Analysis of the Frequency Behaviour for Vertical Motions in Elevator Systems

Knowledge about the transfer function and the frequency behaviour for elevator systems is of interest for several aspects. For example, to analyse the sensitivity of the cabin to specific frequencies, which may cause mechanical and acoustical vibrations and thus results in discomfort. In addition, the frequency behaviour is of high interest while applying control algorithms for active vibration suppression or cabin position control [1]. Due to the different suspension rope length, depending on the cabin’s position, the transfer function is time-varying during the travel on one hand. On the other hand, it depends on the cabin’s payload. Existing literature concentrates on the frequency response analysis lower than 20 Hz [2], while this paper concentrates on methods and measurement signals which are precise enough to determine the frequency behaviour up to 100 Hz. In addition, a wide range of elevator constructions exists, which differs for example in roping, number of rope pulleys or the location of isolation elements. For the model validation of numerous elevator constructions, a method is needed, which may be easily applied to many elevators and preferably does not need additional measurement sensors. At first, this paper describes different measurement possibilities and input shapes for the identification process. It is analysed which input and output signal produce meaningful transfer functions and how they can be compared to each other. Afterwards the different identification methods are described, which is followed by the description how the experiments have been conducted at a real elevator. Finally, the frequency behaviours are discussed, which are obtained at a low-rise elevator for different cabin positions and payloads.