bluuebunny/crossref_metadata_2025 huggingface dataset:
Main Resonance of a Nonlinear Oscillator Under Semi-Active Control
Authors: Shen Yongjun , Yang Shaopu
Published: June 2008

The main resonance of a nonlinear oscillator under semi-active control is investigated, where the bifurcation and singularity are also included. The Main resonance is obtained analytically at first, and then all the bifurcation diagrams are researched and classified in the space composed of the amplitude of excitation and the detuning parameter through singularity theory. It could be proved that the response is the universal unfolding of the winged cusp bifurcation, and all of the bifurcation diagrams of the system are verified through numerical method. It is shown that this analytical method could not only analyze the response of the semi-active control oscillator, but also research the global dynamic behavior.
Nonlinear Bending-Torsion Flutter of a Cantilever Wing Subjected to Parametric Excitation
Authors: Ibrahim R. A. , Castravete S. C.
Published: June 2008

This study deals with the nonlinear flutter of a cantilever wing in the absence and presence of parametric excitation that acts in the plane of highest rigidity. The nonlinear equations of motion in the presence of an incompressible fluid flow are derived using Hamilton’s principle. The regions of parametric instability are obtained for different values of flow speed. In the neighborhood of combination parametric resonance, the nonlinear response is determined using the multiple scales method for different values of flow speed. In the absence of parametric excitations, numerical simulation is performed for flow speeds at the critical flutter speed. It is found that the nonlinear flutter of the two modes depends on initial conditions, and exhibits symmetric periodic oscillations. Under parametric excitation and in the absence of air flow, each mode oscillates at its own natural frequency. In the presence of air flow, the two modes possess the same frequency response. Depending on the flow speed the response could be periodic, quasi-periodic, or chaotic.
Characterization of Intermittent Contact in Tapping Mode Atomic Force Microscopy
Authors: Zhao Xiaopeng , Dankowicz Harry
Published: June 2008

Tapping-mode atomic force microscopy has wide applications for probing the nanoscale surface and subsurface properties of numerous materials in a variety of environments. Strongly nonlinear effects due to large variations in the force field on the probe tip over very small length scales and the intermittency of contact with the sample, however, result in strong dynamical instabilities. These can result in a sudden loss of stability of low-contact-velocity oscillations of the atomic-force-microscope tip in favor of oscillations with high contact velocity, coexistence of stable oscillatory motions, and destructive, nonrepeatable, and unreliable characterization of the nanostructure. In this paper, dynamical systems tools for piecewise smooth systems are employed to characterize the loss of stability and associated parameter hysteresis phenomena.
Robust Controllability of Interval Fractional Order Linear Time Invariant Systems
Authors: Chen Yang Quan , Ahn Hyo-Sung , Xue Dingyu¨
Published: June 2008

We consider uncertain fractional-order linear time invariant (FO-LTI) systems with interval coefficients. Our focus is on the robust controllability issue for interval FO-LTI systems in state-space form. We re-visited the controllability problem for the case when there is no interval uncertainty. It turns out that the stability check for FO-LTI systems amounts to checking the conventional integer order state space using the same state matrix A and the input coupling matrix B. Based on this fact, we further show that, for interval FO-LTI systems, the key is to check the linear dependency of a set of interval vectors. Illustrative examples are presented.
Computational Heat Transfer in Heat Exchanger Analysis and Design (Invited)
Authors: Sunden Bengt
Published: June 2008

Rapid development of computer capacity and advances in numerical solution methods for the governing equations of fluid flow and heat transfer have enabled CFD (computational fluid dynamics) methods to gradually become useful tools in research and development, engineering design and analysis of heat transfer equipment. However, turbulence modelling still presents a problem as accurate and reliable predictions of flow separation, reattachment, impingement and recirculating flow fields are requested. For heat exchangers both laminar and turbulent flow fields are of significance and in addition the geometries are complex, of small dimensions sometimes and turbulators or enhanced surfaces are applied. Still the demands on computers are strong as analysis of full scale equipment requires a huge amount of grid points and the computation times are long. The present paper concerns current CFD methods for thermal problems in analysis and design of heat exchangers. Application examples are presented and associated problems and limitations are discussed.
On Numerical Simulations of a Nonlinear Self-Excited System With Two Non-Ideal Sources
Authors: Palacios J. L. , Balthazar J. M. , Brasil R. M. L. R. F. , Warminski J.
Published: June 2008

In this work, the dynamic behavior of self-synchronization and synchronization through mechanical interactions between the nonlinear self-excited oscillating system and two non-ideal sources are examined by numerical simulations. The physical model of the system vibrating consists of a non-linear spring of Duffing type and a nonlinear damping described by Rayleigh’s term. This system is additional forced by two unbalanced identical direct current motors with limited power (non-ideal excitations). The present work mathematically implements the parametric excitation described by two periodically changing stiffness of Mathieu type that are switched on/off.
New Indices for Measure of Parallel and Series Multi-State System Reliability
Authors: Kapur Kailash , Zaitseva Elena , Levashenko Vitaly
Published: June 2008

