1,721,006 research outputs found
A coordination strategy for distributed multi-agent manufacturing systems
No full textThis paper proposes a distributed multi-agent approach for dynamic part routing in automated manufacturing systems. In particular, each part in the system is associated to an intelligent software agent that must select its next destination autonomously (i.e. ignoring the actions of the other agents) and in real time (i.e. at each time it completes an operation on a workstation). Differently from other existing approaches, we overcome the typical myopia of negotiation algorithms based on dispatching rules by allowing the part agents to take decisions not only about the imminent operation, but also for the subsequent ones. The anticipated decisions are transmitted to workstation agents, which are also designated to detect and resolve conflicts by modifying part agents' decisions. To describe the single agents and their interaction schemes in a formal way, we take advantage of DEVS discrete-event modelling tools, which also allow us to develop a detailed simulation platform for our multi-agent system. The simulation experiments obtained on a detailed model of a manufacturing system derived from the literature confirm the effectiveness of the proposed approach
“Evolutionary adaptation of dispatching agents in heterarchical manufacturing systems”
No full textWe propose a new approach to job flow adaptive operational control in advanced manufacturing systems. The major feature of the method is the distribution of the control tasks among completely autonomous intelligent agents. Namely, agents are implicitly coordinated by a nature-analogous adaptation mechanism, which continuously tunes the free parameters of the control law of each agent. The proposed approach is effective and reactive to severe disturbances and changes in the manufacturing environment. Simulation experiments illustrate the operational distributed approach and its response to fault
Multi-objective evolutionary algorithms for a class of sequencing problems in manufacturing environments
No full textThis paper describes a multi-objective evolutionary algorithm for a typical serial production problem, in which two or more consecutive departments must schedule their internal work, each taking into account the requirements of the other departments. There are various single-objective heuristics to deal with this problem, while the multi-objective formulation calls for innovative approaches. To this aim, we devise a novel evolutionary algorithm, and compare it with two other state-of-art genetic optimizers used in similar contexts. The results obtained on both small-size problems with known Pareto-sets, and larger problems derived from industrial production of furniture confirm the effectiveness of the proposed approach
A decentralized allocation algorithm for distributed supply chains with critical tasks
No full textThis paper considers the problem of allocating tasks to a network of interconnected nodes in a supply chain, considering functional heterogeneity, resource constraints, and critical tasks whose assignment has to be considered mandatory. The proposed approach is an auction-based algorithm which uses a consensus algorithm to obtain a conflict-free solution fulfilling all the constraints. Numerical simulations and a comparison with a centralized optimization algorithm are performed to evaluate the effectiveness of the proposed approach
Precise position control of tubular linear motors with neural networks and composite learning
No full textThis paper examines an adaptive control scheme for tubular linear motors with micro-metric positioning tolerances. Uncertainties such as friction and other electro-magnetic phenomena are approximated with a radial basis function neural network, which is trained online using a learning law based on Lyapunov design. Differently from related literature, the approximator is trained using a composite adaptation law combining the tracking error and the model prediction error. Stability analysis and bounds for both errors are established, and an extensive experimental investigation is performed to assess the practical advantages of the proposed scheme. (C) 2010 Elsevier Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A Self-Sensing Approach for Dielectric Elastomer Actuators Based on Online Estimation Algorithms
Full text linkThis paper develops a position self-sensing approach for a motion actuator based on a dielectric elastomer membrane. The proposed method uses voltage and current measurements to estimate the electrical resistance and capacitance online by means of a high-frequency low-Amplitude voltage component injected in the actuation signal. The actual deformation is subsequently reconstructed using a model-based estimate of the electrical parameters implemented on a field programmable gate array platform (FPGA) with a sampling frequency of 20 kHz. The main peculiarity of the approach is the use of recursive identification and filtering algorithms that avoid the need of charge measurements. The self-sensing algorithm is extensively validated on a precision linear-motion actuator, which uses a nonlinear biasing system to obtain large actuation strokes
- …
