JP4003338B2 - Magnetic bearing control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a magnetic bearing.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, the output of a displacement sensor that detects the displacement of a rotating body supported by a magnetic bearing is compared with a predetermined value by an analog circuit, and the presence / absence of a displacement abnormality is determined based on the comparison result (for example, a special feature). (See Kaihei 2-221597).
However, since the characteristics of an analog circuit are determined by circuit components, it has been difficult to arbitrarily change the determination criterion for the presence or absence of abnormality. Therefore, the magnetic bearing control device including such an analog circuit can be applied only to the same rotating body, and if the rotating body is different, the hardware must be changed.
[0003]
In view of the conventional problems as described above, an object of the present invention is to provide a control device for a magnetic bearing in which an abnormality determination standard can be easily changed.
[0004]
[Means for Solving the Problems]
The control apparatus for a magnetic bearing according to the present invention includes a displacement sensor that detects a displacement of a rotating body that rotates while being supported by the magnetic bearing, a rotation sensor that outputs a pulse according to the number of rotations of the rotating body, and the displacement An A / D converter that converts the output of the sensor into a digital signal and an electromagnet control of the magnetic bearing, and has a memory in which a limit value is stored, and the comparison determination of the limit value and the digital signal And a digital signal processor that outputs a signal notifying of the occurrence of a displacement abnormality , and the digital signal processor detects the number of rotations of the rotating body based on the output of the rotation sensor, and is detected The limit value is changed according to the number of rotations (Claim 1).
In the magnetic bearing control device configured as described above, the digital signal based on the output of the displacement sensor is compared with the limit value stored in the memory by the digital signal processor, and the occurrence of an abnormality in the displacement is determined based on the determination result. A signal indicating that is output. Here, the abnormality criterion is easily changed by changing the limit value . Further, the abnormality determination reference can be changed by changing the limit value according to the number of rotations of the rotating body. In addition, an analog circuit for abnormality determination is not required.
[0005]
In the control apparatus (claim 1), a digital signal processor, even those that outputs a signal indicating the abnormality of the load electromagnet control signal output from the self compared to value where it was stored in the memory Good (claim 2).
In this case, the load abnormality can be monitored by the digital signal processor without adding hardware. Further, by changing the predetermined value, the abnormality determination criteria is easily changed.
[0007]
In the control device (Claim 1 or 2), the digital signal processor may have means for delaying the output of a signal notifying the occurrence of an abnormality for a settable predetermined time (Claim 3 ).
In this case, the digital signal processor outputs a signal notifying the occurrence of an abnormality when the abnormal state continues for a predetermined time set freely.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing the configuration of a magnetic bearing control device according to an embodiment of the present invention. In the figure, a rotating body 1 such as a turbo molecular pump is driven by a motor 11 and supported at a high speed while being supported in a non-contact manner by a magnetic bearing. The displacement of the rotating body 1 during rotation is detected by the displacement sensor 2. The analog displacement signal output from the displacement sensor 2 is converted into a digital displacement signal Sd by an A / D converter 3 and input to a DSP (digital signal processor) 4. The DSP 4 outputs a digital control signal Sc for electromagnet control of the magnetic bearing based on the input digital displacement signal Sd. The D / A converter 5 converts this into an analog current command signal and supplies it to the amplifier 6. The amplifier 6 gives a control current obtained by amplifying it to the electromagnet 7 of the magnetic bearing. In response to this, the electromagnet 7 controls the position of the rotating body 1.
[0009]
The DSP 4 incorporates a memory for storing various predetermined values in addition to the execution program. The memory stores a limit value Sd _lim corresponding to an allowable limit value of displacement for the digital displacement signal (hereinafter referred to as displacement signal) Sd, and also the digital control signal (hereinafter referred to as control signal). ) Regarding Sc, a limit value Sc _lim corresponding to the maximum exciting current that can be supplied to the electromagnet 7 is stored. Since the limit value Sd _lim of the displacement signal has an allowable limit value that varies depending on the rotational speed of the rotating body 1, a plurality of values are stored as a data table corresponding to the rotational speed. In the memory, count numbers C1 and C2 described later are set and stored.
[0010]
The rotation sensor 8 arranged in the vicinity of the rotating body 1 outputs a pulse according to the number of rotations of the rotating body 1, and the output pulse is input to the DSP 4. The DSP 4 receiving the pulse obtains the rotational speed of the rotating body 1 from the reciprocal of the time interval of the pulse input, for example.
On the other hand, the rotational speed command signal from the DSP 4 is sent to the inverter 10, and the inverter 10 controls the rotation of the motor 11 based on this signal.
