Fusion of redundant information in brake-by-wire systems using a fuzzy voter

In safety critical systems such as brake-by-wire, fault tolerance is usually provided by virtue of having redundant sensors and processing hardware. The redundant information provided by such components should be properly fused to achieve a reliable estimate of the safety critical variable that is sensed or processed by the redundant sensors or hardware. Voting methods are well-known solutions for this category of fusion problems. In this paper, a new voting method, using a fuzzy system for decision-making, is presented. The voted output of the proposed scheme is a weighted average of the sensors signals where the weights are calculated based on the antecedents and consequences of some fuzzy rules in a rulebase. In a case study, we have tested the fuzzy voter along with the well-known majority voting method for a by-wire brake pedal that is equipped with a displacement sensor and two force sensors. Our experimental results show that the performance of the proposed voting method is desirable in the presence of short circuits to ground or supply, excessive noise and sensor drifts. Voting error (in terms of mean square error) is reduced by 82% by the proposed fuzzy voting method, compared to majority voting.