Realization problem for singular positive continuous-time systems with delays

The positive realization problem for a class of singular continuous-time linear SISO systems with delays in state and in output is addressed. The notions of canonical forms of matrices and of dual systems are extended for singular linear systems with delays. Necessary and sufficient conditions for positivity of SISO singular continuous-time systems with delays and sufficient conditions for the existence of a positive singular realization are established. A procedure for computation of a positive singular realization of a given transfer function is proposed and illustrated by a numerical example.