JP2018128321A - Rotation angle detection device and rotation angle detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation angle detection device and rotation angle detection method that accurately detect a rotation angle of a rotor.SOLUTION: A rotation angle detection device according to an embodiment comprises: a first calculation unit; a second calculation unit; a third calculation unit; a fourth calculation unit; and an output unit. The first calculation unit is configured to calculate a first rotation angle of a rotor on the basis of signals output from a magnet type angular sensor detecting a magnetic field of a rotation angle detection magnet attached to the rotor, and the second calculation unit is configured to calculate an estimation angular velocity by feed-back control so that a deviation between the first rotation angle and a previously calculated second rotation angle stands at zero. The third calculation unit is configured to calculate an amount of change in the rotation angle on the basis of the estimation angular velocity, and the fourth calculation unit is configured to add the amount of change in the rotation angle to the previously calculated second rotation angle to calculate a second rotation angle. The output unit is configured to output the second rotation angle calculated by the fourth calculation unit as a rotor rotation angle.SELECTED DRAWING: Figure 1

Description

  Embodiments disclosed herein relate to a rotation angle detection device and a rotation angle detection method.

  2. Description of the Related Art Conventionally, a rotation angle detection device that detects a rotation position of a rotating body of a motor, that is, a rotation angle, using a magnetic angle sensor is known (for example, see Patent Document 1).

  In the rotation angle detection device, the rotation speed of the rotating body is integrated from the value detected by the magnetic angle sensor to calculate the rotation angle of the rotating body. In addition, a method of calculating an angle from values (sin signal, cos signal) detected by a sensor and obtaining an angular velocity by differential of the angle is also taken.

JP 2012-10589 A

  However, in the rotation angle detection device, there is a possibility that an error occurs in the calculated rotation angle of the rotating body due to the influence of the magnetic field generated by the current flowing through the motor. That is, the rotation angle of the rotating body cannot be accurately calculated.

  One aspect of the embodiments has been made in view of the above, and an object thereof is to provide a rotation angle detection device and a rotation angle detection method for accurately detecting the rotation angle of a rotating body.

  The rotation angle detection device according to an aspect of the embodiment includes a first calculation unit, a second calculation unit, a third calculation unit, a fourth calculation unit, and an output unit. The first calculation unit calculates a first rotation angle of the rotating body based on a signal output from a magnetic angle sensor that detects a magnetic field of a magnet for detecting a rotation angle attached to the rotating body. The second calculation unit calculates the estimated angular velocity by feedback control such that the deviation between the first rotation angle and the previously calculated second rotation angle is zero. The third calculation unit calculates the rotation angle change amount based on the estimated angular velocity. The fourth calculation unit calculates a new second rotation angle by adding the rotation angle change amount to the previously calculated second rotation angle. The output unit outputs the second rotation angle calculated by the fourth calculation unit as a rotating body rotation angle.

  According to one aspect of the embodiment, the rotation angle of the rotating body can be accurately detected.

FIG. 1 is a diagram illustrating an outline of rotation angle detection according to the embodiment. FIG. 2 is a schematic diagram showing the relationship among a motor, a magnetic angle sensor, and a rotation angle detection device. FIG. 3 is a diagram showing a schematic configuration when the rotor and the permanent magnet for detection are viewed from the axial direction. FIG. 4 is a schematic block diagram of the rotation angle detection device. FIG. 5 is a diagram illustrating processes in the second calculation unit, the third calculation unit, and the fourth calculation unit in terms of transfer functions. FIG. 6 is a diagram illustrating a gain-angular frequency characteristic of a filter having a cutoff frequency. FIG. 7 is a flowchart illustrating the rotation angle detection process according to the present embodiment.

  Hereinafter, a rotation angle detection device and a rotation angle detection method disclosed in the present application will be described with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  Here, the case of detecting the rotation angle of a rotor that is a rotating body of a motor through which an alternating current flows will be described. However, the present invention is not limited to this, as long as it detects the rotation angle of a rotating body such as a generator. Good.

