bluuebunny/crossref_metadata_2025 huggingface dataset:
Tension-Torsion Characteristics of the Canine Anterior Cruciate Ligament—Part II: Experimental Observations
Authors: Butler D. L. , Stouffer D. C.
Published: July 2009

An experimental program was devised to determine whether the canine anterior cruciate ligament (ACL), with an apparent helical twist of its component fiber bundles, could support a torque during axial loading to failure. At the point of first significant failure, the anterior cruciate was found to develop an average maximum torque of 122 ± 26 N-mm (X¯ ± SEM) for the nine tension-torsion tests performed. A nearly linear axial force-torque curve was also observed where the average slope of all tests was 5.2 ± 0.2 mm−1 (X¯ ± SEM). The experimental axial force data was then used to determine material parameters in the constitutive equation for the fascicle and underlying bone. A nonlinear ligament model based on this response was found to reproduce the axial force data adequately and to reasonably predict the observed ligament torque over the entire subfailure loading range. The presence of a ligament torque during axial loading has implications in the design and selection of a ligament substitute. Such a substitute has already been examined in the canine in another study. The results also suggest more refined experiments which could relate the mechanical properties of a ligament to its detailed macrostructure and insertion site geometries.
Model Simulation of Heat and Water Transport Dynamics in an Airway
Authors: Saidel G. M. , Kruse K. L. , Primiano F. P.
Published: July 2009

Heat and water transport processes in the respiratory tract depend on environmental conditions, breathing patterns, and the physiological state of the respiratory system. To study these processes, we have developed a mathematical model of the dynamics of temperature and water vapor in the radial and axial directions of an idealized trachea. The model is expressed as two implicit finite-difference equations and solved using an alternating-direction algorithm. Using these equations, we simulated the effects of inspired gas temperature and humidity, velocity profile, and flow rate on heat and water transport between the gas and airway wall. Under inspired gas conditions of low temperature or high relative humidity, supersaturation occurs. Increasing either the velocity gradient at the wall or the flow rate increases the heat and water transport rates. However, these rates change by only 10 percent when the velocity gradient is doubled, and by about 35 percent when flow rate undergoes a two-fold change. The model can be used with in-vivo data from the trachea to test hypotheses concerning normal and abnormal heat and water transport.
Effects of Fluid Flow on Living Vascular Cells
Authors: Dewey C. F.
Published: July 2009

Shear stress produced by a flowing fluid has been found to cause changes in the structure and function of vascular endothelial cells. They tend to become elongated and aligned with the direction of flow. They respond to changes in fluid shear stress (either from low shear to high shear or vice versa) by transiently increasing fluidphase endocytosis. And they are capable of producing intracellular actin and myosin filaments that are oriented in the flow direction.
Dynamical Relations for Left Ventricular Ejection: Flow Rate, Momentum, Force and Impulse
Authors: Back L. H. , Gordon D. G. , Ledbetter D. C. , Selzer R. H. , Crawford D. W.
Published: July 2009

An investigation was carried out to quantitatively evaluate left ventricular volume flow rate, momentum, force and impulse derived from application of conservation principles for mass and momentum of blood within the ventricle during the ejection phase. An automated digital image processing system was developed and applied to left ventricular angiograms which are computer processed and analyzed frame by frame to determine the dynamical relations by numerical methods. Our initial experience with force and impulse has indicated that neither quantity seemed to be a sensitive indicator of coronary artery disease as evaluated by qualitative angiography for the particular patient group studied. Utilization of the dynamical relations in evaluating human left ventricular performance requires improved means of measurement and interpretation of clinical studies.
Linear Approximations for Swing Leg Motion During Gait
Authors: Lee W. H. , Mansour J. M.
Published: July 2009

The applicability of a linear systems analysis of two-dimensional swing leg motion was investigated. Two different linear systems were developed. A linear time-varying system was developed by linearizing the nonlinear equations describing swing leg motion about a set of nominal system and control trajectories. Linear time invariant systems were developed by linearizing about three different fixed limb positions. Simulations of swing leg motion were performed with each of these linear systems. These simulations were compared to previously performed nonlinear simulations of two-dimensional swing leg motion and the actual subject motion. Additionally, a linear system analysis was used to gain some insight into the interdependency of the state variables and controls. It was shown that the linear time varying approximation yielded an accurate representation of limb motion for the thigh and shank but with diminished accuracy for the foot. In contrast, all the linear time invariant systems, if used to simulate more than a quarter of the swing phase, yielded generally inaccurate results for thigh shank and foot motion.
Elastic Properties of Arteries and Their Influence on the Cardiovascular System
Authors: To¨zeren A.
Published: July 2009

