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ASME 1990 design Technical Conferences, DETC 1990

作者： Park, Jong Sang Choi, Kyung K. Department of Mechanical Engineering Center for Simulation and Design Optimization of Mechanical Systems College of Engineering The University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791805213

A continuum formulation for design sensitivity analysis of critical loads is developed for nonlinear structural systems that are subjected to conservative loading. Both geometric and material nonlinear effects are considered. Sizing design variables such as cross-sectional areas of beam or truss design components and thicknesses of plate or membrane design components, together with their shape design variables, are treated. A continuum approach is used to obtain design sensitivity expressions in integral form. For shape design sensitivity analysis, the material derivative concept and domain method are used to find variations of the critical load due to variations in shape of the physical domain. The total Lagrangian formulation for incremental equilibrium equation and one-point linearized eigenvalue problems are utilized. A numerical method is presented to evaluate continuum design sensitivity expressions using analysis results of established finite element codes. It is found that no adjoint system is necessary for design sensitivity analysis of the critical load. Numerical results show the proposed method for design sensitivity of critical loads is accurate for both sizing and shape design variables. A numerical procedure for optimal design of nonlinear structural systems is presented, using the proposed continuum design sensitivity analysis method. An optimal design problem with a stability constraint is solved. © 1990 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Numerical methods

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Real-time dynamic simulation of a robot with rotor dynamics

Real-time dynamic simulation of a robot with rotor dynamics

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ASME 1990 design Technical Conferences, DETC 1990

作者： Chuang, Li-Ping Kim, Sung-Soo Engineering Mechanics Research Corporation TroyMI United States Center for Simulation and Design Optimization Department of Mechanical Engineering The University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791805213

Rotor dynamics are important for robots that are driven by motors and high gear ratio transmission systems. New generic recursive dynamic formulations of robotic systems with motor rotor effects are presented, where motors can be mounted on inboard or outboard bodies of the actuated joints. An organized form of the system dynamics equations is obtained through adoption of a state vector representation in equation derivation. The influence of rotors on the overall system dynamics are identified. Parallelism of the derived dynamics formulations is then exploited and a real-time parallel computational algorithm is proposed. A seven degree-of-freedom telerobot is used to illustrate rotor dynamics effects in the computational model. A computational speed that is faster than realtime simulation is demonstrated. © 1990 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Degrees of freedom (mechanics)

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Flexible-body dynamics modelling with a reduced-order model

Flexible-body dynamics modelling with a reduced-order model

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ASME 1990 design Technical Conferences, DETC 1990

作者： Yae, K. Harold Inman, Daniel J. Department of Mechanical Engineering Center for Simulation and Design Optimization The University of Iowa Iowa CityIA United States Department of Mechanical and Aerospace Engineering State University of New York at Buffalo BuffaloNY United States

ISBN: (纸本)9780791805213

In the dynamics modeling of a flexible body, finite element analysis employs Guyan's reduction that removes some of the "insignificant" physical coordinates, thus producing a dynamic model that has smaller mass and stiffness matrices. Despite such reduction, the resultant model is still too large for flexible-body dynamic analysis. That warrants further reduction as is frequently used in control design by approximating a large dynamical system with a fewer number of state variables. When the reduced model is being assembled with other bodies in a multi-body mechanism, a problem, however, arises because a model usually undergoes, before being reduced, some form of coordinate transformations that do not preserve the physical meanings of the states. To correct such a problem, we developed a method that expresses a reduced model in terms of a subset of the original states. The proposed method starts with a dynamic model that is originated and reduced in finite element analysis. Then the model is converted to the state space form, and reduced again by the internal balancing method. At this stage, being in the balanced coordinate system, the states in the reduced model have no apparent resemblance to those of the original model. Through another coordinate transformation that is developed in this paper, however, this reduced model is expressed by a subset of the original states. Then finally the model can be represented by the states assigned to the degrees of freedom of the selected nodal points. © 1990 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Dynamic models

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WORKSPACE ANALYSIS OF MULTIBODY MECHANICAL SYSTEMS USING CONTINUATION METHODS

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JOURNAL OF MECHANISMS TRANSMISSIONS AND AUTOMATION IN design-TRANSACTIONS OF THE ASME 1989年第4期111卷 581-589页

作者： JO, DY HAUG, EJ Center for Simulation and Design Optimization and Department of Mechanical Engineering College of Engineering The University of Iowa Iowa City Iowa 52242

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.

