bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of a Semi-Active Shock Absorber for Aircraft Landing Gear
Authors: Maemori Ken’ichi , Tanigawa Naoki , Koganei Reiko , Morihara Toshio
Published: June 2008

We propose an optimization method for a semi-active shock absorber for use in aircraft landing gear, in order to handle variations in the maximum vertical acceleration of an aircraft during landing caused by the variation of the aircraft mass due to the variations in the number of passengers, and the amounts of cargo and fuel. In this optimization, the maximum vertical acceleration of an aircraft is set as an objective function to be minimized. Design variables searched in the first step of this optimization are discrete orifice areas formed by the outer surface of a hollow metering pin and a hole in the semi-active shock absorber. The design variable searched in the second step is a compensating orifice area which is controlled based on the mass variation. Using the optimum target orifice area obtained in the second step, we optimally determine a practical orifice area that is controlled by a stepping motor. The optimizations for a passive shock absorber and for semi-active shock absorbers with target and practical orifice areas indicate that the semi-active shock absorbers can handle aircraft mass variation much better than the optimum passive shock absorber. Furthermore, the robustness of the optimum practical orifice area controlled by a stepping motor is shown via simulation.
A Study of Emission Policy Effects on Optimal Vehicle Design Decisions
Authors: Michalek Jeremy J. , Papalambros Panos Y. , Skerlos Steven J.
Published: June 2008

A methodology is presented for studying the effects of automobile emission policies on the design decisions of profit-seeking automobile producers in a free-entry oligopoly market. The study does not attempt to model short-term decisions of specific producers. Instead, mathematical models of engineering performance, consumer demand, cost, and competition are integrated to predict the effects of design decisions on manufacturing cost, demand, and producer profit. Game theory is then used to predict vehicle designs that producers would have economic incentive to produce at market equilibrium under several policy scenarios. The methodology is illustrated with three policy alternatives for the small car market: corporate average fuel economy (CAFE) regulations, carbon dioxide emissions taxes, and diesel fuel vehicle quotas. Interesting results are derived, for example, it is predicted that in some cases a stiffer regulatory penalty can result in lower producer costs because of competition. This mathematical formulation establishes a link between engineering design, business, and marketing through an integrated optimization model that is used to provide insight necessary to make informed environmental policy.
Robust Topological Design of Cellular Materials
Authors: Seepersad Carolyn Conner , Allen Janet K. , McDowell David L. , Mistree Farrokh
Published: June 2008

A robust topology exploration method is under development in which robust design techniques are extended to the early stages of a design process when a product’s layout or topology is determined. The performance of many designs is strongly influenced by both topology, or the geometric arrangement and connectivity of a design, and potential variations in factors such as the operating environment, the manufacturing process, and specifications of the design itself. While topology design and robust design are active research areas, little attention has been devoted to integrating the two categories of design methods. In this paper, we move toward a comprehensive robust topology exploration method by coupling robust design methods, namely, design capability indices with topology design techniques. The resulting design method facilitates efficient, effective realization of robust designs with complex topologies. The method is employed to design extruded cellular materials with robust, desirable elastic properties. For this class of materials, 2D cellular topologies are customizable and largely govern multifunctional performance. By employing robust, topological design methods, we obtain cellular material designs that are characterized by ranged sets of design specifications with topologies that reliably meet a set of design requirements and are relatively simple and robust to anticipated variability.
Design of Energy Absorbing Structure Using Topology Optimization With a Multi-Material Model
Authors: Jung Daeyoon , Gea Hae Chang
Published: June 2008

To accommodate the dual objectives of many engineering applications, one to minimize the mean compliance for the stiffest structure under normal service condition and the other to maximize the strain energy for energy absorption during excessive loadings, topology optimization with a multi-material model is applied to the design of energy absorbing structure in this paper. The effective properties of the three-phase material are derived using a spherical micro-inclusion model. The dual objectives are combined in a ratio formation. Numerical examples from the proposed method are presented and discussed.
A Taxonomy for Collaborative Design
Authors: Ostergaard Karen J. , Summers Joshua D.
Published: June 2008

A taxonomy that classifies issues affecting the collaborative design process is proposed. These factors, which may inhibit or facilitate the progress or success of a design team, provide a description of collaborative design situations. The taxonomy includes top-level attributes of team composition, communication, distribution, design approach, information, and nature of the problem. An example collaborative design situation is used to illustrate the application of the taxonomy. This taxonomy is an initial step towards the creation of new collaborative support agent-based tools structured upon a fundamental understanding of the collaborative process with a theoretical foundation.
Port-Compatibility and Connectability Based Assembly Design
Authors: Singh Palwinder , Bettig Bernhard
Published: June 2008

