[Tex/LaTex] Help me make the TikZ Petri net look nice!

tikz-pgf

I am trying to draw the following diagram in TikZ:

Their image

My attempt looks like this (note the node labels are slightly different but that's not my problem!):

my attempt

My code is the following:

\documentclass[11pt,a4paper]{report}

\usepackage[USenglish]{babel} 
\usepackage[T1]{fontenc}
\usepackage[ansinew]{inputenc}
\usepackage{lmodern} 

\usepackage{tikz}

\usetikzlibrary{positioning,fit,backgrounds,arrows,shapes,automata,petri}

\tikzset{
    place/.style={
        circle,
        thick,
        minimum size=6mm,
                draw
    },
    transitionV/.style={
        rectangle,
        thick,
        fill=black,
        minimum height=6mm,
        inner xsep=1pt
    }
}

\begin{document}

\title{Test}
\author{Me}
\date{\today}
\begin{figure}[h!]
\centering
\begin{tikzpicture}[node distance=1cm and 2cm,>=stealth',bend     angle=45,thick]
        \node [transitionV,label=above:$q_1$] (q1) {};
        \node [place,tokens=1,label=above:$\alpha_{11}(k)$] (p11) [below= of q1] {}
            edge[pre,bend right,overlay] (q1)
            edge[post,bend left,overlay] (q1);
        \node [place,tokens=2,label=above:$\alpha_{41}(k)$] (p41) [below right=0.25cm and 2cm of q1] {}
            edge[pre] (q1);
        \node [transitionV,label=above:$q_4$] (q4) [below right=0.25cm and 2cm of p41] {}
            edge[pre] (p41);
        \node [place,label=above:$\alpha_{24}(k)$] (p24) [above right=0.25cm and 2cm of q4] {}
            edge[pre] (q4);
        \node [transitionV,label=above:$q_2$] (q2) [above right=0.25cm and 2cm of p24] {}
                edge[pre] (p24);
        \node [place,tokens=1,label=above:$\alpha_{22}(k)$] (p22) [below= of q2] {}
                edge[pre,bend right,overlay] (q2)
                edge[post,bend left,overlay] (q2);
        \node [place,tokens=1,label=above:$\alpha_{31}(k)$] (p31) [above right=0.25cm and 2cm of q1] {}
                edge[pre] (q1);
        \node [transitionV,label=below:$q_3$] (q3) [above right=0.25cm and 2cm of p31] {}
            edge[pre] (p31);
        \node [place,label=above:$\alpha_{23}(k)$] (p23) [below right=0.25cm and 2cm of q3] {}
                edge[pre] (q3)
                edge[post] (q2);
        \node [place,tokens=1,label=below:$\alpha_{12}(k)$] (p12) [above= of q3] {}
                edge[pre,bend left,out=45,in=45,looseness=1.2] (q2)
                edge[post,bend left,out=315,in=315,looseness=1.2] (q1);
\end{tikzpicture}
\caption{Event graph}
\end{figure}

\end{document}

I've exhausted my knowledge of TikZ. Please could someone tell me how I could get my diagram looking nice like the example above? Thanks!

Best Answer

Please ask specific questions of what you want to have, what you have tried, and where you have failed to reach that. Like it stands now, it is no research value for this site and just a "do it for me" post.

I corrected the two main issues I have seen. The rest should be self explanatory from the code you already have.

% arara: pdflatex

\documentclass[11pt,a4paper]{report}
\usepackage[USenglish]{babel} 
\usepackage[T1]{fontenc}
\usepackage[ansinew]{inputenc}
\usepackage{lmodern} 
\usepackage{tikz}
\usetikzlibrary{positioning,arrows,petri}

\tikzset{
    place/.style={
        circle,
        thick,
        minimum size=6mm,
        draw
    },
    transitionV/.style={
        rectangle,
        thick,
        fill=black,
        minimum height=6mm,
        inner xsep=1pt
    }
}

\begin{document}
    \begin{figure}[h!]
        \centering
        \begin{tikzpicture}[node distance=1cm and 2cm,>=stealth',bend angle=45,thick]
        \node [transitionV,label=above:$q_1$] (q1) {};
        \node [place,tokens=1,label=above:$\alpha_{11}(k)$] (p11) [below= of q1] {}
        edge[pre,bend right=70] (q1)
        edge[post,bend left=70] (q1);
        \node [place,tokens=2,label=above:$\alpha_{41}(k)$] (p41) [below right=0.25cm and 2cm of q1] {}
        edge[pre] (q1);
        \node [transitionV,label=above:$q_4$] (q4) [below right=0.25cm and 2cm of p41] {}
        edge[pre] (p41);
        \node [place,label=above:$\alpha_{24}(k)$] (p24) [above right=0.25cm and 2cm of q4] {}
        edge[pre] (q4);
        \node [transitionV,label=above:$q_2$] (q2) [above right=0.25cm and 2cm of p24] {}
        edge[pre] (p24);
        \node [place,tokens=1,label=above:$\alpha_{22}(k)$] (p22) [below= of q2] {}
        edge[pre,bend right=70] (q2)
        edge[post,bend left=70] (q2);
        \node [place,tokens=1,label=above:$\alpha_{31}(k)$] (p31) [above right=0.25cm and 2cm of q1] {}
        edge[pre] (q1);
        \node [transitionV,label=below:$q_3$] (q3) [above right=0.25cm and 2cm of p31] {}
        edge[pre] (p31);
        \node [place,label=above:$\alpha_{23}(k)$] (p23) [below right=0.25cm and 2cm of q3] {}
        edge[pre] (q3)
        edge[post] (q2);
        \node [place,tokens=1,label=below:$\alpha_{12}(k)$] (p12) [above= of q3] {}
        edge[pre,out=0,in=20,,looseness=1.2] (q2)
        edge[post,out=180,in=160,looseness=1.2] (q1);
        \end{tikzpicture}
        \caption{Event graph}
    \end{figure}    
\end{document}

enter image description here