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\begin{document}

\begin{equation}
\begin{cases}
\left(M(q) + r^{2} \times J_{m} \right)q\ddot + \Bigg(C \bigg(q,q\dot \bigg) + r^{2} \times B_{m} \Bigg)q + G(q) = r \times K_{r}I\\
L\dot I  + R I + K_{m}\dot q = u
\end{cases}
\label{eq.1}
\end{equation}






\end{document}