bluuebunny/crossref_metadata_2025 huggingface dataset:
Generation and Evaluation of a Manipulator Workspace Based on Optimum Path Search
Authors: Cwiakala M. , Lee T. W.
Published: January 2010

This paper presents an algorithm using an optimization technique to outline the boundary profile of a manipulator workspace and perform quantitative evaluation of the workspace volume. The algorithm is applicable to general N-link manipulators with not only the revolute joints, but also joints of other types, such as, the prismatic and cylindrical joints. It is a partial-scanning technique which offers significant reduction on the number of scanning points to generate the workspace and the method is particularly efficient in dealing with complicated manipulator geometry. The [3 × 3] dual-number matrix method is used as the basis for analytical formulations, and consequently, computational advantage is gained. A comparative study is given with a previously used algorithm. Several specific examples involving industrial robots of various kinds are given to demonstrate the capability of the algorithm.
Adjustable Straight-Line Linkages—Possible Legged-Vehicle Applications
Authors: Ryan A. D. , Hunt K. H.
Published: January 2010

The stimulus for this paper is the expressed need in proposals for legged vehicles both to propel the vehicle in rectilinear translation parallel to the mean ground-profile beneath it and to allow the chassis-height to be adjustable. Energy considerations point toward having a single propulsion-actuator on each leg-linkage rather than adopting the less economical option of simultaneous actuation at two or more serially connected leg-joints. Of the linkages whose kinematics are here studied some relate more closely to legged vehicles than others do; the paper should be viewed in a general rather than a specific context. Exact and approximate straight-line planar linkages are covered. Derivatives of Richard Roberts’s linkage are put forward as those that are the most promising adjustable linkages whose joints are all turning pairs.
On the Dexterity of Robotic Manipulators—Service Angle
Authors: Yang D. C. H. , Lai Z. C.
Published: January 2010

This paper presents a theoretical study on the dexterity problem of 6R manipulators. Particularly, it deals with the manipulator’s service angle around a reachable point in space. The first part conceptualizes the ideas of service region, free service region and polarities of robots, and shows that the entire service angle can be categorized into a number of free service regions. The remainder of the paper deals with the investigation of basic properties of free service regions. The relationship between free service regions and service angle is subsequently formulated into a set of theorems and criteria. Specific examples are given for illustration.
Automatic Linearization of Constrained Dynamical Models
Authors: Sohoni V. N. , Whitesell J.
Published: January 2010

An approach is presented for automatically generating a linearized dynamical model which is derived from a nonlinear model in the constrained Lagrangian form. Since the corresponding eigenvalue problem is ill-posed and large, a method for condensing the problem is presented which leads to significant improvements in numerical efficiency.
Cam Synthesis and Analysis for an Elastic Follower Linkage
Authors: Flugrad D. R.
Published: January 2010

A cam driving a single lumped mass through a massless, elastic, slider-crank follower linkage is considered. A technique is developed for synthesizing the cam profile to produce a desired output motion at a given design speed. The procedure takes the elasticity and changing geometry of the linkage into account. Analysis equations are also derived to study the output motion at various speeds. The equation of motion for the output link is found to be a Hill equation whose periodicity depends on the changing geometry of the mechanism.
Consideration of Worst-Case Manufacturing Tolerances in Design Optimization
Authors: Balling Richard J. , Free Joseph C. , Parkinson Alan R.
Published: January 2010

The paper discusses the effect of manufacturing tolerances for the design variables on the solution to an optimization problem. Two formulations of the tolerance problem in an optimization context are presented. Linearization is employed to reduce the problems to quadratic and linear programming problems. The formulations and solutions of the two tolerance problems are illustrated with an example application.
Vibration-Proof Design of Boring Bar With Multidegree-of-Freedom Dampers
Authors: Yoshimura Masataka
Published: January 2010

This paper proposes boring bars equipped with multiple-degree-of-freedom dampers in order to increase stability against machining chatter in boring operations. By using the dampers, the modal flexibility at the natural mode, having the greatest receptance, is divided into smaller modal flexibilities at multiple-degrees-of-natural modes. This theoretical analysis clarifies that the division of the modal flexibility into many natural modes results in (1) the decrease of the modal flexibility; (2) the increase of the damping ratio; (3) shift of the vector locus of the receptance frequency response along the real axis toward the positive direction. These changes occur at the natural mode having the greatest receptance value, producing a great increase in stability against machining chatter. Design procedures for the boring bars are described, and the effect of the dampers is demonstrated in actual cutting tests.
A Design Methodology for Obtaining Infinite Stiffness in an Aerostatic Thrust Bearing
Authors: Bryant Michael R. , Velinsky Steven A. , Beachley Norman H. , Fronczak Frank J.
Published: January 2010

