Drive Waveform Adjustments for Linear Resonant Actuator After-Ringing
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Solution Overview
Problem
Haptic feedback in mobile devices using linear resonant actuators (LRAs) faces challenges due to variations in resonant frequency among units, leading to suboptimal drive waveforms that result in residual after-ringing vibrations when waveforms calibrated for one LRA are applied to another with a different resonant frequency, making high-volume manufacturing impractical.
Innovation Solution
A method and system that generate an electrical drive waveform for a target actuator by adjusting a reference drive waveform based on the difference in resonant frequency, using a digital signal processor to apply time and amplitude adjustments, ensuring optimal haptic effects without after-ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a reference drive waveform calibrated for one LRA is applied to another LRA with a different resonant frequency, then manufacturing efficiency is improved, but after-ringing vibrations occur and haptic quality deteriorates
Solution Approach 1:
The patent implements dynamic waveform generation by adjusting the reference waveform parameters (time scaling factor and amplitude scaling factor) based on the target LRA's resonant frequency. This allows the drive waveform to adapt dynamically to each LRA's specific characteristics, eliminating after-ringing while maintaining efficient manufacturing through automated parameter calculation.
Solution Approach 2:
The patent changes key parameters of the drive waveform including time scaling factor (AT), amplitude scaling factor (AA), and frequency content based on the target LRA's resonant frequency. These parameter adjustments transform the fixed reference waveform into a customized waveform that matches each LRA's resonant characteristics, preventing residual vibrations.
2Reliability
If individual LRA resonant frequency measurement and calibration is performed for each unit, then haptic feedback quality is improved, but manufacturing complexity and time increase
Solution Approach 1:
The patent performs preliminary measurement of each LRA's resonant frequency during manufacturing and stores it for later use. This preliminary action enables the system to retrieve the stored resonant frequency and automatically calculate the appropriate waveform parameters without requiring complex real-time adjustment mechanisms, simplifying the overall manufacturing process.
Solution Approach 2:
The patent uses a reference drive waveform as a template and applies parameter transformations (time scaling and amplitude scaling) to create customized waveforms for each LRA. This copying approach with parameter modification is simpler than creating entirely new waveforms for each unit, reducing manufacturing complexity while maintaining quality.
3Reliability
If the drive waveform is optimized for each individual LRA to eliminate after-ringing, then haptic feedback consistency is improved, but the time and resources required for waveform calibration increase
Solution Approach 1:
The patent replaces complex mechanical trial-and-error waveform tuning with automated digital signal processing. The system uses mathematical formulas to calculate the optimal time scaling factor (AT) and amplitude scaling factor (AA) based on the measured resonant frequency, substituting manual calibration time with efficient computational processing.
Solution Approach 2:
The system performs self-calibration by automatically measuring each LRA's resonant frequency, calculating the appropriate waveform parameters, and generating the optimized drive waveform without requiring external intervention. This self-service approach eliminates time-consuming manual calibration while ensuring consistency.
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 ensures that each LRA receives a tailored drive waveform, minimizing after-ringing and enhancing the consistency and quality of haptic feedback across devices with varying resonant frequencies, thereby improving the manufacturing efficiency and user experience.
Implementation Method 1
One or more coils of wire may apply electromagnetic force to the magnets, moving the mass. Current applied to the one or more coils of wire may cause the mass to move with respect to its housing, and vibrate therein.
Implementation Method 2
Taken together, the mass and springs of an LRA form a mechanical resonant system. For a given drive voltage, the greatest mass vibration may be achieved when the drive oscillation frequency equals the mass-spring natural or resonant frequency.
Implementation Method 3
detecting movement of the mass by sensing the back-electromotive force (back-EMF), and adjusting the drive frequency to match the mass-spring natural resonant frequency.
Data Source
AI summary
A method may include generating an electrical drive waveform associated with a target actuator by stretching or compressing a reference drive waveform associated with a reference actuator in a time domain of the reference drive waveform in accordance with a time adjustment factor, wherein the time adjustment factor is determined based on a difference between a resonant frequency of the target actuator and a resonant frequency of the reference actuator. The same or another method may include generating an electrical drive waveform associated with a target actuator by increasing or decreasing an amplitude of a reference drive waveform associated with a reference actuator in accordance with an amplitude adjustment factor, wherein the amplitude adjustment factor is determined based on a difference between a resonant frequency of the target actuator and a resonant frequency of the reference actuator.