bluuebunny/crossref_metadata_2025 huggingface dataset:
Curve Shape Modification and Fairness Evaluation
Authors: Kuragano Tetsuzo , Yamaguchi Akira
Published: May 2009

A method to generate a quintic NURBS curve which passes through the given points is described. In this case, there are four more equations than there are positions of the control points. Therefore, four gradients which are the first derivative of a NURBS equation are assigned to the given points. In addition to this method, another method to generate a quintic NURBS curve which passes through the given points and which has the first derivative at these given points is described. In this case, a linear system will be underdetermined, determined or overdetermined depending on the number of given points with gradients. A method to modify NURBS curve shape according to the specified radius of curvature distribution to realize an aesthetically pleasing freeform curve is described. The differences between the NURBS curve radius of curvature and the specified radius of curvature is minimized by introducing the least-squares method. A criterion for a fair curve is proposed. Evaluation whether the designed curve is fair or not is accomplished by a comparison of the designed curve to a curve whose radius of curvature is monotone. The radius of curvature is specified by linear, quadratic, and cubic function using the least-squares method. A curve whose radius of curvature is reshaped by one of these algebraic functions is considered as a fair curve. The curvature vector of the curve is used to evaluate the fairness. The comparison of unit curvature vectors is used to evaluate the directional similarity of the curve. The comparison of the curvature is used to evaluate the similarity of the magnitude of curvature vectors. If the directional similarity of the designed curve is close to the fair curve, and also the similarity of the curvature is close to the fair curve, the designed curve can be judged as a fair curve.
Computer-Aided Laboratory Work to “Mechanism and Machine Science” Course
Authors: Kuzlyakina Valentina V. , Nagaeva Marina V.
Published: May 2009

Laboratory work is an important element in engineering training, which should correspond to up-to-date tendencies in computer-based technologies in design, production, maintenance and preserving mechanisms. Computer-based laboratory work consists of 16 assignments. Seven assignments are carried out on laboratory stands, the remainder are provided on PC, using programs like “Visual Structure Editor”, “DYNAMO”, “APM Win Machine”. The system Visual Structure Editor (VSE) is designed by specialists of “Machine Mechanics and Computer-Aided Design” department, of the Maritime State University named after adm.G.I.NEVELSKOY, Vladivostok, under the direction of prof. Valentina V. Kuzlyakina. The system APM (Automated Projecting of Mechanism) is designed by the research-and-production centre “APM” under the direction of prof.V.Shelofast, from the city of Korolyov, Moscow area. These systems are multifunctional. They allow project different mechanical systems at the stage of structural and parametrical synthesis, carry out strength calculations and design elements of machines and mechanisms. They are good in operation. Teachers and students easily master the systems. Laboratory works with computer support allow students to pass from a concrete object to modeling on a PC, and to solve complex engineering tasks during the education process.
Design of an Active Control Engine Mount Using a Direct Drive Electrodynamic Actuator
Authors: Park Hyunki , Lee Bo-Ha , Lee Chong-Won
Published: May 2009

This paper is focused on design of a new active control engine mount (ACM), which is both compact in size and cost effective. The ACM, consisting of an electrodynamic actuator as the active element, flat springs and a sliding ball joint, is different in structure from the previous ACM designs based on the conventional hydraulic engine mount. Dynamic characteristics of the proposed ACM are extensively investigated before a prototype ACM, which meets the design specifications, is built in the laboratory. For cost effectiveness, a feed-forward control algorithm without a feedback sensor is used for reduction of the transmitted force through the ACM by the engine. The prototype ACM is then harmonic-tested with a rubber testing machine for verification of its control performance as well as adequacy of modeling. Experimental results show that the proposed ACM is capable of reducing the transmitted force by 20 dB up to the frequency range of 60 Hz.
Development of Beam-To-Beam Contact Detection Algorithms for Rotor-Stator Rubbing Applications
Authors: Roques Se´bastien , Legrand Mathias , Stoisser Carlo Maria , Cartraud Patrice , Pierre Christophe
Published: May 2009

In nuclear power plant turbosets, the design-basis accident consists of a blade-off on the low pressure turbine last stage. During the accidental shutdown, a severe rotor-casing interaction may occur at critical speeds due to large shaft line displacements originated by a high unbalance excitation. The contact between the shaft and the stator, also called the diaphragm in this study, induces an important angular deceleration rate and greatly modifies the turbogenerator dynamics including the amplitude of the loads in the bearings. Therefore the main objective is to verify that the designed turbine is capable of going through critical speeds without catastrophic consequences for the shaft line. To this end, a model of a turbogenerator has been developed to compute rotor speed transients by considering the rotating speed of the rotor as an unknown, which allows for the angular deceleration due to rubbing to be calculated in a more realistic fashion. Lagrange multipliers method is applied to compute contact forces. The diaphragm, which is a non-rotating bladed disks assembly, is modeled by curved and straight beams, and different assumptions for the contact detection are studied to find a compromise between CPU time and accuracy. Results of the numerical tool show that the contact forces are sensitive to the retained assumptions only when heavy rub occurs. Nevertheless, the rotating speed and bearing loads are computed with a satisfactory accuracy, even with an approximation on contact detection that saves CPU time.
Parametric Identification and Health Monitoring of Large Scale Strongly Nonlinear Vehicle Models
Authors: Metallidis P. , Stavrakis I. , Natsiavas S.
Published: May 2009

