bluuebunny/crossref_metadata_2025 huggingface dataset:
Microchannel and Minichannel Heat Exchangers in Advanced Energy Recovery and Conversion Systems
Authors: Hendricks Terry J.
Published: April 2008

Energy recovery is gaining importance in various industrial process applications because of rising energy costs and geopolitical uncertainties impacting basic energy supplies. Various advanced energy recovery / conversion technologies will require high-performance heat transfer characteristics typical of micro- and mini-channel heat exchangers to achieve energy recovery performance targets and requirements. Initial engineering scoping studies have focused on advanced thermoelectric generator (TEG) systems assuming exhaust gas temperatures of 1033 K (1400 °F) and ambient environment temperatures of 300 K. The engineering analysis used a coupled, integrated thermoelectric (TE) system analysis accounting for the heat exchange / heat transfer performance at both the hot and cold sides and optimum TE device performance to properly predict the power output potential, resulting temperatures and temperature differentials, TEG design and interface requirements, and thermal characteristics across a wide spectrum of potential operating temperature conditions. Modular TEG's capturing about 5% of typical industrial process (e.g., glass manufacturing process) exhaust flows appear to have potential power outputs of 4 - 6 kW using advanced TE materials. Hot-side & cold-side heat exchange requirements were quantified and performance metrics evaluated to enable effective implementation of advanced TEG systems in industrial process energy recovery. Hot side heat transfer requirements create serious engineering, and possibly, scientific challenges to enabling energy conversion systems, including TEG's, in industrial process energy recovery. Future advanced heat transfer R&D is necessary and should occur in parallel with on-going advanced TE materials and systems R&D.
An Robust Adaptive Control Scheme for Hydraulic Servo Systems
Authors: Andersen Torben Ole , Hansen Michael Ryygaard
Published: April 2008

The paper looks into Model Reference Adaptive Control (MRAC) based on a linear plant model with constant or slowly varying parameters. The actual plant is non-linear, of a higher model order, subjected to time-varying bounded disturbances, and the measured values may be corrupted by noise. These problems are explored and the adaptive algorithms are modified to counteract instability mechanisms and for improved robustness with respect to bounded disturbances and non-modeled dynamics. The adaptive controller identifies the dominant dynamics and uses feedforward to provide anticipative actions in tracing task while an adaptive feedback part stabilizes the tracking error dynamics. Also the effects of non-modeled high frequency dynamics and bounded disturbances on stability and performance are analyzed. The adaptive control scheme is robust in the sense that it guarantees the existence of a large region of attraction from which all the trajectories remain bounded. The size of the region of attraction depends on the non-modeled dynamics in such a way that if the non-modeled dynamics is infinitely fast, the region of attraction becomes the whole space. Simulation and experimental results are presented and discussed to demonstrate the strength of the proposed algorithm.
Two Dimensional Input Shaping for One Dimensional Continua
Authors: Lofti-Gaskarimahalle Amir , Rahn Christopher D.
Published: April 2008

This paper extends input shaping control to one dimensional continua. Unlike discrete systems where the input is shaped only in the temporal domain, temporal and spatial input shaping can produce zero residual vibration in setpoint position control of distributed strings and beams. For collocated and noncollocated boundary control of strings and domain control of strings and pinned beams, the response to step inputs is solved in closed form using delays. For a clamped beam model, a closed form infinite modal series is used. The boundary controlled string can be setpoint regulated using two-pulse Zero Vibration (ZV) and three-pulse Zero Vibration and Derivative (ZVD) shapers but ZVD is not more robust to parameter variations than ZV. Noncolocated ZV and ZVD boundary control enables rigid body translation of a string with zero residual vibration. Domain controlled strings and pinned beams with spatial input distributions that satisfy certain orthogonality conditions (e.g. midspan point load or uniformly distributed load) can be setpoint regulated with shaped inputs. For the cantilevered beam, modal shaping of the input distribution and ZV or ZVD temporal shaping drives the tip to the desired position with zero residual vibration.
Thermomechanical Modeling of a Wet Shape Memory Alloy Actuator
Authors: Ertel Joel , Mascaro Stephen
Published: April 2008

This paper presents combined thermal and mechanical models of a wet shape memory alloy (SMA) wire actuator. The actuator consists of a SMA wire suspended concentrically in a compliant tube. Actuation occurs as hot and cold water are alternately pumped through the tube to contract and extend the wire, respectively. Although other constitutive models of the behavior of SMA's exist, they generally assume uniform temperature change throughout the SMA actuator. The thermomechanical model presented in this paper accounts for the non-uniform temperature change of the SMA wire due to alternating the temperature of the flow along the wire. The thermal model consists of analysis of the heat transfer between the fluid and the SMA wire. Heat loss to the environment and the temperature change of the fluid through the actuator are taken into account. Based on this analysis the temperature of the wire at segments along its length can be determined as a function of time. The mechanical model approximates the strain-martensite fraction and martensite fraction-temperature relationships. By combining the thermal and mechanical models the strain of the wire can be determined as a function of time. The combined thermomechanical model will be used to model applications in which a wet SMA actuator is desired.
High Precision Assembly of Soft-Polymer Microfluidic Circuits
Authors: Trinkle Christine A. , Morgan Christopher J. , Lee Luke P.
Published: April 2008

