bluuebunny/crossref_metadata_2025 huggingface dataset:
Computation of Compression Loads in Twin Screw Compressors
Authors: Adams G. P. , Soedel W.
Published: February 2008

The compression mechanism in a twin screw compressor consists of two helical rotors. In this work, a method is presented for computing the forces and moments induced on each rotor due to gas compression. These are defined as the compression loads. The helical rotor surfaces are defined by the end profiles, wrap angle and rotor length. The 3D surface of each rotor is mapped to 2D integration regions. These regions correspond to the surfaces associated with individual compression chambers. The compression loads are computed by integrating the chamber pressure over the rotor surfaces. The integrals are evaluated at incremental values of the rotor angular position. The method is presented and implemented for a specific compressor configuration. The compression loads are resolved to forces at the bearing locations. These bearing forces are presented for operating pressures which represent an under-pressure condition. A frequency analysis demonstrates the rich frequency content of the bearing forces due to the sharpness of the compression loads as a function of the rotor angular position. In addition, it is demonstrated that the moment load about the axis of rotation induced on the female is approximately 12 percent of that induced on the male. Therefore, the female rotor motion approaches that of an idler gear.
Experimental Study of Cardan-Joint Dynamics
Authors: Fischer I. S. , de Waal J. K.
Published: February 2008

An experiment has been conducted indicating invalidity of the assumption of negligible intermediate-joint axial forces in Cardan joint (universal joint) dynamic analysis. It has been observed that increased driveline torque induces the radially-inward deflection of the yoke arms of a Cardan joint, while increased speed will deflect the yoke arms outward. Some suggestions are given to optimize Cardan joints for either high torque or high speed.
On Manipulation of Objects in Three-Fingered Grasp
Authors: Chevallier D. P. , Payandeh S.
Published: February 2008

Manipulation of the grasped object is defined as the ability of the mechanical end-effector to create an instantaneous motion of the object with respect to a fixed reference frame (e.g., palm reference frame). This class of manipulation is usually referred to as the fine manipulation whereas a collection of all these instantaneous motions of the object is referred to as the gross manipulation. This paper presents a new method where for a given desired twist of the grasped object, the instantaneous motions of the fingertips can be determined. The results of the paper are divided into two parts. First, for the case where the motion of the object is created through motions of the fingertip in off-tangent planes to the object at the contact points. Second, where a class of motion of the grasped object is achieved through motions of the fingertips which are restricted to the tangent planes. The method of this paper utilizes screw geometry, inner product spaces and information regarding grasp configuration. The method is also illustrated through examples.
A Unifying Framework for Classification and Interpretation of Mechanism Singularities
Authors: Zlatanov D. , Fenton R. G. , Benhabib B.
Published: February 2008

This paper presents a generalized approach to the singularity analysis of mechanisms with arbitrary kinematic chains and an equal number of inputs and outputs. The instantaneous kinematics of a mechanism is described by means of a velocity equation, explicitly including not only the input and output velocities but also the passive-joint velocities. A precise definition of singularity of a general mechanism is provided. On the basis of the six types of singular configurations and the motion space interpretation of kinematic singularity introduced in the paper, a comprehensive singularity classification is proposed.
Kinematic Synthesis of Mechanisms and Robotic Manipulators With Binary Actuators
Authors: Chirikjian G. S.
Published: February 2008

Binary actuators have only two discrete states (denoted “0” and “1”), both of which are stable without feedback. As a result, binary mechanisms and manipulators have a finite number of states. Major benefits of binary actuation are that extensive feedback control is not required, task repeatability can be very high, and two-state actuators are generally very inexpensive (e.g., solenoids, pneumatic cylinders, etc.), thus resulting in low cost robotic mechanisms. This paper develops algorithms for the optimal synthesis of binary manipulators and mechanisms for discrete tasks such as pick-and-place operations.
Instantaneous Kinematics of General Hybrid Parallel Manipulators
Authors: Etemadi-Zanganeh K. , Angeles J.
Published: February 2008

In this paper, we introduce a new class of parallel manipulators, called general hybrid parallel manipulators (GHPM). These are modular manipulators that may contain serial subchains as well as subchains of parallel modules, acting in parallel and connecting a base to a common platform. The instantaneous motion of the GHPM is studied by resorting to the theory of screws. In this context, we define the screw-system annihilator to reduce, systematically, the number of unknowns involved to a minimum. The formulation presented here is general and can be applied to most existing parallel manipulators, multifingered hands, multiple coordinated robots and walking machines. To illustrate the basic symbolical and numerical aspects of the proposed procedure, the analyses of the instantaneous kinematics of two hybrid manipulators are included.
A Direct Rotatability Criterion for Spherical Four-Bar Linkages
Authors: Gupta K. C. , Ma R.
Published: February 2008

