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Application of dithering control for the railway wheel squealing noise mitigation
Seyed Rahim Marjani,Davood Younesian 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.23 No.4
A new methodology for mitigation of the wheel squealing is proposed and investigated based on the dithering control. The idea can be applied in railway lines particularly in urban areas. The idea is clearly presented, and applied to a validated model. A full-scale model including the vehicle, curved track and wheel/rail contact is developed in the time domain to analyze the possibility and level of wheel squeal noise. Comparing the numerical results with a field test, the model is validated in different levels namely i) occurrence, ii) squealing frequency and iii) noise level. Two different approaches are proposed a) dithering of the wheel with piezoelectric patches and b) dithering of the rail with piezoelectric stacks. The noise level as well as the wheel responses is compared after applying the control strategy. A parametric study is carried out and effect of the dithering voltage and frequency on the squealing noise is investigated. It is found that both the strategies perform quite effectively within the saturating threshold of piezoelectric actuators.
제어모멘트자이로 클러스터의 특이점 회피를 위한 디더제어 방안
서현호,최홍택 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.4
인공위성의 자세제어를 위해 제어모멘트자이로를 탑재할 경우 발생할 수 있는 특이점 회피 방안으로서 디더제어를 도입하는 방안을 알아보았다. 그러기 위해서 인공위성의 운동방정식과 제어모멘트자이로 구동법칙을 소개하였다. 이후에 디더제어를 이용하는 방안을 제시하고, 시뮬레이션으로 특이점 회피 가능성을 입증한다. 내부제어루프에 디더제어를 도입할 경우 특이점을 회피할 수 있다는 기존 연구결과에서 확장하여 외부제어루프에 디더제어를 도입함으로써 특이점을 회피할 수 있다는 새로운 아이디어를 확인할 수 있다. We investigate the feasibility of dither control to control the attitude of satellite equipped with control moment gyroscopes cluster. The satellite dynamics and the steering law of control moment gyro cluster is introduced. We present the application method of dither control, and the possibility of singularity avoidance is verified by simulation study. The case of introducing the dither control in the inner loop was well-developed by existing study. We newly extend this idea to the outer loop and verify that the singularity of control moment gyroscopes cluster could be avoided.
Active Autofocus Control Using Source Dithering Technique Based on Fibre-optic Confocal Principle
박정재,김승우 한국정밀공학회 2011 International Journal of Precision Engineering and Vol. No.
A significant process for highly precise measurement in 2-D inspection and 3D surface metrology is accurate and consistent imaging of target being measured. Dithering locking method, one of widely-used focus-locking method, has been only applied to objective modulation type which cause physical influence and image distortion. To overcome this, we have developed an actively locked focus-tracking system based around source dithering technique using fiber-optic confocal principle. Further, the whole measurement system can be simplified through both fiber confocal microscope design with reciprocity and fiber source modulation. It is verified that the proposed focus-tracking system has sub-μm focusing stability and accuracy. By testing focus tracking performance on a LCD panel substrate with a few μm-sized features, the applicability to optical profiler with vision inspection was confirmed.
Active Autofocus Control Using Source Dithering Technique Based on Fibre-optic Confocal Principle
Park, Jung-Jae,Kim, Seung-Woo 한국정밀공학회 2011 International Journal of Precision Engineering and Vol.12 No.4
A significant process for highly precise measurement in 2-D inspection and 3D surface metrology is accurate and consistent imaging of target being measured. Dithering locking method, one of widely-used focus-locking method, has been only applied to objective modulation type which cause physical influence and image distortion. To overcome this, we have developed an actively locked focus-tracking system based around source dithering technique using fiber-optic confocal principle. Further, the whole measurement system can be simplified through both fiber confocal microscope design with reciprocity and fiber source modulation. It is verified that the proposed focus-tracking system has sub-pm focusing stability and accuracy. By testing focus tracking performance on a LCD panel substrate with a few pm-sized features, the applicability to optical profiler with vision inspection was confirmed.
이재영(Jaeyoung Lee),유경종(Kyeongjong You),한영훈(Yeonghoon Han) 한국자동차공학회 2017 한국자동차공학회 부문종합 학술대회 Vol.2017 No.5
We propose a LCD control method based on variable dithering to reduce image sticking caused by orientation change. The proposed method changes dithering patterns to alter the crystal orientation when the image is still and inserts a middle image to remove flicker. Also, the auto light function is implemented by limiting the maximum gradation level and the backlight luminance to change pixel brightness and increasing the dithering pattern size to compensate the reduction in the number of gradation steps. To verify the suggested method, an Ioniq image is used. The analysis results based on the Weibull distribution shows that the proposed method provides the 257% lower probability of the image retention occurrence.