bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Structural Control with Discretely Attached Induced Strain Actuators
Authors: Chaudhry Z. , Rogers C. A.
Published: June 2008

A new configuration where induced strain actuators such as piezoelectric ceramic patches or shape memory alloys are attached to a structure at discrete points (as opposed to being bonded) is presented. This paper specifically addresses discretely attached induced strain actuators like piezoceramic and electrostrictive actuators which are available in the form of plates or patches, and includes actuator flexural stiffness considerations. When activated, such actuators deform along with the structure (like bonded actuators), but in this case the actuator and the structure are free to deform independently. In such a scenario, the in-plane force of the actuator results in an additional moment on the structure and enhanced structural control. Also because now the actuator can be offset from the structure without an increase in the basic flexural stiffness of the structure, the actuator offset distance can be optimized to maximize actuator authority. Enhanced control is demonstrated by comparing the static response of a discretely attached actuator/beam system with its bonded counterpart system. Through a proper choice of the offset distance, the flexural control authority measured in terms of the moment applied to the substrate structure can be increased considerably for stiff and thick substrates. The advantage of this configuration over the bonded configuration is also verified experimentally. The limitations and considerations for the implementation of the concept in realistic structures are also discussed.
A Prototype of Feature-Based Design for Assembly
Authors: De Fazio T. L. , Edsall A. C. , Gustavson R. E. , Hernandez J. , Hutchins P. M. , Leung H.-W. , Luby S. C. , Metzinger R. W. , Nevins J. L. , Tung K. , Whitney D. E.
Published: June 2008

This paper describes a prototype software system that implements a form of feature-based design for assembly. It is not an automated design system but instead a decision and design aid for designers interested in concurrent design. Feature-based design captures design intent (assembly topology, product function, manufacturing, or filed use) while creating part and product geometry. Design for assembly as used here extends existing ideas about critiquing part shapes and part count to include assembly process planning, assembly sequence generation, assembly fixturing assessments, and assembly process costs. This work was primarily interested in identifying the information important to DFA tasks, and how that information could be captured using feature-based design. It was not intended to extend the state of the art in feature-based geometry creation, but rather to explore the uses of the information that can be captured. The prototype system has been programmed in LISP on Sun workstations. Its research contributions comprise integration of feature-based design with several existing and new assembly analysis and synthesis algorithms; construction of feature properties to meet the needs of those algorithms; a carefully chosen division of labor between designer and computer; and illustration of feature-based models of products as the information source for assembly analysis and process design. Some of its functions have been implemented approximately or partially but they give the flavor of the benefits to be expected from a fully functional system.
Feature Extraction for Casting Core Development
Authors: Ganter M. A. , Skoglund P. A.
Published: June 2008

Feature extraction techniques are presented for the generation of casting core patterns from a boundary representation (B-Rep) solid model. Techniques are presented which would allow for automatic extraction of three classes of core features (internal voids, single and multi-surface holes, and boundary perturbations). The task of extracting casting cores from solid models involves recognizing a collection of entities (i.e., slots, bosses, undercut surfaces, local and global concavities, etc.) from the set of lower level entities (i.e., the B-Rep structure). To this end, a combination of solid modeling B-Rep and graph structures and their associated methods will be used for casting core development. Appropriate local features are identified and extracted from the original object, and are grouped into one or more new object(s) (termed a core-object). If the core-object is multiply connected (i.e., composed of multiple objects), it is graph separated into global feature objects. Each of these global feature objects represents a core in the final pattern. Lastly, the geometry of the original part is augmented to add core prints where core geometries were extracted. The core print, as currently developed, combines the extracted core geometry and its convex hull.
Automatic Generation of Tolerance Chains from Mating Relations Represented in Assembly Models
Authors: Wang N. , Ozsoy T. M.
Published: June 2008

This paper presents an algorithm for generating tolerance chains from the mating relations between components of assemblies. The algorithm is developed upon a feature-based assembly modeling strategy that represents each component in close relation to its mating features, dimensions, and tolerances. The mating relations within an assembly are described by a mating graph. Tolerance chains together with their dimensions and tolerances are generated automatically by searching through a mating graph for matching mating features. A prototype program package based on the presented algorithm has been developed, and several examples of various complexity have been tested with success.
Topological and Geometric Consistency in Boundary Representations of Solid Models of Mechanical Components
Authors: Jablokow A. G. , Uicker J. J. , Turcic D. A.
Published: June 2008

