# Joining arrows in xy

I am trying to create a control system block diagram in xymatrix, I have 99% done it, but I can't get the feedback loop arrow to join on to the output from the main system as shown below:

\documentclass[11pt,english]{article}
\usepackage[all,cmtip]{xy}
\usepackage{amsmath,amssymb,mathtools,cancel,mathrsfs}
\begin{document}
\begin{displaymath}
\xymatrix@R=1mm@C=10mm{
\ar[r]^-<<{v_a(s)}^>+   &   *+[o][F]{} \ar[r]   &   *+[F]{\dfrac{1}{R_a+L_as}} \ar[r]^-{i_a(s)} &   *++[F]{K_t} \ar[r]^-{T(s)}                  &   *+[F]{\dfrac{1}{J_ms+b}}\ar[rr]^-{\dot{\theta}_m(s)}    &   \ard/0pt[dll][dll]     &   *+[F]{\dfrac{1}{s}}\ar[r]^-{\theta_m(s)}    &\\
&                       &                                               &   *++[F]{K_e} \arl[llu][llu]^-{e(s)}_>>-     &                                                           &                           &                                               &}
\end{displaymath}
\end{document}


Does anybody know how to join these together? I only started using LaTex on Saturday so apologies if this is something simple! Also, If you have any other formatting tips I would gladly hear them!

On a side note, is it possible to create a Filled arrow like this? --|> rather than ->? All the literature I have looked at doesnt seem to mention it apart from tikz!

Thanks,

Anthony

• It would be a lot easier to draw this in tikz – daleif Jan 20 '16 at 10:59
• Please provide a MWE and not a code snippet. – Alenanno Jan 20 '16 at 11:04
• I've come too far with xy to change in this document now sadly - I have around 40 diagrams!, but in future i probably will learn tikz! – Anthony Jan 20 '16 at 13:34
• @MWijnand the MWE compiles fine on my system. – daleif Jan 20 '16 at 14:00
• @Anthony - Sorry for the confusion, but I thought that there was a figure missing in your question. I see an icon in front of your MWE: "... below: [small icon] Block diagram \documentclass" – Karlo Jan 20 '16 at 14:27

Just add *{} before \ar 'd/0pt[dll][dll] to create an empty entry.

code

\documentclass[11pt,english]{article}
\usepackage[all,cmtip]{xy}
\usepackage{amsmath,amssymb,mathtools,cancel,mathrsfs}
\begin{document}
\begin{displaymath}
\xymatrix@R=1mm@C=10mm{
\ar[r]^-<<{v_a(s)}^>+   &   *+[o][F]{} \ar[r]   &   *+[F]{\dfrac{1}{R_a+L_as}} \ar[r]^-{i_a(s)} &   *++[F]{K_t} \ar[r]^-{T(s)}                  &   *+[F]{\dfrac{1}{J_ms+b}}\ar[rr]^-{\dot{\theta}_m(s)}    &  *{} \ar d/0pt[dll][dll] &   *+[F]{\dfrac{1}{s}}\ar[r]^-{\theta_m(s)}    &\\
&                       &                                               &  *++[F]{K_e} \ar l[llu][llu]^-{e(s)}_>>+     &                                                           &                           &                                               &}
\end{displaymath}
\end{document}


Output

• Perfect! thank you so much for your help! I knew it would be something simple, but its surprising how difficult it is to find that out! – Anthony Jan 21 '16 at 2:10