bluuebunny/crossref_metadata_2025 huggingface dataset:
The “Fractional” Kinetic Equations and General Theory of Dielectric Relaxation
Authors: Nigmatullin Raoul R.
Published: June 2008

Based on the Mori-Zwanzig formalism it becomes possible to suggest a general decoupling procedure, which reduces a wide set of various micromotions distributed over a self-similar structure to a few collective/reduced motions describing the relaxation/exchange behavior of a complex system in the mesoscale region. The frequency dependence of the reduced collective motion contains real and pair of complex-conjugate power-law exponents in the frequency domain and explains naturally the “universal response” (UR) phenomenon discovered by A. Jonscher in a wide class of heterogeneous materials. This strict mathematical result allows in developing a consistent and general theory of dielectric relaxation that can describe wide set of dielectric spectroscopy (DS) data measured in some frequency/temperature range in many heterogeneous materials. Based on this result it becomes possible also to suggest a new set of two-pole elements, which generalizes the conventional RLC-elements and can constitute the basis of new theory of the linear electric circuits.
Frequency Domain Analysis of a Fractional Derivative SDOF System
Authors: Sorrentino Silvio , Garibaldi Luigi
Published: June 2008

This paper presents a study of the frequency domain behaviour of a single degree of freedom (SDOF) system with a fractional derivative model, named Fractional Kelvin-Voigt. Frequency response functions (FRFs) as receptance and transmissibility are analytically studied. Then the model is applied to describe the dynamic behaviour of a magneto-mechanic system in the frequency domain, consisting of a body of para or dia-magnetic material vibrating in a field created by a pair of magnets.
A Robust Tool for Tuning and Evaluation of Automobile Motion Controllers
Authors: Naya Miguel A. , Cuadrado Javier
Published: June 2008

During the last years, our group has worked on real-time formulations for the dynamics of multi-body systems. Now, in order to find out whether such methods are suitable to address real industrial problems, we intend to develop control algorithms for a car on its computer model (virtual prototyping), and evaluate the performance of such controllers when implemented on the corresponding physical prototype. This paper addresses the first part of the work. Two maneuvers are to be considered: straight line and obstacle avoidance. The computer model of the car has been coded in Fortran language. Fuzzy logic has been chosen to design the control algorithms, which have been implemented on the Matlab environment. Several alternatives to connect Fortran and Matlab-based functions have been studied, concluding that the most appropriate election depends on the purpose being pursued: controller tuning or onboard use of an already tuned controller. Simulator capabilities have been given to the program by means of a realistic graphical output and game-type driving peripherals (steering wheel and pedals), so that comparison may be established between human and designed automatic control.
Modeling and Simulation Applied to the Design of Hybrid Electric Drive for Military Vehicles
Authors: Wiederrich J. L. , Chung Ting-Hong , Fryer Gregory , Fatemi Bahram
Published: June 2008

This paper describes how modeling and simulation tools are being developed and used to support the design of hybrid electric drive (HED) for future military ground vehicles. The component and controls models described are being developed in a modular form such that they can be used to construct subsystem level models of various proposed HED architectures with a consistent, high level of fidelity. The objective models must predict system performance adequately to support the making of engineering design decisions concerning architecture, control algorithms and component sizing. A brief introduction to the challenges associated with the design of a hybrid electric drive for future military ground vehicles is provided.
Multi-Pulse Chaotic Motions of a Rotor-Active Magnetic Bearing With Time-Varying Stiffness
Authors: Zhang Wei , Yao Ming-Hui , Zhan Xue-Ping , Bai Li-Lai
Published: June 2008

In this paper, we investigate the Shilnikov type multi-pulse chaotic dynamics for a rotor-active magnetic bearings (AMB) system with 8-pole legs and the time-varying stiffness. The stiffness in the AMB is considered as the time varying in a periodic form. The dimensionless equation of motion for the rotor-AMB system with the time-varying stiffness in the horizontal and vertical directions is a two-degree-of-freedom nonlinear system with quadratic and cubic nonlinearities and parametric excitation. The asymptotic perturbation method is used to obtain the averaged equations in the case of primary parametric resonance and 1/2 subharmonic resonance. It is found from the numerical results that there are the phenomena of the Shilnikov type multi-pulse chaotic motions for the rotor-AMB system. A new jumping phenomenon is discovered in the rotor-AMB system with the time-varying stiffness.
Triggering Mechanisms of Limit Cycle Oscillations in a Two Degree-of-Freedom Wing Flutter Model
Authors: Lee Young S. , Vakakis Alexander F. , Bergman Lawrence A. , McFarland D. Michael , Kerschen Gae¨tan
Published: June 2008