The reliability of multi-state system is analyzed in this paper. In a multi-state system, both the system and its components may experience more than two reliability states. We propose dynamic reliability indices for reliability analysis of this system. Mathematical tools of the multiple-valued logic (the Logical Differential Calculus in particular) are exploited for definition of these indices. These indices estimate the effect on the multi-state system reliability by the state of a system component. We concentrate on series and parallel systems, because these structures are basic for many technical systems and get measures of reliability for the failure and restoration of these systems.
On the Impact of Coupling Strength on Complex System Optimization for Single-Level Formulations
Authors: Allison James , Kokkolaras Michael , Papalambros Panos
Published: June 2008

Design of modern engineering products requires complexity management. Several methodologies for complex system optimization have been developed in response. Single-level strategies centralize decision-making authority, while multi-level strategies distribute the decision-making process. This article studies the impact of coupling strength on single-level Multidisciplinary Design Optimization formulations, particularly the Multidisciplinary Feasible (MDF) and Individual Disciplinary Feasible (IDF) formulations. The Fixed Point Iteration solution strategy is used to motivate the analysis. A new example problem with variable coupling strength is introduced, involving the design of a turbine blade and a fully analytic mathematical model. The example facilitates a clear illustration of MDF and IDF and provides an insightful comparison between these two formulations. Specifically, it is shown that MDF is sensitive to variations in coupling strength, while IDF is not.
Finding Cutter Engagement for Ball End Milling of Tessellated Free-Form Surfaces
Authors: Yao Zhiyang
Published: June 2008

In fabricating free-form surfaces, ball end mills are mainly used to reach the final surface finish requirements. In the milling processes, cutter engagement value measures what portion of the cutter is involved in machining at a given instant of time. This paper presents geometric algorithms for estimating cutter engagement values for ball end milling processes of tessellated free-form surfaces. The cutter engagement value calculated here can be used later on in generating efficient cutter paths, as well as performing adaptive feed rate controls.
Multibody Computational Biomechanical Model of the Upper Body
Authors: Sullivan Sarah R. , Langrana Noshir A. , Sisto Sue Ann
Published: June 2008

In the United States alone, more than 10,000 spinal cord injuries (SCI) are reported each year. This population depends upon their upper limbs to provide a means of locomotion during completion of their activities of daily living. As a result of greater than normal usage of the upper limbs, proper propulsion mechanics are paramount in preventing injuries. Upper limb pain and pathology is common among manual wheelchair users due to the requirements placed on the arms for wheelchair locomotion. During the wheelchair rehabilitation process following an SCI, an individual is prescribed a wheelchair (WC). The use of a patient-specific computational biomechanical model of WC propulsion may help guide rehabilitation that may improve clinical instruction and patient performance. The overall goal of this study is to develop and refine a computational model that may aide in minimizing shoulder pathology.
Selective Clay Milling for Interactive Prototyping
Authors: Song Y. , Vergeest J. S. M. , Langerak T. R.
Published: June 2008

Prototyping plays an important role in industrial product designs. In this paper, for achieving a more intuitive and interactive prototyping, a selective clay milling center is introduced based on a synthesis of clay modeling, 3-Dimensional (3-D) scanning, robot machining and advanced geometric tools. In the system, the product shape design may start either from a physical hand-made clay model or a virtual Computer-Aided Design (CAD) model. Via 3-D scanning techniques, manual modifications of the clay model can be captured in the CAD form and in the meantime, geometric modifications of the CAD model can be fed back to the physical model by an efficient robot machining method, named selective clay milling. This design cycle is repeated until a satisfied prototype iterates. For a better control of the interactions between the manual modeling and robot milling, a 3-D scanning based calibration system has been developed in order to arbitrarily position the workpiece in the design process. With several experiments, the effectiveness of the proposed system is shown and the possible applications of the proposed system in industrial product design are described as well.
Implicit-Explicit Time Integration in Multibody Dynamics
Authors: Arnold Martin , Hippmann Gerhard
Published: June 2008

Robust and efficient time integration methods in multibody dynamics are tailored to the specific structure of the equations of motion. In the present paper we discuss the combination of explicit methods for non-stiff solution components with implicit methods for stiff solution components and constraints. The methods are successfully used in the dynamical simulation of large-scale multibody system models that display a clear partitioning into stiff and non-stiff subsystems.
Product Family Representation and Redesign: Increasing Commonality Using Formal Concept Analysis
Authors: Nanda Jyotirmaya , Thevenot Henri J. , Simpson Timothy W.
Published: June 2008

