A model for assembly sequence planning in a multirobot environment

2002 IFAC15th Triennial World Congress, Barcelona, SpainThis paper presents a model for the selection of optimal assembly sequences for a product in multirobot systems. The objective of the plan is the minimization of the total assembly time (makespan). To meet this objective, the model takes into account, in addition to the assembly times and resources for each task, the times needed to change tools in the robots, and the delays due to the transportation of intermediate subassemblies between different machines. An A* algorithm that solves the problem is also presented, which starts from the And/Or graph for the product (compressed representation of all feasible assembly plans)

Bifurcations and aggregation in large scale systems

This paper deals with the following problem: assume that a qualitative analysis (behaviour modes, bifurcation points, type of atractors .•• ) of a nonlinear dynamical system has been carried out and that afterwards this dynamical system is transformed into a large scale system through a disaggregating process of some (or all) of its variables. The problem at stake is to analyze whether the disagaregation gives rise to new behaviour modes, as a consequence of the appearance of new bifurcations in the disaggregated dynamical system. That leads us to study whether the original system and the disaggregated one are "equivalents" or whether the second one is richer in behaviours than the first one.The paper develops general results for standard disaggregation forms. Furthermore, practical applications of the proposed methodology to urban dynamics models is included .Comisión Asesora de Investigación Científica y Técnica (CAICYT) 1102/8

An Automated Approach for Verification of Software Requirements

In this paper, we present an automated approach for the verification of software requirements. This approach is based on the representation of software requirements in XML and the usage of the XSLT language to automatically verify some desired quality properties. These ideas have been implemented in REM, an experimental requirements management tool that is also described in this paper.Comisión Interministerial de Ciencia y Tecnología (CICYT) GEOZOCO TIC 2000–1106–C02–0

Using Genetic Algorithms with Variable-length Individuals for Planning Two-Manipulators Motion

International Conference on Artificial Neural Networks and Genetic Algorithms. 01/01/1997. NorwichA method based on genetic algorithms for obtaining coordinated motion plans of manipulator robots is presented. A decoupled planning approach has been used; that is, the problem has been decomposed into two subproblems: path planning and trajectory planning. This paper focuses on the second problem. The generated plans minimize the total motion time of the robots along their paths. The optimization problem is solved by evolutionary algorithms using a variable-length individuals codification and specific genetic operators

Attribute Selection for Classification

The selection of attributes used to construct a classification model is crucial in machine learning, in particular with instance similarity methods. We present a new algorithm to select and rank attributes based on weighing features according to their ability to help class prediction. The algorithm uses the same structure that holds training records for classification. Attribute values and their classes are projected into a one-dimensional space, to account for various degrees of the relationship between them. With the user deciding on the degree of this relation, any of several potential solutions can be used as criterion to determine attribute relevance. This low complexity algorithm increases classification predictive accuracy and also helps to reduce the feature dimension problem

Supervised Learning Using Instance-based Patterns

This paper introduces a new classification algorithm of the instance-based learning type. Training records are converted into patterns associated with a known class label, and stored permanently into a trie1-like tree structure along with other helpful information. Classifying new records is done selecting from the trie two best patterns as solutions hypotheses. Best pattern selection is done using standard distance metrics, a strength function and an exclusive values concept. Classification tests done on several data files have shown very accurate results

Defeasible Argumentation of Software Architectures

Defeasible argumentation is typical of legal and scientific reasoning. A defeasible argument is one in which the conclusion can be accepted tentatively in relation with the evidence known so far, but may need to be retracted as new evidence comes in. This paper analyses the role of defeasible argumentation in the explanation and evaluation of architectural decisions. We analyse technical explanations offered by engineers at Twitter and eBay about several architectural decisions adopted in those systems. We generalize these examples in four argumentation schemes. We also study the typical case of reasoning with a formal model of an architecture, and we infer a fifth argumentation scheme. Finally, we apply Hastings’ method of attaching a set of critical questions to each scheme. We show that the existence of critical questions reveals that the inferred schemes are defeasible: in argumentation theory, if a respondent asks one of the critical questions matching a scheme and the proponent of an argument fails to offer an adequate answer, the argument defaults and the conclusion is retracted. This dialogical structure is the basis of typical architectural evaluations. We conclude that the provided evidence supports the hypothesis that defeasible argumentation is employed in architectural evaluation. In this context, a rich catalogue of argumentation schemes is a useful tool for the architect to organize his or her reasoning; critical questions assist the architect in identifying the weak points of his or her explanations, and provide the evaluation team with a checklist of issues to be raised.Universidad de Sevilla VPPI-U

Fault Tolerance as an aspect using JReplica

Reliability and availability are very important trends in the development process of distributed systems. In order to improve these features, object replication mechanisms have been introduced. Programming replication policies for a given application is not an easy task, and this is the reason why transparency for the programmer has been one of the most important properties offered by all replication models. However, this transparency for the programmer is not always desirable. In this paper we present a replication model, JReplica, based on Aspect Oriented Programming (AOP). JReplica allows the separated specification of the replication code from the functional behaviour of objects, providing not only a high degree of transparency, as done by previous models, but also the possibility for programmers to introduce new behaviour to specify different fault tolerance requirements. Moreover, the replication aspect has been introduced at design time, and in this way, UML has been extended in order to consider replication issues separately when designing fault tolerance systems.Comisión Interministerial de Ciencia y Tecnología TIC99-1083-C02-0