SE2051308A1

SE2051308A1 - Improved edge operation for a robotic work tool

Info

Publication number: SE2051308A1
Application number: SE2051308A
Authority: SE
Inventors: Daniel Knopf; Petra Jung
Original assignee: Husqvarna Ab
Priority date: 2020-11-10
Filing date: 2020-11-10
Publication date: 2022-05-11
Also published as: SE545618C2; DE102021129014A1

Abstract

A robotic work tool system (300) comprising a self-propelled robotic work tool (200) arranged to operate on a surface in a work area (305), the robotic work tool (200) comprising a work tool (260) and a body (240) having a shield portion (240-3), the robotic work tool (200) being configured to: determine that the robotic work tool (200) is approaching an edge (320, S, T, H) of the work area (305) and in response thereto lower the shield portion (240-3); move the work tool (260) towards the shield portion (240-3); and operate at the edge (320, S, T, H).

Description

TECHNICAL FIELD This application relates to robotic work tools and in particular to a system and a method for providing an improved processing of work area edges a robotic work tool, such as a lawnmower.

BACKGROUND 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 running along the (outer) edges of the work area with the purpose of keeping the robotic lawnmower inside the work area. The work area may also be limited by objects such as walls or rocks.

Figure 1 shows a schematic view of an example of a typical work area 105, being a garden, in which a robotic work tool 10, such as a robotic lawnmower, is set to operate.

The garden contains a number of obstacles, exemplif1ed herein by a number (2) of trees (T), a stone (S) 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). The garden is enclosed by a boundary wire 120 through which a control signal 125 is transmitted by a signal generator 115 housed in a charging station 110, the control signal 125 generating a magnetic field that can be sensed by the robotic work tool 10. In this example the boundary wire 120 is laid so that so-called islands are formed around the trees and the house. However, it should be noted that the trees and the house may be detected by the robotic lawnmower 10 through use of collision detection, as is known in the art.

As a boundary is detected the robotic lawnmower is arranged to tum back to avoid escaping the work area. As the magnetic sensors are usually arranged in front of the cutting disc, or other work tool, the area between the magnetic sensor and the cutting disc is not cut, or otherwise serviced, as well as other areas which results in an unevenly treated garden.

The same results when a robotic lawnmower encounters an object, such as when it collides with the object. For obvious reasons the cutting disc will not be able to service the area closest to the object which will also result in an unevenly treated garden.

For safety reasons the minimum distance from the cutting disc to the edge (any edge) of the robotic lawnmower l0 is limited to minimize the risk of a person accidentally being harrned by the cutting disc. This prevents an object, such as a foot, hand or probe (P) from being inserted in under the robotic lawnmower far enough to get in contact with the cutting disc l60.

As a result, there will be an area close to any edge, including around obstacles, that is not serviced as well as the rest of the work area. In figure l, this area is indicated by the dotted lines. The same result will be achieved even if the robotic work tool is arranged to operate according to a different style of boundary, such as utilizing satellite and/or beacon navigation as the unevenly serviced area is not a result of the navigation technique, but of the limited disc-to-edge dl Thus, there is a need for an improved manner of providing a more even servicing of work area edges for a robotic work tool, such as a robotic lawnmower.

SUMMARY It is therefore an object of the teachings of this application to overcome or at least reduce those problems by providing a robotic work tool system comprising a self- propelled robotic work tool arranged to operate on a surface in a work area, the robotic work tool comprising a work tool and a body having a shield portion, the robotic work tool being configured to: determine that the robotic work tool is approaching an edge of the work area and in response thereto lower the shield portion; move the work tool towards the shield portion; and operate at the edge.

In one embodiment the robotic work tool is further configured to operate at the edge temporarily whereby the robotic work tool is configured to determine that the operation at the edge is to be cancelled and in response thereto: retum the work tool; return the shield portion; navigate away from the edge and to continue operating in the work area.

In one embodiment the robotic work tool is further configured to reduce its speed as it is detected that the robotic work tool is approaching the edge.

In one embodiment the robotic work tool is further configured to reduce its speed by stopping while lowering the shield portion and moving the work tool.

In one embodiment the robotic work tool is further configured to operate at the edge in a stationary mode.

In one embodiment the robotic work tool is further configured to operate at the edge by following the edge.

In one embodiment the robotic work tool is further configured to determine whether it is possible to lower the shield portion and if not cancel the operation at the edge and retum the work tool; retum the shield portion; navigate away from the edge and to continue operating in the work area.

In one embodiment the robotic work tool is further configured to lower the shield portion and move the work tool towards the shield portion simultaneously.

In one embodiment the robotic work tool is further configured to determine that the robotic work tool is approaching the edge by detecting that the edge is about to be crossed.

In one embodiment the robotic work tool further comprises an outer shell and wherein the shield portion is comprised in the outer shell.

In one embodiment the robotic work tool is further configured to lower the shield portion by lowering the shield portion relatiVe the outer shell.

