Robotic Mower Blade Load Sensing for Adaptive Cutting Schedules

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Solution Overview

Problem

Existing robotic work tools, such as lawnmowers, require expensive equipment and complicated algorithms for grass growth modeling, making scheduling inefficient and costly.

Innovation Solution

A robotic work tool system that determines grass height by measuring the cutting load on the blade and adjusts the work schedule based on this load, eliminating the need for complex grass growth models.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a complicated grass growth model is used to determine scheduling, then the scheduling accuracy is improved, but the device complexity and cost increase

Engineering Contradiction:
Improvescheduling accuracyVSAvoiddevice complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential information needed for scheduling (cutting load indicating grass height) from the complex grass growth model approach. Instead of implementing a full grass growth model with multiple sensors and algorithms, the invention isolates the critical measurement (blade load) that directly indicates grass height, eliminating unnecessary complexity while maintaining scheduling accuracy.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces expensive, complex grass growth modeling equipment with a simple, inexpensive blade load sensor that is already part of the cutting mechanism. The blade load measurement is a byproduct of normal operation, requiring no additional expensive hardware, thus reducing device complexity and cost while providing sufficient scheduling information.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

2Measurement precision

If a complicated grass growth model with expensive equipment is implemented, then the grass height prediction is improved, but the manufacturing cost increases

Engineering Contradiction:
Improvegrass height predictionVSAvoidmanufacturing cost
Core Design Contradiction:
Measurement precisionVSEase of manufacture

Solution Approach 1:

The cutting blade and motor system serves dual purposes: it performs the primary function of cutting grass and simultaneously measures the cutting load to determine grass height. This self-service approach eliminates the need for separate expensive sensors and processing systems, reducing manufacturing cost while maintaining grass height prediction capability.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The motor and blade assembly is designed to perform multiple functions: mechanical cutting and load measurement. By making the existing cutting components multi-functional, the patent eliminates the need for additional expensive equipment dedicated solely to grass height measurement, thereby reducing manufacturing costs while maintaining prediction accuracy.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Productivity

If the work schedule is adjusted based on cutting load, then the productivity is improved, but the complexity of control increases

Engineering Contradiction:
ImproveproductivityVSAvoidcomplexity of control
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent implements a simple feedback mechanism where the cutting load measurement directly influences the work schedule adjustment. The controller monitors blade load and automatically adjusts mowing frequency and timing based on this feedback, improving productivity through adaptive scheduling without requiring complex control algorithms or multiple sensors.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent changes the scheduling parameter (mowing frequency and timing) based on the cutting load parameter. By directly correlating blade load measurements with schedule adjustments, the system achieves improved productivity through simple parameter modification rather than complex multi-variable control, maintaining ease of implementation.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP3520593B1Improved robotic working tool
Publication Date: 2025.12.10 HUSQVARNA AB
  • EP3520593B1 patent drawingFigure 1~2
  • EP3520593B1 patent drawingFigure 3~5

AI summary

A robotic work tool system (200), comprising a charging station (210), a boundary wire (250), a signal generator (240) for generating and transmitting a signal through said boundary wire (250) for demarcating a work area (205) and a robotic work tool (100), said robotic work tool (100) comprising a cutting blade (160) and a motor (165) for driving the cutting blade (160), the robotic work tool (100) being configured to determine a cutting load being exerted on the cutting blade (160) indicating a height of grass in the work area (205) and adapt a work schedule according to said cutting load prior to a next work session, wherein said work schedule includes a cutting height and/or a cutting time.