• Smart Structures and Systems
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• v.1 no.1
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• pp.13-27
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• 2005

Simultaneous precision positioning and vibration suppression of a reciprocating flexible manipulator is investigated in this paper. The flexible manipulator is driven by a multifunctional active strut with fuzzy logic controllers. The multifunctional active strut is a combination of a motor assembly and a piezoelectric stack actuator to simultaneously provide precision positioning and wide frequency bandwidth vibration suppression capabilities. First, the multifunctional active strut and the flexible manipulator are introduced, and their dynamic models are derived. A control strategy is then proposed, which includes a position controller and a vibration controller to achieve simultaneous precision positioning and vibration suppression of the flexible manipulator. Next, fuzzy logic control approach is presented to design a fuzzy logic position controller and a fuzzy logic vibration controller. Finally, experiments are conducted for the fuzzy logic controllers and the experimental results are compared with those from a PID control scheme consisting of a PID position controller and a PID vibration control. The comparison indicates that the fuzzy logic controller can easily handle the non-linearity in the strut and provide higher position accuracy and better vibration reduction with less control power consumption.

• Journal of Magnetics
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• v.20 no.4
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• pp.347-352
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• 2015

The magnetoelectric (ME) characteristics for Terfenol-D/PZT laminate composite dependence on bias magnetic field is investigated. At low frequency, ME response is determined by the piezomagnetic coefficient $d_{33,m}$ and the elastic compliance $s_{33}^H$ of magnetostrictive material, $d_{33,m}$ and $s_{33}^H$ for Terfenol-D are inherently nonlinear and dependent on $H_{dc}$, leading to the influence of $H_{dc}$ on low-frequency ME voltage coefficient. At resonance, the mechanical quality factor $Q_m$ dependences on $H_{dc}$ results in the differences between the low-frequency and resonant ME voltage coefficient with $H_{dc}$. In terms of ${\Delta}E$ effect, the resonant frequency shift is derived with respect to the bias magnetic field. Considering the nonlinear effect of magnetostrictive material and $Q_m$ dependence on $H_{dc}$c, it predicts the low-frequency and resonant ME voltage coefficients as a function of the dc bias magnetic field. A good agreement between the theoretical results and experimental data is obtained and it is found that ME characteristics dependence on $H_{dc}$ are mainly influenced by the nonlinear effect of magnetostrictive material.

• Smart Structures and Systems
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• v.26 no.4
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• pp.469-480
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• 2020

This is the first research on the smart control and vibration analysis of a Graphene nanoplatelets (GPLs) Reinforced Composite (GPLRC) porous cylindrical shell covered with piezoelectric layers as sensor and actuator (PLSA) in the framework of numerical based Generalized Differential Quadrature Method (GDQM). The stresses and strains are obtained using the First-order Shear Deformable Theory (FSDT). Rule of the mixture is employed to obtain varying mass density and Poisson's ratio, while the module of elasticity is computed by modified Halpin-Tsai model. The external voltage is applied to sensor layer and a Proportional-Derivative (PD) controller is used for sensor output control. Governing equations and boundary conditions of the GPLRC cylindrical shell are obtained by implementing Hamilton's principle. The results show that PD controller, length to radius ratio (L/R), applied voltage, porosity and weight fraction of GPL have significant influence on the frequency characteristics of a porous GPLRC cylindrical shell. Another important consequence is that at the lower value of the applied voltage, the influence of the smart controller on the frequency of the micro composite shell is much more significant in comparison with the higher ones.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.11
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• pp.790-800
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• 2013

The optimal structure of 1-3 piezocomposites has been determined by controlling polymer properties, ceramic volume fraction, thickness of composite and aspect ratio of the composite to maximize the TVR (transmitting voltage response), RVS (receiving voltage sensitivity) and FBW (fractional bandwidth) of underwater acoustic transducers. Influence of the design variables on the transducer performance was analyzed with equivalent circuits and the finite element method. When the piezocomposite is vibrating in a pure thickness mode, inter-pillar resonant modes are likely to occur between lattice-structured piezoceramic pillars and polymer matrix, which significantly deteriorate the performance of the piezocomposite. In this work, a new method to design the structure of the 1~3 type piezocomposite was proposed to maximize the TVR, RVS and FBW while preventing the occurrence of the inter-pillar modes. Genetic algorithm was used in the optimal design.

• Smart Structures and Systems
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• v.12 no.5
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• pp.483-499
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• 2013

A new piezoceramic $d_{15}$ shear-induced torsion actuation mechanism representative benchmark is proposed and its experimentations and corresponding 3D finite element (FE) simulations are conducted. For this purpose, a long and thin smart sandwich cantilever beam is dimensioned and built so that it can be used later for either validating analytical Saint Venant-type solutions or for analyzing arm or blade-based smart structures and systems applications. The sandwich beam core is formed by two adjacent rows of 8 oppositely axially polarized d15 shear piezoceramic patches, and its faces are dimensionally identical and made of the same glass fiber reinforced polymer composite material. Quasi-static and static experimentations were made using a point laser sensor and a scanning laser vibrometer, while the 3D FE simulations were conducted using the commercial software $ABAQUS^{(R)}$. The measured transverse deflection by both sensors showed strong nonlinear and hysteretic (static only) variation with the actuation voltage, which cannot be caught by the linear 3D FE simulations.