In one embodiment the robotic work tool is further configured to lower the shield portion by lowering the outer shell.

In one embodiment the robotic work tool is further configured to lower the shield portion by lowering the body.

In one embodiment the robotic work tool is further configured to deterrnine that the edge of the work area is being approached by detecting a boundary wire.

In one embodiment the robotic work tool is further configured to deterrnine that the edge of the work area has been reached by deterrnining that the robotic work tool is at a location indicated by satellite navigation signals corresponding to an edge location.

In one embodiment the robotic work tool is further configured to deterrnine that the edge of the work area has been reached by detecting a collision.

In one embodiment the robotic work tool further comprises a collar having an inner seal and an outer seal j oined by ﬂexible convolutions, wherein the inner seal is arranged to seal a portion of the work tool; the outer seal is arranged to seal against a hole in the body through which the portion of the work tool extends; and the flexible convolutions having a lateral bellow geometery.

In one embodiment a diameter of the inner seal is smaller than a diameter of the outer seal.

In one embodiment the the convolutions are arranged to compress when pushed together, as when the inner seal is brought close to the outer seal, into a bellow shape and wherein the convolutions are arranged to extend into a flat shape when pulled apart, as when the inner seal is brought away from the outer seal.

In one embodiment the convolutions are j oined by j oints and wherein the j oints have a higher ﬂexibility than the convolutions which enables the convolutions to maintain their basic flat shape regardless of position, a main deformation happening in the j oints.

In one embodiment the work tool is movably connected to the shield portion for moving the shield portion so that when the work tool is moved towards the shield portion, the shield portion is lowered.

In one embodiment the robotic work tool further comprises a linking portion and a steerer portion, wherein the linking portion is comprised in a work tool assembly and wherein the steerer portion is connected to the shield portion, wherein the linking portion is arranged to engage the steerer portion so that as the work tool, and consequently the work tool assembly is moved towards the shield portion, the linking portion forces the steerer portion to lower the shield portion.

In one embodiment the robotic work 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 robotic work tool system comprising a self-propelled robotic work tool arranged to operate on a surface in a work area, the robotic work tool comprising a work tool and a body having a shield portion, the method comprising: deterrnining that the robotic work tool is approaching an edge of the work area and in response thereto lowering the shield portion; moving the work tool towards the shield portion; and operating at the edge.

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.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in further detail under reference to the accompanying drawings in which: Figure 1 shows an example of a robotic work tool system being a robotic lawnmower system; Figure 2A shows an example of a robotic lawnmower according to one embodiment of the teachings herein; Figure 2B shows a schematic View of the components of an example of a robotic work tool being a robotic lawnmower according to an example embodiment of the teachings herein; Figure 2C shows a simplif1ed View of the schematic View of figure 2B; Figure 3 shows a schematic View of a robotic work tool system according to an example embodiment of the teachings herein; Figure 4A shows a schematic View of a robotic work tool according to an example embodiment of the teachings herein; Figure 4B shows a schematic View of a robotic work tool according to an example embodiment of the teachings herein; Figure 4C shows a schematic View of a robotic work tool according to an example embodiment of the teachings herein; Figure 4D shows a schematic View of a robotic work tool according to an example embodiment of the teachings herein; Figure 5 shows a corresponding ﬂowchart for a method according to an example embodiment of the teachings herein; Figure 6A shows a schematic View of a robotic work tool haVing a collar according to an example embodiment of the teachings herein; Figure 6B shows a schematic View of a robotic work tool haVing a collar according to an example embodiment of the teachings herein; Figure 6C shows a schematic View of a collar according to an example embodiment of the teachings herein, and Figure 6D shows a schematic View of a collar according to an example embodiment of the teachings herein.

DETAILED DESCRIPTION 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. This inVention may, howeVer, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

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 farrning equipment, or other robotic work tools where a work tool is to be safeguarded against from accidentally extending beyond or too close to the edge of the robotic work tool.

Figure 2A shows a perspective view of a robotic work tool 200, here exemplif1ed by a robotic lawnmower 200, having a body 240 and a plurality of wheels 230 (only one side is shown). The robotic work tool 200 may be a multi-chassis type or a mono-chassis type (as in figure 2A). A multi-chassis type comprises more than one main body parts that are movable with respect to one another. A mono-chassis type comprises only one main body part.

It should be noted that even though the description herein is focussed on the example of a robotic lawnmower, the teachings may equally be applied to other types of robotic work tools, such as robotic floor grinders, robotic ﬂoor cleaners to mention a few examples where a work tool should be kept away from the edges for safety or convenience concems.

It should also be noted that the robotic work tool is a self-propelled robotic work tool, capable of autonomous navigation within a work area, where the robotic work tool propels itself across or around the work area in a pattem (random or predeterrnined).

