bracketsmatrices
I need to have 2 square bracket matrix on the same equation line. I'm able to do just for a single square bracket matrix (for \xi) with below
\xi = \left[ \begin{array}{c}
\xi^1 \\
\vdots \\
\xi^L
\end{array} \right]
Anyone can give me a hint how to add the second square bracket matrix (for x)?
You may want to take a look at easybmat:
\documentclass{article}
\usepackage{easybmat}
%\usepackage{etex} % if you also want tikz, then you also need etex,
%\usepackage{tikz} % and they have to be loaded AFTER easybmat
\newenvironment{bvec}[1]{\begin{BMAT}(r)[0pt]{c}{#1}}{\end{BMAT}}
\newenvironment{pbvec}[1]{\left(\begin{bvec}{#1}}{\end{bvec}\right)}
\begin{document}
$span \{
\begin{pbvec}{ccccc} 1 \\ \vdots \\ \vdots \\ 1 \\ 1 \end{pbvec},
\begin{pbvec}{ccccc} 0 \\ 1 \\ \vdots \\ \vdots \\ 1 \end{pbvec},
\begin{pbvec}{ccccc} 0 \\ 0 \\ 1 \\ \vdots \\ 1 \end{pbvec}
\begin{bvec}{ccccc} \cdots \\ {} \\ \ddots \\ \ddots \\ \cdots \end{bvec}
\begin{pbvec}{ccccc} 0 \\ \vdots \\ \vdots \\ 0 \\ 1 \end{pbvec}
\}$
\end{document}
which results in
There are a few annoying things with BMAT:
{} in the fourth line).It's not at all clear what you want to do; I would split the equation in this way
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{aligned}
\begin{bmatrix}
\dot{\omega}_m \\
\dot{\theta}_m \\
\dot{\omega}_v \\
\dot{I}_m \\
\end{bmatrix}
&=
\begin{bmatrix}
-\frac{C_m}{J_m} & -\frac{P_s K_s \psi}{2 \pi r_s^2 J_m} & 0 & \frac{K_{tm}}{J_m} \\
1 & 0 & 0 & 0 \\
0 & -\frac{P_s K_s \mu_p R_{mp}}{2 \pi r_s J_v} & -\frac{C_v}{J_v} & 0 \\
-\frac{K_{em}}{L_m} & 0 & 0 & -\frac{R_m}{L_m} \\
\end{bmatrix}
\begin{bmatrix}
\omega_m \\
\theta_m \\
\omega_v \\
I_m \\
\end{bmatrix}
\\
&\qquad+
\begin{bmatrix}
0 & 0 \\
0 & 0 \\
\frac{1}{J_v} & 0 \\
0 & \frac{1}{L_m} \\
\end{bmatrix}
\begin{bmatrix}
F_v \\
V_m(t) \\
\end{bmatrix}
\end{aligned}
\end{equation}
\end{document}
The center environment is out of place; the bmatrix environment gives better matrices than \left[\begin{array}{..}...\end{array}\right].
With a reduced column width one can try and squeeze the matrix columns and break at the product. Here's an example at a column width of 229.5pt (3.2 inches or 8 centimeters):
\documentclass[twocolumn]{article}
\usepackage{amsmath}
\begin{document}
\pagestyle{empty}
\begin{equation}
\setlength{\arraycolsep}{1pt}
\begin{aligned}
\begin{bmatrix}
\dot{\omega}_m \\
\dot{\theta}_m \\
\dot{\omega}_v \\
\dot{I}_m \\
\end{bmatrix}
&=
\begin{bmatrix}
-\frac{C_m}{J_m} & -\frac{P_s K_s \psi}{2 \pi r_s^2 J_m} & 0 & \frac{K_{tm}}{J_m} \\
1 & 0 & 0 & 0 \\
0 & -\frac{P_s K_s \mu_p R_{mp}}{2 \pi r_s J_v} & -\frac{C_v}{J_v} & 0 \\
-\frac{K_{em}}{L_m} & 0 & 0 & -\frac{R_m}{L_m} \\
\end{bmatrix}
\\
&\qquad\cdot
\begin{bmatrix}
\omega_m \\
\theta_m \\
\omega_v \\
I_m \\
\end{bmatrix}
+
\begin{bmatrix}
0 & 0 \\
0 & 0 \\
\frac{1}{J_v} & 0 \\
0 & \frac{1}{L_m} \\
\end{bmatrix}
\begin{bmatrix}
F_v \\
V_m(t) \\
\end{bmatrix}
\end{aligned}
\end{equation}
\end{document}
Best Answer
it is very recommended to use
amsmathwhenever one wants to typeset mathematics