Robotic Mower Boundary-Wire Re-Entry Using Signal Peak Alignment
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Solution Overview
Problem
Existing robotic lawnmowers struggle to efficiently return to the defined work area after crossing the boundary wire, leading to potential exit from the designated working space.
Innovation Solution
The control unit of the robotic lawnmower is designed to detect a phase reversal in the induced signal, stop the movement, rotate around a vertical axis, and align with the boundary wire by evaluating extreme values of the received signal to determine a control variable, allowing the lawnmower to re-enter the work area via a short path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the robotic lawnmower uses a receiving coil to detect the boundary wire's electromagnetic field, then it can identify the boundary wire's position, but the lawnmower may cross the boundary wire and leave the defined working area
Solution Approach 1:
The control unit continuously monitors the received signal from the receiving coil and uses feedback control to adjust the lawnmower's movement. When the signal indicates approach to the boundary wire, the system responds by stopping and rotating, preventing boundary crossing and maintaining reliable operation within the work area.
Solution Approach 2:
The system performs preliminary detection of the boundary wire's position using the receiving coil before actual boundary crossing occurs. By detecting the electromagnetic field in advance and responding with stopping and rotation actions, the lawnmower prevents leaving the defined working area.
2Measurement precision
If the robotic lawnmower stops and rotates 360 degrees to detect extreme values of the received signal, then it can accurately align with the boundary wire, but the time required to return to the work area increases
Solution Approach 1:
The system performs a complete 360-degree rotation to ensure accurate detection of the boundary wire's position and precise alignment. This excessive action (full rotation rather than partial scanning) guarantees that the extreme value of the received signal is correctly identified, enabling accurate re-entry into the work area despite the additional time required.
3Productivity
If the control unit rotates the implement around the vertical axis to align with the boundary wire, then the lawnmower can return via a short path, but the complexity of the control system increases
Solution Approach 1:
The control unit integrates multiple functions: it detects the boundary wire's position using the receiving coil, determines the optimal rotation direction, executes the rotation around the vertical axis, and controls the drive wheels for movement. This multi-functional control system achieves efficient return to the work area while managing complexity through integrated control rather than separate specialized components.
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 method ensures the robotic lawnmower efficiently and accurately returns to the work area by aligning with the boundary wire, minimizing the risk of exiting the defined space.
Implementation Method 1
A wire signal is transmitted along a closed loop of wire forming the boundary wire. The boundary wire, carrying the current of the wire signal, generates an electromagnetic field. As the working tool approaches the boundary wire, the field lines of the electromagnetic field, or the magnetic field lines, induce a received signal in a receiving coil of the working tool.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a method for controlling a self-propelled work device (1) for processing a work area (30) bounded by a boundary wire (31). The work device (1) has an electric drive for separately driving the drive wheels (2, 3), whereby the work device (1) can be rotated about a vertical axis (20) by driving the drive wheels (2, 3) in opposite directions. A received signal (40) is induced in a receiving coil (13, 14, 15) of the work device (1), which changes its polarity when it passes over the boundary wire (31). A control unit (10) is configured to stop the work device (1) and rotate it about its vertical axis (20) when the phase of the received signal (40) changes. During the rotation of the work device (1), the received signal (40) is evaluated for an extreme value (E). The value of a control variable is derived from a determined extreme value (E).Depending on the control variable, the working tool is rotated about the vertical axis (20) and stopped when the value of the control variable is reached. The control unit (10) drives the drive wheels (2, 3) of the working tool (1), which has been stopped in its rotational movement, in a direction of travel (7) such that the boundary wire (31) is crossed again and the working tool is returned to the working area (30).