Patent Description:
Automated or robotic power tools such as robotic lawnmowers are becoming increasingly more popular. In a typical deployment a work area, such as a garden, the work area is enclosed by a boundary wire with the purpose of keeping the robotic lawnmower inside the work area. An electric control signal may be transmitted through the boundary wire thereby generating an (electro-) magnetic field emanating from the boundary wire. The robotic working tool is typically arranged with one or more (electro-) magnetic sensors adapted to sense the control signal.

As the seasons change, so does a work area and different areas of work area, such as a garden, may need to be serviced at different times of the year.

The patent application published as <CIT> discloses a method and an electronic search system for operating an automatic device, preferably an automatic lawnmower. The system comprises at least one first electrical cable connected to at least one first signal generator and at least one sensing system arranged on said device. Said sensing system detects at least one magnetic field being transmitted via said cable and propagating through the air, the sensing system transmitting a processed signal to at least one driving means which contributes to the movements of said device in relation to a surface. Said search system comprises means by which the first signal generator of the present invention transmits a current through said first cable, said current during a part of time being is in a state of rest where it is substantially constant, said state periodically being interrupted by at least one first characteristic current pulse.

Thus, there is a need for a simple and elegant manner of enabling changing or assigning temporary work areas for a robotic working tool, such as a robotic lawnmower.

As will be disclosed in detail in the detailed description, the inventors have realized a simple and elegant solution to the problems of the prior art.

It is therefore an object of the teachings of this application to overcome or at least reduce those problems by providing a mobile signal generator arranged to provide a supplemental control signal through a supplemental wire for establishing a supplemental work area for a robotic working tool, said mobile signal generator being arranged without a charging unit for the robotic working tool as per the appended claims.

In one embodiment the mobile signal generator comprises a signal generator, arranged to generate the supplemental control signal, and a battery for providing power to the signal generator.

The mobile signal generator comprises a controller module configured to establish the supplemental control signal.

In one embodiment mobile signal generator comprises a communication interface, wherein the controller module is configured to establish the supplemental control signal by receiving information regarding the supplemental control signal through the communication interface from a charging station and/or a user.

The mobile signal generator further comprises a magnetic sensor arranged to sense the magnetic field generated by a control signal, wherein the controller module is configured to establish the supplemental control signal by receiving information regarding the control signal through the magnetic sensor and establish the supplemental control signal to be the same as the control signal.

In one embodiment the mobile signal generator is arranged to determine a drastic drop in sensed signal strength and in response thereto stop operation.

In one embodiment the mobile signal generator is arranged to determine that a critical battery level has been reached and in response thereto signal a stop command to the robotic working tool.

In one embodiment the mobile signal generator is arranged to adapt the strength of the supplemental control signal based on a length of the supplemental boundary wire.

In one embodiment the mobile signal generator comprises two ports for connecting a single supplemental boundary wire.

In one embodiment the mobile signal generator is arranged outside the supplemental work area.

In one embodiment the mobile signal generator is arranged to be used in a robotic working tool system comprising a signal generator, arranged to generate and transmit a control signal through a boundary wire, the robotic working tool and a charging station for charging the robotic working tool in.

In one embodiment the robotic working tool is a robotic lawnmower.

It is also an object of the teachings of this application to overcome the problems by providing a method for use in a mobile signal generator arranged to provide a supplemental control signal through a supplemental wire for establishing a supplemental work area for a robotic working tool, said mobile signal generator being arranged without a charging unit for the robotic working tool, the method comprising establishing the supplemental control signal and transmitting the supplemental control signal as per the appended claims.

Other features and advantages of the disclosed embodiments will appear from the following detailed disclosure, from the attached dependent claims as well as from the drawings. All references to "a/an/the [element, device, component, means, step, etc.]" are to be interpreted openly as referring to at least one instance of the element, device, component, means, step, etc., unless explicitly stated otherwise.

The invention will be described in further detail under reference to the accompanying drawings in which:.

The disclosed embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. Like reference numbers refer to like elements throughout.

It should be noted that even though the description given herein will be focused on robotic lawnmowers, the teachings herein may also be applied to, robotic ball collectors, robotic mine sweepers, robotic farming equipment, or other robotic working tools where lift detection is used and where the robotic working tool is susceptible to dust, dirt or other debris.

<FIG> shows a perspective view of a robotic working tool <NUM>, here exemplified by a robotic lawnmower <NUM>, having a body <NUM> and a plurality of wheels <NUM> (only one side is shown). The robotic working tool <NUM> may be a multi-chassis type or a mono-chassis type. A multi-chassis type comprises more than one body parts that are movable with respect to one another. A mono-chassis type comprises only one main body part.

