• 제어로봇시스템학회논문지
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• 제18권3호
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• pp.275-284
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• 2012

This paper proposes an attitude and direction control of a single wheel balanced robot. A unicycle robot is controlled by two independent control laws: the mobile inverted pendulum control method for pitch axis and the reaction wheel pendulum control method for roll axis. It is assumed that both roll dynamics and pitch dynamics are decoupled. Therefore the roll and pitch dynamics are obtained independently considering the interaction as disturbances to each other. Each control law is implemented by a controller separately. The unicycle robot has two DC motors to drive the disk for roll and to drive the wheel for pitch. Since there is no force to change the yaw direction, the present paper proposes a method for changing the yaw direction. The angle data are obtained by a fusion of a gyro sensor and an accelerometer. Experimental results show the performance of the controller and verify the effectiveness of the proposed control algorithm.

• 대한임베디드공학회논문지
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• 제8권5호
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• pp.249-254
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• 2013

In this paper we propose nonlinear control system for automatic unmanned vehicle using a RC (Radio Controlled) car which is usually controlled by a remote controller. In the proposed system, a RC car is dissembled and reassembled with several parts enabling it to be controlled by an android mobile platform with Bluetooth communication. In our system, an android mobile smartphone is mounted on the RC car and plays an important role as an eye of the car. The proposed system automatically controls the RC car to follow a lane that we draw on the floor of our laboratory. Also, the proposed RC car system can also be controlled manually using the accelerometer sensor of a smartphone through a Bluetooth module. Our proposed system that has both manual mode and automatic mode consists of several components; a microprocessor unit, a Bluetooth serial interface module, a smartphone, a dual motor controller and a RC toy car. We are now in the development of a group driving system in which one car follows the front car that tracks a lane automatically.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.1093-1098
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• 2017

액체로켓엔진용 산화제펌프의 캐비테이션 시험 중 입출구 배관과 펌프 케이싱에서 계측된 고주파 신호를 분석하였다. 각각의 데이터의 RMS 값을 캐비테이션 수에 따라 표현하였다. 회전수 동기 주파수와 날개 개수 성분, 캐비테이션 불안정성 주파수의 RMS를 계산하였다. 입구 배관의 압력섭동은 캐비테이션 불안정성의 영향을 받았다. 출구 배관의 경우 3x 성분이 탁월하였는데, 인듀서에서 발생한 3x 성분이 임펠러에서 증폭된 결과로 해석된다. 케이싱에 부착된 가속도계에서도 캐비테이션 불안정성에 해당하는 주파수가 확인되었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권5호
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• pp.354-360
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• 1999

PCN-PZT piezoelectric acceleration sensors of annular shear mode voltage type were fabricated and their characteristics have been investigated. Field tests are also carried out. To avoid noise problems from the environmental conditions, acceleration sensors employed solid state micro-electronics for pre-amplifier. The calibration procedures based on the principle of the comparison method were adopted for investigating the characteristics of fabricated acceleration sensors. The voltage sensitivity and resonant frequency of fabricated acceleration sensors were 83mv/g, 23kHz, respectively. The lower and upper frequency limit were 4Hz and 9kHz, respectively. The variation of the voltage sensitivity showed 10% at $-406{\circ}C\; and\; 9%\; at\; 121^{\circ}C$ compared to that of reference temperature at $40^{\circ}C$.

• 한국항공운항학회지
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• 제20권2호
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• pp.18-25
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• 2012

The availability of the GPS signal has been expanded greatly in the field of society overall through the development and construction of the GNSS(Global Navigation Satellite System). Furthermore, in the military, aviation and field of space, the GPS signal is applied widely through the combination of INS consisting of gyroscope and accelerometer, IMU, AHRS with the addition of magnetic sensor. Particularly, the performance of these equipments or sensors is very important with GPS and PAR(Precision Approach Radar) in the flight control of the aircraft. This paper deals with MATLAB simulation and ROLSO(Reduced Order Luenberger State Observer) design to reduce the load of system and realize the stable lateral direction approach control in an appropriate time for reduction of the horizontal error which is importantly considered while an aircraft lands instead of the FOLSO(Full Order Luenberger State Observer) using all measurement values. Consequently, ROLSO is expected to be used for the aircraft's attitude control in the aircraft landing causing the burden to the pilots.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.3412-3420
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• 2015

