One of the hardest things to design about any mobile robot is how it determines its surroundings.  Because they are relatively cheap to use, sonar devises are a common item seen and used to judge distance to anything which may be in the direction the sonar is checking.  Visual data is expensive and extremely complex to interpret but are usually necessary because current sonar devises do not give enough data for a robot to navigate with.  Also, visual data is almost useless at night without high energy lights to brighten up the path.

Rolf Muller and Herbert Peremans, as a part of a European Union project called CILIA, have used advanced computer modeling to try to improve sonar receivers to not only perceive distance but to also keep track of objects and to sense an environment. All sonar works by sending out sound pulses and then interpreting the echo that is received.  Current models use one emitter and one sensor and just use calculations on the speed of sound to determine the distance to the first object which reflects the sound back.  This way they can judge the distance to the closest object and that is all.  However, sonar devises can be much more perceptive than that.  Muller and Peremans were inspired by the bat, which uses sonar to very precisely track small prey at night.  Bats get almost as much information through sonar as we get through vision.  Muller and Peremans were not only inspired by this concept, but decided to use it.  They actually used extremely accurate digital CT scans of bat ears in order to model some more experimental sonar recievers.  Using these sonar “ears” as well as 3 sensors, they used advanced modeling to determine how sound would pass through the ears and how it could be used to help interpret the environment.  To correctly interpret much of the data, such as if the sonar is looking at a corner, which could quickly reflect sound multiple times back to the devise, complex statistical tests are used.

Through extensive testing, they were able to model and eventually will create sonar devises which could be the future of navigational devises on robots.

Sources:

http://www.popsci.com/gear-gadgets/article/2008-03/bat-ears-sonar

http://www.ua.ac.be/main.aspx?c=.APL&n=40650