Figure 2B shows a schematic overview of the robotic work tool 200, also exemplif1ed here by a robotic lawnmower 200. In this example embodiment the robotic lawnmower 200 is of a mono-chassis type, having a main body part 240. The main body part 240 substantially houses all components of the robotic lawnmower 200. The robotic lawnmower 200 has a plurality of wheels 230. In the exemplary embodiment of f1gure 2B the robotic lawnmower 200 has four wheels 230, two front wheels and two rear wheels. At least some of the wheels 230 are drivably connected to at least one electric motor 250. It should be noted that even if the description herein is focused on electric motors, combustion engines may altematively be used, possibly in combination with an electric motor. In the example of figure 2B, each of the wheels 230 is connected to a common or to a respective electric motor 255 for driving the wheels 230 to navigate the robotic lawnmower 200 in different manners.

The robotic lawnmower 200 also comprises a controller 2l0 and a computer readable storage medium or memory 220. The controller 2l0 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 220 to be executed by such a processor. The controller 2l0 is configured to read instructions from the memory 220 and execute these instructions to control the operation of the robotic lawnmower 200 including, but not being limited to, the propulsion and navigation of the robotic lawnmower.

The controller 2l0 in combination with the electric motor 255 and the wheels 230 forms the base of a navigation system (possibly comprising further components) for the robotic lawnmower, enabling it to be self-propelled as discussed under ﬁgure 2A, The controller 2l0 may be implemented using any suitable, available processor or Programmable Logic Circuit (PLC). The memory 220 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 200 may further be arranged with a wireless com- munication interface 2l5 for communicating with other devices, such as a server, a personal computer or smartphone, the charging station, and/or other robotic work tools. Examples of such wireless communication devices are Bluetooth®, WiFi® (IEEE802. l lb), Global System Mobile (GSM) and LTE (Long Term Evolution), to name a few.

The robotic lawnmower 200 also comprises a grass cutting device 260, such as a rotating blade 260 driven by a cutter motor 265. The grass cutting device being an example of a work tool 260 for a robotic work tool 200. As a skilled person would understand the cutter motor 265 is accompanied or supplemented by various other components, such as a drive shaft to enable the driving of the grass cutting device, taken to be understood as included in the cutter motor 265. The cutter motor 265 will therefore be seen as representing a cutting assembly 265 or in the case of another Work tool, a Work tool assembly 265.

For enabling the robotic laWnmoWer 200 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 200 is further configured to have at least one magnetic field sensor 270 arranged to detect the magnetic field (not shoWn) and for detecting the boundary Wire and/or for receiving (and possibly also sending) inforrnation to/ from a signal generator (Will be discussed With reference to ﬁgure l). In some embodiments, the sensors 270 may be connected to the controller 2l0, possibly via filters and an amplifier, and the controller 2l0 may be configured to process and evaluate any signals received from the sensors 270. 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 2l0 to determine Whether the robotic laWnmoWer 200 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 200 may further comprise at least one navigation sensor, such as an optical navigation sensor, an ultrasound sensor, a beacon navigation sensor and/or a satellite navigation sensor 290. The optical navigation sensor may be a camera-based sensor and/or a laser-based sensor. 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. Altematively 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. In embodiments, Where the robotic laWnmoWer 200 is arranged With a navigation sensor, the magnetic sensors 270 are optional.

In one embodiment, the robotic laWnmoWer 200 is arranged to operate according to a map of the Work area 205 (and possibly the surroundings of the Work area 205) stored in the memory 220 of the robotic laWnmoWer 200. The map may be generated or supplemented as the robotic lawnmower 200 operates or otherwise moves around in the work area 205.

In an embodiment where the robotic lawnmower 200 is arranged to navigate both according to satellite navigation sensor(s) 290 and according to magnetic field sensor(s) 270 an increased accuracy is achieved as the position deterrnined based on the satellite navigation sensor may be supplemented or corrected by the input received from the magnetic field sensor 270. Especially as it comes to deterrnining the exact location of a boundary wire 220, (such as when crossing it), the magnetic field sensor 270 is highly accurate and its input may thus supplement or correct any location deterrnined based on input from the satellite navigation sensor 290.

Such supplementations or corrections are an example of corrections that may be made to the map stored in the memory 220.

The navigation sensor 290 is in one embodiment a combination of navigation sensors allowing for a combined navigation based on different techniques. In one such embodiment, the navigation sensor is arranged for SLAM (Simultaneous Location And Mapping) navigation.

The robotic lawnmower 200 also comprises one or more collision detectors 275. In the example of figure 2B, the robotic lawnmower 200 comprises a front collision detector 275, enabling the robotic lawnmower 200 to detect a collision while moving in a forwards direction, i.e. a forwards collision, but it should be noted that the robotic lawnmower 200 may also be arranged with further collision detectors enabling the robotic lawnmower 200 to detect a collision while moving in for example a reverse direction, i.e. a reverse collision.

