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Criterion for the locality of a manipulator arm with respect to an operating point

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART B-JOURNAL OF engineering MANUFACTURE 1996年第4期210卷 385-394页

作者： AbdelMalek, K Department of Mechanical Engineering and Center for Computer Aided Design The University of Iowa Iowa City Iowa USA

Criteria for determining an optimum locality of a manipulator arm are developed. In many cases, in a manufacturing environment, the tools, fixtures and targets that a manipulator has to deal with cannot be relocated. Thus, the choice of the manipulator locality is important. The method presented in this paper uses the notion of a service sphere to determine required orientability at an operating point. The boundary surfaces to the wrist-accessible output ser is determined and positioned such that the service sphere is inside the wrist-accessible output set. To determine boundary surfaces of the wrist-accessible output set, manipulator singularities (internal boundary, and higher order) are computed and substituted into the constraint equation to parameterize singular surfaces. Part of these surfaces may lie internal to the boundary while other parts are a subset of the boundary. Singular surfaces are then intersected to determine second-order singularities. Second-order singularities partition surfaces into subsurfaces. Those subsurfaces on the boundary are determined by perturbing a point on the surface and concluding whether the perturbed point satisfies the constraint equations. The boundary to the wrist-accessible output set is then located with respect to the service sphere. The locality of the manipulator is determined for maximum orientability.

关键词： robotics kinematics optimal locality

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Genetic algorithm-based structural topology design with compliance and topology simplification considerations

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JOURNAL OF MECHANICAL design 1996年第1期118卷 89-98页

作者： Chapman, CD Jakiela, MJ Massachusetts Institute of Technology Department of Mechanical Engineering Computer-Aided Design Laboratory Cambridge MA 02139

The genetic algorithm (GA), an optimization technique based on the theory of natural selection is applied to structural topology design problems. After reviewing the genetic algorithm and previous research in structural topology optimization, we detail the chromosome-to-design representation which enables the genetic algorithm to perform structural topology optimization. Extending our prior investigations, this article first compares our genetic-algorithm-based technique with homogenization methods in the minimization of a structure's compliance subject to a maximum volume constraint. We then use our technique to generate topologies combining high structural performance with a variety of material connectivity characteristics which arise directly from our discretized design representation. After discussing our findings, we describe potential future work.

关键词： Optimization Topology design Genetic algorithms Algorithms

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Working capability analysis of Stewart platforms

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JOURNAL OF MECHANICAL design 1996年第2期118卷 220-227页

作者： Luh, CM Adkins, FA Haug, EJ Qiu, CC Center for Computer-Aided Design and Applied Mathematical and Computational Sciences The University of Iowa Iowa City IA Center for Computer-Aided Design and Department of Mechanical Engineering The University of Iowa Iowa City IA Black & Veatch Kansas City MO

Working capability analysis of planar and spatial Stewart platforms with unilateral constraints on actuator length is carried out using numerical methods based on analytical criteria for the boundary of the accessible output set. Restrictions on achievable motion at singular configurations associated with points interior to the accessible output set are also analyzed. Since movement of the working point on a spatial Stewart platform occurs in three-dimensional space, the boundary of the accessible output set is a two-dimensional surface. Numerical methods used in this analysis map one-dimensional solution sets, permitting the boundary of the accessible output set to be characterized by a family of one dimensional generators. Motion control restrictions inside the accessible output set are similarly characterized by families of interior singular curves, and barriers to motion control across surfaces defined are analyzed.

关键词： Actuators Motion control Numerical analysis Generators

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Synthesis of optimal shape and topology of structures

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JOURNAL OF MECHANICAL design 1996年第1期118卷 68-74页

作者： Kumar, AV Gossard, DC Department of Mechanical Engineering University of Florida Gainesville FL 32611 Computer-Aided Design Laboratory Mechanical Engineering Department Massachusetts Institute of Technology Cambridge MA-02139

In this paper, a method is proposed for the design optimization of structural components where both shape and topology are optimized The boundaries of the shape of the structure are represented using contours of a ''shape density'' function. The contour of the density function corresponding to a threshold value is defined as the boundary of the shape. The shape density function is defined over a feasible domain and is represented by a continuous piece-wise interpolation over the finite elements used for structural analysis. The values of the density function at the nodes serve as the design variables of the optimization problem. The advantage of this shape representation is that both shape and topology of the structure can. be modified and optimized by the optimization algorithm. Unlike previous methods for shape and topology optimization, the material is not modeled as porous or composite using the homogenization method. Instead the material properties of the structure are assumed to depend on the density function and many approximate material property-density relations have been studied. The shape and topology of structural components are optimized with the objective of minimizing the compliance subject to a constraint on the total mass of the structure.

