bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Design of Resonance Suppression Helical Springs
Authors: Lin Yuyi , Hodges P. H. , Pisano A. P.
Published: June 2008

Based on a previously developed and verified helical spring dynamic model, optimization and FFT subroutines have been added to the spring dynamic model as controlling and postprocessing units to form a computer-based optimal design tool. The objective function minimized is the amplitude of spring resonance. Design variables are the coefficients of a polynomial which describes the variation of the diameter of the spring wire along the spring helix. Constraints are the maximum fatigue stress at any location of the spring wire, the minimum and maximum wire diameter, and the maximum required spring force. In a case study for an automobile engine valve spring, resonant harmonic power has been reduced by 47 percent, given the newly designed spring a potential to be used at 8.3 percent higher engine speed before potential valve toss occurs.
Probabilistic Optimal Design Using Successive Surrogate Probability Density Functions
Authors: Eggert R. J. , Mayne R. W.
Published: June 2008

Probabilistic optimization using the moment matching method and the simulation optimization method are discussed and compared to conventional deterministic optimization. A new approach based on successively approximating probability density functions, using recursive quadratic programming for the optimization process, is described. This approach incorporates the speed and robustness of analytical probability density functions and improves accuracy by considering simulation results. Theoretical considerations and an example problem illustrate the features of the approach. The paper closes with a discussion of an objective function formulation which includes the expected cost of design constraint failure.
Dimensional Tolerance Allocation of Stochastic Dynamic Mechanical Systems Through Performance and Sensitivity Analysis
Authors: Lee S. J. , Gilmore B. J. , Ogot M. M.
Published: June 2008

Uncertainties due to random dimensional tolerances within stochastic dynamic mechanical systems lead to mechanical errors and thus, performance degradation. Since design standards do not exist for these systems, analysis and design tools are needed to properly allocate tolerances. This paper presents probabilistic models and methods to allocate tolerances on the link lengths and radial clearances such that the system meets a probabilistic and time dependent performance criterion. The method includes a general procedure for sensitivity analysis, using the effective link length model and nominal equations of motion. Since the sensitivity analysis requires only the nominal equations of motion and statistical information as input, it is straight forward to implement. An optimal design problem is formulated to allocate random tolerances. Examples are presented to illustrate the approach and its generality. This paper provides a solution to the tolerance allocation problem for stochastic dynamically driven mechanical systems.
Dynamics of Initially Curved Plates in the Analysis of Spatial Flexible Mechanical Systems
Authors: Chen D. C. , Shabana A. A.
Published: June 2008

In this paper, the effect of the initial curvature on the nonlinear dynamics of plates in constrained flexible multibody systems is examined. A set of nonlinear differential equations that describe the motion of the elastic bodies which undergo large reference displacements is derived using the principle of virtual work in dynamics. The resulting nonlinear mass matrix is written as the sum of two nonlinear matrices. These are the conventional mass matrix that arises when the effect of initial curvature is neglected and the curvature mass matrix that represents the effect of the initial curvature. It is shown that all the components of the generalized centrifugal forces depend on the initial curvature. In particular, the generalized centrifugal forces associated with the large rigid body translation and the elastic deformation are linear functions of the initial curvature, while the centrifugal forces associated with the finite rotation are quadratic functions of the initial curvature. It is also shown that the generalized Coriolis forces associated with the finite rotation are linear functions of the initial curvature, while other Coriolis components do not depend on the initial curvature. It is demonstrated numerically that the use of the normal modes of vibration of flat plates in the analysis of the initially curved elastic components leads to a significant error in the dynamic response. Numerical results presented in this investigation are obtained using the spatial flexible multibody RSSR mechanism.
Multi-Body Impact Motion with Friction—Analysis, Simulation, and Experimental Validation
Authors: Han Inhwan , Gilmore B. J.
Published: June 2008

When a multi-body system collides with a single body or with another multi-body system, impact dynamics with friction should be considered. This paper presents a general computer oriented analysis of impact dynamics incorporating friction. The presence of friction between sliding contacts during the impact makes the problem difficult since the events such as reverse sliding or sticking, which may occur at different times throughout the impact, must be determined. The boundary representations of the bodies are used to solve for the velocities at the points of contact. Using this information and a classification of the modes of impact, the frictional impact with sliding contact problem is solved. Using a high speed video camera, the resulting computer strategy is experimentally verified. Simulation and experimental results agree.
The Incorporation of Arc Boundaries and Stick/Slip Friction in a Rule-Based Simulation Algorithm for Dynamic Mechanical Systems with Changing Topologies
Authors: Han Inhwan , Gilmore B. J. , Ogot M. M.
Published: June 2008

