bluuebunny/crossref_metadata_2025 huggingface dataset:
Contact Stress Analysis of Spiral Bevel Gears Using Finite Element Analysis
Authors: Bibel G. D. , Kumar A. , Reddy S. , Handschuh R.
Published: February 2008

A procedure is presented for performing three-dimensional stress analysis of spiral bevel gears in mesh using the finite element method. The procedure involves generating a finite element model by solving equations that identify tooth surface coordinates. Coordinate transformations are used to orientate the gear and pinion for gear meshing. Contact boundary conditions are simulated with gap elements. A solution technique for correct orientation of the gap elements is given. Example models and results are presented.
Computerized Design and Generation of Low-Noise Helical Gears with Modified Surface Topology
Authors: Litvin F. L. , Chen N. X. , Lu J. , Handschuh R. F.
Published: February 2008

An approach for the design and generation of low-noise helical gears with localized bearing contact is proposed. The approach is applied to double circular arc helical gears and modified involute helical gears. The reduction of noise and vibration is achieved by application of a predesigned parabolic function of transmission errors that is able to absorb a discontinuous linear function of transmission errors caused by misalignment. The localization of the bearing contact is achieved by the mismatch of pinion-gear tooth surfaces. Computerized simulation of meshing and contact of the designed gears demonstrated that the proposed approach will produce a pair of gears that has a parabolic transmission error function even when misalignment is present. Numerical examples for illustration of the developed approach are given.
Kinematic Transformation Matrices for 3D Surface Contact Joints
Authors: Gutkowski L. J. , Kinzel G. L.
Published: February 2008

A generalized procedure is presented for the development of a pair matrix that describes kinematic joints formed by contact between three-dimensional surfaces. The pair matrix is useful in the matrix-based kinematic analysis procedure put forth by Sheth and Uicker (1971) previously. Any two surfaces may make up the joint as long as the surfaces can be described parametrically, and contact takes place at one point. The corresponding pair matrix is a function of five pair variables.
An Inverse Force Analysis of a Tetrahedral Three-Spring System
Authors: Dietmaier P.
Published: February 2008

A tetrahedral three-spring system under a single load has been analyzed and a closed-form solution for the equilibrium positions is given. Each of the three springs is attached at one end to a fixed pivot in space while the other three ends are linked by a common pivot. The springs are assumed to behave in a linearly elastic way. The aim of the paper at hand was to find out what the maximum number of equilibrium positions of such a system might be, and how to compute all possible equilibrium configurations if a given force is applied to the common pivot. First a symmetric and unloaded system was studied. For such a system it was shown that there may exist a maximum of 22 equilibrium configurations which may all be real. Second the general, loaded system was analyzed, revealing again a maximum of 22 real equilibrium configurations. Finally, the stability of this three-spring system was investigated. A numerical example illustrates the theoretical findings.
Determining Burmester Points from the Analysis of a Planar Platform
Authors: Murray A. P. , McCarthy J. Michael
Published: February 2008

This paper presents a technique for determining the Burmester points of five finitely separated positions in a plane. A Burmester point is the location of the fixed pivot of an RR dyad that can reach each of the five positions. These Burmester points are obtained from a “compatibility platform” constructed from selected relative poles associated with the five specified displacements. We show that the relative position pole of two assembly configurations of this platform is a fixed pivot compatible with the five positions. An example originally presented by Sandor and Erdman is used to verify the calculations.
A Simulated Annealing-Based Approach to Three-Dimensional Component Packing
Authors: Szykman S. , Cagan J.
Published: February 2008

This paper introduces a simulated annealing-based approach to three-dimensional component packing that employs simulated annealing to generate optimal solutions. Simulated annealing has been used extensively for two-dimensional layout of VLSI circuits; this research extends techniques developed for two-dimensional layout optimization to three-dimensional problems which are more representative of mechanical engineering applications. This research also provides a framework in which to solve general component layout problems.
A New Method for Solving Mixed Sets of Equality and Inequality Constraints
Authors: Mullins S. H. , Charlesworth W. W. , Anderson D. C.
Published: February 2008

Presented is a general method for solving sets of nonlinear constraints that include inequalities. Inequality constraints are common in engineering design problems, such as kinematic synthesis. The proposed method uses a modified Newton’s method and introduces a slack variable and a slack constraint to convert each inequality into an equality constraint. Singular value decomposition is used to find the pseudo-inverse of the Jacobian at each iteration. Benefits of this method are that constraint scaling is not an issue and that the method often fails gracefully for inconsistent constraint sets by providing direction for modification of the constraints so that an answer can be found. The method is also competitive with others in terms of the number of function evaluations needed to solve a set of problems taken from the literature.
Design and Analysis of Automotive Serpentine Belt Drive Systems for Steady State Performance
Authors: Beikmann R. S. , Perkins N. C. , Ulsoy A. G.
Published: February 2008

