A Modified Positive Velocity and Position Feedback scheme with delay compensation for improved nanopositioning performance

Acknowledgments This paper was sponsored by the Spanish FPU12/00984 Program (Ministerio de Educacion, Cultura y Deporte). It was also sponsored by the Spanish Government Research Program with the Project DPI2012-37062-CO2-01 (Ministerio de Economia y Competitividad) and by the European Social Fund.Peer reviewedPostprin

Flexure-based nanopositioning systems : integrated design and control

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 209-219).This thesis deals with the design and control of flexure-based mechanisms for applications requiring multi-degree-of-freedom positioning and alignment. Example applications include positioning a probe or sample in atomic force microscopy, alignment of tool and sample in stamping processes, and fine-positioning of wafer steppers in semiconductor manufacturing. Such applications necessitate nanopositioning systems that satisfy critical functional requirements, such as load-capacity, bandwidth, resolution, and range. Therefore, a systematic approach for design and control is an important tool for research and development for flexure-based nanopositioning systems. In this thesis, a novel methodology is presented for generating flexure-based topologies that can meet performance requirements, such as those dictating structural strength or dynamical behavior. We present performance metrics that allow for the generation of topologies that are tuned for a desired level of structural strength or modal separation. The topology generation is aimed as a valuable addition to the design toolkit, facilitating novel designs that could not have been conceived otherwise. The parameters within any particular topology could be adjusted at a subsequent phase through a detailed shape and size optimization. The thesis also proposes a controller generation approach. Unlike existing controller parameterizations, a novel parameterization formulated in this thesis allows for directly tuning the sensitivity transfer function of the closed-loop system. Tuning sensitivity is critical in mitigating the effects of disturbances affecting the system, as well as those arising from cross-coupling and parasitic error motions. Further, an integrated methodology for design and control is presented. This methodology uses the design topology generation approach and controller generation approach proposed in the thesis. The key distinction of our design for control approach is that the design is iterated over topologies and not just parameters within a selected topology. A simple one-degree-of-freedom positioning system example is worked out to detail the steps of the proposed integrated design and control methodology. A novel design topology that is ideally suited for achieving a desired design and control performance is derived using this methodology. Finally, the hardware design and control of a novel flexure-based nanopositioner implementation for scanning probe microscopy are presented to illustrate the effectiveness of the approaches discussed in this thesis.by Vijay Shilpiekandula.Ph.D

Two-degrees-of-freedom PI2D controller for precise nanopositioning in the presence of hardware-induced constant time delay

This work was supported in part by the Spanish Agencia Estatal de Investigacion (AEI) under Project DPI2016-80547-R (Ministerio de Economia y Competitividad) and in part by the European Social Fund (FEDER, EU), and in part by the Spanish FPU12/00984 Program (Ministerio de Educacion, Cultura y Deporte).Peer reviewedPostprin

Design of a high-speed, meso-scale nanopositioners driven by electromagnetic actuators