This paper describes a method of verifying the consistency (i.e., agreement) between the topology and geometry of boundary representation (B-rep) solid models of mechanical components. This verification is well-suited for implementation as an algorithm and has been implemented as such in a polyhedral boundary representation solid modeling system (Jablokow, 1989). This technique and algorithm is important in the design of mechanical components for design documentation, integration with analysis and manufacturing applications, and design data exchange between solid modeling systems. Information regarding boundary representations has typically divided into the geometry and topology. It is important that the two are consistent for a valid solid model. In this work the genus of a solid model of an object is calculated topologically and geometrically and then compared to verify the consistency of the solid model. The genus of an object gives insight as to the geometric complexity of the object. This is equivalent to verifying the Gauss-Bonnet Theorem for the model, and is discussed in the paper.
Global Optimization Using the Multistart Method
Authors: Jain P. , Agogino A. M.
Published: June 2008

Multistart is a stochastic global optimization method for finding the global optimum of highly nonlinear mechanical problems. In this paper we introduce and develop a variant of the multistart method in which a fraction of the sample points in the feasible region with smallest function value are clustered using the Vector Quantization technique. The theories of lattices and sphere packing are used to define optimal lattices. These lattices are optimal with respect to quantization error and are used as code points for vector quantization. The implementation of these ideas has resulted in the VQ-multistart algorithm for finding the global optimum with substantial reductions in both the incore memory requirements and the computation time. We solve several mathematical test problems and a mechanical optimal design problem using the VQ-multistart algorithm.
A Boolean Local Improvement Method for General Discrete Optimization Problems
Authors: Lu Peng , Siddall J. N.
Published: June 2008

The paper proposes a new approach to solving the discrete design optimization problem by combining Boolean logic methods with conventional nonlinear optimization. A continuous variable optimum is first found, and then the Boolean method searches the local region for the discrete variable optimum.
A Multiobjective Optimization Strategy with Priority Ranking of the Design Objectives
Authors: Matsumoto M. , Abe J. , Yoshimura M.
Published: June 2008

Generally, two types of priorities are considered among multiple objectives in the design of machine structures. One of these objectives is named the “hard objective” and is the absolutely indispensable design requirement while the other is called “soft objective” and has a lower priority order. This paper proposes a multiobjective structural optimization strategy with priority ranking of the design objectives. Further, this strategy is demonstrated on the actual example of a motorcycle frame structural design which has three design objectives: (1) an increase in static torsional rigidity, (2) a reduction of dynamic response level, and (3) a decrease in the weight of the motorcycle frame.
Optimal Design of the Path of Chain Link Systems
Authors: Peng J.-P. , Carpino M.
Published: June 2008

A general method for the design of the optimal path for a constant velocity chain system is presented. Both the dynamic effects and the kinematic effects of finite sized links have been incorporated into a dynamic model for arbitrary chain paths. A direct perturbation solution is developed for small amplitude oscillations. This model is then used to optimize chain paths for minimum position error and speed variation. An example of an optimized chain path for an oval configuration operating at low speed is presented.
Synthesis and Steady State Analysis of High-Speed Elastic Cam-Actuated Linkages by a Finite Element Method
Authors: Liu Hsin-Ting J. , Flugrad D. R.
Published: June 2008

A cam driving a lumped inertia through an elastic slider-crank follower linkage with a curved beam coupler is considered. An iterative procedure utilizing the finite element method developed by Midha et al. (1978) is used to synthesize the cam profile to produce a desired output motion at a given design speed and damping coefficient. Nonlinear terms are neglected producing inhomogeneous, periodic, linear, ordinary differential equations. Responses of the synthesized linkages are simulated and found to be satisfactory at the design conditions.
Dynamic Modeling and Stability Analysis of Mechanical Systems with Time-Varying Topologies
Authors: Wang Yu
Published: June 2008

A model is developed for analyzing mechanical systems with a pair of bodies with topological changes in their kinematic constraints. It is built upon the concept of a Poincare´ map rather than following the traditional methods of differential equations. The model provides a set of well-defined and naturally-discrete equations of motion and is capable of giving physical insights of dynamic characteristics of deadbeat convergence of multiple collisions and periodic or chaotic responses. The development of a dynamic model and a local stability analysis are presented.
Global Analysis and Simulation of Mechanical Systems with Time-Varying Topologies
Authors: Wang Yu
Published: June 2008

We apply the discrete time model of a mechanical system with time-varying topologies to determine its regions of stability. The backward mapping method is applied and the associated numerical properties are discussed. The model is combined with conventional numerical techniques to form a computer simulation system which is more reliable and accurate in handling the topological changes. The simulation results of an example system are presented.
Differentiation of Mass and Stiffness Matrices for High Order Sensitivity Calculations in Finite Element-Based Equilibrium Problems
Authors: Bernard J. E. , Kwon S. K. , Wilson J. A.
Published: June 2008

Extension of sensitivity methods to include higher order terms depends on the ability to compute higher order derivatives of the mass and stiffness matrices. This paper presents a method based on the use of cubic polynomials to fit mass and stiffness matrices across a range of interest of the design variable. The method is illustrated through an example which uses Pade´ approximants to expand the solution to a statics problem. The design variable is the thickness of one part of a plate with fixed boundaries. The solution gives a very good approximation over fivefold change in the value of the design variable.
Multibody Dynamics: A Formulation Using Kane’s Method and Dual Vectors
Authors: Agrawal S. K.
Published: June 2008