Microfluidic chips have made it possible to manipulate biological fluidic samples in increasingly smaller volumes—even enabling multiplexed study of individual cells. Performing biological assays using microfluidic technology not only makes them more portable when compared to their traditional counterparts, but also decreases testing time and cost. These biofluidic circuits vary widely in design and function: multiplexed cell electroporation, on-chip cell culturing, cell-cell communication monitoring, protein crystallization, and small volume sample analysis are only a few examples of potential applications. The rapid rate of growth and change in this field creates a need for inexpensive and flexible rapid prototyping of microfluidic chips.
Dilution and Suppression of Partially Premixed Flames in Normal and Microgravity for Different Fuels
Authors: Lock Andrew J. , Briones Alejandro , Aggarwal Suresh K. , Puri Ishwar K. , Hegde Uday G.
Published: April 2008

The suppression of fires and flames is an important area of interest for both terrestrial and space based applications. In this investigation we elucidate the relative efficacy of fuel and air stream inert diluents for suppressing laminar partially premixed flames. A comparison of the effects of fuel and air stream dilution are also made with other fuels. Both counterflow and coflow flames are investigated, with both normal and zerogravity conditions considered for coflow flames. Simulations are conducted for both the counterflow and coflow flames, while experimental observations are made on the coflowing flames. With fuel or air stream dilution, coflow flames are observed to move downstream from the burner after overcoming initial heat transfer coupling. Further increases in diluent result in increases in the flame liftoff height until blow off occurs. The flame liftoff height and the critical volume fraction of extinguishing agent at blow out vary with both equivalence ratio and with the stream in which diluents are introduced. Nonpremixed methane-air flames are more difficult to extinguish than partially premixed flames with fuel stream dilution; whereas, partially premixed methane-air flames are more resistant to extinction than nonpremixed flames with air stream dilution. This difference in efficacy of the fuel and air stream dilution is attributed to the action of the diluent. In leaner partially premixed flames with fuel stream dilution and richer partially premixed flames with air stream dilution the effect of the diluent is to replace the deficient reactant in the system, thus starving the flame. In leaner partially premixed flames with air stream dilution and richer partially premixed flames with fuel stream dilution the effect of the diluent is purely thermal in that it absorbs heat from the flame, until combustion may no longer be sustained. The dilution effect is more effective than the thermal effect. When gravity is eliminated from the 2-D flame the liftoff height decreases and the critical volume fraction of diluent for blow off is also decreased.
Directional Stability Enhancement of a Dual Path Front Hydrostatic Drive by Wire Off-Road Vehicle
Authors: van Doorn William , Lumkes John H.
Published: April 2008

This paper discusses the inherent instability in a dual path front hydrostatic drive wheel, rear caster wheel off-road vehicle. A physical system model is created to simulate behavior to both normal operation and outside environmental inputs. The model starts with a simplified diesel engine and includes the hydraulic pumps, motors, and associated components. The hydraulic motor output is coupled to the ground using the drive wheel geometry. Disturbances are applied to each drive wheel. The force on each wheel is determined independently and combined to create a net vehicle acceleration, rotation, or both. A model based controller is designed to accurately steer the vehicle during both slow working speeds and high transport speeds. The control algorithm uses steering input, speed input, and yaw rate to control pump displacement for each wheel. The controller adjusts ground drive pump displacements when a disturbance is applied to either wheel to maintain longitudinal stability. The controller will be implemented on a vehicle using electro-hydraulic pump control. Steering and speed inputs have been modified for input to the controller rather than manually changing pump displacement. Additionally, joystick control has been implemented as an alternative drive mode. The joystick determines speed and steering input with a single hand while opening up the operator station for better visibility and manufacturing.
Grasp Planning for a Two-Fingered Parallel-Jawed Gripper
Authors: Abhishek A. , Kumar Manish , Garg Devendra P.
Published: April 2008