<Outline of rotation angle detection>
An outline of rotation angle detection according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram showing an outline of rotation angle detection according to the present embodiment.

  The rotation angle detection device calculates the first rotation angle θ based on a signal output from a magnetic angle sensor that detects the magnetism of a magnet attached to the rotation shaft of the motor (external member) (S1).

  The rotation angle detection device calculates a deviation Δθ between the calculated first rotation angle θ and the previously calculated second rotation angle θ ′ (S2).

  The rotation angle detection device calculates the estimated angular velocity ω ′ by feedback control, for example, PI control (proportional integration) so that the deviation Δθ becomes zero (S3). The feedback control may be PID (proportional integral derivative) control.

  The rotation angle detection device multiplies the calculated estimated angular velocity ω ′ by the control period Δt to calculate the rotation angle change amount dθ, adds the rotation angle change amount dθ to the previously calculated second rotation angle θ ′, A new second rotation angle θ ′ is calculated (S4). That is, the second rotation angle θ ′ is updated. The updated second rotation angle θ ′ is used when calculating the deviation Δθ in the next calculation.

  The rotation angle detection device outputs the newly calculated second rotation angle θ ′ as the rotation angle of the motor (rotating body rotation speed).

  Thus, the estimated angular velocity ω ′ is calculated by feedback control so that the deviation Δθ between the first rotation angle θ calculated by the magnetic angle sensor and the previously calculated second rotation angle θ ′ is zero, and By adding the rotation angle change amount dθ calculated based on the estimated angular velocity ω ′ to the previously calculated second rotation angle θ ′, the influence of frequency components (noise) generated by the magnetic field of the alternating current flowing in the motor is reduced. The calculated rotation angle can be calculated.

<Outline of the rotation angle detection device 10>
First, the relationship among the motor 1, the magnetic angle sensor 20, and the rotation angle detection device 10 will be described with reference to FIG. FIG. 2 is a schematic diagram showing the relationship among the motor 1, the magnetic angle sensor 20, and the rotation angle detector 10.

  The motor 1 is an embedded magnet synchronous motor. The motor 1 includes a rotor 3 attached to the rotating shaft 2 and a stator 4 attached to the housing 5. The motor 1 is not limited to an embedded magnet synchronous motor, and may be a surface magnet synchronous motor or the like.

  The rotating shaft 2 is rotatably supported by the housing 5 via a bearing 6. Thereby, the rotor 3 becomes rotatable. The rotary shaft 2 protrudes from the housing 5 to the outside. One end of the rotating shaft 2 is connected to a load (not shown), and a detection permanent magnet 7 is attached to the other end.

  As shown in FIG. 3, a permanent magnet 3 a is embedded in the rotor 3. FIG. 3 is a diagram showing a schematic configuration when the rotor 3 and the detection permanent magnet 7 are viewed from the axial direction. Six permanent magnets 3 a are embedded in the rotor 3, and the number of pole pairs of the rotor 3 is three. The number of pole pairs of the rotor 3 is not limited to this, and the number of pole pairs may be 4, 6 or the like.

  A detection permanent magnet 7 is attached to the tip of the rotating shaft 2 that protrudes outward from the housing 5. The number of pole pairs of the detection permanent magnet 7 is one. Note that the number of pole pairs of the detection permanent magnet 7 is not limited to this, and may be a plurality of pole pairs, which is smaller than the number of pole pairs of the rotor 3.

  Returning to FIG. 2, the stator 4 is configured by, for example, winding a coil around a stator core formed by stacking electromagnetic steel plates. A U-phase, V-phase, and W-phase alternating current flows through the coil. Further, an alternating current having a frequency corresponding to the number of pole pairs and the rotational speed of the rotor 3 flows through the coil.

  The magnetic angle sensor 20 is disposed so as to face the detection permanent magnet 7 attached to the rotating shaft 2 of the rotor 3. The magnetic angle sensor 20 detects a magnetic field generated by the detection permanent magnet 7 using a magnetoresistive element or a Hall element, and outputs a signal related to the rotation angle (rotation position) of the rotor 3 based on the magnetic field.

