http://www.dct.tue.nl/New/Wouw/Automatica2008_vandeWouw.pdf

Performance of convergence-based variable-gain control of optical storage drives

Several new types of optical disc standards have reached the market during the past years, from the well known Compact Disc (CD), and its computer version CD-ROM, through the Digital Versatile Disc (DVD) to the new high density discs, eg. Blu-Ray discs. All these standards have potential problems with surface faults like scratches and fingerprints. Many users have suddenly encountered the problem that a CD-player, a PC or a DVD-player could not play a given disc, since this disc has become too faulty. The main topic of this thesis is to improve the CD-players’ capability to play these discs with surface faults, by improving the two controllers which keep the CD-player positioned on the CD. Some parts of this Ph.D project has been specialised for a specific CDplayer. However, the achieved results can be generalised to the other optical disc player standards. The problem in handling these surface faults is that they result in a faulty signal component in the position signals which are used for positioning the CD-player. The basic idea behind this study is to use feature extraction to remove this faulty signal component from the measured position signals. This Ph.D study contributes with six major technical contributions, which are all described in this thesis. Traditionally the optical parts of CD-players are modelled with simple linear models. However, these models are not ideal for detecting and handling surface faults. Instead a more detailed non-linear model of the optical part of the Compact Disc player is developed. Based on this new optical model and a simple model of the surface faults, a pair of residuals are defined. These residuals have shown better fault detection properties compared with the normally used residuals. In order to compute these new residuals a method to compute the inverse map of the non-linear optical model is introduced. Using this inverse map together with a Kalman estimator, the residuals can be estimated as well as an estimate of the position signals which are more valid during surface faults. Based on the residuals, time-frequency based methods are designed for detecting the surface faults. The results, however, have shown that a better strategy is to improve standard thresholding algorithms. Time-frequency based methods are used to extract features from the surface faults. First of all the faults are classified among different fault classes, and even more importantly, the faults are approximated by the use of timefrequency based methods. These approximations are used for two purposes. The first

/pdf/feature-based-control-of-compact-disc-players-33vlgkj3fm.pdf

Feature Based Control of Compact Disc Players

For nonlinear controlled optical storage drives, a frequency-domain measurement approach is shown to be effective in demonstrating both stability and performance. In an experimental setting based on an industrial optical playback (CD drive) device, the motivation for applying such an approach is illuminated. It is shown that performance can efficiently be assessed using a describing function approach on a model level and using swept-sine measurements on an experimental level. The validity and effectiveness of the approach is extensively shown via closed-loop measurements.

http://www.dct.tue.nl/New/Wouw/CST2006_CD.pdf

Experimental frequency-domain analysis of nonlinear controlled optical storage drives

In this paper an introduction and motivation is given towards an integrated design approach for motion systems using overactuation. Looking to motion systems and their history, the current status of mechatronic motion systems is discussed. One of the main aspects that limit performance in mechanical systems is the presence of vibrations. An overview is presented of several passive and active methods to solve vibration problems. Active vibration control can be regarded as a form of overactuation to improve system performance. It is expected that an integrated overactuated design approach will be advantageous over traditional vibration control solutions, which often make use of adaptations after the mechanical design has been completed. Before a framework for an integrated design approach can be posed, different strategies of overactuation must be investigated. To study the closed-loop characteristics of resonances in mechanical systems with more actuators more closely, some first explorations of a dual-input single-output motion system are made.

http://www.mate.tue.nl/mate/pdfs/3096.pdf

Introduction to an integrated design for motion systems using over-actuation

Optical disc drives are subject to various disturbances and faults. A special type of fault is the so-called disc defect. In this paper we present an approach for disc defect classification. It is based on hierarchical clustering of measured signals that are affected by disc defects. The time-series are mapped into a feature space after which the feature vectors are clustered in a hierarchical fashion. Finally, signals are fitted onto the clusters to obtain single representations for each fault class. The resulting class descriptions can then be used for (on-line) classification of new disc defects. The approach is evaluated by applying it to a set of test data.

http://www.mate.tue.nl/mate/pdfs/5646.pdf

Disc defect classification for optical disc drives

/pdf/classifying-disc-defects-in-optical-disc-drives-by-using-rr7goms5y5.pdf

Classifying disc defects in optical disc drives by using time-series clustering

In miniaturized systems (e.g. optical disk drives) much effort is made to design a structure in such a way that the demands on dimensions (height, width) and desired bandwidth are satisfied. Easier, and often cheaper designs can not be used, because they suffer from lower resonance frequencies, which limit the bandwidth. A method is presented for mechatronic structures that compensates unwanted bandwidth limiting resonance frequencies with an additional piezo electric actuator. Advantage of this method is that no extra sensor is used and that the contribution of the piezo is much easier to tune (when compared to a notch filter), since it is part of the structure. Disadvantage is that the piezo influences the dynamics of the original system, which complicates the choice of a suitable piezo actuator.

Compensation of mode shapes with a piezo electric actuator for an optical drive

/pdf/compensation-of-mode-shapes-with-a-piezo-electric-actuator-3pwe4hjb3s.pdf

H.J. Goossens

Papers

Classifying disc defects in optical disc drives by using time-series clustering

Compensation of mode shapes with a piezo electric actuator for an optical drive

Compensation of mode shapes with a piezo electric actuator