The main emphasis of this paper is on grasp planning for a two-fingered parallel jawed gripper (typically used in industries) utilizing visual feedback for improved grasping for a planar object. Appropriate placement of fingers on the object plays an important role in grasp stability. This task is relatively easier for a priori-known target. But when the model of the object is not known a priori, it becomes difficult to plan the grasp and the usability of manipulator becomes limited. The main difficulty is in deciding upon the grasp points in a random object at a random location. A general approach has been presented in this paper which is applicable to any planar object. The approach uses the 2D features extracted from the image such as centroid, dimensions and principal axes to compute the grasp points' coordinates and the location of grasp axis for stability. A specialized approach is also presented which deals with objects containing only straight edges. The specialized approach utilizes Hough transform and image features in conjunction to enhance the performance of the algorithm. The proposed method can handle abrupt changes in the contour of an object as the algorithm takes object corners into account. Experiments were conducted in the laboratory to test the effectiveness of the proposed algorithm and validate the resuls.
Sensorless Detection of Cavitation in Centrifugal Pumps
Authors: Harihara Parasuram P. , Parlos Alexander G.
Published: April 2008

Analysis of electrical signatures has been in use for some time for estimating the condition of induction motors, by extracting spectral indicators from motor current waveforms. In most applications, motors are used to drive dynamic loads, such as pumps, fans, and blowers, by means of power transmission devices, such as belts, couplers, gear-boxes. Failure of either the electric motors or the driven loads is associated with operational disruption. The large costs associated with the resulting idle equipment and personnel can often be avoided if the degradation is detected in its early stages prior to reaching failure conditions. Hence the need arises for cost-effective detection schemes not only for assessing the condition of the motor but also of the driven load. This prompts one to consider approaches that use no add-on sensors, in order to avoid any reduction in overall system reliability and increased costs. This paper presents an experimentally demonstrated sensorless approach to detecting varying levels of cavitation in centrifugal pumps. The proposed approach is sensorless in the sense that no mechanical sensors are required on either the pump or the motor driving the pump. Rather, onset of pump cavitation is detected using only the line voltages and phase currents of the electric motor driving the pump. Moreover, most industrial motor switchgear are equipped with potential transformers and current transformers which can be used to measure the motor voltages and currents. The developed fault detection scheme is insensitive to electric power supply and mechanical load variations. Furthermore, it does not require a priori knowledge of a motor or pump model or any detailed motor or pump design parameters; a model of the system is adaptively estimated on-line. The developed detection algorithm has been tested on data collected from a centrifugal pump connected to a 3 φ, 3 hp induction motor. Several cavitation levels are staged with increased severity. In addition to these staged pump faults, extensive experiments are also conducted to test the false alarm performance of the algorithm. Results from these experiments allow us to offer the conclusion that for the cases under consideration, the proposed model-based detection scheme reveals cavitation detection times that are comparable to those obtained from vibration analysis with a detection threshold that is significantly lower than used in industrial practice.
Delamination and Blistering Due to Rapid Heating of Moist Composites
Authors: Zehnder Alan T. , Czabaj Michael W.
Published: April 2008

Polyimide matrix composites (PiMC's) allow the advantages of high specific stiffness and strength to be extended to high temperature applications. Hence, PiMC's are desirable for use in high temperature aerospace structures such as space launch propulsion systems, rocket engine components and advanced turbine engines [1,2]. Relative to epoxy matrices, polyimide matrix composites are more expensive and more difficult to fabricate, hence they are likely to be used only in applications where their high temperature properties are truly needed and will be fully exploited. Hence an understanding of and an ability to model the high temperature performance of these materials is critical to their adoption in real-world applications. Among the many issues surrounding these materials, delamination due to the rapid heat-up of moisture saturated composites has emerged as a limiter to the allowable rates of heating. As laminates heat-up, moisture absorbed into the matrix or trapped in voids will vaporize and develop high pressures (up to the vapor pressure of saturated steam, approximately 10 MPa at 320°C) that can cause delamination of existing flaws or can nucleate voids in the matrix leading to failure of the laminate.
Simulation of Distributive Generation Using Fuel Cell Hybrid Systems
Authors: Wolf Brian , Revankar Shripad
Published: April 2008

Fuel cell hybrid technology has the potential to significantly change our current energy infrastructure. Past studies have shown that the combination of fuel cells and turbines can produce power at remarkably high efficiencies with low levels of pollution. The work presented in this paper is an initial step to further development of a hybrid system model. The fuel cell model discussed is used to perform parametric studies to aid in the optimization of a hybrid system. This paper provides an overview of fuel cell hybrid systems and distributive generation. A fuel cell model is implemented in SIMULINK using basic balance equations. Key issues of modeling specifically high temperature fuel cells are discussed along with their transient response and how it may affect the performance of a distributive generation system.
Petri Net Based Modeling and Control Strategies for Flexible Manufacturing Systems
Authors: Abhishek A. , Kumar Manish , Garg Devendra P.
Published: April 2008

