bluuebunny/crossref_metadata_2025 huggingface dataset:
A Decoupled and Prioritized Stochastic Dynamic Programming Approach for Automated Transport of Multiple Particles Using Optical Tweezers
Authors: Banerjee Ashis Gopal , Losert Wolfgang , Gupta Satyandra K.
Published: July 2010

Automated transport of multiple particles using optical tweezers requires the use of motion planning to move them simultaneously while avoiding collisions amongst themselves and with randomly moving obstacles. This paper develops a decoupled and prioritized stochastic dynamic programming based motion planning framework by sequentially applying a partially observable Markov decision process algorithm on every particle that needs to be transported. An iterative version of a maximum bipartite graph matching algorithm is used to assign given goal locations to such particles. The algorithm for individual particle transport is validated using silica beads in a holographic tweezer set-up. Once the individual plans are computed, a three-step method consisting of clustering, classification, and branch and bound optimization is employed to determine the final collision-free paths. Simulation results in the form of sample trajectories and performance characterization plots are presented to illustrate the usefulness of the developed approach.
Hybrid and Adaptive Metamodel Based Global Optimization
Authors: Gu J. , Li G. Y. , Dong Z.
Published: July 2010

Metamodeling techniques are increasingly used in solving computation intensive design optimization problems today. In this work, the issue of automatic identification of appropriate metamodeling techniques in global optimization is addressed. A generic, new hybrid metamodel based global optimization method, particularly suitable for design problems involving computation intensive, black-box analyses and simulations, is introduced. The method employs three representative metamodels concurrently in the search process and selects sample data points adaptively according to the values calculated using the three metamodels to improve the accuracy of modeling. The global optimum is identified when the metamodels become reasonably accurate. The new method is tested using various benchmark global optimization problems and applied to a real industrial design optimization problem involving vehicle crash simulation, to demonstrate the superior performance of the new algorithm over existing search methods. Present limitations of the proposed method are also discussed.
On the Perfect Gravity-Balance of a Spatial N-DOF Manipulator Based on the Localized Pseudo-Base
Authors: Lin Po-Yang , Shieh Win-Bin , Chen Dar-Zen
Published: July 2010

This paper offers an exact solution for the perfect gravity-balance of a class of spatial manipulators with no translational joints. The methodology used is based on the concept of conservation of the gravitational and elastic potential energy of the system. The overall gravitational potential energy of a serial-connected, n-link manipulator is identified to be contributed by n subsystems, where each subsystem is kinematically equivalent to one of the primary links of the manipulator, and possesses the accumulated mass of its post-connected links with a fixed mass center located on the subsystem. The gravitational potential energy of such a subsystem can be fully balanced by the elastic potential energy of the spring fitted between the link and its adjacent pseudo-base. Since the rotation axis of the pseudo-base is required to be in the direction of gravity, n serial-connected RSSR modules are constituted along the primary chain of the manipulator to provide a pseudo-base for each of the primary links. With one linear, zero-free-length spring fitted between each of the primary links of the manipulator and its associated pseudo-base, a static equilibrium of the considered mechanism in any configuration can be reached. A numerical example of the model of a six-DOF industrial robot has demonstrated the success of the proposed methodology.
A Method to Generate and Evaluate a Creative Design Idea by Focusing on Associative Process
Authors: Yamamoto Eiko , Mukai Futoshi , Yusof Nor Fasiha Mohd , Taura Toshiharu , Nagai Yukari
Published: July 2010

In order to support creative design, we propose an approach composed of two methods for generating creative design ideas. The first method involves generating a candidate for a highly creative design idea by focusing on the notion of “polysemy.” The second involves evaluating the generated candidate by using a virtual network. In this study, we focus on concept generation, specifically, the process of synthesizing two concepts. Furthermore, we use design idea features for representations of the design idea. We attempt to create a set of design idea features that allows the realization of highly creative ideas. For verifying the validity of the first method, we confirmed that the estimated scores of originality of all the generated candidates extrapolated the score of the base design idea.
A Design Exploration Method for Adaptive Design Systems
Authors: Wang Chenjie , Krishnamurthy Vivek , Klein Benjamin , Choi Seung-Kyum , Allen Janet K. , Mistree Farrokh
Published: July 2010

In this paper, we introduce a design exploration method for adaptive design systems (DEM-ADS), which is proposed to manage the uncertainty in the system design process. The proposed method includes the local regression model and an inverse design procedure derived from the existing Inductive Design Exploration Method (IDEM). To demonstrate the proposed method, the design of a photonic crystal coupler and waveguide containing two subsystem analyses is presented. The result indicates that the proposed method effectively attains solutions that are robust to uncertainty in the system more efficiently than IDEM.
Three Dimensional Virtual Modeling and Analysis Methods of Embedded Drivetrains
Authors: Mulski Steven , Mauer Lutz
Published: July 2010