The robotic lawnmower also comprises one or several lift detection sensors, enabling to detect that the robotic lawnmower l00 is being lifted and in response thereto deactivating the cutting disc 260 to prevent the cutting disc coming into contact with unwanted objects. In many implementations the collision detector and the lift detection sensors are implemented as the same device, therefore sharing the same reference 275.

Figure 2C shows a further simplif1ed schematic view of a robotic lawnmower 200 according to the teachings herein. For illustrative purposes some components have been omitted. In figure 2C the disc-to-edge distance dl is indicated to ll a front edge 240-e. In the example of figure 2C the body 240 of the robotic laWnmoWer 200 comprises an inner body 240-2 housing most if not all of the components and an outer shell 240-1. As the outer shell 240-1 denote the outer edges of the robotic lawnmower 100, the disc-to-edge distance d1 is from the cutting disc to the edge of the outer shell 240-1 in embodiments Where an outer shell, or other outer body 240-1 is used. As a skilled person Would understand the disc-to-edge distance d1 and the cutting disc 260 of figure 2C f1nds corresponding parts tool-to-edge distance d1 in other embodiments.

Figure 2C also shows a shield portion 240-3 comprised in the outer shell 240-1.

In the example of figure 2C, the shield portion is arranged at a front edge of the outer shell 240-1, front being seen as in the direction of norrnal front travel during operation. The shield portion is also exemplified as extending around the front corners and partially along the sides of the robotic Work tool 200. However it should be noted that other extensions and/or arrangements are also possible. It should also be noted that the shield portion 240-3 may comprise a single portion or a plurality of portions, possibly moVable in relation to one another. For example; the shield portion may extend all around the robotic Work tool 200, one shield portion may be arranged at the front and second shield portion may be arranged at the rear of the robotic Work tool 200, a shield portion 240-3 may be arranged at either or both sides of the robotic Work tool 200.

In one embodiment the shield portion 240-3 is attached to the outer shell and arranged to be loWered in relation to the outer shell 240-1. In one embodiment the shield portion 240-3 is part of or attached to the outer shell and arranged to be loWered along With or as part of the outer shell 240-1. In such an embodiment, the shield portion 240-3 may be loWered (as part of the outer shell 240-1) by the outer shell 240-1 being loWered relatiVe the inner body 240-2. In an altemative or additional embodiment the shield portion 240-3 may be loWered (as part of the outer shell 240-1) by the outer shell 240-1 being loWered along With the inner body 240-2 for example by raising one or more of the Wheels 130 relative the inner body 240-2. As should be noted any, all or some of these embodiments may be combined. 12 Figure 3 shows a robotic work tool system 300 in one embodiment. The schematic View is not to scale. The robotic work tool system 300 of figure 3, corresponds in many aspects to the robotic work tool system 200 of figure l, except that the robotic work tool system 300 of figure 3 comprises a robotic work tool 200 according to the teachings herein. As with figures 2A, 2B and 2C, the robotic work tool is exemplified by a robotic lawnmower, whereby the robotic work tool system may be a robotic lawnmower system or a system comprising a combinations of robotic work tools, one being a robotic lawnmower, but the teachings herein may also be applied to other robotic work tools adapted to operate within a work area.

The robotic work tool system 300 may comprise charging station 3 l0 which in some embodiments is arranged with a signal generator 3 l5 and a boundary wire 320.

The signal generator is arranged to generate a control signal 325 to be transmitted through the boundary wire 320 arranged to enclose a work area 305, in which the robotic lawnmower 200 is supposed to serve. The control signal 325 transmitted through the boundary wire 320 causes a magnetic field (not shown) to be emitted. As an electrical signal is transmitted through a wire, such as the control signal 325 being transmitted through the boundary wire 320, 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 work area 305 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, exemplified herein by a number (2) of trees (T), a stone (S) 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).

In the below several embodiments of how the body of the robotic work tool may be adapted will be disclosed. It should be noted that all embodiments may be combined in any combination providing a combined adaptation of the robotic work tool. 13 It should also be noted that even though all examples given herein are shown with reference to a forwards direction of the robotic work tool, the embodiments may also apply to adapting the distance dl in other directions, for example the reverse direction of the robotic work tool, but also sideways directions. It is fully plausible that a robotic work tool travels along a rock or a wall, with the side of the robotic work tool pressed against or close to the rock or wall. In such a situation the distance dl will be adapted with reference to that side of the robotic work tool 200.

Figure 4A shows a schematic side view of a robotic work tool 200, as in figures 2A, 2B and 2C, exemplified herein by a robotic lawnmower 200. The side view of figure 4A corresponds to the side view of the prior art robotic lawnmower 10 of figure 1, where a disc-to-edge distance d1 is indicated from a cutting disc 260 (or other working tool) to an edge 240-e of the robotic lawnmower 200, here a front edge of an outer shell 240-1 enclosing an inner body 240-2. The edge essentially corresponds to the shield portion 240-3 (and especially in embodiments where the shield portion 240-3 is comprised in the outer shell 240-1).