This paper presents comprehensive and unified strategies to model, analyze, and control flexible manufacturing systems (FMSs) in an uncertain and dynamic environment using Petri Net (PN) based modeling. The proposed methodology enables PN models to accept and assimilate online data at execution time. A measurement system consisting of distributed sensory sources suitable for manufacturing processes is designed and an interface is developed of that system with the modeling software (SHARPE) and MATLAB's Simulink to enable realtime data acquisition and processing. The proposed strategies enable online parameter estimation to impart adaptive and intelligent learning capabilities to PN models.
Mathematical Modeling and Experimental Study on Building Ceiling System Incorporating Phase Change Material (PCM) for Energy Conservation
Authors: Pasupathy A. , Velraj R.
Published: April 2008

Thermal storage plays a major role in a wide variety of industrial, commercial and residential application when there is a mismatch between the supply and demand of energy. Several promising developments are taking place in the field of thermal storage using phase change materials (PCM) in buildings. In the present paper, a detailed study of the thermal performance of a phase change material system for energy conservation in building is analyzed and discussed. An experiment consisting of two identical test houses has been constructed to study the effect of having PCM panel on the roof of the building. One house is constructed without PCM on the room in order to provide a reference case for comparison with the experimental house that includes the phase change material. The PCM is an inorganic eutectic mixture, which has melting temperature in the range of 26 - 28°C. A mathematical model has been developed in which finite volume method is used to predict the thermal behavior of the ceiling system incorporating PCMs. A comparison with the experimental results is also made.
Experimental Investigation of Droplet Dynamics on Solid Surfaces: Spreading and Recoil Effects
Authors: Gatne Kalpak P. , Jog Milind A. , Manglik Raj M.
Published: April 2008

A study of the normal impact of liquid droplets on a dry horizontal substrate is presented in this paper. The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 2000 frames per second. A digital image processing software was used to determine the drop spread and height of the liquid on the surface from each frame. To ascertain the effects of liquid viscosity and surface tension, experiments were conducted with four liquids (water, ethanol, propylene glycol and glycerin) that have vastly different fluid properties. Three different Weber numbers (20, 40, and 80) were considered by altering the height from which the drop is released. The high-speed photographs of impact, spreading and recoil are shown and the temporal variations of dimensionless drop spread and height are provided in the paper. The results show that changes in liquid viscosity and surface tension significantly affect the spreading and recoil behavior. For a fixed Weber number, lower surface tension promotes greater spreading and higher viscosity dampens spreading and recoil. Using a simple scale analysis of energy balance, it was found that the maximum spread factor varies as Re1/5 when liquid viscosity is high and viscous effects govern the spreading behavior.
Control of a Passive Mobility Assistive Robot
Authors: Ryu Ji-Chul , Pathak Kaustubh , Agarwal Sunil K.
Published: April 2008

In this paper, a control methodology for a mobility assistive robot is presented. There are various types of robots that can help the disabled. Among these, mobile robots can help to guide a subject from one place to the other. Broadly, the mobile guidance robots can be classified into active and passive type. From a user's safety point of view, passive mobility assistive robots are more desirable than the active robots. In this paper, a two-wheeled differentially driven mobile robot with a castor wheel is considered as the assistive robot. The robot is made to have passive mobility characteristics by a specific choice of control law which creates damper-like resistive forces on the wheels. The paper describes the dynamic model, the suggested control laws to achieve a passive behavior, and experiments on a mobile robot facility at the University of Delaware. From a starting position, the assistive device guides the user to the goal in two phases. In the first phase, the user is guided to reach a goal position while pushing the robot through a handle attached to it. At the end of this first phase, the robot may not have the desired orientation. In the second phase, it is assumed that the user does not apply any further pushing force while the robot corrects the heading angle. A control algorithm is suggested for each phase. In the second phase, the desired heading angle is achieved at the cost of deviation from the final position. This excursion from the goal position is minimized by the controller. This control scheme is first verified in computer simulation. Then, it is implemented on a laboratory system and the experimental results are presented.
Generalized Eigenvalue Decomposition in Time Domain Modal Parameter Identification
Authors: Zhou Wenliang , Chelidze David
Published: April 2008

This paper is intended to point out the relationship among current time domain modal analysis methods by employing the generalized eigenvalue decomposition. Various well-known time domain modal analysis algorithms are reviewed. Ibrahim Time Domain (ITD), Least Square Complex Exponent (LSCE) and Eigensystem Realization Algorithm (ERA) methods are chosen to do the comparison. Reformulation to these original forms show these three methods can all be attributed to a generalized eigenvalue problem with different matrix pairs. With this general format, we can see that Single-Input Multi-Output (SIMO) methods can easily be extended to Multi-Input Multi-Output (MIMO) case by taking advantage of the generalized Hankel matrix or generalized Toeplitz matrix.
Qualification of a System-in-Package (SiP): A Physics-of-Failure (PoF) Perspective
Authors: Farley Daniel , Dasgupta Abhijit , Caers Jo
Published: April 2008

