Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-04-08
2001-04-10
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
Reexamination Certificate
active
06215218
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
The present invention relates to a control magnetic bearing which is used in a turbo-molecular pump and rotates a rotator without the rotator and the magnetic bearing making any physical contact.
2) Description of Related Art
A control magnetic bearing of this type comprises a mechanical main unit and a controller connected to the main unit by way of a cable.
The mechanical main unit comprises a plurality of displacement sensors for detecting axial and radial displacements of the rotator; plural sets of magnetic bearings for supporting the rotator in both the axial and the radial directions using attractive magnetic forces generated by a pair of electromagnets that constitute each of the magnetic bearings; an electric motor for rotating the rotator; and a protective bearing for limiting a movable range of the rotator. The protective bearing limits the movable range of the rotator in both the axial and radial directions and mechanically supports the rotator when the magnetic bearings lose magnetic forces to support the rotator.
The controller controls an excitation current supplied to the electromagnets, in response to signals output form the displacement sensors and through the use of predetermined control parameters.
The mechanical main unit of such magnetic bearing differs in type according to the application of the magnetic bearing. When the mechanical main unit is changed to another type, control parameters used by the controller must also be changed. The type of the mechanical main unit differs according to the characteristics of the rotator (such as the weight, characteristics frequency, and position of the center gravity of the rotator), the type of electromagnet, and the positional relationships among the rotator, the electromagnets, and the displacement sensors. For this reason, traditionally there have been prepared a plurality of different types of mechanical main units and a plurality of different types of controllers employing different control parameters. The mechanical main units and the controllers are used in combination according to the application.
However, such a traditional practice is uneconomical in that it requires plural types of controllers to conform with the types of the mechanical main unit. The erroneous combination of the mechanical main unit and the controller may make unstable the positional control of the rotator by the magnetic bearings control since parameters set in the controller are not suitable for use with the magnetic bearing. To prevent such unstable positional control of the rotator, desirably the controller automatically identifies the type of the mechanical main unit when it is connected to the mechanical main unit, and checks whether or not the controller is suitable for use with the thus-connected mechanical main unit. The magnetic bearings primarily employ an analog PID control method as a control method for the controllers. Further, the controllers have only the function of outputting a signal to the electromagnets in response to the signals received from the displacement sensors. Thus, the controllers have been unable to identify the type of the mechanical main unit.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a control magnetic bearing capable of automatically identifying the type of a mechanical main unit.
Another object of the present invention is to provide a control magnetic bearing capable of changing a control parameter SET according to the type of a mechanical main unit.
Accordingly, the present invention provides a control magnetic bearing including a mechanical main unit which has a plurality of displacement sensors for detecting displacement of a rotator and a plurality of sets of magnetic bearings for supporting the rotator in a predetermined target position in a non-contacting manner by means of the magnetic forces of attraction generated by a pair of electromagnets that constitute each of the magnetic bearings; and a controller having electromagnetic control means for controlling an excitation current supplied to the electromagnets on the basis of signals output from the displacement sensors, wherein
the electromagnet control means has digital processing means which can be programmed by means of software and outputs a digital control signal for controlling the excitation current on the basis of the digital displacement signal that is calculated from the signals output from the displacement sensors and represents the displacement of the rotator; and
the digital processing means has identification means for identifying the type of the mechanical main unit.
The present invention also provides a control magnetic bearing including a mechanical main unit which has a plurality of displacement sensors for detecting displacement of a rotator, and a plurality of sets of magnetic bearings for supporting the rotator in a predetermined target position in a non-contacting manner by means of the magnetic forces of attraction generated by a pair of electromagnets that constitute each of the magnetic bearings; and a controller having electromagnet control means for controlling an excitation current supplied to the electromagnets on the basis of signals output from the displacement sensors, wherein
the electromagnet control means has a nonvolatile storage device and digital processing means which can be programmed by means of software, and outputs a digital control signal for controlling the excitation current on the basis of the digital displacement signal that is calculated from the signals output from the displacement sensors and represents the displacement of the rotator;
the nonvolatile storage device stores control parameters for identification purposes and a plurality of sets of operation control parameters corresponding to the individual types of mechanical main units; and
the digital processing means has identification means for identifying the type of the mechanical main unit and selecting the set of control parameters corresponding to the result of such identification from the nonvolatile storage device.
By means of the foregoing configuration, the type of the mechanical main unit can be identified, and, on the basis of the result of such identification, a check can be made as to whether or not the controller is compatible with the mechanical main unit.
On the basis of the result of identification of the mechanical main unit, an operation control parameter set suitable for the mechanical main unit can be automatically selected from the plurality of sets of operation control parameters stored in the nonvolatile storage device, an subsequently used. As a result, one type of controller may be used with a plurality of types of mechanical main units, thus reducing the number of types of controllers provided to the magnetic bearing and hence rendering the magnetic bearing economical.
The digital processing means capable of being programmed by means of software comprises, e.g., a microprocessor (MPU) or a digital signal processor. The digital signal processor designates hardware which enables input and output of a digital signal, can be programmed by means of software, and is specifically designed so as to be able to perform high-speed processing operations. The digital signal processor will be hereinafter simply abbreviated “DSP.”
Flash memory, EPROM, or any other suitable storage device may be used as the nonvolatile storage device.
According to one aspect of the present invention, the identification means changes the target position after the rotator has been supported in the target position in a non-contacting manner. On the basis of the response by the rotator, the identification means identifies the type of the mechanical main unit.
Response—which denotes the action of the rotator when the target position of the rotator is changed—varies according to the type of the mechanical main unit. Consequently, the type of the mechanical main unit may be identified by examination of the response by the rotator upon changing of the target position
Koyo Seiko Co. Ltd.
McGinn & Gibb PLLC
Tamai Karl
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