In this paper we propose a framework based on Formal Concept Analysis (FCA) that can be applied systematically to (1) visualize a product family (PF) and (2) improve commonality in the product family. Within this framework, the components of a PF are represented as a complete lattice structure using FCA. A Hasse diagram composed of the lattice structure graphically represents all the products, components, and the relationships between products and components in the PF. The lattice structure is then analyzed to identify prospective components to redesign to improve commonality. We propose two approaches as part of this PF redesign methodology: (1) Component-Based approach, and (2) Product-Based approach. In the Component-Based approach, emphasis is given to a single component that could be shared among the products in a PF to increase commonality. In the Product-Based approach, multiple products from a PF are selected, and commonality is improved among the selected products. Various commonality indices are used to assess the degree of commonality within a PF during its redesign. In this paper, we apply the framework to represent and redesign a family of one-time-use cameras. Besides increasing the understanding of the interaction between components in a PF, the framework explicitly captures the redesign process for improving commonality using FCA.
Analysis of Higher and Lower Order Elements for the Absolute Nodal Coordinate Formulation
Authors: Gerstmayr Johannes , Shabana Ahmed A.
Published: June 2008

A higher order and a reduced order element for the analysis of thin beams using the absolute nodal coordinate formulation are investigated. Additional shape functions are introduced for the existing spatial absolute nodal coordinate beam element in order to increase its accuracy. For thin structures where bending stiffness might be still desired, a cable element is introduced and compared with existing formulations using several examples. Cables that experience low tension or catenary systems, where bending stiffness has an effect on the wave propagation, are examples in which the low order element can be used. The cable element, which does not include torsional stiffness, can be very effective in numerous applications and problems such as the formulation of sliding joints in applications such as the spatial pantograph-catenary system.
Dynamic Displacement Tracking of Force-Loaded Linear Elastic or Viscoelastic Bodies by Eigenstrain-Induced Actuation Stresses
Authors: Irschik Hans , Krommer Michael
Published: June 2008

The present paper is concerned with the dynamics of linear elastic or viscoelastic bodies under the action of transient forces, with prescribed time-dependent boundary conditions, and with given initial conditions, or with a given initial past history. We consider anisotropic linear elastic bodies, or anisotropic linear viscoelastic bodies that are described by a hereditary law of the Boltzmann type. We ask for an additional distribution of actuation stresses such that the resulting displacements of the body under consideration follow exactly some desired trajectories in every point and at every time instant. We present relations that must be satisfied for the actuation stresses in order that this goal of displacement tracking is reached. In order to promote practical realizations, we present several versions of our formulations. To our best knowledge, the theoretical results we are presenting in the present contribution are new. They extend some previous results of our group concerning elastic shape control, i.e. for the case that zero trajectories are tracked; the body then maintains its undistorted initial shape. The actuation stresses we have in mind for enforcing tracking of displacements are induced by eigenstrains, such as thermal expansion strains or piezoelectric parts of strain. Practical applications of our formulations seem to be visible for the dynamics of smart structures.
Gait Analysis Using Multibody Simulation Tools and Inverse Dynamics Procedures
Authors: Silva Miguel , Ambro´sio Jorge
Published: June 2008

The use of inverse dynamics methodologies for the evaluation of intersegmental reaction forces and the moments-of-force at the anatomical joints, in the framework of gait analysis, not only requires that appropriate biomechanical models are used but also that kinematic and kinetic data sets are available. This paper discusses the quality of the results of the inverse dynamics analysis with respect to the filtering procedures used and the kinematic consistency of the position, velocity and acceleration data. A three-dimensional whole body response biomechanical model based on a multibody formulation with natural coordinates is used. The model has 16 anatomical segments that are described using 33 rigid bodies in a total of 44 degrees-of-freedom. In biomechanical applications, one of the advantages of the current formulation is that the set of anatomical points used to reconstruct the spatial motion of the subject is also used to construct the set of natural coordinates that describe the biomechanical model itself. Based on the images collected by four synchronized video cameras, the three-dimensional trajectories of the anatomical points are reconstructed using standard photogrammetry techniques and Direct Linear Transformations. The trajectories obtained are then filtered in order to reduce the noise levels introduced during the reconstruction procedure using 2nd order Butterworth low-pass filters with properly chosen cut-off frequencies. The filtered data is used in the inverse dynamics analysis either directly or after being modified in order to ensure its consistency with the biomechanical model’s kinematic constraints. It is also shown that the use of velocities and accelerations consistent with the kinematic constraints or those obtained through the time derivatives of the spline interpolation curves of the reconstructed trajectories lead to similar results.
Index-Based Performance Assessment and Condition Monitoring of a Mobile Working Machine
Authors: Ho¨ltta¨ Vesa , Repo Matti , Palmroth Lauri , Putkonen Aki
Published: June 2008