Drivetrains are a major source of vibration, noise and system failures. Accordingly, a significant amount of time and effort is being invested developing simulation methods in order to better understand and avoid potentially damaging vibrations, even before prototypes are created for testing. The first step in simulating any drivetrain is creating suitable virtual models to investigate particular phenomena. Too much model detail leads to long computation times and difficulties in interpreting results, while too little may fail to include desired effects. Because the various levels of detail available in multi-body simulation (MBS) are practically limitless, a significant amount of attention must be given in order to choose the appropriate modeling elements. In the simplest form an entire drivetrain can be modeled as several rigid masses connected with torsional springs, which is justifiable for fundamental concept analyses. For other analyses, full three dimensional modeling with complex components may be necessary. Higher frequency analyses may even necessitate the inclusion of material bending for achieving accurate results. The various available elements for modeling specific components must be well understood in order that appropriate choices are made. Modeling requirements for the elements commonly used in the simulation of drivetrains will be discussed. For example: bearings, gearwheels, universal and constant velocity joints, frequency and amplitude dependent mounts, flexible components (e.g. shafts and gearbox housings), etc. Once virtual models are available, various analysis methods are applied in order to aid designers in identifying and quantifying potentially damaging vibrations. Again the application and limitation of these methods must be well understood in order to generate meaningful results. The following methods will be compared and discussed: resonance analysis, linear system analysis, run-up Fast Fourier Transformation analysis, order analysis, transfer path analysis and durability analysis. These drivetrain modeling techniques and analysis methods are not limited to any specific field of engineering, but can be applied to an extensive range of engineering disciplines. Analyses applied to virtual models out of the automotive and wind turbine sectors will be shown.
Engineering Soft Reliability in Product Realization
Authors: Koca Aylin , Brombacher Aarnout C. , Panchal Jitesh H. , Mistree Farrokh
Published: July 2010

Understanding customers-in-context for actual product realization processes (PRPs) has become a pressing need since a large and rapidly increasing share of complaints in the field cannot be attributed to violation of products’ technical specifications. While addressing this problem requires a multidisciplinary approach, more studies in the engineering design domain have of late been proposed on engineering contextual and emotional values in product design. However, it is not yet clear how these findings can be utilized within large-scale operational PRPs. Accordingly, in this paper, we propose an operational method empowering the stakeholders in collaborative PRPs with core decision templates, which provide (i) relevant information on customers-in-context, and (ii) corresponding guidelines to improve underlying processes. The content of these templates builds on the results of user feedback analysis with the subjective-feedback ontology from Soft Reliability, and their structure is based on the compromise Decision-Support Problem templates. Partial application of our method is demonstrated through two industrial cases. We envision that our method can help to evaluate and foresee the impact of new technology as it gets incorporated into the specific ecology of values and activities of its users.
Microstructure-Mediated Integration of Material and Product Design: Undersea Submersible
Authors: Sinha Ayan , Chakraborty Madhusudan , Ghosh Sudipto , Kumar C. S. , Panchal Jitesh H. , Allen Janet K. , McDowell David L. , Mistree Farrokh
Published: July 2010

In this paper, we introduce the construct of microstructure-mediated design of material and product. The microstructure of the material is controlled within feasible bounds to achieve the performance targets of the product. We illustrate the efficacy of this construct via the integrated robust design of a submersible and Al-based matrix composites. The integrated design is carried out using an Inductive Design Exploration Method (IDEM) that facilitates robust design in the presence of model structure uncertainty (MSU). Model structural uncertainty (MSU), originating from assumptions and idealizations in modeling processes, is a form of uncertainty that is often virtually impossible to quantify. In this paper, we demonstrate a method, the Inductive Design Exploration Method (IDEM), that facilitates robust design in the presence of model structural uncertainty. We achieve robustness by trading off the degree of system performance and the degree of reliability based on structural uncertainty associated with system models (i.e., models for performances and constraints). IDEM is demonstrated in the design of a shell of a robotic submersible. The material considered is in-situ Al metal matrix composites (MMCs) due to the advantages that the in-situ MMCs have over the conventional MMCs. This design task is a representative example of integrated materials and product design problems.
A Strategic Platform Design Method for Developing Customized Families of Services
Authors: Moon Seung Ki , Shu Jun , Simpson Timothy W. , Kumara Soundar R. T.
Published: July 2010

