با توجه به کدتون میشه به این صورت اصلاحش کرد:
\documentclass{article}
\usepackage{verbatim,tikz,longtable,booktabs,enumitem}
\usepackage{amsmath,amsfonts,amssymb}
\usepackage[american]{circuitikz}
\usetikzlibrary{calc,fit}
\usepackage{pgfplots}
\usetikzlibrary{arrows.meta}
\begin{document}
\begin{figure}[h!]
\centering
\tikzstyle{block} = [draw, fill=white, rectangle,
minimum height=3em, minimum width=6em, thick]
\tikzstyle{sum} = [draw, fill=white, circle, node distance=1cm, minimum height=2em, minimum width=2em, thick]
{\boldmath
\begin{tikzpicture}[auto, node distance=2cm,>=latex, thick]
\node [name=input, label=above:set, label=below:point] {};
\node [sum, right of=input, xshift=.5cm] (sum) {};
\node [block, right of=sum,node distance=2cm] (controller) {$ PI^\lambda D^\nu $};
\node [block, right of=controller, node distance=3cm] (system) {Plant};
\draw [->] (sum) -- (controller);
\draw [->] (controller) -- node[name=u] {} (system);
\node [right of=system , node distance=2cm, inner sep=0pt] (output1) {};
\node [right of=output1 , node distance=1cm] (output) {};
\draw [->] (input) -- node [above, near end] {$ + $} (sum);
\draw [->] (system) -- node [name=y,above] {output}(output);
\node [coordinate, below of=controller](none){};
\draw [->] (system) -- (output);
\draw [->] (output1) |-(none) -| node[pos=0.95] {$-$} node [near end] {} (sum);
\node [coordinate, above of=controller](none1){};
%\draw [->] ([xshift=-0.2cm]u.south) |- (none1) -| (sum);
\end{tikzpicture}}
\label{fig5}
\end{figure}
\end{document}
خروجی:
