bluuebunny/crossref_metadata_2025 huggingface dataset:
High Frequency Acceleration Feedback in Wave Variable Telerobotics
Authors: Tanner Neal A. , Niemeyer Gu¨nter
Published: April 2008

The human hand is very sensitive to the high frequency accelerations produced by tool contact with a hard object, yet most time delayed telerobots neglect this feedback band entirely in order to achieve stability. We present a control architecture that both incorporates this important information and provides the ability to scale and shape it independently of the low frequency force feedback. Leveraging the clean power flows afforded by wave variables, this augmented controller preserves the passivity of any environment that it renders to the user but is not subject to the limitations of being passive itself. This architecture guarantees stability in the presence of communication delay while achieving a level of feedback not possible with a passive controller. We show experimentally that this feedback augmentation and shaping can present a high frequency acceleration profile to the user’s hand that is similar to that experienced by the slave end effector. We anticipate that these natural haptic cues will make teleoperative systems easier to use and thus more widely applicable.
Utilizing Multimedia Tools in Undergraduate Thermodynamics
Authors: Fridman Ella , Shelangoskie Susan
Published: April 2008

It is well known that the thermodynamics is one of the most complicated subjects for students in the mechanical engineering curriculum. The new web-based Guided Self-Assessment Tool (GSATool) developed at the University of Toledo enables students to become actively engaged in the process of learning, to receive immediate feedback, to recognize their own strengths and weaknesses with the course material, and to better gauge their own learning levels and needs. The present paper describes the GSATool, its specifics and applications.
Strength Enhancement of Styrene Acrylonitrile Co-Polymer via Delay Pack Injection Molding
Authors: Angstadt David C. , Coulter John P. , Hydro Ryan
Published: April 2008

This study investigates the effects of processing of styrene acrylonitrile (SAN) by injection molding using a delayed packing stage. The concept of Delay Pack Injection Molding (DPIM) evolved from an in-situ study of vibration-assisted injection molding (VAIM) which indicated that the beneficial effects of VAIM came not from the vibration itself, but rather from the delay in the onset of packing resulting from the application of the vibration. Conceptually, DPIM involves normal filling of the mold immediately followed by a slight retraction of the injection screw for a specified time period before the final packing pressure is applied. Application of DPIM results in increased birefringence in the molded parts and increases in the ultimate tensile strength of molded parts very similar to the effects seen using VAIM. A parametric study using a design of experiments framework was carried out to determine the delay pack parameters affecting SAN and resulted in a maximum increase in UTS of 11.6%. Observation of birefringence patterns in Delay Pack processed samples shows a significant impact on molecular orientation while observation of failed specimens and their fracture surfaces shows distinctly different modes of crack growth and failure. Growth of craze cracks resulting from tensile loading appeared to be arrested by oriented areas surrounding the part core allowing the specimen to sustain higher loads relative to conventionally molded parts. All of the above observations are consistent with the observed effects of vibration-assisted injection molding.
Performance Evaluation of a Distributed Reconfigurable Controller Architecture for Robotic Applications
Authors: Atta-Konadu Rodney , Lang Sherman Y. T. , Orban Peter , Zhang Chris
Published: April 2008

Recent research in controller architecture has had some focus on reconfigurability and associated concepts such as modularity and openness. These paradigms advocate non-proprietary components such as commercial off-the-shelves (COTS) with standard interconnection interfaces. The tradeoffs of such a controller architecture are performance challenges such as network-induced delays and synchronization problems, especially where non-real time entities such as Ethernet are involved. In our quest to address some of these challenges we have developed a modular control architecture for machine and robotic control as a test platform. The advantage of this architecture is cost-effectiveness and openness, achieved through the use of COTS components. Each machine axis is controlled by a real-time Java micro-controller and all the controllers communicate through a switched-Ethernet communication network. The architecture is designed to support reconfiguration of both hardware and software resources by the use of modularity and service-discovery protocols in the software and hardware design. Therefore devices such as axes and sensors may be reorganized, removed or added easily. Our research presents performance results and applications typical of industrial or real life for our control architecture. The performance criteria analyzed include network delays, synchronization resolutions and error analyses.
Design and Control Approaches for a Novel Planar Biped With Nearly Linear Dynamics
Authors: Agrawal Sunil K. , Fattah Abbas , Oh So-Ryeok
Published: April 2008

In this paper, we propose the design of a planar biped for which the model is nearly linear, i.e., the inertia matrix is a constant and the gravity terms in the equations of motion are still nonlinear, but simplified. The legs are designed such that the inertia matrix is independent of the joint variables. As a result, the nonlinear terms in the centrifugal and Coriolis terms disappear. In this design, each leg has two links that are connected by a revolute joint at the knee. The two legs are connected to each other at the hip. The center of mass (COM) of each leg is located at the hip using counterweights. We assume that the stance leg is locked at the knee during the support phase. For this system, the dynamic model for the swing phase is considered. The stability of these designs is analysed by considering these as linear systems with nonvanishing perturbations. The paper discusses issues of ultimate stability bounds of the system and tracking of desired trajectories.
Computer-Aided Design, Manufacturing, and Modeling of Polymer Scaffolds for Tissue Engineering
Authors: Stone James J.-S. , Thoreson Andrew R. , Langner Kurt L. , Norton Jay M. , Stone Daniel J. , Wang Francis W. , O’Driscoll Shawn W. , An Kai-Nan
Published: April 2008

