US-12616088-B2 - Navigating a robotic mower along a guide wire

US12616088B2US 12616088 B2US12616088 B2US 12616088B2US-12616088-B2

Abstract

A method navigates a robotic mower ( 2 ) by means of a wire ( 8 ). The robotic mower ( 2 ) comprises at least two sensors ( 12; 14 ). The method comprises detecting (S 101 ), by means of the at least two sensors ( 12, 14 ), at least one signal from the wire ( 4 a; 8; 10 ), measuring (S 102 ) a polarity of the at least one signal of the wire ( 4 a; 8; 10 ) by means of each one of the at least two sensors ( 12, 14 ), determining (S 103 ) a direction based on the polarities measured by means of the at least two sensors ( 12, 14 ) and turning (S 104 ) the robotic mower ( 2 ) towards the determined direction.

Inventors

André Lundkvist

Assignees

Globe (jiangsu) Co., Ltd.

Dates

Publication Date: 20260505
Application Date: 20221205

Claims (19)

1 . A method for navigating a robotic mower ( 2 ) by a wire ( 4 a ; 8 ; 10 ), said robotic mower ( 2 ) comprising at least two sensors ( 12 ; 14 ), the method comprising: detecting (S 101 ), by at least two sensors ( 12 , 14 ), at least one signal from the wire ( 4 a ; 8 ; 10 ), the wire including a boundary wire loop ( 4 a ), a charging station loop ( 10 ) and one or several guide wires ( 8 ), the sensors ( 12 , 14 ) configured to sense a magnetic field generated in the boundary wire loop ( 4 a ), the charging station loop ( 10 ) and the one or several guide wires ( 8 ); measuring (S 102 ) a polarity of the at least one signal of the wire ( 4 a ; 8 ; 10 ) by each one of the at least two sensors ( 12 , 14 ), determining (S 103 ) a direction based on the polarities measured by the at least two sensors ( 12 , 14 ) and turning (S 104 ) the robotic mower ( 2 ) towards the determined direction; wherein, signals of the different wires ( 4 a , 8 , 10 ) are encoded differently, the sensed magnetic field is decoded in a control unit ( 22 ) to determine from which loop or wire the sensed magnetic field is received.
2 . The method according to claim 1 , wherein turning (S 104 ) the robotic mower ( 2 ) towards the determined direction comprises rotating the robotic mower ( 2 ) with respect to the wire ( 8 ) such that one of the at least two sensors ( 12 , 14 ) is located above the wire ( 8 ).
3 . The method according to claim 2 , wherein turning (S 104 ) the robotic mower ( 2 ) towards the determined direction comprises rotating the robotic mower ( 2 ) with respect to the wire ( 4 a ; 8 ; 10 ) until one of the at least two sensors ( 12 , 14 ) detects a change of the polarity of the at least one signal of the wire ( 4 a ; 8 ; 10 ).
4 . The method according to any of claim 3 , wherein turning (S 104 ) the robotic mower ( 2 ) towards the determined direction comprises rotating the robotic mower ( 2 ) with respect to the wire ( 4 a ; 8 ; 10 ) until the at least two sensors ( 12 , 14 ) detect the at least one signal of the wire ( 4 a ; 8 ; 10 ) with opposite polarity.
5 . The method according to any of claim 4 , further comprising crossing the wire ( 8 ; 10 ) by a predetermined crossing distance before measuring the polarity of the at least one signal of the wire ( 8 ; 10 ) by each one of the at least two sensors ( 12 , 14 ).
6 . The method according to any of claim 5 , wherein the wire ( 8 ) is a guide wire ( 8 ) arranged within an area (A) delimited by a boundary wire ( 4 ).
7 . The method according to any of claim 5 , wherein the wire ( 4 a ; 10 ) is a wire loop arranged at a charging station plate ( 24 ) of a charging station ( 11 ).
8 . The method according to claim 1 , wherein a boundary wire ( 4 ) configured to delimit a working area within which the robotic mower is allowed to move and configured to make the boundary wire loop ( 4 a ), the boundary wire loop ( 4 a ) is a circle loop in the working area and in a charging station ( 11 ) and configured to guide the robotic mower ( 2 ) into charging contact with the charging station ( 11 ), the guide wire ( 8 ) is a single wire that the robotic mower ( 2 ) follows when returning to the charging station ( 11 ) and/or to move along a way that is otherwise difficult to find, and configured to be guide the robotic mower ( 2 ) when the robotic mower ( 2 ) returns to the charging station and/or to moves along a way that is otherwise difficult to find, the charging station loop ( 10 ) is a circle loop and provided by the charging station ( 11 ) and in charging station ( 11 ), the boundary wire loop ( 4 a ) is narrower than and crosses the charging station loop ( 10 ) to define a predetermined position in the charging station.
