Acoustic Touch Detection Using Natural Frequency Analysis
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Solution Overview
Problem
Existing touch-sensitive devices using acoustic signals struggle to reliably detect sustained contacts, as they cannot differentiate between touch and hold actions due to the absence of vibrations, and are energy-intensive, making them unsuitable for battery-powered devices and multi-touch scenarios.
Innovation Solution
A method combining passive and active acoustic technologies to determine touch event location and duration by analyzing signals at or near natural frequencies of the object, using an exciter to generate bending waves sensed by passive sensors, which reduces energy consumption and allows for reliable hold detection and multi-touch functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If passive acoustic technology is used to detect touch events, then touch location can be determined, but sustained contact (hold action) cannot be detected because no vibrations are generated during hold action
Solution Approach 1:
The patent combines passive acoustic technology (for touch location) with active acoustic technology (for sustained contact detection) into a unified system. The passive sensors detect impact sounds for location, while the same sensors simultaneously monitor for perturbations in active acoustic signals to detect hold actions, merging two detection modes into one integrated approach.
Solution Approach 2:
The patent introduces active acoustic signals as an intermediary medium to enable sustained contact detection. By emitting continuous acoustic signals and monitoring their interaction with the touch surface, the system creates a mediator that reveals information about hold actions without directly relying on vibrations from the user's finger.
2Reliability
If active acoustic technology is used to detect sustained contact, then hold action detection is enabled, but energy consumption increases making it unsuitable for battery-powered devices
Solution Approach 1:
The patent employs periodic emission of active acoustic signals rather than continuous emission. The exciter generates acoustic signals at specific intervals, and the system monitors for perturbations during these periodic windows. This periodic approach maintains the ability to detect sustained contacts while significantly reducing overall energy consumption compared to continuous active acoustic emission.
3Reliability
If signal reflections are suppressed to improve hold detection accuracy, then detection reliability improves, but device complexity and implementation burden increase
Solution Approach 1:
The patent converts the potentially harmful effect of signal reflections into a beneficial feature. Rather than suppressing reflections through complex arrangements, the system analyzes the active acoustic signals in a way that exploits reflection patterns to identify sustained contacts. The reflection characteristics become additional information sources that aid detection rather than obstacles to be eliminated.
4Adaptability or versatility
If multiple natural frequencies are analyzed for touch detection, then multi-touch scenarios can be detected, but signal processing complexity increases
Solution Approach 1:
The patent segments the frequency analysis into distinct natural frequency components of the touch surface. By identifying and analyzing specific resonant frequencies separately, the system can detect multiple simultaneous touches at different locations. Each touch event perturbs the acoustic signals at characteristic frequencies, and segmenting the analysis by frequency allows the system to track multiple independent touch events without overwhelming complexity.
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 enables efficient, low-energy detection of sustained contacts and multi-touch events by leveraging natural frequencies, improving reliability and reducing energy consumption, and is not limited by signal reflections, thus enhancing touch-sensitive device performance.
Implementation Method 1
analyzing the signal generated at or close to N natural frequencies of the object
Implementation Method 2
By creating vibrations in the object whether by impact or friction, like during a drag action, the user actually generates the vibration signals used for the localization of the touch event
Data Source
AI summary
The invention relates to a method for determining the location and duration of a sustained contact of a touch event performed by a user on a surface of an object comprising the steps of: a) determining the location of the touch event, in particular based on an acoustic signal generated by the impact of the touch on the surface, and b) determining the duration of the touch event based on a perturbation of a signal generated in or on the object by a transducer characterized in that step b) comprises analyzing the signal generated at or close to N natural frequencies of the object, with N being one or more. The analysis close to the natural frequencies allows the reliable determination of not only the location of a touch event but also whether the user continues to interact with the surface of the object which is due to the important damping of the generated signal in the presence of the touch. The invention also relates to a touch sensitive device configured to carry out the method.