bluuebunny/crossref_metadata_2025 huggingface dataset:
Partitioning Positional and Normal Space for Fast Occlusion Detection
Authors: Qian Xiaoping , Harding Kevin G.
Published: June 2008

Occlusion detection is a fundamental and important problem in optical sensor inspection planning. Many view-planning algorithms have been developed for optical inspection, however, few of them explicitly develop practical algorithms for occlusion detection. This paper presents a hierarchical space partition approach that divides both positional and surface normal space of an object for fast occlusion detection. A k-d tree is used to represent this partition. A novel concept of δ – occlusion is introduced to detect occlusion for objects in an un-organized point cloud representation. Based on the δ – occlusion concept, several propositions regarding to a range search on a k-d tree have been developed for occlusion detection. Implementation of this approach demonstrated that significant time can be saved for occlusion detection using the partition of both positional and surface normal space.
Automatic Toolpath Generation for Multi-Axis Surface Machining in a Hybrid Manufacturing System
Authors: Ruan Jianzhong , Liou F. W.
Published: June 2008

In a multi-axis hybrid manufacturing system, it is necessary to utilize a machining process to improve surface accuracy and guarantee overall geometry after the deposition process. Due to the complexity of the multi-axis system, it is necessary to find proper orientations of cutting tools for the CNC machine to finish surface machining. This paper presents an algorithm to find collision-free surface machining toolpath for a given workpiece. The concept of the 2-D visibility map and its properties are discussed. The algorithm to compute the 2-D visibility map is presented. With the help of the 2-D visibility map, an optimal a collision free tool approaching direction can be easily decided. Also the type of the surface machining toolpath for different types of surfaces is decided based on topological information and the machining toolpath (CL data for milling tool). The developed planning scheme has been tested via machine simulations and has shown that it can be effectively applied to cutter-path generation for multi-axis surface machining.
Design Shell for Parametric Design at Embodiment Stage
Authors: Vaidya Adwait , Shah Jami
Published: June 2008

The embodiment design stage involves determination of geometric sizes, key parameter values, and matching of component variables to system requirements. This embodiment design stage can be parametrically represented as an iterative design-redesign problem. This paper presents a domain independent characterization of such problems; the characterization includes problem definition, design relations/procedures, and measures of goodness. The paper also discusses representation issues and solution techniques for design-redesign problems. Design tasks are differentiated as domain independent or problem specific and the scope of each design task with respect to the characterization is delineated. A Design Shell implemented on the basis of this characterization is described. This shell can be configured for evaluating designs in any domain. A case study illustrates the use of this Design Shell in characterizing a specific design problem and exploring its design space.
A Modeling Method for Vibration Analysis of a Stator Frame of Turbine Generators and Its Application to a Design System: Vibration Analysis and Analysis System
Authors: Sakamoto Shigeru , Kubo Tadafumi
Published: June 2008

A practical modeling method for predicting vibration characteristics of turbine generator stator frames was developed. The structural parts that compose a stator frame were categorized into three groups: parts that affect ring-mode vibration as mass, parts that affect it as stiffness, and parts that affect it as both. A proper boundary condition, the value of a modal damping ratio, and an accurate representation of exciting forces were examined. The modeling method was then applied to another turbine generator. It was found that the predicted natural frequency agrees with measured one within only a 3% error. Based on the modeling method, a vibration analysis system for design was developed.
Optimal Troubleshooting for Electro-Mechanical Systems
Authors: Paasch Robert , Durgi Parthsarathy
Published: June 2008

When a complex electromechanical system fails, the troubleshooting procedure adopted is often complex and tedious. No standard methods currently exist to optimize the sequence of steps in a troubleshooting process. The ad hoc methods generally followed are less than optimal methods and can result in high maintenance costs. This paper describes the use of behavioral models and multistage decision-making models in Bayesian networks for representing the troubleshooting process. It discusses advantages in using these methods and the difficulties in implementing them. An approximate method to obtain optimal decision sequence for a troubleshooting process on a complex electromechanical system is also described.
Discretizing Continuous Problems for Faster Global Convergence
Authors: Ogot Madara , Aly Sherif
Published: June 2008

Global optimization of mechanical design problems using heuristic methods such as Simulated annealing (SA) and genetic algorithms (GAs) have been able to find global or near-global minima where prior methods have failed. The use of these nongradient based methods allow the broad efficient exploration of multimodal design spaces that could be continuous, discrete or mixed. From a survey of articles in the ASME Journal of Mechanical Design over the last 10 years, we have observed that researchers will typically run these algorithms in continuous mode for problems that contain continuous design variables. What we suggest in this paper is that computational efficiencies can be significantly increased by discretizing all continuous variables, perform a global optimization on the discretized design space, and then conduct a local search in the continuous space from the global minimum discrete state. The level of discretization will depend on the complexity of the problem, and becomes an additional parameter that needs to be tuned. The rational behind this assertion is presented, along with results from four test problems.
On Design of Electro-Thermally Compliant MEMS for Strength
Authors: Saxena Rajat , Saxena Anupam
Published: June 2008

