bluuebunny/crossref_metadata_2025 huggingface dataset:
External Pressure Testing of 4-in-Dia High-Density Polyethylene Pipe1
Authors: Zhao Linping , Beuse Nathaniel M. , Widera G. E. O.
Published: July 2002

Many of the investigations dealing with the determination of the time-to-failure of high-density polyethylene (HDPE) pipes involve internal pressure tests. HDPE pipe, however, can also be subjected to external pressure such as from underwater laying, vacuum, or burial. For the particular case of uniform external pressure, only a small amount of data detailing the time-to-failure of such pipes is available, and no definitive testing procedure exists. Here, an experimental apparatus and corresponding testing procedure are developed to explore remedies for this situation. On the basis of the data thus obtained, a three-coefficient equation relating time, temperature, and pressure is generated. The failure predictions from this design basis equation are in good agreement with the available data existing in the literature.
Sequential Algorithm Based on Number Theoretic Method for Statistical Tolerance Analysis and Synthesis
Authors: Zhou Zhige , Huang Wenzhen , Zhang Li
Published: July 2002

Tolerancing is one of the most important tasks in product and manufacturing process design. In the literature, both Monte Carlo simulation and numerical optimization method have been widely used in the process of statistical tolerance analysis and synthesis, but the computational effort is huge. This paper presents two techniques, quasi random numbers based on the Number Theoretic Method and sequential algorithm based on the Number Theoretic net, to calculate yield and to perform tolerance allocation. An example demonstrates the optimal tolerance allocation design and is employed to investigate the efficiency and accuracy of this solution. This algorithm can efficiently obtain the global optimum, and the amount of calculation is considerably reduced.
On Cross-Flow Fan Similarity: Effects of Casing Shape
Authors: Lazzarotto L. , Lazzaretto A. , Martegani A. D. , Macor A.
Published: July 2002

The limited number of experimental investigations on similarity operation in the literature is not sufficient to state the validity of similarity laws for cross-flow fans. This is also due to the operating conditions occurring in practical applications, where the values of impeller size and rotational speed generally result in low Reynolds numbers and, then, in a non-negligible influence of viscous forces on performance. The analysis is further complicated by the high influence of the casing shape on performance, which can lead to induced effects on similarity operation. An experimental test program is presented in this paper, aimed at understanding the influence of Reynolds number on performance for different casing shapes. Five impellers having similar shape and different dimensions were tested, each one matched with five casings at different rotational speed. The results show that similarity laws can be applied with good approximation above critical blade Reynolds numbers of around 4000 to 15,000, depending on the geometrical characteristics of the casing. The strong scale effect, shown by some authors in the literature, is not observed in these tests.
The Effect of Dynamical Parameters on Precession in Rotary Drilling
Authors: The´ron A. , de Langre E. , Putot C.
Published: July 2002

Precession, which is the rolling motion of the drillstring on the walls of the borehole, is investigated by considering the various possible motions of a rotating disk in a circular hole. Due to the simplicity of the model, closed-form results are derived on the stability of precession and on the evolution of impacting motions towards precession. It is found that increasing coefficients of friction and contact damping have a favoring effect on precession, while the stiffness and damping of the drillstring bending mode have an opposing effect.
Tuning of a Hard Disk Drive Servo Controller Using Fixed-Structure H∞ Controller Optimization
Authors: Ibaraki Soichi , Tomizuka Masayoshi
Published: July 2002

As the storage capacity of hard disk drives (HDDs) increases dramatically, the demand for positioning control accuracy of a read/write head of HDD is becoming more stringent. This paper presents a tuning methodology for fixed-structure controllers using the H∞ optimization. The tuning of a PID (Proportional plus Integral plus Derivative) controller for head positioning of an HDD is presented as an application example. The H∞ optimization problem of fixed-structure controllers can be locally solved by using the transformation into an H∞ synthesis problem of static output feedback control. Simulation and experimental results show the effectiveness of the proposed approach as a fine tuning method to improve controller performance without requiring profound knowledge and experiences in manual loop-shaping.
Robust Stabilization of Axial Flow Compressor Dynamics Via Sliding Mode Design
Authors: Liaw Der-Cherng , Huang Jeng-Tze
Published: July 2002

Issues of the robust stabilization for axial-flow compressor dynamics with respect to the uncertainty in axisymmetric characteristics are presented. This is achieved by the design of sliding mode controllers. By assuming an actuation directly modulating the mass flow such as the close-coupled valve, the domain of attraction for the unstalled operating equilibrium will be enlarged to a great extent. Nonlocal robust stability of the operating equilibrium, with respect to the uncertainty in the unstable branch of axisymmetric compressor characteristic, is also provided by the proposed control laws. Moreover, it is demonstrated that the robust control scheme can be employed to fulfill the task of stall recovery. The proposed stabilization design does not require an explicit form for compressor characteristic.
Improved Tracking Control of Hydraulic Systems
Authors: Eryilmaz Bora , Wilson Bruce H.
Published: July 2002