Many dynamic mechanical systems, such as parts-feeders and percussive power tools, are described by equations of motion which are discontinuous. The discontinuities result from kinematic constraint changes which are difficult to foresee, especially in presence of impact and friction. A simulation algorithm for these types of systems must be able to algorithmically predict and detect the kinematic constraint changes without any prior knowledge of the system’s motion. This paper presents a rule-based approach to the prediction and detection of kinematic constraint changes between bodies with arc and line boundaries. A new type of constraint change, constraint exchange, is characterized. When arc contact exists, stick/slip friction is the difference between pure rolling and rolling with slip. Therefore, stick/slip friction is included in the algorithm. A force constraint is applied to the equations of motion when additional kinematic constraints due to friction would render the coefficient matrix singular. The efficacy of the rule-based simulation algorithm as a design tool is demonstrated through the design and experimental validation of a parts-feeder. The parts-feeder design is validated through two means: (1) a frame-by frame comparison of simulation results with the part motion recorded by high speed video and (2) actual testing.
Automated Hybrid Analysis of Surface Mounted Electronic Assemblies
Authors: Wong T.-L. , Wang J. , Stevens K. K.
Published: June 2008

Simulations of surface mounted electronic assemblies under general mechanical loading conditions have been performed using an hybrid analytical/experimental analysis approach. This method combines analytical techniques with experimentally determined load-deformation characteristics of the surface-mounted assemblies to predict loadings and deformations of the assemblies. An automated analysis procedure which integrated the finite element method, optimization theory, and the hybrid analysis approach was developed. This procedure can be used to study the strength of surface mounted devices located anywhere on a printed circuit board subjected to specified loading conditions.
Cam Motion Synthesis Using Cubic Splines
Authors: Yoon K. , Rao S. S.
Published: June 2008

The application of minimum norm principle, similar to the principle of minimum potential energy, is presented for the general synthesis of cam motion. The approach involves the use of piecewise cubic spline functions for representing the follower displacement. The cubic splines are more convenient and simpler to use compared to general spline functions and also result in smaller peak acceleration and jerk due to the application of the minimum norm principle. A general procedure is presented for application to any cam-follower system. The effectiveness of the approach is illustrated by comparing the results given by the present method with those given by other approaches for a disk cam-translating follower.
Automatic Planning of Smooth Trajectories for Pick-and-Place Operations
Authors: Gosselin C. M. , Hadj-Messaoud A.
Published: June 2008

This paper proposes some new polynomial solutions to the trajectory planning problem encountered in pick-and-place operations. When a robotic manipulator is used for such operations, it is possible to plan the required trajectory in joint space, provided that the inverse kinematic problem has been solved for the initial and final configurations—and possibly for a lift-off and a set-down configuration—and that the workspace is free of obstacles. Polynomial solutions to this problem can be found in the literature. However, they usually provide continuity up to the second derivative only, leading to a discontinuous jerk. The solutions derived in this paper preserve the continuity of the third derivative of the joint coordinates, thereby ensuring smooth trajectories with smooth variations of the actuator currents. Moreover, whenever possible, unique polynomial expressions valid between the initial and final configurations are used in order to simplify the logic. Polynomial formulations without lift-off and set-down configurations are first presented. Then, these intermediate configurations are introduced, leading to a new set of solutions. A global algorithm is then discussed in order to clearly indicate the relationship between the different solutions. Finally, an example illustrating the application to a pick-and-place operation is solved.
Determination of Allowable Manipulator Link Shapes; and Task, Installation, and Obstacle Spaces Using the Monte Carlo Method
Authors: Tu Q. , Rastegar J.
Published: June 2008

The Monte Carlo method is used to solve a number of manipulator link shape design, task space, and obstacle placement problems. The shape of links of manipulators that are to operate within geometrically specified enclosures are determined. Within the enclosure, one or several obstacles may be present. For a specified operating environment, the spaces within which a given manipulator may be installed in order to perform the required tasks are identified. For a given enclosure, the allowable task spaces, and regions within which obstacles may be placed are mapped. By defining weighted distributions for the task and/or obstacle spaces, weighted allowable link shapes, and task and obstacle spaces are determined. The information can be used for optimal link shape synthesis, and for optimal task, obstacle, and manipulator placement purposes. The developed methods are very simple, numeric in nature, and readily implemented on computer. Several examples are presented.
Study of Dominant Performance Characteristics in Robot Transmissions
Authors: Schempf H. , Yoerger D. R.
Published: June 2008

