bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Finite Element Modeling of Carbon Nanotubes Using an Intrinsic Formulation
Authors: Leamy Michael J.
Published: June 2008

This article presents an efficient explicit dynamic formulation for modeling curved and twisted Carbon Nanotubes (CNT’s) based on a recently-developed intrinsic beam description (i.e. the dynamic state given by curvatures, strains, and velocities only) [Hodges, 2003] together with a finite element discretization incorporating atomistic potentials. This approach offers several advantages primarily related to the model’s computational efficiency: 1) the resulting partial differential equations governing motion are in first-order form (i.e. have first-order time derivatives only), 2) the system nonlinearities appear at low order, 3) the intrinsic description incorporating curvature allows low-order interpolation functions to describe generally curved and twisted nanotube centerlines, 4) inter-element displacements, slopes, and curvatures are matched at the element boundaries, and 5) finite rotational variables are absent, along with their inherit complexities. In addition, the developed model and finite element discretization are able to capture the nanotube’s dynamic response, without the expense of calculating the dynamic response of individual atoms as per Molecular Dynamics models. Simulation results are presented which illustrate the dynamic response of a typical CNT to axial, bending, and torsional loading. Results from the simulations are compared to similar results available in the literature, and close agreement is documented.
Placing Multibody System to Equilibrium State by Using Multiple PID Controllers and Genetic Algorithm
Authors: Duras Mario
Published: June 2008

During development of MBS (Multibody System) dynamics simulation tool that evaluates contact forces between bodies, a procedure had to be developed for placing general MBS to equilibrium state. The procedure would be executed before dynamics simulation starts, to ensure stable and convergent simulation from its beginning. As very broad range of stiffnesses is coupled within the same model and additionally contact forces are evaluated, placing system to satisfactory initial state is not a simple task. Algorithm for initial conditions must place bodies to positions that would provide smallest possible (zero) resultant force on each body. After several approaches being tested, usage of PID (Proportional-Integral-Derivative) controllers showed greatest potential for solving the problem in a stable and fast manner. Such controller would be attached to each body and will move bodies to positions with smallest resultant force. To completely model PID controller, three parameters must be evaluated - gains for each controller action. For optimal combination of three parameters - conditions on force convergence and resultant force end value (zero) must be satisfied. Analysis showed that parameters for controller actions cannot be fixed and work successfully for MBSs with different number of DOF (Degrees of Freedom). Based on that, PID controller parameter range has been evaluated by Genetic Algorithm after repeated tests on systems of different types and number of DOF. Parameters choice and PID controller behavior were checked on models of engine timing drives (belt and chain drives with lashes) with several hundred DOF and simple model of Single Valve Train with just few DOF. Tests showed correct choice of PID parameters and stable iteration procedure regardless of DOF number and type of MBS. This paper focuses on determination of PID controller parameters by analyzing influence of MBS structure to procedure for reaching equilibrium state. Analysis is mainly focused on convergence and stability of the procedure.
Friction-Induced Limit Cycling in Flexible Rotor Systems: An Experimental Drill-String System
Authors: van de Wouw N. , Nijmeijer H. , Mihajlovic´ N.
Published: June 2008

Friction-induced limit cycling deteriorates system performance in a wide variety of mechanical systems. In this paper, we study the way in which essential friction characteristics affect the occurrence and nature of friction-induced limit cycling in flexible rotor systems. This study is performed on the level of both numerical and experimental bifurcation analyses. Hereto, an experimental drill-string set-up is used. The synthesis of these numerical and experimental results confirms that friction-induced limit cycling is due to a subtle balance between a velocity weakening characteristic of the friction (Stribeck effect) at lower velocities and viscous friction at higher velocities. Moreover, it is shown how these essential friction characteristics depend on physical conditions such as temperature and normal forces in the frictional contact in the experimental set-up.
Stability Analysis of Complex Multibody Systems
Authors: Bauchau Olivier A. , Wang Jielong
Published: June 2008

The linearized stability analysis of dynamical systems modeled using finite element based multibody formulations is addressed in this paper. The use of classical methods for stability analysis of these system, such as the characteristic exponent method or Floquet theory, results in computationally prohibitive costs. Since comprehensive multibody models are “virtual prototypes” of actual systems, the applicability to numerical models of the stability analysis tools that are used in experimental settings is investigated in this work. Various experimental tools for stability analysis are reviewed. It is proved that Prony’s method, generally regarded as a curve fitting method, is equivalent, and sometimes identical, to Floquet theory and to the partial Floquet method. This observation gives Prony’s method a sound theoretical, footing, and considerably improves the robustness of its predictions when applied to comprehensive models of complex multibody system. Numerical applications are presented to demonstrate the efficiency of the proposed procedure.
Virtual Reality Interactive Design Utilizing Meshless Stress Re-Analysis
Authors: Chipperfield Kurt , Vance Judy
Published: June 2008

