposite directions at each boundary of the sections (1) to (10) (when the electrical angle is switched every 36 degrees).
[0007]
As such a brushless motor, a brushless DC motor (BLDCM) and a permanent magnet synchronous motor (PMSM) are known. Examples of the former include Japanese Patent Application Laid-Open No. 11-356083 and Japanese Patent Application No. 2001-168151 (the present applicant). And those using the commutation control disclosed in Japanese Patent Application Laid-open No. 2000-201461.
[0008]
[Problems to be solved by the invention]
As shown in FIG. 8, BLDCM has a lower rotational speed than PMSM in the low torque load region, but it is possible to improve the rotational speed by performing a weak magnetic field control in the low torque load region. However, by doing so, there is a problem that torque ripple increases as the rotational speed increases, and noise is generated by the torque ripple.
[0009]
On the other hand, the PMSM can easily improve the rotational speed in the low torque load region by the field weakening control, but the rotational speed is reduced in the rated load region, and the motor in the rated load region is smaller than the BLDCM in terms of small size and high output. There is a problem of being inferior.
[0010]
In the electric power steering device, a motor and a control device with a small size, a high output, a low torque ripple, and a low noise are required, and a high rotation speed (for example, emergency avoidance) at a low torque load is also required.
[0011]
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to realize a brushless motor that realizes a high rotational speed at low torque load and suppresses torque ripple in the BLDCM. To provide a drive control device.
[0012]
[Means for Solving the Problems]
The present invention relates to a brushless motor drive control device that reduces torque ripple while realizing a high rotational speed in a low torque load region, and the above object of the present invention is to provide a brushless motor drive control device having a plurality of excitation phases. Excitation phase current command signal generating means for generating a sine wave or trapezoidal excitation phase current command signal including an advance angle from the induction power, torque command value, angular velocity, and rotor rotation angle of the brushless motor for each excitation phase. And excitation current control means for controlling the excitation current for each excitation phase by current feedback control based on the excitation phase current command signal generated by the excitation phase current command signal generation means, and the excitation phase current command by advancing the electrical angle of the signal by an angle portion of the advance, the brushless motor drive control instrumentation, characterized in that performing the field weakening control It is achieved by.
[0016]
The object of the present invention is characterized in that the rotation angle of the rotor of the brushless motor is obtained from an angle estimation signal estimated based on a rotor position signal, a motor current, etc. detected from a rotor position detector. the brushless motor drive control device which, or, when the angular speed of the motor exceeds a predetermined value, the brushless motor driving control, characterized in that it is configured to transition to a magnetic field weakening control due to the advance of the Effectively achieved by the device.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0018]
In the present embodiment, a case where the present invention is applied to a three-phase brushless DC motor is described as an example. However, the present invention is not limited to this, and the brushless of other plural excitation phases (for example, five phases) is described. The present invention can also be applied to a motor. The excitation phase current command signal can be generated by hardware or software. In the present embodiment, this excitation phase current command signal is generated by software.
[0019]
As shown in FIG. 1, the brushless motor drive control device 20 according to the present invention includes each phase current command signal generator 21, each phase current controller 22, a motor drive circuit 23, and a rotor position detector 24. . Here, each phase current command signal generator 21 corresponds to excitation phase current command signal generation means, and each phase current controller 22 and motor drive circuit 23 correspond to excitation current control means.
[0020]
Each phase current command signal generator 21 receives a motor current command signal Iref from an external circuit (not shown), and also receives a rotor position signal RP from the rotor position detector 24. Each phase current command signal generator 21 generates excitation phase current command signals (iaref, ibref, icref) of each excitation phase (a, b, c) based on these input signals. Each phase current controller 22 performs current feedback control via the motor drive circuit 23 based on the excitation phase current command signal (iaref, ibref, icref) generated by each phase current command signal generator 21. The excitation current (ia, ib, ic) of each excitation phase is controlled by using a three-phase current detection signal for two-phase current detection.