The robotic lawnmower <NUM> comprises charging skids <NUM> for contacting contact plates (not shown in <FIG>, but referenced <NUM> in <FIG>) when docking into a charging station (not shown in <FIG>, but referenced <NUM> in <FIG>) for receiving a charging current through, and possibly also for transferring information by means of electrical communication between the charging station and the robotic lawnmower <NUM>. Other means of establishing a charging contact are possible and are incorporated herein.

<FIG> shows a schematic overview of the robotic working tool <NUM>, also exemplified here by a robotic lawnmower <NUM>. In this example embodiment the robotic lawnmower <NUM> is of a mono-chassis type, having a main body part <NUM>. The main body part <NUM> substantially houses all components of the robotic lawnmower <NUM>. The robotic lawnmower <NUM> has a plurality of wheels <NUM>. In the exemplary embodiment of <FIG> the robotic lawnmower <NUM> has four wheels <NUM>, two front wheels and two rear wheels. At least some of the wheels <NUM> are drivably connected to at least one electric motor <NUM>. It should be noted that even if the description herein is focused on electric motors, combustion engines may alternatively be used, possibly in combination with an electric motor.

The robotic lawnmower <NUM> also comprises a grass cutting device <NUM>, such as a rotating blade <NUM> driven by a cutter motor <NUM>. The grass cutting device being an example of a work tool <NUM> for a robotic working tool <NUM>. The robotic lawnmower <NUM> also has (at least) one battery <NUM> for providing power to the motor(s) <NUM> and/or the cutter motor <NUM>. The battery is arranged to be charged through a current received through charging skids <NUM> - or other suitable charging connectors.

The robotic lawnmower <NUM> also comprises a controller <NUM> and a computer readable storage medium or memory <NUM>. The controller <NUM> may be implemented using instructions that enable hardware functionality, for example, by using executable computer program instructions in a general-purpose or special-purpose processor that may be stored on the memory <NUM> to be executed by such a processor. The controller <NUM> is configured to read instructions from the memory <NUM> and execute these instructions to control the operation of the robotic lawnmower <NUM> including, but not being limited to, the propulsion of the robotic lawnmower. The controller <NUM> may be implemented using any suitable, available processor or Programmable Logic Circuit (PLC). The memory <NUM> may be implemented using any commonly known technology for computer-readable memories such as ROM, RAM, SRAM, DRAM, FLASH, DDR, SDRAM or some other memory technology.

The robotic lawnmower <NUM> may further be arranged with a wireless communication interface <NUM> for communicating with other devices, such as a server, a personal computer or smartphone, the charging station, and/or other robotic working tools. Examples of such wireless communication devices are Bluetooth®, WiFi® (IEEE802.11b), Global System Mobile (GSM) and LTE (Long Term Evolution), to name a few.

For enabling the robotic lawnmower <NUM> to navigate with reference to a boundary wire emitting a magnetic field caused by a control signal transmitted through the boundary wire, the robotic lawnmower <NUM> is further configured to have at least one magnetic field sensor <NUM> arranged to detect the magnetic field (not shown) and for detecting the boundary wire and/or for receiving (and possibly also sending) information to/from a signal generator (will be discussed with reference to <FIG>). In some embodiments, the sensors <NUM> may be connected to the controller <NUM>, possibly via filters and an amplifier, and the controller <NUM> may be configured to process and evaluate any signals received from the sensors <NUM>. The sensor signals are caused by the magnetic field being generated by the control signal being transmitted through the boundary wire. This enables the controller <NUM> to determine whether the robotic lawnmower <NUM> is close to or crossing the boundary wire, or inside or outside an area enclosed by the boundary wire.

In one embodiment, the robotic lawnmower <NUM> may further comprise at least one navigation sensor <NUM>. In one embodiment, the navigation sensor <NUM> comprises one or more sensors for deduced navigation. Examples of sensors for deduced reckoning are odometers, accelerometers, gyroscopes, and compasses to mention a few examples. In one embodiment, the navigation sensor <NUM> comprises a beacon navigation sensor and/or a satellite navigation sensor <NUM>. The beacon navigation sensor may be a Radio Frequency receiver, such as an Ultra Wide Band (UWB) receiver or sensor, configured to receive signals from a Radio Frequency beacon, such as a UWB beacon. Alternatively or additionally, the beacon navigation sensor may be an optical receiver configured to receive signals from an optical beacon. The satellite navigation sensor may be a GPS (Global Positioning System) device or other Global Navigation Satellite System (GNSS) device.

