Obstacle detection for a robotic working tool

Abstract

A robotic work tool system (200) comprising a robotic work tool (100) and a beacon marker (280), said robotic work tool (100) comprising a beacon sensor (175) configured to sense a signal being transmitted by the beacon marker (280), said beacon marker (280) marking an area (270) around an obstacle (260) in a work area (205) in which said robotic work tool (100) is arranged to operate, wherein said robotic work tool is configured to determine a proximity to a beacon marker (280) and to adapt its operation accordingly.

Claims

1. An outdoor robotic work tool system comprising an outdoor robotic work tool and a beacon marker, said outdoor robotic work tool comprising a beacon sensor configured to sense a signal being transmitted by the beacon marker, said beacon marker marking an area around an obstacle in a work area in which said outdoor robotic work tool is arranged to operate, wherein said outdoor robotic work tool is configured to: determine a proximity to the beacon marker and to adapt operation of the outdoor robotic work tool based on the proximity to the beacon marker.

2. The outdoor robotic work tool system according to claim 1, wherein the outdoor robotic work tool is further configured to determine the proximity to the beacon marker as a state of being close or not close by comparing a signal strength of the beacon signal to a threshold value, and if the signal strength is above the threshold value, the beacon marker is close, and, if not, the beacon marker is not close.

3. The outdoor robotic work tool system according to claim 1, wherein the outdoor robotic work tool is configured to determine the proximity to the beacon marker by comparing the signal strength of the beacon signal to a model of signal declination.

4. The outdoor robotic work tool system according to claim 1, wherein the outdoor robotic work tool is configured to determine the proximity to the beacon marker by sending a signal to the beacon marker and measuring a two-way response.

5. The outdoor robotic work tool system according to claim 4, wherein the outdoor robotic work tool is configured to determine the proximity to the beacon marker as a state of being close or not close by comparing the two-way response to a threshold value, and if the two-way response time is above the threshold value, the beacon marker is close, and, if not, the beacon marker is not close.

6. The outdoor robotic work tool system according to claim 4, wherein the outdoor robotic work tool is configured to determine a distance to the beacon marker based on the two-way response time.

7. The outdoor robotic work tool system according to claim 1, wherein the outdoor robotic work tool is configured to adapt its operation when determining a proximity to an obstacle by slowing down or making a turn less than 180 degrees.

8. The outdoor robotic work tool system according to claim 1, wherein the beacon marker and the beacon sensor are synchronized.

9. The outdoor robotic work tool system according to claim 1, wherein the outdoor beacon marker is a radio frequency beacon.

10. The outdoor robotic work tool system according to claim 9, wherein said beacon marker comprises fastening means for securing said beacon marker to an obstacle or a pole.

11. The outdoor robotic work tool system according to claim 1, wherein the beacon marker is an ultrasonic beacon.

12. The outdoor robotic work tool system according to claim 1, further comprising a position determining device is a Global Navigation Satellite System device.

13. The outdoor robotic work tool system according to claim 1, wherein the outdoor robotic work tool is a robotic lawnmower including a rotating blade driven by a cutter motor.

14. The outdoor robotic work tool system according to claim 1, wherein the outdoor robotic work tool is a farming equipment, a street sweeper, a snow removal tool, a golf ball retriever robot, a leaves blower robot, a leaves collector robot, snow thrower robot or a mine clearance robot.

15. A method for use in an outdoor robotic work tool system comprising an outdoor robotic work tool and a beacon marker, said outdoor robotic work tool comprising a beacon sensor configured to sense a signal being transmitted by the beacon marker, said beacon marker marking an area around an obstacle in a work area in which said outdoor robotic work tool is arranged to operate, said method comprising determining a proximity to a beacon marker and adapting an operation of the outdoor robotic work tool based on the proximity to the beacon marker.

