bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser Holographic Measurement of Tooth Flank Form of Cylindrical Involute Gear
Authors: Fujio H. , Kubo A. , Saitoh S. , Suzuki M. , Tochimoto S. , Hanaki H. , Honda T.
Published: June 2008

The form deviations of tooth flanks of spur and helical gears obtained by using a laser holographic interferometer are compared with the results of the conventional measuring method using a contacting stylus. The objective tooth flank which has a rough finish compared with optical parts is irradiated with a laser beam in a large incident angle to obtain the reflected ray from it. Image patterns of the interference fringes for tooth flanks with various types of form deviation are obtained, and they are transformed to the form deviations from the target tooth flank form. The algorithm of this transformation is shown: the brightness information of the image of the interference fringe on the CRT is converted to the amplitude of form deviation defined on the plane of action of the gear according to the phase difference of light beam by using the phase stepping method. A partial measuring procedure for helical gears is proposed which achieves the same level of accuracy as the conventional method using a stylus.
Surface Failure and Durability of Induction-Hardened Sintered Powder Metal Rollers and Gears with Various Hardened Depths
Authors: Yoshida A. , Ohue Y. , Karasuno I.
Published: June 2008

In this report, the effect of hardened depth on failure modes and fatigue strengths of induction-hardened sintered powder metal rollers and spur gears was elucidated, including the effect of relative radius of curvature of the rollers. These experimental results were discussed by an amplitude of ratio of orthogonal shear stress to Vickers hardness. Failure mode of the rollers was spalling due to subsurface origin crack with slight micropits and that of the gears was pitting with spall near the pitch point independent of the hardened depth. The depths of spalling cracks agreed almost with the occurring depths of peak amplitude of the ratio of orthogonal shear stress to Vickers hardness. Surface durability of the test rollers increased as the surface hardness increased and the relative radius of curvature decreased. Surface durability of the test rollers and the test gears was hardly influenced by the hardened depth.
Computerized Analysis of Gear Meshing Based on Coordinate Measurement Data
Authors: Kin V.
Published: June 2008

A mathematical model is proposed for the reconstruction of gear tooth surface features based on the manufacturing process deviations measured with the help of a gear inspection (or coordinate measurement) machine. The model is extended to facilitate the computer simulation of meshing between the measured gear and a theoretical master gear, or between two measured gears. This would allow one to predict the transmission errors and bearing contact which are otherwise only possible to investigate using the combination of single-flank testing and a time-consuming work-in and examination procedure. The developed model is applied to the determination of tooth-to-tooth transmission errors of parallel-axis gears and can also be utilized to determine bearing contact and contact stresses and be useful in tooth surface fatigue life calculations.
Global and Discrete Constraint Activity
Authors: Pomrehn L. P. , Papalambros P. Y.
Published: June 2008

The concept of constraint activity, widely used throughout the optimization literature, is extended and clarified to deal with global optimization problems containing either continuous or discrete variables. The article presents definitions applicable to individual constraints and discusses definitions for groups of constraints. Concepts are reinforced through the use of examples. The definitions are used to investigate the ideas of optimization “cases” and monotonicity analysis as applied to global and discrete problems. Relationships to local optimization are also noted.
Geometric Construction of Be´zier Motions
Authors: Ge Q. J. , Ravani B.
Published: June 2008

This paper deals with discrete computational geometry of motion. It combines concepts from the fields of kinematics and computer aided geometric design and develops a computational geometric framework for geometric construction of motions useful in mechanical systems animation, robot trajectory planning and key framing in computer graphics. In particular, screw motion interpolants are used in conjunction with deCasteljau-type methods to construct Be´zier motions. The properties of the resulting Be´zier motions are studied and it is shown that the Be´zier motions obtained by application of the deCasteljau construction are not, in general, of polynomial type and do not possess the useful subdivision property of Bernstein-Be´zier curves. An alternative from of deCasteljau algorithm is presented that results in Be´zier motions with subdivision property and Bernstein basis function. The results are illustrated by examples.
Computer Aided Geometric Design of Motion Interpolants
Authors: Ge Q. J. , Ravani B.
Published: June 2008

This paper studies continuous computational geometry of motion and develops a method for Computer Aided Geometric Design (CAGD) of motion interpolants. The approach uses a mapping of spatial kinematics to convert the problem of interpolating displacements to that of interpolating points in the space of the mapping. To facilitate the point interpolation, the previously unorientable mapping space is made orientable. Methods are then developed for designing spline curves in the mapping space with tangent, curvature and torsion continuities. The results have application in computer animation of three-dimensional objects used in computer graphics, computer vision and simulation of mechanical systems.
Geometric Reasoning Based on Graph Grammar Parsing
Authors: Fu Z. , de Pennington A.
Published: June 2008