A custom computer-controlled rapid prototyping system was designed and developed in this research. This system for bio-manufacturing of polymer scaffolds included 3D motion control components, a nozzle, a pressure controller, and a temperature-controlled reservoir containing a biomaterial. Heating elements built into the reservoir melted the biomaterial. The pressure line attached to the reservoir provided a controllable force that extruded the polymer biomaterial through the nozzle and deposited the polymer biomaterial onto a platform to fabricate scaffolds. A low pressure (830 KPa) system was designed and fabricated to accommodate different temperatures, motion speeds, and viscosities of polymer biomaterials. The reservoir with the nozzle was mounted to servo motor-controlled linear x-y motion devices along with a third servo motor-controlled device that controlled the z-position of the platform. Poly(ε-caprolactone) [PCL] was used to fabricate scaffolds with designed structure that were used in cell and tissue regeneration studies. 3D computer-aided design (CAD) with Pro-Engineer and computational finite element analysis (FEA) programs with MSC_Patran and MSC_Marc were used to model scaffold designs with appropriate architecture and material selection. The CAD models were used in FEA to develop new methods for determining mechanical properties of tissue scaffolds of desired structure and geometry. FEA models were validated by mechanical testing and other published results. Technology developed in this research has potential for the advancement of bio-manufacturing, and design optimization of scaffolds for tissue engineering.
Effect of Film Thickness on Fracture Toughness of Amorphous Diamond-Like Carbon
Authors: Jonnalagadda Krishna , Chasiotis Ioannis
Published: April 2008

Fracture toughness, KIC, measurements were conducted for the first time on hydrogen-free tetrahedral amorphous Diamond-like Carbon (ta-C) MEMS-scale specimens of different thicknesses. Uniform gage microscale specimens with mathematically sharp edge pre-cracks were prepared by microindentation on the SiO2 sacrificial layer. The radial-median crack from the indent propagated into the specimen generating a sharp pre-crack. The crack length was measured by an Atomic Force Microscope (AFM). Freestanding fracture specimens were then obtained by wet etching the SiO2 sacrificial layer. Microtensile tests were performed on the pre-cracked specimens under mode-I loading in fixed grip configuration. In order to investigate the specimen thickness dependence of KIC, fracture tests were conducted on specimens with thicknesses in the range of 0.5-3 μm. KIC was 4.25 ± 0.7 MPa m for 0.5 μm specimens, 4.4 ± 0.4 MPa m for 1 μm specimens, and 3.06 ± 0.17 MPa m for 3 μm thick specimens. The 25% lower fracture toughness of the 3 μm films points to a film thickness dependence of fracture toughness that was attributed to different through-the-thickness stresses in considerably thick ta-C films and compositional changes occurring during post-deposition processing.
Inclined Cavity Effects With Application to Cooling of Biomaterials
Authors: Shrivastava Saurabh , Sammakia Bahgat
Published: April 2008

The present study involves the numerical investigation of the fluid flow pattern and heat transfer inside bio packages. In the proposed bio package, the biomaterials are encased inside a hollow cavity surrounded by phase change materials. The study represents the numerical analysis of Transient Natural Convection inside an inclined two-dimensional rectangular cavity. The angle of inclination of the thermal enclosure is varied from 0° (heated from below) to 180° (heated from above). The inclination effects of the cavity on the cooling performance of biomaterials are studied. Transient natural convection regimes study, have been performed for Aspect ratio (Ar) 0.5 and at Rayleigh number (Ra) 1.63 e08. Temperature and Stream function contours during the Initial transient stage, Quasi-steady stage and the Late Quasi-steady stage are shown for the flow visualization inside the enclosure. Numerical predictions of the influence of angle of inclination on the Nusselt number and the heat transfer rate during the Quasi-steady stage are obtained. The numerical modeling is performed using commercially available computational fluid dynamics (CFD) code, based on finite volume approach. Variation of Nusselt number along the coupled wall with time is shown to be dependent on the orientation of the enclosure.
Cheap and Fast 2-1/2D Rapid Prototyping via Laser Engravers
Authors: Nye T. J.
Published: April 2008

