A Robotic Work Tool Configured for Improved Turning in a Slope, a Robotic Work Tool System, and a Method for Use in the Robot Work Tool

• US 20150366130A1
• Filed: 02/20/2013
• Published: 12/24/2015
• Est. Priority Date: 02/20/2013
• Status: Active Grant

• Current Assignee: Husqvarna AB (HUSQVARNA)
• Original Assignee: Husqvarna AB (HUSQVARNA)
• Inventors: Bergstrm, Jonas, Markusson, Olle, Klackensj, Fredrik
• Granted Patent: US 10,149,430 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A01D 34/008 for automated or remotely controlled operation
• CPC Class Codes: A01D 75/28 Control mechanisms for harvesters or mowers when moving on slopes; Devices preventing lateral pull
• CPC Class Codes: B60L 1/003 to auxiliary motors, e.g. for pumps, compressors
• CPC Class Codes: B60L 15/20 for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• CPC Class Codes: B60L 2200/40 Working vehicles
• CPC Class Codes: B60L 2240/36 Temperature of vehicle components or parts
• CPC Class Codes: B60L 2240/421 Speed
• CPC Class Codes: B60L 2260/32 Auto pilot mode
• CPC Class Codes: B60L 3/0061 relating to electrical machines
• CPC Class Codes: B60L 50/52 characterised by DC-motors
• CPC Class Codes: B60L 50/66 Arrangements of batteries
• CPC Class Codes: B60L 53/16 Connectors, e.g. plugs or sockets, specially adapted for charging electric vehicles
• CPC Class Codes: B60L 8/003 Converting light into electric energy, e.g. by using photo-voltaic systems
• CPC Class Codes: B62D 11/001 control systems B62D11/183 takes precedence
• CPC Class Codes: G05D 1/0212 with means for defining a desired trajectory involving a plurality of land vehicles G05D1/0287
• CPC Class Codes: G05D 1/0259 using magnetic or electromagnetic means
• CPC Class Codes: G05D 1/0265 using buried wires
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility
• CPC Class Codes: Y02T 90/14 : Plug-in electric vehicles
• CPC Class Codes: Y10S 901/01 : Mobile robot

Abstract

Robotic work tool (100) configured for improved turning in a slope (S), said robotic work tool comprising a slope detector (190), at least one magnetic field sensor (170), a controller (110), and at least two driving wheels (130″), the robotic work tool (100) being configured to detect a boundary wire (250) and in response thereto determine if the robotic work tool (100) is in a slope (S), and if so, perform a turn by rotating each wheel (130″) at a different speed thereby reducing a risk of the robotic work tool (100) getting stuck.

Claims

1. A robotic work tool configured for improved turning in a slope, said robotic work tool comprising:

a slope detector,

at least one magnetic field sensor,

a controller, and

at least two driving wheels, the robotic work tool being configured to

detect a boundary wire,

determine if the robotic work tool is in a slope, and

if so, perform a turn by rotating each wheel at a different speed thereby reducing a risk of the robotic work tool getting stuck.

2. The robotic work tool according to claim 1, wherein the robotic work tool is further configured for determining that the robotic work tool is in the slope by using data from said slope detector, being at least one inclinometer, indicating that the robotic work tool is in the slope by indicating an inclination exceeding a certain threshold value.

3. The robotic work tool according to claim 1, wherein the robotic work tool is further configured for avoiding wheel slip during a turn in the slope by:

determining a wheel slip or risk of wheel slip by using data from said slope detector, being at least one accelerometer;

comparing measured acceleration data with data expected for a certain shift of rotational speed of one of the driving wheels; and

reducing the rotational speed of the driving wheel indicating a wheel slip or risk of wheel slip which is indicated by a mismatch between the measured acceleration data and the expected acceleration data.

4. The robotic work tool according to claim 1, wherein the robotic work tool is further configured to reverse the rotational direction of one driving wheel and reduce the rotational speed of the driving wheel having a least expected grip.

5. The robotic work tool according to claim 1, wherein the robotic work tool is further configured to

detect that the robotic work tool is approaching the boundary wire substantially head on, and in response thereto,

reduce rotational speed of either of the driving wheels such that the robotic work tool performs a U-turn.

6. The robotic work tool according to claim 5, wherein the robotic work tool is configured to detect that the robotic work tool is approaching the boundary wire substantially head on by comparing sensor signals from the at least one magnetic field sensor, whereof at least one of the at least one magnetic field sensors is a front magnetic field sensor and if the sensor signals are substantially equal for the front magnetic field sensor determine that the robotic work tool is approaching the boundary wire substantially head on.

7. The robotic work tool according to claim 1, wherein the robotic work tool is further configured to

detect that the robotic work tool is approaching the boundary wire at an angle, and in response thereto,

reduce rotational speed of either of the driving wheels such that the robotic work tool performs an L-turn.

8. The robotic work tool according to claim 7, wherein the robotic work tool is configured to detect that the robotic work tool is approaching the boundary wire at an angle by comparing sensor signals from the at least one magnetic field sensor, wherein at least one of the at least one magnetic field sensors is a front magnetic field sensor and if the sensor signals for the at least one front magnetic field sensor differs by more than a threshold value, determine that the robotic work tool is approaching the boundary wire at an angle.

9. The robotic work tool according to claim 3, wherein the at least one accelerometer is two accelerometers, situated such that each of the accelerometers can measure the acceleration imparted by a change of rotational speed or direction of a corresponding wheel.

10. The robotic work tool according to claim 2, wherein the at least one inclinometer measures at least the sideways inclination of the robotic work tool.

11. The robotic work tool according to claim 10, wherein the sideways inclination of the robotic work tool is used to determine which driving wheel has a least load and consequently least grip.

12. The robotic work tool according to claim 11, wherein a reduction of rotational speed of the wheel having the least load is proportional to a measured inclination.

13. The robotic work tool according to claim 12, wherein the rotational speed of the wheel having the least load is zero when the sideways inclination has reached a predetermined threshold value.

14. The robotic work tool according to claim 13, wherein the predetermined threshold value is determined by a maximum slope of the ground to be serviced.

15. The robotic work tool according to claim 13, wherein the predetermined threshold value is 35 degrees.

16. The robotic work tool according to claim 1, wherein the robotic work tool is a robotic lawnmower.

17. A robotic work tool system comprising a robotic work tool and a boundary wire demarcating a work area, said robotic work tool comprising:

a slope detector,

at least one magnetic field sensor,

a controller, and

at least two driving wheels, the robotic work tool being configured to

detect the boundary wire,

determine if the robotic work tool is on a slope, and

if so, perform a turn by rotating each wheel at a different speed thereby reducing a risk of the robotic work tool getting stuck.

18. A method for use in a robotic work tool for improved turning in a slope, said robotic work tool comprising a slope detector, at least one magnetic field sensor, a controller, and at least two driving wheels, the method comprising:

detecting a boundary wire,

determining if the robotic work tool is in a slope, and if so, performing a turn by rotating each wheel at a different speed thereby reducing a risk of the robotic work tool getting stuck.

19. (canceled)

20. (canceled)