JP2017219098A - Rotation synchronous phase detection device and magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a rotation synchronous phase of the body of rotation of a magnetic bearing device accurately, inexpensively, and stably.SOLUTION: With a rotation synchronous phase detection device 4, when a first revolution speed v1 is accelerating, a speed determination part 43 selects the first revolution speed v1 or a second revolution speed v2 as a revolution speed v for providing to a phase operation part 44 based on the difference between the first revolution speed v1 and the maximum second revolution speed v2_max. When the first revolution speed v1 is decelerating, the speed determination part selects the first revolution speed v1 or the second revolution speed v2 as the revolution speed v for providing to the phase operation part 44 based on the difference between the first revolution speed v1 and the minimum second revolution speed v2_min. In addition, the first revolution speed v1 is detected based on the x shaft displacement and a zero-cross cycle of the y shaft displacement of the body 2 of rotation. The second revolution speed v2 is detected based on the d shaft displacement when the q shaft displacement becomes 0, which is obtained by the dq coordinate conversion on the basis of the x shaft displacement and the y shaft displacement of the body 2 of rotation.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a technique for detecting the rotational speed of a rotating body based on a displacement signal of the rotating body of a magnetic bearing device exemplified by a magnetic bearing and a bearingless motor.

  A magnetic bearing device is a device that supports a rotating body, which is a magnetic body, by magnetic levitation, and feedback-controls an excitation current supplied to an electromagnet that levitates the rotating body based on a displacement signal about the swing of the rotating body. The floating position of the rotating body is controlled (for example, Patent Document 1).

  As shown in FIG. 9, in the magnetic bearing device 9 of Patent Document 1, the current control unit 3 controls the rotation of the rotating body 2 levitated by the electromagnets 1x and 1y. When the rotating body 2 rotates, the rotating body 2 swings due to a mismatch between the center of gravity of the rotating body 2 and the geometric center. The displacement signal (X, Y) around this swing is detected by a displacement sensor (not shown). In the figure, X represents a displacement signal around the swing in the X-axis direction (one radial direction of the rotating body 2), and Y represents a swing signal in the Y-axis direction (the other radial direction orthogonal to the one radial direction). The surrounding displacement signal is shown. At the same time, the rotational synchronization phase θ is detected by a rotary encoder or resolver (not shown). The detected rotation synchronization phase θ is removed from the rotation synchronization component of the displacement signal by the tracking filter function of the current control unit 3. The current control unit 3 calculates a current command value based on the displacement signal from which the rotational synchronization component is removed, and supplies excitation currents Ix and Iy based on the current command value to the excitation coils of the electromagnets 1x and 1y, respectively. As described above, by removing the rotation synchronization component from the displacement signal, the rotor moves at the origin of the displacement coordinate axis.

  The displacement signal has a waveform approximating a sine wave. As an approximation method from the displacement signal to the phase of the sine wave, the following two methods are known. Method [1] calculates the phase of the sine wave by integrating the velocity calculated based on the zero cross period of the displacement signal. Method [2] calculates the speed by applying a PLL (Phase Locked Loop) to the q-axis signal of the displacement signal and integrates it to calculate the phase of the sine wave.

  The method [1] will be specifically described with reference to FIG. The speed of the motor shown in the equation (1) can be calculated with the frequency f as the reciprocal of the interval at which the displacement signal crosses zero when viewed from the origin of the displacement coordinate axis (the geometric center point of the rotor or the orthogonal point of the two pairs of sensors). . By applying equation (2) to this speed, the rotational synchronization phase θ is calculated. The illustrated block configuration is a configuration example in which the frequency is calculated based on the zero cross of the displacement signal in the x-axis direction. The frequency can be calculated by the same method based on the zero cross of the displacement signal in the y-axis direction or the zero cross of the displacement signal in both the x-axis direction and the y-axis direction.

  The method [2] will be specifically described with reference to FIG. Two-phase dq conversion is performed on the x-axis and y-axis displacement signals by the rotation synchronization phase θ, and the d-axis displacement signal (the displacement signal in the magnetic flux direction of the rotating body 2) and the q-axis displacement signal (in orthogonal to the magnetic flux direction). The displacement signal in the direction to be calculated) is calculated. When there is no runout in the rotation, the displacement signal is only the d-axis displacement signal that is a component synchronized with the rotation, so the q-axis displacement signal that is a component perpendicular to the d-axis displacement signal is zero. Using this, only a direct current component is extracted from the q-axis displacement signal by a low-pass filter (LPF), and feedback control is performed so that it becomes zero. The DC component of the q-axis displacement signal is adjusted by PI control so as to coincide with the rotation speed v, and the rotation synchronization phase θ of the displacement signal is calculated by integrating the rotation speed v. In this way, the rotation synchronization phase can be calculated from the displacement signal around the rotating body without using a rotary encoder or resolver.