A display device 9 for displaying information held by the DSP 4 is connected to the DSP 4. The DSP 4 is also connected to a remote personal computer 13 via the serial communication board 12 as necessary. Accordingly, the DSP 4 information can be displayed on the personal computer 13.
[0011]
Next, the abnormality monitoring operation by the magnetic bearing control device will be described.
FIG. 2 is a flowchart showing an abnormality monitoring operation related to the displacement signal Sd and the control signal Sc. The routine shown in the flowchart is executed by the DSP 4 at predetermined sampling times. First, in step 101, the DSP 4 reads the rotation speed N and the displacement signal Sd based on the outputs of the rotation sensor 8 and the displacement sensor 2, respectively. Next, the DSP 4 reads out the displacement signal limit value Sd _lim corresponding to the rotational speed N from the memory and compares it with the displacement signal Sd (step 102).
[0012]
If the displacement signal Sd is equal to or less than the limit value Sd _lim in step 102, the DSP 4 sets the count number C1 of the internal counter to 0 (step 103) and proceeds to the next step 107. On the other hand, if Sd> Sd _lim is satisfied, the DSP 4 increments the count number of the internal counter by 1 (step 104), and determines whether or not the resulting count number C1 is equal to or smaller than the predetermined count number Cx (step 105). ). Here, the DSP 4 proceeds to step 107 if C1 ≦ Cx. The count number Cx in step 105 means that a predetermined time has elapsed since the state of Sd> Sd _lim has been reached, and the number of times corresponding to a grace time for identifying a displacement abnormality is set. If Sd ≦ Sd _lim is satisfied in step 102 while the count number C1 is increasing, the count number C1 is reset in step 103. Therefore, in order for the determination result in step 105 to be no, it is necessary that the state of Sd> Sd _lim continues for a predetermined time.
[0013]
If C1> Cx at step 105, the DSP 4 outputs a displacement abnormality (step 106), and then proceeds to step 107. Displacement abnormality is output from the DSP 4 to the display device 9 and also to the personal computer 13 via the serial communication board 12. The personal computer 13 displays a displacement abnormality and records its history. By these, the monitor can detect the abnormality of displacement.
[0014]
Next, in step 107, the DSP 4 determines whether or not the control signal Sc output by itself is equal to or less than the limit value Sc _lim stored in the memory (step 107). Here, the control signal Sc is, if its is limit value Sc _lim or less, DSP 4 (step 108) the count number C2 of the internal counter as 0, completing the process of the present routine. On the other hand, if Sc> Sc _lim , the DSP 4 increments the count number C2 of the internal counter by 1 (step 109), and determines whether or not the resulting count number C2 is equal to or less than the predetermined count number Cy (step). 110). Here, the DSP 4 ends the process if C2 ≦ Cy. The count number Cy in step 110 means that a predetermined time has elapsed since the Sc> Sc _lim state is reached, and the number of times corresponding to a grace time for identifying a load abnormality is set. If Sc ≦ _Sclim is satisfied in step 107 while the count number C2 is increasing, the count number C2 is reset in step. Therefore, in order for the determination result in step 110 to be no, it is necessary that the state of Sc> Sc _lim continues for a predetermined time.
[0015]
If C2> Cy in step 110, the DSP 4 outputs a load abnormality (step 111) and ends the process. The load abnormality is output from the DSP 4 to the display device 9 and also to the personal computer 13 via the serial communication board 12. The personal computer 13 displays a load abnormality and records its history. Thereby, the supervisor can perceive abnormality of load.
[0016]
Each of the limit values Sd _lim and Sc _lim can be set to a desired value by changing the value stored in the memory of the DSP 4. Therefore, the abnormality determination reference can be easily changed, and the same hardware control device can be applied even if the rotating body to be controlled is different. Similarly, the count numbers Cx and Cy can be set to desired values. Accordingly, it is possible to arbitrarily set the response of abnormality determination.
Further, in the above embodiment, the increase number is 1 in the count in step 104 of FIG. 2, but the increase number may be K, and C1 = C1 + K. Then, if the value of K is increased or decreased in accordance with the value of (Sd−Sd _lim ), the time limit characteristic can be obtained. If the degree of excess of displacement is small, the degree of excess of displacement is relatively slow. When is large, an output of a displacement abnormality can be generated quickly. The same applies to the processing in step 109.
