  Over the past several decades there has been a constant increase in the use
of Unmanned Aerial Systems (UAS). Hence, there has also been a growth in the
number of control algorithms to service the many applications embodied by these
vehicles. Initially UAS were made popular by the military for Reconnaissance,
Intelligence, Surveillance, and Target Acquisition (RISTA) applications.
Now-a-days UAS are used for everything from crop surveys to tourism. Nowhere is
this more evident than with multi-rotor Unmanned Aerial Vehicle (UAV). This
paper presents a survey of control methods for multi-rotor systems, namely
quadrotors. In doing so, we hope to visualize a clear path to what additional
capabilities might be needed in the future. In our examination, we review many
of the notable research organizations and their efforts to expand the utility
of multirotor aircraft. We also summarize the basic literature definitions and
control strategies for autonomous quadrotors.
