JP2001136776A - Detection device for magnetic-pole position and drive device for brushless dc motor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect magnetic-pole position of a rotating body, without being influenced by an offset. SOLUTION: Three-phase magnetism detection signals, whose phases are shifted by 120 deg., are output to a digital conversion part 101 according to the rotation of a rotor 1A. Deformation of the three-phase signals is corrected by a correction part 102. In a signal selection part 103, a maximum signal and a minimum signal are selected from the three-phase signals, and an H-level signal and an L-level signal are allocated respectively. In a mean-value computing part 104, the mean value of the signals to which the level signals are allocated is computed. In a signal comparison part 106, the remaining signals are compared with a mean-value signal, and the level signals are allocated. In a relative magnetic-pole position computing part 105, a relative magnetic pole position within an angle range is detected by the mean-value signal. In an absolute magnetic-pole position detection part 107, the angle range is specified by the three-phase level signals, and an absolute magnetic pole position is detected by the relative magnetic pole position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic pole position detecting device for detecting a magnetic pole position of a rotating body, and a brushless DC motor driving device using the magnetic pole position detecting device.

[0002]

2. Description of the Related Art Conventionally, in a driving apparatus for a brushless DC motor, for example, as described in Japanese Patent Application Laid-Open No. 4-295293, inverted signals are output from output signals of two Hall elements arranged with a phase shift of 90 degrees in electrical angle. To detect the magnetic pole position from the linear approximation area of the signal by switching the signal at the intersection of the four sine wave signals of the non-inverted signal and the inverted signal, and drive the brushless DC motor based on the detected magnetic pole position Has been done.

[0003]

However, in the above magnetic pole position detection, a sine wave signal is used as it is.
If the switching point shifts due to the influence of the offset of the elements constituting the Hall element, the inversion circuit, and the like while the vicinity of the switching point becomes non-linear, a large error occurs in the magnetic pole position detection.
To drive a brushless motor, it is necessary to accurately supply a drive current corresponding to the position of the magnetic pole. However, if the switching point of the sine wave signal is shifted as described above, the drive current flows in the opposite direction, and Problems such as no torque or reverse rotation of the motor occur.

In view of the above problems, the present invention provides a magnetic pole position detecting device capable of accurately detecting a magnetic pole position over the entire period, and further provides a magnetic pole position detecting device for a brushless DC motor driving device. It is an object of the present invention to provide a brushless DC motor drive device capable of performing high-quality motor control by using it for magnetic pole position detection.

[0005]

According to the first aspect of the present invention, there is provided a magnetic sensor which is disposed at an angle of electrical angle of 120 degrees with respect to the rotating direction of the rotating body, and detects the magnetism of the magnetic poles of the rotating body. In a magnetic pole position detection device having three magnetic detection element units that generate signals, and a magnetic pole position detection unit that detects a magnetic pole position of the rotating body based on each of the magnetic detection signals, Signal selecting means for comparing the magnitudes of the three magnetic detection signals which are phase-shifted by 120 degrees in electrical angle, and assigning an H level signal to the maximum magnetic detection signal and an L level signal to the minimum magnetic detection signal; An average value calculating means for calculating an average value of the two magnetic detection signals to which the H level signal and the L level signal are assigned to generate an average value signal; Is compared with the average value signal, and the H level signal when the remaining one magnetic detection signal is equal to or larger than the average value signal, and the L level signal when the remaining one is smaller than the average value signal Signal comparing means for allocating a signal to the remaining one magnetic detection signal, relative magnetic pole position calculating means for calculating a relative magnetic pole position within a predetermined electrical angle range based on the average signal,
An absolute magnetic pole position detecting means for detecting the absolute magnetic pole position based on the determined angular range and the calculated relative magnetic pole position, based on the three level signals; did.

According to a second aspect of the present invention, in the state where the absolute magnetic pole position detecting means stops or starts the rotating body,
A reference signal indicating a magnetic pole position is output in response to the level signal. It is desirable that the absolute magnetic pole position detecting means keeps outputting the reference signal until the absolute magnetic pole position can be detected.

According to a fourth aspect of the present invention, a conversion correction means is connected to each of the magnetic detection element sections, and the conversion correction means converts each of the magnetic detection signals into a digital signal, and converts each of the converted digital signals. The output variation of the magnetic detection element unit is detected from the maximum value and the minimum value, and the variation is corrected.

According to a fifth aspect of the present invention, a drive device for a brushless DC motor is constructed by connecting a drive signal generating device and an inverter to the absolute magnetic pole position detecting device of the magnetic pole position detecting device. A PWM drive signal is generated based on the detected absolute magnetic pole position or the reference signal, and the PWM drive signal is output during inversion to drive the brushless DC motor.

