Tsinghua Throne
Throne UAV is a Chinese micro air vehicle (MAV) developed by the Department of Automation (清华大学自动化系) of Tsinghua University. It was one of the competitors of 2012 and 2013 International Aerial Robotics Competition (IARC), Asian-Pacific region and won the best flight control award in 2012, and best mission completion award and best static judging presentation award in 2013. Throne MAV is a quadrotor, but what distinguish it from all other quadrotor currently available is that Throne MAV is enclosed by a square-shaped fence around itself, and the fence is attached to the extension from the arms  where rotors are installed. The purpose of the fense is to protect the rotor propellers in confined spaces where the MAV is designed to operate. This fence is a direct development of an earlier version of Throne in 2012 competition where it is enclosed in square shaped rail installed in the same manner. It appears that the protective rail has evolved into fence.