Robotic Mower Slope Turning Control

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Solution Overview

Problem

Robotic lawn mowers experience wheel slip and potential stalling when turning on slopes due to uneven ground conditions, leading to inefficiency and possible manual intervention.

Innovation Solution

The robotic work tool employs a slope detector, such as an inclinometer, to determine inclination and an accelerometer to assess wheel slip risk, adjusting the rotational speed of driving wheels to prevent slip by reducing the speed of the wheel with the least grip and potentially reversing its direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the robotic mower turns by rotating drive wheels in opposite directions, then the turn is effective on even ground, but wheel slip occurs on slopes causing wear and possible stalling

Engineering Contradiction:
Improveturning reliabilityVSAvoidwheel slip
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The robotic mower performs a preliminary action by backing away from the boundary wire before executing the turn. This creates additional distance between the mower and the boundary, providing more space for the turning maneuver and reducing the risk of wheel slip during the turn on sloped terrain

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the turning strategy based on real-time conditions. The controller monitors wheel slip detection signals and slope detector signals, and dynamically modifies the turning parameters (such as wheel speed differential and turn radius) to adapt to varying slope conditions, thereby preventing wheel slip while maintaining effective turning

Inventive Principle:
Principle #15Dynamics

2Productivity

If the robotic mower operates on slopes without speed adjustment, then continuous operation is maintained, but wheel slip and lawn wear increase

Engineering Contradiction:
Improvecontinuous operationVSAvoidlawn wear
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system implements a feedback mechanism where wheel slip detection sensors and slope detectors continuously monitor operating conditions. When wheel slip is detected or slope exceeds thresholds, the controller receives feedback signals and automatically adjusts drive wheel speeds to prevent further slip, thereby maintaining continuous operation while reducing lawn wear caused by slipping wheels

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The controller changes operational parameters (drive wheel rotational speed) based on detected slope conditions and wheel slip signals. By dynamically adjusting speed parameters rather than maintaining constant operation, the system prevents wheel slip that causes lawn wear while ensuring continuous mowing productivity

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 effectively mitigates wheel slip during turns on slopes, ensuring continuous operation and reducing wear on the lawn, thereby enhancing the robotic mower's reliability and efficiency.

Implementation Method 1

determining that the robotic work tool is in a slope by using data from said slope detector, being at least one inclinometer

Methodology Applied
Scientific EffectInclinometer measurement:

Implementation Method 2

determining a wheel slip or risk of wheel slip by using data from said slope detector, being at least one accelerometer

Methodology Applied
Scientific EffectAccelerometer measurement: Accelerometer

Implementation Method 3

The electric current fed through the wire will create a magnetic field. The sensors of the robotic lawn mower will notify a controller of the robotic law mower when the robotic lawn mower approaches a boundary wire

Methodology Applied
Scientific EffectMagnetic field detection: Magnetic Field

Data Source

PatentEP2959349B1A robotic work tool configured for improved turning in a slope, a robotic work tool system, and a method for use in the robotic work tool
Publication Date: 2021.01.27 HUSQVARNA AB
  • EP2959349B1 patent drawingFigure 1~2
  • EP2959349B1 patent drawingFigure 3A~6
  • EP2959349B1 patent drawingFigure 4~5

AI summary

Robotic work tool (100) configured for improved turning in a slope (S), said robotic work tool comprising a slope detector (190), at least one magnetic field sensor (170), a controller (110), and at least two driving wheels (130"), the robotic work tool (100) being configured to detect a boundary wire (250) and in response thereto determine if the robotic work tool (100) is in a slope (S), and if so, perform a turn by rotating each wheel (130") at a different speed thereby reducing a risk of the robotic work tool (100) getting stuck.