• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.313-319
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• 2017

This study presents a genetic algorithm (GA) to design a PID controller systematically for an inchworm operated by piezoelectric actuators. The performance index considering overshoot and settling time is adopted to search an optimal PID gain using GA. The piezoelectric actuator shows nonlinear characteristics including hysteresis and residual displacement. The PID feedback system combined with an integrator is used to improve the ability of tracking the complex input signals and suppressing the steady state error. The PID controller tuned by GA can track the various motion contours effectively. However, the PID controller shows an improper residual vibration under the application of high-frequency square input. The input shaper combined with the feedback system can overcome this limitation of the PID controller.

• Journal of KSNVE
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• v.10 no.4
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• pp.584-595
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• 2000

We design a new actuator for high density optical device in order to control the radial tilting motion. The newly designed actuator makes it possible to control the tilting motion actively, while the coventional actuator compress tilting motion with passive spring. First of all, We present 3-dimensional modeling of actuator and accomplish the modal analysis and magnetic analysis of actuator. Due to these results, a new designed actuator has performance of high sensitivity and high second resonance frequency. Secondly, We present the 3-DOF dynamic modeling of the 4-wire spring type actuator. sensitivity analysis is performed to consider the assembling error, such as the difference of mass center and force center. From these results, the sensitivities of rotation due to the assembly error are revealed and design criteria of rotation is presented. And experimental results of a newly designed actuator are presented and compared with theoretical results. Finally, We propose a dynamic tilt compensation and high acceleration actuator for high density optical storage devices.

• Journal of KSNVE
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• v.6 no.4
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• pp.521-528
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• 1996

Recently, higher speed optical disk drives including computer CD-ROM drives tend to be increasingly demanded to read or write the enormous volume of digital data. To this end, both structure and controller designs of the optical pick-ups should be improved concurrently. In this paper, the pick-up during auto-focusing motion is mathematically modelled retaining all its peculiar features. The model turns out a linear time invariant system suitable for a control design namedH${\infty}$ which ensures robust stability in the presence of system uncertainties. Numerical simulations are performed to demonstrate the robustness with appropriate performance specifications being satisfied. In addition, as the implementation issue of it, procedures of temporal discretization as well as model reduction of the controller are also addressed.

• Journal of KSNVE
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• v.6 no.6
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• pp.851-856
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• 1996

The active noise cancellation system showing the effective convergence and stability has been studied by simplifying the controller structures using the weighting factors of control error path to the multi-channel filtered-x LMS algorithm which needs a lot of calculations and the performance has been verified experimentally. Besides, to implement the system performance in a vehicle cabin, experimental work for selecting the suitable numbers and positions of the microphones and speakers was accomplished. Effectively combining a TMS 320C 31 main processor conducting real number calculations and having various functions with other components, the purpose-built system board for active noise cancellation has been designed and with this board, car active noise cancellation system showing maximum stable 10dB noise reduction has been obtained at the car idling conditions above 3000rpm range.

• Journal of KSNVE
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• v.8 no.1
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• pp.8-12
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• 1998

차량을 개발함에 있어 인간의 감성적인 분야에서 가장 중요한 분야의 하나가 진동 소음 및 충격 분야라 할 수 있겠다. 소비자들이 차량에 탑승하였을때 가장 민감하게 느끼기 때문이다. 이러한 소비자들의 감성지수를 만족하기 위한 노력이 각 자동차의 기술연구소, 학계및 국가연구소에서 심도있게 연구되고 있다. 최근에 많이 연구되는 active noise control 및 active suspension control등도 이 분야에 속하는 것들이다. 그러나 아직 이러한 신기술들이 실용화되기 위해서는 많은 상용화 연구가 진행되어야 하는 관계로 산업계에서는 현재의 진동소음저감기술을 좀더 단시간에 차량개발 프로그램에 적용하는데 더욱 큰 노력을 할 필요가 있을 것이다. 따라서 여기에서는 현재 자동차업체에서 수행하는 진동, 소음및 충격시험평가에 대해서만 국한하여 기술하고자한다.urce)을 찾아 직접 그 원인을 차단 및 치유하는 적극적이고 공격적인 방법을 이용하고있다. 본 글에서는 이러한 진동소음 문제를 차량의 개발 단계에서 해결하기 위한 일련의 과정 및 여러가지 개선기법에 대해서 살펴보고 그를 통한 진동소음 문제 해결방법을 제시하고자 한다.

