bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration Analysis of an Unbalanced Rotating Shaft Due to Ball Waviness
Authors: Upadhyay S. H. , Jain S. C. , Harsha S. P.
Published: July 2010

This paper presents an analytical model to investigate the nonlinear dynamic analysis of high speed ball bearings due to ball waviness and unbalanced rotor. The Hertzian contact theory is applied to calculate the elastic deflection and nonlinear contact force, while the rotor has translational and angular motions. In the analytical formulation, the contacts between rolling elements and inner/outer races are considered as nonlinear springs. A nonlinear damping formula, correlating the contact damping force with the equivalent contact stiffness and contact deformation rate is used in the derivation. The numerical integration technique Newmark-β with Newton-Raphson method is used to solve the nonlinear differential equations iteratively. The results are presented in the form of FFTs. The formulation predicts the discrete spectra with specific frequency components for each order of ball waviness. Numerical results obtained from the simulation are validated with respect to those of prior results. Due to an unbalanced rotor, the system is bi-periodically excited. In the vibration spectrum, the peak amplitude of vibrations appears at the wave passage frequency (Nwωroll), rotational frequency (X) and interaction between wave passage and rotational frequencies.
Identification of Failure Precursor Parameters for Cooling Fans
Authors: Oh Hyunseok , Shibutani Tadahiro , Pecht Michael
Published: July 2010

Cooling fans have been a critical part of the thermal management of commercial and military electronic equipment. Although accelerated testing by increasing operating temperatures has been commonly adopted in order to estimate the reliability of cooling fans in a short time frame, the testing time is usually more than 6 months due to the high reliability of current ball bearings. Prognostics and health management is a potential way to solve this problem. The first step in PHM is to identify precursor parameters. This article begins with the identification of precursor parameters from published studies and failure modes, mechanisms, and effects analysis (FMMEA). The health of cooling fans was estimated by monitoring three precursor parameters including acoustic noise, shaft rotational speed, and current consumption. Then the parameter value changes were compared to the failure criteria described in the IPC-9591 standard.
Operational Parameter Study of Aircraft Ground Dynamics
Authors: Rankin James , Krauskopf Bernd , Lowenberg Mark , Coetzee Etienne
Published: July 2010

The dynamics of passenger aircraft on the ground are influenced by the nonlinear characteristics of several components, including geometric nonlinearities, the aerodynamics and interactions at the tyre-ground interface. We present a fully parametrised mathematical model of a typical passenger aircraft that includes all relevant nonlinear effects. The full equations of motion are derived from first principles in terms of forces and moments acting on a rigid airframe, and they include implementations of the local models of individual components. The overall model has been developed from and validated against an existing industry-tested SimMechanics model. The key advantage of the mathematical model is that it allows for comprehensive studies of solutions and their stability with methods from dynamical systems theory, in particular, the powerful tool of numerical continuation. As a concrete example, we present a bifurcation study of how fixed-radius turning solutions depend on the aircraft’s steering angle and centre of gravity position. These results are represented in a compact form as surfaces of solutions, on which we identify regions of stable turning and regions of laterally unstable solutions. The boundaries between these regions are computed directly and they allow us to determine ranges of parameter values for safe operation. The robustness of these results under the variation of an additional parameter, specifically, the engine thrust is investigated. Qualitative changes in the structure of the solutions are identified and explained. Overall our results give new insight into the possible turning dynamics of the aircraft in dependence on three parameters of operational relevance.
Performance of Curved Beam Elements Using the Absolute Nodal Coordinate Formulation
Authors: Sugiyama Hiroyuki , Koyama Hirohisa , Yamashita Hiroki
Published: July 2010

In this investigation, a gradient deficient beam element of the absolute nodal coordinate formulation is generalized to a curved beam for the analysis of multibody systems and the performance of the proposed element is discussed by comparing with the fully parameterized curved beam element and the classical large displacement beam element with incremental solution procedures. Strain components are defined with respect to the initially curved configuration and described by the arc-length coordinate. The Green strain is used for the longitudinal stretch, while the material measure of curvature is used for bending. It is shown that strains of the curved beam can be expressed with respect to those defined in the element coordinate system using the gradient transformation and the effect of strains at the initially curved configuration is eliminated using one-dimensional Almansi strain. This property can be effectively used with non-incremental solution procedure employed for the absolute nodal coordinate formulation. Several numerical examples are presented in order to demonstrate the performance of the gradient deficient curved beam element developed in this investigation. It is shown that the use of the proposed element leads to better element convergence as compared to that of the fully parameterized element and the classical large displacement beam element with incremental solution procedures.
Some Remarks About the Decoupling Approximation of Damped Linear Systems
Authors: Morzfeld Matthias , Ajavakom Nopdanai , Ma Fai
Published: July 2010

