Haptic Waveform Compensation for LRA Oscillation
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Solution Overview
Problem
Haptic feedback in mobile devices using linear resonant actuators is limited by post-playback oscillations and part-to-part variations, which constrain the design of haptic effects and user experience.
Innovation Solution
A method and system that determine the resonant frequency of a haptic transducer and modify the haptic playback waveform to shift the notch frequency to match the resonant frequency, minimizing post-playback oscillations by applying frequency-domain haptic waveform compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the LRA is designed to operate at resonant frequency to achieve maximum vibrational acceleration, then the haptic feedback intensity is improved, but post-playback oscillations increase and fall time increases
Solution Approach 1:
The patent applies preliminary anti-action by introducing a pre-calculated compensation waveform that generates forces opposing the expected post-playback oscillations. This compensation waveform is added to the original haptic waveform before playback, proactively canceling out the resonant oscillations that would otherwise occur after the stimulus ends, thereby reducing ringing without sacrificing the intensity of the primary haptic effect.
Solution Approach 2:
The patent employs feedback by measuring the actual resonant frequency of the LRA through frequency sweep or impedance analysis, then using this measured value to adjust the compensation waveform parameters. This closed-loop approach ensures the compensation is tailored to the specific LRA unit, accounting for manufacturing variations and ensuring optimal cancellation of post-playback oscillations for each device.
2Device complexity
If a fixed haptic waveform is used across different LRA parts, then the device complexity is reduced, but part-to-part variations cause inconsistent haptic performance
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the compensation waveform parameters (particularly the notch frequency and compensation amplitude) based on the measured resonant frequency of each LRA unit. This allows the system to adapt to manufacturing variations in resonant frequency while maintaining consistent haptic performance across different parts, without requiring completely custom waveforms for each unit.
Solution Approach 2:
The patent implements dynamics by transitioning from a static, fixed haptic waveform to a dynamic waveform that is automatically adjusted based on real-time measurements of the LRA's resonant frequency. The system measures the actual resonant frequency and dynamically modifies the compensation waveform parameters accordingly, enabling each LRA unit to operate optimally despite manufacturing variations.
3Ease of manufacture
If the resonant frequency of the LRA varies due to manufacturing tolerances, then the ease of manufacture is improved, but the precision of haptic feedback decreases
Solution Approach 1:
The patent applies self-service by enabling each LRA unit to automatically characterize its own resonant frequency through frequency sweep or impedance analysis performed by the device's processor. Each unit self-calibrates by measuring its unique resonant frequency and automatically generating the appropriate compensation waveform parameters, eliminating the need for manual calibration or factory programming and ensuring precise haptic feedback despite manufacturing variations.
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 effectively reduces post-playback oscillations, ensuring a more controlled and consistent haptic experience by aligning the notch frequency with the resonant frequency of the haptic transducer, thereby enhancing the sharpness and duration of haptic stimuli.
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
determining whether a frequency response of the haptic playback waveform has a notch with a notch frequency at approximately a resonant frequency of the haptic transducer and, responsive to the notch frequency differing from the resonant frequency, modifying the haptic playback waveform for playback to the haptic transducer by shifting the notch frequency to approximately the resonant frequency
Data Source
AI summary
A method for minimizing post-playback oscillation during playback of a haptic playback waveform to a haptic transducer may include determining whether a frequency response of the haptic playback waveform has a notch with a notch frequency at approximately a resonant frequency of the haptic transducer and, responsive to the notch frequency differing from the resonant frequency, modifying the haptic playback waveform for playback to the haptic transducer by shifting the notch frequency to approximately the resonant frequency.