  Next, the rotation angle detection device 10 will be described with reference to FIG. FIG. 4 is a schematic block diagram of the rotation angle detection device 10.

  The rotation angle detection device 10 includes a reception unit 11 and a detection unit 12. The receiving unit 11 receives a signal from the magnetic angle sensor 20.

  The detection unit 12 includes a first calculation unit 13, a second calculation unit 14, a third calculation unit 15, a fourth calculation unit 16, and an output unit 17.

  The first calculator 13 calculates the first rotation angle θ of the rotor 3 based on the signal received by the receiver 11.

  When the rotor 3 rotates once, the magnetic field generated by the detection permanent magnet 7 that rotates with the rotor 3 changes, and a sine wave (cosine wave) for one cycle appears.

  However, the first rotation angle θ calculated based on the signal from the magnetic angle sensor 20 is affected by the magnetic field generated by the alternating current flowing in the coil of the motor 1 (magnetic field generating unit). Therefore, the frequency component of the magnetic field generated by the alternating current flowing through the coil is superimposed on the first rotation angle θ detected by the magnetic angle sensor 20. The frequency component of the magnetic field generated by the alternating current flowing through the coil is a component according to the number of pole pairs and the rotational speed of the rotor 3. That is, according to the number of pole pairs of the rotor 3, a frequency component that is three times the frequency component of the magnetic field generated by the detection permanent magnet 7 is included in the first rotation angle θ.

  The second calculator 14 calculates a deviation Δθ between the first rotation angle θ and the previously calculated second rotation angle θ ′.

The third calculation unit 15 performs feedback control so that the deviation Δθ calculated by the second calculation unit 14 becomes zero, and calculates the estimated angular velocity ω ′ according to the deviation Δθ by the equation (1). The third calculator 15 calculates the estimated angular velocity ω ′ by PI control.

  “Kp” is the gain of the proportional term, and here is “2ζωc”. “Ζ” is an attenuation coefficient, and is set to about 0.5 to 1.5. “Ωc” is a cut-off frequency, and the angular frequency corresponding to the previously calculated estimated angular velocity ω ′ is multiplied by a value larger than the number of pole pairs of the detection permanent magnet 7 and smaller than the number of pole pairs of the rotor 3. Value.

“Ki” is the gain of the integral term, and here is “ωc ² ”.

  The third calculator 15 updates the cutoff frequency ωc according to the calculated estimated angular velocity ω ′.

  The fourth calculation unit 16 multiplies the estimated angular velocity ω ′ calculated by the third calculation unit 15 by the control period Δt to calculate the rotation angle change amount dθ. Then, the fourth calculation unit 16 adds the rotation angle change amount dθ to the previously calculated second rotation angle θ ′ to calculate a new second rotation angle θ ′.

  As will be described in detail later, the second rotation angle θ ′ is a value in which the influence of the frequency component generated by the alternating current flowing in the coil is reduced by the processing from the second calculation unit 14 to the fourth calculation unit 16.

  The output unit 17 outputs the first rotation angle θ or the second rotation angle θ ′ as the rotation angle of the rotor 3 based on the deviation Δθ calculated by the second calculation unit 14. The output unit 17 outputs the second rotation angle θ ′ as the rotation angle of the rotor 3 when the deviation Δθ is equal to or less than a predetermined value. Note that the absolute value of the deviation is used when determining whether the deviation is less than or equal to a predetermined value. The same applies to the following. The output unit 17 outputs the first rotation angle θ as the rotation angle of the rotor 3 when the deviation Δθ is larger than a predetermined value. The predetermined value is a value set in advance, and is a value at which step-out does not occur when the alternating current of the motor 1 is controlled based on the second rotation angle θ ′.

