Adaptive base isolation system to achieve structural resiliency under both short- and long-period earthquake ground motions

Rabiee, Ramin,Chae, Yunbyeong Sage Science Press (UK) 2019 Journal of intelligent material systems and struct Vol. No.

Wireless piezoelectric strain sensing measurement using a frequency modulation technique

Yoon, Hwan-Sik,Kim, Se-hun,Kim, Min-Hyuck,Jung, Dongsoo,Kim, Joo-Hyung,Kim, Hyeon-Ju,Lee, Ho-Saeng Sage Science Press (UK) 2015 Journal of intelligent material systems and struct Vol. No.

<P>A simple wireless strain sensor using a frequency modulation technique is presented. The sensor employs a piezoelectric transducer that produces electric voltage as it is mechanically strained. When the piezoelectric sensor is connected to a single-transistor frequency modulation circuit, the sensor output voltage causes the modulation circuit frequency to shift. This modulated signal is then wirelessly transmitted to a remote station, where a demodulation circuit retrieves the buried strain measurement data in real time. Using this technique, a dynamic strain measurement is possible without any wire connection between the sensing point and the monitoring station. In order to demonstrate the performance of the wireless strain sensor and the measurement system, a wireless measurement of a vibrating cantilevered beam is experimentally conducted. This type of sensor has numerous applications in the strain or vibration measurement of moving or rotating structures such as turbo machinery.</P>

Fabrication and characterization of vibration-driven AlN piezoelectric micropower generator compatible with complementary metal-oxide semiconductor process

Chung, Gwiy-Sang,Lee, Byung-Chul Sage Science Press (UK) 2015 Journal of intelligent material systems and struct Vol. No.

<P>This article describes the aluminum nitride (AlN)-based piezoelectric microgenerator for scavenging energy from ambient vibration. To achieve the low resonance frequency and maximize power density, a parametric study has been carried out by analytical modeling and finite element analysis. The piezoelectric microgenerator consists of AlN piezoelectric thin film with molybdenum (Mo) electrodes and silicon (Si) proof mass. The AlN was deposited on silicon-on-insulator wafer which is used as an insulating layer to defend the leakage current. The Mo electrode provides the excellent c-axis crystal growth of AlN. The fabricated AlN piezoelectric microgenerator can generate up to 6.4 nW at a frequency of 389 Hz and acceleration of 1.0 <I>g</I> (1 <I>g</I> = 9.81 m/s<SUP>2</SUP>). In addition, the output voltage and power density are 22.6 mV<SUB>rms</SUB> and 11.3 nW/mm<SUP>3</SUP>, respectively. The proposed generator is highly suitable for batch processing and has the possibility of harvesting energy from the ambient vibration.</P>

A study on the piezoelectric actuation performance of prestressed piezoelectric unimorph actuators

Sage Science Press (UK) 2014 Journal of intelligent material systems and struct Vol. No.

<P>The actuation performances of the prestressed piezoelectric unimorph actuators piezoelectric unimorph with mechanically prestressed substrate and thin layer unimorph driver are evaluated in terms of actuation displacement and force. During the performance tests, these prestressed piezoelectric unimorph actuators showed highly nonlinear behavior, in which their actuation performances were not proportional to the magnitude of the applied voltage, although normally they exhibit higher actuation performances at higher driving voltages. This means that the nominal piezoelectric material properties from the standard method were no longer valid for evaluating and predicting the actuation performances of the piezoelectric unimorph with mechanically prestressed substrate and thin layer unimorph driver actuators under high-voltage application. In this article, the nonlinear piezoelectric material properties, especially the elastic modulus and the piezoelectric strain coefficient, were obtained by considering the prestress, the applied voltage, and the re-poling treatment of the piezoelectric material inside the prestressed piezoelectric unimorph. Finally, actuation performance simulations were conducted using the nonlinear material properties, and the analytical results were compared and validated with the experimental results.</P>

Frequency response analysis of a delaminated smart composite plate

Huang, Bin,Kim, Heung Soo Sage Science Press (UK) 2015 Journal of intelligent material systems and struct Vol. No.

<P>A frequency analysis of smart composite plate with delamination at ply interface was investigated in this article. The modeling was based on an electro-mechanical coupled improved layerwise theory, with implementing finite element method. Four-node plate elements with Lagrange and Hermite cubic interpolation functions were used for in-plane structural unknowns, electric unknowns, and out-of-plane structural unknowns. The general modal reduction method was applied to solve the second-order differential equation. Numerical results showed significant shift of natural frequencies in the frequency response of tip displacement and three sensor outputs due to the presence of delamination. It is found that the delamination locations also influence the natural frequencies of smart composite structure. Thus, the proposed methodology could be a useful tool to develop system identification and structural health monitoring techniques of smart composite structure.</P>

Power evaluation of flutter-based electromagnetic energy harvesters using computational fluid dynamics simulations

Park, Jinkyoo,Morgenthal, Guido,Kim, Kyoungmin,Kwon, Soon-Duck,Law, Kincho H Sage Science Press (UK) 2014 Journal of intelligent material systems and struct Vol. No.

