I initially had the false impression, that this vacuuming robot, a “Neato XV Signature”, only had three ways to sense its surroundings: The laser which turns in its turret, the pressure-bar in the front with its two switches, and the magnetic sensors in its front corners.
But as it happens, this robot also has two optical “drop-sensors” in front, which statically look straight down at the ground.
I think the main purpose of these drop-sensors, is just to allow it to travel in a straight line. With a robot traveling over real terrain, a simple command to its left and right wheels to turn with the same amount of power, is not sufficient. This robot uses the feedback of its front drop-sensors, to measure the speed of the floor passing underneath.
I was watching it today, as it was having problems for the first time to travel in a straight line. And when I intervened, its display told me to “Please Clean My Left Drop-Sensor.”
These sensors can get dusty easily, and need to be wiped from time to time. And the plastic in front of its base-station also needs to be wiped free of dust, so that the robot can find its base-station again when ‘returning home’.
I now think that some of the malfunctions other people have reported, may in fact have been due to some of these panels not having been cleaned.
Also, it was my initial expectation that this robot stored the location of the base-station, when leaving the closest room, to clean farther reaches of its assigned area. In reality, when returning to the base station, this robot needs to find it again each time. Behind the panel of the base-station, there must be some sort of infrared corner-cubes, which glitter especially brightly in response to the laser, for it to recognize. Well it can happen that we have other objects hanging at the right or wrong distance above the ground, such as a set of curtains, which look unremarkable to the naked eye, but which also glitter to the vision of the infrared laser. And this can result in the robot making a mistaken attempt, to try docking in a corner of the correct room, but in a place where the base-station is not. And so such sources of glitter must also be removed from the room of the base-station.