Equivalent Realization

Definition (Equivalent realization)

We say that two Realizations (A,B,C,D)(A,B,C,D) and (A~,B~,C~,D~)(\tilde{A},\tilde{B},\tilde{C},\tilde{D}) of a given Weighting Pattern are equivalent if ∀u∈C([t0,∞],Rm)\forall u\in C([t_{0},\infty],\mathbb{R}^{m}) and ∀t≥t0\forall t\ge t_{0}, we have ∫t0tCeA(t−τ)Bu(τ) dτ+Du(t)=∫t0tC~eA~(t−τ)B~u(τ) dτ+D~u(t)\int\limits _{t_{0}}^{t}Ce^{A(t-\tau)}Bu(\tau) \, d\tau+Du(t)=\int\limits _{t_{0}}^{t}\tilde{C}e^{\tilde{A}(t-\tau)}\tilde{B}u(\tau) \, d\tau +\tilde{D}u(t)

Lemma (Alternative characterization of equivalence)

Two Realizations (A,B,C,D)(A,B,C,D) and (A~,B~,C~,D~)(\tilde{A},\tilde{B},\tilde{C},\tilde{D}) of a given Weighting Pattern are equivalent if and only if ∀t≥0:CeAtB=C~eA~tB~  ⟺  ∀k∈N:CAkB=C~A~kB~\forall t\geq 0:Ce^{At}B=\tilde{C}e^{\tilde{A}t}\tilde{B}\iff \forall k\in\mathbb{N}:CA^{k}B=\tilde{C}\tilde{A}^{k}\tilde{B}and D=D~D=\tilde{D}

Lemma (Realizations are Equivalent if Laplace Transform is Equivalent)

Two Realizations (A,B,C,D)(A,B,C,D) and (A~,B~,C~,D~)(\tilde{A},\tilde{B},\tilde{C},\tilde{D}) are equivalent if and only if (ABCD)(s)=(A~B~C~D~)(s)\begin{pmatrix}\begin{array}{c|c} A&B \\ \hline C &D \end{array}\end{pmatrix}(s)=\begin{pmatrix}\begin{array}{c|c} \tilde{A}&\tilde{B} \\ \hline \tilde{C} &\tilde{D} \end{array}\end{pmatrix}(s)∀s∈C\forall s \in\mathbb{C} where the Transfer Functions are defined.

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