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American Control Conference (ACC)

作者： Tsung-Chieh Lin Center for Simulation and Design Optimization of Mechanical Systems Department of Mechanical Engineering University of Iowa Iowa IA USA

This paper proposes an input shaper, which is insensitive to the error in estimating the vibration information, to eliminate residual vibration and also to reduce the transit vibration induced by the operation of a flexible mechanical system. The input shaper, which preconditions the command input and suppresses multiple vibration modes, is designed by a pole/zero placement approach based on estimated system poles. This pole/zero placement method provides better performance and easier design procedures than existing input shaping algorithms. Transfer function analysis shows that proposed shaper actually resembles a notch filter that has zero gain and zero derivative at the poles to be suppressed. However, the input alteration due to the shaper limits this approach to point-to-point operations, or relatively slow tracking operations.

关键词： Automatic control Vibration control Tellurium Robotics and automation Robot control Low pass filters Damping Shape control Open loop systems Frequency estimation

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Dextrous workspaces of manipulators, part 2: Computational methods

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Mechanics of Structures and Machines 1993年第4期21卷 471-506页

作者： Weng, J.K. Wu, J.K. Center for simulation and design optimization of mechanical systems Department of mechanical engineering University of Iowa Iowa city United States

In Part 1 of this paper, analytical criteria for dextrous workspaces were presented and analytical solutions of planar examples were used to illustrate the formulation and necessary conditions to determine boundaries of accessible and dextrous accessible output sets. Not all dexterity problems can be solved analytically, however, especially for large-scale systems. Computational methods developed in this part of the paper are needed to successfully analyze dextrous workspaces of spatial manipulators. In order to map one- or two-dimensional regular solution sets of nonlinear algebraic equations, well-developed numerical analysis packages are adopted in this research. A new approach that combines a condition for the null space of the constraint Jacobian matrix with second-order Taylor expansion of the constraint equations to switch solution branches near simple bifurcation points is developed. To determine the existence of an impending void inside candidate regions of the dextrous accessible output. © 1993, Taylor & Francis Group, LLC. All rights reserved.

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IMPLICIT NUMERICAL-INTEGRATION OF CONSTRAINED EQUATIONS OF MOTION VIA GENERALIZED COORDINATE PARTITIONING

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JOURNAL OF MECHANICAL design 1992年第2期114卷 296-304页

作者： HAUG, EJ YEN, J Center for Simulation and Design Optimization and Departments of Mechanical Engineering and Mathematics The University of Iowa Iowa City IA 52242

An implicit, stiffly stable numerical integration algorithm is developed and demonstrated for automated simulation of multibody dynamic systems. The concept of generalized coordinate partitioning is used to parameterize the constraint set with independent generalized coordinates. A stiffly stable, Backward Differentiation Formula (BDF) numerical integration algorithm is used to integrate independent generalized coordinates and velocities. Dependent generalized coordinates, velocities, and accelerations, as well as Lagrange multipliers that account for constraints, are explicitly retained in the formulation to satisfy all of the governing kinematic and dynamic equations. The algorithm is shown to be valid and accurate, both theoretically and through solution of an example.

关键词： simulation Algorithms Kinematics Dynamic systems Equations of motion

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A GEOMETRY-BASED PARAMETERIZATION METHOD FOR SHAPE design OF ELASTIC SOLIDS

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MECHANICS OF STRUCTURES AND MACHINES 1992年第2期20卷 215-252页

作者： CHANG, KH CHOI, KK Center For Simulation And Design Optimization Of Mechanical Systems College Of Engineering University Of Iowa Iowa City Iowa United States

One of the major difficulties in structural shape optimal design is to create a design model by parameterizing a geometric model. Shape design parameterization is more complicated and difficult to handle than sizing design parameterization. First, the optimum shape is highly dependent on the design parameterization selected. An inappropriate design parameterization may result in an impractical design. On the other hand, changing the geometric shape of the design model to reflect successive changes in design parameters is a tedious, complicated, and inefficient process. Manual updates of geometric shape and finite element meshes are quite impractical. In this paper, a shape design parameterization method that is built on the geometric modeler PATRAN is presented. Using this method, a number of geometric entities that represent structural design boundaries are parameterized, and a design parameter linking process can be performed to create geometric features from geometric entities. To support the proposed method in structural shape design, a unified velocity computation method using geometric parametric mapping and an elliptic equation solver is developed for shape design sensitivity computation. The design parameterization and associated velocity field computation methods are general enough to handle a broad range of engineering applications. Finally, automatic finite element mesh and geometric shape update methods are presented, which can be used to easily perform design changes.