Mechanical Engineering curriculum has been changing to increase the amount of design taught to students. Ideally students would manufacture and test their designs, as this process validates the quality of the design and gives invaluable feedback. Designs may not be constructed, however, where there are limitations on time students have for the building phase, where limited shop facilities are available, or where students don’t have the manufacturing skills necessary. Rapid prototyping machines can mitigate these issues, but their initial, support and consumable costs, along with their low productivity, make them inaccessible for most student projects. Even traditional shop construction of designs is of limited feedback value, since a non-functioning design could be the result of faulty design or of poor quality manufacture. This paper will explore the use of a laser engraver machine as a vehicle for low-cost 2D and 2-1/2D rapid prototyping of mechanical designs. Laser engraver machines have low initial (c.$10–20K) and operating costs. They are capable of cutting 2D parts from materials such as paper matte and illustration boards at cutting rates of one meter per minute or more, allowing high throughput of parts cut. Machines typically attach to computers through a printer driver, so operation is as simple as printing a drawing from CAD software. While individual parts are constrained to planar geometry, simple assembly materials (such as glue and small machine screws) allow designs with moving parts to be constructed and tested.
Weakly Nonlinear Instability of an Annular Liquid Sheet Subjected to Unequal Inner and Outer Gas Streams
Authors: Ibrahim Ashraf A. , Jog Milind A.
Published: April 2008

Instability and breakup of annular liquid sheet are encountered in fuel injectors used in gas turbine engines. A weakly nonlinear stability analysis has been carried out for annular liquid fuel sheet subjected to unequal inner and outer gas velocities by a perturbation expansion technique with the initial amplitude of the disturbance as the perturbation parameter. The liquid sheet is considered to move at a uniform axial velocity and is subjected to inner and outer gas streams of differing axial velocities. The breakup length is calculated, and the effect of the various flow parameters is investigated. It is found that the breakup length is reduced by an increase in the liquid velocity and the gas velocities. The inner air stream is more effective in disintegrating the sheet than the outer air stream.
A Toolbox for Tripod Design, Simulation, and Monitoring
Authors: Bi Z. M. , Lang S. Y. T. , Orban Peter E. , Verner Marcel
Published: April 2008

The paper presents a concept and implementation of a toolbox for the design and application of the tripod-based parallel kinematic machines (PKMs). The toolbox is a suite of design tools to support the users from the conceptual design to the actual application of the tripod-based PKMs. These design tools have been individually developed in different languages and they are integrated seamlessly using a Java-based platform. Users can access all of the design tools through a user-friendly graphical interface. It is the first computer-aided design system specially developed for tripod-based PKMs. The toolbox includes some implementations of our innovative methodologies, such as a forward kinematics solver, the concept of joint workspace analysis, on-line monitoring based on forward kinematics, and the concept of motion purity analysis. The paper gives an overview on the toolbox architecture, GUI, and some key technologies.
Vapor Compression Cycles: Control-Oriented Modeling and Validation
Authors: Eldredge Brian D. , Rasmussen Bryan P. , Alleyne Andrew G.
Published: April 2008

This paper presents experimental validation of a dynamic vapor compression cycle (VCC) system model specifically suited for multivariable control design. A moving-boundary lumped parameter modeling approach captures the essential two-phase fluid dynamics while remaining sufficiently tractable to be a useful tool for designing low-order controllers. This research makes two key contributions to the control-oriented dynamic modeling of these systems. First, the moving-boundary approach is used to develop models of evaporators and condensers with receivers, models previously unavailable in the literature. Second, semi-empirical correlations are incorporated for predicting key model parameters. The resulting models are compared to experimental data for validation purposes.
Online Terrain Classification for Mobile Robots
Authors: DuPont Edmond M. , Roberts Rodney G. , Selekwa Majura F. , Moore Carl A. , Collins Emmanual G.
Published: April 2008

Today’s autonomous vehicles operate in an increasingly general set of circumstances. In particular, unmanned ground vehicles (UGV’s) must be able to travel on whatever terrain the mission offers, including sand, mud, or even snow. These terrains can affect the performance and controllability of the vehicle. Like a human driver who feels his vehicle’s response to the terrain and takes appropriate steps to compensate, a UGV that can autonomously perceive its terrain can also make necessary changes to its control strategy. This article focuses on the development and application of a terrain detection algorithm based on terrain induced vehicle vibration. The dominant vibration frequencies are extracted and used by a probabilistic neural network to identify the terrain. Experimental results based on iRobot’s ATRV Jr (Fig. 1) demonstrate that the algorithm is able to identify with high accuracy multi-differentiated terrains broadly classified as sand, grass, asphalt, and gravel.
Comparison of Analytical and Empirical Models to Capture Variations in Off-Road Vehicle Dynamics
Authors: Pearson Paul J. , Bevly David M.
Published: April 2008

This paper develops two analytical models that describe the yaw dynamics of a farm tractor and can be used to design or improve steering control algorithms for the tractor. These models are verified against empirical data. The particular dynamics described are the motions from steering angle to yaw rate. A John Deere 8420 tractor, outfitted with inertial sensors and controlled through a PC-104 form factor computer, was used for experimental validation. Conditions including different implements at varying depths, as would normally be found on a farm, were tested. This paper presents the development of the analytical models, validates them against empirical data, and gives trends on how the model parameters change for different configurations.
On-Machine Visual Modeling System With Object Recognition
Authors: Tian X. , Deng H. , Yamazaki K. , Fujishima M. , Mori M.
Published: April 2008

