• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.202-206
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• 2014

The common vibration energy harvester effectively converts mechanical vibration to electric power at a specific resonance frequency that must match the ambient excitation frequency. The resonance frequencies of energy harvesters are fixed during the design process and could not be changed after fabrication. In this paper, we proposed the new frequency tuning which uses the rotatable spring in order to adjust the spring constants. By this tuning method, the resonance frequency of the system can simply be manipulated using spring rotation. The proposed energy harvester has been successfully tuned to a resonance frequency between 23 and 32 Hz. The experimental results demonstrated that the proposed energy harvester could generate a maximum output power of $60{\mu}W$ with an acceleration of 0.5 g ($1g=9.81m/s^2$), and that the resonance frequency of the harvester was able to tune approximately 31.4%. When the proposed harvester was attached to an automobile engine, the maximum open circuit voltage of 1.78 Vpp was produced at 700 rpm.

• The Journal of the Convergence on Culture Technology
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• v.4 no.4
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• pp.419-427
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• 2018

This paper designs and develops auto-tuning temperature controller with multi-channel, which controller with multi-channel could control a number of control system simultaneously. This controller has multi-channel input and output. And a number of control algorithms run in this controller simultaneously and independently. Firstly we present design method of controller with multi-channel. Secondly we design electrical circuit of sensor input, controller output and power control for temperature control board. And finally we design data protocol for serial communication to monitor control state and present verification of temperature controller with muiti-channel through field experiment.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.5
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• pp.525-532
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• 2014

The sensing of a stack coolant deficiency is very important in that cooling performance of a fuel cell, overheating prevention of a stack or coolant heater. This paper explains the performance comparison between the coolant contact/noncontact level sensors and coolant deficiency sensing logic using the pressure sensor in a stagnant or circulating flow. Throughout the comparison, the pressure sensor is more suitable than the other sensors in terms of the precision, fast response, sensing frequency. After the experiment, the pressure sensor is equipped to an FCEV(Fuel Cell Electric Vehicle) to verify sensing definitely. There was no miss-sensing using pressure sensor while FCEV runs in the conditions of the paved road and cross country road.

• Journal of the Optical Society of Korea
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• v.17 no.4
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• pp.312-316
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• 2013

A novel fiber-optic sensor system is suggested in which fiber Bragg grating sensors are demodulated by a wavelength-sweeping fiber laser source and a spectrometer. The spectrometer consists of a diffraction grating and a 512-pixel photo-diode array. The reflected Bragg wavelength information is transformed into spatial intensity distribution on the photo-diode array. The peak locations linearly correspond to the Bragg wavelengths, regardless of the nonlinearities in the wavelength tuning mechanism of the fiber laser. The high power density of the fiber laser enables obtaining high signal-to-noise ratio outputs. The improved demodulation characteristics were experimentally demonstrated with a fiber Bragg grating sensor array with 5 gratings. The sensor outputs were in much more linear fashion compared with the conventional tunable band-pass filter demodulation. Also it showed advantages in signal processing, due to the high level of photo-diode array signals, over the broadband light source system, especially in measurement of fast varying dynamic physical quantities.

• Journal of Sensor Science and Technology
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• v.28 no.2
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• pp.121-126
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• 2019

The voltage-controlled oscillator is one of the fundamental building blocks that determine the signal quality and power consumption in RF transceivers for wireless sensor networks. Ring oscillators are attractive owing to their small form factor and multi-phase capability despite the relatively poor phase noise performance in comparison with LC oscillators. The phase noise of a ring oscillator can be improved by using a coupled structure that works at a lower frequency. This paper introduces a 2.4 GHz low-noise ring oscillator that consists of two 3-stage coupled ring oscillators. Each sub-oscillator operates at 800 MHz, and the multi-phase signals are combined to generate a 2.4 GHz quadrature output. The voltage-controlled ring oscillator designed in a 65-nm standard CMOS technology has a tuning range of 800 MHz and exhibits the phase noise of -104 dBc/Hz at 1 MHz offset. The power consumption is 13.3 mW from a 1.2 V supply voltage.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.9
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• pp.1071-1084
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• 1992

In this paper, the method for navigation and obstacle avoidance of the autonomous mobile robot is proposed. The proposed algorithms are based on the fuzzy inference system which is able to deal with imprecise and uncertain information. The self-tuning algorithm, which adopts the simplex method, modifies the parameters of membership functions of the input-output linguistic variables by changing the support of these fuzzy sets according to the integral of absolute error(IAE) of the system response. The wall-follwing navigation and obstacle avoidance of the mobile robot are based on range data measured from the internal sensors(encoder) and the outer sensors(sonar sensor). In addition, the algorithm for the obstacle detection proposed in this paper is based on the expert's experience. Finally, the effectiveness of navigation and obstacle avoidance algorithm is demonstrated through simulation and experiment.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.3
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• pp.204-209
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• 2016

In this paper, an unmanned delivery service using drone was proposed and verified the feasibility. The multicopter has GPS for autopilot and a camera for remote control by human operator. The gripper for manipulation of delivery object was designed and evaluated. The multicopter flies to a given position automatically based on GPS, and approaches to the prepared delivery desk by remote control of human operator using the received image from the multicopter. GPS sensor verification and experimental PID tuning were performed to ensure the flight stability. The flight tests were carried out to verify the feasibility of delivery service.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.203-206
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• 2003

Thermo-optic tunable filter, with 4-pairs of H/L layers for DBR, was designed and fabricated. The transmittance characteristics of the filter were measured. Additionally, heating system and temperature sensor system were used in order to observe property of the filter by thermo-optic effect. The tuning efficiency of the filter was measured to be 0.144nm/K$^{-1}$ showing the tuning range of 9.4nm for the temperature variation of 64.7$^{\circ}C$. Filter, lens and fiber were aligned by micro-optical bench.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9C
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• pp.1252-1257
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• 2004

This paper presents a decentralized LQ-PID controller for the TITO system which satisfies the performance of good command following, disturbance rejection, and sensor noise reduction that is design specifications in the frequency domain The procedure is developed by establishing the relationship between the closed-loop state equations including the decentralized PID tuning parameters and the closed-loop state equations of LQR and by selecting the weighting factors Q and R of the cost function in order to satisfy the design specifications in the frequency domain.

• Journal of Sensor Science and Technology
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• v.20 no.4
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• pp.230-233
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• 2011

In this paper, highly-efficient optical gating in a junction device based on vanadium dioxide($VO_2$) thin film grown by a sol-gel method was investigated as a gate terminal of a three-terminal device using infrared light with a wavelength of ~1554.6 nm. Due to the photoinduced phase transition, the threshold voltage of the $VO_2$ junction device, at which the device current abruptly jumps, could be tuned with a sensitivity of ~96.5 V/W by adjusting the optical power of the infrared light directly illuminating the device. Compared with the tuning efficiency of the previous device fabricated using $VO_2$ thin film deposited by a pulsed laser deposition method, the threshold voltage of this device could be tuned by ~76.8 % at an illumination power of ~39.8 mW resulting in a tuning efficiency of ~1.930 %/mW, which is ~4.9 times larger than the previous device.