• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.461-465
• /
• 1996

In servo systems such as the computer hard disk, surface mountiong device and robot manipulators, the high precision and high speed are increasingly demanding. In these examples, the repeatable errors exist and the repetitive controller removes these errors effectively by adding signals calculated from the previous cycle errors to the existing feedback controller. The experimental results of the position tracking control and contact force control show that the repetitive control effectively improves the precision of mechanical servo systems.

• Tribology and Lubricants
• /
• v.38 no.5
• /
• pp.185-190
• /
• 2022

Among the operating limits of a heat pipe, the capillary limit is significantly affected by the characteristics of the wick, which is determined by the capillary performance. The major parameters for determining capillary performance are the maximum capillary pressure and the spreading characteristics that can be expected through the wick. A well-designed wick structure improves capillary performance and helps improve the stability of the heat pipe by enhancing the capillary limit. The capillary performance can be improved by forming a porous microstructure on the surface of the wick structure through surface modification techniques. In this study, a microstructure is formed on the surface of the wick by using a surface modification method (i.e., an electrochemical etching process). In the experiment, specimens are prepared using stainless-steel screen mesh wicks with various fabrication conditions. In addition, the spreading and capillary rise performances are observed with low-surface-tension fluid to quantify the capillary performance. In the experiments, the capillary performance, such as spreading characteristics, maximum capillary pressure, and capillary rise rate, improves in the specimens with microstructures formed through surface modification compared with the specimens without microstructures on the surface. The improved capillary performance can have a positive effect on the capillary limit of the heat pipe. It is believed that the surface microstructures can enhance the operational stability of heat pipes.

• Journal of Institute of Control, Robotics and Systems
• /
• v.19 no.4
• /
• pp.341-348
• /
• 2013

A location estimation algorithm based on the sea-surface beacon is proposed in this paper. The beacon is utilized to provide ultrasonic signals to the underwater vehicles around the beacon to estimate precise position of underwater vehicles (ROV, AUV, Diver robot), which is named as USBL (Ultra Short Baseline) system. It utilizes GPS and INS data for estimating its position and adopts DWT (Discrete Wavelet Transform) de-noising filter and UKF (Unscented KALMAN Filter) elaborating the position estimation. The beacon system aims at estimating the precise position of underwater vehicle by using USBL to receive the tracking signals. The most important one for the precise position estimation of underwater vehicle is estimating the position of the beacon system precisely. Since the beacon is on the sea-waves, the received GPS signals are noisy and unstable most of times. Therefore, the INS data (gyroscope sensor, accelerometer, magnetic compass) are obtained at the beacon on the sea-surface to compensate for the inaccuracy of the GPS data. The noises in the acceleration data from INS data are reduced by using DWT de-noising filter in this research. Finally the UKF localization system is proposed in this paper and the system performance is verified by real experiments.

• Journal of the Semiconductor & Display Technology
• /
• v.18 no.1
• /
• pp.117-122
• /
• 2019

Pipes are widely used in various industries such as automobile, anti-vibration devices, factories and ship building. Chamfering is one of the most critical processes in pipe manufacturing which removes burrs of the pipes for better surface quality. In most cases, the defects of the chamfered surface are originated from the structural vibrations of the chamfering machine. In this study, the dynamic characteristics of a chamfering machine have been analyzed though the experiment and the computer simulation. And the effects of the design parameters affecting the stability of the machine have been investigated to stabilize the machine structure and further to reduce structural vibrations. The result shows that design alterations to stabilize the machine can suppress the defects of the machined surface as well as the vibrations during chamfering.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1920-1925
• /
• 2004

This paper describes a new method for 3D object recognition which used surface segment-based stereo vision. The position and orientation of an objects is identified accurately enabling a robot to pick up, even though the objects are multiple and partially occluded. The stereo vision is used to get the 3D information as 3D sensing, and CAD model with its post processing is used for building models. Matching is initially performed using the model and object features, and calculate roughly the object's position and orientation. Though the fine adjustment step, the accuracy of the position and orientation are improved.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2003.09a
• /
• pp.591-594
• /
• 2003

In this paper, we propose a method to avoidance obstacle in which we assume that obstacle has an unstable limit cycle in the chaos trajectory surface. In order to avoid the obstacle, we assume that all obstacles in the chaos trajectory surface in which has an unstable limit cycle with Van der Pol equation. In this paper show also that computer simulation results are satisfy to avoid obstacle in the chaos trajectory with Chua's circuit equation of one or multi obstacle has an limit cycle with Van der Pol (VDP) efuation and compare to rate of cover in one robot which have random walk and Chua's equation.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.1
• /
• pp.37-42
• /
• 1990

Carbon fiber epoxy composite materials are widely used in the structures of aircrafts, robots and other machines because of their high specific stiffness, high specific strength and damping. In order for the composite materials to be used in the robot structure or machine element, bearing mounting and joining surfaces must be provided, which require accurate machining. In this paper, the machinability and tool wear characteristics of the milling operation of the carbon fiber epoxy composite materials were experimentally measured. The tool wear mechanism and the Taylor tool wear constants were determined. Also, the surface roughness of milling operation was measured w.r.t. cutting speed and feed.

• Journal of Institute of Control, Robotics and Systems
• /
• v.14 no.11
• /
• pp.1103-1109
• /
• 2008

Since the flexible joint robots with motor dynamics are represented by the fifth-order nonlinear sγstem, it is difficult and complex to design the controller for electrically driven flexible-joint (EDFJ) robots. In this paper, we propose a simple adaptive control method to solve this problem. It is assumed that the model uncertainties of the robots dynamics, joint flexibility, and motor dynamics are unknown. For the simple control design, the dynamic surface design method is applied, and all uncertainties in the robot and motor dynamics are compensated by using the adaptive function approximation technique. It is proved that all signals in the controlled closed-loop system are uniformly ultimately bounded. Simulation results for three-link EDFJ manipulators are provided to validate the effectiveness of the proposed control system.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.151.4-151
• /
• 2001

Chattering-free sliding mode control is derived from the reaching law method and Lyapunov stability theorem. Its control input Is composed of continuous term and discontinuous term. By the combination of these terms, the robustness and tracking performance can be improved and the chattering can be avoided. But in the reaching mode, the sliding mode control is sensitive to the modeling uncertainties, parameter variations and disturbances, also it needs a large control input. These result in poor transient responses. In this paper, to overcome these problems in the reaching mode, a time-varying sliding surface is proposed. And it is applied to a 2-link SCARA robot manipulator, experimental results show that the transient response is improved and its ...

• 제어로봇시스템학회:학술대회논문집
• /
• 2002.10a
• /
• pp.97.6-97
• /
• 2002

In this paper, we present an arrayed flexible tactile sensor, which can detect contact normal forces as well as positions. The tactile sensor is developed using Polyvinylidene Fluoride (PVDF) that is known as piezoelectric polymer, and the surface electrode is fabricated using silk-screening technique with silver. We develop a charge amplifier in order to amplify the small signal from the sensor, and a fast signal processing unit by using a DSP chip. The developed tactile sensor is physically flexible and it can be deformed three-dimensionally to any shape so that it can be placed on anywhere on the curved surface. In the future, the developed sensor is applied to a dexterous robotic hand...$\textbullet$ Tactile sensing, PVDF, Robot hand