Rachid Nait-Said

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The risk graph is one of the most popular methods used to determine the safety integrity level for safety instrumented functions. However, conventional risk graph as described in the IEC 61508 standard is subjective and suffers from an interpretation problem of risk parameters. Thus, it can lead to inconsistent outcomes that may result in conservative SILs.(More)
This paper describes a fuzzy-based method of fault detection and diagnosis in a PWM inverter feeding an induction motor. The proposed fuzzy approach is a sensor-based technique using the mains current measurement to detect intermittent loss of firing pulses in the inverter switches. A localization domain made with seven patterns is built with the stator(More)
An important issue faced by risk analysts is how to deal with uncertainties associated with accident scenarios. In industry, one often uses single values derived from historical data or literature to estimate events probability or their frequency. However, both dynamic environments of systems and the need to consider rare component failures may make(More)
An important issue faced by risk analysts is how to deal with uncertainties associated with accident scenarios. In industry, one often uses single values derived from historical data or literature to estimate events probability or their frequency. However, both dynamic environments of systems and the need to consider rare component failures may make(More)
A new stator resistance estimator using fuzzy logic is proposed. The input variables of the fuzzy logic identifier are the input and output of the low-pass (LP) filter used to integrate the back-emf. Simulation results, using Matlab-Simulink, comparing the fuzzy estimator and a classical integrator in a direct torque control (DTC) scheme prove the(More)
The aim of this work is the assessment of the safety level of a complex industrial process by using the LOPA (Layers Of Protection Analysis) method. The estimation of Probability of Failure on Demand (PFD) of independent protection layers (IPLs) is made using Fault Tree Analysis (FTA). The combining of LOPA and FTA methods is used to estimate in a first(More)
This paper intends to present and implement a Barrier and Operational Risk Analysis (BORA) approach in oil and gas process in Algerian industry. This recent approach, despite of its analysis which based on the basic and classical methods such as barrier block diagrams, fault trees (FT) and influence diagrams. It is considered very suitable and practical in(More)
Layers of Protection Analysis (LOPA) described in the IEC 61511 standard is one of the most popular methods that enables the adequacy of the layers of protection for an industrial process to be assessed. LOPA has found much broader application as a relatively simple risk assessment methodology. However, an important issue faced by risk analysts is how to(More)
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