Contestants from around the world met in Pomona, California, this month to test their skills at things like driving a car, walking down stairs, and opening doors. Sounds easy, right? But the competitors weren't people - they were robots!

　　The bots were participating in the final round of the US's DARPA (Defense Advanced Research Projects Agency) Robotics Challenge. This event, which took place on June 5-6, tested robots on how well they could respond during a disaster and the winning team finally took home a $2 million grand prize.

　　The DARPA challenge was created after the 2011 Fukushima nuclear disaster in Japan. An earthquake caused a tsunami, which damaged a nuclear power plant. Workers at the plant needed to shut off an important valve (阀门), but it was too dangerous for humans to reach it. The US scientists at DARPA wondered whether the disaster could have been avoided if a robot had been sent to do the job. So they set up the robotics competition.

　　Turning a valve was just one task a robot might have to perform when entering a disaster zone. In addition to doing this, robots participating in the challenge had to navigate a course containing several other tasks: driving and exiting a vehicle, opening a door, walking over or clearing objects, cutting a hole in a wall, plus climbing a flight of stairs.

Teams had to complete the challenge in one hour, and points were awarded based on how quickly the robots completed a task. They didn't have to attempt all the tasks. To make things even more realistic, challenge organizers caused short computer-system blackouts (断电) that prevented robots and the human operators controlling them from communicating. That means teams had to program their bots