Serpentine belt drive systems with spring-loaded tensioners are now widely used in automotive engine accessory drive design. The steady state tension in each belt span is a major factor affecting belt slip and vibration. These tensions are determined by the accessory loads, the accessory drive geometry, and the tensioner properties. This paper focuses on the design parameters that determine how effectively the tensioner maintains a constant tractive belt tension, despite belt stretch due to accessory loads and belt speed. A nonlinear model predicting the operating state of the belt/tensioner system is derived, and solved using (1) numerical, and (2) approximate, closed-form methods. Inspection of the closed-form solution reveals a single design parameter, referred to as the “tensioner constant,” that measures the effectiveness of the tensioner. Tension measurements on an experimental drive system confirm the theoretical predictions.
On Irrationality in Engineering Design
Authors: Hazelrigg G. A.
Published: February 2008

It is well recognized that virtually all engineering design is suboptimal. The consequence of suboptimal design is that the design can be improved against the desired objective measure, with the result that it fails to provide full potential benefit and it opens the door to competition. In this paper, we define the concept of irrationality in design. Irrationality is a source of suboptimal design that can be addressed through proper project management. It occurs when design engineers make design decisions against different objective measures, with the result that the end design can be suboptimal with respect to all conceivable objective measures of a specified class.
Design of Tactile Fixtures for Robotics and Manufacturing
Authors: Nederbragt W. W. , Ravani B.
Published: February 2008

This paper presents a theoretical framework for the design of tactile sensing fixtures for robotics and manufacturing. The framework presented uses group theory to analyze the symmetry of contact conditions on a fixture to evaluate a fixture design for referencing the sensor frame with respect to the fixture frame. Mechanical fixtures consisting of planar, spherical, and cylindrical surfaces are studied for their usefulness as part of referencing fixtures. The theory developed is used in guiding the design of a simple yet novel touch sensing fixture for part referencing and calibration in manufacturing and robotics.
The Force Workspace: A Tool for the Design and Motion Planning of Multi-Limb Robotic Systems
Authors: Madhani A. , Dubowsky S.
Published: February 2008

The Force Workspace (FW) is a tool for designing mobile robotic systems which apply large forces over large ranges of motion. It can also be used to plan motions that do not violate actuator saturation limits, system-environment force and moment contact constraints such as those due to friction, and kinematic joint limits. The FW is applied to the design analysis and motion planning of a simple robotic climbing machine.
Topological Synthesis of Compliant Mechanisms Using Multi-Criteria Optimization
Authors: Frecker M. I. , Ananthasuresh G. K. , Nishiwaki S. , Kikuchi N. , Kota S.
Published: February 2008

Compliant mechanisms are mechanical devices that achieve motion via elastic deformation. A new method for topological synthesis of single-piece compliant mechanisms is presented, using a “design for required deflection” approach. A simple beam example is used to illustrate this concept and to provide the motivation for a new multi-criteria approach for compliant mechanism design. This new approach handles motion and loading requirements simultaneously for a given set of input force and output deflection specifications. Both a truss ground structure and a two-dimensional continuum are used in the implementation which is illustrated with design examples.
Parallel Disassembly by Onion Peeling
Authors: Chen Shiang-Fong , Oliver J. H. , Chou Shuo-Yan , Chen Lin-Lin
Published: February 2008

For some assembly structures, parallel disassembly of components is necessary in order to reach a particular internal component. Due to the large number of possible combinations, the parallel disassembly problem is not easily solved in a general form. In order to reduce the time complexity of finding a disassembly sequence, this paper introduces a simplified mating graph and develops a data structure to facilitate an efficient parallel disassembly algorithm. This algorithm takes Max {O(N3), O(E)} time to find an efficient sequence to reach a particular component, where N is the number of components and E is the number of mating faces. Separability testing is incorporated to determine whether the query component can be disassembled and moved to infinity without obstruction.
Design Propagation in Mechanical Systems: Kinematic Analysis
Authors: Zou H. , Abdel-Malek K. A. , Wang J. Y.
Published: February 2008

A broadly applicable formulation for investigating design propagations in mechanisms is developed and illustrated. Analytical criteria in terms of the variations of joint position vectors and orientation matrices for planar and spatial mechanisms are presented. Mechanisms are represented using graph theory and closed loops are converted to a tree-like structure by cutting joints and introducing new constraints. The Jacobian matrix in Cartesian space is then transformed to Joint coordinates space. Two cases are considered: a pair of bodies remain connected by one joint after cutting additional joints and a pair of bodies are disconnected after cutting joints. Using this method, a designer has the ability to study the propagated effect of changing a design variable on the design. The presented formulation is validated through a numerical example of a McPherson strut suspension system. The system is analyzed and an assembled configuration is computed after a change in design.
Multiobjective Collaborative Optimization
Authors: Tappeta R. V. , Renaud J. E.
Published: February 2008

