• 항공우주기술
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• 제7권2호
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• pp.31-37
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• 2008

항공기의 변수 추정을 위해서는 비행시험을 통해 얻어진 데이터를 이용해야한다. 비행 시험의 문제점으로 비행중에는 데이터를 재조정하기가 힘들다. 이러한 점을 감안하여 본 논문에서는 변수추정을 위한 비행시험을 대신해서 선회 비행 데이터를 사용하여 주파수영역에서 변수를 추정하는 상용화된 변수추정프로그램(CIFER)으로 스마트 무인기 40% 축소기의 동적 파라미터를 추정하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제16권6호
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• pp.134-142
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• 2012

본 연구는 탄현 에이스 11차 아파트에 위치한 14m 높이의 L형 옹벽의 장기 경사 계측치에 대한 System Identification연구로써, 옹벽구조물이 운용 중에 어떤 하중상태에서 어떻게 거동하는지를 이해하고, 이를 바탕으로 최적 모델을 규명하고, 최종적으로 옹벽의 이상상태를 판단할 수 있는 기준치를 제시하고자 하였다. 본 옹벽은 도심에 위치한 옹벽으로써는 보기 드물게 높고(14m), 인접한 건물과의 거리가 짧아서 붕괴 발생 시 큰 피해 가능성이 있다. 3개의 경사계로와 9개의 대기, 표면, 내부온도계로 구성된 경사 모니터링 시스템이 2004년 10월에 설치되어 2007년 7월까지 운용되었다. 모든 12 채널의 센서가 정상적으로 계측된 5개월 간의 연속된 데이터를 사용하여 두 가지 모델 1) 선형모델과 2) 상태방정식모델에 대하여 system identification을 수행하였다. 가용한 입력온도는 총 9이고, 이로부터 조합 가능한 총 511개의 입력온도 경우의 수에 대하여 규명데이터를 사용하여 시스템규명을 수행하고, 검증데이터에 대한 Fitness를 사용하여 최적모델을 선정하였다. 선형모델은 모델구조가 간단하지만 thermal dynamics를 표현하지 못하고, 약 68%의 Fitness를 얻을 수 있었고, 상태방정식 모델은 모델구조가 상대적으로 복잡하지만 thermal dynamics를 표현할 수 있고, 약 90%의 Fitness를 얻었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.301-307
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• 2005

In this study, simplified whirl flutter analyses using quasisteady aerodynamic theory have been performed for a 2-DOF tilt-rotor system with both pitch and yaw motions of a rotor-nacelle. The present dynamic system consists of the rotor (propeller), forming the gyroscopic and aerodynamic element, supported horizontally by a pylon that is pivoted at some wing attachment point. Several design parameters (or rotor-nacelle system are considered and the effect of whirl flutter stability are also investigated for various design parameters.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.1111-1116
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• 2001

A transient T-F(time-frequency) signal processing technique is applied to a tilt drop and a linear shock test rigs for identification of shock characteristics of hard disk drive (HDD). The T-F technique essentially tracks the shock characteristics of pivot point response as well as head slap and lift-off phenomena. From the T-F analysis result, the shock characteristic in HDD is modeled by the two degree of freedom coupled-dynamic system, which consists of actuator arm and suspension. As shock designing tool, the maximax shock response spectrum is employed for prediction of shock performance. Finally, the shock control technique is tested with newly designed actuator arm and suspension. Experimental head slap test result shows that the shock performance is much higher with the new shockproof designed model than the current model

• Smart Structures and Systems
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• 제32권1호
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• pp.1-7
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• 2023

In modal analysis, the mode shape reflects the vibration characteristics of the structure, and thus it is widely performed for finite element model updating and structural health monitoring. Generally, the acceleration-based mode shape is suitable to express the characteristics of structures for the translational vibration; however, it is difficult to represent the rotational mode at boundary conditions. A tilt sensor and gyroscope capable of measuring rotational mode are used to analyze the overall behavior of the structure, but extracting its mode shape is the major challenge under the small vibration always. Herein, we conducted a feasibility study on a multi-mode shape estimating approach utilizing a single physical quantity signal. The basic concept of the proposed method is to receive multi-metric dynamic responses from two sensors and obtain mode shapes through bridge loading test with relatively large deformation. In addition, the linear transformation matrix for estimating two mode shapes is derived, and the mode shape based on the gyro sensor data is obtained by acceleration response using ambient vibration. Because the structure's behavior with respect to translational and rotational mode can be confirmed, the proposed method can obtain the total response of the structure considering boundary conditions. To verify the feasibility of the proposed method, we pre-measured dynamic data acquired from five accelerometers and five gyro sensors in a lab-scale test considering bridge structures, and obtained a linear transformation matrix for estimating the multi-mode shapes. In addition, the mode shapes for two physical quantities could be extracted by using only the acceleration data. Finally, the mode shapes estimated by the proposed method were compared with the mode shapes obtained from the two sensors. This study confirmed the applicability of the multi-mode shape estimation approach for accurate damage assessment using multi-dimensional mode shapes of bridge structures, and can be used to evaluate the behavior of structures under ambient vibration.

• 한국생산제조학회지
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• 제21권3호
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• pp.479-486
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• 2012

This paper presents a high-speed automatic micro-alignment system that is a part of an inspection machine for small-sized molded lenses of mobile phones, palm-top computers, and so on. This work was motivated by the shortcomings of existing highest-grade commercial machine. A simple tip/tilt/Z parallel mechanism is designed based on kinematic couplings, which is a 3-degree-of-freedom (3-DOF) moderate-cost alignment stage. It is used to automatically adjust the posture of each lens on the tray, which is impossible by the conventional instrument. Amplified piezoelectric actuators are used to ensure the accuracy and dynamic response. Forward kinematic analysis and simulation show that the parasitic motion is small enough compared to the actuator stroke. From the workspace analysis of the moving platform, it is clear that the output motion range satisfies the design requirements.

• Smart Structures and Systems
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• 제2권2호
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• pp.115-126
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• 2006

The Terra-Scope system is an affordable 4-D down-hole seismic monitoring system based on independent, microprocessor-controlled sensor Pods. The Pods are nominally 50 mm in diameter, and about 120 mm long. They are expected to cost approximately $6000 each. An internal 16-bit, extremely low power MCU controls all aspects of instrumentation, eight programmable gain amplifiers, and local signal storage. Each Pod measures 3-D acceleration, tilt, azimuth, temperature, and other parametric variables such as pore water pressure and pH. Each Pod communicates over a standard digital bus (RS-485) through a completely web-based GUI interface, and has a power consumption of less than 400 mW. Three-dimensional acceleration is measured by pure digital force-balance MEMS-based accelerometers. These accelerometers have a dynamic range of more than 115 dB and a frequency response from DC to 1000 Hz with a noise floor of less than $30ng_{rms}/{\surd}Hz$. Accelerations above 0.2 g are measured by a second set of MEMS-based accelerometers, giving a full 160 dB dynamic range. This paper describes the system design and the cooperative shared-time scheduler implemented for this project. Restraints accounted for include multiple data streams, integration of multiple free agents, interaction with the asynchronous world, and hardened time stamping of accelerometer data. The prototype of the device is currently undergoing evaluation. The first array will be installed in the spring of 2006.