关键词： Jacobian matrices Kinematics Manipulators Numerical analysis Computer software Equations of motion Manifolds

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TOPOLOGICAL ANALYSIS OF MULTIBODY SYSTEMS FOR RECURSIVE DYNAMICS FORMULATIONS

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MECHANICS OF STRUCTURES AND MACHINES 1989年第2期17卷 239-258页

作者： HWANG, RS HAUG, EJ Center for Simulation and Design Optimization Department of Mechanical Engineering The University of Iowa Iowa City IOWA 52242 United States

Graph theory is used to characterize the topology of multibody systems for high speed parallel computer dynamic simulation. Decoupled loops are defined for use in the recursive dynamics formulations, wherein Langrange multipliers can be eliminated concurrently within each decoupled loop. A row-scanning process for the non-directed adjacency matrix of a graph is described, to generate an identification array that facilitates compact storage and defines system connectivities. A decision tree search algorithm is employed to generate all spanning trees associated with a closed loop graph. For each spanning tree generated from the decision tree search algorithm, a precedence array is defined. A path matrix for the spanning tree and an outdegree of junction nodes are defined to assist in parallel implementation of recursive dynamics algorithms and are then constructed from the precedence array. Finally, an optimal tree search algorithm that identifies a spanning tree that leads to best solution sequences for parallel implementation of recursive dynamics formulations is presented. © 1989, Taylor & Francis Group, LLC. All rights reserved.

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Dual-rate integration of controlled multibody mechanical systems

Dual-rate integration of controlled multibody mechanical sys...

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IEEE Conference on Decision and Control

作者： W.-S. Lee T. Tak Department of Mechanical and Aerospace Engineering University of Missouri Kansas City MO USA Center of Simulation and Design Optimization College of Engineering University of Iowa Iowa IA USA

A dual-rate integration methodology for high-speed dynamic simulation of controlled multibody mechanical systems is proposed. Using a graphical representation of such systems, a variational approach is adopted to formulate the systems equations in state-space form, in terms of mechanical-subsystem-independent generalized coordinates and control-subsystem state variables. Different integration algorithms and step sizes that account for the different time scales of each subsystem are used to improve efficiency and stability. A coupling between the subsystems is accounted for by extrapolation.< >

关键词： Control systems Mechanical systems Mechanical variables control Differential equations Frequency Tree data structures Cities and towns Aerodynamics Control system synthesis State-space methods

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Real-time dynamics simulation a design optimization tool

Real-time dynamics simulation a design optimization tool

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作者： Dubetz, Martin W. Haug, Edward J. Center for Simulation and Design Optimization Dept. of Electrical and Computer Engineering University of Iowa United States

Recent developments in multibody dynamic formulations that lead to inherently high speed simulation and, more important, to implementation on emergining high speed parallel processing computer architectures are presented and their use as a tool for dynamic system design optimization is outlined. A recursive formulation of equations of motion for vehicle system dynamics are summarized, with reference to detailed derivations cited. Application of the method is made to the Army's High Mobility Multipurpose Wheeled Vehicle (HMMWV), an off-road vehicle with four independent double A-arm suspension subsystems. It is shown that graph theoretic models of the mechanical system lead directly to definition of concurrent computations that permit exploitation of emerging low cost, high speed parallel processing simulation hardware. A network computing implementation of the dynamiçs algorithm on an Alliant FX 8 parallel processor, using the Network Computing System and a high speed graphics workstation is outlined. This implementation demonstrates feasibility of dynamic simulation of the mechanical system at 70 time steps per second and transfer of state information to the graphics workstation to create an animation as the simulation is being carried out;hence real-time simulation. Application of this qualitatively new technology is discussed for real-time man-in-the-loop simulation in support of vehicle and other mechanical system design applications. A design system;using parallel processors, network computing, and high speed graphics subsystems;is described that permits the engineer to modify design parameters and immediately obtain an animation of dynamic performance of the system. This new capability provides a tool that experienced engineers can use effectively to develop a qualitative and quantitative understanding of the dependence of dynamic on design parameters.

