Robotic Work Tool Navigation Between Sheltered Dock and GNSS Handover

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Solution Overview

Problem

Robotic work tools, such as robotic lawnmowers, face challenges in reliably navigating to and accessing service stations, especially when these stations are sheltered from environmental factors, leading to increased wear and tear and difficulty in signal reception.

Innovation Solution

The robotic work tool utilizes deduced reckoning and magnetic field sensors to navigate a predefined distance from a service station where satellite navigation is unreliable, allowing it to exit or enter the station, and then switches to satellite navigation once reliable signals are regained.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the charging station is positioned in direct line of sight with the signal navigation device, then the robotic work tool can reliably receive navigation signals, but the charging station is exposed to environmental factors increasing wear and tear

Engineering Contradiction:
Improvesignal reception reliabilityVSAvoidenvironmental wear and tear
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary location - a handover point - where the robotic work tool temporarily exits the sheltered charging station area to acquire reliable satellite navigation signals. This handover point acts as a mediator between the need for signal reliability and the need to minimize environmental exposure. The tool alternates between operating from the sheltered charging station and positioning at the handover point for navigation signal acquisition.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the charging station is positioned under a roof or shelter, then wear and tear from environmental factors is reduced, but the robotic work tool cannot reliably receive navigation signals

Engineering Contradiction:
Improveenvironmental wear and tearVSAvoidsignal reception reliability
Core Design Contradiction:
Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent segments the operational area into two distinct zones: a sheltered charging station area protected from environmental factors, and an exposed handover point area providing reliable satellite signal reception. The robotic work tool intelligently transitions between these two segmented zones - remaining in the sheltered area for charging and maintenance, and moving to the handover point only when navigation signals are needed.

Inventive Principle:
Principle #1Segmentation

3Object-affected harmful factors

If the robotic work tool continuously operates from the charging station, then environmental exposure is minimized, but navigation signal reception becomes unreliable

Engineering Contradiction:
Improveenvironmental exposureVSAvoidnavigation signal reception
Core Design Contradiction:
Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent implements periodic action by having the robotic work tool regularly alternate between two operational modes: operating from the sheltered charging station and positioning at the exposed handover point to acquire navigation signals. This periodic transition ensures that the tool maintains reliable navigation capability while minimizing overall environmental exposure by remaining in the sheltered area for the majority of operational time.

Inventive Principle:
Principle #19Periodic action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables efficient and reliable navigation to and from service stations, even when sheltered, reducing wear and tear and improving operational reliability.

Implementation Method 1

a satellite navigation device (290) arranged to receive a satellite signal and output current location information

Methodology Applied
Scientific EffectSatellite signal reception: Electromagnetic Induction

Implementation Method 2

a magnetic field sensor (270) arranged to detect a magnetic field

Methodology Applied
Scientific EffectMagnetic field sensing: Magnetic Field

Data Source

PatentEP4068040B1Improved operation for a robotic work tool
Publication Date: 2025.09.24 HUSQVARNA AB
  • EP4068040B1 patent drawingFigure 1~2B
  • EP4068040B1 patent drawingFigure 3
  • EP4068040B1 patent drawingFigure 4

AI summary

A robotic work tool comprising a propulsion device, a satellite navigation device and a controller, wherein the controller is configured to: cause the robotic work tool to exit a service station a predefined distance by operating the propulsion device; determine that the satellite navigation device is receiving reliable signals and then navigate the robotic work tool based on the satellite navigation device.