An LGA (Land Grid Array) laminate-based epoxy-molded RF SiP (system-in-package) containing four wirebonded and three flip-chip dice is qualified using a PoF (Physics-of-Failure) approach. The process includes design and execution of accelerated stress testing. The test results are extrapolated to field environments using acceleration factors derived from virtual qualification (VQ) and virtual testing (VT). In the VQ step, life-cycle loading experienced by the specimen is simulated, potential failure sites are identified, and reliability assessment models for each failure mode are applied for damage analysis. The virtual testing (VT) step is similar to VQ, except that the accelerated loading developed for the experimentation phase is used. The output of the process is a lifetime assessment, based on the accelerated test results and the acceleration factors derived from PoF considerations.
Dynamic Acoustic Measurement Techniques Considering Human Perception
Authors: Genuit Klaus , Bray Wade
Published: April 2008

Dynamic measurement implies determining the content of signals having spectral structure and energy changing with time, sometimes on very short time scales. Dynamic measurements can present challenges to determine sufficient information in both the time and frequency domains. High resolution in frequency prevents finding short-term peak levels and recognizing true crest factors, and vice versa. If the dynamic measurement concerns sound, the much better simultaneous recognition of time and frequency information by the ear/brain than by conventional measurement methods can further complicate the challenge. People have at least three times better simultaneous time/frequency resolution than the familiar Fourier transform moved across the time axis, although quite often a compromise block size can be found that gives time/frequency measurement agreeing with human sound perception of both factors. Unlike technical measuring systems, human hearing is also very sensitive to patterns. The presence of tones, varying tones (amplitude and/or frequency), clicks, rattles, splashing sounds, etc., even at low levels in the presence of other less structured noise of considerably higher level, can dominate perception. Human consciousness effectively performs the opposite of averaging, ignoring the absolute value of slowly varying or stationary signals and focusing on things differing at short time bases from their surroundings in both time and frequency. In dynamic measurement it can be difficult to withdraw the important pattern from the absolute whole. Case studies will be given comparing conventional techniques with three high-resolution time/frequency methods useful in general engineering although developed to model the processes of human sound perception: a hearing model with very rapid time resolution at all frequencies [1], a relative (pattern) measurement technique subtracting a sliding average in both time and frequency from a running instantaneous spectrum [2], and a Fourier-based window deconvolution method giving pure spectral lines regardless of signal-to-block synchronization and permitting multiplication of frequency resolution for a given block length and time resolution [1], [3].
Human Evaluation of Internet-Based Bilateral Teleoperation Using Wave Variables With Adaptive Predictor and Direct Drift Control
Authors: Ching Ho , Book Wayne J.
Published: April 2008

In a conventional bilateral teleoperation, transmission delay over the Internet can potentially cause instability. The wave variables algorithm can solve this problem at the cost of poor transient response. The wave variables algorithm with adaptive predictor and drift control based on our previous work [24] has been proposed to provide stability under time delay with improved performance. The effectiveness of this algorithm is fully evaluated using human subjects with no previous experience in haptics. Three algorithms are tested using Phantom haptic devices as master and slave: conventional bilateral teleoperation with no transmission delay as control, wave variables with 200-300 ms transmission delay one way, and wave variables with adaptive predictor and direct drift control (WAPD) also with 200-300 ms delay one way. For each algorithm the human subjects are asked to perform three simple tasks: free space trajectory tracking, surface contour identification, and maze navigation. The results show WAPD to be superior to regular wave variables algorithm with higher subject ratings.
Nano-and Micro-Actuations of Hard Disk’s Head Positioning System: Actuator Design and Evaluation of Performance
Authors: Han Y. , Tzou H. S.
Published: April 2008

High-density magnetic hard disks are key components in information storage. In high-density hard disk drives (HDD), both super fast track seeking and extremely accurate positioning of the read/write head are required. A new multiDOF piezoelectric micro-actuator with nano-transverse and micro-lateral control of the head positioning system for highdensity hard disk drives is proposed. For the track following control of a head positioning system in the HDD, proper modeling of the system including the voice coil motor (VCM), suspension, slider, and gimbal system is very important. Before further comprehensive analysis of the whole assembly, the design concept and the evaluation of the micro-actuator are focused on in this paper. First, design of the new piezoelectric micro-actuator is illustrated. The design of the new micro-actuator is based on the axial deformation of piezoelectric elements for lateral motion control and the bimorph actuation of piezoelectric elements for transverse nm motion control. Next, mathematical models of the micro-actuator system are defined. Lastly, the micro-actuator system is modeled using the commercial finite element package ANSYS. The results from analytical analysis and FE analysis are compared. Static response of the micro-actuator system is evaluated first, followed by analysis of dynamic response analysis. Static actuations of the new actuator system satisfy both lateral (±0.1μm) and transverse (15nm) specifications. Dynamic analysis of the ultra-precision system suggests that the new piezoelectric micro-actuator improves performance of highdensity hard disk drives by increasing servo bandwidth and decreasing flying height.
Integration of a Thin-Film Evaporation Submodel With a Micro Loop Heat Pipe Solver
Authors: Ghajar M. , Darabi J.
Published: April 2008