In Computer-Aided Design, when creating the solid model of a part, the designer knows how the part will interface with other parts, however this information is not stored with the part model. For catalog parts, it would be useful to be able to embed this assembly information into the part model in order to automate the process of applying mating constraints, to reduce the assembly designer’s effort or to allow for automated exploration of alternative configurations. This research evaluates and compares different schemes for capturing the attributes of assembly interfaces and appending that information to solid models. The schemes studied involve (i) different combinations of ways to constitute ports and include labeling, (ii) different bases for determining port compatibility with respect to design intent, and (iii) different ways of evaluating connectability with respect to part geometry. The scheme that we conclude is best minimizes the number of ways the system will try to put parts together at the expense of effort from the solid model designer to provide more information.
Design Evaluation Method for Miniature Machine Tools Utilizing Form-Shaping Theory
Authors: Mishima Nozomu
Published: June 2008

A microfactory is a system that can perform manufacturing processes within a very limited space such as a desktop. However, design optimization of miniature machine tools in microfactories have not been studied enough. Since the miniature machine tool designs are not supported by existing design experience as normal machine tools are, design guidelines for miniature machine tool are strongly demanded. And a design tool to analyze machine performance without prototyping will be also necessary because the miniature machines have wider design choices than normal machine tools have, based on its small size and less constraints. This paper focuses on a robust design tool combining form-shaping theory with the Taguchi method, to roughly estimate performance of miniature machine tools at its conceptual design stages. The effort not only identifies critical design parameters that have significant influence on the machining tolerance, but also determines which structure has the best theoretical performance. The paper tells that the proposing design evaluation method can help machine tool designers in determining the optimum structure of a miniature machine tool. The study also realizes two designs of miniature mills to measure positioning errors. The measurement ensures the design evaluation method can predict the machine performance well enough for usage in conceptual design stages. The paper concludes that the design evaluation method is applicable to a systematic miniaturization of a machine tool.
Strengthening of Bone Cement by Shape Optimization of Short Fibers
Authors: Zhou Yan , Li Chaodi , Renaud John E. , Mason James J.
Published: June 2008

Poor interfacial properties between reinforcement fibers and a Polymethylmethacrylate (PMMA) matrix may result in debonding between them, which is a major failure mechanism for fiber reinforced bone cement. Optimization of the shape of the fibers can improve load transfer between the fibers and PMMA matrix, thereby providing maximum overall strength performance. This paper presents a procedure for structural shape optimization of short reinforcement fibers using finite element analyses. The composite is modeled by a representative element composed of a single short fiber embedded in PMMA matrix. In contrast to most previous work on this subject, contact elements are employed between the fiber and the matrix to model a low strength interface. Most models assume a perfect bond. Residual stress, due to matrix cure shrinkage and/or thermal stresses, is also included in the model. The design objective is to improve the stiffness of the composite. The results presented show that a threaded end, short fiber results in mechanical interlock between the fibers and the PMMA matrix, which helps to bridge matrix cracks effectively and improve the stiffness of the composite.
Optimal Packaging of Tank Turret System
Authors: Yu Chan , Manoochehri Souran , McKonly Chad
Published: June 2008

Optimal packaging problems occur in many industries and lend themselves to be analyzed by computer-based approaches due to their fast and effective solutions. Unlike other packaging in commercial industries, turret packaging has been done mainly by hand because positioning equipment within the turret with crew is hard to be automated. However, recent development of automated ammunition loading system makes crew unnecessary in turret and this makes it possible to automate the packaging process. This paper introduces a computational methodology that uses genetic algorithms as a search algorithm and solves tank turret packaging problems by integrating part placements with performance analysis of design requirements.
Generalized Random Tunneling Algorithm for Continuous Design Variables
Authors: Kitayama Satoshi , Yamazaki Koetsu
Published: June 2008

A global optimization method for continuous design variables called as Generalized Random Tunneling Algorithm is proposed. Proposed method is called as “Generalized” random tunneling algorithm because this method can treat the behavior constraints as well as the side constraints. This method consists of three phases, that is, the minimization phase, the tunneling phase, and the constraints phase. In the minimization phase, mathematical programming is used, and heuristic approach is introduced in the tunneling and constraint phases. By iterating these phases, global minimum is found. The characteristics of mathematical programming and heuristic approaches are included in the proposed method. Global minimum which may lie on the boundary of constraints is easily found by proposed method. Proposed method is applied to mathematical and structural optimization problems. Through numerical examples, the effectiveness and validity of proposed method have been confirmed.
A Robust Solution to the Spherical Rigid-Body Guidance Problem
Authors: Al-Widyan Khalid , Angeles Jorge
Published: June 2008

In this paper we introduce a robust algorithm to solve the five-attitude spherical Burmester problem associated with exact linkage synthesis. The proposed algorithm solves for the unit vectors determining the four joint centers of the linkage while taking into account all redundant equations available, which enhances the robustness of the algorithm. In order to show the applicability of the proposed algorithm and to validate its robustness, two examples are included.
Designing a Dexterous Reconfigurable Packaging System for Flexible Automation
Authors: Dubey Venketesh N. , Crowder Richard M.
Published: June 2008