A common approximation in the analysis of non-classically damped systems is to ignore the off-diagonal elements of the modal damping matrix. This procedure is termed the decoupling approximation. It is generally believed that errors due to the decoupling approximation should be negligible if the modal damping matrix is diagonally dominant. In addition, the errors are expected to decrease as the modal damping matrix becomes more diagonally dominant. It is shown numerically in this paper that, over a finite range, errors due to the decoupling approximation can increase monotonically at any specified rate while the modal damping matrix becomes more diagonally dominant with its off-diagonal elements decreasing continuously in magnitude. These unexpected drifts in errors due to the decoupling approximation can be observed at any driving frequency. Small off-diagonal elements in the modal damping matrix may not be sufficient to ensure small errors due to the decoupling approximation. Error-criteria based solely upon diagonal dominance of the modal damping matrix cannot be accurate.
Gearbox On-Line Condition Monitoring Using Empirical Mode Decomposition
Authors: Miao Qiang , Wang Dong , Huang Hong-Zhong , Zheng Bin , Fan Xianfeng
Published: July 2010

As a flexible maintenance strategy, Condition Based Maintenance (CBM) has been accepted by industry due to its efficiency and robustness in many engineering practices. Successful implementation of CBM relies on observation of actual health condition of machinery. Therefore, it is crucial to perform condition monitoring in CBM. This paper focuses on quantifying health condition of machinery. Empirical Mode Decomposition (EMD) is employed to decompose signal and extract dominant signatures, which could reflect health condition variation of machinery. Then, a novel index called Health Index (HI) is proposed to describe condition development trends. In order to detect occurrence of early faults, a dynamic threshold is also proposed. In case occurrence of early fault, HI should be higher than its corresponding threshold. This novel condition monitoring method is more appropriate for on-line health monitoring and detection of incipient fault. Two sets of data collected from gearboxes are used to validate the proposed method. The analysis results show that the proposed method is effective in condition monitoring, especially the detection of early faults.
Minimum Energy Control of Multibody Systems Utilizing Storage Elements
Authors: Schiehlen Werner , Iwamura Makoto
Published: July 2010

In this paper, we consider the problem to minimize the energy consumption for controlled multibody systems utilizing passive elastic elements for energy storage useful for robot systems in manufacturing. Firstly, based on the linearized equations of motion, we analyze the relationship between the consumed energy and the operating time, and the optimal trajectory using optimal control theory. Then, we verify the analytical solution by comparing with the numerical one computed considering the full nonlinear dynamics. After that we derive a condition for the operating time to be optimal, and propose the optimal design method for springs. Finally, we show the effectiveness of the design method by applying it to a 2DOF manipulator.
Experimental Study on the Nonlinear Vibration Response of Cone-Shaped Spring Isolator
Authors: Liu Shu-yong , He Qi-wei , Zhang Zhen-hai , Zhu Shi-jian
Published: July 2010

The nonlinear vibration responses of cone-shaped spring isolator system were studied experimentally in this paper. Firstly, the experimental platform was designed and the response of the system under different excitation parameters was researched. The period-2 and period-3 behaviour were observed. When the parameters are in the special range, system exhibits transient chaos behaviour. The phase space attractor was reconstructed with the nonlinear time series analysis method. The Lyapunov exponent was calculated on the basis of reconstruction. The strange non-chaos phenomenon was observed in experiment. Finally, the prediction algorithm was applied to the different signals. This conclusion can be used to identify chaos in experimental flowchart as well.
Fault Diagnosis of Rotating Machinery Due to Clearance Using Hilbert-Huang Transform
Authors: Choi Yeon-Sun
Published: July 2010

The faults in rotating machinery, caused by the clearance between the rotor and the stator, commonly lie on partial rub and looseness. These problems cause malfunctions in rotating machinery since they create strange vibrations coming from impact and friction. However, non-linear and non-stationary signals due to impact and friction are difficult to identify. Therefore, exact time and frequency information are needed for identifying these signals. For this purpose, a newly developed time-frequency analysis method, HHT(Hilbert-Huang Transform), is applied to the signals of partial rub and looseness from the experiment RK-4 rotor kit. Conventional signal processing methods such as FFT, STFT and CWT were compared to verify the effectiveness of fault diagnosis using HHT. The results showed that the impact signals were generated regularly when partial rub occurred but that intermittent impact and friction occurred irregularly when looseness occurred. The time and frequency information was represented exactly by using HHT in both cases, which makes clear fault diagnosis between partial rub and looseness.
A Probabilistic Approach for Determining the Component’s Dimension Under Fatigue Loadings
Authors: Le Xiaobin , Rasty Jahan
Published: July 2010