A foot probe is also indicated by dashed lines in figure 4A showing that an object resembling a foot is unable to be inserted under the robotic lawnmower 200 far enough to reach and thus be exposed to the cutting disc 260.

The center of the cutting disc 260 is also shown herein, exemplified by the shaft (or other part) of the cutter assembly 265. It should be noted that the view is not to scale and some relations have been exaggerated for illustrative purposes.

An edge, exemplified as a boundary wire 320, is also indicated in figure 4A. Other boundaries may be obstacles as discussed in the background with relation to figure 1, and as discussed in relation to figure 3.

It should be noted that even though the description herein is focused on a robotic work tool operating on ground, the teachings herein may also be applied to robotic work tools operating on other surfaces. The ground is thus interchangeable with a general surface.

The functionality of the robotic lawnmower 200 will now be described with simultaneous reference to figures 4A, 4B and figure 5. Figure 5 is a schematic view of a flow chart representing a general method of the teachings herein. 14 As the robotic lawnmower 200 detects 510 the edge 320 the robotic lawnmower 200 reduces 520 its speed. In one embodiment the robotic lawnmower 200 stops. The manner that the robotic lawnmower 200 detects the edge depends on the type of edge. In figure 4A, the edge is exemplified as the boundary wire 320, and in such case the edge is detected through the sensor 270. In embodiments or situations where the edge is marked by GPS coordinates the edge is detected through the navigation sensor 290. In embodiments or situations where the edge is an obstacle the edge is detected through the collision sensor 275.

Figure 4B shows a schematic side View of the robotic lawnmower 200 of figure 4A as the robotic lawnmower 200 has detected the edge and in response thereto has reduced its speed. The shield portion 240-3 is lowered 530. There are many altematives of how to lower the shield portion 240-3 as has been discussed in relation to figure 2C.

In one embodiment, the robotic lawnmower 200 is conf1gured to detect the edge 320 as it is crossed or encountered. In an altemative or additional embodiment the robotic lawnmower 200 is arranged to detect the edge before it is crossed and thus prematurely detect the edge as the robotic lawnmower 200 approaches the edge. The robotic lawnmower may be considered to approach the edge also when the edge is about to be crossed. For examples where the edge is a boundary wire 320, the distance to the edge is easy to determine based on the detected signal strength of the detected magnetic signal emitted by the boundary wire. For boundaries specified by coordinates it is also a simple operation to determine a distance to the edge. The robotic lawnmower 200 is thus enabled to detect the edge prematurely or at a distance before actually reaching the edge and may thus start to lower the shield portion 240-3 prematurely and without stopping the robotic lawnmower 200.

Optionally, the robotic lawnmower 200 is conf1gured to detect 535 whether it is possible to lower the shield portion 240-3 or not. If it is detected 535 that the shield portion cannot be lowered (for example by debris or obstacles on the ground, the edge cutting operation disclosed herein is cancelled 536.

The shield portion 240-3 is lowered at least along the edge that has been detected. In one embodiment the shield portion is lowered down to the ground. In one embodiment the shield portion is lowered so that the relationship between the distance to ground from the shield portion and the distance from the cutting disc 260 to the shield portion 240-3 (i.e. the edge 240-e) satisfies a relationship specified by safety standards.

As the shield portion has been lowered - or as the shield portion is lowered -the cutting disc 260 is moved towards the shield portion 240-3. As discussed in the above, the cutting disc (or other tool) may be moved 540 forwards, rearwards or to the side, depending on where the edge is detected. As can be seen in figure 4B, the probe is still not able to be extended far enough in under the robotic lawnmower 200 to be exposed to the cutting disc even though the distance to the cutting disc dl has been substantially reduced, as shield portion 240-3 is preventing this.

As the robotic lawnmower 200 approaches the edge it is -in one embodiment - configured to simultaneously lower the shield as the cutting disc is moved.

As the shield portion 240-3 has been lowered and the cutting disc 260 moved, the robotic lawnmower 200 continues operating 550 at the edge.

In one embodiment the robotic lawnmower 200 operates in a stationary position at the edge. In one such embodiment, the robotic lawnmower 200 is configured to operate at the edge for a time period, such as 5, l0, or l5 seconds and then terminate the operation at the edge (or continue operating in a different manner).

In one embodiment the robotic lawnmower 200 operates by following the edge. In one such embodiment, the robotic lawnmower 200 is configured to follow the edge for a time period, such as l0, 20, 30, 60 or l20 seconds and then terminate the operation at the edge (or continue operating in a different manner). In an altemative or additional such embodiment, the robotic lawnmower 200 is configured to follow the edge for a distance, such as 0.5, l, 2, 5, l0, l5, 20, or 30 meters and then terrninate the operation at the edge (or continue operating in a different manner). In one embodiment the robotic lawnmower 200 operates by tuming around its center to thereby operate in a wider area around the edge compared to being stationary.