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 218-230).The purpose of this thesis is to generate the design and fabrication knowledge that is required to engineer high-speed, six-axis, meso-scale nanopositioners that are driven by electromagnetic actuators. When compared to macro-scale nanopositioners, meso-scale nanopositioners enable a combination of greater bandwidth, improved thermal stability, portability, and capacity for massively parallel operation. Meso-scale nanopositioners are envisioned to impact emerging applications in data storage and nanomanufacturing, which will benefit from low-cost, portable, multi-axis nanopositioners that may position samples with nanometer-level precision at bandwidth of 100s of Hz and over a working envelope greater than 10x10x10 micrometers3 This thesis forms the foundation of design and fabrication knowledge required to engineer mesoscale systems to meet these needs.The design combines a planar silicon flexure bearing and unique moving-coil microactuators that employ millimeter-scale permanent magnets and stacked, planar-spiral micro-coils. The new moving-coil actuator outperforms previous coil designs as it enables orthogonal and linear force capability in two axes while minimizing parasitic forces. The system performance was modeled in the structural, thermal, electrical, and magnetic domains with analytical and finite-element techniques. A new method was created to model the three-dimensional permanent magnet fields of finite magnet arrays. The models were used to optimize the actuator coil and flexure geometry in order to achieve the desired motions, stiffness, and operating temperature, and to reduce thermal error motions.A new microfabrication process and design-for-manufacturing rules were generated to integrate multilayer actuator coils and silicon flexure bearings. The process combines electroplating for the copper coils, a silicon dioxide interlayer dielectric, and deep reactive-ion etching for the silicon flexures and alignment features.(cont.) Microfabrication experiments were used to formulate coil geometry design rules that minimized the delamination and cracking of the materials that comprise the coil structure. Experiments were also used to measure the previously-unreported breakdown strength of the unannealed, PECVD silicon dioxide interlayer dielectric. The results of this research were used to design and fabricate a meso-scale nanopositioner system. The nanopositioner was measured to have a range of motion of 10 micrometers in the lateral directions, a range of 2 micrometers in the out-of-plane direction, an angular range of 0.5 degrees, and a first mode resonant frequency at 900 Hz. Open-loop calibration has been shown to minimize parasitic in-plane motion to less than 100 nm over the range of motion.by Dariusz S. Golda.Ph.D

A Novel Experimental Platform for the Study of Near-Field Radiative Transport and Measurements from Thin Dielectric Coatings.

Near-field radiative heat transfer (NFRHT) is an active area of research with implications for heat transfer and thermal management technologies in the future. Previous experiments observed that when the gap-size between a hot surface, the emitter, and a cold one, the receiver, reduces to micrometer dimensions significant enhancements in radiative heat flow between the two surfaces, above the value predicted by Stefan-Boltzman law, are observed. Subsequent theoretical studies supported these results and predicted orders-of-magnitude enhancement in radiative heat flow if the gap-size is further decreased to nanoscale. A range of other interesting phenomena are also predicted for this near-field regime. One of the most intriguing of these theoretical predictions is that pertaining to NFRHT enhancements calculated for nanoscale-thin dielectric coatings. In particular, when the gap-size between the emitter and receiver becomes comparable to film thickness, the enhancements in radiative heat flow are predicted to be as large as those for bulk materials, which can result in heat transfer coefficients that are ~20 times that of far-field values for a gap size of ~20 nm. No experiment has proved the validity of theoretical predictions pertaining to NFRHT enhancement from nanoscale-thin dielectric films. Here, a new experimental platform to perform NFRHT experiments is presented. The platform consists of two major components; a microfabricated resistive picowatt-resolution calorimeter and a six degree-of-freedom nanopositioner that can parallelize two planes with ~6 µrad of resolution. While this platform is designed to eventually perform NFRHT measurements between parallel plates, here it is used to measure enhancements of radiative heat flow between a spherical emitter and thin dielectric receiver with varying thickness. Consequently, for the first time, a dramatic increase in near-field radiative heat transfer from thin dielectric films is observed, which is comparable to that obtained between bulk materials, even for very thin dielectric films (50–100 nm) when the spatial separation between the hot and cold surfaces is comparable to the film thickness. These results are attributed to the spectral characteristics and mode shapes of surface phonon polaritons, which dominate near-field radiative heat transport in polar dielectric thin films.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113485/1/yasharg_1.pd