This paper proposes a formulation based on Kane’s method to form the dynamic equations of motion of multibody systems using dual vectors. Both holonomic and nonholonomic systems are considered in this formulation. An example of a holonomic and a nonholonomic system is worked out in detail using this formulation. This algorithm is shown to be advantageous for a class of holonomic systems which has cylindrical joints.
Modeling the Spatial Dynamics of Robotic Manipulators with Flexible Links and Joint Clearances
Authors: Kakizaki T. , Deck J. F. , Dubowsky S.
Published: June 2008

A dynamic modeling method is presented for spatial elastic manipulators that can account for a number of their realistic properties, including bearing clearances, actuator dynamics, and control system characteristics. Forces in the bearing clearances are modeled by nonlinear functions of the links’ relative motions and the internal geometry of the connection, or by experimentally measured properties. A detailed model is given for a revolute connection with radial and axial clearances. Results obtained for a SCARA manipulator show that the combined dynamic effects of bearing clearances, link elasticity, and control system characteristics can significantly degrade the system’s performance.
The Design, Experimentation, and Simulation of a Novel Coulomb Friction Device for Automotive Valve Spring Damping
Authors: Sefler J. F. , Pisano A. P.
Published: June 2008

This investigation contains experimental and computer modeling results of an alternative method for damping automotive valve springs, in which a nondestructive elastomeric sleeve that slides over the spring with an interference fit is used to provide coulomb damping on the outside of the valve spring coils. The damper and valve spring dynamics are modeled using the wave equation with a damping term composed of both viscous and coulomb components. Although the damper is very simple and inexpensive, the reduction in residual spring vibrations are shown to be significant without loss of valve spring performance. Experimental data taken from a 1983 Pontiac family-II, 1.8 liter, four cylinder, single overhead cam engine equipped both with and without the new elastomeric dampers is used to verify the results of the computer simulation and demonstrate the effectiveness of the damper.
Torque Resolver Design for Tendon-Driven Manipulators
Authors: Lee Jyh-Jone , Tsai Lung-Wen
Published: June 2008

Given a set of desired joint torques in an n-DOF tendon-driven manipulator with n + 1 control tendons, the determination of tendon forces is an indeterminate problem. Usually, the pseudo-inverse technique is used to solve for such a problem. In this paper, rather than using the pseudo-inverse technique, an efficient methodology for transforming joint torques (n elements) to motor torques (n + 1 elements) has been developed. This technique, called “torque resolver,” utilizes two circuit-like operators to transform torques between the two different vector spaces. It can be easily programmed on a digital computer or implemented into an analog-circuit system. It is hoped that this technique will make real-time computed-torque control feasible. The technique has been demonstrated through the dynamic simulation of a three-DOF manipulator.
Kinematic Synthesis of Tendon-Driven Manipulators with Isotropic Transmission Characteristics
Authors: Ou Yeong-Jeong , Tsai Lung-Wen
Published: June 2008

This paper presents a methodology for kinematic synthesis of tendon-driven manipulators with isotropic transmission characteristics. The force transmission characteristics, from the end-effector space to the actuator space, has been investigated. It is shown that tendon forces required to act against externally applied forces are functions of the structure matrix, its null vector, and the manipulator Jacobian matrix. Design equations for synthesizing a manipulator to possess isotropic transmission characteristics are derived. It is shown that manipulators which possess isotropic transmission characteristics have much better force distribution among their tendons.
On a Relationship Between the Physical Features of Robotic Manipulators and the Kinematic Parameters Produced by Numerical Calibration
Authors: Goswami A. , Bosnik J. R.
Published: June 2008

Although kinematic parameter estimation is well-established as a technique for improving the positioning accuracy of a robotic manipulator, little attention has been given to the relationship between the parameters of a kinematic model and the corresponding physical features of a manipulator. If each kinematic parameter of a robot corresponds to one and only one of its independent physical features, then a change in the value of an optimal parameter would reflect a change in the corresponding physical feature. This knowledge is of potential value in isolating the sources of wear and damage in a manipulator, and, more generally, in predictive maintenance. In this work, the choice of kinematic model is shown to have a strong effect on the physical feature/kinematic parameter relationship. The most suitable kinematic model for preserving this relationship includes redundant parameters, which may interact numerically among themselves during the parameter estimation process and may complicate the interpretation of results. On the other hand, a kinematic model with no redundant parameters contains too few parameters to establish a comprehensive physical features/kinematic parameters relationship. Multiple-site pose measurement has been explored as a method of preserving the desired relationship even in the presence of redundant parameters.
Collision-Free Path Planning of Articulated Manipulators
Authors: Shiller Zvi , Gwo Yu-Rwei
Published: June 2008

