elem-system_measurement_model+elem+diagram.tex

% https://tex.stackexchange.com/a/239506/173708
\documentclass{standalone}

\usepackage{tikz}       
\usetikzlibrary{arrows, positioning, patterns, calc, decorations.pathmorphing}

\begin{document}

\tikzstyle{block} = [draw, rectangle, inner sep=6pt, minimum width=2cm, minimum height=1cm, align=center]
\tikzstyle{joint} = [draw, circle, minimum size=1em, anchor=center]
\tikzstyle{layer} = [draw, rectangle, dashed, fill=gray!20, minimum width=7cm, minimum height=8mm, align=center, anchor=center]

\begin{tikzpicture}
    [
        >=stealth, 
        auto, 
        node distance=2cm
    ]
    
    % Place nodes
    \node [block] (system) {System};
    \node [block, below=of system] (model) {Model};
    \node [layer] at ($(system)!.5!(model)$) {\textsc{Measurement}};
    \coordinate [left=of system] (infork) {};
    \coordinate [left=of infork] (input) {};
    \coordinate [right=of system] (outfork) {};
    \coordinate [right=of outfork] (output) {};
    \coordinate [above=of system] (disturbances) {};
    \node [joint, label={[inner sep=1pt]210:\tiny\(+\)}, label={[inner sep=1pt]60:\tiny\(-\)}] (sum) at (outfork|-model) {};
    \coordinate (error) at (output|-model) {};
    % Connect nodes
    \draw [->, decorate, decoration={snake, post length=1mm}] (disturbances) -- node {\(d'\)} (system);
    \draw [->] (input) -- node {\(u'\)} (system);
    \draw [->] (system) -- node {\(t'\)} (output);
    \draw [->] (model) -- node {\(y\)} (sum);
    \draw [->] (sum) -- node {\(\epsilon\)} (error);
    \draw [->] (infork) |- node [anchor=south west] {\(u\)} (model);
    \draw [->] (outfork) -| (sum.north) node [very near end] {\(t\)};
\end{tikzpicture}

\end{document}