Piezoelectric Acceleration Transducers Research Articles

Performance enhancement of MEMS-guided four beam piezoelectric transducers for energy harvesting and acceleration sensing

In the present paper, guided four beam (G4B) piezoelectric transducers with enhanced sensitivities have been designed. Based on the suggested G4B structures, piezoelectric energy harvesters (PEHs) and acceleration transducers with higher voltages than their previously reported counterparts and with lower displacements than the single-cantilever PEHs (SC-PEHs) have been proposed. We have shown that it is possible to arrive at much more output voltages in comparison with the conventional PEHs by redesigning the structure of the cantilever beams. In 1 g acceleration, the maximum output voltage obtained from the proposed PEHs has been 13.49 V whereas the output voltage for the conventional G4B-PEH is 2.87 V. This paper for the first time proposes G4B-PEHs with smaller displacements and larger voltages compared to a SC-PEH. The same G4B framework has been studied as a piezoelectric acceleration transducer. The effect of piezoelectric length on the extracted voltage in both unimorph and bimorph cantilevers has been discussed and the optimized length has been calculated. An analytical method is developed to compute the resonance frequencies of different beam shapes whose results are in a good agreement with numerical simulations.

Detrended Fluctuation Analysis and Hough Transform Based Self-Adaptation Double-Scale Feature Extraction of Gear Vibration Signals

This paper presents the analysis of the vibration time series of a gear system acquired by piezoelectric acceleration transducer using the detrended fluctuation analysis (DFA). The experimental results show that gear vibration signals behave as double-scale characteristics, which means that the signals exhibit the self-similarity characteristics in two different time scales. For further understanding, the simulation analysis is performed to investigate the reasons for double-scale of gear’s fault vibration signal. According to the analysis results, a DFA double logarithmic plot based feature vector combined with scale exponent and intercept of the small time scale is utilized to achieve a better performance of fault identification. Furthermore, to detect the crossover point of two time scales automatically, a new approach based on the Hough transform is proposed and validated by a group of experimental tests. The results indicate that, comparing with the traditional DFA, the faulty gear conditions can be identified better by analyzing the double-scale characteristics of DFA. In addition, the influence of trend order of DFA on recognition rate of fault gears is discussed.

Analysis and Application of the Impact Absorption Behavior of the Composite Tube

Composite tube is one new kind of multi-material shell structures. It has both of metal and composite energy absorption advantage. In order to find the energy absorption characteristic of composite tube and put it into use, the Drop-Weight Tear Test (DWTT) was carried out. The LD2Y aluminum was chosen as the inner metal material which was wrapped fiberglass epoxy composite outside. During the test, the displacement signal and velocity signal, acceleration signal were got by piezoelectric acceleration transducer. Furthermore, the DWTT test of the composite tube was simulated in LS-DYNA, and proved the validity of the model by comparing the simulation results with the experiment results. We established the vehicle front longitudinal beam model with the material type of the composite tube, and carried out the simulations of whole car collisions in LS-DYNA according to FMVSS 208. Through the analysis of occupant head injury got from the simulations, we got the result that using the composite tube material could not only elevate the cars safety but also reduce front longitudinal beam weight effectively.

Motion Trajectory Simulation and Measurement of the 5000V Electromagnetic Repulsion Mechanism (ERM)

Successful applications of the ERM depend on accurate simulation models. Firstly, we built up a model on the 5000 volts ERM with ansoft. Then we measured motion trajectories of the ERM prototype respectively by means of a piezoelectric acceleration transducer, a magnetic grating displacement transducer and a linear displacement sensor. Based on the comparative analysis of the results from simulation and measurement, we concluded that the simulation model was reliable on one hand, and on the other hand by means of a linear displacement sensor along with a magnetic grating counterpart, we could obtain accurate motion trajectories with a relative error less than 5%.

Piezoelectric acceleration transducer with increased resistance to zero shift

Comparative analysis is provided for design schemes of piezoelectric shock acceleration transducers and improvements are proposed aimed at expanding the acceleration measurement range under conditions of sudden loading with a high level of high-frequency components, transverse acceleration and setting surface deformation.

Handy measurement for tongue motion and coordination with laryngeal elevation at swallowing.

