Robotic Lawnmower Boundary Calibration for Accurate Virtual Mapping

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Solution Overview

Problem

Existing robotic lawnmower systems face precision issues in defining work area boundaries due to positional drift between the mobile device's perceived and actual positions in the global coordinate system, leading to incomplete cutting or unnecessary processing.

Innovation Solution

A method involving calibration of the mobile device's position using the robotic lawnmower's precise positioning system, defining a capability zone for accurate boundary segment recording, and providing visual and positional guidance on the user interface to enhance precision.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If mobile device positioning relies on GPS, accelerometers and visual odometry, then the system can operate without boundary cables, but positional drift occurs leading to differences between sensed and actual positions

Engineering Contradiction:
Improveinstallation simplicityVSAvoidposition accuracy
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The patent introduces visual markers as an intermediary element between the mobile device and the environment. These markers provide reference points that enable the mobile device to accurately determine its position and orientation through image capture and marker recognition, thereby eliminating positional drift without requiring boundary cables or complex RTK infrastructure

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The system creates a virtual representation of the physical environment by capturing images and detecting marker positions. This virtual model is then used to define work area boundaries digitally, replacing the need for physical boundary cables while maintaining precise position information through the copied spatial relationships

Inventive Principle:
Principle #26Copying

2Ease of manufacture

If virtual markers are placed based on drifted positions, then the boundary definition process is simple, but the work area boundaries become inaccurate causing grass to be left uncut or unnecessary processing

Engineering Contradiction:
Improveboundary definition simplicityVSAvoidboundary accuracy
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

Visual markers serve as intermediary reference objects that mediate between the mobile device's sensing system and the physical environment. By detecting these markers through image capture, the system obtains accurate position and orientation data without drift, enabling precise boundary definition while maintaining ease of operation through intuitive marker-based interaction

Inventive Principle:
Principle #24Intermediary (Mediator)

Data Source

PatentEP4557035B1Robotic lawnmower system
Publication Date: 2026.04.15 HUSQVARNA AB
  • EP4557035B1 patent drawingFigure 1~2
  • EP4557035B1 patent drawingFigure 3~4
  • EP4557035B1 patent drawingFigure 5

AI summary

The present disclosure relates to a method for defining a boundary (31, 39) of a work area (30) in a robotic lawnmower system, having a robotic lawnmower (1), configured to process the work area (30) and to determine its position (xr, yr, zr) in the work area, and a separate, mobile device (11) configured to determine its position (xm, ym, zm) in the work area (30) and having a camera (13) configured to capture images of the work area (30) and a display (15) which provides a user interface, enabling a user to define boundary segments (33, 37) of the work area boundary (31, 39) therein as a set of positions which are transferred to the robotic lawnmower (1). By calibrating in a first position (51) of the robotic lawnmower, and based on the position (xr, yr, zr) determined by the robotic lawnmower (1) and the position of the robotic lawnmower in an image captured by said camera (13), a calibrated position (xm+, ym+, zm+) of the mobile device (11), is determined. Based on this calibration, a first capability zone (35A), within which the mobile device (1) can sense positions with minimum level of estimated alignment with respect to positions sensed by the robotic lawnmower (1) is determined and is presented as an indication in the user interface of the mobile device (11).