Capteurs intelligents : Nouvelles technologies et nouvelles problématiques pour la sûreté de fonctionnement
Résumé
New technologies make way for intelligent sensors by integrating new functionalities: error measurement corrections, self-adjustment, self-diagnosis for measurement and sensor status, on-line reconfiguration, and digital bidirectional communication. Industrialists are taking advantage of more accurate measurements, cost reductions and facilities. For industrial risk prevention, new dependability issues are arising. Functionalities such as self-diagnosis and digital communication seem to be in favour of control systems availability. On the other hand, the high amount of electronics, programmable units, and software aspects implies new failure causes and modes which are usually not well known. Availability assessments of intelligent sensors are quite seldom in literature and usually do not include “intelligent particularities”. In this chapter, a discussion about dependability issues and modelling is presented. An approach is proposed. Both functional and material aspects of the system are included which allow representing sensor functionalities and several kinds of relationship. Faults and failures make up the third part of the model. First analyses show the consequences of these failures on sensor functions, the probability of dysfunction according to time, and the corresponding failure modes. An infrared gas sensor is used for example. Some tools for availability assessment of complex systems can take advantage of these results, especially when dysfunctional behaviour is not well known.