[0009]

According to the first aspect of the present invention, the magnetic detection element detects the magnetism from the magnetic poles of the rotating body and generates three magnetic detection signals that are out of phase by 120 degrees. The magnetic detection signal is selected by a signal selection means, and an H level signal is assigned to the largest magnetic detection signal and an L level signal is assigned to the smallest detection signal according to the magnitude. The average value calculating means calculates an average value of the two magnetic detection signals to which the level signals are assigned, and generates an average value signal.

The average signal changes in a triangular waveform and intersects with the remaining magnetic detection signals to which no level signal is assigned. The signal comparing means compares the remaining magnetic detection signal with the average value signal and assigns an H level signal when the magnetic detection signal is equal to or larger than the average value signal, and assigns an L level signal when the magnetic detection signal is smaller than the average value signal. The level signal of
The phase and the period are the same as the corresponding magnetic detection signal. Since the phase shift of the three level signals is 60 degrees,
Within the period of the electrical angle of 360 degrees, the combination of H and L
Six angular regions are obtained.

In the angle range, the average value signal changes substantially linearly with an ascending slope and a descending slope with a peak at 30 degrees, so that the relative magnetic pole position calculating means calculates the relative magnetic pole position with the magnitude and the slope of the average value signal. Ask for. The absolute magnetic pole position means specifies the angle range by the combination of H and L of the level signal, and detects the absolute magnetic pole position by the relative magnetic pole position.

As described above, the level signal corresponding to the remaining magnetic detection signals is switched from H to L or from L to H in comparison with the average value signal. When the offset of appears, the average value signal and the remaining magnetic detection signal have the same offset,
No change occurs in the switching position. For this reason, the correspondence between the angle range formed by the combination of the level signals and the magnetic pole position is maintained. Since the relative magnetic pole position calculation within the angle range is performed based on the average value signal, the accuracy is higher than that obtained by a sine waveform. Thus, the absolute position of the magnetic pole can be detected with high accuracy without being affected by the offset.

According to the second aspect of the present invention, when the rotating body is started, the absolute magnetic pole position detecting means outputs a reference signal indicating the magnetic pole position corresponding to the level signal. Can be driven from a stopped state. According to the fourth aspect of the present invention, since the conversion correction means corrects the variation of each magnetic detection element, a more accurate average value signal is obtained, and the detection accuracy of the absolute position of the magnetic pole is improved. In addition, since this process is performed by converting the magnetic detection signal into a digital signal and performing digital processing, it can be performed by a computer.

According to the fifth aspect of the present invention, since the magnetic pole position detecting device detects the absolute magnetic pole position with high accuracy, it is possible to generate a high-precision drive signal, and the brushless DC motor can be manufactured with high accuracy and low vibration. Can be driven.

[0015]

Embodiments of the present invention will be described below with reference to examples. FIG. 1 is a diagram illustrating a configuration of a magnetic pole position detecting device and a driving device of a brushless DC motor according to an embodiment. The brushless DC motor 1 has a three-phase winding 1B, a rotor 1A of a two-pole permanent magnet, and a magnetic detecting element 1H.
a, a 1Hb, 1Hc DC motor with a permanent magnet field and two poles is used. Magnetic detection element section 1Ha, 1Hb, 1H
c, each having a Hall element, is disposed at a position shifted by 120 degrees around the rotation center of the rotor 1A, a magnetic signal detected by the Hall element is amplified by an amplifier, and an electrical angle of 120 °.
Three magnetic detection signals whose phases are shifted by degrees are output.

The drive unit for the brushless DC motor 1 is composed of a magnetic pole position detector 3, an inverter 2, and a drive signal generator 4 for providing a drive signal to the inverter.
The drive signal generation device 4 includes a speed controller 201, a PWM signal device 202, and the magnetic pole position detection device 3 includes a digital converter 1
01, correction section 102, signal selection section 103, average value calculation section 104, relative magnetic pole position calculation section 105, signal comparison section 106
And an absolute magnetic pole position detecting unit 107. These are configured as a program in a ROM in the microcomputer or as a hardware analog / digital converter.

The speed controller 201 includes a magnetic pole position detecting device 3
The rotation speed of the motor is calculated from the magnetic pole position signal calculated in step (1), and a voltage command Vord corresponding to the rotation speed is output to the PWM signal device 202. The PWM signal device 202 generates a drive signal DRV for driving the inverter 2 based on the voltage command Vord and the magnetic pole position signal, and outputs the drive signal DRV to the inverter 2 to drive the brushless DC motor 1.

