• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.34-34
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• 2003

Piezoelectric or magnetostrictive materials, known as smart materials, have been researched widely for sensors or actuators in micro system technology. In our research, thick sol-gel lead zirconate titanate(Pb(Zr$\sub$1-x/Ti$\sub$x/)O$_3$) films were fabricated and their characteristics were investigated f3r angular rate sensor applications. The thickness of the PZT films is 1.5${\mu}$m, which is required by a vibration angular rate sensor for a good actuation and sensing. The remnant polarization of the PZT flms is 12.0 ${\mu}$C/$\textrm{cm}^2$. The electromechanical constants of PZT thin film showed the value of susceptance(B) of 4800${\mu}$ s at capacitance of 790pF. The PZT films were applied to the vibration angular rate sensor structure and the vibration of 1.78 ${\mu}$m in amplitude at the resonant frequency of 35.8㎑ was obtained by driving voltage of 5V$\sub$p-p/ of bulk piezoelectric materials with out of phase signal through voltage and inverting amplifier.

• Journal of Internet of Things and Convergence
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• v.6 no.3
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• pp.75-80
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• 2020

Recently, the size of the IoT sensor has been decreased and the collecting direction of the IoT sensor for acquiring the data have been changed from 2D to 3D. It makes sensor structure complex. In the fabrication of the complex structure, 3D printing technology has more useful than traditional manufacturing technologies. Among 3D printing technologies, FDM (fused deposition modeling) is a candidate technology to fabricate a small IoT sensor because the price of the machine and the material is cheap. In the FDM process, a 3D shape is made by depositing the melted filament. Recently, the patent of FDM technology is expired and cheat machines are developed based on the open-source. In the FDM process, mechanical properties of a fabricated part is affected by a lots of factors such as the kind of material and process parameters. Among them, infill is affecting the mechanical properties and the production lead time as well. In this work, a new method to optimize the FDM process with the consideration of mechanical property and production lead time was proposed. To verify the method, the fabrications were performed with the different infill rates. The results of tensile tests were analyzed to verify the proposed method.

• Korean Journal of Applied Biomechanics
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• v.31 no.3
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• pp.183-188
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• 2021

Objective: The purpose of this study was to develop a stretchable joint motion sensor that is based on silver nano-particle. Through this sensor, it can be utilized as an equipment for rehabilitation and analyze joint movement. Method: In this study, precursor solution was created, after that, nozel printer (Musashi, Image master 350PC) was used to print on a circuit board. Sourcemeter (Keithley, Keithley-2450) was used in order to evaluate changes of electric resistance as the sensor stretches. In addition, the sensor was attached on center of a knee joint to 2 male adults, and performed knee flexion-extension in order to evaluate accurate analysis; 3 infrared cameras (100 Hz, Motion Master 100, Visol Inc., Korea) were also used to analyze three dimensional movement. Descriptive statistics were suggested for comparing each accuracy of measurement variables of joint motions with the sensor and 3D motions. Results: The change of electric resistance of the sensor indicated multiple of 30 times from initial value in 50% of elongation and the value of electric resistance were distinctively classified by following 10%, 20%, 30%, 40% of elongation respectively. Through using the sensor and 3D camera to analyze movement variable, it showed a resistance of 99% in a knee joint extension, whereas, it indicated about 80% in flexion phase. Conclusion: In this research, the stretchable joint motion sensor was created based on silver nanoparticle that has high conductivity. If the sensor stretches, the distance between nanoparticles recede which lead gradual disconnection of an electric circuit and to have increment of electric resistance. Through evaluating angle of knee joints with observation of sensor's electric resistance, it showed similar a result and propensity from 3D motion analysis. However, unstable electric resistance of the stretchable sensor was observed when it stretches to maximum length, or went through numerous joint movements. Therefore, the sensor need complement that requires stability when it comes to measuring motions in any condition.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.10
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• pp.733-740
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• 2004

In this paper, an improved algorithm for the extraction of respiration signal from the electrocardiogram (ECG) is proposed. The whole system consists of two-lead electrocardiogram acquisition (lead Ⅰ and Ⅱ), baseline fluctuation elimination, R-wave detection, adjustment of sudden change in R-wave area using moving average, and optimal lead selection. In order to solve the problem of previous algorithms for the ECG-derived respiration (EDR) signal acquisition, we proposed a method for the optimal lead selection. An optimal EDR signal among the three EDR signals derived from each lead (and arctangent of their ratio) is selected by estimating the instantaneous frequency using the Hilbert transform, and then choosing the signal with minimum variation of the instantaneous frequency. The proposed algorithm was tested on 15 subjects, and we could obtain satisfactory respiration signals that shows high correlation (r>0.9) with the signal acquired from the chest-belt respiration sensor.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.51-56
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• 2005