Due to inherent scatters in fatigue test data, the P-S-N curves are normally used to describe material fatigue behaviors. For probabilistic component’s design under fatigue loadings, the component’s dimension should be treated as a random variable because every dimension is certainly with a dimension tolerance. In this design scenario, it is difficult to determine the component’s dimension under fatigue loadings by using the P-S-N curves because stress levels are unknown and random variables. In this paper, a probabilistic approach is presented to build a generic probabilistic design equation which is governed by random variables related to material fatigue behaviors, component conditions and fatigue loadings. The generic probabilistic design equation can be used to determine component’s dimension with a given reliability. One example is presented for explaining the approach in details.
Nonlinear Dynamics of Curved Beam: Parametric Space Classification
Authors: Brezhnev Dmitriy , Shukla Amit
Published: July 2010

Future hypersonic aircraft structure requires enhanced performance, reduced maintenance and shorter turn-around times for persistent strike capabilities. Such development requires further understanding of the hypersonic environment and its interaction with the vehicular structures. A study of the effect of combined harmonic and random excitation of a curved beam, representative of aircraft structure, is presented. A classification of the loading parametric space is developed to understand the trade-offs in the response of the model. Bifurcation diagrams and phase portraits are used to comprehend the complete response dynamics. Further, increased levels of random excitation in conjunction with harmonic loading are studied for its effect on the definition of the parameter space boundaries. The understanding of the representative curved structure’s response to the parameters associated with the operational environment is essential for the design of structures for hypersonic aircrafts of the future.
An Extended Continuation Problem for Bifurcation Analysis in the Presence of Constraints
Authors: Dankowicz Harry , Schilder Frank
Published: July 2010

This paper presents an extended formulation of the basic continuation problem for implicitly-defined, embedded manifolds in Rn. The formulation is chosen so as to allow for the arbitrary imposition of additional constraints during continuation and the restriction to selective parametrizations of the corresponding higher-co-dimension solution manifolds. In particular, the formalism is demonstrated to clearly separate between the essential functionality required of core routines in application-oriented continuation packages, on the one hand; and the functionality provided by auxiliary toolboxes that encode classes of continuation problems and user-definitions that narrowly focus on a particular problem implementation, on the other hand. Several examples are chosen to illustrate the formalism and its implementation in the recently developed continuation package COCO and auxiliary toolboxes, including continuation of families of periodic orbits in a hybrid dynamical system with impacts and friction as well as detection and constrained continuation of selected degeneracies characteristic of such systems, such as grazing and switching-sliding bifurcations.
Invariant Modeling of Mechanical Systems in Terms of Quasi-Velocities and Quasi-Forces
Authors: Aghili Farhad
Published: July 2010

A gauge-invariant formulation for deriving the dynamic equations of constrained multi-body systems (MBS) in terms of (reduced) quasi–velocities is presented. This formulation does not require any weighting matrix to deal with the gauge-invariance problem when both translational and rotational components are involved in the generalized coordinates or in the constraint equations. Moreover, in this formulation the equations of motion are decoupled from those of constrained force and each system has its own independent input. This allows the possibility to develop a simple force control action that is totally independent from the motion control action facilitating a hybrid force/motion control. Tracking force/motion control of constrained multi-body systems based on a combination of feedbacks on the vectors of the quasi–velocities and the configuration variables are presented.
On the Geometric Stabilization for Discrete Hamiltonian Systems With Holonomic Constraints
Authors: Yoshimura Hiroaki , Soya Kenji
Published: July 2010

This paper develops a discrete Hamiltonian system with holonomic constraints with Geometric Constraint Stabilization. It is first shown that constrained mechanical systems with nonconservative external forces can be formulated by using canonical symplectic structures in the context of Hamiltonian systems. Second, it is shown that discrete holonomic Hamiltonian systems can be developed via the discretization based on the Backward Differentiation Formula and also that geometric constraint stabilization can be incorporated into the discrete Hamiltonian systems. It is demonstrated that the proposed method enables one to stabilize constraint violations effectively in comparison with conventional methods such as Baumgarte Stabilization and Gear–Gupta–Leimkuhler Stabilization, together with an illustrative example of linkage mechanisms.
Opinion Extraction From Customer Reviews
Authors: Loh Han Tong , Sun Jie , Wang Jingjing , Lu Wen Feng
Published: July 2010

