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Now showing 1 - 10 of 305
  • Publication
    A Scalable Strategy for Open Loop Magnetic Control of Microrobots Using Critical Points
    (2016-05-11) Guerrero-Bonilla, Luis; Bhattacharya, Subhrajit; Kumar, Vijay
    A novel scalable strategy for open loop control of ferromagnetic microrobots on a plane using a scalable array of electromagnets is presented. Instead of controlling the microrobot directly, we create equilibrium points in the magnetic force field that are stable and attractive on the plane in which the microrobot is to be controlled. The microrobot moves into these equilibrium points rapidly in presence of low viscous forces, and thus controlling the equilibrium points let us control the microrobot precisely. An unit/cell in the array of electromagnets allows precise control of the microrobot in the unit/cell’s domain. Motion synthesis across multiple overlapping domains allows control of the microrobot in large regions across the array. We perform numerical analysis and demonstrate the control of the ferromagnetic microrobot using the proposed method through simulations.
  • Publication
    The Penn Baxter Face Database
    (2017-03-23) Fitter, Naomi T.; Kuchenbecker, Katherine J.
    The Penn Baxter Face Database is composed of Baxter robot face images designed in a variety of expressions and colors. Each of these images was photographed on the physical Baxter robot and assessed by internet raters (N = 568) in an Amazon Mechanical Turk survey. Raters assessed the pleasantness and energeticness of each robot face and also shared how safe and pleased each face made them feel. This project was published in our ICSR 2016 paper entitled “Designing and Assessing Expressive Open-Source Faces for the Baxter Robot.” After hearing of interest from other researchers, we previously released our Baxter face database on GitHub at This dataset, now additionally available on Scholarly Commons, includes the developed Baxter faces, photographs used in the Mechanical Turk survey, editable source files for the studied faces, and bonus faces developed in our subsequent design work with Baxter. These contents may benefit any Baxter users who publish images to the robot's face. The organization of the database is explained in the included ReadMe file.
  • Publication
    The Penn Hand-Clapping Motion Dataset
    (2016-11-27) Fitter, Naomi T; Kuchenbecker, Katherine J
    The Penn Hand-Clapping Motion Dataset is composed of inertial measurement unit (IMU) recordings from the hand motions of 15 naïve people. Each of these individuals participated in an experiment during which they were asked to pantomime various sequences of 10 different motions: back five, clap, double, down five, front five, lap pat, left five, right five, right snap, and up five. The examined motions comprise most typical actions from hand-clapping games like “Pat-a-cake” and “Slide.” This project was published in our IROS 2016 paper entitled “Using IMU Data to Demonstrate Hand-Clapping Games to a Robot.” After hearing of interest from other researchers, we are releasing the corresponding motion dataset, which was originally collected to help us investigate whether we could train highly accurate and rapid classifiers to label hand-clapping game motions performed by everyday people. This dataset, explained further in the included ReadMe file, may interest researchers who investigate human motion.
  • Publication
    Refined Methods for Creating Realistic Haptic Virtual Textures from Tool-Mediated Contact Acceleration Data
    (2012-03-01) Culbertson, Heather; Romano, Joseph M; Castillo, Pablo; Mintz, Max; Kuchenbecker, Katherine J
    Dragging a tool across a textured object creates rich high-frequency vibrations that distinctly convey the physical interaction between the tool tip and the object surface. Varying one’s scanning speed and normal force alters these vibrations, but it does not change the perceived identity of the tool or the surface. Previous research developed a promising data-driven approach to embedding this natural complexity in a haptic virtual environment: the approach centers on recording and modeling the tool contact accelerations that occur during real texture interactions at a limited set of force-speed combinations. This paper aims to optimize these prior methods of texture modeling and rendering to improve system performance and enable potentially higher levels of haptic realism. The key elements of our approach are drawn from time series analysis, speech processing, and discrete-time control. We represent each recorded texture vibration with a low-order auto-regressive moving-average (ARMA) model, and we optimize this set of models for a specific tool-surface pairing (plastic stylus and textured ABS plastic) using metrics that depend on spectral match, final prediction error, and model order. For rendering, we stably resample the texture models at the desired output rate, and we derive a new texture model at each time step using bilinear interpolation on the line spectral frequencies of the resampled models adjacent to the user’s current force and speed. These refined processes enable our TexturePad system to generate a stable and spectrally accurate vibration waveform in real time, moving us closer to the goal of virtual textures that are indistinguishable from their real counterparts.
  • Publication
    Effective properties of nonlinear inhomogeneous dielectrics
    (1992) Ponte-Castañeda, Pedro; deBotton, G.; Li, G.
    We develop a general procedure for estimating the effective constitutive behavior of nonlinear dielectrics. The procedure is based on a variational principle expressing the effective energy function of a given nonlinear composite in terms of the effective energy functions of the class of linear comparison composites. This provides an automatic procedure for converting well-known information for linear composites, in the form of estimates and bounds for their effective dielectric constants, into corresponding estimates and bounds for the effective behavior of nonlinear composites. Further, the procedure is easily implemented, and leads in some cases to exact results. This, exact estimates are given herein for isotropic weakly nonlinear composites with general nonlinearity, and bounds of the Hashin-Shtrikman type are given for the class of two-phase, isotropic dielectric composites with strongly and perfectly non-linear constitutive behavior. The optimality of the bounds is addressed briefly.
