Browsing by Author "Portugal, Paulo"
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- Assessment of PROFIBUS networks using a fault injection frameworkPublication . Carvalho, José Augusto; Carvalho, Adriano; Portugal, PauloIndustrial control systems architectures have been evolving to the decentralization of control tasks. This evolution associated with the time-critical nature of these tasks, increases the dependability requirements for one of their most critical components: the communica¬tion system. Therefore, this is an important aspect on the control system design which must be properly evaluated. In this paper the dependability of a PROFIBUS net-work is assessed. By using of a fault injection framework the network operation is disturbed with fault scenarios which are representative of industrial environments. From these experiments, the stability of the PROFIBUS logical ring is analyzed, the main outages causes are identified and their probabilities are obtained.
- Dependability validation techniques for electronic systemsPublication . Portugal, Paulo; Carvalho, José Augusto; Carvalho, AdrianoDependability 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.
- Experimental analysis of outage times for PROFIBUS networksPublication . Carvalho, José Augusto; Carvalho, Adriano; Portugal, PauloDistributed control systems operation strongly depends on the communication system performance. Therefore, their analysis becomes an important aspect to be considered, particularly in situations where communications have real-time constrains and the network operates on faulty environments. In this paper the behavior of PROFIBUS network in the pres-ence of faults is analyzed. This analysis is performed in an expe-rimental base supported by a real network. The network opera-tion is disturbed through a set of fault injection experiments from which performance metrics related with PROFIBUS out-age times are evaluated.
- Factory automation using OSI technologies: process automation in a transformers manufacturing plantPublication . Tovar, Eduardo; Oliveira, José Luís; Alves, Mário; Azevedo, Rui; Carvalho, Adriano; Sousa, Mário; Portugal, Paulo; Carvalho, José AugustoThis 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.
- A framework for dependability evaluation of PROFIBUS networksPublication . Carvalho, José Augusto; Carvalho, Adriano; Portugal, PauloFieldbus 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.
- Performability evaluation of PROFIBUS-DP multi-master networks in relevant industrial scenariosPublication . Carvalho, José Augusto; Carvalho, Adriano; Portugal, PauloNetwork control systems operation strongly depends on the performance of the communication network. Therefore, their analysis becomes an important aspect to be considered, particularly in situations where network traffic has real-time constrains and the network operates in faulty environments. In this paper, a set of fault injection experi-ments were performed on a Profibus-DP network in order to assess the impact of faults in the network operation. The experiments reproduce typical industrial configurations with different network load conditions and fault scenarios. Based on the results of experiments the Profibus-DP bus cycle time, the message response time and the message worst case response time are assessed