It has been recognized that future intelligent design support environments need to reason about the geometry of products and to evaluate product functionality and performance against given constraints. A first step towards this goal is to provide a more robust information model which directly relates to design functionality or manufacturing characteristics, on which reasoning can be carried out. This has motivated research on feature-based modelling and reasoning. In this paper, an approach is presented to geometric reasoning based on graph grammar parsing. Our approach is presented to geometric reasoning based on graph grammar parsing. Our work combines methodologies from both design by features and feature recognition. A graph grammar is used to represent and manipulate features and geometric constraints. Geometric constraints are used within symbolical definitions of features constraints. Geometric constraints are used within symbolical definitions of features and also to define relative position and orientation of features. The graph grammar parsing is incorporated with knowledge-based inference to derive feature information and propagate constraints. This approach can be used for the transformation of feature information and to deal with feature interaction.
A Linear Scheme for the Displacement Analysis of Micropositioning Stages with Flexure Hinges
Authors: Her I. , Chang J. C.
Published: June 2008

In this paper we present an analytical scheme for the displacement analysis of micropositioning stages with flexure hinges. The proposed scheme is based on linearization of the geometric constraint equations of the stage structure. A design chart for evaluating the stiffness of the flexure hinge is also presented in this paper. This chart provides more accurate estimations than the design formula presently in use. The proposed linear scheme is general, easy to use, yet capable of obtaining results close to those obtained from the finite element analysis.
Generalized Constraint and Joint Reaction Forces in the Inverse Dynamics of Spatial Flexible Mechanical Systems
Authors: Chen D. C. , Shabana A. A. , Rismantab-Sany J.
Published: June 2008

In both the augmented and recursive formulations of the dynamic equations of flexible mechanical systems, the inerita, constraints, and applied forces must be properly defined. The inverse dynamics is a commonly used approach for the force analysis of mechanical systems. In this approach, the system is kinematically driven using specified motion trajectories, and the objective is to determine the driving forces and torques. In flexible body dynamics, however, a force that acts at a point on the deformable body is equipollent to a system, defined at another point, that consists of the same force, a moment that depends on the relative deformation between the two points, and a set of generalized forces associated with the elastic coordinates. Furthermore, a moment in flexible body dynamics is no longer a free vector. It is defined by the location of its line of action as well as its magnitude and direction. The joint reaction and generalized constraint forces represent equipollent systems of forces. Both systems in flexible body dynamics are function of the deformation. In this investigation, a procedure is developed for the determination of the joint reaction forces in spatial flexible mechanical systems. The mathematical formulation of some mechanical joints that are often encountered in the analysis of constrained flexible mechanical systems is discussed. Expressions for the generalized reaction forces in terms of the constraint Jacobian matrices of the joints are presented. The effect of the elastic deformation on the reaction forces is also examined numerically using the spatial flexible multibody RSSR mechanism that consists of a set of interconnected rigid and elastic bodies. The procedure described in this investigation can also be used to determine the joint torques and actuator forces in kinematically driven spatial elastic mechanism and manipulator systems.
Conversions of Feature-Based Design Representations Using Graph Grammar Parsing
Authors: Rosen D. W. , Dixon J. R. , Finger S.
Published: June 2008

In order to trade off required functionality with manufacturing, cost, and other life-cycle considerations, it is necessary to evaluate designs in these secondary view-points. Representations of mechanical components designed with design features must be converted into representations containing relevant secondary viewpoint features. When describing a design verbally, designers often use languages of design features. In other viewpoints, different languages of viewpoint-specific features are used. Thus, translation capability between viewpoint languages is needed to convert from one representation to another. The approach taken here is to use formal graph grammars to define the feature-based design of thin-walled components and the secondary feature languages. Features are defined by graphs that explicitly represent the feature, its geometric entities, and their connectivity. Components are built up by combining feature graphs based on designer specified feature connectivity. To convert from the design to a secondary viewpoint, a three-step process is used where the last step is parsing by a grammar from the secondary viewpoint. To illustrate the conversion process, a converter for tool cost evaluation in injection molding and die casting is developed and applied to an example component.
Using Subgraph Isomorphisms to Recognize and Decompose Boundary Representation Features
Authors: Chuang S.-H. F. , Henderson M. R.
Published: June 2008

