Robust controllability and observability for MIMO in LTI systems with unidirectional perturbation

Robust controllability and observability are studied for multiple input multiple output linear time invariant system, with matrices A=A/sub 0/+rA/sub 1/, B=B/sub 0/+rB/sub 1/, C=Co+rC/sub 1/, where for r=0 the system is controllable and observable. In this paper we present the limits of the open interval of the real parameter r, in which controllability or observability are preserved.