Products are often paired with additional services to satisfy customers’ needs, differentiate product offerings, and remain competitive in today’s market. This research is motivated by the need to provide guidelines and methods to support the design of such services, addressing the lack of knowledge on customized service design as well as methods for designing and evaluating services for mass customization. We extend concepts from module-based product family design to create a method for designing families of services. In particular, we introduce a strategic platform design method for developing customized families of services using game theory to model situations involving dynamic market environments. A module-based service model is proposed to facilitate customized service design and represent the relationships between functions and processes that constitute a service offering. A module selection problem for platform design is considered as a strategic module sharing problem under collaboration, and we use a coalitional game to model module sharing and decide which modules provide more benefit when in the platform based on marginal contribution of each module. To demonstrate implementation of the proposed method, we use a case study involving a family of banking services.
Analytical and Experimental Tooth Contact Pattern of Large-Sized Spiral Bevel Gears in Cyclo-Palloid System
Authors: Kawasaki Kazumasa , Tsuji Isamu
Published: July 2010

The demand of large-sized spiral bevel gears has increased in recent years and hereafter the demand may increase more and more. The large-sized spiral bevel gears with equi-depth teeth are usually manufactured based on Klingelnberg cyclo-palloid system. In this paper, the tooth contact pattern of large-sized spiral bevel gears in this system are investigated analytically and experimentally. First, the tooth contact pattern and transmission errors of such gears are analyzed. The analysis method is based on simultaneous generations of tooth surface and simulations of meshing and contact. Next, the large-sized spiral bevel gears are manufactured and the tooth contact pattern of these gears is investigated experimentally. Moreover, the real tooth surfaces are measured using a coordinate measuring machine and the tooth flank form errors are detected using the measured coordinates. It is possible to analyze the tooth contact patterns of the spiral bevel gears with consideration of the tooth flank form errors expressing the errors as polynomial equations. Finally, the influence of alignment errors due to assembly on the tooth contact pattern is also investigated analytically and experimentally. These analyzed results were compared with experimental ones. As a result, two results showed a good agreement.
Robust Variable Structure Control for Free-Floating Space Robot System With Dual-Arms in Joints Space
Authors: Tang Xiaoteng , Chen Li
Published: July 2010

In this paper, the kinematics and dynamics of free-floating space robot system with dual-arms are analyzed. It is shown that the dynamic equations of the system are nonlinearly according to inertial parameters. In order to overcome these problems, the system is modeled as under-actuated robot system, and the idea of augmentation approach is adopted. It is demonstrated that the dynamic equations of the system can be linearly depending on a group of inertial parameters. Based on this result, a robust variable structure control scheme for free-floating space robot system with dual-arms with uncertain inertial parameters to track the desired trajectories in joint space is proposed, and a planar space robot system with dual-arms is simulated to verify the proposed control scheme. The advantage of the control scheme proposed is that it requires neither measuring the position, velocity and acceleration of the floating base with respect to the orbit nor controlling the position and attitude angle of the floating base. In addition to this advantage, it is computationally simple, because of choosing the controller robust for the uncertain inertial parameters rather than explicitly estimating them online.
Approach to Evaluate and Implement Information Systems That Satisfy Your Goals
Authors: Hart Kathleen M. , Shooter Steven B. , Kim Charles
Published: July 2010

An information system that works in one application and environment may not work in another. Successful adoption of information systems requires that the organization evaluate candidates to ensure that they satisfy intended goals and consider the backgrounds and capabilities of the users. This paper describes an approach for evaluating and implementing information systems that satisfy technical requirements and organizational goals. Integral to this approach is the use of an assessment instrument consisting of objective-driven rubrics that are redundant to ensure consistency. This approach is applied in an NSF-supported CI-TEAM project to evaluate candidate systems to support an online cyber-collaboratory to enhance product dissection and reverse engineering activities in the classroom and to suggest improvements for the next generation system.
Reducing Product Energy Consumption With Leasing
Authors: Intlekofer Koji , Bras Bert , Ferguson Mark
Published: July 2010

Consumer demand and government regulation have led to increasing energy efficiency among consumer products to reduce environmental impacts. Continual improvement of the use-phase energy consumption results in points where it is environmentally beneficial for the product to be replaced with the newest model. Life cycle optimization is used to determine the product life spans that minimize energy consumption. Unfortunately, optimal life spans are found to be significantly shorter than current replacement periods and consumer behavior. This paper introduces the concept of using leasing as a tool for manufacturers to regulate product life spans as well as provide frequent maintenance and upgrades to improve product performance. Leasing offers flexibility that can be used to control product flow with varying replacement intervals necessary to make manufacturing optimal. Because ownership is maintained by manufacturers who are responsible for the product at its end-of-life, remanufacturing becomes an appealing alternative to landfilling, and offers additional energy savings by avoiding significant manufacturing processes. When remanufacturing is combined with optimal life cycles, significant long-term energy savings can be realized. In this paper we reveal some basic trends that could lead to a larger, more detailed study of product replacement and efficiency gains with respect to leasing. Refrigerators, dish washers, clothes washers, and vehicles are used as case studies.
Geometric and Kinematic Analysis of the Hoberman Switch-Pitch Ball and Its Variant
Authors: Wei Guowu , Ding Xilun , Dai Jian S.
Published: July 2010