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design SENSITIVITY ANALYSIS AND optimization OF NONLINEAR STRUCTURAL SYSTEMS WITH CRITICAL LOADS

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JOURNAL OF MECHANICAL design 1992年第2期114卷 305-312页

作者： PARK, JS CHOI, KK Department of Mechanical Engineering and Center for Simulation and Design Optimization of Mechanical Systems College of Engineering The University of Iowa Iowa City IA 52242

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.

关键词： design sensitivity analysis Stability optimization Trusses (Building) Stress design Eigenvalues Shapes Equilibrium (Physics) Numerical analysis Sensitivity analysis Membranes Shape design Finite element analysis

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AN ERROR ANALYSIS AND MESH ADAPTATION METHOD FOR SHAPE design OF STRUCTURAL COMPONENTS

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COMPUTERS & STRUCTURES 1992年第6期44卷 1275-1289页

作者： CHANG, KH CHOI, KK Department of Mechanical Engineering Center for Simulation and Design Optimization of Mechanical Systems College of Engineering The University of Iowa Iowa City IA 52242 U.S.A.

A finite element error analysis and mesh adaptation method that can be used for improving analysis accuracy in carrying out shape design of structural components is presented in this paper. The simple error estimator developed by Zienkiewicz is adopted in this study for finite element error analysis, using only post-processing finite element data. The mesh adaptation algorithm implemented in ANSYS is investigated and the difficulties found are discussed. An improved algorithm that utilizes ANSYS POST1 capabilities is proposed and found to be more efficient than the ANSYS algorithm. An example is given to show the efficiency. An interactive mesh adaptation method that utilizes PATRAN meshing and result-displaying capabilities is proposed. This proposed method displays error distribution and stress contour of analysis results using color plots, to help the designer in identifying the critical regions for mesh refinement. Also, it provides guidance for mesh refinement by computing and displaying the desired element size information, based on error estimate and a mesh refinement criterion defined by the designer. This method is more efficient and effective than the semi-automatic algorithm implemented in ANSYS, and is suitable for structural shape design. This method can be applied not only to set-up a finite element mesh of the structure at initial design but to ensure analysis accuracy in the design process. Examples are given to demonstrate feasibility of the proposed method.

关键词： Structural members

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Linearization and Jacobian evaluation of the dynamics of closed-chain mechanical systems

Linearization and Jacobian evaluation of the dynamics of clo...

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ASME 1992 design Technical Conferences, DETC 1992

作者： Lin, Tsung-Chieh Harold Yae, K. Department of Mechanical Engineering Center for Simulation and Design Optimization University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791809419

This paper presents an analytical/numerical method for linearizing the equations of motion and evaluating the system Jacobian matrices of mechanical system.s with closed chains. The linearization algorithm developed here first identifies and linearizes basic recursive kinematic relationships and then applies the chain rule to the derivation of the equations of motion under the framework of recursive formulation. This method can be incorporated into formulating recursive equations of motion for general multibody dynamic systems, to handle large scale systems. Since no numerical differentiation is used in the proposed algorithm, its accuracy i.s comparable to symbolic, closed-form linearization. Moreover, without the need of repetitious computation to select proper perturbation quantities, this method is computationally more efficient than the finite difference method. © 1992 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Linearization

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A computational environment for dextrous workspace analysis

A computational environment for dextrous workspace analysis

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ASME 1992 design Technical Conferences, DETC 1992

