Feed-Forward Tracking Servo System for High-Data-Rate Optical Recording

Abstract

IBSTRACT. The increased x-ray dose to soft tissue adjacent to plane bone interfaces v x s measured as a function of x-ray quality and depth. The measurements were pwfonned using a thin pol>-ethj-lene-film dosemeter. Experimental data are presented for tl variety of clinically useful x -r a y qualities. Comparison of the results with calculated doses assuming monoenergetic photons jhox-s discrepancies which are attributed to the x-ray spectra. It is shown that 1%-hen the x-ray spectra are broad and of low quality (lorn kvp and low filtration) differences between the measured and calculated values are great.

Double Feedforward Control System Based on Precise Disturbance Modeling for Optical Disk

“…The proposed DFFC system is composed of a feedback control system and two ZPET control systems based on an error prediction mechanism and a trajectory command prediction mechanism. [12][13][14][15][16][17][18][19][20] The ZPET control system based on the error prediction mechanism suppresses tracking error. However, it sometimes has a large tracking error due to parameter variation and modeling error among others.…”

“…The proposed system is constructed using two zero phase error tracking (ZPET) control systems based on error prediction and trajectory command prediction. [13][14][15][16][17][18][19][20] The proposed DFFC system realizes a higher precision tracking control than a conventional E-PTC system.…”

High-Speed Tracking Servo Using Zero Phase Error Tracking-Feed-Forward Method for Professional-Use Optical Disks over 10000 rpm

“…For example, the employment of repetitive control techniques to the gap servo for near-field recording systems was reported. 4,5) We have proposed a high-speed tracking control system that combines a feedback (FB) control system with a feed-forward (FF) control system, which was based on the zero phase error tracking (ZPET) method [6][7][8][9][10] (referred to as the ZPET-FF control). This system has been shown to reduce residual tracking error far better than conventional FB control or repetitive control, 7) and has demonstrated the capability to reduce the residual tracking error on an optical disk rotated at a high speed with an optical system with an objective lens of a numerical aperture (NA) of 0.65.…”

New robust feedforward tracking control structure for optical disk recording system

“…In our previous work, an estimation method of the two sampling forward tracking error e f eedback t (k + 2)[5] [6]. This paper treats the tracking error e t (k) as a periodic function such as Eq.(29).…”

“…Moreover, because the next generation optical disk system will become the narrower track pitch and the more high rotation speed, the tracking servo system of optical disk should be reducing the tracking error caused by periodic disturbance. However, it is difficult for only feedback servo system to reduce the tracking error below the target tolerance [6].…”