A method using subgraph isomorphisms is presented for both computer recognition of shape features and feature-based decomposition of a solid from a boundary representation (B-rep). Prior to the recognition process, the face-edge graph of an object is extracted from a B-rep and is labeled by shape elements as a shape graph, which is an abridged B-rep and is labeled by shape elements as a shape graph, which is an abridged B-rep input to the recognition system. A feature is defined by a user as a feature graph, which is conceptualized from a regional surface shape on a valid solid. Feature recognition is achieved by finding a subgraph from the shape graph of a designed object where the subgraph is isomorphic to a feature graph. Because of the high complexity in subgraph matching, a node classification algorithm is used to reduce the search space. Through this recognition process, the surface of a solid can be decomposed into a collection of features according to a library of feature graphs. The feature relationships are represented in a relationship graph considering the features as nodes and their relationships as arcs. This research shows that the definition of features can be user-definable and consist of valid boundary representation elements in the solid world, and that a heuristically fast algorithm can increase the possibility to recognize features in a reasonable time.
Optimization of Design Utility
Authors: Thurston D. L. , Carnahan J. V. , Liu T.
Published: June 2008

Design optimization is often carried out with respect to a single objective, for example, weight, manufacturing cost, quality or robustness. However, when the design process is completed, a design is evaluated with respect to its performance in all of these areas, and possibly others, in addition to mechanical design considerations. We present a design method whose basic premise is that the process of design should be driven from the very beginning by consideration of how the artifact will ultimately be evaluated. A rigorously determined multiple attribute design evaluation function provides insight necessary to formulate a nonlinear programming problem. A clear distinction is made between design attributes and constraints. The objective function is maximization of utility. Explicit representations of relationships between design decisions and resulting performance in each of several attributes serve as constraints. An illustrative example of automotive bumper beam design optimization is presented. By coupling the physical relationships between the decision variable beam gauge and the attributes weight, deflection and cost, maximization of the overall worth of terms of the best combination of these attributes is possible. The solution can be expressed in terms of elements of a design vector over which the designer has direct control.
Analysis of Explosively Actuated Valves
Authors: Jones B. K. , Emery A. F. , Hardwick M. F. , Ng R.
Published: June 2008

Explosive valves are generally composed of a plunger which is explosively driven along the bore of a cylindrical housing. The plunger is forced to stop at a location designed to alter a particular fluid flow configuration. The stopping point of the plunger is determined by the drag forces between the plunger and the housing and is the critical factor in obtaining the desired flow. One way of calculating these drag forces is to model the valve as a series of thin disks and to assume an elastic interference fit between the disks of the plunger and the disks of the housing. Explosive valves constructed with new materials and new geometries, however, have made it necessary to account for plastic deformations, including strain hardening. This paper introduces an elastic-plastic disk model based on a combination of closed form and finite element results. The behavior of the calculations with elastic-plastic materials is compared to various finite element representations of an explosive valve to verify the disk model and to quantify the effects of plasticity and large deformations. Finally, the elastic-plastic calculations are compared to experimental results obtained from actual valves with various materials and geometries.
A Dynamic System Model for Estimating Surface-Induced Frame Loads During Off-Road Cycling
Authors: Wilczynski H. , Hull M. L.
Published: June 2008

To facilitate the design analysis of off-road bicycle frames, this paper reports a dynamic model of the bicycle/rider system which estimates frame loads for bicycles traveling over rough surfaces. To develop this model, the frame loads at rider contact points were first measured experimentally as a rider coasted over a test track with randomly spaced surface irregularities in both seated and standing positions. Following this measurement, a dynamic system model was developed with the aid of the commercial software package, Dynamic Analysis and Design Software (DADS). The development process consisted of two stages. The first stage involved developing component models (e.g., seat) which could reproduce the essentials of the measured data. The second stage involved identification of parameter values for those parameters shown to most profoundly affect simulated load results. Following parameter identification, simulated loads were statistically tested and were not significantly different from experimental loads. Also, maximum magnitude dynamic loads were compared to corresponding static load magnitudes and were larger for eight of the ten load components measured. With the importance of dynamic loads demonstrated and the model verified, it can now be used advantageously to generate a loading database for design analysis purposes.
A New, Thermally Controlled, Non-Contact Rotor Balancing Method
Authors: Furman B. J.
Published: June 2008

Available alternative rotor balancing techniques applied to rotors manufactured in high volumes often have productivity limitations. A new method has been devised that allows a rotor to be balanced as it rotates, without physical contact. The method accomplishes balance correction by means of deformable torsion elements that permanently relocate discrete masses through local heating under the action of centrifugal forces. The method exploits the elevated temperature, time-dependent deformation behavior of metallic materials under stress to produce controlled incremental deformation through radiative pulse heating. The important aspects of the new method: the physical configuration of the deformable elements, the non-contact, local heating method, and the method of producing controlled incremental deformation of the mass relocation element have been modeled analytically and demonstrated experimentally.
On the Limitations of Predictions of the Dynamic Response of Machines with Clearance Connections
Authors: Deck J. F. , Dubowsky S.
Published: June 2008