[0017]
Next, another example of displacement abnormality monitoring will be described. FIG. 3 is a flowchart showing an abnormality monitoring operation related to the amount of swing (swing) of the rotating body 1. The routine shown in the flowchart is executed by the DSP 4 at predetermined sampling times. The amount of swing is the radial displacement during rotation of the rotator 1. In particular, the rotator 1 enters into inertial center control as the rotational speed rises, and rotates about the center of gravity. This is the displacement after starting to stabilize to a predetermined value. This predetermined value corresponds to the amount of eccentricity of the rotational shape center S with respect to the center of gravity G which is the rotation center of the rotating body 1. The change in the swing amount occurs, for example, when the product in the turbo molecular pump gradually adheres to the wing portion of the rotating body 1. When the product adheres excessively, the rotating body 1 loses its rotational balance and reaches a touchdown. In order to detect such a situation in advance, the abnormality monitoring operation shown in FIG. 3 is performed.
[0018]
In FIG. 3, the DSP 4 reads the number of rotations of the rotating body 1 based on the output pulse of the rotation sensor 8 in step 201. Subsequently, the DSP 4 determines whether or not the read rotational speed has reached a predetermined rotational speed Ns (step 202). The predetermined rotational speed Ns is the rotational speed at which the rotating body 1 is recognized to have entered the inertial center control. Immediately after the start of rotation, the predetermined rotational speed Ns has not yet been reached, so the answer is no and the DSP 4 finishes the first process of this routine. When the rotation speed of the rotating body 1 reaches the predetermined rotation speed Ns in the second and subsequent steps 202, the DSP 4 proceeds to step 203 and reads the displacement signal Sd based on the output of the displacement sensor 2.
[0019]
Next, the DSP 4 compares the read displacement signal Sd with the specified value Sth (step 204), and when the value of the displacement signal Sd is equal to or less than the specified value Sth, the processing is finished. If the value of the displacement signal Sd exceeds the specified value Sth, a warning signal is output (step 205). Here, the specified value Sth is a value corresponding to a predetermined amount larger than the normal displacement amount in the inertial center control, and if this value is exceeded, the rotating body 1 may be touched down. The warning signal is output to the display device 9 and the personal computer 13 as in the case of step 106 or 111 in FIG. Thereby, the supervisor can detect an abnormality in the swing amount and can take appropriate measures such as rotation stoppage.
[0020]
【The invention's effect】
The present invention configured as described above has the following effects.
According to the magnetic bearing control device of the first aspect, the digital signal based on the output of the displacement sensor is compared with the limit value stored in the memory by the digital signal processor, and the occurrence of the abnormality of the displacement is based on the determination result. Therefore, the abnormality determination criterion can be easily changed by changing the limit value . As a result, the same hardware control device can be applied even if the controlled rotating body is different. Further, since the abnormality determination standard can be changed according to the rotation speed, appropriate abnormality determination can always be performed regardless of the rotation speed. Further, since an analog circuit for determining an abnormality is not required, it contributes to cost reduction of the control device.
[0021]
According to the magnetic bearing control device of the second aspect, it is possible to monitor a load abnormality without adding hardware. Further, by changing the Tokoro value, it is possible to easily change the failure determination reference.
[0023]
According to the magnetic bearing control device of the third aspect , the delay time until the signal for notifying the occurrence of abnormality can be freely set, so that the response of abnormality determination can be adjusted.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a magnetic bearing control device according to an embodiment of the present invention.
FIG. 2 is a flowchart showing an abnormality monitoring operation regarding displacement abnormality and load abnormality.
FIG. 3 is a flowchart showing an abnormality monitoring operation related to a swing amount of a rotating body.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotating body 2 Displacement sensor 3 A / D converter 4 DSP
7 Electromagnet 8 Rotation sensor

Claims (3)

A displacement sensor that detects the displacement of the rotating body that rotates while being supported by the magnetic bearing;
A rotation sensor that outputs a pulse according to the number of rotations of the rotating body;
An A / D converter for converting the output of the displacement sensor into a digital signal;
A performs the electromagnet control of the magnetic bearing has a memory in which the limit value has been stored, based on the comparison determination between the digital signal and the limit value, and outputs a signal indicating the abnormality of the displacement digital With a signal processor ,
The digital signal processor detects the number of rotations of the rotating body based on the output of the rotation sensor, and changes the limit value in accordance with the detected number of rotations. . Said digital signal processor, control of the magnetic bearing of claim 1, wherein the outputting the signal indicating the abnormality of the load electromagnet control signal output from the self compared to value where it was stored in the memory apparatus. 3. The control apparatus for a magnetic bearing according to claim 1, wherein the digital signal processor has means for delaying the output of the signal notifying the occurrence of the abnormality for a settable predetermined time .

Images