Buqing Zhang

Multi-level read-only recording using signal waveform modulation

A novel multi-level read-only recording using signal waveform modulation (SWM) is presented. The SWM is realized by inserting a sub-pit/sub-land to the original land/pit. Numerical simulation provides a helpful tool for the write strategy optimization. This method is experimentally validated on the DVD platform. Comparing with 2-level recording, an increase of 50% in capacity can be expected. It shows superiority over signal amplitude modulation (SAM) multi-level in replication processing, capacity increase and servo performance.

An interpolation model to accelerate the frequency-domain response calculation of grounding systems using the method of moments

The transient characteristics of grounding systems are essential for their designs and related electromagnetic-compatibility problems in power systems. Although the method of moments (MoM) is a popular way to analyze the characteristics of grounding systems, it is time-consuming. In this paper, a two-stage method is presented to construct fitted models of the frequency-domain responses of grounding systems to accelerate the calculations of the MoM. In the first stage, the adaptive model-based parameter estimation is used to adaptively choose the most valuable frequency sampling points to construct the initial fitted functions, and then the fitted functions are adjusted in the second stage by comparing the fitted results with those computed by the first principle model at some points. The validation was achieved by a comparison of the numerical results and those obtained by inverse fast Fourier transformation.

High-Sensitivity Actuator with New Magnetic Circuit in Optical Pickup

A lens actuator is an important mechanical–electrical component in optical pickup. For the high-sensitivity actuator used in a super-multi recorder, a novel magnetic circuit is proposed in this paper. This magnetic circuit consists of six thick permanent magnets with regulated placement, two thin permanent magnets, a base yoke, and an upper yoke. Experimental results verified the feasibility of the designed magnetic circuit.

High performance three-axis actuator in super-multi optical pickup with low crosstalk force

This paper presents a novel method to reduce the crosstalk force in main movement, and improve the sensitivity of the three-axis actuator in super-multi optical pickup. A novel magnetic circuit adopting symmetric driving coils and permanent magnets with special placement is developed. Then, the magnetic circuit is optimized with the help of Taguchi method, so as to dramatically improve the flux density and reduce the nonlinearity. Some actuator samples with the optimized parameters are fabricated and tested, and the results show the good performance of the proposed actuator.

Magnetic Circuit Design for Six-Wire Suspension Type Actuator in a Super Multioptical Pickup

We have developed a new magnetic circuit consisting of eight permanent magnets with special placement order. Here, we analyze the magnetic flux density distribution, the driving force distribution, and the interference force using the finite-element method. The driving sensitivity of the actuator at low frequency is nearly twice that of a conventional actuator. We have built several samples and compared their performance with simulation data. The results prove the validity of the proposed magnetic circuit and the design method.

Creating multivariable response surfaces by the two-stage adaptive sampling techniques and its application in the optimization of grounding grids

A fast and efficient adaptive sampling algorithm to obtain the response surface of multivariable objective function is presented. The algorithm is divided into two stages. First, starting with a low-rank interpolation model, the technique systematically increases the rank by optimally choosing new support points in the areas of the highest error until the required accuracy is achieved. Second, the verification between the fitted result and the exact one is carried out. The optimization of grounding grids is performed to show the effectiveness of the proposed algorithm

Analytic solution for damping coefficients of six-wire-suspension actuator in optical pickup

The lens actuator is one of the most important mechanical-electrical components in optical disc systems. It is used for adjusting the attitude and position of the objective lens. When it works, the resonance vibration including the first resonance and higher order resonance will happen near the resonance frequency, which will weaken the servo control capability, thus additional damper glue is necessary to restrain the resonance magnitude. In order to obtain better damping performance, the location of the damper glue and the structure of the damping filler are very important to control the resonance magnitude. In this paper, according to the flow feature of the damper glue, damping models in focusing, tracking and tilting direction are established with the help of Oseen flow equation, and equivalent damping coefficients are derived. Some samples with the design parameters are fabricated and tested, the damping coefficients obtained form the experiment are compared with the theoretical results, which shows the validity of the proposed fluid model and the design method.

Compatible optical pickup actuator for next generation versatile disc system

Nowadays, high-density disc and high-speed optical disk drive have become popular as optical disc has many merits such as cost effectiveness, high data transfer rate, large storage capacity, removability and compatibility. In this paper, we presented a compatible optical pickup actuator for next generation versatile disc (NVD) system. This actuator has high AC sensitivities and good 2nd resonance frequency through finite element method (FEM), and the actuator model properly satisfied the specifications for NVD system. The FEM analyses method is successfully applied to design the optical pickup actuator.

Study on the movement measurement for an objective lens actuator in optical pickup

This paper deals with the actuator movement measurement for objective lens actuator in optical pickup. An optical pickup is an optical apparatus to record and/or reproduce information from an optical disc, and move in a radial direction on the optical disc. The objective lens actuator helps move an objective lens in a tracking direction, a focusing direction, and/or a tilting direction, spot the laser beam on a correct portion of the optical disc. It basically carries out tracking and focusing movements, i.e., a biaxial movement. For high recording density media, the optical pickup actuator requires a triaxial or quadriaxial movement including a tilting movement in addition to the existing biaxial movement. For information recording and/or reproducing correctly, the movement range of the actuator should be proper to accurately follow the disc deviation. Alternative methods of movement measurement have been proposed. One method employed now uses a plane plate reflecting laser beam which describes the movement. It requires two laser devices for tracking direction and the focusing direction measurement respectively. Here we propose a method for describing the tracking and focusing movements on one laser device. In this method an external cone is used, with the same weight as the objective lens. It could reflect laser beam back to the linear CCD. The diameter of the external cone base is equal to that of the objective, which is crucial for a stable placement. The ratio of height to width of the external cone is designed and optimized, so that to satisfy the accuracy of the movement measurement and minimize the device. Measurement with this method has proved satisfactory for certain CD/DVD optical pickup.

Analysis of Foundation Grounding System Buried in a Horizontal Multilayer Soil by Means of the Fictitious Conductivity Concept

The theoretical model for the analysis of grounding system encased in the foundation region in a horizontal multilayer soil is presented. By means of fictitious conductivity concept, the effects of foundation are replaced by a set of equivalent current sources. The analysis of grounding system can be carried out by combining the moment method with additional equivalent current sources. The main advantage of the proposed approach is that it can be linked with the existing codes easily. The results are compared with those found in the literature and obtained by other popular software