The internet offers a new channel for product designers to obtain valuable information about customer’s opinions which are very important to product development, especially at the product concept design stage. Due to the rapid growth of such information, it is difficult for humans to manage and analyze all these information. Therefore, an alternative choice is to perform opinion mining with automatic textual mining techniques. In this research, we propose a hybrid opinion extraction (HOE) framework that can extract features and predict semantic orientation of the expressed opinions, from the free format text. The framework is inspired by capturing the characteristics of the way people express opinions, utilizes both statistical regularities of the patterns and some prior knowledge. Compared to previous work, our opinion mining technique has demonstrated its better performance in terms of extracting features and predicting semantic orientations of opinions. Thus it has the potential to be adopted by product designers as an efficient tool for quickly obtaining customer feedback.
Design of a Four Legged Parallel Mechanism to Improve the Dexterity of Walking Robot
Authors: Kim ChiHyo , Park KunWoo , Kim TaeSung , Lee MinKi
Published: July 2010

This paper designs a four legged parallel mechanism to improve the dexterity of three layered parallel walking robot. Topology design is conducted for a leg mechanism composed of four legs, base and ground, which constitute a redundant parallel mechanism. This mechanism is subdivided into four sub-mechanism composed of three legs. A motor vector is adopted to determine the 6×8 Jacobian of the redundant parallel mechanism and the 6×6 Jacobian of the sub-mechanisms, respectively. The condition number of the Jacobian matrix is used as an index to measure a dexterity. We analyze the condition numbers of the Jacobian over the positional and orientational walking space. The analytical results show that a sub-mechanism has lots of singularities within workspace but they are removed by a redundant parallel mechanism improving the dexterity. This paper presents a parallel typed walking robot to enlarge walking space and stability region. Seven types of three layered walking robots are designed by inserting an intermediate mechanism between the upper and the lower legged parallel mechanisms. They provide various types of gaits to walk rough terrain and climb over a wall with small degrees of freedom.
A Parametric Study on the Baumgarte Stabilization Method for Forward Dynamics of Constrained Multibody Systems
Authors: Flores Paulo , Machado Margarida , Seabra Eurico , Tavares da Silva Miguel
Published: July 2010

This paper presents and discusses the results obtained from a parametric study on the Baumgarte stabilization method for forward dynamics of constrained multibody systems. The main purpose of this work is to analyze the influence of the variables that affect the violation of constraints, chiefly the values of the Baumgarte parameters, the integration method, the time step and the quality of the initial conditions for the positions. In the sequel of this process the formulation of the rigid multibody systems is reviewed. The generalized Cartesian coordinates are selected as the variables to describe the bodies’ degrees of freedom. The formulation of the equations of motion uses the Newton-Euler approach that is augmented with the constraint equations that lead to a set of differential algebraic equations. Furthermore, the main issues related to the stabilization of the violation of constraints based on the Baumgarte approach are revised. Special attention is also given to some techniques that help in the selection process of the values of the Baumgarte parameters, namely those based on the Taylor’s series and Laplace transform technique. Finally, a slider crank mechanism with eccentricity is considered as an example of application in order to illustrated how the violation of constraints can be affected by different factors such as the Baumgarte parameters, integrator, time step and initial guesses.
Mechanics of Heterogeneous Fluctuating Elastic Rods
Authors: Su Tianxiang , Purohit Prashant K.
Published: July 2010

Biofilaments, such as actin and DNA, have for long been modeled as thermally fluctuating elastic rods with homogeneous material properties. Such models are adequate if the length scale of the filaments being studied is much larger than the scale of the heterogeneity. However, advanced single molecule experimental techniques have now made it possible to probe the properties of biomolecules at the scale of a few nanometers. The data emerging from these experiments ought to be greeted with appropriately detailed models. In this paper we study the mechanics of a thermally fluctuating elastic rod whose moduli are a function of position. Such a rod can be used as a model for DNA whose sequence specific properties are known or for a protein oligomer in an AFM where some of the monomers might be unfolded. The mechanics of these rods is understood by first evaluating a partition function through path integral techniques. We develop a computational technique to efficiently evaluate the partition function and use it to obtain the force-extension relation of a fluctuating rod with two different bending moduli as would be the case for a partially unfolded protein oligomer stretched in an AFM. The variance of the transverse fluctuations of the protein oligomer is also evaluated and are found to agree with the results of a Monte Carlo simulation.
GPU Collision Detection Using Spatial Subdivision With Applications in Contact Dynamics
Authors: Mazhar Hammad
Published: July 2010

This work concentrates on the issue of rigid body collision detection, a critical component of any software package employed to approximate the dynamics of multibody systems with frictional contact. This paper presents a scalable collision detection algorithm designed for massively parallel computing architectures. The approach proposed is implemented on a ubiquitous Graphics Processing Unit (GPU) card and shown to achieve a 40x speedup over state-of-the art Central Processing Unit (CPU) implementations when handling multi-million object collision detection. GPUs are composed of many (on the order of hundreds) scalar processors that can simultaneously execute an operation; this strength is leveraged in the proposed algorithm. The approach can detect collisions between five million objects in less than two seconds; with newer GPUs, the capability of detecting collisions between eighty million objects in less than thirty seconds is expected. The proposed methodology is expected to have an impact on a wide range of granular flow dynamics and smoothed particle hydrodynamics applications, e.g. sand, gravel and fluid simulations, where the number of contacts can reach into the hundreds of millions.
Simulation of Deformation of Diaphragm Spring Grooved With Spiral Slits by FE Method
Authors: Qi Yingxia , Wu Yinong , Zhang Hua , Chen Xi
Published: July 2010

