Navigation for a robotic working tool

{
  "publication_number": "US10646997B2",
  "country": "US",
  "kind": "B2",
  "title": "Navigation for a robotic working tool",
  "abstract": "A robotic work tool system, comprising a robotic work tool, said robotic work tool comprising a controller being configured to cause said robotic work tool to operate in a first operating mode, which first operating mode is based on a current position, said current position being determined based on signals received from a position determining device, such as Global Navigation Satellite System device; determine that said received signals are not reliable, and in response thereto cause said robotic work tool to operate according to second operating mode, which second operating mode is not based on a current position being determined based on said received signals.",
  "claims": [
    "1. A robotic lawnmower system comprising a robotic lawnmower, said robotic lawnmower comprising a controller being configured to: cause the robotic lawnmower to navigate a work area to execute a mowing pattern on the work area in a first operating mode, wherein the first operating mode is based on a current position, said current position being determined based on received signals that are received from a Global Navigation Satellite System device; determine that said received signals are not reliable, and in response thereto cause said robotic lawnmower to navigate the work area according to a second operating mode, wherein the second operating mode is not based on a current position being determined based on said received signals; determine that said received signals are reliable again, and in response thereto switch to said first operating mode; and determine if a counter is lower than a threshold value when said received signals are reliable again and if so, cause said robotic lawnmower to execute a turn to re-enter a section where said signals are not reliably received and increase said counter.",
    "2. The robotic lawnmower system according to claim 1, wherein the controller is further configured to determine an expected position and cause said robotic lawnmower to steer towards said expected position.",
    "3. The robotic lawnmower system according to claim 1, wherein the controller is further configured to determine an expected movement line and cause said robotic lawnmower to steer towards said expected movement line.",
    "4. The robotic lawnmower system according to claim 1, wherein the second operating mode is a random mowing pattern.",
    "5. The robotic lawnmower system according to claim 1, wherein the second operating mode is an expanding circle mowing pattern.",
    "6. The robotic lawnmower system according to claim 1, wherein the second operating mode is based on a deduced reckoning mowing pattern.",
    "7. The robotic lawnmower system according to claim 1, wherein the controller is configured to determine that said robotic lawnmower encounters a boundary wire and in response thereto increase said counter.",
    "8. The robotic lawnmower system according to claim 1, wherein the controller is configured to determine that said robotic lawnmower executes a turn and in response thereto increase said counter.",
    "9. The robotic lawnmower system according to claim 1, wherein the controller is further configured to start a timer as said signals are determined not to be reliable; and determine if the timer is lower than a threshold value when said received signals are reliable again and if so, cause said robotic lawnmower to execute a turn to re-enter a section where said signals are not reliably received.",
    "10. The robotic lawnmower system according to claim 1, wherein the controller is configured to store a map and to adapt operation of the robotic lawnmower based on a current position in the work area based on the map.",
    "11. The robotic lawnmower system according to claim 10, wherein the controller is configured to adapt the operation of the robotic lawnmower by initiating said second operating mode when the controller determines that the robotic lawnmower is close to or about to enter a blackout area.",
    "12. The robotic lawnmower system according to claim 10, wherein the controller is configured to update the map each time the robotic lawnmower leaves or enters a blackout area.",
    "13. The robotic lawnmower system according to claim 1, wherein causing the robotic lawnmower to navigate the work area comprises causing the robotic lawnmower to autonomously execute the mowing pattern.",
    "14. A robotic lawnmower system comprising a robotic lawnmower, said robotic lawnmower comprising a controller being configured to: cause the robotic lawnmower to navigate a work area to execute a mowing pattern on the work area in a first operating mode, wherein the first operating mode is based on a current position, said current position being determined based on received signals that are received from a Global Navigation Satellite System device; determine that said received signals are not reliable, and in response thereto cause said robotic lawnmower to navigate the work area according to a second operating mode, wherein the second operating mode is not based on a current position being determined based on said received signals; measure a distance traveled as said signals are determined not to be reliable; determine that said received signals are reliable again, and in response thereto switch to said first operating mode; and determine if the distance traveled is lower than a threshold value when said received signals are reliable again and if so, cause said robotic lawnmower to execute a turn to re-enter a section where said signals are not reliably received.",
    "15. A method for use in a robotic lawnmower system comprising a robotic lawnmower, said method comprising: causing said robotic lawnmower to navigate a work area to execute a mowing pattern on the work area in a first operating mode, which first operating mode is based on a current position, said current position being determined based on signals received from a Global Navigation Satellite System device; determining that said received signals are not reliable, and in response thereto causing said robotic lawnmower to navigate the work area according to second operating mode, which second operating mode is not based on a current position being determined based on said received signal; storing a map and adapting operation of the robotic lawnmower based on a current position in the work area based on the map; and updating the map each time the robotic lawnmower leaves or enters a blackout area.",
    "16. The method of claim 15, wherein causing the robotic lawnmower to navigate the work area comprises causing the robotic lawnmower to autonomously execute the mowing pattern."
  ],
  "description_excerpt": "This application relates to a method and a robotic work tool system for an improved navigation for a robotic work tool.\n\nContemporary robotic work tools are becoming more and more advanced and are able to perform more and more advanced tasks such as executing advanced operation patterns.\n\nIn the example of lawnmower robots the advanced working pattern may be a complicated mowing pattern based on the layout of a garden including bushes, garden islands and other structures. To successfully navigate such complicated areas some contemporary robotic work tools employ satellite navigation.\n\nA satellite navigation or sat nav system is a system of satellites that provide autonomous geo-spatial positioning with global coverage. It allows small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few metres, or even centimetres, using signals transmitted along a line-of-sight by radio from satellites. Receivers calculate the precise time as well as position and carrier phase, which can be used as a reference for scientific experiments. A satellite navigation system with global coverage may be termed a global navigation satellite system or GNSS (Global Navigation Satellite System).\n\nThe use of GNSS systems requires good reception of satellite signals to work reliably. The satellite signals may sometimes be blocked by buildings, roofs, awnings, foliage or trees. To improve the accuracy of GNSS systems a reference receiver, or beacon, within a short distance from the target receiver can be used. This is called differential GNSS. There are several",
  "cpc": [
    "B25J 9/1643",
    "A01D 34/008",
    "B25J 9/1664",
    "G05D 1/0219",
    "G05D 1/0265",
    "G05D 1/0274",
    "G05D 1/0278",
    "G05D 1/245",
    "G05D 1/247",
    "G05D 1/248",
    "G05D 1/6484",
    "G05D 2105/15",
    "G05D 2107/23",
    "G05D 2109/10",
    "G05D 2111/36",
    "G05D 2111/52",
    "G05D 2111/54",
    "G05D 2201/0208",
    "Y10S 901/01",
    "Y10S 901/09"
  ],
  "ipc": [
    "A01D 34/00",
    "B25J 9/16",
    "B60W 60/00",
    "G05D 1/02"
  ],
  "assignees": [
    "Husqvarna AB"
  ],
  "inventors": [
    "Peter Reigo",
    "Patrik Jägenstedt",
    "Magnus Öhrlund"
  ],
  "filing_date": "2017-01-17",
  "publication_date": "2020-05-12",
  "grant_date": "2020-05-12",
  "priority_date": "2013-11-12",
  "application_number": "US-201715407576-A",
  "family_id": "53057726",
  "cited_by_count": 12,
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}