<Filter processing>
The rotation angle detection device 10 calculates the second rotation angle θ ′ by performing the same function as the low-pass filter having the cutoff frequency ωc with the above configuration. That is, the fourth calculation unit 16 calculates a new second rotation angle θ ′ in which a frequency larger than the cutoff frequency ωc is reduced (cut) by a function equivalent to that of the low-pass filter having the cutoff frequency ωc. Here, these filter functions will be described.

  The processing in the second calculation unit 14, the third calculation unit 15, and the fourth calculation unit 16 of the rotation angle detection device 10 described above is shown in FIG. 5 as a transfer function. FIG. 5 is a diagram showing the processes in the second calculation unit 14, the third calculation unit 15, and the fourth calculation unit 16 in terms of transfer functions.

  As shown in FIG. 5A, the process by the feedback control of the third calculation unit 15 is “Kp + (Ki / s)” in the transfer function, and the process in the fourth calculation unit 16 is “1” in the transfer function. / S ".

When FIG. 5A is summarized, as shown in FIG. 5B, the transfer function is “(Kps + Ki) / (S ² + KpS + Ki)”, and it can be seen that it functions as a low-pass filter.

When the gain “Kp” is “2ζωc” and the gain “Ki” is “ωc ² ”, “ωc” is a cutoff frequency that exhibits the same function as the low-pass filter.

  The gain-angular frequency characteristic of the filter having such a cutoff frequency ωc is as shown in FIG. FIG. 6 is a diagram illustrating a gain-angular frequency characteristic of a filter having a cutoff frequency ωc.

  In the present embodiment, the cut-off frequency ωc corresponds to an angular velocity obtained by multiplying the previously calculated estimated angular velocity ω ′ by a value larger than the number of pole pairs of the detection permanent magnet 7 and smaller than the number of pole pairs of the rotor 3. Angular frequency. That is, the cut-off frequency ωc is a value larger than the frequency generated by the detection permanent magnet 7 and smaller than the frequency generated by the alternating current flowing in the coil.

  As a result, the angular frequency corresponding to the angular velocity obtained by multiplying the previously calculated estimated angular velocity ω ′ by the number of pole pairs of the rotor 3, which is a frequency component generated by the magnetic field of the alternating current flowing in the coil, is reduced. On the other hand, the angular frequency corresponding to the estimated angular velocity ω ′ calculated last time, which is a frequency component generated by the magnetic field of the permanent magnet 7 for detection, is not reduced. Therefore, the rotation angle of the rotor 3 can be accurately detected.

  If the cutoff frequency ωc is increased, the amount of reduction in the frequency component caused by the magnetic field of the alternating current flowing through the coil is reduced, and the rotation angle of the rotor 3 cannot be detected accurately. For this reason, it is desirable to reduce the cutoff frequency ωc.

  However, if the cut-off frequency ωc is too small, the frequency component generated by the magnetic field of the alternating current flowing in the coil can be sufficiently reduced. However, when the amount of change in the rotational speed of the rotor 3 becomes large, the detection frequency There is a possibility that the frequency component generated by the magnetic field of the permanent magnet 7 may be reduced.

  Therefore, the cut-off frequency ωc takes these points into consideration and reduces the frequency component generated by the magnetic field of the alternating current flowing in the coil, and the rotor 3 rotates even when the amount of change in the rotational speed of the rotor 3 increases. The angle is set so that the angle can be accurately detected.

  When the estimated angular velocity ω ′ decreases and becomes near zero, when the cutoff frequency ωc corresponding to the estimated angular velocity ω ′ is used, the cutoff frequency ωc becomes near zero, and the second rotation angle θ ′ is used. There is a possibility that the rotation angle of the rotor 3 cannot be detected.

  Therefore, when the estimated angular velocity ω ′ is equal to or lower than a predetermined low angular velocity, the cutoff frequency ωc is set to a predetermined frequency. The predetermined frequency is a preset value.

<Rotation angle detection process>
Next, the rotation angle detection process according to the present embodiment will be described with reference to the flowchart of FIG. FIG. 7 is a flowchart for explaining the rotation angle detection process.