Six different transmission types suitable for robotic manipulators were compared in an experimental and theoretical study. Single-degree-of-freedom mechanisms based on the different transmissions were evaluated in terms of force control performance, achievable bandwidth, and stability properties in hard contact tasks. Transmission types considered were (1) cable reducer, (2) harmonic drive, (3) cycloidal disk reducer, (4) cycloidal cam reducer, (5) ball reducer, and (6) planetary/cycloidal gear head. Open loop torque following error, attenuation and phase lag, and closed loop bandwidth and stability margin were found to be severely dominated by levels of inertia, stiffness distribution and variability, stiction, coulomb and viscous friction, and ripple torque. These aspects were quantified and shown to vary widely among all transmissions tested. The degree of nonlinearity inherent in each transmission affected its open and closed loop behavior directly, and limited the effectiveness of controller compensation schemes. Simple transmission models based on carefully measured transmission characteristics are shown to predict stability margins and achievable force-control bandwidths in hard contact to within a 5 to 15 percent error margin.
The Generating Space for Parabolic Motion Error Spiral Bevel Gears Cut by the Gleason Method
Authors: Gosselin C. J. , Cloutier L.
Published: June 2008

Because of their inherent pseudo-conjugate natures, spiral bevel gears cut by the Gleason method basically transmit motion in a nonuniform manner. This motion nonuniformity, or motion error, repeated at each tooth engagement and at high speeds and loads, can cause vibrations in transmissions and contact-entry impact loads on gear teeth which affect the life of a gearset. It is customary to make small changes to machine settings in order to produce gear pairs with vastly improved kinematics. Therefore, machine setting changes must be carefully chosen such as to produce appropriate unloaded kinematical motion error that will cancel tooth bending deflection and contact deformation at a given load, and thus reduce noise and vibrations due to motion nonuniformity. This paper presents a study on the effects of machine settings, such as cutter tilt, machine center to back and offset, on the unloaded kinematical motion error. Applying CAD Boolean operations on the results, it is found that, for a given speed ratio, an infinite number of cutter tilt, work offset and machine center to back combinations will produce gear sets with convex parabolic motion error curve of any desired amplitude. Moreover, the amplitude of motion error curves can be linked directly to contact bias on the tooth flank. Thus, gear sets with any parabolic motion error in the unloaded state can be produced, such as to cancel tooth bending deflection and contact deformation in the loaded state.
Geometric Design and Machining of Variable Pitch Lead Screws with Cylindrical Meshing Elements
Authors: Yan Hong-Sen , Liu Jen-Yu
Published: June 2008

This paper derives the surface geometry and machine tool settings for a double threaded variable pitch lead screw with four cylindrical meshing elements. A 4-axis machining center with a rotary milling head attachment is adopted for the manufacturing of the profiles of the screws. And, based on the developed surface equations and the required settings, the authors develop a computer program for solid modeling to simulate the surface geometry of such a mechanism before and after machining. The result of this work is necessary for the task of computer-aided design and manufacturing of the variable pitch lead screw transmission mechanisms for industrial applications, e.g., in shuttleless weaving looms.
Load Distribution in Double Enveloping Worm Gears
Authors: Simon V.
Published: June 2008

A method for the determination of load sharing among the instantaneously engaged worm threads and gear teeth of double enveloping worm gears and for the calculation of load distribution along their instantaneous contact lines is presented. The bending and shearing deflection of worm thread and gear tooth, the contact deformation, the axial deformation of worm body, and the manufacturing and alignment errors of worm and gear are included. The obtained system of integral equations is solved by using approximations and an iterative technique. The corresponding computer program is developed. By using this program, the load distribution in the classical and in a new type of double enveloping worm gear drives is calculated. The influence of design parameters on load distribution factor and on maximum tooth pressure is investigated and discussed.
Inverse Kinematics of the General 6R Manipulator and Related Linkages
Authors: Raghavan M. , Roth B.
Published: June 2008

This paper elaborates on a method developed by the authors for solving the inverse kinematics of a general 6R manipulator. The method is shown to be applicable to determining the joint variables associated with all series-chain manipulators and closed-loop linkages constructed in a single loop with revolute, prismatic, or cylindric joints. The method is shown to yield a single polynomial, of minimum degree, in terms of just one of the joint variables. Once the roots of this polynomial are found, the remaining variables are then usually determined from linear sets of equations. It is shown that this method works equally well for general geometries and for special geometries such as those chararcterized by intersecting or parallel joint axes.
Complex Robotic Inverse Kinematic Solutions
Authors: Pohl E. D. , Lipkin H.
Published: June 2008

A new method exploiting complex numbers in the inverse kinematic solution of serial robotic manipulators is presented. If a prescribed end effector location is outside of the manipulator workspace, complex joint values result. While they cannot be implemented physically, they may be mapped to real numbers. The result approximates the prescribed location. For many industrial manipulators, mapped solutions may be explained using spherical and planar dyads. An important criterion characterizes error minimization properties, and is illustrated for a 3R regional robot.
Closed-Form Direct Position Analysis of a 5–5 Parallel Mechanism
Authors: Innocenti C. , Parenti-Castelli V.
Published: June 2008

