Building elevators are limited to about 800 meters. Above that height, elevator cables become too thick and too heavy for practical use. One solution is to eliminate the cable. The key to the cordless elevator is the linear motor technology now being applied to the development of magnetically levitated rail transportation systems. Under consideration is a linear synchronous motor that propels a passenger car along the track like guide way running the length of the elevator shaft. The motor works by the interaction of an electromagnetic field from electric coils on the guide way with magnets on the car [28].
If we assume that the motor has negligible friction, the system may be represented by the model shown in Figure AP9.7. Determine K so that the phase margin of the system is 45°. For the gain K selected, determine the system bandwidth. Also calculate the maximum value of the output for a unit step disturbance for the selected gain.
