Pfthb

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 :

documentclassarticle

usepackage[utf8]inputenc

usepackagetikz

usetikzlibraryshapes,arrows

usetikzlibrarypositioning, quotes

begindocument

tikzstyleblock = [draw, fill=white, rectangle, 
 minimum height=6em, minimum width=12em]

tikzstylesum = [draw, fill=white, circle, node distance=2cm]

tikzstyleinput = [coordinate]

tikzstyleoutput = [coordinate]

begincenter

begintikzpicture[auto, node distance=4cm,>=latex']
 node [input, name=input] ;

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

 node [block, right of=sum] (controller) beginarray dotx(t)=&Ax(t)+Bu(t)\ x(0)=&x_0 endarray;

 !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);
endtikzpicture

endcenter

enddocument

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:

documentclassarticle

usepackage[utf8]inputenc
usepackageamsmath
usepackagetikz
usetikzlibraryarrows,positioning

begindocument

tikzsetblock/.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

begincenter

begintikzpicture[auto, node distance=2cm,>=latex']
 node [input, name=input] ;

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

 node [block, right=of sum,align=left] (controller) 
 $beginarrayr@,l dotx(t)=&Ax(t)+Bu(t)\ x(0)=&x_0 endarray$;

 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);
endtikzpicture
endcenter

Like this?

documentclassminimal
usepackage[utf8]inputenc
usepackagetikz
usetikzlibraryshapes,arrows
usetikzlibrarypositioning, quotes
newlengthmywidth
setlengthmywidth2cm

begindocument

tikzstyleblock = [draw, fill=white, rectangle, 
 minimum height=6em, minimum width=12em]
tikzstylesum = [draw, fill=white, circle, node distance=2cm]
tikzstyleinput = [coordinate]
tikzstyleoutput = [coordinate]

begincenter
begintikzpicture[auto, node distance=4cm,>=latex']
 node [input, name=input] ;
 node [sum, right=mywidth of input] (sum) B;
 node [block, right=mywidth of sum] (controller) $beginarrayccc dotx(t)&=&Ax(t)+Bu(t)\ x(0)&=&x_0 endarray$;
 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);
endtikzpicture

endcenter

enddocument