IEEE Transactions on Automatic Control, Vol.47, No.7, 1212-1213, 2002
Comments on "Upper matrix bounds for the discrete algebraic Riccati matrix equation"
In the above paper, new methods to obtain upper matrix bounds for a discrete algebraic Riccati equation (DARE) (1) have been established, but the author assumes that the system matrix A is nonsingular and DARE (1) has a positive-definite solution. In this note, some similar results can be obtained when a solution is positive-semidefinite and there are no extra assumption that A is nonsingular.