We show numerically that the triggering mechanisms of limit cycle oscillations (LCOs) due to aeroelastic instability are composed of a series of resonance captures. We consider a two degree-of-freedom (DOF) wing model with cubic nonlinear stiffnesses in the support, assuming quasi-steady aerodynamics and subsonic flow around the wing. Then, we establish the slow flow dynamics model, using the complexification / averaging technique and considering three frequency components; i.e., the two linear natural frequencies corresponding to heave and pitch and the superharmonic component which appears as three times the pitch frequency. It turns out that the LCO triggering mechanisms consist of mainly three stages: (i) transient resonance capture (TRC); (ii) escape; and (iii) permanent resonance capture (PRC). We examine the characteristics of each stage by way of time response, wavelet transform, phase plane, and instantaneous energy.
Virtual Training Environment for a 3-Axis CNC Milling Machine
Authors: Wasfy Tamer M. , Wasfy Ayman M. , El-Mounayri Hazim , Aw Daniel
Published: June 2008

A virtual training environment for a 3-axis CNC milling machine is presented. The key elements of the environment are: (a) textured 3D photo-realistic virtual models of the machines and lab; (b) machine simulator for the machines’ controls and moving parts; (c) semi-empirical model of the machining operation; (d) hierarchical knowledge-base for process training; (e) unstructured knowledge-base for lecture delivery; (f) natural-language human-like intelligent virtual tutors. Applications of the AVML include: training students to operate manufacturing machines in a safe environment, allowing students and researchers to view and interact with highly accurate physical simulation of manufacturing machines, and optimization of the manufacturing process plan by testing various plans on the virtual machine before actual machining. The virtual training environment will significantly reduce the cost and increase the accessibility and safety of advanced manufacturing training.
Dynamic Response of a Piezoelectric Flextensional Microactuator
Authors: Cheong Jongpil , Tadigadapa Srinivas , Rahn Christopher D.
Published: June 2008

Microactuators capable of providing high resolution displacement and controlled force have many applications in RF MEMS, microfluidics, and motion control. This paper theoretically and experimentally investigates the dynamic response of a piezoelectric flextensional microactuator consisting of a clamped beam that buckles in response to contraction of a bonded PZT support. The DRIE and solder bonding fabrication process produces beams with initial curvature that affects their dynamic response. Unlike previous research where sinusoidal initial beam shapes are analyzed, polynomial initial beam shape enables more accurate prediction of beam natural frequencies and frequency response when compared with experimental results. The inclusion of squeeze film damping between the beam and PZT support enables the model to predict frequency response. Experiments show that mounting the PZT with soft carbon tape limits PZT vibration.
Contact Modeling Technique of a Flexible Piston and Cylinder Using Modal Synthesis Method
Authors: Kim W. K. , Sohn S. H. , Cho H. J. , Bae D. S. , Choi J. H.
Published: June 2008

In this paper, contact modeling technique and dynamics analysis of piston and cylinder system are presented by using modal synthesis method. It is very important to select mode shapes representing a global or local behavior of a flexible body due to a specified loading condition. This paper proposes a technique to generate the static correction modes which are nicely representing a motion by a contact force between a piston and cylinder. First normal modes of piston and cylinder under a boundary condition are computed, and then static correction modes due to a contact force applied at contacted nodes are added to the normal modes. Also, this paper proposes an efficient dynamics analysis process while changing the shape of the piston and cylinder. In optimization process or design study, their geometric data can be changed a bit. The slight changes of their contact surfaces make a high variation of the magnitude of a contact force, and it can yield the different dynamic behavior of an engine system. But, since the variations of the normal and correction modes are very small, the re-computation of their normal and correction modes due to the change of contact surfaces can be useless. Until now, whenever their contact surfaces are changed at a design cycle, the modes have been recomputed. Thus, most engineers in industries have been spent many times in very tedious and inefficient design process. In this paper, the normal and correction modes from the basic geometry of the piston and cylinder are computed. If the geometry shape is changed, nodal positions of the original modal model are newly calculated from an interpolation method and changed geometry data. And then the updated nodes are used to compute a precise contact force. The proposed methods illustrated in this investigation have good agreement with results of a nodal synthesis technique and proved that it is very efficient design method.
Development of a New Multi-Flexible Body Dynamics (MFBD) Platform: A Relative Nodal Displacement Method for Finite Element Analysis
Authors: Bae Dae Sung
Published: June 2008