Flexible bearing system composed of diaphragm springs are a key component part of miniature Stirling cooler with linear motors. The stress distribution, the natural frequency, and visualization of the deformation of the diaphragm spring are investigated by finite Element method. From the calculation results of deformation pattern, it is confirmed that the calculation models and methods are appropriate. The stress calculation results reveal that the stress concentrations occur in some special parts of the diaphragm spring, such as root, and middle narrowest parts of the arms. The axial stiffness has the linear relation while the radial stiffness has the non-linear but hyperbolic relation with the disc thickness. The calculation results are in good agreement with the experimental results. The calculation results have been used to optimize the shapes of the diaphragm spring and manufacturing process.
Theoretical and Experimental Investigations of Nonlinear Vibrations for a Beam Structure
Authors: Cao Dong-xing , Yao Ming-hui , Zhang Wei , Wang Qian
Published: July 2010

This paper discusses theoretical and experimental investigations of the planar nonlinear vibrations and chaotic dynamics of a beam structure composed of two beams with right-angled L-shape. Differential equations of motion for the L-shape beam structure with two-degree-of-freedom are derived firstly by application of the substructure synthesis method and the Lagrangian equation. Then, the method of multiple scales is utilized to obtain a four-dimensional averaged equation of the structure. Based on the averaged equations, numerical simulations are presented to analyze the nonlinear responses and chaotic dynamics of the L-shape beam structure. The bifurcation diagram, phase portrait, amplitude spectrum and Poincare map are plotted to illustrate that the periodic solutions and chaotic motions occur in the planar nonlinear vibrations of the L-shaped beam structure under certain conditions. Finally, the experimental apparatus and schemes for measuring the amplitude of nonlinear vibrations for the L-shape beam structure are introduced briefly. Then, the detailed analysis for experimental data and signals which represent the nonlinear responses of the beam structure are given.
Nonlinear Dynamics of Duffing System With Fractional Order Damping
Authors: Cao Junyi , Ma Chengbin , Xie Hang , Jiang Zhuangde
Published: July 2010

In this paper, nonlinear dynamics of Duffing system with fractional order damping is investigated. The four order Runge-Kutta method and ten order CFE-Euler methods are introduced to simulate the fractional order Duffing equations. The effect of taking fractional order on the system dynamics is investigated using phase diagrams, bifurcation diagrams and Poincare map. The bifurcation diagram is also used to exam the effects of excitation amplitude and frequency on Duffing system with fractional order damping. The analysis results show that the fractional order damped Duffing system exhibits period motion, chaos, period motion, chaos, period motion in turn when the fractional order changes from 0.1 to 2.0. A period doubling route to chaos is clearly observed.
Computed Torque Control Method for Under-Actuated Manipulator
Authors: Zelei Ambrus , Kova´cs La´szlo´ L. , Ste´pa´n Ga´bor
Published: July 2010

The paper presents the dynamic analysis of a crane-like manipulator system equipped with complementary cables and ducted fan actuators. The investigated under-actuated mechanical system is described by a system of differential-algebraic equations. The position/orientation control problem is investigated with respect to the trajectory generation and the fine positioning of the payload. The closed form results include the desired actuator forces as well as the nominal load angle corresponding to the desired motion of the payload. Considering a PD controller, numerical simulation results and also experiments demonstrate the applicability of the concept of using complementary actuators for controlling the swinging motion of the payload.
Simulation Based Design of Electromechanical Actuators With Modelica
Authors: Budinger Marc , Liscoue¨t Jonathan , Cong Yu , Mare´ Jean-Charles
Published: July 2010

This article deals with a methodology for the computer-aided design of electromechanical actuators. In the frame of the preliminary design, it focuses on the selection and sizing of various components used in the actuator architectures. The addressed design criteria are the mass and reliability for given effort and speed profiles. The developed library of components for the simulation takes advantage of the non-causal and object oriented characteristics of the Modelica language. Thus, the library models can carry out an inverse simulation of the energy flows going from the mechanical load to the power source. Additionally, the number of parameters to be entered by the user has been minimized by the use of scaling laws, which return all the parameters that are necessary for the simulation. At the end of the article, the proposed approach is illustrated with the sizing and comparison of actuator architectures for an aircraft landing gear steering system.
Self-Learning Control of Free-Floating Dual-Arm Space Robot Based on Fuzzy Adaptive Compensator
Authors: Jie Liang , Li Chen
Published: July 2010

