“…The authors of [33], [34], [36] generalized the notion of stability margin as known from single-input single-output systems to multivariable control and investigated this property in connection with LQ-regulators. On the other hand, expressions for the l/O-behaviour of the original closed-loop system in terms of the closed-loop approximate model and the given open-loop model uncertainty bound are given in [7], [9], [10], [17], [19]j [27]. This provides a basis to check the behaviour of the closed-loop system according to the given design specifications and to assess the possible effects of the plant uncertainties.…”