Pressure-volume relations of aorta and arteries are considered using a fiber-fluid continuum analysis. A Windkessel model is revised to investigate the effects of the exponential pressure-volume relation of the present study on the cardiovascular system. It is shown that the elastic properties of the fibers in large blood vessels play an important role in the circulation of blood in health and in disease.
An Isolated Rat Liver Model for the Evaluation of Thermal Techniques to Quantify Perfusion
Authors: Valvano J. W. , Allen J. T. , Walsh J. T. , Hnatowich D. J. , Tomera J. F. , Brunengraber H. , Bowman H. F.
Published: July 2009

An isolated, thermally regulated, perfused rat liver model system is presented. The model was developed to evaluate thermal methods to quantify perfusion in small volumes of tissue. The surgically isolated rat liver is perfused with an isothermal oxygenated Krebs-Ringer bicarbonate buffer solution via the cannulated portal vein. A constant-pressure head variable-resistance scheme is utilized to control the total flow to the liver. Total flow is quantified by hepatic vein collection. The spatial distribution of perfusion within the liver is determined using two independent methods. In the first method, radio-labelled microspheres are injected into the portal vein, and the regional flow distribution is determined from the relative radioactivity of each section of tissue. In the second method, the tissue is thermally perturbed, and the time constant of the tissue temperature recovery is measured. The regional distribution is determined from the relative time constants of each section of tissue. Both methods require the measurement of total liver flow to determine the absolute perfusion at each point. Results obtained by the two methods were well correlated (0.973). The rat liver system offers a stable, controllable, and measurable perfusion model for the evaluation of new perfusion measurement techniques.
The Intraaortic Balloon Pump: A Nonlinear Digital Computer Model
Authors: Kuklinski W. S. , Jaron D. , Ohley W. J. , Greenall R. K.
Published: July 2009

A computer based model for in-series cardiac assistance by intraaortic balloon pumping was developed in this study. The model, obtained from the Navier-Stokes and Continuity equations, was capable of computing pressures, volumetric flow rates and radii through the arterial system. The model was used to study the effects of a wide range of assist device timing adjustments on the benefits of ventricular assistance under conditions corresponding to those measured during animal experiments. The model was also used to study the relationship between device timing adjustments and the benefits of ventricular assistance under constant cardiovascular state conditions. Such studies are important in isolating the response of the system to assist device phasing from the response associated with system state. The results obtained in this study demonstrate that the hemodynamic response of the cardiovascular system to intraaortic balloon pumping is a sensitive function of both the state of the cardiovascular system and phasing of the assist device.
Patterns of Flow in the Left Coronary Artery
Authors: Sabbah H. N. , Walburn F. J. , Stein P. D.
Published: July 2009

The purpose of this investigation is to describe our preliminary observations of the overall pattern of flow in a mold of the left coronary artery of a pig. Flow in the coronary mold was visualized by the injection of dye into the sinus of Valsalva. Studies were performed during steady flow at rates of 100, 200, 300, 400 and 500 mL/min. Studies were also performed during pulsatile flow, using a pulse duplicator that simulated the magnitude and phasic pattern of coronary flow at rest and during reactive hyperemia. At conditions that simulated rest, mean coronary flow was adjusted to 121 mL/min of which 24 mL/min (20 percent) was systolic. During simulated reactive hyperemia, mean flow was 440 mL/min. Visualization of flow revealed the absence of disturbances of turbulence during both steady and pulsatile flow in the left anterior descending (LAD) and left circumflex (CIRC) coronary arteries throughout the entire range of flow studied. Prominent spiraling of flow occurred during steady and pulsatile flow. Spiraling of flow was not observed in the LAD at rest during pulsatile flow, but developed during simulated reactive hyperemia. Helical flows were observed in the CIRC both during simulated rest and reactive hyperemia. These observations suggest that helical flows may be characteristic features of flow in the left coronary artery; whereas turbulence may not be a feature of this flow field. Whether the spiraling of flow that we observed relates to the spiral distribution of early atheroma reported by others, is undetermined.
Theory and Experiment for the Effect of Vascular Microstructure on Surface Tissue Heat Transfer—Part I: Anatomical Foundation and Model Conceptualization
Authors: Weinbaum S. , Jiji L. M. , Lemons D. E.
Published: July 2009

A new theoretical model supported by ultrastructural studies and high-spatial resolution temperature measurements is presented for surface tissue heat transfer in a two-part study. In this first paper, vascular casts of the rabbit thigh prepared by the tissue clearance method were serially sectioned parallel to the skin surface to determine the detailed variation of the vascular geometry as a function of tissue depth. Simple quantitative models of the basic vascular structures observed were then analyzed in terms of their characteristic thermal relaxation lengths and a new three-layer conceptual model proposed for surface tissue heat transfer. Fine wire temperature measurements with an 80-μm average diameter thermocouple junction and spatial increments of 20 μm between measurement sites have shown for the first time the detailed temperature fluctuations in the microvasculature and have confirmed the fundamental assumptions of the proposed three-layer model for the deep tissue, skeletal muscle and cutaneous layers.
Theory and Experiment for the Effect of Vascular Microstructure on Surface Tissue Heat Transfer—Part II: Model Formulation and Solution
Authors: Jiji L. M. , Weinbaum S. , Lemons D. E.
Published: July 2009