The paper presents the closed form direct displacement analysis for a class of Stewart platform-type parallel mechanisms whose general feature consists of six legs which meet five distinct points both in the base and in the movable output link. Out of the two possible arrangements, only one is here analyzed in detail. Given a set of actuator displacements the analysis provides all the possible locations of the platform relative to the base. The analysis results in a 40th degree polynomial equation in one unknown. The roots of the equation provide in the complex field forty closures of the mechanism. This new result has been numerically verified by the inverse displacement analysis.
Movable Spatial 6R Mechanisms With Three Adjacent Parallel Axes
Authors: Lee Chung-Ching , Yan Hong-Sen
Published: June 2008

Based on derived matrix loop equations and their algebraic manipulations, we obtain the necessary mobility criteria, and prove that there are only three types of movable spatial 6R mechanisms with three adjacent parallel axes. The first type is a general form of Sarrus 6R mechanism. The second type can be regarded as a combination of spherical and planar 4R mechanisms. The third type is a hybrid linkage, first mentioned by Waldron. All these three types are proper linkages confirmed by iteration and optimization methods.
On the Special Bases of Two- and Three-Screw Systems
Authors: Tsai M. J. , Lee H. W.
Published: June 2008

The geometries of screw systems are well-defined in some special bases such as in the principal coordinate systems. However, it is not easy to construct the principal coordinate system of a screw system from a given set of screws. Methods of finding the special bases of two- and three-systems by means of linear algebra are presented. Geometric characteristics and their difference between screw systems are discussed and illustrated in the special bases.
A Unified Theory for Finite, Infinitesimal, and Hybrid Kinematic Synthesis
Authors: James P. A. , Roth B.
Published: June 2008

In this paper we derive an analytic method for obtaining infinitesimal kinematic synthesis results as a limiting process from finitely separated position kinematics. New relationships are introduced and a new numerical method is presented. Within the scope of linear, analytic theories, the loci associated with infinitesimal position theory and the loci associated with hybrid finite-infinitesimal position theory are shown to always be limiting cases of the corresponding finite theory. These new methods serve to unify finite, infinitesimal, and hybrid kinematic synthesis theories.
Finitely and Multiply Separated Synthesis of Link and Geared Mechanisms Using Symbolic Computing
Authors: Dhingra A. K. , Mani N. K.
Published: June 2008

A computer amenable symbolic computing approach for the synthesis of six different link and geared mechanisms is presented. Burmester theory, complex number algebra, and loop closure equations are employed to develop governing equations for the mechanism to be synthesized. Closed-form and iterative solution techniques have been developed which permit synthesis of six-link Watt and Stephenson chains for function, path, and motion generation tasks with up to eleven precision points. Closed-form solution techniques have also been developed for the synthesis of geared five-bar, six-bar, and five-link cycloidal crack mechanisms, for synthesis tasks with up to six finitely and multiply separated precision points. The symbolic manipulation language MACSYMA is used to simplify the resulting synthesis equations and obtain closed-form solutions. A design methodology which demonstrates the feasibility and versatility of symbolic computing in computer-aided mechanisms design is outlined. A computer program which incorporates these synthesis procedures is developed. Two examples are presented to illustrate the role of symbolic computing in an automated mechanism design process.
Elastic Potential Synthesis—A Generalized Procedure for Dynamic Synthesis of Machine and Mechanism Systems
Authors: Idlani S. , Streit D. A. , Gilmore B. J.
Published: June 2008

By synthesizing a mechanism to govern the deflection of a linear spring, this paper presents a method to generate a specified elastic potential energy function. This synthesis approach, termed Elastic Potential Synthesis, can be employed to modify machine dynamics and therefore reduce actuator force/torque requirements. The design method presented is based on a system energy model. The maximum number of synthesis precision points are identified for both tension/compression and torsional springs. Examples are presented which demonstrate the power of this methodology.
A Classification of Robot Compliance
Authors: Patterson T. , Lipkin H.
Published: June 2008

The concept of compliant axes is developed from the compliance matrix eigenvalue problem. It is shown that the necessary and sufficient conditions for the existence of a compliant axis are two collinear eigenscrews with eigenvalues of equal magnitude and opposite sign. This leads to a new classification of compliance matrices based on the number of compliant axes. Selected matrices from the literature illustrate both the compliant axis concept and the classification.
A Generalized Stiffness Matrix Method for Force Distribution of Robotic Systems with Indeterminancy
Authors: Gao Xiaochun , Song Shin-Min , Zheng Chun Qi
Published: June 2008

Foot forces in walking machines and finger forces in multi-fingered grippers are usually indeterminate due to the multi-closed-chain geometry of the systems. While many methods were proposed to solve the force distribution of such systems, a method called stiffness matrix method [2] was developed based on the concept that the force must satisfy the equations of material deformations. However, only leg compliances were considered in the stiffness matrix method. In this paper, the stiffness matrix method is generalized to include all the major system compliances, i.e., those of legs (fingers), actuators and terrain (object to be grasped). Based on the developed generalized stiffness matrix method, an example of foot force analysis of a quadruped is presented to demonstrate the effects of different system compliances on the foot forces.
Motions With Minimal Joint Torques for Redundant Manipulators
Authors: Pueh Lee Heow
Published: June 2008

