Browsing by Author "Huang, Jeng-Sheng"

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Nonplanar modeling and experimental validation of a spindle-disk system equipped with an automatic balancer system in optical disk drives
(2007-05-01)
Chao, Paul C. -P.
;
Sung, Cheng-Kuo
;
Wu, Szu-Tuo
;
Huang, Jeng-Sheng
;
電控工程研究所
Non-planar dynamic modeling and experimental validation of a spindle-disk system equipped with an automatic ball-type balancer system (ABS) in optical disc drives are performed in this study. Recent studies about planar dynamic modeling and analysis have shown the capability of the ABS in spindle-disk assembly via counteracting the inherent imbalance. To extend the analysis to be practical, non-planar dynamic modeling are conducted in this study to re-affirm the pre-claimed capability of the ABS system, along with experiments being designed and conducted to validate the theoretical findings. Euler angles are first utilized to formulate potential and kinetic energies, which is followed by the application of Lagrange's equation to derive governing equations of motion. Numerical simulations are next carried out to explore dynamic characteristics of the system. It is found that the levels of residual runout (radial vibration), as compared to those without the ABS, are significantly reduced, while the tilting angle of the rotating assembly can be kept small with the ABS installed below the inherent imbalance of the spindle-disk system. Experimental study is also conducted, and successfully validates the aforementioned theoretical findings. It is suggested that the users of the ABS need to cautiously operate the spindle motor out of the speeds close to the resonances associated with various degrees of freedom. In this way, the ABS could hold the expected capability of reducing vibration in all important directions, most importantly in radial directions.
Precision micro-/nano-machining in a scanning electron microscope by run-to-run control based on image feedbacks
(2009-04-01)
Liao, Lun-De
;
Chao, Paul C. -P.
;
Lin, Yu-Jhu
;
Chiu, Chi-Wei
;
Miaou, Shaou-Gang
This study aims to perform the micro-/nano-machining with an atomic force microscopy (AFM) tip in a scanning electron microscope (SEM) via run-to-run (R2R) controller and digital image feedbacks. The R2R is assisted by the technique of exponentially weighted moving average (EWMA). This "EWMA feedback" controller is a popular R2R control scheme, which primarily uses data from past process runs to adjust settings for the next run. On the other hand, the digital images are obtained by using the wavelet transform and binarization in order to recognize machining results, and then return feedback of the digital image information to the controller; finally obtain the next input data for the actuating controller to achieve the targeted machining precision. The experimental results for preliminary machining in micro-level indicate that the EWMA controller based on image feedbacks performs with satisfactory results at reducing the process variation, particularly at the first few production runs, thereby making it possible to further reduce the bias and bring the process output closer to its target as soon as the process begins to operate. It is seen that the proposed EWMA controller with digital image feedbacks is easy to implement and provides a good approximation to the optimal variable discount factor, which can reduce the error of the machining process from initial 40% without control to 0.7% with the proposed R2R. More importantly, such a reduction can be achieved at no loss of long-term stability. With sure precision of AFM, the aforementioned resulted micro-machining precision can easily be extended to nano-levels. Therefore, this study demonstrates a successful micro-/nano-machining operation in the environment of a SEM, by employing the designed R2R controller with digital image feedbacks. (c) 2009 Elsevier B.V. All rights reserved.