Tracking control for hydraulic systems is a key system requirement, as these devices must often follow prescribed motions. Tracking control of hydraulic systems has been approached using both linear and nonlinear control laws. The latter provides improved performance, but at the expense of additional sensors. Further, the control laws often employ hydraulic fluid bulk modulus—a difficult-to-characterize quantity—as a parameter. To overcome these difficulties, we have developed a control design procedure that requires no additional sensors and is robust to variations in the bulk modulus. A dual approach of singular perturbation theory and Lyapunov techniques form the basis for the procedure. For the cases of a small-amplitude sinusoidal input and large-amplitude polynomial input, a candidate system achieved good tracking performance and exhibited outstanding robustness. The ability to accomplish good tracking in a robust manner with no additional sensors provides advantages over other nonlinear tracking algorithms.
Coordinated Longitudinal and Lateral Motion Control of Vehicles for IVHS
Authors: Lee Hyeongcheol , Tomizuka Masayoshi
Published: July 2002

This paper presents a systematic design of the combined control of vehicle longitudinal and lateral motions for the Intelligent Vehicle Highway Systems (IVHS). A fully coordinated control of the steering and the accelerating/braking actions is presented to maximize the ability of distributing the traction forces in a desired way. This control method covers a broad range of driving condition by removing several conventional simplification on vehicle dynamics, such as the linearized lateral traction force assumption, the bicycle model assumption, and the non-slip assumption. The nominal traction force concept is also introduced to handle the unknown traction forces. Robust Adaptive Control (RAC) by backstepping for MIMO nonlinear systems is utilized to control the unmatched nonlinear vehicle dynamics, in the presence of parametric uncertainties and uncertain nonlinearities.
Transparency and Stability Robustness in Two-Channel Bilateral Telemanipulation
Authors: Fite Kevin B. , Speich John E. , Goldfarb Michael
Published: July 2002

This paper presents a two-channel architecture and design approach that enables a simultaneous increase in the transparency and stability robustness of a bilateral teleoperation system, and additionally provides a high degree of transparency robustness to uncertainty in the operator and environment dynamics. The former is provided by the use of a loop-shaping filter incorporated on the master-to-slave motion command, and the latter by local feedback loops around both the master and slave manipulators. The proposed architecture and design approach are illustrated on a single-degree-of-freedom example with and without a communication channel time delay. Finally, the implications of scaling on the stability of the teleoperator loop are discussed.
Multi-Rate Feedforward Tracking Control for Plants With Nonminimum Phase Discrete Time Models
Authors: Gu Yuping , Tomizuka Masayoshi
Published: July 2002

This paper is concerned with performance enhancement of tracking control systems by multi-rate control. The feedback controller is updated at the same rate as the sampling rate of the output measurements. The feedforward controller processes the desired output signal for high accuracy tracking, and its output is updated at a rate N-times faster than the sampling rate of the output measurements. The discrete time model of the controlled plant may possess unstable zeros, and the zero phase error tracking controller (ZPETC) is used as a feedforward controller. Inter-sample behavior of the plant is included in evaluating the tracking performance of the multi-rate system. Illustrative examples are given to show advantages of the proposed multi-rate feedback/feedforward control scheme.
Thermal Math Modeling and Analysis of an Electronic Assembly
Authors: Shukla K. N.
Published: July 2002

This paper presents a mathematical model for a three-dimensional thermal analysis of a circuit board with multiple heat dissipating sources. The model considers the three-dimensional flat plate with discrete surface heat sources and integral transform technique is employed to determine the temperature distribution. The calculation procedure for the thermal characteristics of a circuit board, with surface mounted components, is presented and the solution is compared with those obtained from the finite element method. Also, the temperature distribution of a two-layered circuit board is presented in terms of Green’s function.
IGBT Package Design for High Power Aircraft Electronic Systems
Authors: Sarvar Farhad , Whalley David C. , Low Ming K.
Published: July 2002

This paper will discuss the design of semiconductor packages having integrated air cooled heatsinks for use in high power electronic systems. It will demonstrate how simple models of the heat transfer from the heatsink fins, which are based on empirical correlations, may be utilized in combination with either simple analytical models or two-dimensional finite difference (FD) models of the heat conduction from the semiconductor die through the multilayer package structure to the base of the fins. These models allow the rapid evaluation of performance under both steady-state and transient overload conditions, and can be used to rapidly explore a wide range of design options before selecting candidate layouts for more detailed evaluation using 3D analysis tools. Wind tunnel experiments, which will also be reported, have been carried out to verify the modeling results for different semiconductor device layouts. These trials demonstrate excellent agreement between the models and experimental results.
Blood Flow in Abdominal Aortic Aneurysms: Pulsatile Flow Hemodynamics
Authors: Finol Ender A. , Amon Cristina H.
Published: July 2002

