Computation of positive stable realizations for linear continuous-time systems

Conditions for the existence of positive stable realizations with system Metzler matrices for proper transfer function are established. It is shown that there exists a proper stable realization of transfer function of second order if and only if the transfer function has real negative poles. Sufficient conditions for the existence of positive stable realizations of transfer function of third order are established. A method based on the decomposition of transfer functions into the first, second and third orders transfer functions for computation of positive stable realizations is proposed. A method for computation of positive stable realizations of transfer functions with real negative poles and zeros is given.