<FIG> shows a schematic view of a robotic working tool system <NUM>. The schematic view is not to scale. The robotic working tool system <NUM> comprises a robotic working tool <NUM>. As with <FIG>, the robotic working tool is exemplified by a robotic lawnmower, whereby the robotic working tool system may be a robotic lawnmower system or a system comprising a combinations of robotic working tools, one being a robotic lawnmower, but the teachings herein may also be applied to other robotic working tools adapted to operate within a work area.

The robotic working tool system <NUM> also comprises charging station <NUM> which is arranged with a signal generator <NUM> and a boundary wire <NUM>.

The signal generator is arranged to generate a control signal <NUM> to be transmitted through the boundary wire <NUM>. To perform this, the signal generator is arranged with a controller and memory module <NUM>. The controller and memory module <NUM> operates and functions in a similar manner as the controller <NUM> and memory <NUM> of the robotic working tool <NUM>. The controller and memory module <NUM> may also be the controller and memory module of the charging station, hereafter simply referred to as the controller <NUM>.

In one alternative or additional embodiment the controller and memory module <NUM> may also comprise or be connected to a communication interface (not shown explicitly but considered to be part of the controller and memory module). The communication interface is enabled for communicating with other devices, such as a server, a personal computer or smartphone, a robotic working tool <NUM>, another signal generator and/or another charging station using a wireless communication standard. Examples of such wireless communication standards are Bluetooth®, WiFi® (IEEE802.11b), Global System Mobile (GSM) and LTE (Long Term Evolution), to name a few.

The boundary wire <NUM> is arranged to enclose a work area <NUM>, in which the robotic lawnmower <NUM> is supposed to serve. The control signal <NUM> transmitted through the boundary wire <NUM> causes a magnetic field (not shown) to be emitted. In one embodiment the control signal <NUM> is a sinusoid periodic current signal. In one embodiment the control signal <NUM> is a pulsed current signal comprising a periodic train of pulses. In one embodiment the control signal <NUM> is a coded signal, such as a CDMA signal.

As an electrical signal is transmitted through a wire, such as the control signal <NUM> being transmitted through the boundary wire <NUM>, a magnetic field is generated. The magnetic field may be detected using field sensors, such as Hall sensors. A sensor - in its simplest form - is a coil surrounding a conductive core, such as a ferrite core. The amplitude of the sensed magnetic field is proportional to the derivate of the control signal. A large variation (fast and/or of great magnitude) results in a high amplitude for the sensed magnetic field. The variations are sensed and compared to a reference signal or pattern of variations in order to identify and thereby reliably sense the control signal.

The work area <NUM> is in this application exemplified as a garden, but can also be other work areas as would be understood. The garden contains a number of obstacles (O), exemplified herein by a number (<NUM>) of trees (T) and a house structure (H). The trees are marked both with respect to their trunks (filled lines) and the extension of their foliage (dashed lines). As can be seen in <FIG>, the boundary wire <NUM> has been laid so that so-called islands are formed around the trees' trunks and the house (H). This requires that more boundary wire is used, than if the work area was without such obstacles. It should be noted that any distances between wires are greatly exaggerated in this application in order to make the distances visible in the drawings.

As can also be seen in <FIG>, the charging station <NUM> is fastened into the ground by one or several pegs <NUM> in order to keep the charging station stable as the robotic lawnmower <NUM> drives up on it to be charged, and off it once charged and ready to operate. The charging station <NUM> is also, for the same reason, arranged with a bottom plate <NUM> that is designed to be larger than the corresponding robotic lawnmower <NUM>. As a skilled person would understand, the larger the bottom plate <NUM>, the more stable the installation. The bottom plate <NUM> is therefore usually rather bulky.

The charging station <NUM> also comprises a charging unit <NUM>, connected to two charging plates <NUM>, for delivering a charging current to the robotic lawnmower <NUM> upon docking. The charging unit <NUM> is connected to a power supply <NUM>. As the charging requires significant current, the power supply <NUM> is external. Usually, the charging station is simply connected to a wall outlet in a house or similar structure.