JP-A-8-28562 JP 2012-110166 A

  In the conventional method for detecting the rotational synchronization phase (Patent Document 1), clock pulse detection applied to suppress the rotational displacement of the rotating body is performed by a rotary encoder attached to the rotating body. Since the rotary encoder is expensive, the detection cost of the rotation synchronization phase is high. In addition, the rotary encoder is not suitable for high-speed rotation because it is attached to the rotating shaft. Even if a resolver is applied instead of the rotary encoder, the cost becomes high.

  Patent Document 1 describes a method for detecting a speed from a displacement signal without requiring a rotary encoder or resolver. However, this method can only detect several times per rotation, and further has a timing to detect due to noise. Since it changes, detection accuracy becomes low.

  On the other hand, since the method [1] detects a zero-crossing point, the detected value has a characteristic that the detection value is hardly affected by a sudden change in the rotation speed. In addition, the method [2] described above exists as a method for detecting the velocity from other displacement signals. However, since this method converts the displacement signal into a detection value as it is, the detection timing is the same as the displacement signal. Highly accurate detection is possible.

  However, any of the above methods has a problem in stability because the displacement signal changes greatly when the rotation speed changes suddenly due to a sudden change in the rotation speed command or the motor load.

  In view of the above circumstances, an object of the present invention is to inexpensively and stably measure the rotational synchronization phase of a rotating body of a magnetic bearing device with high accuracy.

  Therefore, the rotational synchronization phase detection device of the present invention is based on the zero cross period of one radial displacement of the magnetically levitated rotating member and the other radial displacement orthogonal to the one radial direction. A displacement in a direction perpendicular to the magnetic flux direction of the rotating body obtained by coordinate conversion based on the first speed detection unit for detecting the rotation speed of the first rotation direction and the displacement in the one radial direction and the displacement in the other radial direction. A second speed detector for detecting a second rotational speed of the rotating body based on the displacement in the magnetic flux direction when 0, and the first rotational speed and the second rotational speed A phase calculator that calculates a rotation synchronization phase of the rotating body.

  One aspect of the rotation-synchronized phase detection device provides the phase calculation unit based on a difference between the first rotation speed and the maximum second rotation speed when the first rotation speed is accelerating. While selecting either the first rotation speed or the second rotation speed as the rotation speed, when the first rotation speed is decelerating, the first rotation speed and the minimum second And a speed determination unit that selects either the first rotation speed or the second rotation speed as the rotation speed to be provided to the phase calculation unit based on the difference between the rotation speed and the second rotation speed.

  One aspect of the rotation-synchronized phase detection device further includes a change rate limiting processing unit that limits the change rate of the rotation speed provided to the phase calculation unit.

  One aspect of the magnetic bearing device of the present invention is based on the rotational synchronization phase of the rotating body based on one radial displacement of the rotating body magnetically levitated by the electromagnet and the other radial displacement orthogonal to the one radial direction. And a current control unit that controls an excitation current provided to the electromagnet based on the one radial displacement, the other radial displacement, and the detected rotational synchronization phase. With.

  According to the present invention described above, the rotational synchronization phase of the rotating body of the magnetic bearing device can be measured inexpensively and stably with high accuracy.

The block block diagram of the magnetic bearing apparatus in embodiment of this invention. The block block diagram of the rotation synchronous phase detection apparatus in the embodiment. The flowchart of the detection of the rotation synchronous phase in the embodiment. Change in rotational speed over time by method [1]. Change in rotational speed over time by method [2]. Changes in the actual rotational speed of the rotating body during acceleration of the rotating body, the rotational speed detected by the method [2], and the maximum detected rotational speed over time. Changes in the rotational speed of the actual rotating body during acceleration of the rotating body, the rotational speed detected by the technique [1], the rotational speed detected by the technique [2], and the rotational speed determined by the embodiment. The block block diagram of the rotation synchronous phase detection apparatus in other embodiment of this invention. The block block diagram of the conventional magnetic bearing apparatus. The block block diagram of the rotation synchronous phase detection system based on the method [1]. The block block diagram of the rotation synchronous phase detection system based on method [2].

