Capacitive Control Panel for Independent Touch and Force Sensing
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Solution Overview
Problem
Capacitive control panels face limitations due to binary sensitivity to mechanical force and increased complexity from combining capacitive touch and mechanical force sensing techniques, with force sensors being sensitive to both applied forces and nearby objects, leading to interference and reduced flexibility in user input responses.
Innovation Solution
Implementing a capacitive sensing system with separate force and touch sensors using mutual-capacitance techniques, where the force sensor electrodes are arranged to minimize sensitivity to proximity, allowing for independent measurement of force and touch inputs using the same capacitive sensing technology, reducing interference and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional mechanical switches are used for force sensing, then binary force detection is achieved, but analogue sensitivity to force magnitude is lost
Solution Approach 1:
The patent replaces conventional mechanical switches with a capacitive sensing system that uses electrical fields to detect both touch proximity and force magnitude. The capacitive sensor measures changes in capacitance caused by dielectric compression under applied force, enabling analogue force detection without mechanical moving parts.
2Adaptability or versatility
If both capacitive touch sensors and mechanical force sensors are combined, then both touch and force sensing capabilities are achieved, but control circuitry complexity increases
Solution Approach 1:
The patent implements a universal capacitive sensing system where a single capacitive sensor structure performs both touch detection and force magnitude measurement functions. By measuring capacitance changes and their rate of change, the system distinguishes between touch proximity and applied force without requiring separate sensor types or complex control circuitry.
3Measurement precision
If capacitive force sensors are used, then analogue force measurement is achieved, but sensitivity to nearby objects increases
Solution Approach 1:
The patent employs a feedback-based differentiation technique where the system measures both the capacitance value and its rate of change over time. By analyzing the temporal characteristics of capacitance changes, the system distinguishes between genuine force applications (which cause rapid capacitance changes) and proximity effects from nearby objects (which cause slower capacitance variations), effectively filtering out false readings.
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 a control panel with enhanced sensitivity to force magnitude and touch proximity, reducing false readings from nearby objects and simplifying the control circuitry, resulting in a more flexible and robust user interface.
Implementation Method 1
The capacitance between the lower and upper electrodes 26, 28 as measured by the capacitance measurement circuit 21 depends on the magnitude of their separation.
Implementation Method 2
The force compresses the dielectric material 24, and thus brings the lower and upper electrodes 26, 28 closer together.
Data Source
AI summary
A control panel for proximity and force sensing, includes a cover layer, a first electrode layer including a first force sensor electrode, a second force sensor electrode positioned in a second electrode layer or on a support layer, and a dielectric substrate at least a portion of which is compressible and is positioned between the first and second force sensor electrodes. The support layer is positioned to support at the vicinity of the second force sensor electrode support location so that compression of the dielectric substrate and the separation of the first and second force sensor electrodes depends on the magnitude of a force applied to the cover layer. Touch sensor electrodes are positioned on one or more of the electrode layers such that their capacitance depends on proximity of an object such as a finger. Controllers measure the capacitance of the force and touch sensor electrodes respectively and output force and touch proximity signals.