The desire to maintain high positional accuracy has led to many unique bearing designs which achieve high, and even infinite, stiffness. This paper presents a design procedure for an aerostatic thrust bearing and demonstrates that infinite stiffness may be attained by proper selection of the bearing’s geometric parameters. The bearing is comprised of two main components; the bearing housing and a flexible membrane that deflects due to changes in load. The current analysis employs plate equations to approximate the behavior of the membrane. Optimization techniques are utilized in the design algorithm and the results are presented in the form of a design chart or nomograph. Additionally, so that the results may be extended to other bearing sizes and gas properties, scaling laws are developed based on a dimensional analysis of the associated variables.
Geometric Design of a Walking Machine for Optimal Mobility
Authors: Song Shin-Min , Waldron K. J.
Published: January 2010

The design of the geometry of a walking machine depends to a considerable extent on the applications for which the machine is intended. Nevertheless, there are some very general principles and approaches which may be applied. This paper deals with the geometric design of a hexapodal walking machine which is to possess optimum mobility on varied terrain. This problem both illustrates, and serves as a vehicle for, the development of these general principles. Since one of the most important features of legged locomotion is the gait, the fundamental gaits of a 2N-legged (N≥2) walking machine on both flat and irregular terrain are introduced first. The motion of the machine is assumed to be quasi-static. The mobility of a walking machine using these gaits, mainly centered on the hexapodal case, is then discussed. The principles obtained in gait and mobility studies are then applied to the design of the geometry of a hexapod, which includes both body-leg layout and leg walking volumes (working spaces), so that the hexapod may possess the optimum mobility.
A Variational Principle for the Hygrothermoelastodynamic Analysis of Mechanism Systems
Authors: Sung C. K. , Thompson B. S.
Published: January 2010

A variational theorem is presented that may be employed for systematically establishing the equations governing the dynamic response of flexible planar linkage mechanisms simultaneously subjected to both mechanical and hygrothermal loadings. This theoretical development is motivated by recent research advocating that high-speed mechanisms should be fabricated in polymeric fibrous composite materials in order to achieve high-performance characteristics. The constitutive behavior of some of these materials is, however, dependent upon the ambient environmental conditions, and hence mathematical models must be developed in order to predict the response of mechanism systems fabricated with these materials. This class of mechanism systems is modeled herein as a set of continua in which elastic deformations are superimposed upon gross rigid-body motions. By permitting arbitrary independent variations of the system parameters for each link, approximate equations of motion, energy balance, mass balance, and boundary conditions may be systematically constructed. As an illustrative example, the derivation of a problem definition for the flexible connecting-rod of a slider-crank mechanism subjected to hygrothermal loading is presented.
Development of Knowledge Base for Designing Linkage-Type Dwell Mechanisms: Part 1—Theory
Authors: Kota Sridhar , Erdman Arthur G. , Riley Donald R.
Published: January 2010

Linkage-type mechanisms have certain advantages over cams for dwell applications. The design of a typical six-link dwell mechanism involves adding an output dyad to the basic four-bar mechanism that generates either a circular arc or a straight line portion of the coupler curve. The entire motion characteristics of these four-bar mechanisms should be considered in order to design a suitable dwell linkage. Part 1 of this paper is devoted to the study of four-bar linkages which generate straight line, circular arc and symmetrical curves. Part 2 discusses how the design experience gained in this study can be applied to develop an expert system for designing linkage-type dwell mechanisms. Using path curvature theory and design charts developed by Tesar, et al., hundreds of four-bar straight-line mechanisms are systematically investigated. Based on the typical shapes of coupler curves these mechanisms are then classified. A synthesis technique has been developed to design four-bar mechanisms for circular arc generation. Symmetrical coupler curves with straight-line or circular-arc segments, which are required for designing double-dwell mechanisms, are studied. This paper is part of the research that is underway to develop an “expert system” for designing mechanisms to generate straight lines, circular arcs, symmetrical curves, parallel motion and dwell.
Restraint Analysis of a Rigid Body Using Frictional Elastic Contacts
Authors: Kerr D. R. , Sanger D. J.
Published: January 2010

This paper presents the analysis of restraint of a rigid body in contact with any arrangement of point contacts having known frictional properties. A necessary condition for the solution of this problem is that the elastic properties of the contacts are also known. The relationship between externally applied loads and contact forces in the presence of limiting friction is established, as is the means for evaluating the resulting bodily motion, with or without slip at the contacts. An example is given to illustrate the application of the theoretical basis to a device such as a robot gripper that relies on friction for restraint.
A Comparative Study on Some Different Formulations of the Dynamic Equations of Constrained Mechanical Systems
Authors: Unda J. , Garci´a de Jalo´n J. , Losantos F. , Enparantza R.
Published: January 2010