In this paper, meso and micro scale electro-thermally compliant electro mechanical systems are synthesized for strength with polysilicon as the structural material. Local temperature and/or stress constraints are imposed in the topology optimization formulation. This is done to keep the topology thermally intact and also to keep local stresses below their allowable limit. Relaxation performed on both temperature and stress constraints allows them to be ignored when the material densities approach their non-existing states. Noting that both local constraints can be large in number with the number of cells, an active constraint strategy is employed. Honeycomb parameterization, which is a staggered arrangement of hexagonal cells, is used to represent the design region. This ensures at least a common edge between any two neighboring cells and thus avoids the appearance of both checkerboard and zero-stiffness singularities without any additional computational load.
Introduction to Compliant Long-Dwell Mechanism Synthesis Using Buckling Arc Theory
Authors: So¨nmez U¨mit
Published: June 2008

A new type of compliant approximate dwell mechanism design is introduced. This new compliant mechanism includes an initially straight flexible beam and a flexible arc. Approximate dwell motion is obtained by incorporating the snap-through buckling motion of the flexible arc. Load-deflection curves of flexible mechanism components are modeled by fitting polynomials to the analytical nonlinear large deflection response. The kinematic synthesis of the compliant mechanism is done quasi-statically using loop closure theory and large deflection relations of flexible parts.
Suspension Synthesis for N:1 Roll Center Motion
Authors: Raghavan Madhusudan
Published: June 2008

A dimensional synthesis procedure to achieve prescribed roll center height variation of a vehicle’s sprung mass with respect to wheel jounce-rebound is presented. This may be used to size the relative lengths of the control arms of a short-long arm suspension mechanism in order to (i) fix the roll center with respect to ground, or (ii) fix the roll center relative to the sprung mass, or (iii) have the roll center move at a prescribed rate relative to the sprung mass, during wheel jounce-rebound. These design selections have a significant impact on the ride-handling characteristics of a vehicle. Numerical examples are provided to demonstrate the synthesis procedure.
Kinematic Synthesis of RPS Serial Chains
Authors: Su Hai-Jun , McCarthy J. Michael
Published: June 2008

This paper examine the geometric design of the five degree-of-freedom RPS serial chain. This constrained robot can be designed to reach an arbitrary set of ten spatial positions. It is often convenient to consider tasks with fewer positions, and here we study the cases of seven through ten position synthesis. A generalized eigenvalue elimination technique yields analytical solutions for cases seven and eight. While cases nine and ten are solved numerically using homotopy continuation. An numerical example is provided for an eight position task.
Dimensional Synthesis of CRR Serial Chains
Authors: Perez Alba , McCarthy J. M.
Published: June 2008

This paper presents the kinematic synthesis of a CRR serial chain. This is a four-degree-of-freedom chain constructed from a cylindric joint and two revolute joints in series. The design equations for this chain are obtained from the dual quaternion kinematics equations evaluated at a specified set of task positions. In this case, we find that the chain is completely defined by seven task positions. Furthermore, our solution of these equations has yielded 52 candidate designs, so far; there may be more. This synthesis methodology shows promise for the design of constrained serial chains.
Analytical Determination of Principal Twists and Singular Directions in Robot Manipulators
Authors: Bandyopadhyay Sandipan , Ghosal Ashitava
Published: June 2008

The identification of principal twists of the end-effector of a manipulator undergoing multi-degree-of-freedom motion is considered to be one of the central problems in kinematics. In this paper, we use dual velocity vectors to parameterize se(3), the space of twists, and define an inner product of two dual velocities as a dual number analog of a Riemannian metric on SE(3). We show that the principal twists can be obtained from the solution of an eigenvalue problem associated with this dual metric. It is shown that the computation of principal twists for any degree-of-freedom (DoF) of rigid-body motion, requires the solution of at most a cubic dual characteristic equation. Furthermore, the special nature of the coefficients yields simple analytical expressions for the roots of the dual cubic, and this in turn leads to compact analytical expressions for the principle twists. We also show that the method of computation allows us to separately identify the rotational and translational degrees-of-freedom lost or gained at singular configurations. The theory is applicable to serial, parallel, and hybrid manipulators, and is illustrated by obtaining the principal twists and singular directions for a 3-DoF parallel, and a hybrid 6-DoF manipulator.
Interpolation Algorithm and Its Error Prediction of a Tripod-Based Parallel Kinematic Machine
Authors: Wang Yang , Huang Tian , Gosselin Clement M.
Published: June 2008