This paper investigates geometry and kinematics of the Hoberman switch-pitch ball and its variant as an extended case of the ball. The paper starts from examining the geometry of the ball variant and its composition and decomposes it into loops each of which is an eight-bar radial linkage. Based on this, the paper investigates the geometry of the eight-bar radial linkage and the variant and subsequently extends the study to their kinematics. The Hoberman switch-pitch ball as a special case of the ball variant with bevel gears is investigated and a numerical example is employed to illustrate the kinematic characteristics of the eight-bar radial linkage and the Hoberman switch-pitch ball.
On the Mobility of Spatial Group 2 Mechanisms
Authors: Ting Kwun-Lon , Xue Changyu , Wang Jun , Currie Kenneth R.
Published: July 2010

Spatial linkages are classified into four groups according to the number of fundamental equations or virtual loops that govern linkage displacement. The number of virtual loops represents the complexity of a spatial linkage as that of planar or spherical multiloop linkages. The concept of generalized branch points offers the explanation of how branches are formed in spatial group 2 linkages. In this paper, the mobility analysis is carried out based on the similarity of the mobility features rather than the specific or individual linkage structure. A branch rectification scheme is presented and demonstrated with examples.
Comparative Analysis of Two Numerical Methods of Rollover Simulation of a Semitrailer for Hydrogen Transport
Authors: Valladares David , Castejo´n Luis , Carrera Marco , Miralbe´s Ramo´n , Malo´n Hugo , Marti´n Carlos
Published: July 2010

Nowadays, the use of the Finite Element Method [1] by means of simulation computer tools has made possible a substantial step forward in the field of calculation and optimization of vehicle structures. More specifically, these modern calculation tools are achieving great cost reductions corresponding to the experimental tests necessary to verify the appropriate performance of a vehicle in impact cases. On the other hand, great efforts will have to be done to develop correct numerical models for calculation. Once these numerical models have been validated with experimental tests, elimination of experimental costs compensates for these calculation efforts. A greater flexibility in decision making with respect to design and optimization alternatives will be achieved as well. The objective of this paper is to obtain an appropriate test simulation methodology for a specific vehicle and a specific impact case: There have been carried out the simulations of two different rollover test typologies in order to verify an adequate and safe behaviour of a semitrailer designed for hydrogen transport. After results of these two simulations are obtained, they will be compared in order to set which is the most restrictive and therefore the most appropriate. A lightened configuration has been also considered so as to carry out a sensibility analysis of material and thickness of some structural parts over numerical results in both test typologies in order to verify these simulations.
On the Branch Formation of Linkages
Authors: Ting Kwun-Lon , Xue Changyu , Wang Jun , Currie Kenneth R.
Published: July 2010

A spatial linkage with the displacement governed by two fundamental equations can be regarded as a virtual double loop system. The mobility of the linkage is affected by the mobility of each individual “loop” as well as the interaction between the loops. The current use of branch points for branch identification is limited to linkages with simple topology, such as Stephenson-type linkages, which are simplified versions of group 2 mechanisms. However, in a general spatial group 2 linkage, both the fundamental equations are equivalent to virtual five-bar loops. Branch points in Stephenson-type linkages should be generalized to explain and define the interaction between two virtual five-bar loops. The concept of generalized branch points offers the explanation of how branches are formed in spatial group 2 linkages. This paper presents the theoretical background for the mobility analysis of complex spatial linkages.
A Method for Developing Design for Environment Guidelines for Future Product Design
Authors: Telenko Cassandra , Seepersad Carolyn C. , Webber Michael E.
Published: July 2010

Design for environment principles and guidelines help designers create greener products during the early stages of design when life cycle analysis is not feasible. However, the available guidelines are not exhaustive and a general methodology for discovering guidelines has yet to be proposed. In this paper, a method for identifying green design guidelines is presented, which aims to fulfill the need for more comprehensive guidelines. The method combines typical aspects of product design, such as customer needs analysis, with reverse engineering and life cycle analysis. Although reverse engineering is commonly applied to studies of disassembly and recyclability, the methodology and case study herein show how reverse engineering can be applied to areas of product utilization and energy consumption in particular. A general description of the methodology helps readers apply it to their own studies, and a case study of electric kettles shows how each step of the method was applied to reveal four new design guidelines.
Academic Engineering Design Education in a Realistic Environment
Authors: Albers Albert , Sauter Christian , Maier Thomas , Geier Martin , Ottnad Jens
Published: July 2010