9 . A method for guiding a robotic mower ( 2 ) along a wire ( 4 a , 8 , 10 ) to a predetermined position, said robotic mower ( 2 ) comprising at least one sensor ( 12 ; 14 ), the method comprising: navigating (S 10 ) the robotic mower ( 2 ), by the at least one sensor ( 12 , 14 ) detecting at least one signal of the wire ( 4 a , 8 , 10 ), such that the at least one sensor ( 12 , 14 ) is located above the wire ( 4 a , 8 , 10 ) and controlling (S 11 ) the robotic mower ( 2 ) to straddle along the wire ( 4 a , 8 , 10 ) towards the predetermined position using a polarity of at least one signal of the wire ( 4 a , 8 , 10 ) measured by the at least one sensor ( 12 , 14 ); wherein, the wire ( 4 a , 8 , 10 ) includes a boundary wire loop ( 4 a ), a charging station loop ( 10 ) and one or several guide wires ( 8 ), the sensors ( 12 , 14 ) are configured to sense a magnetic field generated in the boundary wire loop ( 4 a ), the charging station loop ( 10 ) and the one or several guide wires ( 8 ); the charging station loop ( 10 ) is a first wire loop ( 10 ), the boundary wire loop ( 4 a ) is a second wire loop ( 4 a ), both the first wire loop ( 10 ) and the second wire loop ( 4 a ) are in a charging station ( 11 ) and cross with each other to define the predetermined position in the charging station ( 11 ); controlling (S 11 ) the robotic mower ( 2 ) to straddle along the wire ( 4 a , 8 , 10 ) towards the predetermined position using a polarity of at least one signal of the wire ( 4 a , 8 , 10 ) measured by the at least one sensor ( 12 , 14 ) further comprising: detecting (S 12 ), by the at least one sensor ( 12 , 14 ), that the robotic mower ( 2 ) has entered the first wire loop ( 10 ) by measuring a polarity of at least one signal of the first wire loop ( 10 ), detecting a change of the polarity of the at least one signal of the first wire loop ( 10 ), and in response to detecting that the robotic mower ( 2 ) has entered the first wire loop ( 10 ), detecting (S 14 ), by the at least one sensor ( 12 , 14 ), that the robotic mower ( 2 ) has entered the second wire loop ( 4 a ) by measuring a polarity of at least one signal of the second wire loop ( 4 a ), so that the robotic mower returns to the predetermined position in the charging station; signals of the different wires ( 4 a , 8 , 10 ) are encoded differently, and the sensed magnetic field is decoded in a control unit ( 22 ) to determine from which loop or wire the sensed magnetic field is received.
10 . The method according to claim 8 , further comprising, in response to detecting that the robotic mower ( 2 ) has entered the wire loop ( 10 ), controlling (S 13 ) the robotic mower ( 2 ) to drive straight forward for a predetermined distance.
11 . The method according to claim 9 , wherein the robotic mower ( 2 ) comprises at least two sensors ( 12 , 14 ), the method further comprising, in response to detecting that the robotic mower ( 2 ) has entered the second wire loop ( 4 a ), turning (S 15 ) the robotic mower ( 2 ) such that the at least two sensors ( 12 , 14 ) are both inside or both outside of the second wire loop ( 4 a ), and, in response thereto, controlling the robotic mower ( 2 ) to drive straight forward.
12 . The method according to claim 11 , wherein the second wire loop ( 4 a ) is a portion of, or electrically connected with, a boundary wire ( 4 ) delimiting an area (A).
13 . The method according to claim 12 , wherein the wire ( 8 ) is a guide wire ( 8 ) arranged within the area (A) delimited by the boundary wire ( 4 ).
14 . A robotic mower ( 2 ) comprising at least two sensors ( 12 ; 14 , and adapted to: detect, by at least two sensors ( 12 , 14 ), at least one signal from a wire ( 4 a ; 8 ; 10 ), measure a polarity of the at least one signal of the wire by each one of the at least two sensors ( 12 , 14 ), determine a direction based on the polarities measured by the at least two sensors ( 12 , 14 ) and turn towards the determined direction; wherein, the wire ( 4 a , 8 , 10 ) includes a boundary wire loop ( 4 a ), a charging station loop ( 10 ) and one or several guide wires ( 8 ), the sensors ( 12 , 14 ) are configured to sense a magnetic field generated in the boundary wire loop ( 4 a ), the charging station loop ( 10 ) and the one or several guide wires ( 8 ); wherein signals of the different wires ( 4 a , 8 , 10 ) are encoded differently, and the sensed magnetic field is decoded in a control unit ( 22 ) to determine from which loop or wire the sensed magnetic field is received.