In this paper, an NC interpolation algorithm for a tripod-based parallel kinematic machine is investigated. The algorithm can be implemented in two steps, the rough interpolation in the Cartesian space and the precise interpolation in the actuator space. The upper bound of the theoretical interpolation error due to the interpolation algorithm in the precise interpolation and nonlinear mapping is analyzed. The representation of the interpolation error distribution within the Cartesian space is depicted in terms of the variations of the interpolation period and the programming velocity. It was concluded that this error is sufficiently small and may be neglected.
Computer Simulation of Path and Motion Generation With Six-Bar Linkage
Authors: Yi Lu , Leinonen Tatu
Published: June 2008

The basic tool of path or motion generation synthesis for more than four prescribed positions is analytical calculation, but its process is quite complicated and far from straightforward. A novel computer simulation mechanism of six-bar linkage for path or motion generation synthesis is presented in this paper. In the case of five-precision points, using the geometric constraint and dimension-driving techniques, a primary simulation mechanism of four-bar linkage is created. Based on the different tasks of path and motion generation for kinematic dimensional synthesis, the simulation mechanisms of path and motion generation with Stephenson I, II and Watt six-bar linkages are developed from the primary simulation mechanism. The results of kinematic synthesis for five prescribed positions prove that the mechanism simulation approach is not only fairly quick and straightforward, but is also advantageous from the viewpoint of accuracy and repeatability.
The Radius of Curvature of a Coupler Curve of the Single Flier Eight-Bar Linkage
Authors: Pennock Gordon R. , Kinzel Edward C.
Published: June 2008

The paper begins with a graphical technique to locate the pole; i.e., the point in the plane of motion which is coincident with the instantaneous center of zero velocity of the coupler link. Since the single flier linkage is indeterminate, the Aronhold-Kennedy theorem cannot locate this instantaneous center of zero velocity. The technique that is presented here is believed to be an original contribution to the kinematics literature and will provide geometric insight into the velocity analysis of an indeterminate linkage. The paper then presents an analytical method, referred to as the method of kinematic coefficients, to determine the radius of curvature and the center of curvature of the path traced by an arbitrary coupler point of the single flier eight-bar linkage. This method has proved useful in curvature theory since it separates the geometric effects of the linkage from the operating speed of the linkage.
An Analytical Comparison Between Ball and Crossed Roller Bearings for Utilization in Actuator Modules for Precision Modular Robots
Authors: Kang Seong-Ho , Tesar Delbert
Published: June 2008

A modular robot system is a collection of actuators, links, and connections that can be arbitrarily assembled into a number of different robot configurations and sequences. High performance modular robots require more than just sophisticated controls. They also need top-quality mechanical components. Bearings in particular must operate well at low speed, have high rotational accuracy, be compact for low weight, and especially be stiff for high positional accuracy. To ensure the successful use of bearings in precision modular robots, knowledge of the bearing properties and requirements are investigated. Background information on various topics such as modular robots, precision modular actuators, and their error sources are described with respect to precision engineering. Extensive literature on thin section bearings is reviewed to examine their use in precision robotic applications. Theoretical studies are performed to calculate bearing stiffness adopting a methodology based on Hertzian theory. This approach is applied to analyze two proposed designs of equivalent-sized crossed roller and four-point bearings, principal bearings used for transmitting all the payload and mass of the robot structure. The maximum deflections and contact stresses for the proposed actuator assembly and loading conditions are estimated and compared including a range of general bearing properties such as friction, cost, and shock resistance.
The Robust Design of a Two-Wheeled Quasiholonomic Mobile Robot
Authors: Salerno Alessio , Angeles Jorge
Published: June 2008

The robust design of a novel mobile robot, which comprises two driving wheels and an intermediate body carrying the payload, is the subject of this paper. We prove that, by virtue of the robot architecture, the kinetostatic model of the system is isotropic. Moreover, regarding the robot dynamic response, a robust design problem is formulated by minimizing the design bandwidth of the generalized inertia matrix of the robot over its architecture parameters. Furthermore, design conditions are given for the robot performance in trajectory-tracking to be feasible. Finally, a numerical comparison of two design solutions, one feasible and one robust, is provided by means of simulation runs. We demonstrate that the robust design solution doubles robot performance in trajectory-tracking, while reducing the oscillations of the intermediate body, by 40%, when compared with the feasible solution.
An Evolving, Model-Based Quality Function Deployer
Authors: Zhu Liang , Kazmer David
Published: June 2008

A dynamic, model-based decision making framework is described to support design and manufacture of engineered products. While the framework is inspired by the multiple stages of Quality Function Deployment, the presented framework differs by through the use of quantitative models relating engineering decisions to performance measures. The number of variables, model behavior, and model fidelity are intended to evolve as the design progresses. The Extensive Simplex Method is utilized to identify the feasible space of dynamic model and reveal trade-offs between the decision variables. The methods are demonstrated by various applications of product design and manufacturing process, including the case study of a mechanical actuator design. While promising, further research work is required to extend the methods to non-linear and probabilistic models as well as user interface design.
Using LCA to Find Improvements for Hydrogen Production From Wind Electrolysis
Authors: Spath Pamela L. , Mann Margaret K.
Published: June 2008

