bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comprehensive Parametric Finite Element Study on the Development of Strain Concentration in Concrete Coated Offshore Pipelines
Authors: Nourpanah N. , Taheri F.
Published: October 2012

The strain concentration at the field joint (FJ) of the commonly used concrete coated offshore pipelines is considered and discussed in this paper. The details of a 3D finite element (FE) modeling framework, developed using the commercial software ABAQUS, are presented. The numerical results are verified against the experimental results available in the literature. The FE model considered in this study captures several nonlinear phenomena associated with the problem, including the plastic deformation of the steel and anticorrosion layer (ACL) material, the cracking and crushing of the concrete, and also the large deformation effects. The developed FE framework is subsequently used to perform a parametric study to assess the effect of each influencing parameter on the strain concentration factor (SCF) developed within the FJ region. The influence of the geometric features of the coated pipe and the relevant mechanical properties of the materials as well as various combined loading scenarios are investigated. Results indicate that pipeline diameter, thickness, and coating thickness affect the SCF more than the strength of either concrete coating or ACL. Also, the postyield properties of the steel, especially the strain hardening capacity, may significantly influence the SCF. The combination of the internal pressure loading (causing a biaxial stress state) or tensile loading with the primary bending load is found to also increase the SCF significantly after steel yielding is initiated. Moreover, these combined loading scenarios cause different and more severe plastic deformation patterns in the FJ.
Universal Weight Function Consistent Method to Fit Polynomial Stress Distribution for Calculation of Stress Intensity Factor
Authors: Scarth Douglas A. , Xu Steven X.
Published: October 2012

Procedures for the analytical evaluation of flaws in nuclear pressure boundary components are provided in Section XI of the ASME B&PV Code. The flaw evaluation procedure requires calculation of the stress intensity factor. Engineering procedures to calculate the stress intensity factor are typically based on a polynomial equation to represent the stress distribution through the wall thickness, where the polynomial equation is fitted using the least squares method to discrete data point of stress through the wall thickness. However, the resultant polynomial equation is not always an optimum fit to stress distributions with large gradients or discontinuities. Application of the weight function method enables a more accurate representation of the stress distribution for the calculation of the stress intensity factor. Since engineering procedures and engineering software for flaw evaluation are typically based on the polynomial equation to represent the stress distribution, it would be desirable to incorporate the advantages of the weight function method while still retaining the framework of the polynomial equation to represent the stress distribution when calculating the stress intensity factor. A method to calculate the stress intensity factor using a polynomial equation to represent the stress distribution through the wall thickness, but which provides the same value of the stress intensity factor as is obtained using the Universal Weight Function Method, is provided in this paper.
Effects of Torsion on Equivalent Bending Moment for Limit Load and EPFM Circumferential Pipe Flaw Evaluations
Authors: Hoang Phuong H. , Hasegawa Kunio , Bezensek Bostjan , Li Yinsheng
Published: October 2012

The circumferential flaw evaluation procedures in ASME Boiler and Pressure Vessel Code Section XI nonmandatory Appendix C are currently limited to straight pipes under pressure and bending loads without consideration of torsion loading. The Working Group on Pipe Flaw Evaluation of the ASME Boiler and Pressure Vessel Code is developing guidance for considering the effects of torsion by a mean of an equivalent bending moment, which is a square root of sum square combination of bending moment and torsion load with a weighted factor for torsion moment. A torsion weighted factor, Ce, is established in this paper using large strain finite element limit load analysis with elastic perfectly plastic materials. Planar flaws and nonplanar flaws in a 10.75 in. (273 mm) OD pipe are investigated. Additionally, a finite element J-integral calculation is performed for a planar through wall circumferential flaw with elastic plastic materials subjected to bending and torsion load combinations. The proposed Ce factor for planar flaws is intended for use with the ASME B&PV Code Section XI, Appendix C for limit load and Elastic Plastic Fracture Mechanics (EPFM) circumferential planar flaw evaluations.
Design Limits for Buckling in the Creep Range
Authors: Jawad Maan , Griffin Donald
Published: October 2012

A methodology is introduced for calculating the allowable buckling stress in equipment operating in the time-dependent (creep) range. Norton's equation coupled with various procedures such as the stationary stress method, classical creep buckling equations, and the isochronous stress–strain diagrams are utilized to obtain a practical design approach for equipment operating in the time-dependent range. Various components are investigated such as slender columns, cylindrical shells, spherical components, and conical transition sections.
Large Eddy Simulation for Local Entropy Generation Analysis of Turbulent Flows
Authors: Sheikhi M. R. H. , Safari Mehdi , Metghalchi Hameed
Published: October 2012