This investigation focuses on the development of modifications to the Collaborative Optimization (CO) approach to multidisciplinary systems design, that will provide solution capabilities for multiobjective problems. The primary goal of this paper is to provide a comprehensive overview and development of mathematically rigorous optimization strategies for Multiobjective Collaborative Optimization (MOCO). Collaborative Optimization strategies provide design optimization capabilities to discipline designers within a multidisciplinary design environment. To date these CO strategies have primarily been applied to system design problems which have a single objective function. Recent investigations involving multidisciplinary design simulators have reported success in applying CO to multiobjective system design problems. In this research three Multiobjective Collaborative Optimization (MOCO) strategies are developed, reviewed and implemented in a comparative study. The goal of this effort is to provide an in depth comparison of different MOCO strategies available to system designers. Each of the three strategies makes use of parameter sensitivities within multilevel solution strategies. In implementation studies, each of the three MOCO strategies is effective in solving a multiobjective multidisciplinary systems design problem. Results indicate that these MOCO strategies require an accurate estimation of parameter sensitivities for successful implementation. In each of the three MOCO strategies these parameter sensitivities are obtained using post-optimality analysis techniques.
A Linear Piezomotor Integrated by a Monolithic Flexural Frame
Authors: Zhu Zhenqi , Zhang Bi
Published: February 2008

A novel linear piezomotor is developed for machine tool applications. This paper presents the design strategy for this high stiffness linear piezomotor with nanometer resolution. The linear piezomotor consists of three piezoelectric actuators and one monolithic flexural frame. The design strategy is to reduce the total number of mechanical elements and interfaces and to integrate all the elements into the frame. The finite element method is used in the design process. The design strategy should also be applicable to other positioning systems where a high stiffness and high positioning resolution are required.
Multidisciplinary Analysis and Optimization of Discrete Problems Using Response Surface Methods
Authors: Korngold J. C. , Gabriele G. A.
Published: February 2008

The objective of this paper is to present a new algorithm to efficiently optimize multidisciplinary, coupled nonhierarchic systems with discrete variables. The algorithm decomposes the system into contributing disciplines, and uses designed experiments within the disciplines to build local response surface approximations to the discipline analysis. First and second order Global Sensitivity Equations are formulated and approximated by experimental data to build approximations to the global design space. The global approximation is optimized using branch and bound or simulated annealing. Convergence is rapid for systems with near quadratic behavior. The algorithm is demonstrated on a unique multidisciplinary learning tool, the Design and Manufacturing Learning Environment. This environment provides multimedia simulation for product life cycle disciplines, including design, manufacturing, marketing, and sales.
Optimal Hierarchical Decomposition Synthesis Using Integer Programming
Authors: Krishnamachari R. S. , Papalambros P. Y.
Published: February 2008

Decomposition synthesis in optimal design is the process of creating an optimal design model by selecting objectives and constraints so that it can be directly partitioned into an appropriate decomposed form. Such synthesis results are not unique since there may be many partitions that satisfy the decomposition requirements. Introducing suitable criteria an optimal decomposition synthesis process can be defined in a manner analogous to optimal partitioning formulations. The article presents an integer programming formulation and solution techniques for synthesizing hierarchically decomposed optimal design problems. Examples for designing a pressure vessel, an automotive caliper disc brake and a speed reducer are also presented.
Hierarchical Decomposition Synthesis in Optimal Systems Design
Authors: Krishnamachari R. S. , Papalambros P. Y.
Published: February 2008

Optimal design of large systems is easier if the optimization model can be decomposed and solved as a set of smaller, coordinated subproblems. Casting a given design problem into a particular optimization model by selecting objectives and constraints is generally a subjective task. In system models where hierarchical decomposition is possible, a formal process for selecting objective functions can be made, so that the resulting optimal design model has an appropriate decomposed form and also possesses desirable properties for the scalar substitute functions used in multicriteria optimization. Such a process is often followed intuitively during the development of a system optimization model by summing selected objectives from each subsystem into a single overall system objective. The more formal process presented in this article is simple to implement and amenable to automation.
Involute Gear Pumps Versus Lobe Pumps: A Comparison
Authors: Mimmi G. C. , Pennacchi P. E.
Published: February 2008