Although hydrogen is generally considered to be a clean fuel, it is important to recognize that its production may have negative impacts on the environment. Examining the resource consumption, energy requirements, and emissions from a life cycle point of view gives a complete picture of the environmental burdens associated with hydrogen production. The National Renewable Energy Laboratory has performed a life cycle assessment (LCA) on a renewable hydrogen production process that employs wind/electrolysis. The results of the LCA showed areas where improvements would have the greatest reduction in stressors (i.e., resources, energy, and pollutants).
Modeling Test, Diagnosis, and Rework Operations and Optimizing Their Location in General Manufacturing Processes
Authors: Shi Zhen , Sandborn Peter
Published: June 2008

This paper presents a test, diagnosis, and rework analysis model for use in manufacturing process modeling. The approach includes a model of functional test operations characterized by fault coverage, false positives, and defects introduced in test, in addition to rework and diagnosis (diagnostic test) operations that have variable success rates and their own defect introduction mechanisms. The model accommodates multiple rework attempts on a product instance. The model is applied within a framework for optimizing the location(s) and characteristics (fault coverage/test cost, rework success rate/rework cost) of Test/Diagnosis/Rework (TDR) operations in a general manufacturing process. A new search algorithm called Waiting Sequence Search (WSS) is applied to traverse a general process flow to perform the cumulative calculation of a yielded cost objective function. Real-Coded Genetic Algorithms (RCGAs) are used to perform a multi-objective optimization that minimizes yielded cost. An example of a general complex process flow is used to demonstrate the feasibility of the algorithm.
A Structured Approach to Dimensioning and Tolerancing: Graphical Representation of the Problem
Authors: Islam M. N.
Published: June 2008

In this paper a methodology is presented which provides a structured way of solving Dimensioning and Tolerancing (D&T) problems on new product design. The methodology is interactive and suitable for use in a Concurrent Engineering (CE) environment. The proposed methodology helps to represent all relationships necessary for solving D&T problems in a matrix form known as Dimensional Requirements/Dimensions Matrix. This graphical representation assists the CE team to visualize the overall picture of the D&T problem and to foresee the ramifications of their decisions in regard to the selection of dimensions and tolerances; this will help the CE team in determining the dimensions and tolerances of a product in a systematic way.
Life Cost-Based FMEA Using Empirical Data
Authors: Rhee Seung J. , Ishii Kosuke
Published: June 2008

Failure Mode and Effect Analysis (FMEA) is a design tool that helps designers identify risks. The traditional FMEA involves ambiguity with the definition of risk priority number: the product of occurrence, detection difficulty, and severity subjectively measured in a 1 to 10 range. Life-cost Based FMEA alleviates this ambiguity by using the estimated cost of failures. Yet, the methods still relies on judgment of experts in determining variables such as frequency, detection time, fixing time, delay time, and parts cost. To resolve this subjectivity, this paper proposes a systematic use of empirical data for applying life-cost-based FMEA. A case study of a large scale particle accelerator shows the advantages of the proposed approach in predicting life cycle failure cost, measuring risk and planning preventive, scheduled maintenance and ultimately improving up-time.
Manufacturability Evaluation Shell: A Re-Configurable Environment for Technical and Economic Manufacturability Evaluation
Authors: Tharakan Prashanth Varkey , Zhao Zuozhi , Shah Jami
Published: June 2008

The process of manufacturability evaluation is composed of a series of generic tasks. Though domain knowledge is utilized to evaluate manufacturability the evaluation method itself is independent of domain. Manufacturability has different levels of abstraction – process level, workshop level and machine level. Currently existing assessment tools address manufacturability in specific domains and stages. In the emerging markets of increasing competition, streamlining the PRP involves designing with manufacturing capability in mind, and knowledge and application of new technology and processes. This paper proposes a generic domain independent shell for manufacturability that is configurable and customizable to any domain or process. The paper presents the three stages of manufacturability and its relevance to a domain independent approach to manufacturability assessment. The paper presents the problems plaguing current systems and charts out the requirements for a new generic shell that can overcome these shortcomings. The paper then presents the architecture of the shell and presents issues of implementation and two case studies (2.5D milling and injection-molding) as a proof of concept of the functioning of the shell.
Feature Conglomerator: Helping Users Identify Cost Effective Feature Interpretations
Authors: An Qian , Hayes Caroline C.
Published: June 2008

