Autonomous Mower Orientation via Horizon Mapping
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Solution Overview
Problem
Autonomous mowers face challenges in determining their orientation when stationary, leading to potential collisions upon resuming operation, as single GPS receivers cannot determine orientation and additional sensors like magnetometers are less accurate or costly.
Innovation Solution
The use of horizon mapping, where a mower's control system maintains a horizon map associating horizon features with known positions, allowing it to determine orientation by comparing image-captured horizon features with stored maps, even when stationary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple GPS receivers are used to determine orientation when stationary, then orientation accuracy is improved, but device cost and complexity increase significantly
Solution Approach 1:
The patent replaces the mechanical/GPS-based orientation determination system with an optical imaging system. Instead of using multiple GPS receivers to calculate orientation through geometric relationships, the system uses a single camera to capture horizon features and compares these features against pre-stored horizon maps to determine orientation. This substitution eliminates the need for multiple expensive GPS receivers while maintaining orientation accuracy.
Solution Approach 2:
The patent creates a digital copy of the horizon environment through imaging. By capturing an image of the horizon and comparing it to pre-stored horizon maps that represent the expected horizon appearance from different orientations, the system determines orientation without physically moving the mower or using multiple position sensors. The horizon image serves as a copy that encodes orientation information.
2Device complexity
If magnetometers are used to determine orientation, then device cost is reduced compared to multiple GPS receivers, but measurement accuracy is substantially lower
Solution Approach 1:
The patent replaces magnetic field-based orientation detection with optical imaging-based detection. Instead of using magnetometers that measure magnetic field orientation, the system uses a camera to capture visual horizon features and compares these against pre-stored horizon maps. This optical approach provides accuracy comparable to or better than magnetometers while avoiding the lower accuracy issues of magnetic field-based systems.
3Device complexity
If the mower starts moving to determine orientation from GPS readings, then orientation can be determined with a single GPS receiver, but collision risk increases when parked facing obstacles
Solution Approach 1:
The patent performs orientation determination before the mower needs to resume operation. By capturing horizon images and comparing them to pre-stored horizon maps while the mower is stationary, the system determines orientation in advance. This preliminary action eliminates the need to move the mower to determine orientation, thereby preventing potential collisions with obstacles while maintaining the ability to use a single GPS receiver for location tracking.
Data Source
AI summary
A mower's control system can maintain horizon maps that associate horizon features with known relative positions. When a mower's orientation is unknown, the control system can obtain an image that captures the horizon from the mower's current viewpoint. The control system can process the image to detect any horizon features that appear within the image and to determine their positions within the image. The control system can then access a horizon map to identify matching horizon features. The control system can compare the known relative positions of any matching horizon features with the positions of the horizon features within the image to thereby determine the mower's current orientation.