A practical optical force-feedback microphone

Karatzas, L.S.; Keating, David; Usher, M. J.

doi:10.1177/014233129401600204

Cited by 7 publications

(4 citation statements)

References 34 publications

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“…The system in ( 7) displays a damped oscillatory response, which is typical of many feedback-controlled transduction processes encountered in cantilever positioning in atomic force microscopy, 93 optical force feedback microphones, [94][95][96] or the control of complex deexcitation lifetimes encountered in many types of spectroscopies, e.g., nuclear magnetic, 97 electron-spin, 98,99 microwave, [100][101][102] and multiphoton fluorescence, e.g., Förster resonance, 103 and in lock-in applications 104 or in other control and identification schemes. 105 The desired closed-loop dynamics are specified in the form (6) with aD = bD = 0.5, which corresponds to a first-order transfer function with a time constant of 2 s. All the simulations were carried out by using the Matlab ® /Simulink ® software and the FOTF code 106 for fractional-order systems available within the FOMCON toolbox (www.fomcon.net).…”

Section: Preliminary Examplementioning

confidence: 99%

Measurement and control of emergent phenomena emulated by resistive-capacitive networks, using fractional-order internal model control and external adaptive control

Galvão

Hadjiloucas

2019

Review of Scientific Instruments

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A fractional-order internal model control technique is applied to a three-dimensional resistive-capacitive network to enforce desired closedloop dynamics of first order. In order to handle model mismatch issues resulting from the random allocation of the components within the network, the control law is augmented with a model-reference adaptive strategy in an external loop. By imposing a control law on the system to obey first order dynamics, a calibrated transient response is ensured. The methodology enables feedback control of complex systems with emergent responses and is robust in the presence of measurement noise or under conditions of poor model identification. Furthermore, it is also applicable to systems that exhibit higher order fractional dynamics. Examples of feedback-controlled transduction include cantilever positioning in atomic force microscopy or the control of complex de-excitation lifetimes encountered in many types of spectroscopies, e.g., nuclear magnetic, electron-spin, microwave, multiphoton fluorescence, Förster resonance, etc. The proposed solution should also find important applications in more complex electronic, microwave, and photonic lock-in problems. Finally, there are further applications across the broader measurement science and instrumentation community when designing complex feedback systems at the system level, e.g., ensuring the adaptive control of distributed physiological processes through the use of biomedical implants.

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Section: Preliminary Examplementioning

confidence: 99%

Measurement and control of emergent phenomena emulated by resistive-capacitive networks, using fractional-order internal model control and external adaptive control

Galvão

Hadjiloucas

2019

Review of Scientific Instruments

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“…For example, the Doppler frequency shift of light reflected from a microphone membrane is used to measure the membrane's velocity in [13]. A Fabry-Perot cavity was incorporated into the interferometers used in [14,15]. In the latter study, a Pockel's cell is used for highspeed switching between interference signals with a fixed 90 • phase difference.…”

Section: Introductionmentioning

confidence: 99%

“…With the exception of [11,14], each of the optical microphones discussed above is operated in an open loop, in other words without the presence of feedback. In a feedback-controlled microphone, a control loop is integrated into the sensor in order to detect and nullify the microphone's membrane deflection, caused by the sound pressure, using an opposing pressure that is produced by electrostatic, electromagnetic or other electrical means.…”

Section: Introductionmentioning

confidence: 99%

“…This microphone used electrostatic actuation of a pressure-gradient-type microphone capsule, while modulation of an LC oscillator's frequency by the variation in capsule capacitance was used as the feedback signal. In a follow-up study to [19], the potential and associated advantages for using a Fabry-Perot interferometer for the feedback sensor were investigated in detail, but no microphone prototypes employing the interferometer were constructed [14]. Overall the study lacked evidence demonstrating the advantages of feedback microphones for aeroacoustics applications.…”

Section: Introductionmentioning

confidence: 99%

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A novel design of a feedback-controlled optical microphone for aeroacoustics research

Radcliffe¹,

Naguib²,

Humphreys³

2010

Meas. Sci. Technol.

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This study constitutes a proof of concept of a new feedback-controlled optical microphone for potential use in phased ‘beam-forming’ arrays utilized in aeroacoustics research. In the new microphone design, a fiber-optic lever sensor is employed as a means for measuring the center displacement of a stretched thin membrane caused by incident acoustic pressure. The membrane is constructed from polyvinylidene-fluoride which exhibits piezoelectric properties allowing actuation of the membrane in a feedback system to nullify the optically detected deflection. The feedback provision was used to actively modify sensor parameters, most notably membrane stiffness, resonant frequency and damping. Testing of a prototype microphone was performed using a plane wave tube calibrator. Using feedback control, the fundamental resonant frequency of the prototype capsule was increased from 3.61 to 5.1 kHz, a 41% increase. Also, feedback was used for dc attenuation, equivalent to ‘stiffening’ of the microphone membrane. The results demonstrate that feedback control is an effective method for improving the microphone's transient response, as well as for ‘self-tuning’ and matching of microphone parameters in sensing arrays.

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Optical sensors for monitoring water uptake in plants

Hadjiloucas

Karatzas

Keating

et al. 1995

J. Lightwave Technol.

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The monitoring of water uptake in plants is becoming increasingly important. Optical sensors offer considerable advantages over conventional methods and several sensors have been developed including an optical potometer that monitors water uptake from individual roots, the detection of xylem cavitation using audio acoustic emissions with an interferometric force feedback microphone, and an optical fiber displacement transducer that detects changes in leaf thickness in relation to leaf-water potential.

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A practical optical force-feedback microphone

Cited by 7 publications

References 34 publications

Measurement and control of emergent phenomena emulated by resistive-capacitive networks, using fractional-order internal model control and external adaptive control

Measurement and control of emergent phenomena emulated by resistive-capacitive networks, using fractional-order internal model control and external adaptive control

A novel design of a feedback-controlled optical microphone for aeroacoustics research

Optical sensors for monitoring water uptake in plants

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