关键词： Structural elements (Construction) Optimization Optimization algorithms Materials properties Interpolation Density Shapes design Composite materials Topology Structural analysis Finite element analysis

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design OF A SELF-CLOSING COMPLIANT "MOUSE TRAP" FOR MICRO ASSEMBLY

DESIGN OF A SELF-CLOSING COMPLIANT "MOUSE TRAP" FOR MICRO AS...

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ASME 1996 International Mechanical engineering Congress and Exposition, IMECE 1996

作者： Saitou, Kazuhiro Jakiela, Mark J. Computer-Aided Design Laboratory Department of Mechanical Engineering Massachusetts Institute of Technology CambridgeMA United States

ISBN: (纸本)9780791815410

A design of a micro latching fastener - a micro "mouse trap" - is presented, which has self-closing compliant latches that clamp a free planar part inserted between them. The self-closing of the latches is induced by the insertion of the part which releases the potential energy stored in the "cocked" state of the device, in the manner of a mouse trap. The closed latch can re-open by cocking the micro mouse trap. The self-closing action of the micro mouse trap allows the inaccurate insertion of the free part and leads to very accurate final positioning, with the insertion force required to induce the self-closing being very small. The micro mouse trap is also reusable since the release of the clamped part is done non-destructively. The micro mouse trap can be used, for instance, for assembly and temporal clamping/positioning of micro-scale parts, and electromechanical/opto-mechanical connectors. © 1996 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Potential energy

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A mixed design approach for probabilistic structural durability 6th

A mixed design approach for probabilistic structural durabil...

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6th AIAA/NASA/ISSMO Symposium on Multidisciplinary Analysis and Optimization, 1996

作者： Choi, Kyung K. Yu, Xiaoming Chang, Kuang-Hua Center for Computer-Aided Design Department of Mechanical Engineering University of Iowa Iowa CityIA52242 United States

In this paper, a mixed approach for probabilistic structural durability design of mechanical systems is proposed. In this approach, a deterministic design optimization that considers structural crack initiation and crack propagation lives at critical points of the structural component as design constraints is performed first. After an optimal design is obtained, a reliability analysis is performed to determine if the deterministic optimal design is reliable. If the probability of the failure of the deterministic optimal design is found unacceptable, a reliability-based design approach that employs a set of interactive design steps, such as trade-off analysis and what-if study, is used to obtain a nearoptimal design that is reliable with an affordable computational cost. A 3-D tracked vehicle roadarm is employed to demonstrate the feasibility of the proposed approach. © 1996 by Kyung K. Choi, Xiaoming Yu, and Kuang-Hua Chang.

关键词： Reliability analysis

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design sensitivity analysis for hyperelastic structures using a meshless method 6th

Design sensitivity analysis for hyperelastic structures usin...

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6th AIAA/NASA/ISSMO Symposium on Multidisciplinary Analysis and Optimization, 1996

作者： Chang, Kuang-Hua Grindeanu, Iulian Choi, Kyung K. Chen, Jiun-Shyan Department of Mechanical Engineering and Center for Computer-Aided Design The University of Iowa Iowa CityIA52242 United States

In this paper, a continuum-based design sensitivity analysis (DSA) method for hyperelastic structures using a meshless method, the Reproducing Kernel Particle Method (RKPM), is presented. The Yeoh’s energy density function is employed to describe the hyperelastic structural behavior. The meshless method completely eliminates mesh distortion or entanglement encountered in using finite element analysis (FEA) for large deformation structural analysis and structural shape design optimization. Both adjoint variable and direct differentiation methods are developed for material and shape design variables. An infinitely long rubber tube and a 2-D rubber band are employed as examples to demonstrate the feasibility of the method. © 1996 by K-M;Chang I. Grindeanu, K.K, Choi, and J-S. Chen.