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

[First embodiment]
A magnetic bearing device 10 illustrated in FIG. 1 includes electromagnets 1x and 1y, a rotating body 2, a current control unit 3, and a rotation synchronization phase detection device 4. The electromagnets 1x and 1y magnetically float the rotating body 2. The current controller 3 is based on the x-axis displacement (displacement in one radial direction), the y-axis displacement (displacement in the other radial direction orthogonal to the one radial direction) of the rotating body 2 and the rotation synchronization phase θ. , 1y, excitation currents Ix and Iy are calculated. The rotation synchronization phase detector 4 detects the rotation synchronization phase θ of the rotating body 2 provided to the current control unit 3.

  As shown in FIG. 1, the electromagnets 1 x and 1 y are arranged in a pair so as to face each other with the rotating body 2 interposed therebetween. The x-axis displacement of the rotating body 2 is detected by a well-known displacement sensor whose illustration is omitted in the x-axis direction of the rotating body 2 magnetically levitated by the pair of electromagnets 1x. On the other hand, the y-axis displacement of the rotating body 2 is detected by a well-known displacement sensor whose illustration is omitted in the y-axis direction of the rotating body 2 magnetically levitated by the pair of electromagnets 1y.

  As illustrated in FIG. 2, the rotation synchronization phase detection device 4 includes a first speed detection unit 41, a second speed detection unit 42, a speed determination unit 43, and a phase calculation unit 44.

  The first speed detector 41 detects the first rotational speed v1 of the rotating body 2 based on the zero cross period of the x-axis displacement and the y-axis displacement of the rotating body 2.

  In the second speed detector 42, the q-axis displacement (displacement in the direction orthogonal to the magnetic flux direction of the rotating body 2) obtained by dq coordinate conversion based on the x-axis displacement and the y-axis displacement of the rotating body 2 becomes zero. The second rotational speed v2 of the rotating body 2 is detected based on the d-axis displacement (displacement in the magnetic flux direction).

  When the first rotation speed v1 is accelerating, the speed determination unit 43 sets the rotation speed v to be supplied to the phase calculation unit 44 based on the difference between the first rotation speed v1 and the maximum second rotation speed v2_max. One of the first rotation speed v1 and the second rotation speed v2 is selected. On the other hand, when the first rotational speed v1 is decelerating, the first rotational speed is used as the rotational speed v provided to the phase calculation unit 44 based on the difference between the first rotational speed v1 and the minimum second rotational speed v2_min. Either v1 or the second rotation speed v2 is selected.

  The phase calculation unit 44 uses either the first rotation speed v1 or the second rotation speed v2 provided as the rotation speed v from the speed determination unit 43 for the calculation based on the above-described equation (2), thereby rotating the rotating body 2. Is calculated.

  A process of detecting the rotation synchronization phase θ of the rotating body 2 of the present embodiment will be described with reference to the flowchart of FIG.

  S1: The first speed detection unit 41 detects the first rotation speed v1 of the rotating body 2 based on the zero cross period of the x-axis displacement and the y-axis displacement of the rotating body 2 detected by the displacement sensor (hereinafter referred to as a technique). [1]). On the other hand, the d-axis displacement when the q-axis displacement of the d-axis displacement and the q-axis displacement obtained by dq conversion of the x-axis displacement and the y-axis displacement of the rotating body 2 detected by the displacement sensor becomes zero. Based on this, the second rotational speed v2 of the rotating body 2 is detected (hereinafter referred to as method [2]).

  S2: The speed determination unit 43 determines whether the first rotation speed v1 is accelerating or decelerating.

  When it is determined that the value of the first rotation speed v1 is increased and the rotator 2 is accelerating, the speed determination unit 43 determines the difference between the first rotation speed v1 and the maximum second rotation speed v2_max. It is determined whether the absolute value of is greater than or equal to a threshold value (S2 in FIG. 3). The maximum second rotational speed v2_max means the maximum value of the second rotational speed v2 sampled within a predetermined time.

