914 research outputs found

    Submodular Function Maximization for Group Elevator Scheduling

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    We propose a novel approach for group elevator scheduling by formulating it as the maximization of submodular function under a matroid constraint. In particular, we propose to model the total waiting time of passengers using a quadratic Boolean function. The unary and pairwise terms in the function denote the waiting time for single and pairwise allocation of passengers to elevators, respectively. We show that this objective function is submodular. The matroid constraints ensure that every passenger is allocated to exactly one elevator. We use a greedy algorithm to maximize the submodular objective function, and derive provable guarantees on the optimality of the solution. We tested our algorithm using Elevate 8, a commercial-grade elevator simulator that allows simulation with a wide range of elevator settings. We achieve significant improvement over the existing algorithms.Comment: 10 pages; 2017 International Conference on Automated Planning and Scheduling (ICAPS

    Quality and quantity of service in lift groups

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    This research was focused on quality of service experienced by passengers in lift systems where multiple cars are sharing same shafts (multi car lift systems) and destination control. These modern lift systems have opportunities and constraints for control algorithms arising by existing and additional quality of service criteria. These additional criteria have rarely been considered in existing literature, control algorithms or traffic analysis. The overall aim of the research was to determine and analyse existing and new quality of service criteria for destination control systems and multi car lift systems in terms of traffic handling and developing lift control concepts considering these criteria. Therefore, the impact on passengers’ quality of service was reviewed using psychology of waiting principles. Detailed definition and analysis was done for reverse journeys in destination control systems and departure delays with a focus on multi car lift systems. To develop and analyse control algorithms known event based traffic simulation, round trip time calculation and Monte Carlo simulation were extended and applied. Traffic control algorithms and concepts were developed to improve passenger experience when using lifts. Additional to dispatching algorithms equations for improved lift kinematics and controlled stopping distances were derived to reduce departure delays in multi car lift systems. Possible improvements were shown in case studies. Compared to traditional lift systems, special opportunities and constraints of a circulating multi car lift system in traffic handling were explored and analysed. New cycle time calculations for shuttle and local group applications were developed. Results were provided using case studies, and necessary control concepts were addressed. With the results of this research, better understanding and assessments of multi car lift systems and destination controls are possible. The traffic control algorithms explored help to build better lift controllers, considering passengers perception. The introduced traffic analysis methods for circulating multi car lift systems support lift planning

    A brief review on vertical transportation research and open issue

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    Book of Proceedings of the International Joint Conference-CIO-ICIEOM-IIE-AIM (IJC 2016), "XX Congreso de Ingeniería de Organización", "XXII International Conference on Industrial Engineering and Operations Management, "International IISE Conference 2016, "International AIM Conference 2016". Donostia-San Sebastian (Spain), July 13-15, 2016Vertical transportation refers to the movements of people in buildings. High-rise buildings have emerged as a common construction nowadays. In such buildings, the vertical transportation is extremely difficult to manage, specially, when the people arrive at the same time at specific floors wanting to travel to other floors. To solve such situations, the installation of elevator group control systems (EGCS) is a usual practice. EGCS are used to manage multiple elevators in a building to efficiently transport passengers. EGCSs need to meet the demands by assigning an elevator to each landing call while optimizing several criteria. This paper reviews the most relevant contributions in vertical transportation industr

    Genetic and tabu search approaches for optimizing the hall call-car allocation problem in elevator group systems

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    The most common problem in vertical transportation using elevator group appears when a passenger wants to travel from a floor to other different floor in a building. The passenger makes a hall call by pressing a landing call button installed at the floor and located near the cars of the elevator group. After that, the elevator controller receives the call and identifies which one of the elevators in the group is most suitable to serve the person having issued the call. In this paper, we have developed different elevator group controllers based on genetic and tabu search algorithms. Even though genetic algorithm has been previously considered in vertical transportation problems, the use of tabu search approaches is a novelty in vertical transportation and has not been considered previously. Tests have been carried out for high-rise buildings considering diverse sizes in the group of cars. Results indicate that the waiting time and journey time of passengers were significantly improved when dealing with such soft computing approaches. Also, a quickly evaluable solution quality function in the algorithms allows suitable computational times for industry implementation

    QOBJ modeling: A new approach in discrete event simulation

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    This paper deals with a new discrete event simulation modeling concept, calledqobj, which comes from two well-known paradigms:objects andqueuing networks. The first provides important conceptual tools for model organization, while the second one allows for nice visualization of models' internal state and processes. Thanks to the integration of these two paradigms, theqobj concept allows the suppression of several dichotomies characterizing current simulation modeling approaches. For instance,qobj allows the description of system elements which are both mobile and able to do processing, and allows the dynamic instantiation of static and mobile elements during simulation. The design of lift group models for an industrial project illustrates the main features of theqobj concep