Description

BRIEF DESCRIPTION OF DRAWINGS

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

(2) FIG. 1 shows a schematic overview of a robotic work tool according to one embodiment of the teachings of this application;

(3) FIG. 2 shows a schematic view of a robotic working tool system according to one embodiment of the teachings of this application;

(4) FIG. 3 shows a schematic view of a robotic working tool system in operation according to one embodiment of the teachings of this application; and

(5) FIG. 4 shows a schematic view of a beacon marker according to one embodiment of the teachings of this application.

DETAILED DESCRIPTION

(6) 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; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

(7) FIG. 1 shows a schematic overview of a robotic work tool 100 having a body 140 and a plurality of wheels 130. In the exemplary embodiment of FIG. 1 the robotic work tool 100 has 4 wheels 130, two front wheels 130 and the rear wheels 130. At least some of the wheels 130 are drivably connected to at least one electric motor 150. It should be noted that even if the description herein is focussed on electric motors, combustion engines may alternatively or additionally be used possibly in combination with an electric motor.

(8) In the example of FIG. 1, the rear wheels 130 are connected to each an electric motor 150. This allows for driving the rear wheels 130 independently of one another which, for example, enables steep turning.

(9) The robotic work tool 100 also comprises a controller 110. The controller 110 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 a computer readable storage medium (disk, memory etc) 120 to be executed by such a processor. The controller 110 is configured to read instructions from the memory 120 and execute these instructions to control the operation of the robotic work tool 100. The controller 110 may be implemented using any suitable, publically available processor or Programmable Logic Circuit (PLC). The memory 120 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.

(10) The robotic work tool 100 further may have at least one sensor 170, in the example of FIG. 1 there are two sensors 170, arranged to detect a magnetic field (not shown). The sensors are connected to the controller 110 and the controller 110 is configured to process any signals received from the sensors 170. The sensor signals may be caused by the magnetic field caused by a control signal being transmitted through a boundary wire (for more details on charging stations, control signals and boundary wires, see the description below with reference to FIG. 2). This enables the controller 110 to determine whether the robotic work tool 100 is inside or outside an area enclosed by a boundary wire.

(11) It should be noted that the teachings herein may also be used for a robotic work tool that is configured to operate in a work area, where the work area is not bounded by a boundary wire. Examples of such robotic work tools are tools arranged to physically detect a boundary by collision detection, or a robotic work tool that uses a position determination system (such as GNSS) to maintain a position within the work area, which work area is specified by coordinates.

(12) The robotic work tool 100 may also or alternatively be arranged with a position determining device 190, such as a GNSS (Global Navigation Satellite System) device 190. In one embodiment the GNSS device is a GPS (Global Positioning Service) device 190. The GNSS device 190 is connected to the controller 110 for enabling the controller 110 to determine a current position for the robotic work tool 100 using the GNSS device and to control the movements of the robotic work tool 100 based on the position.

(13) Alternatively, the robotic work tool 100 may be arranged to operate within the work area solely or mainly based on the position determining device 190. A user may then establish a work area through coordinates and the robotic work tool will ensure that it stays within those coordinates based on the signals received by the position determining device 190.

(14) Other examples of position determining devices 190 include optical (such as laser) position determining devices, other radio frequency position determining systems, such as ultrawideband (UWB) beacons and receivers.

(15) The robotic work tool 100 may further be arranged with at least one sensor 195 for providing signals for deduced reckoning navigation. Examples of such deduced reckoning navigation sensors 195 are odometers, accelerometers, gyroscopes and compasses.

(16) The deduced reckoning sensor(s) may be used to navigate in areas where satellite reception is not possible, i.e. areas hereafter referred to as shadowed areas.

(17) The controller 110 is connected to the motors 150 for controlling the propulsion of the robotic work tool 100 which enables the robotic work tool 100 to service an enclosed area without leaving the area.

(18) The robotic work tool 100 also comprises a work tool 160, which may be a grass cutting device, such as a rotating blade 160 driven by a cutter motor 165. The cutter motor 165 is connected to the controller 110 which enables the controller 110 to control the operation of the cutter motor 165. The controller is also configured to determine the load exerted on the rotating blade, by for example measure the power delivered to the cutter motor 165 or by measuring the axle torque exerted by the rotating blade. The robotic work tool 100 is, in one embodiment, a lawnmower robot. In one embodiment the robotic work tool 100 is a farming equipment. In one embodiment the robotic work tool 100 is a golf ball collecting tool.