Recently the analysis of multi flexible body dynamics has been a hot issue in the area of the computational dynamics research. There have been two main streams of research. One is the extension of conventional FEA theory for the multi flexible body systems, using either the total Lagrangian or updated Lagrangian method. The other is the extension of the multi body dynamics theory. The latter is the topic of this research. One essential requirement of a shape function in FEA theory is ability to represent the rigid body motion. This research proposes to use the moving reference frame to represent the rigid body motion. Therefore, the shape function does not need to have ability to represent the rigid body motion. The moving reference frame covers the rigid body. Since the nodal displacements are measured relative to its adjacent moving nodal reference frame, they are still small for a truss structure undergoing large deformations if the element sizes are small. As a consequence, many element formulations developed under small deformation assumptions are still valid for structures undergoing large deformations, which significantly simplifies the equations of equilibrium. Several numerical examples are analyzed to demonstrate the efficiency and validity of the proposed method.
A Methodology for Creating Ontologies for Engineering Design
Authors: Ahmed Saeema , Kim Sanghee , Wallace Ken M.
Published: June 2008

This paper describes a methodology for developing ontologies for engineering design. The methodology combines a number of methods from social science and computer science, together with taxonomies developed in the field of engineering design. A case study is used throughout the paper focusing upon the use of an ontology for searching, indexing and retrieving of engineering knowledge. An ontology for indexing design knowledge can assist the users to formulate their queries when searching for engineering design knowledge. The root concepts of the ontology were elicited from engineering designers during an empirical research study. These formed individual taxonomies within the ontology and were validated through indexing a set of ninety-two documents. Relationships between concepts are extracted as the ontology is populated with instances. The identified root concepts were found to be complete and sufficient for the purpose of indexing. A thesaurus and an automatic classification are being developed as a result of this evaluation. The methodology employed during the test case is presented in this paper. There are six separate stages, which are presented together with the research methods employed for each stage and the evaluation of each stage. The main contribution of this research is the development of a methodology to allow researchers and industry to create ontologies for their particular purpose and to develop a thesaurus for the terms within the ontology. The methodology is based upon empirical research and hence, focuses upon understanding a user’s domain models as opposed to extracting an ontology from documentation.
Shape Recovery From Medical Image Data Using Extended Superquadrics
Authors: Bhabhrawala Talib , Krovi Venkat
Published: June 2008

Rapid and representative reconstruction of geometric shape models from surface measurements has applications in diverse arenas ranging from industrial product design to biomedical organ/tissue modeling. However, despite the large body of work, most shape models have had limited success in bridging the gap between reconstruction, recognition, and analysis due to conflicting requirements. On one hand, large numbers of shape parameters are necessary to obtain meaningful information from noisy sensor data. On the other hand, search and recognition techniques require shape parameterizations/abstractions employing few robust shape descriptors. The extension of such shape models to encompass various analysis modalities (in the form of kinematics, dynamics and FEA) now necessitates the inclusion of the appropriate physics (preferably in parametric form) to support the simulation based refinement process. Thus, in this paper we discuss development of a class of parametric shape abstraction models termed as extended superquadrics. The underlying geometric and computational data structure intimately ties together implicit-, explicit- and parametric- surface representation together with a volumetric solid representation that makes them well suited for shape representation. Furthermore, such models are well suited for transitioning to analysis, as for example, in model-based non rigid structure and motion recovery or for mesh generation and simplified volumetric-FEA applications. However, the development of the concomitant methods and benchmarking is necessary prior to widespread acceptance. We will explore some of these aspects further in this paper supported with case studies of shape abstraction from image data in the biomedical/life-sciences arena whose diversity and irregularities pose difficulties for more traditional models.
A New Look at the Stability Analysis of Delay-Differential Equations
Authors: Kalma´r-Nagy Tama´s
Published: June 2008

It is shown that the method of steps for linear delay-differential equations combined with the Laplace-transform can be used to determine the stability of the equation. The result of the method is an infinite dimensional difference equation whose stability corresponds to that of the transcendental characteristic equation. Truncations of this difference equation are used to construct numerical stability charts. The method is demonstrated on a first and second order delay equation. Correspondence between the transcendental characteristic equation and the difference equation is proved for the first order case.
Parameter Identification of Nonlinear Hybrid Parameter Multibody Dynamic System With Contacts Using a Polynomial Interpolated Taylor Series Method
Authors: Wong Simon C. , Barhorst Alan A.
Published: June 2008

This research work is in the area of structural health monitoring and structural damage mitigation. It advances the method of parameter identification of structures with significant nonlinear response dynamics. The method integrates a nonlinear hybrid parameter multi-body dynamic system (HPMBS) modeling technique with a parameter identification scheme based on a polynomial interpolated Taylor series (PITS) methodology. This work advances the model based structural health monitoring state-of-the-art, by providing a tool to accurately estimate damaged structure parameters through significant nonlinear damage. The significant nonlinear damage implied includes effects from loose bolted joints, dry frictional damping, large articulated motions, etc. Note that currently most damage detection algorithms in structures are based on finding changed stiffness parameters and generally do not address other parameters such as mass, length, damping and joint gaps. The scope of work is the extension of damage detection practice from linear structure to nonlinear structures in civil and aerospace applications. To experimentally validate the developed methodology, we have built a nonlinear HPMBS structure. This structure is used as a test-bed to fine-tune the modeling and parameter identification algorithms. Also, it can be used to simulate bolted joints in aircraft wings, expansion joints of bridges, or the interlocking structures in a space frame. The developed technique has the ability to identify unique damage, such as systematic isolated and noise induced damage that exists in group members and isolated elements. Here, not just the damage parameters such as Young’s modulus are identified, but other structural parameters, such as distributed mass, damping and friction coefficients, can also be identified.
Sub-Optimum H2 Rational Approximations to Fractional Order Linear Systems
Authors: Xue Dingyu¨ , Chen YangQuan
Published: June 2008

