Autonomous Mower Boundary Sensing With Pseudo-Random Wire Signals
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Solution Overview
Problem
Conventional autonomous mower navigation systems are complex, expensive, and prone to interference, requiring significant computational capacity and GPS technology, while traditional methods using simple periodic signals are susceptible to noise and require additional processing power.
Innovation Solution
A system utilizing inductive sensors to receive return-to-zero encoded signals with pseudo-random sequences, transforming them into non-return-to-zero representations, digitally sampling, and filtering using a reference data array to determine the autonomous mower's location within a defined work area, allowing for accurate and efficient navigation without the need for complex synchronization or reconstruction of boundary signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS technology and complex navigation systems are used, then navigation accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces GPS satellite-based electromagnetic positioning with a ground-based inductive sensing system that uses magnetic fields generated by boundary wires. The mower uses inductive sensors to detect the magnetic field presence and determine position relative to the boundary, eliminating the need for GPS receivers and complex satellite signal processing while achieving comparable navigation accuracy.
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the boundary wire and the mower's navigation system. The boundary wire generates a magnetic field that serves as a detectable signal, allowing the mower to determine its position without direct line-of-sight to satellites or complex visual markers. This intermediary field simplifies the overall system architecture.
2Device complexity
If simple periodic signals are used for robot confinement, then device complexity is reduced, but reliability deteriorates due to interference susceptibility
Solution Approach 1:
The patent uses periodic square wave signals transmitted through the boundary wire at a specific frequency (e.g., 120 Hz). This periodic transmission creates a consistent magnetic field that the inductive sensors can reliably detect. The periodic nature allows the system to distinguish between actual boundary signals and random electromagnetic interference, improving reliability while keeping the signal structure simple.
Solution Approach 2:
The patent changes the signal parameter from simple continuous periodic waves to modulated square waves with specific duty cycles and frequencies. By encoding position information in the timing and characteristics of the magnetic field presence/absence, the system achieves reliable differentiation between boundary signals and interference without requiring complex signal structures.
3Reliability
If modulated codes and complex signals are used to reduce interference effects, then signal reliability is improved, but use of energy increases due to additional computing power required
Solution Approach 1:
The patent extracts only the essential position-determining information from complex signal processing. Instead of using sophisticated modulated codes that require extensive decoding algorithms, the system uses simple magnetic field presence/absence detection. The inductive sensors only need to detect whether the magnetic field is present and measure basic signal characteristics, eliminating the need for complex computational interference rejection while maintaining reliability.
Solution Approach 2:
The patent employs a simple, low-cost sensing approach that sacrifices signal processing sophistication for energy efficiency. The inductive sensors use basic electromagnetic induction principles rather than advanced signal processing algorithms, reducing computational energy requirements while maintaining sufficient reliability for boundary detection and navigation.
4Measurement precision
If return-to-zero encoded signals with pseudo-random sequences are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent pre-encodes the boundary wire signal with a known pseudo-random sequence pattern before transmission. The mower's processor already has this reference pattern stored, allowing it to simply correlate the received signal with the expected pattern. This preliminary encoding simplifies the mower's task to pattern matching rather than complex signal generation or reconstruction, improving location determination accuracy while keeping processing relatively simple.
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
The solution provides accurate and efficient autonomous mower navigation with reduced processing power and noise sensitivity, enabling cost-effective operation within defined work areas while avoiding interference from other signals.
Implementation Method 1
at least one inductive sensor for receiving signal data comprising a return-to-zero encoded signal including at least one pseudo-random sequence transmitted over a wire defining a work area
Data Source
AI summary
A method for autonomous mower navigation includes receiving a return-to-zero encoded signal including a pseudo-random sequence, transforming the received signal to a non-return-to-zero representation, digitally sampling the non-return-to-zero signal representation in a time domain, filtering the sampled signal utilizing a reference data array based on the return-to-zero encoded signal to produce a filter output, and determining a location of the autonomous mower relative to a defined work area based on an evaluation of the filter output.