\section{Electric-Powered Wheelchairs}\label{EPW}
Though Electric-Powered Wheelchairs (EPWs) were created in the early 20\textsuperscript{th} century, their popularity increased only after the invention of the transistor, MOSFET and microprocessor, which enabled significant improvements in their design and control (Cooper et al, 2003). The main components of the control system of an EPW are the input device, the controller and motors (see \hyperref[fig:epw]{Figure 1.1}). The driving commands issued by the user with the help of the access device are translated into speed and directional commands by the controller and relayed to the motors that are coupled to the rear left and right wheels, resulting in desired movement of the wheelchair. Additionally, the controller may receive information about the environment from sensors placed on the wheelchair as in the case of robotic wheelchairs explained in \hyperref[accessdevice]{section 1.2.2} (Ding \& Cooper, 2005; Velázquez, 2010).

\begin{figure}
\centering
\includegraphics[trim=0mm 7mm 0mm 0mm, clip,width=0.9\textwidth]{epw}
\caption[EPW - Components]{Main components for the control of an electric-powered wheelchair}
\label{fig:epw}
\end{figure}