ROBOTIC WORK TOOL SYSTEM, AND METHOD FOR DEFINING A WORKING AREA PERIMETER

A robotic work tool system (200) for defining a working area perimeter (105) surrounding a working area (150) in which a robotic work tool (100) is intended to operate. The robotic work tool system (200) comprises a boundary definition unit (300) comprising at least one position unit (175) for receiving position data; and at least one controller (210) for controlling operation of the boundary definition unit (300). The controller (210) being configured to receive, from the position unit (175), position data while the boundary definition unit (300) is moved around the working area (150) to define a preliminary working area perimeter (110). The controller (210) is further configured to identify, based on the received position data, a geometry of the preliminary working area perimeter (110) approximately corresponding to a predefined geometry; and to adjust the identified geometry to define an adjusted working area perimeter (105), wherein the identified geometry is adjusted to correspond to the predefined geometry.

TECHNICAL FIELD

This disclosure relates to a robotic work tool system as well as a method for defining a working area perimeter surrounding a working area in which a robotic work tool is subsequently intended to operate.

BACKGROUND

A robotic work tool is an autonomous robot apparatus that is used to perform certain tasks, for example for cutting lawn grass. A robotic work tool may be assigned an area, hereinafter referred to as a working area, in which the robotic work tool is intended to operate. This working area may be defined by the perimeter enclosing the working area. This perimeter may include the borders, or boundaries, which the robotic work tool is not intended to cross.

There exist different ways of setting these boundaries for the robotic work tool. Traditionally, the boundaries, or the perimeters, for the working area have been set manually by a user or operator. The user manually sets up a boundary wire around the area, or lawn, which defines the area to be mowed. A control signal may then be transmitted through the boundary wire. The control signal may preferably comprise a number of periodic current pulses. As is known in the art, the current pulses will typically generate a magnetic field, which may be sensed by the robotic work tool. The robotic work tool may accordingly use these signals from the wire to determine whether the robotic work tool is close to, or is crossing a boundary wire. As the robotic work tool crosses the boundary wire, the direction of the magnetic field will change. The robotic work tool will be able to determine that the boundary wire has been crossed and take appropriate action to return into the working area. However, these boundary wires are typically very time consuming to put into place, as the user has to perform this procedure manually. Furthermore, there is a risk that the boundary wires may become damaged, which will prevent the robotic work tool from operating properly within the working area.

In view of the above, another way to set the boundaries for a robotic work tool has been proposed, namely a way that does not use physical boundary wires. The robotic work tool may use a satellite navigation device and/or a deduced reckoning navigation sensor to remain within a working area by comparing the successive determined positions of the robotic work tool against a set of geographical coordinates defining the boundary of the working area. This set of boundary defining positions may be stored in a memory, and/or included in a digital (virtual) map of the working area.

The above-described non-physical boundaries for a working area may reduce the time necessary for installation and setting the boundaries for the working area. The non-physical boundaries may be smooth to install. Generally, they may be set by moving a device, which is able to receive position data, around the working area in order to establish the set of geographical coordinates defining the boundary of the working area in which the robotic work tool is intended to operate. As the boundaries are easy to set, they are also easy to move if the working area, for example, changes. Accordingly, non-physical boundaries provide a flexible solution for defining a working area.

SUMMARY

The inventors of the various embodiments of the present disclosure have realized that even if using non-physical boundaries has many advantages, there do exist drawbacks with the installation of the above proposed wireless working area perimeter that has not yet been addressed. The inventors have realized that even if non-physical boundaries of a working area generally may define accurate boundaries at large open spaces, the installation of the non-physical perimeter may be less accurate when it comes to tight corners or other restricted areas where it may be difficult to manoeuvre the device receiving the position data. Thus, in some cases the installation of the non-physical perimeter will not create a working area as accurately as the working area utilizing a physical boundary wire. The resulting working area perimeter may accordingly be quite rough and may perhaps not fulfilling the user's requirements. Furthermore, if a user tries to accurately cover tight corners or other restricted areas where it may be difficult to manoeuvre the device receiving the position data, this may be very time consuming.

