The Modelling and Simulation of the Dynamic Behaviour of a Lift Car-Rope Suspension System

Vibration may influence all lift components and affect the ride quality of a lift. In particular, lateral and longitudinal vibrations of hoist, compensating ropes and travelling cables can occur and car vibrations may take place. The design methodology of lift systems requires performing a thorough dynamic analysis in order to predict the dynamic loads and to evaluate the response of the system during various operational modes. The dynamic response of the lift system may be caused by a number of sources of excitations such as the inertial load due to the lift system acceleration/deceleration profile, periodic excitation caused by building sway, excitation at the sheave from the drive machine and excitation at the car due to the car-guide rail interaction. These various sources of excitations may lead to an adverse dynamic behaviour of the lift system due to its nonlinear and nonstationary nature. The aim of this research is to describe, analyse and appraise the dynamic behaviour of a lift car-rope suspension system under various operational conditions. The objectives of this thesis are to establish valid techniques that can be used to model the lift car-rope suspension system, to derive a nonstationary and nonlinear mathematical model that describes the dynamic behaviour of the lift car-rope suspension system and to develop an efficient computer model; which can be employed to simulate and predict the dynamic response of the lift car-rope suspension system. A mathematical model that describes the motion of the lift car-rope suspension system in a lift installation has been derived. An algorithm to account for the nonstationary and nonlinear nature of the lift car-rope suspension system was developed. Various linear and nonlinear phenomena were observed. The nonstationary and nonlinear behaviour of the lift car-rope suspension system has been demonstrated through computer simulation. The results show that nonlinear coupling may lead to extensive modal interactions in the system. Experimental tests were carried out in order to validate the model and the techniques which were used. Thus a valid model was developed to analyse the dynamic behaviour of a lift car-rope suspension system and consequently to predict various linear and nonlinear resonance phenomena and to prevent unwanted vibrations.