Measures of robustness with reduced order observers-an example

An attempt is made to show how the measures of robustness introduced by R.V. Patel and M. Toda (1980) and by R.K. Yedavalli (1985) are affected when some nonmeasurable states have to be estimated using the Luenberger observers for the LWR design. This is illustrated by designing stability-robust reduced-order observers for an LQR feedback system for the F-15 aircraft, and computing the robustness measures referred to above. The numerical results show that the addition of observers to the system decreases the robustness bounds. The effect of varying the weighting matrix in the LQR theory on the robustness measures is also reported