\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,concmath,amsfonts}
\pagestyle{empty}
\begin{document}
\begin{equation*}
  \tau = M(\theta) (\ddot \theta_d + K_v \dot e + K_p e) + 
    C(\theta,\dot \theta) \dot \theta + N(\theta,\dot \theta),
\end{equation*}
\end{document}