This paper presents an on-machine modeling system that tries to bridge the gap between the design and the machining. This system is able to build a comprehensive solid model of the CNC machining workspace after the workpiece and fixtures have been installed onto the working table. This solid model can be used for simulation to enhance its credibility. For this purpose, one prototype of a 3D visual modeling system is proposed and designed. In order to accurately calibrate CCD cameras upon the absolute coordinate frame of the machining center, a practical calibration method is presented at first. To segment the target part and extract its 2D features on the captured images, the techniques of Image Decomposition and a modified Standard Hough Transform (SHT) are designed. Using these 2D features, the 3D visual stereovision system, powered by a designed feature matching engine, is capable of obtaining the 3D features of the target part. Furthermore, the part has been identified by the object recognition technology. This recognition includes part recognition and pose recognition. In the part recognition, the part is recognized and an initial pose transform is obtained. Using this initial pose transform, the pose optimization method, named as Dual Iterative Closest Lines (DICL), is designed to locate the optimum position and orientation of the solid model of the recognized part. Finally, this modeling system is tested on a machining center. The experimental result indicates the innovation and feasibility of the proposed modeling system.
Federated Product Models for Enabling Simulation-Based Product Lifecycle Management
Authors: Bajaj Manas , Paredis Christian J. J. , Rathnam Tarun , Peak Russell
Published: April 2008

Across product lifecycle processes, engineers continually analyze product behavior and refine product specifications. Owing to the collaborative and multi-disciplinary nature of product realization, engineers work on subsets of a product’s specification, also known as a product view, and use their expertise to analyze domain-specific (e.g., electrical, structural, thermal) product behavior. In this paper, we present the notion of a product view federation that embodies engineering processes related to the creation, enrichment and reuse of a particular product view. We make the first step towards answering the following question — Can one formalize the process of creating a product view federation from component federates to enable knowledge reuse? We describe and exemplify one particular graph-based inference approach for creating the product view federation.
Mixed Mathematical and Physical Modeling for Nonlinear Systems
Authors: Kiriakidis Kiriakos
Published: April 2008

The paper proposes a finite series expansion to approximate general nonlinear dynamic models to arbitrary accuracy. The method produces an approximation of nonlinear dynamics in the form of an aggregation of linear models, weighted by unimodal basis functions, and results in a linear growth bound on the approximation error. Furthermore, the paper demonstrates that the proposed approximation satisfies the modeling assumptions for analysis based on linear matrix inequalities and hence widens the applicability of these techniques to the area of nonlinear control.
Ionic Liquids Incorporating Nanomaterials as Lubricants for Harsh Environments
Authors: Harrison Benjamin , Czerw Richard , Konchady Manohar S. , Pai Devdas M. , Lopatka Matt W. , Jones Paul B.
Published: April 2008

Ionic liquids are salts that are liquid at ambient temperatures, and they produce virtually no hazardous vapors. As lubricating liquids, ionic liquid lubricants are of interest for reducing wear in circumstances where conventional lubricants are impractical such as in aerospace applications and high temperature vacuum bearings. The synthetic flexibility of ionic liquids allows control of the liquidous temperature range, good polymer compatibility, and high thermal stability. In this paper, a variety of ionic liquids were synthesized to build a library for testing. The liquids were thermally characterized by DSC and TGA, and mechanically characterized by pin-on-disk and 4-ball testing. Several chiral ionic liquids were synthesized as candidates for MEMS testing. The chiral nature of the liquids should help prevent crystallization in MEMs applications. Additionally, nanomaterials incorporated into the lubricants imparted lower friction coefficients and enhanced thermal stability.
Noncontinuum Gas-Phase Heat Transfer From a Heated Microbeam to the Adjacent Substrate
Authors: Gallis M. A. , Torczynski J. R. , Rader D. J. , Bainbridge B. L.
Published: April 2008

Noncontinuum gas-phase heat transfer in two microscale geometries is investigated using two computational methods. The motivation is microscale thermal actuation produced by heating-induced expansion of a near-substrate microbeam in air. The first geometry involves a 1-μm microgap filled with gas and bounded by parallel solid slabs. The second geometry involves a heated I-shaped microbeam 2 μm from the adjacent substrate, with gas in between. Two computational methods are applied. The Navier-Stokes slip-jump (NSSJ) method uses continuum heat transfer in the gas, with temperature jumps at boundaries to treat noncontinuum effects. The Direct Simulation Monte Carlo (DSMC) method uses computational molecules to simulate noncontinuum gas behavior accurately. For the microgap, the heat-flux values from both methods are in good agreement for all pressures and accommodation coefficients. For the microbeam, there is comparably good agreement except for cases with low pressures and near-unity accommodation coefficients. The causes of this discrepancy are discussed.
Problem-Based Collaborative Projects In and Between Freshman and Sophomore Engineering Courses
Authors: Azemi Asad , Esparragoza Ivan
Published: April 2008

