Duanyi Xu

Time Optimal Seek Control For A Coupled Dual Stage Disk Drive Actuator

A unified expression and three typical kinds of seeking trajectories of the time optimal control of a dual stage disk drive actuator with passive coupling between the two stages are presented. Necessary conditions for finding the optimal control for the problem with state-variable constraints are applied to derive the solution. Numerical calculations and computer simulations were performed to get the trajectories. The experimental trajectories of 1/3 full stroke for a disk drive are also presented. A DSP (Digital Signal Processor) based control system is used to implement the optimal control. The time optimal seek control features cooperative control of the two stages of the actuators, and seek time can decrease as compared with one-stage seeking when the fine actuator locked onto the coarse actuator.

Analysis and study on measurement of jitter and its precision

Jitter is defined by the variation of each pit length and timing variations between data and clock frequency on discs. As a comprehensive item, it relates with error rate directly. In this paper, the definition, determined and influence factors of jitter n are analyzed. According to the analysis, measurement methods of jitter are provided. The precision of a method. The methods precision and demand are calculated and explained in detail.

Holographic element for CD pickup-to-play DVD

A holographic element for the common CD pick-up to play DVD is designed in this paper. The focus of holographic element is the same as that of the objective lens of CD player. The holographic element is fixed before the objective lens. The focus of DVD player with this holographic element is 8.5 mm, the number aperture is 0.75, and the focusing beam spot is 0.5 um. DVD player with the holographic element is characteristic of compensating the main optical error met in the common CD player well.

Data analysis method of DVD disk parameters affected by replication process

The process of replication, such as molding, clamping, injection, metalizing, even extrusion and printing, put an important impact on the quality of the finished DVD discs. They are crucial to duplicator, but not so easy to detect by conventional analysis methods provided by current commercial off-line tester. We introduce a data-analysis method to enlarge the effects of replication process on the disc parameters, by means of eliminating the disturbance from pre- replication process. This method is named RES (Remainder Elimination of the effect Stamper) parameters. An example is given to show the status of discs edges affected by molding, and the selection of different molding patterns is analyzed.

Using a modified repetitive control for improving optical disk tracking accuracy

The principle of modified repetitive control is analyzed. According to the model of tracking actuator, a simplified design method of modified repetitive control was introduced. The simulation result shows the modified system has good performance. Compared with classical control system, it increases servo accuracy and steady state robustness, decreasing error signal greatly.

Two-actuator cooperative seek control for optical disk drives

Slow access speed is still the problem to limit applications of rewritable optical disk drives. Dual stage actuators with a coarse and a fine actuator are used in optical disk drives. In this paper, the two-actuator cooperative seek control method, based on time optimal seek control, is presented, and the average seek time is analyzed theoretically.

High-speed data recording system based on optical disk array

In this paper, a high speed data recording system based on optical disk array is presented on the basis of careful analyses of the techniques to improve the data recording speed of the commercial optical drives. An ultra high speed and mass storage capacity are achieved in this system. Flexibility and portability are also gained by the design.

One-dimensional modeling of magneto-optical read channel

In this 1D model of Magneto-Optical read channel, the isolated step response is modeled to be a Q function, and an equalizer parameter designing method based on the least square error criterion is given, which is suitable for both linear equalizers and feedback equalizers. The detection method can adopt the threshold detection and Viterbi detection. Although the model is linear, it is easy to simulate the non-linear characteristics like bloom or jitter in Magneto-Optical recording.

Study and analysis of a new servo system in an optical disk player

In this paper, the objective of servo system in an optical disc player is discussed. The traditional servo method, zero- order indifferent PID adjustment, is analyzed. Based on the analysis, a new servo system, 1-order indifferent PI&PID adjustment, is provided. In the new adjustment method, the main error of low frequency from ECC and Imbalance will be reduced to minimum in theory. In the end of the paper, the stability of the new servo system is analyzed in detail.

Antipiracy technology study on optical disks

The software industry loses billions of dollars each year due to software piracy. And CD-ROM technology is one of the most successful and fast growing methods for quickly and economically distributing information. So it is an urgency to find a good method to protect CD-ROM from being pirated. In this chapter, we will discuss some new technologies of anti- piracy. According to these discussions, we will put forward our new anti-piracy method.