Routh-Padé approximants for 2-D non-separable-denominator discrete-time systems using VEGA

A Routh-Pade approximation method is presented for obtaining stable reduced order model of 2-D non-separable-denominator discrete-time system. The proposed method preserves initial power-series-expansion-coefficients/Markov-parameters of the system as well as minimizes the errors between a set of subsequent power-series-expansion-coefficients and/or Markov-parameters of the 2-D system and those of the model while preserving stability. All the operations involved are carried out in the z domain, thus avoiding extra calculations and the complexity. Vector Evaluated Genetic Algorithm (VEGA) is used for optimization. A numerical example is provided to show the effectiveness of the proposed theory.