This paper presents a design for a reconfigurable packaging system that can handle cartons of different shape and sizes and is amenable to ever changing demands of packaging industries for perfumery and cosmetic products. The system takes structure of a multi-fingered robot hand, which can provide fine motions, and dexterous manipulation capability that may be required in a typical packaging-assembly line. The paper outlines advanced modeling and simulation undertaken to design the packaging system and discusses the experimental work carried out. The new packaging system is based on the principle of reconfigurability, that shows adaptability to simple as well as complex carton geometry. The rationale of developing such a system is presented with description of its human equivalent. The hardware and software implementations are also discussed together with directions for future research.
Approximate Motion Synthesis of Open and Closed Chains via Parametric Constraint Manifold Fitting: Preliminary Results
Authors: Larochelle Pierre M.
Published: June 2008

In this paper we present a novel dyad dimensional synthesis technique for approximate motion synthesis. The methodology utilizes an analytic representation of the dyad’s constraint manifold that is parameterized by its dimensional synthesis variables. Nonlinear optimization techniques are then employed to minimize the distance from the dyad’s constraint manifold to a finite number of desired locations of the workpiece. The result is an approximate motion dimensional synthesis technique that is applicable to planar, spherical, and spatial dyads. Here, we specifically address the planar RR, spherical RR and spatial CC dyads since these are often found in the kinematic structure of robotic systems and mechanisms. These dyads may be combined serially to form a complex open chain (e.g. a robot) or when connected back to the fixed link they may be joined so as to form one or more closed chains (e.g. a linkage, a parallel mechanism, or a platform). Finally, we present some initial numerical design case studies that demonstrate the utility of the synthesis technique.
Geometric Design of Cylindric PRS Serial Chains
Authors: Su Hai-Jun , Wampler Charles W. , McCarthy J. Michael
Published: June 2008

This paper considers the design of the cylindric PRS serial chain. This five degree-of-freedom robot can be designed to reach an arbitrary set of eight spatial positions. However, it is often convenient to choose some of the design parameters and specify a task with fewer positions. For this reason, we study the three through eight position synthesis problems and consider various choices of design parameters for each. A linear product decomposition is used to obtain bounds on the number of solutions to these design problems. For all cases of six or fewer positions, the bound is exact and we give a reduction of the problem to the solution of an eigenvalue problem. For seven and eight position tasks, the linear product decomposition is useful for generating a start system for solving the problems by continuation. The large number of solutions so obtained contraindicates an elimination approach for seven or eight position tasks, hence continuation is the preferred approach.
On the Effects of Weights in Rational Motion Design
Authors: Purwar A. , Ge Q. J.
Published: June 2008

The effect of weights on curves and surface design is a well-researched topic in Computer Aided Geometric Design (CAGD). However, the influence of weights in the realm of rational motion approximation and interpolation has been largely unexplored. In this paper, we present a thorough mathematical exposition on the influence of weights on rational motion design. This leads naturally to providing the motion designer with guidelines on how to use weights for rational motion design. Several examples are presented towards the end.
Type Synthesis of Three-DOF Translational Parallel Mechanisms
Authors: Yu Jingjun , Bi Shusheng , Zong Guanghua , Zhao Tieshi , Huang Zhen
Published: June 2008

This paper presents a simple but effective type synthesis method for spatial parallel mechanisms with three translational degrees of freedom based on the screw theory. Firstly all possible connecting-chain structures of three-DOF parallel mechanisms are enumerated. According to the reciprocal relationship between screw constraint forces and the motion screw, a novel synthesis method is presented. By using this method, type synthesis for three-DOF translational parallel mechanisms has been made in a systematic and detailed way. As a result, some novel parallel mechanisms generating spatial translation have been obtained. To verify the significance of type synthesis for this kind of mechanism, the paper also gives a concrete application instance, which is used for a micromanipulator for manipulating the bio-cells.
Planar Translational Cable-Direct-Driven Robots: Hardware Implementation
Authors: Williams Robert L. , Vadia Jigar
Published: June 2008

We present hardware results of a planar, translational cable-direct-driven robot (CDDR). The motivation behind this work was to present kinematics and statics modeling of the CDDR along with the method to maintain positive cable tension and implement them on CDDR hardware for experimental verification. Only translational CDDR is considered in this article; we attempt to keep zero orientation by control. We ignore gravity here because the end-effector is supported on a base plate with negligible friction. Results are presented and analyzed for two linear profiles and one circular profile.
Cable-Based Metrology System for Sculpting Assistance
Authors: Williams Robert L. , Albus James S. , Bostelman Roger V.
Published: June 2008

