Thesis (PH.D.) - Cairo University - Faculty Of Engineering - Department Of Aerospace Engineering

Contact - free levitation of rotor by means of active magnetic bearing has been a research topic for more than two decades During this time , active magnetic bearings have evolved into an industry product that due to its numerous advantages over conventional bearing technology Now a day this device has many practical applications Because magnetic bearing systems are fast and unstable , a controller is required to return the rotor to its equilibrium position and eliminate disturbances at any time So in our thesis we deal with the control design problem for a vertical shaft - type magnetic bearing system The fundamental equations of motion of the rotor were obtained using Euler's angles and Lagrange equations , together with equations representing the electromagnet forces and control voltage Two controllers for linear discrete - time are presented The first is a single input single output (SISO) decentralized controller using relative Gain Array method (RGA) to choose suitable input and output pairs Several methods for pole placement are used , and a comparison between these methods is done to get the best for controller design The second is a centralized controller using both Linear Quadratic Regulator (LQR) and robust pole placement Also a comparison between the two methods is done to select the superior one A minimum order observer - based discrete - time control system is designed to estimate the motion of the rotor , in case we cannot measure all the state variables Simulation with MATLAB program is used to test the magnetic bearing system The controller system is joint to both linear and nonlinear models

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