• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.929-933
• /
• 2004

A robot manipulator is usually operated in two modes: free motion and constraint motion according to the fact whether the robot comes into contact with the environment or not. At the moment of contact, impact occurs, and sometimes, it can possibly degrade the robot's performance such as vibration and at worst, shortens its lifetime. In this article, a new proposed algorithm is described by introducing a command signal modification method on the basis of impedance control and a validity of the proposed algorithm is demonstrated by showing the simulation study.

• 대한인간공학회지
• /
• 제16권1호
• /
• pp.15-27
• /
• 1997

The objectives of this study were twofold; (1) to determine an optimal handle size of a signal billy, based on the subjective assessment of grip comfort and (2) to investigate the relationship between hand anthropometry and the optimal handle size. Thirty-seven university male students were asked to rate seven cylindrical handles of different diameters in barehanded and gloved conditions, respectively. Among these handles, 3.5cm diameter of the handle size was found to be the most comfortable, in both bardhanded and gloved conditionsl. However, no statistically significant reduction in grip comfort occurred within handle diameter ranging from 2.5cm to 4.0cm. As the handle diameter was deivated from the range, grip discomfort in creased significantly. A Spearman rank correlation coefficient test revealed that hand anthropometries such as finger lengths, hand circumference, and hand thickness were statistically significant factors on the determination of the optimal handle size. The implications of these findings were discussed. The results of this study can be used as guidelines in designing the hand tools for power grip.

• ETRI Journal
• /
• 제37권4호
• /
• pp.677-684
• /
• 2015

Recently, orthogonal frequency-division multiplexing (OFDM) was applied to VLC systems owing to its high rate capability. On the other hand, a real-valued unipolar OFDM signal for VLC significantly reduces bandwidth efficiency. For practical implementation, channel estimation is required for data demodulation, which causes a further decrease in spectral efficiency. In addition, the large fluctuation of an OFDM signal results in poor illumination quality, such as chromaticity changes. This paper proposes a spectrally efficient method based on a hidden-pilot-aided precoding technology for VLC with less flickering than a conventional OFDM-based method. This approach can obtain channel information without any loss of bandwidth efficiency while ensuring illumination quality by reducing the flickering effect of an OFDM-based VLC. The simulation results show that the proposed method provides a 6.4% gain in bandwidth efficiency with a 4% reduction in flicker compared to a conventional OFDM-based method.

• 대한전자공학회논문지
• /
• 제24권5호
• /
• pp.896-904
• /
• 1987

In this paper, a design method for sequential circuit which is easy to have Built-in Self Test is kproposed using the functional advantages of multifunctional BILBO and LSSD. To achieve the hardware reduction, it is designed that a multifunctional BILBO has double operational functions of NLFSR and LFSR, when neccessary, and that test signal could be used as an input-output signal in the same line. By applying the proposed multifunctional BILBO to the sequential PLA, the test patterns and the additional circuit could be reduced in test operation and the propagation delay is vanished in normal operation, as we expected. Above them, the partitioned method for large scale sequential circuit is also suggested and it is observed that test patterns and additional circuit in them reduced by this method.

• 선박안전
• /
• 통권36호
• /
• pp.71-78
• /
• 2014

If we don't know the intention of altering course of a target ship when being in a head-on or a crossing situation, we may be confused about our decision making to change our course for collision avoidance and be in a danger of collision. In order to solve these problems, we need to develop an automatic detection system on altering course of a target ship for efficient collision avoidance. In this paper, we proposed an early detection system on altering course of a target ship using the steering wheel signal. This system will contribute to the reduction of collision accidents and also be used to the VTS system and the analysis of marine accidents.

• Journal of Power Electronics
• /
• 제16권1호
• /
• pp.388-397
• /
• 2016

An error-compensated pulse width modulator (ECPWM) is proposed to improve the baseband harmonic performance and the switching loss of voltage source inverters (VSIs). Selecting between harmonic distortion and switching loss is a design tradeoff in the conventional space vector pulse width modulation. In this work, an accumulated difference in produced and desired phase voltages is considered to adjust the reference signal. This mechanism can compensate for the voltage error in the previous carrier period. With error compensation every half-carrier period, the proposed ECPWM allows one-half reduction in carrier frequency without scarifying baseband harmonic distortion. The proposed modulator is applied to a three-phase VSI with R-L load and a motor-speed-control system for experiments. The measured efficiency and operating temperature of switches confirm the effectiveness of the proposed scheme.

• Journal of Power Electronics
• /
• 제6권2호
• /
• pp.139-145
• /
• 2006

This paper describes the ultra precise position estimation of a servomotor using a sinusoidal encoder based on Arcsine Interpolation Method for the cost reduction of circuit design. The amplitude and offset errors of the sinusoidal encoder output signals, from the encoder itself and analog signal processing procedures, are effectively compensated and on-line tuned by utilizing a low cost programmable differential amplifier without any special expensive equipment. For a theoretical evaluation of the practical resolution of this system, the relationship between the amplitude of ADC(Analog to Digital Converter) input signal errors and the anticipated resolution is also addressed. The performance of the proposed method is verified by comparing it with speed control characteristics of the servomotor driving system using a digital incremental 50,000ppr encoder in the experiments.

• Journal of Power Electronics
• /
• 제10권4호
• /
• pp.365-373
• /
• 2010

This paper proposes a hybrid single carrier sinusoidal modulation suitable for multiphase multilevel inverters. Multiphase multilevel inverters are controlled by hybrid modulation to provide multiphase variable voltage and a variable frequency supply. The proposed modulation combines the benefits of fundamental frequency modulation and single carrier sinusoidal modulation (SC-SPWM) strategies. The main characteristics of hybrid modulation are a reduction in switching losses and improved harmonic performance. The proposed algorithm can be applied to cascaded multilevel inverter topologies. It has low computational complexity and it is suitable for hardware implementations. SC-SPWM and its base modulation design are implemented on a TMS320F2407 digital signal processor (DSP). A Complex Programmable Logic Device realizes the hybrid PWM algorithm and it is integrated with a DSP processor for hybrid SC-SPWM generation. The feasibility of this hybrid modulation is verified by spectral analysis, power loss analysis, simulation and experimental results.

• 동력기계공학회지
• /
• 제10권4호
• /
• pp.165-171
• /
• 2006

An experiment to observe reduction of pressure fluctuation in the compressing system utilizing snubber has done. The experiment measured pressure at inlet and outlet of snubber. It used an air compressor as a model of hydrogen one. Snubber with buffer and snubber without buffer were used to get comprehensive comparison between both of that snubber. An analysis by using Fast Fourier Transform (FFT) method was conducted to verify working pressure frequency. With this method pure signal of static pressure was filtered from noisy signal. The experiment was run for several speeds of piston movement. It was controlled by adjustable frequency regulator that controled rotation of actuator motor. This was connected to the piston-reciprocating compressor with V-belt. From result obtained, the fluctuation was increasing proportionally when frequency of driver motor was increased.

• 정보저장시스템학회논문집
• /
• 제7권1호
• /
• pp.42-46
• /
• 2011

Holographic Data Storage System (HDSS), one of the next generation data storage devices, is a 2-dimensional page oriented memory system using volume hologram. HDSS has many noise sources such as crosstalk, scattering and inter pixel interference, etc. The noise source is changing intensity of the light used for carrying the data signal in HDSS. The inter pixel interference results in decrease of Signal to Noise Ratio and increase of Bit Error Rate. In order to improve these problems, this paper proposes to compensate the inter pixel interference with simple interference mask.