<P>H- and T-shaped cross sections are known to be susceptible to rotational single-degree-of-freedom aerodynamic instabilities. Here, such self-excited aerodynamic response of a T-shaped cantilever structure is used to extract energy, which is then converted into electric power through an electromagnetic transducer. The complex fluid–structure interaction between the cantilever harvester and wind flow is analyzed numerically and experimentally. To study the dynamic response of the cantilever and estimate the power output from the harvester, numerical simulations based on the vortex particle method are performed to determine the aerodynamic damping of the harvester section and to analyze the stability behavior of the section. The estimated aerodynamic damping parameter together with the mechanical and electrical damping parameters in the harvester are used to find the critical wind speed of flutter onset as well as the optimum load resistance. Wind tunnel experiments are conducted to validate the simulation results.</P>

Force Feedback Control of a Medical Haptic Master using an Electrorheological Fluid

Han, Young-Min,Kang, Pil-Soon,Sung, Kum-Gil,Choi, Seung-Bok Sage Science Press (UK) 2007 Journal of intelligent material systems and struct Vol. No.

<P>This study presents force feedback control performance of a spherical haptic device featuring an electrorheological (ER) fluid that can be used for minimally invasive surgery (MIS). As a first step, a spherical ER joint composed of rotational and stationary electrodes is designed and optimized based on mathematical torque modeling. The active force produced in MIS is generally small, even though the passive force is large. In order to meet this agreement, both clutch and brake mechanism are adopted for the ER joint. In this operation, the active (small) force feedback by the rotational electrodes and/or semi-active (large) force feedback are achieved by the stationary electrode. Subsequently, the master device is manufactured by integration of the spherical ER joint with AC motor. In order to achieve desired force trajectories, a sliding mode controller, which is robust to uncertainty, is formulated by considering mechanical friction and hysteretic behavior of the ER fluid as uncertainty. The controller is then experimentally realized. Tracking control performances for various force trajectories are presented in time domain.</P>

Field Test on Vibration Control of Vehicle Suspension System Featuring ER Shock Absorbers

Choi, Seung-Bok,Han, Young-Min,Song, Hyun Jung,Sohn, Jung Woo,Choi, Hyoung Jin Sage Science Press (UK) 2007 Journal of intelligent material systems and struct Vol. No.

<P>This study presents vibration control responses of a passenger vehicle equipped with continuously controllable electrorheological (ER) shock absorbers. As a first step, four ER shock absorbers (two for front parts and two for rear parts) are designed and manufactured based on the damping force levels and mechanical dimensions required for the middle-sized passenger vehicle. After experimentally evaluating the field-dependent damping force property and controllability, the manufactured ER shock absorbers are incorporated with the suspension of a car to be tested. Subsequently, the skyhook control algorithm, which is simple, but very effective in real field, is formulated by considering vertical, pitch, and roll motions. The controller is then realized by integrating feedback sensors, such as accelerometer and the field test is undertaken under bump and random road conditions. The control responses for the ride quality and steering stability are evaluated in both time and frequency domains. In addition, the performance comparison between conventional suspension and ER suspension is carried out.</P>

Frontal Crash Mitigation using MR Impact Damper for Controllable Bumper

Woo, David,Choi, Seung-Bok,Choi, Young Tae,Wereley, Norman M. Sage Science Press (UK) 2007 Journal of intelligent material systems and struct Vol. No.

<P>This study presents performance characteristics of a magnetorheological (MR) impact damper for controllable bumper in vehicle systems. Recently, several mechanisms are proposed in order to minimize the injury of vehicle occupants during frontal collision. One of the promising candidates is the MR fluid which undergoes significant instantaneous reversible changes in material characteristics when subjected to a magnetic field. Using this salient property, a new type of MR impact damper is devised in this work. The proposed damper is integrated with bellows to induce the flow motion and the motion is operated under flow mode. The field-dependent damping force is evaluated by computer simulation with various conditions. In order to investigate the effectiveness of the proposed impact damper, a lumped parameter mathematical model of frontal vehicle crash system including MR impact damper is developed and realized in order to evaluate acceleration peak reductions and transmitted force in the frontal collision.</P>

Online Phase Tracking of Interferometric Optical Fiber Sensors for Vibration Control

Chang, Young-Hwan,Kim, Do-Hyung,Han, Jae-Hung,Lee, IN Sage Science Press (UK) 2007 Journal of intelligent material systems and struct Vol.18 No.4

<P>Online phase tracking of an extrinsic FabryU2014;Perot interferometer (EFPI) and experimental vibration control of a composite beam with a sensing patch are investigated. EFPI sensors have nonlinearity due to their interferometric characteristics. We propose a new sensing patch for compensation of this interferometric nonlinearity. This newly developed sensing patch consists of an EFPI sensor and another sensor that can produce directional information. Therefore, it uses the advantages of their components used in conjuction in order to overcome the disadvantages of the components used separately. A sensing patch that comprises an EFPI sensor and a piezoceramic is fabricated, and the characteristics are experimentally investigated. A simple and practical logic is applied to real-time tracking of the optical phase of an interferometer. The experimental results show that the proposed sensing patch does not suffer from the nonlinear behavior of conventional EFPI sensors and the hysteretic behavior of piezoelectric materials. Moreover, it has excellent strain resolution and a wide dynamic sensing range. The application of a sensing patch has been also investigated: vibration control with this sensing patch has been performed using a fuzzy logic controller (FLC), and the possibility of using a sensing patch as a sensoriactuator is considered.</P>