A swing arm actuator for a small form factor optical drive

Small form factor optical drives for mobile application require high performance actuators that satisfy tight geometrical size requirements. We have designed a swing arm type actuator that allows the integration of a complete miniaturized optical pickup unit on the actuator. The performance of the actuator has been simulated by the FEM method and is compared with experimental results. Finally the manufactured actuator was used to read out a Blu-ray ROM disc.     

Design of swing arm type actuators considering thermal and dynamic characteristics

The present state of the design of swing arm actuators for optical disc drives is to obtain the highly efficient dynamic characteristics within a very compact volume. As a necessary consequence, the need of the small form factor (SFF) storage device has arisen as a major interest in the information storage technology. Due to the size constraint, the thermal stability of the optical pick-up head is important: therefore, the actuator is designed to emit the heat, which is generated by the optical pick-up, along the structural body easily. In this paper, we suggest the miniaturized swing arm type actuator that has effective heat emission quality as well as satisfies the dynamic requirements for the SFF optical disk drive (ODD). The actuator is targeted to be installed in CF-II card size drive to be competitive with flash memory or mini hard disk drive used in mobile electric devices; therefore the dimension of the actuator is required as 11.0 mm × 2.5 mm × 25.0 mm (width × height × length). Because of its small size, the dynamic requirements are severe to ensure the enough gain-margin for the system control together with satisfying the DC/AC sensitivity conditions. Moreover, due to the small size, the maximum pick-up temperature is critical in design because the system has high possibility to reach the shut-down temperature. For the operating mechanism, it uses a tracking electromagnetic (EM) circuit for the focusing motion together and the initial model is designed and promoted by the design of experiments (DOE) only considering the dynamic characteristics. New concept design is suggested based on the topology optimization method considering the thermal conductivity. Furthermore, the new design is modified by DOE to maintain the high sensitivity and to have wide control bandwidth and decreasing mass and inertia. The final design of a swing arm type actuator for SFF ODD is suggested and its dynamic characteristics are verified.     

Development of a nanometer resolution flatness measurement system for the ceramic surface by using Blue-ray optical pickup

This study proposes a new type of measurement system for the flatness of ceramic surface. The system proceeds the measurement with the optical pickup head of blue ray. It used the light source emitted from the optical pickup head which reflected by the ceramic surface and the reflective light was received by the photo diodes in the optical pickup head then to be calculated into focusing error signal. Then, we can automatically lock focus and analyze the data on the measurement surface by the program to get the flatness of the ceramic surface. The advantages of this measuring method are that no need to use expensive interference system, easier to set up and operate, the over-all cost of detection devices is low, the size of components is small, and the measurement accuracy can up to sub-micron level. The resolution of this measurement system is up to 20 nm.     

Design of swing arm actuator for small and slim optical disc drives

Recent advancements in mobile devices have fueled a requirement for information storage systems with characteristics such as subminiature size, low cost, and minimum power consumption. Small optical disk drives could provide a good solution, because their storage media is cheaper than those of hard disk drives or flash memories. In this paper, we proposed the miniaturized swing arm type actuator that had a new focusing mechanism for small and slim optical disk drives (ODD). Initial model was designed by EM and structural analyses. Based on results of DOE, optimization procedures of EM circuits were performed with design variables using variable metric method (VMM). And, structural parts were designed to maintain the high sensitivity of the actuator. Finally, the swing arm type actuator for small and slim ODDs was suggested and its dynamic characteristics were checked.     

