US Patent 7515991 Self-propelled cleaning device and method of operation thereof

In cleaning using a self-propelled cleaning device, firstly the cleaning device moves alongside a wall surface and then a reference direction is set. Next, the cleaning device advances alongside the wall surface at a prescribed distance, makes a right-angle turn, and travels in the reference direction. When the cleaning device reaches the surface of an opposing wall, it moves in a spiraling manner. At that time, the orientation angle of the cleaning device, which is estimated using a gyro sensor, is checked and corrected. If an obstacle is encountered while traveling, the cleaning device travels on a path that avoids the obstacle or travels in a spiral manner in a region in front of the obstacle.