In previous studies we have considered several types of positive displacement rotary pumps and deeply analyzed the generation of the flow rate and the design limits. This has been done in order to evaluate the main performance indexes; one of which, the flow rate irregularity, is related to the possibility that the pump becomes a source of vibration and noise. A second index is the specific flow rate, related to the delivery capacity of the pump. In this paper, following our previous researches, we analyzed internal involute gear pumps and internal lobe pumps, that have similar operations but different performances. The design parameters and the way to optimize the performances are proposed for both cases. Finally a comparison is made between the two types of pumps with optimum design parameters.
Quasi-Static and Dynamic Analysis of Narrow-Faced Helical Gears With Profile and Lead Modifications
Authors: Maatar M. , Velex P.
Published: February 2008

A systematic analysis of the influence of tooth shape modifications on the dynamic behavior of single stage narrow-faced helical gears is proposed. Calculations are performed using a 3D model with 36 degrees of freedom including torsional, flexural and axial generalized displacements of the gear-shaft-bearing system. Two approximate equations giving the normalized static transmission error STE and load factor RF are deduced. It is shown that, for a given gear set, there exists a unique representation of STE and RF valid over a large range of profile, lead modification amplitudes and transmitted loads. The role of the extent of the profile relief (long, short and intermediate) and the shape of lead modifications (parabolic, elliptic crowning, linear chamfers) is discussed. The paper is concluded by the analysis of the dynamic transmission error of a gear set with various tooth shape modifications selected from static considerations.
A Novel Automotive Steering Linkage
Authors: Fahey S. O’F. , Huston D. R.
Published: February 2008

This brief outlines results of a numerical study involving a novel mechanism called the Fahey eight-member mechanism (FEMM), that has application to automotive steering. This mechanism is considered in terms of a planar kinematics steering model. We derive the governing kinematics and compare results between a synthesized FEMM and two synthesized Ackermann-type steering linkages. Results suggest that FEMM better approximates ideal steering geometry, and could allow an extended range of motion for moderate speed operations.
Gear Stress Reduction Using Internal Stress Relief Features
Authors: Fredette L. , Brown M.
Published: February 2008

This paper discusses research into the possibility of reducing gear tooth root stresses by adding internal stress relief features. For many years, gear designs have improved with the incremental addition of design features. Materials have improved, surfaces are selectively hardened with heat treatment and carborization, and shot peening is used to improve surface properties. All of these improvements are related to material attributes. Little has been done to change the gear geometry to improve durability and strength. Although the exterior of the gear is governed by the necessary involute profile of the teeth, nothing prevents interior changes. In this study holes were drilled along the axis of a test gear segment in an effort to provide stress relief in critical areas. A finite element model was constructed for use in a systematic test of the effect of hole size and hole placement on tooth root stress. A constant force was applied at the pitch diameter, and all results were normalized with respect to the values obtained for a solid gear. Results show that it is possible to reduce the tooth root tensile stress considerably without producing stresses in the holes greater than on an unmodified gear. These results were verified by photoelastic testing on greatly oversized plastic models. Since gear teeth fail due to fatigue over many cycles, even a slight reduction in the root tensile stress produces a great increase in fatigue life.
Structure-Based Connectionist Network for Fault Diagnosis of Helicopter Gearboxes
Authors: Jammu V. B. , Danai K. , Lewicki D. G.
Published: February 2008

A new method of diagnosis is introduced for helicopter gearboxes that relies on the knowledge of the gearbox “structure” and characteristics of the “features” of vibration for component fault isolation. Both the structural knowledge and featural knowledge in this method are defined as the fuzzy weights of a connectionist network that maps each sampled set of vibration features, obtained from a signal analyzer, into fault possibility values associated with individual gearbox components. The structural weights in this network are defined to represent the influence of gearbox component faults on the overall vibration sensed by each accelerometer, and the featural weights are defined to denote the influence of components faults on individual vibration features. Given the extremely complex structure of helicopter gearboxes which prohibits accurate modeling of the effect of faults on their vibration, the structural weights in this method are defined based on the root mean square value of the frequency response of a simplified lumped-mass model of the gearbox. The experimental evaluation of the method based on vibration data from two different gearboxes is included in a separate paper.
Experimental Evaluation of a Structure-Based Connectionist Network for Fault Diagnosis of Helicopter Gearboxes
Authors: Jammu V. B. , Danai K. , Lewicki D. G.
Published: February 2008