This paper presents a comparative theoretical and numerical study on the efficiency of several numerical methods for the dynamic analysis of constrained mechanical systems, also called in the literature multibody systems. This comparative study has been performed between methods based on the use of “reference point” coordinates and those based on the use of “natural” coordinates. This study embraces different possibilities to formulate the differential equations of motion. The relative efficiency of the resulting algorithms has been analyzed theoretically in terms of the number of multiplications needed to evaluate the mechanism accelerations. This efficiency has also been studied implementing the methods into computer codes and testing them with different examples. Conclusions on the relative efficiency of the methods are finally presented.
Lateral Stability Behavior of Railway Freight Car System With Elasto-Damper Coupled Wheelset: Part 1—Wheelset Model
Authors: Ahmed A. K. W. , Sankar S.
Published: January 2010

A general model of single rail vehicle wheelset with elasto-damper coupling between the wheels, has been developed as a first step in developing a railway freight truck model with elasto-damper coupled wheelset (EDCW). By choosing different coupler parameters, various stiffness-damper combinations, as well as rigid axle (conventional wheelset) could be simulated. The mathematical model of EDCW has been validated by comparing the model under limiting cases with those of published results for conventional system. In this paper, the results of linearized stability analysis of EDCW model on tangent track are presented and discussed. The investigation showed that wheelset coupler parameters have significant influence on the stability behavior of the wheelset, and there is an optimal coupler parameter which can improve the wheelset critical speed over the conventional system.
The Computer-Aided Optimal Heating of Forging Ingots Using the Finite-Element Method
Authors: Reddy B. S. , Sharan A. M.
Published: January 2010

This investigation involves the axisymmetric transient temperature calculations using the finite-element analysis during heating of an ingot. Two types of nonlinearities are considered: the first one is the nonlinear variations of the material properties and the second one is the nonlinear radiative boundary conditions. Based on the temperature distribution the thermal stresses are calculated. These results are compared with the results obtained by the two-dimensional finite-element and finite-difference methods. The effect of the variation of the slenderness ratio of the ingot on the temperature and stress distribution are also studied. The optimal heating schedule of the ingot is obtained considering the maximum allowable stresses based on various failure theories and the maximum temperature as constraints.
Synthesis of Harmonic Motion Generating Linkages—Part II: Path and Motion Generation
Authors: Farhang K. , Midha A. , Hall A. S.
Published: January 2010

This paper, a sequel to a companion paper on function generation, discusses the path and motion generation problems in the synthesis of linkages with relatively small input cranks. The point on the floating link (i.e., the coupler of a crank-rocker linkage or the connecting rod in a slider-crank linkage) traces an approximate ellipse. This fact serves as a major distinction between the method described herein and the conventional, more general, synthesis techniques. In other words, only elliptical paths may be generated by the path (or coupler) points in the synthesis of linkages with small cranks. Higher-order path and motion generation, in which velocity, acceleration, slope and the rate of change of slope of the coupler path may be specified, are also addressed in this paper.
Hybrid Twist and Wrench Control for a Robotic Manipulator
Authors: Lipkin H. , Duffy J.
Published: January 2010

Three necessary conditions derived from classical geometry are proposed to evaluate formulations for the simultaneous twist and wrench control of rigid bodies, and for any theory to be meaningful it must be invariant with respect to (1) Euclidean collineations, (2) change of (Euclidean) unit length, and (3) change of basis. It is demonstrated in this paper that a previously established theory of hybrid control for robot manipulators is in fact based on the metric of elliptic geometry and is thus noninvariant with respect to (1) and (2). A new alternative invariant formulation based on the metric of Euclidean geometry and an induced metric of projective geometry is presented in terms of screw theory. An example of insertion illustrates both the invariant and noninvariant methods.
The Optimal Design of Squeeze Film Dampers for Flexible Rotor Systems
Authors: Chen W. J. , Rajan M. , Rajan S. D. , Nelson H. D.
Published: January 2010

Optimization techniques are employed to design squeeze film dampers for minimum transmitted load to the bearing and foundation in the operational speed range. The rotor systems are modeled by finite element formulation. The maximum transmitted load in the operational speed range is the objective function that is minimized using mathematical nonlinear programming (NLP) techniques. The damper design parameters are the radius, length, and radial clearance. Stability of the equilibrium solutions are investigated in the design procedure. Design derivatives have been determined in closed form expressions without resolution of the inherently nonlinear problem. A parametric study of the transmitted force is carried out to show the influence of damper parameters on the response and to demonstrate the merits of applying optimization techniques in damper design. Two numerical examples are presented that illustrate the effectiveness of optimizing squeeze film damper designs for reducing transmitted load.
Reliability Analysis of Robot Manipulators
Authors: Bhatti P. K. , Rao S. S.
Published: January 2010

A probabilistic approach to robot kinematics is presented and the concept of manipulator reliability is introduced to obtain a better evaluation of the performance of manipulators. Techniques are presented to compute this reliability and its relationship to the geometric parameters such as tolerances and arm configuration are discussed. The aspects of accuracy and repeatability of manipulators are explained in terms of manipulator reliability. The reliability of a two-link planar manipulator and the Stanford arm are considered for numerical illustration.
On Dynamic Loads in Parallel Shaft Transmissions: Part II—Parameter Study
Authors: Lin H.-H. , Huston R. L. , Coy J. J.
Published: January 2010

