• 한국안전학회지
• /
• 제18권1호
• /
• pp.44-49
• /
• 2003

Permanent magnet synchronous motor(PMSM) is widely used in many applications such as an electric vehicle. compressor drives of air conditioner and machine tool spindle drives. PMSM drive system have become a popular choice in various application, due to their excellent power to weight ratio. This paper is proposed maximum torque control for field weakening operation of PMSM drive. At low speeds, the reluctance torque is used to maximize the output for a given current level. This is achieved maximum torque per ampere(MTPA) by selecting an optimal value of the direct stator current component. At high speeds, the system reaches a point at which the inverter will not be able to supply the desired voltage. In this case it is necessary to make use of an increased value the direct current component. The proposed control algorithm is applied to PMSM drive system, the operating characteristics controlled by maximum torque control are examined in detail by simulation.

• 한국안전학회지
• /
• 제14권4호
• /
• pp.108-113
• /
• 1999

This paper presents a study on fuzzy speed and flux controller used in a vector control of a CRPWM(Current Ragulated PWM) induction motor drive. In this paper, an approach for an easier design of the fuzzy controller is presented in order to obtain the desired value for the response time with minimal overshoot and to improve the steady state performance for speed step commands. The fuzzy controller is constructed only upon the knowledge of the motor behaviour and the desired speed response, and provides fast and robust control by reducing the effects of nonlinearities, parameter changes and load disturbance. The results of applying the fuzzy logic controller to an IM drive system are compared with those obtained by application of a conventional PI controller. The fuzzy controller provided a better response than the PI controller.

• 한국안전학회지
• /
• 제17권1호
• /
• pp.39-44
• /
• 2002

This paper shows error in the polarization direction on ultrasonic transducers how sensitive the shear ultrasonic waves are to a little misoriented plies according to the angle variation of shear ultrasonic waves $0{\circ},\;45{\circ}$ and $90{\circ}$. Also, it is shown that shear waves, particularly the transmission mode with the transmitter and receiver perpendicular to cach other, have high sensitivity for detecting anomalies in fiber orientation and ply layup sequence that may occur in the manufacturing of composite laminates. Experimental results are agreed with a modeling solutions which was based on decomposition of shear wave polarization vector as it propagates through the composite laminates. This wave appeared considerably to be sensitive to CFRP composites to thickness direction along in-plane fibers.

• 한국안전학회지
• /
• 제30권3호
• /
• pp.93-99
• /
• 2015

Economic burden of work-related musculoskeletal disorder(WMDs) is increasing. Known causes of WMDs include improper posture, repetition, load, and temperature of workplace. Among them, improper postures play an important role. A smart sensor called SensorTag is employed to estimate the trunk postures including flexion-extension, lateral bend, and the trunk rotational speeds. Measuring gravitational acceleration vector in the smart sensor along the tri-orthogonal axes offers an orientation of the object with the smart sensor attached to. The smart sensor is light in weight and has small form factor, making it an ideal wearable sensor for body posture measurement. Measured data from the smart senor is wirelessly transferred for analysis to a smartphone which has enough computing power, data storage and internet-connectivity, removing need for additional hardware for data post-processing. Based on the estimated body postures, WMDs risks can be conviently gauged by using existing WMDs risk assesment methods such as OWAS, RULA, REBA, etc.

• 한국안전학회지
• /
• 제12권3호
• /
• pp.120-131
• /
• 1997

This paper presents an approximate reanalysis methods of structures based on substructuring for an effective optimization of large-scale structural systems. In most optimal design procedures the analysis of the structure must be repeated many times. In particular, one of the main obstacles in the optimization of structural systems are involved high computational cost and expended long time in the optimization of large-scale structures. The purpose of this paper is to evaluate efficiently the structural behavior of new designs using information from previous ones, without solving basic equations for successive modification in the optimal design. The proposed reanalysis procedure is combined Taylor series expansions which is a local approximation and reduced basis method which is a global approximation based on substructuring. This technique is to choose each of the terms of Taylor series expansions as the basis vector of reduced basis method in substructuring system which is one of the most effective analysis of large -scale structures. Several numerical examples illustrate the effectiveness of the solution process.