A novel cable-based metrology system is presented wherein six cables are connected in parallel from ground-mounted string pots to the moving object of interest. Cartesian pose can be determined for feedback control and other purposes by reading the lengths of the six cables via the string pots and using closed-form forward pose kinematics. This paper focuses on a sculpting metrology tool, assisting a human artist in generating a piece from a computer model, but applications exist in manufacturing, rapid prototyping, robotics, and automated construction. The proposed real-time cable-based metrology system is less complex and more economical than existing commercial Cartesian metrology technologies.
An XZ Micropositioning Mechanism (XZMM) With Out-of-Plane Translation
Authors: Jensen Kimberly A. , Howell Larry L.
Published: June 2008

This paper introduces the XZ Micropositioning Mechanism (XZMM) that is fabricated in the x-y plane and translates components in the x-z direction using one linear input. The positioning platform of the mechanism remains parallel to the substrate throughout its motion. The XZMM has been tested and actuated using thermal actuation and achieves an out-of-plane output displacement of 41 micrometers with a 27 micrometer x-direction input.
On the Design of Nesting Forces for Exactly Constrained, Robust Mechanical Assemblies
Authors: Pearce Eric , Parkinson Alan , Chase Kenneth
Published: June 2008

In this research we investigate the design of nesting forces for exactly constrained, robust mechanical assemblies. Exactly constrained assemblies have a number of important advantages including the ability to assemble over a wide range of conditions. Such designs often require nesting forces to keep the design properly seated. To date, little theory has been developed for the design of nesting forces. We show how the effects of tolerances on nesting forces, a key issue, can be analyzed and apply the analysis to a simple design problem. For the example problem, good agreement is achieved with results from Monte Carlo simulation.
On the Geometry of 3D Orientation Measurement Using a New Class of Wireless Angular Position Sensors
Authors: Ge Q. J. , Rastegar J. , Pereira Carlos
Published: June 2008

This paper deals with the geometric issues that arise in designing a system for measuring the orientation of an object in three dimensional space using a new class of wireless angular position sensors. The wireless sensors are waveguides that receive and record the electromagnetic energy emitted by a polarized RF source. The angular position of the waveguide relative to the source is indicated by the energy level. A system equipped with multiple waveguides is used as a 3D orientation sensor. This paper explores the geometry for orientation measurement using the system and provides the guidelines for sensor design.
Kinematics of Wheeled Mobile Robots With Toroidal Wheels on Uneven Terrain
Authors: Chakraborty Nilanjan , Ghosal Ashitava
Published: June 2008

This paper deals with the kinematic analysis of a wheeled mobile robot (WMR) moving on uneven terrain. It is known in literature that a wheeled mobile robot, with a fixed length axle and wheels modeled as thin disk, will undergo slip when it negotiates an uneven terrain. To overcome slip, variable length axle (VLA) has been proposed in literature. In this paper, we model the wheels as a torus and propose the use of a passive joint allowing a lateral degree of freedom. Furthermore, we model the mobile robot, instantaneously, as a hybrid-parallel mechanism with the wheel-ground contact described by differential equations which take into account the geometry of the wheel, the ground and the non-holonomic constraints of no slip. Simulation results show that a three-wheeled WMR can negotiate uneven terrain without slipping. Our proposed approach presents an alternative to variable length axle approach.
Topology and Shape Optimization of an Interbody Fusion Implant for Lumbar Spine Fixation
Authors: Tovar Andre´s , Gano Shawn E. , Renaud John E. , Mason James J.
Published: June 2008

The goal of this research is to obtain the optimum design of a new interbody fusion implant for use in lumbar spine fixation. A new minimally invasive surgical technique for interbody fusion is currently in development. The procedure makes use of an interbody implant that is inserted between two vertebral bodies. The implant is packed with bone graft material that fuses the motion segment. The implant must be capable of retaining bone graft and supporting spinal loads while fusion occurs. Finite element-based optimization techniques are used to drive the design. The optimization process is performed in two stages: topology optimization and then shape optimization. The different load conditions analyzed include: flexion, extension, and lateral bending.
Issues in Integration of Design and Manufacturing for Mechatronics
Authors: Dong Hui , Wood William H.
Published: June 2008

Design for manufacture (DfM) has made significant strides by recommending incremental changes to design details. As DfM is pushed further upstream in the design process, it becomes an integral part of design. In the earliest stages of design, designers must consider the manufacturing implications of all of their decisions and trade them against other aspects of design performance. We present a decision-based framework for system-level DfM that focuses on the entire design process. To examine this methodology, we present issues arising from the development of an integrated design process for mechatronic products that includes both DfM evaluations and heuristic DfM design practices as ways to shape the early design process. Integrating DfM into design search must happen at the system level, doing so requires improving the overall design synthesis process.
Improving Life Cycle Assessment by Including Spatial, Dynamic and Place-Based Modeling
Authors: Reap John , Bras Bert , Newcomb Patrick J. , Carmichael Carol
Published: June 2008

