1,720,972 research outputs found
Design of supervisors to avoid deadlock in flexible assembly systems
No full textModern production systems exhibit a high degree of resource sharing that can lead to deadlock conditions. Deadlock arises when some parts remain indefinitely blocked because each of them requests access to a resource held by some other parts. One of the tasks of the control system lies in preventing such situations from occurring by proper resource management.
This article addresses the deadlock problem for an important class of production facilities, that is, flexible assembly systems, that can perform both manufacturing or assembly operations. In particular, we develop an approach to deadlock avoidance based on a supervisory control that works by inhibiting or enabling the events involving resource allocation. The article proposes two supervisors characterized by easy implementation, efficiency, and flexibility in resource management. The analysis of some case studies, performed by discrete event simulation, confirms the effectiveness of the approach
Real Time Optimization of Traffic Signal Control: Application to an Urban Area Isolated Intersection
No full textThis paper investigates the issue of urbantraffic signal control using a real time optimization modelfor signalized areas proposed in the related literature. The adopted model is modified to take into account the traffic scenarios, the different types of vehicles in the area, as well as pedestrians. The technique is applied to a real case study, consisting of two coordinated intersections located in the urban area of Bari (Italy). On the basis of traffic observations, optimal selection of the phases in the semaphoric cycle is performed under different congestion scenarios. Results show the ability of the strategy to minimize the vehicle queue lengths in the area
A signal timing plan formulation for urban traffic control
No full textThis paper addresses urban traffic control using an optimization model for signalized areas. The paper modifies and extends a discrete time model for urban traffic networks proposed in the related literature to take into account some real aspects of traffic. The model is embedded in a real time controller that solves an optimization problem from the knowledge of some measurable inputs. Hence, the controller determines the signal timing plan on the basis of technical, physical, and operational constraints. The actuated control strategy is applied to a case study with severe traffic congestion, showing the effectiveness of the technique
Real Time Optimization of Traffic Signal Control: Application to an Urban Area Isolated Intersection
No full textThis paper investigates the issue of urbantraffic signal control using a real time optimization modelfor signalized areas proposed in the related literature. The adopted model is modified to take into account the traffic scenarios, the different types of vehicles in the area, as well as pedestrians. The technique is applied to a real case study, consisting of two coordinated intersections located in the urban area of Bari (Italy). On the basis of traffic observations, optimal selection of the phases in the semaphoric cycle is performed under different congestion scenarios. Results show the ability of the strategy to minimize the vehicle queue lengths in the area
Natural Ventilation for Passive Cooling by Means of Optimized Control Logics
Full text linkNatural ventilation is one of the most efficient solutions to improve thermal comfort in buildings, particularly for passive and hybrid cooling. This paper analyses the potential of building automation systems for ventilative cooling in residential buildings. In relation to internal and external temperature, an optimized control strategy of window opening is developed to ensure adequate levels of indoor thermal comfort, reducing energy consumption for cooling. In particular, the control of ventilation is calibrated by an optimized variable set-point and a Particle Swarm Optimization (PSO) method is adopted with objective function that minimizes the thermal discomfort hours. The PSO algorithm is implemented in MATLAB and integrated with TRNSYS energy simulation software. A case study focusing on an existing Italian typical building of the’60s, situated in the Mediterranean climatic context is presented. Thermal comfort analysis, according to the adaptive thermal comfort theory (EN 15251-2007), shows that the optimized control logics for natural ventilation determines a significant reduction of overheating discomfort in reference to the case with ventilation only for indoor air quality at fixed hours. Combining the passive cooling system with an active cooling, there are also reductions in energy consumptions for cooling. The results show how the proposed optimized control logics increase the potentialities of natural ventilation strategies to the improvement of energy and thermal performance of buildings, integrating or replacing the conventional efficiency strategie
Decentralized Fault Diagnosis by Petri Nets and Integer Linear Programming
No full textThis paper addresses the problem of decentralized on-line fault diagnosis in the Petri net framework by using integer linear programming. The decentralized architecture consists of a set of local sites communicating with a coordinator that determines whether the behaviour of a system is normal or faulty. In particular, a protocol is presented for the communication between the local sites and the coordinator, and the rules for the coordinator to decide the global diagnosis results are proposed. (C) 2017, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved
Innovative Baseline Estimation Methodology for Key Performance Indicators in the Electro-Mobility Sector
No full textThe Key Performance Indicators (KPIs) are usually adopted to evaluate the progress of the stated objectives in a specific framework. In a context where no suitable data are available, the correct estimation of KPIs values is an open issue. Hence, a new methodology is needed to evaluate the baseline values of KPIs. This paper presents an innovative approach to estimate the baseline values for a set of KPIs, that can be already existing or defined for the first time, in absence of historical data. The proposed approach makes use of data retrieved by different suitable sources, such as surveys, questionnaires, etc., comparing them with existing data in similar contexts to estimate KPIs baseline values. A case study is presented and the proposed methodology is applied to estimate specific KPIs in the electro-mobility sector
A Decision Support System for Supply Chain Configuration
No full textThe design of a supply chain network provides the main structure for supply chain operations, since the network is a key element in the competitiveness and investments of an extended production system. The configuration of the network is essential for business to pursue a competitive advantage. We adopt a methodology based on three layers. In the first layer, the performance of the entities candidate to join the network is evaluated and efficient elements are individuated. The second layer develops a model to configure the network. Finally, the third layer is devoted to evaluate and validate the solution proposed in the first two levels. The overall decision process is the result of the interaction of the modules dedicated to each decision layer
Decentralized Diagnosis by Petri Nets and Integer Linear Programming
Full text linkThis paper proposes a novel decentralized on-line fault diagnosis approach based on the solution of some integer linear programming problems for discrete event systems in a Petri net framework. The decentralized architecture consists of a set of local sites communicating with a coordinator that decides whether the system behavior is normal or subject to some possible faults. To this aim, some results allow defining the rules applied by the coordinator and the local sites to provide the global diagnosis results. Moreover, two protocols for the detection and diagnosis of faults are proposed: they differ for the information exchanged between local sites and coordinator and the diagnostic capability. In addition, a sufficient and necessary condition under which the second presented protocol can successfully diagnose a fault in the decentralized architecture is proved. Finally, some examples are presented to show the efficiency of the proposed approach
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