In this paper the conceptual three-layer representation of surface tissue heat transfer proposed in Weinbaum, Jiji and Lemons [I], is developed into a detailed quantitative model. This model takes into consideration the variation of the number density, size and flow velocity of the countercurrent arterio-venous vessels as a function of depth from the skin surface, the directionality of blood perfusion in the transverse vessel layer and the superficial shunting of blood to the cutaneous layer. A closed form analytic solution for the boundary value problem coupling the three layers is obtained. This solution is in terms of numerically evaluated integrals describing the detailed vascular geometry, a capillary bleed-off distribution function and parameters describing the shunting of blood to the cutaneous layer. Representative heat transfer results for typical physiological conditions are presented.
A Computational Method for Stress Analysis of Adaptive Elastic Materials With a View Toward Applications in Strain-Induced Bone Remodeling
Authors: Hart R. T. , Davy D. T. , Heiple K. G.
Published: July 2009

A computational method has been developed to obtain numerical results in the stress analysis of adaptive elastic materials. The method is based on a 3-dimensional finite element model that can change geometry and material properties based on the local strain. The solution procedure is iterative; the model is updated in time steps based on the current remodeling to provide incremental remodeling predictions. The method provides a vehicle for examination of different continuum models and their corresponding parameters for strain-induced remodeling in long bone. Use of the method with simple models of theoretical interest is presented. Results show agreement with available analytical results as well as the importance of coupled remodeling effects not previously examined.
Evaluation of Local Blood Flow Velocity in Proximal and Distal Coronary Arteries by Laser Doppler Method
Authors: Kajiya F. , Tomonaga G. , Tsujioka K. , Ogasawara Y. , Nishihara H.
Published: July 2009

A high resolution laser Doppler velocimeter using an optical fiber was developed to evaluate detailed characteristics of phasic blood flow in the coronary artery. Local blood flow velocities were measured in the proximal (0.27 ± 0.05 cm i.d.) and the distal portion (0.09 ± 0.02 cm i.d.) of the left circumflex coronary artery of anesthetized, open-chest dogs. The velocity waveform in the central axial region of the vessel and the velocity profile across the vascular lumen were compared in the proximal and the distal portions.
An Experimental Study of Coronary Artery Fluid Mechanics
Authors: Altobelli S. A. , Nerem R. M.
Published: July 2009

Preserved baboon and canine hearts were perfused using an in-vitro pulsatile flow system. Flow rate and pulsation frequency were controlled, and velocity profile measurements were made at several sites on the left epicardial coronary arteries of each heart. Velocity profiles were measured using a multi-channel, pulsed ultrasonic Doppler velocimeter, and the data were processed with a laboratory microcomputer system. Flow in the left main coronary artery appeared to be similar to descriptions of developing curved tube flow, but an unexplained oscillation of the velocity profiles was observed in this artery. Near the bifurcation of the main coronary artery into the anterior descending and the circumflex, the pattern of velocity profile skewing appeared to be determined by the angle through which the daughter vessels turned from the main and the overall curvature of the “plane” of bifurcation. Several diameters downstream from the bifurcation the flow appeared to be quasi-steady.
The Influence of Muscle Model Complexity in Musculoskeletal Motion Modeling
Authors: Audu M. L. , Davy D. T.
Published: July 2009

A comparative study of four different muscle models in a musculoskeletal motion problem is made. The models vary in complexity from the simple input-output model to the more complex model of Hatze [I]. These models are used to solve a minimum time kicking problem using an optimal control algorithm. The results demonstrate the strong influence of the model choice on the various predicted kinematic and kinetic parameters in the problem. The study illustrates some of the advantages and disadvantages involved in trade-offs between model complexity and practicability in musculoskeletal motion studies. The results also illustrate the importance of appropriate detailed parameter estimation studies in the mathematical modeling of the musculoskeletal system.
The Effect of a Lathyritic Diet on the Sensitivity of Tendon to Strain Rate
Authors: Haut R. C.
Published: July 2009

While the tensile failure properties of rat-tail tendon depend on strain rate, the sensitivity to strain rate decreases with age, especially during sexual maturation. The object of this study was to determine the effect of an experimental model of chronic lathyrism on age-dependent changes in the sensitivity of developing tendon strength to strain rate. Tensile failure experiments were conducted at high and low strain rate on tendons excised from test and control animals aged 1 to 6 mo. The tensile “yield” response of tendon was significantly affected by the diet resulting in a reduced tensile strength and failure strain. While the sensitivity of tendon failure to strain rate was slightly elevated by the experimental diet, age-dependent changes compared with controls. Since the diet supplement is thought to inhibit covalent crosslinking of collagen in the developing tendon, other factors are likely responsible for decrease in the sensitivity of tendon strength to strain rate during maturation.
A Model of Tension and Compression Cracks With Cohesive Zone at a Bone-Cement Interface
Authors: Clech J. P. , Keer L. M. , Lewis J. L.
Published: July 2009

