scholarly journals ADAPTIVE MECHANICAL FILTER FOR PIEZOELECTRIC ACCELEROMETER

2021 ◽  
pp. 60-68
Author(s):  
A.L. Perederko
Keyword(s):  
Mechanical Load ◽  
Relative Displacement ◽  
Electrical Signal ◽  
Viscoelastic Materials ◽  
Sensing Element ◽  
Accelerometer Sensor ◽  
Piezoelectric Accelerometer ◽  
Mechanical Filter ◽  
Short Period ◽  
Data Acquisition Unit

When conducting dynamic tests, when simulating shock effects, the measurement system - from the sensor to the data acquisition unit is subject to significant overloads. In this circuit, the accelerometer is the most vulnerable link. Therefore, piezoelectric accelerometers have become widely used in measuring shocks as more reliable and durable, but they also have a number of disadvantages. Thus, under broadband vibration effects, excitation in the region of mechanical resonance is observed. That is, the material of the sensor crystal may not have an excessive mechanical load, but generate a large amount of output charge due to the resonance of the sensor. This increases the electrical signal and can lead to saturation or, in many cases, damage to the signal shapers and amplifiers following the sensor. The result of such modes of operation is the loss of data due to the displacement of direct current over time. There is often a shift of the zero level of the output signal. When piezoelectric elements are in resonance, there may be a relative displacement of the sensing element. This state of overload leads to the appearance of parasitic output charges, which leads to a change in the generated charge in a short period of time. Due to mechanical overload, under the action of high-intensity shocks, physical destruction of the sensor is also possible. In many cases, the use of mechanical filters made of viscoelastic materials, which are placed between the object of measurement and the piezoelectric accelerometer (sensor), prevents the undesirable consequences of these shortcomings and improves the process of measuring shocks. The use of mechanical filters made of viscoelastic materials makes it possible to significantly reduce the amplitude of oscillations of the piezoelectric accelerometer (over -12 dB) and shift its resonant frequency towards higher frequencies. That is, the use of mechanical filters significantly reduces the mechanical load on the sensor, which makes the process of measuring vibration (especially shock) more predictable.

Frequency Response Analysis of Piecewise Nonlinear Vibration Isolator

2005 ◽  
Author(s):  
Patrick Stahl ◽  
G. Nakhaie Jazar
Keyword(s):  
Low Frequency ◽  
High Amplitude ◽  
Relative Displacement ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
State Behavior ◽  
Vibration Isolators ◽  
Short Period ◽  
Secondary Suspension ◽  
Low Amplitude

Non-smooth piecewise functional isolators are smart passive vibration isolators that can provide effective isolation for high frequency/low amplitude excitation by introducing a soft primary suspension, and by preventing a high relative displacement in low frequency/high amplitude excitation by introducing a relatively damped secondary suspension. In this investigation a linear secondary suspension is attached to a nonlinear primary suspension. The primary is assumed to be nonlinear to model the inherent nonlinearities involved in real suspensions. However, the secondary suspension comes into action only during a short period of time, and in mall domain around resonance. Therefore, a linear assumption for the secondary suspension is reasonable. The dynamic behavior of the system subject to a harmonic base excitation has been analyzed utilizing the analytic results derived by applying the averaging method. The analytic results match very well in the transition between the two suspensions. A sensitivity analysis has shown the effect of varying dynamic parameters in the steady state behavior of the system.

scholarly journals Noncontact respiration rate monitoring based on sensing exhaled air

2014 ◽  
Vol 9 (3) ◽  
Author(s):  
A.H. Alkali ◽  
R. Saatchi ◽  
H. Elphick ◽  
D. Burke ◽  
R. Evans
Keyword(s):  
Respiration Rate ◽  
Air Flow ◽  
Electrical Signal ◽  
Sensing Element ◽  
Important Indicator ◽  
Respiration Monitoring ◽  
Flow Sensing ◽  
Exhaled Air ◽  
Processing Techniques ◽  
Signal Processing Techniques

Respiration rate is the average number of times air is inhaled and exhaled per minute. Respiration rate is an important indicator of a person’s health and therefore, it needs to be measured accurately. Existing respiration monitoring systems are generally contact based that means the sensing element needs to be attached to the subject's body. The attached sensor can cause distress in some children, affecting their respiration rate. The device can also become dislodged interrupting the monitoring. This work presents an air flow sensing approach to noncontact respiration rate monitoring. The exhaled air is guided through a small funnel to a chamber that contains a heating element. The heated air leaves the chamber and is then detected by a thermistor that converts the air flow temperature variations to an electrical signal. The signal is amplified, filtered and digitised. Signal processing techniques are used to extract respiration rate from the signal in real time. The device provides respiration rate at distances from 15 to 30 cm from the subject’s face.

scholarly journals The task of direct piezoeffect for a bi-morth plate

2018 ◽  
Vol 196 ◽  
pp. 01006
Author(s):  
Dmitriy Shlyahin ◽  
Olesya Ratmanova
Keyword(s):  
Boundary Conditions ◽  
Mechanical Load ◽  
Mixed Boundary ◽  
Electrical Signal ◽  
Radial Coordinate ◽  
Piezoceramic Plate ◽  
Three Dimensional Model ◽  
Support Plate ◽  
First Case ◽  
Metal Support

The research focuses on the dynamic axisymmetric task for a round bi-morph structure consisting of a metal support plate and a piezoceramic axially polarized plate. Its bending oscillations are carried out because of the actions of mechanical load (normal stresses) on its end surface, which is an arbitrary time and radial coordinate function. The rigid and hinged support of the plate cylindrical surface is taken into account. The value of the induced field is calculated by determining the potential on the metal support plate. To solve the task of the theory of the elasticity in a three-dimensional model, the authors apply the Hankel finite integral transformations along the axial coordinate and generalized transformation along the radial variable. Besides, at each stage of the study the standardization procedure is carried out. In the first case it is connected with the use of mixed boundary conditions along the radial coordinate to the mixed form, and in the second case heterogeneous boundary conditions are presented as homogenious. The obtained calculation ratios make it possible to determine the optimal thickness of the piezoceramic plate, which allows to make the most effective transformation of the external mechanical effect into an electrical signal. In addition, it is possible to determine changing characteristics of electromagnetic field according to the height of the piezoceramic plate. This principle can be used in the calculation and design of bi-morph systems with graded-varying thickness and rigidity.

Application of a Mechanical Filter to an Artificial Heart

1996 ◽  
Vol 118 (2) ◽  
pp. 187-192
Author(s):  
M. Arabia ◽  
F. Pistella
Keyword(s):  
Resonant Frequency ◽  
Artificial Heart ◽  
Mechanical Load ◽  
Reciprocating Motion ◽  
Friction Forces ◽  
Maximum Value ◽  
Mechanical Filter ◽  
Inertial Component ◽  
Order Of Magnitude

A mechanical filter developed to improve the performances of an artificial heart whose electrical motor has a reciprocating motion is presented. The filter phases the mechanical load strongly reducing its inertial component (which is of the same order of magnitude as the useful load). The analysis reported for a prototype developed by us shows that when its rate is equal to the first resonant frequency of the filter, a reduction of about 50 percent for the maximum value of the torque due to inertial and friction forces is obtained.

Forecast and Processing of Weak Electrical Signals in Clivia miniata by RBF Neural Networks

2011 ◽  
Vol 216 ◽  
pp. 388-392
Author(s):  
Jin Li Ding ◽  
Lan Zhou Wang
Keyword(s):  
Test System ◽  
Electrical Signal ◽  
Rbf Neural Networks ◽  
Base Function ◽  
Electrical Signals ◽  
Short Period ◽  
Forecasting System ◽  
Clivia Miniata ◽  
Set Up ◽  
Radial Base Function

Original weak electrical signals in Clivia miniata were tested by a touching test system of self-made double shields with platinum sensors. Tested data of electrical signals denoised by the wavelet soft threshold and using Gaussian radial base function (RBF) as the time series at a delayed input window chosen at 50. An intelligent RBF forecasting system was set up to forecast the signal in plants. Testing result shows that it is feasible to forecast the plant electrical signal for a short period. The forecast data can be used as an important preferences for the intelligent automatic control system based on the adaptive characteristic of plants to achieve the energy saving on agricultural production both the greenhouse and /or the plastic lookum.

Comportement d'un pieu bi-fonction, fondation et échangeur de chaleur

2003 ◽  
Vol 40 (2) ◽  
pp. 388-402 ◽  
Author(s):  
Lyesse Laloui ◽  
Matteo Moreni ◽  
Laurent Vulliet
Keyword(s):  
Heat Exchanger ◽  
Skin Friction ◽  
Mechanical Load ◽  
Relative Displacement ◽  
Loading Test ◽  
Mechanical Loads ◽  
Pipe System ◽  
Under Construction ◽  
Thermal Influence

The behaviour of a pile subjected to thermo-mechanical loads was studied in situ with the aim of quantifying the thermal influence on the bearing capacity of heat exchanger piles. To accomplish this, a pile situated in a building under construction was equipped with a pipe system to inject heat into it using a special heat pump. Load cells, deformation gauges, and thermometers were installed to evaluate the behaviour of the pile during seven tests with coupled thermo-mechanical loads. The temperature variations applied to the pile were of the order of 15°C and the mechanical load reached 1300 kN. The results permitted the quantification of three significant effects brought about by the temperature increase: (i) pile uplift, (ii) mobilization of skin friction due to the relative displacement of the pile with respect to the ground, (iii) additional load generated in the pile by constrained dilation.Key words: heat exchanger pile, in situ test, loading test, thermo-mechanical loads, mobilization of skin friction.

scholarly journals A Novel Approach to a Piezoelectric Sensing Element

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
M. Martinez ◽  
A. Artemev
Keyword(s):  
Thin Plate ◽  
Piezoelectric Materials ◽  
Piezoelectric Element ◽  
Electrical Signal ◽  
Sensing Element ◽  
Plate Structures ◽  
Sensing Applications ◽  
Novel Approach ◽  
Voltage Signal ◽  
Piezoelectric Structures

Piezoelectric materials have commonly been used in pressure and stress sensors; however, many designs consist of thin plate structures that produce small voltage signals when they are compressed or extended under a pressure field. This study used finite element methods to design a novel piezoelectric pressure sensor with a C-shaped piezoelectric element and determine if the voltage signal obtained during hydrostatic pressure application was enhanced compared to a standard thin plate piezoelectric element. The results of this study demonstrated how small deformations of this C-shaped sensor produced a large electrical signal output. It was also shown that the location of the electrodes for this sensor needs to be carefully chosen and that the electric potential distribution varies depending on the poling of the piezoelectric element. This study indicated that the utilization of piezoelectric materials of different shapes and geometries embedded in a polymer matrix for sensing applications has several advantages over thin plate solid piezoelectric structures.

Detection of UV Rays Using CdTe Quantum Dots

2015 ◽  
Vol 5 (1) ◽  
pp. 15-27 ◽  
Author(s):  
A. Anbarasi ◽  
R. Kalpana ◽  
A. Arivarasan ◽  
R. Jayavel ◽  
B. Venkataraman
Keyword(s):  
Quantum Dots ◽  
Detection System ◽  
Fluorescence Emission ◽  
Band Gap Energy ◽  
Electrical Signal ◽  
Uv Detection ◽  
Cdte Quantum Dots ◽  
X Rays ◽  
Sensing Element ◽  
Uv Rays

Development of simple UV detection system using CdTe quantum dots (QDs) as primary detector with scintillating property on exposure to UV rays is reported. CdTe, CdTe/ZnS and CdTe/CdS QDs were synthesized in aqueous phase using mercaptosuccinic acid (MSA) as a capping agent and studied for its properties like crystallite size, band gap energy, fluorescence emission intensity and uniformity in size distribution. The prepared QDs were exposed to different radiations such as infrared (IR), ultraviolet (UV) and X-rays. The fluorescent emission was recorded by an optoelectronic circuit in terms of electrical signal. The result of this study shows that CdTe/ZnS QDs is better suited for the detection and measurement of UV rays. Hence these QDs could be used as a sensing element while fabricating nanosensor for UV detection.

scholarly journals Parametric study of a triboelectric transducer in total knee replacement application

2020 ◽  
Vol 32 (1) ◽  
pp. 16-28 ◽  
Author(s):  
Alwathiqbellah Ibrahim ◽  
Geofrey Yamomo ◽  
Ryan Willing ◽  
Shahrzad Towfighian
Keyword(s):  
Knee Joint ◽  
Total Knee Replacement ◽  
Knee Replacement ◽  
Mechanical Load ◽  
Structural Parameters ◽  
New Technology ◽  
Electrical Signal ◽  
Motion Simulator ◽  
Total Knee ◽  
Self Powered

Triboelectric energy harvesting is a relatively new technology showing promise for biomedical applications. This study investigates a triboelectric energy transducer for potential applications in total knee replacement both as an energy harvester and a sensor. The sensor can be used to monitor loads at the knee joint. The proposed transducer generates an electrical signal that is directly related to the periodic mechanical load from walking. The proportionality between the generated electrical signal and the load transferred to the knee enables triboelectric transducers to be used as self-powered active load sensors. We analyzed the performance of a triboelectric transducer when subjected to simulated gait loading on a joint motion simulator. Two different designs were evaluated: one made of Titanium on Aluminum (Ti-PDMS-Al) and the other made of Titanium on Titanium (Ti-PDMS-Ti). The Ti-PDMS-Ti design generates more power than Ti-PDMS-Al and was used to optimize the structural parameters. Our analysis found these optimal parameters for the Ti-PDMS-Ti design: external resistance of 304 MΩ, a gap of 550 µm, and a thickness of the triboelectric layer of 50 µm. Those parameters were optimized by varying resistance, gap, and the thickness while measuring the power outputs. Using the optimized parameters, the transducer was tested under different axial loads to check the viability of the harvester to act as a self-powered load sensor to estimate the knee loads. The forces transmitted across the knee joint during activities of daily living can be directly measured and used for self-powering, which can lead to improving the total knee implant functions.

scholarly journals Total energy and energy spectral density of elastic wave radiation from propagating faults

1964 ◽  
Vol 54 (6A) ◽  
pp. 1811-1841 ◽  
Author(s):  
N. A. Haskell
Keyword(s):  
Total Energy ◽  
Fault Plane ◽  
Relative Displacement ◽  
Point Sources ◽  
Time Function ◽  
Displacement Discontinuity ◽  
Source Distribution ◽  
Wave Radiation ◽  
Short Period ◽  
Fault Displacement

abstract Starting with a Green's function representation of the solution of the elastic field equations for the case of a prescribed displacement discontinuity on a fault surface, it is shown that a shear fault (relative displacement parallel to the fault plane) is rigorously equivalent to a distribution of double-couple point sources over the fault plane. In the case of a tensile fault (relative displacement normal to the fault plane) the equivalent point source distribution is composed of force dipoles normal to the fault plane with a superimposed purely compressional component. Assuming that the fault break propagates in one direction along the long axis of the fault plane and that the relative displacement at a given point has the form of a ramp time function of finite duration, T, the total radiated P and S wave energies and the total energy spectral densities are evaluated in closed form in terms of the fault plane dimensions, final fault displacement, the time constant T, and the fault propagation velocity. Using fault parameters derived principally from the work of Ben-Menahem and Toksöz on the Kamchatka earthquake of November 4, 1952, the calculated total energy appears to be somewhat low and the calculated energy spectrum appears to be deficient at short periods. It is suggested that these discrepancies are due to over-simplification of the assumed model, and that they may be corrected by (1) assuming a somewhat roughened ramp for the fault displacement time function to correspond to a stick-slip type of motion, and (2) assuming that the short period components of the fault displacement wave are coherent only over distances considerably smaller than the total fault length.

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