Ornithopter refers to an airborne aircraft that moves up and down like a bird or an insect's wings, or a flapping machine. The flapping wing not only produces lift, but also produces a forward thrust. During the spring and autumn period, people tried to make flying wooden birds. Fifteenth-century Italian Da Vinci sketched the flapping machine. In 1930, a model of an Italian flapping machine was flown. Since then, there have been many designs of flaps, but because of problems in control technology, materials and structure, the flapping machine is still in the stage of model making and imagination. In 2013, scientists at Festo, a technology company, developed a robotic bird that can simulate birds' flight and flapping its wings in a very realistic way: smartbird. The study said the flapping wing could not produce an upward thrust, but the bird can fly and land like a real bird, which is the ultimate in the flapping machine.