Near-Field Radiative Thermal Transport and Energy Conversion

Thermal radiation occurs when electromagnetic energy is emitted from one body and absorbed by another body. The net energy transferred between bodies, called radiative heat transfer, is well-understood when the distance between them is large compared to the wavelength of the electromagnetic waves. However, a question of fundamental interest is: what happens when the distance between the radiating bodies is smaller than or comparable to the wavelength of the radiation? That is, what happens when the bodies are brought into the “near-field?” Countless theoretical treatments now exist in the literature indicating that the radiative heat transfer can increase by orders of magnitude when the spacing between bodies is reduced to tens or hundreds of nanometers, and these predictions are largely supported by a handful of experimental studies. Moreover, computational work suggests that near-field radiation between parallel plates can have important, novel applications. However, their realization has thus far been prohibited by the technical difficulty in positioning parallel plates across nanoscale gaps. My first research objective was to measure near-field radiative heat transfer between parallel plates separated by less than a single micrometer, a goal which had eluded researchers for nearly half a century. Using a pair of microscale devices and a custom-built nanopositioner, we systematically demonstrated heat flux enhancements of 100-fold compared to the far-field by decreasing the inter-plate distance between parallel silica plates from 10 μm to approximately 60 nm. I then modified this approach to utilize a single planar microdevice situated across a vacuum gap from a macroscopic planar surface. By using devices with lesser curvature and higher mechanical stiffness, I reduced the minimum attainable gap size between silica plates to approximately 25 nanometers and measured a near-field heat flow 1,200 times higher than that of the far field, representing a significant improvement over the previous demonstration. Most importantly, replacing one of the microdevices with a macroscopic surface enabled a greater degree of flexibility in materials processing, opening up new opportunities for novel measurements. My second objective was to use this new technique to demonstrate novel near-field-enabled thermal diode using a doped silicon microdevice and an extended vanadium dioxide thin film. Because the emissive and absorptive properties of vanadium dioxide change dramatically when it undergoes an insulator-metal transition at 68 degrees Celsius, the radiative heat flow can change depending on the direction of the temperature difference. For a vacuum gap size of approximately 140 nanometers, I measured that the heat flow from metallic vanadium dioxide to doped silicon exceeds the heat flow from doped silicon to insulating vanadium dioxide by a factor of approximately two. Computational modeling showed that this rectification could be further improved by decreasing the thickness of the vanadium dioxide film. Finally, I demonstrated the first near-field power output enhancement in a thermophotovoltaic system. For a doped silicon emitter at 655 kelvin radiating at an indium arsenide-based cell, I measured a 40-fold increase in the electrical output power from the cell by reducing the vacuum gap spacing from 10 micrometers to approximately 60 nanometers. Additional experiments were carried out with a cell having a different bandgap energy, and its performance was compared to the first cell. Moreover, a detailed mathematical model was developed to identify ways to improve the device efficiency in the future. These studies represent an important milestone in near-field-enabled energy conversion.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/146129/1/fiorino_1.pd

Nanotechnology: a systems and control approach

Recent years have seen significant advances in the field of nanosciences and nanotechnology. A significant part of research in nanotechnology deals with developing tools and devices to probe and manipulate matter at the atomic, molecular and macro-molecular levels. Surprisingly in spite of the potential for engineers to contribute substantially to this area, most of the contributions till date have come from physicists and biologists. Engineering ideas primarily from systems theory and control significantly complement the physical studies performed in this area of research. This thesis demonstrates this by the application of systems ideas and tools to address two of the most important goals of nanotechnology, interrogation and positioning of materials at the nanoscale. The atomic force microscope (AFM), a micro-cantilever based device is one of the foremost tools in the interrogation and manipulation of matter at the atomic scale. The AFM operating in the most common tapping-mode has a highly complex dynamics due to the nonlinear tip-sample interaction forces. A systems approach is proposed to analyze the tapping-mode dynamics. The systems perspective is further exploited to develop analytical tools for modeling and identifying tip sample interactions. Some of the distinctly nonlinear features of tapping-mode operation are explained using the asymptotic theory of weakly nonlinear oscillators developed by Bogoliubov and Mitropolski. In the nanopositioning front, through the design and implementation of nanopositioning devices, a new paradigm for the systematic design of nanopositioners with specific bandwidth, resolution and robustness requirements is presented. Many tools from modern robust control like nominal and robust H infinity designs and Glover McFarlane designs are exploited for this. The experimental results demonstrate the efficacy of these design schemes. There is significant improvement in performance compared to the current schemes employed in industry

Probing Radiative Thermal Transport at the Nanoscale.

