cascade1
\documentclass{standalone} \usepackage[utf8]{inputenc} \usepackage{amsmath,amsfonts,amssymb} \usepackage{tikz} \usetikzlibrary{shapes,positioning} \usetikzlibrary{narrow} \tikzset{block/.style={draw, rectangle, line width=2pt, minimum height=3em, minimum width=3em, outer sep=0pt}} \tikzset{sumcircle/.style={draw, circle, outer sep=0pt, label=center:{{$\sum$}}, minimum width=2em}} \tikzset{every picture/.style={auto, line width=1pt, >=narrow,font=\small}} \begin{document} \begin{tikzpicture} \node[block](GP2){$G_{P2}$}; \node[block, left=12mm of GP2](GP1){$G_{P1}$}; \node[block, left=12mm of GP1](GR1){$G_{R1}$}; \node[sumcircle, left=8mm of GR1](sum2){}; \node[block, left=12mm of sum2](GR2){$G_{R2}$}; \node[sumcircle, left=8mm of GR2](sum1){}; \coordinate[left=8mm of sum1](input); \coordinate[right=12mm of GP2](output); \draw[->](input)--node[xshift=-2mm](R2){$R_2$}(sum1); \draw[->](sum1)--(GR2); \draw[->](GR2)--node[](R1){$R_1$}(sum2); \draw[->](sum2)--(GR1); \draw[->](GR1)--node[](U){$U$}(GP1); \draw[->](GP1)--node[](Y1){$Y_1$}(GP2); \draw[->](GP2)--node[](Y2){$Y_2$}(output); \node[block, below=10mm of U](M1){$MA$}; \node[block, below=6mm of M1](M2){$MB$}; \draw[->](Y2)|-(M2); \draw[->](M2)-|(sum1); \draw[->](Y1)|-(M1); \draw[->](M1)-|(sum2); \end{tikzpicture} \end{document}