In the magnetic pole position detecting device 3, the digital converter 101 digitally samples the three magnetic detection signals output from the magnetic detector elements 1Ha, 1Hb, 1Hc by an analog / digital converter, and performs three-phase sampling. Obtain digital detection value. The digitized three-phase magnetic detection signal is output to the correction unit 102, which corrects signal distortion due to variations in circuit elements of the Hall element and the amplifier. That is, when the motor is at a low speed, the maximum value MAX and the minimum value MIN of the magnetic detection signals of each of the three phases are detected,
The amplitude error is obtained by calculation. If there is an amplitude error, it is determined whether or not it is within a predetermined allowable range. If it is out of the allowable range, the correction is performed by setting the amplitude correction amount. Thus, the three-phase magnetic detection signals have substantially the same waveform.

The signal selection unit 103 selects the maximum and minimum three-phase magnetic detection signals at each time, assigns an H level signal to the maximum magnetic detection signal, and sets the minimum magnetic detection signal. Is assigned an L level signal. The level signal is output to the absolute magnetic pole position detection unit 107, the two magnetic detection signals to which the level signal is assigned are output to the average value calculation unit 104, and the remaining one magnetic detection signal is output to the signal comparison unit 106. . The average value calculation unit 104 calculates an average value of the two magnetic detection signals to which the level signals are assigned, and outputs an average value signal.

The signal comparing section 106 compares the remaining one magnetic detection signal with the average value signal, and if the remaining magnetic detection signal is equal to or larger than the average value signal, the H level signal. The L level signal is assigned to the remaining magnetic detection signals. The relative magnetic pole position calculator 105 detects a relative magnetic pole position within each angle range based on the average signal calculated by the average calculator 104. The absolute magnetic pole position detecting unit 107 determines which angle range the magnetic pole is in based on the level signal assigned to each magnetic detection signal, and determines the angle range and the relative magnetic pole position calculated by the relative magnetic pole position calculating unit 105. The absolute position of the magnetic pole of the rotor 1A is detected, and a magnetic pole position signal indicating the absolute position of the magnetic pole is output to the speed controller 201 and the PWM signal device 202.

FIG. 2 is a diagram showing electric signals generated corresponding to electric angles when the rotor 1A makes one rotation. The U, V, and W phase magnetic detection signals detected by the magnetic detection element units 1Ha, 1Hb, and 1Hc are shifted in phase by 120 degrees in a sine wave as shown in FIG. The magnetic detection signal is converted into a digital signal by the digital conversion unit 101, and the correction unit 102 corrects signal distortion. In the corrected magnetic detection signal, the signal selection unit 103 selects a maximum signal and a minimum signal as values, and assigns H and L level signals.

The average value calculation section 104 calculates the average value of the maximum and minimum magnetic detection signals and outputs an average value signal G.
This average value signal G intersects the remaining magnetic detection signals to which no level signal is assigned at the center point. When there is no offset in the magnetic detection signal, the center point indicates the position where the magnetism is zero. The signal comparing section 106 compares the remaining magnetic detection signal with the average signal, and outputs the H level signal when the magnetic detection signal is equal to or larger than the average signal, and the L level signal when the magnetic detection signal is smaller than the average signal. To the magnetic detection signal. As a result, level signals having the same phase and cycle are obtained corresponding to the U, V, and W magnetic detection signals shown in FIG. Since the three level signals are out of phase by 60 degrees, a combination of H and L forms six angle ranges in electrical angle.

FIG. 3 is a diagram showing the relationship between the combination of H and L of the level signal and the angle range in the electrical angle. The angle reference value is the center value of each angle range, and indicates the position where the gradient of the average signal is inverted. In each angle range, the average signal has a downward gradient and an upward gradient at the boundary of the angle reference value. Therefore, two angular positions correspond to the average value signal having the same value as the relative magnetic pole position. In order to detect this distinction, the relative magnetic pole position calculation unit 105 detects the inversion gradient by reversing the sign of the magnetic detection signal. That is, the relationship between the average value signal and the angle as shown in (c) is obtained in the data table.

When an average signal is input, it is determined whether the average signal is rising or falling according to the change. In the case of a downward gradient, the sign of the average value signal is inverted, and the relative magnetic pole position is detected from the data table. The absolute magnetic pole position detection unit 107 specifies an angle range by a combination of level signals as shown in FIG. 3 and, based on the relative magnetic pole position, as shown in FIG. Detect the magnetic pole.

In driving the brushless DC motor 1, when the power is turned on and the motor starts to be driven, the rotor 1A does not rotate, so that the gradient of the average value signal cannot be determined. Therefore, the absolute magnetic pole position detection unit 107 outputs a reference signal having a constant value corresponding to the level signal. The drive signal generation device 4 generates P
Create a WM signal and drive the motor. This reference signal is
As in the case of the level signal, switching between H and L is performed at the point where the magnetic pole is 0. Therefore, there is no deviation between the drive current and the magnetic pole position, and the motor does not reversely rotate or no torque is output. .