In view of the above, it is therefore a general object of the aspects and embodiments described throughout this disclosure to provide a solution for defining an improved working area perimeter, which is not restricted by tight corners or other restricted areas and which is easy to define.

This general object has been addressed by the appended independent claims. Advantageous embodiments are defined in the appended dependent claims.

According to a first aspect, there is provided a robotic work tool system for defining a working area perimeter surrounding a working area in which a robotic work tool is subsequently intended to operate.

In one exemplary embodiment, the robotic work tool system comprises a boundary definition unit. The boundary definition unit comprises at least one position unit configured to receive position data. The robotic work tool system further comprises at least one controller for controlling operation of the boundary definition unit. The at least one controller is configured to receive, from the at least one position unit, position data while the boundary definition unit is moved at least a portion of a lap around the working area to define a preliminary working area perimeter. The at least one controller is further configured to identify, based on the received position data, a geometry of the preliminary working area perimeter approximately corresponding to a predefined geometry. Thereafter, the at least one controller is configured to adjust the identified geometry of the preliminary working area to define an adjusted working area perimeter.

In some embodiments, the at least one controller is configured to adjust the identified geometry to correspond to the predefined geometry.

In some embodiments, the predefined geometry comprises of at least one from the group comprising: a right-angled corner, a corner at a junction between two straight lines and a curve portion with a certain radius of curvature. The radius of curvature may be selectable.

In some embodiments, the at least one controller is configured to identify a geometry approximately corresponding to a predefined geometry by identifying, based on the received position data, a first substantially straight perimeter segment extending along a first axis. The at least one controller is further configured to identify, based on the received position data, a second substantially straight perimeter segment extending along a second axis transversal to said first perimeter segment. In some embodiments, the at least one controller may be configured to adjust the identified geometry of the preliminary working area to define an adjusted working area perimeter by adjust a corner portion at an intersection between said first and second axes to a conform to the predefined geometry. The radius of curvature on the corner portion may be set, for example, automatically to connect a tangent of the curvature to where either of the first and the second substantially straight perimeter segment ends.

In some embodiments, the robotic work tool system further comprises a user interface configured to display the preliminary working area perimeter and the working area perimeter. The user interface may be configured to receive user input from a user during the user's operation and interaction with said user interface. The at least one controller may be configured to adjust the identified geometry based on the received user input. For example, received user input may identify a predefined geometry to adjust the identified geometry with.

In some embodiments, the boundary definition unit further comprises at least one sensor unit configured to obtain sensed input data while the boundary definition unit is moved at least a portion of a lap around the working area to define a preliminary working area perimeter. The at least one controller is further configured to identify a geometry approximately corresponding to a predefined geometry based on sensed input data. In some embodiments, the sensed input data is associated with environmental data. The sensed input data indicates that a geometry approximately corresponding to a predefined geometry is identified when an obstacle is located in front of the boundary definition unit. In other embodiments, the sensed input data is associated with a direction of the boundary definition unit. The sensed input data indicates that a geometry approximately corresponding to a predefined geometry is identified when a change of the direction is above a threshold

In some embodiments, the at least one controller is configured to output a notification when a geometry approximately corresponding to a predefined geometry is identified.

In some embodiments, the at least one position unit is configured to use a Global Navigation Satellite System (GNSS). The at least one position unit may be configured to use Real-Time Kinematic (RTK) positioning.

In some embodiments, the boundary definition unit is the robotic work tool. The robotic work tool may be a robotic lawn mower.

According to a second aspect, there is provided a method implemented by the robotic work tool system according to the first aspect.