This paper gives an insight about compression and tension cracks as encountered at a bone-cement interface. Within the context of continuum theory of fracture, an analytical solution is presented for the problem of a bimaterial interface edge crack under uniaxial tension or compression, assuming no tangential slip along the crack faces since cement pedicles penetrate into the cancellous bone several millimeters. Also essential to the solution are cohesive zone effects that account for a strengthening mechanism over the crack faces. The solution provides a methodological framework for quantifying the influence of the cohesive zone on the magnitude of the stress singularity. Mode I crack tip stress intensity factors are calculated at different stages of the loading and unloading phases under uniaxial tension or compression. Finally, an inelastic mechanism is presented that gives theoretical support to explain the formation of interfacial compression cracks, a phenomenon that was not previously appreciated and that arises from the rigid cement being forced into the more compliant cancellous bone.
The Influence on Long Jump Performance of the Aerodynamic Drag Experienced During the Approach and Aerial Phases
Authors: Ward-Smith A. J.
Published: July 2009

A new analysis of long jump performance is presented, in which mathematical models of both the approach and aerial phases are considered. Equations describing each phase have been set down and solved by numerical integration. It is demonstrated that both wind and altitude have important effects on long jump performance, and some representative calculations have been made. Increased jump lengths, resulting from wind assistance or altitude, are shown to be primarily attributable to the increased sprinting speed attained during the approach phase. The present work indicates that previous calculations of the increment in jump length due to altitude which Beamon enjoyed when he established his world record at the Mexico Olympics of 1968 may have been underestimated by a wide margin.
The Elongation and Orientation of Cultured Endothelial Cells in Response to Shear Stress
Authors: Levesque M. J. , Nerem R. M.
Published: July 2009

Vascular endothelial cells appear to be aligned with the flow in the immediate vicinity of the arterial wall and have a shape which is more ellipsoidal in regions of high shear and more polygonal in regions of low shear stress. In order to study quantitatively the nature of this response, bovine aortic endothelial cells grown on Thermanox plastic coverslips were exposed to shear stress levels of 10, 30, and 85 dynes/cm2 for periods up to 24 hr using a parallel plate flow chamber. A computer-based analysis system was used to quantify the degree of cell elongation with respect to the change in cell angle of orientation and with time. The results show that (i) endothelial cells orient with the flow direction under the influence of shear stress, (ii) the time required for cell alignment with flow direction is somewhat longer than that required for cell elongation, (iii) there is a strong correlation between the degree of alignment and endothelial cell shape, and (iv) endothelial cells become more elongated when exposed to higher shear stresses.
Epicardial Coronary Blood Flow Including the Presence of Stenoses and Aorto-Coronary Bypasses—I: Model and Numerical Method
Authors: Rooz E. , Wiesner T. F. , Nerem R. M.
Published: July 2009

A computer model and numerical method for calculating left epicardial coronary blood flow has been developed. This model employs a finite-branching geometry of the coronary vasculature and the one-dimensional, unsteady equations for flow with friction. The epicardial coronary geometry includes the left main and its bifurcation, the left anterior descending and left circumflex coronary arteries, and a selected number of small branches. Each of the latter terminate in an impedance, whose resistive component is related to intramyocardial compression through a linear dependence on left ventricular pressure. The elastic properties of the epicardial arteries are taken to be non-linear and are prescribed by specifying the local small-disturbance wave speed. The model allows for the incorporation of multiple stenoses as well as aorto-coronary bypasses. Calculations using this model predict pressure and flow waveform development and allow for the systematic investigation of the dependence of coronary flow on various parameters, e.g., peripheral resistance, wall properties, and branching pattern, as well as the presence of stenoses and bypass grafts. Reasonable comparison between calculations and earlier experiments in horses has been obtained.
Hydrodynamics of Fiuidizatlon and Heat Transfer: Supercomputer Modeling
Authors: Gidaspow Dimitri
Published: July 2009

A review of the hydrodynamic models of fluidization is presented. Three hydrodynamic models have been programmed on supercomputers to predict the variation of void fractions, pressure, and gas and solid velocities as a function of position and time. The ability of the models to predict bubbles in fluidized beds, bed-to-wall heat transfer coefficients, and product distributions in gasifiers shows their great potential as new research and development tools. These supercomputer models should aid in improving the performance of chemical plants processing solids that are reported to have been performing below their design expectations for the last 20 years (Merrow, 1985).
Energy Release Protection for Pressurized Systems. Part II: Review of Studies Into Impact/Terminal Ballistics
Authors: Brown Samuel J.
Published: July 2009

