How often have you said to yourself, “You know, I sure wish someone would build a robotic bat head.”
What? Never? In fact, you say, the whole idea sounds…well, batty?
Not too surprising, I suppose. After all, bats have suffered a serious image problem throughout most of western history. (In the Orient, they are often considered a symbol of good luck.) It’s probably got a lot to do with their nocturnal habits and their (to our eyes) grotesque facial features, but in reality, bats are nothing to be frightened of.
In fact, they have lots to teach us—and we may be in a better position to learn some of it, thanks to the development of a robotic bat head by researchers from Project CIRCE (which stands for Chiroptera-Inspired Robotic Cephaloid, if you must know).
The researchers, who come from universities in the U.K., Belgium, Denmark and Germany, recently unveiled the Bat-Bot, which can emit and detect ultrasound (sound so high-pitched it’s out of the normal range of human hearing) in the same band of frequencies used by bats for echolocation: the technique of sending out extremely high-pitched sounds and using the resulting echoes for orientation.
There are more than 900 species of bats world-wide. About 700 of those species use echolocation to operate very effectively at night, with a distinct advantage over their prey–primarily insects.
Bats and humans both make sound by moving air past vibrating vocal chords. Humans normally emit sound from their mouths. So do some bats, but in others, the sound actually comes out of their noses—which may explain why some bats have very strange-looking noses (add in the big ears that are also needed for echolocation and you also have much of the reason for bats’ gargoylish good looks).
The sound emitted by the bat travels through the air as a wave. Just like a water wave, the sound wave bounces off any object it encounters, creating echoes that make their way back to the bat’s ears. The echoes from nearby objects return to the bat sooner than the echoes from far-away objects, and the position of the objects relative to the bat can be determined by which ear picks up more of the echoes. The complex folds in the bat’s ear also help the bat determine whether an object is above or below it—echoes from below hit the folds at a different place than echoes from above, altering the sound.
The bat’s brain computes all of this on the fly—literally. It can also determine the size of an object by the intensity of the echo, and if the object is moving (as insects tend to do), it can even tell in which direction it’s moving by the pitch: the sound waves echoing back from an object moving toward the bat are compressed, and therefore higher in pitch, than the sound waves echoing back from an object moving away from the bat. (This is the Doppler Effect, which also explains why the sound of a car seems to get lower after it zooms past you.)
During their work on the Bat-Bot, the CIRCE researchers conducted CT scans on about 20 bat species. They found that the ear-shape of bats varies enormously from species to species—and that ear shape directly correlates to echolocation effectiveness. The researchers created the first high-resolution computer model of bat ears, and have now made a number of simplified model ears out of nylon, which they’ll begin using on Bat-Bot to learn more about how ear shape influences sound reception.
The ultimate goal is to develop effective air-based sonar (as opposed to the familiar water-based sonar used by submarines and fishermen). That could have a number of potential uses (for example, the researcher have already found that you can use echolocation to identify different species of plants), but the primary goal is an echolocation system for robots.
Currently available echolocation systems are too simple to give an autonomous robot enough information to enable it to move around in a strange environment safely. Engineers trying to build such robots would love to have an echolocation system as good as that of bats; right now they’re forced to use relatively clunky camera-based or laser-ranging systems.
There are also biological projects to which Bat-Bot can contribute data. For example, the European Union is starting up Project CILIA in September. It will examine how cilia—tiny hairs—on insects, fish and in the inner ears of mammals help organisms (including ourselves) extract information from the environment.
Boldly building a Bat-Bot, buddy, isn’t batty a bit.