The results of experimental and analytical studies of the dynamic response of machines with flexible links and connection clearances are presented. These results suggest that both a large amount of variability and high sensitivity to small parameter changes and operating conditions are inherent properties of the dynamic response of such systems. This work indicates that the accuracy of dynamic force predictions given by computer simulations for such systems may be fundamentally limited, and therefore such simulations should be used with care in system design.
Kinematic and Static Force Analysis of Rocker-Pin Jointed Silent Chains with Involute Sprockets
Authors: Bucknor N. K. , Freudenstein F.
Published: June 2008

A quasi-static model has been developed for a silent (inverted-tooth) chain drive incorporating a rocker-pin-jointed chain and involute-toothed sprockets. The kinematic effects of rocker-pin clearances and link/sprocket engagement are modeled and the influence of various model parameters on the chain drive torque-ratio variation, due to chordal action, is examined. In some cases, this variation is found to be less than that for equivalent pin-jointed chain drives. Additionally, the center distances corresponding to the maximum and minimum torque variation are not fixed, as in the case of a pin-joined chain. An optimization method is used in determining the governing geometric constrains as multiple joint configurations can occur, given the rocker-pin joint clearances. The resulting system of equations is fully constrained for a physically consistent chain configuration.
Kinematics of the Ball Screw Mechanism
Authors: Lin M. C. , Ravani B. , Velinsky S. A.
Published: June 2008

This paper studies the kinematics of the Ball Screw Mechanism (BSM) with the aim of developing a foundation for understanding the motion of the balls and their contact patterns with the contacting elements. It is shown that there is always slip between the balls and the nut or screw, and therefore, the no-slip condition assumed in the BSM literature is not attainable. The effect of contact deformation on the motion of the balls is also studied and is used to develop the pattern of the constant sliding lines of contact between the ball and the screw or the nut. The results have applications in efficiency analysis, design, wear evaluation and finite element modeling of the BSM.
Design of the Ball Screw Mechanism for Optimal Efficiency
Authors: Lin M. C. , Velinsky S. A. , Ravani B.
Published: June 2008

This paper develops theories for evaluating the efficiency of the ball screw mechanism and additionally, for designing this mechanism. Initially, a quasi-static analysis, which is similar to that of the early work in this area, is employed to evaluate efficiency. Dynamic forces, which are neglected by the quasi-static analysis, will have an effect on efficiency. Thus, an exact theory based on the simultaneous solution of both the Newton-Euler equations of motion and the relevant kinematic equations is employed to determine mechanism efficiency, as well as the steady-state motion of all components within the ball screw. However, the development of design methods based on this exact theory is difficult due to the extensive computation necessary and thus, an approximate closed-form representation, that still accounts for the ball screw dynamics, is derived. The validity of this closed-form solution is proven and it is then used in developing an optimum design methodology for the ball screw mechanism based on efficiency. Additionally, the self-braking condition is examined, as are load capacity considerations.
Surface Geometry of Variable Pitch Cylindrical Cams with Conical Meshing Elements
Authors: Liu Jen-Yu , Yan Hong-Sen
Published: June 2008

This paper presents mathematical expressions for the surface geometry of variable pitch cylindrical cams with four conical meshing elements based on the theory of conjugate surfaces. The unit normal of the element is derived, with given surface geometry of the meshing element, by differential geometry. The contact lines of the conjugate surface are defined according to the equation of meshing and the specified input-output relation. By the coordinate transformation of contact lines, we have the complete profile of the variable pitch cylindrical cam. The results of this work are instrumental in computer-aided manufacturing of variable pitch cylindrical cams for industrial applications.
The Design of High-Speed Dwell-Rise-Dwell Cams Using Linear Quadratic Optimal Control Theory
Authors: Fabien B. C. , Longman R. W. , Freudenstein F.
Published: June 2008

This paper uses linear quadratic optimal control theory to design high-speed Dwell-Rise-Dwell (D-R-D) cams. Three approaches to D-R-D cam design are compared. In the first approach the cam is designed to be optimal at a fixed operating speed, i.e., a tuned cam design is obtained. In the second approach the cam profile is determined by minimizing a sum of quadratic cost functions over a range of discrete speeds, thus producing a cam-follower system which is optimal over a range of speeds. The third technique uses trajectory sensitivity minimization to design a cam which is insensitive to speed variations. All design methods are formulated as linear quadratic optimal control problems and solved using an efficient numerical procedure. It is shown that the design techniques developed can lead to cams that have significantly lower peak contact stress, contact force and energy loss when compared to a polydyne cam design. Furthermore, the trajectory sensitivity minimization approach is shown to yield cams that have lower residual vibration, over a range of speeds, when compared to a polydyne cam design.
On the Finite Screw System of the Third Order Associated with a Revolute-Revolute Chain
Authors: Huang C.
Published: June 2008

