Reflective Stasis Wheel Sensing for Stuck Robot Detection
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Solution Overview
Problem
Existing coverage robots face challenges in detecting stasis conditions, such as being stuck or losing contact with the surface, which can lead to inaccurate motion detection and potential damage or inefficiency in cleaning tasks.
Innovation Solution
The implementation of a stasis indication wheel with reflective portions and a suspension system that allows movement other than rotation, combined with a signal emitter and receiver, enables the detection of stasis conditions by monitoring transitions between reflective and non-reflective sections as the wheel rotates and moves vertically or tilts, and a drive current monitoring system to determine if the robot is stuck or free-wheeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional odometric monitoring system using rotatable wheels is used to detect motion, then the robot can monitor distance traveled, but it cannot accurately detect stasis conditions when the robot is stuck or loses contact with the surface
Solution Approach 1:
The wheel is segmented into multiple reflective portions with different reflectivity characteristics (highly reflective, moderately reflective, and non-reflective sections). This segmentation allows the optical sensor to detect different wheel states based on reflected light intensity, enabling accurate stasis detection when the robot is stuck or losing contact with the surface.
Solution Approach 2:
An intermediary optical detection system using light reflection as a mediator is introduced between the wheel and the controller. The optical sensor detects changes in reflected light from the segmented wheel, providing indirect but accurate information about wheel rotation and robot motion status, thereby improving stasis detection capability.
2Measurement precision
If the wheel is rigidly fixed to monitor rotation accurately, then odometric monitoring is precise, but the wheel cannot adapt to surface variations or robot tilting
Solution Approach 1:
The wheel is made dynamic by allowing it to rotate freely on its axis while the entire wheel assembly can tilt and adjust its orientation relative to the robot body. This dynamic configuration enables the wheel to adapt to surface variations and robot tilting while the optical sensor continuously monitors rotation for accurate odometric measurement.
Solution Approach 2:
The invention merges two functions into a single wheel assembly: (1) the wheel rotates to provide traction and enable robot movement, and (2) the segmented reflective portions on the wheel serve as an optical encoder for motion detection. This combination allows the wheel to be both adaptive to surface conditions and precise in motion monitoring.
3Reliability
If multiple sensors are added to detect stasis conditions accurately, then detection reliability improves, but device complexity increases
Solution Approach 1:
The segmented wheel serves multiple functions: it provides traction for robot movement, acts as an optical encoder for odometric monitoring, and enables stasis detection through its reflective portions. This multi-functionality improves detection reliability without requiring separate dedicated sensors for each function, thereby avoiding increased system complexity.
Solution Approach 2:
The wheel itself serves as the detection element through its segmented reflective portions. As the wheel rotates or tilts, the varying reflectivity patterns automatically provide information about robot motion and stasis conditions to the optical sensor, eliminating the need for additional complex sensing mechanisms.
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
This solution effectively detects stasis conditions, ensuring the robot's safety and efficiency by accurately determining its movement status and preventing damage from obstacles or cliffs, thereby enhancing its cleaning performance.
Implementation Method 1
A signal emitter is disposed remotely from the wheel and positioned to direct a signal that sequentially is intercepted by the first and second reflective portions of the wheel. A signal receiver is positioned to receive the signal as reflected by the wheel
Data Source
AI summary
A coverage robot includes a drive configured to maneuver the robot as directed by a controller, a stasis indication wheel rotatable about a first axis perpendicular to a direction of forward travel, and a suspension supporting the wheel. The stasis indication wheel defines a first reflective portion and a second reflective portion. The second reflective portion is substantially less reflective than the first reflective portion. The suspension permits movement of the wheel in a direction other than rotation about the first axis. A signal emitter is disposed remotely from the wheel and positioned to direct a signal that sequentially is intercepted by the first and second reflective portions of the wheel. A signal receiver is positioned to receive the reflected signal by the rotating wheel. Communication between the emitter and the receiver is affected by rolling transitions between the first and second reflective portions during permitted movement of the wheel.