In order to assess whether or not there is a need for protection against the failure of a pressure system, the engineer must evaluate the hazards associated with rupture. The hazards are divided into two categories: (a) force/displacement and (b) degenerative. Force/displacement is classified into (1) kinetic energy associated with the atmosphere: blast, (2) kinetic energy of objects (fragmentation and impact of missiles), and (3) kinetic energy associated with foundations: soil foundation motion. The first article of this series [Energy release protection from pressurized systems: Part I Review of studies into blast and fragmentation, Appl Mech Rev38 (Dec), 1625–1651 (1985)] has set the stage for this paper, which reviews the studies into predicting the performance (mechanics) of a receptor (target, containment, barricade, shelter) that is impacted by a missile. The study into the prediction of target missile performance or terminal ballistics has occupied interests of man since the development of a projectile as a weapon. One of the earliest publications of terminal ballistics is reported by Robins (1742). A number of experimental studies during the 1800s are reported by Holie (1950). These early experiments set the pattern for the reliance on experimental programs to define semiempirical formula to predict missile–target responses (such as penetration, perforation, spalling, and scabbing) into the 20th century. This is due to the fact that theoretically derived equations to predict missile target performance have enjoyed only limited success because of the complexity of the problems to be solved. Numerical methods essentially had to wait for the development of the high speed digital computers in the early 1960s. Historically the finite difference methods have received the earliest use in simulating impact. They tend to be more computationally cost effective than finite element programs. However, because of the generality of the finite element method to idealize structures geometrically for a considerable range of mechanics problems, it has received the greater attention of research and development over the last two decades and is capable of solving wave propagation, nonlinear material, and nonlinear large deformation problems. The computer codes developed to solve impact problems are generally characterized as either Lagrangian or Eulerian. In this paper, a brief discussion will be provided covering the development of target/missile formulas, associated experimental programs and numerical methods.
Mechanics of Distributed Cracking
Authors: Bazˇant Zdeneˇk P.
Published: July 2009

This paper reviews some interesting recent results on mesh sensitivity and strain localization instability, nonlocal and micromechanics models, and the size effect in failure due to distributed cracking.
Applied Mechanics Problems in the Oil and Gas Industry
Authors: Roegiers Jean-Claude
Published: July 2009

The petroleum industry offers a broad spectrum of problems that falls within the domain of expertise of mechanical engineers. These problems range from the design of well production equipment to the evaluation of formation responses to production and stimulation. This paper briefly describes various aspects and related difficulties with which the oil industry has to deal, from the time the well is spudded until the field is abandoned. It attempts to delineate the problems, to outline the approaches presently used, and to discuss areas where additional research is needed. Areas of current research activity also are described; whenever appropriate, typical or pertinent case histories are used to illustrate a point.
Control of Machine Tools and Robots
Authors: Koren Yoram
Published: July 2009

The principal control structure of CNC machine tools and industrial robots is similar, since in both systems each axis of motion is separately controlled with a position feedback loop. Nevertheless, the control of robots is more complex, since they include more degrees of freedom and the motion of each joint is not independent of other joints. This paper compares the conventional control schemes of both systems, and summarizes recent developments in adaptive control of machine tools and robots.
Dynamic Simulation of Flexible Manufacturing Systems (FMS)
Authors: Ranky Paul G.
Published: July 2009

The simulation method to be used in FMS should be multilevel and dynamic and should incorporate solid modeling techniques. This means that operation control simulation in FMS should rely on information sources provided from different levels of the organization; thus there should be an overall planning level and a dynamic, or real-time, level. One should also conclude from this article that, without understanding the design principles and operating rules of FMS, the simulation model created will be inadequate and in most cases misleading. Because of this, FMS simulation should be performed by a team, incorporating the manufacturing system designers as well as the simulation experts.
CAD in the CIM Environment: Where Do We Go From Here?
Authors: Allen Dell K. , Van Twelves W.
Published: July 2009

The importance of computer-aided design (CAD) has not been fully appreciated as it relates to computer integrated manufacturing (CIM). The CAD product definition model can provide essential information for many down-stream production, estimating, tooling, and quality assurance functions in the CIM environment. However, the product definition model may be inaccurate or incomplete, thus causing incomplete communication with possible scrap, re-work, and missed production deadlines. Other problems are related to the fact that many of our expert designers are retiring and taking their expertise with them. Merely being able to make 2D or 3D drawings on a CAD workstation does not make its operator a designer. A knowledge of production processes, tolerances, surface finish, and material selection is needed to supplement a designers knowledge of user needs, product functional requirements, operating conditions, cost, quality, and reliability targets. One of the most promising methods for providing timely and accurate information to the designer on an “as-needed” basis is through the use of expert design systems. Such systems promise to bridge the knowledge gap between CAD and CAM and help to incorporate these functions into the overall CIM environment.
Advanced Material Handling
Authors: Ammons Jane C. , McGinnis Leon F.
Published: July 2009

With the advent of automation in manufacturing and warehousing, material handling is being seen as a focal point of total system integration and control. In contrast to mechanical design problems, this paper addresses current issues in the design and operation of material handling systems from an overall systems viewpoint. Topics reviewed include automated storage and retrieval systems, order picking, order sortation and accumulation, and transportation. The purpose is to overview essential issues, describe representative research, and identify critical needs for future study.
Model Validation of a Magnetic Ball Levitation System
Authors: Hanasoge Aravind , Omran Ashraf , Alberts Thomas
Published: July 2009