Interactive design gives engineers the ability to modify the shape of a part and immediately see the changes in the part’s stress state. Virtual reality techniques are utilized to make the process more intuitive and collaborative. The results of a meshless stress analysis are superimposed on the original design. As the engineer modifies the design using subdivision volume free-form deformation, the stress state for the modified design is computed using a Taylor series approximation. When the designer requests a more accurate analysis, a stress re-analysis technique based on the pre-conditioned conjugate gradient method is used with parallel processing to quickly compute an accurate approximation of the stresses for the new design.
Irreversible Passive Energy Transfer in the Damped Response of Coupled Oscillators With Essential Nonlinearity
Authors: Kerschen G. , Lee Y. S. , Vakakis A. F. , McFarland D. M. , Bergman L. A.
Published: June 2008

We study, numerically and analytically the dynamics of passive energy transfer from a damped linear oscillator to an essentially nonlinear end attachment. This transfer is caused either by fundamental or subharmonic resonance capture, and in some cases is initiated by nonlinear beat phenomena. It is shown that, due to the essential nonlinearity, the end attachment is capable of passively absorbing broadband energy both at high and low frequencies, acting, in essence, as a passive broadband boundary controller. Complicated transitions in the damped dynamics can be interpreted based on the topological structure and bifurcations of the periodic solutions of the underlying undamped system. Moreover, complex resonance capture cascades are numerically encountered when we increase the number of degrees of freedom of the system. The ungrounded, essentially nonlinear end attachment discussed in this work can find application in numerous practical settings, including vibration and shock isolation of structures, seismic isolation, flutter suppression and packaging.
Vibration and Guiding of Moving Media With Edge Weave Imperfections
Authors: Kartik V. , Wickert J. A.
Published: June 2008

This paper examines the steady-state forced vibration of a moving medium that is guided by a partial elastic foundation, and where geometric imperfections on the medium’s edge act as an excitation source. Such a system is of technical interest in the areas of web handling and magnetic tape transport where externally-pressurized air bearing guides are sometimes used to control lateral position. The axially-moving strip is modeled here as a string that is guided by elastic foundation segments and that is subjected to traveling wave excitation as the edge imperfections interact with the foundations. The equation of motion for this “moving medium and moving load” system incorporates a skew-symmetric Coriolis acceleration component that arises from convection. The governing equation is cast in the state-space form, with one symmetric and one skew-symmetric operator, as is characteristic of gyroscopic systems. Through modal analysis, the forced response of the system is obtained to the complex harmonic excitation associated with the interaction between the edge weave and the guides. Parameter studies are presented in the transport speed, foundation stiffness, guide placement, guide width, and imperfection wavelength. Of potential technological application, for a given wavelength of the edge imperfection, it is possible to reduce the medium’s vibration at a certain location by judiciously selecting the locations and spans of the foundation segments.
Document-Driven Design for Distributed CAD Services in Service-Oriented Architecture
Authors: Wang Yan , Nnaji Bart O. , Chiang Wei-Shan
Published: June 2008

Current CAD systems only support interactive geometry generation, which is not ideal for distributed engineering services in enterprise-to-enterprise collaboration with a generic thin-client service-oriented architecture. This paper proposes a new feature-based modeling mechanism, document-driven design, to enable batch mode geometry construction for distributed CAD systems. A semantic feature model is developed to represent informative and communicative design intent. Feature semantics is explicitly captured as trinary relation, which provides good extensibility and prevents semantics loss. Data interoperability between domains is enhanced by schema mapping and multi-resolution semantics. This mechanism aims to enable asynchronous communication in distributed CAD environments with case of design alternative evaluation and reuse, reduced human errors, and improved system throughput and utilization.
Enhancing Undergraduate Mechanical Engineering Education With Computer Aided Engineering
Authors: Schonning Alexandra , Cox Daniel
Published: June 2008