Solutions to the governing equations of a spur gear transmission model, developed in Part I, are presented. Factors affecting the dynamic load are identified. It is found that the dynamic load increases with operating speed up to a system natural frequency. At operating speeds beyond the natural frequency the dynamic load decreases dramatically. Also, it is found that the applied load and shaft inertia have little effect upon the dynamic load. Damping and friction decrease the dynamic load. Finally, tooth stiffness has a significant effect upon dynamic loading: the higher the stiffness, the lower the dynamic loading. Also, the higher the stiffness the higher the rotating speed required for peak dynamic response.
Singularities in Motion and Displacement Functions for the RCRCR Linkage
Authors: Litvin F. L. , Tan J.
Published: January 2010

The previously proposed approach (Litvin et al, 1986b) is applied for determination of singularities in motion and displacement functions for the RCRCR linkage. Singularities in motion occur at positions where an overconstrained group of links becomes movable at least locally while the driving link is fixed. The determination of displacement functions is based on modeling of the linkage by two open kinematic chains formed by: (a) links of an overconstrained group of links and (b) the driving link and the frame. Conditions of “assembly” of the open chains provide invariants—scalar products—that yield the appropriate equations that relate the parameters in motion of the driving link and the overconstrained group of links. The number of linkage configurations is proposed to determine through the number of singularity positions that are simulated with a certain combination of the linkage design parameters.
Computer-Aided Design of the RSSR Function Generating Spatial Mechanism Using the Selective Precision Synthesis Method
Authors: Dhall S. , Kramer S. N.
Published: January 2010

Planar function generating mechanisms may be synthesized for a limited number of precision points by carrying out a kinematic inversion about the output link. However, this becomes quite difficult for spatial mechanisms. In this paper the general RSSR spatial function generating mechanism is synthesized using the Selective Precision Synthesis technique. In this computer-aided design method, nonlinear constraint equations relating the generated and desired rotations of the output crank are formulated. These constraints which define accuracy neighborhoods around each of the “n” prescribed output crank rotations are then solved using the Generalized Reduced Gradient Method of optimization. The mathematical formulation, the general procedure of synthesis, and numerical examples are presented in this paper.
Accurate Motion of a Robot End-Effector Using the Curvature Theory of Ruled Surfaces
Authors: Ryuh B. S. , Pennock G. R.
Published: January 2010

In robotics, there are two methods of trajectory planning: the joint interpolation method which is appropriate for fast transition of the robot end-effector; and the cartesian interpolation method which is appropriate for slower motion of the end-effector along straight path segments. Neither method, however, is sufficient to allow a smooth, differentiable, transition of position and orientation of the end-effector. In this paper, we propose a method of trajectory planning that will permit more accurate motion of a robot end-effector. The method is based on the curvature theory of a ruled surface generated by a line fixed in the end-effector, referred to as the tool line. The orientation of the end-effector about the tool line is included in the analysis to completely describe the six degree-of-freedom motion of the end-effector. The linear and angular properties of motion of the end-effector, determined from the differential properties of the ruled surface, are utilized in the trajectory planning.
Manipulator Configurations Based on Rotary-Linear (R-L) Actuators and Their Direct and Inverse Kinematics
Authors: Kohli D. , Lee Soo-Hun , Tsai Kao-Yueh , Sandor G. N.
Published: January 2010

In this paper, a new type of two-degree-of-freedom actuator called the rotary-linear (R-L) actuator is described. The R-L actuator permits a rotation and a translation along the axis of rotation, thus simulating a cylinder pair. The R-L actuators are then used in type synthesis of mechanical manipulator chains. Closed-loop three-, four, five, and six-degree-of-freedom chains containing four to nine links, R-L actuators, revolute pairs (R), prismatic pairs (P), cylindrical pairs (C), and spheric pairs (S) are then obtained. A class of manipulator configurations where the hand is connected to the ground via six-degree-of-freedom dyads or triads and containing three grounded R-L actuators is treated for inverse kinematics. Since all the actuators are on the ground in this configuration, higher payload capacities and smaller actuator sizes can be expected from these configurations. In addition, generally, the computations required for inverse kinematics are also significantly less than those required for serial link open-loop manipulators. The direct kinematics, however, is much more involved and computationally intensive for these manipulators than for serial-link manipulators. The direct kinematics of an example manipulator is derived and requires solution of a 16th-order polynomial equation. Numerical examples are presented for illustration.
Three-Position Function Generation of Planar Four-Bar Mechanisms With Equal Deviation Transmission Angle Control
Authors: Barker C. R. , Shu Gwo-Huey
Published: January 2010

