【正文】
G T P G – P) = – I 由此解出 P; 判斷 P的正定性,若 P正定,系統(tǒng)大范圍漸近穩(wěn)定,且 v (x) =x T (k) P x (k) 是這個(gè)系統(tǒng)李氏函數(shù)。 例: 設(shè)離散系統(tǒng)的狀態(tài)方程為 試確定系統(tǒng)在平衡點(diǎn)處漸近穩(wěn)定的條件。 )(0 0)1(21 kxkx ??????????解: 選 Q = I, 代入矩陣方程 G T P G – P) = – I ??????????????????????????????????1001000022121211212212121121pppppppp????????????????????????????????1001002212121121222122121111pppppppp???????????????????????1001)1()1()1()1(2222211221122111??????pppp?????????????????1001)1()1()1()1(2222211221122111??????pppp???????????1)1(0)1(1)1(222221122111????ppp????????????)1(10)1(12222122111??ppp?????????????????22222111110011??ppP要使 P正定對(duì)稱矩陣,則要求 1,121 ?? ?? 且要求特征根位于單位圓內(nèi),與經(jīng)典理論判定一致。 例: 設(shè)離散系統(tǒng)的狀態(tài)方程為 試確定系統(tǒng)在平衡點(diǎn)處漸近穩(wěn)定的條件。 0)(00100010)1( ????????????? kkxkkx解: 選 Q = I, 代入矩陣方程 G T P G – P) = – I ?????????????????????????????????????????????????????1000100010010001001001000333231232221131211333231232221131211pppppppppkpppppppppk??????????????????????????????????????????????10001000100100010000333231232221131211232221331332123111pppppppppkpppkppkppkpp??????????????????????????????????????1000100010)(0000333231232221131211222321321233133111ppppppppppkppkppkppkkpp1001)(00001332232232131223313311123321221131211????????????????????pppkppppkppkkppppppppp??????????????????????????????????????????????10001000100100010000333231232221131211232221331332123111pppppppppkpppkppkppkpp120000001332222332322323323121131211???????????????ppppkpkpppppppp2332222233231211312111312000001kpkkpppppppp????????????????????????????????22213000120001kkkP10 ?? k)(010012 kkGI ????????????????? ??????1001)(00001332232232131223313311123321221131211????????????????????pppkppppkppkkppppppppp 試寫出下列系統(tǒng)的幾個(gè) Lyapunov函數(shù) 并確定該系統(tǒng)原點(diǎn)的穩(wěn)定性 ?????????????????????21213211xxxx??1422212211???????xxxxxx?? 試確定下列線性系統(tǒng)平衡狀態(tài)的穩(wěn)定性 試確定下列二次型是否為正定的。 313221232221 242113 xxxxxxxxxQ ??????? 試確定下列二次型是否為負(fù)定的。 試確定下列非線性系統(tǒng)的原點(diǎn)穩(wěn)定性。 )()(2221221222211211xxxxxxxxxxxx???????????2221 xxV ??考慮下列二次型函數(shù)是否可以作為一個(gè)可能的 Lyapunov函數(shù): )1( ?Tss K0 x y 0 x y b b 0 x y b b a a a a b b (a) (c) (b) N(x) r=0 x(t) c(t) G(jω ) N(x) r=0 x(t) c(t) G(jω ) y y1