• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1921-1930
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• 1997

This paper presents the effective technique to design a six-axis load cell by using experimental design with an orthogonal array. A binocular structure is used as a basic sensing element for a load cell instead of the parallel plate structure. The finite element method is adopted to obtain strain distributions of the sensing element, and by doing the analysis of variances, its results are utilized in determining the factor which is more influential to the output strain. Calibration test results show that the developed six-axis loa cell with the maximum capacities of 196 N in forces and 19.6 N. m in moments is evaluated to be useful with the coupling error less than 2.5%.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.601-607
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• 2003

The column type is used as the sensing element of the load cell to measure the large force in the range of 10$^4$~ 10$^{7}$ N. However. it is not easy to handle the load with large capacity due to its size. It is, therefore, necessary to design a compact load cell with a low aspect ratio. Thus this paper showed the characteristic evaluation of compact load cell with respect to the shape of supporting plate. The supporting plate of the load cell was an annular type with inner(D$_{i}$) and outer(D$_{o}$) diameters. Using the strain distribution obtained from FEM. the supporting plate was designed to get the stable output voltage of the load cell. The three designed supporting plates were manufactured, and the result of characteristic experiment of the load cell, using the 10 MN hydraulic force standard machine, was compared with FEM.M.M.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.269-278
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• 2003

In this study, the method of the finite element modeling for free vibration control of beam-type smart structures with bonded plate-type piezoelectric sensors and actuators is proposed. Constitutive equations for the direct piezoelectric effect and converse piezoelectric effect of piezoelectric materials are considered. By using the variational principle, the equations of motion for the smart beam finite element are derived, The proposed 2-node beam finite element is an isoparametric element based on Timoshenko beam theory. Therefore, by analyzing beam-type smart structures with smart beam finite elements, it is possible to simulate the control of the structural behavior by applying voltages to piezoelectric actuators and monitoring of the structural behavior by sensing voltages of piezoelectric sensors. By using the smart beam finite element and constant-gain feed back control scheme, the formulation of the free vibration control for the beam structures with bonded plate-type piezoelectric sensors and actuators is proposed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.771-780
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• 2010

This paper describes the design process of a six-component force/torque (F/T) sensor. The new six-component F/T sensor having leaf spring ends has been developed using a cross beam structure as the basic sensing element. Fundamental strain analysis of both ends fixed beam having a leaf spring structure is performed by finite element analysis. In order to obtain similar output sensing strains from the six component loads and minimize coupling strains, the optimal location of strain gages is determined and the strain gages are connected so that the bridge circuits with four strain gages would be balanced. Using leaf spring ends instead of rigid fixed ends, remarkable increment in output sensing strain can be achieved for two component forces. Several modifications in design result in a similar sensing strain of approximately $400\;{\mu}m/m$ for the six-component forces and moments, and a reduced coupling strain of $0\;{\mu}m/m$ between the forces and moments.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.601-603
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• 2005

Refocusing methods are used to compensate optical performance degradation of high resolution satellite camera during on-orbit operation. Due to mechanical vibration during launch and thermal vacuum environment of space where camera is exposed, the alignment of optical system may have error. The focusing error is dominant of misalignment and caused by the de-space error of secondary mirror of catoptric camera, which is most sensitive to vibration and space environment. The high resolution camera of SPOT, Pleiades and KOMPSAT2 have refocusing device to adjust focusing during orbital operation while QuickBird of US does not use on orbit refocusing method. For the Korsch type optical configuration which is preferred for large aperture space remote sensing camera, secondary mirror and folding mirror are available as refocusing element.

• Current Optics and Photonics
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• v.6 no.3
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• pp.288-296
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• 2022

We propose and experimentally demonstrate a novel photonic compressive sensing (CS) scheme for acquiring sparse radio frequency signals with adjustable compression ratio in this paper. The sparse signal to be measured and a pseudo-random binary sequence are modulated on consecutively connected chirped pulses. The modulated pulses are compressed into short pulses after propagating through a dispersive element. A programmable optical filter based on spatial light modulator is used to realize spectral segmentation and demultiplexing. After spectral segmentation, the compressed pulses are transformed into several sub-pulses and each of them corresponds to a measurement in CS. The major advantage of the proposed scheme lies in its adjustable compression ratio, which enables the system adaptive to the sparse signals with variable sparsity levels and bandwidths. Experimental demonstration and further simulation results are presented to verify the feasibility and potential of the approach.

