In this thesis, a sliding mode output feedback algorithm is proposed to control the vibration of a flexible rotor supported by magnetic bearings. The dynamic model of the rotor system is developed using Hamilton's principle. The rotor system has an infinite number of modes in theory and a method is presented for reducing the order of the system model for the development of control algorithms. The sliding mode control law is designed to be robust to uncertainties in the rotor unbalance and transient disturbances. A boundary layer has been introduced around each sliding hyperplane to eliminate the chattering phenomenon. A novel approach for determining the control gains for cases when the number of states is greater than the number of sensors is presented. A study to determine the effects of control parameters on the closed-loop performance of the rotor system is presented. The experimental apparatus for the digital implementation and validation of the control law is described including the characterization of the sensor and amplifier components. The results of modal impact and run-up tests to obtain the natural frequencies of the system experimentally are given. Furthermore, the effects of changes in the airgap of the magnets are presented with respect to the amplitude of steady-state displacement and natural frequency calculation. It is found that misidentification of the airgap can affect not only the steady-state performance, but the frequencies of the rotor system as well. In addition, experimental and theoretical responses are compared and it is shown that trends noted theoretically are also observed experimentally. Finally, conclusions and recommendations for future work are given.
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