This work describes our effort at the Delaware County Campus of Penn State to enhance the freshman engineering design and graphics and sophomore engineering computer programming courses by incorporating problem-based collaborative robotics projects in and between these courses. The robotics project in the engineering design and graphics course, ED&G 100, focuses on the mechanical and overall design aspect of a robot, and the projects in the engineering computer programming course, CMPSC 201, focus on the programming aspects. Lego Mindstorms and Handy Board controller have been chosen for building the robots and programming them, respectively. The collaborative projects have been designed with the intention of increasing learning, through collaboration among students and faculty. The projects also encourage teamwork by working with students from different disciplines, promote analytical skills by working to solve an open-ended problem, and provide practical experience and learning by doing through working with robots. To emphasize the importance of communication skills, at the end of the semester each team is also expected to present a report for the final project using PowerPoint. A detailed discussion of this collaborative work and the advantages and disadvantages of such an approach is discussed.
Development of an Antagonistic SMA Actuator for Instar Rifle Stabilization System
Authors: Barnes Brian , Brei Diann , Luntz Jonathan , LaVigna Chris
Published: April 2008

Shape memory alloys are notoriously slow and suffer from creep and controllability issues [1,2]. This paper presents three methods to address these issues: a high-stress cyclic conditioning regime to reduce creep to operationally insignificant levels, an unconventional pulse-width-modulated duty cycle with heatsink to increase frequency to the ten hertz range, and simple position feedback control strategy for motion control. These methods are discussed within the context of a simple antagonistic leveraged SMA actuation system developed for an INertially STAbilized Rifle (INSTAR). An overview of design and basic parameter models for the L-Lever is provided along with benchtop experimental characterization of the quasistatic and dynamic behavior. The actuator was integrated into a one degree of freedom INSTAR platform to demonstrate the insitu methods via barrel control. The methods discussed in this paper led to a fast, low-creep, controllable actuator with outstanding authority resulting in precise barrel control with capabilities to greatly increase shooter accuracy.
Fuel Optimization for Power, Heat and CHP Systems Including Emissions Regulations and Ambient Conditions
Authors: Gonzalez-Chapa Manuel-Angel , Vega-Galaz Jose-Ramon
Published: April 2008

Combined Heat and Power systems have been used all around the world due to their effective and viable way of transforming energy from fossil fuel. Indeed, the advantage of lower greenhouse gas emissions compared to those obtained in conventional power or conventional heat generation systems have been an important factor giving CHP systems an advantage over these conventional ones. Certainly CHP has been, and continues to be, a good practice while renewable technologies become more economically. While these technologies emerge it is important to continue minimizing these greenhouse gas emissions from conventional and CHP units as much as possible. This paper deals with the fuel optimization of power, heat and CHP systems including emissions and ambient conditions constraints. Ambient conditions variations are evaluated before solving the optimization and then introduced to the problem to consider their effects.
Discharge Coefficient and Effectiveness Measurement for Conical Shaped Film Cooling Holes
Authors: Zuniga H. A. , Krishnan Vaidyanathan , Sleiti A. K. , Kapat J. S. , Bharani Sanjeev
Published: April 2008

Experimental measurements of discharge coefficient and effectiveness of conical shaped film cooling holes with 1°, 2° and 3° uniform diffusion angle are presented. All film holes are inclined at 35° with hole length to diameter ratio, L/D = 3.5, pitch to diameter ratio, PI/D = 3 with a constant density ratio of 1.26 and with nitrogen as the coolant. Results show that conical film holes have higher discharge coefficients than their cylindrical counterparts. For conical holes, the local distribution and laterally averaged effectiveness values decrease with increasing blowing ratio from 0.45 to 1. The configuration with 3° uniform diffusion angle has the highest effectiveness values and outperforms the conical holes with 1°, 2° diffusion angles by 40% in the proximity of the holes (X/D ≪ 5) at a blowing ratio of 0.45. Results are compared to base line cylindrical as well as to fan shape film holes available in open literature. The average effectiveness of the conical holes can reach values comparable to those achieved by fan shaped film holes at the same blowing ratio.
Multiple Autonomous Underwater Crawler Control for Mine Reacquisition
Authors: Welling Douglas M. , Edwards Dean B.
Published: April 2008

Autonomous Underwater Vehicles (AUVs) are currently being used by the Navy for mine countermeasures. AUVs include both submarine and tracked crawlers. Recent search strategies have been implemented using both submarines and crawlers; submarines to sweep large areas to detect possible mines, and crawler to re-acquire the possible mines and perform classification. The primary scope of this paper is the control strategies for the crawlers to best cover an area. Both a motion controller and a mine reacquisition scheduling system were developed. Simulations were performed using Autonomous Littoral Warfare Systems Evaluator - Monte Carlo (ALWSEMC) to complete studies on optimal crawler control strategies. These simulations included 1 submarine and 3 crawlers. Two reacquisition scheduling systems were compared, one using a closest target strategy, and one using fuzzy logic that used additional information available to the crawler to best utilize time and resources. It was found that a fuzzy logic scheduling system outperformed the baseline system by reducing the amount of time to reacquire all targets.
Tensile Test Apparatus for Micro-Scale Specimens on Scanning Electron Microscope Using Sub-Pixel Digital Image Correlation
Authors: Pradhan Sailesh , Chu T. C.
Published: April 2008