The article presents a method for obtaining motions with minimal joint torques for redundant mechanical manipulators. The existing methods based on the local resolution of redundancy do not guarantee that singular configurations, which lead to large joint torques and joint accelerations, will also be avoided while optimizing joint torques. For the present method, the degrees of redundancy are resolved at the global level. It is observed that motions with optimal joint torques are usually associated with large joint speeds and joint accelerations, compared with the joint speeds and joint accelerations for motions with minimal joint speeds or joint accelerations. To overcome this problem, the optimization criterion for minimal joint torques is modified by combining it separately with the optimization criteria for both minimal joint speeds and minimal joint accelerations. The resulting optimal motions, with smaller joint speeds and joint accelerations, are achieved at the expense of having larger joint torques.
Application of Rational B-Splines to the Synthesis of Cam-Follower Motion Programs
Authors: Tsay D. M. , Huey C. O.
Published: June 2008

A procedure employing rational B-spline functions for the synthesis of cam-follower motion programs is presented. It differs from earlier techniques that employ spline functions by using rational B-spline basis functions to interpolate motion constraints. These rational B-splines permit greater flexibility in refining motion programs. Examples are provided to illustrate application of the approach.
The Degree Code—A New Mechanism Identifier
Authors: Tang C. S. , Liu Tyng
Published: June 2008

An important step in the structural synthesis of mechanisms requires the identification of isomorphism between the graphs which represents the mechanism topology. Previously used methods for identifying graph isomorphism either yield incorrect results for some cases or their algorithms are computationally inefficient for this application. This paper describes a new isomorphism identification method which is well suited for the automated structural synthesis of mechanisms. This method uses a new and compact mathematical representation for a graph, called the Degree Code, to identify graph isomorphism. Isomorphic graphs have identical Degree Codes; nonisomorphic graphs have distinct Degree Codes. Therefore, by examining the Degree Codes of the graphs, graph isomorphism is easily and correctly identified. This Degree Code algorithm is simpler and more efficient than other methods for identifying isomorphism correctly. In addition, the Degree Code can serve as an effective nomenclature and storage system for graphs or mechanisms. Although this identification scheme was developed specifically for the structural synthesis of mechanisms, it can be applied to any area where graph isomorphism is a critical issue.
Automatic Analysis of Kinematic Structure of Planetary Gear Trains
Authors: Hsu Cheng-Ho , Lam Kin-Tak
Published: June 2008

This paper presents a systematic algorithm for the automatic analysis of the kinematic structure of planetary gear trains with any number of degrees of freedom. The canonical displacement graphs and rotation graphs are introduced to represent the kinematic structure of planetary gear trains. Next, a single identification number method is presented to identify the displacement isomorphism of planetary gear trains. Then, nonfractionated multi-DOF planetary gear trains can be identified from their rotation graphs. Finally, an interactive computer program is developed for the automatic analysis of the kinematic structure of planetary gear trains. The result of this work is beneficial to the development of the new planetary gear trains.
A Systematic Approach to Power-Flow and Static-Force Analysis in Epicyclic Spur-Gear Trains
Authors: Pennestri` E. , Freudenstein F.
Published: June 2008

It is well known that the circulating power in gear trains can be many times greater than the input power. Such circumstances require that in the design of split-power gear drives, a preliminary power-flow analysis be carried out. In this investigation a systematic method for the power-flow and static-force analysis of spur-gear drives is presented. The manner in which the procedure is applied has some similarities with an algorithm for kinematic analysis previously suggested by one of the authors. Following a brief review of previous work, the theoretical bases of the new methodology of analysis are discussed and numerical examples developed.
The Mechanical Efficiency of Epicyclic Gear Trains
Authors: Pennestri` E. , Freudenstein F.
Published: June 2008

The analysis of mechanical efficiency constitutes an important phase in the design analysis of gear drives. The objective of this investigation has been the development of a general algorithm for the determination of efficiency in split-power spur-gear trains. The model includes meshing losses only; for a more realistic estimation other sources can be considered separately. The systematic nature of the formulation, based on the dual correspondence between the kinematic structure of the gear drive and a labelled graph, allows a ready coding of the efficiency analysis in a general computer program. The numerical results are in line with those given by other authors using different methodologies.
Type Synthesis of Vehicle Planar Suspension Mechanism Using Graph Theory
Authors: Liu T. S. , Chou C. C.
Published: June 2008