15 . The robotic mower ( 2 ) according to claim 14 , adapted to perform a method for navigating a robotic mower ( 2 ) by a wire ( 4 a ; 8 ; 10 ), said robotic mower ( 2 ) comprising at least two sensors ( 12 ; 14 ), the method comprising: detecting (S 101 ), by at least two sensors ( 12 , 14 ), at least one signal from the wire ( 4 a ; 8 ; 10 ), measuring (S 102 ) a polarity of the at least one signal of the wire ( 4 a ; 8 ; 10 ) by each one of the at least two sensors ( 12 , 14 ), determining (S 103 ) a direction based on the polarities measured by the at least two sensors ( 12 , 14 ) and turning (S 104 ) the robotic mower ( 2 ) towards the determined direction.
16 . A system comprising a wire ( 4 a , 8 , 10 ) and the robotic mower ( 2 ) according to claim 14 .
17 . A robotic mower ( 2 ) comprising at least one sensor ( 12 ; 14 , and adapted to: navigate, by the at least one sensor ( 12 , 14 ) detecting at least one signal of a wire ( 4 a , 8 , 10 ), such that the at least one sensor ( 12 , 14 ) is located above the wire ( 4 a , 8 , 10 ) and straddle along the wire ( 4 a , 8 , 10 ) towards a predetermined position using a polarity of at least one signal of the wire ( 4 a , 8 , 10 ) measured by the at least one sensor ( 12 , 14 ); wherein, the wire ( 4 a , 8 , 10 ) includes a boundary wire loop ( 4 a ), a charging station loop ( 10 ) and one or several guide wires ( 8 ), the sensors ( 12 , 14 ) are configured to sense a magnetic field generated in the boundary wire loop ( 4 a ), the charging station loop ( 10 ) and the one or several guide wires ( 8 ); the charging station loop ( 10 ) is a first wire loop ( 10 ), the boundary wire loop ( 4 a ) is a second wire loop ( 4 a ), both the first wire loop ( 10 ) and the second wire loop ( 4 a ) are in a charging station ( 11 ) and cross with each other to define the predetermined position in the charging station ( 11 ); controlling (S 11 ) the robotic mower ( 2 ) to straddle along the wire ( 4 a , 8 , 10 ) towards the predetermined position using a polarity of at least one signal of the wire ( 4 a , 8 , 10 ) measured by the at least one sensor ( 12 , 14 ) further comprising: detecting (S 12 ), by the at least one sensor ( 12 , 14 ), that the robotic mower ( 2 ) has entered the first wire loop ( 10 ) by measuring a polarity of at least one signal of the first wire loop ( 10 ), detecting a change of the polarity of the at least one signal of the first wire loop ( 10 ), and in response to detecting that the robotic mower ( 2 ) has entered the first wire loop ( 10 ), detecting (S 14 ), by the at least one sensor ( 12 , 14 ), that the robotic mower ( 2 ) has entered the second wire loop ( 4 a ) by measuring a polarity of at least one signal of the second wire loop ( 4 a ); signals of the different wires ( 4 a , 8 , 10 ) are encoded differently, and the sensed magnetic field is decoded in a control unit ( 22 ) to determine from which loop or wire the sensed magnetic field is received.
18 . The robotic mower ( 2 ) according to claim 17 , adapted to perform a method for navigating a robotic mower ( 2 ) by a wire ( 4 a ; 8 ; 10 ), said robotic mower ( 2 ) comprising at least two sensors ( 12 ; 14 ), the method comprising: detecting (S 101 ), by at least two sensors ( 12 , 14 ), at least one signal from the wire ( 4 a ; 8 ; 10 ), measuring (S 102 ) a polarity of the at least one signal of the wire ( 4 a ; 8 ; 10 ) by each one of the at least two sensors ( 12 , 14 ), determining (S 103 ) a direction based on the polarities measured by the at least two sensors ( 12 , 14 ) and turning (S 104 ) the robotic mower ( 2 ) towards the determined direction.