This paper presents the experimental evaluation of the Structure-Based Connectionist Network (SBCN) fault diagnostic system introduced in the preceding article (Jammu et al, 1998). For this, vibration data from two different helicopter gearboxes: OH-58A and S-61, are used. A salient feature of SBCN is its reliance on the knowledge of the gearbox structure and the type of features obtained from processed vibration signals as a substitute to training. To formulate this knowledge, approximate vibration transfer models are developed for the two gearboxes and utilized to derive the connection weights representing the influence of component faults on vibration features. The validity of the structural influences is evaluated by comparing them with those obtained from experimental RMS values. These influences are also evaluated by comparing them with the weights of a connectionist network trained through supervised learning. The results indicate general agreement between the modeled and experimentally obtained influences. The vibration data from the two gearboxes are also used to evaluate the performance of SBCN in fault diagnosis. The diagnostic results indicate that the SBCN is effective in detecting the presence of faults and isolating them within gearbox subsystems based on structural influences, but its performance is not as good in isolating faulty components, mainly due to lack of appropriate vibration features.
On the Topology of Sheet Metal Parts
Authors: Lipson H. , Shpitalni M.
Published: February 2008

This paper analyzes the topological properties of sheet metal parts represented schematically (zero thickness, zero bend radii). Although such parts are usually non-manifold objects, the paper establishes a general topological invariant f = s + b + e + w − v − gnm + m regarding the number of facets, components, bends, free edges, welds, vertices holes and volumes, respectively. Corresponding Euler operators are derived, providing a basis for a modeling system for sheet metal parts. With this invariant, it is possible to reason about manufacturing processes, such as number of components and arrangement of bend lines and weld lines, using only a single qualitative model of the product. This capability is particularly useful in the preliminary stage of conceptual design. A corresponding topological invariant v − e + f = s + m − gnm is also proposed for general sheet models and thin walled objects.
Effects of Gear Dimensions and Tooth Surface Modifications on the Loaded Transmission Error of a Helical Gear Pair
Authors: Umeyama M. , Kato M. , Inoue K.
Published: February 2008

Analysis of the loaded transmission error proved that the actual contact ratio and the effective contact ratios are the valid indices. In order to calculate the loaded transmission error, deformations of a pair of teeth are estimated using Hertzian formulas for the approach deformation and approximate formulas based on the FEM for the bending deflection. The actual contact ratio εr is defined using the rotational angle during which a tooth pair is actually in contact with each other. εr increases with the increase of applied loads. The effective contact ratio, εn, is determined geometrically by gear dimensions and modified tooth surfaces based on the path of contact. Adopting these ratios, the following characteristics are derived. 1) The loaded transmission error correlates to εr when it is smaller than εn and correlates to εn when εr exceeds εn. 2) Loaded transmission errors have their minimums and maximums at the same values of εr. 3) No load transmission error is the largest among the maximums. 4) Gear pairs with higher values of εn show lower loaded transmission error.
Curvatures and Sliding Ratios of Conjugate Surfaces
Authors: Chen N.
Published: February 2008

A new approach for curvatures of conjugate surfaces is provided in this paper. The main characteristic of the approach is that relative curvatures and geodesic torsions of the conjugate surfaces are directly calculated in terms of the normal curvatures and geodesic torsions of the generating surface on two nonorthogonal tangents of surface curvilinears in the global surface system. Based on the curvature equations, sliding velocities and sliding ratios of the conjugate surfaces are studied. The approach is illustrated by a numerical example of a plane enveloping globoidal worm-gear drive.
Design of Antibacklash Pin-Gearing
Authors: Gu Inhoy
Published: February 2008

This paper draws attention to pin gearing for its antibacklash gear property. The gear tooth curve derived from a cycloidal curve furnishes the pin gearing with kinematic antibacklash, low pressure angle, and no interference among other features. The pins on one side of a centerline are contacting the forward faces of the mating tooth gear. Simultaneously the pins on the other side of the centerline are contacting the backward faces of the gear. The correct center distance can be maintained by applying a force directed to each other center for multiple contacts. A generating method of gear manufacture is also suggested. Contact and bending deformations as well as the gear stress are analyzed to help its engineering design.
Fuzzy Heuristics for Sequential Linear Programming
Authors: Mulkay E. L. , Rao S. S.
Published: February 2008

Numerical implementations of optimization algorithms often use parameters whose values are not strictly determined by the derivation of the algorithm, but must fall in some appropriate range of values. This work describes how fuzzy logic can be used to “control” such parameters to improve algorithm performance. This concept is shown with the use of sequential linear programming (SLP) due to its simplicity in implementation. The algorithm presented in this paper implements heuristics to improve the behavior of SLP based on current iterate values of design constraints and changes in search direction. Fuzzy logic is used to implement the heuristics in a form similar to what a human observer would do. An efficient algorithm, known as the infeasible primal-dual path-following interior-point method, is used for solving the sequence of LP problems. Four numerical examples are presented to show that the proposed SLP algorithm consistently performs better than the standard SLP algorithm.
Optimal Configuration Design: An Integrated Approach Using Grammars
Authors: Schmidt L. C. , Cagan J.
Published: February 2008

