SOME ESTIMATES PERTAINING TO SENSITIVITY AND ROBUST STABILITY OF INPUT-OUTPUT SYSTEMS

The estimates derived in this paper strengthen the available results o n sensitivity and robust stability of input-output systems. Two types of estimates are discussed: the ''sensitivity type,'' which establishe s a bound for the output change when the system is perturbed but the i nput remains the same, and the ''robustness type,'' which gives a boun d for the output change when the input changes but the perturbation do es not. First, estimates for general systems over abstract extended sp aces are derived; these results are then applied to (1) two frequently used control configurations, and (2) systems governed by vector integ ral and differential equations on the time domain [0, infinity). The a pplications of the estimates are illustrated by several examples.