Robotic Lawnmower Section Navigation via Virtual Boundaries

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Solution Overview

Problem

Robotic work tools, such as lawnmowers, face difficulties accessing and exiting areas partially blocked by objects due to their irregular navigation patterns, leading to uneven coverage of work areas, and existing solutions like guide cables are cumbersome and ineffective in ensuring adequate time spent in these areas.

Innovation Solution

A robotic work tool system that divides the work area into virtual sections, using a controller to adjust its trajectory upon encountering section boundaries, ensuring adequate time spent in each section through a combination of boundary wires, GNSS navigation, and deduced reckoning, allowing for even mowing and improved access to difficult areas.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the robotic work tool uses irregular random working behavior to avoid tracks, then the risk of track formation is reduced, but the ability to access partially blocked areas deteriorates

Engineering Contradiction:
Improverisk of track formationVSAvoidaccess to partially blocked areas
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The work area is divided into multiple sections, with the controller programmed to navigate to specific sections that have not been adequately serviced. This segmentation allows the robot to systematically target difficult-to-reach areas while maintaining irregular overall patterns to avoid track formation.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The controller dynamically adjusts the working pattern by identifying and prioritizing sections with insufficient service coverage. The navigation behavior changes from purely random to targeted when specific sections need attention, combining the benefits of both irregular patterns and focused access.

Inventive Principle:
Principle #15Dynamics

2Ease of operation

If guide cables are installed to help the robotic lawnmower find its way into/out of blocked areas, then navigation to these areas is improved, but the complexity of installation and the risk of premature exit increase

Engineering Contradiction:
Improvenavigation to blocked areasVSAvoidinstallation complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The mechanical guide cable system is replaced with an electronic navigation system. The controller uses virtual section boundaries and coordinate-based navigation to guide the robot into and out of blocked areas, eliminating the need for physical cables and their complex installation.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Instead of using physical guide cables, the system creates a virtual copy of the area layout with defined sections and boundaries stored in the controller. This virtual mapping allows the robot to navigate complex areas without physical guides.

Inventive Principle:
Principle #26Copying

3Reliability

If the robotic work tool exits an area when encountering a guide cable, then it avoids getting stuck, but it may exit too early and not spend enough time servicing the area

Engineering Contradiction:
Improveavoidance of getting stuckVSAvoidtime spent servicing area
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The controller continuously monitors the service status of each section and uses this feedback to determine when to enter and exit areas. By tracking which sections have been adequately serviced, the controller ensures the robot spends sufficient time in difficult-to-reach areas while still being able to exit when necessary.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The controller pre-defines section boundaries and service requirements before operation begins. This preliminary setup allows the robot to know in advance how much time and effort should be devoted to each section, preventing both premature exit and excessive dwelling.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP3230815B1Improved navigation for a robotic working tool
Publication Date: 2020.05.06 HUSQVARNA AB
  • EP3230815B1 patent drawingFigure 1~2
  • EP3230815B1 patent drawingFigure 3~4
  • EP3230815B1 patent drawingFigure 5

AI summary

A robotic work tool system (200) comprising a charging station (210) and a robotic work tool (100) configured to work within a work area (205) being divided into at least one section (405), the robotic work tool comprising a controller (110) for controlling the operation of the robotic work tool (100) to cause the robotic work tool to move along a trajectory, the robotic work tool (100) being configured to determine that a section boundary is encountered, and if so change the trajectory of the robotic work tool (100) to cause the robotic work tool to remain in the section.