Optimal Continuum Synthesis of Partially Compliant Mechanisms for Prescribed Non-smooth Paths

Ashok Kumar Rai and Anupam Saxena

ABSTRACT: In this paper, we synthesize partially compliant continua for prescribed non-smooth paths. In a novel contribution, optimal layout design of partially compliant mechanisms entails topology, shape and size synthesis with initially curved frame and rectilinear truss members of chosen materials. The analysis of partially compliant mechanisms having both pin joints as well as deformable members that can bend and/or stretch, is made possible through geometrically nonlinear finite element analysis in this work. Appearance of structural members in the base mesh is manipulated through discrete topology design variables that model member moduli. Element cross sections, end slopes of frame elements and nodal coordinates govern local shape and size. Deflection characteristics get enhanced not only by introducing the curvature in frame elements that influence both local bending and stretching, but also by the inclusion of truss elements that introduce only local stretching when needed. This along with the singularities introduced by the pin joints helps achieve a prescribed non-smooth path. We employ geometrically nonlinear finite element analysis using frame and truss elements to compare the design and prescribed paths using Fourier shape descriptors. As some variables are discrete, we employ a stochastic search through genetic algorithm. Numerical examples presented in this paper serve to illustrate the design intent.

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