The finite displacements of the outermost body of a revolute-revolute chain are investigated. All possible screws of the finite twists of the outermost body of an R-R chain are shown to form a screw system of the third order. The analytic expression of the screw system is given. The finite screw systems of special structures of an R-R chain as well as the degenerate forms of the finite 3-system in infinitesimal kinematics and in displacing two points of a body are also discussed.
Application of the Weighted Least Squares Parameter Estimation Method to the Robot Calibration
Authors: Zak G. , Benhabib B. , Fenton R. G. , Saban I.
Published: June 2008

Significant attention has been paid recently to the topic of robot calibration. To improve the robot’s accuracy, various approaches to the measurement of the robot’s position and orientation (pose) and correction of its kinematic model have been proposed. Little attention, however, has been given to the method of estimation of the kinematic parameters from the measurement data. Typically, a least-squares solution method is used to estimate the corrections to the parameters of the model. In this paper, a method of kinematic parameter estimation is proposed where a standard least-squares estimation procedure is replaced by weighted least-squares. The weighting factors are calculated based on all the a priori available statistical information about the robot and the pose-measuring system. By giving greater weight to the measurements made where the standard deviation of the noise in the data is expected to be lower, a significant reduction in the error of the kinematic parameter estimates is made possible. The improvement in the calibration results was verified using a calibration simulation algorithm.
Kinematics, Workspace, and Design of a Dual-Arm Spatial Robot in Zero Gravity
Authors: Agrawal Sunil Kumar , Garimella R.
Published: June 2008

In the current literature on space robotics, an important idea that is overlooked is that the features of a space robot system need not be the same as those designed for use on earth. The differences arise due to conservation of linear and angular momentum applicable to free-floating manipulators. The objectives of this paper are: (1) to build a kinematic model of a robot system operating in space with two human-like arms, (2) to develop algorithms for determining inverse solutions and workspace, and (3) to provide guidelines for design of multi-arm robot systems for space applications. We show from these studies that inertial parameters such as link masses play an important role in determining the inverse solutions and workspace boundaries.
A Class of Parallel Manipulators Based on Kinematically Simple Branches
Authors: Podhorodeski R. P. , Pittens K. H.
Published: June 2008

Parallel manipulators consisting of serial branches acting in parallel on a common end effector are examined. All nonredundant, six DOF manipulators corresponding to this in-parallel class of structures are enumerated. A specific in-parallel structure, three branches with two actuated joints per branch (3–2,2,2), is chosen as most promising based upon performance considerations. A class of kimematically simple (KS) serial-chain branch joint layouts suitable for the chosen in-parallel structure is defined. Arguments based upon kinematic equivalency of the branches and mobility of the assembled in-parallel manipulator chain are used to show that there exist only five unique branch joint-layouts belonging to the KS class. It is demonstrated that the solution to the inverse displacement problem for in-parallel manipulators based on the KS branches can be expressed in a closed form. Furthermore, the 3–2,2,2 in-parallel manipulators are shown to belong to a family of manipulators whose forward displacement solutions can be resolved through roots of a 16th order polynomial.
Optimization of Planar, Spherical and Spatial Function Generators Using Input-Output Curve Planning
Authors: Liu Zheng , Angeles J.
Published: June 2008

A general scheme for the optimization of planar, spherical and spatial bimodal linkages for function generation is proposed. The problem is solved here following two basic steps: (i) planning input-output ((I/O) curves based on design requirements and selecting data from the planned curve; and (ii) setting up an optimization procedure to minimize a performance index.
On the Rotatability of Spherical N-Bar Chains
Authors: Liu Yung-Way , Ting Kwun-Lon
Published: June 2008

This paper established the spherical counterparts of Ting’s rotatability laws of planar linkages. Generally speaking, similar rotatability properties exist between a pair of adjoining links in planar and spherical linkages and the concept of invariant link rotatability is valid for spherical linkage only if it is referred to that between adjoining links. The established spherical rotatability criteria are also valid for single and multiple degree of freedom nR3C, nR2C1P, nR1C2P and nR3P spatial linkages.
Position Kinematics of a Three-Limbed Mixed Mechanism
Authors: Husain M. , Waldron K. J.
Published: June 2008

Although robotics has traditionally focused on the serial chain structures typical of industrial robots, fully parallel structures such as the Stewart Platform have also found considerable industrial use. Actively coordinated mechanisms which have combinations of serial and parallel characteristics have been practically employed, and can be expected to become more important in the future. There has been very little study of the kinematic and static characteristics of these mechanisms which have combinations of the characteristics of fully serial and fully parallel structures. This work addresses the direct and inverse position kinematics of such a hybrid mechanism with combination of serial and parallel structure which has multiple, actively controlled actuators. While not the most general possible configuration, this particular case does include many important features of the general mechanism, and the solution obtained gives useful insight for developing a general theory of forward and inverse kinematics which will be equally applicable to serial, parallel and combination structures. Such a theory is necessary for rational design of hardware and software for such systems.
Kinematic Analysis and Synthesis of Three-Input, Eight-Bar Mechanisms Driven by Relatively Small Cranks
Authors: Farhang K. , Basu P. S.
Published: June 2008