  • Publication
    Smart-Cut Layer Transfer of Single-Crystal SiC Using Spin-on-Glass
    (2012-07-03) Lee, Jae-Hyung; Bargatin, Igor; Park, Joonsuk; Milaninia, Kaveh M; Theogarajan, Luke S; Sinclair, Robert; Howe, Roger T
    The authors demonstrate “smart-cut”-type layer transfer of single-crystal silicon carbide (SiC) by using spin-on-glass (SoG) as an adhesion layer. Using SoG as an adhesion layer is desirable because it can planarize the surface, facilitate an initial low temperature bond, and withstand the thermal stresses at high temperature where layer splitting occurs (800–900 °C). With SoG, the bonding of wafers with a relatively large surface roughness of 7.5–12.5 Å rms can be achieved. This compares favorably to direct (fusion) wafer bonding, which usually requires extremely low roughness (<2 Å rms), typically achieved using chemical mechanical polishing (CMP) after implantation. The higher roughness tolerance of the SoG layer transfer removes the need for the CMP step, making the process more reliable and affordable for expensive materials like SiC. To demonstrate the reliability of the smart-cut layer transfer using SoG, we successfully fabricated a number of suspended MEMS structures using this technology.
  • Publication
    Body-Biased Complementary Logic Implemented Using AIN Piezoelectric MEMS Switches
    (2009-01-01) Sinha, Nipun; Jones, Timothy S.; Guo, Zhijun; Piazza, Gianluca
    This paper reports on the first implementation of low voltage complementary logic (< 1.5 V) by using body-biased aluminum nitride (AlN) piezoelectric MEMS switches. For the first time, by using opposite body biases the same mechanical switch has been made to operate as both an ntype and p-type (complementary) device. Body-biasing also gives the ability to precisely tune the threshold voltage of a switch. The AlN MEMS switches have shown extremely small subthreshold slopes and threshold voltages as low as 0.8 mV/dec and 30 mV, respectively. Furthermore, this work presents a fully mechanical body-biased inverter formed by two AlN MEMS switches operating at 100 Hz with a ± 1.5 V voltage swing.
  • Publication
    A Course in Micro- and Nanoscale Mechanics
    (2003-01-01) Carpick, Robert W
    At small scales, mechanics enters a new regime where the role of surfaces, interfaces, defects, material property variations, and quantum effects play more dominant roles. A new course in nanoscale mechanics for engineering students was recently taught at the University of Wisconsin - Madison. This course provided an introduction to nanoscale engineering with a direct focus on the critical role that mechanics needs to play in this developing area. The limits of continuum mechanics were presented as well as newly developed mechanics theories and experiments tailored to study and describe micro- and nano-scale phenomena. Numerous demonstrations and experiments were used throughout the course, including synthesis and fabrication techniques for creating nanostructured materials, bubble raft models to demonstrate size scale effects in thin film structures, and a laboratory project to construct a nanofilter device. A primary focus of this paper is the laboratory content of this course, which includes an integrated series of laboratory modules utilizing atomic force microscopy, self-assembled monolayer deposition, and microfluidic technology.
  • Publication
    Measurement of interfacial shear (friction) with an ultrahigh vacuum atomic force microscope
    (1996-03-01) Carpick, Robert W; Agraït, N.; Ogletree, D. F; Salmeron, Miguel
    We have studied the variation of frictional force with externally applied load for a Pt-coated atomic force microscope tip in contact with the surface of mica cleaved in ultrahigh vacuum. At low loads, the frictional force varies with load in almost exact proportion to the area of contact as predicted by the Johnson-Kendall-Roberts (JKR) theory [K. L. Johnson, K. Kendall, and A. D. Roberts, Proc. R. Sec. London Ser. A 324, 301 (1971)] of elastic adhesive contacts. The friction-load relation for a deliberately modified tip shape was proportional to an extended JKR model that predicts the area-load relation for nonparabolic tips, The tip shape was determined experimentally with a tip imaging technique and was consistent with the predicted friction behavior. This demonstrates that the frictional force is proportional to the area of contact between the tip and sample. Using the JKR/extended JKR model, interfacial surface energies and shear strengths can be estimated.
  • Publication
    Effective-medium theory for infinite-contrast two-dimensionally periodic linear composites with strongly anisotropic matrix behavior: Dilute limit and crossover behavior
    (2008-09-18) Willot, François; Pellegrini, Yves-Patrick; Idiart, Martín I.; Castañeda, Pedro Ponte
    The overall behavior of a two-dimensional lattice of voids embedded in an anisotropic elastic matrix is investigated in the limit of vanishing porosity f. An effective-medium model (of the Clausius-Mossoti type), which accounts for elastic interactions between neighboring voids, is compared to fast Fourier transform numerical solutions and, in the limits of infinite anisotropy, to exact results. A crossover between regular and singular dilute regimes is found, driven by a characteristic length which depends on f and on the anisotropy strength. The singular regime, where the leading dilute correction to the elastic moduli is an O(f1/2), is related to strain localization and to change in character—from elliptic to hyperbolic—of the governing equations.