A method is presented to efficiently compute a collision free path for manipulators with polyhedral links moving among polyhedral obstacles. The method is based on an analytical representation of the boundaries of configuration space obstacles (CSOB), obtained by modeling the contacts between manipulator links and obstacle as higher kinematic pairs. The contact conditions and manipulator kinematics are expressed in terms of homogeneous transformations, providing analytic relations between the joint angles and the contact variables. The set of joint angles associated with permissible contact variables forms the boundary of the CSOB. Using these analytical relations, the free space is efficiently divided into free-cells. Each contiguous set of free-cells is then represented by a connected graph that is of polynomial complexity in the number of geometric features of the obstacles and links. The shortest collision-free path on the graph is found using a best-first search. Examples are presented which demonstrate the method for a two link planar manipulator.
Trajectory Planning in Joint Space for Mechanical Manipulators
Authors: Tsai K. Y. , Kohli D. , Arnold J.
Published: June 2008

In this paper, we present a novel method of mapping the task space onto the joint space. This map divides the joint space into patches (disjointed regions) and an n ways accessible region in the task space is exactly covered by n patches. This mapping allows one to predict the task space paths corresponding to the joint space paths without solving inverse kinematics along the path. The map is then utilized for joint space planning. Numerical examples are presented for illustration.
Trajectory Planning in Task Space for General Manipulators
Authors: Tsai K. Y. , Kohli D.
Published: June 2008

This paper contains two new works, namely (i) general task space structure of any n d.o.f. manipulator, and (ii) general procedure of determining admissibility of paths in task space for general manipulators. Several examples are presented to illustrate the general theory.
Inverse Kinematics of General 6R and 5R,P Serial Manipulators
Authors: Kohli D. , Osvatic M.
Published: June 2008

In this paper we present a solution to the inverse kinematics problems for serial manipulators of general geometry. The method is presented in detail as it applies to a 6R manipulator of general geometry. The equations used are derived using power products and dialytic elimination. In doing this, all variables except one, a tangent half angle of a joint variable, can be eliminated. The result is a 16 by 16 matrix in which all terms are linear in the suppressed variable. The unique design of this matrix allows the suppressed variable to be solved as an eigenvalue problem. Substituting these values of the suppressed variable back into the equations, all other joint variables can be found using linear equations. The result is the 16 solutions expected for the 6R case. The same technique is also applicable to manipulators with prismatic joints. We present the solution technique for all six possible 5R,P manipulators through numerical examples. The primary distinction between the technique presented in this paper and the recently published Raghavan and Roth (1990) solution is that they removed two spurious imaginary roots of multiplicity four from a 24th order polynomial to obtain a 16th order polynomial for 6R and 5R,P cases. In our formulation, the 16th degree polynomial can be derived directly without having to remove any spurious imaginary roots. Another distinction is that the solution procedure can be reduced to an eigenvalue problem. This results in significant gains in computation time.
Forward Kinematics of the General 6–6 Fully Parallel Mechanism: An Exhaustive Numerical Approach Via a Mono-Dimensional-Search Algorithm
Authors: Innocenti C. , Parenti-Castelli V.
Published: June 2008

A new numerical method for the solution of the direct position analysis of the six d.o.f. fully parallel mechanism with general geometry, often referred to as generalized Stewart platform mechanism, is presented. The main feature of the method, making it attractive with respect to the methods available in the literature, is the ability to find out all the real solutions of the direct position analysis. The effectiveness of the new algorithm relies upon the solution of only one equation in one unknown. That equation is strictly representative of the problem, i.e., it is free from extraneous roots and every solution of the direct position analysis entails the existence of a root for the equation. A case study is reported.
Forward Kinematics of Nonpolyhedral Parallel Manipulators
Authors: Merlet Jean-Pierre
Published: June 2008

Forward kinematics has been studied for polyhedral parallel manipulators. We present here an algorithm for the forward kinematic of nonpolyhedral manipulators the plates of which have a symmetry axis. We show that there will be at most 352 possible solutions and exhibit a configuration with eight solutions.
Coordinate System Independent Form of Instantaneous Invariants in Spatial Kinematics
Authors: Lee C. , Yang A. T. , Ravani B.
Published: June 2008

This paper presents explicit equations for the instantaneous invariants of spatial kinematics that are coordinate systems independent. This eliminates the need for laborious coordinate transformations necessary in the determination of the canonical coordinate systems. It provides for a direct method for the calculation of instantaneous invariants based on information specifying the rigid body motion in any arbitrary task coordinate systems. Explicit equations are presented for instantaneous invariants up to the third order for spatial and spherical motions and up to the fourth order for planar motions. The results provide for a useful tool in design and analysis of mechanisms and motions based on instantaneous invariants. Examples are presented to illustrate the theory.
Kinematics of the Cycloidal Internal Combustion Engine Mechanism
Authors: Shih A. J.
Published: June 2008