In addition to the boundary wire <NUM>, the charging station is also, usually, connected to one or more guide wires <NUM>. Guide wires <NUM> may be used to enable the robotic lawnmower <NUM> to find its way to a specific area, such as into (and/or out of) areas that are difficult to reach. Guide wires <NUM> may alternatively or additionally be used to enable the robotic lawnmower <NUM> to find its way to the charging station <NUM>. Guide wires <NUM> may alternatively or additionally be used to divide a work area <NUM> into two separate work areas. In the example of <FIG>, there are two guide wires, a first guide wire <NUM>-<NUM> arranged to lead the robotic lawnmower <NUM> in to the area behind the trees T, and a second guide wire <NUM>-<NUM> arranged to lead the robotic lawnmower <NUM> to the charging station <NUM>. The second guide wire <NUM>-<NUM> may also or alternatively be used to divide the work area <NUM> into two halves, one to the left of the second guide wire <NUM>-<NUM> and one to the right of the second guide wire <NUM>-<NUM>.

The use of guide wires <NUM> to demarcate work areas has been around for several years, and a skilled person would understand how such uses may be implemented without further details.

The inventors have realized and identified several problems associated with using guide wires <NUM> to demarcate a work area <NUM>.

One problem that has been realized is that there is only a limited number of ports for guide wires <NUM> in a charging station, and the number of sub-areas is thus limited. A number of technical solutions have been proposed over the years of how to utilize a limited guide wire to establish several (i.e. more) sub areas. All these proposal - ingenious as they may be - may be difficult for an end-user to understand and to correctly plan for.

Another problem lies in that as the guide wire <NUM>-<NUM> need be connected to the charging station <NUM>, it is difficult to install the guide wire for a sub-area far away from the charging station <NUM>. Especially if there are obstacles that should not be disturbed in the way between the wanted subarea and the charging station <NUM>.

A similar problem lies in that guide wires <NUM>-<NUM> are not allowed by safety standards to extend beyond the boundary wire <NUM>, whereby they are useless for setting up a sub area outside the work area <NUM>. The obvious solution to setting up such a remote o external sub area is to simply move the charging station and set up a new boundary wire. However, as the charging station <NUM> is pegged down, needs to be connected to a power supply <NUM> and as all guide wires <NUM> as well as the original boundary wire <NUM> need be disconnected, this is not such a simple task as technically skilled users may believe, especially not for most end-users who may lack in practical or technical skills as their expertise may lay elsewhere in non-technical fields. As is known, persons skilled in areas such as finance, business methods, mathematics, computer software, psychology, and aesthetics often lack technical knowledge.

The charging station <NUM> may also be heavy or otherwise cumbersome to carry or transport making it unsuitable to be moved.

The inventors are therefore - after insightful and inventive reasoning - proposing the simple and elegant solution of providing a mobile signal generator that can be used at any location for setting up a boundary to demark a sub area, remotely or internally to an existing work area <NUM>.

<FIG>, <FIG> each shows an example embodiment of a robotic working tool system <NUM>, herein exemplified by a robotic lawnmower system, according to an embodiment of the teachings herein. In <FIG>, the sub area or supplemental <NUM> is external to the existing work area <NUM>. In <FIG>, the sub area or supplemental <NUM> is internal to the existing work area <NUM>, where the robotic lawnmower is inside the supplemental area in <FIG> and outside of it in <FIG>. It can also be noted that the mobile signal generator <NUM> need not be arranged inside a work area as it need not be accessed by the robotic lawnmower <NUM>. It may even be beneficial to place the mobile signal generator <NUM> outside the supplemental work area as it is then (better) protected from the robotic lawnmower <NUM> during operation. <FIG> and <FIG> shows a situation where the mobile signal generator <NUM> is arranged outside the supplemental work area <NUM> and <FIG> shows a situation where the mobile signal generator <NUM> is arranged inside the supplemental work area <NUM>.

An external supplemental work area <NUM> may be used for temporarily setting up a work area externally, such as when an area needs to be worked on or such as when lending ones robotic lawnmower to a friend or neighbour. An external supplemental work area <NUM> may also or alternatively be used for a secondary home, such as a summer cabin. This allows for an easy installation and for theft protection as the mobile signal generator <NUM> may be easily (as will be discussed below) transported to and from the cabin along with the robotic lawnmower <NUM>.

An internal supplemental work area <NUM> may be used for temporarily setting up a work area internally, such as when an area needs to be worked on specifically or when an area is not to be worked on. In the latter case, the supplemental work area <NUM> can be used to keep a robotic lawnmower <NUM> out of it, protecting what is inside the supplemental work area <NUM>, or alternatively, the supplemental work area <NUM> can be used to keep a robotic lawnmower <NUM> inside it, protecting what is outside the supplemental work area <NUM>. In <FIG> the supplemental area is used to keep the robotic lawnmower inside supplemental area to provide particular operation in that area. In <FIG> the supplemental area is used to keep the robotic lawnmower outside the supplemental area to prevent operation in that area.