In one exemplary implementation, the method is performed by a robotic work tool system for defining a working area perimeter surrounding a working area in which a robotic work tool is subsequently intended to operate. The method comprises receiving, from at least one position unit of a boundary definition unit, position data while the boundary definition unit is moved at least a portion of a lap around the working area to define a preliminary working area perimeter. The method thereafter comprises identifying, based on the received position data, a geometry of the preliminary working area perimeter approximately corresponding to a predefined geometry; and adjusting the preliminary working area to define an adjusted working area perimeter by adjusting the identified geometry.

In some embodiments, the method further comprises adjusting the identified geometry to correspond to the predefined geometry.

In some embodiments, the method further comprises identifying a geometry approximately corresponding to a predefined geometry by identifying, based on the received position data, a first substantially straight perimeter segment extending along a first axis. The method further comprises identifying, based on the received position data, a second substantially straight perimeter segment extending along a second axis transversal to said first perimeter segment. The method may thereafter comprise adjusting a corner portion at an intersection between said first and second axes to conform to the predefined geometry.

In some embodiment, the method further comprises identifying a geometry approximately corresponding to a predefined geometry based on sensed input data, received from a user interface of the robotic work tool system.

In some embodiments, the method further comprises outputting a notification when a geometry approximately corresponding to a predefined geometry is identified.

Some of the above embodiments eliminate or at least reduce the problems discussed above. A robotic work tool system and method are thus provided which may define an accurate working area perimeter in a flexible and simplified way. The working area may be easy to define, while still being defined with a high precision. By identifying geometries that only approximately correspond to a predefined geometry when defining the working area perimeter, it may be possible to refine the perimeter surrounding the working area, such that corners or other restricted areas may be taken into account. By adjusting these identified geometries such that an adjusted working area perimeter is defined, the precision of the working area may be further improved.

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. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. 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 steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

DETAILED DESCRIPTION

In one of its aspects, the disclosure presented herein concerns a robotic work tool system for defining a working area perimeter surrounding a working area in which a robotic work tool subsequently is intended to operate.FIG.1illustrates a schematic overview of a robotic work tool100in such a working area150. As will be appreciated, the schematic view is not to scale. If the working area150is a lawn and the robotic work tool100is a robotic lawn mower, the working area150is the area to be mowed by the robotic work tool100. As seen inFIG.1, the working area150is surrounded by a working area perimeter105, which sets the boundaries for the working area150, i.e. defines the boundaries for the working area150. The robotic work tool100is intended to operate within the working area150and remain within this area due to the defined working area perimeter105. By defining the working area perimeter105, the robotic work tool100will not cross the perimeter and only operate within the enclosed area, i.e. the working area150.

With reference toFIG.2, a first embodiment according to the first aspect will now be described.FIG.2shows a schematic view of a robotic work tool system200, the robotic work tool system200comprises a boundary definition unit300and at least one controller210. The boundary definition unit300may be, for example, a robotic work tool100. The robotic work tool100may be the robotic work tool100that is intended to operate within the working area150. Alternatively, the boundary definition unit300may be a mobile device such as a smartphone, a remote control or a position device. The at least one controller210may be, for example, a controller210located in the boundary definition unit300. In such embodiments, the boundary definition unit300may correspond to the robotic work tool system200. According to another example, the at least one controller210may be located in a device230that is separated from the boundary definition unit300. When the at least one controller210is located in another device230than in the boundary definition unit300, the separate device230is communicatively coupled to the boundary definition unit300. They may be communicatively coupled to each other by a wireless communication interface. Additionally, or alternatively, the wireless communication interface may be used to communicate with other devices, such as servers, personal computers or smartphones, charging stations, remote controls, other robotic work tools or any remote device, which comprises a wireless communication interface and a controller. Examples of such wireless communication are Bluetooth®, Global System Mobile (GSM) and Long Term Evolution (LTE), 5G or New Radio (NR), to name a few.