The application of the characteristics of cycloidal curves for the four-stroke rotary internal combustion engine mechanism is introduced. The major components of the cycloidal engine mechanism include a flywheel, a stationary sun gear, planetary gears, rotary bars, and rotary pistons. The rotary pistons are fixed to bars driven by pins of the planetary gears, and these pins follow a common trajectory of epicyloidal or hypocycloidal curve. Several combustion chambers are created by the rotary pistons. As the flywheel makes a complete revolution, the relative motion between rotary pistons and the specially positioned intake ports, exhaust ports, and fuel injector generate four-stoke cycles within each of the combustion chambers. The constraint and classification of the application of different cycloidal curves for the rotary engine mechanism are then presented. Further, the mathematical modeling is developed. The position, velocity, and acceleration analyses of the rotary pistons of the cycloidal engine mechanisms are presented.
Analysis and Comparison of Epicycloidal and Hypocycloidal Internal Combustion Engine Mechanisms
Authors: Shih A. J.
Published: June 2008

The analysis and comparison of epicycloidal and hypocycloidal mechanisms for the rotary four-stroke internal combustion engine are presented. The mathematical modeling for velocity and acceleration analyses of rotary pistons, based on the continuity of contact between the bar and the pin on the planetary gear, is developed. Expressions for the compression ratio and the transmission angle of cycloidal engine mechanisms are also derived. Two cycloidal engine mechanisms, one epicycloidal and the other hypocycloidal, with the same gear ratio and range of flywheel angle for the four-stroke cycle are analyzed and compared. The detailed kinematic analysis results identify the similarities and differences of these two cycloidal engine mechanisms. Several interesting features are observed and discussed.
Optimum Synthesis of Coupler Curve and Uniform Rotary Motion Driven Multiloop Mechanisms Generating Complex Output Motions
Authors: Bagci C. , Burke D.
Published: June 2008

Article presents analytical optimum synthesis techniques to synthesize coupler curve driven multiloop mechanisms to generate programmed rotary and linear output motions driven by uniform rotary input motion. Error minimization technique minimizing errors in the loop-closure equations is used. Velocity, acceleration, and higher order derivative constraints can be introduced. Solution of design equations formed requires no iteration. Only four types of coupler curve driven six-bar second loop dyads (RPR, RRR, RPP, and RRP) are obtainable. More loops are added to form eight-bar or ten-bar mechanisms. Crank-rocker 4R four-bar mechanism generates the driver coupler curve. Optimum design process, and related software program for graphics interactive synthesis of multiloop mechanisms containing the aforementioned dyads are presented. Third loops forming eight-bar mechanisms to improve efficiency and enlarge strokes are also included. Application examples are given.
A Nondifferentiable Optimization Algorithm for Constrained Minimax Linkage Function Generation
Authors: Issac K. Kurien
Published: June 2008

This paper describes a nondifferentiable optimization (NDO) algorithm for solving constrained minimax linkage synthesis. Use of a proper characterization of minima makes the algorithm superior to the smooth optimization algorithms for minimax linkage synthesis and the concept of following the curved ravines of the objective function makes it very effective. The results obtained are superior to some of the reported solutions and demonstrate the algorithm’s ability to consistently arrive at actual minima from widely separated starting points. The results indicate that Chebyshev’s characterization is not a necessary condition for minimax linkages, while the characterization used in the algorithm is a proper necessary condition.
Five-Bar Path Generation Synthesis by Continuation Methods
Authors: Starns G. , Flugrad D. R.
Published: June 2008

This paper demonstrates the synthesis of a geared five-bar path generating mechanism using continuation methods. The gear ratio can be varied resulting in a solution set of geared five-bars passing through seven prescribed path positions. The development differs from past approaches in that convergence of the synthesis equations is not dependent on the choice of initial values and, furthermore, the method can be employed by a designer to select a geared-five-bar path generator with a wide range of possible gear ratios. Two examples demonstrate the method.
Minimization of Deviations of Gear Real Tooth Surfaces Determined by Coordinate Measurements
Authors: Litvin F. L. , Kuan C. , Wang J. C. , Handschuh R. F. , Masseth J. , Maruyama N.
Published: June 2008

The deviations of a gear’s real tooth surface from the theoretical surface are determined by coordinate measurements at the grid of the surface. A method has been developed to transform the deviations from Cartesian coordinates to those along the normal at the measurement locations. Equations are derived that relate the first order deviations with the adjustment to the manufacturing machine tool settings. The deviations of the entire surface are minimized. The minimization is achieved by application of the least-square method for an overdetermined system of linear equations. The proposed method is illustrated with a numerical example for hypoid gear and pinion.
Engineering Constraint Management Based on an Occurrence Matrix Approach
Authors: Agrawal R. , Kinzel G. L. , Srinivasan R. , Ishii K.
Published: June 2008

