In the RIS days, it was hard to make a robot that could map out its surroundings using only LEGO's official parts, since there was no distance sensor like the US sensor. Now with the NXT, it can be a lot easier. This week's inspiration is to create a robot that can at least partially map out obstacles in its surroundings. For example, can your robot display a "map" of a room, showing where the obstacles are in it? If you wanted to take it even further, you could try to make the robot "store" the map in memory and then navigate around obstacles using the map (this might be pretty advanced, since you would need a system to tell the robot its position, so that it would know if it was getting near the position of an object on the map).
One very nice example of a radar robot was posted on the blog earlier, here. This robot spun around 360 degrees and mapped objects within a certain range, like radar. This method seems relatively easy, but has the drawback of only detecting one side of objects; it can't see how far back objects extend and it can't detect objects that are behind other objects. It also has a limited range. It would be ideal if you could get a robot to make a more complete map, showing whole objects. However, this I admit seems extremely hard to do... I haven't even been able to think of a system that would do this, much less design one. But, like the LEGO MINDSTORMS motto, the possibilities are endless!
P.S. You can see other posts in this series here.