Under the watchful eyes of five high-speed cameras, a small, pale-blue bird named Gary waits for the signal to fly. The researcher points her finger to a perch about 20 inches away. The catch here is that the perch is covered in Teflon, making it seemingly impossible to stably grasp. Gary's successful touchdown on the Teflon -- and on other perches of varying materials -- is teaching researchers how they might create machines that land like a bird. Even the most advanced robots come nowhere near the grasping ability of animals when dealing with objects of varying shapes, sizes and textures. So, the researchers gathered data about how Gary and two other birds land on different kinds of surfaces, including a variety of natural perches and artificial perches covered in foam, sandpaper and Teflon. The perches in this research weren't your average pet store stock. The researchers split them in two, lengthwise, at the point that approximately aligned with the center of a parrotlet's foot. As far as the bird was concerned, the perches felt like a single branch but each half sat atop its own 6-axis force/torque sensor. This meant the researchers could capture the total forces the bird put on the perch in many directions and how those forces differed between the halves -- which indicated how hard the birds were squeezing. After the birds flapped to all nine force-sensing perches of assorted size, softness and slipperiness, the group began analyzing the first stages of landing. Comparing different perch surfaces, they expected to see differences in how the birds approached the perch and the force with which they landed, but that's not what they found.
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