This paper discusses control problem of free-floating dual-arm space robot system with unknown payload parameters to track desired trajectory in inertial space, when the attitude of base is controlled and its location is uncontrolled. Combining the relationship of the linear momentum conversation and the Lagrange approach, the full-controlled dynamic equation and the Jacobian relation of free-floating dual-arm space robot are analysed and established. Based on the above results, for the case of free-floating dual-arm space robot system with unknown payload parameters, a composite control scheme is designed on the base of a computed torque controller and a fuzzy compensator to track desired trajectories in inertial space, i.e., balancing the effect of system unknown payload parameters on computed torque controller with fuzzy adaptive compensator, in order to ensure the whole closed-loop control system asymptotic stability with the existence of unknown payload parameters. The mentioned control scheme can effectively overcome the effect of system unknown payload parameters and control both the base attitude and the end-effector of dual-arm space robot, so that they can track the desired trajectory in inertia space, with obvious advantages neither the mentioned control scheme needs to measure and feedback the position, velocity and acceleration of the floating base, nor the mentioned control scheme needs to requirements for the dynamic equations of the system inertial parameters in linear function. A two planar dual-arm space robot system is simulated to verify the effectiveness of the proposed control scheme.
A Robust Initial Matching Scheme for Free-Form Object Geometry
Authors: Feng Hsi-Yung Steve , OuYang Daoshan , Jahangir Nimun A. , Song Hao
Published: July 2010

The problem of matching two point cloud data sets, or identifying the correct rigid-body transformation between them, arises in various areas such as manufacturing inspection and object recognition. Existing methods establish the correspondence between the two data sets via the measure of shortest Euclidean distance and rely on an iterative procedure to converge to the solution. The effectiveness of such methods is highly dependent on the initial condition for the numerical iteration. This paper proposes a robust scheme to automatically generate the needed initial matching condition. The initial matching scheme undertakes the alignment in a global manner and yields a rough match of the data sets. Instead of directly minimizing the distance measure between the data sets, the focus of the initial matching is on the alignment of shape features. This is achieved by evaluating Delaunay pole spheres for the point cloud data sets and analyzing their distributions to map out the intrinsic features of the underlying surface shape. The initial matching result is then fine-tuned by the final matching step via existing methods such as the iterative closest point method. Extensive case studies have shown that the proposed initial matching scheme is able to significantly improve the matching accuracy.
Defining Objects for Virtual Engineering
Authors: McCorkle Douglas S. , Bryden Kenneth M.
Published: July 2010

The technology progression over the past decade has redefined the product engineering process. Some of the challenges facing the engineering community are the advent of ubiquitous computing, software integration, and data avalanche. Engineering objects are being defined and implemented to help engineers meet these challenges. As defined in this research, engineering objects have several inherent abilities that enable them to adapt to surroundings and distinguish themselves from other objects coexisting in the same environment. These objects manage information by grouping it based on its physical counterpart, enabling users to interact intuitively with information through a single engineering object interface, and making information gathering from disparate software packages unnecessary. This paper discusses software objects as a theoretical foundation for implementing engineering objects and providing engineers with a platform to create virtualized products more naturally and rapidly.
EHK Index Method for Calculating Discrete Fourier Transform
Authors: Khalil Ethar H.
Published: July 2010

A new mathematical model has been achieved, for the calculation of DFT and its inversion depending on the indices which represent the shortest way for referring to the elements, pixels or pixels in each slide dealing with 1-D, 2-D, and 3-D digital signals respectively. This method indicates clearly the contribution factor of each input signal element in each output signal element.
A Extended Algorithm for Generation of Fibrous Form in the Emergent Design System
Authors: Sato Koichiro , Ujiie Yoshiki , Matsuoka Yoshiyuki
Published: July 2010

In the early design process called conceptual design and basic design, diverse ideas of design must be obtained from global solution search under the constraint of unclear design conditions. It is difficult to apply the conventional engineering design method from the necessity of the setting of the objective function in the early design process. Therefore, in a previous study, the emergent design system, which is applicable from the early design process, has been proposed. In this study, the degree of freedom in an emergent design solution was extended, to form a method with two types of form elements: existing form elements (matrix element) and fiber form elements. To help construct the system, a differentiation phenomenon, which is seen in the morphogenesis of organisms with diverse forms, was introduced into the form generation algorithm in this system, and the relationship between the input parameters and the newly defined evaluation indexes was analyzed.
A Method for Extraction of Potential Emotional Quality by Analysing Emotional Response Towards Unexplored Design: Application to Product Sound Quality
Authors: Yanagisawa Hideyoshi , Murakami Tamotsu , Yoshinaga Ryo , Ohtomi Koichi , Hosaka Rika
Published: July 2010