• Structural Engineering and Mechanics
• /
• 제46권3호
• /
• pp.433-445
• /
• 2013

Vibration-based structural identification has become an important tool for structural health monitoring and safety evaluation. However, various kinds of uncertainties (e.g., observation noise) involved in the field test data obstruct automation system identification for accurate and fast structural safety evaluation. A practical way including a data preprocessing procedure and a vector backward auto-regressive (VBAR) method has been investigated for practical bridge identification. The data preprocessing procedure serves to improve the data quality, which consists of multi-level uncertainty mitigation techniques. The VBAR method provides a determinative way to automatically distinguish structural modes from extraneous modes arising from uncertainty. Ambient test data of a cantilever beam is investigated to demonstrate how the proposed method automatically interprets vibration data for structural modal estimation. Especially, structural identification of a truss bridge using field test data is also performed to study the effectiveness of the proposed method for real bridge identification.

• International Journal of Safety
• /
• 제11권2호
• /
• pp.5-9
• /
• 2012

The discharge properties of super high-pressure mercury lamp are due to resistance heating for energy input, and results in temperature increase. The cooling equilibrium state is reached by the heat conduction, convection and radiation. In order to predict the fluid flow and heat transfer in and around the mercury lamp accurately, its visualization is of utmost importance. Such visualization is carried out by CFD program in this study. We focus on Anode shape to calculate four cases, namely AA, AB, AC and AD separately, and compare the temperature distribution and velocity vector in each case to predict cooling capacity and fluid flow properties. It can be concluded that the shape of anode plays an important role that affects the fluid flow and heat transfer in a mercury lamp.

• 한국안전학회지
• /
• 제13권1호
• /
• pp.54-63
• /
• 1998

This paper proposes a theoretical analysis of a closed loop adaptive speed control system for control the inverter driven permanent magnet synchronous motor(PMSM). This control system utilizes a mechanically sensorless state observer for the generation of all controller feedback information. The observer processes measurements of stator frame voltage and current to produce estimates of rotor position and speed and rotor frame currents. It is shown that the identity observer, when properly formulated, has the same linearized error dynamics as the extended kalman filter(EKF). Consequently, it is shown that the gains within the identity observer can be designed in a manner identical to that of the EKF. In this way, the designability of the nonlinear observer is assured, as is the optimality of its performance for small errors. A sequence of simulation are performed and they demonstrate the successful performance.

• 한국식품위생안전성학회지
• /
• 제6권3호
• /
• pp.133-137
• /
• 1991

5'-XMP를 5'-GMP로 전환하는 효소인 XMP aminase[EC 6.3.4.1]의 활성을 증가시키기 위하여 XMP aminase의 유전자를 함유한 1.7kb gua A gene fragment를 pLC 34-10으로부터 분리하여 pBR 322에 subcloning 한 뒤 trp promoter를 가지고 있는 대장균 발현 벨터 pDR 720에 도입하였다. 재조합된 pXAR 64에 존재하는 gua A 유전자는 trp Promoter에 의하여 발현이 증대되었으며 $3-{\beta}-indoleacrylic$ acid에 의하여 XMP aminase의 생성이 유도되었다. XMP aminase의 비활성은 pLC 34-10을 함유한 균주에 비하여 약 17배 증가되었다.

• 대한안전경영과학회지
• /
• 제11권1호
• /
• pp.87-91
• /
• 2009

본 논문은 상대적으로 새로운 기법인 Parzen Density Estimation과 Multi-class SVM을 이용한 지능형 고장 탐색과 진단 방법을 제안하고 있다. 본 연구에서는 롤링 베어링을 대상으로 고장을 탐색하고 진단하기 위한 방법을 제안하는데 Parzen Density Estimation과 Multi-class SVM은 고장 클래스를 잘 표현할 수 있다. Parzen Density Estimation은 새로운 패턴 데이터의 거절과 알려진 데이터 패턴의 밀도의 평가에 의해 새로운 패턴을 찾아낼 수 있고, Multi-class SVM 기반의 방법은 여러 클래스의 고장을 support vector로 표현하여 고장 패턴을 찾아낼 수 있다. 본 연구에서는 실제의 다중 클래스를 가지는 롤링 베어링의 고장 데이터를 사용하여 고장 패턴을 탐색하는 과정을 보여주는데, 커널함수의 적절한 파라미터의 선택에 의한 Multi-class SVM 기반의 방법이 multi-layer perceptron이나 Parzen Density Estimation 방법보다 우수함을 입증한다.