Further study of linear PMSM driven ropeless lifts with consideration of imperfections by simulation

Abstract

To provide a satisfactory lift service to super high-rise buildings (while maintaining a small footprint for the lift hoistways), ropeless multi-car per hoistway system may be the trend. In our previous paper, a simplified machine model and two primitive controllers were adopted and various features of such a ropeless lift car driven by a linear permanent magnet synchronous motor were illustrated by simulation. In this paper, imperfections including pole saliency, various types of friction such as Coulomb, viscous and Stribeck friction, cogging force and end-effect, etc. were considered. The controllers, control interval and simulation interval were improved in both quantity and quality to arrive at a controllably stable operation. For safety during a genuine power failure, the free-falling terminal speed was estimated both by analytical calculation and computer simulation with consideration of such imperfections. It was confirmed that a desirable operation could be achieved by having smaller and practical winding resistance and inductances, larger and practical permanent magnet magnetic flux, and an optimal pole pitch. This paper could be considered an enhanced version of the pervious paper in that the illustration is more realistic when imperfections are considered. It is hoped that experimenters would further verify the findings in this paper so that such technology could become popularly employed in the future lift industry. Practical application: Multi-dimensional multi-car in a hoistway configuration involving linear permanent magnet synchronous machines would become popular in the near future. This paper introduces a more comprehensive mathematical framework by taking into account of the imperfections in the design and evaluation of controllers as well as the drive performance for a multi-car lift system. The results may give lift designers and researchers a hint on how to design the machines and the controllers with the consideration of imperfections in terms of winding design with variation in resistance, inductance, magnetic field strength, pole pitch, saliency and different types of friction. The paper is aimed at providing lift designers and researchers with a more realistic picture to welcome the new age of multi-car multi-dimensional lift technology.