The objective of academic education for mechanical design engineers is to convey qualifications which are necessary for product development in an industrial environment. The goal of the work described here is to improve engineering design education and to provide a more active learning experience. Design students should be familiarized with modern methods and technologies which they will most likely encounter during their future career. Design cannot be taught sufficiently in lectures alone [1, 2] and requirements on graduates in product development are continuously increasing. Not only professional skills but also social skills as well as proficiency with new technologies and methodologies become increasingly important [3]. For meeting these requirements the Karlsruhe Education Model for Product Development (KaLeP) [4] was developed at the Institute of Product Development (IPEK) at the University of Karlsruhe in Germany. In this contribution we present KaLeP, the role of modern design tools like CAD/PDM and wikis in education, the course projects for Machine Design and Integrated Product Development including training concept as well as the technical and organizational environment in which these courses take place.
Design Considerations for a Discrete Angular Joint for Use in Digital Robot Systems
Authors: Kean Michael , Cipra Raymond J.
Published: July 2010

The goal of this work is to investigate the design of a joint suitable for use in a digital robot. Digital robotics, for the purposes of this paper, refers to robots with discrete joint output positions and binary input. For each proposed design, the input is a linear position, and the output is an angular position. Utilizing the kinematics of each design, the mechanical advantage is generated and corresponding design charts are generated for both a two and three position slotted slider as well as a rotating angular slotted block driven by either a rack and gear or a modified Geneva drive.
Analysis of Elliptical Rolling Contact Joints in Compression
Authors: Montierth Jacob R. , Todd Robert H. , Howell Larry L.
Published: July 2010

This paper presents elliptical rolling contact joints as an alternative to circular rolling contact and conventional revolute joints where high quality force transmission—low friction and backlash—with variable output are desired. Parameters specific to the joint and its position are defined in terms of relative link angles and elliptical surface geometry. These relationships allow elliptical rolling contact joints to be incorporated in vector loop summations used in kinematic analysis. Notably, elliptical rolling contact is developed as the more general case of which circular rolling contact is a subset. Elliptical rolling contact joints are shown to offer several benefits over circular rolling contact, including: reduced Hertz contact stresses, variable output velocity, maximum use of contact interface by distributing small rotations across surfaces of small curvature, reduced forces on constraining members, and no-slip pure rolling provided exclusively by connecting links (or flexures) without the need for gear teeth or friction.
Simultaneous Trajectory Tracking and Stiffness Control of Cable Actuated Parallel Manipulator
Authors: Yu Kun , Lee Leng-Feng , Krovi Venkat N.
Published: July 2010

Cable-actuated parallel manipulators combine benefits of large workspaces, significant payload capacities and high stiffness by virtue of the cable actuation. However, redundant/surplus cables are required to overcome the unidirectional nature of forces exertable by cables. This leads to actuation redundancy which needs to be resolved in order to realize some of the benefits. We study the implication of using actuation redundancy to tailor the workspace (task space) stiffness of the cable robot system. Suitable trajectory tracking control schemes are developed that additionally achieve secondary goal of active stiffness control to improve disturbance rejection, under positive control input constraint We demonstrate the performance of these control schemes using a point-mass cable robot system modeled within a virtual prototyping (VP) implementation framework.
Numerical Experiments in Using Voronoi Cell Finite Elements for Topology Optimization
Authors: Gibert James M. , Fadel Georges M.
Published: July 2010

This paper provides two separate methodologies for implementing the Voronoi Cell Finite Element Method (VCFEM) in topological optimization. Both exploit two characteristics of VCFEM. The first approach utilizes the property that a hole or inclusion can be placed in the element: the design variables for the topology optimization are sizes of the hole. In the second approach, we note that VCFEM may mesh the design domain as n sided polygons. We restrict our attention to hexagonal meshes of the domain while applying Solid Isotropic Material Penalization (SIMP) material model. Researchers have shown that hexagonal meshes are not subject to the checker boarding problem commonly associated with standard linear quad and triangle elements. We present several examples to illustrate the efficacy of the methods in compliance minimization as well as discuss the advantages and disadvantages of each method.
The Study of the Interaction of Humans With Wheelchairs to Improve the Design
Authors: Gooch Shayne , Hollingsworth Laura , Medland Tony
Published: July 2010

