Many contemporary robotic working tools, such as robotic lawnmowers, are designed to work in a work area defined by a boundary wire. A signal generator is configured to transmit a current signal through the boundary wire which generates a magnetic field around the boundary wire that the robotic work tool is configured to detect and thereby determine if and when it crosses the boundary wire. This enables the robotic work tool to remain inside the work area. To increase the safety of the robotic work tool, the robotic work tool is configured to determine, based on the sensed magnetic field, whether or not it is within the work area or not, and not only if it crosses the boundary wire. This enables for a safer operation in that the robotic work tool can not be activated outside the work area. To enable such operation the robotic work tool is configured to detect the magnetic field emanating from the boundary wire all through the work area.
Also, other robotic work tool systems that are arranged adjacent or in a relatively close proximity to a work area of the robotic work tool may disturb the robotic work tool if the signals transmitted by the other robotic work tool systems interfere with the signals (and the generated magnetic field) of the robotic work tool. This may cause the robotic work tool to malfunction or discontinue its operation which may lead to unsafe operation.
Also, some contemporary robotic work tools are configured to sense a magnetic field emanating from a cable loop (or other transmitter) arranged in close proximity to a charging station to enable the robotic work tool to return to the charging station without having to follow a specific boundary wire or guide cable.
To enable such operation(s), the signal generator must supply a current that is strong enough to generate a magnetic field that can be sensed or detected throughout the work area. As robotic work tools are designed to operate in diverse work areas often of different size, it is difficult for the designers to set the current strength appropriately and the current strength is usually set too high for most applications to ensure that the magnetic field will be detectable throughout the whole (or most of the) work area. This leads to unnecessarily high power consumption.
There is thus a need for a robotic work tool system where the robotic work tool is capable of detecting the magnetic field all through the work area without wasting power.