Force Sensor Units with Segmented Spacers for Curved Surfaces
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Solution Overview
Problem
Planar force sensor units face incorrect actuation due to external influences like mechanical stress, temperature changes, and pressure, especially when applied to non-flat surfaces, leading to permanent local stress and incorrect actuation in applications such as steering wheel rims and vehicle seats.
Innovation Solution
The design incorporates second spacer elements with lower mechanical resistance to compression, arranged at a distance from the first spacer elements, which are protected from unwanted compression, ensuring the conductor tracks are stretched even on curved surfaces, preventing unwanted contact between conductor tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the sensor unit is mounted on a curved surface under mechanical tension, then the sensor can be applied to non-flat surfaces like steering wheel rims, but the spacers experience permanent local compression leading to incorrect actuation
Solution Approach 1:
The conductor track pattern is subdivided into multiple contact areas by the spacer elements, creating independent sensing zones. This segmentation allows the sensor to maintain functionality across curved surfaces while reducing false actuation, as each segment responds independently to local pressure changes rather than the entire sensor being affected by global mechanical stress.
Solution Approach 2:
The patent applies different mechanical properties to different parts of the sensor structure. The spacers have varying heights and compression characteristics, with some spacers being more compliant than others. This local differentiation allows the sensor to adapt to curved surfaces in high-compression areas while maintaining stability in low-compression areas, preventing incorrect actuation.
2Length of stationary object
If the spacers are made smaller to reduce sensor thickness, then the sensor profile is minimized for aesthetic purposes, but the spacers become more susceptible to permanent compression from cover tension and temperature fluctuations
Solution Approach 1:
The sensor employs a composite structure combining multiple materials with different mechanical properties. The spacers are made from elastomeric materials with specific durometer ratings, while the carrier films use different elastomeric compositions. This material composite approach allows thin spacers to maintain sufficient mechanical resilience against compression from cover tension and temperature variations.
Solution Approach 2:
The patent varies key parameters of the spacer elements, including height, width, and material durometer, to optimize performance. By adjusting these parameters, the spacers can be made thin enough to minimize sensor profile while maintaining adequate compression resistance. The conductor track resistance values are also varied across different contact areas to compensate for differences in spacer compression characteristics.
3Measurement precision
If the conductor tracks are made more sensitive to detect subtle forces, then measurement precision is improved, but the sensor becomes more prone to incorrect actuation from external influences like temperature and pressure
Solution Approach 1:
The evaluation circuit analyzes resistance changes from multiple contact areas and uses this feedback to distinguish between genuine actuation and false signals caused by environmental factors. By comparing resistance patterns across multiple segmented contact areas, the system can identify and filter out incorrect actuation while maintaining high sensitivity to legitimate force application.
Solution Approach 2:
The sensor uses multiple contact areas with varying sensitivity thresholds. Some contact areas are designed to respond to lighter forces while others require greater pressure. This partial action approach allows the sensor to detect subtle forces in sensitive areas while requiring higher forces in areas more susceptible to false actuation from external influences like temperature and pressure changes.
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
This design effectively reduces incorrect actuation by maintaining the integrity of the sensor unit on curved surfaces, ensuring accurate actuation only when desired pressure is applied, thus enhancing the reliability of force and pressure sensor systems.
Implementation Method 1
elastically deformable spacers... The carrier films are elastically prestressed relative to each other by the spacers
Implementation Method 2
The conductor track patterns on the films are at least partially formed by resistive coatings exhibiting a predetermined electrical surface resistance. The position of an actuation and the resulting contact between the conductor tracks of the first and second carrier films can thus be determined from the resistance between these two conductor tracks.
Data Source
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AI summary
The invention relates to an extensive sensor unit for force and/or pressure sensor systems, comprising first and second insulating carrier films (1, 2), which are arranged one over the other and bear first and second conducting track patterns (3, 4) on their surfaces that face one another, between which conducting track patterns elastically deformable first spacing elements (5, 6, 7) for elastically preloading the carrier films are arranged. At least one of the conducting track patterns is divided by the first spacing elements into a plurality of contact regions, in which contact between the first and second conducting track patterns can be established when force is applied to at least one of the films. The conducting track patterns are formed partially by resistive coatings having specified electrical sheet resistance and have terminals for connecting to an evaluation circuit, which outputs an output signal in accordance with the position of the resistance values produced by compression of the first spacing elements. A number of second spacing elements (7) is arranged on at least one of the conducting tracks facing each other, which second spacing elements are arranged at a distance from each other and have less mechanical resistance to compression than the first spacing elements.