A new methodology is developed for local entropy generation analysis of turbulent flows using large eddy simulation (LES). The entropy transport equation is considered in LES and is solved along with continuity, momentum, and scalar transport equations. The filtered entropy equation includes several unclosed source terms that contribute to entropy generation. The closure is based on the filtered density function (FDF) methodology, extended to include the transport of entropy. An exact transport equation is derived for the FDF. The unclosed terms in this equation are modeled by considering a system of stochastic differential equations (SDEs). The methodology is employed for LES of a turbulent shear layer involving transport of passive chemical species, energy, and entropy. The local entropy generation effects are obtained from the FDF and are analyzed. It is shown that the dominant contribution to entropy generation in this flow is due to combined effects of energy transfer by heat and mass diffusion. The FDF results are assessed by comparing with those obtained by direct numerical simulation (DNS) of the same layer. The FDF predictions show favorable agreements with the DNS data.
Physicochemical Properties and Combustion Performance of Gas Oil–Fuel Additives
Authors: Pirouzfar V. , Zarringhalam Moghaddam A. , Mirza B.
Published: October 2012

The current paper reviews the effects of the oxygenated and nitrogenated additives to see the results of the physicochemical efficiency and performance through engine tests work by gas oil mixtures. The oxygenated compounds used in the formulations compose of 2-methoxy ethyl ether (MXEE), nitromethane, and nitroethane. The presence of ethanol and MXEE significantly alter the characteristics of flash point and distillation curve behaviors and marking up the cetane number, improving the fuel's performance in engine tests. The fuel formulations comprising 2–5% v/v additives, 5–10% v/v ethanol, and diesel 90–95% v/v were produced. The soot formation can be reduced by more than 50%, 30%, and 27% by application of the diesel formulations; E-NE5–10, E-NM5–10, and E-MX5–10, respectively.
Effects of Reactor Design on the Torrefaction of Biomass
Authors: Dhungana Alok , Basu Prabir , Dutta Animesh
Published: October 2012

Torrefied biomass is a green alternative to coal, and thus the interest in the torrefaction process is rising fast. Different manufacturers are offering different patented designs of torrefier with data on varying operating and process conditions each claiming their superiority over others. The choice of torrefaction technology has become exceptionally difficult because of a near absence of a comparative assessment of different types of reactors on a common base. This work attempts to fill this important knowledge gap in torrefaction technology by reviewing available types of reactors, and comparing their torrefaction performance common basis and examining the commercial implication of reactor choice. After reviewing available patent and technologies offered, torrefiers are classified broadly under two generic groups: indirectly heated and directly heated. Four generic types of reactors, convective heating, fluidized bed, rotating drum and microwave reactor were studied in this research. Convective and fluidized beds have direct heating, rotating reactors has indirect heating while microwave involves a volumetric heating (a subgroup of direct heating) mechanism. A standard sample of biomass (25 mm diameter × 64 mm long poplar wood) was torrefied in each of these types of reactors under identical conditions. The mass yield, energy density and energy yield of the wood after torrefaction were measured and compared. Rotating drum achieved lowest mass yield but highest energy density. The difference between two direct heating, convective heating and fluidized beds was small. Microwave provided only localized torrefaction in this series of tests. Indirectly heated reactors might be suitable for a plant near the biomass source while directly heated plant would give better value at the user end.
Fuel Use and CO2 Emissions Under Uncertainty From Light-Duty Vehicles in the U.S. to 2050
Authors: Bastani Parisa , Heywood John B. , Hope Chris
Published: October 2012

On-road transportation contributes 22% of the total CO2 emissions and more than 44% of oil consumption in the U.S. technological advancements and use of alternative fuels are often suggested as ways to reduce these emissions. However, many parameters and relationships that determine the future characteristics of the light-duty vehicle (LDV) fleet and how they change over time are inherently uncertain. Policy makers need to make decisions today given these uncertainties, to shape the future of light-duty vehicles. Decision makers thus need to know the impact of uncertainties on the outcome of their decisions and the associated risks. This paper explores a carefully constructed detailed pathway that results in a significant reduction in fuel use and greenhouse gases (GHG) emissions in 2050. Inputs are assigned realistic uncertainty bounds, and the impact of uncertainty on this pathway is analyzed. A novel probabilistic fleet model is used here to quantify the uncertainties within advanced vehicle technology development, and life-cycle emissions of alternative fuels and renewable sources. Based on the results from this study, the expected fuel use is about 500 and 350 × 109 l gasoline equivalent, with a standard deviation of about 40 and 80 × 109 l in years 2030 and 2050, respectively. The expected CO2 emissions are about 1360 and 840 Mt CO2 equivalent with a spread of about 130 and 260 Mt CO2 equivalent in 2030 and 2050, respectively. Major contributing factors in determining the future fuel consumption and emissions are also identified and include vehicle scrappage rate, annual growth of vehicle kilometres travelled in the near term, total vehicle sales, fuel consumption of naturally aspirated engines, and percentage of gasoline displaced by cellulosic ethanol. This type of analysis allows policy makers to better understand the impact of their decisions and proposed policies given the technological and market uncertainties that we face today.
Experimental Study of a Sand–Air Heat Exchanger for Use With a
High-Temperature Solar Gas Turbine System
Authors: Al-Ansary Hany , El-Leathy Abdelrahman , Al-Suhaibani Zeyad , Jeter Sheldon , Sadowski Dennis , Alrished Abdulaziz , Golob Matthew
Published: October 2012