The necessary and sufficient conditions for the full input rotatability in a spherical four-bar linkage are proved. The direct criterion is: for all twist angles α in the range [0, π], the excess (deficit) of the sum of the frame and input twist angles over (from) π should, in absolute value, be greater than that for the coupler and follower twist angles; the difference between the follower and input twist angles, in absolute value, should be greater than that for the coupler and follower twist angles. Application of the direct criterion to full rotatability of other links are discussed and some variations in the form of the criterion are developed.
The Kinematics of Spatial Double-Triangular Parallel Manipulators
Authors: Mohammadi Daniali H. R. , Zsombor-Murray P. J. , Angeles J.
Published: February 2008

Two versions of spatial double-triangular mechanisms are introduced, one with three and one with six degrees of freedom. Using dual-number quaternion algebra, a formula for the direct kinematics of these manipulators is derived. Numerical examples are included.
A Loop-Closure Theory for the Analysis and Synthesis of Compliant Mechanisms
Authors: Howell L. L. , Midha A.
Published: February 2008

Compliant mechanisms gain at least some of their motion from flexible members. The combination of large-deflection beam analysis, kinematic motion analysis, and energy storage makes the analysis of compliant mechanisms difficult. The design of mechanisms often requires iteration between synthesis and analysis procedures. In general, the difficulty in analysis has limited the use of compliant mechanisms to applications where only simple functions and motions are required. The pseudo-rigid-body model concept promises to be the key to unifying the compliant and rigid-body mechanism theories. It simplifies compliant mechanism analysis by determining an equivalent rigid-body mechanism that accurately models the kinematic characteristics of a compliant mechanism. Once this model is obtained, many well known concepts from rigid-body mechanism theory become amenable for use to analyze and design compliant mechanisms. The pseudo-rigid-body-model concept is used to develop a loop-closure method for the analysis and synthesis of compliant mechanisms. The method allows compliant mechanisms to be designed for tasks that would have earlier been assumed to be unlikely, if not impossible, applications of compliant mechanisms.
Modeling of a Finger-Follower Cam System With Verification in Contact Forces
Authors: Hsu Wensyang , Pisano A. P.
Published: February 2008

A lumped/distributed-parameter dynamic model is developed to investigate the dynamic responses of a finger-follower cam system by considering a hydraulic lash adjuster with an oscillating pivot, and frictional forces between sliding surfaces. The measured force data at low speed are employed to derive an algorithm to determine the dynamic Coulomb friction coefficients at contact points. The contact position between the cam and the follower with moving pivot is determined by a constraint equation method. A hydraulic lash adjuster acting as the pivot of the follower is also modeled with the effects of oil compressibility and oil refill mechanism. Simulated contact forces at three different speeds are shown to have good agreement with experimental data. The separation between the hydraulic lash adjuster and the follower is predicted at a camshaft speed of 2535 rpm, and experiment indicates at 2520 rpm.
Structural Optimization by Density Distribution for Maximization of Natural Frequency
Authors: Kawabe Yoshiko , Yoshida Shinobu
Published: February 2008

This paper proposes a basic method for designing light and rigid structures that have a maximum natural frequency for a designated mode. A design variable “density,” related to the material properties of a three-dimensional solid element, is introduced into the finite element method (FEM). Thus, a structure is expressed as a density distribution inside its design domain, and the optimal structure is obtained by searching for the most suitable such distribution.
A Qualitative-Quantitative Approach to V-Belt Mechanics
Authors: Sorge F.
Published: February 2008

A simplified formulation is adopted for the theoretical problem of tension distribution and radial penetration of a V-belt along the pulley groove. The trajectory portrait of the second order differential system describing the belt behavior is carefully analyzed and asymptotic approximations for the tension solutions are derived which are well suited for design purposes.
Dynamic Load Analysis of Spur Gears Using a New Tooth Profile
Authors: Yoon K. Y. , Rao S. S.
Published: February 2008

A novel method was presented by the authors to minimize the static transmission error using cubic splines (C.S.) for gear tooth profile. A reduction in the transmission error is expected to reduce the gear vibration and noise by lowering the dynamic tooth load in a meshing cycle. To establish this fact, a dynamic analysis of the gear drive with involute tooth and modified tooth profiles (using C.S.) is performed. For this, first the tooth deformation is found and then the tooth dynamic load is determined for all reasonable speeds. A parametric study is conducted to establish the superiority of the C.S. based gear profile over the involute profile as well as the other profiles based on the use of linear and parabolic tip reliefs.
Tolerance Analysis for Sheet Metal Assemblies
Authors: Liu S. C. , Hu S. J. , Woo T. C.
Published: February 2008

