An apparatus and method for controlling the movement of an elevator
mechanism in a tape drive system. The mechanism of the present invention
employs a tachometer to detect the magnetic decoupling of a cartridge
from a cartridge reel motor. A holding torque is placed on the cartridge
reel motor. A voltage or current ramp is supplied to the elevator
mechanism, wherein the elevator mechanism raises and magnetically
decouples the tape cartridge from the cartridge reel motor. As the
coupling force is broken, the torque placed on the cartridge reel motor
causes the motor to turn. The tachometer detects the magnetic decoupling
of the cartridge from the cartridge reel motor by sensing the angular
displacement of the motor. In response, the controller decreases the
voltage or current ramp to adapt to the load reduction on the elevator
mechanism, and thereby more smoothly continue the elevator motion.