Robotic Work Tool Collision Detection on Slopes Using Adaptive Thresholds

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Solution Overview

Problem

Existing robotic work tools, such as lawnmowers, face issues with false collision detection due to high threshold settings, leading to erratic behavior and increased wear on surfaces, as they struggle to differentiate between slopes and actual collisions, and may collide abruptly with living objects.

Innovation Solution

A robotic work tool equipped with a motor, inclination sensor, and controller that adapts the collision threshold based on inclination data, allowing for dynamic adjustment of the power threshold to accurately detect collisions and prevent unnecessary contact with objects or surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a high collision threshold is set to avoid false positives, then false collision detections are reduced, but the robotic work tool pushes harder against objects before detection, causing increased wear on surfaces

Engineering Contradiction:
Improvecollision detection accuracyVSAvoidsurface wear
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The collision threshold is made dynamic rather than fixed. The controller continuously monitors motor power consumption and compares it against a dynamically adjusted threshold. When the robotic work tool encounters increased resistance (such as climbing a slope), the threshold adapts accordingly, allowing the system to distinguish between normal operational variations and actual collisions, thereby reducing false positives while maintaining sensitive collision detection.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system changes the parameter of collision threshold based on operating conditions. By monitoring motor power consumption and comparing it against adaptive thresholds, the system adjusts its sensitivity to collision detection based on the current operational context, enabling accurate collision detection without causing excessive surface wear.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If a high collision threshold is set to avoid false positives, then false collision detections are reduced, but the robotic work tool exhibits erratic behavior on slopes and hills

Engineering Contradiction:
Improvecollision detection accuracyVSAvoidoperation on varied terrain
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The collision detection system dynamically adjusts its threshold based on real-time motor power consumption data. When operating on slopes or varied terrain, the system recognizes the increased power demand as a normal condition and adjusts the collision threshold accordingly, preventing false collision detections and erratic behavior while maintaining reliable collision detection on flat surfaces.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system modifies the collision detection parameter (threshold) based on operating conditions detected through motor power monitoring. This allows the robotic work tool to maintain stable operation on slopes and hills by adapting the collision threshold to match the increased power consumption associated with climbing, rather than reacting erratically to normal terrain variations.

Inventive Principle:
Principle #35Parameter changes

3Measurement precision

If a low collision threshold is set to detect collisions early, then collision detection sensitivity is improved, but false positives increase due to slopes and terrain variations

Engineering Contradiction:
Improvecollision detection sensitivityVSAvoidfalse positive rate
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

Rather than using a fixed low threshold that causes false positives, the system employs a dynamic threshold that adapts to current operating conditions. The controller monitors motor power consumption and adjusts the collision threshold in real-time, maintaining high sensitivity for detecting actual collisions while automatically raising the threshold during normal operations on slopes or varied terrain to prevent false positives.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The collision detection parameter (threshold) is changed based on operational context. By monitoring motor power consumption and comparing it against adaptive thresholds, the system maintains high collision detection sensitivity while reducing false positives caused by terrain variations such as slopes and hills.

Inventive Principle:
Principle #35Parameter changes

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 reduces false positives and wear on surfaces by dynamically adjusting the collision threshold based on inclination, ensuring safer and more efficient operation on varied terrain, including slopes, and minimizing discomfort when encountering living objects.

Implementation Method 1

an inclination sensor and a controller for controlling the operation of the robotic work tool

Methodology Applied
Scientific EffectGravitation: Gravitation

Data Source

PatentEP3567999B1Improved collision detection for a robotic work tool
Publication Date: 2022.01.12 HUSQVARNA AB
  • EP3567999B1 patent drawingFigure 1A~2
  • EP3567999B1 patent drawingFigure 3~4
  • EP3567999B1 patent drawingFigure 5

AI summary

A robotic work tool comprising a motor for driving at least one wheel, an inclination sensor and a controller for controlling the operation of the robotic work tool, the controller being configured to; receive a signal indicating a collision; determine if the signal indicating a collision is above a collision threshold level and, if so, determine that a collision has been detected, the robotic work tool being characterized in that the controller is further configured to: receive an indication of an inclination; and to adapt the collision threshold accordingly based on said indication of an inclination.