Robotic Mower Navigation Margin for Boundary-Safe Positioning
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Solution Overview
Problem
Existing robotic mowers face challenges in accurately determining their position within a work area, leading to increased maximum dead reckoning distances and potential safety risks when position uncertainty occurs.
Innovation Solution
A method and robotic mower design that utilize both a positioning unit and a dead reckoning sensor to calculate a position uncertainty distance, align generated trajectories, and execute safety operations when a navigation margin falls below a predetermined value, ensuring accurate and robust navigation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the robotic mower relies solely on a positioning unit to determine its position, then the device complexity is reduced, but the measurement precision of the position deteriorates leading to increased position uncertainty
Solution Approach 1:
The patent combines a positioning unit (GPS/RTK) with a dead reckoning sensor system to create a hybrid navigation system. The positioning unit provides absolute position references while the dead reckoning sensors (accelerometers, gyroscopes, wheel encoders) provide continuous position updates between positioning fixes. This merging of systems resolves the contradiction by maintaining high measurement precision without excessive device complexity, as the dead reckoning components are standard in modern robotic mowers.
Solution Approach 2:
The patent introduces an intermediary calculation layer that fuses data from the positioning unit and dead reckoning sensors through trajectory alignment and position uncertainty calculation. This intermediary processing layer reconciles the two positioning methods, using the positioning unit data to correct drift in the dead reckoning system while maintaining continuous position estimates. This mediator approach enables accurate position determination without requiring the positioning unit to operate at maximum precision continuously.
2Reliability
If the maximum dead reckoning navigating distance is increased to maintain navigation when position cannot be reliably obtained, then the reliability of navigation is improved, but the measurement precision of position deteriorates due to accumulated error
Solution Approach 1:
The patent implements a feedback mechanism where the position uncertainty distance is continuously calculated and used to adjust the navigation behavior. When the distance to the boundary minus the position uncertainty distance (navigation margin) falls below a threshold, the system triggers a safety operation. This feedback loop ensures navigation reliability by continuously monitoring position accuracy and taking corrective action before boundary violations occur, rather than relying on fixed maximum dead reckoning distances.
Solution Approach 2:
The patent makes the navigation safety parameters dynamic rather than static. The maximum effective dead reckoning distance is not a fixed value but is dynamically determined by the real-time position uncertainty calculation and the distance to the boundary. This dynamic approach allows the system to maintain navigation longer when position uncertainty is low and trigger safety operations sooner when uncertainty increases, optimizing both navigation reliability and position accuracy.
3Reliability
If the robotic mower uses boundary wires to limit the work area, then the safety of boundary containment is improved, but the ease of operation deteriorates due to installation complexity
Solution Approach 1:
The patent replaces the mechanical boundary wire system with an electronic/software-based boundary definition system. Instead of physical wires that require installation and maintenance, the work area boundary is defined through software coordinates and GPS/RTK positioning. This substitution eliminates the installation complexity of boundary wires while maintaining reliable boundary containment through the enhanced positioning system that calculates position uncertainty and triggers safety operations before boundary violations.
Data Source
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AI summary
A method for navigating a robotic mower (2) limited by a boundary (6), and a robotic mower (2) configured to perform the method. The robotic mower (2) repeatedly determines (S100) its position by means of a positioning unit (8), navigates (S102) based on the determined position, determines (S104) that a new position of the robotic mower (2) cannot be accurately obtained, determines (S106) a position uncertainty distance (R) based on the positions obtained by the positioning unit (8) and a dead reckoning sensor (10) provided in the robotic mower (2), calculates (S108) a distance (D) to the closest boundary, determines (S110) a navigation margin as the difference between the distance (D) to the closest boundary (6) and the position uncertainty distance (R), and executes (S112) a safety operation if the navigation margin equals a predetermined value.