This paper is an extension of earlier work on mapping of three-position function generation of planar four-bar mechanisms. Previously, it has been shown that all of the potential solutions to a given problem may be represented in an αβ-plane which can be subdivided into mechanism types. Further, the regions in the αβ-plane may represent two possible forms of assembly plus a change of form class which are not valid solutions. In this paper, we provide a third-order polynomial which defines the locus in the αβ-plane of solutions which have equal deviation of their transmission angle from the ideal of 90° throughout the entire range of motion. When these solutions are mapped into a Cartesian plane, the ground pivot locations produce curves similar to the familiar Burmester curves for four-position synthesis problems. Additional advantages of the approach are that the input link is automatically a crank, the desired link length ratio can be controlled, and the solutions are free of defects.
Analysis, Properties, and Design of a Stewart-Platform Transducer
Authors: Kerr D. R.
Published: January 2010

This paper analyzes the behavior of a force transducer that has the form of a Stewart platform with instrumented elastic legs. The algebraic relationship between externally applied wrench and resulting leg extensions is derived, using the algebra of dual vectors. Using this model, and by suitable choice of dimensions, it is shown how the transducer can be designed to give the most advantageous behavior. A simple illustrative example is given.
Computational Scheme for Dynamic Analysis of Parallel Manipulators
Authors: Sugimoto K.
Published: January 2010

Equations are derived for dynamic analysis of a parallel manipulator. Using the motor algebra, an equation for the equilibrium condition of forces and moments at each link is derived and unneeded parameters are eliminated from these equations to give equations for calculating the joint torques needed to drive the parallel manipulators. As a result, it is shown that, just as for a serial manipulator, the joint torques in a parallel manipulator can be found from the transposed Jacobian. The method derived here is applied to the Stewart Platform, which is a special case of a parallel manipulator and the result obtained is dynamically considered to confirm the appropriateness of this method.
Some Factors Influencing Friction Brake Performance: Part 1—Investigation of Full-scale Brake Systems
Authors: Barecki Z. , Scieszka S. F.
Published: January 2010

In this paper the effect on braking torque of the geometry of contact between brake shoes and drums is presented. It is shown that elastic deformation as well as errors in dimensional and assembly errors substantially affect the value of the braking torque. Investigations of pressure distribution on friction lining, brake factor, brake element deformation, and wear of linings carried out on mine winder installations are presented.
Synthesis of Parallel Micromanipulators
Authors: Hara A. , Sugimoto K.
Published: January 2010

A synthesis method has been developed for the parallel micromanipulator used in a precise positioning. Elastic deformation at notches are used as joint displacements. Since the joint displacements are very small and the micromanipulator makes only a minute motion, the input/output relation can be put in the form of a Jacobian. Each row of the Jacobian designates six elements of a force and moment. By locating the passive joints in a connecting chain so that the virtual work done by the force/moment and the virtual displacement of the passive joints becomes zero, the mechanism that has the given Jacobian is determined. Planar and spatial mechanisms whose Jacobians are diagonal matrices are shown as examples of the synthesis.
On the Dead-Center Positions of Planar Linkage Mechanisms
Authors: Yan Hong-Sen , Wu Long-long
Published: January 2010

In dead-center positions, a mechanism loses its mobility and has zero mechanical advantage. Based on the concept of instant centers, we develop a methodology to generate planar linkage mechanisms in dead-center positions. This methodology also can be applied to generate planar toggle linkage mechanisms. All possible configurations of six-bar planar linkage mechanisms, with one degree of freedom, in dead-center positions are listed.
The Optimum Kinematic Design of a Spherical Three-Degree-of-Freedom Parallel Manipulator
Authors: Gosselin C. , Angeles J.
Published: January 2010

In this paper, the design of a spherical three-degree-of-freedom parallel manipulator is considered from a kinematic viewpoint. Three different design criteria are established and used to produce designs having optimum characteristics. These criteria are (a) symmetry (b) workspace maximization, and (c) isotropy. The associated problems are formulated and their solutions, one of them requiring to resort to a numerical method, are provided. Optimum designs are thereby obtained. A discussion on singularities is also included.
Multi-Level Design Optimization Using Global Monotonicity Analysis
Authors: Azarm S. , Li W.-C.
Published: January 2010

This paper describes application of global monotonicity analysis within a mutli-level design optimization framework. We present a general formulation and solution procedure, based on a bottom-level global monotonicity analysis, for a design optimization problem which is decomposed into three levels of subproblems. A well-known gear reducer example illustrates application of the method.
Cycloid Drives With Machining Tolerances
Authors: Blanche J. G. , Yang D. C. H.
Published: January 2010