Thermal radiative emission from a hot to a cold surface plays an important role in many applications, including energy conversion, thermal management, lithography, data storage, and thermal microscopy. While thermal radiation at length scales larger than the dominant wavelength is well understood in terms of Planck’s law and the Stefan-Boltzmann law, near-field thermal radiation is not. With constantly advancing micro- and nanofabrication techniques and ever smaller devices a substantial need for a better and more reliable understanding of the fundamental physics governing nanoscale radiative heat transfer has arisen. Unfortunately, and in stark contrast to the abundance of theoretical and numerical work, there have only been limited experimental efforts and achievements. The central challenge in the field is to accurately and unambiguously characterize radiative heat transport between well-defined surfaces across nanometer distances. The key scientific and technological questions that I have experimentally addressed during my doctoral study include: How does radiative heat transfer between an emitter and a receiver depend on their spatial separation (gap size), and does the radiative heat flux increase by over five orders of magnitude as the gap size is reduced to a few nanometers, as theoretically predicted? Can polar dielectric and metallic thin films support substantial near-field heat flow enhancement? For single-digit nanometer gaps, is the widely used theoretical framework of fluctuational electrodynamics (still) applicable? To address these challenging questions in gap sizes as small as tens of nanometers, we developed a nanopositioning platform to precisely control the gap between a microfabricated emitter device and a suspended receiver/calorimeter device which enables simultaneous measurement of the radiative heat flow across the gap. Further, we employed an atomic force microscope (AFM) in conjunction with stiff custom-fabricated scanning thermal microscopy (SThM) probes to explore the extreme near-field characterized by gaps of a few nanometers. In both approaches, high vacuum, vibration isolation and temperature control are implemented for accurate thermal measurements and for maintaining a stable gap. Finally, we performed state-of-the-art fluctuational electrodynamics-based calculations and analysis to compare theoretical predictions with experimental observations.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/116634/1/baisong_1.pd

Precision Control of Piezo Electric Actuator

芝浦工業大学201

Control strategies and motion planning for nanopositioning applications with multi-axis magnetic-levitation instruments

This dissertation is the first attempt to demonstrate the use of magnetic-levitation (maglev) positioners for commercial applications requiring nanopositioning. The key objectives of this research were to devise the control strategies and motion planning to overcome the inherent technical challenges of the maglev systems, and test them on the developed maglev systems to demonstrate their capabilities as the next-generation nanopositioners. Two maglev positioners based on novel actuation schemes and capable of generating all the six-axis motions with a single levitated platen were used in this research. These light-weight single-moving platens have very simple and compact structures, which give them an edge over most of the prevailing nanopositioning technologies and allow them to be used as a cluster tool for a variety of applications. The six-axis motion is generated using minimum number of actuators and sensors. The two positioners operate with a repeatable position resolution of better than 3 nm at the control bandwidth of 110 Hz. In particular, the Y-stage has extended travel range of 5 mm ÃÂ 5 mm. They can carry a payload of as much as 0.3 kg and retain the regulated position under abruptly and continuously varying load conditions. This research comprised analytical design and development, followed by experimental verification and validation. Preliminary analysis and testing included open-loop stabilization and rigorous set-point change and load-change testing to demonstrate the precision-positioning and load-carrying capabilities of the maglev positioners. Decentralized single-input-single-output (SISO) proportional-integral-derivative (PID) control was designed for this analysis. The effect of actuator nonlinearities were reduced through actuator characterization and nonlinear feedback linearization to allow consistent performance over the large travel range. Closed-loop system identification and order-reduction algorithm were developed in order to analyze and model the plant behavior accurately, and to reduce the effect of unmodeled plant dynamics and inaccuracies in the assembly. Coupling among the axes and subsequent undesired motions and crosstalk of disturbances was reduced by employing multivariable optimal linear-quadratic regulator (LQR). Finally, application-specific nanoscale path planning strategies and multiscale control were devised to meet the specified conflicting time-domain performance specifications. All the developed methodologies and algorithms were implemented, individually as well as collectively, for experimental verification. Some of these applications included nanoscale lithography, patterning, fabrication, manipulation, and scanning. With the developed control strategies and motion planning techniques, the two maglev positioners are ready to be used for the targeted applications