A systematic methodology is applied for performing parametric identification and health monitoring in the suspension substructures of complex vehicle models. The equations of motion of these models are derived by applying the method of finite elements. As a consequence, they involve a quite large number of degrees of freedom. In addition, they include strongly nonlinear terms. In particular, the main nonlinearities arise due to the function of the suspension dampers and springs. Moreover, the action of the bushings connecting the suspension subsystems to the vehicle body are also characterized by a strongly nonlinear behavior. Since the resulting number of degrees of freedom is large, an appropriate coordinate condensation technique is first applied. This reduces drastically the dimension of the original system and allows the application of numerical methods, which are effective for dynamical systems with relatively small dimension. More specifically, this feature is exploited here by applying a statistical system identification methodology in order to perform parametric identification and fault detection studies in the suspension subsystems of the vehicle models examined. In the second part of this study, the methodology developed is applied and yields numerical results related to parametric identification and fault detection in the suspensions of the vehicle systems examined, which exhibit strongly nonlinear behavior, even in the presence of considerable measurement noise and model errors.
Periodic Steady State Response of Complex Vehicle Models Using Multi-Level Substructuring
Authors: Stavrakis I. , Theodosiou C. , Natsiavas S.
Published: May 2009

A systematic methodology is presented for investigating long term ride dynamics of large order vehicle models in a computationally efficient way. First, the equations of motion for each of the main structural components of the vehicle are set up by applying the finite element method. As a consequence of the geometric complexity of these components, the number of the resulting equations is so high that the classical coordinate reduction methodologies become numerically ineffective to apply. In addition, the composite model possesses strongly nonlinear characteristics. However, the method applied overcomes some of these difficulties by imposing a multi-level substructuring procedure, based on the sparsity pattern of the stiffness matrix. In this way, the number of the equations of motion of the complete system is substantially reduced. Subsequently, this allows the application of appropriate numerical methodologies for predicting response spectra of the nonlinear models to periodic road excitation. Results obtained by direct integration of the equations of motion are also presented. Where possible, the accuracy and validity of the applied methodology is verified by comparison with results obtained for the original models.
Torsional Vibration Suppression by the Roller Type Centrifugal Vibration Absorbers
Authors: Ishida Yukio , Inoue Tsuyoshi , Fukami Tomohiko , Ueda Motohiko
Published: May 2009

The centrifugal pendulum vibration absorber (CPVA) has been used for a long time as a method to suppress torsional vibrations. Recently, the roller type CPVA, that has a similar characteristic but simpler structure, has been investigated and started to be used in some automobile engines. However, the dynamical characteristics of the roller type CPVA are not known well. In this study, the nonlinear equations motion of the roller type CPVA are derived and their characterictics are investigated theoretically and experimentally. Especially, the difference between pendulum type CPVA and roller type CPVA is discussed from the viewpoint of the effect of a vibration suppression.
A Procedure for the Inclusion of Transverse Shear Deformation in a Beam Element Based on the Absolute Nodal Coordinate Formulation
Authors: Mikkola Aki , Dmitrochenko Oleg , Matikainen Marko
Published: May 2009

In this study, a procedure to account for transverse shear deformation in the absolute nodal coordinate formulation is presented. In the absolute nodal coordinate formulation, shear deformation is usually defined by employing the slope vectors in the element transverse direction. This leads to the description of deformation modes that are, in practical problems, associated with high frequencies. These high frequencies, in turn, complicate the time integration procedure burdening numerical performance. In this study, the description of transverse shear deformation is accounted for in a two-dimensional beam element based on the absolute nodal coordinate formulation without the use of transverse slope vectors. In the introduced shear deformable beam element, slope vectors are replaced by vectors that describe the rotation of the beam cross-section. This procedure represents a simple enhancement that does not decrease the accuracy or numerical performance of elements based on the absolute nodal coordinate formulation. Numerical results are presented in order to demonstrate the accuracy of the introduced element in static and dynamic cases. The numerical results obtained using the introduced element agree with the results obtained using previously proposed shear deformable beam elements.
Mathematical Techniques for the Design of Band Gap Materials
Authors: Fuster-Garcia E. , Romero-Garcia V. , Garci´a-Raffi L. M. , Sa´nchez-Pe´rez J. V.
Published: May 2009