스마트폰은 일상생활의 필수 요소가 되었으며, 스마트폰의 내장된 센서는 사용자의 상황인지를 위해 유용하게 활용될 수 있다. 하지만, 동적 상황 인지를 통해 안전 및 사고예방을 위한 연구가 미흡한 상황이다. 본 논문에서는 모바일 디바이스의 가속도 센서, 마이크, GPS 센서를 이용해 위험상황을 동적으로 인지할 수 있는 기법을 제안한다. 본 동적인지기법의 센싱 기법에 대한 아키텍쳐와 프로세스를 제안하며, 아키텍쳐의 적합성을 검증을 위해 모바일 어플리케이션을 개발한다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2015년도 추계학술발표대회
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• pp.1361-1364
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• 2015

본 연구에서는 노인들이 일상에서 많이 행동하는 7가지 유형의 행동의 특징을 추출하고, 총 7가지 분류 알고리즘에 적용하여 가장 인식률이 높은 알고리즘을 도출하고자 하였다. 행동패턴은 정상보행, 절름발이, 지팡이, 느린 보행, 허리가 굽은 상태에서 보행, 스스로 휠체어 끌 때 그리고 누군가가 휠체어를 끌어줄 때 총 7가지로 구성하였다. 행동패턴의 특징은 3축 가속도 센서의 값, 평균, 표준편차, 수직 및 수평축의 데이터를 사용하였다. 분류 알고리즘은 Naive Bayes, Bayes Net, k-NN, SVM, Decision Tree, Multilayer perception, Logistic regression을 사용하였다. 연구결과 k-NN 알고리즘의 인식률이 98.7%로 다른 분류알고리즘에 비해 인식률이 높게 나타났다.

• Nuclear Engineering and Technology
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• 제42권6호
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• pp.704-711
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• 2010

Modal testing requires measuring the vibration of many points, for which an accelerometer, a gab sensor and laser vibrometer are generally used. Conventional modal testing requires mounting of these sensors to all measurement points in order to acquire the signals. However, this can be disadvantageous because it requires considerable measurement time and effort when there are many measurement points. In this paper, we propose a method for modal testing using a camera image. A camera can measure the vibration of many points at the same time. However, this task requires that the measurement points be classified frame by frame. While it is possible to classify the measurement points one by one, this also requires much time. Therefore, we try to classify multiple points using pattern recognition. The feasibility of the proposed method is verified by a beam experiment. The experimental results demonstrate that we can obtain good results.

• Structural Monitoring and Maintenance
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• 제6권1호
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• pp.33-46
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• 2019

In present study, Operational Modal Analysis (OMA) was employed to carry out the dynamic and vibration analysis of the threshing unit of the combine harvester thresher as a mechanical component. The main study is to find the causes of vibration and to decrease it to enhance the lifetime and efficiency of the threshing unit. By utilizing OMA, structural modal parameters such as mode shapes, natural frequencies, and damping ratio was calculated. The combine harvester was excited by engine to vibrate different parts and accelerometer sensor collected acceleration signals at different speeds, and OMA was utilized by nonparametric and frequency analysis methods to obtain modal parameters while vibrating in real working conditions. Afterwards, finite element model was designed from the thresher and updated using the data obtained from the modal analysis. Using the conducted analyses, it was specified that proximity of the thresher pass frequency to one of the natural frequencies (16.64 Hz) was the most important effect of vibration in the thresher. Modification process of the structure was carried out by increasing mass required for changing the natural frequency location of the first mode to 12.4 Hz in order to reduce resonance and vibration of the thresher.

• 한국지진공학회논문집
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• 제23권5호
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• pp.261-268
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• 2019

This paper proposes damage indices efficient on evaluating the seismic safety of cable-stayed bridges, especially dual-plane, cable-stayed bridges with H-type pylons. The research assumes that the location of accelerometers is already defined as given in the 2017 Ministry of the Interior and Safety (MOIS) guideline. In other words, the paper does not attempt to suggest optimal sensor location for the seismic safety evaluation of cable-stayed bridges. The proposed damage indices are based on those for building structures widely applied in the field already. Those include changes in natural frequencies and changes in relative lateral displacements. In addition, the study proposes other efficient damage indices as the rotation changes at the top of pylons and in the midspan of the girder system. Sensitivity analysis for various damage indices is performed through dynamic analysis using selected earthquake ground motions. The paper compares the effectiveness of the damage indices.