Spatial, temporal, and thermal contributions to focusing contrast by time reversal in a cavity

Hudin, Charles; Lozada, José; Hayward, Vincent

doi:10.1016/j.jsv.2013.11.016

Cited by 11 publications

(3 citation statements)

References 27 publications

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“…The benefits brought by a long duration T can be minimal if it exceeds the attenuation time [12]. Besides, the design of repetition time Tr of focused field generation should take attenuation factors into account to avoid degradation in wave field contrast [18]. In the frequency domain, the bandwidth of emitted time-reversed signals E TR (ω) should result in a resolution cell comparable to a typical size of a fingertip.…”

Section: Design Tradeoffs In Realizing Localized Tactile Feedback Usi...mentioning

confidence: 99%

Improvements on focused tactile feedback using time reversal mirror

Huang,

2024

Health Monitoring of Structural and Biological Systems XVIII

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This paper discusses two improvements to localized tactile feedback on a transparent surface using time reversal mirror (TRM) of ultrasonic guided waves. A mock-up device comprising a glass plate of 150 × 200 × 1 mm 3 with a 12-element sparse piezoelectric actuator array bonded at the boundary of the plate is constructed together with driving electronics. The transfer function from each actuator to an arbitrary focus point is first recorded using a laser doppler vibrometer. The re-emission waveforms are then generated by convolving the time-reversed transfer function with a target signal to control the shape of the vibration at the focus point. The re-emitted waveforms are compressed to binary signals to improve the peak displacement of the focused wave field. The mock-up device obtains a peak amplitude of 19 μm on the plate with a peak-to-peak driving voltage of 150 V. Two improvements to the tactile feedback using ultrasonic TRM are described. First, the undesired conversion of ultrasonic vibration to audible spectra resulting from the coupling of the fingertip and the plate surface is investigated. The authors show that despite the inevitable frequency shift, the tone of the audible leakage can be controlled by the repetition period of the TRM. Second, the tactile feeling of a single-point focus of ultrasonic guided wave is acute and hard to detect due to its small resolution cell compared to the size of a fingertip. The authors propose a dual-point focus scheme, the distance of which is less than that of two-points discrimination, to enlarge the perceivable region without changing the spectra of the re-emission signals.

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Section: Design Tradeoffs In Realizing Localized Tactile Feedback Usi...mentioning

confidence: 99%

Improvements on focused tactile feedback using time reversal mirror

Huang,

2024

Health Monitoring of Structural and Biological Systems XVIII

View full text Add to dashboard Cite

show abstract

“…The temporal contrast is a measure of how concentrated (or compressed) in time the time-reversed signal is. It is calculated by measuring the energy ratio between the peak at the time of reversal t ¼ 0 and the rest of the signal in the temporal domain (Hudin et al, 2014). We will use two alternative measures of the temporal contrast, each is better suited to describe a particular characteristic of the temporal reversion, the root mean square (RMS) temporal contrast (TC RMS ) and the peak temporal contrast (TC peak ;Alberti et al, 2019).…”

Section: F Formulas and Definitionsmentioning

confidence: 99%

Time reversal focusing in the audible range using a tunable sonic crystal

Gomez

Spiousas

Eguía

2021

The Journal of the Acoustical Society of America

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Time reversal (TR) focusing of acoustical waves is a widely studied phenomenon that usually requires a chaotic cavity or disordered scattering medium to achieve spatial and frequency decorrelation of the acoustic field when using a single channel. On the other hand, sonic crystals were disregarded as scattering media for the TR process because of their periodic structure and previous results showing poor spatial focusing when compared to a disordered medium. In this paper, an experimental realization of a tunable sonic crystal, which can achieve single-channel TR focusing amplitudes in the audible range comparable to those obtained in a disordered scattering medium, is presented. Furthermore, the tunable nature of the system allows it to switch the time-reversed pulse on and off by changing its geometrical configuration. A robustness analysis with respect to the perturbations in the sonic crystal configurations is also presented, showing that the time-reversed pulses with high temporal and spatial contrasts are preserved only for configurations that are close to the original one.

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“…This implies an additional knowledge resulting from an identification procedure. One limitation is that the focus pattern and its transient are not controlled, and external parameters can mitigate the effects [24]. As a matter of fact, this brief overview shows that the two last techniques actually rely on similar devices, and so they could be combined.…”

Section: Introductionmentioning

confidence: 99%

Generating controlled localized stimulations on haptic displays by modal superimposition

Enferad

Giraud-Audine

Giraud

et al. 2019

Journal of Sound and Vibration

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In the field of tactile feedback, researchers try to generate localized stimulations on screens. Some solutions such as time reversal or phased array use vibration induced in the screen equipped with piezoelectric ceramics. We propose to use the modal basis to reproduce a specified velocity field on such devices. We explain the theory and propose a methodology to practically synthesize the voltages to achieved a controlled focusing in a given time. Experiments on a simple demonstrator are in good agreement with the theory for various velocity fields and a reduced number of modes.

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Spatial, temporal, and thermal contributions to focusing contrast by time reversal in a cavity

Cited by 11 publications

References 27 publications

Improvements on focused tactile feedback using time reversal mirror

Improvements on focused tactile feedback using time reversal mirror

Time reversal focusing in the audible range using a tunable sonic crystal

Generating controlled localized stimulations on haptic displays by modal superimposition

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