Improvement of dynamic characteristics for optical pickup actuator by magnetic circuit

 As disk rotational speed of optical disk drives (ODD) increases, an optical pickup actuator has a high servo bandwidth for its focusing and tracking control to follow dynamic disturbances by high rotational speed in ODD. However, the servo bandwidth is limited by some vibration modes due to the flexibility of the moving part in the actuator. In this paper, the influence of the driving forces generated by VCM on excitation of flexible modes of the moving part in high frequency range is analyzed. Especially, in order to reduce the first flexible mode affecting the servo bandwidth, it is attempted to modify force distribution on coils. The magnetic simulation is performed by using finite element analysis, and compared with experimental results. Finally, it is shown that flexible mode vibration can be suppressed by proper design of magnetic circuit. Received: 20 June 2002 / Accepted: 29 August 2002     

基于虚拟仪器技术的力矩器特性测试仪

力矩器是光盘系统中的核心组件,其动态性能直接决定着光学头读写光盘的质量。本文基于力矩器低频段内特性参数的在线测试要求,提出了基于虚拟仪器技术的力矩器特性测试仪技术方案,完成了测试仪整体方案设计、硬件平台的搭建以及软件系统的应用开发。     

采用DVD光学头的微流细胞计的细胞分析

一、引言流动血细胞计是当细胞通过盛满液流的设备时,单个生物细胞的物理或者生化特征被检测出来的一个系统。这些系统往往基于光学或者阻抗的测量方法,其中光学流动细胞计是最重要的商业化产品。物理参数如细胞密度或者单个细胞尺寸可以通过基于直流/低频交流阻抗测试法或者高频信号的库尔特计数器(Coulter Counter)获取。使用阻抗频谱参数仪,膜电容和细胞浆电导率等可以在细胞流经时获取。     

悬线有夹角的三维悬线式蓝光光学头力矩器的仿真研究

对具有聚焦、循迹和倾斜补偿功能的悬线带夹角的三个运动自由度的蓝光光学头三维悬线式力矩器建立了模型,以有限元作为分析手段,分析了其空间磁场和受力情况。模态分析得到力矩器循迹、聚焦和倾斜三个模态分别为50.470Hz、54.754Hz和205.23Hz,分别与实验比较误差小于1%。等效阻尼系统来模拟阻尼胶的阻尼效果,谐响应分析得到力矩器的特性曲线多普勒曲线。通过与实验比较,所建立的模型能够真实地反映该力矩器的特性。     

Design of swing arm type actuator and suspension for micro optical disk drive

One of the trends on information storage device is focused on the development of micro-optical devices with optical flying head (OFH). Many different types of sliders for OFH and optical component systems have been introduced in the literature. However, the important issues on the mechanical system, which consists of suspension, swing arm and voice coil motor (VCM) part has not been discussed up to date. In this research, a swing arm type actuator with suspension for micro optical disk drive is designed and developed, basically focused on the mechanical issues, which should be solved for real application.     

Precision positioning of a three-axis optical pickup via a double phase-lead compensator equipped with auto-tuned parameters

The objective of this study is to design an intelligent control servo scheme for the three-axis optical pickups employed in the next-generation optical disc drives. The three-axis pickup owns the capability to move the lens holder in three directions of focusing, tracking and tilting, which is required particularly for higher data-density optical disks and precision measuring instruments to annihilate non-zero lens tilting. The intelligent controller utilizes a commercially often-used double phase-lead compensator equipped with the capability of auto-tuning on control parameters. In this way, the model uncertainty of the pickups caused by manufacturing tolerance and the coupling between three different DOFs of the three-axis pickup can be overcome to render desired precision data-reading. In the initial stage of the study, Lagrange??s equations are employed to derive equations of motion for the lens holder. A double-lead controller equipped with a fuzzy logic parameter tuning algorithm is then designed to perform dynamic decoupling and forge control efforts toward the goals of precision tracking, focusing and zero tilting simultaneously. Along with the controller, a genetic algorithm is developed to search the optimal designed parameters of previously designed auto-tuning algorithm. Finally, the experiments are conducted to show the effectiveness of the controller. With validated performance, the designed intelligent controller is ready to be employed for the next-generation optical disc drives.     

