Artículos

Definition and Empirical Evaluation of Voters for Redundant Smart Sensor Systems

Definición y Evaluación Empírica de Algoritmos de Voteo para Sistemas Redundantes de Sensado Inteligente

H. Benítez Pérez¹, J.L. Ortega Arjona² and G. Reza Latif Shabgahi³

¹ Departamento de Ingeniería de Sistemas Computacionales y Automatización, IIMAS, UNAM, Apdo. Postal 20–726, Admon. No. 20, Del. A. Obregón, México D. F., CP. 01000, México;
e–mail: hector@uxdea4.iimas.unam.mx

² Departamento de Matemáticas, Facultad de Ciencias, UNAM, Ciudad Universitaria, CP. 04510, México City, México

³ Telematics Dept, Technology Faculty, The Open University, Milton Keynes, MK7 6AA, UK. Internet
e–mail: g.latif@sees.bangor.ac.uk

Article received on August 23, 2005; accepted on October 02, 2007

Abstract

This study is the first attempt for integration voting algorithms with fault diagnosis devices. Voting algorithms are used to arbitrate between the results of redundant modules in fault–tolerant systems. Smart sensors are used for FDI (Fault Detection and Isolation) purposes by means of their built in intelligence. Integration of fault masking and FDI strategies is necessary in the construction of ultra–available/safe systems with on–line fault detection capability. This article introduces a range of novel software voting algorithms which adjudicate among the results of redundant smart sensors in a Triple Modular Redundant (TMR) system. Techniques to integrate replicated smart sensors and fault masking approach are discussed, and a classification of hybrid voters is provided based on result and confidence values, which affect the metrics of availability and safety.Thus, voters are classified into four groups: Independent–diagnostic safety–optimised voters, Integrated–diagnostic safety–optimised voters, Independent–diagnostic availability–optimised voters and Integrated–diagnostic availability–optimised voters. The properties of each category are explained and sample versions of each class as well as their possible application areas are discussed.

Keywords: Ultra–Available System, Smart Sensor, Fault Masking, Triple Modular Redundancy.

Resumen

Este estudio es una primer aproximación para la integración de algoritmos de voteo con dispositivos de diagnóstico de fallas. Los algoritmos de voteo son usados para arbitrar entre los resultados de elementos redundantes en sistemas tolerantes a fallas. Los sensores inteligentes son usados para propósitos de detección y separación de fallas (FDI) dada la capacidad su capacidad de inteligencia construida. La integración de enmascaramiento de fallas y las estrategias de FDI is necesaria en la construcción de sistemas altamente disponibles y seguros con la capacidad de detección de fallas en línea. Este artículo introduce un rango de algoritmos de voteo los cuales adjudican un resultado entre los resultados generados por los sensores inteligentes en un módulo de redundancia triple. Las técnicas para integrar los sensores inteligentes replicados y la aproximación de enmascaramiento de fallas son revisadas en este artículo. Una clasificación de algoritmos de voteo híbrido es provista con base en el resultado y los valores de confianza los cuales afectan las métricas de disponibilidad y seguridad de estos algoritmos. De hecho los algoritmos de voteo son clasificados en cuatro grupos: Diagnóstico–Independiente con seguridad–optimizada, Diagnóstico–Integrado con seguridad–optimizada, Diagnóstico–Independiente con disponibilidad–opitimizada y Diagnóstico–Integrado con disponibilidad–optimizada. Las propiedades de cada categoría son revisadas asi como muestras de sus implementaciones son discutidas.

Palabras clave: Sistemas con Alta Disponibilidad, Sensores Inteligentes, Enmascaramiento de Fallas, Redundancia Modular Triple.

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Acknowledgements

The authors gratefully acknowledge the support of CONACYT Scholarship number 71391 project I35561–A and DISCA–IIMAS UNAM and UNAM–PAPIIT (IN101307 and IN105303) México, and the High Performance Computing Proyect within the "Macroproyecto Tecnologas para la Universidad de la Información y la Computación" of the Universidad Nacional Autónoma de México (UNAM).

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