The rigourous study of band gap materials in the last years has given as a result that these systems have interesting properties for technological purposes. However, the use of this materials for specific applications requires new tools and methods that help us to obtain optimized materials and realistic simulations. In this work we present two tools that let us obtain these realistic simulations based on experimental data and to optimize the band gap materials for specific uses. Also we present results for the specific case of Sonic Crystals in the audible frequency range.
Vehicle System Modeling for HEV Systems Development
Authors: Che Judy , Jennings Mark
Published: May 2009

The sheer complexity of engineering propulsion systems for hybrid electric vehicles (HEV) demands the use of model-based development processes supported by comprehensive, robust vehicle system models. A Vehicle System Modeling (VSM) process has been developed to provide high-quality, application-appropriate vehicle system models in time to support critical HEV engineering activities. The process seeks to manage the complexity of the large number of model variants that are required to support a vehicle program. Additionally, it drives model development and aligns modeling activities with program timing. This paper describes the key elements of the VSM process and presents an application example. The application example illustrates the process by which a highly detailed HEV system model is created from an initial, base conventional vehicle system model via integration of high fidelity component models into a re-usable vehicle system modeling framework. The component models come from a variety of modeling tools and environments, which introduces additional complexity that must be managed. Results generated from the model show the complex system interactions that must be addressed by the vehicle control strategy. This re-enforces the notion that such modeling is required to achieve robust system designs.
Interactive Mesh-Free Stress Analysis for Mechanical Design Assembly With Haptics
Authors: Faas Daniela , Fischer Andrew , Vance Judy M.
Published: May 2009

This paper describes a virtual reality application that performs fast stress reanalysis coupled with virtual reality and haptics that allows rapid evaluation of multiple designs throughout the product design process. The Interactive Virtual Design Application (IVDA) allows the engineer to interactively explore new design geometry while simultaneously examining the finite element analysis results. In the presence of other parts in the assembly, the new shape can be analyzed and modified, taking into consideration mating part fits. This approach supports concurrent product design and assembly methods prototyping. A “two-step” approach utilizing Taylor series approximations and Pre-conditioned Conjugate Gradient methods is used to perform quick reanalysis during interactive shape modification. The virtual environment provides an immersive three-dimensional workspace. Haptics are used to provide feedback of the stress gradient as the part geometry is changed, thus facilitating the designer’s understanding of the impact of shape change on product performance.
Nonlinear Dynamic Characterization of Oil-Free Wire Mesh Dampers
Authors: Ertas Bugra , Luo Huageng
Published: May 2009

The present work focuses on the dynamic characterization of oil-free wire mesh dampers. The research was focused on determining nonlinear stiffness and damping coefficients while varying the excitation amplitude, excitation frequency, and static eccentricity. Force coefficients were extracted using a forced response method (FRM) and also a transient vibration method. Due to the nonlinearity of the dampers, controlled amplitude tests were required for the forced excitation method, whereas the transient response was analyzed using a Hilbert Transform procedure. The testing using both methods showed that eccentricity has minimal influence on force coefficients, whereas increasing excitation amplitude and frequency yield decreasing stiffness and damping trends. In addition to the parameter identification tests, a rotating test was performed demonstrating high-speed damping capability of the oil-free wire mesh dampers to 40,000 rpm, which was also simulated using an nonlinear rotordynamic response to imbalance analysis.
Automated Duty Cycle Classification for Online Monitoring Systems
Authors: Timusk Markus A. , Lipsett Michael G. , Mechefske Chris K.
Published: May 2009

Transient operation of machinery can greatly complicate the task of vibration-based online condition monitoring. Because the operating mode of a machine affects the physical response and hence the diagnostic parameters, real-time information regarding the operating mode is likely to improve the performance of an online fault detection system. This paper proposes a method for automated duty cycle classification to augment the performance of vibration-based online condition monitoring systems for applications such as gearboxes, motors, and their constituent components. Experimental work is carried out on the swing machinery of an electromechanical excavator, which demonstrates how such a method might function on actual dynamic signals gathered from an operating machine. Several variations of the system are tested.
Design and Simulation of a Miniaturized Tubular Electro-Thermal Actuator
Authors: Yang Peng , Mechefske Chris K. , Lai Yongjun
Published: May 2009