In this paper, we propose a procedure to achieve rational approximation to arbitrary fractional order linear time invariant (FO-LTI) systems with sub-optimum H2-norm. Through illustrations, we show that the rational approximation is simple and effective. It is also demonstrated that this sub-optimum approximation method is effective in designing integer order controllers for FO-LTI systems in general form. Useful Matlab codes are also given in the appendices.
Molecular Dynamics Simulations of Carbon Nanotube-Based Oscillators
Authors: Xiao Shaoping , Andersen David R. , Hou Wenyi
Published: June 2008

A [10, 10]/[5,5] nanotube-based oscillator is studied using molecular dynamics in this paper. The inner tube can oscillate inside the outer tube with a stable frequency of 55GHz, if this nanomechanical system is insulated. When temperature effects are considered, it is found that the nanooscillator will stop due to the temperature-related interlayer friction between the outer tube and the inner tube. A nanoelectromechanical system (NEMS) is designed by coating electrodes on the top of the outer tube. The electromagnetic forces, induced by the WRITE voltage pulses that are applied on the electrodes, can overcome the interlayer friction. The frequency of the proposed NEMS oscillator depends on the frequency of the WRITE voltage pulses.
Internally Resonant Nonlinear Free Vibrations of Horizontal/Inclined Sagged Cables
Authors: Rega G. , Srinil N. , Chucheepsakul S.
Published: June 2008

Internally resonant dynamics in the nonlinear free vibrations of suspended cables are analytically investigated by means of a multi-mode Galerkin-based discretization and second-order multiple scales. Emphasis is placed on planar 2:1 internal resonances. The equations of motion of a general inclined cable model, which account for the dynamic extensibility effects and the system asymmetry due to inclined equilibrium, are considered. By considering higher-order effects due to quadratic nonlinearities, approximate closed-form solutions of nonlinear amplitudes, frequencies and dynamic configurations associated with the resonant nonlinear normal modes reveal the dependence of cable nonlinear response on different resonant and non-resonant modes. Based on the modal convergence properties performed on the resonantly activated cables, the illustrative results provide hints for proper reduced-order model selections from the asymptotic solution. The underlying effects of cable inclination and cable sag are presented. The theoretical predictions are validated by finite difference numerical time laws of the original system equations of motion.
A Decision Support Formulation for Design Teams: A Study in Preference Aggregation and Handling Unequal Group Members
Authors: See Tung-King , Lewis Kemper
Published: June 2008

Supporting the decision of a group in engineering design is a challenging and complicated problem when issues like consensus, consistency, conflict, and compromise must be taken into account. In this paper, we present two developments extending the Group Hypothetical Equivalents and Inequivalents Method (Group-HEIM) and making it applicable to new classes of group decision problems. The first extension focuses on handling forms of value functions other than the traditional L1-norm. The second extension focuses on updating the formulation to place unequal importance on the preferences of the group members. Typically, there are some group members whose experience, education, and/or knowledge makes their input more important. The formulation presented in this paper allows team leaders to emphasize the input from certain group members. Illustration and validation of the developments are presented using a vehicle selection problem. Data from twelve engineering design teams is used to demonstrate the application of the method.
Towards Agent-Based Grid-Enabled and Sensor-Driven Fire Dynamics Simulation Harnessed Over Bluetooth and Wi-Fi Devices
Authors: Michopoulos John G. , Tsompanopoulou Panayota , Houstis Elias N. , Joshi Anupam , Avancha Sasikanth , Zhang Haiping
Published: June 2008

The present paper is motivated by the need to develop technological infrastructure for informed and reliable decision support in various crisis and disaster management situations. It describes our prototype data-driven fire hazard simulator capable of predicting fire propagation dynamics that allows the user to take decisions based on reliable micro-future predictions of fire propagation based on potential personnel actions. Several heterogeneous technologies are integrated to achieve this goal. The GRID is utilized for running legacy codes enabling fire-propagation prediction. Sensor networks are used to enable simulation steering and correction. Base-stations enable data and communications coordination. Handheld or other wearable devices are terminal and initial points of interaction of the first responders with the rest of the system. Agent middleware is utilized to coordinate all heterogeneous software present. A demonstration of the first incarnation of this infrastructure is implemented over Bluetooth and WiFi enabled communications between the handheld devices and the base-stations involved.
An Accurate Solution for the Numerical Integral Method of Non-Linear Dynamic Systems
Authors: Li Yongqiang , Liu Jie
Published: June 2008