19 . A system comprising a wire ( 4 a , 8 , 10 ) and the robotic mower ( 2 ) according to claim 17 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a continuation application of PCT application filing PCT/CN2020/106138 filed on Jul. 31, 2020. All the above are hereby incorporated by reference, including any appendices or attachments thereof, for all purposes. TECHNICAL FIELD The present invention generally relates to a method for navigating a robotic mower along a signal wire, e.g., back to a charging station when a battery of the robotic mower needs to be recharged. BACKGROUND ART Robotic mowers, also called self-propelled lawnmowers, are generally known. These robotic mowers are provided with a rechargeable battery. When the remaining power in the battery is below a certain level the robotic mower is programmed to return to the charging station to recharge the battery. There are different possibilities for returning the robotic mower to the charging station. One possible method is that the robotic mower, upon a command to return to the charging station, continues its movement until a boundary wire is detected nearby and then follows the boundary wire to the charging station that is provided somewhere along the boundary wire. Another option when returning to the charging station is to use a guide wire, which the robotic mower follows back to the charging station. The use of a guide wire often enables a shorter and faster way back to the charging station compared to following the boundary wire. The guide wire can also be beneficial to use when the robotic mower needs to navigate through a narrow passage. A common approach is to use a signal level of a signal source, such as the guide wire, boundary wire or a signal emitted at the position of the charging station. However, the signal level usually depends on the length of the corresponding wire, and this may be different in different sites, such as smaller or larger gardens. Further, the signal level can be different depending on whether a user decides to route the wire on the surface of the ground or bury it under the surface, and on weather conditions. This may increase the time the robotic mower needs in order to find the charging station. As a result, the mower usually needs to reserve a substantial portion of the battery capacity for the search and navigation towards the charging station. SUMMARY An object of the present invention is to provide a reliable and efficient solution for navigating a robotic mower by means of a wire. According to an aspect of the present invention this object is achieved by a method for navigating a robotic mower by means of a wire, e.g., for returning the robotic mower to a charging station when the robotic mower needs to be recharged. Therein, the robotic mower comprises at least two sensors. The method comprises detecting, by means of the at least one sensor, at least one signal from the wire. The method further comprises detecting, by means of the at least two sensors, at least one signal from the wire, measuring a polarity of the at least one signal of the wire by means of each one of the at least two sensors, determining a direction based on the polarities measured by means each of the at least two sensors and turning the robotic mower towards the determined direction. This is based on the idea to use a polarity of a signal of the wire instead of the strength of the signal. The wire forms a part of an electric circuit. A current through the wire creates a magnetic field around the wire. The sensors are adapted to measure this magnetic field. For example, the sensors are magnetic field sensors. Accordingly, on one side of the wire, the sensors detect an opposite polarity (e.g., upwards or downwards) compared to the other side of the wire (e.g., downwards or upwards, respectively). By measuring the polarity and knowing the direction of the current flow, the mower can thus reliably detect on which side of the wire the measuring sensor is located. The at least two sensors are spaced apart from one another. When the two sensors measure the same polarities, they are both on the same side of the wire. There are four different possibilities (++, −−, +− and −+) of combinations of polarities. The charging station is located on a known section of the wire, so the mower may immediately deduce from the two measured polarities whether it is located on the wire in the direction of the charging station or not. The guide wire leads to the charging station, and a predetermined combination of polarities measured by the at least two sensors (e.g., +−) indicates the correct direction. In an exemplary embodiment, turning the robotic mower towards the determined direction comprises rotating the robotic mower with respect to the wire such that one of the at least two sensors is located above (in particular, straight above) the wire. This allows to very efficiently and reliably follow the wire. In an exemplary embodiment, turning the robotic mower towards the determined direction comprises rotating the robotic mower with re