This paper presents a graph theory-based approach to optimum type synthesis of vehicle suspension mechanisms using an expert system. Kinematic chain isomorphism is identified, using an extended degree method to facilitate the enumeration of kinematic structures. Rules representing design criteria and the flow value theory based on energy loss calculation are incorporated in the rule base to evaluate and select mechanisms among those that are enumerated in the database. Statistical variance calculation serves to complement the flow value theory. A new method called the extended flow value method is devised for isomorphism checking of labeled graphs. In the spirit of increasing emphasis on the riding quality of vehicles, several novel suspension configurations are created to ensure maintenance ease and vibration damping efficiency.
An Elastodynamic Analysis and Control of Flexible Linkages Using Piezoceramic Sensors and Actuators
Authors: Liao C. Y. , Sung C. K.
Published: June 2008

This paper presents an analytical and experimental study on the elastodynamic analysis and control of flexible linkages mechanisms using piezoceramic sensors and actuators. A mixed variational principle is developed to provide the basis for deriving the finite element equations which govern the dynamic responses of the flexible links, behavior of the piezoelectric materials and their coupling relationships, while being subjected to both mechanical and electric boundary conditions. The piezoceramic devices featuring the characteristics of smart materials capable of sensing and controlling elastodynamic responses of the flexible links are employed in an LQG/LTR (Linear Quadratic Gaussian with Loop Transfer Recovery) control scheme to ensure a stable performance. Finally, a four-bar linkage mechanism with one flexible link is utilized as an illustrative example. The results show that the midspan vibration of the flexible link has been greatly suppressed and the control/observer spillover-induced instability has been avoided.
Double Crank External Geneva Mechanism
Authors: Al-Sabeeh A. K.
Published: June 2008

A designer specified motion characteristics can be obtained using the double crank external Geneva mechanism presented in this work. This mechanism basically consists of double cranks and double curved slots that work together in generating the desired output motion. In other words, the profiles of the slots are defined based on the specified output motion. This feature opens the door for big motion improvements, such as minimizing the maximum acceleration and eliminating infinite jerk. Furthermore, it allows for stepping angles larger than 120 deg (the upper limit for simple Geneva mechanism) and even operates at smaller overall pressure angle. In this paper, the equations defining the slot profiles for some desired output motion are derived. The expression for the pressure angle as a function of the crank displacement angle is obtained. The equations are put into application by an example design of double slotted replacement Geneva mechanism, showing the applicability of the approach and the improvement gained in reducing the pressure angle.
Design Sensitivity Derivatives for Isoparametric Elements as an Integrated Part of Finite Element Analysis
Authors: Zumwalt K. W. , El-Sayed M. E. M.
Published: June 2008

This work presents an approach for incorporating design sensitivity calculations into the finite element analysis. The formulation depends on the implicit differentiation approach and requires few additional calculations to obtain the design sensitivity derivatives. The implicit differentiation approach is developed and implemented to calculate the design sensitivities for continuum and structural isoparametric elements. To demonstrate the developed approach test cases using different structural and continuum element types are presented.
A Simulation Technique for the Improvement of Robot Calibration
Authors: Zak G. , Fenton R. G. , Benhabib B.
Published: June 2008

Industrial robots may not be off-line programmable, unless their accuracy is improved by a suitable calibration procedure. However, proper calibration is a time-consuming and expensive procedure due to the highly accurate measurement equipment required and due to the significant amount of data that must be collected. These considerations prevent wider application of currently available calibration methods to robots in industrial environment. To provide the necessary tools for the optimization of the calibration process, in this paper, a computer simulation of the robot calibration and a systematic method for the evaluation of this calibration are developed. Simulated experiments are conducted to demonstrate the operation of the proposed method. Analysis of the data obtained in these experiments shows the capability of the simulation for comparison of alternative calibration procedures/set-ups and for prediction of the expected accuracy of the robot after an actual calibration is performed.
Collision-Free Path Planning by Using Nonperiodic B-Spline Curves
Authors: Yang D. C. H.
Published: June 2008

This paper presents a method and an algorithm for the planning of collision-free paths through obstacles for robots end-effectors or autonomously guided vehicles. Fifth-order nonperiodic B-spline curves are chosen for this purpose. The main ideas are twofold: first, to avoid collision by moving around obstacles from the less blocking sides; and second, to assign two control points to all vertices of the control polygon. This method guarantees the generation of paths which have C3 continuity everywhere and satisfy the collision-free requirement. In addition, the obstacles can be of any shape, and the computational complexity and difficulty are relatively low. A computer code is developed for the implementation of this method. Case studies are given for illustration.
Optimum Design of a Gearbox for Low Vibration
Authors: Inoue K. , Townsend D. P. , Coy J. J.
Published: June 2008

