• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.140-145
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• 2009

Recently, lots of research activities have been carried out to provide advanced smart control functions applying a computer networking technology to telemeter/telecontrol systems. In this paper, we suggest client/server architecture with specially designed remote and local control software for applicant those to greenhouse model. The server system collects and integrates various datas related sensor or actuator, and stores in database maintaining high quality of remote I/O control operation. Where as the client system simply operation such as control panel on the internet web browser. Implemented system well communicate interactively both monitoring and control status of greenhouse including multimedia informations. In this study we also analyze the extent of the performance enhancement in terms of overall throughput and data transfer time effected by packet size.

• Smart Structures and Systems
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• v.7 no.1
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• pp.41-57
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• 2011

A deeper understanding of the effectiveness of adopting devices mounting shape memory alloy (SMA) elements in applications targeted to the mitigation of vibrations is pursued via an experimental approach. During a seismic event, less than 1000 loading-unloading cycles of the alloy are required to mitigate the earthquake effects. However, the aging effects during the time of inactivity prior to the oscillations (several decades characterized by the yearly summer-winter temperature wave) should be considered in order to avoid and/or minimize them. In this paper, the results obtained by carrying out, in different laboratories, fatigue tests on SMA specimens are compared and discussed. Furthermore, the effects of seismic events on a steel structure, with and without SMA dampers, are numerically simulated using ANSYS. Under an earthquake excitation, the SMA devices halve the oscillation amplitudes and show re-centering properties. To confirm this result, an experimental campaign is conducted by actually installing the proposed devices on a physical model of the structure and by evaluating their performance under different excitations induced by an actuator.

• Elastomers and Composites
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• v.47 no.4
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• pp.272-281
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• 2012

Flexible/stretchable electronics have recently focused, since their applications extend to emerging flexible displays, sensors, dielectric elastomer actuator and generators, and smart surgical tools. Flexible/stretchable electrodes should be synchronized with employing mechanical deformations of either flexing or stretching modes. Thus, the research area is one of the tough subjects, since the electrodes should keep their basic functions of electrodes under various mode of mechanical deformations. In this review, we discuss the recent development in the preparation and properties of such flexible/stretchable electrodes.

• Smart Structures and Systems
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• v.4 no.6
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• pp.809-828
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• 2008

Real-time hybrid testing is an attractive method to evaluate the response of structures under earthquake loads. The method is a variation of the pseudodynamic testing technique in which the experiment is executed in real time, thus allowing investigation of structural systems with time-dependent components. Real-time hybrid testing is challenging because it requires performance of all calculations, application of displacements, and acquisition of measured forces, within a very small increment of time. Furthermore, unless appropriate compensation for time delays and actuator time lag is implemented, stability problems are likely to occur during the experiment. This paper presents an approach for real-time hybrid testing in which time delay/lag compensation is implemented using model-based response prediction. The efficacy of the proposed strategy is verified by conducting substructure real-time hybrid testing of a steel frame under earthquake loads. For the initial set of experiments, a specimen with linear-elastic behavior is used. Experimental results agree well with the analytical solution and show that the proposed approach and testing system are capable of achieving a time-scale expansion factor of one (i.e., real time). Additionally, the proposed method allows accurate testing of structures with larger frequencies than when using conventional time delay compensation methods, thus extending the capabilities of the real-time hybrid testing technique. The method is then used to test a structure with a rate-dependent energy dissipation device, a magnetorheological damper. Results show good agreement with the predicted responses, demonstrating the effectiveness of the method to test rate-dependent components.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.219-222
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• 2003

$0.2(PbMg_{1/3}Nb_{2/3}O_3)-0.8(PbZr_{0.475}Ti_{0.525}O_3)$ 조성을 이용하여 $5{\times}5{\times}5mm^3$의 적층형 세라믹 액츄에이터 소자를 tape casting 방법으로 제작하였다. 전극재로서는 Ag-Pd를 이용하여 총 50층의 layer를 적층하였으며, 적층된 액츄에이터를 $1100^{\circ}C$의 온도에서 소결하였다. X-ray diffractometer를 이용하여 제작된 소자와 열화된 소자의 구조적인 특성을 분석하였다. 제작된 소자의 열화 특성을 알아보기 위하여 60 Hz 의 triangular wave를 인가하여 열화전과 후의 p-E hystcresis loop의 변화를 살펴보았으며, 인가된 전압의 변화에 따라서 소자에서 발생되는 양의 열을 측정하였다. 파괴된 소자의 파단면에 대한 SEM 분석을 통하여 소자의 파괴 메카니즘을 알아보도록 하였다. 이로부터 전기적 기계적 열화가 소자의 동작에 미치는 영향에 대해서 알아 보았다.

• Smart Structures and Systems
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• v.7 no.5
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• pp.365-378
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• 2011

Piezo-based active structural health monitoring (SHM) requires amplifiers specifically designed for capacitive loads. Moreover, with the increase in number of applications of wireless SHM systems, energy efficiency and cost reduction for this type of amplifiers is becoming a requirement. General lab grade amplifiers are big and costly, and not built for outdoor environments. Although some piezoceramic power amplifiers are available in the market, none of them are specifically targeting the wireless constraints and low power requirements. In this paper, a piezoceramic transducer amplifier for wireless active SHM systems has been designed. Power requirements are met by two digital On/Off switches that set the amplifier in a standby state when not in use. It provides a stable ${\pm}180$ Volts output with a bandwidth of 7k Hz using a single 12 V battery. Additionally, both voltage and current outputs are provided for feedback control, impedance check, or actuator damage verification. Vibration control tests of an aluminum beam were conducted in the University of Houston lab, while wireless active SHM tests of a wind turbine blade were performed in the Harbin Institute of Technology wind tunnel. The results showed that the developed amplifier provided equivalent results to commercial solutions in suppressing structural vibrations, and that it allows researchers to perform active wireless SHM on moving objects with no power wires from the grid.

