[Tex/LaTex] Block diagram with Tikz

Question

It's the first time I'm using Tikz on Latex. I have to draw this block diagram (this is a low resolution snip from a paper)

In Tikz I have done this:

That is very similar but I need some adjustments, like the u_i arrow and the node sum after the H(s) block.

Is there anybody that can help me with this?
my code:

    \tikzstyle{block} = [draw, fill=white, rectangle, 
minimum height=2em, minimum width=3em]
\tikzstyle{sum} = [draw, fill=white, circle, radius=1mm, node distance=1.5cm]
\tikzstyle{input} = [coordinate]
\tikzstyle{output} = [coordinate]
\tikzstyle{pinstyle} = [pin edge={to-,thin,black}]

\begin{tikzpicture}[auto, node distance=2cm,>=latex']
\node [input, name=input] {};
\node [input, above of=input](input1) {};
\node [sum, right of=input] (sum) {};
\node [block, right of=sum] (controller) {$K(s)$};
\node [sum, right of=controller] (sum1) {};
\node [block, right of=sum1] (filterinv) {$H^{-1}(s)$};
\node [block, right of=filterinv] (system) {$G(s)$};
\node [output, right of=system] (output) {};
\node [output, above of=output] (output1) {};
\node [block, below of=filterinv] (filter) {$H(s)$};
\node [block, above of=controller] (delay) {$D(s)$};
\node [sum, below of=sum1] (sum2) {};

\draw [->] (filterinv) -- node[name=u] {$u_{i}$} (system);
\draw [draw,->] (input) -- node {$s_{i-1}$} (sum);
\draw [->] (sum) -- node {$e_{i}$} (controller);
\draw [->] (system) -- node [name=q] {$q_{i}$}(output);
\draw [->] (q) |- (filter);
\draw [->] (filter) -- node {} (sum2);
\draw [->] (controller) -- node {} (sum1);
\draw [->] (sum1) -- node[name=xi] {$\xi_{i}$} (filterinv);
\node [input, below of=sum1](input2) {};
\draw [draw,->] (input2) -- node {$r_{i}$} (sum2);
\draw [->] (sum2) -| node[pos=0.99] {$-$} 
    node [near end] {$\tilde{s}_i$} (sum);
\draw [->] (delay) -| node[] {} 
    node [near end] {} (sum1);
\draw [draw,->] (input1) -- node[pos=0.15] {$u_{i-1}$} (delay);
\draw [->] (u) |- node[pos=0.99] {$u_i$} 
    node [near end] {} (output1);

\end{tikzpicture}

Answer 1

You already did it all the work, so I just will explain what I've changed in your code.

You used tikset which has been deprecated in front of tikzstyle (see: Should \tikzset or \tikzstyle be used to define TikZ styles?).

The second big change was to replace right of = syntax by the new right= of from positioning library (section "17.5.3 Advanced Placement Options" in pgfmanual). And also used on grid option to better align all elements.

As I've used on grid, inputs and outputs are still defined as nodes with inner sep=0pt instead of coordinates. on grid option doesn't work as expected with coordinates (see: How does the 'on grid' node positioning in TikZ actually work?)

The missalignment between filter and sum2 node was due to using different node distance for sum nodes and all other ones. I've kept different distance but placed filter with a intersection coordinate (filter) at (sum2-|filterinv).

\documentclass[tikz, border=2mm]{standalone}

\usetikzlibrary{positioning,arrows}

\begin{document}

\tikzset{%
    block/.style={draw, fill=white, rectangle, 
            minimum height=2em, minimum width=3em},
    input/.style={inner sep=0pt},       
    output/.style={inner sep=0pt},      
    sum/.style = {draw, fill=white, circle, minimum size=2mm, node distance=1.5cm, inner sep=0pt},
    pinstyle/.style = {pin edge={to-,thin,black}}
}

\begin{tikzpicture}[auto, node distance=2cm, on grid, >=latex']

\node[input] (input) {};
\node[input, above = of input] (input1) {};
\node [sum, right = of input] (sum) {};
\node [block, right = of sum] (controller) {$K(s)$};
\node [sum, right = of controller] (sum1) {};
\node [block, right = of sum1] (filterinv) {$H^{-1}(s)$};
\node [block, right = 2.5cm of filterinv] (system) {$G(s)$};
\node [output, right = of system] (output) {};
\node [output, above = of output] (output1) {};
\node [block, above = of controller] (delay) {$D(s)$};
\node [sum, below = of sum1] (sum2) {};
\node [block] (filter) at (sum2-|filterinv) {$H(s)$};

\draw [draw,->] (input) node[above right] {$s_{i-1}$} -- (sum);
\draw [->] (sum) -- node {$e_{i}$} (controller);
\draw [->] (controller) -- node {} (sum1);
\draw [->] (sum1) -- node[name=xi] {$\xi_{i}$} (filterinv);
\draw [->] (filterinv) -- node[name=u, pos=.3] {$u_{i}$} (system);
\draw [->] (system) -- (output) node [name=q, above left] {$q_{i}$};

\draw [->] ([xshift=-5mm]q.south) |- (filter);
\draw [->] (filter) -- node {} (sum2);
\draw [draw,<-] (sum2) -- ++(90:.6cm) node[above]{$L_i+r_i$};

\draw [->] (sum2) -| node[pos=0.99, right] {$-$} 
    node [pos=.25, above] {$\tilde{s}_i$} (sum);

\draw [draw,->] (input1) node[above right] (ui-1) {$u_{i-1}$} -- (delay);
\draw [->] (delay) -| node[] {} 
    node [near end] {} (sum1);

\draw [->] (u.east|-system) |-  
    (output1) node[above left] (ui) {$u_i$};

\node[text=red, above left= 5mm and 6mm of ui.west] (veh) {vehicle $i$};
\draw[red, dashed] (veh.east)-|(ui.west)|-([yshift=-3mm]filter.south)-|(ui-1.east)|-(veh.west);

\end{tikzpicture}
\end{document}