In one embodiment the supplemental work area <NUM> is determined to be a stay-in-area by attaching the boundary wires to the connector ports in a first (standard) manner, and the supplemental work area <NUM> is determined to be a stay-out-area by attaching the boundary wires to the connector ports in a second (opposite) manner. In an embodiment, the wires are connected to a connector that attaches to the connector ports on the mobile signal generator. By simply turning the wire connector, the boundary wire may be connected in the first or the second manner in a simple manner.

In one embodiment the supplemental work area <NUM> is determined to be a stay-in-area by transmitting the control signal in a first (standard) manner, and the supplemental work area <NUM> is determined to be a stay-out-area by transmitting the control signal in a second (reverse polarity) manner. In one such embodiment, the mobile signal generator is configured to receive a command to switch (or reverse) the polarity of the control signal. In one embodiment, the mobile signal generator comprises a switch or button (possibly virtual) as part of the user interface, arranged for switching the polarity of the control signal as transmitted, based on the position of the switch. This enables an operator to simply flip the switch (or push the button) to determine the kind of supplemental work area to be used. The switch may be marked appropriately to indicate its use. In an alternative or additional embodiment the mobile signal generator is arranged to receive a command through the communication interface (for example from a user device) indicating which polarity and thus which use of the supplemental area) that is to be used. This enables a user to simply set up the mobile signal generator for example through a smartphone of the user.

In one embodiment the supplemental work area <NUM> is determined to be a stay-in-area by arranging the mobile signal generator and the attached or connected boundary wire in a first (standard) manner or position, and the supplemental work area <NUM> is determined to be a stay-out-area by arranging the mobile signal generator and the attached or connected boundary wire a second (opposite) manner or position. In such an embodiment it is possible to set up the mobile signal generator and the attached boundary wire (especially useful in embodiments where the boundary wire is internally connected) to provide a stay-in or stay-out area by simply placing the mobile signal generator up-side-up or up-side-down. As the mobile signal generator is flipped, so should the boundary wire also be, and the supplemental area is determined accordingly to be stay-in or stay-out.

In one embodiment, the mobile signal generator comprises two sets of connector ports; a first set and a second set. In one such embodiment the supplemental work area <NUM> is determined to be a stay-in-area by connecting the boundary wire to the first connector port set, and the supplemental work area <NUM> is determined to be a stay-out-area by connecting the boundary wire to the second connector port set. In one embodiment, the first set is arranged on one side of the mobile signal generator, and the second set is arranged on another side of the mobile signal generator.

The robotic lawnmower system <NUM> comprises in addition to all or some of the components of the robotic lawnmower system <NUM> as discussed in relation to <FIG>, a mobile signal generator <NUM>. As for the signal generator <NUM> of the charging station <NUM>, the mobile signal generator <NUM> comprises a controller module <NUM> for controlling the operation of the mobile signal generator <NUM>.

The inventors have realized that by arranging the mobile signal generator <NUM> without a charging unit <NUM> or other charging means for the robotic lawnmower <NUM> the mobile signal generator <NUM> therefore does not require any high-power power supply, such as a wall outlet. In fact, as the inventors have realized, as the main purpose of the mobile signal generator <NUM> is only to provide a control signal, which are even required to operate at low current levels, the mobile signal generator <NUM> only comprises a battery <NUM> for providing power to the mobile signal generator <NUM>.

Furthermore, as the mobile signal generator <NUM> is not arranged to charge the robotic lawnmower <NUM>, the mobile signal generator also does not need to be pegged down or to have a bulky bottom plate, whereby the mobile signal generator <NUM> may be designed to have a sleek and small overall size and extent, as well as being low-weight.

The mobile signal generator <NUM> according to herein is thus possible to provide in a physical implementation weighing less than a kilogram and having a physical extent of less than <NUM> dm<NUM>, even <NUM> dm<NUM>, making the mobile signal generator <NUM> according to herein truly mobile.

Additionally, in one embodiment, the mobile signal generator is arranged with ports (referenced <NUM> in <FIG>) only for a few supplementary boundary wires <NUM>. In one such embodiment, the number of ports correspond to two wires. In another embodiment, the number of ports is two, corresponding to a single supplementary boundary wire <NUM> further reducing the needed size of the mobile signal generator <NUM>.