This paper addresses the importance of integrating Computer Aided Engineering (CAE) software and applications in the mechanical engineering curriculum. Computer aided engineering tools described include Computer-Aided Design, Computer-Aided Manufacturing, and Computer-Aided Analysis tools such as finite element (FE) modeling and analysis. The integration of CAE software tools in the curriculum is important for three primary reasons: it helps students understand fundamental engineering principles by providing an interactive and visual representation of concepts, it provides students an opportunity to explore their creative ideas and designs while keeping prototyping costs to a minimum, and it teaches students the valuable skill of more efficiently designing, manufacturing and analyzing their products with current technology making them more marketable for their future engineering careers. While CAE has been used in the classroom for decades, the mechanical engineering program at the University of North Florida is making an aggressive effort in preparing the future engineering workforce through computer-aided project-centered education. The CAE component of this effort includes using CAE software when teaching stress, strain, dynamics, kinematics, vibrations, finite element modeling and analysis, design and design for manufacturing, manufacturing and technical communication concepts. This paper describes CAE projects undertaken in several of the mechanical engineering courses at UNF in an effort to share creative teaching techniques for others to emulate.
Nonlinear Vibrations of a Beam With a Tip Mass Attached to a Rotating Hub
Authors: Warminski Jerzy , Balthazar Jose´ Manoel
Published: June 2008

A model of a light beam mounted to a rigid hub and forced by an external torque has been analysed in the paper. An additional loading caused by a small mass attached to the end of the beam and the influence of mass moment of inertia of the hub have been also taken into account. The motion of a flexible light beam is a composition of slewing motion and undesired vibrations, which can be crucial if the stiffness of the structure is not high, comparing to the external dynamical load. The nonlinear model of the beam proposed in [2], [3] have been applied to explain behaviour of the system. That model has taken into account bending, tension and a non-linear curvature, which differs the system from the classical approach [4] or the approach presented in [5] for large displacement of a beam model. The influence of the mass moment of inertia of the hub and the tip-mass is investigated in the paper. Differential equation of motion and dynamical boundary conditions are derived by applying the Hamilton’s principle whilst the reduced model have been obtained by virtue of the Galerkin’s procedure.
Comparison of Exact and Approximate Frequency Response of a Piecewise Linear Vibration Isolator
Authors: Nakhaie Jazar G. , Mahinfalah M. , Rastgaar Aagaah M. , Nazari G.
Published: June 2008

In this paper an investigation is carried out to classify the steady state responses of asymmetric piecewise linear vibration isolators as double hitting, single hitting, and no hitting. In each class, the analysis has been carried out using a set of coupled nonlinear algebraic equations following Natsiavas and Gonzalez [1]. Applying perturbation technique, a closed form analytic expression of the frequency response is also derived for symmetric conditions. The exact frequency response is utilized to validate the analytic results obtained by perturbation techniques. Direct comparison indicates the results obtained by averaging method are mathematically and practically close to the exact solution.
Uncertainty Analysis by Dimension Reduction Integration and Saddlepoint Approximations
Authors: Huang Beiqing , Du Xiaoping
Published: June 2008

Uncertainty analysis, which assesses the impact of the uncertainty of input variables on responses, is an indispensable component in engineering design under uncertainty such as reliability based design and robust design. However, uncertainty analysis is not an affordable computational burden in many engineering problems. In this paper, a new uncertainty analysis method is proposed with the purpose of accurately and efficiently estimating the cumulative distribution function (CDF), probability density function (PDF) and statistical moments of a response given the distributions of input variables. The bivariate dimension-reduction method and numerical integration are used to calculate the moments of the response; then Saddlepoint Approximations are employed to estimate the CDF and PDF of the response. The proposed method requires neither the derivatives of the response nor the search of the Most Probable Point (MPP), which is needed in the commonly used First - or Second - Order Reliability Methods (FORM or SORM). The efficiency and accuracy of the proposed method is illustrated with three example problems. The method is more accurate and efficient for estimating the full range of the distribution of a response than FORM and SORM. This method provides results as accurate as Monte Carlo simulation, with a significantly reduced computational effort.
Experimental Investigation on the Micro-Step Control Disturbance Rejection Under Random Excitations
Authors: Selk Ghafari Ali , Behzad M.
Published: June 2008

Effect of random signals with various powers, as current loads, on positioning and disturbance rejection problems on micro-step PID closed loop control system is addressed in this paper. Experimental results due to implementing different white noise power, speed, and a 0.3 N.m disturbance load torque show that, Random noise source changes current profile and affects the accuracy of positioning in tracking and disturbance rejection problems. Performance of the PID proposed controller under the implementation of random noise on phases of the HSM has been proved to be accurate enough even under disturbance torque acting on the system.
Study of Dynamic Characteristics of Friction: A Comparative Analysis of the Velocity Dependent and the LuGre Friction Model
Authors: Jafri Firoz Ali , Thompson David F.
Published: June 2008