An emotional quality is a product quality that is evaluated by the customer’s subjective impressions, feelings and emotions. In the design of emotional qualities, one of the most important and difficult issues is setting quantitative evaluation criteria to evaluate such qualities. The customer’s sensitivity towards such qualities is diverse and latent. In our previous study, we proposed a quantification method of emotional qualities with attention paid to its diversity [1]. The method analyzes the diversity of emotional qualities and formulates their evaluation criteria based on the results of sensory tests. The authors formalized several emotional qualities expressed by adjectives using the proposed method with existing products. However, the variety of existing products was limited. The obtained evaluation criteria may not cover a design space where future designs would appear. In this paper, we propose a method to cover such untouched design space using composite samples in order to extract a potential factor of emotional quality for the future design. To create such a composite sample, we set efficient design features that take into consideration the completeness of design space and the diversity of a target emotional quality. In the method, we conduct two sets of sensory tests. One is using only existing design samples and another is using composite samples. We compare the results of the two tests in order to examine the repeatability of emotional scores among different sets of subjects and changes introduced by adding created samples. We apply the proposed method to extract potential emotional factors of product sound quantify. Using results of the sensory test with the created sound samples, we found two emotional evaluation factors. The first factor negatively related to loudness. The second factor related to lower sharpness and the existence of a perceivable peak tone around 500Hz. Most product makers are aware of the need to reduce loudness, i.e., the first factor. We found the second factor as a new evaluation criterion.
MBS Software Development With Matlab for Teaching and Industrial Usages
Authors: Garci´a de Jalo´n Javier , Hidalgo Andre´s F. , Callejo Alfonso
Published: July 2010

In this article, two formulations implemented in Matlab™ for the dynamic simulation of multibody systems are described. The developed framework allows a rapid development of programs and a clean implementation of algorithms, offering many aids to make the data pre and post-process. However, Matlab is not efficient at all when working with small matrices, as happens with multibody systems. This work describes a global formulation and a topologic (semi-recursive) formulation. Both are applied to two real, medium-large cases: an automobile and a semi-trailer truck. In both cases the pure Matlab results are presented, and also the improvements which can be achieved when some of the functions are programmed in C/C++ and are executed as MEX-functions. It can be proved that execution times can be lowered between one and two orders of magnitude, beating those of some commercial programs.
A Mass-Spring Model Approach for Interactive Simulation of Wire Harnesses
Authors: Sazawa Shinichi , Abe Hideki , Hashima Masayoshi , Sato Yuichi
Published: July 2010

We present a method to simulate wire harnesses interactively, without ignoring physical accurateness. Our method relies on a mass-spring model, which is widely used in such areas as cloth simulation and hair simulation. Although a mass-spring model gives shapes of flexible objects with small computational cost, a considerable disparity of bending and stretching spring coefficients gives rise to serious instabilities of the differential equation to be solved. To solve this problem, we adopted a combination of successive leapfrog integrations and final fast projection to satisfy inextensibility. We applied this technique to simulate 3D industrial product models equipped with 20 to 30 wire harnesses and obtained a good operational response with the required physical accuracy.
High Speed Portable Wireless Data Acquisition System for High Data Rate Applications
Authors: Cosar Emre I. , Bocca Maurizio , Eriksson Lasse M.
Published: July 2010

Communication between a sink node and a PC can constitute a bottleneck for high data rate applications of wireless sensor networks (WSNs) including, but not limited to, structural health monitoring, condition monitoring, wireless surveillance and patient health monitoring. In this paper, we evaluate four different data acquisition alternatives for data-intensive WSN applications. We will concentrate especially on optimizing UART (universal asynchronous receiver transmitter) communication in conjunction with WSN applications. Furthermore, we propose a new method for sink node to PC communication, which is based on using a USB-connected data acquisition (DAQ) board that samples the node external I/O. This method can provide an efficient solution to transfer data from the sink node to PC at a reasonable cost. Wireless sink node converts the data received from the network into analog signal levels, which are sampled through the DAQ board connected to a PC, and the original data is reconstructed offline. Tests on a wooden bridge built to scale with six wireless sensor nodes and a sink node show that with the proposed method it is possible to collect the data from the network and transfer them onto the PC significantly faster than with the 115.2 kbps UART communication regularly used in WSN applications.
Automatic Condition Monitoring and Early Fault Detection of Gearbox
Authors: Wang Dong , Miao Qiang , Wang Chengdong , Xiong Jingqi
Published: July 2010