Numerical predictions of blood flow patterns and hemodynamic stresses in Abdominal Aortic Aneurysms (AAAs) are performed in a two-aneurysm, axisymmetric, rigid wall model using the spectral element method. Physiologically realistic aortic blood flow is simulated under pulsatile conditions for the range of time-averaged Reynolds numbers 50⩽Rem⩽300, corresponding to a range of peak Reynolds numbers 262.5⩽Repeak⩽1575. The vortex dynamics induced by pulsatile flow in AAAs is characterized by a sequence of five different flow phases in one period of the flow cycle. Hemodynamic disturbance is evaluated for a modified set of indicator functions, which include wall pressure pw, wall shear stress τw, and Wall Shear Stress Gradient (WSSG). At peak flow, the highest shear stress and WSSG levels are obtained downstream of both aneurysms, in a pattern similar to that of steady flow. Maximum values of wall shear stresses and wall shear stress gradients obtained at peak flow are evaluated as a function of the time-average Reynolds number resulting in a fourth order polynomial correlation. A comparison between predictions for steady and pulsatile flow is presented, illustrating the importance of considering time-dependent flow for the evaluation of hemodynamic indicators.
Elastic-Plastic Finite Element Analysis of Partial Slip Rolling Contact
Authors: Xu Biqiang , Jiang Yanyao
Published: July 2002

The finite element model with the implementation of a robust cyclic plasticity theory was used to simulate the elastic-plastic stresses for the partial slip (stick-slip) line rolling contact. Detailed rolling contact stresses and strains were obtained for up to 40 rolling passes. The partial slip condition greatly affects the residual stress in the rolling direction and the residual shear strain within a thin layer of material near the contact surface. The residual stress in the axial direction was not significantly influenced by the partial slip condition. An increase in friction coefficient drives the location of maximum shear strain to the contact surface. In addition, a comparison was made between the finite element results and the results obtained from an approximate method.
Approximation of Power Flow Between Two Coupled Beams Using Statistical Energy Methods
Authors: Tan Yung-Chang , Castanier Matthew P. , Pierre Christophe
Published: July 2002

In this work, an investigation is performed into developing a general framework for predicting the power flow between coupled component structures with uncertain system parameters. A specific example of two coupled beams is considered, in which a torsional spring is attached at the coupling point to adjust the coupling strength. The power flow in the nominal system is formulated using component mode synthesis (CMS). First, the parameter-based statistical energy method, which employs free-interface component modes, is applied to obtain approximations for the ensemble-averaged power flow with each beam length having a uniformly-distributed random perturbation. Then, using fixed-interface component modes and constraint modes, the Craig-Bampton method of CMS is employed to formulate the nominal power flow equation in terms of the constraint-mode degrees of freedom. This fixed-interface CMS method is seen to provide a systematic and efficient platform for power flow analysis. Using this CMS basis, a general approximation for the ensemble-averaged power flow is formulated regardless of the probability distribution of the random parameters or the coupling strengths between the substructures. This approximation is derived using Galerkin’s method, in which each modal response is expanded in locally linear interpolation functions in the random system parameters. The proposed general framework is numerically validated by comparisons with wave approximations from the literature for this two-coupled-beam system.
Epoxy Nanocomposite Capacitors for Application as MCM-L Compatible Integral Passives
Authors: Bhattacharya Swapan K. , Tummala Rao R.
Published: July 2002

Polymer/ceramic composite emerges as a novel material system for application as integral capacitors for the next generation of microelectronic industry where the discrete passive components such as capacitors, resistors, and inductors are likely to be replaced by the embedded components. In this study, epoxy based nanocomposites are selected due to their low-cost and low temperature processing advantages in comparison to the traditional polymers used in the microelectronic industry today. Other potential advantages of epoxy materials could be their aqueous based fabrication process and availability in the form of dry films for direct lamination onto substrates. This paper reports dielectric properties of epoxy nanocomposites made from three commercially available resin composites (i) a solvent based photodefinable epoxy, (ii) an aqueous based photodefinable epoxy, and (iii) a non-photodefinable epoxy. Possible avenues for achieving higher capacitance density in polymer/ceramic composites for future needs have been discussed. Deposition of polymer/ceramic thin films on a 300 mm×300 mm PWB and glass substrates has been demonstrated using a state-of-the-art meniscus coater. The end goal of this study is to develop a defect-free manufacturable process for depositing and patterning particulate epoxy composite capacitors on large area PWB substrates. It is believed that the large area process will reduce the overall manufacturing costs and increase process yield, thus facilitate the economic viability of the integral passive technology.
A Generic Trajectory Verifier for the Motion Planning of Parallel Robots
Authors: Merlet Jean-Pierre
Published: July 2002

In this paper we consider the problem of trajectory verification for a classical Gough-Stewart platform i.e. we want to verify if a given trajectory obeys various criteria which define its validity, for example that the trajectory lies fully inside the workspace of the robot and is singularity-free. We propose an almost real-time method that may deal with almost any trajectory and any validity criterion and can manage uncertainties on the specified trajectory, for example to take into account control errors.
Rolling of Thin Strip and Foil: Application of a Tribological Model for “Mixed” Lubrication
Authors: Le HR , Sutcliffe M. P. F.
Published: July 2002

