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The Nonregular Dynamical System Chapter | 5 151


                           Setting
                                                        C
                                                  	     
       ⎛    ⎞
                                                                   x 1
                                                     01 −1
                                               y =              ⎝  x 2  ⎠
                                                     01     0
                                                                   x 3
                                                    2
                           and defining the function   : R → R;X  →  (X) by the formula
                                                 (X) = ϕ D (X 1 ) + ϕ Z (X 2 ),

                           we may write relations (5.18) equivalently as

                                                     y L ∈ ∂ (Cx).
                              It is easy to see that

                                                   2
                                                                       2 T
                                        rank{(B AB A B)}= rank{(C CA CA ) }= 3,
                           and a simple computation shows that the transfer function
                           H(s) = C(sI − A) −1 B
                                   ⎛                                                    ⎞
                                              2
                                     2
                               1    s C 4 L 3 + s C 4 L 2 + sC 4 R 2 + sC 4 R 3 + 1  C 4 L 3 s(sL 2 + R 2 )
                                                                         L 2
                            =      ⎝                                                    ⎠  ,
                              D(s)             C 4 s(sL 2 + R 2 )     C 4 L 3  s(sL 2 + R 1 + R 2 )
                                                                       L 2
                           where
                                      3         2          2          2
                              D(s) = s C 4 L 3 L 2 + s C 4 L 3 R1 + s C 4 L 3 R 2 + s C 4 R 1 L 2 + sC 4 R 1 R 2
                                       2
                                     + s C 4 R 3 L 2 + sC 4 R 3 R 1 + sC 4 R 3 R 2 + sL 2 + R 1 + R 2 ,
                           is positive real. Thus the existence of a matrix R that satisfies condition (G1)
                           also is a consequence of the Kalman–Yakubovich–Popov lemma. A simple com-
                           putation shows that the matrix

                                                   ⎛                  ⎞
                                                       1
                                                     √      0     0
                                                       C 4
                                                           √
                                                   ⎜                  ⎟
                                               R =  ⎜  0    L 3   0   ⎟
                                                   ⎝                  ⎠
                                                                 √
                                                      0     0     L 2
                           is convenient. The matrix R ∈ R n×n  is symmetric and positive definite. We see
                           that
                                        ⎛             ⎞  ⎛       ⎞   ⎛           ⎞
                                          C 4  0   0       0   0          0    0
                                 −2  T  ⎜      1      ⎟  ⎜       ⎟   ⎜    1   1  ⎟
                                        ⎜ 0
                               R   C =             0 ⎟  ⎝ 1    1 ⎠ =  ⎜          ⎟  = B.
                                               L 3                       L 3
                                        ⎝             ⎠              ⎝        L 3 ⎠
                                           0   0    1      −10          −  1   0
                                                   L 2                   L 2
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