• Smart Structures and Systems
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• 제24권3호
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• pp.293-301
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• 2019

Bolted joints are commonly used in civil infrastructure and mechanical assembly structures. Monitoring and identifying the connection status of bolts is the frontier problem of structural research. The existing research is mainly on the looseness of a single bolt. This article presents a study of assessing the loosening/tightening health state and identifying the loose bolt by using ultrasonic guided wave in a bolt group joint. A bolt-tightening index was proposed for evaluating the looseness of a bolt connection based on correlation coefficient. The tightening/loosening state of the bolt was simulated by changing the bolt torque. More than 180 different measurement tests for total of six bolts were conducted. The results showed that with the bolt torque increases, value of the proposed bolt-tightening index increases. The proposed bolt-tightening index trend was very well reproduced by an analytical expression using a function of the torque applied with an overall percentage error lower than 5%. The developed damage index based on the proposed bolt-tightening index can also be applied to locate the loosest bolt in a bolt group joint. To verify the effectiveness of the proposed method, a bolt group joint experiment with different positions of bolt looseness was performed. Experimental results show that the proposed approach is effective to detect and locate bolt looseness and has a good prospect of finding applications in real-time structural monitoring.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
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• pp.63-63
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• 2003

There are many actuators and sensors used for attitude control system for KOMPSAT such as Reaction Wheel Assembly, Magnetic Torque Assembly, Dual Thruster Module, Solar array Drive, Three Axis Magnetometer, Conical Earth Sensor, Fine Sun Sensor Assembly, Coarse Sun Sensor Assembly, Gyro Reference Assembly and so on. For KOMPSA T satellite it has been considered using the Magnetic Torquer (MTQ) generating the magnetic dipole moment. In general, the magnetic dipole moment for satellite attitude control system is used for dumping out the excessive reaction wheel momentum so that the reaction wheel speed is not saturated. The objective of this study is to analyze the magnetic field characteristics generated by the Magnetic Torquer using the Maxwell 2D Field Simulator software. Currently, the developing model (DM) of the MTQ is being developed and manufactured at a company under the supervision of KARL MTQ is an electromagnet consisting of a ferromagnetic cylindrical core on which an excitation coil is wound. A current is passed through the coil to produce a dipole momentum in the ferromagnetic core. The configuration of the MTQ will be introduced in the presentation. The 2 dimensional model of the MTQ is drawn as axisymmetric models in RZ plane, and each corresponding material is assigned to the each MTQ object, the core, coil, and background. After the boundary conditions, current sources, and solution parameters are set up, the magnetic field intensities, directions, and other values specified by users can be calculated by using the finite element analysis. The theoretical magnetic field quantities obtained by the Maxwell 2D Simulator can be used for the basis of the development of the MTQ.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1445-1449
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• 2005

The ram assembly is important equipment in fueling machine of PHWR(Pressurized Heavy Water Reactor) plant where fuel replacement is possible while the plant is in service. Troubles in the ram assembly can cause lots of difficulties in power plant operation. The ram assembly is typically composed of the B-ram, the L-Ram and the C-Ram. The B-ram is focused in this paper because it plays the most important role in the ram assembly. Among the ram fault phenomena, ram stuck phenomena are the most frequent cases in the B-ram, which has a ball screw mechanism driven by a hydraulic motor. Ram stuck phenomena are due to ball wear and damage in ball nut that increase in proportion to the number of fuel replacement. It is required to predict ram stuck phenomena before they occur. In this paper, a method is proposed for predicting ram stuck phenomena using a discrete wavelet transform. The discrete wavelet transform provides information on both the time and frequency characteristics of the input signals. The proposed method uses the frequency bandwidths of coefficients of discrete wavelet decompositions and detail coefficients of discrete wavelet transform to predict ram stuck phenomena. The signal used in this paper is a torque-related signal such as a hydraulic service outlet pressure signal in a hydraulic driving system or a current signal in a DC motor driving system. Finally, the validity of the proposed method is shown via experiment using ball nut characteristic test equipment that simulates ram stuck phenomena due to increased ball friction in ball nut.

• 한국산학기술학회논문지
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• 제17권6호
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• pp.687-692
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• 2016

엔진에 터보차져를 사용하게 되면 엔진의 출력도 향상되지만 동시에 엔진의 온도도 높아지게 된다. 특히 피스톤의 경우는 냉각이 문제가 된다. 이러한 문제를 해결하기 위하여 오일 젯을 사용하는데, 오일 젯은 오일을 피스톤의 밑 부분에 분사하여 피스톤을 냉각시키는 것이다. 오일 젯이 사용된다면, 오일의 분사로 인하여 오일 유량의 증가및 피스톤으로부터의 열전달에 의하여 높아진 오일 온도 문제를 해결하기 위하여 오일 펌프 용량 증대와 오일 쿨러의 사용이 필요하다. 그러나 용량 증대 오일 펌프와 오일 쿨러를 사용하면 엔진의 마찰 토크가 증가하는 원인이 된다. 본 연구에서는 오일 젯, 오일 쿨러 및 오일 펌프의 용량 증대로 인하여 엔진의 마찰 토크가 증가하는 정도에 대하여 연구하였다. 또한 각 부품의 사양을 변경함에 따라 마찰 토크가 얼마나 영향을 받는가도 측정되었다. 저속에서는 오일 펌프와 오일 쿨러에 의한 영향이 크고 고속에서는 오일 쿨러에 의한 영향이 큼을 알 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.243-247
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• 2004