Feature Conglomerator is a manufacturing planning tool for use in 3 and 5 axis prismatic CNC machining domains. Feature extractors typically have many choices (i.e. interpretations) of how they may subdivide complex volumes into component features. Unfortunately, it may be difficult for the feature extractor to identify the interpretation which will result in the best manufacturing plan. The basic assumption behind this work is that much of the information needed to identify the best feature interpretation is not available during feature extraction. However, it does become available during manufacturing planning. Thus, if the initial features identified can be adjusted and refined during manufacturing planning, interpretation decisions can be better informed. This approach can be contrasted to that of Chang [1], which also refines features during manufacturing planning, in that this work is based on an information needs analysis to determine the most strategic time at which to make feature refinement decisions. This approach further blurs the line between feature extraction and process planning to make better informed feature interpretation decisions.
Flexible Multibody Systems With Large Deformations Using Absolute Nodal Coordinates for Isoparametric Solid Brick Elements
Authors: Ku¨bler Lars , Eberhard Peter , Geisler Johannes
Published: June 2008

In this paper a formulation for flexible Multibody Systems (MBS) is proposed where flexible bodies are described using absolute coordinates for isoparametric brick elements. The use of absolute coordinates allows for large deformations and provides an accurate description of rigid body motion and inertia in the case of large rotations without additional considerations. Further, constant mass matrices are obtained for isoparametric elements. Brick elements are important, e. g. if general solid bodies with low stiffness, i. e. not negligible large deformations, are part of the MBS and cannot be modeled using beam, plate, or shell elements. Since only nodal translational degrees of freedom are used for brick elements additional questions arise. For example, imposing joint constraints for relative rotations between two bodies requires a nodal reference frame at connection points. An approach is proposed to define such a reference system utilizing displacement information of three finite element nodes.
Comparison of the Absolute Nodal Coordinate and the Floating Frame of Reference Formulation by Means of a Simplified Strain Formulation
Authors: Gerstmayr J.
Published: June 2008

The floating frame of reference (FFR) formulation and the absolute nodal coordinate (ANC) formulation are often used for the modeling of multibody systems. In the present work a simplified strain model is derived for the ANC formulation which is equivalent to the (small strain) FFR formulation. The simplified strain model is based on a co-rotated reference configuration and the deformation is assumed to be small with respect to this configuration. This configuration is described by a translation vector and a rotation matrix which are both determined from the motion of the body with respect to its fixed reference. The ANC formulation with simplified strain leads to a constant mass matrix. The stiffness matrix consists of two parts: One part depends on the small-strain stiffness matrix of the body in the fixed reference configuration which is rotated by the rotation matrix and a second nonlinear part which depends quadratically on small strains. Both formulations represent displacements and deformations differently but lead to exactly the same results in the case of equivalent floating reference configurations. The relationship of both formulations is compared in a 2D example problem of a rotating hinged plate. A detailed description of the modelling in both cases as well as numerical results are presented.
Comparison of Physical Experiments and Computer Simulation With ANCF: Large Deformation of a Thin Cantilever Beam
Authors: Yoo Wan-Suk , Lee Jeong-Han , Sohn Jeong-Hyun , Park Su-Jin , Dmitrochenko Oleg , Pogorelov Dmitri
Published: June 2008

Many papers have studied computer-aided simulations of elastic bodies undergoing large deflections and large deformations. But there have not been many attempts to check the validity of the numerical formulations used in these studies. The main aim of this paper is to demonstrate the validity of one of such numerical formulations, the absolute nodal coordinate formulation (ANCF), by comparing the results it generates with the results of real experiments. Large oscillations of a thin cantilever beam are studied in this paper to numerically model the beam that also accounts for the effects of an attached endpoint weight and damping forces. The experiments were carried out using a high-speed camera and a data acquisition system.
A Modular Dynamic Model for Multibody System Adapted to Interactive Simulation
Authors: Seguy N. , Joli P. , Feng Z. Q. , Pascal M.
Published: June 2008

This paper presents a modular model of rigid multibody system using the acceleration-based augmented Lagrangian formulation. An important effort on the formulation of the governing equations has been made in order to meet the requirements for interactive simulation in computer aided design. Each body has been considered as an independent numerical component with its own numerical parameters, own mechanical parameters and own numerical integration scheme. Non-holonomic and holonomic constraints have been implemented in this formulation. This present work can be considered as an extended formulation of Bayo et al. [1] to the problem of interactive design and particular attention is paid to define the criteria of numerical stability.
Constraint Gradient Projective Method for Stabilized Dynamic Simulation of Constrained Multibody Systems
Authors: Terze Zdravko , Naudet Joris , Lefeber Dirk
Published: June 2008

Constraint gradient projective method for stabilization of constraint violation during integration of constrained multibody systems is in the focus of the paper. Different mathematical models for constrained MBS dynamic simulation on manifolds are surveyed and violation of kinematical constraints is discussed. As an extension of the previous work focused on the integration procedures of the holonomic systems, the constraint gradient projective method for generally constrained mechanical systems is discussed. By adopting differentialgeometric point of view, the geometric and stabilization issues of the method are addressed. It is shown that the method can be applied for stabilization of holonomic and non-holonomic constraints in Pfaffian and general form.
A Hybrid Global-Topological Real-Time Formulation for Multibody Systems
Authors: Cuadrado Javier , Dopico Daniel
Published: June 2008