Drawing from the substantial body of literature on life cycle assessment / analysis (LCA), the article summarizes the methodology’s limitations and failings, discusses some proposed improvements and suggests an additional improvement. After describing the LCA methodology within the context of ISO guidelines, the article summaries the limitations and failings inherent in the method’s life cycle inventory and impact assessment phases. The article then discusses improvements meant to overcome problems related to lumped parameter, static, site-independent modeling. Finally, the article suggests a remedy for some of the problems with LCA. Linking industrial models with spatially explicit, dynamic and site-specific ecosystem models is suggested as a means of improving the impact assessment phase of LCA.
Continuous Quality Improvement and Optimization of Design Tolerances Using Demerit Score System
Authors: Abraham Alex , Roy Ram Naresh
Published: June 2008

Continuous improvement is a concept that has gained wide popularity in every sphere of human activity in recent times and the area of production engineering is no exception. This is a far cry from ancient times when people were afraid or forbidden to innovate, usually under authoritative duress. Continuous quality improvement has been proven to bring in reduction in failure rates and cost of repairs. Quality improvement is not ‘putting out fires’ or ‘identification and removal of a spike’, but rather, it continually questions the existing systems and methods. This paper introduces a novel, inexpensive and practical tool for quality improvement, to be called ‘demerit scores’, or a system of negative weights that continually keeps tab on the production scenario with the objective to improve. This tool is useful for building robustness into the design by optimizing design tolerances for increasing productivity and reducing costs of production. The technique is illustrated with two examples in this paper.
Modeling Variation Propagation Through a Manufacturing Process
Authors: Kern Daniel , Thornton Anna
Published: June 2008

Companies are under increased pressure to manufacture products that have a high level of quality. Manufacturing products with a high level of quality in a cost-effective manner requires the products to be designed so that they can be manufactured with an acceptable level of variation. Creating a new design that can be produced with the necessary level of variation has historically been a very challenging problem. A new method for calculating the effect a manufacturing process has on the mean and standard deviation of a distribution is presented. This new method is founded on the concept of characterizing a manufacturing process with two math functions called DeltaP and SigmaP. DeltaP and SigmaP represent the theory of Process Imparted Dimensional Change and Process Imparted Variation. Using these functions, closed-form solutions for the mean and standard deviation of a distribution exiting a manufacturing process can be calculated. The authors present the background of the theory as well as the derivation of the closed form solutions for the output mean and standard deviation from a generic manufacturing process. The derivation is followed by a simple example to demonstrate the method.
Design of Winding With Two Rovings for Cost Efficiency and Quality in Robotized Filament Winding
Authors: Polini W. , Sorrentino L.
Published: June 2008

This work deals with the design of winding with two rovings of asymmetric and complex shape parts by means of robotized filament winding technology. The adopted criteria aim to decrease significantly the winding time and, therefore, the manufacturing costs by preserving the composite part quality through the design of a system that is able to control the orientation of both the rovings on the die during winding, thus avoiding their torsion. A cell composed of an industrial robot opportunely equipped with a new feed and deposition system has been designed and implemented. Two rovings are unwound by two spools fixed to a creel and, then, they are conveyed towards the new feed and deposition system connected to the robot end-effector. The rovings pass through the roving-guide system, where they are paired off in a single roving that is guided towards the deposition head. The deposition head controls the orientation of the single roving on the die during winding. The new system working and its interaction with the most critical process parameters have been evaluated through experimental tests. This work belongs to a research project aiming to develop an integrated environment to wind complex shape parts through a robotized cell.
Automated Manufacturability Analysis for Injection-Molded and Die-Cast Parts
Authors: McAdams Daniel A. , Bidkar Rahul A.
Published: June 2008

In this article, a mathematical framework to automatically evaluate the manufacturability of injection-molded and die-cast parts is presented. The framework includes both a logical algorithm for the general problem of feature recognition and an implemented mathematical and numerical algorithm to solve key outstanding challenges in feature recognition for manufacturability analysis. A novel feature recognition method is developed that is based on decomposing the part into elemental cubes and then, making use of their individual manufacturability, the manufacturability of the part as a whole is evaluated. This article discusses a procedure to obtain a 3D binary representation of the solid model in a simple fashion and further develops feature recognition techniques to extract critical manufacturability information from this 3D binary array. The outstanding challenges addressed by the method presented include the finding of parting surfaces, undercuts, holes, and bosses in the context of an injection-molded or diecast part. The algorithm is implemented using a combination of C++ code and Unigraphics solid modeling software. A short example is presented.
On Prediction of Passive Contact Forces of Workpiece-Fixture Systems
Authors: Xiongand Cai-Hua , Xiong You-Lun , Wang Michael Yu
Published: June 2008

