On July 16, 1993, the elevator in Yokohama's 70-story Landmark ToweT, operating at a peak speed of 45 km/hr {28 mph), was inaugurated as /.he fastest super-fast elevator. To Teach such a speed without leaving passengers' stomachs on the ground flo err, the lift accelemtes f oT longer periods, rather than more precipitously. Going up it reaches full speed only at the 27th floor; it begins to decelerate 15 floor-s later. The result is a peak acceleration similar to that of other skyscraper elevators-a bit less than a tenth of the force of gravity.
Admirable ingenuity has gone into making this safe and comfortable. Special ceramic brakes had to be developed; ·imn ones would melt. Computercontrolled systems damp out vibrations. The lift has been streamlined to reduce wind noise as it hurtles up and down. One proposed system for the elevator's vertical position is shown in the following diagram.
R(s) +~ _ ~0---- Desired _ vertical position I Controller Elevator dynam1cs (K+l) 1 s(s 2+3s+3)
Elevator Vertical Position Control Determine the range of K joT a stable system.
Y(s)
Ve rtical po sition Problem