(19) The robotic work tool 100 may also be a vacuum cleaner, a floor cleaner, a street sweeper, a snow removal tool, a mine clearance robot or any other robotic work tool that is required to operate in a work area in a methodical and systematic or position oriented manner.

(20) The robotic work tool 100 also has (at least) one battery 180 for providing power to the motors 150 and the cutter motor 165. Alternatively or additionally the robotic work tool may have a fuel tank 180 for supplying fuel to any other type of engine 150. In one embodiment the robotic work tool is arranged with solar panel for supplying power to the battery 180.

(21) FIG. 2 shows a schematic view of a robotic work tool system 200 comprising a charging station 210 and a boundary wire 250 arranged to enclose a working area 205, the working area 205 not necessarily being a part of the robotic work tool system 200, in which the robotic work tool 100 is supposed to service. As stated above, the robotic work tool 100 may be arranged to operate solely using the position determining device in which case no boundary wire 250 nor signal generator (to be disclosed) is part of the system 200. The charging station 210 has a charger 220 coupled to, in this embodiment, two charging plates 230. The charging plates 230 are arranged to co-operate with corresponding charging plates (not shown) of the robotic work tool 100 for charging the battery 180 of the robotic work tool 100. The charging station 210 also has, or may be coupled to, a signal generator 240 for providing a control signal (not shown) to be transmitted through the boundary wire 250. As is known in the art, the control signal will generate a magnetic field around the boundary wire 250 which the sensors 170 of the robotic work tool 100 will detect. As the robotic work tool 100 (or more accurately, the sensor 170) crosses the boundary wire 250 the direction of the magnetic field will change. The robotic work tool 100 will thus be able to determine that the boundary wire has been crossed. The use of more than one sensor 170 enables the controller 110 of the robotic work tool 100 to determine how the robotic work tool 100 is aligned with relation to the boundary wire 250 by comparing the sensor signals received from each sensor 170. This enables the robotic work tool to follow the boundary wire 250, for example when returning to the charging station 210 for charging.

(22) Optionally, the charging station 210 also has a guide cable 260 for enabling the robotic work tool to find the entrance of the charging station 210. In one embodiment the guide cable 260 is formed by a loop of the boundary wire 250. In one embodiment the guide wire 260 is used to generate a magnetic field for enabling the robotic work tool 100 to find the charging station without following a guide cable 260.

(23) FIG. 3 shows another schematic view of a robotic work tool system 200 according to the teachings herein, such as the robotic work tool system 200 of FIG. 2, being depicted here at a larger scale.

(24) The work area 205 is shown here to include two obstacles 260 and being delimited by a boundary 250. It should be noted that there may be more or less than two obstacles 260.

(25) The boundary 250 may be effected through navigation coordinates or a boundary wire or other suitable means for defining a boundary for a work area for robotic work tools.

(26) Two obstacles 260A and 260B are shown in the example embodiment of FIG. 3, one obstacle being a virtual obstacle 260A and one being an actual obstacle 260B. An obstacle marker in the form of a beacon marker 280 is arranged on or in each obstacle 260. The beacon markers 280 emit each a signal that marks an area 270 around the obstacle 260. As can be seen in FIG. 3, the areas 270 may be of different size/radius. The area 270A for the virtual obstacle 260A being larger than the area 270B for the physical obstacle 260B. It should be noted that the area 270 of a beacon marker 280 may be regulated and possibly user settable by increasing or decreasing the signal power, or by programming the robotic work tool to detect a signal at a certain strength. The size relationship of the areas 270 in FIG. 3 are only examples and any internal relationship of sizes is possible and within the scope of this application.