A computational approach to design that integrates conceptual design, configuration design, and component selection tasks overcomes some of the barriers to successful design automation. FFREADA is an implementation of a general design generation and optimization algorithm featuring hierarchical ordering of grammar-based design generation processes at different levels of abstraction. FFREADA is used to generate near-optimal hand-held drill power trains in a space exceeding 200 million designs that are not limited to any particular functional architecture or component configuration. Drill power train designs with values within 1 percent of the optimal solution are found in minutes by sampling 302,000 design states on average. Optimal configurations are found for drill power trains with three different torque requirements.
Collaborative Optimization of Systems Involving Discrete Design at the Discipline Level
Authors: Balling R. J. , Gale D. L
Published: February 2008

The multidisciplinary design optimization technique known as collaborative optimization is applied to two example problems to illustrate the flexibility that the technique extends to disciplinary design teams. In the first problem, disciplinary design variables are discrete-valued representing the cross-sectional dimensions of standardized shapes for structural members in a frame. In the second problem, discrete disciplinary design variables are used to represent the choice between different structural configurations of a truss tower. In both problems, disciplinary design was performed by the non-gradient-based strategy, exhaustive search. Nevertheless, system-level optimization was performed by a gradient-based strategy using simple formulas for the necessary gradients.
Designing Dynamically Compensated and Robust Cam Profiles With Bernstein-Be´zier Harmonic Curves
Authors: Srinivasan L. N. , Ge Q. Jeffrey
Published: February 2008

This paper deals with the problem of designing dynamically compensated cam profiles to minimize residual vibrations in high-speed cam-follower systems. The traditional Polydyne method is modified and extended to achieve significant improvement in residual vibration characteristics. First, cam displacement curves are represented by Bernstein-Be´zier harmonic curves as opposed to polynomial curves. These recently developed harmonic curves are low in harmonic content and therefore the resulting cam profiles are less prone to induce resonant vibrations in the follower system. Second, the design procedure is expanded such that the residual vibrations of the resulting cam-follower system is not only extinguished at the design speed but also made insensitive to speed variations. Numerical examples are given in the end.
Finite Element Analysis and Design of a Trochoidal-Type Machine Without Apex Seals
Authors: Kannan V. , Shung J. B.
Published: February 2008

A two-dimensional model for a trochoidal-type machine without apex seals using finite element method has been developed with the help of Cosmos/M V1.65, and is evaluated by using a classical free-body technique. The minimum running clearance required to avoid contact between rotor and chamber is determined by an iterative procedure using the finite element model. The variation in the minimum required running clearance with the variation in the design parameters is studied. Guidelines for using the results of this study for an optimal design of a trochoidal-type machine without apex seals are presented.
Singularity-Free Evolution From One Configuration to Another in Serial and Fully-Parallel Manipulators
Authors: Innocenti C. , Parenti-Castelli V.
Published: February 2008

Among the several ways adopted for the characterization of manipulator performances is identification of the typologies of maneuvers allowed by the manipulator kinematic arrangement. The multiplicity of configurations corresponding to a given hand position for serial manipulators, or to a given set of input values for fully-parallel manipulators, makes one wonder whether a manipulator can perform the maneuver of changing its configuration without meeting singularities. The paper shows that singularity-free configuration change is possible both for general-geometry serial and fully-parallel architectures. Results are reported that shed light on potential performances of manipulators and allow, in perspective, a deeper exploitation of their structural peculiarities.
Closed-Form Primitives for Generating Locally Volume Preserving Deformations
Authors: Chirikjian G. S.
Published: February 2008

In this paper, methods for generating closed-form expressions for locally volume preserving deformations of general volumes in three dimensional space are introduced. These methods have applications to computer aided geometric design, the mechanics of materials, and realistic real-time simulation and animation of physical processes. In mechanics, volume preserving deformations are intimately related to the conservation of mass. The importance of this fact manifests itself in design, and in the realistic simulation of many physical systems. Whereas volume preservation is generally written as a constraint on equations of motion in continuum mechanics, this paper develops a set of physically meaningful basic deformations which are intrinsically volume preserving. By repeated application of these primitives, an infinite variety of deformations can be written in closed form.
An Effective Mixed Annealing/Heuristic Algorithm for Problems in Mechanical Design
Authors: Ogot M. M. , Alag S. S.
Published: February 2008