A mechanical model of cold rolling of foil is coupled with a sophisticated tribological model. The tribological model treats the “mixed” lubrication regime of practical interest, in which there is “real” contact between the roll and strip as well as pressurized oil between the surfaces. The variation of oil film thickness and contact ratio in the bite is found by considering flattening of asperities on the foil and the build-up of hydrodynamic pressure through the bite. The boundary friction coefficient for the contact areas is taken from strip drawing tests under similar tribological conditions. Theoretical results confirm that roll load and forward slip decrease with increasing rolling speed due to the decrease in contact ratio and friction. The predictions of the model are verified using mill trials under industrial conditions. For both thin strip and foil, the load predicted by the model has reasonable agreement with the measurements. For rolling of foil, forward slip is overestimated. This is greatly improved if a variation of friction through the bite is considered.
Effect of Flow Regime and Void Fraction on Tube Bundle Vibration
Authors: Taylor C. E. , Pettigrew M. J.
Published: July 2002

Two-phase cross flow occurs in industrial heat exchangers such as condensers, boilers, and steam generators. Under certain flow regimes and fluid velocities, the fluid forces result in tube vibration and possibly tube damage due to fretting or fatigue. Prediction of these fluid forces requires an understanding of the flow regimes found in heat exchanger tube bundles. Measurements of void fraction within a tube array were taken as an initial step in determining the two-phase flow patterns. The tests were conducted in a Freon 134a test loop at about 1 MPa and 30°C. The measurements were compared against void fraction models commonly used in heat exchanger thermalhydraulic simulation codes and against available flow regime maps. Not surprisingly, the results indicate that a drift-flux model more accurately predicts the void fraction within a tube array. The measurements also confirm the existence of nonuniform void fraction radially around the tube. Based on these measurements and available literature, appropriate void fraction models for use in flow-induced vibration design guidelines are discussed.
A Model of Pre-Strain Effects on Fracture Toughness
Authors: Cosham Andrew
Published: July 2002

A simple theoretical model for predicting the effect of tensile pre-strain on fracture toughness has been developed using the local approach. The HRR singularity is assumed to describe the stress-strain field around the crack tip. A stress-modified critical strain-controlled model is assumed to describe ductile fracture (and a critical stress-controlled model for cleavage fracture). The Rice and Tracey void growth model is used to characterize the variation of the critical strain with the stress state. The model further assumes that the fracture process does not change with increasing pre-strain. The effect of pre-strain is expressed in terms of an equation for the ratio of the fracture toughness of the pre-strained material to that of the virgin material. The model indicates that the effect of tensile pre-strain on fracture resistance can be characterized in terms of the effect of pre-strain on the stress-strain characteristics of the material, the critical fracture strain for a stress state corresponding to that during pre-strain, and several parameters that relate to the conditions for ductile fracture (or cleavage fracture). Previous experimental studies of the effect of pre-strain on toughness are summarized and compared with the predictions of the model.
On the Estimation of Nonstationary Functional Series TARMA Models: An Isomorphic Matrix Algebra Based Method1
Authors: Fouskitakis George N. , Fassois Spilios D.
Published: July 2002

Functional Series Time-dependent AutoRegressive Moving Average (TARMA) models form an important class of nonstationary stochastic models offering high parsimony, tracking of “fast” and “slow” variations, high accuracy and resolution, as well as accurate capturing of both resonances and antiresonances. This paper considers the estimation of Functional Series TARMA models with polynomial functional spaces based upon a novel matrix algebra that is isomorphic to that of the noncommutative ring of time-varying polynomial operators expressed in terms of the model’s functional spaces. The Generalized estimation method introduced offers important advantages, such as the use of properly contracted functional spaces that is necessary for the elimination of asymptotic bias errors, the ability to handle AR and MA functional spaces of different dimensionalities, as well as improved accuracy through a streamlined realization. The method’s excellent performance characteristics are confirmed via Monte Carlo experiments and comparisons with an earlier Polynomial-Algebraic approach and the adaptive Recursive Maximum Likelihood ARMA method.
Numerical Study of Wire Bonding—Analysis of Interfacial Deformation Between Wire and Pad
Authors: Takahashi Yasuo , Inoue Michinobu
Published: July 2002

The purpose of the present study is to understand the interfacial deformation between pad and wire and the effect of the pad thickness, the pad hardness, and the tool shape on the interfacial deformation. The relationship between the bondability and the interfacial deformation (surface exposure to produce the clean surface) is summarized, because the bondability is largely affected by the interfacial deformation. A simple model of wire bonding is proposed for the numerical analysis. The model is based on the finite element method for rate sensitive materials and applicable to very large deformation processes. The numerical simulation made it possible to visualize the interfacial contacting process which occurs for several milli-seconds. It was suggested that the periphery bond is produced easily as the pad thickness decreases and the pad hardness increases. On the other hand, it was found that the thick pad and the groove tool can help the center bond formation. These results is explained by the distributions of the interfacial extension and the equivalent stress on the bonding interface. Also, the damage to the substrate (Si chip) is discussed, based on the numerical results.
Optimal Machine Tool Setting for Hypoid Gears Improving Load Distribution
Authors: Simon Vilmos
Published: July 2002