A number of analytical and numerical models have been developed by various researchers to predict the behavior of loop heat pipes (LHP). However, none of those models use the thin-film evaporation principles in the capillary structures to evaluate the local evaporative heat transfer coefficients. In this work, principles of the thin film evaporation are applied in a submodel and combined with our previously developed loop solver model to more accurately simulate the performance of a flat micro loop heat pipe. The resulting code predicts the heat removal capability, surface temperature, and local and average heat transfer coefficients at various applied heat loads. The results indicate that extremely high cross-sectionally averaged evaporative heat transfer coefficients can be achieved. The modeling results are verified by experimental data.
Cascade Control With Friction Compensasion Based on Artificial Neural Network for a Hydraulic Actuator
Authors: Machado Cla´udio L. E. d’Elia , Guenther Raul , De Negri Victor Juliano , Gomes Sebastia˜o Ci´cero Pinheiro
Published: April 2008

This paper addresses the friction compensation in hydraulic actuators using an artificial neural network combined with a suitable control technique. The proposed neural network is trained off-line and allows calculate an estimative of the friction force on-line very quickly based on the hydraulic force and on the cylinder velocity. The estimated friction force is introduced directly in the force line of the system using a cascade controller, in which the hydraulic actuator is interpreted as two interconnected subsystems: a mechanical one driven by a hydraulic one. The convergence properties of the closed loop system are established using the Lyapunov method. Experimental results validate the main theoretical results of the proposed strategy.
Transition of Neural Signals on Adaptive Cylindrical Paraboloidal Shells
Authors: Han Y. , Tzou H. S.
Published: April 2008

Cylindrical paraboloidal shells are common structures in communication systems, precision opto-mechanical systems and high-precision modern aerospace structures. Sensing is essential to validate the high performance of these modern structures. The purpose of this study is 1) to investigate microscopic neural signal generations from infinitesimal piezoelectric sensors over a cylindrical paraboloidal shell panel with curvature changes and 2) to determine the dominant signal component resulting from longitudinal or circumferential membrane strains and longitudinal or circumferential bending strains. Mathematical models of the cylindrical paraboloidal shells are presented first, followed by definition of the transverse mode shape function. Then, the microscopic signal generations of distributed sensors laminated on a cylindrical paraboloidal shell panel with simply-supported boundary conditions are investigated for three different cases: the ratio of meridian to radial distance of parabola at 1:4 (shallow), 1:1 (baseline) and 2:1 (deep). Analyzing these three cases suggests that as the shell changes from shallow to deep, 1) the circumferential membrane neural signals dominate more lower modes before the circumferential bending signals become dominant for nm as the mode increases and 2) the neural signals become localized where the curvature is small. Due to non-constant radius of curvature, these signal transitions on the cylindrical paraboloidal shells are rather unique, which has not been observed in other shells.
Determining LGA Contact Design Specifications by Investigating Sensitivity of LGA Contact Performance to LGA Contact Geometric Tolerance
Authors: Zheng Tieyu , Wang Mingji , He Shijiang
Published: April 2008

This paper presents a numerical DOE to investigate the sensitivity of the mechanical performance of LGA contacts, e.g. contact working range, wiping distance and force, to four key design parameters: contact free height, contact thickness, contact material yield strength and the coefficient between the contact and its landing pad. Multiple cases were analyzed and the normalized response surfaces of the performance are presented. By keeping the linear terms of the response surfaces, the performance variances relative to the nominal can be estimated. The methodology using the estimated variances to define LGA contact design specification is also presented.
Dynamics of Micromanipulation Using a Compliant Micromanipulator
Authors: Krishnan Sandeep , Saggere Laxman
Published: April 2008

Attractive forces present at the micro and nano scales are a hindrance to error-free manipulation of micro-scale objects using manipulator devices as they cause the micro-scale objects to become adhered to the end-effector of the manipulator. This paper presents a dynamic model for controlled release of a polystyrene microsphere adhered to the end-effector of a compliant micromanipulator due to Van Der Waal's forces applying the principle of the inertial release technique. The inertial release is effected through step input actuation forces of the manipulator. Various actuation parameters such as the velocity and rise time for successful inertial release of adhered microspheres are investigated.
Modeling Transient Response of Hybrid Vehicle With Stability Algorithm
Authors: Anstrom Joel R.
Published: April 2008