In this paper, modeling, simulation and experimental validation of a magnetic ball suspension system are presented. Non-linear empirical expressions for inductance and electromagnetic force are determined using experimental data. A simple PID controller and a Gain scheduling PID controller are designed based on the linearized model. The controllers are used in real time levitation and tracking of a steel ball. Numerical simulation is carried out using Simulink. The derived model is verified by comparing the simulation results with experimental results.
Control of Space Structures Using Cable Actuators
Authors: Issa Jimmy , Mukherjee Ranjan , Shaw Steven W.
Published: July 2009

We explore the use of cable actuators for vibration suppression in space structures. The dynamics of the structure and cable-structure interaction are modeled using finite elements. It is found that the cable has two distinct effects on the structure. The first is a parametric effect, which changes the stiffness of the structure, and the second is a direct effect resulting from an external force on the structure. A general control scheme is designed using passivity analysis, where the input is the cable tension. The study is divided into two parts. In the first part, control by stiffness variation is investigated placing special emphasis on cable placement on the structure. In the second study, control by the direct force is examined and numerical and experimental results are presented.
Path Force Control for Friction Stir Welding Processes
Authors: Zhao Xin , Kalya Prabhanjana , Landers Robert G. , Krishnamurthy K.
Published: July 2009

In Friction Stir Welding (FSW) processes, force control can be used to achieve good welding quality. This paper presents the systematic design and implementation of a FSW path force controller. The path force is modeled as a nonlinear function of the FSW process parameters (i.e., plunge depth, tool traverse rate, and tool rotation speed). An equipment model, which includes a communication delay, is constructed to relate the commanded and measured tool rotation speed. Based on the dynamic process and equipment models, a feedback controller for the path force is designed using the Polynomial Pole Placement technique. The controller is implemented in a Smith Predictor–Corrector structure to compensate for the inherent equipment communication delay and the controller parameters are tuned to achieve the best closed loop response possible given equipment limitations. In the path force controller implementation, a constant path force is maintained, even in the presence of gaps, and wormhole generation during the welding process is eliminated by regulating the path force.
Semi-Autonomous Teleoperation of Multiple Wheeled Mobile Robots Over the Internet
Authors: Lee Dongjun
Published: July 2009

We propose a semi-autonomous teleoperation control framework for wheeled mobile robots with nonholonomic constraints and second-order Lagrangian dynamics over the Internet. The proposed control architecture consists of the two control-loops: 1) local autonomous formation control, which, residing in the common workspace of the robots, ensures rigid formation-keeping among the robots regardless of human-command, varying-delay/packet-loss of the Internet, and external disturbance without any holding-fixture (e.g. fixture-less cooperative grasping); and 2) teleoperation-loop, which enables a (remote or coexisting) human operator to stably tele-drive the overall team maneuver (e.g. grasped object’s centroid motion) over the Internet with haptic-feedback. Simulation is performed to validate/highlight properties of the proposed control framework.
Indirect Adaptive Control of a Class of Marine Vehicles
Authors: Morel Yannick , Leonessa Alexander
Published: July 2009

A nonlinear adaptive framework for bounded-error tracking control of a class of non-minimum phase marine vehicles is presented. The control algorithm relies on a special set of tracking errors guaranteeing satisfactory tracking performance and stable internal dynamics. First, the design of a model-based nonlinear control law, providing asymptotic stability of the error dynamics, is presented. This control algorithm solves the tracking problem for the considered class of marine vehicles, assuming full knowledge of the system model. Then, the analysis of the zero dynamics is carried out, which illustrates the efficacy of the chosen set of tracking errors in stabilizing the internal dynamics. Finally, an indirect adaptive technique is used to address parametric uncertainties in the model. The resulting adaptive control algorithm guarantees Lyapunov stability of the tracking errors and of the parameter estimates, and convergence of the tracking errors to zero. Numerical simulations illustrate the performance of the adaptive algorithm.
A Multiobjective Solution Approach to Fault Detection and Isolation of LPV Systems
Authors: Cai Xuejing , Wu Fen
Published: July 2009

In this paper, we consider the fault Detection and isolation (FDI) problem for faulty linear parameter-varying (LPV) systems subject to disturbances and propose a observer-based solution by using multiobjective optimization techniques. To simply the design process, a general faulty LPV system will be constructed from standard LPV description by converting actuator/system component faults into sensor faults at first. Then a bank of LPV FDI filters will be designed to identify each fault. Each FDI filter could generate a residual signal to track individual fault with minimum error and suppressing the effects of disturbances and other fault signals. The design of FDI filters will be formulated as multiobjective optimization problems in terms of linear matrix inequalities (LMIs) and can be solved efficiently. Two numerical examples are also presented to demonstrate the proposed fault detection and isolation approach on both LPV and LTI systems.
Reverse Dynamic Optimization of Variable Displacement Engine Operation and System Integration
Authors: Baglione Melody L. , Duty Mark J.
Published: July 2009