In one embodiment the robotic lawnmower 200 operates at the edge at a reduced speed. This prevents or reduces the risk that the lowered shield portion 240-l or 16 the cutting disc 260 (which may also have been lowered along with lowering the body 240) are damaged by colliding with obstacles (rocks, roots or Structures) on the ground.

It should be noted that the manners of operating at the edge may be combined by combining any, some or all of them.

Above several examples are given of how to determine that the operation at the edge is to be terrninated. As it is deterrnined that the edge operation is to be terrninated and the robotic lawnmower 200 is to retum to normal operation, the robotic lawnmower 200 retums 560 the cutting disc 260 (or other tool) to its original position. The robotic lawnmower 200 also retums 570 the shield portion 240-3 to its original position. And, the robotic lawnmower 200 navigates 580 away from the edge. As when the robotic lawnmower 200 approaches the edge it is configured to possibly simultaneously lower the shield as the cutting disc is moved, the robotic lawnmower 200 is configured to possibly simultaneously raise the shield as the cutting disc is retumed as the robotic lawnmower 200 moves away from the edge.

The manner of navigating away from the edge depends on how the robotic lawnmower 200 was operating by the edge, but it would be obvious to a skilled person how to instruct a robotic lawnmower 200 to move away from an edge so this will not be discussed in any detail. Only one example will be given, namely to reverse for a short distance and then tum followed by forwards propulsion away from the edge, as is common when encountering a boundary wire or colliding with an obstacle. As the robotic lawnmower 200 moves away from the edge, it resumes 590 its normal operation (including its normal speed).

The robotic lawnmower 200 of the teachings herein is thus conf1gured to adapt the edge-to-ground distance temporarily and consequently adapt the disc-to-edge distance dl temporarily as well to improve servicing the edge areas.

As is also indicated in figure 4B, the safety standards have been maintained as the probe is still prevented from reaching the cutting disc 260, even though the disc- to-edge distance dl has been reduced, all while satisfying the safety standards as the disc-to-edge distance dl is still limited by the edge-to-ground distance.

In one embodiment the robotic lawnmower 200 is further configured to determine that an edge has been reached by detecting a boundary wire, or rather a 17 distance to the boundary wire indicating an imminent turning. In one alternative or additional embodiment the robotic lawnmower 200 is further configured to deterrnine that an edge has been reached by deterrnining that the robotic lawnmower 200 is at a location indicated by satellite navigation signals corresponding to an edge location where a turn is to be effected. In one embodiment the corresponding edge being the edge forwards in the current direction of travel.

In one alternative or additional embodiment the robotic lawnmower 200 is further configured to deterrnine that an edge has been reached by detecting a collision. In one embodiment the corresponding edge being the edge where the collision is detected.

In one alternative or additional embodiment the robotic lawnmower 200 is further configured to deterrnine that an edge has been reached by analysing images received from the optical navigation sensor 290.

In one alternative or additional embodiment the robotic lawnmower 200 is further configured to deterrnine that an edge has been reached by analysing sound signals received from the ultrasound navigation sensor 290, In one alternative or additional embodiment the robotic lawnmower 200 is further configured to deterrnine that an edge has been reached by analysing magnetic signals received from the magnetic sensor 270, for example by detecting the boundary wire 320.

It should be noted that any, some or all manners of detecting that the edge is being approached may be combined.

Figures 4C and 4D each shows a schematic side view of a robotic work tool 200, as in figures 2A, 2B, 2C, 4A and 4B, exemplified herein by a robotic lawnmower 200. Figures 4C and 4D shows an embodiment, where the cutting assembly 265 is operably connected to the shield portion 240-3 so that as the cutting assembly is moved, the shield portion is also biased or caused to move. This enables for use of only one driving means for moving both the cutting assembly 265 and the shield portion 240-3. There are many altematives for how to make one part move when another part moves, and figures 4C and 4D only shows one example. In this example, a linking portion 266, such as a rim, roll or protrusion, comprised in the cutting assembly 265 is arranged to 18 engage a steering portion connected to the shield portion 240-3, in this example an arrn 241. The arrn 241 is arranged to move or pivot around a pivot point P and as the cutting assembly moves forwards, the linking portion 266 forces the steering portion 241 to pivot downwards, and thus move the shield portion 240-3 downwards, the pivot point thus guiding the shield portion. The cutting device 260 is thus movably or operationally connected (through the cutting assembly 265 and the steerer portion 241) to the shield portion 240-3 for moving the shield portion 240-3 so that when the cutting disc 260 is moved forwards (i.e towards the shield portion), the shield portion is lowered.

If the steerer portion is spring based it will bound back as the cutting assembly 265 moves back. Altematively, the linking portion may be arranged to run inside grooves of the steerer portion, the linking portion thus also lifting the steerer portion as the cutting assembly moves back again.