An experimental study of the heat transfer characteristics of the bulk flow of sand in a sand–air heat exchanger is conducted. The study is conducted in the context of the development of a high-temperature solar gas turbine (HTSGT) system. This system is being developed by King Saud University and the Georgia Institute of Technology with the aim of demonstrating the feasibility of using sand as the heat transfer and energy storage medium in central receiver systems. Experiments are conducted on silica sand and olivine sand, both of which are attractive options due to their wide availability. The apparatus includes a tube bank consisting of eight electrically heated tubes arranged in three rows in a staggered formation. Heat transfer coefficient results are reported for bare and finned tubes for sand feed velocities of 1–3 mm/s. They were found in the range of 80–160 W/m2 K.
A Novel Compact Torsional Spring for Series Elastic Actuators for Assistive Wearable Robots
Authors: Carpino Giorgio , Accoto Dino , Sergi Fabrizio , Luigi Tagliamonte Nevio , Guglielmelli Eugenio
Published: October 2012

The introduction of intrinsic compliance in the actuation system of assistive robots improves safety and dynamical adaptability. Furthermore, in the case of wearable robots for gait assistance, the exploitation of conservative compliant elements as energy buffers can mimic the intrinsic dynamical properties of legs during locomotion. However, commercially available compliant components do not generally allow to meet the desired requirements in terms of admissible peak load, as typically required by gait assistance, while guaranteeing low stiffness and a compact and lightweight design. This paper presents a novel compact monolithic torsional spring to be used as the basic component of a modular compliant system for series elastic actuators. The spring, whose design was refined through an iterative FEA-based optimization process, has an external diameter of 85 mm, a thickness of 3 mm and a weight of 61.5 g. The spring, characterized using a custom dynamometric test bed, shows a linear torque versus angle characteristic. The compliant element has a stiffness of 98 N·m/rad and it is capable of withstanding a maximum torque of 7.68 N·m. A good agreement between simulated and experimental data were observed, with a maximum resultant error of 6%. By arranging a number of identical springs in series or in parallel, it is possible to render different torque versus angle characteristics, in order to match the specific applications requirements.
A Process Oriented Hybrid Resource Integration Framework for Product Variant Design
Authors: Li Yuliang , Zhao Wei , Hu Lichen
Published: October 2012

Design resources such as design tools, knowledge, and data play important roles in the product variant design. The requirements for these resources as well as the resource integration mechanisms are evolving along the life-cycle based product design process. It is expected by designers that not only right design resources but also appropriate integration methods can be found and applied timely to realize design variations efficiently and effectively. In this paper, a hybrid design resource integration framework is proposed based on the design process and resource modeling in order to satisfy the evolutionary requirements for design resources in the process. The integration framework is divided into two levels, namely the abstract integration of virtual resource classes into task templates in the design process modeling and the concrete integration of resource instances into design activities in the design project runs. Based on the two-level integration framework, a hybrid integration mechanism including flexible and stiff integration models and three integration transition methods is proposed to adapt to the from-abstract-to-concrete design evolution process. The system structure and behavior models are given, according to the analysis of integration framework. A hypo-pneumatic spring design case is used to demonstrate the utility of the hybrid integration system. Design results obtained based on the resource integration tool and the traditional manual design approach are compared to assess the tool performance, which shows substantive improvements of design efficiency and efficacy.
A Three Degree of Freedom Pseudo-Rigid-Body Model for the Design of a Fully Compliant Bistable Micromechanism
Authors: Masters Nathan D. , Howell Larry L.
Published: October 2012

A three degree-of-freedom (3DOF) Pseudo-Rigid-Body Model (PRBM) has been developed and used in the design of a new class of Self-Retracting Fully compliant Bistable Micromechanism, or SRFBM. The SRFBM provides small-displacement linear travel bistability and is suitable for low-power microswitching applications. The design process involved a combination of single and multiple degree-of-freedom PRBM and finite element models to quickly proceed from a rigid-body concept to fully compliant fabrication-ready geometry. The 3DOF model presented here was developed to more accurately model the behavior of the tensural pivots—a new class of compliant segment used to avoid combined compressive loading of flexible segments. Four SRFBM designs were fabricated and tested for bistability, on-chip actuation, critical force, and fatigue tests. These tests validate the models used in the design process and demonstrate the functionality and reliability of the SRFBM.
Dynamic Modeling of Multiple Robot Arms With Joint and Link Flexibility
Authors: Zhang Cheng-Xin , Yu Yue-Qing
Published: October 2012