Condition based maintenance (CBM) improves decision-making performances for a maintenance program through machinery condition monitoring. Therefore, it is a key step to trace machinery health condition for CBM. In this paper, a novel method is proposed to establish a health evaluation index named automatic evaluation index (AEI) and its corresponding dynamic threshold using Wavelet Packet Transform (WPT) and Hidden Markolv Model (HMM). In this process, WPT is used to decompose signal into detail signals and exhibits prominent gear fault features. In addition, HMM employed here is to recognize two concerned states of gear in the whole life validation, including normal gear state and early gear fault state. It is also important to build a dynamic threshold to differentiate the two states automatically. The proposed dynamic threshold not only renews by itself according to the history values of AEI but also easily and automatically detects occurrence of gear early fault. Finally, a set of whole life time data ending in gear failure is used to verify the proposed method effectively. Further, some related parameters included in this method are discussed and the obtained results show that condition monitoring performance of the proposed method is excellent in detection of gear failure.
Model Based Analysis of Steam-Whip Instability Onsets Occurred in a Power Plant
Authors: Pennacchi Paolo , Vania Andrea
Published: July 2010

The characteristics of the steam flow as well as the mechanical and geometrical properties of the seals play an important role in the generation of steam-whirl instability phenomena in rotating machines. The hardening of the seal stiffness caused by a raise of the steam flow and pressure often gives a significant contribution to the occurrence of unstable vibrations. With regard to model-based investigations the increase of the cross-coupled coefficients used to model the seal stiffness can cause important changes in the eigenvalues and eigenmodes of the mathematical model of a rotating machine. In particular, the real part of the eigenvalue associated with the first flexural normal mode of the turbine shaft may become positive causing the conditions for the occurrence of unstable vibrations. The threshold level of the steam flow that causes instability conditions can be used to define the stability margin of the power unit. This paper shows the results of investigations carried out with model-based techniques by means of which the dynamic behavior of a large power unit affected by steam-whirl instability phenomena have been successfully studied.
Application of Robust Regression Methods to Rotor Balancing Using High Breakdown Point and Bounded-Influence Estimators
Authors: Pennacchi Paolo , Vania Andrea , Chatterton Steven
Published: July 2010

In industrial field, the main practical problem of rotating machinery concerns rotor balancing. Balancing masses are often selected by means of weighted least squares method. The weighted method allows reducing the amplitude of vibrations at selected rotating speeds such as critical speeds or operating conditions. Usually these weights are manually selected by the operator. In this paper, an automatic procedure based on robust regression methods is introduced. In particular the analysis is focused on high breakdown point and bounded-influence estimators. Theoretical aspects and properties of these methods are investigated. The effectiveness and robustness of the proposed procedure is shown by means of simulations of a 180 MW gas turbo-generator of a power plant. Different unbalance conditions are considered as well as data corruption.
A Parallel Algorithm for Solving Complex Multibody Problems With Stream Processors
Authors: Heyn Toby , Tasora Alessandro , Anitescu Mihai , Negrut Dan
Published: July 2010

This paper describes a numerical method for the parallel solution of the differential measure inclusion problem posed by mechanical multibody systems containing bilateral and unilateral frictional constraints. The method proposed has been implemented as a set of parallel algorithms leveraging NVIDIA’s Compute Unified Device Architecture (CUDA) library support for multi-core stream computing. This allows the proposed solution to run on a wide variety of GeForce and TESLA NVIDIA graphics cards for high performance computing. Although the methodology relies on the solution of cone complementarity problems known to be fine-grained in terms of data dependency, a suitable approach has been developed to exploit parallelism with low overhead in terms of memory access and thread synchronization. Additionally, a parallel collision detection algorithm has been incorporated to further exploit available parallelism. Initial numerical tests described in this paper demonstrate a speedup of one order of magnitude for the solution time of both the collision detection and the cone complementarity problems when performed in parallel. Since stream multiprocessors are becoming ubiquitous as embedded components of next-generation graphic boards, the solution proposed represents a cost-efficient way to simulate the time evolution of complex mechanical problems with millions of parts and constraints, a task that used to require powerful supercomputers. The proposed methodology facilitates the analysis of extremely complex systems such as granular material flows and off-road vehicle dynamics.
Perturbation Analysis of a Nonlinear Resonator
Authors: Nudehi Shahin S. , Farooq Umar , Motato Eliot
Published: July 2010

A perturbation analysis of a Helmholte type resonator with one of the resonator ends replaced by a membrane is studied in this work. A membrane is known to exhibit nonlinear behavior under certain conditions, and thus when attached to a resonator system modifies the dynamic characteristics of the original system. This modified Helmholtz resonator system modeled by coupled nonlinear differential equations is investigated by using the singular perturbation theory. The resonant frequency of nonlinear resonator in the primary resonance case is analytically obtained by using the first order approximate solutions. A good agreement is seen when the frequency response of first order approximate system is compared with the numerically simulated results.