Well, this is by far one of the more interesting robot sensing devices I've seen in a while. It's like your standard
bump sensor whiskers on steroids.
A group of researchers from schools that I can't pronounce have come up
with the ultimate robot whiskers solution - a motor spins the whisker
in a semicircular motion and an accelerometer attached to the end
monitors the acceration. When the whisker hits an object the end of the
whisker vibrates at a certain frequency depending on how far up the
whisker the object hit. The acceleromter, coupled with sensors that
determine the angle of the whisker can then accurately pinpoint the
location of the obstacle.
In theory it sounds pretty easy to implement. I'll have to add it to
the "to build" list. Apparently, the biological counterpart is how
insects navigate their way around the world.