Mechanical stability of a latching MEMS variable optical attenuator

The mechanical stability of a latching shutter-insertion variable optical attenuator formed by deep reactive ion etching of bonded silicon-on-insulator (BSOI) is considered. The device can be continuously adjusted or latched into a discrete set of attenuation states using a rack-and-tooth mechanism. Simple numerical and analytic theories are developed to describe the effect of latching. The dynamics of the mechanism are characterized using internal actuation and it is shown that the use of a levered mechanism gives rise to several underdamped, low-frequency in-plane resonances during analog adjustment. Elastic nonlinearity is also identified. Vibration testing is then performed using an external piezoelectric transducer. It is shown that the effect of engaging the latch is to upshift the frequency of the most important mechanical resonance, reducing sensitivity to vibration in fixed attenuation states.     

Free-Form Simulation of Sequential Etching and Surface Characterization for 3-D MEMS Fabrication

A new diffusion-based simulation model of isotropic wet etching and free-form surface characterization method for 3-D free-form microelectromechanical systems (MEMS) fabrication is presented in this paper. To simulate the etching process, a diffusion-based model solved by the finite-element method (FEM) has been developed, allowing extraction of more accurate etch-front data at discrete time steps. In the developed method, free-form MEMS objects are modeled as B-spline functions with material concentration. Finite elements are generated by discretization in the parametric domain of the free-form object and mapping back to the Euclidean space. Points on the etch front are extracted using a Z-map method. The extracted point data are characterized to obtain a B-spline representation of the etch-front surface. Examples from the isotropic etching simulation of 2-D and 3-D objects with both regular and free-form geometry are presented. The developed method allows the simulation of 3-D objects with free-form input and free-form mask opening and facilitates the simulation of sequential etching of free-form objects with irregular mask openings. This paper also discusses applications of the developed method in MEMS process planning that can be realized by taking advantage of the better control of geometry that it provides in MEMS fabrication.     

Integrated 3-D analysis and analysis-guided synthesis of flightimage sequences

This paper is concerned with three-dimensional (3D) analysis, and analysis-guided syntheses, of images showing 3-D motion of an observer relative to a scene. There are two objectives of the paper. First, it presents an approach to recovering 3D motion and structure parameters from multiple cues present in a monocular image sequence, such as point features, optical flow, regions, lines, texture gradient, and vanishing line. Second, it introduces the notion that the cues that contribute the most to 3-D interpretation are also the ones that would yield the most realistic synthesis, thus suggesting an approach to analysis guided 3-D representation. For concreteness, the paper focuses on flight image sequences of a planar, textured surface. The integration of information in these diverse cues is carried out using optimization. For reliable estimation, a sequential batch method is used to compute motion and structure. Synthesis is done by using (i) image attributes extracted from the image sequence, and (ii) simple, artificial image attributes which are not present in the original images. For display, real and/or artificial attributes are shown as a monocular or a binocular sequence. Performance evaluation is done through experiments with one synthetic sequence, and two real image sequences digitized from a commercially available video tape and a laserdisc. The attribute based representation of these sequences compressed their sizes by 502 and 367. The visualization sequence appears very similar to the original sequence in informal, monocular as well as stereo viewing on a workstation monitor     

Design and modeling of a continuously variable piezoelectric RF MEMS switch

A structure for a piezoelectrically actuated capacitive RF MEMS switch that is continuously variable between the ON state and the OFF state has been proposed. The device is based on variable capacitance using a cantilever fixed at both ends that is actuated using a lead zirconate titanate thin film. Because the device is contactless, the reliability issues common in contact-type RF MEMS switches can be avoided. A comprehensive mathematical model has been developed in order to study the performance of the device, and allow for design optimization. Electrical measurements on test structures have been compared with the performance predicted by the model, and the results used to design a prototype RF MEMS switch. The model and simulations indicate the proposed switch structure can provide an insertion loss better than 0.7 dB and an isolation of more than 10 dB between 6 and 14 GHz with an actuation voltage of 22.4 V. The state of the device is continuously variable between the ON state and the OFF state, with a tunable range of capacitance of more than 15\(\times \).     

Analysis of a sampling technique applied to biological images

This correspondence examines the classification potential of two techniques based on spiral sampling of binary images of zooplankton. Image pixels are rearranged into a one-dimensional sequence by selecting samples in a spiral manner starting from the edge of the image and proceeding toward the center. The properties of this sample sequence are examined by Fourier transform and correlation techniques, using images from six major zooplankton categories of varying orientation and size. The ability of features extracted from spiral sequences to classify zooplankton samples, and their classification accuracy are investigated.     

A dither technique applied to a constant fuel-rate problem

A constant fuel-rate problem is defined. A solution to the constant fuel-rate problem is proposed which consists of a dither adaptive control technique. An illustration of this technique is presented as an analog computer solution to a simple problem.     