Real-time performance assessment and condition monitoring are potential new features in mobile working machines that have to run in a wide range of operating conditions. Condition monitoring and performance assessment are needed to be able to proactively correct impending faults before severe failures or machine stoppage occur. This paper presents a data-driven approach for machine performance assessment and condition monitoring based on indices representing the performance of a subsystem. Instead of adding new sensors, the indices are computed using existing data from the machine control system. Metrics for machine performance follow-up are derived from these multidimensional data, which have strong nonlinear correlations in certain measurement variables. Although the indices describe primarily the technical performance of the machine, they have proven to be valuable also in terms of condition monitoring of various machine functions. The indices summarize in a concise and easily comprehensible manner changes in performance.
Instability of a Whirling Conducting Rod in the Presence of a Magnetic Field: Application to the Problem of Space Tethers
Authors: Valverde J. , van der Heijden G.
Published: June 2008

We study the effect of a magnetic field on the behaviour of a slender conducting elastic structure subject to end forces. Both statical (buckling) and dynamical (whirling) instability are considered and we also compute post-buckling configurations. The theory used is the geometrically exact Cosserat rod theory. We consider two types of boundary conditions: the traditional welded boundary conditions (for tether-like applications) and a novel set of boundary conditions that give rise to exact helical post-buckling solutions. Our results are relevant for current designs of electrodynamic space tethers and potentially for future applications in nano- and molecular wires.
Natural Frequency Analysis of Liquid-Filled Tanks
Authors: Amini Rouzbeh , Warner Grant , Nayeb-Hashemi Hamid
Published: June 2008

Traditionally, the cantilever modal shape of liquid-filled tanks has been considered as the most critical mode. However, recent research has demonstrated that natural frequencies associated with some circumferential modes might be close to the frequency of earthquake excitation. This can lead to a resonance phenomenon, and consequently failure of the tanks. In this paper, we perform Natural Frequency Analysis of fluid-filled tanks, using finite element analysis. Modeling and solution employ ADINA potential-based flow elements, which require the assumption of inviscid, irrotational and incompressible flow. The problem is solved for different geometries and water levels of tanks; the results are compared with the current results in the literature and the difference is demonstrated.
Differential-Geometric Methods in Multibody Dynamics and Control
Authors: Maißer P.
Published: June 2008

This paper presents a differential-geometric approach to the multibody system dynamics regarded as a point dynamics in a n-dimensional configuration space Rn. This configuration space becomes a Riemannian space Vn the metric of which is defined by the kinetic energy of the multibody system (MBS). Hence, all concepts and statements of the Riemannian geometry can be used to study the dynamics of MBS. One of the key points is to set up the non-linear Lagrangian motion equations of tree-like MBS as well as of constrained mechanical systems, the perturbed equations of motion, and the motion equations of hybrid MBS in a derivative-free manner. Based on this approach transformation properties can be investigated for application in real-time simulation, control theory, Hamilton mechanics, the construction of first integrals, stability etc. Finally, a general Lyapunov-stable force control law for underactuated systems is given that demonstrates the power of the approach in high-performance sports applications.
Validating Portability of STEP-NC Tool Center Programming
Authors: Venkatesh S. , Odendahl D. , Xu X. , Michaloski J. , Proctor F. , Kramer T.
Published: June 2008

A joint effort between Boeing and the National Institute of Standards and Technology (NIST) was undertaken for validating and evaluating STEP AP238 (STEP-NC) Conformance Class 1 (CC1) for 5-axis machining. STEP-NC is a new manufacturing standard to support “design anywhere, build anywhere, and support anywhere.” The joint Boeing/NIST validation intended to prove that five-Axis AP-238 programs with tool center programming (TCP), as opposed to that of axis movement data, are portable. Current RS274 “G code” part programs that use axis movement data are bound to a single CNC, are ineffective on different machine tools, and cannot be used for the exchange of information between process planning, work preparation, tooling, and other production processes. All of these obstacles add considerable time and cost to the production life cycle of a machine part. This paper discusses the joint Boeing/NIST STEP-NC TCP validation work. The major findings were that STEP-NC TCP geometrical data is portable across different 5-axis configuration CNCs. This came with a caveat, that although CNC programs can be “data-neutral”, they are not necessarily “process-neutral”.
Stability of Up- and Down-Milling Using Chebyshev Collocation Method
Authors: Butcher Eric A. , Nindujarla Praveen , Bueler Ed
Published: June 2008

The dynamic stability of the milling process is investigated through a single degree-of-freedom model by determining the regions where chatter (unstable) vibrations occur in the two-parameter space of spindle speed and depth of cut. Dynamic systems like milling are modeled by delay-differential equations (DDEs) with time-periodic coefficients. A new approximation technique for studying the stability properties of such systems is presented. The approach is based on the properties of Chebyshev polynomials and a collocation representation of the solution at their extremum points, the Chebyshev collocation points. The stability properties are determined by the eigenvalues of the approximate monodromy matrix which maps function values at the collocation points from one interval to the next. We check the results for convergence by varying the number of Chebyshev collocation points and by simulation of the transient response via the DDE23 MATLAB routine. The milling model used here was derived by Insperger et al. [14]. Here, the specific cutting force profiles, stability charts, and chatter frequency diagrams are produced for up-milling and down-milling cases for one and four cutting teeth and 25 to 100 % immersion levels. The unstable regions due to both secondary Hopf and flip (period-doubling) bifurcations are found which agree with the previous results found by other techniques. An in-depth investigation in the vicinity of the critical immersion ratio for down-milling (where the average cutting force changes sign) and its implication for stability is presented.
Shape Transformers for Material and Shape Selection
Authors: Pasini Damiano
Published: June 2008