The at least one controller210of the robotic work tool system200is configured to control the operation of the boundary definition unit300. In one embodiment, the at least one controller210is embodied as software, e.g. remotely in a cloud-based solution. In another embodiment, the at least one controller210may be embodied as a hardware controller. The at least one controller210may be implemented using any suitable, publicly available processor or Programmable Logic Circuit (PLC). The at least one controller210may 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 a computer readable storage medium (disk, memory etc.) to be executed by such a processor. The controller210may be configured to read instructions from a memory120,220and execute these instructions to control the operation of the boundary definition unit300including, but not being limited to, the propulsion of the boundary definition unit300. The memory120,220may 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 work tool100, which is intended to operate within the working area150, may be realized in many different ways. While the present disclosure will mainly be described in general terms of an autonomous robot designed for mowing a lawn, it should be understood that the robotic work tool100described herein may be implemented into any type of autonomous machine that may perform a desired activity within a desired working area. Examples of such types of autonomous machines include, without limitation, cleaning robotic work tools, polishing work tools, repair work tools, surface-processing work tools (for indoors and/or outdoors), and/or demolition work tool or the like.

FIG.3shows a schematic overview of one exemplary boundary definition unit300. As previously described, the boundary definition unit300may be exemplified in a variety of ways, but here the boundary definition unit300is exemplified as a robotic work tool100. The robotic work tool100may be, for example, a robotic lawnmower. As will be appreciated, the schematic view is not to scale.FIG.3shows a boundary definition unit300having a body140and a plurality of wheels130. However, the boundary definition unit300is not limited to a boundary definition unit300having one single integral body. Alternatively, the boundary definition unit300may have a separate front and rear carriages. Furthermore, in cases where the boundary definition unit300is exemplified as a smartphone or other similar device, it is appreciated that, the boundary definition unit300will not have any wheels.

The boundary definition unit300comprises at least one position unit175. The at least one position unit175is configured to receive position data. The position unit175may comprises a satellite signal receiver190, which may be a Global Navigation Satellite System (GNSS) satellite signal receiver. An example of such a system is Global Positioning System (GPS). The at least one position unit175may be configured to use, for example, Real-Time Kinematic, RTK, positioning. In advantageous embodiments, the at least one position unit175may use RTK-GNSS positioning. A RTK-GNSS system is based on satellite communication. The at least one position unit175may be connected to the controller210for enabling the controller210to determine current positions for boundary definition unit300.

In some embodiments, the at least one position unit175may further comprise a deduced reckoning navigation sensor195for providing signals for deduced reckoning navigation, also referred to as dead reckoning. Examples of such deduced reckoning navigation sensors195are odometers, inertial measurement units (IMUS) and compasses. These may comprise, for example, wheel tick counters, accelerometers and gyroscopes. Additionally, visual odometry may be used to further strengthen the dead reckoning accuracy. Thus, in some embodiments, the at least one controller210may be configured to use dead reckoning to extrapolate the position data if the quality, or the strength, of the position data received from the satellite signal receiver190goes below an acceptable level. The dead reckoning may then be based on the last known position received from the satellite signal receiver190.

According to the present disclosure, the at least one controller210is configured to receive, from the at least one position unit175, position data while the boundary definition unit300is moved at least a portion of a lap around the working area150to define a preliminary working area perimeter110. Thus, the at least one controller210continuously receives position data relating to the position of boundary definition unit300while the boundary definition unit300is caused to move.

The at least one controller210is thereafter configured to identify, based on the received position data, a geometry approximately corresponding to a predefined geometry. Thus, the at least one controller210is configured to identify whether there is any portion of the preliminary working area perimeter110, which approximately corresponds to a predefined geometry. The predefined geometry may have any shape. For example, the predefined geometry may comprise of at least one from the group comprising a right-angled corner, a corner at a junction between two straight lines and a curve portion with a certain radius of curvature. The radius of curvature may be selectable and may accordingly be of any appropriate radius. This means that the at least one controller210identifies if there is a geometry that is similar to a predefined geometry, for example a right-angled corner, but which does not completely, or exactly, correspond to a right-angled corner. Such identified geometry only approximately corresponds to the predefined geometry. It may thus be likely that the identified geometry is supposed to reflect the right-angled corner, but that the boundary definition unit300, for some reason, has not been able to be moved along the working area150, all the way into the right-angled corner, such that the received position data correctly reflects the right-angled corner in the perimeter surrounding the working area150.

