Capacitive Sensor Network for Pressure and Shear Stress Detection
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Solution Overview
Problem
Existing sensor systems for measuring pressure forces, particularly in applications like shoe soles, face challenges in achieving high spatial resolution with a low thickness and high flexibility while accurately distinguishing between compression and shear forces, and require a large number of electrical connections, which complicates manufacturing and increases the risk of electrical faults.
Innovation Solution
A sensor network system using a thin sheet of elastically deformable dielectric material with capacitive sensors arranged in a configuration that allows for reduced electrical connections, featuring electrodes printed on flexible insulating materials, and a measurement system that can differentiate between normal pressure and shear forces by analyzing variations in electrical capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of capacitive pressure sensors are integrated to manufacture a sensor network with high spatial resolution, then measurement precision is improved, but device complexity increases due to the greater number of electrical connections required
Solution Approach 1:
The patent combines multiple sensing functions (normal pressure sensing and shear force sensing) into a single capacitive sensor unit. By configuring electrodes in a specific pattern where the same capacitor can detect both normal pressure (through thickness variation) and shear forces (through surface area variation), the system reduces the number of separate sensors and their corresponding electrical connections while maintaining high spatial resolution
Solution Approach 2:
The capacitive sensor is designed to perform multiple functions simultaneously - it can measure both normal pressure forces and shear forces using the same electrode configuration and capacitance measurement. This multi-functionality eliminates the need for separate sensor arrays for different force types, thereby reducing electrical connection requirements while achieving comprehensive force measurement with high spatial resolution
2Reliability
If a rigid printed circuit substrate with multi-level electrical tracks is used to support capacitive sensors, then electrical connection reliability is improved, but adaptability decreases due to inability to conform to flexible surfaces like shoe soles
Solution Approach 1:
The patent employs flexible thin film substrates instead of rigid printed circuit boards to support the capacitive sensor electrodes. This flexible substrate can conform to curved surfaces such as shoe soles while maintaining electrical connectivity. The thin film structure provides both the mechanical flexibility needed for adaptability and sufficient electrical conductivity for reliable signal transmission
Solution Approach 2:
The sensor system is designed with dynamic characteristics that allow it to adapt to deformation. The flexible substrate and electrode configuration enable the sensor network to maintain functional integrity during bending and stretching, transforming the static rigid structure into a dynamic flexible system that can accommodate various surface geometries while preserving electrical connections
3Length of moving object
If the dielectric material is made very thin to reduce sensor thickness, then device compactness is improved, but manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The patent incorporates alignment marks and positioning features in the electrode configuration that are created during the manufacturing process. These preliminary positioning elements guide the subsequent assembly steps, ensuring that even very thin dielectric layers can be assembled with adequate precision. The electrode patterns themselves are designed with built-in alignment features that facilitate accurate positioning during manufacturing
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 system achieves high spatial resolution pressure force measurements with reduced electrical connections, maintaining flexibility and accuracy in distinguishing between compression and shear forces, and is suitable for applications in medical, sports, and recreational fields.
Implementation Method 1
The electrical capacitance of a capacitive sensor is given by the formula of a capacitor between two plates: C=ε.S/L where C represents the electrical capacitance of the capacitive sensor, S the surface of the facing electrodes, L the distance between the two electrodes and ε the dielectric constant of the material between the electrodes. Under the effect of a normal pressure force, the variation in thickness L of the dielectric material produces an inversely proportional variation in the electrical capacitance C of the sensor.
Implementation Method 2
Under the effect of a shearing force, a variation in the surface S of the facing electrodes produces a proportional variation in the electrical capacitance of the sensor.
Implementation Method 3
a sheet of elastically deformable dielectric material in compression and in shear
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
The present invention relates to a system and to a process for manufacturing a system comprising a network of sensors including a sheet of dielectric material that is elastically deformable under compressive and shear stress, each cell (20) of the network comprising a first capacitive sensor (10) for sensing normal pressure in a first direction (Z), a second capacitive sensor (30) for sensing sheer stress in a second direction (X) and a third capacitive sensor (50) for sensing sheer stress in a third direction (Y). According to the invention, each capacitive sensor (10, 30, 50) comprises a first electrode (1, 3, 5) fixed to the first side of the sheet of dielectric material and a second electrode (2, 4, 6) fixed to the second side of the sheet of dielectric material, said first electrodes (1, 3, 5) of the capacitive sensors of a given cell (20) being connected in series to a first electrically conductive track (11) connecting a row of cells of the network of sensors.