Approximate kinematic equations are developed for the analysis and design of three-input, eight-bar mechanisms driven by relatively small cranks. Application of a method in which an output link is presumed to comprise a mean and a perturbational motion, along with the vector loop approach, facilitates derivation of the approximate kinematic equations. The resulting constraint equations are, (i) in the form of a set of four nonlinear equations relating the mean link orientations, and (ii) a set of four linear equations in the unknown perturbations (output link motions). The latter set of equations is solved, symbolically, to obtain the output link motions. The approximate equations are shown to be effective in the synthesis of three-input, small-crank mechanisms.
Synthesis of Single-Input and Multiple-Output Port Mechanisms with Springs for Specified Energy Absorption
Authors: Jenuwine J. G. , Midha A.
Published: June 2008

A means of synthesis of single-input and multiple-output port mechanisms for specified energy absorption is formulated for multiple precision points. The synthesis presented makes use of an extension of the loop closure method which includes expressions for energy absorption by linear spring elements. The configuration considered locates spring elements at two output ports of a multi-loop, planar mechanism. Economies realized for the symmetric mechanism are discussed for both one- and two-plane symmetry. Synthesis examples are included for both the general and symmetric mechanism. Special applications presented include synthesis of a constant force mechanism and synthesis of a mechanism suited to the energy absorption requirements of an automotive crashworthiness system.
Concurrent Mechanism and Control Design for the Slewing of Flexible Space Structures
Authors: Yang Li-Farn , Chew Meng-Sang , Juang Jer-Nan
Published: June 2008

An integrated single-step design approach to the synthesis of a mechanical device and an active controller is presented for slew maneuvers of flexible space structures. A mechanical device consists of a noncircular gear pair that acts as a varying gear ratio transmission between an electro-mechanical actuator and a flexible structure. Such a system has been introduced as an analytical application in minimizing flexural vibrations in the slewing maneuver of flexible space structures such as large solar panels and satellites in space. Only a simple regulator-type feedback controller is called for to control this complex electro-mechanical-and-structural system and the purpose is to design this complex system in an integrated procedure to achieve low flexural vibrations of the structure. Numerical simulations of the slewing control tasks for a planar articulated double-beam structure are presented.
Application of Composite Plate Theory and the Finite Element Method to the Dynamics and Stress Analysis of Spatial Flexible Mechanical Systems
Authors: Kremer J. M. , Shabana A. A. , Widera G. E. O.
Published: June 2008

This investigation concerns itself with the dynamic and stress analysis of thin, laminated composite plates consisting of layers of orthotropic laminae. It is assumed that the bonds between the laminae are infinitesimally thin and shear nondeformable. The finite element formulation presented is sufficiently general to accept an arbitrary number of layers and an arbitrary number of orthotropic material property sets. In the dynamic formulation presented, the laminae is assumed to undergo large arbitrary rigid body displacements and small elastic deformations. The nodal shape functions of the laminae are assumed to have rigid body modes that need to describe only large rigid body translations. Using the expressions for the kinetic and strain energies, the lamina mass and stiffness matrices are identified. The nonlinear mass matrix of the lamina is expressed in terms of a set of invariants that depend on the assumed displacement field. By summing the laminae kinetic and strain energies, the body mass and stiffness matrices are identified. It is shown that the body invariants can be expressed explicitly in terms of the invariants of its laminae. Numerical examples of a spatial RSSR mechanism are presented in order to demonstrate the use of the present formulation.
Backlash Control via Redundant Drives: An Experimental Verification
Authors: Tsai Lung-Wen , Chang Sun-Lai
Published: June 2008

In this paper, the concept of using redundant unidirectional drives for the control of gear backlash is demonstrated with a two-DOF (Degree-Of-Freedom) prototype manipulator. Two experiments, one with redundant drives and the other without redundant drives, were conducted to establish a proof of the concept. The experimental results demonstrated that the concept can improve the repeatability of a manipulator by an order of magnitude.
General Algorithm for Automatic Generation of the Workspace for n-link Planar Redundant Manipulators
Authors: Kwon Sang-Joo , Youm Youngil , Chung Wan Kyun
Published: June 2008

An efficient algorithm to simulate the workspace for a n-link redundant manipulator with rotating base is developed. The unique feature of the algorithm is its ability to automatically generate the binary angle selection code for the given manipulator. This code system makes it possible to avoid repetitions in calculating positions and plotting arcs for the workspace and thus saves considerable computing and graphic time. Two types of workspace are possible using this algorithm. Numerical examples including the workspace of human arm motion and that of a 20-link system are demonstrated to illustrate the effectiveness of the algorithm.
Genetic Algorithms as an Approach to Configuration and Topology Design
Authors: Chapman C. D. , Saitou K. , Jakiela M. J.
Published: June 2008