Design parameters for a new micro tensile testing arrangement have been presented. The device is well suited for conducting in-situ tensile test experimentation on the SEM using SPDIC technique to obtain strains and material properties of free-standing thin film specimens. A high precision, high resolution hybrid linear actuator is employed to apply the necessary tensile force. Resolution of linear motion of the actuator is around ±0.3μm. Applied forces are measured using a high precision load cell. The DAQ device is a laboratory computer running a measurement and automation software. Use of the apparatus facilitates real time capturing of images of specimens undergoing strain. Key features of the apparatus are ease of use, portability and simplicity of the entire design while maintaining high accuracy and precision data acquisition capabilities. Coupled with SPDIC techniques, the apparatus can be used to measure in-plane displacements with a resolution up to 10nm.
Modeling and Control of a Horizontal Two-Link Rigid/Flexible Robot
Authors: Lee Ho-Hoon
Published: April 2008

This paper proposes a trajectory control scheme for a horizontal two-link rigid/flexible robot having a payload at the free end. First, a new distributed-parameter dynamic model, consisting of two ordinary differential equations and one partial differential equation, is derived using the extended Hamilton’s principle, and then a trajectory-tracking control scheme is designed based on the distributed-parameter dynamic model, where the Lyapunov stability theorem is used as a mathematical tool. The proposed control is a collocated control, free from the so-called spillover instability. The proposed control consists of a PD control for the rigid dynamics, a proportional control for the flexible dynamics, and feed forward and dynamics compensation. With only two joint actuators, the proposed trajectory control guarantees stability throughout the entire trajectory-tracking control and asymptotic stability at desired goal positions. The theoretical results have been evaluated with control experiments.
Processing and Characterization of Hybrid Nanoparticle Infused Structural Fiber Composites
Authors: Akinyede Oladapo , Mohan Ram , Kelkar Ajit , Sankar Jag , Pandya Ashish
Published: April 2008

Effective conventional manufacturing techniques are required to integrate the nanomaterial configurations into material systems at a larger component and structural level to obtain the enhanced benefits offered by the material configurations at the nano length scale. A low cost manufacturing process based on vacuum assisted resin transfer molding (VARTM) is demonstrated for the effective processing of fiber composite laminates using modified epoxy resin systems dispersed with nano and sub-micron alumina oxide particles. The effect of alumina oxide particles on the thermo physical properties (glass transition temperature, etc), are studied via differential scanning calorimetry and thermal gravimetric analysis. Higher glass transition temperatures with the alumina oxide and other nano particulate systems provide an opportunity to use conventional resin systems in high temperature applications. Ultrasonic mixing is employed to uniformly disperse the particles into an epoxy resin system. The flow characteristics of the modified resin system are not significantly different than the neat resin system and allowed the use of traditional VARTM processes successfully. The details of the resin modification and current studies on particulate modification for better interfacial bond are discussed in this paper. Wear performance for reinforced plastics are also investigated in this paper. Composite laminates with S2 glass and modified resins are fabricated. The mechanical behavior of the fabricated composite laminates with the neat and modified resin system using different sized and loading of alumina oxide particles are presented and discussed.
Design and Control of a 3-D Wearable Cobot
Authors: Li Xiaobo , Chua Jason Yap , Moore Carl A.
Published: April 2008

Cobots are specially designed robots that use continuously variable transmissions (CVTs) instead of traditional motor driven joints. With a cobot, the human experiences haptic effects through physical contact with the cobot’s end-effector. Safety is maintained through shared human-cobot control where the cobot velocity vector is split into 1) a speed that is proportional to the human’s input power and 2) a direction that is determined by the CVTs. We believe that cobots are an attractive choice for telerobotic master controllers because they are safe in contact with humans and are able to produce stable high quality virtual surfaces that can constrain the motion of the master to directions suitable for telerobotic task completion. This paper presents the design and control of a 3-D arm-wearable cobot for telerobotic operation. In our design a master cobot attaches to the user’s arm so that the user’s natural arm motions can be sensed and transmitted as the control signals for the slave robot. Furthermore, since the wearable arm is a cobot, virtual motion constraints may be safely placed on the master. Herein we describe the design of the wearable arm cobot and introduce a novel power assist mode, which makes it possible to control the cobot’s position relative inertia. The effectiveness of this control mode is investigated using simulations.
Stiffness Analysis of a Tripod With a Passive Link
Authors: Bi Z. M. , Lang S. Y. T. , Zhang D.
Published: April 2008

