Nanotechnology is the science of understanding matter and the control of matter at dimensions of 100 nm or less. Encompassing nanoscale science, engineering, and technology, nanotechnology involves imaging, measuring, modeling, and manipulation of matter at this level of precision. An important aspect of research in nanotechnology involves precision control and manipulation of devices and materials at a nanoscale, i.e., nanopositioning. Nanopositioners are precision mechatronic systems designed to move objects over a small range with a resolution down to a fraction of an atomic diameter. The desired attributes of a nanopositioner are extremely high resolution, accuracy, stability, and fast response. The key to successful nanopositioning is accurate position sensing and feedback control of the motion. This paper presents an overview of nanopositioning technologies and devices emphasizing the key role of advanced control techniques in improving precision, accuracy, and speed of operation of these systems.

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A Survey of Control Issues in Nanopositioning

Is your memory hierarchy stopping your microprocessor from performing at the high level it should be? Memory Systems: Cache, DRAM, Disk shows you how to resolve this problem. The book tells you everything you need to know about the logical design and operation, physical design and operation, performance characteristics and resulting design trade-offs, and the energy consumption of modern memory hierarchies. You learn how to to tackle the challenging optimization problems that result from the side-effects that can appear at any point in the entire hierarchy.As a result you will be able to design and emulate the entire memory hierarchy. . Understand all levels of the system hierarchy -Xcache, DRAM, and disk. . Evaluate the system-level effects of all design choices. . Model performance and energy consumption for each component in the memory hierarchy.

Memory Systems: Cache, DRAM, Disk

In this paper, a neuro-optimal control scheme for a class of unknown discrete-time nonlinear systems with discount factor in the cost function is developed. The iterative adaptive dynamic programming algorithm using globalized dual heuristic programming technique is introduced to obtain the optimal controller with convergence analysis in terms of cost function and control law. In order to carry out the iterative algorithm, a neural network is constructed first to identify the unknown controlled system. Then, based on the learned system model, two other neural networks are employed as parametric structures to facilitate the implementation of the iterative algorithm, which aims at approximating at each iteration the cost function and its derivatives and the control law, respectively. Finally, a simulation example is provided to verify the effectiveness of the proposed optimal control approach. Note to Practitioners-The increasing complexity of the real-world industry processes inevitably leads to the occurrence of nonlinearity and high dimensions, and their mathematical models are often difficult to build. How to design the optimal controller for nonlinear systems without the requirement of knowing the explicit model has become one of the main foci of control practitioners. However, this problem cannot be handled by only relying on the traditional dynamic programming technique because of the "curse of dimensionality". To make things worse, the backward direction of solving process of dynamic programming precludes its wide application in practice. Therefore, in this paper, the iterative adaptive dynamic programming algorithm is proposed to deal with the optimal control problem for a class of unknown nonlinear systems forward-in-time. Moreover, the detailed implementation of the iterative ADP algorithm through the globalized dual heuristic programming technique is also presented by using neural networks. Finally, the effectiveness of the control strategy is illustrated via simulation study.

Neural-Network-Based Optimal Control for a Class of Unknown Discrete-Time Nonlinear Systems Using Globalized Dual Heuristic Programming

This paper presents a new method for the design of compensators for linear time-invariant dual-input/single-output (DISO) systems in continuous time or discrete time. The new method reduces the problem to two single-input/single-output (SISO) design problems, which are well suited to frequency-response design techniques. The first part of the method is the design of a stabilizing compensator for an auxiliary feedback system. The auxiliary compensator parameterizes the two output blocks of the single-input/dual-output compensator such that the zeros of the parallel system formed by cascade of the compensator with the plant are stable. The auxiliary compensator also determines the relative contribution to the output of the two parallel subsystems of the DISO system. The second SISO compensator design is used to ensure that the feedback system is stable and that performance and robustness specifications are achieved. This paper includes a discrete-time-design example for a dual-stage actuator system for a disk drive including implementation results. Straightforward extensions for multi-input/single-output systems are discussed.

On compensator design for linear time-invariant dual-input single-output systems

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

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

A flexure-based rotary electrostatic microactuator is described. This microactuator is for application in a high track-density hard disk drive (HDD). It is fabricated using a high aspect-ratio stencil electroplating process. This paper emphasizes the practical system-level issues that affect the device design. The micro-actuator is demonstrated in a 3.5" form-factor HDD. With a servo bandwidth of 5 kHz, a one-track seek can be completed in under 0.2 ms. This batch-fabricated electro-static microactuator provides a low-cost, high-performance solution for achieving very high track-densities.

Electrostatic microactuator and design considerations for HDD applications

One of the limitations inherent in high-track-density hard disk drive design is the effect of actuator mechanical resonant modes on the head-positioning servo. The first servo bandwidth limiting mode is the so-called "butterfly mode," which is the major mode in the head mechanical transfer functions and can not be avoided through mechanical design. A special active damping technique has been developed for rotary actuators of 3-1/2" drives. With an additional sensor on the actuator and an external feedback loop, the butterfly mode can be damped and stiffened while the system stability is maintained. A theoretical system model, based on FEM, modal superposition and feedback control, is developed for analytical prediction of system stability and dynamics. Drive level experiments are conducted on actuators of two different designs, and show that the butterfly mode can be totally damped such that the gain of the head mechanical transfer function is close to 1/s/sup 2/. The end arm mode is also damped by about 8 dB for one actuator design. Servo improvement is also studied. It shows that the butterfly mode notch filter can be removed, and the phase margin can be improved by 7 degrees.

Active damping in HDD actuator

The present invention teaches the realization of a stable feedback control by selecting an optimal notch filter in an apparatus, such as a hard disk drive, that employs a positioning apparatus, such as an actuator, for positioning an object. The present invention further teaches the derivation of a frequency characteristic of a control loop excluding a notch filter by employing a method that does not damage a positioning apparatus. The present invention further teaches the method of adjusting a notch filter in accordance with a change of the resonant frequency of an actuator caused by the temperature fluctuations to prevent any deterioration of a feedback control performance.

Method and apparatus for suppressing mechanical resonance in a disk drive storage device using a notch filter

The present invention makes possible the calibration of the tracking error signal and the focus error signal repeatedly when an optical disk drive is in the normal operation mode. Errors (offset and amplitude error) of the focus error signal and the tracking error signal are detected during at least three track jumps by making use of a track jump performed once per rotation of disk in the track following mode. An offset value of the focus error signal is calculated based on the amplitude of a tracking error signal generated during at least two track jumps by adding a positive or negative offset to the original target value of the focus error signal, and values of offset and amplitude error of the tracking error signal are calculated based on a maximum value and a minimum value of a tracking error signal generated during at least one track jump without modifying the original target value of the focus error signal.

Method and apparatus for calibrating focus and tracking error signals in an optical drive with measuring offsets during track jumps

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