The dynamic models of the cooperation of multiple robot arms with both joint and link flexibility are developed in absolute coordinates. Based on the dynamic model, the forward dynamic models have been developed according to the constraints among the cooperating manipulators. Assuming the actual mass center of the cooperated object, instead of the nominal rigid position determined by the kinematics of the rigid link counterpart, to be the boundary constraint and to satisfy the anticipated trajectory, the inverse dynamic equations are obtained. The perfect input for the specified task can be calculated from the proposed inverse dynamic model, while the proposed forward dynamic model can be used for numerical simulation. The proposed dynamic models lay the foundation for the design and control of this kind of system. The effectiveness of the method is demonstrated through simulation of two flexible-link and flexible-joint 3R robot arms cooperating a rigid object.
Dynamic Simulation and Optimization of Underactuated Robotic Fingers
Authors: Sie Laura M. , Gosselin Cle´ment M.
Published: October 2012

This paper describes the dynamic simulation and optimization of underactuated robotic fingers. Previous studies conducted on this subject have neglected inertial and frictional effects, resulting in less realistic simulation results. In this paper, the application of ADAMS, a mechanical system simulation software, in modeling the dynamic behaviour of underactuated mechanical fingers is described. The study also demonstrates that ADAMS can be used to optimize the design of a given gripper finger by varying a single design parameter.
The Kinematics of a Class of 3-DOF 4-Legged Parallel Manipulators
Authors: Joshi Sammer A. , Tasi Lung-Wen
Published: October 2012

In this paper, a class of 3-DOF, 4-legged parallel manipulators are enumerated. The general architecture of such manipulators consists of a moving platform, a fixed base, and four supporting legs that meet the fixed base at four distinct points and the moving platform at four distinct points. One of the four legs is passive whereas each of the remaining three legs is driven by a linear actuator. To gain a better understanding of the mechanisms, a methodology for analyzing the kinematics of such manipulators is presented. The Tricept manipulator is used as an example to illustrate the methodology.
Real-Time Inverse Kinematics for Humans
Authors: Mi Zan , Yang Jingzhou , Abdel-Malek Karim , Mun Joung H. , Nebel Kyle
Published: October 2012

A general methodology and associated computational algorithm for predicting realistic postures of digital humans (mannequins) is presented. The basic plot for this effort is a task-based approach, where we believe that humans assume different postures for different tasks. The underlying problem is characterized by the calculation (or prediction) of the joint displacements of the human body in such a way to accomplish a specified task. In this work, we have not limited the number of degrees of freedom associated with the model. Each task has been defined by a number of human performance measures that are mathematically represented by cost functions that evaluate to a real number. Cost functions are then optimized, i.e., minimized or maximized subject to a number of constraints. The problem is formulated as a multi-objective optimization algorithm where one or more cost functions are considered as objective functions that drive the model to a solution. The formulation is then validated against existing posture prediction algorithms and confirmed with human experimental data.
The Design of Stacked Linkages for Motion Generation
Authors: Mirth John A.
Published: October 2012

This paper introduces the concept of “stacked linkages” and develops an algorithm for the design of such linkages. A stacked linkage is defined as a linkage whose geometry is repeatedly stacked upon itself to produce a multiloop linkage where each loop in the linkage has a motion that is identical to every other loop within the linkage. The special geometry required by a stacked linkage produces a relatively simple design algorithm that can be applied to synthesize linkages of varying complexity. The synthesis process is based upon the ability to reduce the motion of a complex linkage to an equivalent motion for a four-bar linkage. The four-bar linkage can then be synthesized and stacked upon itself to give a complex linkage with the desired total motion. This method allows the designer to do a preliminary analysis of the linkage motion characteristics (such as transmission angles, circuits, and branching) by examining the motion characteristics of a simple four-bar chain. The algorithm presented in this paper is limited to the case of rigid body guidance for two design positions. Other cases may be possible with further development.
A Graphical Method to Find the Secondary Instantaneous Centers of Zero Velocity for the Double Butterfly Linkage
Authors: Foster David E. , Pennock Gordon R.
Published: October 2012

This paper presents a graphical technique to locate the secondary instantaneous centers of zero velocity for a well-known indeterminate linkage; namely, the double butterfly linkage. Only one of the secondary instant centers needs to be located with the proposed technique; the remaining instant centers can be located from the Aronhold-Kennedy theorem. An important step in the graphical method is to regard the double butterfly linkage as two six-bar linkages. This is accomplished by replacing the ternary link connected to ground by two binary links, removing the pin which connects the two coupler links, and attaching a slider to each coupler link at the coupler pin. A key concept is to instantaneously freeze the aforementioned binary links and regard each six-bar linkage as a four-bar linkage. The paper shows how these ideas can be related to locate the absolute instant centers for the two coupler links of this eight-bar linkage.
On Mobillity Analysis of Linkages Using Group Theory
Authors: Rico Jose´ Mari´a , Ravani Bahram
Published: October 2012