• Journal of the Korean Magnetics Society
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• v.26 no.2
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• pp.62-66
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• 2016

We designed a model composed a ring type magnet, a yoke, and a sensing coil buried in a projectile for calculating the muzzle velocity based on the voltage induced from sensing coil by simulation. The muzzle velocity was calculated from the master curve obtained through the voltage induced from sensing coil by simulation. The induced voltage increased with increasing the diameter of sensing coil. The projectile's velocity was proportional to the induced voltage when the sensing coil was buried in projectile. The projectile will be surely exploded at the target region by inputting the information of muzzle velocity variation corrected the diameter effect of induced voltage of sensing coil.

• Structural Engineering and Mechanics
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• v.19 no.5
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• pp.477-501
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• 2005

In this study, a new smart beam finite element is proposed for the finite element modeling of beam-type smart structures that are equipped with bonded plate-type piezoelectric sensors and actuators. Constitutive equations for the direct piezoelectric effect and converse piezoelectric effect of piezoelectric materials are considered in the formulation. By using a variational principle, the equations of motion for the smart beam finite element are derived. The proposed 2-node beam finite element is an isoparametric element based on Timoshenko beam theory. The proposed smart beam finite element is applied to the free vibration control adopting a constant gain feedback scheme. The electrical force vector, which is obtained in deriving an equation of motion, is the control force equivalent to that in existing literature. Validity of the proposed element is shown through comparing the analytical results of the verification examples with those of other previous researchers. With the use of smart beam finite elements, simulation of free vibration control is demonstrated by sensing the voltage of the piezoelectric sensors and by applying the voltages to the piezoelectric actuators.

• Computers and Concrete
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• v.23 no.6
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• pp.399-408
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• 2019

Structural health monitoring is important for the safety of lives and asset management. In this study, numerical models were developed for the piezoresistive behavior of smart concrete based on finite element (FE) method. Finite element models were calibrated with experimental data collected from compression test. The compression test was performed on smart concrete cube specimens with 75 mm dimensions. Smart concrete was made of cement CEM II 42.5 R, silica fume, fine and coarse crushed limestone aggregates, brass fibers and plasticizer. During the compression test, electrical resistance change and compressive strain measurements were conducted simultaneously. Smart concrete had a strong linear relationship between strain and electrical resistance change due to its piezoresistive function. The piezoresistivity of the smart concrete was modeled by FE method. Twenty-noded solid brick elements were used to model the smart concrete specimens in the finite element platform of Ansys. The numerical results were determined for strain induced resistivity change. The electrical resistivity of simulated smart concrete decreased with applied strain, as found in experimental investigation. The numerical findings are in good agreement with the experimental results.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.4
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• pp.93-100
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• 1998

Pyoelectric infrared detectors based on La-modified PbTiO3 (PLT) thin films have been fabricated by RF magnetron sputtering and micromachining technology. The detectors form Pb$_{1-x}$ La$_{x}$Ti$_{1-x}$ O$_{3}$ (x=0.05) thin film ferroelectric capacitors epitaxially grown by RF magnetron sputtering on Pt/MgO (100) substrate. The sputtered PLT thin film exhibits highly c-axis oriented crystal struture that no poling trealization for sensing applications is required. This is an essential factor to increase the yield for realization of an infrared image sensor. Micromachining technology is used to lower the thermal mass of the detector by giving maximum sensor efficiency. Polyimide is coated on top of the sensing elements to support the fragile structure and the backside of the MgO substrate is selectively eteched to reduce the heat loss. The sensing element exhibited a very high detectivity D* of 8.5*10$^{8}$ cm..root.Hz/W at room temperature and it is about 100 times higher than the case of micromachining technology is not used. a sensing system that detects the position as well as the existence of a human body is realized using the array sensor.sor.