An existing full car dynamic model (HVOSM.VD2) was expanded previously to enable simulation of electric, hybrid electric, and fuel cell vehicles with integrated vehicle stability systems. A prototype range extending series hybrid electric vehicle was constructed with independent front wheel drives. A hybrid vehicle stability assist (VSA) algorithm was developed to perform proportional control of yaw rate through left/right distribution of front motor torques while simultaneously blending anti-lock braking and traction control with electric drive within hybrid system power limits. The new model, Hybrid Electric Vehicle Dynamic Environment, Virtual (HEVDEV), was validated and used to simulate the Hybrid VSA safety system in the prototype. Skid pad testing was performed to validate HEVDEV simulations of steady state turning behavior. Further simulations using proportional control of differential front wheel torque predicted stable Hybrid VSA performance during step-steer and braking-in-a-turn dynamic maneuvers within hybrid drive-train power limitations. This study focuses on system transient behavior during step steer inputs using more power intensive PID control algorithms, several front to rear weight distributions, and recent trends in HEV and Fuel Cell component specifications. Conclusions are made about component specifications for successful Hybrid VSA systems in future Plug-In hybrid electric (PHEV) and Fuel Cell (FCV) Vehicles.
Sensitivity Analysis in Yield Optimization of MEMS Tunable Capacitors
Authors: Shavezipur Mohammad , Ponnambalam Kumaraswamy , Khajepour Amir , Hashemi Seyed Mohammad
Published: April 2008

The fabrication of MEMS tunable capacitors faces many uncertainties in which the fabricated dimensions differ from nominal values. This deviation in a tunable capacitor may cause significant variation in the capacitance-voltage response. In this paper, the effect of uncertainty in parallel-plate tunable capacitors is studied to maximize the yield under given criteria. A new method for yield optimization of tunable MEMS capacitors is developed. The method can take into account any arbitrary distribution and is not restricted to normality assumptions. The optimal designs verified by Monte-Carlo simulation exhibits considerable improvement in the yield. A sensitivity analysis is then performed to refine the design variables and maximize the yield based on the most effective parameters. When the fabrication process is already established and cannot be changed, the method can be employed to estimate the final yield for the process. The advantage of this method is demonstrated by numerical examples where the yield using initial design parameters is compared to the yield of the device with optimum parameters.
Static Friction Models for Vehicle Simulation Study
Authors: Song Xubin , Smedley Daniel G.
Published: April 2008

The history of the challenge of friction modeling is briefly reviewed. Then this paper focuses on the modeling and simulation study of the friction related dynamics in the Simulink® environment, because Matlab®/Simulink® are popular engineering software tools for both industry and academia. Matlab® and Simulink® are the proprietary products of MathWorks, Inc. In this paper, the static friction models are studied through Simulink® by applying fixed and variable step sizes. The comparison shows that the static Karnopp model is not only numerically tractable but also can be inclusive of the fundamental friction characteristics of both stick slip and correct friction predictions. Finally this paper presents an improved Karnopp model for clutch modeling with the use of Simulink®, and the simulation shows that this model is computationally tractable with smooth dynamics.
Macro/Micro-Scale Modeling of Laser Cladding Process
Authors: Cao Y. , Choi J.
Published: April 2008

Laser cladding process inherently includes multi-scale, highly non-linear, and non-equilibrium transport phenomena due to non-uniform and rapid heat flow caused by the laser and the material interaction. Therefore, there is a growing demand to develop systematic modeling and simulation approaches for the multi-scale problem. To address this issue, a process model of solidification microstructure evolution has been studied by utilizing a phase-field method. The phase-field method has become a widely used computational tool for the modeling of solidification microstructure evolution with the advantage of avoiding tracking the interface explicitly and satisfying interfacial boundary conditions. In present work, the numerical solutions of a phase-field model have been analyzed. The linking of macro-scale process and solidification microstructure evolution was examined by considering the relationship of macro- and micro-parameters. The effects of laser power on clad height and surface roughness have also been studied. The predicted results for pure metal dendrite growth were compared with the microsolvability theory and a good agreement was found. Different solidification morphologies of different locations in the melt pool are also investigated. It was found that it is not the mass transfer but the heat transfer in the melt pool that dominates the solidification process.
Design and Modelling of Novel Linearly Tunable Capacitors
Authors: Shavezipur Mohammad , Khajepour Amir , Hashemi Seyed Mohammad
Published: April 2008

MEMS-based tunable capacitors with electrostatic actuation are well-known for their wide tuning ranges, high Q-factors, fast responses, and small sizes. However, tunable capacitors exhibit very high sensitivity near pull-in voltage which counters the concept of tunability. In this research, two novel designs are presented that improve the high sensitivity in capacitance-voltage (C-V) curve. In the first design, the nonlinear deformation of supporting beams is studied to develop a new nonlinear spring. The variable stiffness coefficients of such springs improve the linearity of the C-V curve, and by delaying the pull-in, the maximum tunability is also increased without using complex geometries. In the second design, an asymmetric non-parallel-plate capacitor is introduced, in which the C-V response has lower sensitivity at high voltages. The design concept can be applied to highly tunable capacitors to improve the sensitivity and maintain high tunability. The numerical results demonstrate low sensitivity and high linearity and tunability for the new designs.
On Stability Analysis and Parametric Design of Supply Networks Under the Presence of Transportation Delays
Authors: Sipahi Rifat , Lammer Stefan , Helbing Dirk , Niculescu Silviu-Iulian
Published: April 2008

