In addition to different time constants and devia—
tions，non—linearity also considerably changes the way
in which the manipulated variables P r-P and q affect
the controlled variables．Figs．4 and 5 show respons—
es of the bottom product compositions to feed thermal
condition q leaving from its initial value by+5％ at
the beginning and then back to its initial value．It is
observed that the leaving and back transients between
two steady本文来自辣*文#论~文%网，
毕业论文 www.751com.cn 加7位QQ324~9114找原文state values have completely different last——
ings in the high—and very high—purity systems．This
phenomenon iS called asymmetric dynamics，which iS
a severe and distinct non—linearity【l2-13]
．
P=T2／T1
can be used to describe the difference of leaving and
back time．The larger the value P is，the stronger
the asymmetric behavior iS．The degree of asymmet—
ric behavior increases with increasing purity(Table
2)．Asymmetric behavior on overhead end is stronger
than that on the bottom end．Furthermore， asym—
metric dynamics in the lOW—and moderate—purity sys—
tem is not obvious．Due to strong asymmetric dynam—
ic behavior in high—and very high—purity systems，
linear analysis of relationship between manipulated
variables(P r—Ps and q)and product compositions is
not accurate for tight control of high．．and very high——
purity system s．
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