This paper presents a method for selecting materials, cross-section shapes, and combinations thereof. The novelty of the method is the definition of Shape Transformers. These parameters are dimensionless measures of the geometric quantities of a cross-section. They describe the shape properties of a cross-section regardless of size and are thus invariant to any scaling imposed on the cross-section size. Shape Transformers are valuable with modelling the equation of mechanics and with the development of selection charts for optimum design. The rationale of the approach is that the fundamental equations of mechanics can be expressed by a product of four separable factors: the functional requirements, the material properties, the Shape Transformers, and the geometric quantities of a rectangle as defined by its cross-section size. This permits general expressions of performance indices to be derived for any scaling transformation. For example, indices for selecting materials and cross-sectional shapes that minimize the mass of beams are given for stiffness design. The last part of the paper illustrates how Shape Transformers facilitate a graphical exploration of performance data. The whole range of cross-sectional shapes can be visualized at a glance for each material. Lines of iso-performance enable efficiency comparison of materials and/or shapes for a given cross-section scaling. Shape Transformers assist design choices and give insight into optimum selection.
Transversal Nonlinear Dynamics of Stretched Chain on Elastic Foundation
Authors: Manevitch Leonid I. , Musienko Andrey I.
Published: June 2008

We present analytical and numerical study of short wavelength breathers in the system of asymmetric nonlinear oscillators coupled by stretched weightless beam. The study is focused on modulations of the nonlinear normal mode with shortest wavelength. A small parameter is introduced as ratio of distance between the particles in the chain and characteristic wavelength of modulation. It is shown that in main asymptotic approach the problem can be reduced to Nonlinear Schro¨dinger Equation (NSE). Breathers (envelope solitons) are localized oscillating solutions of this equation. We reveal the stability and high mobility of such solutions in their numerical study based on integrating of exact discrete equations of motion. We study breathers, localized on chain ends, and radiation of breathers from chain ends, induced by variable external force.
PSO Driven Genetic Range Genetic Algorithms
Authors: Arakawa Masao
Published: June 2008

This paper deals with development of Genetic Range Genetic Algorithms (GRGAs). In GRGAs, one of the key is to set a new searching range, it needs to be followed after current searching situations, to be focused on local minute search and to be scattered as widely as possible for global search. However, first two strategies have a possibility of early stage convergence, and random scattering cause vain function calls to produce the range which seems no chance to prosper for a number of generations. In this paper, we propose a new method of setting it by using Particle Swarm Optimization (PSO) to overcome dilemma of the conventional method.
Equations of Nonlinear Motion of Viscoelastic Beams
Authors: Mahmoodi S. Nima , Khadem Siamak E. , Esmailzadeh Ebrahim
Published: June 2008

A viscoelastic nonlinear beam with cubic nonlinearities is considered. In order to obtain the equations of nonlinear motion of the beam for large deformation vibrations, the Lagrangian dynamics and Hamilton principle is used. It is considered that the beam vibrates in two directions, one in longitudinal direction and the other in the transverse direction. Large amplitude vibrations cause the nonlinearities in inertia and geometry terms. Also, due to viscoelastic property of the beam, a nonlinear damping term is appeared in the equations of motion. Using the condition of inextensible beams, the equation of motion and boundary conditions of bending vibration of a Kelvin-Voigt viscoelastic beam has been obtained. Finally, if one considers the damping coefficient to be equal to zero in the obtained equation of motion of viscoelastic system then, an equation of motion for the elastic beam will be obtained.
Multi-Resolution Modeling of Feature-Based Solids Based on Non-Manifold Topological Framework
Authors: Lee Sang Hun , Lee Kyu-Yeul
Published: June 2008

The requirements of multi-resolution models of feature-based solids, which represent an object at many levels of feature detail, are increasing for engineering purposes, such as analysis, network-based collaborative design, virtual prototyping and manufacturing. To provide multi-resolution models for various applications, it is essential to generate adequate solid models at varying levels of detail (LOD) after feature rearrangement, based on the LOD criteria. However, the non-commutative property of the union and subtraction Boolean operations is a severe obstacle to arbitrary feature rearrangement. To solve this problem we propose a new approach based on the non-manifold topological representation and the merge-and-select algorithm for non-manifold Boolean operations. In this approach, the merge-and-select algorithm is modified to satisfy the commutative law between union and subtraction operations by considering the history of the Boolean operations. Because this algorithm guarantees the same resulting shape as the original and reasonable shapes at the intermediate LODs for an arbitrary rearrangement of its features, various LOD criteria can be applied for multiresolution modeling in different applications.
Modeling of Evolutionary Design Database
Authors: Xue D. , Yang H. , Tu Y. L.
Published: June 2008