• Composites Research
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• v.29 no.4
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• pp.145-150
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• 2016

Polyvinylidene fluoride (PVDF) as a representative polymer with the piezoelectric property has been studied since the 1960s. Crystalline structure of poly(vinylidene fluoride) polymer is composed of five different crystal structure of the polymer as a semi-crystalline. Among the various crystal structures, ${\beta}-type$ crystal exhibits a piezoelectricity because the permanent dipoles are aligned in one direction. Generally ${\beta}-form$ crystal structure can be obtained through the transformation of the ${\alpha}-form$ crystal structure by the stretching and it can increase the amount through the after treatment as poling process after stretching. ${\beta}-form$ crystal structure the PVDF fibers produced by wet spinning is formed through a diffusion mechanism of a polar solvent in the coagulation bath. However, it has a disadvantage that the diffusion path of the solvent remains as pores in the fiber because the fiber solidification occurs simultaneously with the diffusion of the polar solvent. These pores play a role in reducing effect of poling process owing to effect of disturbances acting on the polarization by the electric field. In this work, the drying method using the microwave was introduced to remove more effectively the residual solvent and the pore within PVDF fibers produced through wet-spinning process and piezoelectric PVDF fibers was produced by transformation of the remaining ${\alpha}$ form crystal structure into ${\beta}-crystal$ structure through the stretching process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.6
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• pp.253-258
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• 2011

Electro-mechanical coupling performance ($k_t$) of a 1-3 type Piezo-composite was analyzed numerically using FEM. The calculated physical properties of the PZT ceramics were compared with the experimental data and the accuracy of the numerical method was verified. Also the $k_t$ of the composite was analyzed with the vol% and the material properties of the constitutional parts, and the aspect ratio of the PZT rod. As the simulated results, the $k_t$ increased rapidly when the vol% of the PZT ceramics increased up to 30 vol% and saturated the constant value in the above region. And the composite using the soft matrix polymer than the hard one have the superior $k_t$ characteristics. The $k_t$ was greatly influenced by the aspect ratio of the PZT rod up to 30 vol% of PZT ceramics. To improve the $k_t$ characteristics, it is useful that the composite consist of the relatively flexible polymers and the PZT material having the excellent piezoelectric characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.11
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• pp.869-874
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• 2010

Magnetoelectric composites with compositions (1-x)[0.5PZT-0.25PNN-0.25PZN](ferroelectric) - x[$(Ni_{0.9}Zn_{0.1})Fe_2O_4$](ferrite) in which x varies as 0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0 were prepared by conventional ceramic process. The presence of two phases (ferroelectric phase with large grain and ferrite phase with small grain) in the particulate ceramic composites was confirmed by XRD, SEM and EDX. The ferroelectric and magnetic properties of the composites were studied by measuring the P-E and M-H hysterisis loop on the composite composition (x=0, 0.1, 0.2, 1), they were strongly affects of the phase content in composite. The magnetoelectric votage was measured as a function of DC magnetic field and the maximum magnetoelectric voltage coefficient of 14 mV/cm Oe was observed in x=0.2(80 mol% ferroelectric and 20 mol% ferrite phase).

• Structural Monitoring and Maintenance
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• v.5 no.2
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• pp.297-311
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• 2018

Plate and shell structure is widely applied in engineering, i.e. building roofs, aircraft wings, ship platforms, and satellite solar arrays. Its vibration problem has become increasingly prominent due to the tendency of lightening, upsizing and flexibility. As a new smart material with great actuating force and toughness, macro-fiber composite (MFC) is composed of piezoelectric fiber and epoxy resin basal body, which can be directly pasted onto the surface of plate and shell and is suitable for vibration control. This paper deduces the actuation equation of MFC coupled plate in different boundary conditions, an equivalent finite element modeling method is proposed which uses MFC actuating force as the applied excitation, and on this basis the active control simulation and experiment of MFC over plate and shell structure vibration are accomplished. The results indicate that MFC is able to implement effective control over plate and shell structure vibration in multi-band range. The comparison between experiment and simulation proves that the actuation equation deduced herein, effective and practicable, can be applied into the simulation calculation of MFC vibration control over plate and shell structure.

• Composites Research
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• v.28 no.3
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• pp.75-80
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• 2015

Poly(vinylidene fluoride-trifluoroethylene; P(VDF-TrFE)) is one of the most promising electroactive polymers with numerous application potentials in many fields of industry. Because of its good electro-mechanical properties P(VDF-TrFE) has been used for a number of sensors and actuators and also can be used for monitoring composite structure behaviors as a sensor. Three different ways (Electrical poling, annealing-cooling, and pressing) to enhance ${\beta}$-phase of P(VDF-TrFE) film were carried out. A microscopic analysis was conducted using X-ray diffraction to investigate the effect of such treatments on piezoelectric properties of P(VDF-TrFE) film. From the results, poling, annealing-cooling, and pressing were all effective to enhance ${\beta}$ crystallinity of P(VDF-TrFE) film and the maximum increase rate was 62.80% from 45.29% of the control group.