METHOD FOR GENERATING A REPRESENTATION OF A WORKING AREA OF AN AUTONOMOUS LAWN MOWER AND AUTONOMOUS LAWN MOWER SYSTEM

• US 20180284806A1
• Filed: 03/12/2018
• Published: 10/04/2018
• Est. Priority Date: 03/28/2017
• Status: Active Grant

• Current Assignee: Honda Research Institute Europe GmbH (Honda Motor Company)
• Original Assignee: Honda Research Institute Europe GmbH (Honda Motor Company)
• Inventors: EINECKE, Nils, REBHAN, Sven, FRANZIUS, Mathias, DEIGMOLLER, Jorg, MURO, Keiji
• Granted Patent: US 10,824,163 B2
• Time in Patent Office: Days
• CPC Class Codes: A01D 2101/00 Lawn-mowers
• CPC Class Codes: A01D 34/008 for automated or remotely controlled operation
• CPC Class Codes: G05D 1/0088 characterized by the autonomous decision making process, e.g. artificial intelligence, predefined behaviours using knowledge based models G06N5/00
• CPC Class Codes: G05D 1/0219 ensuring the processing of the whole working surface
• CPC Class Codes: G05D 1/0221 involving a learning process
• CPC Class Codes: G05D 1/0257 using a radar radar systems designed for anti-collision purposes between land vehicles or between land vehicle and fixed obstacles G01S13/931
• CPC Class Codes: G05D 1/0265 using buried wires
• CPC Class Codes: G05D 1/0268 using internal positioning means
• CPC Class Codes: G05D 1/0274 using mapping information stored in a memory device navigation using map-matching G01C21/30

Abstract

A method and a system can generate a representation of a working area of an autonomous lawn mower. The system can include an autonomous lawn mower and a base station, and a boundary wire forming a closed loop which can be connected with the base station. The lawn mower and the base station interact such that the lawn mower can determine whether it is in its home position, a predetermined position that is taken when the mower returns to the base station. The lawn mower further includes a memory, for storing values from a movement sensor. A trajectory is generated based on the values, wherein a processor is configured to calculate an error between the position and orientation according to the trajectory and the home position. This total position error and total orientation error is then used to correct the position and corresponding orientations of the trajectory.

Claims

1. A method for generating a representation of a working area of an autonomous lawn mower, the method comprising the steps of:

positioning the autonomous lawn mower in a home position at a base station;

leaving the home position and determining that the home position has been left;

following a boundary wire until the base station is reached again;

recording measured values from movement sensors of the autonomous lawn mower while moving;

maneuvering the autonomous lawn mower into the home position and determining that the home position in base station is reached again on the basis of an interaction between the base station and the autonomous lawn mower;

generating a trajectory of the autonomous lawn mower on the basis of the recorded measured values, the trajectory being defined by positions and corresponding orientations of the autonomous lawn mower;

correcting the positions or corresponding orientations by a position error or an orientation error respectively;

storing the corrected trajectory as representation of the working area.

2. The method according to claim 1, wherein

leaving the home position is determined based on an interaction between the base station and the autonomous lawn mower.

3. The method according to claim 1, wherein

correction of orientations along the trajectory is performed before correction of the positions along the trajectory is performed on positions calculated on the basis of the corrected orientations.

4. The method according to claim 1, wherein

the trajectory is represented as a polygon.

5. The method according to claim 4, wherein

the polygon is reduced by a polygon simplification algorithm of the group consisting of Douglas-Peucker algorithm, Reuman-Witkam algorithm and Opheim algorithm.

6. The method according to claim 5, wherein

the degree of simplification depends on an estimated accuracy of the generated trajectory.

7. The method according to claim 1, wherein

the correction of the position is done dependent on a travelled distance from the start and the orientation correction is done dependent on an accumulated absolute rotation.

8. The method according to claim 1, wherein

a configuration of the autonomous lawn mower is done automatically based on the representation of the working area or a length of the boundary wire is set automatically.

9. The method according to claim 1, wherein

the measured values include data of a g-sensor and based on the g-sensor data and the trajectory a 3D-representation is created.

10. The method according to claim 1, wherein

the movement along the boundary wire and recordation of measured values is repeatedly performed and for each repetition a corresponding trajectory is generated and

the trajectories are then merged to generate the representation of the working area.

11. The method according to claim 10, wherein

the repetitions of the movement along the boundary wire include clock-wise and counter-clock-wise movements.

12. The method according to claim 10, wherein

the merging is done by selecting the trajectory having the smallest total position error or total orientation error when the base station is reached again.

13. The method according to claim 1, wherein

the orientation is calculated based on differential drive equations or based on a rotation sensor, e.g. an inertial measurement unit IMU.

14. The method according to claim 1, wherein

the representation of the working are is transferred to a remote terminal for further processing.

15. A system including an autonomous lawn mower with at least one movement sensor, a base station and a boundary wire forming a closed loop and being connected with the base station, the autonomous lawn mower and the base station being capable to interact with each other such that the autonomous lawn mower can determine whether it is in its home position, the autonomous lawn mower further comprising a memory, for storing measured values from its at least one movement sensor and a processor to generate a trajectory based on the measured values, wherein the processor is further configured to calculate an total error between the position and orientation according to the trajectory and the home position after reaching the home position again and to correct the position and corresponding orientations of the trajectory by a position error or an orientation error respectively.

16. The system according to claim 15, wherein

the at least one movement sensor is from the group of wheel rate counters, IMUs, compass, g-sensor and visual sensors.