The cycloidal speed reducer, or cycloid drive, is an epicyclic gear train in which the profile of the planet gear is an epitrochoid and the annular sun gear has rollers as its teeth. The cycloid drive has very high efficiency and small size, in comparison with a conventional gear mechanism, making it an attractive candidate for limited space applications. On the other hand, in this type of transmissions there exist two major drawbacks, namely, backlash and torque ripple. Backlash, the angle through which the output shaft can rotate when the input shaft is held fixed, has a degrading effect on the output accuracy. Torque ripple, the variation in mechanical advantage as the input shaft rotates, causes vibrations and could lead to dynamic instability of the machinery. If the cycloid drive were manufactured to the ideal dimensions, there would be no backlash nor torque ripple. However, in reality, there will always be some machining tolerances. In this paper an analytical model is developed which models the cycloid drive with machining tolerances. Consequently, the effect of machining tolerances on backlash and torque ripple are investigated. It is found that both the backlash and the torque ripple are inherent periodic functions of the input crank angle.
A Hydrodynamic Analysis of Fluid Flow Between Meshing Spur Gear Teeth
Authors: Wittbrodt M. J. , Pechersky M. J.
Published: January 2010

A hydrodynamic analysis of the pumping action resulting from the meshing of spur gear teeth was performed. Both compressible (for air) and incompressible (for oil) flow cases were considered. The computed results included the velocity of the fluid at the minimum flow area between the meshing teeth. The pressure and temperature in the mesh region were also computed for the compressible flow case. The velocities were computed as a function of the mesh angle with the pitch line velocity as the normalizing parameter. The calculations required a detailed analysis of the involute geometry to compute the proper mesh region volumes and exit flow areas. For the incompressible calculations with wide face gears, it was found the peak fluid velocity could greatly exceed the pitch line velocity. For the compressible calculations, it was found that sonic conditions could be reached at the minimum flow area leading to the possibility of shock formation downstream of this region. Parametric results for both sets of calculations, including backlash, diametral pitch, and other factors, are presented.
Enumeration of Basic Kinematic Chains Using the Theory of Finite Groups
Authors: Tuttle E. R. , Peterson S. W. , Titus J. E.
Published: January 2010

A procedure for systematically and completely enumerating all nonfractionated planar kinematic chains having N links and F degrees of freedom has been developed. This procedure employs the theory of finite symmetry groups to eliminate isomorphic chains. The analysis of 8-, 9-, and 10-link chains having 1, 2, and 3 degrees of freedom, respectively, is presented as an example.
Euler Parameters in Computational Kinematics and Dynamics. Part 1
Authors: Nikravesh P. E. , Wehage R. A. , Kwon O. K.
Published: January 2010

This paper presents useful and interesting identities between Euler parameters and their time derivatives. Using these identities, kinematic constraints and equations of motion for constrained mechanical systems are derived. These equations can be developed into a computer program to systematically generate all of the necessary equations to model mechanical systems. The compact form of these equations makes it possible to develop a general-purpose computer program for dynamic analysis of mechanical systems suitable for operation on small computers with limited memory space.
On the Intrinsic Properties of Point Trajectories in Three-Dimensional Kinematics
Authors: Hsia L. M. , Yang A. T.
Published: January 2010

In this paper we derive analytical expressions for curvature, torsion, and radius of osculating sphere of the point trajectory in three-dimensional kinematics. Corresponding to a design position we obtain equations of loci of points tracing straight lines, helical curves, and spherical curves. It is hoped that the result of this study will provide another step toward rational design of spatial mechanisms and control systems for robot manipulators.
Monotonicity Analysis and Recursive Quadratic Programming in Constrained Optimization
Authors: Zhou J. , Mayne R. W.
Published: January 2010

This paper considers the use of an active set strategy based on monotonicity analysis as an integral part of a recursive quadratic programming (RQP) algorithm for constrained nonlinear optimization. Biggs’ RQP method employing equality constrained subproblems is the basis for the algorithm developed here and requires active set information. The monotonicity analysis strategy is applied to the sequence of search directions selected by the RQP method. As each direction is considered, progress toward optimum occurs and a new constraint is added to the active set. As the active set is finalized the basic RQP method is followed unless a constraint is to be dropped. Testing of the proposed algorithm illustrates its promise as an enhancement to Biggs’ original procedure.
A Constant Force Generation Mechanism
Authors: Nathan R. H.
Published: January 2010

A mechanism is described that generates a constant, unidirectional force at any given point on a hinged lever, for all positions of the lever within a full rotation. It is shown how one of several selected geometric parameters of the mechanism may be preadjusted automatically to equilibrate the system, using force feedback from the output load. The constant force generator is introduced into a parallelogram four-bar mechanism, and it is shown that this system may replace links of a kinematic chain to achieve static balancing of the chain plus any additional masses or vertical forces.
On the Minimum Number of Counterweights for Multi-Loop Spatial Linkages
Authors: Zhang Q.-X. , Chen N.-X.
Published: January 2010

This paper offers extensions to the force-balancing theory and the techniques of spatial linkages given in [9-12]. It incorporates another technique for determining the minimum number of counterweights needed for a full balance and discusses the minimum number of counterweights without attachment to any common floating link of loops. Some examples are given to illustrate the application of these results.
Kinematic Synthesis and Analysis of the Rack-and-Gear Mechanism for Four-Point Path Generation With Prescribed Input Timing
Authors: Claudio M. , Kramer S.
Published: January 2010