A computer program was developed for designing a low vibration gearbox. The code is based on a finite element shell analysis, a modal analysis, and a structural optimization method. In the finite element analysis, a triangular shell element with 18 degrees-of-freedom is used. In the optimization method, the overall vibration energy of the gearbox is used as the objective function and is minimized at the exciting frequency by varying the finite element thickness. Modal analysis is used to derive the sensitivity of the vibration energy with respect to the design variable. The sensitivity is representative of both eigenvalues and eigenvectors. The optimum value is computed by the gradient projection method and a unidimensional search procedure under the constraint condition of constant weight. The computer code is applied to a design problem derived from an experimental gearbox in use at the NASA Lewis Research Center. The top plate and two side plates of the gearbox are redesigned and the contribution of each surface to the total vibration is determined. Results show that even the optimization of the top plate alone is effective in reducing total gearbox vibration.
Global Local Finite Element Method (GLFEM) in Gear Tooth Stress Analysis
Authors: Moriwaki I. , Fukuda T. , Watabe Y. , Saito K.
Published: June 2008

The present study is concerned with an application of the global local finite element method (GLFEM) to a gear tooth stress analysis. The GLFEM is a numerical analysis technique which combines finite element solutions and classical analytical ones on the basis of the energy principle. In this method, the classical analytical solutions give an almost exact stress field to the elements in which the stress varies very rapidly and/or the stress concentration is found. A fine subdivision, therefore, is not required. In the application of the conventional finite element method to the gear tooth stress analysis, the fine subdivision is required especially at the positions near tooth bottom and the load applied point. Hence, only two-dimensional analysis is available for common use. Furthermore, in order to determine an exact location of a critical section on which a fillet stress is maximum, we must use complicated procedures, e.g., an iteration of subdivision for searching the maximum nodal stress. In the present paper, the GLFEM is applied to the gear tooth stress analysis to show that even the rough subdivision enables us to make the precise three-dimensional analysis. It also guarantees an easy determination of the critical section. Thus, we show the effective future of the GLFEM to the gear tooth stress analysis.
Size Effect in Bending Strength of Carburized Gear Teeth
Authors: Kato M. , Inoue K. , Deng G. , Jeong B. S.
Published: June 2008

This paper deals with the bending strength and the size effect of carburized fine module gears. The fine module test gears (m = 1–1.5) are made of a low-carbon alloy steel, and they are carburized to have various effective case depths. The bending fatigue tests are performed using these gears. From the test results, the AGMA recommendation of the effective case depth is confirmed to be valid in view of the bending strength. The SN curves are obtained and they are expressed by the experimental formulas. The fatigue strength of fine module gears are compared with the strength of gear of m = 5, and the size factor is evaluated. In order to make clear the size effect, the fracture mechanics is applied to the fatigue test results. The fatigue life is assumed to be the crack propagation process, and the maximum initial length of crack is evaluated. This crack length is proportional to the thickness of nonmartensitic layer at the fillet. The size effect is discussed on the basis of stress intensity factor and the thickness of nonmartensitic layer.
Loads of Planet Wheels in Planetary Gears
Authors: Mierzejewski W. , Szopa T.
Published: June 2008

This paper presents a probabilistic model of loads of the planet wheels for the planetary gears with so called “floating driving wheels.” A model was used to determine the probability distribution of the planet wheel load. The examples of application of the obtained results to the planetary gears with three and five planet wheels are presented. The results confirm that the nonuniformity of the planet wheels load may be significant.
Belt Vibration Considering Moving Contact and Parametric Excitation
Authors: Yue M. G.
Published: June 2008

The contacting point between belt and pulley is not fixed but moves along the pulley during vibration and that influences on the free span length of the belt. The concept vibrating length is introduced and that will affect the dynamic behavior of the belt. Parametric excitation can occur through periodic variations in belt tension and speed arising from loading of the pulleys by belt-driven accessories and from engines in automotive applications. Violent oscillations develop and resonance will occur when the frequency of excitation is close to twice or three times the natural frequency for varying tension and speed case, respectively.
Transmission Analysis—Automatic Derivation of Relationships
Authors: Hedman A.
Published: June 2008

A method for derivation of relationships for general mechanical transmission systems is given. It is adapted for computer-aided analysis and synthesis of the kinematics, loads, and power flows. Losses are included. All relationships are handled by a computer program. No manual dealing with equations is necessary. The user only describes the transmission systems: (1) The transmission units, e.g., gear transmissions, planetary gear trains, clutches and input shafts. (2) How the shafts of those units are connected. Then, the computer program formulates the relationships, and a computer algebra program performs algebraic eliminations. Symbolic, non-numerical, relationships between speeds and torques of two arbitrary shafts can be derived, e.g., the overall efficiency. Special algorithms handle the power flows in split-power transmissions. The method saves time and eliminates the risk for human errors.
A Study on Transmission Error in Timing Belt Drives (Effect of Production Error in Polychloroprene Rubber Belt)
Authors: Kagotani M. , Koyama T. , Ueda H.
Published: June 2008

