Elevator – industrial lift truck – or stationary lift for vehicle – With call registration means – Shared by plural load supports
Reexamination Certificate
2000-10-23
2001-12-11
Salata, Jonathan (Department: 2837)
Elevator, industrial lift truck, or stationary lift for vehicle
With call registration means
Shared by plural load supports
C187S386000, C187S387000
Reexamination Certificate
active
06328135
ABSTRACT:
TECHNICAL FIELD
This invention relates to operation of a group of elevators in which elevator operational parameters are adjusted in a manner to tend to increase the entropy of the system, thereby to reduce elevator car bunching.
BACKGROUND ART
Very sophisticated elevator dispatching systems have been employed to assign hall calls to elevator cars of a group in such a manner as to minimize waiting for service by intended passengers as well as to minimize impact on service to passengers already on board. Elevator systems, however, have a characteristic called “bunching” when all or most of the elevators seem to be positioned in close proximity to one another, that is, clustered about some level of the building. It is known that despite the considerable capability of the dispatchers, passenger service suffers whenever bunching occurs. To overcome this problem, there have been many attempts to provide specific algorithmic modifications to the system as a consequence of tendencies for elevator cars to become bunched, changing car assignments that have been made by the sophisticated dispatcher based on the additional information provided by the bunching algorithm. However, to the extent that information is available, it is believed clear that no algorithm designed to mitigate bunching has improved elevator service, and in fact most have caused elevator service to deteriorate still further.
DISCLOSURE OF INVENTION
Objects of the invention include reducing bunching of elevator cars in a group without altering dispatcher call assignments; reducing bunching of elevator cars in a group without causing deterioration of passenger service; and improved passenger service in an elevator group using a sophisticated dispatcher, by mitigating bunching.
This invention is predicated on the concept that small changes in some operating parameters of elevators in a group having high entropy (highly complex) operation may cause large differences in the behavior of the elevator group. This invention is also predicated on the discovery that bunching of elevator cars in a group is minimized when elevator system operation exhibits high entropy. This invention is further predicated on the discovery that moderate traffic is the most complex while very light and very heavy traffic exhibit less complexity. This invention is additionally predicated on the discovery that raw elevator car position/direction data has, in any practical sense, no pattern repetition, but reduction of the canonical representation of the data (to eliminate pattern differences which are due only to the labeling of the elevator cars) provides pattern repetition, the similarity distance of which can be measured by known algorithms, including Lyapunov exponent algorithms and entropy estimation algorithms.
According to the present invention, complexity of elevator group behavior as a function of traffic rate is first determined over a period of time to find a threshold traffic rate having maximum complexity, then, during operation, system operational parameters are adjusted as a function of traffic rate, which have an effect of adjusting the effective traffic rate toward the traffic rate of maximum complexity, in order to ensure frequently occurring periods with high system complexity, and consequentially, low bunching. These adjustments may include reducing or increasing door dwell time, reducing or increasing maximum acceleration or velocity, changing the fraction of time in which a swing car, such as a VIP car or a combined passenger/freight elevator carries regular passenger traffic, or the time a swing car spends in one or another group. Increasing the time required for the elevator group to respond to traffic when traffic rate is below the threshold provides a result similar to an increase in traffic rate thereby increasing the complexity of group behavior, and may be considered to be an increase in effective traffic rate, and vice versa.
Attempts to deal with bunching in the prior art deal with a single car, or a pair of cars, such as by changing a hall call assignment. In contrast, the present invention will apply small perturbations to the entire elevator group, which will be basically invisible to the dispatching scheme, while tending to increase complexity, and thereby reduce bunching. The perturbations themselves increase complexity, since it is inherent that the behavior of a system having variations in its parameters is more complex than the behavior of a system with invariant parameters. In addition, since the perturbations are oriented in a manner which tends to naturally increase the effective complexity, there is a tendency to assure periods of complex behavior which will reduce bunching.
Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing.
REFERENCES:
patent: 4473134 (1984-09-01), Uetani
patent: 5260526 (1993-11-01), Sirag
patent: 5260527 (1993-11-01), Sirag
patent: 5338904 (1994-08-01), Powell et al.
patent: 5668356 (1997-09-01), Powell et al.
patent: 5672853 (1997-09-01), Whitehall et al.
patent: 5808247 (1998-09-01), Thangavelu
Copeland George S.
Sirag, Jr. David J.
Otis Elevator Company
Salata Jonathan
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