Although detested and at the same time revered by people all over the world, bats are undoubtedly remarkable creatures when it comes to their ability to fly. While birds do perform the most nimble aerobatics, and most fishes swim superbly in water, bats possess the most refined powered flight mechanism, unmatched in the animal kingdom. Now a team of scientists has studied the way bats fly, and have built the first robot to mimic their flight mechanism. They have named the robot Bat Bot, or B2.
The scientists had a tough time when they tried to imitate the natural flight of a bat. Bats have flexible membranes on their wings, and use more than 40 active and passive joints with each flap of their wings. Moreover, they have bones with the capability to deform each time the bat beats its wings. The scientists found it very difficult to replicate the complete suite of biological tricks that bats use regularly.
In creating the Bat Bot, the scientists have achieved an engineering marvel. The Bat Bot weighs only about 94 grams—about as heavy as two golf balls. It has a carbon-fiber skeleton with a head filled with its on-board computer and sensors. The five micro-sized motors are strung along its backbone, and the entire skeletal structure has a silicone membrane stretched over it. A trio of roboticists at Caltech, led by Soon-Jo Chung, designed the Bat Bot capable of autonomous flapping flight. They unveiled it in the journal Science Robotics. At present, Bat Bot can perform only four main components of the movements of a bat’s wing—the shoulder, elbow, wrist bend, and the side-to-side tail swish.
According to Chung, his team had to give up the thought of simply mechanizing the flapping wings of a bat, joint by joint. They quickly understood the impossible task of incorporating all the forty joints in the design of Bat Bot, as it would only have resulted in a heavy robot, incapable of any type of flight.
After a careful study of a bat’s flight mechanism, including the biological studies documented by Dan Riskin of the Discovery Channel, the team tried to understand, among the 40 joints, those absolutely vital for the flight. Finally, they settled on a total of nine joints for the Bat Bot.
Although the Bat Bot is a sophisticated and advanced piece of machinery, it is still a very simple bat compared to the natural animal. For instance, Bat Bot does not have knuckles or joints in its carbon fiber fingers, and Bat Bot cannot actively twist its wrists that normal bats can do naturally.
Chung’s team had to make additional simplifications as well. For instance, the hyper-thin silicon membrane of Bat Bot has uniform flexibility, whereas the wing membrane of an actual bat has variable levels of stiffness in different places.
In spite of the above differences, Bat Bot does make elegant flights, almost indistinguishable from that of its biological cousin. While gliding through the air, Bat Bot has grace and fluidity, independently tucking and extending its wrists, shoulders, elbows, and legs.