At the oral stage of swallowing, the tongue plays a major role and proper tongue performance is necessary to form the bolus and transfer it to the pharynx. For the present study we built a prototype device for safe and handy objective estimation of tongue motion and coordination with laryngeal elevation at swallowing. The device records tongue pressure by means of two strain gauge pressure transducers aligned 20 mm apart on a brass strap placed along the palatal midline. Laryngeal vibration is recorded with piezo-electric acceleration transducers. Time differences between pressure onset at the anterior and posterior transducers and the first spike from laryngeal vibration are measured. Ten healthy subjects were asked five times to swallow 5 mL of water. Pressure onset at the anterior transducer preceded posterior pressure by 294 +/- 164 ms. Given the distance between the transducers, the tongue contracted (squeezed) at a speed of 93 +/- 60 mm s(-1). Laryngeal vibration occurred 671 +/- 175 ms after the onset of anterior pressure. There was considerable variation in these parameters between subjects. Though the data is limited, the device successfully and easily revealed certain aspects of tongue motion and coordination with laryngeal elevation.

Method of protection of acceleration transducers from unmeasurable effects

Firstly, reduction in the DS is achieved at too high a cost. The thickness of the packing is comparable with that of the transducer base. This invariably leads to reduction in the impact strength of the object surface-adhesive-~packing-adhesive-transducer joint since the side component of the impact acceleration creates an additional moment by acting on such a system. This can lead to failure of the joint. Secondly, even the use of these packings produces a relatively small reduction in the sensitivity to deformation (in impact mode, about I0 times for packing thickness hp = 3 mm) which in many cases is not enough. Finally, the method in the technical description practically does not ensure protection of the transducer from the unmeasurable high-frequency overlaps which can lead to the so-called phenomenon of "zero shift" [3]. This, in turn, leads to partial or total loss of the measuring information. In order to extend the field of application of the transducers and to ensure reliable measurements, efforts were made to establish methods of mounting piezoelectric acceleration transducers which effectively lower (eliminate) the effect of the unmeasurable actions. Specialists point to the mechanical filter UA 0559 made by the Danish firm "Briule and Kier" in the form of a component adapter between the object surface and the transducer body, the main component of which, is the rubber packing and to the method of mounting the transducer on plasticized epoxy compound, i.e., a method in which the elastic adhesive layer in essence acts as a mechanical filter [2]. As in the case of textolite packings, use of this filter leads to increase in transverse sensitivity of the transducer and decrease in the cohesive strength for side impact. It is not possible to use the epoxy compound proposed in [2] in our case since the joint has to be subjected to heat treatment. What is most important in this is the fact that such a method has limited scope for varying the filtering properties, whereas, conditions of the tests often compel investigators to intensify one or the other effect of protection from the unmeasurable actions.

Selection of measuring facilities for the strain-effect coefficient of piezoelectric acceleration transducers

Selection of measuring facilities for the strain-effect coefficient of piezoelectric acceleration transducers

VESPA: a servohydraulic shock testing machine

Equipment installed in Swiss civil defense shelters and military fortifications is systematically shocktested. A set of three so-called shock parameters (test table acceleration, velocity and displacement) is defined as test criteria that are simulated on shock testing machines. Some years ago the NC Laboratory Spiez made operational a new vertical shock testing machine, called VESPA. This fully hydraulically driven machine allows to simulate in both directions (,,up and ,,down) a wide range of acceleration-time-histories with test objects weighing up to ten tons. In the tests the motion of the shock table and, if needed, the response of the test object are measured by piezoelectric acceleration transducers. The displacement-time-history of the test table is measured by a special device developed by the NC Laboratory Spiez.

Transverse sensitivity of piezoelectric accelerometric transducers

The transverse sensitivity of piezoelectric acceleration transducers is caused by the lack of coincidence between the transducer's sensitivity axis and the polarization vector of the piezoelectric plate. This fact should be taken into consideration both in the production of piezoelectric elements, and in the design of transducers and their manufacture.

Piezoelectric acceleration transducers

FIELD: measurement technology, design of electric, mechanical and electromechanical transmitter and methods of their attachment to examined objects. SUBSTANCE: invention refers predominantly to acceleration transducers produced on base of piezoceramic bimorphs of cantilever type, it can be employed to measure parameters of detonations in electron system controlling automobile engine and vibrations in various spheres of technology. Piezoelectric acceleration transmitter has bimorph sensitive element made fast to solid base with current leads. Key structural feature of transducer lies in fabrication of solid base from two parts interjoined rigidly. Main part carries bimorph sensitive element with current leads. Peripheral part has section half as large as area of section of main part in point of their joining, end sections of peripheral part are points of attachment of transducer. Peripheral part of base can be manufactured in the form of bar that can be S-shaped. Main part can be produced in the form of cylinder. Peripheral and main parts of base can be made monolithic as single unit. Base can be made of brass. EFFECT: reduced effect of mechanical deformations on conversion factor of transducer. 6 cl, 3 dwg, 3 tbl