A method for the determination of optimal machine tool setting for manufacturing modified (mismatched) hypoid gears based on improved load distribution and reduced transmission errors is presented. The applied load distribution calculation is based on the conditions that the total angular position errors of the gear teeth being instantaneously in contact under load must be the same, and along the contact line of every tooth pair instantaneously in contact, the composite displacements of tooth surface points—as the sums of tooth deformations, geometrical surface separations, gear body bending and torsion, deflections of the supporting shafts, misalignments, and composite tooth errors—should correspond to the angular position of the gear. The tooth deformations consists of the bending and shearing deflections of gear teeth and of the local contact deformations of the mating surfaces. The tooth deflections are calculated by the finite element method. As the equations governing the load sharing and load distribution are nonlinear, an approximate and iterative technique is used to solve this system of equations. The method is implemented by a computer program. Using the program that was developed the influence of machine tool setting parameters for pinion manufacture on maximum tooth contact pressure, load distribution factor, and transmission errors is investigated. By successively choosing the optimal value for every machine tool setting parameter, and by applying the optimal set of these parameters, the maximum tooth contact pressure is reduced by 5.8%, the load distribution factor by 5.9%, and the angular position error of the driven gear by 65.4%, in regard to the hypoid gear pair manufactured by the machine tool setting determined by the commonly used method.
On the Study of Piezoresistive Stress Sensors for Microelectronic Packaging
Authors: Lwo Ben-Je , Kao Ching-Hsing , Chen Tung-Sheng , Chen Yao-Shing
Published: July 2002

Stress measurements in microelectronic packaging through piezoresistive sensors take the advantage of both in-situ and nondestructive. In this study, test chips with both p-type and n-type piezoresistive stress sensors, as well as a heat source, were first designed, then manufactured by a commercialized foundry so that the uniformity of the test chips was expected. Both temperature and stress calibrations were next performed through a special designed MQFP (Metal Quad Flat Package) and four-point bending (4PB) structure, respectively. Measurements of stresses which are produced due to both manufacturing process and thermal effects on the test chips were finally executed, and approximately linear relationships were observed between stress and temperature as well as stress and input power. It is concluded that n-type piezoresistive stress sensors are able to extract stress in microelectronic packaging with good accuracy.
Synthesis of Planar, Compliant Four-Bar Mechanisms for Compliant-Segment Motion Generation
Authors: Saggere L. , Kota S.
Published: July 2002

Compliant four-bar mechanisms treated in previous works consisted of at least one rigid moving link, and such mechanisms synthesized for motion generation tasks have always comprised a rigid coupler link, bearing with the conventional definition of motion generation for rigid-link mechanisms. This paper introduces a new task called compliant-segment motion generation where the coupler is a flexible segment and requires a prescribed shape change along with a rigid-body motion. The paper presents a systematic procedure for synthesis of single-loop compliant mechanisms with no moving rigid-links for compliant-segment motion generation task. Such compliant mechanisms have potential applications in adaptive structures. The synthesis method presented involves an atypical inverse elastica problem that is not reported in the literature. This inverse problem is solved by extending the loop-closure equation used in the synthesis of rigid-links to the flexible segments, and then combining it with elastic equilibrium equation in an optimization scheme. The method is illustrated by a numerical example.
Rotor/Seal Experimental and Analytical Study on Full Annular Rub
Authors: Yu J. J. , Goldman P. , Bently D. E. , Muzynska A.
Published: July 2002

Rotor/seal full annular rub, including synchronous (forward) and reverse (backward) precessions, has been investigated both experimentally and analytically. Of particular interest is the finding of reverse precessional full annular rub (dry whip) that occurs repeatedly in small clearance cases without any outside disturbance. The experimental results include rub triggering mechanism, mass unbalance, and rotative speed effects. A simplified mathematical model is used to interpret experimental results. Nonlinear solutions for both synchronous and reverse precessions are obtained along with instability zones. Mass unbalance effect on shifting from synchronous response to reverse rub and destabilizing factors such as dry friction, rotor damping, and seal stiffness, are discussed.
Synchronous Response Estimation in Rotating Machinery
Authors: Maslen E. H. , Sortore C. K. , Vázquez J. A. , Knospe C. R.
Published: July 2002