In this paper, a new method for solving the non-linear dynamic systems by numerical integral method is established. This exact solution is calculated by means of the Duhamel integral. The system equations are satisfied continuously and not discretely as done traditionally. The essential difference of the present method from other works is that the performance of dynamics systems can be traced continuously. Comparisons between the proposed method with traditional techniques are presented. Examples investigated include the large amplitude nonlinear vibration of a simple pendulum of conservation systems, the period of vibration and chaos in the forced vibration of the Van der Pol oscillator of a non-conservation system. The results obtained indicate that the accuracy of the proposed method supersede that of the traditional techniques.
Approximation and Identification of Fractional Systems
Authors: Benchellal Amel , Poinot Thierry , Trigeassou Jean-Claude
Published: June 2008

Heat transfer problems obey to diffusion phenomenon. They can be modelled with the help of fractional systems. The simulation of these particular systems is based on a fractional integrator where the non integer behaviour acts only on a limited spectral band. Starting from frequential considerations, a more general approximation of the fractional system is proposed in this communication. It makes it possible to define a state-space model for simulation of transients, and to carry out an output-error technique in order to estimate the parameters of the model. A real application on a thermal system is presented to illustrate the advantages of the proposed model.
POEMS: Parallelizable Open-Source Efficient Multibody Software
Authors: Critchley James H. , Mukherjee Rudranarayan M. , Ziegler John L. , Anderson Kurt S.
Published: June 2008

This paper introduces POEMS (Parallelizable Open source Efficient Multibody Software) as a modular research package being developed to serve as a backbone software for collaborative research in multibody dynamics. POEMS aims to serve as a repository for archiving efficient implementations of relevant algorithms as well as be applied to real world problems. It contains a growing number of solvers, integrators, and capabilities of modeling system with varied topologies. This software is written in C++ as an object oriented modular code that lends itself very well towards its continuing development as an optimized, customizable, and parallelizable computational tool for multibody dynamics research and application.
Design of an Automobile Seat With Regulations Using Axiomatic Design
Authors: Shin M. K. , Kang B. S. , Kim Y. I. , Yi S. I. , Park G. J.
Published: June 2008

The automobile seat must satisfy various safety regulations for the passenger’s safety. In many design practices, each component is independently designed by concentrating on a single regulation. However, since multiple regulations can be involved in a seat component, there may be a design confliction among the various safety regulations. Therefore, a new design methodology is required to effectively design an automobile seat. The axiomatic approach is employed to consider multiple regulations. The Independence Axiom is used to define the overall flow of the seat design. Functional requirements (FRs) are defined by safety regulations and components of the seat are classified into groups which yield design parameters (DPs). The classification is carried out to keep the independence in the FR-DP relationship. Components in the DP group are determined by using the orthogonal arrays of the design of experiments (DOE). Numerical analyses are utilized to evaluate the safety levels by using a commercial software system for nonlinear transient finite element analysis.
High Performance Low Cost Implementation of FPGA-Based Fractional-Order Operators
Authors: Jiang Cindy X. , Hartley Tom T. , Carletta Joan E.
Published: June 2008

Hardware implementation of fractional-order differentiators and integrators requires careful consideration of issues of system quality, hardware cost, and speed. This paper proposes using field programmable gate arrays (FPGAs) to implement fractional-order systems, and demonstrates the advantages that FPGAs provide. As an illustration, the fundamental operators to a real power is approximated via the binomial expansion of the backward difference. The resulting high-order FIR filter is implemented in a pipelined multiplierless architecture on a low-cost Spartan-3 FPGA. Unlike common digital implementations in which all filter coefficients have the same word length, this approach exploits variable word length for each coefficient. Our system requires twenty percent less hardware than a system of comparable quality generated by Xilinx’s System Generator on its most area-efficient multiplierless setting. The work shows an effective way to implement a high quality, high throughput approximation to a fractional-order system, while maintaining less cost than traditional FPGA-based designs.
Numerical and Experimental Approaches on the Motion of a Tethered System With Large Deformation, Rotation and Translation
Authors: Takehara Shoichiro , Terumichi Yoshiaki , Nohmi Masahiro , Sogabe Kiyoshi , Suda Yoshihiro
Published: June 2008

