扫地机器人，怎么不撞墙？

The robot sends out laser beams in all directions. 机器人向四周射出激光。 It measures how far the walls are. 它量出墙离自己有多远。 It draws a map of your room. 它给房间画了一张地图。 Sensors on its bumper feel the furniture. 保险杠上的感应器能摸到家具。 Then it turns and avoids them. 它就转弯绕开。 When the battery is low, it goes home. 电快用完时，它自己回去充电。