The continuously improved performance of personal computers enables the real-time motion simulation of complex multibody systems, such as the whole model of an automobile, on a conventional $1,200 PC, provided the adequate formulation is applied. There exist two big families of dynamic formulations, depending on the type of coordinates they use to model the system: global and topological. The former leads to a simple and systematic programming while the latter is very efficient. In this work, a hybrid formulation is presented, obtained by combination of one of the most efficient global formulations and one of the most systematic topological formulations. In this way, it is developed a new formulation which shows, at the same time, easiness of implementation and a high level of efficiency. In order to verify the advantages that the new formulation has over its predecessors, the analysis of four examples is carried out using the three formulations and the corresponding results are compared: a planar mechanism which goes through a singular position, a car suspension with stiff behaviour, and a 6-dof robot with changing configurations, and the full model of a car vehicle. Furthermore, the last example is also analyzed by using a commercial tool, so as to provide the readers with a well-known reference for comparison.
A Non-Incremental Nonlinear Finite Element Solution for Cable Problems
Authors: Sugiyama Hiroyuki , Mikkola Aki M. , Shabana Ahmed A.
Published: June 2008

In this investigation, a nonlinear finite element method for the large deformation and rotation of cable problems is presented. This method is based on the finite element absolute nodal coordinate formulation that guarantees the continuity of all the displacement gradients and leads to a constant mass matrix. The classical cable theory is first reviewed and the assumptions used in this linear theory are defined in order to demonstrate the basic differences between the linear theory and the nonlinear finite element formulation proposed in this paper for cable applications. The elastic cable forces in the absolute nodal coordinate formulation are obtained in this investigation using a general continuum mechanics approach that accounts for the effect of all geometric nonlinearities. It is shown in this investigation that the use of the general continuum mechanics approach leads to a simpler and more efficient formulation as compared to the use of the assumptions of the linear theory that employs a local finite element coordinate system. The results obtained using the absolute nodal coordinate formulation show a good agreement with the results obtained using the classical cable theory when linear cable problems are considered. The results of this investigation obtained using explicit numerical integration also show the potential of the proposed finite element formulation in the nonlinear analysis of cables that experience large rotations and large deformations. It is also shown that the use of perturbation methods to linearize the finite element equations of motion leads to modal characteristics results that are in a good agreement with the linear theory. The generalization of the procedure presented in this paper to three-dimensional cable problems is demonstrated and the computer implementation in multibody algorithms is discussed.
Implementing the Extended Reduced Order Physical Model Into Commercialized Software Packages: Implementing Modal Constraints Into Software Packages
Authors: Sagane Takahito , Kinoshita Takao , Tajima Hiroshi , Seto Kazuto
Published: June 2008

In this paper, the extended reduced order physical model, which is developed to represent dynamics of flexible structures in multibody systems, is implemented to general multibody formulations. The elastic deformations are described using vibration modes associated with the rigid bodies that are effectively defined using dynamic properties of the system in this reduced order modeling method. The recursive formulation and the augmented formulation are used to develop the constraint equations associated with the connections between the reference body and the several rigid bodies in the modal representations used to modal elastic deformations. For this purpose, the n-body constraint is developed for the recursive formulations, while these constraint equations are transformed into the form that is suitable for the augmented formulation using the singular value decomposition or QR decomposition. The use of the formulations in this paper allows for the implementation of the extended reduced order physical model into the commercial multibody codes such as SIMPACK, ADAMS, and DADS.
Asperity Spring Friction Model With Application to Belt-Drives
Authors: Wasfy Tamer M.
Published: June 2008

An asperity spring friction model that uses a variable anchor point spring along with a velocity dependent force is presented. The model is incorporated in an explicit timeintegration finite element code. The friction model is used along with a penalty-based normal contact model to simulate the dynamic response of a two-pulley belt-drive system. It is shown that the present friction model accurately captures the stick-slip behavior between the belt and the pulleys using a much larger time-step than a pure velocity-dependent approximate Coulomb friction model.
Modeling and Control of Flexible Transporter System With Arbitrarily Time-Varying Cable Lengths
Authors: Zhang Yuhong , Agrawal Sunil K. , Hagedorn Peter
Published: June 2008

A systematic procedure for deriving the system model of a cable transporter system with arbitrarily time-varying lengths is presented. Two different approaches are used to develop the model, namely, Newton’s Law and Hamilton’s Principle. The derived governing equations are nonlinear partial differential equations. The same results are obtained using the two methods. The Rayleigh-Ritz method is used to obtain an approximate numerical solution of the governing equations by transforming the infinite order partial differential equations into a finite order discretized system. A Lyapunov controller which can both dissipate the vibratory energy and assure the attainment of the desired goal is derived. The validity of the proposed controller is verified by numerical simulation.
Dynamics Analysis of the Time-Varying Operation of Belt-Drives
Authors: Leamy Michael
Published: June 2008

