Commit b822ce71 by Olle Kjellqvist

 \documentclass{standalone} \usepackage{tikz, amsmath} \usetikzlibrary{shapes, positioning, arrows} \begin{document} \begin{tikzpicture}[auto, >=latex, node distance=1.3cm, line width=0.2mm] \tikzstyle{block} = [draw, rectangle, minimum height=0.7cm, minimum width=1cm] \tikzstyle{sum} = [draw, circle,label=center:{$+$}, minimum width=1em] % We start by placing the blocks \node [coordinate, name=input] {}; \node [sum, right=1cm of input] (sum) {}; \node [block, right of=sum] (controller) {$C(s)$}; \node [sum, right of=controller] (add_load) {}; \node [coordinate, above=.6cm of add_load] (load) {}; \node [block, right of=add_load] (system) {$P(s)$}; \node [block, below=0.6cm of add_load] (negative) {$-1$}; \node [sum, right of=system] (add_noise) {}; \node [coordinate, above=.6cm of add_noise] (noise) {}; \node [coordinate, right of=add_noise] (output) {}; % We draw an edge between the controller and system block to % calculate the coordinate u. We need it to place the measurement block. \draw [->] (input) -- node[name=r] {$r$} (sum); \draw [->] (sum) -- node[name=e] {$e$} (controller); \draw [->] (controller) -- node[name=u0] {$u$} (add_load); \draw [->] (add_load) -- (system); \draw [->] (system) -- node {$z$} (add_noise); \draw [->] (add_noise) -- node[name=y] {$y$} (output); \draw [->] (y) |- (negative); \draw [->] (negative) -| (sum); \draw [->] (noise) -- node {$n$} (add_noise); \draw [->] (load) -- node {$d$} (add_load); \end{tikzpicture} \end{document} ~ ~ ~ ~
 \documentclass{standalone} \usepackage{tikz} \usetikzlibrary{shapes, positioning, arrows} \begin{document} \begin{tikzpicture}[auto, node distance=2cm, >=latex, line width=0.2mm] % Define the usual nice things for block diagrams \tikzstyle{block} = [draw, rectangle, minimum height=1cm, minimum width=1cm] \tikzstyle{sum} = [draw, circle, node distance=1cm] % We start by placing the blocks \node[block] (P) {$P$}; \node[coordinate, left of=P] (input){}; \node[coordinate, right of=P] (output){}; % Now we draw the edges \draw[->](input) -- node {$u$} (P); \draw[->](P) -- node {$y$} (output); \end{tikzpicture} \end{document}