This research introduces an evolutionary design database model to describe design requirements and design results developed at different design stages from conceptual design to detailed design. In this model, the evolutionary design database is represented by a sequence of worlds corresponding to the design descriptions at different design stages. The design requirements and design results in each world are modeled using a database representation scheme that integrates both geometric descriptions and non-geometric descriptions. In each world, only the differences with its ancestor world are recorded. When the design descriptions in one world are changed, these changes are then propagated to its descendant worlds automatically. Consistency of the design descriptions in descendant worlds is also checked when design descriptions in an ancestor world are changed. Case study is conducted to show the effectiveness of this evolutionary design database model.
Vortex-Induced Vibration of a Cylinder Spring-Supported in a Narrow Channel: Influence of Spring Stiffness on the Interaction of Cylinder Vibration and Unsteady Fluid Flow
Authors: Aritomi Shunsuke , Maruyama Shinichi , Ito Kenya , Yoshizawa Masatsugu
Published: June 2008

This paper deals with the nonlinear interaction between vortex-induced vibration of a spring-supported cylinder and unsteady fluid flow in a narrow channel. In particular, we remark the stiffness of the spring with which the cylinder is supported, and investigate the influence of the stiffness on the above nonlinear interactions. Such a problem becomes very important in micro systems where the force acting on a surface area can’t be neglected compared with that acting on a volume, and the flow is laminar at low Reynolds number. In this paper, the motion of the cylinder and the fluid velocity are synchronously measured with an angular displacement meter and a PIV system. Furthermore, the theoretical results are obtained by solving the simultaneous equations governing motion of the cylinder and fluid flow numerically, in order to compare with the experimental results. Finally, we examine the unsteady fluid force acting on the cylinder theoretically.
Vibration Reduction of a Vision-Based Controlled Flexible Arm: Theoretical and Experimental Aspects
Authors: Wang Shuxin , Wen Bingquan , Yu Hongbo , Yun Jintian
Published: June 2008

For vision-based controlled flexible arm, the accuracy of the finite dimensional dynamic models and stability become very important for controller design. This paper addresses the issue of selecting the shape function and mode in developing finite dynamic models, and designs suitable controller for a flexible arm with vision-based control. Input of the controller is the measured position error of the beam tip, which can be directly obtained by camera. In spite of the observed differences between actual system and simulated system, experimental results are good enough to validate the arm model. Simulation and experimental results show that the PID controller is acceptable. It is also stressed that two factors, the camera sampling rate and a dead band in the velocity command, will influence the properties of the control system for vision-based controlled flexible arm.
Stress Analysis and Life Assessment of Rotor and Retaining Ring of Generator for Fossil Power Plant
Authors: Lee Ji-Moon , Kim Cheol-Hong , Ju Young-Ho
Published: June 2008

In addition to the higher centrifugal forces during normal operation in 3600 rpm, a generator rotor body is subjected to the contact pressures from shrink-fit between generator rotor and retaining ring. To obtain the structural reliability and life assessment of the generator, the finite element models were developed and structural analyses were carried out. The stress distributions and the critical locations of the rotor body were identified. Further, the fatigue life is performed to estimate the remaining life of generator, The critical crack size and probability of failure are also evaluated based on the analysis results. The critical sizes of a crack of generator are predicted using linear elastic fracture mechanics. These results will be applied to the development of a larger 1000MW capacity generator.
Results of Vibration Control of a Maglev Vehicle Utilizing a Linear Generator
Authors: Suzuki Erimitsu , Watanabe Ken
Published: June 2008

To make the superconducting magnetically levitated transport (maglev) system more attractive, it has been important to enhance the ride comfort by controlling vehicle vibration. Maglev vehicle vibrations have been reduced in previous experiments by controlling only the secondary suspension between the car bodies and bogies. However, by doing so, it has been difficult to reduce vibration for the characteristic and relatively high frequencies of the primary suspension between the bogies and guideway. Recently, control of the primary suspension is being considered. Power collecting coils of a linear generator system, which is being tested as an onboard power source, can also generate additional forces that can be used to control vibrations. Because this type of vibration control can apply damping directly to the primary suspension, it can reduce vibrations of relatively higher frequencies that are difficult to reduce by controlling only the secondary suspension. A maglev vehicle model that focuses on vertical and pitching motions is used to examine the effectiveness of reducing vibrations by using a linear generator damping force control in the primary suspension and linear quadratic (LQ) control of the actuators in the secondary suspension. Experimental results using the linear generator on a full-scale maglev vehicle on the Yamanashi Maglev Test Line are described.
Motion and Vibration of Multi-Vehicles on a 3D Trajectory
Authors: Nakagawa Chihiro , Fujita Katsuhisa
Published: June 2008