Synchronous response estimation attempts to determine the forced response (displacement) of a rotor at critical points which cannot be measured directly. This type of prediction, if accurate and reliable, has broad potential use in the rotating machinery industry. Many machines have close clearance points on their shafts, such as seals, which can easily be damaged by excess vibration. Accurate estimates of the actual level of vibration at these points could usefully assist machine operators in troubleshooting and in protecting the equipment from expensive damage. This type of response information can be used both to generate less conservative alarm limits and, if magnetic bearings are available, to directly guide the bearing controllers in restricting the rotor motion at these critical points. It is assumed that the disturbance forces acting upon the rotor are predominantly synchronous. The response estimate is constructed using the measurable response in conjunction with an estimator gain matrix derived from a model of the transmissibilities of the rotor system. A fundamental performance bound is established based on the single-speed set of measurements by bounding the response to the unmeasurable component of the disturbance force. Acknowledging that some model uncertainty will always exist, a robust performance analysis is developed using structured singular value (μ) analysis techniques. Assuming some reasonable levels of uncertainty for the model parameters (natural frequencies, modal dampings, mode shapes, bearing stiffnesses, and dampings) the results of the estimator construction and analysis establish feasibility of the proposed estimation. Two reference rotor models that are representative of industrially sized machines are used to demonstrate and evaluate the estimation. The unmeasurable response estimation errors consistently lie below 25 μm for the examples examined.
Embedded Self-Sensing Piezoelectric Active Sensors for On-Line Structural Identification
Authors: Giurgiutiu Victor , Zagrai Andrei N.
Published: July 2002

The benefits and limitations of using embedded piezoelectric active sensors for structural identification at ultrasonic frequency are highlighted. An analytical model based on structural vibration theory and theory of piezoelectricity was developed and used to predict the electro-mechanical (E/M) impedance response, as it would be measured at the piezoelectric active sensor’s terminals. The model considers one-dimension structures and accounts for both axial and flexural vibrations. Experiments were conducted on simple specimens in support of the theoretical investigation, and on realistic turbine blade specimen to illustrate the method’s potential. It was shown that E/M impedance spectrum recorded by the piezoelectric active sensor accurately represents the mechanical response of a structure. It was further proved that the response of the structure is not modified by the presence of the sensor, thus validating the latter’s noninvasive characteristics. It is shown that such sensors, of negligible mass, can be permanently applied to the structure creating a nonintrusive sensor array adequate for on-line automatic structural identification and health monitoring. The sensor calibration procedure is outlined. Numerical estimation of the noninvasive properties of the proposed active sensors in comparison with conventional sensors is presented. Self-diagnostics capabilities of the proposed sensors were also investigated and methods for automatic self-test implementation are discussed. The paper underlines that the use of piezoelectric wafer active sensors is not only advantageous, but, in certain situations, may be the sole investigative option, as in the case of precision machinery, small but critical turbine-engine parts, and computer industry components.
Modal Reduction of a Nonlinear Rotating Beam Through Nonlinear Normal Modes
Authors: Pesheck Eric , Pierre Christophe , Shaw Steven W.
Published: July 2002

A method for determining reduced-order models for rotating beams is presented. The approach is based on the construction of nonlinear normal modes that are defined in terms of invariant manifolds that exist for the system equations of motion. The beam considered is an idealized model for a rotor blade whose motions are dominated by transverse vibrations in the direction perpendicular to the plane of rotation (known as flapping). The mathematical model for the rotating beam is relatively simple, but contains the nonlinear coupling that exists between transverse and axial deflections. When one employs standard modal expansion or finite element techniques to this system, this nonlinearity causes slow convergence, leading to models that require many degrees of freedom in order to achieve accurate dynamical representations. In contrast, the invariant manifold approach systematically accounts for the nonlinear coupling between linear modes, thereby providing models with very few degrees of freedom that accurately capture the essential dynamics of the system. Models with one and two nonlinear modes are considered, the latter being able to handle systems with internal resonances. Simulation results are used to demonstrate the validity of the approach and to exhibit features of the nonlinear modal responses.
Monitoring Cutting Forces In Turning: A Model-Based Approach
Authors: Stein Jeffrey L. , Huh Kunsoo
Published: July 2002

The importance of monitoring the cutting force in the turning process has been well recognized in industry as well as in the open literature. This paper proposes a cutting force monitoring approach that does not utilize force dynamometers but rather estimates the cutting force based on the spindle motor current and speed as well as a model that relates these measurements to the cutting force. Motor current and speed can not only be inexpensively and reliably measured but, in addition, can be shown, along with the properly chosen model for the model-based estimator, to accurately estimate the cutting force. This method is demonstrated on a CNC lathe and its advantages and limitations are discussed.
System Dynamics and Control of a Linear Compressor for Stroke and Frequency Adjustment
Authors: Huang B. J. , Chen Y. C.
Published: July 2002