<FIG> shows a schematic view of the components of a mobile signal generator <NUM> according to herein. As discussed above, the mobile signal generator <NUM> comprises a controller module <NUM>. In one embodiment the controller module <NUM> comprises a processor (or other controller) <NUM> and a memory <NUM>. The processor <NUM> and memory <NUM> may be arranged to operate in a similar manner as the controller <NUM> and memory <NUM> of the robotic lawnmower <NUM> and no further details will be given thereto. In one embodiment the controller module <NUM> also comprises a signal generator <NUM> arranged to generate and transmit a supplemental control signal <NUM> through the supplemental boundary wire <NUM> when connected to the ports <NUM>. In the example of <FIG>, there are two connector ports <NUM> for connecting one supplemental boundary wire <NUM>.

In one embodiment the controller module <NUM> may also comprise a communication interface <NUM> for communicating with the charging station <NUM> for receiving settings regarding for example the control signal <NUM>, or with another device for example for receiving commands or settings from a user. In one embodiment, the communication interface <NUM> comprises a wireless interface, such as discussed in relation to the communication interface <NUM> of the robotic lawnmower <NUM> as well as in connection to the communication interface of the controller module <NUM> of the charging station <NUM> above. In one embodiment, the communication interface <NUM> comprises or is connected to a wired interface, such as a universal serial bus (USB) interface. This allows the mobile signal generator <NUM> to be connected to, by being plugged in to, for example the charging station <NUM> for receiving settings regarding the control signal <NUM>.

The mobile signal generator <NUM> may thus receive information from the charging station <NUM>, either by being plugged in to or through a wireless connection, regarding the control signal <NUM> used for the main boundary wire <NUM>, or for any signal used for a guide wire, which enables the mobile signal generator <NUM> to mimic the signal generator <NUM> of the charging station <NUM>, whereby the same robotic lawnmower <NUM> may be used without any modifications needed to be done or settings to be changed on the robotic lawnmower <NUM>.

Furthermore, by connecting to a second charging station and receiving information regarding that charging stations signals, the mobile signal generator <NUM> may be arranged to be used with a different system as well, the mobile signal generator thus being mobile also in respect of which system and/or robotic lawnmower the mobile signal generator <NUM> supplements.

In one embodiment the mobile signal generator <NUM> comprises a magnetic sensor <NUM>, for example such as the magnetic sensors <NUM> discussed above in relation to the robotic lawnmower <NUM>. This enables the mobile signal generator <NUM> to sense and record any control signal that is transmitted through any wire. The mobile signal generator <NUM> is thus arranged to supplement any signal generator, even such that are not designed or arranged to share information regarding the control signal being used. The mobile signal generator <NUM> according to herein may thus also be used with and to supplement almost any prior art robotic lawnmower system without any modification having to be made to neither the charging station nor the robotic lawnmower of the prior art system.

In such embodiments discussed above, the supplemental control signal <NUM> is thus effectively the same as the control signal <NUM>.

The mobile signal generator <NUM> is in one embodiment arranged to use a different control signal than the control signal <NUM> of the signal generator <NUM> of the charging station <NUM>. In such embodiments, the supplemental control signal <NUM> is thus effectively not the same as the control signal <NUM>. In such embodiments, the charging station may be arranged to provide the mobile signal generator <NUM> with a control signal that the robotic lawnmower <NUM> will accept. Additionally or alternatively, the charging station may be arranged to provide the robotic lawnmower <NUM> with the control signal that will be used by the mobile signal generator <NUM>. In one such embodiment, the mobile signal generator <NUM> is arranged to provide the charging station with information on which control signal that will be used. Enabling the mobile signal generator to operate with a control signal that is different from that of the main system, enables for the use of two (or more) robotic lawnmowers to operate in the same work area as both will be provided with a control signal. The two robotic lawnmowers may also be set up to work in different areas (possibly overlapping at least partially).

The mobile signal generator <NUM> may also, in some embodiments, comprise a user interface <NUM>. The user interface may be provided as at least one physical button, a series of (LED) lights, a screen such as a touch screen, or any other known manner of providing a user interface. In one embodiment, the user interface is comprised of one or two push buttons; one for turning on the generator, and possibly one for establishing the control signal <NUM>, as well as at least one LED light for indicating battery and/or operational status (including, but not limited to, one or all of the status of the mobile signal generator (on/off), the status of the supplemental control signal, or status of the supplemental boundary wire <NUM>). Such a simple interface is highly energy efficient.