In this paper, we conduct numerical analysis to study the effects of friction on the dynamic response of a single degree of freedom mechanical system. Two different friction models, the velocity dependent friction model and the LuGre friction model, have been used to model the friction interface. Bifurcation analysis has been conducted using equilibrium and limit cycle continuation methods. With system viscous damping as the bifurcation parameter, a reverse subcritical Hopf bifurcation is observed in the case of velocity dependent model. In the case of the LuGre model for the same bifurcation parameter, a reverse supercritical Hopf bifurcation is observed at lower velocities but at higher velocities it changes to a reverse subcritical Hopf bifurcation. A fold bifurcation of the limit cycles is also seen at higher velocities for the LuGre model.
Status of Digital Human Body Modeling From the Aspect of Information Inclusion
Authors: Horva´th Imre , Zhang Bing , Moes Niels C. C. , Molenbroek Johan
Published: June 2008

This paper surveys the current state of art of digital human body modeling with a focus on information inclusion and analyzes the results from the aspects of design and engineering. It presents the results of a literature study, which intended to investigate the modeling approaches within the mentioned categories, and to investigate the fidelity of models based on the information content. In view of the fact that modeling is always a simplified representation of reality, models with different information contents are developed for different applications. It is also discussed in this paper that the information content of human body models however reflects not only the aspect of application, but also the level of fidelity, or functional sophistication. Taking into consideration the sorts of information needed to model human body as a complex organic system, the authors propose an information content-based categorization. The major categories of aspect models of human body that have been incorporated in a stratified reasoning scheme are: morphological, material, structural, mechanical, physiological and behavioral models. One conclusion is that remarkable progress has been achieved in terms of sophistication of models (i.e., of information inclusion and processing methods). Another conclusion is that further increase of the fidelity of models will not be possible without the proper treatment of the concomitant complexities. Integration of various aspect models and real time computational processing of human models are inevitable in several fields of application. However, development of human body models of such a high sophistication goes together with an exponential growth in the required capacities. This leads us to a trade-off problem in digital human body modeling.
A Conceptual Design Tool With Error Warning
Authors: Iino Kenji , Hatamura Yotaro
Published: June 2008

Collecting design error or failure information in a database (FKDB: Failure Knowledge Database) gives an organization an effective place for designers to study and learn past events so they will not repeat the same mistakes in their own design. When a designer makes an error, however, he had not foreseen the mistake at all. Once made, the error may seem trivial and even predictable, however, at the time of design, the problem and facts that surround the error are completely concealed from the designers mind. The designer, therefore, has no intention to look at past failure information that relate to the error he is repeating at the time of his design. This often makes the FKDB, despite of all the efforts in collecting the information it holds, a mere collection of past failure cases waiting for its passive use; the designer may occasionally look it up for the purpose of general study. A group of people including one of the authors, in the past, developed a conceptual design tool, Creative Design Engine (CDE) that helps the designer by displaying mechanisms, machines, sub-assemblies, and related information that realize functional requirements that the designer wants to accomplish. The tool effectively brings the designer’s consciousness to ideas new to him or something that escaped his mind at the time of conceptual design. We analyzed this tool and laid out the modifications necessary so that it not only displays design solutions and alternative options to the designer but also gives warnings to the designer about design error he is about to make during conceptual design. The application will constantly monitor the designer’s intention to compare it to known failures in the FKDB.
Application of Vibration Analysis in Ball Bearing Fault Detection
Authors: Bakhtiary-Nejad F. , Nayeb A. H. , Yeganeh S. E.
Published: June 2008

In this paper, existence of localized defects in a ball bearing has been diagnosed using vibration analysis. First, different kinds of faults which occur in ball bearings have been investigated. Then an analytical model has been proposed for determining the damaged ball bearing vibrations due to a localized defect. Also various methods of fault detection have been evaluated. Next, in order to examine the ball bearings, a testing set-up has been designed and constructed. Then by preparing a computer program, which calculates defect frequencies, some ball bearings have been tested. The test results were originally derived in time-domain. Then by using vibration analysis of healthy and damaged ball bearings in frequency-domain, a fault detection method for ball bearings has been proposed.
Active Damping Guide Roller Design Based on Integrated Structure/Controller Optimization With a Structured Controller
Authors: Fu Wujun , Zhu Changming
Published: June 2008

In this paper, the integrated structure/controller optimization has been applied to design the active damping guide roller to suppress the elevator lateral vibration. The guide rollers and their corresponding controller are considered as the design variables, simultaneously. And the weighted sum of the suspension deflection, the elevator’s acceleration and the control force are regarded as optimization functions to be minimized. Because a structured controller is used, this optimization problem can be solved by Genetic Algorithm directly. The control scheme is validated for a scaled elevator in the lab. The numerical results show that the integrated structure/controller design can provide an alternative method to achieve better ride comfort with a “sky-hook” damper controller compared to the sequential design.
Some Observations of Mode Localizations in Flexibly Coupled Two Rotors
Authors: Kunitoh Yohta , Yabuno Hiroshi , Inoue Tsuyoshi , Ishida Yukio
Published: June 2008