The rack and gear mechanism is synthesized for generating four prescribed path points with input coordination. This mechanism has a number of advantages over the well-known four-bar linkage. First, the transmission angle is always at its optimum value of 90 deg since the rack is always tangent to the gear. Second, with both translation and rotation of the rack occurring, multiple outputs are available. Other advantages include the generation of monotonic functions for a wide range of motion and nonmonotonic functions for the full range of motion as well as nonlinear amplified motions. In this work, the mechanism is made to satisfy a number of practical design requirements such as having a completely rotatable input crank, elimination of the branching defect and others. The method of solution developed in this work employs the Burmester Four-Precision-Point Algorithm with additional relations utilizing the Complex Number Method of Mechanism Synthesis. The solution is programmed on the DEC/PDP 11/70 and is available to interested readers.
Deterministic and Stochastic Multiobjective Optimization of Beam and Shell Structures
Authors: Eschenauer H. , Kneppe G. , Stenvers K. H.
Published: January 2010

This paper presents application examples of vector optimization (Pareto-optimization) especially for the design of beam and shell components. A deterministic as well as a stochastic optimization model is formulated. Stochastic models will be important in the future because many factors in fabrication and operation are of random nature (fabrication tolerances, loads, etc.). For the special case of a sandwich beam these influences are demonstrated by means of a sensitivity analysis. For all examples presented (shell-flange structure, sandwich beam, panel-truss structure) the solution of the optimization problem results from transformation into scalar substitute problems by means of preference functions. In the examples, various optimization algorithms (e.g., sequential linear programming) were tested.
QR Decomposition for State Space Representation of Constrained Mechanical Dynamic Systems
Authors: Kim S. S. , Vanderploeg M. J.
Published: January 2010

This paper presents a numerical solution method for dynamic analysis of constrained mechanical systems. This method reduces a coupled set of differential and algebraic equations to state space form. The reduction uses an independent set of velocities which lie on the tangent plane of the constraint surface. The tangent plane is defined by the nullspace of constraint Jacobian matrix. The nullspace basis is found using QR decomposition of the constraint Jacobian matrix. Because the nullspace basis is not unique, directional continuity of the nullspace is difficult to preserve each time the Jacobiar is decomposed. This paper presents an updating algorithm that is used instead oj repeated decomposition. This preserves directional continuity of the Jacobian matrix and increases efficiency. State equations are then derived in terms of independent accelerations and therefore can efficiently be integrated. Generalized velocities are integrated with constraints to obtain positions. This method has demonstrated minimal constraint violations and improved efficiency. Numerical examples with singular configurations and redundant constraints are presented to demonstrate the effectiveness of the method.
Optimal Design of Cooling Fans for Industrial Electric Motors
Authors: Woodard J. K. , Johnson G. E.
Published: January 2010

Various industrial electric motors use a combination of internal and external fans to remove internally generated heat. In recent years as the electrical efficiency of motors has improved, the power drawn by the cooling fans has become a large percentage of the total motor losses. This paper presents an optimization approach to the selection of the cooling fan dimensions. The design objective is to obtain minimum power input to the fans while maintaining adequate cooling capacity. To illustrate the method, the cooling fan design for a 30 hp, 3600 rpm, a-c motor is considered. The optimal fan dimensions result in a 70 percent reduction in fan power.
Third-Order Surface Application to Determine the Tooth Contact Pattern of Hypoid Gears
Authors: Takahashi Koichi , Ito Norio
Published: January 2010

In the conventional theory for hypoid gears tooth surfaces are represented by second-order surfaces. However, for developing an excellent tooth bearing, this theory is not accurate enough because higher-order surfaces are required. This paper presents a new theory using third-order tooth surfaces instead of the conventional second-order surfaces. The results are useful for drawing accurate patterns of the tooth bearing and eliminating the need for trial-and-error methods to improve the tooth bearing.
Survey of Power Tower Technology
Authors: Hildebrandt A. F. , Dasgupta S.
Published: January 2010

With a national commitment to solar energy, the power tower concept could generate 40 gigawatts of electricity and double this amount in process heat by the year 2000. This technology lends itself to immediate integration into existing energy grids through repowering of existing oil and gas fired utilities. Recent technology has shown advances in receiver design, in heliostat fields surrounding the power tower, heliostat cost, and storage. Calculations indicate an energy amplification factor [EAF] of 20 for solar energy plants; i.e., the ratio of the electric energy produced over the lifetime of a power plant to the thermal energy required to produce the plant.
Comparisons of Measured and Simulated Performance for CSU House I
Authors: Mitchell J. W. , Beckman W. A. , Pawelski M. J.
Published: January 2010

