Subminiature transducer measures unsteady pressures

Transducer has thin piezoelectric sensing element of 0.051-cm-thick lead zirconate titanate crystal which is cut as a conical frustum. Sensing crystal and titanium wire are protected from mechanical shock and vibration. Transducer is insensitive to mechanical vibrations of instrument plug on which it is mounted

Piezoelectric Based Energy

In the present paper a review on piezoelectric sensing of mechanical deformations and its uses is highlighted

Piezoelectric sensing coating for real time impact detection and location on aircraft structures

Flexible, light weight and low cost electroactive coating has been fabricated by the dispersion of inorganic ferroelectric submicron particles in a polyurethane matrix. BaTiO3 particles have a mean diameter of 300 nm. The poling process and the influence of volume fraction of BaTiO3 on the piezoelectric activity of the coating have been reported. This spray coating has been realized on 1.6 * 1.6 m2 poly(epoxy)/carbon fiber reinforced composite. Impact detection has been also performed. A well-known cross correlated algorithm has been successfully employed to localize impact in a 90 * 90 cm2 area of the composite

Modelling smart structures with segmented piezoelectric sensors and actuators

In this paper, a number of finite element models have been developed for comprehensive modelling of smart structures with segmented piezoelectric sensing and actuating patches. These include an eight-node solid-shell element for modelling homogeneous and laminated host structures as well as an eight-node solid-shell and a four-node piezoelectric membrane elements for modelling surface bonded piezoelectric sensing and actuating patches. To resolve the locking problems in these elements and improve their accuracy, assumed natural strain and hybrid stress formulations are employed. Furthermore, piezoelectric patches are often coated with metallization. The concept of electric nodes is introduced that can eliminate the burden of constraining the equality of the electric potential for physical nodes lying on the same metallization. A number of problems are studied by the developed finite element models and comparisons with other ad hoc element models are presented.postprin

A low frequency dual-band operational microphone mimicking the hearing property of Ormia ochracea

This paper introduces a directional MEMS microphone designed for hearing aid applications appropriate to low frequency hearing impairment, inspired by the hearing mechanism of a fly, the female Ormia ochracea. It uses both piezoelectric and capacitive sensing schemes. In order to obtain a high sensitivity at low frequency bands, the presented microphone is designed to have two resonance frequencies below the threshold of low frequency hearing loss at approximately 2 kHz. One is around 500 Hz and the other is slightly above 2 kHz. The novel dual sensing mechanism allows for optimization of the microphone sensitivity at both frequencies, with a maximum open-circuit (excluding pre-amplification) acoustic response captured via differential piezoelectric sensing at approximately – 46 dB (V) ref. 94 dB (SPL) at the resonance frequencies. The corresponding minimum detectable sound pressure level is just below -12 dB. The comb finger capacitive sensing was employed due to a lower electrical response generated from a ground referenced single-ended output by the piezoelectric sensing at the first resonance frequency compared to the second resonance frequency. The capacitive sensing mechanism, connected to a charge amplifier, generates a -28.4 dB (V) ref. 94 dB (SPL) acoustic response when the device is excited at either of the two resonance frequencies. Due to the asymmetric geometry and the 400 µm thick substrate, the device is predicted to perform as a bi-directional microphone below 3 kHz, which is shown by the measured directional polar patterns

Pizzicato excitation for wearable energy harvesters

A new technique based on the plucking of flexible piezoelectric material can be used to boost energy harvested to power portable electronic devices

A MEMS microphone inspired by Ormia for spatial sound detection

This work introduces a MEMS microphone with two pairs of orthogonal and joined sensor membranes, with independent acoustic directionality responses, leading to a 3D sound localization potential. This single microphone can thus be regarded as two individual bi-directional microphones. Combining this architecture with the fly Ormia ochracea’s tympana mechanism, this microphone is also the first biomimetic MEMS microphone with piezoelectric sensing, designed for 2D sound localization

Housing influence on multi-band directional MEMS microphones inspired by Ormia ochracea

A new bio-inspired multi-band directional MEMS microphone based on the hearing properties of the fly Ormia ochracea is presented, together with the behavioral influence of 3D-printed housings. The multi-user foundry fabricated microphone operates on four frequency bands, all below 10 kHz and acts as a pressure gradient directional microphone with figure of eight polar pattern, or as an omni-directional microphone depending on the housing. The influence of an open or closed backside housing on the frequency response and directionality is shown, leading to the loss of directionality with no acoustic access to the backside of the fly-ear inspired microphone membrane

On the Use of Piezoelectric Sensors in Structural Mechanics: Some Novel Strategies

In the present paper, a review on piezoelectric sensing of mechanical deformations and vibrations of so-called smart or intelligent structures is given. After a short introduction into piezoelectric sensing and actuation of such controlled structures, we pay special emphasis on the description of some own work, which has been performed at the Institute of Technical Mechanics of the Johannes Kepler University of Linz (JKU) in the last years. Among other aspects, this work has been motivated by the fact that collocated control of smart structures requires a sensor output that is work-conjugated to the input by the actuator. This fact in turn brings into the play the more general question of how to measure mechanically meaningful structural quantities, such as displacements, slopes, or other quantities, which form the work-conjugated quantities of the actuation, by means piezoelectric sensors. At least in the range of small strains, there is confidence that distributed piezoelectric sensors or sensor patches in smart structures do measure weighted integrals over their domain. Therefore, there is a need of distributing or shaping the sensor activity in order to be able to re-interpret the sensor signals in the desired mechanical sense. We sketch a general strategy that is based on a special application of work principles, more generally on displacement virials. We also review our work in the past on bringing this concept to application in smart structures, such as beams, rods and plates