The present embodiment is configured as described above. For example, when a uniform offset occurs in the magnetic detection signal, the center point of the magnetic detection signal is shifted from the magnetic zero point as shown in FIG. Will shift. At this time, the same offset appears in the average value signal, and no change occurs in the position of intersection with the magnetic detection signal. Therefore, a level signal corresponding to the magnetic pole is obtained as shown in FIG.

On the other hand, when the method as in the present embodiment is not employed, for example, in the detection where the magnetic field is zero at the zero point of the magnetic detection signal, the level signal shown by the solid line in FIG. Can be This level signal is shifted with respect to the level signal when the offset indicated by the dotted line is not received. This shift is up to 6 depending on the offset amount.
It reaches 0 degrees. Therefore, if the motor is driven using the magnetic pole positions detected in this embodiment, the motor can be driven with high accuracy. In the present embodiment, three magnetic pole detection elements are used. However, the present invention is not limited to this. For example, two magnetic pole detection elements may be used to calculate another magnetic detection signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment.

FIG. 2 is a diagram showing a signal waveform.

FIG. 3 is a diagram showing a correspondence relationship between a combination of level signals and an angle range.

FIG. 4 is an explanatory diagram showing an effect of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Brushless DC motor 1A 2-pole permanent magnetic rotor 1B 3-phase winding 1Ha, 1Hb, 1Hc Magnetic detecting element unit 2 Inverter 3 Magnetic pole position detecting device 4 Drive signal generating device 101 Digital converting unit 102 Correcting unit 103 Signal selecting unit 104 Average Value calculation unit 105 Relative magnetic pole position calculation unit 106 Signal comparison unit 107 Absolute magnetic pole position detection unit 201 Speed controller 202 PWM signal device

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H019 BB03 BB05 CC03 DD01 EE14 5H560 BB04 BB07 BB12 DA02 DA19 EB01 GG04 JJ15 SS01 TT12 XA12 5H611 AA01 BB07 BB08 QQ01 QQ03 RR02

Claims (5)

[Claims] 1. Three magnetic detecting element units which are arranged at an electrical angle of 120 degrees with respect to the rotating direction of a rotating body and detect the magnetism of magnetic poles of the rotating body to generate a magnetic detection signal, and A magnetic pole position detecting device that detects a magnetic pole position of the rotating body based on the detection signal;
It is generated by the magnetic sensing element unit and has an electrical angle of 120
A signal selecting means for comparing the magnitudes of the three magnetic detection signals whose phases are shifted by degrees, assigning an H level signal to the maximum magnetic detection signal and an L level signal to the minimum magnetic detection signal, Average value calculating means for calculating an average value of two magnetic detection signals to which a level signal and an L level signal are assigned to generate an average value signal, and calculating the remaining one magnetic detection signal to which no level signal is assigned. An H level signal when the remaining one magnetic detection signal is equal to or greater than the average value signal as compared with the average value signal;
Signal comparing means for assigning the L level signal to the remaining one magnetic detection signal when the signal is smaller than the average signal;
Relative magnetic pole position calculating means for calculating a relative magnetic pole position within a predetermined electrical angle range based on the average value signal; and determining the angular range in which a magnetic pole position exists based on the three level signals. A magnetic pole position detecting device for detecting an absolute magnetic pole position based on the calculated angular range and the calculated relative magnetic pole position. 2. The apparatus according to claim 1, wherein said absolute magnetic pole position detecting means outputs a reference signal indicating a magnetic pole position corresponding to said level signal when said rotating body is stopped or started. Magnetic pole position detector. 3. The magnetic pole position detecting device according to claim 2, wherein the absolute magnetic pole position detecting means keeps outputting the reference signal until the absolute magnetic pole position can be detected. 4. A conversion correction means is connected to each of said magnetic detection element parts, said conversion correction means converts each magnetic detection signal into a digital signal, and calculates a maximum value and a minimum value of each converted digital signal. 4. The magnetic pole position detecting device according to claim 1, wherein an output variation of the magnetic detecting element is detected and the variation is corrected. 5. A brushless DC motor drive device comprising: a drive signal generation device and an inverter connected to an absolute magnetic pole position detection device of the magnetic pole position detection device according to claim 1, A drive device for a brushless DC motor, wherein the drive signal generating means generates a PWM drive signal based on the detected absolute magnetic pole position or the reference signal, and outputs the PWM drive signal during inversion to drive the brushless DC motor.