Prediction of passive forces in a frictional workpiece-fixture system is an important problem, since the contact forces have a strong influence on clamp design and on workpiece accuracy during machining. This paper presents a general method for the computation of the contact forces. First, based on the rigid-body kinematics, an indeterminate system of static equilibrium is defined, in which the passive, frictional contact forces cannot be determined arbitrarily as in an actively controlled robotic multi-finger grasp. Then, we define a locally elastic contact model to describe the nonlinear coupling between the contact forces and elastic deformations at the contact point. This model captures the essence of the passive contact. Further, a set of “compatibility” equations are given so that the elastic deformations among all passive contacts in the workpiece-fixture system result in a consistent set of rigid-body displacement of the workpiece in its global system. Finally, combining the locally elastic contact model and the “compatibility” conditions, we transform the force computation problem into a determinate system of nonlinear equations governing all of the elastic deformations at all of the passive contacts. By solving the resulting nonlinear equations with frictional constraints, we can accurately predict all contact forces in the frictional workpiece-fixtures system. This method is illustrated with example cases. The method presented here may also have an application to other passive, indeterminate problems such as power grasps in robotics.
Assembly Quality Method: Integrating Design for Assembly Cost-Effectiveness (DAC) to Improve Defect Prediction
Authors: Shibata Hirokazu , Cheldelin Brent , Ishii Kosuke
Published: June 2008

The complexities in assembly processes have a strong correlation with the occurrences of defects. This paper develops a design-based complexity factor derived from the “Design for Assembly” method for evaluating assembly to augment factors not captured by the process-based complexity factor proposed by the authors. The authors collected extensive field data including consumer audio equipment assembled at various manufacturing sites around the world, and used defect data for validating the metrics. The quantitative correlation between the design-based complexity factor and defect rates will provide mechanical designers with guidelines for improving the original design.
Shaping Minimum Strain Energy Curves for FF-TLOM
Authors: Broek J. J. , Kooijman A. , de Smit A. , Horva´th I.
Published: June 2008

Free Form Thick Layered Object Manufacturing (FF-TLOM) technology is based on foam cutting with a curved heated flexible cutting blade. Three single parameters shape the flexible blade. An infinite amount of blade shapes can be selected. However, many of these shapes are not suitable for cutting. Blade shapes with less than two inflexions can be applied successfully. When two inflexions are involved the blade; more than one different stable blade shape can be realized. For tool path creation and cutting procedures the blade shape must be known. A 2-D calculation algorithm based on (Kallay, 1987) is used. The calculation result is a minimum strain energy curve of a prescribed length, which is represented by a chain of segments. The shape is unfolded by rotating each segment under conditions of total energy decrease until no improvements are achieved. In this paper the process parameters are analyzed for sensitivity and influence on the accuracy and conditions of the blade shaping process. An overview of these parameters is given and the accuracy, computing time and trustworthiness of the implemented algorithm is checked. Typical FF-TLOM process characteristics are considered for its influence on the blade shape The elastic energy of curves is presented for a complete range of blade shapes. Regions of bi-stable blade shapes are perceived based on more than one blade inflexion. Finally a selection is presented for those minimum strain curves, which are applicable for the FF-TLOM technology.
A Step Towards Automated Design of Rotary-Platen Multi-Shot Molds
Authors: Li Xuejun , Gupta Satyandra K.
Published: June 2008

This paper describes an improved algorithm for automated design of rotary-platen type of multi-shot molds for manufacturing multi-material objects. The algorithm described in this paper accounts for geometric constraints resulting from the rotary-platen process and it can handle significantly more complex interfaces. Our algorithm works in the following manner. First, we classify the multi-material object into several basic types based on the relationships among different single material components in the object. For every basic type, we find a manufacturing sequence based on the precedence constraints resulting due to accessibility and disassembly requirements. Then, starting from the last mold stage, we generate the mold pieces for every mold stage based on the manufacturing sequence. We expect that the algorithm described in this paper will provide the necessary foundations for automating the design of rotary-platen molds and therefore will help in significantly reducing the mold manufacturing lead-time associated with these types of molds.
Draping 2D Patterns Onto 3D Surfaces
Authors: Joneja Ajay , Tam Angela , Jing Fu
Published: June 2008

We describe a simple new CAD operator that allows draping of given 2D patterns onto the surface of a 3D mold. The 2D pattern is any closed, connected polygon or a polygonal approximation of a shape bounded by curves. The mold is typically described in terms of any standard surface representation scheme, such as NURBS or B-Splines. The draping is achieved by mapping skeletal lines on the 2D pattern onto corresponding geodesic curves on the 3D surface. If the mold surface is developable, our method gives a draping with zero distortion. A useful application in the CAD of footwear is demonstrated as a motivation for this work. A simple software program has been implemented to test the operator, and examples are provided to demonstrate its use.
Flexible Multibody System Applications Using Nodal and Modal Coordinates
Authors: Wallrapp Oskar , Wiedemann Simon
Published: June 2008

