It doesn’t fly on its own yet – the robo-bat is still attached to a kind of arm in a wind tunnel. It does, however, mimic the wing shape and motion of the lesser dog-faced fruit bat. The robot itself is linked to a device called a force transducer, which records the amount of energy needed to move the wings and the aerodynamic forces on their structure.
Besides understanding how bats fly, data collected from experiments with the robo-bat could tell engineers how to design small robots that flap a pair of wings instead of fly with propellers or rotors.
The robot, about eight inches long, has bones of plastic, made on a 3-D printer, that are the same proportions as those in real bats. The skin is made of silicone. The joints are bent by tiny motors that pull on cables, which function similarly to tendons.
Scientists and engineers study bird and bat flight because it is actually a pretty complicated process. While flapping wings provide lift, they also push the animal down as they move up. They also don’t move in a simple up-and-down motion, since they have to provide thrust as well. Preliminary results from the robo-bat show that the folding of wings on the upstroke reduces the force of air pushing downwards by 50 percent.
Bat wings themselves are complex structures. Unlike bird wings they cover a big part of the length of the body. Also, they are webbing supported by analogues to finger bones rather than the feathers that birds use. The skin that makes up the wings is so strong it can stretch to four times its length without tearing.
The robot isn’t a perfect simulation (yet), but it can still tell scientists a lot. For example, when they tested the first versions, they found that certain joints suffered more damage than others. That showed where the stress occurs in real animals and why their ligaments are located where they are, as well as their muscular structure.
The experiments with the robot appear in the journal Bioinspiration and Biomimetics. Joseph Bahlman, a graduate student at Brown, led the project, working in the lab of professors Kenneth Breuer and Sharon Swartz, who have studied the anatomy of bats and their flight characteristics.
via Brown University
Credit: Breuer and Swartz labs/Brown University