Alternatively, the user interface <NUM> is provided (at least partially) through a secondary device through the communication interface <NUM>, whereby the mobile signal generator <NUM> may be controlled through a second device, such as a smartphone, being connected to the mobile signal generator <NUM>.

The mobile signal generator <NUM> also comprises a battery <NUM>. In one embodiment the battery is arranged with or connected to a charging port <NUM> for receiving a charging current through. The charging port <NUM> is in one embodiment wireless. Alternatively or additionally, the charging port <NUM> is in one embodiment wired. In one such embodiment, the charging port <NUM> is connected to the wired interface of the communication interface <NUM> as is indicated in <FIG>, by the charging port <NUM> being connected to both the battery <NUM> and the controller module <NUM>. In one particular such embodiment a common USB interface is used both for the communication interface <NUM> and for the charging port <NUM>. In one embodiment the charging port is a solar panel for enabling solar powered charging. In one embodiment, the battery and the charging port are part of or comprised in a solar panel arrangement, wherein the mobile signal generator is solar powered.

In one embodiment, the mobile signal generator <NUM> is configured to adapt the strength of the supplemental control signal based on the length of the supplemental boundary wire <NUM>. This allows for energy to be saved, thereby increasing the operating time for the mobile signal generator, and/or allowing for a reduced size of the battery and therefore making the mobile signal generator <NUM> even more mobile.

In one such embodiment, the mobile signal generator <NUM> is arranged to receive an indication of the wire length through the communication interface <NUM>. Alternatively or additionally, the mobile signal generator <NUM> may be arranged to receive the indication of the wire length through the user interface <NUM>. A user may thus, for example, input the length of the boundary wire being used either through the user interface <NUM> or through a separate device such as a smart phone.

In one alternative or additional such embodiment, the mobile signal generator <NUM> is arranged to receive an indication of the wire length by measuring the length of the wire. The length can be measured or approximated by measuring the resistance in the wire. Assuming a specific thickness and/or resistance per unit of length, the resistance will be proportional to the length and a measurement of the resistance will therefore give an indication of the length of the wire. The measurement may be done at any point where a known voltage is applied to the wire, by measuring the resulting current.

The mobile signal generator <NUM> may also comprise a wire spool or reel <NUM> on which a wire can be wound up for easy storage. As the mobile signal generator is primarily to be used for supplemental work areas <NUM>, which assembly are of a smaller size, normally a shorter supplemental boundary wire is needed. Such a shorter wire may therefore be wound up internally for easy and simple storage and transport. Exactly how long the wire can be depends on the current design. Having an internal spool <NUM> also allows for a simple attachment to the ports <NUM> and the boundary wire thus may not need to be disconnected for transport.

<FIG> shows a flowchart of a general method according to the teachings herein. The mobile signal generator <NUM> establishes which control signal will be used. As discussed above, the control signal may be established by the mobile signal generator <NUM> receiving information regarding the control signal from the charging station. Alternatively, the mobile signal generator <NUM> receives information regarding the control signal from a user. In yet an alternative, the mobile signal generator <NUM> receives information regarding the control signal from a sensor <NUM>. The sensor may be similar to the magnetic field sensor <NUM> of the robotic lawnmower.

And also as an alternative, the mobile signal generator <NUM> establishes the control signal to be used by providing information regarding the control signal to the charging station. These alternatives are not exclusive but may be in addition to one another. For example, the mobile signal generator <NUM> may both receive information regarding the control signal from the sensor <NUM> and provide this information to the charging station <NUM>. As the supplemental control signal has been established, the supplemental control signal is transmitted <NUM> through the supplemental boundary wire <NUM>.

In one embodiment, the mobile signal generator is configured to determine whether the supplemental area is set up as a stay-in-area or as a stay-out-area.

In one such embodiment, the mobile signal generator may adapt its operation based on whether the supplemental area is set up as a stay-in-area or as a stay-out-area. The operation may be adapted as regards what action is to be taken if the control signal is lost.

In an alternative or additional embodiment, the mobile signal generator is arranged to signal or present the use of the supplemental area to a user through the communication interface and/or through the user interface.

In one embodiment, the mobile signal generator is configured to determine whether the supplemental area is set up as a stay-in-area or as a stay-out-area by determining the position of a switch (as discussed above).

In an alternative or additional embodiment where the mobile signal generator is arranged with a magnetic sensor <NUM>, the mobile signal generator is configured to determine whether the supplemental area is set up as a stay-in-area or as a stay-out-area by sensing the resulting magnetic field being emitted by the transmitted control signal.

