Balance survey / analysis of vertical transport installations using the Nyquist stability criterion

Abstract

Operation of vertical transport installations is based on adjustable electrical drive systems which must ensure the technical conditions regarding the variation in time of the speed, the current of the main motors and the accelerations at start and brake phases. Electric drives are part of the fast process of automation equipment. In the case of a vertical transport installation, speed is the characteristic which has to be controlled in command phase, while the dependent factor is the tachograph. The adjustment determines the dependence of the quantity in the process – based on a default law - with respect to the independent quantities and also to the process dependents, thus reducing the influence of the perturbations to the process. There are different ways to define the stability of an automatic system. The balance survey / analysis also approaches the determination of the functions of variation in time of the main actuation motor current and speed (main motor rpm), at the moments of starting the vertical transport installation, and the study of the variation in time of the speed in the case of a load shock. To perform calculations needed for stability assessment and draw all the diagrams a Turbo C 2.0 program was written by the authors.