Traditional tolerance analyses such as the worst case methods and the statistical methods are applicable to rigid body assemblies. However, for flexible sheet metal assemblies, the traditional methods are not adequate: the components can deform, changing the dimensions during assembly. This paper evaluates the effects of deformation on component tolerances using linear mechanics. Two basic configurations, assembly in series and assembly in parallel, are investigated using analytical methods. Assembly sequences and multiple joints beyond the basic configurations are further examined using numerical methods (with finite element analysis). These findings constitute a new methodology for the tolerancing of deformable parts.
Synthesis of Optimal Shape and Topology of Structures
Authors: Kumar A. V. , Gossard D. C.
Published: February 2008

In this paper, a method is proposed for the design optimization of structural components where both shape and topology are optimized. The boundaries of the shape of the structure are represented using contours of a “shape density” function. The contour of the density function corresponding to a threshold value is defined as the boundary of the shape. The shape density function is defined over a feasible domain and is represented by a continuous piece-wise interpolation over the finite elements used for structural analysis. The values of the density function at the nodes serve as the design variables of the optimization problem. The advantage of this shape representation is that both shape and topology of the structure can be modified and optimized by the optimization algorithm. Unlike previous methods for shape and topology optimization, the material is not modeled as porous or composite using the homogenization method. Instead the material properties of the structure are assumed to depend on the density function and many approximate material property-density relations have been studied. The shape and topology of structural components are optimized with the objective of minimizing the compliance subject to a constraint on the total mass of the structure.
A Convex Cutting Plane Algorithm for Global Solution of Generalized Polynomial Optimal Design Models
Authors: Lo Chihsiung , Papalambros P. Y.
Published: February 2008

Global optimization algorithms for generalized polynomial design models using a global feasible search approach was discussed in a previous article. A new convex cutting plane algorithm (CONCUT) based on global feasible search and with improved performance is presented in this sequel article. Computational results of the CONCUT algorithm compared to one using linear cuts (LINCUT) are given for various test problems. A speed reducer design example illustrates the application of the algorithms.
System Configuration: Concurrent Subsystem Embodiment and System Synthesis
Authors: Chen Wei , Allen J. K. , Mistree F.
Published: February 2008

In this paper, we introduce a method for preliminary system configuration. Two steps are typically associated with preliminary system configuration, namely, selecting components that embody subsystems and then synthesizing the subsystems to create the system itself. We show how we can perform these two steps concurrently using a modification of Taguchi’s method of robust design. This method is effective in dealing with both discrete and continuous variables simultaneously. We illustrate the method for the preliminary design of a solar powered irrigation system. Our focus in this paper is on explaining our approach rather than on the results per se.
Multiobjective Optimization of a Leg Mechanism With Various Spring Configurations for Force Reduction
Authors: Shieh W.-B. , Tsai L.-W. , Azarm S. , Tits A. L.
Published: February 2008

In this paper, the design of a two degree-of-freedom leg mechanism is accomplished by a two-stage optimization process. In the first stage, leg dimensions are optimized with respect to three design objectives: minimize (i) peak crank torque for an entire walking cycle, (ii) leg size, and (iii) vertical actuating force. Following the optimization of leg dimensions, in the second stage, spring elements with various placement configurations are considered for further reduction of the actuating force and crank torque. Several tradeoff solutions are obtained and a comparison between various spring configurations is made. It is shown that the inclusion of spring elements can significantly reduce the actuating force and crank torque.
Generating the Swept Area of a Body Undergoing Planar Motion
Authors: Ling Zhi-Kui , Chase T. R.
Published: February 2008

The swept area of a two-dimensional object undergoing motion in its plane of definition is the union of the area occupied by the object at all positions during the motion. A methodology for determining a close approximation to an exact swept area of a convex object with a known arbitrary motion is developed here. The resulting swept areas are used as constraints in the geometric design of the links in an interference-free complex planar mechanism. Criteria for determining individual points falling on the border of the swept area are derived from envelope theory. These points are determined at a reference position of the sweeping body using generalized moving centrodes. The swept area is constructed from these points plus sections of the border of the moving body at some selected positions. Overlap of the swept area onto itself, caused by the body moving back to an area which it occupied previously, is processed by dividing the overall swept area into sub swept areas which are free of overlap. An eleven-step swept area generation algorithm is presented along with an example.
Working Capability Analysis of Stewart Platforms
Authors: Luh Chi-Mei , Adkins F. A. , Haug E. J. , Qiu C. C.
Published: February 2008

