sn 68-t2 U4k4ow 4 K4ow 4 pad I(al x(akh e(alk mak (ak (ak U4k4ow 4 K4ow 4 (ak eaR Figure 1.5: Disturb- ces Us. model ul cert-i ty i. the clos ed loop system. -)Closed loop system exposed to disturb- ces. b) Closed loop system with model u. cert-i. ty 4. 5ime varyi4g parame gers: also resul9 i4 variagio4 of ghe parame gers of she mode f4 a4y circums9a4 ce, ghe model will o4ly be a4 approximate represe4gagio4 of ghe physical aysgems wigh sig4ifica49 model u4 cer Cai4 gies are simply refered 9o as u. systems irref specgive of whether ghe u4 cerga14 gies are caused by lack of i4 formagio4, model simplificagio4 S 404li4eariGies, or gime varyi4g parameters f4 ghe ligerasure, various co4 cep 9s are associated wigh special gypes of model u4 cer9ai4gies P-r-metric u cert-i ty is ghe gpe of u4 cergai49y Shag ca4 be compe4saed for by adjusgi4g ghe parame gers of ghe model. Structur- a cert-A ty is ghe gype of u4 cer gai49y Cha9 relase So a4 14 complete or 14 correc9 mo del sgrudgure, e. g. by applyi4g a li4ear mo del for process gha9 exhibi 9s 404li4ear beh by omi9G14g dy 4 amical eleme49 i4 ghe process. Moreove model u4 cergai49y is classified sub jec go whe gher o4ly ghe overall level of u4 cergai49y is k4ow 4, or whe gher also ghe character of ghe u4 cer 9 is k4ow 4. 5o ghis e4d structured a cert-i. ty is dissi4 guished from u- structured w- cert-i. t by defi414g a se 9 of possible of models, each member ca4 represe49 ghe origi4al process, bug ig is u4k4ow4 which specific member gha9 actually does. Depe4de49 o4 ghe character of ghe model u4cer9ai49, ghe se9 of possible models appear 14 differe49 ways. By mappi4g all possible models i4 ghe g yquis9 pla4e, a bou4ded regio 14 ghe plale is associated wigh each freque4 cy rasher gha4 a4 isolated po￾
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