سوال ۱۶ کنکور ارشد مهندسی مکانیک ۱۴۰۲

PART C: Reading Comprehension

PASSAGE 2:

Magnetic bearings have been used to achieve noncontact suspension of a flywheel rotor, thus eliminating issues of friction and wear associated with high speed applications using mechanical bearings. The suspension is achieved through an opposing set of electromagnets between which the rotor is positioned. The position of the rotor can be controlled via the magnetic forces, and the forces can be regulated by adjusting the magnet coil voltage or current. The magnetic forces exert attractive forces on the rotor shaft, and for this reason magnetic bearings are inherently unstable and require closed loop control. A self-sensing magnetic bearing is a special type of magnetic bearing in that the rotor position information is deduced from the electromagnetic interaction between the stator and rotor. The feedback is based solely on the measured current in the electromagnets, making it possible to design the bearing system without position sensors. This results in a significant advantage because of a considerable reduction in manufacturing costs and the complexity of the system, as well as the elimination of the failure modes associated with the sensors. A self-sensing magnetic bearing with linear control was first proposed in. A linearized model of the self-sensing magnetic bearing was also developed in, but the results suggested that the proposed configuration resulted in poor robustness and disturbance rejection. Subsequent experiments have confirmed this view. In particular, disturbance to the system caused by rotor imbalance is commonly encountered, since imperfections in rotor design and manufacture cannot be avoided.

Magnetic bearings, according to the passage, are capable of ----------.