• Smart Structures and Systems
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• v.31 no.5
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• pp.437-454
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• 2023

Real-time hybrid simulation (RTHS), which has the advantages of a substructure pseudo-dynamic test, is widely used to investigate the rate-dependent mechanical response of structures under earthquake excitation. However, time delay in RTHS can cause inaccurate results and experimental instabilities. Thus, this study proposes a model-based adaptive control strategy using a Kalman filter (KF) to minimize the time delay and improve RTHS stability and accuracy. In this method, the adaptive control strategy consists of three parts-a feedforward controller based on the discrete inverse model of a servohydraulic actuator and physical specimen, a parameter estimator using the KF, and a feedback controller. The KF with the feedforward controller can significantly reduce the variable time delay due to its fast convergence and high sensitivity to the error between the desired displacement and the measured one. The feedback control can remedy the residual time delay and minimize the method's dependence on the inverse model, thereby improving the robustness of the proposed control method. The tracking performance and parametric studies are conducted using the benchmark problem in RTHS. The results reveal that better tracking performance can be obtained, and the KF's initial settings have limited influence on the proposed strategy. Virtual RTHSs are conducted with linear and nonlinear physical substructures, respectively, and the results indicate brilliant tracking performance and superb robustness of the proposed method.

• Smart Structures and Systems
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• v.14 no.6
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• pp.1173-1196
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• 2014

Real-time dynamic substructuring tests have been conducted on a cable-deck system. The cable is representative of a full scale cable for a cable-stayed bridge and it interacts with a deck, numerically modelled as a single-degree-of-freedom system. The purpose of exciting the inclined cable at the bottom is to identify its nonlinear dynamics and to mark the stability boundary of the semi-trivial solution. The latter physically corresponds to the point at which the cable starts to have an out-of-plane response when both input and previous response were in-plane. The numerical and the physical parts of the system interact through a transfer system, which is an actuator, and the input signal generated by the numerical model is assumed to interact instantaneously with the system. However, only an ideal system manifests a perfect correspondence between the desired signal and the applied signal. In fact, the transfer system introduces into the desired input signal a delay, which considerably affects the feedback force that, in turn, is processed to generate a new input. The effectiveness of the control algorithm is measured by using the synchronization technique, while the online adaptive forward prediction algorithm is used to compensate for the delay error, which is present in the performed tests. The response of the cable interacting with the deck has been experimentally observed, both in the presence of delay and when delay is compensated for, and it has been compared with the analytical model. The effects of the interface delay in real-time dynamic substructuring tests conducted on the cable-deck system are extensively discussed.

• Smart Structures and Systems
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• v.14 no.6
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• pp.1247-1267
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• 2014

Real-Time Hybrid Simulation (RTHS) is a novel approach conceived to evaluate dynamic responses of structures with parts of a structure physically tested and the remainder parts numerically modelled. In RTHS, delay estimation is often a precondition of compensation; nonetheless, system delay may vary during testing. Consequently, it is sometimes necessary to measure delay online. Along these lines, this paper proposes an online delay estimation method using least-squares algorithm based on a simplified physical system model, i.e., a pure delay multiplied by a gain reflecting amplitude errors of physical system control. Advantages and disadvantages of different delay estimation methods based on this simplified model are firstly discussed. Subsequently, it introduces the least-squares algorithm in order to render the estimator based on Taylor series more practical yet effective. As a result, relevant parameter choice results to be quite easy. Finally in order to verify performance of the proposed method, numerical simulations and RTHS with a buckling-restrained brace specimen are carried out. Relevant results show that the proposed technique is endowed with good convergence speed and accuracy, even when measurement noises and amplitude errors of actuator control are present.

• Smart Structures and Systems
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• v.16 no.5
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• pp.759-780
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• 2015

Based on the theory of piezoelasticity, the static performance of a piezoelectric bilayer cantilever fully covered with electrodes on the upper and lower surfaces is studied. Three models are considered, i.e., the sensor model, the driving displacement model and the blocking force model. By establishing suitable boundary conditions and proposing an appropriate Airy stress function, the exact solutions for piezoelectric bilayer cantilevers are obtained, and the effect of ambient thermal excitation is taken into account. Since the layer thicknesses and material parameters are distinguished in different layers, this paper gives unified solutions for composite piezoelectric bilayer cantilevers including piezoelectric bimorph and piezoelectric heterogeneous bimorph, etc. For some special cases, the simplifications of the present results are compared with other solutions given by other researches based on one-dimensional constitutive equations, and some amendments have been found. The present investigation shows: (1) for a PZT-4 piezoelectric bimorph, the amendments of tip deflections induced by an end shear force, an end moment or an external voltage are about 19.59%, 23.72% and 7.21%, respectively; (2) for a PZT-4-Al piezoelectric heterogeneous bimorph with constant layer thicknesses, the amendments of tip deflections induced by an end shear force, an end moment or an external voltage are 9.85%, 11.78% and 4.07%, respectively, and the amendments of the electrode charges induced by an end shear force or an end moment are both 1.04%; (3) for a PZT-4-Al piezoelectric heterogeneous bimorph with different layer thicknesses, the maximum amendment of tip deflection approaches 23.72%, and the maximum amendment of electrode charge approaches 31.09%. The present solutions can be used to optimize bilayer devices, and the Airy stress function can be used to study other piezoelectric cantilevers including multi-layered piezoelectric cantilevers under corresponding loads.