In many mechanical systems, the mathematical model can be characterized by m nonlinear equations in n unknowns. The m equations could be either equality constraints or active inequality constraints in a constrained optimization framework. In either case, the mathematical model consists of (n-m) degrees of freedom, and (n-m) unknowns must be specified before the system can be analyzed. In the past, designers have often fixed the set of (n-m) specification variables and computed the remaining n variables using the n equations. This paper presents constraint management algorithms that give the designer complete freedom in the choice of design specifications. An occurrence matrix is used to store relationships among design parameters and constraints, to identify dependencies among the variables, and to help prevent redundant specification. The interactive design of a torsion bar spring is used to illustrate constraint management concepts.
The Calculation of the Volumetric Properties of Sweep-Generated Solids Via Line Integration
Authors: Al-Daccak M. , Angeles J.
Published: June 2008

A key issue in the geometric and mechanical analyses of machine elements with complex shapes such as turbine blades and bevel gears is the accurate and economic computation of their volumetric properties, namely, volume, centroid coordinates, and inertia tensor. A method is proposed here for the computation of these properties that is applicable to sweep-generated solids based only on their 2D generating contour and their sweeping parameters. Thus, the direct 3D calculations of the volumetric properties of such solids are reduced to simple 2D calculations. Comparisons of numerical results are presented, which show that the volumetric properties of this class of solids can be effectively performed in a computationally reduced fashion which, additionally, enhances the accuracy of the computed values.
A New Analytical Approach for the Determination of the Transient Response in Elastic Mechanisms
Authors: Xu T. , Lowen G. G.
Published: June 2008

Recent work on multi-regime per cycle machinery has shown that for such systems the transient response of the link deflections, which is governed by the homogeneous solution to a Hill-type differential equation, cannot be neglected in a meaningful simulation. Based on mathematical work by E. T. Whittaker, a new analytical approach for obtaining such transient responses is given. It is achieved by the determination of the characteristic exponent in the stable regions of the Floquet solution to the Hill’s equation involved. This technique is applied to a specific elastic mechanism. Several sample computations show that the transient response may vary from near-periodic to totally aperiodic.
Integrated Strength and Manufacturing Process Design Using a Shape Optimization Approach
Authors: Grandhi R. V. , Modukuru S. C. , Malas J. C.
Published: June 2008

Intense competition in the manufacturing industry is forcing major changes in cost reduction in every step of the product development cycle starting from the design conception through production. One technique to reduce manufacturing cost is to employ simultaneous engineering between design and manufacturing using sensitivity analysis and iterative techniques. This integrated approach allows those decisions that significantly affect the product and process designs to be made more intelligently up-front. This paper considers a simultaneous design of product and manufacturing process. The product requirements include strength properties, whereas the manufacturing process goals include cost, quality, and microstructure to produce defect-free parts on a repeatable basis. The concept is demonstrated by designing a turbine disk manufactured using a forging process.
Systematic Construction of the Equations of Motion for Multibody Systems Containing Closed Kinematic Loops
Authors: Nikravesh P. E. , Gim Gwanghun
Published: June 2008

This papers presents a systematic method for deriving the minimum number of equations of motion for multibody system containing closed kinematic loops. A set of joint or natural coordinates is used to describe the configuration of the system. The constraint equations associated with the closed kinematic loops are found systematically in terms of the joint coordinates. These constraints and their corresponding elements are constructed from known block matrices representing different kinematic joints. The Jacobian matrix associated with these constraints is further used to find a velocity transformation matrix. The equations of motions are initially written in terms of the dependent joint coordinates using the Lagrange multiplier technique. Then the velocity transformation matrix is used to derive a minimum number of equations of motion in terms of a set of independent joint coordinates. An illustrative example and numerical results are presented, and the advantages and disadvantages of the method are discussed.
Tuning Parameters in Engineering Design
Authors: Otto K. N. , Antonsson E. K.
Published: June 2008

In the design and manufacture of mechanical devices, there are parameters whose values are determined by the manufacturing process in response to errors introduced in the devices’s manufacture or operating environment. Such parameters are termed tuning parameters, and are distinct from design parameters which the designer selects values for as a part of the design process. This paper introduces tuning parameters into the design methods of: optimization, Taguchi’s method, and the method of imprecision (Wood and Antonsson, 1989). The details of the mathematical formulation, along with a design example, are presented and discussed. Including tuning parameters in the design process can result in designs that are more tolerant of variational noise.
An Energy Efficient Quadruped with Two-Stage Equilibrator
Authors: Shin E. , Streit D. A.
Published: June 2008