In order to evaluate a wheelchair design it is necessary to look at the capabilities of the user and the chair’s intended purpose. Whilst some chairs are only required to provide infrequent mobility indoors, others need to enable the user to travel great distances out doors over rough terrain. In this respect the chair should be considered in the same manner as any other ‘inclusive’ product (or be useable by all). There is a need to better understand the capabilities of different users and how this affects their ability to use a wheelchair for the express purpose required. A detailed experimental investigation was carried out into the wheelchair propulsion characteristics of people with paraplegia and tetraplegia. In this investigation, subjects’ posture, applied forces, and their strategies in applying forces to the wheel rims were studied. Three distinct postures and corresponding techniques were observed and subsequently modelled in a constraint-modelling environment. Here rules were developed that allowed these differing postures to be applied to a manikin representation and their effect upon the wheelchair mobility evaluated. From this study the needs for these classes of individuals were identified in order to allow the wheelchairs to be evaluated. Where conflicts existed between the chair and the user, different modifications in both chair and posture were proposed and assessed. Where no simple modifications exist such a study can provide the basis for a more radical and improved design.
Methodology for Selection, Sequencing, and Deployment of Activities in a Capstone Design Course Using the TIDEE Web-Based Assessment System
Authors: McCormack Jay , Beyerlein Steve , Feldon David F. , Davis Denny , Davis Howard , Wemlinger Zachary , Gerlick Robert , Howe Susannah
Published: July 2010

Assessment of design process, design products, team process, and professional practice are natural fits in an engineering capstone design course. In order for instructors and students to fully experience the value of capstone course assessment activities, the activities must not only be carefully developed but must also be deployed in an appropriate manner. Course designers must choose an optimal set of assignments based on local needs, while balancing time intensive design project activities with professional growth experiences. Instructors must facilitate the complete cycle of usage of a single assignment in order to ensure that the value is understood before and after completion of the assessment. This paper introduces guidelines for achieving effectiveness in selecting, timing, and sequencing assessment activities, preparing for activity deployment, and implementing a facilitation plan. Additionally this paper reports on the feedback from students and faculty using the system that highlights the importance of naturalistically integrating assessment.
Singularity and Sub-Branch Identification of Two-DOF Seven-Bar Parallel Manipulators
Authors: Wang Jun , Ting Kwun-Lon , Xue Changyu , Currie Kenneth R.
Published: July 2010

Mobility analysis of multi-DOF multiloop planar linkages is much more complicated than the single-DOF planar linkages and has been little explored. This paper offers a unified method to treat the singularity (dead center position) and sub-branch identification of the planar two-DOF seven-bar linkages regardless of the choice of the inputs or fixed links. This method can be extended for the singularity analysis of other multi-DOF multiloop linkages. Based on the concept of joint rotation space and N-bar rotatability laws, this paper presents a general method for the sub-branch identification of the seven-bar linkages. It offers simple explanation and geometric insights for the formation of branch, singularity and sub-branch of the two-DOF seven-bar linkages. The presented algorithm for sub-branch identification is suitable for automated computer-aided mobility identification. Examples are employed to demonstrate the proposed method.
Design Optimization of a Special Class of Steel Structures via Genetic Algorithms and Stochastic Sampling
Authors: Hamza Karim , Nassef Ashraf O. , Shalaby Mohammed
Published: July 2010

This paper addresses the design optimization of a special class of steel structures, which is clear-span building built up via off-shelf standard steel-sections. The problem is of particular importance in small to medium span buildings due to an attractive opportunity for reduction of the manufacturing cost compared to trusses and custom-built beams. The problem is also difficult from an optimization perspective as it exhibits both continuous and discrete variables, as well as discontinuities and flat regions in the topology of the objective function. Genetic algorithms (GA) and a special stochastic sampling technique are considered for the problem, as well as a mixed GA and stochastic sampling approach. The stochastic sampling is guided via heuristic rules based on knowledge specific to the problem, and is thus perceived well suited to the optimization task. While all the tested algorithms produced satisfactory results, the mixed approach seemed to yield the most consistent performance.
Representing User Activity and Product Function for Universal Design
Authors: Kostovich Vincent , McAdams Daniel A. , Moon Seung Ki
Published: July 2010

This paper presents a product analysis framework to improve universal design research and practice. Seventeen percent of the US population has some form of a disability. Nevertheless, many companies are unfamiliar with approaches to achieving universal design. A key element of the framework is the combination of activity diagrams and functional models. The framework is applied in the analysis of 20 pairs of products that satisfy a common high level need but differ with one product intended for fully able users and the other intended for persons with some disability or reduced functioning. Discoveries based on the analysis include the observation that differences in typical and universal products can be categorized functionally, morphologically, or parametrically different than typical products. Additionally, simple products appear to be made more accessible through parametric changes whereas more complex products require functional additions and changes.
Are We There Yet? Investigating the Role of Design Process Architecture in Convergence Time
Authors: Devendorf Erich , Lewis Kemper
Published: July 2010

