Piezoelectric Touchscreen Haptics via Moiré Fringes
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Solution Overview
Problem
Conventional haptic vibration systems in mobile devices are bulky, energy-intensive, and lack localized feedback, making them inefficient for providing user-perceptible and spatially precise tactile experiences on touchscreens.
Innovation Solution
A touchscreen system utilizing piezoelectric transducers arranged in specific configurations to generate localized haptic excitations through Moiré fringes, allowing for higher frequency operation and more efficient energy use by employing beating frequencies and modulation techniques to create perceivable vibrations without directly driving transducers at human-perceptible frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional rotary mass or linear resonant actuators are used to generate haptic excitations, then user feedback can be provided, but the devices become bulky and consume relatively large amounts of energy
Solution Approach 1:
The patent replaces conventional mechanical haptic actuators (rotary mass or linear resonant actuators) with piezoelectric transducers that generate bending waves directly on the touchscreen panel. This substitution eliminates bulky mechanical components while maintaining haptic feedback functionality, thereby reducing both device volume and energy consumption.
Solution Approach 2:
The patent changes the operating parameters by using high-frequency excitations (above human audible range) that are inaudible but perceptible through bone conduction and skin vibration. This parameter change allows for more efficient energy use and smaller transducer sizes compared to conventional low-frequency mechanical actuators.
2Manufacturing precision
If conventional vibration systems are used, then haptic feedback can be provided, but the vibrations are non-localised and cannot provide spatially precise tactile feedback
Solution Approach 1:
The patent segments the haptic feedback system by using multiple piezoelectric transducers distributed across the touchscreen panel, each capable of independent control. This segmentation enables localized haptic feedback at specific touch positions while maintaining overall system simplicity through the use of standard piezoelectric materials and straightforward control electronics.
Solution Approach 2:
The patent implements local quality by enabling each region of the touchscreen to generate haptic excitations independently based on local touch events. The system applies excitations locally at the touched position rather than generating global vibrations, achieving spatially precise tactile feedback without requiring complex mechanical structures.
3Manufacturing precision
If piezoelectric transducers are driven at high frequencies, then shorter wavelengths and improved spatial resolution are achieved, but the frequencies are above the range perceptible by human skin
Solution Approach 1:
The patent uses bone conduction as an intermediary mechanism to transmit high-frequency vibrations from the touchscreen panel through the user's skull to the inner ear, where they are perceptible. This intermediary pathway allows high-frequency excitations (which provide superior spatial resolution) to be perceived by humans without requiring the frequencies to be within the direct skin perception range.
Solution Approach 2:
The patent changes the perception parameter by utilizing bone conduction and internal vibration perception rather than relying solely on external skin vibration. This parameter change enables perception of high-frequency excitations that would otherwise be inaudible and imperceptible to human skin, thereby achieving both high spatial resolution and human perceptibility.
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 system achieves localized and efficient haptic feedback with reduced energy consumption, enabling thinner, more compact designs and improved user experience by leveraging high-frequency piezoelectric transducers and advanced signal processing to modulate vibrations effectively.
Implementation Method 1
one or more first piezoelectric transducers arranged to generate excitations in the touchscreen panel
Implementation Method 2
a panel capable of supporting bending waves... a plurality of vibration exciters coupled to the panel to apply bending waves to the panel
Implementation Method 3
signal processing means arranged to apply signals to the vibration exciters so as to steer bending waves applied to the panel by the plurality of vibration exciters whereby the amplitude of the applied bending waves is maximised at the sensing area touched by the user
Data Source
AI summary
A touchscreen system for generating localised haptic excitations includes a touchscreen panel for measuring force and/or capacitance. The touchscreen system includes one or more first piezoelectric transducers arranged to generate excitations in the touchscreen panel along a first line. The touchscreen system includes one or more second piezoelectric transducers arranged to generate excitations in the touchscreen panel along a second line which is inclined to the first line at an angle. The touchscreen system includes a pressure and/or capacitance sensing module connected to the touchscreen panel and configured to measure a force and/or capacitance from the touchscreen panel. The touchscreen system includes a haptic driving module connected to the first and second piezoelectric transducers and configured to generate user perceptible haptic excitation by driving the first piezoelectric transducers at a first frequency, and driving the second piezoelectric transducers at a second frequency, wherein the difference of the first and second frequencies is a beating frequency, and the beating frequency is a frequency perceptible by human skin, or by driving the first and second piezoelectric transducers at a carrier frequency which is modulated at a modulation frequency which is a frequency perceptible by human skin. The angle is selected to cause Moiré fringes between excitations generated along the first line and the second line.