Design and simulation of a new type of tubular steel electro-thermal actuator capable of vertical displacement is presented. The Tubular Thermal Actuator (TTA) consists of several multiple cascaded chevron-shaped structures, which are connected together by a top ring, as a platform to carry vertical displacement. The TTA is made from a 20 μm thick steel tube with an outer diameter of 1mm by laser micromachining technology. A finite element model was developed to simulate the behavior of the actuator and study the dominant heat transfer mode at this scale. The actuator could generate more than 7 μm linear motion and 2 mN forces at the top ring. In order to avoid operating the tubular actuator at its natural resonant frequencies, modal analysis has also been conducted.
Visual Steering Commands for Trade Space Exploration: User-Guided Sampling With Example
Authors: Stump Gary , Lego Sara , Yukish Mike , Simpson Timothy W. , Donndelinger Joseph A.
Published: May 2009

Recent advancements in computing power and speed provide opportunities to revolutionize trade space exploration, particularly for the design of complex systems such as automobiles, aircraft, and spacecraft. In this paper, we introduce three Visual Steering Commands to support trade space exploration and demonstrate their use within a powerful data visualization tool that allows designers to explore multidimensional trade spaces using glyph, 1-D and 2-D histogram, 2-D scatter, scatter matrix, and parallel coordinate plots; linked views; brushing; preference shading and Pareto frontier display. In particular, we define three user-guided samplers that enable designers to explore (1) the entire design space, (2) near a point of interest, or (3) within a region of high preference. We illustrate these three samplers with a vehicle configuration model that evaluates the technical feasibility of new vehicle concepts. Future research is also discussed.
Automated Synthesis of MEMS Fabrication Sequences Using Graph Grammars
Authors: Jawalkar Saneet A. , Campbell Matthew I.
Published: May 2009

The design of any MEMS component is subject to stringent manufacturing constraints. The knowledge about these constraints seems to be available to designers who have experienced the details of MEMS fabrication. In this paper, we put forth the idea of automatically generating a fabrication sequence for surface micro-machined MEMS components using the knowledge stored in grammar rules. As an analogy to CAD tools used in mechanical systems, we envision creating a tool which has the Pro-Engineer approach of determining fabrication sequences for a machine tool based on the final part shape. This tool could be an integral addition to the current MEMS design software so that the designers can freely draft devices and then allow an automated process to determine the fabrication sequence. In this paper we give a brief introduction about the graph grammars. Data from already designed MEMS components is extracted in the form of rules to create an expert system. We have also included an example of generation of the fabrication sequence for several MEMS components.
A Nonlinear Acoustic Resonator
Authors: Farooq Umar , Nudehi Shahin S.
Published: May 2009

An acoustic resonator of Helmholtz type with a membrane attached to one of its ends is studied in this work. A membrane possesses a geometric nonlinearity of cubic type. This work examines that when attached to the resonator, a membrane can be exploited to attenuate vibrations for a variable frequency range in an acoustical system. This can be viewed as a parallel to vibration absorption for the structural systems. The coupled nonlinear mathematical model of Helmholtz resonator with a membrane attachment is investigated by applying a perturbation technique to obtain a set of second order differential equations. These equations are then numerically solved. The simulations of system frequency response show that the vibration suppression could be achieved for a wide frequency range.
Robust Design Optimization of a Tracked Vehicle System
Authors: Kim Min-Soo , Choi Jinhwan , Lee Soon-Geul , Song In-Ho , Yoon Jun-Shik , Baek SungHo
Published: May 2009

This study presents the robust optimization for the dynamic responses of a heavy military tracked vehicle system. In this study, the tracked vehicle model has 954 degrees-of-freedom, which consists 189 bodies in total; 37 bodies for the chassis such as sprocket, road wheel, road arm, etc., 76 track link bodies for each track subsystem, 36 revolute joints and 152 bushing elements. The design objective is to minimize the maximum vertical acceleration of hull and its’ variance and satisfy the wheel travel constraints for torsion bars and the hydro-pneumatic suspension units within ±1σ ranges. In order to avoid the difficulty of design sensitivity analysis and overcome the numerical noise, a meta-model based optimization is employed. In this approach, first, the space filling methods and the classical DOE methods are used to generate sampling points. Second, the meta-models are constructed from the Kriging, RBF and RSM methods. Finally, a well-developed numerical optimizer sequentially solves the approximate optimization problem. In the numerical test, the robust optimization of the tracked vehicle system, having 11-random design variables, is solved in only 26 analyses.
Bifurcation Phenomena Caused by Two Nonlinear Dynamic Absorbers
Authors: Ikeda Takashi
Published: May 2009

The characteristics of two nonlinear vibration absorbers simultaneously attached to structures under harmonic excitation are investigated. The frequency response curves are theoretically determined using van der Pol’s method. It is found from the theoretical analysis that pitchfork bifurcations may appear on a part of the response curves which are stable in a system with one nonlinear dynamic absorber. Three steady-state solutions with different amplitudes appear just after the pitchfork bifurcation. After that, Hopf bifurcations may occur depending on the values of the system parameters, and amplitude- and phase-modulated motion including a chaotic vibration appears after the Hopf bifurcation. Lyapunov exponents are numerically calculated to prove the occurrence of a chaotic vibration. In addition, it is also found that only Hopf bifurcations, not pitchfork bifurcations, can occur even when the linear and nonlinear dynamic absorbers are combined.
PDM Implementation in Indian Industries: An Impact Study on Technology Adoption
Authors: Jebaraj C. , Balakrishnan G.
Published: May 2009