This paper presents a generalization of Kutzbach-Gru¨bler criterion for mobility analysis of kinematic chains based on group theory. This new mobility criterion applies to exceptional linkages and reduces to a group theoretic representation of Kutzbach-Gru¨bler criterion for trivial linkages. Furthermore, it is shown that using sets and groups of Euclidean displacements, one can distinguish between trivial, exceptional, and paradoxical linkages. Using these concepts, formal definitions of trivial, exceptional, and paradoxical linkages are presented and it is shown that there are two classes of paradoxical linkages. In addition, a new class of linkages is identified that have partitioned mobility. This work builds upon and extends the work of Herve´ and Fanghella and Galletti in application of group theory to analysis of kinematic chains.
Kinematics of a Spatial Three Degree-of-Freedom Robot With Rolling Contact Joints
Authors: Collins Curtis L.
Published: October 2012

A rolling contact joint is formed when two adjacent links roll without slipover each other. When the rolling profiles are circular, the joint can be physically realized by a pair of revolute joints coupled by gears or cables. In this paper, we investigate the forward, inverse, and rate kinematics of a spatial three degree-of-freedom serial chain with rolling contact joints that have equal circular profiles. We show analytically and geometrically that there are 32 inverse kinematic solutions. Singularities occur whenever the point of interest on the end effector lies on either of two planes defined by the lines of contact between the joints.
Multiloop Kinematotropic Mechanisms
Authors: Galletti Carlo , Giannotti Elena
Published: October 2012

Starting from single-loop kinematic chains whose pairs present different connectivities when the chains are displaced in different positions, the paper shows how to assemble multiloop chains with numbers of degrees of freedom that change due to continuous variations in the position variables of the chains. This special mobility property is called kinematotropy. The paper provides a method (based on the displacement group theory) to form chains that allow any desired change in the number of degrees of freedom, with a sudden or gradual increment of this number. Several examples are presented and applications are discussed.
Enumeration and Classification of 12-Bar Planar Simple-Jointed Kinematic Chains Using a Hierarchical Approach
Authors: Butcher Eric A. , Hartman Chris
Published: October 2012

The complete set of 12-bar planar simple-jointed kinematic chains is enumerated using the stratified or hierarchical representation, of Fang and Freudenstien (1990) in which post-priori isomorphism testing is not needed. This is achieved by directly enumerating the simplified and contracted graphs from which the kinematic chains are built up. The number obtained is compared with those from previous studies, and the list is catagorized by the link sets and by the numbers of major vertices and edges in the simplified graphs. A major feature of the technique is the use of an efficient rote-based technique for eliminating degenerate chains.
Higher Order Local Analysis of Singularities in Parallel Mechanisms
Authors: Mu¨ller Andreas
Published: October 2012

A purely algebraic approach to higher order analysis of (singular) configurations of rigid mulitbody systems with kinematic loops (CMS) is presented. It takes advantage of the special structure of the matrix Lie algebra se(3). The generating algebra of the special Euclidean group SE(3). The CMS configuration space is considered as analytic variety V. In regular configurations V has manifold structure but this is lost in singular points. In such points the concept of a tangent vector space does not makes sense but the tangent space(a cone) to V can still be defined. It is shown that this tangent cone can be determind algebraically. Moreover the tangent space to the configuration space is a surface of maximum degree 4, a vector space for regular points. It is the structure of the tangent cone to V that gives the complete geometric picture of the configuration space around a (singular) point. The approach is valid for general multiloop CMS and examplified in detail on the four- and fife-bar mechanism. Results are also shown shown for a Hexapod strucure.
Type Synthesis of 3-DOF Spherical Parallel Manipulators Based on Screw Theory
Authors: Kong Xianwen , Gosselin Cle´ment M.
Published: October 2012

A spherical parallel manipulator (SPM) refers to a 3-DOF parallel manipulator in which the moving platform has only three pure rotational degrees of freedom of motion relative to the base. A method is proposed for the type synthesis of SPMs based on screw theory. The wrench systems of a spherical parallel kinematic chain (SPKC) and its legs are first analyzed. A general procedure is then proposed for the type synthesis of SPMs. The type synthesis of legs for SPKCs, the type synthesis of SPKCs, as well as the input validity check of SPMs are dealt with in sequence. SPKCs with and without inactive joints are synthesized. The number of over-constraints of each SPKC is also given. The phenomenon of dependent joint groups in a SPKC is revealed for the first time. The input validity check of SPMs is also simplified.
Face Gearing With a Conical Involute Pinion: Part 1 — The Conical Involute Gear: Definition, Geometry and Generation
Authors: Tan Jie
Published: October 2012

Generating action of a plane in general motion is studied. Involute helicoid is generated by a plane in linear motion on a rotating blank, with surface equations derived in terms of the orientation of the basic plane and the relative motion. The conical involute gear is defined with the basic rack geometry and installation. Conditions of gear integrity are obtained. Limits on gear tooth are determined with the transverse rack. Methods of kinemtic-geometrical nature, the concept of axes of meshing in particular, are applied in favor over pure analytical approaches to facilitate intuitive understanding of the processes.
Rotation Singularities in the DELTA-Like Manipulators
Authors: Di Gregorio Raffaele
Published: October 2012