In distributed design individual designers have local control over design variables and seek to minimize their own individual objectives. The amount of time required to reach equilibrium solutions in decentralized design can vary based on the design process architecture chosen. There are two primary design process architectures, sequential and parallel, and a number of possible combinations of these architectures. In this paper a game theoretic approach is developed to determine the time required for a parallel and sequential architecture to converge to a solution for a two designer case. The equations derived solve for the time required to converge to a solution in closed form without any objective function evaluations. This result is validated by analyzing a distributed design case study. In this study the equations accurately predict the convergence time for a sequential and parallel architecture. A second validation is performed by analyzing a large number of randomly generated two designer systems. The approach in this case successfully predicts convergence within 3 iterations for nearly 98% of the systems analyzed. The remaining 2% highlight one of the approach’s weaknesses; it is susceptible to numerically ill conditioned problems. Understanding the rate at which distributed design problems converge is of key importance when determining design architectures. This work begins the investigation with a two designer case and lays the groundwork to expand to larger design systems with multiple design variables.
A Frequency Domain Finite Element Approach for Three-Dimensional Gear Dynamics
Authors: Cooley Christopher G. , Parker Robert G. , Vijayakar Sandeep M.
Published: July 2010

A finite element formulation for the dynamic response of gear pairs is proposed. Following an established approach in lumped parameter gear dynamic models, the static transmission error is used as the excitation in a frequency domain solution of the finite element vibration model. The nonlinear finite element/contact mechanics formulation provides superior calculation of static transmission error and average mesh stiffness that is used in the dynamic simulation. The frequency domain finite element calculation of dynamic response correlates to numerically integrated (time domain) finite element dynamic results and previously published experimental results. Simulation time with the proposed formulation is two orders of magnitude lower than numerically integrated dynamic results. This formulation admits system level dynamic gearbox response, which may include multiple gear meshes, flexible shafts, rolling element bearings, and housing structures.
Novel Two-Stage Electrical Energy Generators for Highly-Variable and Low-Speed Linear or Rotary Input Motions
Authors: Murray R. , Rastegar J.
Published: July 2010

A novel class of two-stage, vibration-based electrical energy generators is presented for linear or rotary input motions in applications which the input speed is relatively low and varies significantly over time such as wind mills, turbo-machinery used to harvest tidal flows, devices for harnessing coastal wave energy, and the like. Current technologies use magnet-and-coil based electrical generators in such machinery. However, to make the generation cycle efficient, gearing or other similar mechanisms must be used to increase the input speed. Variable speed-control mechanisms are also usually needed to achieve high energy conversion efficiency. Additionally, in many applications, such as those where energy is to be harvested from very low frequency oscillations of a platform such as a buoy or a ship, the use of speed increasing mechanisms such as gearing or the like is impractical. In this paper, a novel class of two-stage electrical energy generators that could operate with very low speed and highly variable input rotations and/or oscillations is described. The first stage consists of simple linkage mechanisms, which are used to excite vibratory elements. These two-stage generators are designed to convert low-speed and highly variable input rotations and oscillations to relatively high and constant frequency vibratory motions, which are then used to generate electrical energy using mechanical to electrical energy conversion devices such as piezoelectric elements. The design of a number of such two-stage generators together with a discussion of their potential applications is presented. Specifically, the computer simulated output of a small wave energy harvester design is presented.
Determining the Static Joint Torques of a Digital Human Model Considering Balance
Authors: Yang Jingzhou James , Xiang Yujiang , Kim Joo
Published: July 2010

This paper presents a methodology for determining the static joint torques of a digital human model considering balance for both standing and seating tasks. An alternative and efficient formulation of the Zero-Moment Point (ZMP) for static balance and the approximated (ground/seat) support reaction forces/moments are derived from the resultant reaction loads, which includes the gravity and externally applied loads. The proposed method can be used for both standing and seating tasks for assessing the stability/balance of the posture. The proposed formulation can be beneficial to physics-based simulation of humanoids and human models. Also, the calculated joint torques can be considered as an indicator to assess the risks of injuries when human models perform various tasks.
Upper-Extremity Prostheses: A Renewed Approach
Authors: Johnson Alwyn P. , Veatch Bradley
Published: July 2010

Upper-extremity (UE) prostheses are increasingly more functional and proportionately more costly, rendering them largely unattainable for impoverished amputees in the United States (US) and abroad. Recognizing the increasing need for appropriate devices, PhysioNetics, LLC is developing a heavy-duty, transradial body-powered (BP) UE prosthesis which can be prescribed with minimal instruction. The design of the key components, the split-hook terminal device [TD] and universal adjustable interface is presented in this paper. The TD is primarily fabricated from plastics to eliminate galvanic corrosion in saltwater environments, weighs 5.4 oz (153 g) and uses inexpensive rubber bands to generate pinch force. Unique gripping contours provide versatile grasp and replicate five (5) prehension patterns while six (6) discrete force settings provide 2 – 17 lbf (8.9 – 76 N) of pinch. Three (3) universal interface sizes (small, medium, and large) accommodate most amputees and comfortably support axial loads up to 40 lbf (178 N). Estimated manufacturing cost for a complete unit is less than US$250. Field testers report lower but comparable comfort to their individually custom-fabricated interfaces, and are highly satisfied with fit and function of the prosthesis overall. Ongoing development includes reduction of manufacturing costs, increasing interface comfort and implementing task-specific variant designs.
Characterization and Performance Optimization of 2D Lattice Materials With Hexagonal Bravais Lattice Symmetry
Authors: Elsayed Mostafa S. A. , Pasini Damiano
Published: July 2010

