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Vibration Modeling of Gas Turbine with Possible Faults
, M.Sc. Thesis Sharif University of Technology ; Zohoor, Hassan (Supervisor)
Abstract
Vibrational modeling of a gas turbine considering simultaneous faults is considered. Faults including: unbalance, misalignment, and rotor crack are selected to be modeled. Oil film forces of hydrodynamic bearings are chosen as the supports of the rotor. Modeling starts with choosing an appropriate finite element model for the rotor which includes the effects of shear deflection, rotary inertia, gyroscopic moment, and rotor cross section variation. Modeling of unbalance is in fact a part of rotor finite element modeling. The forces that origniate form misalignment are computed using the static relations of a rigid coupling. Modeling of bearing faults along with bearing forces is performed...
Designing a Mechanism for Fault Diagnosis of Space Reaction Wheel by Piezoelectric Sensors and Neglecting the Rotor Inertia
, M.Sc. Thesis Sharif University of Technology ; Salarieh, Hassan (Supervisor) ; Zabihollah, Abolghasem (Supervisor)
Abstract
A Reaction Wheel (RW) is a torque actuator which is used for attitude control of a satellite. Reaction Wheels usually consist of a brushless DC motor which rotates a flywheel. When the flywheel is accelerated by the motor, the reaction torque of the motor applies to the base of the RW and therefore the satellite can rotate along the RW spin axis. Due to frictionless surrounding of a satellite in space, a very small disturbance in a reaction wheel structure during its function may lead to instability of satellite and decrease the satellite precision and performance. There are some important sources of disturbance in an RW. Some of them are: 1- Unbalances in wheel (offset of center of gravity...
Estimation and Control of Harmonic Disturbances Due to Mass Unbalance and Sensor Runout in Three-Pole Active Magnetic Bearing
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor) ; Manzuri, Mohammad Taghi (Co-Advisor)
Abstract
Disturbances due to sensor runout and mass unbalance are the main sources of harmonic disturbances in active magnetic bearing systems. Existence of this type of the disturbance not only causes harmonic vibrations in the system but also changes the steady-state position of the axis of rotation from the geometric center of the AMB. In this research, an observer-based control method used to estimate and reject this disturbance. Proposed integral observer estimates dc and harmonic content of the sensor runout and also estimates the states of the system at the same time with good precision. Lyapunov method is used to prove asymptotic stability of the proposed observer and demonstrated that sensor...