We herein investigate the motion and vibration of multi-vehicles that follow complicated three-dimensional trajectories. A roller coaster is used as the multi-vehicle model. The equations of motion and the constraint conditions of the model are set up using a differential-algebraic equation (DAE). In previous reports, we examined the motion and vibration of a single-vehicle roller coaster. In the present paper, we examine a multi-vehicle roller coaster. We herein propose and analyze the constraint conditions between the vehicles. In the simulation, we investigate differences in motion and vibration among the coupled vehicles. The motions of multi-vehicles in the simulation and the experiment shared a number of similar tendencies. In addition, we propose a theory by which to evaluate the yaw angle, which is expressed in the x-y (s-u) plane defined as the ground surface, and analyze the influence on the yaw direction. Finally, we examine the validity of the proposed simulation method.
Multibody Dynamics Modeling of Submerged Cable Systems With Elastic Segments
Authors: He Manli , Wang Shuxin , Li Xiaoping
Published: June 2008

A method for dynamic analysis of submerged cable system with elastic segments is presented based on the finite segment formulation in which elastic segments of a cable are described using shape functions of finite element method (FEM). The simulation model is tested by available experimental data to be computationally efficient and numerically stable. The method is also proved by the experimental results of the Small Oceanic Buoy System which has been developed by Oceanic Engineering Center of China.
Nonlinear Dynamic Analysis of a Belt-Drive Using the Absolute Nodal Coordinate Formulation
Authors: Garci´a-Vallejo Daniel , Kerkka¨nen Kimmo S. , Mikkola Aki M.
Published: June 2008

In this paper, the applicability of the absolute nodal coordinate formulation for the modeling of belt-drive systems is studied. A successful and effective analyzing method for belt-drive systems requires the exact modeling of the rigid body inertia during an arbitrary rigid body motion, accounting of shear deformation, description of nonlinear deformations and a simple as well as realistic description of the contact. The absolute nodal coordinate formulation meets the challenge and is a promising approach for the modeling of belt-drive systems. In this study, a recently proposed two-dimensional shear deformable beam element based on the absolute nodal coordinate formulation has been modified to obtain a belt-like element. The belt-like element allows the user to control the axial and bending stiffness through the use of two parameters. In this study, the interaction between the belt and the pulleys is modeled using an elastic approach in which the contact is accounted for by the inclusion of a set of external forces that depend on the penetration between the belt and pulley.
Optimal Linear and Nonlinear Control Design for Chaotic Systems
Authors: Rafikov Marat , Balthazar Jose´ Manoel
Published: June 2008

In this work, the linear and nonlinear feedback control techniques for chaotic systems were been considered. The optimal nonlinear control design problem has been resolved by using Dynamic Programming that reduced this problem to a solution of the Hamilton-Jacobi-Bellman equation. In present work the linear feedback control problem has been reformulated under optimal control theory viewpoint. The formulated Theorem expresses explicitly the form of minimized functional and gives the sufficient conditions that allow using the linear feedback control for nonlinear system. The numerical simulations for the Ro¨ssler system and the Duffing oscillator are provided to show the effectiveness of this method.
A Grammatical Approach to Support Real-Time Design of Customized Products
Authors: Siddique Zahed , Ninan Jiju A.
Published: June 2008

In order to support design of customized products requires generating models of the customized product, performing analysis of these customized products to determine feasibility, and optimization to increase performance. Internet based mass customization systems can be used to not only gather information from the customer, but also to provide real-time feed-back to the customer with product model and analysis information. Consequently, the design analysis, evaluation and optimization need to be automated and enhanced to enable operation over the internet. In this paper product family architecture information are first categorized and then utilized to develop a grammatical approach that captures both configuration and scaling information for entire range of possible customized products to generate detail CAD and FEA models. Analysis, selection of components, and optimization are automatically performed on the models of user-customized products. Solid model of the customized product, along with analysis results, are shown back to the user in real-time as feedback. The proposed setup is demonstrated through the use of a bicycle frame family.
On Some Peculiarities Encountered in the Identification of Nonlinear Gear-Pair Systems
Authors: Giagopulos D. , Salpistis C. , Natsiavas S.
Published: June 2008

This study investigates issues related to parametric identification of a typical power train component with nonlinear characteristics. In particular, a gear-pair system supported on bearings with rolling elements is selected. This model accounts for gear backlash and bearing stiffness nonlinearities. A Bayesian statistical framework is first adopted in order to estimate the optimal values of the gear and bearing model parameters. This is achieved by combining experimental information from vibration measurements with theoretical information built into a parametric mathematical model of the system. Then, characteristic numerical results are presented. The emphasis is put on explaining some of the peculiar results obtained by applying classical gradient-based optimisation methodologies for the strongly nonlinear system examined. Some serious difficulties, associated with the existence of irregular response or the coexistence of multiple motions, are first pointed out. A solution to some of these problems, through the application of a suitable genetic algorithm, is then presented.
A Methodology for Trading-Off Performance and Robustness Under Uncertainty
Authors: Mourelatos Zissimos P. , Liang Jinghong
Published: June 2008

