Showing papers in "Journal of Mechanisms Transmissions and Automation in Design in 1989"

Computations with Imprecise Parameters in Engineering Design: Background and Theory

Abstract: A technique to perform design calculations on imprecise representations of parameters has been developed and is presented. The level of imprecision in the description of design elements is typically high in the preliminary phase of engineer­ ing design. This imprecision is represented using the fuzzy calculus. Calculations can be performed using this method, to produce (imprecise) performance parameters from imprecise (input) design parameters. The Fuzzy Weighted Average technique is used to perform these calculations. A new metric, called the y-level measure, is in­ troduced to determine the relative coupling between imprecise inputs and outputs. The background and theory supporting this approach are presented, along with one example. Engineering design, both in practice and research, is evolv­ ing rapidly, especially in the development of computer-base d tools. Emphasis is moving from the later stages of design, to computational tools for preliminary design. In an earlier paper [35], a general approach to computational tools in preliminary engineering design and a model of the design pro­ cess was described. The primary aim of this model is to pro­ vide a structure for the development of tools to assist the designer in: managing the large amount of information en­ countered in the design process; determining a design's func­ tional requirements and constraints; evaluating the coupling between the design parameters; and carrying out the process of choosing between alternative design concepts. We are particularly interested in developing tools to assist the designer in the. preliminary phase of engineering design, by making more information available on the performance of design alternatives than is available using conventional design techniques. The most important design decisions (and poten­ tially the most costly, if wrong) are made at the preliminary stage. Our hypothesis is that increased information, over what is available by traditional design methods, will enable these decisions to be made with greater confidence and reduced risk. The effect will be greater, the earlier in the design cycle addi­ tional information can be made available. The preliminary phase of the engineering design process is one that embodies many functions: concept generation; evaluation of imprecise descriptions of simplified versions of the design; judgment of design feasibility; etc. [14, 15, 28]. The concept generation and simplification processes will not be addressed by the research reported here; rather our aim is to provide a technique for representing, manipulating, and evaluating the approximate, or imprecise, parametric descrip­ tions of the (preliminary) design artifact.

Optimum Selection of Discrete Tolerances

Abstract: Tolerancing involves considerations from all phases of the life cycle of a product including design, manufacturing, assembly, and inspection. Along with minimum cost and maximum functionality and interchangeability, the practice of tolerancing urges a designer to choose an appropriate manufacturing (or inspection) process as well. This situation is formalized as a discrete optimization problem. For an optimum selection of tolerances from a given discrete model involving various manufacturing processes, minimization of manufacturing cost is achieved under the constraint of tolerance stack-up. A random variable and its standard deviation are associated with a dimension and its tolerance. This probabilistic approach enables a trade-off between performance and tolerance (cost). But it also suggests probabilistic optimization. With the aid of a notion called the reliability index [8], tolerance selection is formulated as an integer programming problem. A branch and bound algorithm for ensuring optimum selection is developed by exploiting the special structure of the constraints. To make the enumeration tree small, monotonic relations among the reliability index, cost, and tolerance are examined. The algorithm is tested with examples.

Analysis, Properties, and Design of a Stewart-Platform Transducer

Abstract: Analyse, proprietes et conception d'un capteur d'effort ayant une structure mecanique du type plateforme de Stewart

Cycloid drives with machining tolerances

Abstract: 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. 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

The mechanics and positioning of highly flexible manipulator limbs

Abstract: Etude mecanique et positionnement d'un bras de manipulateur ayant une tres grande flexibilite

FDL ― A language for function description and rationalization in mechanical design

Abstract: Presentation du langage FDL (Function description language) pour decrire les fonctions des composants et rationaliser la conception mecanique

Multi-level design optimization using global monotonicity analysis

Abstract: Optimisation a plusieurs niveaux de la conception a l'aide d'une analyse de monotonicite globale

Kinematic Analysis of Tendon-Driven Robotic Mechanisms Using Graph Theory.

Abstract: Analyse cinematique par la theorie des graphes d'un mecanisme de robot utilisant des commandes par câbles

On the dead-center positions of planar linkage mechanisms

Abstract: 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.

Design and implementation of a prototype intelligent CAD system

Abstract: Conception et implantation d'un prototype intelligent de systeme de conception assistee par ordinateur

Workspace analysis of multibody mechanical systems using continuation methods

Abstract: A new approach to numerical analysis of workspaces of multibody mechanical systems is presented, based on manifold theory and computational continuation methods. Generalized coordinates that define the kinematics of a system are classified and interpreted from an input-output point of view. Boundaries of workspaces, which depend on the classification of generalized coordinates, are defined as sets of points for which Jacobian matrices of the kinematic equations are row rank deficient. This criterion generalizes the conventional determinant criteria for applications with square Jacobian matrices. Numerical methods for tracing families of one dimensional trajectories on a workspace boundary are outlined. Open and closed loop manipulator examples are analyzed, using a manifold mapping computer program.

Position Errors Due to Clearances in Journal Bearings

Abstract: The positional errors due to clearances in journal bearings intended to approximate revolute joints are analyzed. Equations are presented which relate joint geometry external loads, and errors. The paper treats the case common in serial chain manipulators where the revolute joint's nominal rotational angle is controlled, and it is desired to determine the errors that result from the clearances

A vehicle handling model with active suspensions

Abstract: This paper presents two vehicle models used to investigate the effects of active suspensions. One is a linear seven degree of freedom ride model. The second is a nonlinear ten degree of freedom ride and handling model. The seven degree of freedom model is used to study ride effects. The active suspension substantially reduced the motion of the sprung mass. The ten degree of freedom model is used to study the effects of the active suspension on the directional response characteristics of the vehicle. The handling characteristics exhibited by the active suspension are very similar to those of the passive suspension

On the Design of Wire Rope

Abstract: In recent work, a design methodology for multi-lay wire strands has been developed. The current paper expands on this earlier work to study wire ropes in which the strand is a basic component. Wire ropes with the three types of cores, independent-wire-rope-core (IWRC), fiber-core (FC), and wire-strand-core (WSC), are considered. This work further generalizes the previously developed linearized theory which, through substantiation with experiment, is felt to be reasonably accurate for most wire rope behavior. The theory is then utilized to examine various parameters in the design of wire ropes.

Shape Optimization of Cam Profiles Using a B-Spline Representation

Abstract: Optimisation de la forme d'une came en utilisant une spline B pour representer l'acceleration

Electro-Rheological-Fluid-Based Articulating Robotic Systems

Abstract: The limitations of the current generation of robotic systems has triggered a new research thrust for predicting the elastodynamic response of assemblages of articulating flexible-bodied systems. This research thrust is extended herein by proposing the fabrication of robotic systems in either monolithic or ultra-advanced composite laminated high-strength, high-stiffness materials in which are incorporated electro-rheological fluids. These multiphase fluid systems, which change their rheological behavior instantaneously when subjected to an externally applied electrical field, provide a potential for tailoring the vibrational characteristics of these hybrid materials form which the structural members of the proposed robotic systems are fabricated. This paper is focused on developing the necessary design tools for predicting the vibrational response of flexible multibodied articulating systems fabricated with this new class of advanced materials

Some Further Results on Monotonicity in Globally Optimal Design

Abstract: Many problems of globally optimal design have been solved by using monotonicity analysis. Extended monotonicity principles are obtained by exploiting nonstrict monotonicity of the objective function and of the constraints. Ways to detect monotonicity and branching rules using monotonicity results are also discussed. Several illustrative examples from the literature are solved in an easier way than previously.