The wide application of stochastic optimization methods in mechanical design has been partially hindered due to (a) the relatively long computation time required, and (b) discretization of the design space at the onset of the optimization process. This work proposes a new stochastic algorithm, the Mixed Annealing/Heuristic Algorithm (MAH), which addresses both these issues. It is based on the Simulated Annealing algorithm (SA) and the Heuristic Optimization Technique (HOT). Both these algorithms have been successfully applied to problems in mechanical design and up to now have been considered as competing algorithms. MAH capitalizes on each of their individual strengths and addresses their weaknesses, thereby considerably reducing the computational effort required to attain the final solution. A pseudo-continuous approach for configuration generation is employed, making the discretization of the design space no longer necessary. The effectiveness of MAH is demonstrated via three problems in kinematic synthesis. Comparison of the results with other stochastic optimization methods illustrates the potential of this technique.
Stability and Accuracy Analysis of Baumgarte’s Constraint Violation Stabilization Method
Authors: Yoon S. , Howe R. M. , Greenwood D. T.
Published: February 2008

When Baumgarte’s Constraint Violation Stabilization Method (CVSM) is used in the simulation of Lagrange equations of motion with holonomic constraints, it is shown that, with suitable assumptions on the integration step size h and the eigenvalues (λ’s) of the linearized system, the constraint variables are effectively integrated by the same algorithm as that used for the state variables. A numerical stability analysis of the constraint violations can be performed using this so-called pseudo-integration equation. A study is also made of truncation errors and their modeling in the continuous time domain. This model can be used to determine the effectiveness of various constraint controls and integration methods in reducing the errors in the solution due to truncation errors. Examples are presented to illustrate the use of a higher-order truncation error model which leads to an accurate quantitative steady-state analysis of the constraint violations.
Redundancy Resolution of Robotic Manipulators Using Normalized Generalized Inverses
Authors: Wang J. T.
Published: February 2008

A dynamical formulation based upon the undetermined force method is presented for analyzing redundant robotic manipulators. The equivalence between this dynamical formulation and the general solution of kinematic constraint equations is then obtained through use of a normalized generalized inverse. This leads to a special form of the dynamical equations, called the N-inverse form of the dynamical equations. A class of problems, associated with the optimization of quadratic objective functions, are then studied. We find that the N-inverse form of the dynamical equations is the solution of this class of problems. Examples, including local minimization of joint torques and global minimization of kinetic energy, are presented.
A Two-Dimensional Formulation for Path-Placement in the Workcells of Planar 3-R Robots
Authors: Soman N. A. , Davidson J. K.
Published: February 2008

A new systematic formulation is presented that determines suitable locations for a workpiece, and its associated task-motion, in the workspace of a three-hinged planar (SCARA) robotic workcell. It determines all acceptable positions for the first joint of the robot relative to the workpiece; therefore, all solutions are represented as an area in two dimensions, unlike existing methods of motion-planning that present them as a volume in a three-dimensional joint-space for the same planar robot. This simplifies the solution-space by reducing its dimension from three to two. All possible acceptable designs appear in a graphical form that can be readily visualized and directly measured in a Cartesian frame of reference in the workcell. Applications include locating workpieces with tool-paths for fusion welding and for deposition of adhesives.
Accelerating Product Development by the Exchange of Preliminary Product Design Information
Authors: Krishnan V. , Eppinger S. D. , Whitney D. E.
Published: February 2008

In this paper, we discuss the problem of reducing product development lead time by overlapping coupled development activities through the exchange of preliminary design information. We present an approach, called iterative overlapping, in which downstream development activities begin with unfinalized upstream design information and accommodate design changes in subsequent iterations. In the absence of careful control, iterative overlapping could involve excessive downstream rework leading to an increase in lead time. We formulate the iterative overlapping problem and model iterations and design changes to determine how to overlap the activities for lead time reduction. The model is illustrated with application to an automobile door panel development process.
Motion Interpolation With G2 Composite Be´zier Motions
Authors: Ge Q. J. , Kang Donglai
Published: February 2008

This paper deals with smooth motion interpolation. It presents two geometric algorithms for synthesizing composite Be´zier motions with second-order geometric continuity (G2). The first one is a direct algorithm for constructing a G2 spline motion that approximates a set of displacements; the second one is an inverse design algorithm for a G2 spline motion that interpolates through a set of displacements. The results are useful for computer aided motion animation, and Cartesian trajectory generation for CNC machines and robot manipulators.
Displacement and Force Analysis of Five-Rod Suspension With Flexible Joints
Authors: Knapczyk J. , Dzierz˙ek S.
Published: February 2008

The paper presents a vector algebraic method for the displacement and force analysis of the five-rod wheel suspension mechanism, used as a rear suspension in some modern cars. Displacement equations are derived by using the solutions of the vector tetrahedron equations obtained as the closure or constraint equations for spatial multi-loop mechanisms. The method gives the possibility of reducing the system of constraint equations from the original five to two. The resultant equations are expressed in recursive notation, which isrelatively concise in form and convenient for programming, providing a very efficient and accurate algorithm. The system of force and torque equilibrium equations is solved in an explicit way. Flexible joints with experimentally determined linearized compliance matrices are taken into consideration, leading to an algorithm for elastokinematic analysis of the mechanism. Graphical illustration of the results is also presented.
A Closed Solution for the Elastic-Dynamic Behavior of an Industrial Press Feed Mechanism and Experimental Verification
Authors: Xu Tao , Lowen G. G.
Published: February 2008