A PVC membrane electrode for lead ion based on 1-phenyl-2-(2-quinolyl)-1,2-dioxo-2-(4-bromo) phenylhydrazone (PQDBP) as ionophore was demonstrated. The optimum composition of the membrane was 30 wt% poly(vinyl chloride), 60 wt% dibutyl phthalate as a plasticizer, 4 wt% ionophore and 6 wt% sodium tetraphenylborate as additive. The electrode exhibits a Nernstian response (28.7 mV decade$^{-1}$) for Pb$^{2+}$ over a wide concentration range (1.0 ${\times}$ 10$^{-1}$ to 1 ${\times}$ 10$^{-6}$ M) with a detection limit of 6.0 ${\times}$ 10$^{-7}$ M. This sensor has a short response time and can be used for at least 2 months without any divergence in potentials. The proposed electrode could be used in a pH range of 3.0-6.0 and revealed good selectivities for Pb$^{+2}$ over a wide variety of other metal ions. It was successfully applied as an indicator electrode for the potentiometric titration of lead ion with potassium chromate and for the direct determination of lead in mine.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.3
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• pp.260-270
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• 2011

The electromechanical impedance(E/M)-based method detects local structural damages based on variations of electrical impedance signatures which are obtained from piezoelectric sensors bonded to the structure and excited in high frequency band. In this method, temperature changes may result in significant impedance variations and lead to erroneous diagnostic results of the structure. To tackle this problem, a new technique providing a 2-dimensional damage feature related to the temperature information is proposed to distinguish the structural damage from the undesirable temperature variation. For experimental tests to validate the proposed method, damages are introduced by bolt loosening to a bolt-jointed steel beam, and impedance signals are measured under varying temperature conditions through a piezoelectric sensor attached on the beam. A freely suspended piezoelectric sensor is additionally utilized to obtain temperature information indirectly from resistance signatures. From a relationship between the damage index (from a constrained sensor) and the temperature (from a freely suspended sensor or a temperature sensor), damages can be detected more clearly under varying temperature compared to other conventional approaches.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.284-288
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• 2003

In this paper, a mobile robot system which have trajectory of metal tape- type is designed and manufactured. The mobile robot for manless-transportation consists of sensor-part with ultrasonic and infrared sensor, motor-part with motor and encoder, user interface-part, central control-part and computer interface-part. The ultrasonic sensor detects obstacles which can appear during the mobile robot is move. The infrared sensor has ability which detect the metal tape trajectory and then lead the robot to a correct position. By using the mobile robot, the flexiblity of a moving trajectory is improved and cost which can happen in using a mobile robot system having trajectory is cut as well.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.448-452
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• 2007

Many industrial operations require continuous or nearly-continuous operation of machines, which if interrupted can result in significant financial loss. The condition monitoring of these machines has received considerable attention recent years. Rapid developments in semiconductor, computing, and communication with a remote site have led to a new generation of sensor called "smart" sensors which are capable of wireless communication with a remote site. The purpose of this research is the development of smart sensor using which can on-line perform condition monitoring. This system is addressed to detect conditions that may lead to equipment failure when it is running. Moreover it will reduce condition monitoring expense using low cost MEMS accelerometer. This sensor can receive data in real-time or periodic time from MEMS accelerometer. Furthermore, this system is capable for signal preprocessing task (High Pass Filter, Low Pass Filter and Gain Amplifier) and analog to digital converter (A/D) which is controlled by CPU. A/D converter that converts 10bit digital data is used. This sensor communicates with a remote site PC using TCP/IP protocols. Wireless LAN contain IEEE 802.11i-PSK or WPA (PSK, TKIP) encryption. Developed sensor executes performance tests for data acquisition accuracy estimations.

• Smart Structures and Systems
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• v.16 no.2
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• pp.329-345
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• 2015

As commonly known, sensor errors and faulty signals may potentially lead structures in vibration to catastrophic failures. This paper presents a new approach to deal with sensor errors/faults in vibration control of structures by using the Fault detection and isolation (FDI) technique. To demonstrate the effectiveness of the approach, a space truss structure with semi-active devices such as Magneto-Rheological (MR) damper is used as an example. To address the problem, a Linear Matrix Inequality (LMI) based fixed-order $H_{\infty}$ FDI filter is introduced and designed. Modeling errors are treated as uncertainties in the FDI filter design to verify the robustness of the proposed FDI filter. Furthermore, an innovative Fuzzy Fault Tolerant Controller (FFTC) has been developed for this space truss structure model to preserve the pre-specified performance in the presence of sensor errors or faults. Simulation results have demonstrated that the proposed FDI filter is capable of detecting and isolating sensor errors/faults and actuator faults e.g., accelerometers and MR dampers, and the proposed FFTC can maintain the structural vibration suppression in faulty conditions.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.7
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• pp.346-352
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• 2006

In Brushless DC Motor, there are Permanent Magnets (PMs) with driving circuit and sensor for detecting to rotor position and rotation speed. In the case of using hall IC sensor which response to magnetic flux, that is required to additional sensor magnet for rotor position detecting. Most of BLDC motor, However, take asymmetrical overhang of PM in rotor instead of additional sensor magnet for operating of hall IC sensor. The asymmetrical overhang of PM occur rotor thrust to z-axis direction that is lead to not only damage of bearing but also intensive noise and vibration. Therefore, the analysis of magnet overhang effect in the side of vibration and drive to hall If sensor is required to precise. In this paper, 2-D Finite Element Method is used to solve precise field computation and thrust of z-axis direction considering asymmetrical magnet overhang. And also the z-axis thrust from the analysis result is compared to experimental result. In conclusion, the purpose of this paper minimize to noise and vibration of BLDC Motor as analyzes to asymmetrical magnet overhang effect.