Methods and apparatus for closed-loop control of magnetic bearings
AssigneeNoise Cancellation Technologies, Inc.
InventorsAlan R. D. Curtis, James E. Joseph
Life of this patent
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Abstract
A magnetic bearing control system for a rotating shaft, for example, includes a plurality of electromagnets disposed around and in close proximity to the surface of the shaft. The control system provides a bias current to the electromagnets to maintain the shaft in a null position. Levitation of the shaft is controlled by a levitation controller, and disturbance rejection is effected by a disturbance rejection controller. Flux sensors, suitably located near the electromagnets, determine the magnitude and polarity of the flux resident in the gap between each electromagnet and the shaft. The controller determines the size of the gap based on the flux and generates a corresponding control signal to maintain the position of the shaft within the bearing.
Claims39
A control system for use in controlling a magnetically permeable body movably mounted within a plurality of magnetic bearings, each of the magnetic bearings comprising an electromagnet having a coil wound about a magnetically permeable core integral with at least one of the magnetic bearings, wherein each of the magnetic beatings is disposed adjacent and in close proximity to the body, forming a gap intermediate the body and the electromagnet, wherein electric current flowing through the coil generates magnetic flux having a given polarity and magnitude permeating the body through the core and across the gap, comprising:
- a first flux sensor for generating indicia of flux resident in said gap;
- and
- a controller for sampling said flux indicia and providing at least one control signal to said electromagnet to control the current flowing through said coil and the position of the body based on at least said flux indicia, said controller including
- a levitation controller for controlling levitation of the body based on at least said flux indicia;
- and
- a disturbance rejection controller for effecting disturbance rejection of the body based on at least said flux indicia.
The control system of 5, wherein said controller provides said second signal to the second electromagnet based on at least said flux indicia generated by said first sensor.
A method of controlling a magnetic bearing supporting a magnetically permeable rotating shaft wherein the magnetic bearing includes an electromagnet having a coil wound about a core disposed adjacent and in close proximity to the shaft to form a gap between the electromagnet and the shaft, wherein current flowing in the coil generates magnetic flux permeating the core and the shaft across the gap, comprising the steps of:
- sensing the flux resident in the gap;
- providing a control signal to the electromagnet to control the current flowing in the coil based on at least the sensed flux, comprising the steps of:
- providing a levitation control signal to the electromagnet to control levitation of the shaft based on at least the sensed flux;
- and
- providing a disturbance rejection control signal to the electromagnet for effecting disturbance rejection of the shaft based on at least the sensed flux.
Dependencies are inferred from the claim text.