The system stiffness of a tripod parallel kinematic mechanism (PKM) with 3-DOF is investigated in this paper. The tripod PKM has rotations of a motion platform about the x and y axes and translation along the z axis. The motion on the other axes is constrained by a passive link. The stiffness model considers the compliances of three main components: the fixed-length links, the passive link, and the linear actuators. The modeling procedure for the kinetostatic stiffness model is introduced. A case study is provided to demonstrate evaluation of the stiffness of our prototype tripod machine. The developed model differs from the others in the sense that the stiffness on the motion axes is determined by both the active links and the passive link; but the stiffness on the constrained motion axes depends merely on the passive link.
Dynamic Reoptimization of a SNAC Controller for Velocity Tracking in a Nano Array
Authors: Unnikrishnan Nishant , Balakrishnan S. N.
Published: April 2008

Online trained neural networks have become popular in designing robust and adaptive controllers for dynamic systems with uncertainties in their system equations because of their universal function approximation property. The uniqueness of the method proposed in this work is that the online function approximating network can be used to re-optimize in real time an existing Single Network Adaptive Critic (SNAC) based optimal controller that has already been designed for a nominal system. The controller redesign is carried out in two steps: (i) synthesis of an online neural network that captures the unknown functions in the plant equations on-line (ii) re-optimization of the existing optimal SNAC controller to drive the states of the plant to a desired reference by minimizing a predefined cost function. The neural network weight update rule for the online networks has been derived using Lyapunov theory that guarantees both the stability of the error dynamics as well as boundedness of the weights. This approach has been applied to control the frictional dynamics of a nano-scale array of particles to track a predefined value of average sliding velocity. Here, the system is in an output feedback form where all states are not available for measurement. This is a significant step towards optimal control of systems at nano levels. Numerical results from simulation studies are presented.
Water Hammer Induced Vibration of a Fluid Filled Pipe
Authors: Jia Yi , Me´dici Ezequiel , Just-Agosto Frederick , Serrano David , Castillo Luciano
Published: April 2008

The objectives of this study are to analyze the behavior of a pipe under different valve open and closure times and to predict water hammer-induced transient maximum pressure, deflection and frequency of vibration in a fluid filled pipe. The model that integrated a classical formulation of water hammer problem and beam vibration equation was developed and a numerical simulation including frictional losses has been carried out. The MacCormak and Runge-Kutta methods were used to solve governing partial differential equations in order to investigate water hammer induced vibration of a fluid filled pipe. The results show that fluid flow rate does not change the vibration frequency of pipe. The peak wave pressures, maximum pipe deflections at various valve open and closure times, and the frequencies of vibration with variation of fluid speed and pipe geometrical configuration are presented.
Single Cell Electrophysiological Analysis via Sub-Micrometer Openings
Authors: Li Sha , Lin Liwei
Published: April 2008

Single cell electrophysiological analyses were demonstrated via sub-micrometer openings using micro-and nano-machining technologies. In the prototype demonstration, a 6GΩ seal resistance was achieved on a HeLa cell, a cervical cancer cell line with size between 10~20μm, using the microfabricated electrophysiological system with opening size of 500nm in diameter and the measured electrolyte pipette resistance is 200kΩ. In a second experiment on a vacuolar yeast cell of 3~5μm in size, using a device with 800nm opening, a 500MΩ seal resistance was achieved and the measured electrolyte pipette resistance is 1MΩ.
Closed Loop Control of Resin Flow in VARTM Using a Multi-Segment Injection Line and Real-Time Adaptive, Model-Based Control
Authors: Nalla Ajit R. , Glancey James L.
Published: April 2008

To improve process controllability during VARTM, a new resin injection line was designed and tested. The injection line, which consists of multiple segments each independently operated, allows for the control of resin flow to different locations within the mold. Simulation of different injection line configurations for various mold geometries is studied. Performance of a prototype line is quantified with a laboratory size mold used to demonstrate the potential value and benefits of this approach. Specific performance metrics, including resin flow front controllability, total injection time and void formation are used to compare this new approach to conventional VARTM injection methods. Computer-based closed loop controller strategies are designed that use point sensor feedback of resin location. In addition, an adaptive control algorithm that uses a finite element model to provide real-time updates of the injection line configuration is presented. Experimental validation of two different control strategies is presented, and demonstrates that real-time, model-based control is possible in VARTM.
Modeling the Femtosecond Laser Pulse-Train Ablation of Dielectrics
Authors: Jiang L. , Tsai H. L.
Published: April 2008

Recently, a new laser micromachining technique using multiple femtosecond pulses with a picosecond-to-nanosecond separation as a train group has demonstrated the ability to increase the ablation quality of dielectrics and semiconductors. However, the mechanisms involved in the technique are not fully understood. This study employs the plasma model recently developed by the authors to analyze the femtosecond pulse-train ablation of dielectrics. It is found that the transient significantly varying optical properties are the important reasons that lead to the advantages of the pulse-train technique. It has demonstrated that there exits a constant ablation-depth zone with respect to fluence, which has also been observed experimentally. By using the pulse-train technology, it is possible to obtain repeatable nanostructures, even when the laser system is subject to some fluctuations in fluences.
A New Two Phase Extension of Modified Brinkman Formulation for Fluid Flow through Porous Media
Authors: Belhaj Hadi , Mustafiz Shabbir , Ma Fuxi , Islam M. R.
Published: April 2008