In this paper, we discuss the motion of a tethered system. In general, a tether is a cable or wire rope, and a tethered system consists of a tether and attached equipment. A tethered subsatellite in space is an example of this system. We consider the tethered system consisting of a very flexible body (the tether) and rigid bodies at one end as our analytical model. A flexible body in planer motion is described using the Absolute Nodal Coordinate Formulation. Using this method, the motion of a flexible body with large deformation, rotation and translation can be expressed with the accuracy of rigid body motion. The combination of flexible body motion and rigid body motion is performed and the interaction between them is discussed. We also performed experiments to investigate the fundamental motion of the tethered system and to evaluate the validity of the numerical formulation. The first experiments were conducted using a steel tether and rubber tether in gravity space. We also conducted experiment of the motion of the tethered system with a rigid body in microgravity space. The numerical solutions using the proposed methods for the modeling and formulation for the tethered system are in good agreement with the experimental results.
Analytical Solutions to Surface Location Error in Milling
Authors: Schmitz Tony L. , Mann Brian P.
Published: June 2008

This paper provides two new analytical solutions to the computation of surface location errors, or part geometric errors that arise due to forced vibrations of the cutting tool, during stable milling. The two approaches are based on frequency domain and harmonic balance analyses. Comparisons between the analytical results, time domain simulation, and experiment are included.
The Effect of Wheel-Rail Interactions on Wagon Dynamics in Braking
Authors: Durali Mohammad , Jalili Mohammad Mahdi
Published: June 2008

The rail-wheel interactions and their effects on the wagon dynamics has been studied in this article. Also the effects of braking on wagon and rail vibrations are studied. The model consists of a wagon with body, two bogies and four wheels having 21 degrees of freedom in a planar arrangement. The rail system is treated as a Timoshenko beam supported by sleepers, ballast, subballast, and subgrade. To determine rail-wheel contact forces, Hertzian nonlinear contact theory and Kalker theory have been used. The model is simulated for a number of working conditions and the results are validated by comparing to previous works in the literature.
Dynamic Hybrid Modeling of the Vertical Z Axis in an HSM Machining Center: Towards Virtual Machining
Authors: Tani Giovanni , Bedini Raffaele , Fortunato Alessandro , Mantega Claudio
Published: June 2008

The paper describes the dynamical real-time simulation of the Z axis of a five axis machining center for high speed milling. The axis consists of a mechanical structure: machine head and electro-mandrel, a CNC Control System provided with feed drives and a Pneumatic System to compensate the weight of the entire vertical machine head. These three sub-systems have been studied and modeled by means of: • FEM modeling of the mechanical structure; • an equation set to represent the main functions of the CNC; • an equation set to represent the functioning of the Pneumatic System. These different modeling sub-systems have been integrated to obtain the entire actual dynamical behavior of the Z axis. A particular analysis was developed to represent the friction phenomena by a specific analytical model. Experimental activity was developed to test and validate the different modeling sub-systems, and other experimental tests were performed on the machining center to compare simulation outputs with experimental responses.
An Activity-Based Costing Method for Product Family Design in the Early Stages of Development
Authors: Park Jaeil , Simpson Timothy W.
Published: June 2008

As the marketplace is changing so rapidly, it becomes a key issue for companies to best meet customers’ diverse demands by providing a variety of products in a cost-effective and timely manner. In the meantime, an increasing variety of capability and functionality of products has made it more difficult for companies that develop only one product at a time to maintain competitive production costs and reclaim market share. By designing a product family based on a robust product platform, overall production cost can be more competitive than competitors selling one product at a time while delivering highly differentiated products. In order to design cost-effective product families and product platforms, we are developing a production cost estimation framework in which relevant costs are collected, estimated, and analyzed. Since the framework is quite broad, this paper is dedicated to refining the estimation framework in a practical way by developing an activity-based costing (ABC) system in which activity costs are mapped to individual parts in the product family, which is called cost modularization, and the activity costs affected by product family design decisions are reconstructed to make the costs relevant to these decisions. A case study involving a family of power tools is used to demonstrate the proposed use of the ABC system.
Comparison of Reduction Methods for Deformable Multibody Dynamics
Authors: Nikravesh Parviz E. , Lin Yi-Shih
Published: June 2008

Several well-known reduction methods for deformable multibody dynamics have been reviewed and compared. All of these methods have been borrowed from structural analysis. A recently proposed reduction method that is derived from the equations of motion, based on a mode condensation process, is also reviewed and compared against the other methods. The general conclusion of this investigation is that the standard condensation methods that are based only on fixed/non-moving boundary conditions should not be used in multibody dynamics. However, when the standard normal modes are accompanied by other properly selected modes, accurate results can be achieved. Similar results can also be obtained by the mode condensation method. The paper pays specific attention to two methods known as the Craig-Bampton reduction and the mode condensation.
Nonlinear Dynamic Analysis and Chaotic Behavior in Atomic Force Microscopy
Authors: Pishkenari Hossein Nejat , Jalili Nader , Alasty Aria , Meghdari Ali
Published: June 2008

