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As the demands on safety and reliablity of automatically co-
ntrolled system become more stringent,a good control system has
to not only achieve the performacne requirements but also
guara- tee the safety concern. In this thesis, an UIFIO
(unknown input fault isolation obs- erver) will be firstly
proposed with eigenstructure assignment and the corresponding
numerical algorithm will also be summari- zed. With the
flexiblity provided by output feedback in multiva- riable
systems beyond closed-loop eigenvalure assignment, the f- ault
diagnostic observer decouples the structured uncertanity f- rom
residual outputs and performs isolation for any possible co-
mbination of failure occurrences. Furthermore, since the
robust- ness of the diagnostic observer relative to
unstructured uncert- ainty depends on the condition number of
closed-loop eigenvecto- r set, two constrained approximations
for minimizing condition number of closed-loop eigenvector
assignment based on the UIFIO are proposed. With these two
approximation methods, a locally optimal solution of closed-
loop eigenvector set can be found to suppress the effects
induced by unstructured uncertanity.
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