Ndtyjky

I am trying to draw a picture representing a control theory graph.

I am pretty much there, but there are two problems:

1. I need to have a dot above the x(t) in the first equation in the big box. When I put it in maths mode, it draws four lines instead of two, or, depending on how I split the maths mode, it puts it all on one line. Any ideas on how to get that damned dot above the x without changing the layout of the box?




2. The RHS arrow with the y(.) above it is too long. I would like to get it back down to a length close to the LHS arrow with the v(.), it would just look nicer!

Here is my code :

documentclass{article}



usepackage[utf8]{inputenc}



usepackage{tikz}



usetikzlibrary{shapes,arrows}



usetikzlibrary{positioning, quotes}



begin{document}



tikzstyle{block} = [draw, fill=white, rectangle, 

    minimum height=6em, minimum width=12em]



tikzstyle{sum} = [draw, fill=white, circle, node distance=2cm]



tikzstyle{input} = [coordinate]



tikzstyle{output} = [coordinate]



begin{center}



begin{tikzpicture}[auto, node distance=4cm,>=latex']

    node [input, name=input] {};



    node [sum, right of=input] (sum) {B};



    node [block, right of=sum] (controller) {begin{array} dot{x}(t)=&Ax(t)+Bu(t)\ x(0)=&x_0 end{array}};



    !node [sum, right of=controller, node distance=3.651cm] (mat) {C};

    node [sum, below of=controller] (K) {K};

    node [output, right of=controller] (output) {C};

    node [input, name=end, right of=output, node distance=5cm] {};

    coordinate [below of=sum] (measurements) {};

    coordinate [right of=output](fin) {};

    coordinate[left of =output, xshift=2.7cm] (nodek) {};

    draw [draw,->] (input) -- node {$v(bullet)$} (sum);

    draw [->] (sum) -- node {$u(bullet)$} (controller);

    draw [->] (controller) -- node[name=(x)] {$x(bullet)$} (mat) {};

    draw [->] (output) -- node {$y(bullet)$} (fin);

    draw [-] (nodek) |- (K);

    draw [->] (K) -| (sum);

end{tikzpicture}



end{center}



end{document}

Similar to jak123's nice answer but with some slight differences:

• Rather than introducing a new length mywidth I make use of the node distance=2cm key.


• I also switch to the tikzset syntax instead of tikzstyle.


• I drop superfluous elements of the code.

Here is what went wrong in your code

• You forgot to add the column specifiers in the array, which is why it did not work.


• You were loading but not using the positioning library.


• Several coordinates were redundant.

So here is the result:

documentclass{article}



usepackage[utf8]{inputenc}

usepackage{amsmath}

usepackage{tikz}

usetikzlibrary{arrows,positioning}



begin{document}



tikzset{block/.style={draw, fill=white, rectangle, 

    minimum height=6em, minimum width=12em},

sum/.style={draw, fill=white, circle, node distance=2cm},

input/.style={coordinate},

output/.style={coordinate}}



begin{center}



begin{tikzpicture}[auto, node distance=2cm,>=latex']

    node [input, name=input] {};



    node [sum, right= of input] (sum) {B};



    node [block, right=of sum,align=left] (controller) 

    {$begin{array}{r@{,}l} dot{x}(t)=&Ax(t)+Bu(t)\ x(0)=&x_0 end{array}$};



    node [sum, right=of controller] (mat) {C};

    node [sum, below=1cm of controller] (K) {K};

    coordinate [below=of sum] (measurements) {};

    coordinate [right=1.5cm of mat](fin) {};

    draw [draw,->] (input) -- node {$v(bullet)$} (sum);

    draw [->] (sum) -- node {$u(bullet)$} (controller);

    draw [->] (controller) -- node[name=x,above,midway] {$x(bullet)$} 

    coordinate[midway] (x) (mat);

    draw [->] (mat) -- node[midway,above] {$y(bullet)$} (fin);

    draw [-] (x) |- (K);

    draw [->] (K) -| (sum);

end{tikzpicture}

end{center}

Like this?

documentclass{minimal}

usepackage[utf8]{inputenc}

usepackage{tikz}

usetikzlibrary{shapes,arrows}

usetikzlibrary{positioning, quotes}

newlength{mywidth}

setlength{mywidth}{2cm}



begin{document}



tikzstyle{block} = [draw, fill=white, rectangle, 

    minimum height=6em, minimum width=12em]

tikzstyle{sum} = [draw, fill=white, circle, node distance=2cm]

tikzstyle{input} = [coordinate]

tikzstyle{output} = [coordinate]



begin{center}

begin{tikzpicture}[auto, node distance=4cm,>=latex']

    node [input, name=input] {};

    node [sum, right=mywidth of input] (sum) {B};

    node [block, right=mywidth of sum] (controller) {$begin{array}{ccc} dot{x}(t)&=&Ax(t)+Bu(t)\ x(0)&=&x_0 end{array}$};

    node [sum, right=mywidth of controller] (mat) {C};

    node [sum, below=1cm of controller] (K) {K};

    node [output, right=mywidth of controller] (output) {C};

    node [input, name=end, right=mywidth of output] {};

    coordinate [below=mywidth of sum] (measurements) {};

    coordinate [right=mywidth of output] (fin) {};

    coordinate[left = mywidth/2 of output] (nodek) {};

    draw [draw,->] (input) -- node {$v(bullet)$} (sum);

    draw [->] (sum) -- node {$u(bullet)$} (controller);

    draw [->] (controller) -- node[name=(x)] {$x(bullet)$} (mat) {};

    draw [->] (mat) -- node {$y(bullet)$} (fin);

    draw [-] (nodek) |- (K);

    draw [->] (K) -| (sum);

end{tikzpicture}



end{center}



end{document}