Vehicle Occupant Restraint System with Anticipatory Webbing Retraction
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Solution Overview
Problem
Existing vehicle occupant restraint systems, such as those described in JP 2018-138411 A, often retract seatbelt webbing after an acceleration is applied, potentially causing occupants to be displaced from a normal seated position, and increasing webbing tension before acceleration is undesirable for comfort. There is a need to balance comfort and occupant protection.
Innovation Solution
A vehicle occupant restraint system that includes a seatbelt device with a take-up mechanism driven by a motor, a road surface condition detection unit, and a controller that estimates anticipated acceleration and adjusts webbing tension before the acceleration occurs, ensuring the occupant remains seated by retracting the webbing when estimated acceleration exceeds a threshold and the time to acceleration occurrence is short.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor is driven after acceleration is applied to retract the webbing, then the occupant protection is improved, but the occupant may be displaced from normal seated position and comfort deteriorates
Solution Approach 1:
The system performs preliminary action by detecting road surface conditions and anticipating acceleration before it occurs. The controller computes estimated acceleration and time to acceleration occurrence, then drives the motor in advance to retract the webbing by a predetermined amount before the actual acceleration happens. This preliminary retraction ensures the occupant remains in normal seated position while being protected during the acceleration event.
Solution Approach 2:
The system uses feedback from road surface condition detection and vehicle status detection to continuously monitor and adjust webbing tension. The controller receives feedback about the vehicle's acceleration state and road conditions, then dynamically controls the motor to retract or release webbing accordingly. This closed-loop feedback mechanism optimizes both occupant protection and comfort by adjusting webbing tension based on real-time conditions.
2Reliability
If the webbing tension is increased before acceleration is applied, then the occupant protection is improved, but the occupant comfort deteriorates
Solution Approach 1:
The system applies preliminary action by retracting the webbing by a predetermined amount only when the computed time to acceleration occurrence is shorter than or equal to a predetermined value. This means the webbing tension is increased in advance only when acceleration is imminent, not continuously. The motor is driven to retract the webbing before acceleration occurs, providing protection only when needed while maintaining comfort during normal driving conditions.
Solution Approach 2:
The system dynamically adjusts webbing tension based on real-time road surface conditions and vehicle status. The controller computes estimated acceleration and compares it with a threshold, then dynamically controls the motor to retract or release webbing. This dynamic adjustment ensures the webbing is tight only when acceleration is anticipated, providing protection when needed while maintaining comfort during normal operation.
Data Source
AI summary
A CPU of an ECU is configured to compute an estimated acceleration that is estimated to be applied to a vehicle and a remaining time that is taken from present time to acceleration occurrence time at which the estimated acceleration occurs from a road surface condition detected by a road surface condition detection unit and a vehicle status detected by a vehicle speed determination unit and a steering angle velocity determination unit. The CPU is configured to, when the remaining time becomes shorter than or equal to a predetermined value, drive a retractor motor. The webbing is retracted before an occupant moves with an acceleration that is applied to the vehicle, so the occupant is held in a normal seated position. The retractor motor is driven when the time that is taken from present time to acceleration occurrence time becomes shorter than or equal to the predetermined value.