    Optimal car dispatching for elevator groups using genetic algorithms

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    The car dispatching problem in an elevator group consists of assigning cars to the hall calls at the same time that car call are served. The problem needs to coordinate the movements of individual cars with the objective of operating efficiently the whole group. In this paper, we propose an elevator group control system based on a genetic algorithm which makes use of a novel fitness function to evaluate the individuals. The fitness function allows a quick execution of the algorithm. Tests are provided for various types of high-rise buildings to assess the elevator service performance. Comparative simulations show that our genetic algorithm outperforms traditional conventional algorithms developed in the industry. It is important to note that the algorithm is quickly evaluated allowing a real-life implementatio

    Design and analysis of a tool for planning and simulating dynamic vertical transport

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    Nowadays, most of the main companies in the vertical transport industry are researching tools capable of providing support for the design process of elevator systems. Numerous decisions have to be taken to obtain an accurate, comfortable, and high-quality service. Effectively, the optimization algorithm is a key factor in the design process, but so are the number of cars being installed, their technical characteristics, the kinematics of the elevator group, and some other design parameters, which cause the selection task of the elevator system to be a complex one. In this context, the design of decision support tools is becoming a real necessity that most important companies are including as part of their strategic plans. In this article, the authors present a user-friendly planning and simulating tool for dynamic vertical traffic. The tool is conceptualized for giving support in the planning and design stage of the elevator system, in order to collaborate in the selection of the type of elevator (number, type of dynamic, capacity, etc.) and the optimization algorithm

    Modelling of a rope-free passenger transportation system for active cabin vibration damping

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    Conventional vertical passenger transportation is performed by lifts. Conventional traction-drive electrical lifts use ropes to transfer the rotational motion of an electrical motor into a vertical motion of the cabin. The vertical passenger transportation system discussed in this paper does not use any ropes, the motor directly provides a driving force, which moves the cabin. This new propulsion is realized through an electrical linear motor. The use of the linear motor requires a new design of the passenger transportation system (PTS), which includes reducing the weight of the car through lightweight construction. The reduced stiffness of the lightweight design renders the construction more vulnerable to vibrations. In order to improve ride quality of the transportation system it is necessary to develop new concepts to damp the vibrations. One way to increase stiffness characteristics of the system is to introduce active damping components to be used alongside passive damping components. It is essential to derive a dynamic model of the system in order to design and also later control these damping components in the best possible way. This paper describes the fundamental steps undertaken to derive a dynamic model for designing and controlling active damping components for the new type of vertical PTS. The model is derived as a Multi-Body System (MBS), where the connections between the bodies are modelled as spring damper elements. The derivation of the MBS is demonstrated on a transportation system, consisting of three main components: a sledge, holding the rotor of the linear motor; a mounting frame, which is used to provide support for the cabin; and the actual cabin. The modelling of the propulsion system, thus the electrical part of the PTS, will not be the focus of this work

    Evaluating a holistic energy benchmarking parameter of lift systems by using computer simulation

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    At present, there are benchmarking parameters to assess the energy performance of lifts, e.g. one in Germany adopted by VDI (4707-1/2), one internationally published by ISO (BS EN ISO 25745-2:2015), and the other in Hong Kong adopted by The Hong Kong Special Administrative Region (HKSAR) Government. These parameters are mainly checking the energy consumed by a lift drive without considering real time passenger demands and traffic conditions; the one in Hong Kong pinpointing a fully loaded up-journey under rated speed and the two in Europe pinpointing a round trip, bottom floor to top floor and return with an empty car, though including energy consumed by lighting, displays, ventilation etc. A holistic normalization method by Lam et al [1] was developed a number of years ago by one of the co-authors of this article, which can assess both drive efficiency and traffic control, termed J/kg-m, which is now adopted by the HKSAR Government as a good practice, but not specified in the mandatory code. In Europe, the energy unit of Wh has been used but here, Joule (J), i.e. Ws, is adopted to discriminate the difference between the two concepts. In this article, this parameter is evaluated under different lift traffic scenarios using computer simulation techniques, with an aim of arriving at a reasonable figure for benchmarking an energy efficient lift system with both an efficient drive as well as an efficient supervisory traffic control

    A study into the influence of the car geometry on the aerodynamic transient effects arising in a high rise lift installation

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    One of the main goals in designing a high-speed lift system is developing a more aerodynamically efficient car geometry that guarantees a good ride comfort and reduces the energy consumption. In this study, a three-dimensional computational fluid dynamics (CFD) model has been developed to analyse an unsteady turbulent air flow around two cars moving in a lift shaft. The paper is focused on transient aerodynamic effects arising when two cars pass each other in the same shaft at the same speed. The scenarios considered in the paper involve cars having three different geometries. Aerodynamic forces such as the drag force that occur due to the vertical opposite motions of the cars have been investigated. Attention is paid to the airflow velocity and pressure distribution around the car structures. The flow pattern in the boundary layer around each car has been calculated explicitly to examine the flow separation in the wake region. The results presented in the paper would be useful to guide the lift designers to understand and mitigate the aerodynamic effects arising in the lift shaft
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