Model reduction technique applied to a nuclear reactor turbine system

A method has been developed for determining a low-order model for a large multivariable system from its measured input-output data. It is based on the use of a matrix pseudo-inverse to estimate the parameters of the model which minimize the sum of the squares of the errors between the responses of the original system and the low-order model at the sampling instants. A recursive algorithm is proposed which makes it useful for on-line applications. The method is used to obtain low-order models for a nuclear reactor turbine system. The outputs of the low-order models and those of the large-scale model (consisting of 11 non-linear differential equations and 36 algebraic equations) are compared for the turbine system.     

Loop shaping and a zero-placement technique as applied to the benchmark problem

A classical and a ‘quasi-modern’ approach are taken to develop robust control laws for the 1992 ACC benchmark problem of Wie and Bernstein. In both approaches, copious use of loop-shaping à la Bode design is employed. The quasi-modern approach reported herein is a zero-placement technique, which is a variant on LQG/LTR. This approach allows for the direct selection of the zeros of the loop transfer function, leading to the desired loop shape. Therefore, undesirable pole-zero cancellations may be avoided. The modern and quasi-modern approaches are closely related, and can lead to similar control laws. Though the problem addressed here is SISO, the zero-placement approach can be used on MIMO systems. However, in the case discussed herein, the classically designed controller has superior performance and stability robustness.     

Application of a multilayered magnetostrictive film to a micromachined 2-D optical scanner

A novel two-dimensional (2-D) optical scanner has been designed, manufactured and characterized. This scanner features a large mirror (8/spl times/6 mm) and is therefore suitable for industrial applications where cheap optical sources and lenses are requested. This scanner uses a multilayer film for its actuation. This film is well known for its high magnetostriction. The mechanical design has been optimized using conventional mechanical considerations as well as finite-element simulations. The device has been characterized in two configurations. Depending on the direction of the applied magnetic field, the magnetostrictive properties of the active film or the electromagnetic force are selectively used. Using this last, total optical deflection angles of 32/spl deg/ and 11/spl deg/ for an applied magnetic field of 0.3 mT are obtained. The ratio of the corresponding resonant frequencies is around 4.5, allowing a nice scanning pattern. Compared to our previous prototype on the same project , the mechanical-magnetic sensitivity has been improved by about a factor 24 when the magnetostriction is used, and by about a factor 75 when the electromagnetic force is used.     

应用OpenGL再现三维航迹

提出了一种在OpenGL中绘制三维航迹的新算法，并介绍了航迹的绘制过程。     

Optimization of a MEMS variable capacitor with high linearity and large tuning ratio

Microsystem Technologies - A novel micro-electro-mechanical system variable capacitor with a nonplanar top plate and a side leverage electrode structure is proposed to achieve a large tuning ratio...     

General model of n-D system with variable coefficients and its reduction to 1-D system with variable structure

A general model of an n-D linear discrete system with variable coefficients and its solution are presented. A method for reduction of this model to an equivalent 1-D system with a variable structure is given.     

An interactive parallel coordinates technique applied to a tropical cyclone climate analysis

A highly interactive visual analysis system is presented that is based on an enhanced variant of parallel coordinates — a multivariate information visualization technique. The system combines many variations of previously described visual interaction techniques such as dynamic axis scaling, conjunctive visual queries, statistical indicators, and aerial perspective shading. The system capabilities are demonstrated on a hurricane climate data set. This climate study corroborates the notion that enhanced visual analysis with parallel coordinates provides a deeper understanding when used in conjunction with traditional multiple regression analysis.     

Adding a True 3-D Display to a Raster Graphics System

This Experimental 3-D Graphics System Can Be Added to Standard Raster Graphics Systems at Modest Expense. It Promises Much Broader Access to Effective 3-D Display.     

Object pose from 2-D to 3-D point and line correspondences

In this paper we present a method for optimally estimating the rotation and translation between a camera and a 3-D object from point and/or line correspondences. First we devise an error function and second we show how to minimize this error function. The quadratic nature of this function is made possible by representing rotation and translation with a dual number quaternion. We provide a detailed account of the computational aspects of a trust-region optimization method. This method compares favourably with Newton's method which has extensively been used to solve the problem at hand, with Faugeras-Toscani's linear method (Faugeras and Toscani 1986) for calibrating a camera, and with the Levenberg-Marquardt non-linear optimization method. Finally we present some experimental results which demonstrate the robustness of our method with respect to image noise and matching errors.This work has been supported by the Esprit programme through the SECOND project (Esprit-BRA No. 6769).     

Real-Time Temperature Compensation of MEMS Oscillators Using an Integrated Micro-Oven and a Phase-Locked Loop

We present a new temperature compensation system for microresonator-based frequency references. It consists of a phase-locked loop (PLL) whose inputs are derived from two microresonators with different temperature coefficients of frequency. The resonators are suspended within an encapsulated cavity and are heated to a constant temperature by the PLL controller, thereby achieving active temperature compensation. We show repeated real-time measurements of three 1.2-MHz prototypes that achieve a frequency stability of $pm$ 1 ppm from $-20 ^{circ}hbox{C}$ to $+80 ^{circ}hbox{C}$, as well as a technique to reduce steady-state frequency errors to $pm$0.05 ppm using multipoint calibration.$hfill$[2009-0074]      

A mold and transfer technique for lead-free fluxless soldering and application to MEMS packaging

This paper demonstrates a technique to premold and transfer lead-free solder balls for microelectrocmechanical systems (MEMS)/electronics packaging applications. A reusable bulk micromachined silicon wafer is used to mold a solder paste and remove excess flux prior to transfer to a host wafer that may contain released MEMS. This technique has been used to fabricate low temperature thin film MEMS vacuum packages. Long term (>5 months) reliability of these packages at room temperature and pressure is demonstrated through integrated Pirani gauges. These packages have survived over 600 hours in an autoclave (130/spl deg/C, 85% RH, 2 atm) and more than 1300 temperature cycles (55/spl deg/C to 125/spl deg/C).     

