Capacitive Input Surface Layout for Uniform Press Detection
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Solution Overview
Problem
Tactile force sensing devices fail to determine the presence of a pressing operation on a sensor operating surface with uniform criteria when the hardness of the surface is non-uniform, leading to inconsistent detection based on varying material properties.
Innovation Solution
An input device with a foam layer having regions of differing hardnesses and detection electrodes of varying areas, where the larger area electrodes compensate for displacement differences due to varying foam hardness, ensuring consistent electrostatic capacitance values for uniform detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a tactile force sensing device uses a non-uniform hardness sensor operating surface, then the sensor can provide varied tactile feedback, but it becomes impossible to determine pressing operations using fixed detection criteria
Solution Approach 1:
The patent applies local quality by making each detection electrode have a specific area tailored to its local position on the sensor operating surface. The electrode area is determined based on the displacement characteristics of that particular region, allowing each local area to be optimized for its specific mechanical properties while maintaining uniform detection thresholds across the entire surface.
Solution Approach 2:
The patent changes the parameter of detection electrode area to compensate for variations in foam layer hardness. By adjusting the electrode area parameter according to the displacement characteristics of different regions, the system maintains consistent electrostatic capacitance values for pressing operations across the non-uniform surface.
2Measurement precision
If the detection electrode area is increased to compensate for larger displacement in softer foam regions, then detection consistency is improved, but the device complexity increases
Solution Approach 1:
The patent applies preliminary action by determining the area of each detection electrode in advance, based on predetermined displacement characteristics of the foam layer at different positions. This pre-planned configuration allows the system to achieve uniform detection thresholds without requiring real-time adjustments or complex control algorithms.
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
Enables consistent detection of pressing operations across varying hardness regions using a common threshold, maintaining consistent tactile sensation and accurate detection regardless of foam layer hardness, without requiring threshold adjustments.
Implementation Method 1
the capacitive sensing unit detects a capacitance of each capacitor of the plurality of capacitors that varies according to an external force applied to the second electrode plate
Data Source
AI summary
An input device includes an input section having an operating surface configured to be operated by an manipulating body, and a plurality of detection electrodes provided on a back side of the operating surface, wherein the input section includes portions where displacements with respect to a pressing operation on the operating surface by the manipulating body with a predetermined pressing force differ depending on positions on the operating surface, and the plurality of detection electrodes have a smaller area as a displacement in a case where the pressing operation performed with the predetermined pressing force on the operating surface at pressing positions overlapping the plurality of detection electrodes in a plan view becomes larger.