In porous media research, Modified Brinkman’s equation is a very recent development. It is important as it incorporates the concept of viscous effect to inertial effect in a fluid flow system when Darcy’s, Forchheimer’s and Brinkman’s terms are brought all together. So far, researchers have developed the modified equation in its two-dimensional forms; however, limited to only one phase. In reality, petroleum reservoirs experience the multiphase conditions. Therefore, the simulation of a multidimensional, multiphase scenario is mostly desired, the highlight of this paper. The paper presents the formulation of two-dimensional, transient pressure and saturation equations for oil and water phases, one equation for each phase. The difference between phases is noticeable explicitly in their respective saturation, permeability, viscosity and velocity terms. The equations are then solved numerically to generate relative permeability curves. The simultaneous solution of pressure and saturation terms in the governing equations required additional relationships: the phase saturation constraint and capillary pressure as function of saturation. Finally, the numerical results are compared and validated with the experimental results. The implication of this study is manifold. The formulated equations including the solution part for the multiphase conditions are new. The new comprehensive model will describe fluid flow in reservoirs prone to high velocity or fractures more accurately than ever described by Darcy’s or other aforementioned equations.
Effects of Various Modeling Schemes on Mist Film Cooling Simulation
Authors: Li Xianchang , Wang Ting
Published: April 2008

Numerical simulation is performed in this study to explore film-cooling enhancement by injecting mist into the cooling air with a focus on investigating the effect of various modeling schemes on the simulation results. The effect of turbulence models, dispersed-phase modeling, inclusion of different forces (Saffman, thermophoresis, and Brownian), trajectory tracking, and mist injection scheme is studied. The effect of flow inlet boundary conditions (with/without air supply plenum), inlet turbulence intensity, and the near-wall grid density on simulation results is also included. Using a 2-D slot film cooling simulation with a fixed blowing angle and blowing ratio shows a 2% mist injected into the cooling air can increase the cooling effectiveness about 45%. The RNG k-ε model, RSM and the standard k-ε turbulence model with the enhanced wall treatment produce consistent and reasonable results while the turbulence dispersion has a significant effect on mist film cooling through the stochastic trajectory calculation. The thermophoretic force slightly increases the cooling effectiveness, but the effect of Brownian force and Saffman lift is imperceptible. The cooling performance is affected negatively by the plenum in this study, which alters the velocity profile and turbulence intensity at the jet exit plane. The results of this paper can serve as the qualification reference for future more complicated studies including 3-D cooling holes, different blowing ratios, various density ratios, and rotational effect.
Shared Control for Upper Extremity Rehabilitation in Virtual Environments
Authors: O’Malley Marcia K.
Published: April 2008

Interest in the rehabilitation applications for robots has been increasing. For example, various devices have been developed to aid in reaching movements of stroke, traumatic brain injury (TBI), and spinal cord injury (SCI) patients. Typically these devices provided guided reaching movements for elbow and shoulder. The robotic aspect allows for repeatability, along with additional data for post-session analysis. To date, robotic rehabilitation systems with haptic feedback have not fully exploited the capabilities of a haptic display device. The simulators primarily focus on obeying the physical laws that govern such systems in order to re-create realistic environments for rehabilitative tasks, or the robotic devices are employed only for their ability to carry the impaired limb through various trajectories. This paper will present a novel active assistance paradigm for interactions in virtual environments displayed via haptic interfaces. The author’s recent research efforts have focused on the design of perceptual overlays in virtual environments that are active rather than passive. Passive virtual fixtures have been the primary perceptual overlay in haptics, and have been used extensively as “virtual rulers” in teleoperation environments to improve operator performance of pick-and-place tasks. Active assistance in the form of shared control between the haptic device and the human operator has the potential to elicit even better performance in virtual and remote environment interactions, and also has implications for improving training effectiveness. The intended applications include stroke rehabilitation and training for pilots, manufacturing, and surgery. A description of perceptual overlays and details of the shared control paradigm are presented, along with results from some preliminary experiments on shared control haptic assistance for training in virtual environments.
Micro Investment Molding: Method for Creating Injection Molded Hollow Parts
Authors: Lippmann Julian M. , Geiger Emil J. , Pisano Albert P.
Published: April 2008

Micro investment molding combines traditional injection molding with investment casting to create hollow parts on the microscale. Silicon micromolds are manufactured using photolithography and reactive ion etching. Then, a sacrificial element is placed in the mold. Plastic is injected into the mold and around the sacrificial element using an injection molding press. After removing the plastic part from the mold, liquid etchant dissolves the sacrificial element leaving a hollow plastic part. To demonstrate the process microneedles were formed. Using 32 μm diameter aluminum bond wire as the sacrificial element hollow, in-plane, microneedles were formed out of Cyclic Olefin Copolymer (Ticona Topas®). The longest needle has an overall length of 280 μm, cross-sectional dimensions of 130 μm × 100 μm and an approximate inner diameter of 35 μm.