Experiments on a transmission error caused by production errors in polychloroprene rubber timing belts were performed under a quasistatic condition and an initial tension. The experimental results were compared with the computed results obtained using the measurement results of the production error in the belt. It was confirmed that the transmission error, having a period of one revolution of the belt, was mainly caused by a single pitch error, a change in cross-sectional area of the load carrying cords and a change in modulus of elasticity for one revolution of the belt. As the experimental results coincided quite well with the computed ones, it was concluded that the measurement methods for the single pitch error and the belt elongation factor, and the arrangement methods of these values used to compute the transmission error were valid. Further, it was found that the transmission error due to the production error in the belt lessens when the initial tension becomes smaller.
Maximum Transmission Efficiency of a Steel Belt Continuously Variable Transmission
Authors: Guebeli M. , Micklem J. D. , Burrows C. R.
Published: June 2008

A mathematical model of the power transmission through a Van Doorne steel belt continuously variable transmission is developed. The approach is based on a simplified viscous oil shear stress model. This enables the determination of the power transmission loss resulting from shearing the oil film along the traction line. The power to maintain the necessary hydraulic clamping forces is taken into account to optimize the power transmission efficiency. The analytical solution is evaluated numerically and compared with experimental results. Variations in the hydraulic pump displacement that are determined by the required ratio adjustment dynamics show that with a sufficiently small pump, peak efficiencies exceeding 97 percent are possible.
Decomposition of the Design Process
Authors: Kusiak A. , Wang J.
Published: June 2008

In concurrent engineering, an attempt is made to perform design and other related activities simultaneously rather than in series as in the case of traditional design. This may result in a reduction of the duration of the design project, cost savings, and better quality of the final design. However, the concurrent engineering approach might increase the complexity of the design process and make it more difficult to manage. One way to reduce the complexity of a large scale design project is to apply decomposition. This paper presents a methodology for decomposition of a design process to enhance concurrency. The incidence matrix is used to represent the relationship between tasks and design parameters. The decomposition of a task-parameter incidence matrix is discussed. The constraint-variable decomposition, which is a special case of the task-parameter decomposition, is also presented for the management of constraints. Clustering of tasks involved in the design process allows one to determine a potential group of tasks that might be performed simultaneously or tasks that need a special attention during the design process. As a result of decomposition, the design cycle might be reduced. Another advantage of grouping tasks is the simplification of scheduling and management of the design project. Finally, the proposed approach provides a systematic way of decomposing a design problem into subproblems.
Design Considerations for Materials with Negative Poisson’s Ratios
Authors: Lakes R. S.
Published: June 2008

This article presents a study of the implications of negative Poisson’s ratios in the design of components subjected to stress. When the Poisson’s ratio becomes negative, stress concentration factors are reduced in some situations and unchanged or increased in others. Stress decay according to Saint Venant’s principle can occur more or less rapidly as the Poisson’s ratio decreases. Several design examples are presented, including a core for a curved sandwich panel and a flexible impact buffer.
Centrically Loaded Bolt Joints
Authors: Gerbert G. , Ba˚stedt Ha˚kan
Published: June 2008

Externally loaded bolt joints of different design are investigated. The bolt load is substantially lower than that predicted by the mounting stiffnesses of bolt and abutment. A load application fraction n is introduced in VDI 2230 and some thumb rules are suggested. New fractions are determined which are much lower than the suggested ones. It appears that the application fraction n is almost independent of the location of the external load in practical design but it is influenced by the layout of the bolt joint.
Incorporating Finite Element Analysis into Component Life and Reliability
Authors: August R. , Zaretsky E. V.
Published: June 2008

A method for estimating a component’s design survivability by incorporating finite element analysis and probabilistic material properties was developed. The method evaluates design parameters through direct comparisons of component survivability expressed in terms of Weibull parameters. The analysis was applied to a rotating disk with mounting bolt holes. The highest probability of failure occurred at, or near, the maximum shear stress region of the bolt holes. Distribution of material failure as a function of Weibull slope affects the probability of survival. Where Weibull parameters are unknown for a rotating disk, it may be permissible to assume Weibull parameters, as well as the stress-life exponent, in order to determine the qualitative effect of disk speed on the probability of survival.
Stress Analysis of a Silicon-Wafer Slicer Cutting the Crystal Ingot
Authors: Chonan S. , Jiang Z. W. , Yuki Y.
Published: June 2008

In-plane stress distribution in a spinning free-clamped slicing blade is studied analytically. The blade is subjected to a stationary, distributed, in-plane slicing load along the inner periphery, while it is clamped and tensioned initially in the radial direction along the outer boundary. The radial, hoop, and shear stresses in the blade are given by sum of the stresses from the tensioning, spinning, and edge loading. The solution is obtained by introducing the Laˆme potential functions and the two-dimensional elasticity theory. Numerical results are presented for an actual SUS301 blade cutting a 6-in.-diameter silicon ingot at 1550 rpm. Results obtained show that the contribution of the slicing load on the stress distribution is not significant; further the overall stress distribution is approximated by that of the initial tensioning except for the case of the shear stress distribution.