关键词： Speed

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A recursive formulation for real-time dynamic simulation

A recursive formulation for real-time dynamic simulation

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ASME 1988 design Technology Conferences, DETC 1988

作者： Bae, D.-S. Hwang, R.S. Haug, E.J. Center for Simulation and Design Optimization Department of Mechanical Engineering The University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791826584

A new recursive algorithm for real-time, interactive dynamic simulation, animated graphics, and design variation analysis is presented for mechanical systems with closed loops. State vector kinematic relations that represent translational and rotational motion are defined, to simplify the formulation and to relieve computational burden. Recursive equations of motion are first derived for a single loop multi-body system. Faster than real-time performance is demonstrated for a closed loop robot, using an Alliant FX/8 multiprocessor. The algorithm is extended to multi-loop, multibody systems for parallel processing real-time simulation in companion papers [1,2]. Performance of the algorithm on a shared memory multi-processor is compared with that achieved with other dynamic simulation algorithms. A vehicle example is used to demonstrate efficiency of the algorithm for real-time simulation and graphics rendering in a network environment, for use as an interactive design tool. © 1988 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Machine design

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A dynamic simulation approach to machine component life prediction

A dynamic simulation approach to machine component life pred...

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ASME 1988 design Technology Conferences, DETC 1988

作者： Liu, T.S. Haug, E.J. Dopker, B. Department of Mechanical Engineering National Chiao Tung University Hsinchu Taiwan Center for Simulation and Design Optimization and Department of Mechanical Engineering The University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791826584

A system simulation approach is presented for dynamic stress analysis and life prediction of components of machines that undergo nonsteady gross motion and elastic deformation. The method employs finite element structural analysis, coupled gross motionelastic deformation dynamics, and computer-based fatigue analysis, A computer aided engineering methodology is developed for life prediction by linking together software from dynamics, structures, and fatigue life estimation;to compliment conventional fatigue experiments. Dynamic stress analysis is carried out using either an uncoupled gross motion-elastic deformation method or a more accurate approach that takes into account the coupling between large displacements and elastic deformation. With the aid of vehicle operational scenarios, stress/strain histories at critical regions in vehicle components during a projected service life are simulated. A local strain approach is used to calculate cumulative fatigue damage at notches, which is used in assessing fatigue life of components during the design phase;i.e., prior to availability of experimental data A vehicle example is presented, using a simplified dynamicstress analysis method. The more general and accurate fuUy coupled dynamic-stress analysis method will be illustrated in a subsequent paper. © 1988 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Forecasting

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A network implementation of real-time dynamic simulation with interactive animated graphics

A network implementation of real-time dynamic simulation wit...

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ASME 1988 design Technology Conferences, DETC 1988

作者： Dubetz, M.W. Kuhl, J.G. Haug, E.J. Department of Electrical and Computer Engineering The University of Iowa Iowa CityIA United States Center for Simulation and Design Optimization Department of Mechanical Engineering The University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791826584

This paper presents a network based implementation of real-time dynamic simulation methods. An interactive animated graphics environment is presented that permits the engineer to view high quality animated graphics rendering of dynamic performance, to interact with the simulation, and to study the effects of design variations, while the simulation is being carried out. An iiidusuy standard network computing system is employed to interface the parallel processor that carries out the dynamic simulation and a high speed graphics processor that creates and displays animated graphics. Multi-windowing and graphics processing methods that are employed to provide visualization and operator control of the simulation are presented. A vehicle dynamics application is used to illustrate the methods developed and to analyze communication bandwidth requirements for implementation with a compute server that is remote from the graphics workstation. It is shown that, while massive data sets are generated on the parallel processor during realtime dynamic simulation and extensive graphics data are generated on the workstation during rendering and display, data communication requirements between the compute server and the workstation are well within the capability of existing networks. © 1988 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Parallel processing systems

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