This paper presents results of an investigation on the system dynamics and the controller design of a linear compressor for stroke and frequency adjustment. A system dynamics model was derived and identified experimentally. A control system was designed based on the system dynamics model. The control system used a PDF (Pseudo-Derivative-Feedback) algorithm. The results of step response test for stroke regulation show that, it takes about 0.2 s for the regulation with small overshoot and negligible steady-state error. For the step change of operating frequency, it takes about 0.4 s to reach steady state with small tracking error. The control system also has very good performance for disturbance rejection. The transient periods are about 0.2 s with stroke variation to within 10%. The controller is shown to have the capability to replace the conventional crank-shaft mechanism as in a reciprocating compressor. The controller can also be used to regulate both stroke and frequency of the compressor during operation. The performance can thus be very flexible and efficient for a system using the linear compressor and the present control system.
Semi-Ellipsoidal Controlled Invariant Sets for Constrained Linear Systems
Authors: O’Dell Brian D. , Misawa Eduardo A.
Published: July 2002

This paper investigates an alternative approximation to the maximal viability set for linear systems with constrained states and input. Current ellipsoidal and polyhedral approximations are either too conservative or too complex for many applications. As the primary contribution, it is shown that the intersection of a controlled invariant ellipsoid and a set of state constraints (referred to as a semi-ellipsoidal set) is itself controlled invariant under certain conditions. The proposed semi-ellipsoidal approach is less conservative than the ellipsoidal method but simpler than the polyhedral method. Two examples serve as proof-of-concept of the approach.
Dynamics Analysis and Control of a Holonomic Vehicle With a Continuously Variable Transmission
Authors: Tahboub Karim A. , Asada Harry H.
Published: July 2002

This paper presents kinematic and dynamic analysis of a holonomic vehicle with continuously-variable transmission. Four ball wheels, independently actuated by DC motors, enable for moving the vehicle in any direction within the plane and rotating it around its center. The angle between the two beams holding the balls can be changed to alter the gear ratio and other dynamic characteristics of the vehicle. This feature is exploited in augmenting the vehicle stability, optimizing output power, selecting an appropriate gear ratio, and in impedance matching. A simple adaptive friction-compensation-based controller is proposed to handle the complex friction properties.
Ground-Coupled Heat and Moisture Transfer from Buildings Part 1–Analysis and Modeling*
Authors: Deru Michael P. , Kirkpatrick Allan T.
Published: July 2002

Ground-heat transfer is tightly coupled with soil-moisture transfer. The coupling is threefold: heat is transferred by thermal conduction and by moisture transfer; the thermal properties of soil are strong functions of the moisture content; and moisture phase change includes latent heat effects and changes in thermal and hydraulic properties. A heat and moisture transfer model was developed to study the ground-coupled heat and moisture transfer from buildings. The model also includes detailed considerations of the atmospheric boundary conditions, including precipitation. Solutions for the soil temperature distribution are obtained using a finite element procedure. The model compared well with the seasonal variation of measured ground temperatures.
Analyzing Industrial Furnace Efficiency Using Comparative Visualization in a Virtual Reality Environment
Authors: Freitag Lori , Urness Timothy
Published: July 2002

We describe an interactive toolkit used to perform comparative analysis of two or more data sets arising from numerical simulations. Several techniques have been incorporated into this toolkit, including (1) successive visualization of individual data sets, (2) data comparison techniques such as computation and visualization of the differences between data sets, and (3) image comparison methods such as scalar field height profiles plotted in a common coordinate system. We describe each technique in detail and show example usage in an industrial application aimed at designing an efficient, low-NOx burner for industrial furnaces. Critical insights are obtained by interactively adjusted color maps, data culling, and data manipulation. New paradigms for scaling small values in the data comparison technique are described. The display device used for this application is the CAVE virtual reality theater, and we describe the user interface to the visualization toolkit and the benefits of immersive 3D visualization for comparative analysis.
Impact of Machining Parameters on Machine Reliability and System Productivity
Authors: Freiheit Theodor , Hu S. Jack
Published: July 2002

This paper analyzes the impact of machining parameter selection on machining system productivity. The method involves prediction of machine tool reliability from mechanical failure based on process choices and production rate. The machine reliability is then input to a machining system production configuration to estimate productivity. Through a simple turning model example, it is demonstrated that an optimal production rate for maximum productivity exists. The best system configuration for maximum productivity is shown to be affected by the level of machine reliability and the choice of process parameters.
Design of a PZT Bimorph Actuator Using a Metamodel-Based Approach
Authors: Cappelleri David J. , Frecker Mary I. , Simpson Timothy W. , Snyder Alan
Published: July 2002

The design of a variable thickness piezoelectric bimorph actuator for application to minimally invasive surgery is proposed. The actuator is discretized into five segments along its length, where the thicknesses of the segments are used as design variables in the problem of optimizing both the force and deflection at the tip. Metamodeling techniques are used to construct computationally inexpensive approximations of finite element simulations and to rapidly explore the design space and the Pareto frontier. A prototype device and experimental verification of the analytical results are also discussed.
In-Plane Packaging Stress Measurements Through Piezoresistive Sensors
Authors: Lwo Ben-Je , Chen Tung-Sheng , Kao Ching-Hsing , Lin Yu-Lin
Published: July 2002