Working capability analysis of planar and spatial Stewart platforms with unilateral constraints on actuator length is carried out using numerical methods based on analytical criteria for the boundary of the accessible output set. Restrictions on achievable motion at singular configurations associated with points interior to the accessible output set are also analyzed. Since movement of the working point on a spatial Stewart platform occurs in three-dimensional space, the boundary of the accessible output set is a two-dimensional surface. Numerical methods used in this analysis map one-dimensional solution sets, permitting the boundary of the accessible output set to be characterized by a family of one dimensional generators. Motion control restrictions inside the accessible output set are similarly characterized by families of interior singular curves, and barriers to motion control across surfaces defined are analyzed.
Numerical Algorithms for Mapping Boundaries of Manipulator Workspaces
Authors: Haug E. J. , Luh Chi-Mei , Adkins F. A. , Wang Jia-Yi
Published: February 2008

Numerical algorithms for mapping boundaries of manipulator workspaces are developed and illustrated. Analytical criteria for boundaries of workspaces for both manipulators having the same number of input and output coordinates and redundantly controlled manipulators with a larger number of inputs than outputs are well known, but reliable numerical methods for mapping them have not been presented. In this paper, a numerical method is first developed for finding an initial point on the boundary. From this point, a continuation method that accounts for simple and multiple bifurcation of one-dimensional solution curves is developed. Second order Taylor expansions are derived for finding tangents to solution curves at simple bifurcation points of continuation equations and for characterizing barriers to control of manipulators. A recently developed method for tangent calculation at multiple bifurcation points is employed. A planar redundantly controlled serial manipulator is analyzed, determining both the exterior boundary of the accessible output set and interior curves that represent local impediments to motion control. Using these methods, more complex planar and spatial Stewart platform manipulators are analyzed in a companion paper.
A General Approach to the Determination of Planar and Spatial Cam Profiles
Authors: Tsay Der Min , Wei Hsien Min
Published: February 2008

A systematic development for the theory of envelopes with proof is presented. It offers a simple and general procedure to determine the planar and spatial cam profiles. Based on the theory, a planar or spatial cam profile is defined as the envelope of its follower surfaces represented in a parametric form in different relative positions of the cam and the follower. The procedure is illustrated by determining the 2D and 3D cam profiles with analytical formulations. To demonstrate its accuracy and effectiveness, the results are then compared to those obtained by an earlier approach using the screw theory.
A Numerical Method for Load Distribution in Threaded Connections
Authors: Zhao Hua
Published: February 2008

The Virtual Contact Loading Method is developed in this paper to study the load distributions in bolt-nut connectors and threaded pipe joints. A simplified three-dimensional computational model is proposed in order to simulate the threaded connections. The calculated results for the bolt-nut connectors agree well with those from previous analytical and numerical methods. This method is of satisfactory efficiency and accuracy.
The Bulging of Bolted Guideways
Authors: Zhu Zhenqi , Zhang Bi
Published: February 2008

As bolted joints affect the overall accuracy and stiffness of a machine tool, their behaviors have always been important to consider in a machine design process. The bulging phenomenon of a bolted guideway needs to be investigated under different loading conditions. A considerable amount of research has been reported on bolted joints; however, none is focused on the bulging of a bolted guideway. In this article, the bulging of three types of guideways is studied using the finite element method and the results are verified by the experiments using capacitance sensors. It turns out that the bulging occurs in such a way that the lower portion of a guideway expands while the top portion around the bolt sinks in the order of micrometers. The results would help the machine tool builders to reduce or eliminate the errors induced by the bulging effect from their products. The results are also useful to other applications of bolted joints where three-dimensional deformation occurs.
Composite Design Methodology: Design of Composite Trails for the U.S. Army’s M198 Howitzer, A Case Study
Authors: Sancaktar E. , West M. , Miner K. R.
Published: February 2008

Analysis and design of a fiber reinforced organic composite trail pair for the U.S. Army M198 Howitzer is presented as a case study in composite material design methodology. For this purpose mechanics analysis is performed using the computer program: MIC-MAC composites design and ANSYS 4.4A finite element analysis. The analyses includes composite lamination, material optimization, adhesive bonding, buckling, deflection, stress and failure analysis and validates the practicability of the proposed constant cross-section graphite/epoxy trail. The use of PC based spreadsheet MIC-MAC program, initially, allows efficient and inexpensive evaluation of several alternative designs including different geometries and materials before the finite element program is employed with the few final design choices to rule out failure in stress, deflection and buckling modes. However, superposition principles need to be used to describe the complex loading configuration as a collection of mechanically equivalent individual load modes such as midspan loaded beam, cantilever beam under torsion, in-plane loaded plate etc. in order to be able to utilize the MIC-MAC program initially. Fabrication plans are also proposed for the trail pair.
Kinematic Analysis of Epicyclic-Type Transmission Mechanisms Using the Concept of Fundamental Geared Entities
Authors: Hsieh Hsin-I , Tsai Lung-Wen
Published: February 2008