A first consideration of the applications of mechanical equilibrators to legged locomotion is presented. Equilibrators are shown to eliminate “geometric work” while allowing simultaneous dual actuation of each leg joint of a quadruped. Gravitational forces on both the vehicle body and legs are decoupled from actuator force/torque requirements. In addition, for slow speeds and when leg kinetic energy is ignored, both joint actuator torques and joint actuator work approach zero. Dynamic simulation demonstrates that proper equilibrator design can reduce peak torque of leg actuators by more than 90 percent and offer a vehicle specific resistance 70 percent smaller than that of tracked vehicles.
The Trajectory Analysis of Bevel Planetary Gear Trains
Authors: Lin Chen-Chou , Tsai Lung-Wen
Published: June 2008

In this paper, the trajectory of bevel planetary gear trains has been studied. The parametric equations of trajectory are derived. It is shown that the trajectory generated by a tracer point on the planet of a bevel planetary gear train is analogous to that of a spur planetary gear train. Two cases, gear ratio equal to one and two, are presented in detail including the geometric description, plane of symmetry, extent of trajectory, number of nodes (cusps) and their locations. The criteria for the existence of cusps are verified algebraically, and interpreted from geometrical point of view.
Computer-Aided Design of High-Contact-Ratio Gears for Minimum Dynamic Load and Stress
Authors: Lin Hsiang Hsi , Lee Chinwai , Oswald F. B. , Townsend D. P.
Published: June 2008

This paper presents a numerical procedure for minimizing dynamic effects on high-contact-ratio gears by modification of the tooth profile. The paper examines and compares both linear and parabolic tooth profile modifications of high-contact-ratio gears under various loading conditions. The effects of the total amount of modification and the length of the modification zone were systematically studied at various loads and speeds to find the optimum profile design for minimizing the dynamic load and the tooth bending stress. Parabolic profile modification is preferred over linear profile modification for high-contact-ratio gears because of its lower sensitivity to manufacturing errors. For parabolic modification a greater amount of modification at the tooth tip and a longer modification zone are required. Design charts are presented for high-contact-ratio gears with various profile modifications operating under a range of loads. A procedure is illustrated for using the charts to find the optimum profile design.
Stress Analysis in Double Enveloping Worm Gears by Finite Element Method
Authors: Simon V.
Published: June 2008

A method and a corresponding computer program are developed for stress analysis in the worm and the gear of double enveloping worm gears by finite elements. By using this program stress distributions in the worm thread and the gear tooth are calculated, and the influence of the design parameters and of the load position on deflections and stresses is investigated. On the basis of the obtained results, by using regression analysis and interpolation functions, equations are derived for the calculation of deflections and stresses in the worm thread and in the gear tooth of double enveloping worm gears.
A Three-Dimensional Analysis of the Base Flexibility of Gear Teeth
Authors: Stegemiller M. E. , Houser D. R.
Published: June 2008

This paper presents the development of a simple model which computes the deflection of the base of wide face width gear teeth. The model was developed using the results of numerous finite element analyses of gear teeth and a nondimensional analysis of the results. Tooth end effects are considered through the application of the moment image method. The method is very simple and allows easy implementation in three-dimensional gear tooth deflection analysis schemes.
Solving Parametric Design Problems Requiring Configuration Choices
Authors: Ramaswamy R. , Ulrich K. , Kishi N. , Tomikashi M.
Published: June 2008

The solution of many design problems involves two steps: the designer (1) creates a configuration by making component choices and (2) selects values for the parameters associated with the components in that configuration. For example, in automobile design a configuration decision may be to use disk brakes and a single turbocharger. Consequently, the parametric values to be chosen include disk radius and turbo inlet area. Mathematical models used to represent such problems and to evaluate chosen alternatives are often large, nonlinear, and involve both discrete and continuous variables. Because no single design algorithm will usually suffice in solving such problems, currently available computer tools are typically limited to a small range of problems or to parts of large problems. We believe a computer environment that allows flexible access to a diverse set of tools can help designers rapidly generate high quality solutions to a broad range of problems. In this paper, we test this belief on a design problem taken from a commercial auto manufacturer. We propose a framework for dealing with the general class of problems, and we describe the implementation of a novel design system that integrates math programming with knowledge-based and graph theoretic tools.
Quantitative Inference in a Mechanical Design ‘Compiler’
Authors: Ward A. C. , Seering W. P.
Published: June 2008

This paper presents the ideas underlying a computer program that takes as input a schematic of a mechanical or hydraulic power transmission system, plus specifications and a utility function, and returns catalog numbers from predefined catalogs for the optimal selection of components implementing the design. Unlike programs for designing single components or systems, this program provides the designer with a high level “language” in which to compose new designs. It then performs some of the detailed design process for him. The process of “compilation,” or transformation from a high to a low level description, is based on a formalization of quantitative inferences about hierarchically organized sets of artifacts and operating conditions. This allows design compilation without the exhaustive enumeration of alternatives. The paper introduces the formalism, illustrating its use with examples. It then outlines some differences from previous work, and summarizes early tests and conclusions.
Bolted Joints Under Tensile Service Loads: The Effect of Torsion in the Bolt on In-Service Clamping Loads
Authors: Newnham J. , Curley L.
Published: June 2008

