Abstract
This paper is concerned with the sensitivity problem for linear time-invariant multivariable feedback control systems. Based on the theory of perturbation bounds for pseudoinverse matrices, it is shown that the sensitivity property depends upon, not only the smallest singular value of the return difference matrix T, but also the condition number of T, i. e., the ratio of the largest singular value of T to the smallest singular value of T. In order to achieve lower sensitivity, the smallest singular value of T should be larger and the condition number of T should be smaller.
