Robot Localization Using Retroreflective Boundary Markers
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Solution Overview
Problem
Current GPS systems and localization methods for outdoor autonomous robots, such as lawn mowers, are inadequate due to insufficient resolution and interference from tree cover and terrain variations, leading to inaccuracies in boundary detection and potential damage to non-mow zones.
Innovation Solution
An autonomous mobile mowing robot uses a combination of retroreflective boundary markers, lidar or radar sources, and a data processor to determine its position through trilateration and scan matching, adjusting scan rates and power levels to improve accuracy and reduce noise, while using fanned laser beams to account for terrain variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS systems are used for outdoor robot localization, then the robot can determine its position over large areas, but the resolution is insufficient to prevent damage to non-mow zones and tree cover interferes with signal accuracy
Solution Approach 1:
The patent introduces boundary markers as intermediary objects placed along the property boundary. These markers reflect laser signals back to the robot, enabling precise position determination without relying on GPS signals that are blocked by tree cover. The markers serve as a local reference system that works independently of satellite signals.
Solution Approach 2:
The patent replaces the electromagnetic GPS system with an optical laser-based localization system. By using laser beams to measure distances to boundary markers and calculating position through triangulation, the system achieves higher precision while being unaffected by tree cover that blocks GPS satellites.
2Measurement precision
If triangulation with multiple beacons is used to determine robot position, then position accuracy improves, but the system complexity and power requirements increase
Solution Approach 1:
Instead of having multiple beacons actively transmitting signals, the patent uses passive boundary markers that reflect the robot's own laser signals. This inversion reduces system complexity by eliminating the need for multiple powered beacon units while maintaining triangulation capability through the robot's single active laser source.
Solution Approach 2:
The robot uses its own laser source to illuminate the boundary markers and detect the reflected signals. The system is self-sufficient, requiring no external powered beacons, as the robot's navigation laser serves dual purposes for both obstacle detection and position determination through reflection off the markers.
3Measurement precision
If a sweeping beacon detector is used to detect boundary markers, then the robot can locate markers, but terrain tilt and slant cause the detector to miss markers
Solution Approach 1:
The patent transitions from a single-point beacon detector to a laser line scanner that projects a fan-shaped laser beam creating a plane of illumination. This dimensional change from point to plane allows the system to detect markers even when the robot is tilted, as the extended laser plane has a higher probability of intersecting with markers on uneven terrain.
Solution Approach 2:
The patent uses a rotating or steerable laser source that dynamically adjusts the laser beam direction. This dynamic capability allows the laser to sweep across a wider area and compensate for robot tilt, maintaining marker detection capability on uneven terrain where a fixed single-point detector would fail.
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 system enhances the accuracy of robot localization within defined boundaries, preventing damage to non-mow zones and improving operational efficiency by accurately determining its position and orientation amidst varying environmental conditions.
Implementation Method 1
the markers are configured to cause the beam to fan out in a predetermined manner... the markers are retroreflective markers
Implementation Method 2
a laser or other radiation source and detector carried by the robot body... the laser is controlled to cause the beam to fan out
Implementation Method 3
a radiation detector... configured to detect radiation reflected from the markers
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A location estimation system for use with an autonomous lawn mowing robot, comprises a plurality of synthetic surfaces positioned with respect to a mowable space in an environment, a radiation source coupled to the lawn mowing robot, a detector coupled to the lawn mowing robot and configured to detect radiation reflected by objects in the environment, and a controller configured to controllably direct radiation from the radiation source to scan the environment, and to vary at least one of an output power of the directed radiation and a scan rate of the directed radiation, as a function of detected radiation reflected from one or more of the synthetic surfaces.