A new linearized two-degree-of-freedom model of an industrial press feed mechanism and its experimental verification are presented. By introducing a double cantilever model of the coupler with an assumed quarter sine shape function and replacing the nonlinear clutch spring by a linear torsional spring with a deflection dependent stiffness, it was possible to develop a set of two linear differential equations, which could be fully solved in an analytic manner for the dynamic responses of the coupler strain and the clutch windup angle during the feeding stroke. An associated parametric study shows insights pertaining to the relationship between the system and component frequencies and allows the formulation of certain design rules regarding the magnitudes of the coupler and clutch windup angle deflections.
An Inverse Force Analysis of a Planar Two-Spring System
Authors: Pigoski T. M. , Duffy J.
Published: February 2008

A closed-form inverse force analysis was performed on a planar two-spring system. The two springs were grounded to pivots at one end and attached to a common pivot at the other. A known force was applied to the common pivot of the system, and it was required to determine all of the assembly configurations. By variable elimination, a sixth degree polynomial in the resultant length of one spring was derived, and from this, six real solutions of the point of application of force were obtained. Following this, the applied force was incremented along a line and the six paths of the moving pivot were tracked starting from the zero-load configurations. An analysis of these results showed stability phenomena indicating the workspace of this system contained regions of negative spring stiffness and points of catastrophe.
Incremental Kinematic Analysis of Mechanisms
Authors: Konkar R. , Cutkosky M.
Published: February 2008

Kinematic design is an important aspect of the design of mechanical systems with moving parts. The performance of such systems may suffer from the presence of parts that bind during their motion causing jams, or that execute undesired motions. Kinematic analysis needs to be conducted and the design of the system modified. Analysis-redesign-reanalysis cycles are common in reaching a satisfactory design. If the system is large and the incidence of redesign frequent, then it becomes imperative to have fast analysis methods. This work addresses this problem by providing computational techniques for doing incremental kinematic analysis. The mechanism is represented as a graph of objects with connection constraints among them. A recursive procedure traverses the graph to establish instantaneous kinematic properties. A store-and-reuse strategy is employed to increase the efficiency of re-analysis runs. This involves storing intermediate results of computations for reuse in case of incremental redesign or iterative analysis. The store-and reuse strategy is also applicable when retrieving elements of previous designs, and their associated kinematic analyses, and adapting them to new design problems. A comparative, quantitative study of the normal, “from-scratch” method and the incremental method is provided to prove the greater efficiency of the latter.
Kinestatic Analysis of General Parallel Manipulators
Authors: Ling Shou-Hung , Huang Ming Z.
Published: February 2008

Robotic mechanisms in general can be of either serial-chain, parallel-chain, or hybrid (a combination of both parallel and serial chains) geometry. While it can be asserted that kinematic theories and techniques are well established for fully serial-chain manipulators, the same assertion cannot be made when it is considered in the general context. In this article, we present a general procedure for systematic formulation and characterization of the instantaneous kinematics for a robotic mechanism with a general parallel-chain geometry. A kinestatic approach based on screw system theory is adopted in this treatment. The resulting equation is a compact Jacobian matrix of the system which includes attributes from not only the active joints but also the passive constraints. An example has been provided to demonstrate the methodology as well as its theoretical feasibility.
Circuit Rectification for Four Precision Position Synthesis of Four-Bar and Watt Six-Bar Linkages
Authors: Mirth J. A. , Chase T. R.
Published: February 2008

The circuit defect arises in precision position based linkage synthesis when a potential solution linkage cannot be moved between all precision positions without disassembly. Circuit rectification consists of reducing the potential solution space to include only those linkages that are free of the circuit defect. Circuit rectification for four precision position synthesis of Watt six-bar linkages is developed here. Circuit rectification of four-bar linkages is refined in the process. An example demonstrates the synthesis of a new Watt I sofa bed linkage free of the circuit defect.
A Hybrid Approach to Solving the Position Equations for Planar Mechanisms
Authors: Bawab S. , Kinzel G. L.
Published: February 2008

In this paper, a straightforward approach is developed to solve the nonlinear position equations for a linkage when a closed-form solution to some of the equations can be obtained. This is done with the aid of dependency checking concepts that organizes a system 2n equations and 2n unknowns (variables) into smaller sets of equations. When a set of two equations and two unknowns is obtained, the variables are analyzed using a closed-form (non-iterative) solution approach. Otherwise, an iterative approach such as the Newton-Raphson method is used for the analysis.