The DELTA robot and the manipulators derived from the DELTA robot are a relevant class of translational manipulators. In this paper the mobility analysis of these parallel translational manipulators is developed in full. The manufacturing and mounting conditions that guarantee the pure translation of the platform are analytically derived. Moreover, it is presented the demonstration that these manipulators can assume singular configurations, named rotation singularities, in which they are not able to impose the platform translation any longer. Finally, the geometric and analytic conditions that make it possible to find all the singular configurations of these manipulators are provided.
Kinematic Analysis of Bevel Epicyclic Gear Trains Using Graph Notation
Authors: Nelson Carl A. , Cipra Raymond J.
Published: October 2012

A kinematic analysis technique is introduced to find the velocities of all links in bevel epicyclic gear trains. The method relies on previous work in graph theory. It improves on existing techniques used for analysis of planar geared mechanisms in its ability to accurately solve the kinematics of spatial geared mechanisms, particularly bevel gear trains. Computer software has been developed to demonstrate its usefulness. This discussion is limited to gear trains whose input and output axes are collinear, such as automotive automatic transmissions, although the methodology presented is readily extended to other cases besides the case of collinear input and output axes.
Singularity Analysis of Spatial Stewart-Gough Platforms With Planar Base and Platform
Authors: Pernkopf Friedrich , Husty Manfred L.
Published: October 2012

In the neighborhood of a singularity a parallel manipulator becomes uncontrollable due to actuator saturation. Therefore it is important to know where all singularities of such a manipulator are. This paper presents a new and geometric approach to compute the singularities of all spatial Stewart-Gough platform manipulators which have anchor points of base and platform in planes. It is shown that these manipulators have a geometrically exceptional home pose and it is described how singularity free regions can be found. The developed methods are used to evaluate the singularity free orientation capability of a manipulator along any prescribed trajectory.
Geometric Modelling of Elliptical Gears Generated by Shaper Cutters
Authors: Figliolini Giorgio , Angeles Jorge
Published: October 2012

The geometric modeling of elliptical gears is formulated using envelope theory, by means of a suitable shaper-cutter with involute tooth profile. A general algorithm producing the pitch curves of elliptical gears and their rack with any number of lobes is proposed. Evolutes of pitch curves can be also obtained in order to choose a suitable shaper-cutter, even for pitch curves with concave-convex profiles. The complete modeling of both meshing elliptical gears and their rack is reported, several graphical results being shown for design and analysis purposes. Computer animations are also supported.
Determining the Effective Spring Rate of Air Cylinders Used to Close Cam-Follower Joints
Authors: Norton R. L. , O’Brien C. , Duperry P. , Hall J. R.
Published: October 2012

Cam-follower systems in industrial machinery often use air cylinders to close the cam-follower joint. These cylinders provide a nonlinear spring characteristic to the system. This study experimentally determines the thermodynamic behavior of an air cylinder in this application and shows it to be an essentially isothermal device. Information is presented to allow the designer to properly size an air cylinder for a particular application considering valving, connections, and accumulator size.
Design and Tesing of a Halo Orthosis to Reduce Pin Loosening Using Constraint Analysis
Authors: Stamper Richard E. , Kuester W. Matthew , Meek Matthew P.
Published: October 2012

A halo orthosis is a medical device used for restricting motion of the skull and cervical spine during accident and surgery recovery situations where minimal movement of the skull and spine is required for proper healing. Pin loosening is one of the most common complications with a commonly cited incident rate of 36%. The root cause of the loosening is related to changes in the skull geometry at the pin site and the inability of current halo systems to adapt to those changes. We hypothesize that the inability of current halo systems to adapt to these small pin site geometry changes is driven by the over constrained nature of the skull relative to the halo ring when viewed as a mechanism in the context of the Grubler / Kutzbach criteria. Accordingly, an exactly constrained 3-pin halo ring design is proposed. A prototype of the exactly constrained halo ring that is instrumented to measure pin forces was fabricated along with a skull model that simulates radial recession of the bone at the pin sites. The testing suggests that the pin forces in the exactly constrained 3-pin halo are less sensitive to the radial recession of the pin sites than the current over constrained 4-pin halo configurations. The average pin force in the over constrained 4-pin design decreased by 63% after 0.52 mm of simulated radial recession at two of the pin sites. The average pin force in the exactly constrained 3-pin design decreased by 1% after 0.52 mm of simulated radial recession at two of the pin sites.
Design of Mechanisms for Storage, Folding, and Delivery of an Intra-Ocular Lens (IOL) During Cataract Surgery
Authors: Erdman Arthur G. , Loftness Paul E.
Published: October 2012