A new methodology for the speed ratio analysis of epicyclic-type transmission mechanisms is presented. First, the kinematic characteristics associated with various operation modes of fundamental geared entities are investigated. Then, it is shown that the overall speed ratio of an epicyclic gear mechanism can be expressed in terms of its fundamental geared entities. This method leads to an automated derivation of the speed ratio of an epicyclic-type transmission mechanism without the need of a symbolic manipulation software.
Mesh Reduction Using an Angle Criterion Approach
Authors: Khan M. Asif , Vance Judy M.
Published: February 2008

Surface polygonization is the process by which a representative polygonal mesh of a surface is constructed for rendering or analysis purposes. This work presents a new surface polygonization algorithm specifically tailored to be applied to a large class of models which are created with parametric surfaces having triangular meshes. This method has particular application in the area of building virtual environments from computer-aided-design (CAD) models. The algorithm is based on an edge reduction scheme that collapses two vertices of a given triangular polygon edge onto one new vertex. A two step approach is implemented consisting of boundary edge reduction followed by interior edge reduction. A maximum optimization is used to determine the location of the new vertex. The criterion that is used to control how well the approximate surface represents the actual surface is based on examining the angle between surface normals. The advantage of this approach is that the surface discretization is a function of two, user-controlled variables, a boundary edge angle error and a surface edge angle error. The method presented here differs from existing methods in that it takes advantage of the fact that for many models, the exact surface representation of the model is known before the polygonization is attempted. Because the precise surface definition is known, a maximum optimization procedure, that uses the surface information, can be used to locate the new vertex. The algorithm attempts to overcome the deficiencies in existing techniques while minimizing the number of triangular polygons required to represent a surface and still maintaining surface integrity in the rendered model. This paper presents the algorithm and testing results.
Complex Modal Analysis of a Flat Belt Pulley System With Belt Damping and Coulomb-Damped Tensioner
Authors: Kraver T. C. , Fan G. W. , Shah J. J.
Published: February 2008

The effects of damping on rotational vibratory solutions of a multiple pulley—flat viscoelastomeric belt system with rotary arm tensioner is developed. A complex model procedure is developed to solve both underdamped and overdamped cases. This complex modal procedure allows for future extension to include nonsymmetric rotational models, such as transverse belt vibration coupling. The modal solution enables rapid analysis over a spectrum of frequencies. Seven pulley system experimental results reported in the literature support the analytical development. Belt damping has significant vibration and belt tension amplitude effects. Tensioner spring rate and coulomb damping has minor effects.
Finite Element Analysis of Load-Deflection and Creep Characteristics of Compressed Rubber Components for Vibration Control Devices
Authors: Lee B. S. , Rivin E. I.
Published: February 2008

Elastomeric (rubber-like) materials are extensively used in various machine design applications, particularly for flexible elements of vibration/shock/noise control devices and of power transmission couplings. In order to have high performance characteristics, such elements should accommodate large static and dynamic loads and/or large deflections in a limited size. In many applications high damping, low creep and substantial nonlinearity of the load-deflection characteristic are required. These contradictory requirements are often impossible to satisfy just by selecting special rubber blends. It was demonstrated in [9] that for unbonded rubber flexible elements of a cylindrical shape loaded in a radial direction, desirable nonlinear load-deflection characteristics can be naturally obtained, and creep rate can be significantly reduced as compared with conventional shapes of bonded rubber elements loaded in compression. This paper presents the second part of the study [9]. It applies the Finite Element Method to analyze large deformations of nonlinear components made of viscoelastic materials. Some convenient and efficient methods are proposed to determine material constants for the analytical study of static load-deflection characteristics and creep. These proposed methods result in good agreement between the numerical results and the experimental results in [9]
The Deployment of Curved Closed Tubes
Authors: Greschik G. , Park K. C.
Published: February 2008

A critical review of previous work on the unfurling of helically curved tubes (Greschik et al, 1994, 1996) is conducted, which leads to the proposition of a continuous and smooth deployment concept akin to the Collapsible Tube Mast (Aguirre, 1985) for curved tubes. This involves the collapse of the cross section and the subsequent roll-up of its halves one upon the other onto a storage drum. The concept’s applicability to closed tubes is investigated and a method for the alleviation of the deleterious membrane strains in the stowed state is proposed.
Thermoelastoplastic Stress Analysis of a Thick-Walled Tube of Nonlinear Strain Hardening
Authors: Jahanian S.
Published: February 2008

