The present invention is embodied in an actuator arm which is mounted to a primary actuator. The primary actuator positions the actuator arm, with a read/write head mounted to the actuator arm, across a data storage disk. The actuator arm comprises an inboard portion, an outboard portion and a pair of bimorph actuators. The inboard portion has a longitudinal axis and is attached to the primary actuator. The outboard portion has the read/write head mounted onto it. The pair of bimorph actuators are deflectable together in a common direction and are connected between the inboard and the outboard portions. Upon deflection of the bimorph actuators in the same direction, the outboard portion is translated along an at least nearly straight line transverse to the longitudinal axis of the inboard portion. This transverse motion allows the read/write head to be kept substantially within a plane parallel to the surface of the data storage disk, preventing damage caused by possible contact between slider and the disk surface from rolling the slider due to out-of-plane motions. Further, the use of bimorph actuators provide increased displacements of the read/write head. Also, since the head displacement is not a function of microactuator's position along the actuator arm, the actuator arm can be shorter, allowing for use in compact disk drives.

Disk drive actuator arm with microactuated read/write head positioning

This paper presents a piezoelectric-based microactuator concept that could provide an economical and easily integrated option for dual stage actuation used in rigid disk drives (RDDs). The design and operation of a prototype version is described. Manufacturability of the actuator and its integration in the RDD assembly is assessed. Approaches to providing the voltages required to drive the microactuator to achieve displacement specifications are shown. A model for the dynamic performance is shown, and experimental results are presented. Issues involving dual-input single-output control loop integration are discussed.

Piezoelectric microactuator for dual stage control

The well-accepted basis for developing a mechatronic system is a synergetic concurrent design process that integrates different engineering disciplines. In this paper, a general model is derived to mathematically describe the concurrent design of a mechatronic system. Based on this model, a concurrent engineering approach, called design for control (DFC), is formally presented for mechatronic systems design. Compared to other mechatronic design methodologies, DFC emphasizes obtaining a simple dynamic model of the mechanical structure by a judicious structure design and a careful selection of mechanical parameters. Once the simple dynamic model is available, in spite of the complexity of the mechanical structure, the controller design can be facilitated and better control performance can be achieved. Four design scenarios in application of DFC are addressed. A case study is implemented to demonstrate the effectiveness of DFC through the design and control of a programmable four-bar linkage.

Design for control-a concurrent engineering approach for mechatronic systems design

The hard disk drive is one of the finest examples of the precision control of mechatronics, with tolerances less than one micrometer achieved while operating at high speed. Increasing demand for higher data density as well as disturbance-prone operating environments continue to test designers' mettle. Explore the challenges presented by modern hard disk drives and learn how to overcome them with Hard Disk Drive: Mechatronics and Control.Beginning with an overview of hard disk drive history, components, operating principles, and industry trends, the authors thoroughly examine the design and manufacturing challenges. They start with the head positioning servomechanism followed by the design of the actuator servo controller, the critical aspects of spindle motor control, and finally, the servo track writer, a critical technology in hard disk drive manufacturing. By comparing various design approaches for both single- and dual-stage servomechanisms, the book shows the relative pros and cons of each approach. Numerous examples and figures clarify and illustrate the discussion.Exploring practical issues such as models for plants, noise reduction, disturbances, and common problems with spindle motors, Hard Disk Drive: Mechatronics and Control avoids heavy theory in favor of providing hands-on insight into real issues facing designers every day.

Hard Disk Drive: Mechatronics and Control

A MEMS microactuator provides a low-cost and high-performance solution to realize high track densities of HDD, because of the batch fabrication process and its clean mechanical characteristics. However, the servo system to control such a dual-stage system tends to be more complicated than a conventional HDD system. In this paper, a simple and efficient design method of a dual-stage servo controller for HDD applications is described. The experimental results of the track following control with the dual-stage actuator using a conventional VCM and a MEMS microactuator showed that the fourth-order servo controller can achieve a high bandwidth of more than 2 kHz.

Dual-stage servo controller for HDD using MEMS microactuator

Maintaining the trend towards higher track densities and data rates in rotating memory devices require track following servo systems of increasing bandwidth for reliable storage and retrieval (R/W) of data. The bandwidth requirements are even more severe in the emerging portable computing applications. Increase in bandwidth under strict constraints on over-sampling is limited by the presence of mechanical resonance modes and other nonlinearities in the voice coil motor (VCM) actuators. One approach to overcoming the problem is by using a dual or a compound actuator. In such a mechanism, a VCM is used as a primary stage while the recording head is mounted on the secondary stage which in turn is mounted on the VCM. The secondary stage provides rapid small-motion and position correction to the recording head. Several dual-stage configurations have been proposed using electrostatic, piezoelectric and electromagnetic secondary actuators. The paper proposes a piezoelectric stack micro-actuator design for a disk drive. It preserves the present suspension and head assembly. A prototype of the actuator is designed, fabricated, and tested. The test results are presented. A dual actuator tracking servo system is proposed. The scheme is a promising alternative for providing high bandwidth actuation for future high performance drives.

Dual stage actuators for high density rotating memory devices

This paper reports a novel high bandwidth moving-coil actuator. A special design in actuator construction leads to generation of pure torque in the actuator. With this special design the lateral quasi-rigid body vibration mode can be substantially suppressed. 2D FEA was carried out for the electromagnetic design to optimize the electromagnetic parameters and dimensions of the actuator. A 3D FEM solver was used to predict the characteristics of mechanical dynamics of the actuator. The electromagnetic characteristics, mechanical dynamics and performance of the actuator were measured. The results from simulation and experiment match quite well. The results show that the quasi-rigid body vibration mode is substantially suppressed and the primary resonance frequency is about 10 kHz in the novel actuator.

Design of a high bandwidth moving-coil actuator with force couple actuation for HDDs]

A novel high bandwidth actuator assembly (HBX4) is developed for the applications of high TPI recording in hard disk drives. The novel design in voice coil motor (VCM) construction, with flat moving-coil, is as simple as a conventional one. The VCM generates orthogonal force or pure torque. A 3D finite element analysis (FEA) is conducted in the electromagnetic design to optimize some critical electromagnetic parameters and the main dimensions. A 3D FEA is also carried out to predict the dynamic performance. The study shows that the lateral quasirigid body vibration mode (QR mode), which limits the servo bandwidth in a conventional actuator, has been substantially suppressed. Measurement of the characteristics of a prototype is carried out and the result is discussed.

Development of a single coil coupled force VCM actuator for high TPI magnetic recording

In this paper, in order to measure the Young's modulus of bulk single crystal silicon, a linear microactuator is designed and fabricated. C-V curve is measured and the Young's modulus is extracted. The result agrees well with the data published.

Qinghua Li

Papers

Dual stage actuators for high density rotating memory devices

Design of a high bandwidth moving-coil actuator with force couple actuation for HDDs]

Development of a single coil coupled force VCM actuator for high TPI magnetic recording

Determination of Young's modulus of bulk single crystal silicon by C-V measurement

Design and study of a moonie pzt microactuator slider driven device for hard disk drives