\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,  thick]
	{\boldmath
		\begin{tikzpicture}[auto, node distance=2cm,>=latex, thick]
		\node [name=input] {};
		\node [sum, right of=input] (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 [name=output, right of=system , node distance=4cm] (output) {};
		\draw [->] (input) -- node [above] {set  $\quad +$} (sum);
		\draw [->] (input) -- node [below] {point  $\quad -$} (sum);
		\draw [->] (system) -- node [name=y,above] {output}(output);
		\node [coordinate, below of=controller](none){};
		
		\draw [->] (system) -- (output);
		\draw [->] (output) |-(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}