Mode localizations in a weakly coupled two-span rotor system are theoretically and experimentally discussed. One rotor has a slight unbalance and the other one is well-assembled. First, the equations governing the whirling motions of the coupled rotors are expressed due to nonlinearity in each span and the weakness of the coupling. The averaged equations are obtained by the method of multiple scales and it is shown that the nonlinear normal modes are bifurcated from the linear normal modes. It results from this bifurcation that the number of nonlinear normal modes exceeds the equivalent degree of freedom of the two-span rotor system, i.e., 2-degree under the assumption that the trajectory of the whirling motion is circle. Also, it is theoretically clarified that whirling motion caused by the unbalance in the rotor is localized in the rotor with unbalance or in one without unbalance depending on the rotational speed. Furthermore, these mode localizations are experimentally confirmed.
Time Delayed Negative Velocity Feedback Design for Active Control of Structures
Authors: Phohomsiri Phailaung , Udwadia Firdaus E.
Published: June 2008

In this paper, we present velocity feedback control design with significant time delays for the active control of structures. Because of the presence of significant time delays, we study the infinite dimensionality of the system with time-delayed control and introduce the concept of the so-called non-system poles. Analytical results related to performance and stability analysis of the new control design are provided. The non-system poles are shown to influence both system stability and system performance and cannot therefore be ignored in time-delayed control systems. We then apply the time delayed negative velocity feedback control methodology to a single-degree-of-freedom system subjected to random ground acceleration. The numerical results show good stability characteristics and effective behavior of the proposed control methodology.
Problem of Uniqueness of Non-Linear Joint Parameter Identification by Force-State Mapping Without Knowing the Joint Model
Authors: Wang J. H. , Huang H. Y.
Published: June 2008

The technique of Force-State Mapping is an important method to identify the parameters of non-linear joints. There are two approaches with the concept of Force-State Mapping, i.e., the time domain and frequency domain approaches. The advantages of the frequency domain approach compared to time domain approach are (1) the number of data points for identification can be drastically reduced; (2) it is possible to select arbitrarily the data in frequency domain for identification. In this work, an example is given to show that the above conclusion (i.e., the advantages of the frequency domain approach) is false. The result identified by the frequency domain approach is data and model dependent. One obtains different parameters when different data or model are used for identification. The reason for the non-uniqueness of the solution is that the joint force can’t be determined completely by a few discrete data in the frequency domain provided that the mathematical model of the joint is not exactly known in advance.
Dynamic Modeling and Experiment Verification of a Piezoelectric Part Feeder
Authors: Chao Paul C. P. , Huang Jeng-Sheng , Chiu Chi-Wei , Wu-Chi Jen Yin
Published: June 2008

The study is aimed to perform dynamic modeling of the part-feeder powered by piezoelectric actuation. This part-feeder consists mainly of a horizontal platform vibrated by a pair of parallel piezoelectric beams. The parts to be transported on the platform march forward owing to their intermittent impacts on the platform. The dynamic modeling technique used herein is essentially the Rayleigh-Ritz method, which first incorporates material properties and constitutive equations of the piezoelectric materials, and then captures the complex dynamics of the parallel-beam piezo-feeder by three lower-order assumed modes in the transverse direction of the vibrating beams. With the three approximated assumed modes in hand, the system dynamics is then represented by three coupled discrete equations of motion. Based on these equations, displacement and velocity of the platform can be approximately obtained. Based on the approximated motions of the platform, the marching speed of the parts with intermittent impacts on the platform can be predicted. Numerical computations are conducted to acquire the estimated marching speed of the parts, along with the experimental study. The comparison between the theoretical predicted transporting speed of the part and the experiment counterparts.
Suppression of Internal Resonances of Rubber Isolators Using Dynamic Vibration Absorbers
Authors: Du Yu , Nikolaidis Efstratios , Burdisso Ricardo A.
Published: June 2008

This paper presents methods to improve the performance of rubber isolators by controlling their Internal Resonances (IRs). IRs are associated with isolators’ internal elastic motions that are due to their inertia. It is well known that IRs degrade the isolator performance as predicted by ideal massless isolator models. However, to the best of the authors’ knowledge, there are no reported works on the suppression of such IRs to improve the isolator performance. This paper proposes two novel approaches to suppress IRs. The first approach uses passive dynamic vibration absorbers (PDVA’s) directly embedded into the isolator. The effectiveness of this approach is investigated analytically using a three degree-of-freedom vibration model. It is shown that the PDVA’s are very effective in attenuating the IRs and improve the isolator’s performance at high frequencies. However, the PDVA’s are ineffective at low frequencies. To overcome this limitation, an active control force is added between the DVA masses, forming the hybrid DVA (HDVA) approach. The effectiveness of both the PDVA and the HDVA approaches is demonstrated experimentally. It is shown that, compared to the original isolator, in the isolation region of the experimental system, adding PDVA’s reduces the force transmissibility by 18.5% and the overall noise radiated by the foundation by 4.3 dB. Furthermore, the HDVA approach reduces the force transmissibility and radiated noise by 92.2% and 9.1 dB, respectively.
An Investigation on Human Vibration Analysis Using Image Processing Method
Authors: Hoviattalab Maryam , Narimani Roya , Mirbagheri Alireza
Published: June 2008

