Robotic vacuum cleaners are known in the art. In general robotic vacuum cleaners are equipped with drive arrangement in the form of a motor for moving the cleaner across a surface to be cleaned. The robotic vacuum cleaners are further equipped with intelligence in the form of microprocessor(s) and navigation means for causing an autonomous behaviour such that the robotic vacuum cleaners can freely move around and clean a space in the form of e.g. a room.
In many fields of technology, it is desirable to use robots with an autonomous behaviour such that they can freely move around a space without colliding with obstacles.
As an a example, robotic vacuum cleaners exist in the art with the capability of more or less autonomously vacuum cleaning a room in which furniture such as tables and chairs and other obstacles such as walls and stairs are located. Traditionally, these robotic vacuum cleaners have navigated a room by means of using e.g. ultrasound or light waves or laser beams. Further, the robotic vacuum cleaners typically must be complemented with additional sensors, such as stair sensors, wall-tracking sensors and various transponders to perform accurately. Such sensors are expensive and affect the reliability of the robot.
A large number of prior art robotic vacuum cleaner use a technology referred to as Simultaneous Localization and Mapping (SLAM). SLAM is concerned with the problem of building a map of an unknown environment by a robot while at the same time localizing the robot in the environment using the map. This is often done using a horizontal scanning laser for range measurement, combined with odometry, which provides an approximate position of the robot as measured by the movement of the wheels of the robot.
US 2009/0306822 A1 discloses a robot that scans its environment along a horizontal plane, thereby creating a two dimensional (2D) signature of its environments and landmarks located therein.
US 2002/0091466 discloses a mobile robot with a first camera directed toward the ceiling of a room for recognizing a base mark on the ceiling and a line laser for emitting a linear light beam toward an obstacle, a second camera for recognizing a reflective linear light beam from the obstacle. The line laser emits a beam in the form of straight line extending horizontally in front of the mobile robot. This also creates also a 2D signature of the environment of the robot.
A 2D map or signature of the environment may lead to problems since the robot or robotic vacuum cleaner may not be able to deduce its position from the 2D signatures and thus it may get lost or disoriented.
The use of a base mark on the ceiling and markers on the ceiling in general poses certain disadvantages. First, the robot will need to have two cameras with at least one camera “looking” up towards the ceiling and another camera looking in the direction of movement and thus in the direction of the laser beams from the horizontal line laser, this is expensive and complicates the build up of the robot. Further, the user has to position at least one base mark on the ceiling by using a chair or ladder.
In addition known robotic vacuum cleaners require thus quite a substantial initial effort by the user until they operate smoothly and clean a surface or area autonomously.