How can I shift the system node right of control1 but vertically centered between control1 and control2?
\tikzstyle{controller} = [draw, fill=blue!20, rectangle,
minimum height=3em, minimum width=6em]
\tikzstyle{block} = [draw, fill=yellow!20, rectangle,
minimum height=3em, minimum width=6em]
\tikzstyle{sum} = [draw, circle, node distance=1.5cm]
\tikzstyle{disturbance} = [draw=none, node distance=1.5cm, line width=0pt]
\tikzstyle{input} = [coordinate]
\tikzstyle{output} = [coordinate]
\node [input, name=input] {};
\node [sum, right of=input] (sum) {};
\node [controller, right of=sum] (control1){Control1};
\node [controller, above of=control1] (control2) {Control2};
\node [block, right of= control1, node distance=5cm, yshift=-1.4cm] (system) {System};