Surgical techniques for extraction of a cataract and implantation of a replacement intraocular lens (IOL) into the eye have improved dramatically in recent years. An important advance has been the development of foldable IOLs, which can be inserted into the eye through incisions approximately 50% smaller than those required for rigid IOLs. This paper reports on another evolutionary step in cataract surgery: the design of mechanisms for handling foldable IOLs during surgery. Mechanism designs are discussed for retrieving an IOL from its sterile storage container, folding the IOL in a desired configuration, and finally, placing the IOL accurately into a delivery tube.
Design Optimization of a Cartesian Parallel Manipulator
Authors: Kim Han Sung , Tsai Lung-Wen
Published: October 2012

This paper introduces a new 3-DOF translational parallel manipulator named the Cartesian Parallel Manipulator (CPM). The manipulator consists of a moving platform that is connected to a fixed base by three limbs. Each limb is made up of one prismatic and three revolute joints and all joint axes are parallel to one another. In this way, each limb provides two rotational constraints to the moving platform and the combined effects of the three limbs lead to an over-constrained mechanism with three translational degrees of freedom. The manipulator behaves like a conventional X-Y-Z Cartesian machine due to the orthogonal arrangement of the three limbs. Two actuation methods are analyzed. However, the rotary actuation method is discarded because of the existence of singularities within the workspace. For the linear actuation method, there exists a one-to-one correspondence between the input and output displacements of the manipulator. However, each limb structure is exposed to a relatively large moment about an axis perpendicular to the prismatic joint axis. In order to compensate for this shortcoming, a method to maximize the stiffness is suggested. Finally, a numerical example of the optimal design is presented.
Dynamic Analysis of a Feed Fine-Tuning Test Platform for the Large Radio Telescope
Authors: Wang Qi-Ming , Wang Jinsong , Zhang Hui
Published: October 2012

In this paper, a feed fine-tuning test platform (FFTTP), which consists of double Stewart-platform structures, is developed. The FFTTP is now used for the pre-research of the large radio telescope in China. It can measure the pose and trace the position of the end-effector, simultaneously. The device is introduced in detail firstly. And the forward dynamic problem of the FFTTP is discussed using Lagrange approach. Especially, the corresponding constraint equations are adopted to solve the motion-coupling problem between two mobile platforms. Finally, an example is given, and the simulating results indicate that this approach is effective to assure the stability of the end-effector. The results of the paper are the foundation to study the control precision of the FFTTP.
On the Development of Reactionless Spatial 3-DOF Parallel-Piped Mechanisms
Authors: Gosselin Cle´ment M. , Wu Yangnian
Published: October 2012

In this paper, the design and dynamic balancing of a novel 3-DOF parallel mechanism referred to as parallelepiped mechanism are addressed. Two types of actuation schemes of the mechanism are considered. The balancing equations are derived by imposing that the center of mass of the mechanism is fixed and that the total angular momentum is constant with respect to a fixed point. Optimization is performed to determine the counter-weights and counter-rotations based on the balancing conditions. The dynamic simulation software ADAMS is used to simulate the motion of the 3-DOF parallelepiped mechanisms and to verify that the mechanisms are reactionless at all times and for any trajectory. A numerical example of a reactionless 3-DOF parallelepiped mechanism is given. It is shown that 3-DOF parallelepiped mechanisms can be completely balanced and used to synthesize 6-DOF reactionless manipulators. Additionally, the inverse and direct kinematic problems of the 3-DOF parallelepiped mechanisms as well as simulation tools for demonstrating the characteristics of the mechanisms are also introduced in this paper.
Geometric Design of Spatial PRR Manipulators Using Polynomial Elimination Techniques
Authors: Lee Eric , Mavroidis Constantinos
Published: October 2012

This paper studies the geometric design of spatial open loop prismatic-revolute-revolute (PRR) robot manipulators. Four spatial positions and orientations are defined and the dimensions of the geometric parameters of the PRR manipulator are computed so that the manipulator will be able to place its end-effector at these four pre-specified locations. Denavit and Hartenberg parameters and 4×4 homogeneous matrices are used to formulate the design equations. Polynomial Elimination techniques are used to solve these equations and twelve geometrically different solutions are found.
A Finger Mechanism for Adaptive End Effectors
Authors: Dubey Venketesh N. , Crowder Richard M.
Published: October 2012

This paper presents design and analysis of a rigid link finger, which may be suitable for a number of adaptive end effectors. The design has evolved from an industrial need for a tele-operated system to be used in nuclear environments. The end effector is designed to assist repair work in nuclear reactors during retrieval operation, particularly for the purpose of grasping objects of various shape, size and mass. The work is based on the University of Southampton’s Whole Arm Manipulator, which has a special design consideration for safety and flexibility. The paper discusses kinematic issues associated with the finger design, and to the end of the paper specifies the limits of finger operating parameters for implementing control laws.
Enumeration of Contact Geometries for Kinematic Registration Using Tactile Sensing Fixtures
Authors: Nederbragt Walter W. , Ravani Bahram
Published: October 2012