• Journal of KSNVE
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• v.6 no.6
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• pp.791-800
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• 1996

Linear LQG controller has been investigated to control flexible link manipulators. The performance and complexity of these depend largely on the model upon which the controller is designed. In this study, the flexible modes of the link manipulator are considered to have uncertain parameters, which can be represented by random variable and these parameters are reflected on the weighting of performance. In this method, the exact modelling for the flexible modes is not necessary. The order of the resulting controller is much lower than the one based on a full model. Through numerical study, it is shown that the performance and the stability-robustness of the proposed controller reaches reasonably the one based on the full model.

• Journal of the Ergonomics Society of Korea
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• v.29 no.4
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• pp.455-463
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• 2010

Work-related musculoskeletal disorders (WMSDs) are recognized as leading causes of significant human suffering, loss of productivity, and economic burdens on our society. WMSDs are associated with work patterns that include fixed or constrained body positions, continual repetition of movements, force concentrated on small parts of the body, cold environment and vibration. Main effort to protect workers from WMSDs should focus on avoiding repetitive patterns of work through engineering controls which may include mechanization, ergonomic design of tools and equipment, and workplace layout. Where elimination of the risk factors is not practical, administrative controls involving job rotation, job enlargement and enrichment, teamwork should be considered.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.185-189
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• 1992

This paper prsents an end-point control of a one-link flexible arm with a payload by using closed loop control. Tip position of arm is shifted by the base motion according to DC servomotor, whivh is driven by a feedback signal composed of the tip displacement and the estimated tip velocity. The shifting problem of the arm from initial position to desired position is considered by the variation of the displacement gain Gd and velocity agin Gv. Theoretical results are obtained by applying the method of the Laplace transform to the governing equations and the method of numerical inversion. This system is composed of a flexible arm with payload, DC servomotor, and a ballscrew mechanism. The flexible arm is mounted on a mobile stage driven by a servomotor and ballscrew. In controlling the tip displacement of flexible arm, the fundamental bode vibration is supressed more rapidly with an increase of the velocity feedback gain Gv and the feedback displacemenmt gain Gd. Theretical responses are approximately in good agreement with those obtained experimentally.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.10
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• pp.851-855
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• 2002

This paper proposes a method of fault detection and diagnosis of agitators based on the wavelet analysis of the current and vibration signals. The wavelet transform has received considerable interest in the fields of acoustics, communication, image compression, vision. and seismic since it provides the fast and effective means of analyzing signals recorded during operation. Neural network is used to diagnose the fault. Specifically, the proposed approach consists of (i) fault detection, (ii) feature extraction, and (iii) classification of fault types. The results show an effective application of the wavelet analysis on the monitoring of an agitator.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.713-720
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• 2009

Numerous applications of position controlling devices using servoing technique and transmission of energy through belt drives are practiced in the industry. Belt drive is a simple, lightweight, low cost power transmission system. Belt drives provide freedom to position the motor relative to the load and this phenomenon enables reduction of the robot arm inertia. It also facilitates quick response when employed in robotics. In this paper, precision positioning of a belt driven mechanism using a feed-forward compensator under maximum acceleration and velocity constraints is proposed. The proposed method plans the desired trajectory and modifies it to compensate delay dynamics and vibration. Being an offline method, the proposed method could be easily and effectively adopted to the existing systems without any modification of the hardware setup. The effectiveness of the proposed method is demonstrated through computer simulation and experimental results.