In pressure vessel technology or nuclear power plants, some of the mechanical components are often subjected to rapid heating. If the temperature gradient during such process is high enough, thermoelastoplastic stresses may be developed in the components. These plastic deformations are permanent and may result in the incremental deformation of the structure in the long term. Accordingly, determination of thermoelastoplastic stresses during this process is an important factor in design. In this paper, a thick-walled cylinder of nonlinear strain hardening is considered for the thermoelastoplastic analysis. The properties of the material are assumed to be temperature dependent. The cylinder is subject to rapid heating of the inside surface while the outside surface is kept at the room temperature. A quasi-static and uncoupled thermoelastoplastic analysis based on incremental theory of plasticity is developed and a numerical procedure for successive elastic approximation is presented. The thermoelastoplastic stresses developed during this process are also presented. The effect of strain hardening and temperature dependency of material on the results are investigated.
Globally Optimal Force Allocation in Active Mechanisms With Four Frictional Contacts
Authors: Sreenivasan S. V. , Waldron K. J. , Mukherjee S.
Published: February 2008

Mechanisms interacting with their environments that possess complete contact force controllability such as multifingered hands and walking vehicles are considered in this article. In these systems, the redundancy in actuation can be used to optimize the force distribution characteristics. The resulting optimization problems can be highly nonlinear. Here, the redundancy in actuation is characterized using geometric reasoning which leads to simplifications in the formulation of the optimization problems. Next, advanced polynomial continuation techniques are adapted to solve for the global optimum of an important nonlinear optimization problem for the case of four frictional contacts. The algorithms developed here are not suited for real-time implementation. However, these algorithms can be used in off-line force planning, and they can be used to develop look-up tables for certain applications. The outputs of these algorithms can also be used as a baseline to evaluate the effectiveness of sub-optimal schemes.
On the Design of Zero Reaction Manipulators
Authors: Papadopoulos E. , Abu-Abed A.
Published: February 2008

In a number of industrial, space, or mobile applications, reaction forces and moments transmitted by a manipulator to its base are undesirable. In this paper, we analyze the problem of force and torque transmission in robotic systems, and propose design and planning methods that can eliminate it, or reduce it. Based on force and moment transmission analysis, a three DOF redundant manipulator design is selected. Dynamic reaction forces are eliminated by force balancing. Reaction moments are eliminated by following reactionless paths, whose planning is simplified by rendering the dynamics configuration-invariant. Reactionless Workspaces are defined in which any end-effector path can result in zero dynamic reactions. An example is used to demonstrate the usefulness of the proposed methods. An important advantage of these methods is that the manipulator can be used either as a redundant, or as a reduced DOF reactionless system.
Inverse Kinematics of Serial-Chain Manipulators
Authors: Lee Hong-You , Reinholtz Charles F.
Published: February 2008

This paper proposes a unified method for the complete solution of the inverse kinematics problem of serial-chain manipulators. This method reduces the inverse kinematics problem for any 6 degree-of-freedom serial-chain manipulator to a single univariate polynomial of minimum degree from the fewest possible closure equations. It is shown that the univariate polynomials of 16th degree for the 6R, 5R-P and 4R-C manipulators with general geometry can be derived from 14, 10 and 6 closure equations, respectively, while the 8th and 4th degree polynomials for all the 4R-2P, 3R-P-C, 2R-2C, 3R-E and 3R-S manipulators can be derived from only 2 closure equations. All the remaining joint variables follow from linear equations once the roots of the univariate polynomials are found. This method works equally well for manipulators with special geometry. The minimal properties may provide a basis for a deeper understanding of manipulator geometry, and at the same time, facilitate the determination of all possible configurations of a manipulator with respect to a given end-effector position, the determination of the workspace and its subspaces with the different number of configurations, and the identification of singularity positions of the end-effector. This paper also clarifies the relationship between the three known solutions of the general 6R manipulator as originating from a single set of 14 equations by the first author.
Computer-Aided Sketching of Epicyclic-Type Automatic Transmission Gear Trains
Authors: Chatterjee G. , Tsai Lung-Wen
Published: February 2008

The enumeration of epicyclic gear mechanisms in the form of graphs gives rise to the need of a methodology for reverse transformation, that is, for constructing the mechanisms from graphs. This paper addresses the issue by discretizing an epicyclic gear mechanism into Fundamental Geared Entities. Further, these geared entities are shown to be a conglomeration of four primitives; namely, the carrier, sun, ring, and the planet gear. An algorithm is formulated to create the entities from a graph by using these primitives. The entities are then connected together to form a mechanism.
Synthesis of Optimal Nonorthogonal Routes
Authors: Szykman S. , Cagan J.
Published: February 2008