This paper uses group theory for enumeration of contacts between geometric elements necessary for kinematic registration or part referencing in robotics. The results are applied to type synthesis of tactile sensing mechanical fixtures. Kinematic registration is an important step in robot calibration and in data driven automation. Although the scope of the paper is limited to geometric contacts involving points, lines, planar surfaces, cylindrical surfaces, and spherical surfaces, the techniques developed are general and can be applied to other geometric features and non tactile sensing elements used in robotic calibration and part referencing.
Workspace and Design Analysis of Cable-Suspended Planar Parallel Robots
Authors: Fattah Abbas , Agrawal Sunil K.
Published: October 2012

In this paper, we present a method to obtain the workspace of cable-suspended planar parallel robots. The significant difference between regular parallel robots and cable-suspended parallel robots is that the cables in cable-suspended robots can only carry tension forces. Hence, static equilibrium equations must be used to compute the forces in the cable robot. The workspace is characterized as the set of points where the reference point on the end-effector platform can reach with tensions in the cables. In this paper, we address this problem for robots with two, three, or more cables. Then, we study the question of design of the cable robot to determine the number of cables, location of the suspension points of the cables, and size of the moving platform to attain the largest workspace.
Leg Stiffness and Articulated Leg Design for Dynamic Locomotion
Authors: Schmiedeler James P. , Waldron Kenneth J.
Published: October 2012

A number of legged robots capable of dynamic running have been constructed, although, in most cases, very little explanation has been given for how the stiffness of the legs was selected. This paper proposes that a reasonable design value for a robot’s leg stiffness is the effective leg stiffness of an animal having the same mass. It further details a simple, kinetostatic analysis of articulated legs that can be used to determine the leg design geometry for a desired stiffness. The technique allows the designer to exploit the non-linearities in the leg mechanism to achieve an advantageous non-linear leg stiffness. An example of the method is given, and preliminary experimental results with the corresponding prototype leg are presented.
Optimal Force Distribution for Tethered Climbing Robots in Unstructured Environments
Authors: Hong Dennis W. , Cipra Raymond J.
Published: October 2012

One of the inherent problems of multi-limbed mobile robotic systems is the problem of multi-contact force distribution; the limbs in contact with its environment form closed kinematic chains, thus the contact forces and moments required to support it and those required by its tasks are indeterminate. A new computationally efficient analytical method for finding the optimal solution for the contact force distribution for a tethered multi-limbed robot climbing in unstructured environments is presented. The optimal solution is found by first finding the entire solution space for the contact force distribution for a statically stable stance under friction constraints, and then choosing an optimal solution in this solution space which maximizes the objectives given by the chosen optimization criteria. This approach will allow more options and freedom in choosing the final solution that not only satisfies the static equilibrium and friction constraints, but also can satisfy other special conditions under consideration at that instant. Finding the entire solution space first will give an intuitive visual map of how well the solution space is formed for the given conditions of the system, and choosing a solution in that space next will provide robustness against disturbances and indicate where this solution is positioned in the solution space to give insight into the quality of the chosen solution and the complex interactions of the many forces which are otherwise very difficult to see.
A High Precision Robotic Docking End Effector for 1 Micron Accuracy
Authors: Derby Stephen J. , McFadden John
Published: October 2012

Precision operations, including assembly, need an accurate platform as a base. The described robotic end effector can achieve 1 micron or smaller repeatability while being relocatable to the required task workspace.
A Characterization of the Workspace Boundary of Three-Revolute Manipulators
Authors: Saramago Sezimaria F. P. , Ottaviano Erika , Ceccarelli Marco
Published: October 2012

The aim of this work is to characterize the boundary workspace of three-revolute open chain manipulators by analyzing cusp points. A study is presented for the characteristic points of the workspace boundary of the three-revolute manipulators by using an algebraic formulation.
Procedure for Rapid Fabrication of Non-Assembly Mechanisms With Embedded Components
Authors: De Laurentis Kathryn J. , Kong Fung Felix , Mavroidis Constantinos
Published: October 2012

In this paper, the application of Rapid Prototyping in fabricating non-assembly robotic systems and mechanisms with inserts is presented. Previous work demonstrated the use of the Rapid Prototype Stereolithography and Selective Laser Sintering techniques to fabricate prototypes of mechanical mobile joints. As examples of their applicability, the joint designs were then used to fabricate complex multi-articulated, multi-link, multi-loop systems in one step, without requiring assembly while maintaining the joint desired mobility. Expanding upon this, current research explores methods of insertion of component parts during the rapid prototype process. A rapidly prototyped mobile vehicle, RP MOVe, was fabricated to show this method and is presented here.
Rapid Embedded Programming: A Tool for Education
Authors: Burns Daniel , Sugar Thomas G.
Published: October 2012

At ASU, new commercially available automatic code-generation tools are used to progress from controller design, to simulation, and finally to implementation on embedded hardware. Case studies highlighting a force-feedback joystick, a robotic hovercraft, and motor servo-control with encoder feedback are presented. Using these software tools, design iterations and multiple controllers are quickly simulated and downloaded to the actual hardware, providing students an appreciation for rapid embedded system design.