  The first calculator 13 calculates the first rotation angle θ based on the signal from the magnetic angle sensor 20 (S10). The second calculator 14 calculates a deviation Δθ between the first rotation angle θ and the previously calculated second rotation angle θ ′ (S11).

  The third calculator 15 performs feedback control so that the deviation Δθ becomes zero, calculates the estimated angular velocity ω ′ (S12), and updates the cutoff frequency ωc according to the calculated ω ′ (S13).

  The fourth calculator 16 multiplies the estimated angular velocity ω ′ by the control period Δt to calculate the rotation angle change amount dθ (S14). The fourth calculator 16 adds the rotation angle change amount dθ to the previously calculated second rotation angle θ ′ to calculate a new second rotation angle θ ′ (S15).

  The output unit 17 compares the deviation Δθ with a predetermined value (S16), and when the deviation Δθ is equal to or smaller than the predetermined value (S16: No), outputs the second rotation angle θ ′ as the rotation angle of the rotor 3 ( S17). When the deviation Δθ is larger than the predetermined value (S16: Yes), the output unit 17 outputs the first rotation angle θ as the rotation angle of the rotor 3 (S18).

<Effect of embodiment>
Based on a deviation Δθ between the first rotation angle θ calculated based on the signal from the magnetic angle sensor 20 and the second rotation angle θ ′ calculated last time, the deviation Δθ becomes zero by feedback control. An estimated angular velocity ω ′ is calculated. Further, the rotation angle change amount dθ is calculated based on the estimated angular velocity ω ′, and the second rotation angle θ ′ is calculated by adding the rotation angle change amount dθ to the previously calculated second rotation angle θ ′. Then, the calculated second rotation angle θ ′ is output as the rotation angle of the rotor 3.

  Thereby, it is possible to calculate the rotation angle in which the influence of the frequency component generated by the magnetic field of the alternating current flowing through the coil is reduced. Therefore, for example, the alternating current flowing through the coil can be accurately controlled according to the calculated rotation angle of the rotor 3, the efficiency of the motor 1 can be improved, and the occurrence of step-out can be suppressed.

  Further, even when the magnetic angle sensor 20 is disposed close to the motor 1, it is possible to calculate a rotation angle in which the influence of the frequency component caused by the alternating current flowing in the coil is reduced, and the rotation angle detection device 10 and the motor 1 can be calculated. The containing system can be miniaturized.

  Further, the cutoff frequency ωc is set based on the previously calculated estimated angular velocity ω ′, and a new second rotation angle θ ′ in which a frequency larger than the cutoff frequency ωc is reduced is calculated. The second rotation angle θ ′ is output as the rotation angle of the rotor 3.

  Thereby, the second rotation angle θ ′ in which the frequency component generated by the magnetic field of the alternating current flowing in the coil is reduced can be calculated, and the rotation angle of the rotor 3 can be accurately calculated.

  The cut-off frequency ωc is dynamically set to a frequency that is higher than the frequency generated by the magnetic field of the detection permanent magnet 7 and lower than the frequency generated by the magnetic field of the alternating current flowing in the coil.

  Thereby, it can suppress that the frequency component produced by the magnetic field of the permanent magnet 7 for a detection is reduced. Moreover, the frequency component produced by the magnetic field of the alternating current which flows into a coil can be reduced. Therefore, the rotation angle of the rotor 3 can be accurately detected.

  When the deviation Δθ is larger than a predetermined value, the first rotation angle θ is output as the rotation angle of the rotor 3.

  Thus, when the deviation Δθ is large, the motor 1 is stepped out by controlling the alternating current of the coil, for example, based on the first rotation angle θ detected by the magnetic angle sensor 20. Can be suppressed.

<Modification>
In the above embodiment, when the deviation Δθ is larger than the predetermined value, the output unit 17 outputs the first rotation angle θ as the rotation angle of the rotor 3, but the deviation Δθ is larger than the first predetermined value, and In the case of the second predetermined value or less, the rotation angle between the first rotation angle θ and the second rotation angle θ ′ may be output as the rotation angle of the rotor 3. The first predetermined value and the second predetermined value are preset values. For example, the first predetermined value corresponds to the predetermined value.