For the first time, a closed-form analysis is presented for the time-varying operation of belt-drives. The analysis is developed as a perturbation away from the analysis of a steadily rotating belt-drive. The intent is to derive expressions for the span tensions, the pulley tension distributions, and the driven pulley angular velocity; and to document the existence of a lone slip zone for a belt-drive operating under time-varying conditions. A lone slip zone on the trailing edge of each pulley is well-known for steady operating conditions [Johnson, K.L., 1984],[Smith, D.P., 1999]. An alternative computational solution using an in-house finite element code is also presented, which demonstrates excellent agreement with the response quantities predicted by the analytical solution, and which also verifies the existence of a lone slip zone preceded by a stick zone.
A New Type Component Mode Synthesis Beam Element Based on the Absolute Nodal Coordinate Formulation
Authors: Iwai Riki , Kobayashi Nobuyuki
Published: June 2008

This paper establishes a new type component mode synthesis method for a flexible beam element based on the absolute nodal coordinate formulation. The deformation of the beam element is defined as the sum of the global shape function and the analytical clamped-clamped beam modes. This formulation leads to a constant and symmetric mass matrix as the conventional absolute nodal coordinate formulation, and makes it possible to reduce the system coordinates of the beam structure which undergoes large rotations and large deformations. Numerical examples show that the excellent agreements are examined between the presented formulation and the conventional absolute nodal coordinate formulation. These results demonstrate that the presented formulation has high accuracy in the sense that the presented solutions are similar to the conventional ones with the less system coordinates and high efficiency in computation.
Early Development of Fractional Order Control
Authors: Manabe Shunji
Published: June 2008

Early developments of Fractional Order Control (FOC) in 1950s and 60s are presented. It was known that the open-loop transfer function of a good control system shows a fractional order integral form with a fractional order between 1 and 2. Investigation was conducted about the optimum fractional order, the waveform of step response, and the effect of saturation and time delay on it. The result has been used as a design guide for control system of ordinary integer order.
Optimal Fractional-Order Damping
Authors: Hartley Tom T. , Lorenzo Carl F.
Published: June 2008

In this note, we consider the single term optimal fractional-order damper for an otherwise undamped oscillator. First, we find the single term damper that minimizes the time domain integral of the squared step error (2-norm) and the integral of the time-weighted squared error (Hilbert-Schmidt-Hankel-norm). Next we consider a more intuitive frequency domain approach that insures the maximally flat magnitude response. Time- and frequency-domain plots are given for comparison with the integer-order solutions.
Dynamic Analysis of the Optical Disk Drive System Equipped With an Automatic Ball Balancer With Consideration of Torsional Motion
Authors: Wang Chun-Chieh , Sung Cheng-Kuo , Chao Paul C. P.
Published: June 2008

This study is dedicated to evaluate the stability of an automatic ball-type balance system (ABS) installed in Optical Disk Drives (ODD). There have been researchers devoted to study the performance of ABS by investigating the dynamics of the system, but few consider the motions in torsional direction of ODD foundation. To solve this problem, a mathematical model including the foundation is established. The method of multiple scales is then utilized to find all possible steady-state solutions and perform related stability analysis. The obtained results are used to predict the level of residual vibrations and then the performance of the ABS can be evaluated. Numerical simulations are conducted to verify the theoretical results. It is obtained from both analytical and numerical results that the spindle speed of the motor ought to be operated above primary translational and secondary torsional resonances to stabilize the desired steady-state solutions for a substantial reduction in radial vibration.
Modeling of the Dynamics of Jointed Beam Structures
Authors: Song Yaxin , McFarland D. Michael , Bergman L. A. , Hartwigsen C. J. , Vakakis Alexander F.
Published: June 2008

Mechanical joints can have significant effects on the dynamics of assembled structures. The goal of our work is to develop physics based, reduced-order, finite element models that are capable of replicating the effects of joints on vibrating structures. Various studies have shown that micro and macro-slip along the joint interface cause the interface stiffness to change and introduce energy dissipation, leading to the observed hysteresis. The authors recently developed the so-called adjusted Iwan beam element (AIBE) for finite element analysis of jointed beam structures. The element consists of two adjusted Iwan models that are arranged to give two-dimensional beam behavior. The adjusted Iwan model is a combination of springs and frictional sliders that exhibits hysteretic behavior due to the stick-slip behavior of the sliders. In this paper, the sensitivity of the performance of an adjusted Iwan model, particularly its capacity to dissipate energy, to variations in its parameters is studied. Parametric analysis is also carried out on the adjusted Iwan beam element to investigate the effects of joint parameters on dynamic responses of jointed beams. Hammer tests are conducted on a jointed beam and its monolithic counterpart. The decay envelopes of impulsive responses for the two systems exhibit distinctly different dynamic properties. To verify that the adjusted Iwan beam element is capable of actually modeling the effects of joints on a vibrating structure, numerical simulations are performed of two hammer tests with different forcing levels. The joint parameters of the jointed beam are identified from the experimentally-obtained acceleration response from one hammer test by using a multi-layer feed-forward neural network (MLFF). Then, using the identified joint parameters, acceleration responses of the jointed beam in the other hammer test are predicted. The capability of the AIBE to capture the effects of bolted joints on the dynamic responses of beam structures is demonstrated through good agreement between simulated and experimental results.
On the Development of a Model Updating Strategy of Non-Linear Vibrating Structures
Authors: Kerschen Gae¨tan , Golinval Jean-Claude
Published: June 2008