Shorter product life cycles, growing product complexity and the need for a large number of product variants have made Product Data Management (PDM) increasingly important for many manufacturing industries. Since, many industries in India either have implemented PDM or are considering implementation, it is the right time to study the real impact of PDM in Indian industries. This impact study was made by the responses obtained through a survey questionnaire. The main objective of the survey is to study the impact of PDM implementation on productivity. The variables of productivity measurement in terms of Key Performance Areas have been identified using Performance Objective-Productivity model. The questionnaire has been designed and administered and the responses received have been analysed using SPSS software. General descriptive statistics including mean and standard deviation along with paired t-test and Pearson’s correlation studies have been employed for analysing the importance of the measures of productivity. A user driven PDM evaluation framework and methodology based on the two stage Quality Function Deployment (QFD) technique has been developed to select the most suitable PDM product for a specific industry. A simple model to measure the Return on Investment for PDM implemented industries based on Port and Mackrell’s [24] work has been developed. Thus, methodologies have been developed and demonstrated with case studies to overcome the issues identified in the survey.
A Framework for Collaborative Top-Down Assembly Design
Authors: Zhang Shuting , Chen Xiang , Gao Shuming , Yang Youdong
Published: May 2009

This paper presents a system framework to support the collaborative top-down assembly design. As the first step, the framework is devised to enable distributed designers to conduct collaborative layout design, 3D skeleton design and detailed design of a product in a top-down manner in a distributed environment. To effectively support the collaborative top-down assembly design, a multi-resolution and distributed product assembly model is proposed as a product representation in the framework. With the help of the framework the designers could conduct those design activities of top-down assembly design that need plenty of collaboration such as the collaborative determination of assembly relationship and coupled structural parameters. A variation propagation mechanism is also developed to guarantee the consistency of the distributed assembly model. A preliminary system prototype based on replicated client-server architecture is implemented.
Stress Intensity Factor Calculation Using a Weight Function Method
Authors: Sun Rui , An Zongwen , Huang Hong-Zhong , Ma Qiming
Published: May 2009

Propagation of a critical unstable crack under the action of static or varying stresses is determined by the intensity of strain field at tips of the crack. Stress intensity factor (SIF) is an important parameter in fracture mechanics, which is used as a criterion to judge the unstable propagation of a crack and plays an important role in calculating crack propagation life. SIF is related to both geometrical form and loading condition of a structure. In the paper, a weight function method is introduced to study crack propagation of center through cracks and edge cracks in a finite-size plate. In addition, finite element method, linear regression, and polynomial interpolating technique are used to simulate and verify the proposed method. Comparison studies among the proposed and current methods are performed as well. The results show that the weight function method can be used to calculate SIF easily.
Wearable Haptic Device for an IPT System Based on Pneumatic Muscles
Authors: Iltanen Mika , Ellman Asko , Laitinen Joonas
Published: May 2009

The human haptic system has an important role to play in human interaction with Virtual Environments (VEs). Unlike the visual and auditory systems, the haptic sense is capable of both sensing and acting on the environment and is an indispensable part of many human activities. In order to provide the realism needed for effective and compelling applications, VEs need to provide inputs to, and mirror the outputs of, the haptic system. These characteristics are the most important issues in the design of confined spaces and mechanical constructions using 6 DOF input devices in Immersive Projection Technology (IPT) or Cave-like systems. Inputs to the haptic system are in the form of haptic displays and outputs are actuator action commands, where the primary input/output variables are displacements and forces. The idea of total free movement in the IPT system was one of the corner stones of the present study. Therefore the force feedback system should also be wearable. The observer is able to reach objects placed above and below, grip them, and move freely in virtual space. This paper discusses the hardware and software structure of the haptic force feedback system for an IPT system, the theoretical functionality of McKibben actuators and the measured performance of a glove. Force control is based on fast solenoid valves, PID controller and a developed pneumatic muscle model. Muscle actuators are attached to the forearm and control the electronics and valves to a wearable backpack. A developed sensing and force-reflecting exoskeleton applies force to all four fingers and also the thumb. The device has five active DOFs, one for each finger. An ascension motion tracking device is used to track the position and orientation of the forearm. A Fifth Dimensional Technologies fiber optics data glove is used to measure the position of the fingers and provides better information on finger movements. Virtools 4.0 software and VRPN interface was used to connect the data glove, feedback device and PC-cluster.
Acoustic Barriers Based on Sonic Crystals
Authors: Romero-Garci´a V. , Fuster-Garcia E. , Garci´a-Raffi L. M. , Sa´nchez-Pe´rez J. V.
Published: May 2009

