DETC2002/DAC-34147 TOPOLOGY OPTIMIZATION OF COMPLIANT MECHANISMS USING EVOLUTIONARY ALGORITHM WITH DESIGN GEOMETRY ENCODED AS A GRAPH

ABSTRACT This paper describes an intuitive way of defining geometry design variables for solving structural topology optimization problems using an evolutionary algorithm (EA). The geometry representation scheme works by defining a skeleton which represents the underlying topology/connectivity of the continuum structure. As the effectiveness of any EA is highly dependent on the chromosome encoding of the design variables, the encoding used here is a graph which reflects this underlying topology so that the genetic crossover and mutation operators of the EA can recombine and preserve any desirable geometric characteristics through succeeding generations of the evolutionary process. The overall optimization procedure is applied to design a straight-line compliant mechanism : a large displacement flexural structure that generates a vertical straight line path at some point when given a horizontal straight line input displacement at another point. INTRODUCTION Structural design optimization is an area that has seen active research over the last three decades due to the natural desire of engineers to build artifacts and structures that not just satisfy their functional requirements, but also perform those functions in an optimal way. It is now possible for designers to discover not just the optimal shape but also the optimal topology of a structure that will maximize one or more of its performance characteristics. Among the most popular techniques of topology and shape design optimization for discrete structures is the ground structure approach (Zhou and Rozvany, 1991) while those for continuum structures are the homogenization/microstructures approac