% ---------------------------------------------------------------
% Observador de Luenberger (nível de blocos)
%   Planta:     x_dot = A x + B u ,  y = C x
%   Observador: xhat_dot = A xhat + B u + L (y - C xhat)
% Bibliotecas (chunk .qmd): arrows.meta, positioning, calc
% ---------------------------------------------------------------
\begin{tikzpicture}[>=Latex, line width=0.9pt,
  big/.style={draw, minimum width=3.2cm, minimum height=1.6cm, fill=blue!8, align=center},
  sum/.style={draw, circle, minimum size=8mm, inner sep=0pt}]

  \node (u)             at (-1.5,0) {$u$};
  \node[big] (plant)    at (1.8,0)  {Planta\\$\dot{\mathbf{x}}=\mathbf{A}\mathbf{x}+\mathbf{B}u$\\$y=\mathbf{C}\mathbf{x}$};
  \node (y)             at (5.6,0)  {$y$};

  \node[big] (obs)      at (1.8,-3.0) {Observador\\$\dot{\hat{\mathbf{x}}}=\mathbf{A}\hat{\mathbf{x}}+\mathbf{B}u+\mathbf{L}(y-\mathbf{C}\hat{\mathbf{x}})$};
  \node (xhat)          at (5.6,-3.0) {$\hat{\mathbf{x}}$};

  % u para planta e observador
  \fill (-0.4,0) circle (1.6pt);
  \draw[->] (u) -- (plant);
  \draw[-]  (-0.4,0) -- (-0.4,-3.0);
  \draw[->] (-0.4,-3.0) -- (obs);

  % saída da planta
  \draw[->] (plant) -- (y);

  % y realimentado ao observador
  \fill (4.6,0) circle (1.6pt);
  \draw[-]  (4.6,0) -- (4.6,-1.6);
  \draw[->] (4.6,-1.6) -- (4.6,-3.0) -- (obs.east -| 4.6,-3.0);

  % estado estimado
  \draw[->] (obs) -- (xhat);

  \node[font=\small, gray!60!black] at (1.8,-4.4)
        {Erro $\;e=\mathbf{x}-\hat{\mathbf{x}}\;\Rightarrow\; \dot{e}=(\mathbf{A}-\mathbf{L}\mathbf{C})e$};

\end{tikzpicture}