Control of a magnetic bearing device is addressed by parameter varying control. Within the structure of decentralized PID controllers we compare linear interpolation and switching strategies with and without hysteresis. Piecewise LPV decentralized PID controllers are found to be an interesting alternative. Our method exploits the possibility to pre-compute for every parameter value an H∞ optima...

A rotor supported on active magnetic bearings (AMBs) is levitated inside an air gap by electromagnets controlled in feedback. In the event of momentary loss of levitation due to an acute exogenous disturbance or external fault, reestablishing levitation may be prevented by unbalanced forces, contact forces, and the rotor’s dynamics. A novel robust control strategy is proposed for ensuring levit...

Experimental results demonstrate that μ synthesis provides an excellent tool for increasing the dynamic stiffness of thrust magnetic thrust bearings. Accurate system modeling and appropriate uncertainty descriptions are critical to obtaining such results and are described in detail. Both complex μ and mixed μ synthesis were used to design controllers. The performance of the μ controllers is com...

The equations of motion of a two-degrees-of-freedom mass in a magnetic bearing are non-linear in displacement, with geometric coupling of the magnetic bearing coupling the horizontal and vertical components of rotor motion. The non-linear forced response is studied in two ways: (1) using imbalance force; (2) using non-imbalance harmonic force. In the forced response, only periodic motion is inv...

Acknowledgments My special thank goes to my advisor Dr. Marcio S. de Queiroz. I thank him for all his continued support in all stages of this project. I would also like to extend my sincere gratitude to my committee members Dr. Kemin Zhou and Dr. Yitshak Ram for their valuable support and guidance. Abstract A solution to the problem of AMB control with reduced electrical power losses will be pr...

In this paper the development of mathematical model of voltage-input and current-input active magnetic bearing (AMB) system in deterministic form is presented. The AMB system, which is open-loop unstable and highly coupled due to nonlinearities inherited in the system such as gyroscopic effect and mass imbalance, requires a dynamic controller that can stabilize the system. In order to synthesiz...

In this paper, we address the problem of controlling an active magnetic bearing with reduced ohmic power losses. A solution is proposed which introduces an exponentially decaying bias ßux in the nonlinear control law. To avoid control singularities, the closed-loop system is exponentially stabilized at a faster rate than the bias decay. In the steady state, the proposed controller has zero bias...

Recovery of iron from iron-rich diasporic bauxite ore via reductive roasting followed by magnetic separation has been explored recently. However, the efficiency of alumina extraction in the non-magnetic materials is absent. In this paper, a further study on the digestion of alumina by the Bayer process from non-magnetic material obtained after magnetic separation of reduced iron-rich diasporic ...

OBJECTIVES To investigate the resetting effects of transcranial magnetic stimulation over motor cortex on orthostatic tremor, characterized by high-frequency electromyographic discharges in weight-bearing muscles, particularly orthostatic tremor (OT) associated with cerebellar cortical atrophy; and to compare our results with those obtained in primary OT, for which transcranial magnetic stimula...

A Multivariable Control System is designed for an Electromagnetic Bearing and Rotating Shaft System. The Linear Quadratic Gaussian with Loop Transfer Recovery (LQG/LTR) methodology is used to design a robust Model Based Compensator (MBC). The electromagnetic bearing consists of an electromagnetic actuator, operated in magnetic "attractive" force mode, with permanent magnet biased coils. The per...