Environmental noise problems become an standard topic across the years. Acoustic barriers have been purposed as a possible solution because they can act creating an acoustic attenuation zone which depends on the sound frequency, reducing the sound transmission through it. It was demonstrated that at high sound frequencies the effect of the barriers is more pronounced than at low frequencies, due to the diffraction in their edges. Sonic Crystals (SCs) are periodic arrays of scatterers embedded in a host material with strong modulation of its physical properties, that produces band gaps attenuation in frequencies related with their geometry. These frequencies are explained by the well known Bragg’s diffraction inside the crystal. SCs present different high symmetry directions, where the Bragg’s peaks appears in different frequencies ranges due to the variation of the geometry in each direction. Recently, some authors have studied the possibility to use SCs to reduce noise in free-field condition. Also, it was showed that SCs built by trees are acoustic systems that present acoustic band gaps in low frequency range due to the geometric distribution of the trees. These results led us think that these structures are a suitable device to reduce noise, this means SCs could be use as acoustic barriers. Nevertheless the technological application of these devices for controlling the noise present some problems. First, the angular dependence of the frequencies attenuated when the sound impinges over the SC. Second, the fact that the necessary space to put the SC is bigger than in the case of the traditional acoustic barriers. Finally, the necessity of some robust and long-lasting materials to use them outdoors. In this paper we show the possibility to use different materials (rigid, mixed or soft) to make scatterers, explaining their advantages or disadvantages. These materials in conjunction with some optimization methods will allow us find some solutions to the problems mentioned above. We will relate both acoustic systems, acoustic barriers and SCs, making a comparison of the main properties of each one and then, we will present the technological possibilities to design acoustic barriers based on SCs.
A Simplified Systematic Method of Acquiring Design Specifications From Customer Requirements
Authors: Sun Nuogang , Zhang Youyun , Mei Xuesong
Published: May 2009

Faithfully obtaining design specifications from customer requirements is essential for successful designs. The natural lingual, inexact, incomplete and vague attributes of customer requirements make it very difficult to map customer requirements to design specifications. In general design process, the design specifications are determined by designers based on their experience and intuition, and often a certain target value is set for a specification. However, it is on one hand very difficult, on the other hand unreasonable, so a suitable limit range rather than a certain value is preferred at the beginning of design, especially at the concept design process. In this paper, a simplified systematic approach of transforming customer requirements to design specifications is proposed. First, a two-stepped clustering approach for grouping customer requirements and design specifications based on HOQ matrix is presented, by which the mapping is limited to within each group. To further simplify the inference mapping rules of customer requirements and design specifications, the minimal condition inference mapping rules for each design specification are extracted based on rough set theory. In the end, a suitable value range is determined for a specification by applying the fuzzy rule matrix.
Determining the Force and Moment Workspaces of Redundantly-Actuated Spatial Parallel Manipulators
Authors: Garg Venus , Nokleby Scott B. , Carretero Juan A.
Published: May 2009

In this study, the concept of force and moment-workspaces is introduced. The force-moment capability analysis of parallel-manipulators is used to generate the force and moment workspaces. Force and moment workspaces of the manipulator are used to visualize the boundary of the workspace along with the sustainable/applicable value of force or moment depending on the maximum limits of the manipulator’s actuators. A method which analytically sets the greatest number of actuators to their maximum values is used for the determination of the force and moment workspaces. Four cases, two for finding the maximum magnitude of force with the value of moment either prescribed or associated and two for finding the maximum magnitude of moment with a prescribed or associated force, are explained and discussed. The redundantly-actuated 3-RRRS (all revolute joints actuated), six degree-of-freedom parallel manipulator is used as an example case for the analysis. The results show that a more even force/moment distribution is achieved for points lying inside the boundary of the maximum reachable workspace. It is shown that the proposed force and moment workspaces are an effective design tool for parallel manipulators. In addition, these force and moment workspaces can be seen as an efficient tool for task planning.
A Large Deformation Finite Element for Pipes Conveying Fluid Based on the Absolute Nodal Coordinate Formulation
Authors: Stangl Michael , Gerstmayr Johannes , Irschik Hans
Published: May 2009

