Recently the nice folks at Kyodo America loaned me a robotic lawnmower, a LawnBott, to use on my lawn.
In a word, it is fantastic!
A small wire is buried around the perimeter of the lawn. When the mower begins mowing, it moves randomly across the lawn. A load sensor in the motor tells it when it is mowing high grass and when it is going over mowed grass. When it hits high grass, it spirals around until the area is smooth. When it senses cut grass, it continues forward until it hits high grass to mow.
When it hits the perimeter wire, it turns around and moves in a different direction. It does the same when it hits an object like a post or rock or tree trunk. When it finishes the timed mowing period, it heads for the perimeter wire and follows it home to a small charging station, ready to go to work again when the schedule commands.
The lawn shown is approximately 4,000 sq. ft. It took the LawnBott barely an hour and a half to make it smooth. The mower works every other day for an hour, keeping the lawn perfectly mowed at all times.
Neighbors, children (and dogs!) are fascinated by this process. I often see them standing in a group on the sidewalk talking and pointing at my hardworking little mower.