Robotic Boundary Sensing With Dynamic Magnetic Sensor Selection

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Solution Overview

Problem

Robotic working tools, such as lawnmowers, face erratic behavior due to increased internal interference as they move away from boundary wires, leading to erroneous signal determinations and false operations, especially when external interference is amplified by variable gain amplifiers.

Innovation Solution

A robotic working tool with a controller that selectively chooses which magnetic sensors to listen to based on detected signal strength, ignoring heavily interfered signals to avoid erratic behavior, requiring minimal modifications such as a software upgrade.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If variable gain amplifiers are used to amplify the detected signal, then the signal strength is improved, but internal interference is also amplified leading to erroneous signal determinations

Engineering Contradiction:
Improvesignal strengthVSAvoidinternal interference
Core Design Contradiction:
Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The controller continuously monitors the signal strength from multiple magnetic sensors and dynamically selects which sensor to use based on real-time feedback. When a sensor's signal falls below a threshold (indicating high interference), the controller switches to another sensor, creating a feedback loop that adapts to changing interference conditions and prevents erroneous determinations.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system changes the operational parameter of signal selection by comparing signal strength thresholds and switching between different sensors based on these parameters. This dynamic parameter adjustment allows the system to optimize signal quality while avoiding sensors affected by internal interference.

Inventive Principle:
Principle #35Parameter changes

2Area of stationary object

If the robotic working tool moves away from the boundary wire, then the work area coverage is improved, but the signal strength decreases and interference increases

Engineering Contradiction:
Improvework area coverageVSAvoidsignal detection accuracy
Core Design Contradiction:
Area of stationary objectVSMeasurement precision

Solution Approach 1:

The system divides the sensing function across multiple magnetic sensors positioned at different locations within the robotic tool. By segmenting the detection task across multiple sensors, the system can select the sensor providing the clearest signal even when the tool is far from the boundary wire, thereby maintaining measurement precision while expanding work area coverage.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The controller uses continuous feedback from multiple sensors to monitor signal strength and automatically selects the sensor with the strongest, least interfered signal. This feedback mechanism ensures accurate boundary detection regardless of the tool's distance from the boundary wire, enabling expanded work area coverage without sacrificing measurement precision.

Inventive Principle:
Principle #23Feedback

3Reliability

If multiple magnetic sensors are used to improve signal reliability, then the interference resistance is improved, but the device complexity increases

Engineering Contradiction:
Improvesignal reliabilityVSAvoidsensor system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The system implements dynamic sensor selection where the controller actively chooses which magnetic sensor to use based on real-time signal strength comparisons. This dynamic approach allows multiple sensors to be present in the system without requiring all to be actively processed simultaneously, thereby improving signal reliability while managing device complexity through selective activation.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The magnetic sensors collectively serve the system's reliability needs through a self-selecting mechanism. The controller automatically evaluates signal strengths and selects the most reliable sensor without external intervention, allowing the sensor array to improve reliability while the simple selection logic keeps overall system complexity manageable.

Inventive Principle:
Principle #25Self-service

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

This solution effectively reduces internal interference impact, ensuring consistent operation by prioritizing reliable sensor input, even in areas with significant interference, thereby preventing false polarity changes and erratic movements.

Implementation Method 1

at least a first and a second magnetic sensor arranged to sense a magnetic boundary signal emitted by a boundary wire

Methodology Applied
Scientific EffectMagnetic field detection: Magnetic Field

Data Source

PatentEP3724738B1A robotic working tool and work area boundary sensing method
Publication Date: 2023.08.23 HUSQVARNA AB
  • EP3724738B1 patent drawingFigure 1A~1B
  • EP3724738B1 patent drawingFigure 2
  • EP3724738B1 patent drawingFigure 3

AI summary

The present disclosure related to a robotic working tool100comprising a controller110and at least a first and at least a second magnetic sensor arranged to sense a magnetic signal. The controller 110is configured to detect a first magnetic signal; determine a signal strength of the detected first magnetic signal;determine if the signal strength of the detected magnetic signal is above or below a threshold value, and if the signal strength is above the threshold value, accept signal detection input for the first magnetic signal from a first set of sensors, and if the signal strength is below the threshold value, accept signal detection input for the first magnetic signal from a second set of sensors, wherein the second set of sensors is a subset of the first set.The disclosure also relates to a method for use in the robotic working tool and a computer readable medium for carrying computer instructions that when loaded into a controller of a robotic working tool, cause the robotic working tool to operate according to a method.