Autonomous Landing of a UAV on a Moving Ground Vehicle in a GPS Denied Environment

Teams of autonomous air and ground agents can enable operations in search and rescue environments that are too remote or dangerous for humans but often require extensive positioning and communication infrastructure. A straightforward approach that maximizes the use of modern robotics tools is implemented to achieve a rotary wing unmanned air vehicle (UAV) landing on a moving unmanned ground vehicle (UGV) without the aid of GPS or other external positioning systems. Landing uses positioning information from a "fractal" visual fiducial marker that embeds smaller markers within larger ones that allows the estimation of a 6 degree-of-freedom (DOF) pose at all altitudes during landing. All computations are performed onboard the vehicle using low cost sensors and computers and no communications are required between the UAV and UGV. Trials were conducted in both software-in-the-loop (SITL) simulations and outdoor experiments and demonstrated this algorithm to be effective at performing landing maneuvers. Landing was performed using a small custom-built quadrotor and a Clearpath Warthog UGV at speeds of up to 2.5 m/s.