THE STRANGENESS INDEX OF A LINEAR DELAY DIFFERENTIAL-ALGEBRAIC EQUATION OF RETARDED TYPE

This paper deals with an index concept for linear delay differential algebraic equations (DDAEs) of retarded type with constant coefficients. These systems can be transformed to a nondelayed system by a standard approach of introducing additional state variabels. The index of the DDAE is usually defined to be the index of the nondelayed part of the DDAE, but in this paper it is shown that it is possible, under certain conditions, to construct an augmented nondelayed system that has a lower index by using a different approach in the construction of the nondelayed system.