The modelling, simulation and experimental testing of the dynamic responses of an elevator system

Vertical vibrations affect passenger comfort during an elevator travel. This work presents the results of a study of vertical vibrations caused by torque ripple generated at the elevator drive system. Tests are performed on a 1:1 roping configuration laboratory model; the acceleration response at the suspended masses and at the drive machine, the machine shaft velocity and the three phase current intensities supplied to the machine are measured during several travels. The machine torque is estimated from the current intensities. Anon stationary model of an elevator is then developed to simulate the acceleration response. The model accommodates the drive system dynamics. The machine parameters are computed by means of the Finite Element Method simulation software FLUX. FLUX computes the amplitudes of the torque ripple and the radial forces at the air-gap. As the torque ripple computed by FLUX is smaller than that torque estimated from the machine currents, the latter is added as a perturbation to the controller generated torque. With respect to the car– counterweight–sheave–ropes assembly a five degree-of-freedom lumped-parameter model (LPM) and a novel distributed-parameter one (DPM) are developed. The elevator dynamics represented by the DPM is described by a partial differential equation set that is discretised by expanding the vertical displacements in terms of the linear stationary mode shapes of a system composed of three masses constrained by the suspension rope. The models are implemented in the MATLAB/Simulink computational environment and the system response is determined through numerical simulation. It is shown that the LPM forms a good approximation of the DPM. The frequency content of the computed and measured accelerations demonstrates that the elevator car vibrates at frequencies generated at the machine, especially when they are close to the system natural frequencies.