Variable displacement engines are a proven technology for improving fuel economy without sacrificing performance. To achieve the most benefit, variable displacement needs to be properly integrated into the vehicle system. A reverse tractive road load demand model, dynamic optimization methodology, and Matlab®/Simulink® based tool are developed to address the challenge of properly matching variable displacement engines and their control strategies to specific vehicle applications for improved overall vehicle system efficiency. Using a reverse model and a dynamic programming algorithm, optimal variable displacement control strategies considering the gear shift and torque converter clutch interaction effects for various drive cycles are developed virtually. The development of an optimal control strategy facilitates better integration of variable displacement into vehicle system designs.
Modeling and Control of Hybrid Electric Vehicles for Fuel and Emission Reduction
Authors: Kum Dongsuk , Peng Huei , Bucknor Norman
Published: July 2009

Control of Hybrid Electric Vehicles (HEVs) is an active research area. Much of the past research focused on one aspect of hybrid vehicle performance–fuel economy. While fuel economy is important for HEVs, reduction of emissions is another major performance of interest, due to ever-tightening emission regulations. Minimization of fuel consumption may have a trickle-down effect but does not guarantee reduced emissions. In fact, over-zealous pursuit of fuel consumption reduction may compromise emission. This paper investigates the emissions formation mechanism, develops an emission model that predicts tail-pipe emissions, and formulates a supervisory control problem of emissions reduction. The Dynamic Programming (DP) technique is employed to solve the optimal control problem of parallel HEVs for both emission reduction and fuel economy. The DP solution of the optimal control problem shows that tail-pipe emissions could be significantly reduced with negligible loss of fuel economy.
An Improved Method for Calculating Iterative Learning Control Convergence Rate
Authors: Barton Kira , Alleyne Andrew , Bristow Doug
Published: July 2009

In Iterative Learning Control (ILC), the lifted system is often used in design and analysis to determine convergence rate of the learning algorithm. Computation of the convergence rate in the lifted setting requires construction of large NxN matrices, where N is the number of data points in an iteration. The convergence rate computation is O(N2) and is typically limited to short iteration lengths because of computational memory constraints. In this article, we present an alternative method for calculating the convergence rate without the need of large matrix calculations. This method uses the implicitly restarted Arnoldi method and dynamic simulations to calculate the ILC norm, reducing the calculation to O(N). In addition to faster computation, we are able to calculate the convergence rate for long iteration lengths. This method is presented for multi-input multi-output, linear time-varying discrete-time systems.
Vision-Based Methods for Mobile Robot Localization and Wheel Sinkage Estimation
Authors: Reina Giulio , Milella Annalisa , Foglia Mario
Published: July 2009

External perception based on vision plays a critical role in developing improved and robust localization algorithms for mobile robots, as well as in gaining important information about the vehicle and the traversed terrain. This paper presents two novel methods to improve mobility on rough terrains by using visual input. The first method consists of a stereovision algorithm for 6-DoF ego-motion estimation, which integrates image intensity information and 3D stereo data using an Iterative Closest Point (ICP) approach. The second method aims at estimating the wheel sinkage of a mobile robot on deformable soil, based on the visual input from an onboard monocular camera, and an edge detection strategy. Both methods were implemented and experimentally validated on an all-terrain mobile robot, showing that the proposed techniques can be successfully employed to improve the performance of ground vehicles operating in uncharted environments.
On the Dynamics of Coupled Parametrically Forced Oscillators
Authors: Moehlis Jeff
Published: July 2009

It is well known that an autonomous dynamical system can have a stable periodic orbit, arising for example through a Hopf bifurcation. When a collection of such oscillators is coupled together, the system can display a number of phase-locked solutions which can be understood in the weak coupling limit by using a phase model. It is also well known that a stable periodic orbit can be found for a parametrically forced dynamical system, with the phase of the periodic orbit being locked to the forcing. Here we discuss the periodic solutions which occur for a collection of such parametrically forced oscillators that are weakly coupled together.
Experiments in Predictive Coordination of a Fuel Cell/Ultracapacitor Hybrid
Authors: Greenwell Wesley , Vahidi Ardalan
Published: July 2009

A rule-based and a model predictive power management strategy are evaluated in experiments for power management of a fuel cell/ultracapacitor hybrid. The two degrees of freedom provided by use of two dc/dc convertors enable independent low-level control of the DC BUS voltage and the current split between the fuel cell and ultracapacitor. The high-level control objectives are to respond to rapid variations in load while minimizing damaging fluctuations in fuel cell current and maintaining the ultracapacitor charge (or voltage) within allowable bounds. Experiments show that both strategies can be tuned to meet these control objectives; however the predictive nature of the model predictive scheme coupled with its ability to aggressively push the ultracapacitor to its constraint line results in smoother fuel cell current transients.
Dynamic Systems Modeling of Cortisol Stress Response
Authors: Tilbury D. M. , Felt B. T. , Kaciroti N. , Wang L. , Tardif T.
Published: July 2009