Thereafter, the at least one controller210is configured to adjust the identified geometry of the preliminary working area perimeter110to define an adjusted working area perimeter105. Thus, the identified geometry is adjusted, or replaced, such that a new adjusted working area perimeter105is defined, which better reflects the perimeter surrounding the working area150. In some embodiments, the at least one controller210may be configured to adjust the identified geometry to correspond to the predefined geometry. In these embodiments, if the at least one controller210may identify that a geometry approximately corresponds to a predefined geometry, such as a right-angled corner, the identified geometry may be adjusted to be a right-angled corner.

By introducing the above proposed robotic work tool system200, the previously described disadvantages are eliminated or at least reduced. With the provided robotic work tool system200, it is possible to refine a defined preliminary working area perimeter110, such that a more accurate adjusted working area perimeter105is defined. As the process of defining the working area perimeter105is relatively easy to perform, without having to use physical boundaries, the provided solution is flexible while still providing a working area perimeter105, which is also accurate when it comes to tight corners or other restricted areas where it may be difficult to manoeuvre the device300receiving the position data. By identifying geometries that only approximately correspond to a predefined geometry when defining the working area perimeter105, it may be possible to refine the perimeter surrounding the working area150, such that corners or other restricted areas may be taken into account. By adjusting these identified geometries such that an adjusted working area perimeter105is defined, the precision of the working area150may be further improved. Thus, the provided robotic work tool system200provides a working area perimeter105that is easy to define, while still being defined with a high precision.

An example of a working area perimeter105that is adjusted in accordance with the present disclosure is illustrated inFIG.4. As seen inFIG.4, the received position data corresponds to the solid line110, i.e. the defined preliminary working area perimeter110. However, it is desirable that the working area perimeter surrounds the complete working area150, i.e. also within right-angled corners, such the robotic work tool100can operate within the complete working area150. Thus, the robotic work tool system200according to the present disclosure, recognizes and identifies a geometry which approximately corresponds to a predefined geometry, i.e. the curved solid line110approximately corresponds to a right-angled corner, illustrated as the dashed line105inFIG.4. The work tool system200according to the present disclosure then adjusts the identified geometry, i.e. the curved corner, of the preliminary working area110, to be a right-angled corner and thereby defines an adjusted working area perimeter105. As is also seen inFIG.4, the adjusted working area perimeter105more accurately reflects the working area150.

In one embodiment, the at least one controller210may be configured to identify a geometry approximately corresponding to a predefined geometry by identifying, based on the received position data, a first substantially straight perimeter segment extending along a first axis. The at least one controller210may further be configured to identify, based on the received position data, a second substantially straight perimeter segment extending along a second axis transversal to said first perimeter segment. In this embodiment, the at least one controller210may further be configured to adjust the identified geometry of the preliminary working area110to define an adjusted working area perimeter105by adjusting a corner portion at an intersection between said first and second axes to conform to the predefined geometry. The radius of curvature on the corner portion may be set automatically to connect a tangent of the curvature to where either of the first and the second substantially straight perimeter segment ends. Thus, the robotic work tool system200may take some intelligent decisions on where the working area perimeter105was intended to be located.

In one embodiment, the robotic work tool system200may further comprise a user interface250, as illustrated inFIG.2. The user interface250may for example be a touch user interface. The user interface250may be in an apparatus230separated from the boundary definition unit300, but it may be appreciated that the user interface250may be located at the boundary definition unit300. The user interface250may be in the same apparatus as the at least one controller210. However, in one embodiment the user interface250may be located in a device separate from the at least one controller210.