In order to determine how bolted joints behave under conditions of tensile external loading, tests were conducted on bolts which had been tightened into joints by means of (a) elastic range, (b) yield, and (c) over-yielding tightening. The loading tests showed that the maximum clamp load which the bolt would exert on the joint without permanent extension was the uniaxial tensile yield load of the bolt. This was observed even when torsional stress was present in the as-tightened bolt, and for all three tightening methods.
Theoretical and Experimental Study of the Stress Concentration Factor in Diesel Engine Crankshafts
Authors: Guagliano M. , Terranova A. , Vergani L.
Published: June 2008

The paper deals with the bending stress concentration evaluation of a marine diesel engine crankshaft. Experimental strain gauge tests were conducted on a full scale single crank to measure the stress concentration near the crank fillet. A three-dimensional finite element schematization of the crankshaft and the linear elastic calculations conducted show the stress field along the most overstressed zone and how it is influenced by different load conditions. It is now possible to calculate accurately the stress concentration factor Kt. However, a mesh of a mechanical element with a complex geometry like crankshaft is very expensive and difficult. Therefore a bidimensional model of the crankshaft has been also considered: experimental tests and numerical analyses under different load conditions were also carried out in this case. The agreement between the results obtained from these different kinds of analyses is good. The values of the stress concentration factors obtained from bidimensional and three-dimensional analysis with the same boundary and load conditions are similar. A plane model of crankshaft can be utilized to determine the theoretical stress concentration factor Kt with considerable saving of calculation time.
Extensions to the Taguchi Method of Product Design
Authors: Otto K. N. , Antonsson E. K.
Published: June 2008

The Taguchi method of product design is an experimental approximation to minimizing the expected value of target variance for certain classes of problems. Taguchi’s method is extended to designs which involve variables each of which has a range of values all of which must be satisfied (necessity), and designs which involve variables each of which has a range of values any of which might be used (possibility). Tuning parameters, as a part of the design process, are also demonstrated within Taguchi’s method. The method is also extended to solve design problems with constraints, invoking the methods of constrained optimization. Finally, the Taguchi method uses a factorial method to search the design space, with a confined definition of an optimal solution. This is compared with other methods of searching the design space and their definitions of an optimal solution.
A Bayesian Estimation of Reliability Measures of Stepwise Exponential Distribution System
Authors: Hu M. H.
Published: June 2008

This paper presents an analysis method for reliability measures of a system with step changes in failure and repair rates. Both failure and repair time have exponential functions of time. Such a system is called a stepwise exponential distribution system. This kind of failure process can take place in various kinds of equipment. This paper deals with the system having components in a series arrangement. Bayesian statistics are used in defining prior and posterior probability density functions of failure and repair rates. These functions provide information for the estimation of several reliability measures: (1) failure and repair rates, (2) mean time to failure, (3) mean time to repair, (4) reliability function and (5) availability. A sample problem is given to illustrate the methodology. Bayesian estimation of the stepwise exponential distribution model is useful in the planning predictive maintenance of equipment.
A General Approach for Robust Optimal Design
Authors: Parkinson A. , Sorensen C. , Pourhassan N.
Published: June 2008

This paper describes a general, rigorous approach for robust optimal design. The method allows a designer to explicitly consider and control, as an integrated part of the optimization process, the effects of variability in design variables and parameters on a design. Variability is defined in terms of tolerances which bracket the variation of fluctuating quantities. A designer can apply tolerances to any model input and can analyze how the tolerances affect the design using either a worst case or statistical analysis. As part of design optimization, the designer can apply the method to find an optimum that will remain feasible when subject to variation, and/or the designer can minimize or constrain the effects of tolerances as one of the objectives or constraints of the design problem.
A Mathematical Model for Geometric Tolerances
Authors: Etesami F.
Published: June 2008

This paper presents a mathematical model for specifying geometric tolerances. This model along with a syntax of tolerance specification will be referred to as the Tolerance Specification Language (TSL). TSL can be used to interpret ANSI Y14.5 geometric tolerancing specifications. The formalization of TSL is based on a set theoretic approach, especially on the concept of offset solids. In this model there is no classification of tolerance types, and there are no restrictions on the use of feature types. Instead, TSL allows the designer to control a feature from expanding, shrinking, or deforming beyond a specified tolerance value. All the tolerancing assertions in TSL apply to surface features and generate uniform tolerance zones. Using two and one dimensional tolerance specification facilities, TSL can approximate ANSI statements that apply to derived features, or generate non-uniform tolerance zones. The appendix of this paper discusses many examples from ANSI and their equivalent TSL form.