The atomic force microscope (AFM) system has evolved into a useful tool for direct measurements of intermolecular forces with atomic-resolution characterization that can be employed in a broad spectrum of applications. In this paper, the nonlinear dynamical behavior of the AFM is studied. This is achieved by modeling the microcantilever as a single mode approximation (lumped-parameters model) and considering the interaction between the sample and cantilever in the form of van der Waals potential. The resultant nonlinear system is then analyzed using Melnikov method, which predicts the regions in which only periodic and quasi-periodic motions exist, and also predicts the regions that chaotic motion is possible. Numerical simulations are used to verify the presence of such chaotic invariant sets determined by Melnikov theory. Finally, the amplitude of vibration in which chaos is appeared is investigated and such irregular motion is proven by several methods including Poincare maps, Fourier transform, autocorrelation function and Lyapunov exponents.
Vibration Isolation Control Via Simultaneous Left and Right Eigenvector Assignment
Authors: Wu T. Y. , Wang K. W.
Published: June 2008

The objective of this research is to investigate the feasibility of utilizing the simultaneous left and right eigenvector assignment concept for vibration isolation feedback control design. The purpose of the right eigenvector assignment method is to alter the closed-loop system modes such that the modal components corresponding to the concerned regions (isolation end of an isolator) have relatively small amplitude. Correspondently, the design goal of left eigenvector assignment is to alter the left eigenvectors of the closed-loop system so that they are as closely orthogonal to the system’s forcing vectors as possible. With this approach, one can achieve both disturbance rejection and modal confinement concurrently for the purpose of vibration isolation. In this research, a new formulation is developed so that the desired left eigenvectors of this integrated system are selected through solving a generalized eigenvalue problem, where the orthogonality indices between the forcing vector and the left eigenvectors are minimized. The components of right eigenvectors corresponding to the concerned regions are minimized concurrently. To realistically implement the algorithm, an integrated closed-loop system with state estimator is developed. Numerical simulations are performed to evaluate the effectiveness of the proposed method on concurrent disturbance rejection and modal confinement for a isolator rod design. Frequency responses of the isolator in the selected frequency range are illustrated. It is shown that with the simultaneous left-right eigenvector assignment technique, both disturbance rejection and modal confinement can be achieved, and thus the vibration amplitude in the isolated regions can be suppressed significantly.
Torsion Vibration Analysis of a Cardan Shaft Driven by a Permanent Magnet Electric Motor
Authors: Sopanen Jussi , Laurila Lasse , Hirvonen Markus
Published: June 2008

An analytical model of a double cardan shaft driveline is presented. The model has been derived by using a Lagrangian dynamics formulation and it includes description of the torsion flexibility of the shafts. The cardan shaft model is used in a coupled simulation with a direct torque controlled permanent magnet synchronous motor. Mechanical and electrical non-idealities affecting the dynamics of the driveline are studied. The modeled non-idealities include unequal joint angles, incorrect phasing of the cardan joints and current measurement errors in the supply of the electric motor. The results show that the control system of the electric drive tries to correct the transmission error caused by the mechanical non-idealities. This in turn leads to fluctuating torque and undesirable dynamic loads.
Closed-Form Solution of Natural Frequencies of a Cantilever Beam Under Longitudinal Rotation of the Support
Authors: Esmaeili Mehdi , Durali Mohammad , Jalili Nader
Published: June 2008

This paper presents the modeling steps towards development of frequency equations for a cantilever beam with a tip mass under general base excitations. More specifically, the beam is considered to vibrate in all the three directions, while subjected to a base rotational motion around its longitudinal direction. This is a common configuration utilized in many vibrating beam gyroscopes and well drilling systems. The governing equations are derived using Extended Hamilton’s Principle with general 6-DOF base motion. The natural frequency equations are then extracted in closed-form for the case where the base undergoes longitudinal rotation. For validation purposes, the resulting natural frequencies are compared with two example case studies; one with a beam on a stationary base and the other one with a rotor having flexible shaft.
Passive, Non-Linear, Mechanical Structures for Seismic Attenuation
Authors: DeSalvo Riccardo
Published: June 2008

Gravitational Wave detectors aim to detect strain perturbations of space-time of the order of 10−21 ~ 10−22 at frequencies between one Hz and a few kHz. This space-time strain, integrated over a few Km long interferometers, will induce movements of suspended mirrors of the order of 10−18 ~ 10−19m. Seismic motion in this frequency band varies between 10−6 and 10−12 m. Required seismic attenuation factors, as large as 10−12, by far exceed the performance of motion sensors, and are only obtained by means of a chain of passive attenuators. High quality springs in configurations yielding non-linear response are used to generate attenuation at low frequency. Similarly non-linear mechanisms are used in the horizontal direction. A description of some of these systems and some of the technical challenges that they involve are presented.
Geometric Simplification to Stream 3D Models for Collaborative Product Design
Authors: Li W. D. , Lu W. F. , Cai Y. L.
Published: June 2008

