Robust control of vertical motions in ultra-high rise elevators

Abstract

Abstract The advent of ultra-high rise buildings has brought control over elevator vertical motion to the forefront. Unlike traditional low/mid-rise elevators, relatively high speed coupled with long rope lengths result in the need to address flexible low-frequency modes and non-linear dynamics. Research in this direction has only been initiated recently and primarily confined to the industry. This paper presents a practical methodology for designing high-performance controllers for elevator vertical motion for high-rise buildings. The methodology is directed towards satisfying several needs including scalability and ease of tuning of the control system. The former is important for adaptability to different hoistways, while the latter becomes necessary on account of performance degradation, experienced due to normal wear and tear. This is accomplished by developing a scalable lumped parameter model at several ultra-high rise hoistways leading to an alternate scalable empirical model based on a few prominent features in the vertical dynamics. A tunable controller based only on these features is developed. Simulation studies show that the controller meets a set of standardized tests that are typically used for evaluating elevator performance. A problem that arises in an ultra-high rise on account of the changing nature of dynamics as the elevator transits from one floor to another leading to the question of closed-loop non-linear stability is not a feature of the standardized tests. The problem of stability around a trajectory is reduced to a multi-variable Popov criterion and the tunable controller is shown to meet these requirements