A novel pipe finite element conveying fluid, suitable for modeling large deformations in the framework of Bernoulli Euler beam theory, is presented. The element is based on a third order planar beam finite element, introduced by Berzeri and Shabana, on basis of the absolute nodal coordinate formulation. The equations of motion for the pipe-element are derived using an extended version of Lagrange’s equations of the second kind for taking into account the flow of fluids, in contrast to the literature, where most derivations are based on Hamilton’s Principle or Newtonian approaches. The advantage of this element in comparison to classical large deformation beam elements, which are based on rotations, is the direct interpolation of position and directional derivatives, which simplifies the equations of motion considerably. As an advantage Lagrange’s equations of the second kind offer a convenient connection for introducing fluids into multibody dynamic systems. Standard numerical examples show the convergence of the deformation for increasing number of elements. For a cantilever pipe, the critical flow velocities for increasing number of pipe elements are compared to existing works, based on Euler elastica beams and moving discrete masses. The results show good agreements with the reference solutions applying only a small number of pipe finite elements.
Structural Optimization of Components in Controlled Mechanical Systems
Authors: Albers Albert , Ottnad Jens , Ha¨ußler Pascal , Minx Johannes
Published: May 2009

The importance of computer aided engineering in product development processes and research has been increasing rapidly throughout the past years. Today’s software can e.g. help to optimize complex components regarding different objectives or conditions. The capability of these tools has been proved in many industrial applications. They are used in order to improve the products on the one hand and to reduce the development time, and therefore, the costs of the product development on the other hand. New studies in the field of structural optimization concentrate on dynamically loaded parts in mechanical systems. In the state-of-the-art process and methods it is assumed that there exists a set of external loads or load functions acting on the part. The fact that due to geometric modifications caused by an optimization process, changes of the system’s dynamic properties and its overall behaviour may be neglected. In order to take into account the interaction between part and system with all its consequences for the optimization process, a simulation of the complete system is integrated into the optimization process within the research work presented in this paper. Dynamic systems today very often are controlled. The control has a major influence on the dynamic characteristics of the system. Therefore the target is to take into account the aspects of the control system as well during a topology optimization process of the mechanical part in a mechatronic system. Here, a hybrid multibody system simulation, that is, a MBS containing flexible bodies, in conjunction with a Co-Simulation of the control system is integrated into the optimization process. A humanoid robot is an example for such a complex mechatronic system. The goal of the collaborative research centre 588 “learning and cooperating multimodal robots” at the University of Karlsruhe (TH) is the development of robots that can help the human fulfilling everyday tasks in a human environment. The research work presented in this paper is a contribution towards the integration of existing isolated methods into a continuous process. The benefits will be illustrated by an example. The focus is set on the design of the mechanical parts in conjunction with an automatic parameter adaption (optimization) of the control system. Finite element analysis, multibody simulation, control design tools, parameter optimization and topology optimization are tied together into one process to allow an efficient optimization of structures “within” their surrounding mechatronic system.
A Dual Environment for 3D Modeling With User-Defined Free Form Features
Authors: Langerak Thomas R. , Vergeest Joris S. M.
Published: May 2009

Modeling with free form features has become the standard in Computer-Aided Design (CAD). With the increasing complexity of free form CAD models, features offer a high-level approach to modeling shapes. However, in most commercial modeling packages, only a static set of free form features is available. Researchers have tried to solve this problem by coming up with methods for user-driven free form feature definition, but failed to connect their methods to a means to instantiate these user-driven free form features on a target surface. Reversely, researchers have proposed tools for modeling with free form features, but these methods are time-intensive in that they are as of yet unsuitable for pre-defined features. This paper presents a new method for user-driven feature definition, as well as a method to instantiate these user-defined features on a target surface. We propose the concept of a dual environment, in which the definition of a feature is maintained simultaneously with its instance on a target surface, allowing the user to modify the definition of an already instantiated feature. This dual environment enables dynamic feature modeling, in which the user is able to change the definition of instantiated features on-the-fly. Furthermore, the proposed instantiation method is independent from the type of shape representation of the target surface and thereby increases the applicability of the method. The paper includes an extensive application example and discusses the results and shortcomings of the proposed methods.
Global Analyses of Multi-Degree-of-Freedom Nonlinear Vibration Isolation System
Authors: Yu Xiang , Zhu Shijian , Liu Shuyong
Published: May 2009

The abundant and complex dynamics of high-dimensional nonlinear systems have drawn increasing attentions in recent years, but further analyses have been confined because of the inefficiency of some analytic methods for high-dimensional systems. This paper focuses on the bifurcation and global analyses of a multi-degree-of-freedom nonlinear vibration isolation system using numerical methods. Firstly, the equations of motion of the multi-degree-of-freedom nonlinear vibration isolation system for onboard machine are formulated. Then, exhaustive bifurcation analyses are carried out and six branches are illustrated in the bifurcation diagrams revealing that several different types of stable motions may coexist in certain parameter regimes. A cell mapping method is modified to analyze the global characteristics including the locations and basins of the coexistent attractors of the multi-degree-of-freedom nonlinear vibration isolation system.
A Simulation Framework for Assembly/Disassembly Process Modeling
Authors: Iacob Robert , Mitrouchev Peter , Le´on Jean-Claude
Published: May 2009

