Robotic Mower Home Finding Path Variation

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Solution Overview

Problem

Robotic lawn mowers often damage turf along boundary wires or borders due to repetitive paths to the charging station, causing wear and ruts from consistent wheel contact in the same areas.

Innovation Solution

A robotic mower home finding system with a vehicle control unit that changes the path each time it returns to the charging station by offsetting the path from the boundary wire, either randomly or incrementally, using a traction drive system to minimize turf damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the robotic mower follows the same path along the boundary wire to return home, then it can reliably find the charging station, but it causes turf damage and ruts from repeated wheel contact

Engineering Contradiction:

Improvereliability of home findingVSAvoidturf damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system dynamically changes the return path by varying the offset distance from the boundary wire using a random number generator. Instead of following a fixed path, the mower selects different offset distances (e.g., 10cm, 20cm, 30cm) for each return trip, causing the wheels to contact different turf areas and preventing repetitive wear and rut formation while maintaining reliable home finding through boundary wire detection

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the path parameter (offset distance from boundary wire) by generating random values within a specified range. This parameter variation ensures that the return path differs each time, distributing wheel contact across multiple turf areas rather than concentrating wear on a single repeated path, thereby reducing turf damage while preserving navigation reliability

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If the robotic mower varies the return path to minimize turf damage, then it reduces wear and ruts, but it increases system complexity

Engineering Contradiction:

Improveturf damageVSAvoidsystem complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The system uses the existing boundary wire detection capability and onboard random number generator to autonomously determine varied return paths without requiring external intervention or complex additional hardware. The mower self-manages path variation by combining random offset selection with boundary wire following, achieving turf protection through simple, self-contained logic that minimizes system complexity

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Instead of using complex mechanical path variation mechanisms (such as adjustable wheel positions or physical path markers), the system substitutes a computational approach using a random number generator and control algorithm. This electronic/software-based solution achieves path variation without adding mechanical complexity, maintaining system simplicity while enabling diverse return paths to protect the turf

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8433468B2Robotic mower home finding system

Publication Date: 2013.04.30 DEERE & CO

AI summary

A robotic mower home finding system includes a charging station connected to an outer boundary wire loop, and a vehicle control unit on the robotic mower that directs a traction drive system to drive the robotic mower along a path offset a specified distance from an outer boundary wire loop toward the charging station. The vehicle control unit changes the specified distance randomly or incrementally so that the robotic mower does not take the same path to the charging station each time.