Vehicle Seat Occupancy Detection via Webbing Retraction
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Solution Overview
Problem
Current vehicle seat occupancy detection systems are inaccurate, particularly when occupants wear head or face apparel, and seatbelt-based systems fail to account for slack, leading to potential hazards during mode transitions in autonomous vehicles.
Innovation Solution
A vehicle seat occupancy detection system that includes a seatbelt retractor with a motor to retract slack in the seatbelt webbing, combined with position and buckle sensors, which provide accurate occupancy status determination by calculating the length of webbing used by the occupant, allowing safe hand-off between autonomous and non-autonomous modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If camera systems are used to detect occupant presence, then occupancy detection is attempted, but detection accuracy deteriorates when occupants wear head or face apparel such as hats or hoodies
Solution Approach 1:
The system divides the occupancy detection function into multiple independent sensing channels: camera-based visual detection, seat position sensing, and seatbelt webbing length measurement. Each sensor type detects different aspects of occupancy, and the system integrates these segmented data sources to overcome the limitations of any single method, particularly when occupants wear head apparel that obscures camera detection.
Solution Approach 2:
The seatbelt retractor system is given multiple functions: its primary function of controlling seatbelt tension is enhanced with an additional function of measuring webbing length to detect occupancy. The same mechanical component (retractor) serves both safety restraint and sensing purposes, providing universal occupancy detection that works regardless of what the occupant is wearing on their head or face.
2Measurement precision
If seatbelt-based position sensors are used to determine occupancy, then occupancy status can be inferred from seatbelt usage, but accuracy deteriorates due to slack in the seatbelt
Solution Approach 1:
The system performs preliminary retraction of the seatbelt webbing to remove all slack before taking the occupancy measurement. By pre-tensing the webbing through controlled retraction, the system ensures that subsequent measurements of webbing length accurately reflect actual occupancy without being corrupted by loose or slack webbing, thereby eliminating the information loss problem.
Solution Approach 2:
The system continuously monitors seatbelt webbing length through sensors in the retractor mechanism and uses this feedback to determine occupancy status. The feedback loop allows the system to distinguish between webbing extension caused by occupancy versus webbing extension caused by slack, enabling accurate occupancy detection by comparing measured length against expected length for various occupancy states.
3Reliability
If multiple sensors are combined to improve occupancy detection accuracy, then detection reliability improves, but device complexity increases
Solution Approach 1:
The system merges the occupancy detection function with existing seatbelt retractor components. Rather than adding completely separate sensing systems, the invention integrates occupancy sensing into the already-present mechanical retractor mechanism, combining multiple functions (tension control and occupancy sensing) into a single integrated system that reduces overall complexity while maintaining high reliability.
Solution Approach 2:
Existing seatbelt components are given multiple functions: the retractor mechanism simultaneously performs its traditional tensioning function and new occupancy sensing function. This multi-functionality approach allows the system to achieve reliable occupancy detection without adding separate dedicated sensing hardware, thereby improving reliability while minimizing the increase in device complexity.
Data Source
AI summary
A computer that may be programmed to: in response to receiving an indication that a vehicle is approaching a geofence boundary, retract slack in a webbing associated with a seat in the vehicle by actuating a seatbelt retractor; then receive measurement data from one or more sensors associated with the seat; using the data, determine whether an occupant occupies the seat; and when no occupant occupies the seat, then transmit an instruction to stop the vehicle.