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Optimal kinematic design of a link-drive mechanism with prescribed velocity characteristics
Bojan Vohar, Karl Gotlih, Jože Flašker, 2003, kratki znanstveni prispevek

Opis: The paper presents an example of a link-drive mechanism for a deep drawing mechanical press. Because of its characteristics such a drive is much more appropriate than conventional crankshaft or eccentric drive. The existing design of the drive has proved unsatisfactory and does not meet all the demands and constraints, which are ideal for deep drawing process. Optimization of the drive is therefore necessary. The intention is to achieve the required velocity characteristics in a defined area of movement. Firstly, the drive is analyzed and a mathematical model is made and prepared for optimization procedure. The process is time-dependent, so it cannot be used directly in the optimization algorithm. Mathematical model is transformed intoa form suitable for the standard non-linear optimization procedure and then optimization is carried out. The method used is sequential quadratic programming. The final objective of the optimization process is to find such dimensions of link-drive members that the given requirements are satisfied in the best possible manner.
Ključne besede: mechanics, dynamics of mechanical systems, closed kinematic chains, mathematical modelling, non-linear optimization, drive optimization, drive dimensioning, kinematic analysis, link-drive mechanism, deep drawing press
Objavljeno: 01.06.2012; Ogledov: 1613; Prenosov: 95
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Optimization of elastic systems using absolute nodal coordinate finite element formulation
Bojan Vohar, Marko Kegl, Zoran Ren, 2006, kratki znanstveni prispevek

Opis: An approach to a shape optimization of elastic dynamic multibody systems is presented. The proposed method combines an appropriate shape parameterization concept and recently introduced finite element type using absolute nodal coordinate formulation (ANCF). In ANCF, slopes and displacements are used as the nodal coordinates instead of infinitesimal or finite rotations. This way one avoids interpolation of rotational coordinates and problems with finite rotations. ANCF elements are able to describe nonlinear deformation accurately; therefore, this method is very useful for simulations of lightweight multibody structures, where large deformations have to be taken into account. The optimization problem is formulated as a nonlinear programming problem and a gradient-based optimization procedure is implemented. The introduced optimization design variables are related to the cross-sectional parameters of the element and to the shape of the whole structure. The shape parameterization is based on the design element techniqueand a rational B ezier body is used as a design element. A body-like design element makes possible to unify the shape optimization of both simple beams and beam-like (skeletal) structures.
Ključne besede: mechanics, dynamics of material systems, multibody systems, elastic mechanical systems, manipulators, dynamically loaded beams, optimum shape design, absolute nodal coordinate formulation, design element technique, finite element method
Objavljeno: 31.05.2012; Ogledov: 1416; Prenosov: 99
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