使用 Tikz 绘制带有 2 个 90 度角的箭头

Question

我试图做一个tikzpicture描述如下过程的东西：

有没有办法创建一条带有 2 个断点的线，就像添加的更粗的线一样？

% Definition of blocks:
\tikzset{block/.style    = {draw, thick, rectangle, minimum height = 3em,minimum width = 3em,node distance = 2.4cm},
  sum/.style      = {draw, circle, node distance = 1.5cm}, % Adder
  input/.style    = {coordinate}, % Input
  output/.style   = {coordinate} % Output
    ncbar angle/.initial=90,
    ncbar/.style={
        to path=(\tikztostart)
        -- ($(\tikztostart)!#1!\pgfkeysvalueof{/tikz/ncbar angle}:(\tikztotarget)$)
        -- ($(\tikztotarget)!($(\tikztostart)!#1!\pgfkeysvalueof{/tikz/ncbar angle}:(\tikztotarget)$)!\pgfkeysvalueof{/tikz/ncbar angle}:(\tikztostart)$)
        -- (\tikztotarget)
    },
    ncbar/.default=0.5cm,
  }

% Defining string as labels of certain blocks.
\newcommand{\suma}{\Large}
\newcommand{\inte}{$\displaystyle \int$}
\newcommand{\derv}{\Large $\frac{d}{dt}$}

\begin{tikzpicture}[auto, thick, node distance=2cm, >=triangle 45]
    \draw
    %% Drawing the blocks of first filter :
    node [input, name=input1] {} 
    node [sum, right of=input1] (sum1) {\suma}
    node [block, right of=sum1] (inte1) {\inte}
    node [block, right of=inte1] (inte2) {\inte}
    node [block, right of=inte2] (gain1) {\Large $\frac{1}{V_{c}(t_{f}-t)}$}
    node [block, right of=gain1] (gain2) {\derv}
    node [block, right of=gain2] (gain3) {$N'V_{c}$}
    node [sum, right of=gain3] (sum2) {\suma}
    node [block, above of=gain1] (gain4) {$0.5N'$};

    % Joining blocks. 
    % Commands \draw with options like [->] must be written individually
    \draw[->](input1) -- node {$a_{T}$}(sum1);
    \draw[->](sum1) -- node {$\ddot{y}$} (inte1);
    \draw[->](inte1) -- node {$\dot{y}$} (inte2);
    \draw[->](inte2) -- node {$y$} (gain1);
    \draw[->](gain1) -- node {$\lambda$} (gain2);
    \draw[->](gain2) -- node {$\dot{\lambda}$} (gain3);
    \draw[->](sum1) -- node {$\ddot{y}$} (inte1);
    \draw[->](gain3) -- node {} (sum2);
    \draw[->](sum1) |- node {} (gain4);
    \draw[->](gain4) -| node {} (sum2);
    \draw  (sum2) to [ncbar] (sum1);
\end{tikzpicture}

但是当我使用 [ncbar] 时出现错误

谢谢。

Answer 1

正如评论中提到的，TikZ 是否有与 PSTricks \ncbar 命令等效的命令？描述了几种制作这种线的方法。正如您所指出的，沿着这样的路径添加节点似乎不起作用。

实现相同目的的另一种方法是分两步制定路径，并通过相对于第一个节点的坐标进行，例如

\draw  (sum2) -- node {1} ++(0,-2cm) -| (sum1) node[pos=0.25] {2} node[pos=0.75] {3};

這可以讓您node像pos往常一樣使用。

\documentclass[landscape]{article}
\usepackage{tikz}
\usetikzlibrary{calc,arrows}
% Definition of blocks:
\tikzset{block/.style    = {draw, thick, rectangle, minimum height = 3em,minimum width = 3em,node distance = 2.4cm},
  sum/.style      = {draw, circle, node distance = 1.5cm}, % Adder
  input/.style    = {coordinate}, % Input
  output/.style   = {coordinate}, % Output
}

% Defining string as labels of certain blocks.
\newcommand{\suma}{\Large}
\newcommand{\inte}{$\displaystyle \int$}
\newcommand{\derv}{\Large $\frac{d}{dt}$}
\begin{document}


\begin{tikzpicture}[auto, thick, node distance=2cm, >=triangle 45]
    \draw
    %% Drawing the blocks of first filter :
    node [input, name=input1] {} 
    node [sum, right of=input1] (sum1) {\suma}
    node [block, right of=sum1] (inte1) {\inte}
    node [block, right of=inte1] (inte2) {\inte}
    node [block, right of=inte2] (gain1) {\Large $\frac{1}{V_{c}(t_{f}-t)}$}
    node [block, right of=gain1] (gain2) {\derv}
    node [block, right of=gain2] (gain3) {$N'V_{c}$}
    node [sum, right of=gain3] (sum2) {\suma}
    node [block, above of=gain1] (gain4) {$0.5N'$};

    % Joining blocks. 
    % Commands \draw with options like [->] must be written individually
    \draw[->](input1) -- node {$a_{T}$}(sum1);
    \draw[->](sum1) -- node {$\ddot{y}$} (inte1);
    \draw[->](inte1) -- node {$\dot{y}$} (inte2);
    \draw[->](inte2) -- node {$y$} (gain1);
    \draw[->](gain1) -- node {$\lambda$} (gain2);
    \draw[->](gain2) -- node {$\dot{\lambda}$} (gain3);
    \draw[->](sum1) -- node {$\ddot{y}$} (inte1);
    \draw[->](gain3) -- node {} (sum2);
    \draw[->](sum1) |- node {} (gain4);
    \draw[->](gain4) -| node {} (sum2);

    \draw  (sum2) -- node {1} ++(0,-2cm) -| (sum1) node[pos=0.25] {2} node[pos=0.75] {3};
\end{tikzpicture}
\end{document}