The objective of this paper is to present a model updating strategy of non-linear vibrating structures. Because modal analysis is no longer helpful in non-linear structural dynamics, a special attention is devoted to the features extracted from the proper orthogonal decomposition and one of its non-linear generalisations based on auto-associative neural networks. The efficiency of the proposed procedure is illustrated using simulated data from a three-dimensional portal frame.
Order Reduction of Nonsmooth Structural Systems With Multiple Surfaces of Discontinuity
Authors: Butcher Eric A. , Lu Rongdong
Published: June 2008

A technique for order reduction of nonsmooth vibrating systems in structural form of arbitrary dimension with multiple surfaces of discontinuity is presented. By utilizing methods based on the bilinear frequency relation which approximates the nonlinear normal mode (NNM) frequencies and mode shapes, reduced order models are constructed which retain the form of the nonsmooth nonlinearity of the full model and more accurately represent the NNM dynamics in the full model than do reduced models obtained via linear transformations. The technique is applied to multi-degree-of-freedom systems with nonsmooth nonlinearities of deadzone and saturation type in which the full and reduced models are compared by direct numerical simulation. The advantages of the present technique include obtaining a reduced order model which uses a subset of the original physical coordinates and can easily accommodate large order systems and multiple nonsmooth nonlinearities with several surfaces of discontinuity. These characteristics make the method practical for use in large-scale structural dynamics applications in which the linear part of the model dominates the dynamics.
Order Reduction of Nonlinear Time Periodic Systems Using Invariant Manifolds
Authors: Sinha S. C. , Redkar Sangram , Butcher Eric A. , Deshmukh Venkatesh
Published: June 2008

The basic problem of order reduction of linear and nonlinear systems with time periodic coefficients is considered. First, the equations of motion are transformed using the Lyapunov-Floquet transformation such that the linear parts of new set of equations are time invariant. At this stage, the linear order reduction technique can be applied in a straightforward manner. A nonlinear order reduction methodology is also suggested through a generalization of the invariant manifold technique via Time Periodic Center Manifold Theory. A ‘reducibility condition’ is derived to provide conditions under which a nonlinear order reduction is possible. Unlike perturbation or averaging type approaches, the parametric excitation term is not assumed to be small. An example consisting of two parametrically excited coupled pendulums is given to show applications to real problems. Order reduction possibilities and results for various cases including ‘parametric’, ‘internal’, ‘true internal’ and ‘combination’ resonances are discussed.
A POD-Based Identification of the Reduced Dynamics of an Exact Nonlinear Rod Loaded Transversely
Authors: Georgiou Ioannis T. , Kanavis Christos E.
Published: June 2008

Reduced dynamics of a nonlinear exact rod is derived by restricting the coupled nonlinear equations of motion onto Proper Orthogonal Modes (POD) identified by a Proper Orthogonal Decomposition of the finite element approximation to the dynamics. For the case of a dominant POD mode, the reduced dynamical system is a geometrically exact nonlinear oscillator. Numerical integration reveals that the phase portrait of the reduced system, for the case of zero dissipation, has Hamiltonian structure. For harmonic forcing at low frequencies, the reduced system predicts exceptionally well the dynamics of the nonlinear rod over a wide range of forcing amplitude. For forcing frequencies in the order of the fundamental frequency for linear bending motions, the reduced model predicts very well the qualitative changes of the dynamics but it underestimates the critical parameters at which the qualitative changes occur at high levels of forcing amplitudes. It is conjectured that the reduced model stemming from the restriction of the full order system onto a single dominant POD describes the dynamics of a nonlinear normal mode of vibration. The POD method can be used to identify the normal modes of vibration of coupled systems with complicated nonlinearities.
Measuring Vibration Isolator’s Shock Characteristics by Air Gun
Authors: Weng Xuetao , Huang Yingyun , Zhu Shijian , Wang Yu
Published: June 2008

A method of measuring vibration isolator’s shock characteristics is advanced in this paper. An anvil is impacted by the bullet from an air gun and hence obtains some initial velocity. Then the vibration isolator absorbs the shock load of the anvil’s inertia. The force acting on the vibration isolator and the displacement of the vibration isolator are measured with a force measuring steel block and a laser displacement sensor respectively. Hence the problem how to act controllable shock load and how to measure the data under shock condition is solved.