[0021]
The motor drive circuit 23 is composed of a total of six transistors (field effect transistor FETs) T _{1 to} T ₆ arranged on the power supply side (upper side) and on the ground side (lower side). Yes. In these six transistors, corresponding transistors are connected in series on the upper stage side and the lower stage side, and the connection of each transistor pair (T ₁ -T ₂ , T ₃ -T ₄ , T ₅ -T ₆ ) connected in series. The part is connected to the outer ends of the respective excitation coils of the three-phase brushless DC motor 30. The gate drive signal _GT 1 _{~GT 6} of transistor _T 1 through T _6, based on a rotor position signal RP detected from the rotor position detector 24, the phase current through each phase current command signal generator 21 Generated by the controller 22.
[0022]
The commutation timing is generated by the rotor position signal RP. The rotor position signal RP is sent to each phase current command signal generator 21 after being detected by the rotor position detector 24. The rotor position detector 24 may be configured by either a Hall element, a resolver, or an encoder.
[0023]
FIG. 2 is a waveform diagram showing an example of the motor current command signal (Iref) and the excitation phase current command signals (iaref, ibref, icref) of each excitation phase. As shown in the figure, the amplitude of the excitation phase current command signal of each energized excitation phase is the same as the amplitude of the motor current command signal when the current is not commutated, and the sign is opposite. The amplitude of the excitation phase current command signal of the excitation phase that is not energized is zero.
[0024]
As shown in FIG. 2, at the time of commutation, the a-phase excitation phase current command signal iaref of the commutation phase that is not energized, for example, at an electrical angle of 30 degrees rises from zero. The c-phase excitation phase current command signal icref of the commutation phase that has been energized falls toward zero.
[0025]
In the above configuration, a method of realizing a high rotation speed of the brushless DC motor in the low torque load region and a method for suppressing an increase in torque ripple associated therewith will be described below.
[0026]
1. By advancing the current waveform having commutation control, a weakening magnetic field is realized and a high rotational speed is realized.
[0027]
That is, as shown in FIG. 3, the excitation phase current command signal (rectangular wave indicated by a dotted line) of each excitation phase is advanced by an angle θ (advance angle) waveform (rectangular wave indicated by a solid line in the figure). A current command signal is generated by each phase current command signal generator 21, and each phase current controller 22 is based on excitation phase current command signals (iaref, ibref, icref) generated by each phase current command signal generator 21. Thus, the excitation current (ia, ic) of each excitation phase is controlled by current feedback control via the motor drive circuit 23. By advancing, part of the current works in the direction of weakening the magnetic field, and the other part works in the direction of generating motor torque. The technique of “weakening magnetic field” is a technique that uses the property that the maximum value of the rotational speed is inversely proportional to the total magnetic flux, and weakens the magnetic field to lower the total magnetic flux and increase the rotational speed. Moreover, since it is commutation control, a torque ripple can be suppressed low. That is, in the commutation control, the current falls and rises more slowly than in the conventional rectangular wave during commutation, so that there is little change in current. By adding an advance angle function to the commutation control function, a weak magnetic field in the low torque region can be realized, and torque ripple is also smaller than when the conventional rectangular wave is advanced.
[0028]
2. By advancing the current waveform of the trapezoidal wave, a weak magnetic field is realized and a high rotational speed is realized.
[0029]
That is, as shown in FIG. 4, the excitation phase current command signal (trapezoid wave indicated by a dotted line) of each excitation phase is advanced by an angle θ (advance angle) waveform (trapezoid wave indicated by a solid line in the figure) A current command signal is generated by each phase current command signal generator 21, and each phase current controller 22 is based on excitation phase current command signals (iaref, ibref, icref) generated by each phase current command signal generator 21. Thus, the excitation current (ia, ic) of each excitation phase is controlled by current feedback control via the motor drive circuit 23.
[0030]
The trapezoidal wave can suppress the torque ripple because the current change at the time of commutation is gentle compared to the rectangular wave.
[0031]
3. By advancing the current waveform of a sine wave, a weak magnetic field is realized and a high rotational speed is realized.
