pid_structure.tex

\begin{tikzpicture}[ auto, node distance=1.5cm, >=Latex,
    signal_label/.style={fill=white, inner sep=1.5pt, font=\small},
    block/.style={draw, fill=white, rectangle, align=center,
      minimum height=2*\ht\strutbox, minimum width=7*\ht\strutbox,
      font=\small},
  sum/.style={draw, fill=white, circle, inner sep=1pt} ]

  % Nodes

  \node [signal_label] (input_text) {задание};
  \node [sum, right=0.6cm of input_text] (sum1) {\Large $\Sigma$};

  % Main control loop distance
  \node [sum, right=6.5cm of sum1] (sum2) {\Large $\Sigma$};

  % Branch point (error signal)
  \node [coordinate, right=1.2cm of sum1] (branch) {};

  % PID Blocks: positioned exactly between branch and sum2
  \node [block] (integral) at ($(branch)!0.5!(sum2)$)
    { \textbf{I} $K_I \int_{0}^{t} e(t) dt$ };
  \node [block] (prop) at ($(integral.center) + (0, 1.2)$)
    { \textbf{P} \qquad $K_P e(t)$ };
  \node [block] (deriv) at ($(integral.center) + (0, -1.2)$)
    { \textbf{D} \qquad $K_D \frac{de}{dt}$ };

  % Process and output nodes
  \node [block, right=0.6cm of sum2] (process) {\textbf{процесс}};

  \node [signal_label, right=0.6cm of process] (out_text) {выход};

  \node [coordinate] (end_point) at ($(out_text.east) + (0.6,0)$) {};
  \node [coordinate] (feedback_node) at ($(out_text.east)!0.5!(end_point)$) {};

  % Connections

  \draw [->] (input_text) -- node[above, pos=0.8, font=\footnotesize] {$+$}
  (sum1);

  \node [signal_label] (err_text) at (branch) {ошибка};
  \draw [->] (sum1) -- (err_text);

  % Signal branching to PID components
  \draw [->] (err_text) -- (integral);
  \draw [->] (err_text) |- (prop);
  \draw [->] (err_text) |- (deriv);

  % Signal summing from PID components
  \draw [->] (prop) -| (sum2);
  \draw [->] (integral) -- (sum2);
  \draw [->] (deriv) -| (sum2);

  \draw [->] (sum2) -- (process);
  \draw [->] (process) -- (out_text);

  \draw [->] (out_text) -- (end_point);

  % Feedback loop
  \draw [->] (feedback_node) |- ++(0,-2.0) -| node[left,
    pos=0.98,font=\footnotesize] {$-$} (sum1);

\end{tikzpicture}