Capacitive Sensor Array Force Detection via Flexible Overlay
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Solution Overview
Problem
Current capacitive touch-sensing technologies face challenges in accurately measuring force applied to touch-sensing surfaces, particularly in distinguishing between conductive and non-conductive objects and in resolving multiple touches, due to limitations in capacitance measurement and sensor array design.
Innovation Solution
A flexible capacitive sensor array with a highly flexible overlay, such as PMMA, is used to determine force magnitude by correlating capacitance measurements with a 3D lookup table, allowing for accurate detection of force and displacement through interpolation and extrapolation, and distinguishing between conductive and non-conductive objects based on capacitance profile ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitive touch-sensing technologies are used, then the device structure remains simple, but the ability to accurately measure force and distinguish between conductive and non-conductive objects deteriorates
Solution Approach 1:
The sensor array is divided into multiple independently addressable sensor elements arranged in a matrix pattern. Each sensor element can be individually controlled and read, allowing for spatial resolution of touch locations and force measurements across different regions of the touch surface.
Solution Approach 2:
The invention transitions from traditional single-axis or two-axis touch detection to three-dimensional sensing by incorporating force magnitude measurement along the Z-axis. This is achieved through measuring capacitance changes caused by deflection of the flexible overlay, adding a vertical dimension to the sensing capabilities.
2Measurement precision
If capacitance measurement methods are used to detect touch, then the sensing mechanism remains simple, but the ability to resolve multiple simultaneous touches deteriorates
Solution Approach 1:
The sensor array is segmented into multiple independently addressable sensor elements arranged in a matrix pattern. Each sensor element can be individually controlled and read, allowing for spatial resolution of touch locations and force measurements across different regions of the touch surface.
Solution Approach 2:
The system uses capacitance measurements from multiple sensor elements to determine touch location and force magnitude. The flexible overlay's deflection creates measurable capacitance changes that provide feedback about the applied force, enabling the system to resolve multiple simultaneous touches by analyzing the spatial distribution of capacitance changes.
3Measurement precision
If conventional touch-sensing surfaces are used, then the manufacturing process remains simple, but the sensitivity and accuracy of force detection deteriorates
Solution Approach 1:
The invention uses a flexible overlay made of thin film material that can deflect in response to applied force. This flexible structure is integrated with the sensor array, allowing the overlay to move closer to or farther from the sensor elements based on the magnitude of applied force, thereby modulating the capacitance signal.
Solution Approach 2:
The touch-sensing surface is constructed as a composite structure combining the flexible overlay material with the sensor array substrate. This composite design allows the flexible overlay to transmit mechanical force to the sensor elements while maintaining electrical isolation where needed, enabling force-sensitive capacitance measurements.
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 enables precise measurement of force applied to touch-sensing surfaces, effectively differentiating between conductive and non-conductive objects and resolving multiple touches, enhancing user interaction accuracy and sensitivity.
Implementation Method 1
determine a magnitude of force applied to a touch-sensing surface by a contact, based on a set of capacitance measurements from the capacitive sensor array
Implementation Method 2
A flexible capacitive sensor array with a highly flexible overlay, such as PMMA, is used to determine force magnitude by correlating capacitance measurements
Data Source
AI summary
A method for detecting a magnitude of force applied to a capacitive sensor array may comprise receiving a plurality of capacitance measurements affected by a contact at a touch-sensing surface, and determining a magnitude of a force applied to the touch-sensing surface at a location of the contact based on the location of the contact and a capacitance measurement of the first plurality of capacitance measurements.