Simulations of Assembly/Disassembly (A/D) processes covers a large range of objectives, i.e. A/D sequencing, path finding, ergonomic analysis …, where the 3D shape description of the component plays a key role. In addition, the A/D simulations can be performed either from an automated or interactive point of view using standard computer equipment or through immersive and real-time simulation schemes. In order to address this diversity of configurations, this paper presents a simulation framework for A/D analysis based on a new simulation preparation process which allows a simulation process to address up to two types of shape representations, i.e. B-Rep NURBS and polyhedral ones, at the same time, thus handling efficiently the configurations where 3D shape representations of assemblies play a key role. In order to illustrate the simulation preparation process some specific steps are addressed. To this end, the automatic identification of contacts in a 3D product model and their corresponding list is described. After this first stage of identification, an interpretation of the results is needed in order to have the complete list with the mechanical contacts for a product. During the preparation process, three major stages of the framework are detailed: model tessellation, surface merging and contacts identification. Our framework is based on STEP exchange format. The contacts are related to basic geometrical surfaces like: planes, cylinders, cones, spheres. Some examples are provided in order to illustrate the contributions of the proposed framework. This software environment can assist designers to achieve a satisfactory assembly analysis rapidly and can reduce the lead-time of product development. Further consequences of the present work is its ability to produce models and treatments that improve integration of assembly models in immersive environments taking into account of the haptic and visual models needed.
On Fractional Hamilton Formulation Within Caputo Derivatives
Authors: Baleanu Dumitru , Muslih Sami I. , Rabei Eqab M.
Published: May 2009

The fractional Lagrangian and Hamiltonian dynamics is an important issue in fractional calculus area. The classical dynamics can be reformulated in terms of fractional derivatives. The fractional variational principles produce fractional Euler-Lagrange equations and fractional Hamiltonian equations. The fractional dynamics strongly depends of the fractional integration by parts as well as the non-locality of the fractional derivatives. In this paper we present the fractional Hamilton formulation based on Caputo fractional derivatives. One example is treated in details to show the characteristics of the fractional dynamics.
Initialization of Fractional Differential Equations: Theory and Application
Authors: Lorenzo Carl F. , Hartley Tom T.
Published: May 2009

It has been known that the initialization of fractional operators requires time-varying functions, a complicating factor. This paper simplifies the process of initialization of fractional differential equations by deriving Laplace transforms for the initialized fractional integral and derivative that generalize those for the integer-order operators. A companion paper in this conference determines the Laplace transforms for initialized fractional integrals of any order and fractional derivatives of order less than one. This paper extends the theory for the Laplace transform of the derivative to higher order and provides applications.
Dynamical Equations With Non-Ideal Constraints: New and Old Alternatives
Authors: Banerjee Arun K. , Lemak Mark
Published: May 2009

This paper deals with the motion of mechanical systems with non-ideal constraints, defined as constraints where the forces associated with the constraint do work. The first objective of the paper is to show that two newly published formulations of equations of motion of systems with such non-ideal constraints are unnecessarily complex for situations where the non-ideal constraint force does not depend on the ideal constraint force, because they introduce and then eliminate these non-working constraint forces. We point out that a method already exists for nonideal constraints, namely, Kane’s equations, which are simpler because, among other things, they are based on automatic elimination of non-working constraints. The examples considered in these recent publications are worked out with Kane’s method to show the applicability and simplicity of Kane’s method for non-ideal constraints. A second objective of the paper is to present an alternative form of equations for systems where the non-ideal constraint force depends on the ideal constraint force, as in the case of Coulomb friction. The formulation is shown to lend itself naturally to also analyzing impact dynamics. The method is applied to the dynamics of a slug moving against friction on a moving ellipsoidal surface. Such a crude model may simulate, in essence, propellant motion in a tank in zero-g, or during docking of a spacecraft.
Effect of Body Flexibility on Impacts Studied on Rods and Beams
Authors: Seifried Robert
Published: May 2009

The effect of body flexibility on the impact process is studied through longitudinal impacts on rods and transverse impacts on beams. An experimental setup is presented using Laser-Doppler-Vibrometers in order to measure the displacement and velocity of the colliding bodies during impact. For the numerical investigation, modally-reduced models are used in combination with local Finite Element contact models. Performed on a microscale, these experimental and numerical investigations yield a good understanding of the effect of flexibility influencing the impact, and therefore, the coefficient of restitution. The investigations show that impacts of steel spheres on rods and beams yield strong structural vibrations. In the case of the rod impacts, the coefficient of restitution decreases monotonically with increasing initial velocity. In the case of the beams, the strong bending vibrations which are initiated, cause multiple successive impacts within a very short time period. This results in highly nonlinear behavior and uncertainty for the coefficient of restitution.