Force-Sensing Resistors Calibration for Touch Detection

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Solution Overview

Problem

Existing touch-sensitive display technologies in portable electronic devices face challenges in accurately detecting touch locations and providing reliable tactile feedback due to limitations in force sensing and calibration methods, leading to potential inaccuracies and inefficiencies in user interaction.

Innovation Solution

The method involves using force-sensing resistors to detect touches on a touch-sensitive display, calibrating the resistors by adjusting their gain based on the touch location, and employing piezoelectric actuators to provide tactile feedback by modulating force applied to the display, ensuring accurate force measurement and user interaction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If force sensors are used to detect touch location, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvetouch location detection accuracyVSAvoidsensor array complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The display surface is divided into multiple regions, each with its own force sensor. This segmentation allows independent calibration and optimization of each sensor's performance while maintaining overall system functionality. The force sensors are distributed across the display surface to provide localized measurement capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The force sensors serve multiple functions: detecting touch location, measuring applied force magnitude, and providing calibration data for the display system. This multi-functionality reduces the need for separate specialized components, thereby managing device complexity while improving measurement precision.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Manufacturing precision

If calibration is performed manually, then manufacturing precision is improved, but productivity decreases

Engineering Contradiction:

Improvesensor calibration accuracyVSAvoiddevice assembly speed

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The system performs preliminary calibration actions automatically during the manufacturing process. Calibration data is captured and stored before the device reaches the end user, eliminating the need for manual calibration procedures during assembly. This preliminary automated calibration improves both manufacturing precision and productivity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The display system performs self-calibration using built-in force sensors and processing circuitry. The system automatically adjusts calibration parameters without requiring external manual intervention, thereby maintaining high calibration accuracy while significantly increasing assembly speed and productivity.

Inventive Principle:

Principle #25Self-service

3Measurement precision

If multiple force sensors are used, then measurement precision is improved, but loss of energy increases

Engineering Contradiction:

Improveforce sensing accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The force sensors operate in a periodic manner, activating only when touch events are detected or during scheduled calibration intervals. This periodic operation significantly reduces energy consumption compared to continuous monitoring, while maintaining the measurement precision required for accurate touch detection and force sensing.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system replaces continuous mechanical force sensing with intermittent electronic measurement. Instead of continuously monitoring all sensors, the system uses electronic signal processing to detect and measure force only when necessary, reducing energy consumption while preserving measurement precision through targeted sensing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 approach enhances the accuracy of touch location detection and provides effective tactile feedback, improving user interaction by compensating for changes in resistance over time, temperature, and humidity, thus enhancing the overall performance of portable electronic devices with touch-sensitive displays.

Implementation Method 1

receiving signals from force-sensing resistors... determining a location of the touch... calibrating the force-sensing resistors

Methodology Applied

Scientific EffectPiezoresistive Effect: Piezoresistive Effect

Implementation Method 2

employing piezoelectric actuators to provide tactile feedback by modulating force applied to the display

Methodology Applied

Scientific EffectPiezoelectric Effect: Piezoelectric Effect

Data Source

PatentEP2320309B1Portable electronic device including touch-sensitive display and method of controlling same

Publication Date: 2014.02.12 BLACKBERRY LTD

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AI summary

A method includes receiving signals from force-sensing resistors, detecting a touch on a touch-sensitive display and determining a location of the touch, receiving, from force-sensing resistors, signals related to the touch, and calibrating the force-sensing resistors by adjusting the gain for a first force-sensing resistor, of the force-sensing resistors, based on at least the signals and the location of the touch.