clambered over debris, and helped human searchers recover a number of bodies.
In 2001, in the first actual appearance of robots in warfare, the U.S. military used PackBots in the Afghanistan campaign to search caves for Al-Queda operatives and to locate hidden weapons and mines.These 42-pound, backpack-size units were not truly autono- mous because they required human operators; but if they and other military robots are developed further as envisioned, we might one day see a single soldier monitoring several self-directing units, thus achiev- ing the military dream of force multiplication: “You could have 10 people on the battlefield doing what once took 40 soldiers,” notes Ronald Arkin of Georgia Tech, who has written software for military robots.
EIGHT LEGS TO TWO
Treads are good for tackling steep grades, but less so for stairs. In fact, for typical human environments that can include stairs or varied sur- faces such as a deep-pile rug or a tile floor, neither treads nor wheels work as well as legs and feet, although not necessarily only two of each. Robots that walk on four or more legs remain balanced even if not all the legs are on the ground.That inherent stability can be valu- able for the broken terrain to be found in the field, or in NASA- sponsored expeditions of planetary exploration, and requires fewer cognitive resources to maintain balance.
Rodney Brooks’s Genghis robot illustrated that multilegged walk- ing on flat surfaces and over obstacles can be achieved with only limited computational power. My I-Cybie robot dog is not the most advanced robot toy on the market and operates at a low level of artificial intelligence; nevertheless, it manages to shuffle along nicely on four legs (it can even right itself to stand firmly on those legs if you tip it over, and can also work its way around obstacles, walking off in a new direction when it bumps into something). One multilegged ro- bot that has dealt with extremely rough terrain is the eight-legged Dante II. In 1994, this unit semiautonomously walked and rappelled