Altematives that may be used to supplement, combine with or replace the arrangement of figure 4C and figure 4D include a linking portion arranged to push the steerer portion along guides (represented by the pivot point P in figures 4C and 4D) of or attached to for example the outer shell or the body of the robotic lawnmower 200. One altemative is where the steerer portion 241 is part of the outer shell 240-1, for example grooves in the outer shell 240-1, where the outer shell 240-1 is forced to pivot or otherwise lower as the cutting assembly 265 is moved thereby also lowering the shield portion 240-3.

In the examples of figures 4C and 4D focus has been on moving the cutting assembly forwards, but it should be noted that similar embodiments may be used for moving the cutting assembly in any direction.

The inventors have further realised that since the cutting disc 260 or other tool is movably arranged, the housing or body 240 of the robotic work tool 200 may in some embodiments be provided with a large hole through which the shaft 265 (or other portion) of the work tool assembly 265 extends that allows the shaft to move forwards and backwards (or in other directions). The inventors are therefore proposing an inventive collar 610 that may be used to cover such a hole 245 in the body 240. Figures 6A and 6B shows an embodiment of such a collar 610. The collar 610 is arranged to change its shape along with the movement of the shaft. As can be seen in figure 6A, the 19 work tool 260 is in a normal (or rearwards) position, and the collar 610 has a first shape. As can be seen in figure 6B, the work tool 260 is in a forwards (or norrnal) position, and the collar 610 has a second shape. The first and second shape provides for a tight fit to be provided around the shaft regardless of position.

Figures 6C and 6D shows schematic views of the collar 610 in the first and second position respectively. As can be seen, the positions are similar and may even be mirrored versions of one another. The collar 610 comprises an outer sealing 620 and an inner sealing 630. The outer sealing 620 is arranged to seal against the hole 245 of the body 240. And the inner sealing 630 is arranged to seal against a portion of the work tool 260, presumably against a housing of the shaft (or other portion) of the work tool assembly 265, but other altematives exist and depends on the design of the work tool 260.

In one embodiment, and as can be seen in figures 6C and 6D, the inner seal 630 is round, for example circular in its extension. In one embodiment, and as can be seen in figures 6C and 6D, the outer seal 620 is of a so-called stadium shape (i.e. two semi-circular ends connected by (substantially) straight lines) in its extension. This allows for the inner seal 630 to be at a constant or equal distance from the outer seal 620 in the two end positions.

The diameter of the inner seal 630 is smaller than the diameter of the outer seal 620.

The collar 610 also comprises ﬂexible convolutions 615 having a lateral bellow geometry. The convolutions 615 are arranged to compress or retract when pushed together, as when the inner seal 630 is brought close to the outer seal 620 (see areas C in figures 6C and 6D), into a bellow shape. The convolutions 615 are also arranged to extend into a ﬂat shape when pulled apart, as when the inner seal 630 is brought away from the outer seal 620 (see areas E in figures 6C and 6D). In one embodiment the j oints 616 of the convolutions 615 have a higher ﬂexibility than the convolutions 615 which enables the convolutions to maintain their basic ﬂat shape regardless of position, the main deformation happening in the j oints 616.

In one embodiment the convolutions 615 are made of rubber, plastic or other flexible material.

Claims

1. 1. A robotic Work tool system (300) comprising a self-propelled roboticWork tool (200) arranged to operate on a surface in a Work area (3 05), the robotic Worktool (200) comprising a Work tool (260) and a body (240) having a shield portion (240-3), the robotic Work tool (200) being configured to: determine that the robotic Work tool (200) is approaching an edge (320, S,T, H) of the Work area (305) and in response thereto lower the shield portion (240-3); move the Work tool (260) towards the shield portion (240-3); and operate at the edge (320, S, T, H).

2. The robotic Work tool system (300) according to claim 1, Wherein therobotic Work tool (200) is further configured to operate at the edge temporarily Wherebythe robotic Work tool (200) is configured to determine that the operation at the edge is tobe cancelled and in response thereto: retum (560) the Work tool (260); retum (570) the shield portion (240-3); navigate away (580) from the edge (320, S, T, H) and to continue (590) operating in the Work area (3 05).

3. The robotic Work tool system (3 00) according to claim 1 or 2, Wherein therobotic Work tool (200) is further configured to reduce (520) its speed as it is detectedthat the robotic Work tool (200) is approaching the edge (320, S, T, H).

4. The robotic Work tool system (3 00) according to claim 3, Wherein therobotic Work tool (200) is further configured to reduce (520) its speed by stopping WhileloWering the shield portion (240-3) and moving the Work tool (260).

5. The robotic work tool system (3 00) according to any preceding claim,wherein the robotic work tool (200) is further conf1gured to operate at the edge in a stationary mode.

6. The robotic work tool system (300) according to any preceding claim,wherein the robotic work tool (200) is further conf1gured to operate at the edge byfollowing the edge.