This paper introduces a novel approach to three dimensional routing optimization. Examples of routing tasks for engineering applications include routing of pipes, wires and air ducts. Traditionally, routing algorithms perform Manhattan, or orthogonal, routing. Nonorthogonal routing can be less costly than Manhattan routing and for applications such as automotive or aerospace design, Manhattan routing is impractical due to spatial limitations. The research presented in this paper uses simulated annealing as the basis of a nonorthogonal routing optimization algorithm. Several examples comparing the two approaches are given.
Diagnostic Modeling and Diagnosability Evaluation of Mechanical Systems
Authors: Clark G. E. , Paasch R. K.
Published: February 2008

Consideration of diagnosability in product design promises to increase product quality by reducing maintenance time without increasing cost or decreasing reliability. Methods for investigating the diagnosability of mechanical and electro-mechanical systems are described and are applied to the Bleed Air Control System (BACS) on the Boeing 747-400. The BACS is described and a diagnostic model is developed using information from the system Failure Modes and Effects Analysis. Emphasis is placed on the relationships between the system’s functions and its components. Two metrics for the evaluation of system diagnosability and two metrics for the evaluation of component diagnosability are defined. These metrics emphasize diagnostic ambiguity and are combined with the probability of different system failures to weight the effects of each failure. Three modified systems are produced by reassigning functions from one component to another. The resulting effects on the system and component diagnosability are evaluated. We show that by changing these relationships system diagnosability can be improved without adding sensors or other components.
A Flat Composite Panel Design Advisory System Using Knowledge Based and Case Based Reasoning
Authors: Lambright J. P. , Ume C.
Published: February 2008

A method of cooperatively using Knowledge Based and Case Based Reasoning is proposed to assist designers in the design of flat composite panel structures. A Prototype Design Advisory system is constructed of heuristic and experiential rules which are acquired from composites design experts, and published text which is implemented in the CLIPS Knowledge Based System shell. The system includes design cases of previous composites design scenarios implemented in a Case Based Reasoning System using DesignMUSE. The cases all depict design of composites applied to commercial and military aircraft. The application of heuristic rules and prior similar design cases is focused upon the early stages of the design process. It is believed that such a design advisory system can aid in preventing unforeseen mistakes during the design and manufacture of composite structures, can assist in predicting the results of candidate designs, and can ultimately reduce the design cycle time.
Negotiation in Constraint-Based Design
Authors: Kusiak A. , Wang J. , He D. W.
Published: February 2008

A design problem usually involves multiple perspectives, each with own set of constraints that may interact. The objective of this paper is to develop a methodology to assist in negotiation of constraints from multiple perspectives. The proposed approach is based on qualitative reasoning that provides each perspective with negotiation information for making design decisions. A qualitative constraint network is used to characterize the qualitative and quantitative relationship between design variables. It provides means for tracking dependencies among perspectives for a set of constraints and determines the impact of design changes. When a conflict occurs, effective negotiation strategies are generated. A negotiation procedure for an ill-structured negotiation process is presented. The effectiveness of the negotiation process is improved with the procedure proposed. A valve design problem illustrates the concepts discussed in the paper.
A Procedure for Robust Design: Minimizing Variations Caused by Noise Factors and Control Factors
Authors: Chen Wei , Allen J. K. , Tsui Kwok-Leung , Mistree F.
Published: February 2008

In this paper, we introduce a small variation to current approaches broadly called Taguchi Robust Design Methods. In these methods, there are two broad categories of problems associated with simultaneously minimizing performance variations and bringing the mean on target, namely, Type I—minimizing variations in performance caused by variations in noise factors (uncontrollable parameters). Type II—minimizing variations in performance caused by variations in control factors (design variables). In this paper, we introduce a variation to the existing approaches to solve both types of problems. This variation embodies the integration of the Response Surface Methodology (RSM) with the compromise Decision Support Problem (DSP). Our approach is especially useful for design problems where there are no closed-form solutions and system performance is computationally expensive to evaluate. The design of a solar powered irrigation system is used as an example.
Analysis of Design Parameters in Platform Manipulators
Authors: Ji Zhiming
Published: February 2008

Multi-loop parallel structures of platform manipulators present challenge to their design analysis. For studying the workspace of the 3-6 class of platforms, we developed the “vertex space” concept in Ji (1994). This paper extends the “vertex space,” concept to other structures for analysing and comparing their workspaces. We classify the vertices of the platform manipulators into types A and B. The platform manipulators are then divided into four groups based on their vertex types. Design parameters in platform manipulators are studied in terms of their functions and effects to vertex spaces and workspace.
Design of an Engagement Guiding Mechanism for Roller Chain Drives
Authors: Kong Liexiao , Sabbaghian M.
Published: February 2008