The user interface250may be configured to display the preliminary working area perimeter110and/or the adjusted working area perimeter105. It may be displayed to a user/operator who is operating the user interface250. In one embodiment, the preliminary working area perimeter110may be displayed in the user interface250associated with the adjusted working area perimeter105, in a way similar as illustrated inFIG.4.

The user interface250may be configured to receive user input from a user during the user's operation and interaction with the user interface250. The at least one controller210may be configured to adjust the identified geometry based on the received user input. Thus, the user may manipulate the defined preliminary working area perimeter110by interacting with the user interface250.

In one exemplary embodiment, the received user input may identify a predefined geometry to adjust the identified geometry with. According to this embodiment, a user, or operator, may decide which predefined geometry that may replace an identified geometry that approximately corresponds to a predefined geometry. Thus, if the robotic work tool system200identifies that a portion of the preliminary working area perimeter110approximately corresponds to a right-angled corner, the user may choose whether this portion should be adjusted to correspond to a right-angled corner. Alternatively, the user might want to select another predefined geometry and adjust the identified portion to be adjusted to correspond to a curve portion with a certain curvature. In some embodiments, the user may also select the radius of curvature.

In another exemplary embodiment, the received user input may be a portion drawn on freehand of the user. Then, the at least one controller210may be configured to adjust the identified geometry of the preliminary working area110by replacing the identified geometry of the preliminary working area110with the drawn freehand portion to define the adjusted working area perimeter105.

FIG.5schematically illustrates an example embodiment of a view of the user interface250. The user interface250may display the adjusted working area perimeter105that the robotic work tool system200has defined. If the user for some reason would like to refine the defined working area perimeter105even further, it may be possible to do that with the user interface250. It may be possible to, for example, move the defined adjusted working area perimeter105away from the real boundary of the working area150by touching and dragging the adjusted working area perimeter105towards a new working area perimeter515.

By providing the user interface250as described above, a fast and simple adaptation of the defined working area perimeter105may be achieved. For example, if it for some reason is not desirable that the robotic work tool100is driven too close to a physical edge530when the robotic work tool100is operating in the working area150, this may be achieved by adjusting the defined working area perimeter105to be located a bit further away from the physical edge530.

In some embodiments, the boundary definition unit300may further comprise at least one sensor unit170. The at least one sensor unit170is configured to obtain sensed input data. The at least one sensor unit170may be configured to obtain the sensed input data while the boundary definition unit300is moved at least a portion of a lap around the working area150to define a preliminary working area perimeter110. In these embodiments, the at least one controller210may be configured to identify a geometry approximately corresponding to a predefined geometry based on sensed input data.

The obtained sensed input data may, for example, be associated with environmental data. Alternatively, the obtained sensed input data may be associated with a direction of the boundary definition unit300. The obtained sensed input data may be, without limitations, photo data, odometric data, position data, direction data etc. The at least one sensor unit170may be, for example, at least one of a single camera, a stereo camera, a Time-Of-Flight (TOF) camera, a radar sensor, a lidar sensor, an ultrasonic sensor, a compass and, a position unit.

As previously described, the boundary definition unit300may be a smartphone or some kind of device, which comprises a position unit175. Alternatively, the boundary definition unit300may be a robotic work tool100. It is mainly in these embodiments that the boundary definition unit300may further comprise at least one sensor unit170. A robotic work tool100may be driven by an operator who manually steers the robotic work tool100using e.g. a remote control when defining the preliminary working area perimeter110. A remote control may be, by way of example, implemented as a software application in a mobile phone. The robotic work tool100may be driven at least a portion of a lap around the working area150in order to define a perimeter around the working area150. Preferably, the robotic work tool100may be driven a complete lap or substantially a complete lap in order to define a preliminarily perimeter around the working area150.