作者： Wang, J.Y. Wu, J.K. Department of Mechanical Engineering Center for Simulation and Design Optimization of Mechanical Systems University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791897720

This paper presents an interactive engineering environment for dextrous workspace analysis of manipulators. The environment contains a mechanical system modeling tool, an automatic differentiation package, and numerical solvers that map onedimensional and two-dimensional solution sets of nonlinear parametrized kinematic constraint equations. Row-rank deficiency of constraint sub-Jacobian matrices is used as a necessary condition for characterizing the boundaries of the workspaces and dextrous workspaces of manipulators. A cursor driven animation capability, developed in an interactive graphics environment allows the user to retrieve system configurations by dragging the cursor along solution branches. An animation of the assembled configuration along that solution branch is then displayed. Thus, a better understanding of the kinematic behavior of mechanical systems that limits their dexterity can be obtained. A construction backhoe mechanical system is used to demonstrate the capability of the method developed. © 1992 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Animation

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design sensitivity analysis and optimization tool (DSO) for sizing design applications

Design sensitivity analysis and optimization tool (DSO) for ...

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4th Symposium on Multidisciplinary Analysis and optimization, 1992

作者： Chang, Kuang-Hua Choi, Kyung K. Perng, Jyh-Hwa Department of Mechanical Engineering Center for Simulation and Design Optimization of Mechanical Systems The University of Iowa Iowa CityIA52242 United States

A structural design software system, design Sensitivity Analysis and optimization tool (referred to as DSO) that provides the designer with a graphics-based menu- driven design environment to perform easy design optimization for general applications is presented in this paper. Three design stages, pre-processing, design sensitivity analysis, and post-processing, are implemented in the DSO to allow the designer to carry out the design process systematically. A framework, including database, user interface, foundation class, and remote module, has been designed and implemented to facilitate software development for the DSO. Moreover, a number of dedicated commercial software/packages have been integrated in the DSO to support the design procedures, e.g., PATRAN is used as a geometric modeler to create geometric and finite element models;ANSYS, MSC/NASTRAN, and ABAQUS are used to perform finite element analyses;and the HARWELL QP Solver and a VMA design optimization Tool (DOT) are used for design trade-off and optimization, respectively. In the DSO, instead of parameterizing a finite element model, design parameters are defined on a geometric model associated with physical quantities, and the continuum design sensitivity analysis theory is implemented to compute design sensitivity coefficients using post-processing data from the analysis codes. Also, a four-step interactive design process is developed to support effective design improvement. The DSO successfully integrates structural CAD (Computer-Aided design), CAE (Computer-Aided Engineering), DSA (design Sensitivity Analysis), and OPT (optimization) disciplines. Integration of manufacturing to support a concurrent engineering environment is being researched. In this paper, both engineering and software aspects of the DSO for sizing design applications are discussed, and a tracked vehicle road wheel is given as a sizing design application to demonstrate the DSO’s easy and convenient design optimization process. © 199

关键词： Computer aided engineering

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design sensitivity analysis of structural vibration and noise

Design sensitivity analysis of structural vibration and nois...

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4th Symposium on Multidisciplinary Analysis and optimization, 1992

作者： Choi, Kyung K. Shim, Inbo Department of Mechanical Engineering Center for Simulation and Design Optimization of Mechanical Systems The University of lowa Iowa CityIA52242 United States

Sizing and configuration design sensitivity analyses (DSA) of frequency response are developed for design guidance and optimization to control vibration and noise of the coupled structural-acoustic systems. The continuum method with material derivative is employed to define design derivatives. A variational approach with non-selfadjoint operators for complex variables is used to retain the continuum elasticity formulation throughout derivation of design sensitivity results. Sizing design variables, such as thickness and cross-sectional area of design components, and configuration design variables, such as position and orientation of design components, are considered for the DSA. A numerical method for the continuum DSA is developed to evaluate the design sensitivity of displacement and pressure performance measures by postprocessing analysis results from established FEA codes. The numerical method is tested using examples, and accurate design sensitivity results are obtained using frequency response analysis of an established FEA code. © 1992 by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Numerical methods

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