7. The robotic work tool system (300) according to any preceding claim,wherein the robotic work tool (200) is further conf1gured to deterrnine (535) whether itis possible to lower the shield portion (240-3) and if not cancel (536) the operation atthe edge and return (560) the work tool (260); return (570) the shield portion (240-3); navigate away (580) from the edge (320, S, T, H) and to continue (590) operating in the work area (305).

8. The robotic work tool system (300) according to any preceding claim,wherein the robotic work tool (200) is further conf1gured to lower the shield portion(240-3) and move the work tool (260) towards the shield portion (240-3) simultaneously.

9. The robotic work tool system (300) according to any preceding claim,wherein the robotic work tool (200) is further conf1gured to deterrnine that the roboticwork tool (200) is approaching the edge (320, S, T, H) by detecting that the edge is about to be crossed.

10. l0. The robotic work tool system (300) according to any preceding claim,wherein the robotic work tool (200) further comprises an outer shell (240-l) andwherein the shield portion (240-3) is comprised in the outer shell (240-l).

11. The robotic work tool systeni (3 00) according to claini 10, wherein therobotic work tool (200) is further conf1gured to lower the shield portion (240-3) bylowering the shield portion (240-3) relative the outer shell (240-1).

12. The robotic work tool system (3 00) according to claini 10, wherein therobotic work tool (200) is further conf1gured to lower the shield portion (240-3) bylowering the outer shell (240-1).

13. The robotic work tool system (300) according to any preceding claini,wherein the robotic work tool (200) is further configured to lower the shield portion(240-3) by lowering the body (240).

14. The robotic work tool systeni (300) according to any preceding claini,wherein the robotic work tool (200) is further conf1gured to deterrnine that the edge ofthe work area (305) is being approached by detecting a boundary wire (320).

15. The robotic work tool systeni (300) according to any preceding claini,wherein the robotic work tool (200) is further conf1gured to deterrnine that the edge ofthe work area (3 05) has been reached by deterrnining that the robotic work tool (200) is at a location indicated by satellite navigation signals corresponding to an edge location.

16. The robotic work tool systeni (300) according to any preceding claini,wherein the robotic work tool (200) is further conf1gured to deterrnine that the edge of the work area (3 05) has been reached by detecting a collision.

17. The robotic work tool systeni (300) according to any preceding claini,wherein the robotic work tool (200) further coniprises a collar (610) having an innerseal (630) and an outer seal (620) joined by ﬂexible convolutions (615), wherein the inner seal (630) is arranged to seal a portion of the work tool (260); the outer seal (620) is arranged to seal against a hole (245) in the body (240)through which the portion of the work tool (260) extends; andthe ﬂexible convolutions (615) having a lateral bellow geometery.

18. The robotic work tool system (3 00) according to claim 17, wherein a diameter of the inner seal (630) is smaller than a diameter of the outer seal (620).

19. The robotic work tool system (300) according to claim 17 or 18, whereinthe convolutions (615) are arranged to compress when pushed together, as when theinner seal (630) is brought close to the outer seal (620), into a bellow shape and whereinthe convolutions (615) are arranged to extend into a ﬂat shape when pulled apart, as when the inner seal (63 0) is brought away from the outer seal (620).

20. The robotic work tool system (300) according to claim 17, 18 or 19,wherein the convolutions (615) are j oined by j oints (616) and wherein the j oints (616)have a higher ﬂexibility than the convolutions (615) which enables the convolutions(615) to maintain their basic ﬂat shape regardless of position, a main deformation happening in the j oints (616).

21. The robotic work tool system (3 00) according to any preceding claimwherein the work tool (260) is movably connected to the shield portion (240-3) formoving the shield portion (240-3) so that when the work tool (260) is moved towardsthe shield portion (240-3), the shield portion (240-3) is lowered.

22. The robotic work tool system (3 00) according to claim 21 whereinrobotic work tool (200) further comprises a linking portion (266) and a steerer portion(241), wherein the linking portion (266) is comprised in a work tool assembly (265) andwherein the steerer portion is connected to the shield portion (240-3), wherein thelinking portion (266) is arranged to engage the steerer portion (241) so that as the worktool (260), and consequently the work tool assembly (265) is moved towards the shieldportion (240-3), the linking portion (266) forces the steerer portion (241) to lower theshield portion (240-3).23. The robotic Work tool system (300) according to any preceding claini

23. Wherein the robotic Work tool (200) is a robotic lawnniower.

24. A method for use in a robotic Work tool system (300) coniprising a self-propelled robotic Work tool (200) arranged to operate on a surface in a Work area (305),the robotic Work tool (200) coniprising a Work tool (260) and a body (240) having ashield portion (240-3), the niethod con1prising: deterrnining that the robotic Work tool (200) is approaching an edge (320, S,T, H) of the Work area (305) and in response thereto loWering the shield portion (240-3); moving the Work tool (260) towards the shield portion (240-3); and operating at the edge (320, S, T, H).