  On the other hand, when the value of the first rotation speed v1 decreases and it is determined that the rotating body 2 is decelerating, the speed determination unit 43 determines the difference between the first rotation speed v1 and the minimum second rotation speed v2_min. It is determined whether the absolute value of is greater than or equal to a threshold value. The minimum second rotation speed v2_min means the minimum value of the second rotation speed v2 sampled within a predetermined time.

  S3: If the absolute value is greater than or equal to the threshold value, the speed determination unit 43 selects the first rotation speed v1.

  S4: When the absolute value is less than the threshold value, the speed determination unit 43 selects the second rotation speed v2.

  S5: The speed determination unit 43 determines the first rotation speed v1 selected in S3 or the second rotation speed v2 selected in S4 as the rotation speed v used for the calculation in the phase calculation unit 44.

  S6: The phase calculation unit 44 calculates the rotation synchronization phase θ of the rotating body 2 by using the rotation speed v determined in S5 for calculation based on the equation (2). This rotation synchronization phase θ is provided to the current control unit 3.

  Then, the current control unit 3 generates an excitation current Ix to be applied to the electromagnets 1x and 1y based on the x-axis displacement and the y-axis displacement of the rotating body 2 and the rotation synchronization phase θ of the rotation body 2 provided from the rotation synchronization phase detector 4. Iy is calculated.

  As described above, according to the magnetic bearing device 10 of the present embodiment, it is determined whether the first rotational speed v1 of the rotating body 2 is accelerating or decelerating. Then, when the first rotation speed v1 is accelerating, the absolute value of the difference between the first rotation speed v1 and the maximum second rotation speed v2_max is compared with a threshold value. On the other hand, when the first rotation speed v1 is being decelerated, the absolute value of the difference between the first rotation speed v1 and the minimum second rotation speed v2_min is compared with a threshold value.

  4 and 5, the solid lines indicate the rotational speeds detected by the methods [1] and [2], respectively, while the dotted lines indicate the actual rotational speed of the rotating body 2. Therefore, the smaller the speed difference between the solid line and the dotted line, the smaller the speed detection error. As shown in FIG. 4, when the rotational speed of the rotating body 2 is increasing, the rotational speed of the rotating body 2 detected by the method [1] is low in accuracy, but the actual rotating body 2 is rotated. It varies as well as the speed. On the other hand, as shown in FIG. 5, the value of the rotational speed of the rotating body 2 detected by the method [2] vibrates according to the displacement of the rotating body 2 when the speed changes from zero. However, since the vibration is gradually reduced by the PI control, the difference between the rotational speed (solid line) by the method [2] and the actual rotational speed (dotted line) is small. That is, the difference in rotational speed between the method [1] and the method [2] becomes small.

  Here, when a constant speed is used as a determination value for switching the detection method, the detection method is frequently switched when the fluctuation of the rotation speed due to the method [2] vibrates as shown in FIG. Therefore, the detected value of the rotational speed becomes unstable. Further, when the speed difference between the method [1] and the method [2] is used as a determination value, the detection method is switched every time the speed difference becomes 0, and the detection value becomes unstable.

  Therefore, in the present embodiment, the maximum second rotation speed v2_max is used for calculating the difference from the first rotation speed v1 instead of the second rotation speed v2 when the rotating body 2 is accelerated. Based on the absolute value of the difference, either the first rotational speed v1 or the second rotational speed v2 is selected as the rotational speed v used for the calculation of the rotational synchronization phase θ in the phase calculation unit 44. Is done. This avoids frequent switching of detection methods. On the other hand, when the rotating body 2 is decelerated, the reverse of the case where the rotational speed is increasing occurs. Therefore, the minimum second rotational speed v2_min is selected.

FIG. 6 shows changes over time in the actual rotational speed of the rotating body 2, the rotational speed of the rotating body 2 detected by the method [2], and the maximum detected rotational speed when the rotating body 2 is accelerated. According to the flowchart of FIG. 3, the rotational speed v used for the calculation in the phase calculation unit 44 is selected by the following value, for example.
0 <time <t1: v = v2
t1 <time <t2: v = v1
t2 <time: v = v2
FIG. 7 shows the actual rotational speed of the rotating body 2 when the rotating body 2 is accelerated, the rotational speed detected by the method [1], the rotational speed detected by the method [2], and the speed determining unit 43 of the present invention. The change of the rotation speed with time was shown. Over the entire time, the actual rotation speed of the rotating body 2 and the rotation speed determined by the present embodiment are substantially the same value, and the rotation speed v of the rotating body 2 can be detected with high accuracy. Then, the rotational speed v of the rotating body 2 is provided to the phase calculation unit 44, so that the rotation synchronization phase θ of the rotating body 2 can be detected accurately and stably.