In embodiments where the obtained sensed input data may be associated with environmental data, the sensed input data may indicate that a geometry approximately corresponding to a predefined geometry is identified when an obstacle is located in front of the boundary definition unit300. Thus, when the boundary definition unit300moves along the perimeter along the working area150and identifies an obstacle, or object, located in front of it, the boundary definition unit300has to make a sharp turn in order to avoid the obstacle and to further define the perimeter surrounding the working area150. When a sharp turn is made, it is likely that the defined preliminary working area110will not completely correspond with the desired perimeter surrounding the working area150, for example due to the turning radius of the boundary definition unit300. It is thus advantageous that the sensed input data may indicate that a geometry approximately corresponding to a predefined geometry is identified such that the preliminary working area perimeter110can be adjusted to define an adjusted working area perimeter105.

Furthermore, by using sensed input data to indicate that a geometry approximately corresponding to a predefined geometry is identified when an obstacle is located in front of the boundary definition unit300, it may be possible to adjust the working area perimeter110without the boundary definition unit300actually having to entering this area. When the at least one controller210may receive sensed input data that indicates that a geometry approximately corresponding to a predefined geometry is identified, a geometry that the working area perimeter should be adjusted with could be suggested directly. For example, if the obstacle represents a corner, i.e. a wall straight ahead of the boundary definition unit300, the sensed input data will indicate that a geometry approximately corresponding to a predefined geometry is identified. Thereafter, the at least one controller210may be configured to adjust the geometry of preliminary defined working area perimeter110with a right-angled corner without the boundary definition unit300actually having to enter this corner.

In embodiments where the obtained sensed input data may be associated with a direction of the boundary definition unit300, the sensed input data may indicate that a geometry approximately corresponding to a predefined geometry is identified when a change of the direction is above a threshold. Thus, when the boundary definition unit300is moved along the perimeter along the working area150and makes a sharp turn, i.e. a turn which changes the direction more than a threshold, it is likely that the defined preliminary working area110will not completely correspond with the desired perimeter surrounding the working area250, for example due to that the turn was not made exactly when it was intended. It is thus advantageous that the sensed input data may indicate that a geometry approximately corresponding to a predefined geometry is identified such that the preliminary working area perimeter110can be adjusted to define an adjusted working area perimeter105.

In some embodiments, the at least one controller210may be configured to output a notification when a geometry approximately corresponding to a predefined geometry is identified. Thus, a user of the robotic work tool system200may be informed about that the robotic work tool system200has identified a portion of the preliminary working area perimeter110that is to be redefined. This may be advantageous for the user to know, such that the user may have the possibility to pay extra attention to the redefined portions of the working area perimeter105. Alternatively, this may be an indicator to the user, in cases when the user wants to be involved in the adjustments of the preliminary working area perimeter110, that the user might have to take some action.

It has to be mentioned that the at least one controller210may further be configured to connect all portions and geometries of the defined working area perimeter105, such that the working area perimeter105may be represented by a closed loop. Thus, the provided robotic work tool system200may define a working area perimeter105that completely surrounds a working area150. This will prevent a robotic work tool100from leaving the defined working area150. For example, if several portions of the defined working area perimeter has been redefined, the at least one controller210assures that all these portions are connected to a continuous working area perimeter105.

FIG.7illustrates an example where the boundary definition unit300has been moved from point A to point B in order to define at least a portion of the working area perimeter105around the working area150. As can be seen inFIG.7, boundary definition unit300is not necessarily moved a complete lap around the working area150, but enough to define the working area150. In this example, the at least one controller210may be configured to close the loop by connecting point A with point B by interpolating the “missing” portion of the lap around the working area105such that a closed loop around the working area150is defined. This portion is marked as a dashed line between points B and A inFIG.7. Accordingly, a “connected” working area perimeter105, i.e. an enclosed area, may be defined regardless of whether the boundary definition unit300is moved a complete lap around the working area150or not. This may also prevent problems that may arise if the boundary definition unit300does not finish the lap around the working area exactly in the same place at the boundary definition unit300started the lap.

