Motorized Seatbelt Retractor Low-Friction Detection
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Solution Overview
Problem
Existing motorized retractors for vehicle safety belts do not effectively enhance occupant safety during difficult driving conditions, such as low friction road conditions, by immediately increasing restraining forces or frequently changing them, which can lead to unstable belt forces and inadequate warning for drivers, especially inexperienced ones.
Innovation Solution
A method that detects low friction road conditions using ABS and deceleration sensors, and triggers the motorized retractor to apply three distinct restraining forces based on predetermined brake pressure thresholds, with gradual increases in force levels to warn and secure the occupant, preventing frequent and unnecessary force changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motorized retractor immediately increases restraining forces when detecting low friction road conditions, then the occupant safety is improved, but the belt forces become unstable and cause panic reactions
Solution Approach 1:
The patent applies dynamics by implementing a multi-stage restraining force system that adapts to different braking situations. The motorized retractor transitions through three distinct force levels (first, second, and third restraining forces) based on braking behavior detection, allowing the system to dynamically adjust rather than apply immediate maximum force. This dynamic approach stabilizes belt forces while maintaining occupant safety.
Solution Approach 2:
The system applies preliminary action by first detecting low friction road conditions and monitoring braking behavior before escalating restraining forces. The control unit initially applies a first restraining force, then only increases to second and third forces if specific braking threshold violations occur. This preliminary detection and gradual escalation prevents panic reactions while ensuring safety.
2Speed
If the motorized retractor frequently changes restraining forces to respond to braking situations, then the response to dangerous situations is improved, but the belt forces become unstable and reduce occupant comfort
Solution Approach 1:
The patent implements periodic action through a structured three-stage force application system with predetermined thresholds. Instead of continuous force adjustments, the system applies forces in distinct periodic stages (first restraining force, second restraining force, third restraining force) triggered by specific braking behavior patterns. This periodic structure maintains stability while ensuring timely response to dangerous situations.
3Reliability
If the motorized retractor applies high restraining forces to secure the occupant, then the occupant safety is improved, but the driver experiences panic reactions due to sudden force application
Solution Approach 1:
The system applies beforehand cushioning by first detecting low friction road conditions and monitoring braking behavior before applying higher restraining forces. The control unit initially applies a moderate first restraining force, and only escalates to stronger second and third forces if the driver fails to respond appropriately to the initial warning. This cushioning approach prevents panic reactions while maintaining safety.
4Measurement precision
If the motorized retractor uses multiple sensor signals and complex algorithms to detect low friction conditions, then the detection accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent applies universality by using a brake pressure sensor that serves multiple functions: it detects both the magnitude of braking force applied and the duration of braking, enabling low friction condition detection without requiring separate dedicated sensors for each parameter. The control unit processes brake pressure signals to determine both instantaneous and temporal characteristics, reducing overall system complexity while maintaining detection accuracy.
Data Source
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AI summary
The present invention relates to a method for triggering a motorized retractor for a safety belt system of a vehicle, including: -detecting a low friction road condition (LowMu) when an ABS-sensor generates a signal (ABS) and a longitudinal deceleration sensor senses a deceleration (Ax) which is lower than a predetermined value, or a brake pressure sensor detects a brake pressure (BRP), which exceeds a predetermined value and a longitudinal deceleration sensor senses a deceleration (Ax) which is lower than a predetermined value, and -triggering the motorized retractor when the low friction road condition (LowMu) is detected and the brake pressure (BRP) sensed by a brake pressure sensor exceeds or falls below a predetermined threshold (Th1,Th2,Th3) to apply at least one different restraining force (L1,L2,L3) in the safety belt system.