Vehicle Occupant Restraint System with Speed-Dependent Thresholds
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Solution Overview
Problem
Existing vehicle occupant restraint systems may unnecessarily increase seatbelt tension during high steering angle velocities due to slip, leading to discomfort, as they do not effectively differentiate between vehicle speed and inertial movement, resulting in inappropriate webbing take-up.
Innovation Solution
A vehicle occupant restraint system with a controller that adjusts steering angle velocity and acceleration thresholds based on vehicle speed, increasing these thresholds as speed decreases to prevent premature webbing take-up and ensure appropriate restraint timing, especially during side slips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the steering angle velocity threshold is set to trigger webbing take-up, then occupant protection is improved, but comfort deteriorates due to unnecessary tension during slip conditions
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the steering angle velocity threshold based on vehicle speed. At higher vehicle speeds, a lower steering angle velocity threshold triggers webbing take-up, while at lower vehicle speeds, a higher threshold is required. This resolves the contradiction by ensuring occupant protection at high speeds while preventing unnecessary webbing tension and discomfort during slip conditions at low speeds, where high steering angle velocity may occur without corresponding high lateral acceleration.
2Force
If the webbing tension is increased during high steering angle velocity, then inertial movement of occupant is reduced, but unnecessary tension is applied during slip conditions
Solution Approach 1:
The patent changes the parameter of webbing tension by controlling motor activation through speed-dependent steering angle velocity thresholds. Webbing tension is increased only when the threshold is exceeded at appropriate vehicle speeds, providing necessary restraint force during genuine cornering maneuvers while avoiding unnecessary tension during slip conditions where high steering angle velocity does not correspond to high lateral acceleration.
Solution Approach 2:
The system uses feedback by continuously monitoring vehicle speed and steering angle velocity to dynamically determine whether webbing take-up should be activated. This feedback mechanism ensures that webbing tension is applied only when both the steering angle velocity threshold is exceeded and the vehicle speed is appropriate, preventing unnecessary tension during slip conditions while maintaining protection during genuine cornering.
3Ease of operation
If a fixed steering angle velocity threshold is used, then the system is simple to operate, but it cannot differentiate between high-speed cornering and low-speed slip conditions
Solution Approach 1:
The patent applies dynamics by making the steering angle velocity threshold dynamic rather than fixed. The threshold automatically adjusts based on vehicle speed, being lower at high speeds and higher at low speeds. This resolves the contradiction by maintaining system simplicity in operation while achieving adaptability to differentiate between high-speed cornering and low-speed slip conditions, as the speed-dependent threshold automatically adapts to the current driving context.
Data Source
AI summary
A vehicle occupant restraint system is configured to, when a vehicle speed is higher than or equal to a vehicle speed threshold, a steering angle velocity is higher than or equal to a steering angle velocity threshold set for each vehicle speed, and an estimated lateral acceleration is higher than or equal to an acceleration threshold, drive a retractor motor. The steering angle velocity threshold is as a condition to drive the retractor motor. Therefore, by setting an appropriate steering angle velocity threshold according to an amount of movement of an occupant with inertia in a vehicle width direction, the vehicle occupant restraint system is able to take up a webbing when the occupant is estimated to move with inertia by a relatively large amount in the vehicle width direction. The amount of movement with inertia varies for each vehicle speed even at the same steering angle velocity.