In our previous works, the piezoresistive sensors have been demonstrated to be accurate and efficient tools for stress measurements in microelectronic packaging. In this study, we first designed test chips with piezoresistive stress sensors, temperature sensors as well as heats, and the test wafers were next manufactured through commercialized IC processes. Piezoresistive sensors on silicon strips, which were cut directly from silicon wafers at a specific angle, were then calibrated, and highly consistent piezoresistive coefficients were extracted at various wafer sites so that both normal and shear stress on the test chips can be measured. Finally, we packaged the test chips into 100-pin PQFP structures with different batches and measured internal stresses on the test chips inside the packaging. After measuring packaging induced stresses as well as thermal stresses on several batches of PQFPs, it was found that the normal stress diversities were obvious from different batches of the packaging structure, and the shearing stresses were approximately zero in all of the PQFPs at different chip site.
Quantitative Analysis of Inner Force Distribution and Load Capacity of Grasps and Fixtures
Authors: Xiong Youlun , Ding Han , Wang Michael Yu
Published: July 2002

This paper focuses on a quantitative analysis for grasp planning and fixture design based on an analytical description of point contact restraint. In the framework, the analysis deals with the fundamental concepts of restraint cone, freedom cone, force-determinacy and relative form closure. A method is presented to quantify the performance of a fixture (or grasp) with two major characteristics of inner force distribution and load capacity. Two different fixturing (or grasp) models of simplex grasp and elastic grasp are presented. It is shown that the performance of these two types of grasp (or fixturing) could be measured with different performance indices. A minimax index (MMI) and a volume measure are defined for evaluating a simplex grasp, while a measure using the tolerable range of differential motion in the twist space or the allowable load polyhedron in the wrench space would be suitable for quantifying robustness and load capability of an elastic fixture system. Furthermore, for fixture system design a geometric analysis and reasoning procedure is described for the design of locators, clamps and supplementary supports. The aim of these proposed analysis and design techniques is to provide a scientific foundation for automated grasping/fixturing system design in the engineering practice.
Parallel Structures and Their Applications in Reconfigurable Machining Systems
Authors: Gopalakrishnan, V. , Fedewa, D. , Mehrabi, M. G. , Kota, and S. , Orlandea N.
Published: July 2002

Reconfigurable Machine Tools (RMTs), assembled from machine modules such as spindles, slides and worktables are designed to be easily reconfigured to accommodate new machining requirements. Their goal is to provide exactly the capacity and functionality, exactly when needed. In this paper, we present a novel parallely-actuated work-support module as a part of an RMT to meet the machining requirements of specific features on a family of automotive cylinder heads. A prototype of the proposed module is designed/built and experimental results regarding its performance are presented.
Kinematic Analysis of 3-DOF Position Mechanisms for Use in Hybrid Kinematic Machines
Authors: Tsai Lung-Wen , Joshi Sameer
Published: July 2002

This paper introduces a new kinematic architecture called the hybrid kinematic machine. A hybrid kinematic machine typically consists of a position mechanism and an orientation mechanism that can be arranged in series or in parallel to achieve the notion of modular and reconfigurable machining centers. To demonstrate the concept, four parallel manipulators with translational motion characteristics have been identified. The kinematics of these mechanisms are described. Then, the well-conditioned workspace of each mechanism is maximized, and the stiffness properties are mapped. A comparison of the workspace volume and stiffness properties of these four mechanisms indicates that the 3-RUU manipulator appears to be the best design among the four architectures.
Jacobian Analysis of Limited-DOF Parallel Manipulators
Authors: Joshi Sameer A. , Tsai Lung-Wen
Published: July 2002

This paper presents a methodology for the Jacobian analysis of limited degrees-of-freedom (DOF) parallel manipulators. A limited-DOF parallel manipulator is a spatial parallel manipulator which has less than six degrees-of-freedom. It is shown that a 6×6 Jacobian matrix, which provides information about both architecture and constraint singularities, can be derived by making use of the theory of reciprocal screws. The 3-UPU and 3-RPS parallel manipulators are used as examples to demonstrate the methodology.
Path Tracking Based on Closed-Loop Control for a Quadruped Robot in a Cluttered Environment
Authors: Chen Xuedong , Watanabe Keigo , Kiguchi Kazuo , Izumi Kiyotaka
Published: July 2002

In this paper, the path tracking control is studied for a quadruped robot, named TITAN-VIII, walking in a cluttered environment. A simple and efficient algorithm of path planning is proposed, which is characterized by finding turning-point in the walking environment for the robot. The generalized gait algorithm based on the static stability is presented for the continuous and omnidirectional crawl of the robot. Especially, the real-time robot localization in the walking environment, which is the key to the settlement of the path tracking control, is realized by dead-reckoning for the quadruped robot. Based on the above work, we design the closed-loop control architecture so that the robot is able to track the desired path in an obstacle-strewn environment. The reliability and effectiveness of the proposed method is demonstrated through the experimental results.