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Control of an Active Magnetic Bearing-Rotor System


A common disturbance encountered in rotor operations is the sinusoidal disturbance caused by mass unbalance. This natural phenomenon imparts a force on the rotor with frequency equal to the rotor speed. To help regulate the rotor and reject this disturbance, many researchers have investigated the use of Active Magnetic Bearings (AMBs) and digital control as a viable replacement for the traditional rotary journal bearing. The non-contact nature of AMBs allows for greater speeds and opens the possibility for new applications. Stability is an important design consideration as is the ability to provide disturbance rejection for varying rotor speeds and over the rotor's operational range.

An internal model principle type controller is implemented in this dissertation for its premium on stability and straightforward design parameters of the controller characteristics. The plug-in structure provides narrow performance enhancements while minimally disturbing the underlying stability of the closed-loop system. The internal model is realized through cascaded notch filters which allows for intuitive design of the internal model. Stability can easily be satisfied through a filter design formulation. These control strategies are applied on an AMB-rotor system with great rejection performance.

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