Throughout the past decades a considerable amount of work has been dedicated to the development and application of formalisms to simulate flexible bodies in a multibody system (MBS). The two most common approaches to describe the deformation of a flexible body with respect to their floating frame of reference are to apply the linear finite element formulation and the linear modal approach using global mode shapes. On the field of flexible body modelling, this paper discusses two topics: a) the consideration of quadratic terms in the equations of deformation and b) the presentation of methods for global mode preparation to reduce the computer time for dynamic simulations without loss of accuracy regarding deformations. The proposed methods are applied in two examples, for the deformation of a stabilisation linkage of a car’s front suspension and for the simulation of the deployment of a flexible solar array.
A Novel Approach for the Dynamic Analysis and Simulation of Constrained Mechanical Systems
Authors: Ko¨vecses Jo´zsef , Piedboeuf Jean-Claude
Published: June 2008

In this paper we will outline a formulation for the dynamics of constrained systems. This formulation relies on the D’Alembert-Lagrange principle and the physically meaningful decomposition of the virtual displacements and the generalized velocities for the system where a redundant, non-minimum set of variables is used. The approach is valid for general constrained system with holonomic and/or nonholonomic constraints. We will also discuss a potential application of this formulation in improving the accuracy and stability of the simulation of constrained systems. This application will be demonstrated by an example drawn from space robotics.
Motion and Vibration of a Moving Body on the 3D Trajectory Considering Running Resistance
Authors: Fujita Katsuhisa , Funakoshi Yuji , Hayami Yoshiko , Yamamoto Yoshinori
Published: June 2008

The motion and vibration of a moving body running on the complicated 3 dimensional trajectory considering the running resistance are investigated in this paper. A roller coaster is treated with here as the concrete example of a moving body. The equations of motion of a roller coaster in which a trajectory and a vehicle are coupled are derived by using the differential-algebraic equation (DAE). The dynamic behavior of a roller coaster which moves forward due to the gravity acceleration neglecting the running resistance has been reported in our former papers. In this paper, we take the effect of an air resistance and a rolling resistance into consideration. The influences of these resistances on the required time from the starting point to the arriving one and the vibration response of a vehicle are investigated. Moreover, it is shown that the numerical solutions have a better coincidence with the experimental results which have been obtained by measuring an actual roller coaster.
Motion of a Tethered System Under Attitude Control With Large Deformation, Rotation and Translation
Authors: Takehara Shoichiro , Terumichi Yoshiaki , Nohmi Masahiro , Sogabe Kiyoshi
Published: June 2008

In this paper, we discuss about the motion of a system consisting of a very flexible body and rigid bodies at its end under attitude control to the end body. A tethered subsatellite in space is known as an example of this system. We consider two mathematical models for flexible body. First, the flexible body motion in a plane is described by using Finite Element Method formulation. Second, the flexible body in planer motion is described by using Absolute Nodal Coordinate formulation. In this method, it is easy to describe the motion of the flexible body with large deformation, rotation and translation displacement. We can consider interaction between the deflection of the flexible body and the motion of the rigid bodies in these methods. Furthermore we attempt to control the attitude of the end body using a reaction wheel. The flexible body motion is influenced on the motion of the rigid bodies under attitude control of end body. The control technique consists of an attitude control by the reaction wheel and a control by the reaction wheel with the joint torque control to cancel accumulation of angular momentum. First, eigenvalue analysis is carried out where control gain changes. Second, the motion under controlled system is discussed under free vibration. We compared these results. Furthermore we treat large deformation problem. The end of flexible body moves horizontally. As a result, we confirm the interaction between flexible body and rigid body under the attitude control.
Stability and Dynamic Analysis of the SET (Short Electrodynamic Tether)
Authors: Valverde J. , Escalona J. L. , Domi´nguez J. , Freire E.
Published: June 2008

Space-tethers are very slender and flexible structures that are deployed in space. In recent times space-tethers have been the object of numerous studies in the field of astronautics. One of such structures is the SET (Short Electrodynamic Tether). The distinguishing characteristic of the SET is that it orbits with the axis of smallest moment of inertia normal to the orbit plane. The SET is in continuous rotation around this same axis, which allows it to maintain the aforementioned operating position. In most other cases, space-tethers orbit within the orbit plane. The SET is not perfectly straight after deployment. This fact could make the rotation unstable from the structural point of view, as predicted by the linear study of unbalanced rotors (supercritical velocities). However, if non-linear terms in the elastic and internal damping forces are considered in the model (hysteresis causes instability) the resulting motion of the structure could remain bounded. This assertion was shown in a previous study by the authors, through dynamic simulations of the system. In order to confirm these results, the present paper studies the stability of the SET’s solutions. A modified Jeffcott model will be the object of this study. The paper will end with a comparison of the results obtained with those rendered by previous works.
Rosenbrock-Nystrom Integrator for SSODE of Mechanical Systems
Authors: Sandu Adrian , Negrut Dan , Sandu Corina , Haug Edward J. , Potra Florian A.
Published: June 2008