On a roller chain drive, if the incoming engaging roller moves tangent to the pitch circle at the moment of engagement, no roller-sprocket impact should occur. Based on such a notion, an engagement guiding mechanism is proposed to make this possible. The algorithm of kinematic design of the mechanism is presented. Comparisons between the new model and a conventional model show significant improvements made in the kinematic properties of the engaging roller.
Kinematic and Geometric Models of Gear Drives
Authors: Litvin F. L. , Seol I. H. , Kim D. , Lu J. , Wang A. G. , Egelja A. , Zhao X. , Handschuh R. F.
Published: February 2008

A methodology is proposed for the modification of gear tooth surfaces that reduces the impact of gear drive misalignment, the shift of the bearing contact (accompanied in some cases with edge contact), and the occurrence of discontinuous functions of transmission errors. The proposed approach is tested by computerized simulation of meshing and contact for unloaded and loaded gear drives. Applications of geometry modifications to the design of spur and helical involute gears, double-circular helical gears, face-gear drives, face-milled spiral bevel gears with constant tooth height and worm-gear drives are represented.
Computerized Design, Generation and Simulation of Meshing and Contact of Modified Involute, Klingelnberg and Flender Type Worm-Gear Drives
Authors: Seol I. H. , Litvin F. L.
Published: February 2008

The worm and worm-gear tooth surfaces of existing worm-gear drive designs are in line contact at every instant and the gear drive is very sensitive to misalignment. Errors of alignment cause shifting of the bearing contact and transmission errors. Methods for computerized simulation of meshing and contact of misaligned worm-gear drives of existing design are proposed. Also, modification of worm-gear drive geometry that provides a localized and stable bearing contact with reduced sensitivity to misalignment is described. Methods for computerized simulation of meshing and contact of worm-gear drives with the existing and modified geometry are represented. Numerical examples that illustrate the developed theory are provided. The proposed approach has been applied for modification of involute, Klingelnberg and Flender type worm-gear drives.
A Framework for Efficiency Evaluation of Multi-Degree-of-Freedom Gear Trains
Authors: Innocenti C.
Published: February 2008

The paper proposes a new approach to the efficiency evaluation of any one- or multi-degree-of-freedom gear trains. The suggested approach generalizes the known procedures developed for two-degree-of-freedom gear trains. It is based on the determination of a vector whose components are the torques delivered to the shafts of the gear train. Furthermore the paper shows that, for a notable category of gear trains, such a vector can have only a finite number of directions, which implies that a limited number of experimental data suffices for estimating the efficiency at any operational condition. Examples of application of the proposed methodology are provided.
Computerized Design and Analysis of Face-Milled, Uniform Tooth Height Spiral Bevel Gear Drives
Authors: Litvin F. L. , Wang A. G. , Handschuh R. F.
Published: February 2008

Face-milled spiral bevel gears with uniform tooth height are considered. An approach is proposed for the design of low-noise and localized bearing contact of such gears. The approach is based on the mismatch of contacting surfaces and permits two types of bearing contact either directed longitudinally or across the surface to be obtained. Conditions to avoid undercutting were determined. A Tooth Contact Analysis (TCA) was developed. This analysis was used to determine the influence of misalignment on meshing and contact of the spiral bevel gears. A numerical example that illustrates the developed theory is provided.
An Analytical Expression for the Time-Varying Contact Length in Perfect Cylindrical Gears: Some Possible Applications in Gear Dynamics
Authors: Maatar M. , Velex P.
Published: February 2008

This paper presents an analytical expression of the time-varying contact length between perfect involute spur and helical gears. It is shown that contact lengths can be expressed as Fourier series whose numerical expansions correlate very well with the results of numerical time-step simulations based on contact length discretization. Finally, some possible examples of application in gear dynamics are suggested.
A Simple Model for the Axial Thrust in V-Belt Drives
Authors: Sorge F.
Published: February 2008

Simple formulas can relate axial thrust and torque of rubber V-belt drives, taking into consideration the radial penetration of the belt.
Dynamic Analysis of Flexible Mechanisms With Clearances
Authors: Wang Yu , Wang Zaiping
Published: February 2008

A finite element method in time is presented for the periodic solution of vibrating elastic mechanisms with clearances. The solution of motion is made possible by utilizing time finite elements which discretize the solution period into a number of time intervals. The periodic response is described in terms of a set of temporal nodes of all spatial degrees of freedom of the system, yielding a block-diagonal nonlinear algebraic system to be solved iteratively. The suggested method is applied to an example problem of cam-driven valve train, demonstrating the effectiveness of the method in dealing with multiple clearance nonlinearities.