Lawnmower Boundary Wire Burst Coding for Robust Position Detection
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Solution Overview
Problem
Existing systems for controlling self-propelling lawnmowers within boundary wires are complex, expensive, and sensitive to interference, requiring synchronization and complex electronics for signal reception.
Innovation Solution
A method and system using DC-balanced alternating current encoded with a data frame comprising a recognition code, randomly transmitted in bursts, with a cryptographic True Random Number Generator to enhance robustness against interference, and restricting contiguous bits to increase reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed phasing with alternating voltage signals is used to determine lawnmower position, then position determination is achieved, but the electronics in the control unit become complex and expensive
Solution Approach 1:
The patent changes the signal parameter from fixed phasing to random phase transmission. The boundary wire transmits signals with random phases instead of fixed phasing, which simplifies the control unit electronics while maintaining position determination accuracy through correlation-based detection of the random signal patterns.
Solution Approach 2:
The patent employs periodic transmission of identification signals at specific frequencies (e.g., 1-100 kHz) through the boundary wire. This periodic action allows the lawnmower to detect and correlate signals over time, enabling position determination without requiring complex real-time electronics.
2Measurement precision
If fixed phasing signal transmission is used, then position determination is possible, but the system becomes very sensitive to interference
Solution Approach 1:
The system transmits identification signals periodically at specific frequencies through the boundary wire. This periodic transmission creates a structured signal pattern that can be distinguished from random interference through correlation detection, reducing sensitivity to electromagnetic interference while maintaining position determination accuracy.
Solution Approach 2:
The lawnmower continuously monitors and correlates received signals from the boundary wire, using feedback from signal strength and phase information to determine position. This feedback mechanism allows the system to distinguish genuine boundary wire signals from interference by looking for consistent correlation patterns.
3Object-affected harmful factors
If convolution method is used to compare received signal with reference pattern, then electromagnetic resistance is improved, but the method becomes more complex
Solution Approach 1:
The system uses continuous correlation feedback between received signals and reference patterns stored in the lawnmower. By continuously comparing incoming signals with stored reference patterns and adjusting based on correlation strength, the system achieves electromagnetic resistance through a relatively simple iterative process rather than complex convolution calculations.
4Object-affected harmful factors
If electrical signals are transmitted in bursts with predetermined pattern, then electromagnetic resistance is improved, but synchronization is required for signal reception
Solution Approach 1:
The lawnmower performs self-synchronization by automatically detecting and adapting to the transmission pattern of the boundary wire signals. The system includes synchronization circuitry that autonomously locks onto the periodic signal structure and adjusts its reception timing accordingly, eliminating the need for external synchronization commands or complex coordinated control between transmitter and receiver.
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 a robust and interference-resistant system for determining the lawnmower's position within the boundary wire, reducing complexity and cost while improving resistance to electromagnetic interference.
Implementation Method 1
Two signals with alternating voltage are applied simultaneously by a signal generator to the border delimitation wire. The two signals create alternating electromagnetic fields, which are detected by receiving coils in the lawnmower.
Implementation Method 2
The two signals create alternating electromagnetic fields, which are detected by receiving coils in the lawnmower.
Data Source
Figure 1~2
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Figure 5~9
AI summary
The present invention relates to a method and a system for controlling a self- propelling lawnmower (2), the system comprises the self-propelling lawnmower (2) having a control unit (8) and at least one sensor (12; 14; 16), a boundary wire (4) and a signal generator (6). The self-propelling lawnmower (2) is configured to move across an area (A) surrounded by the boundary wire (4). By encoding a data frame with a recognition code in an alternating current that is Direct Current, DC- balanced and that is randomly transmitted within a predetermined period of time (T), by means of the signal generator (6), to the boundary wire (4) a system robust against interference is accomplished. The data frame burst (30) is received by a sensor (12; 14; 16) and decoded by a control unit (8) in the lawnmower. By comparing the received recognition code with a stored recognition code the control unit (8) determines that the lawnmower (2) is on the inside of the boundary wire (4) if the received recognition code matches the stored recognition code, and on the outside if the received recognition code matches the inverse of the stored recognition code.