关键词： Finite element method

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Probabilistic structural durability prediction 6th

Probabilistic structural durability prediction

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6th AIAA/NASA/ISSMO Symposium on Multidisciplinary Analysis and Optimization, 1996

作者： Chang, Kuang-Hua Yu, Xiaoming Choi, Kyung K. Center for Computer-Aided Design Department of Mechanical Engineering University of Iowa Iowa CityIA52242 United States

In this paper, an efficient reliability analysis method for durability of structural components subjected to external and inertia loads with time-dependent variable amplitudes is presented. This proposed method is able to support reliability analysis of crack initiation and crack propagation lives of practical applications, considering uncertainties such as material properties, manufacturing tolerance, and initial crack size. Three techniques are employed to support the probabilistic durability prediction: (i) strain-based approach for multi-axial crack initiation life prediction and linear elastic fracture mechanics (LEFM) approach for crack propagation life prediction, (ii) statistics-based approach for reliability analysis, and (Hi) sensitivity analysis and optimization methods for searching the most probable point (MPP) in the random variable space to compute the fatigue failure probability using the first-order reliability analysis method (FORM). A two-point approximation method (TPA) is employed to speed up the MPP search. A tracked vehicle roadarm is presented to demonstrate feasibility of the proposed method. © 1996 by Kuang-Hua Chang, Xiaoming Yu, and Kyung K. Choi.

关键词： Reliability analysis

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Direct differentiation methods for the design sensitivity of multibody dynamic systems

Direct differentiation methods for the design sensitivity of...

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ASME 1996 design engineering Technical Conferences and computers in engineering Conference, DETC-CIE 1996

作者： Serban, Radu Freeman, Jeffrey S. Department of Mechanical Engineering Center for Computer-Aided Design The University of Iowa Iowa CityIA52242-1000 United States

ISBN: (纸本)9780791897591

Methods for formulating the first-order design sensitivity of multibody systems by direct differentiation are presented. These types of systems, when formulated by Euler-Lagrange techniques, are representable using differential-algebraic equations (DAE). The sensitivity analysis methods presented also result in systems of DAE's which can be solved using standard techniques. Problems with previous direct differentiation sensitivity analysis derivations are highlighted, since they do not result in valid systems of DAE's. This is shown using the simple pendulum example, which can be analyzed in both ODE and DAE form. Finally, a slider+crank example is used to show application of the method to mechanism analysis. © 1996 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Sensitivity analysis

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Kinematic sensitivity analysis of the spatial four-bar mechanism

Kinematic sensitivity analysis of the spatial four-bar mecha...

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ASME 1996 design engineering Technical Conferences and computers in engineering Conference, DETC-CIE 1996

作者： Zou, Hong-Liu Abdel-Malek, Karim Wang, Jia-Yi Department of Mechanical Engineering The University of Iowa Iowa CityIA52242 United States Department of Mechanical Engineering Center for Computer-Aided Design The University of Iowa Iowa CityIA52242 United States Center for Computer-Aided Design The University of Iowa Iowa CityIA52242 United States

ISBN: (纸本)9780791897591

An analytical formulation for computing kinematic sensitivity of the spatial four-bar mechanism is presented. The experimental code developed is used to compute an assembled configuration for the mechanism due to a design variation. The mechanism is modeled into a graph where a body is defined as a node and a kinematic joint is defined as an edge. The spherical joint is cut to convert the model into a spanning tree structure. Cutting an edge introduces the spherical constraint. The variation of this constraint is computed while maintaining the joint-attachment vectors and orientation matrices as variables. The variation of these variables determine the new kinematic design of the system. A recursive formulation is introduced to obtain the state variation of a body in terms of the state variation of a junction body and of the relative coordinates along the chain. The Jacobian matrix is then transformed from Cartesian coordinate space to joint coordinate space using velocity transformation matrices. Kinematic sensitivity analyses due to changing a jointattachment vector and an orientation are presented. © 1996 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Mechanisms

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