Management of interconnected manufacturing units, supply networks, constitutes a timely, but challenging problem in Physics, Operations Research and Mathematics, as it carries very rich dynamics. At the first stage, a very well understanding of the underlying mechanisms and interactions within the hierarchical construct of such networks is required. For this pursuit, a more realistic approach is proposed in this paper, which takes into account the presence of naturally existing transportation delays of supplies in between individual production units. In general, the presence of delays in the dynamics imports another source of instability, which needs to be addressed. However, it is well-known that a thorough stability analysis against delays carries complications, thus it is non-trivial. We present analytical techniques to tackle such difficulties, surfacing allowable transportation delays within the supply network that guarantees stable stock levels. This, in parallel, enables the selection of production rates assuring the supply network to operate in a stable regime. Moreover, we show that under certain parametric settings, the supply network dynamics may become highly sensitive against the presence of delays, which in turn, initiates an undesirable phenomenon called bullwhip effect. We present case studies demonstrating the bullwhip effect and suggesting parametric selections to avoid this undesired behavior within supply networks.
Vibration Control Schemes of Semi- Active Hydro-Pneumatic Dampers for Military Vehicle Suspension
Authors: Eslaminasab N. , Golnaraghi M. F.
Published: April 2008

Hydro-pneumatic dampers are widely used in military and heavy vehicle suspension systems, where large suspension travel (more than 20 inches) is expected. Due to the nonlinear characteristics of these elements, suspension system performance and in particular ride comfort and road handling capabilities of the vehicle are altered. Although these nonlinear characteristics are inherent in nearly all vehicles suspension systems, their effects are dominant in certain maneuvers and especially in off-road conditions where the suspension system experiences rather large displacements. This paper investigates the control of a hydropneumatic damper suspension system, a highly nonlinear system comprised of a pneumatic spring (gas-spring) and a hydraulic damper. First, the hydro-pneumatic damper of a military vehicle is modeled. The model is validated using experiments performed with a dynamometer test machine. Based on the validated model, a 2DOF quarter car model is developed, simulated and analyzed. Secondly, the performance of two well-known semiactive control methods - Skyhook and Rakheja-Sankar (R-S) - are investigated as applied to suspension control in the 2DOF car model. To analyze the performance of these control strategies in the suspension systems where the nonlinear components exist, the method of averaging is deployed. Finally, a new control strategy based on Skyhook and R-S is proposed to address ride comfort and road handling utilizing the variable stiffness gas-spring together with a semiactive damper. The results of this new controller are then compared to that of several well known suspension control methods such as Skyhook to demonstrate the effectiveness of the method.
Experiments on Complex Repetitive Impact Dynamics of a Built-Up Beam Structure
Authors: Ervin Elizabeth K. , Wickert Jonathan A.
Published: April 2008

This paper investigates the experimental dynamics of a beam structure that supports an attached rigid body and that can impact a comparatively compliant base structure. The problem area is motivated by impact phenomena that are observed in certain structures internal to nuclear reactors. The assembly is subjected to base excitation at specified frequency and acceleration, and the resulting displacement and velocity time histories are recorded and used to obtain spectra, phase diagrams, and Poincare´ sections. The measurements validate simulation results obtained by using a constraint and modal mapping method based on the two sets of modes when the structure is in-contact, and when it is not-in-contact. Generalized coordinates are mapped across the impact discontinuities in the modal representation. The forced response simulation predicts the test specimen's response over a range of excitation frequencies. The specimens are fabricated as single integral structures from acrylnitrile butadene styrene plastic through rapid prototyping technology in order to eliminate the undesirable dissipation and flexibility arising from joints and connections. The experimental system can exhibit complex response characteristics, and the influences on complexity of deadband clearance and of asymmetry in the point of impact are examined in the experiments.
Capturing Real Life Variability in Virtual Testing
Authors: Bardot D. M. , Emery A. F.
Published: April 2008

The motivation for this work is the need to analyze the behavior of an engineering system subjected to the hostile environment of a fire. The specific goal is to estimate the survivability of a component potted in insulating foam. The foam undergoes an endothermic reaction and through this heat sink protects the component. Because the operating conditions are stochastic and because the properties of the foam can only be estimated, the usual deterministic analysis cannot be used. Instead, Bayesian inference is used to estimate the critical foam parameters and the operating conditions are described in terms of probabilities. The survivability is then expressed in terms of a probability distribution. Because the computations are very computationally expensive, recourse was made by expressing the computed results as a response surface defined in terms of a Gaussian process.