This paper presents preliminary results for using dynamic systems models to describe cortisol responses to stressful events. Linear, single-input single-output discrete-time models are used. Choices that must be made regarding interpolation and input modeling are discussed in some detail. Results are presented that indicate an impulse model for the stressful input gives a better fit than no input, and that logarithmic transformation of the data before model fitting gives no better results than using the raw data. The issue of stability of the resulting models is discussed. In addition, the paper discusses how the resulting dynamic systems models can be used for statistical analysis, as well as for predicting future stress responses.
HIL Simulation of a Track Type Tractor for Autonomous Controller Testing
Authors: Sleiman Nicolas , Reyer Julie A.
Published: July 2009

The mining industry is introducing several autonomous mining operations, however the development of these algorithms is extremely expensive. This paper discusses the integration of a Hardware In the Loop (HIL) simulation to earthmoving equipment to aid in the development of autonomous mining operations. The benefit of this simulation is to save time and money for engineers developing the autonomous features. The hardware setup contained machine components that were connected to the Electronic Control Modules (ECMs). The ECMs used in the lab setup were the same as those on the actual tract type tractors. Those ECMs receive input signals based on which they command the solenoids. The HIL simulator converts the analog outputs into digital ones. Then the HIL sends out digital or simulated outputs to the ECMs such as pressure and fuel levels. The results of this work compare simulated data and real machine test data of an autonomous feature. A comparison is presented between the autonomous feature and a human operator. Finally potential of the HIL is demonstrated examining the autonomous feature with different soil conditions.
Distributed Control and Collision Avoidance for Multiple Vehicles With Limited Sensing Using Constraint Forces
Authors: Zou Yunfei , Pagilla Prabhakar
Published: July 2009

A new, distributed control algorithm for multiple vehicles with limited sensing capability for each vehicle is developed in this paper. It is assumed that each vehicle can sense other vehicles in the group in only a limited region around it. Coordination of multiple vehicles in the presence of distance constraints is considered. The objective for each vehicle within the group is to reach a target point from any given initial location without any collisions. The notion of constraint forces is used to develop a distributed algorithm that is capable of achieving this objective. The distributed algorithm is scalable and allows for addition (removal) of vehicles to (from) the group. Simulation studies conducted on a number of examples show the effectiveness of the proposed distributed algorithm. A representative sample of the results from these studies is shown and discussed.
Video Tracking Control Algorithms for Unmanned Air Vehicles
Authors: Bencatel Ricardo , Correia Joa˜o , Sousa Joa˜o Borges , Gonc¸alves Gil M. , Pereira Elo´i
Published: July 2009

We present and discuss a modular flight control system suitable for video tracking natural structures with Unmanned Air Vehicles (UAVs), like rivers, roads or canals. The control system is modeled in the framework of hybrid automata, where each state corresponds to different control algorithms. We implemented four nonlinear turn-rate control algorithms and compared them in a simulation environment to assess tracking performance.
Developing and Automating Time Delay System Stability Analysis of Machinery Systems Using the Matrix Lambert W Function Method
Authors: Pietarila Kristel M. , Fales Roger
Published: July 2009

Stability analysis of time delayed (TD) systems is not easy to conduct since the addition of delays within a dynamic model results in irrational system equations. Traditional analysis methods involve adding model approximates representing delays. These approximates make the system equations rational, but can drive stable TD systems to instability as approximate accuracy is improved. A more advanced method would be an invaluable tool for simplifying the stability analysis procedure for TD systems. A new method for analyzing TD system stability without adding TD approximates to the system has been presented by Asl et al. [1, 2]. This method involves using the Lambert W function to obtain analytic solutions for a set of delay differential equations. The research presented in this paper discusses the development and automation of TD system stability analysis for a complex machinery system utilizing this new method, the matrix Lambert W (MLW) function TD stability analysis method.
Motion Simulation Based on Human Vestibular Sensors
Authors: Rodri´guez Carlos F. , Ochoa Lleras Nicola´s
Published: July 2009

This article presents a methodology for the definition of vehicle simulator motion cues based on the biomechanical response of the vestibular organs to motion stimuli. The proposed method begins with an extension of the human motion perception model which includes the simulator kinematics. The goal of this procedure is to define the motion cues so that they reproduce vestibular sensor signals matching those of a reference motion, in terms of the Sensor-State vector. This vector is estimated by using dynamic models of the vestibular organs’ biomechanics. A definition of equivalent motion based on properties of these models is introduced. This definition allows for the proposal of a strategy to imitate the vestibular sensor signals. The methodology has been tested in simulation with a 3-dof planar motion simulator, resulting in satisfactory results. Finally, the potential of the proposed methodology is discussed.