Weak robust controllability and observability of uncertain linear systems

This paper introduces notions of weak robust observability, lull informatio n weak robust controllability, and partial information weak robust controll ability for a class of uncertain linear systems in which the uncertainty sa tisfies an integral quadratic constraint. The paper gives characterizations of these properties in terms of the existence of suitable solutions to Ric cati differential equations of the type which occur in H-infinity control. Furthermore, it is shown that the conditions of weak robust observability a nd full information weak robust controllability are necessary but not suffi cient for partial information weak robust controllability.