Hazard in Sequential Circuits Designed on Spool Type Valve as Fluid Logic Elements

Abstract

Fluid logic elements, the Boolean expression of which is a conditioned disjunction (ABC)=(A∧C)∨(B∧C), have been utilized in sequential circuits of machines. The problem of sequential circuits is to determine whether or not they will respond to an input change in the manner predicted by the flow table. This paper gives an algorithmic approach to the problem through the use of ternary algebla. First, a contact vector, in which one input variable energizes one or more contacts variables, is defined, and hazards in a combined network resulting from the simultaneous changing of two or more contact variables are discussed. Second, a feedback vector associated with a state vector being a certain function of a contact vector and a feedback vector, is also introduced in sequential circuits. The technique is described that will detect any type of hazard or race condition that could result in an incorrect terminal state.