Difficulty in using multicolumn and multirow table commands

Question

I am trying to implement the following table (picture seen) in LaTeX. I am facing difficulty in writing the code since it consists of both multicolumn and multirow table commands. I truly appreciate if you guys can help me with it:

Here is the initial part of code using multicolumn and multirow, I can't understand where I am getting it wrong:

\begin{table}[tp]
\toprule
\renewcommand{\arraystretch}{1.3}
\setlength{\arrayrulewidth}{0.15mm}
\setlength{\doublerulesep}{0.12mm}
\caption{VSI Parameters}  
\label{tab:2}
\centering
\begin{tabular}{t|t|t|t}
\hline
\hline
\multicolumn{2}{*}{\textbf{VSI Controller}  \\
                       \textbf{Parameters} \\
&  \textbf{Minimum}  &  \textbf{Maximum}   \\
&    \textbf{Value}  &   \textbf{Value}    \\\otoprule
\hline
\hline
\multirow{4}{*}{Outer Control Loops} & \math{k_{p1}} & \SI{0.002}{} \\
& \math{T_{i1}} & \SI{0.0001}{} \\
& \math{k_{p2}} & \SI{0.01}{} \\
& \math{T_{i2}} & \SI{0.0001}{} \\ \hline  



\end{tabular}
\end{table}

EDITED: @Bernard: I really like your format; if I opt for it in making all my tables, what is the modified code for the below table in my script:

\begin{table}[tp]
\toprule
\renewcommand{\arraystretch}{1.3}
\setlength{\arrayrulewidth}{0.15mm}
\setlength{\doublerulesep}{0.12mm}
\caption{Step Changes}
\label{tab:1}
\centering
\begin{tabular}{t|t|t}
\hline
\hline
Step Change   &  Initial &  Final \\
Number        &    $\math{(W)}$  &   $\math{(W)}$ \\\otoprule
\hline
\hline
\SI{1}{}   &   \SI{0}{}  &   \SI{500}{}\\
\hline
\SI{2}{}    &   \SI{500}{}    &   \SI{250}{}\\
\hline
\SI{3}{}    &   \SI{250}{}    &   \SI{750}{}\\
\hline
\hline
\end{tabular}
\end{table} 

Answer 1

Here is a solution, using makecell, siunitx, caption and booktabs. I removed all vertical rules for a more professional look:

\documentclass{article}

\usepackage{makecell, caption, booktabs, multirow, siunitx}
\renewcommand\theadfont{\bfseries}
\renewcommand\cellalign{lc}
\newcommand{\otoprule}{\midrule[\heavyrulewidth]}
\usepackage{lipsum, fancyvrb}

\begin{document}

\lipsum[3]

\begin{table}[tp]

  \renewcommand{\arraystretch}{1.3}
  \caption{VSI Parameters}
  \label{tab:2}
  \centering
  \begin{tabular}{@{}p{25mm}>{$}c<{$}@{\hskip1.5em}S[table-format=1.4]S[table-format=1.1]@{}}
    \toprule
    \multicolumn{2}{@{}l}{\bfseries\makecell{VSI Controller\\ Parameters}} & {\thead{Minimum\\Value}} & {\thead{Maximum\\Value}} \\
    \otoprule
    \multirowcell{4}{Outer Control \\ Loops} & k_{p_1} & 0.002 & 5 \\
                                   & T_{i_1} & 0.0001 & 0.5 \\
                                   & k_{p_2} & 0.01 & 3 \\
                                   & T_{i_2} & 0.0001 & 0.5 \\
    \midrule
    \multirowcell{4}{Inner Control \\ Loops} & k_{p_3} & 0.1 & {\Verb+15+} \\
                                   & T_{i_3} & 0.001 & 0.5 \\
                                   & k_{p_4} & 0.1 & {\Verb+10+} \\
                                   & T_{i_4} & 0.001 & 0.5 \\
    \bottomrule
  \end{tabular}
\end{table}

\end{document} 

Answer 2

Something like this? Note that I've had to change your code quite a bit as I had no idea what half of the commands were meant to do or where to find them. For example, I've used c column types, $...$, removed \otoprule and \toprule (which makes no sense outside a tabular with booktabs, and I've no idea what else might define it) etc.

\documentclass[conference]{IEEEtran}
\usepackage{siunitx,array,multirow}

\begin{document}
\begin{table}[tp]
% \toprule% you can only use this within a tabular and if you load booktabs
\renewcommand{\arraystretch}{1.3}
\setlength{\arrayrulewidth}{0.15mm}
\setlength{\doublerulesep}{0.12mm}
\caption{VSI Parameters}
\label{tab:2}
\centering
\begin{tabular}{|c|c|c|c|}
\hline
\multicolumn{2}{|c|}{\textbf{VSI Controller}}  &\textbf{Minimum}  &  \textbf{Maximum}   \\
\multicolumn{2}{|c|}{\textbf{Parameters}} & \textbf{Value}  &   \textbf{Value}    \\%\otoprule
\hline
\multirow{4}{*}{Outer Control Loops} & $k_{p1}$ & \SI{0.002}{} &\\
& $T_{i1}$ & \SI{0.0001}{} &\\
& $k_{p2}$ & \SI{0.01}{} &\\
& $T_{i2}$ & \SI{0.0001}{} &\\ \hline

\end{tabular}
\end{table}
\end{document}

This at least compiles, though it is not an especially professional-looking table:

But, if you are submitting using a designated class, you should probably be following their formatting guidelines for tables anyway. (If they have any.)

Answer 3

EDit: I changed to your given document class.

Okay, to help you to get a start for your table please see the following MWE:

%\documentclass[a4paper,12pt]{article}
\documentclass[conference]{IEEEtran}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\usepackage{booktabs}
\usepackage{multirow,array}
\usepackage{siunitx}


\begin{document}
Test
\begin{table}

\renewcommand{\arraystretch}{1.3}
\caption{VSI Parameters}  
\label{tab:2}
\centering
\begin{tabular}{p{4cm}ccc}
\toprule
\multicolumn{2}{c}{\textbf{VSI Controller}} &  \textbf{Minimum}  &  \textbf{Maximum}   \\
                 &                          &    \textbf{Value}  &   \textbf{Value}    \\
\midrule
\multirow{4}{*}{Outer Control Loops} % first colum for 4 rows
                 & ${k_{p1}}$               & \SI{0.002}{}       & 5 \\
                 & ${T_{i1}}$               & \SI{0.0001}{}      & 0.5\\
                 & ${k_{p2}}$               & \SI{0.01}{}        & 3\\
                 & ${T_{i2}}$               & \SI{0.0001}{}      & 5\\ 
\bottomrule
\end{tabular}
\end{table}
\end{document}

I did a little pretty printing to make the table better visable for the creation.

Command \multicolumn{2}{c}{\textbf{VSI Controller}} spans two columns and centers the text. In your code the closing } is missing.

Command \multirow{4}{*}{Outer Control Loops} defines for 4 rows in your case the first column. The second column is written after the usual &. In the next rows just let the first column be empty (please study the given table code).

How to go on depends on your code and used packages. But this code is a start to prepare your table. I do not like table lines so I deleted them to show you an alternative ...

Result with article:

Result with IEEEtran: