Assessment of velocity-acceleration feedback in optimal control of smart piezoelectric beams

Beheshti-Aval, S.B.,Lezgy-Nazargah, M. Techno-Press 2010 Smart Structures and Systems, An International Jou Vol.6 No.8

Most of studies on control of beams containing piezoelectric sensors and actuators have been based on linear quadratic regulator (LQR) with state feedback or output feedback law. The aim of this study is to develop velocity-acceleration feedback law in the optimal control of smart piezoelectric beams. A new controller which is an optimal control system with velocity-acceleration feedback is presented. In finite element modeling of the beam, the variation of mechanical displacement through the thickness is modeled by a sinus model that ensures inter-laminar continuity of shear stress at the layer interfaces as well as the boundary conditions on the upper and lower surfaces of the beam. In addition to mechanical degrees of freedom, one electric potential degree of freedom is considered for each piezoelectric element layer. The efficiency of this control strategy is evaluated by applying to an aluminum cantilever beam under different loading conditions. Numerical simulations show that this new control scheme is almost as efficient as an optimal control system with state feedback. However, inclusion of the acceleration in the control algorithm increases practical value of a system due to easier and more accurate measurement of accelerations.

Some precautions to consider in using wavelet transformation for damage detection analysis of plates

Beheshti-Aval, S.B.,Taherinasab, M.,Noori, M. Techno-Press 2013 Smart Structures and Systems, An International Jou Vol.11 No.1

Over the last two decades Wavelet Transformation (WT) method has been widely utilized for the damage identification of structures. The main objective of this paper is to discuss and present some of common shortcomings and limitations of mathematical software, as well as other precautionary measures that need to be considered when using them for wavelet analysis applications. Due to popular usage of MATLABMATLAB(R) comparing to other mathematical tools among researchers for data processing of structural responses through WT analysis, this software was chosen for specific study. To the best of the authors' knowledge, these limitations and observations have not been previously identified or discussed in the literature. In this work, a square plate with a severe damage, in form of a crack, parallel to the left edge of the plate is selected for a pilot study. The steady state harmonic response is used for measuring the deflection shape across the line parallel to one edge and perpendicular to the damage. Several criteria and cases such as the smallest size damage that can be detected, correlation between the crack width and the number of sampling points, and the influence of the damage thickness on the accuracy of the result are investigated.

Using harmonic class loading for damage identification of plates by wavelet transformation approach

Beheshti-Aval, S.B.,Taherinasab, M.,Noori, M. Techno-Press 2011 Smart Structures and Systems, An International Jou Vol.8 No.3

In this paper, the harmonic displacement response of a damaged square plate with all-over part-through damage parallel to one edge is utilized as the input signal function in wavelet analysis. The method requires the properties of the damaged plate, i.e., no information about the original undamaged structure is required. The location of damage is identified by sudden changes in the spatial variation of transformed response. The incurred damage causes a change in the stiffness or mass of the plate. This causes a localized singularity which can be identified by a wavelet analysis of the displacement response. In this study via numerical examples shown by using harmonic response is more versatile and effective compared with the static deflection response, specially in the presence of noise. In the light of the obtained results, suggestions for future work are presented and discussed.

Hydrogen Gas Detection Using MOS Capacitor Sensor Based on Palladium Nanoparticles-Gate

Leila Fekri Aval,Seyed Mohammad Elahi 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.1

In this study a palladium nanoparticles-gate MOS capacitorhydrogen sensor with Pd/SiO2/Si structure has been fabricated. The palladium nanoparticles by chemical method aresynthesized and then characterized by transmission electronmicroscope (TEM), X-ray diffraction (XRD) and UV-VISspectrum. Also, the preferred orientation and grain size of thepalladium nanoparticles have been studied. Hydrogen absorptionand desorption of the palladium nanoparticles at the low andhigh pressure and as function of time have been investigated. The sensing mechanism of the hydrogen detection by MOScapacitor sensor has been explained and theoretical andexperimental results have been compared. At 287 K, comparedto another Pd MOS capacitor hydrogen sensor and ultrathin Pd MOS capacitor, the palladium nanoparticles gate MOS capacitorshowed much faster response and recovery speed. The time interval for reaching to 95% of the steady state signal magnitude(t95%) for 1% and 2% hydrogen in nitrogen were 2 s and 1.5 s respectively. The time interval for recovery transients from 95% to10% of steady state signal magnitude (t10%) for 1% and 2% hydrogen in nitrogen were 10 s and 11 s respectively. The presentedsensor illustrates a designing of hydrogen detectors with very fast response and recovery speed.

Assessment of velocity-acceleration feedback in optimal control of smart piezoelectric beams

S.B. Beheshti-Aval,M. Lezgy-Nazargah 국제구조공학회 2010 Smart Structures and Systems, An International Jou Vol.6 No.8

Most of studies on control of beams containing piezoelectric sensors and actuators have been based on linear quadratic regulator (LQR) with state feedback or output feedback law. The aim of this study is to develop velocity-acceleration feedback law in the optimal control of smart piezoelectric beams. A new controller which is an optimal control system with velocity-acceleration feedback is presented. In finite element modeling of the beam, the variation of mechanical displacement through the thickness is modeled by a sinus model that ensures inter-laminar continuity of shear stress at the layer interfaces as well as the boundary conditions on the upper and lower surfaces of the beam. In addition to mechanical degrees of freedom, one electric potential degree of freedom is considered for each piezoelectric element layer. The efficiency of this control strategy is evaluated by applying to an aluminum cantilever beam under different loading conditions. Numerical simulations show that this new control scheme is almost as efficient as an optimal control system with state feedback. However, inclusion of the acceleration in the control algorithm increases practical value of a system due to easier and more accurate measurement of accelerations.

Some precautions to consider in using wavelet transformation for damage detection analysis of plates

S.B. Beheshti-Aval,M. Taherinasab,M. Noori 국제구조공학회 2013 Smart Structures and Systems, An International Jou Vol.11 No.1

Over the last two decades Wavelet Transformation (WT) method has been widely utilized for the damage identification of structures. The main objective of this paper is to discuss and present some of common shortcomings and limitations of mathematical software, as well as other precautionary measures that need to be considered when using them for wavelet analysis applications. Due to popular usage of MATLAB® comparing to other mathematical tools among researchers for data processing of structural responses through WT analysis, this software was chosen for specific study. To the best of the authors’ knowledge, these limitations and observations have not been previously identified or discussed in the literature. In this work, a square plate with a severe damage, in form of a crack, parallel to the left edge of the plate is selected for a pilot study. The steady state harmonic response is used for measuring the deflection shape across the line parallel to one edge and perpendicular to the damage. Several criteria and cases such as the smallest size damage that can be detected, correlation between the crack width and the number of sampling points, and the influence of the damage thickness on the accuracy of the result are investigated.

The fiber element technique for analysis of concrete-filled steel tubes under cyclic loads

S.B.B.Aval,A. A. Golafshani,M.A.Saadeghvaziri 국제구조공학회 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.6

Using harmonic class loading for damage identification of plates by wavelet transformation approach

S.B. Beheshti-Aval,M. Taherinasab,M. Noori 국제구조공학회 2011 Smart Structures and Systems, An International Jou Vol.8 No.3

In this paper, the harmonic displacement response of a damaged square plate with all-over partthrough damage parallel to one edge is utilized as the input signal function in wavelet analysis. The method requires the properties of the damaged plate, i.e., no information about the original undamaged structure is required. The location of damage is identified by sudden changes in the spatial variation of transformed response. The incurred damage causes a change in the stiffness or mass of the plate. This causes a localized singularity which can be identified by a wavelet analysis of the displacement response. In this study via numerical examples shown by using harmonic response is more versatile and effective compared with the static deflection response, specially in the presence of noise. In the light of the obtained results, suggestions for future work are presented and discussed.

A Hybrid Friction-yielding Damper to Equip Concentrically Braced Steel Frames

S.B. Beheshti-Aval,H. Mahbanouei,F. Zareian 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.4

This paper introduces the design of a new combination of friction/hysteretic damper installed in the middle of cross bracingfor dissipating seismic energy. Due to its relative simplicity and easy application, with no need for any special material ortechnology, this high-performance system has gained more attention than any other energy dissipation devices. Choosingappropriate slip load and maximum sliding movement values in this system, in comparison with its counterpart i.e. circular ringyielding dissipator, this combined system may inherit the advantages of both friction and steel yielding damper. In weak-tomoderateground motions, it dissipates energy by friction and in strong ground motions, it absorbs energy by yielding Thesecircular damper systems can be used to rehabilitate existing buildings whose slender braces are only designed based onresistance of tension forces. Also because of failure localization in this simple-type system, a distorted and damaged dampercan be promptly replaced with a new one after a strong earthquake.

Accuracy of linear measurement using cone-beam computed tomography at different reconstruction angles

Nikneshan, Sima,Aval, Shadi Hamidi,Bakhshalian, Neema,Shahab, Shahriyar,Mohammadpour, Mahdis,Sarikhani, Soodeh Korean Academy of Oral and Maxillofacial Radiology 2014 Imaging Science in Dentistry Vol.44 No.4

Purpose: This study was performed to evaluate the effect of changing the orientation of a reconstructed image on the accuracy of linear measurements using cone-beam computed tomography (CBCT). Materials and Methods: Forty-two titanium pins were inserted in seven dry sheep mandibles. The length of these pins was measured using a digital caliper with readability of 0.01 mm. Mandibles were radiographed using a CBCT device. When the CBCT images were reconstructed, the orientation of slices was adjusted to parallel (i.e., $0^{\circ}$), $+10^{\circ}$, $+12^{\circ}$, $-12^{\circ}$, and $-10^{\circ}$ with respect to the occlusal plane. The length of the pins was measured by three radiologists, and the accuracy of these measurements was reported using descriptive statistics and one-way analysis of variance (ANOVA); p<0.05 was considered statistically significant. Results: The differences in radiographic measurements ranged from -0.64 to +0.06 at the orientation of $-12^{\circ}$, -0.66 to -0.11 at $-10^{\circ}$, -0.51 to +0.19 at $0^{\circ}$, -0.64 to +0.08 at $+10^{\circ}$, and -0.64 to +0.1 at $+12^{\circ}$. The mean absolute values of the errors were greater at negative orientations than at the parallel position or at positive orientations. The observers underestimated most of the variables by 0.5-0.1 mm (83.6%). In the second set of observations, the reproducibility at all orientations was greater than 0.9. Conclusion: Changing the slice orientation in the range of $-12^{\circ}$ to $+12^{\circ}$ reduced the accuracy of linear measurements obtained using CBCT. However, the error value was smaller than 0.5 mm and was, therefore, clinically acceptable.