Vehicle Seat Strain Gage Layout for Accurate Occupant Detection
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Solution Overview
Problem
Motor vehicle seat sensors for detecting seat occupation and occupant posture are unreliable and prone to malfunction.
Innovation Solution
A motor vehicle seat with a strain gage maintained under tension, using a flexible electrically conductive elastomer arranged in a grid pattern on the seat cushion, backrest, and headrest, secured by non-flexible elements to reduce hysteresis and enhance accuracy, along with a method to detect malfunctions by comparing electrical currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a strain element is used to detect force on the motor vehicle seat, then force detection capability is provided, but hysteresis occurs causing measurement errors
Solution Approach 1:
The strain element is pretensioned during installation to a predetermined tension level, establishing a preliminary stressed state. This preliminary action ensures the strain element operates in its linear elastic range during normal use, reducing hysteresis effects and improving measurement accuracy and reliability.
Solution Approach 2:
The patent changes the physical state of the strain element by applying a specific pretension force, transforming it from an unstressed state to a pre-stressed state. This parameter change optimizes the strain element's mechanical properties, reducing hysteresis and improving measurement consistency.
2Measurement precision
If multiple strain elements are arranged in a grid pattern to detect force magnitude and location, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The strain gage is divided into multiple discrete strain elements arranged in a grid pattern. Each strain element independently measures force at its location, and the combined data provides both magnitude and location information. This segmentation enables precise force mapping across the seat surface.
Solution Approach 2:
The strain elements are arranged in a two-dimensional grid pattern across the seat surface, adding spatial distribution capability. This dimensional arrangement transforms single-point measurement into area-wide force detection, enabling location determination in addition to magnitude measurement.
3Measurement precision
If the strain element is maintained under tension to reduce hysteresis, then measurement accuracy is improved, but the strain gage requires additional securing mechanisms
Solution Approach 1:
The strain element is pretensioned during the installation process as a preliminary action. This initial tensioning is performed once during setup, and the strain gage is then secured in this pre-stressed state using simple securing elements, eliminating the need for complex continuous adjustment mechanisms.
Solution Approach 2:
The patent uses identical strain elements with standardized securing mechanisms across multiple measurement points. This standardization allows for replicated, simple securing solutions rather than requiring unique complex mechanisms for each strain element.
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
The solution improves the accuracy of force detection and location measurement, reduces measurement errors, and allows for early detection of strain gage malfunctions, even when the seat is unloaded.
Implementation Method 1
a strain gage connected to the padding and including a strain element to detect a force acting on the motor vehicle seat
Implementation Method 2
The elastomer may, for example, be electrically conductive on account of the use of graphite
Data Source
AI summary
A motor vehicle seat includes a seat cushion, a backrest connected to the seat cushion, a headrest connected to the backrest, a padding arranged on at least one of the seat cushion, the backrest, and the headrest, and a strain gage connected to the padding and including a strain element to detect a load acting on the motor vehicle seat. The strain element is maintained mechanically under tension.