• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.91-99
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• 2018

Mechanical Properties of Rock Slope as a safe and effective interpretation should be thoroughly investigated. Clinometer, however, this new measurement due to the restrictions of the research for the joint orientation is needed. In this study, characteristics of the joint orientation can be used to analyze the joint orientation of developing a joint survey system that can be applied to the field. The system is developed and Analysis software to hardware. Hardware is composed to measure the joint orientation of measuring module, measuring the transfer of data transfer module. From the software is measuring module from the data to analyze the orientation of the joint development, and drone joint orientation survey system named. Can not be measured by the investigation, including regional development approach is a system that has been difficult if the Field Application of the lab test results of the joint orientation and effectively.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.2
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• pp.54-60
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• 2018

In this paper, we propose an efficient automatic control method for the collision avoidance of drones. In general, the drones are controlled by transmitting to the flight control (FC) module the received PWM signals transmitted from a RC controller which transduce movements of the knob into PWM signal. We implemented the collision avoidance module in-between receiver and FC module to monitor and change the throttle, pitch and roll control signals to avoid drone collision. In order to avoid the collision, a LiDAR distance sensor and a servo-motor are installed and periodically measure the obstacle distance within -45 degrees from 45 degrees in flight direction. If the collision is predicted, the received PWM signal is changed and transmitted to the FC module to prevent the collision. We applied our proposed method to a hexacopter and the experimental results show that the safety is improved because it can prevent the collision caused by the inadvertency or inexperienced maneuver.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.543-547
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• 2002

We have constructed two extended-cavity diode lasers which are phase-locked with a 9.2 GHz frequency offset. We adopted a digital servo circuit for the phase-locking. The relative linewidth of the phase-locked lasers was less than 2 Hz. Using the measured beat spectrum, we found the carrier concentration to be about 93 %. We measured phase noise and relative frequency stability of the lasers. The Allan deviation at the gate time of 20 s was $2.7{\times}10^{-19}$.

• Korean Journal of Optics and Photonics
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• v.17 no.6
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• pp.514-518
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• 2006

We have transferred highly stable 100 MHz RF through a 23 km fiber network. The fiber-induced phase noise due to the vibration and the temperature fluctuation in the optical path is detected and is compensated by configuring a noise-canceling servo. The transfer instability was $6{\times}10^{14}$ at 1 s of averaging time and $2{\times}10^{-17}$ at 10000 s of averaging time. The single sideband phase noise was greatly reduced by more than 20 dB below the Fourier frequency of 1 kHz. The transferred RF has nearly the same stability as the original reference frequency.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1320-1329
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• 1990

A static performance tester for a torque rod assembly was developed to evaluate the three characteristics of the rod rubber bushing : radial spring characteristic, thrust spring characteristic, and rotational torque characteristic. Among the various schemes considered in the conceptual design stage, the final versatile type was determined to perform three different tests in one machine. The performance testing machine carried out radial spring test, thrust spring test, and torque test of the torque rod assembly. Static performance of the torque rod assembly was evaluated with the tester developed and fatigue strength of the assembly was also tested with the servo-hydraulic structural fatigue testing machine. The life of the component was found to be related with the rubber quality and adhesionability between the rubber and the steel rod. The optimum rubber hardness was experimentally found by changing the chemical compositions of rubber, and the adhesion was improved by optimizing the shape of the outer section of a the rubber, this study ensured the development of a reliable torque rod assembly.

• International Journal of Control, Automation, and Systems
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• v.4 no.3
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• pp.325-332
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• 2006

The dynamic responses of human standing postural control were investigated when subjects were exposed to long-term horizontal vibration. It was hypothesized that the motion of standing posture complexity mainly occurs in the mid-sagittal plane. The motor-driven support platform was designed as a source of vibration. The AC Servo-controlled motors produced anterior/posterior (AP) motion. The platform acceleration and the trunk angular velocity were used as the input and the output of the system, respectively. A method was proposed to identify the complexity of the standing posture dynamics. That is, during AP platform motion, the subject's knee, hip and neck were tightly constrained by fixing assembly, so the lower extremity, trunk and head of the subject's body were individually immovable. Through this method, it was assumed that the ankle joint rotation mainly contributed to maintaining their body balance. Four subjects took part in this study. During the experiment, the random vibration was generated at a magnitude of $0.44m/s^2$, and the duration of each trial was 40 seconds. Measured data were estimated by the coherence function and the frequency response function for analyzing the dynamic behavior of standing control over a frequency range from 0.2 to 3 Hz. Significant coherence values were found above 0.5 Hz. The estimation of frequency response function revealed the dominant resonance frequencies between 0.60 Hz and 0.68 Hz. On the basis of our results illustrated here, the linear model of standing postural control was further concluded.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.8
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• pp.1-8
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• 2000

We have achieved a high aspect ratio track-following microactuator (TFMA) which is capable of driving 0.3 ${\mu}m$ magnetic head for hard disk drive (HDD). it was fabricated on silicon on insulator (SOI) wafer with 20 ${\mu}m$ trick active silicon and 2 ${\mu}m$ thick thermally grown oxide and piggyback electrostatic principle was used for driving TFMA. The first vibration mode frequency of TFMA was 18.5 kHz which is enough for a recording density of higher than 10 Gb/in$^2$. Its displacement was 1.4 ${\mu}m$ when 15 V dc bias plus 15 V ac sinusoidal driving input was applied and its electrostatic force was 50 N. The fabricated actuator shows 7.51 dB of gain margin and 50.98$^{\circ}$ of phase margin for 2.21 kHz servo-bandwidth.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.1
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• pp.82-89
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• 1998

PI controller has been used in the servo system. However the time response of the system designed using the PI control scheme does not provide with desirable time response in case of variation in system parameters or perturbation like a torque disturbance. LMFC(Linear model following controller) is being used to make the response of the system follow that of the model even though the parameter variation or the perturbation occurs. In this paper, a design method, RMFC(Robust Model Following Controller) is proposed, which use an auxiliary model in addition to the LMFC, which affords robustness against the low frequency load torque disturbance. The proposed method is more useful to rejecting the low frequency torque disturbance than LMFC. Proposed method is verified by simulation and experiment.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.3
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• pp.1-18
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• 1995

This paper deals with the vibration absorbers of gravitational and centrifugal pendulum types for vibration controls of ship's substructures such as radarmasts, bridgewings and funnels. The mathematical model of such a vibrating system with an absorber is described as a 2 degree of freedom system and an efficient formulation for optimum design of the absorber is presented. For investigation applicability of the two types of the absorbers to a structure system, numerical calculations and experiments hove been performed with variation of mass ratios for each type. According to the results of investigations, the vibration absorber of gravitational type proved to be more useful and efficient than one of centrifugal pendulum type in a view point of mass ratio.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.167-170
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• 2015

In this paper, we propose the Micturition training and Automatic feeding system to enable busy modern people can grow pets more efficiently. This system will be able to operate a smart phone application with a Bluetooth, furthermore, by using the Wifi access the Internet from anywhere and to operate remotely. This system is divided micturition board feeding unit. micturition board consists of a water pressure sensor for detecting micturition and recorder module, speaker for voice output, feeding unit consists of two servo motor for auto feeding and Bluetooth sensor for remote control. Both micturition board and feeding unit produced Arduino board and C language-based Arduino sketch program, feeding unit was able to communicate with the library to support Bluetooth communication.