2004
Authors
Portugal, PJ; Carvalho, AD;
Publication
WFCS 2004: IEEE INTERNATIONAL WORKSHOP ON FACTORY COMMUNICATION SYSTEMS, PROCEEDINGS
Abstract
The paper presents a framework to evaluate dependability of fieldbus networks. An hierarchical modeling approach is proposed, which considers both the effects of different kinds of faults - permanent, transient and common-cause - and the interaction between hardware and software components. Stochastic Petri Nets are used as the modeling technique to obtain dependability models, with emphasis in the use of analytical/numerical methods to provide model's solutions.
2002
Authors
Portugal, P; Carvalho, J; Carvalho, A;
Publication
PROCEEDINGS OF THE SIXTH EUROPEAN SPACE POWER CONFERENCE (ESPC)
Abstract
Dependability has become an essential parameter on system design. The fulfillment of the system function, either in mission oriented or in continuous operation, requires knowledge about all possible failure modes. If a fault occurrence causes a mis-operation it should be approached a design for a dependable system. Some issues should be performed both at system design and development stages, in order to build a robust system, by evaluating correctly failure conditions and guaranteeing the fulfillment of the system function. The main one is the validation process as well as it conditions the modelling methods associated to and the techniques to be adopted. This paper presents an approach for analysis of validation techniques for electronic systems. The analysis points out two directions, verification techniques needed to support the design at different phases and fault forecasting techniques to assess systems behavior for modelling faults activation and occurrence.
2001
Authors
Carvalho, A; Portugal, P;
Publication
IECON'01: 27TH ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY, VOLS 1-3
Abstract
The paper focus dependability modelling and evaluation of fieldbus networks in the presence of permanent faults. Several architectures are analysed, considering different operating modes, topologies and fault types. Two measures of dependability are evaluated: reliability and asymptotic unavailability. The aim is to compare these various design solutions, to define essential parameters and to study their effects on fieldbus dependability.
1996
Authors
Carvalho, A; Tovar, E; Oliveira, J; Alves, M; Sousa, M; Portugal, P;
Publication
BALANCED AUTOMATION SYSTEMS II: IMPLEMENTATION CHALLENGES FOR ANTHROPOCENTRIC MANUFACTURING
Abstract
The work presented in this paper consisted on the integration of several areas within a factory by using different communication standards. The described implementation satisfies several types of requirements, which include not only the functional requirements, but also the preservation of previous investments. The fulfilment of the latter imposed the use of heterogeneous technologies, both in terms of vendors and generations. This resulted in additional difficulties for the integration that were overcome. The use of OSI based technologies, such as those developed in the scope of CCE-CNMA, contributed to the success of this work.
2003
Authors
Carvalho, J; Portugal, P; Carvalho, A;
Publication
2003 IEEE INTERNATIONAL SYMPOSIUM ON INDUSTRIAL ELECTRONICS, VOLS 1 AND 2
Abstract
Fieldbus networks have been assuming a high acceptance in the industrial environment, replacing the old centralized control architectures. Due to time critical nature of the tasks involved in these environments, the fulfillment of dependability attributes is usually required. Therefore the dependability is an important parameter on system design, which should be evaluated. Several factors can affect system dependability. The environmental ones are the most common and due to the particularity of the industrial environment this susceptibility is increased. In this paper it is proposed a framework based on fault injection techniques, supported by a hardware platform which emulates a fault set, representative of industrial environment scenarios, intending to disturb data communications on a PROFIBUS network. From these fault injection experiments, relevant data is gathered and a further analysis is carried out to evaluate dependability attributes.
1996
Authors
Tovar, E; Oliveira, J; Alves, M; Azevedo, R; Carvalho, A; Sousa, M; Portugal, P; Carvalho, J;
Publication
FLEXIBLE AUTOMATION AND INTELLIGENT MANUFACTURING 1996
Abstract
This paper presents the work carried out in order to improve one of the areas of a factory plant, integrating it within the factory using different communication standards. The implementation described satisfies a set of data flow requirements and claims to be an example of different vendors and technologies integration. Distribution transformers have always been dried within ovens heated for the effect This drying process has several drawbacks: a low efficiency, dependence on the transformer volume and requiring a long time to complete. The new approach, presented in this paper, eliminates all those constraints.
The access to the final selection minute is only available to applicants.
Please check the confirmation e-mail of your application to obtain the access code.