When performing dynamic analysis of a constrained mechanical system, a set of index 3 Differential-Algebraic Equations (DAE) describes the time evolution of the system. The paper presents a state-space based method for the numerical solution of the resulting DAE. A subset of so called independent generalized coordinates, equal in number to the number of degrees of freedom of the mechanical system, is used to express the time evolution of the mechanical system. The second order statespace ordinary differential equations (SSODE) that describe the time variation of independent coordinates are numerically integrated using a Rosenbrock type formula. For stiff mechanical systems, the proposed algorithm is shown to significantly reduce simulation times when compared to state of the art existent algorithms. The better efficiency is due to the use of an L-stable integrator and a rigorous and general approach to providing analytical derivatives required by it.
Tonal Tuning of a Variable Inertia Vibration Absorber: A Feasibility Study
Authors: Fallahi Behrooz , Megahed Said , Seif Mohammed
Published: June 2008

The primary goal of this study is to investigate the dynamics of a new class of adaptive Tuned Vibration Absorber (TVA): A variable effective inertia absorber. In particular, the accuracy of linearization of the dynamic equations, the effect of the moving mass on the dynamics of the absorber, and steady state vibration of the primary system are investigated. It is shown that the linearized model is accurate. Two simulations using the nonlinear model are reported. These simulations show effectiveness of the absorber on reducing the displacement and acceleration of the primary system. In a third simulation, the block is moved from a detuned position to a tuned position and nonlinear differential equation of the motion is solved. The results show a significant decrease of the vibration of the primary system.
A Shape Description Model by Using Sensor Data From Touch
Authors: Chiroiu Venturia , Munteanu Ligia , Nicolescu Cornel Mihai
Published: June 2008

In this paper we consider the problem of recognizing the shape of a 3D object using tactile sensing by a dexterous robot hand. Our approach uses multiple fingers to slide along the surface of the object. From the sensing contact points we extracts a number of 3D points belonging to the surface of the object. The unknown surface Γ of the object is determined by using an “n-ellipsoid” model (Bonnet [1]). The set of parameters that define the surface Γ is determined such that the n-ellipsoid best fits the set of data points.
An Efficient Method for Contact/Impact Problems in Multibody Systems: Tree Topologies
Authors: Anderson Kurt S. , Sadowski Michael J. A.
Published: June 2008

This paper presents an algorithm for the efficient numerical analysis and simulation of contact/impact problems in tree topology multi-rigid-body dynamic systems. The algorithm can accommodate the jumps in structure which occur in the equations of motion of general multi-rigid-body tree systems due to a contact/impact event between bodies, or due to the locking of joints. The presented method uses a generalized momentum balance approach to determine the velocity jumps which take place across impacts in such multibody dynamic systems, and where necessary explicitly determines impact impulsive loads (both working and non-working). The presented method does not suffer from the performance (speed) penalty encountered by most other momentum balance methods given its O(n) overall cost, and exact direct embedded consideration of the all constraints. Due to these characteristics, the presented algorithm offers superior computing performance relative to other methods in situations involving both large n and potentially many unilateral constraints.
Dynamic Modeling and Simulation of Satellite Tethered Systems
Authors: Mankala Kalyan K. , Agrawal Sunil K.
Published: June 2008

The objective of this paper is to study the dynamic simulation of a tether as it is deployed or retrieved by a winch on a satellite orbiting around earth. In an effort to understand the problem incrementally, the following three models were developed: (a) Model 1: A tether with constant length moves on earth in the plane of constant gravity; (b) Model 2: A tether is deployed from a drum on earth in the plane of constant gravity, i.e., length of the cable changes during deployment; (c) Model 3: A tether is deployed from a drum on an orbiting satellite. These models have been chosen to bring different aspects as well as levels of difficulty in the analysis. For example, in Model 1, the length of cable is fixed and the gravity direction is constant during motion. The equations of motion for this model are derived using Newton’s laws and Hamilton’s principle to show the equivalence of the two methods. In Model 2, free length of the cable changes during deployment. The changing length of the cable introduces coupled nonlinearities into the motion. Model 3 includes the orbital effect on the motion of deployed cable. Each of these three dynamic models characterized by partial differential equations are first converted to a finite number of ordinary differential equations using Ritz’s procedure and are then numerically integrated using Matlab ODE solvers.