(27) As a robotic work tool 100 comes close to a beacon marker 280 it will detect a signal transmitted by the beacon marker 280 through a beacon sensor 175 arranged in the robotic work tool (see FIG. 1). The beacon sensor 175 is coupled to the controller 110 for determining the proximity to the beacon marker 280. Alternatively the beacon sensor 175 is arranged to determine the proximity to the beacon marker 280 by itself and signal that a beacon marker is close by to the controller as the proximity of a beacon marker 280 is determined.

(28) In one embodiment the robotic work tool 100 is configured to determine the proximity to a beacon marker by comparing the signal strength (SSI) of the beacon signal, or a radio signal strength indicator (RSSI) of the beacon signal.

(29) In one embodiment the robotic work tool 100 is configured to determine the proximity to a beacon marker as a state close or not close by comparing the signal strength of the beacon signal to a threshold value. If the signal strength is above the threshold value, the beacon is close, and, if not, it is not close.

(30) In one embodiment the robotic work tool 100 is configured to determine the proximity to a beacon marker by comparing the signal strength of the beacon signal to a model of signal declination. In this embodiment the robotic work tool 100 is configured to know at what signal strengths the beacon signal is transmitted. This enables for determining a more precise distance to the beacon marker 280 and the robotic work tool 100 may take different actions depending on the actual distance. Such different actions may be to slow down or make a turn less than 180 degrees depending on the distance. For example, the robotic work tool may be configured to slow down if the distance is 5 m, to turn 90 degrees if the distance is 2 m, and to turn 180 degrees if the distance is less than 1 m.

(31) In one embodiment the robotic work tool 100 is configured to determine the proximity to a beacon marker by sending a signal to the beacon and measure the two-way response time or alternatively phrased to measure the time of arrival (TOA).

(32) In one embodiment the robotic work tool 100 is configured to determine the proximity to a beacon marker as a state close or not close by comparing the two-way response to a threshold value. If the two-way response is above the threshold value, the beacon is close, and, if not, it is not close.

(33) In one embodiment the robotic work tool 100 is configured to determine a more precise distance to the beacon marker 280 based on the two-way response. This enables for determining a more precise distance to the beacon marker 280 and the robotic work tool 100 may take different actions depending on the actual distance. Such different actions may be to slow down or make a turn less than 180 degrees depending on the distance. For example, the robotic work tool may be configured to slow down if the distance is 5 m, to turn 90 degrees if the distance is 2 m, and to turn 180 degrees if the distance is less than 1 m.

(34) In one embodiment the beacon marker 280 and the beacon sensor 175 are synchronized wherein the robotic work tool 100 need not transmit a signal to the beacon marker 280, but merely measures the time of arrival from a known last transmission time. Such an embodiment may operate in a manner similar to measure the two-way response time.

(35) FIG. 4 shows a schematic view of a beacon marker 280. The beacon marker 280 is arranged to be fastened to an obstacle or a pole 260 (indicated with dashed lines). The beacon marker 280 may be fastened through various fastening means 281, such as, but not limited to, straps, belts, adhesive tape, Velcro to name a few examples.

(36) In one embodiment the beacon marker 280 is a radio frequency beacon emitting a radio frequency signal and the beacon sensor 175 is a radio frequency receiver (or transceiver).

(37) In one embodiment the beacon marker 280 is an ultrasonic beacon emitting an ultrasonic signal and the beacon sensor 175 is an ultrasonic receiver (or transceiver).

(38) This has one benefit in that an obstacle 260 is simple to mark by simply arranging a beacon marker on or adjacent to the obstacle 260. This is especially so for virtual obstacles 260A.

(39) This finds particular use in setting up temporary working areas, something of importance for robotic work tools 100 such as mine clearing robots. It is also useful in sensitive areas or areas having many holes and other hazards.

(40) This also has the benefit of that it is easy to mark obstacles that are above ground at its outer perimeter, such as sun chairs. Robotic work tools 100 may otherwise become stuck under such obstacles if collision detection is used.

(41) As has been stated above, collision detection increases the wear and tear of the robotic work tool 100, alternatively, the collision detection systems may be highly sensitive to dirt and debris and may become blocked rendering the collision detection inefficient.

(42) The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.