The genetic algorithm, a search and optimization technique based on the theory of natural selection, is applied to problems of structural topology design. An overview of the genetic algorithm will first describe the genetics-based representations and operators used in a typical genetic algorithm search. Then, a review of previous research in structural optimization is provided. A discretized design representation, and methods for mapping genetic algorithm “chromosomes” into this representation, is then detailed. Several examples of genetic algorithm-based structural topology optimization are provided: we address the optimization of cantilevered plate topologies, and we investigate methods for optimizing finely-discretized design domains. The genetic algorithm’s ability to find families of highly-fit designs is also examined. Finally, a description of potential future work in genetic algorithm-based structural topology optimization is offered.
Application of the Monomial Method to Shape Optimization
Authors: Burns S. A.
Published: June 2008

The monomial method is an alternative to Newton’s method for solving systems of nonlinear algebraic equations. It possesses several properties not shared by Newton’s method that enhance performance, yet does not require substantial computational effort beyond that required for Newton’s method. Previous work has demonstrated that the monomial method treats problems in structural design very effectively. This paper combines the monomial method with the method of generalized geometric programming to treat the problem of structural shape optimization of continuum structures modeled by finite elements.
Robust Optimal Design for Worst-Case Tolerances
Authors: Emch G. , Parkinson A.
Published: June 2008

Engineering models can and should be used to understand the effects of variability on a design. When variability is ignored, brittle designs can result that will not function properly or that will fail in service. By contrast, robust designs function properly even when subjected to off-nominal conditions. There is a need for better analytical tools to help engineers develop robust designs. In this paper we present a new approach for developing designs that are robust to variability induced by worst-case tolerances. An advantage of this approach is that tolerances may be placed on any or all model inputs, whether design variables or parameters. The method adapts nonlinear programming techniques in order to determine how a design should be modified to account for variability. We tested the method under relatively severe conditions on 13 problems, with excellent results. Using this approach, a designer can account for the effects of worst-case tolerances, making it possible to build robustness into an engineering design.
Hybrid Approach to Plant Layout Design Using Constraint-Directed Search and an Optimization Technique
Authors: Fujita K. , Akagi S. , Nakatogawa T.
Published: June 2008

A hybrid type approach to plant layout design is presented using a constraint-directed search procedure and a mathematical optimization technique. In layout design, a plant must be arranged to satisfy spatial constraints imposed by its components. In our approach the whole space of a plant building is divided into the finite compartments with a modular size in order to separate the description of the layout into the combinatorial part and the sizing part. The approach consists of two steps. In the first step, a constraint-directed search procedure is applied to find a combinatorial solution among plant components so as to satisfy the spatial layout conditions. In the second step, an optimization technique is applied to determine the actual dimensions of components so as to minimize a measure of an overall size of a plant building considering size of components. The approach is implemented with an object-oriented programming environment and the system can automatically produce a layout from the declarative representation of layout conditions. Finally, the approach has been applied to the design of a nuclear power plant in order to check its validity and effectiveness.
Blending and Joining Using Cyclides
Authors: Srinivas Y. L. , Dutta D.
Published: June 2008

We consider the use of Dupin cyclides in geometric modeling. These are algebraic surfaces of degree four with interesting properties such as rational parametric forms and closure under offsets. We have been focusing on methods for expanding the geometric coverage of solid modelers, and the cyclide as a new primitive offers promise. In this paper, we briefly describe the cyclide and discuss in details two applications. The first is the modeling of blending surfaces, an important problem in geometric modeling. We outline methods to use various forms of the cyclide in variable-radius blending. Next, we consider the problem of automatic joining of pipes, and describe a general method rooted in the definition of a cyclide for its solution. Implemented examples are provided for both applications.
Geometric Design and Fabrication of Developable Bezier and B-spline Surfaces
Authors: Bodduluri R. M. C. , Ravani B.
Published: June 2008

In this paper we study Computer Aided Geometric Design (CAGD) and Manufacturing (CAM) of developable surfaces. We develop a direct representation of developable surfaces in terms of plane geometry. It uses control planes to determine a surface which is a Bezier or a B-spline interpolation of the control planes. In the Bezier case, a de Casteljau type construction method is presented for geometric design of developable Bezier surfaces. In the B-spline case, de Boor type construction for the geometric design of the developable surface and Boehm type knot insertion algorithm are presented. In the area of manufacturing or fabrication of developable surfaces, we present simple methods for both development of a surface into a plane and bending of a flat plane into a desired developable surface. The approach presented uses plane and line geometries and eliminates the need for solving differential equations of Riccatti type used in previous methods. The results are illustrated using an example generated by a CAD/CAM system implemented based on the theory presented.
Automatic Finite Element Mesh Generation Over Intersecting Rigid Body-Movable Subdomains for the Automation of Parametric Conceptual Design
Authors: Yang H. , Hoeltzel D. A.
Published: June 2008