In one embodiment where the mobile signal generator is arranged with a magnetic sensor <NUM>, the mobile signal generator is configured to determine whether the control signal from the main system (i. e the control signal <NUM>) is detectable. If the signal is not detectable, the mobile signal generator may be arranged to interrupt all operations. This is also useful for preventing theft of the robotic lawnmower or the mobile signal generator, as it will only be able to operate in the vicinity of the main or original system.

In another or alternative such embodiment, the mobile signal generator is arranged to determine 'the main control signal <NUM>, to compare it to a storage of known control signals and only operate if a match is found. This enables the mobile signal generator to only operate with preapproved systems, which enables for an increased safety of use as only trusted systems may be used with the mobile signal generator.

As is known, a robotic lawnmower <NUM> is configured to stop operating as a control signal is lost. This is in order to prevent the robotic lawnmower <NUM> from escaping the work area in case of a power failure of the signal generator. However, and as the inventors have realized, if an internal supplemental area <NUM> is being used for keeping the robotic lawnmower <NUM> inside the supplemental area <NUM> and with the same supplemental control signal <NUM> as the control signal <NUM>, the robotic lawnmower <NUM> will still sense the control signal <NUM> even after the supplemental control signal <NUM> dies or is otherwise lost. This will inevitably lead to the robotic lawnmower <NUM> escaping the supplemental area <NUM>. The inventors have, however, realized a simple and elegant solution to this. By configuring the robotic lawnmower <NUM> to not only stop operation if a signal is lost, but also stop operation if there is a sudden drop in sensed signal strength, the robotic lawnmower <NUM> is enabled to detect when the supplemental control signal is lost.

In one embodiment where the mobile signal generator <NUM> is arranged with a sensor <NUM>, the mobile signal generator <NUM> may be configured to also sense the overall control signal and to sense a drastic or sudden change in signal strength, and thereby determine that the main control signal has been lost and in response thereto stop operation of the robotic lawnmower <NUM>. The operation may be stopped by communicating to the robotic lawnmower <NUM> to stop. Alternatively or additionally the operation maybe stopped by simply discontinuing the supplemental control signal which effectively will cause the robotic lawnmower <NUM> to stop as all control signals are lost.

In one embodiment the sudden drop or change is characterized by a change in signal strength of <NUM> %, <NUM> %, <NUM> % or a higher percentage of the sensed signal strength.

The mobile signal generator <NUM> (and/or the robotic lawnmower) may thus <NUM> sense a change in the signal and stop operation accordingly. In one embodiment, the mobile signal generator <NUM> is configured to detect that the battery level has reached a critical (low) level and then signal the robotic lawnmower <NUM> to stop operating. This ensures that the robotic lawnmower <NUM> stop inside the supplemental work area <NUM> even if the mobile signal generator <NUM> runs out of power. In such an embodiment the robotic lawnmower <NUM> is configured to receive such signalling from the mobile signal generator and act accordingly, i.e. to stop operating.

It should be noted that the mobile signal generator <NUM> may be configured to signal the robotic lawnmower <NUM> regarding other commands as well.

In one embodiment, the mobile signal generator <NUM> is configured to signal the robotic lawnmower <NUM> through the communications interface <NUM>. In one embodiment, the mobile signal generator <NUM> is configured to signal the robotic lawnmower <NUM> through transmitting a coded message through the boundary wire by adapting the supplemental control signal <NUM> accordingly. The robotic lawnmower <NUM> may thus sense the coded message as part of sensing the control signal and receive any command, such as a stop operating command.

Claim 1:
A mobile signal generator (<NUM>) arranged to provide a supplemental control signal (<NUM>) through a supplemental wire (<NUM>) for establishing a supplemental work area (<NUM>) for a robotic working tool (<NUM>), said mobile signal generator (<NUM>) being arranged without a charging unit for the robotic working tool (<NUM>), wherein the mobile signal generator (<NUM>) comprises a controller module (<NUM>) configured to establish the supplemental control signal (<NUM>) and wherein the mobile signal generator (<NUM>) is characterized in that it further comprises a magnetic sensor (<NUM>) arranged to sense the magnetic field generated by a control signal (<NUM>), wherein the controller module (<NUM>) is configured to establish the supplemental control signal (<NUM>) by receiving information regarding the control signal (<NUM>) through the magnetic sensor (<NUM>) and establish the supplemental control signal (<NUM>) to be the same as the control signal (<NUM>).