Mathematical optimization plays an important role in engineering design, leading to greatly improved performance. Deterministic optimization however, may result in undesired choices because it neglects uncertainty. Reliability-based design optimization (RBDO) and robust design can improve optimization by considering uncertainty. This paper proposes an efficient design optimization method under uncertainty, which simultaneously considers reliability and robustness. A mean performance is traded-off against robustness for a given reliability level of all performance targets. This results in a probabilistic multi-objective optimization problem. Variation is expressed in terms of a percentile difference, which is efficiently computed using the Advanced Mean Value (AMV) method. A preference aggregation method converts the multi-objective problem to a single-objective problem, which is then solved using an RBDO approach. Indifference points are used to select the best solution without calculating the entire Pareto frontier. Examples illustrate the concepts and demonstrate their applicability.
On the Dynamic Isotropy of Mechanisms With Two Degrees of Freedom
Authors: Di Gregorio Raffaele , Cammarata Alessandro , Sinatra Rosario
Published: June 2008

The comparison of mechanisms with different topology or with different geometry, but with the same topology, is a necessary operation during the design of a machine sized for a given task. Therefore, tools that evaluate the dynamic performances of a mechanism are welcomed. This paper deals with the dynamic isotropy of 2-dof mechanisms starting from the definition introduced in a previous paper. In particular, starting from the condition that identifies the dynamically isotropic configurations, it shows that, provided some special cases are not considered, 2-dof mechanisms have at most a finite number of isotropic configurations. Moreover, it shows that, provided the dynamically isotropic configurations are excluded, the geometric locus of the configuration space that collects the points associated to configurations with the same dynamic isotropy is constituted by closed curves. This results will allow the classification of 2-dof mechanisms from the dynamic-isotropy point of view, and the definition of some methodologies for the characterization of the dynamic isotropy of these mechanisms. Finally, examples of applications of the obtained results will be given.
Multiple Time Scale Analysis of Delay Differential Equations Modeling Mechanical Systems
Authors: Erneux Thomas
Published: June 2008

The response of two nonlinear oscillators subject to a large delay is investigated by using a two-time multiple scale analysis. The first problem has been proposed by Johnson and Moon [13] as a model for machine-tool vibrations. The second problem has been formulated by Minorsky [22] in his study of a delayed control. For both problems, we derive slow time amplitude equations and show analytically that the delay is responsible for a secondary bifurcation to quasiperiodic oscillations. For Minorsky’s equation, higher order bifurcations are further analyzed for very large delays.
Transient and Steady-State Stochastic Analysis of Nonlinear Oscillators Using the Fokker-Planck-Kolmonogrov Equation
Authors: Rook Todd
Published: June 2008

An efficient technique to calculate the transient and stationary probability distribution functions (PDF) of the response of SDOF oscillators with piecewise continuous nonlinearities is presented. The method compares favorably with previous methods in reproducing stationary distributions and chaotic attractors, but further work is needed in calculating Lyapunov exponents to the desired accuracy.
Act and Wait Concept in Force Controlled Systems With Discrete Delayed Feedback
Authors: Insperger Tama´s , Ste´pa´n Ga´bor
Published: June 2008

A 1 DOF model of force control is considered with discrete delayed feedback. The act and wait control concept is introduced as a special case of periodic control: the feedback gain is constant for a sampling period (act), then it is zero for a certain number of periods (wait), then it is constant again, etc. It is shown that by applying the act and wait concept, the stability properties of the system improve and the force error caused by the Coulomb friction decreases. If the period of gain variation is larger than the feedback delay, then the system performance changes radically: the stability properties improve significantly, and the optimal control parameters can provide dead beat control. This way, by using the act and wait concept, the delay effects are eliminated from the system.
Efficient Genetic Algoritm Based Robust Design Method for Compressor Fan Blades
Authors: Kumar Apurva , Keane A. J. , Nair P. B. , Shahpar S.
Published: June 2008

This paper presents an efficient genetic algorithm based methodology for robust design that produces compressor fan blades tolerant against erosion. A novel geometry modeling method is employed to create eroded compressor fan blade sections. A multigrid Reynolds-Averaged Navier Stokes (RANS) solver HYDRA with Spalart Allmaras turbulence model is used for CFD simulations to calculate the pressure losses. This is used in conjunction with Design of Experiment techniques to create Gaussian stochastic process surrogate models to predict the mean and variance of the performance. The Non-dominated Sorting Genetic Algorithm (NSGA-II) is employed for the multiobjective optimization to find the global Pareto-optimal front. This enables the designer to trade off between mean and variance of performance to propose robust designs.