  In a conventional system for detecting the rotation synchronization phase (for example, Patent Document 1), a rotary encoder or resolver is applied. However, since this rotary encoder or resolver needs to be provided on a rotating shaft, as a high-speed rotation detecting means, It is not the best means.

  On the other hand, the rotation synchronization phase detection device 4 of the present embodiment is highly stable, that is, suppresses vibration fluctuations in the detection value of the rotation speed from only the displacement sensor without using a rotary encoder or a resolver. The high-accuracy rotation synchronization phase θ obtained can be acquired. Therefore, the magnetic bearing device 10 which is space-saving, inexpensive and stably highly accurate than before can be realized.

[Second Embodiment]
The rotation synchronization phase detection device 4 illustrated in FIG. 8 includes a change rate restriction processing unit 45 that restricts the change rate of the first rotation speed v1 or the second rotation speed v2 provided to the phase calculation unit 44.

  In the present embodiment, the rate of change of the rotational speed v is subjected to restriction processing before the rotational speed v determined in S5 of FIG. A known change rate limiting method may be applied to this limiting process. As a known change rate limiting method, for example, there is a change rate limiting method disclosed in Patent Document 2. In the control processing of this embodiment to which this restriction method is applied, for example, the rotational speed v is controlled within the specified range of the torque limiter by limiting the rate of change giving priority to the disturbance observer.

  According to the rotation-synchronized phase detection device 4 of the second embodiment described above, the rate of change is changed by the rate-of-change restriction processing unit 45 in the process in which the rotational speed v of the rotating body 2 is provided from the speed determining unit 43 to the phase calculating unit 44. Restriction processing is performed. Therefore, the change in the value of the rotation speed v when the first rotation speed v1 and the second rotation speed v2 detected by the method [1] and the method [2] are switched becomes gradual, and momentarily when the switching is performed. The pulsation of the detected value of the rotational speed v is suppressed. Therefore, in addition to the effects of the first embodiment, it is possible to detect the rotational speed v with higher stability, and to detect the rotational synchronization phase θ of the rotating body 2 more accurately and stably.

DESCRIPTION OF SYMBOLS 1x, 1y ... Electromagnet 2 ... Rotor 3 ... Current control part 4 ... Rotation synchronous phase detection apparatus 41 ... First speed detection part 42 ... Second speed detection part 43 ... Speed determination part 44 ... Phase calculation part 45 ... Change rate limiting processing unit 10 ... magnetic bearing device

Claims (4)

A first speed detector for detecting a first rotational speed of the rotating body based on a zero cross period of one radial displacement of the rotating body that floats magnetically and the other radial displacement orthogonal to the one radial direction; ,
Based on the displacement in the magnetic flux direction when the displacement in the direction orthogonal to the magnetic flux direction of the rotating body obtained by coordinate conversion based on the displacement in the one radial direction and the displacement in the other radial direction is 0 A second speed detector for detecting a second rotational speed of the rotating body;
A rotation synchronization phase detection apparatus comprising: a phase calculation unit that calculates a rotation synchronization phase of the rotating body based on either the first rotation speed or the second rotation speed. When the first rotation speed is accelerating, the first rotation speed and the rotation speed to be provided to the phase calculation unit based on the difference between the first rotation speed and the maximum second rotation speed While selecting one of the second rotation speeds, when the first rotation speed is decelerating, the phase calculation is performed based on the difference between the first rotation speed and the minimum second rotation speed. The rotation synchronization phase detection device according to claim 1, further comprising a speed determination unit that selects one of the first rotation speed and the second rotation speed as a rotation speed to be provided to the unit. The rotation synchronization phase detection apparatus according to claim 1, further comprising a change rate limiting processing unit that limits a change rate of a rotation speed provided to the phase calculation unit. The rotation synchronization phase of the rotating body is detected based on one radial displacement of the rotating body magnetically levitated by the electromagnet and the other radial displacement orthogonal to the one radial direction. The rotation-synchronized phase detection device according to item 1,
A magnetic bearing device comprising: a current control unit that controls an excitation current provided to the electromagnet based on the one radial displacement, the other radial displacement, and the detected rotation synchronization phase.

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