Researchers at the University of Illinois at Urbana-Champaign have duplicated the control
functions that allow birds to successfully perform a soft landing-in this case, perching on a human hand. By replicating the features that enable birds to make a soft landing, including the flapping wings that help them change direction, the researchers could develop the first micro aerial vehicle (MAV) capable of swooping down to perch on a human hand. The craft forgoes a vertical tail, which birds also lack, to allow for enough agility to land on a small surface. Articulated wings help the robo-bird complete the maneuver successfully.Of all maneuvers executed by flapping wing aircraft in a gliding phase, a perched landing is arguably the most challenging. Perching is routinely used by birds to land on objects such as tree branches, power wires, or building ledges. According to the researchers, there are two factors that make perching challenging to engineer: the maneuver’s duration is very short, on the same order as the aircraft dynamics, and a high level of position accuracy is required for a successful perched landing. A typical perching maneuver consists of two phases-a gliding phase to bring the bird to a suitable position with respect to the landing spot, and a rapid pitch up (usually to a post-stall angle of attack) accompanied by an instantaneous climb and rapid deceleration. The researchers noted that the success of the maneuver can be severely impeded by the lateral-directional motion (yaw and roll), particularly when the perched landing has to be accomplished on a small surface such as an electric pole or a human palm. In the absence of a vertical tail, wing articulation is a promising capability which can be used for both longitudinal and lateral-directional control.