有限元分析软件在光学头力矩器设计中的应用

一、简介力矩器是光学头系统的核心元件。在光学头读取光盘的过程中,力矩器根据聚焦、循迹和倾斜误差信号实时地驱动物镜运动,使得聚焦光斑消除光盘的起伏振动等因素导致的光斑位置偏移,实现高质量的信     

Excitation pulse shape effects in drop test simulation of the actuator arm of a hard disk drive

For a head actuator assembly (HAA) of a hard disk drive, the deflection of the tip of the arm relative to the pivot can be used as an indicator of its response to shock. To study the pulse shape effects in a shock analysis, the actuator arm of an HAA subjected to different acceleration pulse shapes, such as half-sine, triangular and dual-quadratic, was simulated by using a dynamic finite element package. It has been found that, for the three acceleration pulses, the peak displacements have opposite behaviors for 0.1- and 1-ms pulse widths. The above phenomena have been explained in terms of a power spectrum analysis. It has been found that the relative magnitude of the peak displacement of the actuator arm is mainly determined by the power magnitude of the acceleration pulse at the resonant frequency. A simple mathematical theory was developed to predict the location of a cross-over interval which divides the power spectrum curve into two major regions where opposite behaviors are observed. The theoretical pulse width is correlated with a pulse width based on a threshold value as normally used in experiments. B.J. Shi: On leave from School of Mechanical and Electronic Engineering, Shandong Institute of Architecture and Engineering, Jinan 250014, China     

Design of suspension and swing arm for improved shock resistance in the micro optical disk drives

One of the trends on information storage device is focused on the development of micro optical disk with optical flying head (OFH). The OFH in the small form factor ODD consists of optical slider, suspension, swing arm, and so on. In order for a slider with OFH to be successfully implemented in the system, the shock performance of the head-gimbal assembly should be guaranteed for mobile applications. We design development model of suspension and swing arm for improved shock resistance using topology optimization and shape optimization. The objective of the suspension design is to decrease the equivalent mass with increasing first torsional frequency. The objective of the swing arm design is mass reduction for reducing power consumption and fast access time. In this paper, we suggest a design method for the improvement of the dynamic performance of suspension and swing arm for the OFH considering shock characteristics.     

Design and analysis of two-wire focusing actuator for small-sized ODD with linear VCM type’s actuator

Recent advancements in mobile devices have fueled a requirement for information storage systems with characteristics such as subminiature size, low cost, and minimum power consumption. Small optical disk drives could provide a good solution, because their storage media is cheaper than those of hard disk drives or flash memories. In this study, we design and analysis a linear voice coil motor (VCM) types actuator for the coarse and fine tracking motions and a two-wire spring types actuator for a fine focusing motion in order to apply them to small-sized optical disk drives of high data capacity. And, we make the mathematical model of a two-wire spring types actuator and find proper conditions to suppress the tilt motion of the lens holder for various focusing offset positions without sacrificing the sensitivity. Based on them, we design and modify the magnetic circuit and the structural part. Finally, we verify that the designed actuator had the proper dynamic characteristics and that it could be used in small optical disk drives by simulations and experiments.     

Design of an integrated optical pickup with NA of 0.85 for small form factor optical disk drives

We design an integrated optical pickup for small form factor optical disk drives. The specifications of the pickup are compatible with those of the Blu-ray disk (BD) in terms of numerical aperture (NA) of the objective lens, the wavelength of the laser diode, and the thickness of the cover layer. The objective lens unit with NA of 0.85 consists of two aspherical refractive lenses and a diffractive optical element for compensation of the chromatic aberration. Each element of objective lens unit will be fabricated on a wafer as an array type, and the three wafers will be aligned and bonded to form an objective lens array. Therefore, elements of the objective lens unit are designed to have sufficient alignment tolerances for various directions such as de-center and tilt. The optical performances of the objective lens unit are evaluated by simulation against various disturbances such as wavelength change of emitting light from laser diode, misalignments, etc. We also design a quarter wave plate, a polarized holographic optical element, and the shape of photodiode integrated circuit array to generate focusing and tracking error signals. The entire height of the pickup including working distance is 2 mm, and the effective pupil diameter of the objective lens unit is less than 1 mm.     

