Robustness of pole assignment in a specified circular region for discrete-time grey systems

New sufficient conditions are proposed to guarantee robust pole location within a specified circular region for a discrete-time grey system. By mathematical analysis, the proposed new approach is proved to be less conservative than the existing technique reported in the literature. The proposed method, instead of solving the Lyapunov matrix equation, requires only the simple computation of the spectral radius of a non-negative matrix. Examples are given to demonstrate the use of the proposed method and to illustrate the improvement in that method.