The heating system for CSU House I is simulated using TRNSYS, and simulation results are compared to the measured performance. The heating system is composed of a liquid collection and storage system, a domestic hot water system, and an air delivery system. The components were modeled using standard TRNSYS components. Measured weather data from the site were employed as the driving function. Measured energy quantities, including the useful gain from solar, that supplied to the house and the domestic hot water system, and the auxiliary were compared to those from the simulation for three periods of six to eleven days each. Comparisons were made on both a daily basis and over the entire period. The simulated energy quantities are found to agree with the data within the accuracy of the measurements. Simulated hourly values of storage tank temperatures are compared to those measured. Although there are differences of up to 5°C between the two at times, the agreement is generally within 2°C. These results help establish the validity of simulation methods for system analysis. Conventional engineering techniques can be used to formulate component models and determine parameter values. Verified simulation models can be then used to predict long term system performance.
Performance of Heat Pumps at Elevated Evaporating Temperatures—With Application to Solar Input
Authors: Kush E. A.
Published: January 2010

As part of the study of Solar Assisted Heat Pump (SAHP) systems, the performance of the heat pump component itself under conditions attendant to series solar input is being investigated. Notably the effect of high source temperatures, for which current heat pumps are not designed, and the associated thermodynamic potential to raise performance are of interest. This paper presents theoretical predictions, results of systematic experiments run on a special heat pump simulator, and interpretation/analysis of how high Coefficients of Performance (COP) heat pumps can be used in installed SAHP systems. The latter aspect is vital for—although results have shown that substantial increase in COP can be achieved even using off-the-shelf heat pump components—the more difficult problem is supplying sufficient solar energy to the heat pump with a practical, cost-competitive system. The approach taken to the high temperature heat pump study makes the results generally applicable to any vapor compression heat pump with related evaporating temperatures.
Dynamic Simulation of a Central Receiver Solar-Electric Power Plant
Authors: Willcox W. , Beckman J.
Published: January 2010

A numerical dynamic simulation model of the thermal-hydraulic characteristics of a sodium-cooled advanced central receiver solar electric power plant has been developed. The model was used to determine the optimum receiver temperature control system configuration. Independent feedback control of each of the 24 receiver panels was found to be an adequate method of receiver outlet coolant temperature control. The degree of hydraulic panel coupling was found to be small. Arbitrarily inducing instability in one panel does not affect the operation or control of the other panels. The results should also be applicable to similar molten salt receivers.
Experimental Comparison of Control Strategies for Solar Energy Systems Incorporating Dual Storage Tanks
Authors: Wolfson R. L. T. , Harvey H. S.
Published: January 2010

Two identical solar collector systems were operated side by side for a 67 day period. Data acquisition and control of both systems were accomplished by a minicomputer. One system’s control strategy kept its two storage tanks at the same temperature, simulating a single tank. The other system employed a dual temperature strategy designed to allow greater flexibility in adjusting to varying isolation. The dual temperature strategy showed a modest 4 percent gain in energy delivered to a load.
High-Flux Solar Absorber Concept for Central Receiver Power Plants
Authors: Pomeroy B. D. , Roberts J. M. , Narayanan T. V.
Published: January 2010

For cylindrical receivers with a capacity of about 400 MW/t, an aim-at-the-belt focusing strategy can produce average fluxes the order of 0.5 MW/m2 with peaks as high as 2 MW/m2. An absorber concept is described which uses liquid sodium coolant and a three-header configuration to efficiently capture this solar power. The mechanical design of this absorber is discussed and thermal performance estimates are presented showing the solar-capture efficiency over a range of solar intensities. The sodium-flow characteristics and some potential flow-control problems are also described. A thermal-stress analysis is presented which shows that a limiting factor on the flux capability may be tube-wall creep/fatigue failure and not the heat-transfer capability of sodium.
Mean Wind Loading on Parabolic-Trough Solar Collectors
Authors: Randall D. E. , McBride D. D. , Tate R. E.
Published: January 2010

Two wind-tunnel force and moment tests have been conducted on parabolic-trough solar collector configurations. The two tests were conducted in different flow field environments, one a uniform flow infinite airstream, the second a simulated atmospheric boundary layer flow with the models simulating a ground-mounted installation. The force and moment characteristics of both isolated single-module troughs and of trough modules within array configurations have been defined over both operational and stow attitudes. The influence of various geometric design parameters for collector modules and arrays has been established. Data indicate that forces and in general the pitching moment increase with mounting height and with trough aspect ratio. Collector modules interior to large arrays experience wind force reductions as high as 50–65 percent, while appropriate fences or berms surrounding the arrays can provide exterior modules with protection of this order.
Structural Dynamic Analysis of Wind Turbine Systems
Authors: Thresher R. W.
Published: January 2010

The paper presents an overview of the dynamic analysis of horizontal axis wind turbines. The major emphasis of the paper is the review of current analysis methods and the comparison of results with experimental data. The current capabilities for predicting turbine system natural frequencies are discussed and the design implications of frequency placement are reviewed. The prediction of cyclic loads, using the dynamic analysis computer codes, is examined and comparisons are made between the code predictions and field test data. Finally, the dynamic analysis needs for advanced turbine systems are considered.