A reliable model of an elevator’s vertical motion is of tremendous value in many aspects of elevator design, installation and service. The challenges in developing and validating a dynamic model for an elevator arise from the large size of the dynamic system involved, its position-dependent or time-varying nature and from the limited number of variables available for measurement.
An example of vertical motion is from the geared traction elevators. They achieve their vertical motion from an AC electric motor that is directly coupled to a worm (gear) shaft. The worm gear in turn rotates a ring gear. A drive sheave or pulley is attached to the ring gear. Steel cables or “hoist ropes” run from the top of the elevator car, over the drive sheave, to the top of the counterweight. The downward force caused by gravity acting on the weight of the car and counterweight creates friction between the steel cables and the drive sheave, thus creating “traction.” As the drive sheave rotates, the elevator car is raised or lowered.