As written in the title I need to let the lines go into the center of the circle. [Code Part at: %Pfeile von den Dots zu den K-Kreisen ] I don't want to use coordinates, only the nodes in reference to each other.

```
    \documentclass{standalone}
\usepackage{tikz}
\begin{document}
    \begin{tikzpicture}
    [thick,node distance = 12ex, 
    box/.style={fill=white,rectangle, draw=black}, 
    blackdot/.style={inner sep = 0, minimum size=3pt,shape=circle,fill,draw=black},
    plus/.style={fill=white,circle,inner sep = 0,thick,draw},
    metabox/.style={inner sep = 3ex,rectangle,draw,dotted,fill=gray!20!white}
    circle/.style={fill=white, circle, draw=black}
    ]

\node(Sum1) [box, minimum size = 6ex]{$\sum_{1}^{}$};
\node(Sum2) [box, minimum size = 6ex, below of = Sum1, yshift = 2 ex]{$\sum_{2}^{}$};

\node(k1) [plus, left of = Sum1, minimum size = 6 ex]{$k_1$};
\node(k2) [plus, right of = Sum2, minimum size = 6 ex]{$k_2$};

\node(dot1) [blackdot, right of = Sum1, xshift = -4ex]{};
\node(dot2) [blackdot, left of = Sum2, xshift = 4ex]{};

%Pfeile von den Dots zu den K-Kreisen
\node(Hilfspunkt2) [draw=none, fill=none, below of = dot2, yshift=4ex]{};
\draw [-] (dot2) -- (Hilfspunkt2){};
\draw [->] (Hilfspunkt2) -| (k2){};
\node(Hilfspunkt1) [minimum size = 0.1mm, above of = dot1, yshift=-4ex]{};
\draw [-] (dot1) -- (Hilfspunkt1){};
\draw [->] (Hilfspunkt1) -| (k1){};

%Pfeile zu den k-Kreisen
\node(out1)   [right of = k2, minimum size=0pt, inner sep = 0pt, xshift = -3ex]{};
\node(out2)   [left of = k1, minimum size=0pt, inner sep = 0pt, xshift = 3ex]{};
\draw[->](out1) -- (k2) node[below, xshift = 6 ex]{$v_2$};
\draw[->](out2) -- (k1)node[below, xshift = -6 ex]{$v_1$};

%Verbindung zwischen Sum-Boxen und den Nodepunkten
\draw[-](Sum1) -- (dot1){};
\draw[-](Sum2) -- (dot2){};

%Pfeile von den K-Kreisen zu den Sum-Boxen
\draw[->](k1) -- (Sum1)node[below, xshift=-6ex]{$u_1$};
\draw[->](k2) -- (Sum2)node[below, xshift=6ex]{$u_2$};

%Eckpfeile von den Nodepunkten zu den k-Kreisen
\draw[->] (dot1) -| (k2) node[xshift=-4ex, yshift=8ex]{$y_1$};
\draw[->] (dot2) -| (k1) node[xshift=4ex, yshift=-8ex]{$y_2$};

    \end{tikzpicture}
\end{document}

```