Vibration measurement is an important tool in many research fields; there are several methods for measuring vibration of a system. In conventional methods accelerometers are fixed to the body, so there is a systemic error due to fixing an external object to the body surface that interferes with the true vibration of the body. We have proposed image processing as a new method to record and determine the frequency response of human body. This method provides vibration measuring without using contacting sensors. Moreover the main advantage is its lower noise sensitivity in comparison to accelerometers. Further more another important point is the fact that all devices used in our developed measurement system are usually available in the biomechanics laboratory where a Gait system is functioning. This gives the opportunity for such laboratory to add vibration measurement to its capabilities without much excessive costs.
Improved Description of Elastic Forces for the Absolute Nodal Coordinate Based Plate Element
Authors: Matikainen Marko K. , Mikkola Aki M.
Published: June 2008

In this study, the improved description of elastic forces for the absolute nodal coordinate based plate element is introduced. The absolute nodal coordinate formulation, which utilizes global displacements and slope coordinates as nodal variables, can be used in large rotation and deformation dynamic analysis of beam and plate structures. The formulation avoids difficulties that arise when a rotation is interpolated in three-dimensional applications. In the absolute nodal coordinate formulation, a continuum mechanics approach has become the dominating procedure when elastic forces are defined. It has recently been perceived, however, that the continuum mechanics based absolute nodal coordinate elements suffer from serious shortcomings, including Poisson’s locking and poor convergence rate. These problems can be circumvented by modifying the displacement field of a finite element in the definition of elastic forces. This allows the use of the mixed type interpolation technique, leading to accurate and efficient finite element formulations. This approach has been previously applied to two- and three-dimensional absolute nodal coordinate based finite elements. In this study, the improved approach for elastic forces is extended to the absolute nodal coordinate plate element. The introduced plate element is compared in static examples to the continuum mechanics based absolute nodal coordinate plate element, as well as to commercial finite element software.
Minimax Design of Statistics-Based Control With Noise Uncertainty for Highway Bridges
Authors: Pham Khanh D.
Published: June 2008

An approach for the statistical control of infinite horizon, linear quadratic systems subject to noise uncertainties is presented. The solution lies in the same solution space as the infinite horizon, statistical feedback solution but is designed for a least favorable system model. The impetus for this approach is the active control of seismically induced vibrations in newly constructed 91/5 highway over-crossing in Southern California where the hydraulic actuators working in parallel with passive isolation bearings are now capable of alleviating excessive displacement of bearings and damage to bridge piers during near fault ground motions.
Nonlinear Response of Parametrically-Excited MEMS
Authors: Rhoads Jeffrey F. , Shaw Steven W. , Turner Kimberly L. , Moehlis Jeff , DeMartini Barry E. , Zhang Wenhua
Published: June 2008

Due to the position-dependent nature of electrostatic forces, many microelectromechanical (MEM) oscillators inherently feature parametric excitation. This work considers the nonlinear response of one such oscillator, which is electrostatically actuated via non-interdigitated comb drives. Unlike other parametrically-excited systems, which feature only linear parametric excitation in their equation of motion, the oscillator in question here exhibits parametric excitation in both its linear and nonlinear terms. This complication proves to significantly enrich the system’s dynamics. Amongst the interesting consequences is the fact that the system’s nonlinear response proves to be qualitatively dependent on the system’s excitation amplitude. This paper includes an introduction to the equation of motion of interest, a brief, yet systematic, analysis of the equation’s nonlinear response, and experimental evidence of the predicted behavior as measured from an actual MEM oscillator.
A New High Precision Fitting Approach for NURBS Tool Paths Generation
Authors: Yang Xujing , Chen Zezhong C.
Published: June 2008

