JPS627385A - 3-phase brushless motor controller - Google Patents

Abstract

PURPOSE:To reduce the irregular rotation of a 3-phase brushless motor by supplying a phase current to cancel a ripple in phase magnetic flux distribution to delete a torque ripple. CONSTITUTION:The stator of a 3-phase brushless motor 3 is secured, and a rotor is externally rotated at an equal speed. At this time each phase current I(theta) is obtained to cancel an irregular magnetic flux by measuring a counterelectromotive force E(theta) generated at the stator. Then, the phase current I(theta) is normalized, allotted for bits, and stored in ROMs 7-9. When the motor is driven, a rotating angle is detected by a resolver 4 to read a torque ripple correcting pattern from the ROMs 7-9, thereby controlling a power amplifier PA.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improvement of a seven-three-phase brushless motor control device, and particularly relates to a reduction in rotational unevenness.

[Traditional technique?]

Fig. 3 id is a conceptual diagram of conventional three-phase brush motor control (standing position). In the figure, the PAi-i power amplifier, the peak is the inverter, (2) is the pace drive circuit of the inverter I+, (3) is a three-phase brushless motor, (4)
is a resolver that is connected to the rotor of the three-phase brushless morph (3) and outputs the rotor angle signal, and (5) is a resolver (
4) Resolver that converts the output signal into a digital signal
Digital converter (hereinafter referred to as R/D), (61 is PW
M reference triangular wave generator, 6 is a speed error signal, 2 is a comparator that compares the triangular wave signal (6) and the speed error signal θ, +171 is a power amplifier PA that converts the mechanical angle signal of the resolver into an electrical angle and outputs it as a PWM signal. ROM output to
, CNT2 is a three-phase brushless control device.

The conventional three-phase brushless motor control device is configured as described above, and converts the rotor angle signal i R/D (5) of the three-phase brushless motor (3) into a digital signal using, for example, a resolver (4). This signal and the comparator (1
At 61, the digital signal of the speed error signal θ6 compared with the reference triangular wave output from the triangular wave generator (6) is converted to RO.
Input to Mαθ, 1! The air angle and PWM signals are converted and input to the power amplifier FA.

Incidentally, the magnetic flux distribution of the rotor of the three-phase brushless motor (3) in the above control method is a trapezoidal waveform having a constant value in a range of 120° or more in the ti angle, as shown in FIG. 4(a). With a rotor like this.

The magnetic flux perpendicular to each phase winding of a stator with three-phase windings is
As the rotor rotates, it forms a trapezoidal waveform as shown in FIG. 4(b) (dotted line). Therefore, when the angle range of each phase is the flat part of the trapezoidal wave, if a flat phase current as shown in Fig. 4 (C) is passed, the torque of each phase will be ,
Since it is proportional to the product of Φ and the magnetic flux Φ, ∼Φ0 perpendicular to it, in Fig. 4(a).

becomes.

Therefore, the generated torque T is T - T, (θ) +'r8 (θ) + -TT (-2 of 'X
Work, X@, ---(2).

[Problem that the invention seeks to solve]

In the magnetic flux perpendicular to each phase winding of the stator of the three-phase brushless motor mentioned above, ripples as shown in Figure 4(b) (solid line) actually exist due to causes such as unevenness in one winding and variations in the magnetic material. . When a flat current for each phase as shown in Fig. 4 (C) is passed through this, the torque of each phase is
There was a problem in that ripples as shown in Figure (d) (solid line) were included, causing uneven rotation during rotation at very low speeds.

This invention was made to solve this problem, and its purpose is to reduce the unevenness in one rotation.

[Means for solving problems]

The three-phase brushless motor control device according to the present invention is designed to know the magnetic flux distribution of each phase by measuring the entire magnetic flux distribution, and then call out a current from a ROM pattern to cancel the ripple included in the two distribution widths and send it to each phase.

[For production]

In the present invention, by reducing torque ripple, it is possible to provide highly accurate control of a three-phase brushless motor with no unevenness in one rotation.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which FA and fil-(6) are exactly the same as the conventional device described above. (7) to (9) are ROMs programmed with a pattern for flowing each phase current that cancels out the ripples present in the magnetic flux distribution of each phase, and αC to 2 is the ROM of (7) to (9) above. Digital-to-analog converters (hereinafter referred to as D/A) provided for each phase that multiply the output data and the speed error signal θ (analog signal x digital signal) and convert it into an analog signal, tL3 to α9 are Triangle wave generator (6)
A comparator provided for each phase compares the reference triangular wave signal outputted by the D/A (D/A) with the current command signal outputted by the D/A (11 to 3) and converts it into a PWM signal. CNT1 is a three-phase brushless motor control device.

First, the contents of ROMs (7) to (9) will be explained. Fix the stator of the three-phase brushless motor (3),
Give constant speed rotation to the rotor from the outside. The back electromotive force E(θ) generated in the stator at this time is.

E(-x, xΦ(...(31
K: is a proportionality constant, so by measuring the back electromotive force E(, we can know Φ(.Theoretical torque T of a three-phase brushless motor is.

T-2KXIXΦ...(4) m. That is, by measuring the back electromotive force E (θ), the current value (θ) of each phase that cancels out the magnetic flux unevenness can be found. Then, by normalizing this process and allocating bits, it becomes a ROM pattern.

It is clear that the torque of each phase generated by flowing the force (θ) obtained above into each phase becomes flat in the electrical angle range of 120°. This situation is shown in Figure 2 (a) to (d).
Shown below.

〔Effect of the invention〕

As described above, the present invention has the effect of eliminating torque ripples and reducing nine-turn irregularities by causing phase currents to flow so as to cancel out ripples in the magnetic flux distribution of each phase.

[Brief explanation of drawings]

FIG. 1 is an overview diagram showing an embodiment of the present invention, and FIG. 2 (a
) is a distribution diagram of the magnetic flux perpendicular to each phase winding of the stator of a three-phase brushless motor versus electrical angle, Figure 2(b) is a distribution diagram of each phase current versus electrical angle, and Figure 2(C) is a distribution diagram of each phase current versus electrical angle. A distribution diagram of the phase torque with respect to the electrical angle, Figure 2(d) is a diagram showing the output torque of a three-phase brushless motor, Figure 3 is an overview diagram showing a conventional three-phase brushless motor control device, and Figure 4 (Riha Fig. 4(b) is a magnetic flux distribution diagram with respect to the electrical angle of the rotor of a three-phase brushless motor.
dotted line). The actual (real #il) distribution diagram, Figure 4 (C) is the distribution diagram of each phase current with respect to electrical angle in the conventional method, Figure 4 (d)
is the ideal (dotted line) for the electrical angle of each phase torque. It is a distribution map of reality (solid line). In the figure, (1) is an inverter, (2) is a base drive circuit, PA is a power amplifier, (3) is a three-phase brushless motor, (4) is a resolver, (5) is an R/D converter, (
6) is a triangular wave generator, (71~+9), αη is RO
M, 1ll) ~42 are D/A converters, (13~(l
e is a near 7H l/-p, and CNT1 and CNT2 are three-phase brushless motor control devices. Note that the same symbols in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] In a three-phase brushless motor control device comprising one three-phase brushless motor, a resolver that outputs the rotation angle of the three-phase brushless motor, and a power amplifier that rotates the three-phase brushless motor, the resolver An R/D (resolver-digital) converter that converts the output signal into a digital signal, three ROMs (read only memory) that generate a torque ripple correction pattern from the digital output signal of the R/D converter, and the R/D converter.
A three-phase brushless motor control device characterized by comprising three D/A converters that multiply an OM output and a current command and convert it into an analog signal.