The current paper examines the static performance of 2D infinite lattice materials with hexagonal Bravais lattice symmetry. Two novel microscopic cell topologies are proposed. The first topology is a semi-regular lattice that has the modified Schafli symbol 34.6, which describes the type of regular polygons surrounding the joints of the lattice. Here, 34.6 indicates four (4) regular triangles (3) successively surrounding a node followed by a regular hexagon (6). The second topology is an irregular lattice that is referred here as Double Hexagonal Triangulation (DHT). The lattice material is considered as a pin-jointed micro-truss where determinacy analysis of the material micro structure is used to distinguish between bending dominated and stretching dominated behaviours. The finite structural performance of unit cells of the proposed topologies is assessed by the matrix methods of linear algebra. The Dummy Node Hypothesis is developed to generalize the analysis to tackle any lattice topology. Collapse mechanisms and states of self-stress are deduced from the four fundamental subspaces of the kinematic and the equilibrium matrices of the finite unit cell structures, respectively. The generated finite structural matrices are employed to analyze the infinite structural performance of the lattice using the Bloch’s theorem. To find macroscopic strain fields generated by periodic mechanisms, the Cauchy-Born hypothesis is adopted. An explicit expression of the microscopic cell element deformations in terms of the macroscopic strain field is generated which is employed to derive the strain energy density of the lattice material. Finally, the strain energy density is used to derive the material macroscopic stiffness properties. The results showed that the proposed lattice topologies can support all macroscopic strain fields. Their stiffness properties are compared with those of lattice materials with hexagonal Bravais symmetry available in literature. The comparison showed that the lattice material with 34.6 cell topology has superior isotropic stiffness properties. When compared with the Kagome’ lattice, the 34.6 lattice generates isotropic stiffness properties, with additional stiffness to mass ratio of 18.5% and 93.2% in the direct and the coupled direct stiffness, respectively. However, it generates reduced shear stiffness to mass ratio by 18.8%.
Inventing a New Method in Statics Through Knowledge in Kinematics
Authors: Shai Offer , Reich Yoram
Published: July 2010

Suppose we designed an innovative structure, such as a deployable tensegrity structure, and suppose that while doing so, we are faced with a problem for which no available method could solve. The problem is such that if left without solution could hamper the further development of this structure. Infused Design (ID) is a method for transferring knowledge including solutions and methods between diverse disciplines. If an appropriate method is missing from a particular discipline, ID could be used to invent a new method by transforming methods from other disciplines. This paper reports on inventing a new method that allows finding relations between forces in a tensegrity structure thus determining which element would be a strut and which a cable. The invention process is described in detail. As an approach that has proved useful in inventing several design methods, ID constitutes a fertile source for extending our engineering and scientific knowledge.
Measuring Inter-Particle Forces at an Interface With Optical Tweezers and a Long Working-Distance Objective Lens
Authors: McAdams Daniel R. , Cole Daniel G.
Published: July 2010

In this effort, an optical tweezers setup is used to measure the forces between polystyrene microspheres on the interface between mineral oil and water. Colloidal interaction between particles on an interface is more complicated than their interaction in bulk. Knowing the forces between colloidal particles on an oil-water interface is important in order to improve aggregation and emulsion models and understand many phenomena in fluid dynamics and rheology. A two beam trap is used to control the distance between two interfacial particles. A long working-distance objective allows for the interface to be significantly far from the coverslip and for an extremely sensitive force measurement. The forces were found to follow a combination of Coulomb’s law and dipole-dipole interaction, but for much less charge than is specified by the manufacturer to be on the surface of the microspheres. These measurements will aid in the creation of models that can predict interfacial colloid phenomena.
Interactive Functional Reparameterization of Geometric Models
Authors: Johnson David E. , Riesenfeld Richard , Cohen Elaine , Drake Sam
Published: July 2010

Engineering designs are often determined by functional considerations, yet modeled with purely geometric parameters. Because of this, a difficult part of a design engineer’s job is tracking how changes to the geometric model might alter the functional performance of the design. This paper proposes a design interface that uses temporary functional views of geometric models to augment design engineers, helping them explore design space while continuously apprising them of the implications that modifications have on a design. The basic approach of the proposed interface is to use fast, interactive analysis tools in combination with feedback mechanisms to create temporary, functional design handles on top of the underlying geometric parametric structure. This design exploration tool is implemented in a research CAD system and demonstrated on illustrative examples.