In new models of CNC machines, NURBS interpolation function can process tool paths represented in NURBS form (called NURBS tool paths) so that cutters can conduct NURBS motions, which can machine sculptured surfaces with high surface accuracy and finish. However, most CAM systems could not convert the tool paths with discrete cutter locations into NURBS tool paths, and the conventional data fitting methods can not calculate a NURBS curve to represent the given cutter locations in high precision. In this work, a new high precision fitting approach is proposed for generating NURBS tool paths. The main contribution of this work is to propose NURBS tool paths and fit the tool paths through the cutter locations more precisely with fewer control points. Since NURBS tool paths can make accurate and smooth sculpture surfaces, this approach can promote the usage of NURBS tool paths in manufacturing industry.
Product Structure Modelling for the Made-to-Order Environment
Authors: Ni Qianfu , Yarlaggada Prasad K. D. V. , Lu Wen Feng
Published: June 2008

Product structure is the key information widely used by various business activities performed at different departments and different stages. In the made-to-order environment, product structure representation becomes more complicated because each product can have many variants with slightly different constitutions to fulfill different customer requirements. In such a context, product structure management comes to two interrelated functions: family structure management and variant structure management. At the same time, these two functions need to be seamlessly integrated to ensure the consistency of a family structure and its variant structure. From the business process perspective, throughout the entire product lifecycle, different business activities look at product structure with different purposes. Some activities are carried out based on variants and deem individual variants as different products and some need to be performed based on an entire family. As such, it is imperative to develop a product structure model that is capable of flexibly representing product families and product variants to serve up different processes in a product lifecycle. In this paper, a product structure model based on a master-variant pattern is proposed. The model can explicitly represent common characteristics of a family and particular characteristics of individual variants. Moreover, the variant structure representation is built on the top of the family structure representation. As a result, it provides an effective means to synchronize two types of structures. It also makes product family and variant concepts transparent to various business processes so that effective support can be provided to processes integration in the made-to-order environment.
Experimental Parameter Identification of a Time Delayed Oscillator
Authors: Mann Brian P. , Young Keith A. , Helvey Amy M. , Zapata Raul E.
Published: June 2008

This paper departs from the more traditional focus of systems with time delays — the loss of stability — to examine an intrinsic benefit of time-delayed systems and a novel approach for parametric identification. For instance, it is well-known that the presence of a time delay will result in an infinite dimensional phase space and can compromise the stability characteristics of a dynamical system. This paper explores the utilization the system higher dimensional transients to provide benefit to the common problem of system identification. Observations are first made about which experimental milling tests can be utilized for parameter identification. A model for the milling experiment is then introduced and a temporal finite element analysis is performed to transform the original delay equations into the form of a dynamic map. Experimental data is then examined with empirical Floquet theory and principal orthogonal decomposition to estimate the reduced order dynamics, or truncated state space dimension, and to identify the empirical Floquet multipliers of the system. Parametric identification is performed through the optimization of model parameters that satisfy the characteristic equation.
Real-Time Multibody Analysis Environment for Driving Simulator
Authors: Shiiba Taichi , Suda Yoshihiro
Published: June 2008

Driving simulator requires real-time calculation of vehicle dynamics in response to driver’s input, such as steering maneuver, and throttle and brake pedal operation. The authors had developed a driving simulator with a 91-DOF multibody vehicle model, and this driving simulator has been used for the purpose of ‘virtual proving ground’, which means a virtual handling and ride test environment of automobiles with a driving simulator. Multibody analysis results can be evaluated through body sensory information such as acceleration produced by 6-axis motion base and visual information by computer graphics. For real-time analysis with multibody vehicle model, the authors developed an original MATLAB-based multibody analysis program This paper deals with the details about the environment of real-time multibody analysis for driving simulator and its performance, and applications of virtual proving ground.
Trajectory Tracking of a Pneumatic Robot and Its Application in Tele-Calligraphy
Authors: Hu Xudong , Chen Ying , Zhu Zuchao , Wu Chuanyu
Published: June 2008

Pneumatic devices is widely used in industry mainly in the state of open-loop control. In this paper, a pneumatic robot has been implemented in which pneumatic servo control is used to build a close-loop control system. An analytical model of an optimal state-feedback + PI is derived mathematically to describe the current design of the pneumatic robot. Based on this model, its control strategy and simulation are presented. The results show that the optimal state-feedback + PI model can satisfy the requirements of trajectory tracking of the pneumatic robot. A tele-calligraphy system, which can mimic a Chinese calligraphy, is built to test the trajectory tracking characteristics. The experimental results confirm that the pneumatic device can track the trajectory accurately.
A Method to Identify the Stiffness of Engine Mounts Using Experimental Modal Analysis
Authors: Tomatsu Taro , Okada Takeshi , Ikeno Tetsuro , Shiomi Kazuyuki , Okuma Masaaki
Published: June 2008