Finite element modal analysis of an HDD considering the flexibility of spinning disk–spindle, head–suspension–actuator and supporting structure

This paper presents a finite element method to analyze the free vibration of a flexible HDD (hard disk drive) composed of the spinning disk–spindle system with fluid dynamic bearings (FDBs), the head–suspension–actuator with pivot bearings, and the base plate with complicated geometry. Finite element equations of each component of an HDD are consistently derived with the satisfaction of the geometric compatibility in the internal boundary between each component. The spinning disk, hub and FDBs are modeled by annular sector elements, beam elements and stiffness and damping elements, respectively. It develops a 2-D quadrilateral 4-node shell element with rotational degrees of freedom to model the thin suspension efficiently as well as to satisfy the geometric compatibility between the 3-D tetrahedral element and the 2-D shell element. Base plate, arm, E-block and fantail are modeled by tetrahedral elements. Pivot bearing of an actuator and air bearing between spinning disk and head are modeled by stiffness elements. The restarted Arnoldi iteration method is applied to solve the large asymmetric eigenvalue problem to determine the natural frequencies and mode shapes of the finite element model. Experimental modal testing shows that the proposed method well predicts the vibration characteristics of an HDD. This research also shows that even the vibration motion of the spinning disk corresponding to half-speed whirl and the pure disk mode are transferred to a head–suspension–actuator and base plate through the air bearing and the pivot bearing consecutively. The proposed method can be effectively extended to investigate the forced vibration of an HDD and to design a robust HDD against shock.     

Dynamic model with sensor and actuator for an articulated robotic arm

In this paper, the dynamic model with sensor and actuator for the articulated robotic arm is obtained by using the combination of the structural, the sensor, and the actuator dynamic models. The proposed approach is validated comparing the simulation results against the experimental results.     

A U-shaped actuation system for dual-stage actuators used in hard disk drives

In this paper, we propose an actuation system, called U-shaped actuation, for dual-stage actuator to suppress the arm mode flutter. We manufactured an actuator using this actuation method and measured the frequency response. We found that the frequency response had an in-phase arm mode frequency and that there was little difference between each head at arm sway and suspension sway mode. Next, we designed a controller and compared its sensitivity function with that of conventional actuation. By applying stabilizing control to the in-phase arm mode, NRRO of the arm flutter of the outer and inner arms was suppressed by 10.9 and 13.2?%, respectively.     

Mechanics of flexible interconnect in lateral tape open drives

A mechanics modeling is presented in this paper with focus given to understanding effect of flexible printed circuit cable’s dynamic effect on tape head actuator’s lateral motion in advanced, high capacity tape drives. The flexible printed circuit cable which connects the actuator to printed circuit board is first examined through establishment of analytical model to predict its profile with considerations of boundary conditions and mechanical design parameters. Secondly, equivalent stiffness produced by the flexible printed circuit cable when the linear tape head actuator is positioned along its lateral positions is examined. Finally, effect of tape head actuator’s voice coil motor is studied and modeled as a magnetic suspension, contributing to stability and controllability of the actuator lateral motion dynamics. Validated by calibrated laboratory experiments, the work presented in this paper can add to the literature regarding dynamics and control of LTM in modern LTO drives.     

Application of astigmatic method and snell’s law on the thickness and refractive index measurement of a transparent plate

In this study, a thickness and refractive index measuring system for the transparent plate has been proposed. The measuring system is composed of an astigmatic measurement module and a light spot measurement module using a DVD optical pickup, a laser diode and a quadrant photodiode detector. Both of the thickness and refractive index of a transparent plate are converted into the focusing error of DVD pickup based on astigmatic method and the light spot displacements based on snell’s law in our proposed system. The thickness and the refractive index are simultaneously calculated by means of two nonlinear formulas. The accuracy of the proposed system is 99 % verified by a height Gauge and the refractive index by the TF-166.