New 3-D display that can display 3-D images at long distances and that can control their 3-D positions using changing size as a cue to depth perception

This paper presents a new three-dimensional (3-D) display that can display 3-D images at long distances of tens or hundreds of meters in the depth direction and that can control their 3-D positions to meet new requirements for outdoor use. The proposed display uses changing size as a cue to depth perception, i.e., the smoothly expanding motion of virtual images formed with optical systems according to the forward movements of the users to display 3-D images at more distant positions in the depth direction than positions where virtual images are formed with optical systems because conventional 3-D displays that use binocular disparity are only able to display 3-D images at short distances in the depth direction. The feasibility of the proposed display was evaluated by subjective tests using a moving minivan in which observers viewed a test pattern that overlapped the real view ahead of the automobile observed through the windshield. The results obtained from the subjective tests revealed that the test pattern was observed at long distances over tens and hundreds of meters in the depth direction and that the position in the depth direction of the test pattern could be controlled by changing the rate at which the motion of the test pattern smoothly expanded. These results demonstrated that the proposed display was feasible.     

A Unified Algebraic Approach to 2-D and 3-D Motion Segmentation and Estimation

In this paper, we present an analytic solution to the problem of estimating an unknown number of 2-D and 3-D motion models from two-view point correspondences or optical flow. The key to our approach is to view the estimation of multiple motion models as the estimation of a single multibody motion model. This is possible thanks to two important algebraic facts. First, we show that all the image measurements, regardless of their associated motion model, can be fit with a single real or complex polynomial. Second, we show that the parameters of the individual motion model associated with an image measurement can be obtained from the derivatives of the polynomial at that measurement. This leads to an algebraic motion segmentation and estimation algorithm that applies to most of the two-view motion models that have been adopted in computer vision. Our experiments show that the proposed algorithm out-performs existing algebraic and factorization-based methods in terms of efficiency and robustness, and provides a good initialization for iterative techniques, such as Expectation Maximization, whose performance strongly depends on good initialization. This paper is an extended version of [34]. The authors thank Sampreet Niyogi for his help with the experimental section of the paper. This work was partially supported by Hopkins WSE startup funds, UIUC ECE startup funds, and by grants NSF CAREER IIS-0347456, NSF CAREER IIS-0447739, NSF CRS-EHS-0509151, NSF-EHS-0509101, NSF CCF-TF-0514955, ONR YIP N00014-05-1-0633 and ONR N00014-05-1-0836. René Vidal received his B.S. degree in Electrical Engineering (highest honors) from the Universidad Católica de Chile in 1997 and his M.S. and Ph.D. degrees in Electrical Engineering and Computer Sciences from the University of California at Berkeley in 2000 and 2003, respectively. In 2004, he joined The Johns Hopkins University as an Assistant Professor in the Department of Biomedical Engineering and the Center for Imaging Science. He has co-authored more than 70 articles in biomedical imaging, computer vision, machine learning, hybrid systems, robotics, and vision-based control. Dr. Vidal is recipient of the 2005 NFS CAREER Award, the 2004 Best Paper Award Honorable Mention at the European Conference on Computer Vision, the 2004 Sakrison Memorial Prize, the 2003 Eli Jury Award, and the 1997 Award of the School of Engineering of the Universidad Católica de Chile to the best graduating student of the school. Yi Ma received his two bachelors' degree in Automation and Applied Mathematics from Tsinghua University, Beijing, China in 1995. He received an M.S. degree in Electrical Engineering and Computer Science (EECS) in 1997, an M.A. degree in Mathematics in 2000, and a PhD degree in EECS in 2000 all from the University of California at Berkeley. Since August 2000, he has been on the faculty of the Electrical and Computer Engineering Department of the University of Illinois at Urbana-Champaign, where he is now an associate professor. In fall 2006, he is a visiting faculty at the Microsoft Research in Asia, Beijing, China. He has written more than 40 technical papers and is the first author of a book, entitled “An Invitation to 3-D Vision: From Images to Geometric Models,” published by Springer in 2003. Yi Ma was the recipient of the David Marr Best Paper Prize at the International Conference on Computer Vision in 1999 and Honorable Mention for the Longuet-Higgins Best Paper Award at the European Conference on Computer Vision in 2004. He received the CAREER Award from the National Science Foundation in 2004 and the Young Investigator Program Award from the Office of Naval Research in 2005.