  Thereby, for example, when the alternating current flowing through the coil is controlled based on the output rotation angle, the current control of the motor 1 is prevented from becoming unstable due to a sudden change in the current due to the switching of the rotation angle. Can do.

  In this case, the output unit 17 outputs the first rotation angle θ as the rotation angle of the rotor 3 when the deviation Δθ becomes larger than the second predetermined value.

  Further, when the deviation Δθ is larger than the first predetermined value and equal to or smaller than the second predetermined value, the output unit 17 may set the rotation angle to a value closer to the first rotation angle θ as the deviation Δθ increases. Thereby, as the deviation Δθ increases, the rotation angle gradually becomes a value close to the first rotation angle θ, and it is possible to further suppress the current control from becoming unstable due to a sudden change in current.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

1: Motor (magnetic field generator)
2: Rotating shaft 3: Rotor (rotating body)
4: Stator 7: Permanent magnet for detection (magnet)
DESCRIPTION OF SYMBOLS 10: Rotation angle detection apparatus 12: Detection part 13: 1st calculation part 14: 2nd calculation part 15: 3rd calculation part 16: 4th calculation part 17: Output part 20: Magnetic angle sensor

Claims (7)

A first calculation unit that calculates a first rotation angle of the rotating body based on a signal output from a magnetic angle sensor that detects a magnetic field of a magnet for detecting a rotation angle attached to the rotating body;
A second calculator that calculates an estimated angular velocity by feedback control such that a deviation between the first rotation angle and the previously calculated second rotation angle is zero;
A third calculation unit that calculates a rotation angle change amount based on the estimated angular velocity;
A fourth calculator that calculates the new second rotation angle by adding the rotation angle change amount to the previously calculated second rotation angle;
An output unit that outputs the second rotation angle calculated by the fourth calculation unit as a rotating body rotation angle. The fourth calculation unit includes:
2. The rotation angle detection device according to claim 1, wherein the second rotation angle is calculated by reducing a frequency greater than a cutoff frequency based on the second rotation angle calculated last time. The fourth calculation unit includes:
The new second rotation in which a frequency greater than the cutoff frequency, which is a frequency greater than the frequency generated by the magnetic field of the magnet and smaller than the frequency generated by the magnetic field of the magnetic field generation unit other than the magnet, is reduced. The rotation angle detection device according to claim 2, wherein an angle is calculated. The output unit is
The rotation angle detection device according to any one of claims 1 to 3, wherein when the deviation is larger than a predetermined value, the first rotation angle is output as the rotation body rotation angle. The output unit is
When the deviation is greater than a first predetermined value and less than or equal to a second predetermined value, a rotation angle between the first rotation angle and the second rotation angle calculated by the fourth calculation unit is Output as the rotating body rotation angle,
The rotation angle detection according to any one of claims 1 to 3, wherein when the deviation is larger than the second predetermined value, the first rotation angle is output as the rotating body rotation angle. apparatus. The output unit is
When the deviation is greater than a first predetermined value and less than or equal to the second predetermined value, a value close to the first rotation angle is output as the rotating body rotation angle as the deviation increases. The rotation angle detection device according to claim 5. A first calculation step of calculating a first rotation angle of the rotating body based on a signal output from a magnetic angle sensor for detecting a magnetic field of a rotation angle detecting magnet attached to the rotating body;
A second calculation step of calculating an estimated angular velocity by feedback control such that a deviation between the first rotation angle and the previously calculated second rotation angle is zero;
A third calculation step of calculating a rotation angle change amount based on the estimated angular velocity;
A fourth calculation step of calculating a new second rotation angle by adding the rotation angle change amount to the previously calculated second rotation angle;
An output step of outputting the second rotation angle calculated in the fourth calculation step as a rotating body rotation angle.

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