The dynamometers which had made in a long time ago could not control the input/output quantity of water minutely and was sensitive to a noise since it was controlled by an analog control method. Therefore, a fully digital controlled system was urgently required to be robust against various noises. In this paper, the new system which can control the amount of circulated water in dynamometer was developed. This system is consisted of an industrial digital type controller and a servo motor. The industrial PLC was used as a main controller for the developed system, and the actuator and servo motor were used to control the inlet and outlet valve independently. The torque signal of load cell was fed back to the main controller to regulate the diesel engines load. Generally, an input/output valve position of the old dynamometer was fixed with a proper situation for an engine output test and the torque was changed according to the time interval. However, the torque value for the dynamometer could not be constantly kept because of the variation of the input water flow and fluid characteristic. Therefore, the automatic control of an inlet and outlet valve should be performed to keep the constant torque. So, the PID control method was applied to solve this problem. Also, the development of a web-based remote control system was described in this paper. This software will give us the convenience of operation, the more efficient operations, and the reduced operator workload for operation of the dynamometer. The application results of the system have been verified at actual diesel engine field.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.36-41
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• 2014

Electro-Mechanical Actuator installed on aircraft consists of a decelerator which magnifies the torque to rotate an axis connected with aircraft control surface, a control section which controls the motor assembly through receiving orders from cockpit and a motor assembly which rotates the decelerator. EMA controls aircraft attitued, position, landing, takeoff, etc. It is important part of a aircraft. Aircraft maneuvering make vibration of EMA. Vibration may cause the vibration fatigue. For that reason, it is necessary to analyze the system safety. In this paper, first EMA is modeled in finite element method and analyzed the response from input vibration. second EMA is tested and analyzed from modal experimental data. third EMA Fe model is updated and re analyzed. and EMA is verified safety with $3{\sigma}$ stress and S/N curves.

• 제어로봇시스템학회논문지
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• 제15권5호
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• pp.538-542
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• 2009

Industrial manipulators have been mostly used in large companies such as automakers and electronics companies. In recent years, however, demands for industrial manipulators from small and medium-sized enterprises are on the increase because of shortage of manpower and high wages. Since these companies cannot hire robot engineers for operation and programming of a robot, intuitive teaching and playback techniques of a robot manipulator should replace the robot programming which requires substantial knowledge of a robot. This paper proposes an intuitive teaching and playback algorithm used in assembly tasks. An operator can directly teach the robot by grasping the end-effector and moving it to the desired point in the teaching phase. The 6 axis force/torque sensor attached to the manipulator end-effector is used to sense the human intention in teaching the robot. After this teaching phase, a robot can track the target position or trajectory accurately in the playback phase. When the robot contacts the environment during the teaching and playback phases, impedance control is conducted to make the contact task stable. Peg-in-hole experiments are selected to validate the proposed algorithm since this task can describe the important features of various assembly tasks which require both accurate position and force control. It is shown that the proposed teaching and playback algorithm provides high positioning accuracy and stable contact tasks.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.278-282
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• 2001

The purpose of this study is to introduce a new spacer damper for the bundle transmission lines network. It has the special design, the main characteristics and advantage of this new kind of spacer damper. An Existing spacer damper with bolted clamps, although widely used, is a method of connection with certain disadvantage both as regards assembly on the conductor and in the course of time. Even if tightening torque is correctly applied by using bolt with share head or torque wrench during working time, the aeolian vibration could involve untightening during life time, so the cable can move into the Jaws and wire's breakage appear. To salve this problems, France, Japan and other countries had developed a spacer damper with an automatic system through many years. This new spacer damper is an original automatic clamping device (beltless) which does not require special tool for its installation. This device prevents clamp unlocking problems, ensures a simple installation and ensures a reliable-tightening during life time. Therefore, it is necessary to localize this boltless spacer damper with automate clamping device.

• Elastomers and Composites
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• 제44권4호
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• pp.366-372
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• 2009

본 연구에서는 휴대폰 카메라용 렌즈모듈의 구조를 최적화하기 위한 연구를 수행하고자 한다. 휴대폰 카메라용 렌즈모듈의 안정적인 작동을 위해 경통부와 외장부간 결합력의 적절한 유지가 필요한데, 본 연구에서는 유한요소해석을 사용하여 적절한 결합력 유지를 위한 나사 간섭부 설계변수의 영향에 대해 고찰하였다. 또한 실험계획법을 적용하여 렌즈모듈 설계변수 최적화를 위한 연구를 수행하고, 실험계획법 결과에 대한 통계적인 분석을 통해 최적 조건을 선정하여 결합토크의 크기를 원하는 범위 내로 유지하고 동시에 산포를 감소시킴으로써 제품품질 향상에 기여하고자 한다.

• 한국정보통신학회논문지
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• 제16권5호
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• pp.1095-1101
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• 2012

본 논문은 DSP 제어기와 IGBT 구동기를 이용하는 조립과 공급의 자동처리를 위한 BLDC 서보 모터 제어시스템 설계를 제안한다. 조립, 공급 자동처리 시스템은 다양한 동작을 위해 서보모터의 토크, 속도, 위치 제어를 필요로한다. 본 논문은 이러한 서보제어를 벡터제어와 공간벡터 PWM 기법을 이용하여 구현한다. 제어기의 CPU 로서 PWM 파형발생기, A/D 컨버터, SPI 통신 포트 및 많은 입/출력 포트를 갖는 TMS320F240 DSP를 채택하였다. 이 제어시스템은 메인 호스트 PC 가 위로부터의 명령을 전달하고 끝단의 서보제어기의 상태들을 모니터링하는 세 개의 부 DSP시스템을 관리하는 3레벨의 계층적 구조로 이루어져 있다. 각 부 DSP 시스템은 DSP와 IPM을 사용하여 BLDC 서보모터를 제어하는 8개의 BLDC 서보모터제어부를 운영한다. 호스트 시스템과 중간의 DSP는 RS-422을 이용하여 통신하며, 주프로세서와 제어기는 SPI 포트를 이용하여 통신한다.