One of the challenging problems that hinder the development of collaborative design systems is the contradiction of large CAD files and the limited speed to share them over the Internet and Web. 3D streaming technique, which can allow effective and efficient dispatch and access of large-volume CAD data as a series of patched streams across the Internet, provides a promising solution to overcome the obstacle. Geometric simplification (or decimation) of 3D models is the key algorithm to realize the streaming technique. In this paper, a new geometric simplification algorithm has been developed, in which two criteria are the crucial elements to control the collapse process for edges in 3D VRML models to reduce the amount of information. The major feature of the algorithm is that it has incorporated some advantages of the previously developed vertex decimation approach and edge collapse approach. Meanwhile, the mechanism of adaptive threshold parameters adopted in this work enhances the adaptability of the algorithm for various applications. Through case studies and comparisons with some related works, the algorithm shows good performance and potentials in terms of efficiency, adaptability and robustness.
Maximally Robust Sway Free Point-to-Point Transportation of Boom Crane Loads by a FIR Filtering Approach of the Motion Commands
Authors: Glossiotis G. , Antoniadis I.
Published: June 2008

A new method for sway suppression of boom crane loads is implemented, which is based on the application of appropriate filters on the motion commands. A typical boom crane mechanism is considered, which accomplishes independently the luffing and hoisting motions, needed for load grabbing, transfer and final positioning. The resulting dynamic model of the crane mechanism leads to a strongly non-linear and time varying problem. Property designed Finite Impulse Response (FIR) filters are then applied to the typical motion commands of the system. The resulting filtered motion commands are shown to effectively suppress the payload sway during and after the motion of the mechanism, leading to a minimization of the operating cycle of the crane. Additionally, due to the smooth nature of the resulting motion, decreased stresses result on the crane structure and the motion components, and thus, the life cycle of the equipment can be extended.
A Study of Convergence and Mapping in Multiobjective Optimization Problems
Authors: Ferguson Scott , Gurnani Ashwin , Donndelinger Joseph , Lewis Kemper
Published: June 2008

In this paper, we investigate the issue of convergence in multiobjective optimization problems when using a Multi-Objective Genetic Algorithm (MOGA) to determine the set of Pareto optimal solutions. Additionally, given a Pareto set for a multi-objective problem, the mapping between the performance and design space is studied to determine design variable configurations for a given set of performance specifications. The advantage of this study is that the design variable information is obtained without having to repeat system analyses. The tools developed in this paper have been applied to develop a Technical Feasibility Model (TFM) used by General Motors as well as a simple multiobjective optimization problem in this paper. The multi-objective problem is primarily used to illustrate the developed methodology.
Dynamic Simulation of Travelling Wave Ultrasonic Motors for Aerospace Application
Authors: Pirrotta Simone , Sinatra Rosario , Meschini Alberto , Poli Stefano
Published: June 2008

In this paper a dynamic simulation of a new model for a Travelling Wave Ultrasonic Motor for antennas’ reflectors positioning, developed by Alenia Spazio S.p.A. (Roma, Italy) within an Italian Space Agency (ASI) development Program, is described. The dynamic equations for the stator and the rotors of the ultrasonic motor are assumed into a differential system, whose equations are coupled by terrms which represent interface generalized forces. Neglecting transient conditions, the complete mathematic model of the system is solved and an iterative process is developed, in order to obtain the motor’s running curves for different operation parameters, geometric dimensions and physical features of the system. The algorithm is implemented in Matlab® environment and a Graphical User Interface is constructed for user-friendly managing. This model represents a simple and powerful aid to determine final motor design that can satisfy specifications or to predict motor’s behaviour under different working conditions, as orbital ones.
Role of Multibody Dynamics in the Design of Chain Drive Systems
Authors: Prescott William C. , Moss Keith D. , Powell Michael S.
Published: June 2008

Some of the most common warranty claims in the automotive business today are noise and vibration (NVH) complaints. Compounding the problem is use of extended warranties leaving the OEM subject to claims for longer periods of time. CAE tools that can help predict and eliminate such problems earlier in the design cycle can dramatically reduce overall warranty claims during the product’s lifecycle. Presented in this paper is the chain drive application from an automotive OEM. The focus of the project is to identify sources of clatter, whine and rattle from a balancer chain. Multibody Dynamics Simulation (MBS) software will be used to build a virtual version of the chain system. The MBS tools are then used to predict the impact forces between the chain and different components of the system. MBS software is also used to evaluate different designs to determine which designs best reduce the clatter of the chain.