This paper presents a new method for identifying the stiffness of engine mounts under the condition of being built in a structural system as in practical use. A conventionally standard method is to use a dynamic stiffness measurement equipment that can deal with only an individual mount. In the new method, the stiffness values of mounts built in a structural system are identified using the modal parameters of the system which are obtained by experimental modal analysis. Vibration testing of the structural system in an operational condition can make it possible to consider preload effect caused by the gravitational and driving force, such as thrust force, applied to the structural system. Additionally, vibration testing using an impact hammer is widely available so that the new method can make it much easier to identify the stiffness of mounts in various situations than the conventional method. In this paper, the validity of the method is demonstrated using both a simulation study using a finite element model and an actual trial for an actual outboard engine. The result shows the dependence of the mount stiffness on the gravitational force and the thrust force at the propeller of the outboard engine.
Damage Location Assessment in a Composite Panel by Means of Electronic Speckle Pattern Interferometry Measurements
Authors: Zanarini Alessandro
Published: June 2008

The assessment of structural damage location in composite honeycomb sandwich panels is here pursued by means of a complete experimental non-destructive approach on a pre-damaged sample. In the experiments proposed full field displacement maps were acquired by means of optical non-contact Electronic Speckle Pattern Interferometry (ESPI) technology [1, 2], in order to obtain high spatial definition and locate small defects on the sample, like debondings, material separations, voids, cracks and delaminations. When dealing with holographic/speckle interferometry it is important to find the stressing technique able to produce singularities in the state of the object surface. Four different loading approaches were taken to detect the flaws: acoustic, thermal, static and harmonic excitation. The displacement maps acquired depict with high accuracy the inhomogeneous local behavior of the structure induced by the defects. Results are reported from the different loading approaches and discussed in detail.
A Comparison of Optimized Stacked-Ply Flywheel Designs That Are Based on Different Failure Criteria
Authors: Fabien Brian C.
Published: June 2008

This paper presents some approaches to the optimal design of stacked-ply composite flywheels. The laminations of the disk are constructed such that the principal fiber direction is either tangential or radial. Here, optimization problems are formulated to maximize the energy density of the flywheel. This is accomplished by allowing arbitrary, continuous, variation of the orientation of the fibers in the radial plies. The paper compares designs based on minimizing cost functions related to the (i) the maximum stress, (ii) the maximum strain and (iii) the Tsai-Wu failure criteria. It is shown that the optimized designs provide an improvement in the flywheel energy density when compared to a standard stacked-ply design. The results also show that, for a given disk design, the estimate of the energy density can vary greatly depending on the failure criteria employed.
Machine Fault Detection Using Neuro-Fuzzy Inference System and Genetic Algorithms
Authors: Samanta B.
Published: June 2008

A study is presented to show the performance of machine fault detection using adaptive neuro-fuzzy inference system (ANFIS) and genetic algorithms (GAs), termed here as GA-ANFIS. The time domain vibration signals of a rotating machine with normal and defective gears are processed for feature extraction. The extracted features from original and preprocessed signals are used as inputs to GA-ANFIS for two class (normal or fault) recognition. The number and the parameters of membership functions used in ANFIS along with the features are selected using GAs maximizing the classification success. The results of fault detection are compared with GA based artificial neural network (ANN), termed here as GA-ANN. In GA-ANN, the number of hidden nodes and the selection of input features are optimized using GAs. For each trial, the GA-ANFIS and GA-ANN are trained with a subset of the experimental data for known machine conditions. The trained GA-ANFIS and GA-ANN are tested using the remaining set of data. The procedure is illustrated using the experimental vibration data of a gearbox. The results compare the effectiveness of both types of classifiers (ANFIS and ANN) with GA based selection of features and classifier parameters.
A Study on Dynamic Analysis of the Electrostatic Actuator
Authors: Kim Jinam , Lee Sangkyu , Moon Wonkyu , Choi Jinhwan , Park Ilhan
Published: June 2008

A numerical simulation method is developed to analyze dynamic response of electrostatic actuator, which is electromechanical coupled system. The developed method is applied to find a dynamic response of a cantilever-type switch model, which is a basic component of electro-mechanical coupled system driven by electrostatic force. First, point charges model on conductor is proposed as a lumped parameter model of electrical part. Then, this model is easily incorporated into a multi-body dynamics analysis algorithm, the generalized recursive dynamics formula previously developed by our research group. The resulting motion of equation of a coupled overall system is formulated as a differential algebraic equation form including electrical and mechanical variables together and is simultaneously solved in every time step. To implement this approach into the useful dynamics analysis tool, we used multibody dynamics software (RecurDyn) based on the generalized recursive formula using relative coordinate. The developed numerical simulation tool is evaluated by applying to many different driving condition and switch configuration. The final analysis model will be added to RecurDyn as a basic module for dynamics analysis of electro-mechanical coupled system.