Note: This page is taken from n.wikia.com.
(As written in the N in-game help)
Like happy little puppies, these robots will eagerly scamper along the ground towards you. Unlike most puppies, they'll kill you if they get close enough.Floorchasers (also called floorguards) are generally stationary, harmless and cute – until the player lands on the floor they guard. Then they charge towards the ninja with amazing speed... and kill him upon contact with an electrical discharge similar to that of the zap drone. If the player dodges the floorguards' attack, however, they will continue going in the same direction until they reach the end of the platform or the edge of a map. If the ninja is still in the same place as he was during the first charge, they will move in the opposite direction... and so on. Fortunately, they are only able to move on horizontal surfaces, and not slopes and curves. If there is a horizontal one way platform bridging a gap between tiles, they cannot pass along it.
One must keep in mind that they are very fast, with speed slightly greater than the ninja at a full sprint. Therefore, the player can't outrun them for long distances, so they'll need to jump before the floorguards touch them. When the player can't jump (in unit-width areas for example), life becomes hard, like in 1.4's 45-3: manimal lust.