An approach for the automatic generation and refinement of three-dimensional finite element meshes subdivided by multiply connected, rigid body movable subdomains has been developed. A combination of computational geometry and geometric modeling techniques have been employed to implement parametric computer-aided design based on the finite element method. Nonconvexity of an overall three-dimensional domain has been handled by combining convex geometric primitives as subdomains for the construction of a three-dimensional domain. A clipping technique is employed for determining intersection points between subdomains bounded by traingulated surface, following their rigid body movements. To demonstrate the utility of this approach to parametric redesign, a series of meshes that model a hip joint prosthesis and a reciprocating internal combustion engine, as assemblies of parametrically-defined geometric primitives, has been developed.
Geometric Elimination of Constraint Violations in Numerical Simulation of Lagrangian Equations
Authors: Yoon S. , Howe R. M. , Greenwood D. T.
Published: June 2008

Conventional holonomic or nonholonomic constraints are defined as geometric constraints. The total enregy of a dynamic system can be treated as a constrained quantity for the purpose of accurate numerical simulation. In the simulation of Lagrangian equations of motion with constraint equations, the Geometric Elimination Method turns out to be more effective in controlling constraint violations than any conventional methods, including Baumgarte’s Constraint Violation Stabilization Method (CVSM). At each step, this method first goes through the numerical integration process without correction to obtain updated values of the state variables. These values are then used in a gradient-based procedure to eliminate the geometric and energy errors simultaneously before processing to the next step. For small step size, this procedure is stable and very accurate.
Experimental Compliance Breakdown of Industrial Robots
Authors: Demeester F. , Van Brussel H.
Published: June 2008

An engineering tool is described, enabling a static compliance breakdown of a machine (with fixed or varying geometry) from a modal analysis performed at a quasi-static frequency. The most interesting feature of the method is that the compliances of the constitutive machine components can be determined independent from the instantaneous configuration of the machine. Real-life test results on a fixed-configuration beamlike structure and on a variable-configuration industrial robot show the accuracy and the power of the method but also reveal some stringent requirements for the motion sensors needed. Some new results on the need for correction of the influence of gravity on the accelerometer signals at low frequencies are also included.
Computation of Spatial Displacements from Redundant Geometric Features
Authors: Ge Q. J. , Ravani B.
Published: June 2008

This paper follows a previous one on the computation of spatial displacements (Ravani and Ge, 1993). The first paper dealt with the problem of computing spatial displacements from a minimum number of simple features of points, lines, planes, and their combinations. The present paper deals with the same problem using a redundant set of the simple geometric features. The problem for redundant information is formulated as a least squares problem which includes all simple features. A Clifford algebra is used to unify the handling of various feature information. An algorithm for determining the best orientation is developed which involves finding the eigenvector associated with the least eigenvalue of a 4 × 4 symmetric matrix. The best translation is found to be a rational cubic function of the best orientation. Special cases are discussed which yield the best orientation in closed form. In addition, simple algorithms are provided for automatic generation of body-fixed coordinate frames from various feature information. The results have applications in robot and world model calibration for off-line programming and computer vision.
Design and Fabrication of Microelectromechanical Systems
Authors: Kota S. , Ananthasuresh G. K. , Crary S. B. , Wise K. D.
Published: June 2008

An attempt has been made to summarize some of the important developments in the emerging technology of microelectromechanical systems (MEMS) from the mechanical engineering perspective. In the micro domain, design and fabrication issues are very much different from those of the macro world. The reason for this is twofold. First, the limitations of the micromachining techniques give way to new exigencies that are nonexistent in the macromachinery. One such difficulty is the virtual loss of the third dimension, since most of the microstructures are fabricated by integrated circuit based micromachining techniques that are predominantly planar. Second, the batch-produced micro structures that require no further assembly, offer significant economical advantage over their macro counterparts. Furthermore, electronic circuits and sensors can be integrated with micromechanical structures. In order to best utilize these features, it becomes necessary to establish new concepts for the design of MEMS. Alternate physical forms of the conventional joints are considered to improve the manufacturability of micromechanisms and the idea of using compliant mechanisms for micromechanical applications is put forth. The paper also reviews some of the fabrication techniques and the micromechanical devices that have already been made. In particular, it discusses the fabrication of a motor-driven four-bar linkage using the “boron-doped bulk-silicon dissolved-wafer process” developed at The University of Michigan’s Center for Integrated Sensors and Circuits.