Force Sensing via Structure-Borne Sound Propagation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing force-sensitive input interfaces for smartphones require additional hardware or impose unnatural usage restrictions, limiting their usability and attractiveness to users and manufacturers.
Innovation Solution
A method and system that estimates force applied to a touchscreen using built-in sensors by emitting and receiving inaudible sound signals above 18 kHz, correlating the signals to determine the change in sound propagation, and computing the applied force without modifying the phone's hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional hardware sensors (capacitive or contact piezoelectric) are added to commodity phones for force sensing, then force-sensitive input capability is improved, but device cost and complexity increase
Solution Approach 1:
The patent makes the phone's existing speaker and microphone serve a dual purpose: their primary audio functions plus force sensing. The speaker emits ultrasonic sound waves and the microphone receives them, and when force is applied to the screen, it modulates these sound waves. This self-service approach eliminates the need for additional force sensing hardware while utilizing components already present in the device.
Solution Approach 2:
The speaker and microphone are made multi-functional by using them both for audio processing and force sensing. The same hardware components perform multiple roles: the speaker generates both audible and ultrasonic sound waves, while the microphone captures both voice and the modulated sound waves caused by screen deformation under applied force.
2Device complexity
If built-in sensors are used for force sensing without additional hardware, then device complexity is reduced, but sensing capability and reliability are limited
Solution Approach 1:
The patent employs mechanical vibration in the form of ultrasonic sound waves emitted by the speaker. These high-frequency vibrations travel through the phone's internal structure and are received by the microphone. When force is applied to the touchscreen, it causes deformation that modulates the vibration pattern of the sound waves, providing a reliable physical basis for force detection that is independent of software processing.
Solution Approach 2:
The patent replaces traditional mechanical force sensing hardware (piezoelectric sensors, capacitive sensors) with an acoustic field-based sensing mechanism. Instead of using mechanical or electrical sensors directly on the screen, the system uses sound wave propagation through the phone's structure, which is modulated by the mechanical deformation caused by applied force. This substitution achieves reliable force sensing without additional mechanical sensing components.
3Measurement precision
If ultrasonic sound signals (>18 kHz) are used for force sensing, then measurement precision is improved, but potential user annoyance increases
Solution Approach 1:
The patent changes the frequency parameter of the sound signal to ultrasonic ranges (>18 kHz). This parameter change serves two purposes: first, it provides sufficient resolution for detecting subtle screen deformations caused by applied force; second, it moves the operating frequency beyond the range of human hearing, thereby eliminating user annoyance while maintaining high measurement precision.
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
Provides a force-sensitive input interface for commodity phones without additional hardware, enhancing usability and user experience by accurately detecting force applied to the touchscreen and phone body, while being resistant to background noise and interference.
Implementation Method 1
emitting a sound signal from a speaker of the mobile device while a force is applied to the touchscreen; receiving the sound signal emitted from the speaker with a microphone in the mobile device
Implementation Method 2
Force sensing based on structure-borne sound propagation
Data Source
AI summary
ForcePhone is a novel system for enabling phones to recognize the force applied to their touchscreen and/or body. ForcePhone uses built-in sensors to measure the applied force via a physical property called structure-borne sound propagation. The phone plays an inaudible sound through the phone's speaker. When the phone is free to vibrate, the sound from the speaker easily travels through its body to the phone's microphone. When a force is applied to the phone, vibration is restricted and the sound traveling through the pathway is degraded. ForcePhone estimate the amount of applied force by monitoring the change in sound degradation.