[0032]
As shown in FIG. 5, which is "2." The trapezoidal wave is replaced with a sine wave, for the same reason, it is possible to suppress the torque Cripple.
[0033]
4). FIG. 6 is a diagram showing an input / output state of signals to each phase current command signal generator in the fourth embodiment of the present invention. As shown in FIG. 6, induced electromotive force (EMF) waveform, and the torque command value Tref, the angular velocity ω and the excitation phase current and a rotation angle θ of the rotor, including the advance in phase current command signal generator 21 seeking command signal, based thereon, the current full I readback controlled via the motor driving circuit 23, controls the excitation current of each excitation phase (ia, ic). Here, the rotation angle θ of the rotor is obtained from an angle estimation signal estimated based on the rotor position signal RP detected from the rotor position detector 24, the motor current, and the like.
[0034]
The purpose of the present invention is to improve the rotational speed in the high rotational speed region (low torque load region) and suppress the torque ripple. However, in the rated load region (normal rotational speed region), the motor current is completely torque-generated without being advanced. It is more efficient to work.
[0035]
Therefore, it may be configured to switch from the normal commutation control to any one of the control means 1 to 4 as the transition from the normal rotation speed region to the high rotation speed region.
[0036]
The control means is switched when the rotational speed (angular speed) of the motor exceeds a predetermined value, and a reference angular speed value is stored in each phase current command signal generator 21. The actual angular velocity is compared, and when the actual angular velocity exceeds the reference value, the control unit may be switched to any one of the control units 1 to 4 by a switching unit (not shown).
[0037]
【The invention's effect】
According to the brushless motor drive control device of the present invention, a brushless motor with a small size, high output, and low torque ripple can be realized, thereby realizing low noise and high rotation speed in a low torque load region.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a brushless motor drive control device according to the present invention.
FIG. 2 is a waveform diagram showing an example of a motor current command signal and an excitation current command signal for each excitation phase in a three-phase brushless motor.
FIG. 3 is a waveform diagram showing an excitation current command signal in the first embodiment of the present invention.
FIG. 4 is a waveform diagram showing an excitation current command signal (trapezoidal wave) in the second embodiment of the present invention.
FIG. 5 is a waveform diagram showing an excitation current command signal (sine wave) in the third embodiment of the present invention.
FIG. 6 is a diagram illustrating an input / output state of a signal to each phase current command signal generator in a fourth embodiment of the present invention.
FIG. 7 is a waveform diagram showing an example of an excitation current of each excitation phase in a five-phase brushless motor.
FIG. 8 is a diagram showing the relationship between the rotational speed and the torque in comparison between the conventional BLDCM and PMSM.
[Explanation of symbols]
20 brushless motor drive control device 21 each phase current command signal generator 22 each phase current controller 23 motor drive circuit 24 rotor position detector 30 three phase brushless motor a, b, c excitation phase ia a phase excitation current ib b phase Excitation current ic c phase excitation current iaref phase a excitation phase current command signal ibref phase b excitation phase current command signal icref phase c excitation phase current command signal Iref motor current command signals GT1 to GT6 gate drive signals T1 to T6 Transistor RP Rotor position signal

Claims (3)

In a brushless motor drive control device having a plurality of excitation phases,
Excitation phase current command signal generating means for generating a sine wave or trapezoidal excitation phase current command signal including an advance angle from the induction power, torque command value, angular velocity, and rotor rotation angle of the brushless motor for each excitation phase. When,
Excitation current control means for controlling the excitation current for each excitation phase by current feedback control based on the excitation phase current command signal generated by the excitation phase current command signal generation means,
By advancing the electrical angle of the excitation phase current command signal by an angle portion of the advance, the brushless motor drive control device and performing field weakening control.   The brushless motor drive control device according to claim 1, wherein the rotation angle of the rotor is obtained from an angle estimation signal estimated based on a rotor position signal, a motor current, or the like detected from a rotor position detector. . When the angular speed of the motor exceeds a predetermined value, the brushless motor drive control apparatus according to claim 1 or 2, characterized in that it is configured to transition to a magnetic field weakening control by the advance.

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