In one embodiment, the at least one controller210of the robotic work tool system200may be configured to, after that a closed loop surrounding the working area150has been defined, drive the robotic work tool100, which is intended to operate within the defined working area150, one lap around the working area150guided by the defined working area perimeter105. The lap may e.g. be driven with the outer wheels130of the robotic work tool100located at the defined working area perimeter105. Then it may be possible for a user to view how the working area perimeter105has been defined. Thereby, it may be possible to verify that all areas of the working area150are covered properly by the robotic work tool system200and that all geometries correspond to predefined geometries.

In one advantageous embodiment, the robotic work tool100may be a robotic lawn mower.

According to a second aspect, there is provided a method implemented in the robotic work tool system200according to the first aspect. The method will be described with reference toFIG.8.

In one embodiment, the method800may be performed by a robotic work tool system200for defining a working area perimeter105surrounding a working area150in which a robotic work tool100is subsequently intended to operate. The method800starts with step810of receiving, from at least one position unit175of a boundary definition unit300, position data while the boundary definition unit300is moved at least a portion of a lap around the working area150to define a preliminary working area perimeter110. The method800thereafter continues with step820of identifying, based on the received position data, a geometry approximately corresponding to a predefined geometry; and step830of adjusting the preliminary working area perimeter110to define an adjusted working area perimeter105by adjusting the identified geometry.

In some embodiments, the method800may further comprise the step840of adjusting the identified geometry to correspond to the predefined geometry.

In some embodiments, the method800may further comprise identifying a geometry approximately corresponding to a predefined geometry by identifying, based on the received position data, a first substantially straight perimeter segment extending along a first axis. The method800may further comprise identifying, based on the received position data, a second substantially straight perimeter segment extending along a second axis transversal to said first perimeter segment. The method800may thereafter comprise adjusting a corner portion at an intersection between said first and second axes to conform to the predefined geometry.

In some embodiment, the method800may further comprise identifying a geometry approximately corresponding to a predefined geometry based on sensed input data, received from a user interface250of the robotic work tool system200.

In some embodiments, the method800may further comprise step850of outputting a notification when a geometry approximately corresponding to a predefined geometry is identified.

With the proposed method800, it may be easy to define a working area perimeter105, while the perimeter105is still being defined with a high precision. By identifying geometries that only approximately correspond to a predefined geometry when defining the working area perimeter105, it may be possible to refine the perimeter surrounding the working area150, such that corners or other restricted areas may be taken into account. By adjusting these identified geometries such that an adjusted working area perimeter105is defined, the precision of the working area150may be further improved.

FIG.9shows a schematic view of a computer-readable medium as described in the above. The computer-readable medium900is in this embodiment a data disc900. In one embodiment, the data disc900is a magnetic data storage disc. The data disc900is configured to carry instructions910that when loaded into a controller, such as a processor, execute a method or procedure according to the embodiments disclosed above. The data disc900is arranged to be connected to or within and read by a reading device, for loading the instructions into the controller. One such example of a reading device in combination with one (or several) data disc(s)900is a hard drive. It should be noted that the computer-readable medium can also be other mediums such as compact discs, digital video discs, flash memories or other memory technologies commonly used. In such an embodiment, the data disc900is one type of a tangible computer-readable medium900.

The instructions910may also be downloaded to a computer data reading device, such as the controller210or other device capable of reading computer coded data on a computer-readable medium, by comprising the instructions910in a computer-readable signal which is transmitted via a wireless (or wired) interface (for example via the Internet) to the computer data reading device for loading the instructions910into a controller. In such an embodiment, the computer-readable signal is one type of a non-tangible computer-readable medium900.

References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc. Modifications and other variants of the described embodiments will come to mind to one skilled in the art having benefit of the teachings presented in the foregoing description and associated drawings. Therefore, it is to be understood that the embodiments are not limited to the specific example embodiments described in this disclosure and that modifications and other variants are intended to be included within the scope of this disclosure. Still further, although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Therefore, a person skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the appended claims. As used herein, the terms “comprise/comprises” or “include/includes” do not exclude the presence of other elements or steps. Furthermore, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion of different claims does not imply that a combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality.