3D Boundary Sensor Assembly for Slope-Aware Robotic Mowers

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Solution Overview

Problem

Robotic lawn mowers face challenges in accurately detecting boundary wires due to surface slopes and oblique angles, which affect the reliability of existing boundary sensing systems.

Innovation Solution

A robotic mower equipped with a boundary sensor assembly featuring three inductive sensors oriented along perpendicular axes, including a vertical and horizontal component, to detect magnetic field components and calculate the distance and orientation relative to the boundary wire, accounting for yaw, pitch, and roll angles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single vertical sensor is used to detect the boundary wire, then the device complexity is low, but the measurement precision deteriorates when the mower encounters slopes or approaches the wire at oblique angles

Engineering Contradiction:
Improvesensor assembly complexityVSAvoidboundary wire detection accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent transitions from a single vertical sensor to a three-dimensional sensor array with components oriented along x, y, and z axes. This multi-dimensional arrangement enables the system to detect magnetic field components in all spatial directions, allowing accurate boundary wire detection regardless of mower orientation, slope, or approach angle.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The sensor assembly is segmented into multiple independent inductive sensors, each oriented along a specific axis (x, y, or z). This segmentation allows each sensor to measure a specific component of the magnetic field, and the combined data from all sensors provides complete spatial information for accurate boundary detection under varying conditions.

Inventive Principle:
Principle #1Segmentation

2Measurement precision

If multiple sensors oriented along different axes are used to account for slopes and oblique angles, then the measurement precision improves, but the device complexity increases

Engineering Contradiction:
Improveboundary wire detection accuracyVSAvoidsensor assembly complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The three-axis sensor assembly serves multiple functions simultaneously: it detects the boundary wire's magnetic field, determines the mower's orientation relative to the wire, compensates for slope effects, and provides data for navigation control. This multi-functionality justifies the increased device complexity by delivering comprehensive detection capabilities in a single integrated assembly.

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

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

Enhances the accuracy of boundary detection and navigation, allowing the mower to maintain a consistent distance from the boundary wire and perform autonomous course corrections with improved precision and reliability.

Implementation Method 1

a first inductive sensor oriented along a first axis, and a second inductive sensor oriented along a second, different, axis

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP2684438B1Boundary sensor assembly for a robotic lawn mower, robotic lawn mower and robotic lawn mower system
Publication Date: 2018.04.04 DEERE & CO
  • EP2684438B1 patent drawingFigure 1
  • EP2684438B1 patent drawingFigure 2~3
  • EP2684438B1 patent drawingFigure 4~5

AI summary

A robotic mower sensor assembly (119) for detecting a boundary wire signal. The sensor assembly (119) includes a plurality of analog inductive sensors with a first inductive sensor (120) oriented along a first axis (Z) and a second inductive sensor (122) oriented along a second, different axis (X). Each inductive sensor (120, 122, 124) is configured to generate a signal indicative of the distance of the robotic mower (100) from the boundary wire (103, 104). A control unit (101) communicating with the sensor assembly (119) is configured to operate the robotic mower (100) in response to the signals from the sensor assembly (119) which are indicative of the distance of the robotic mower (100) from the boundary wire (103, 104).