Evolving Path Generation Compliant Mechanisms (PGCM) using Local-search based Multi-objective Genetic Algorithm

Path generation compliant mechanisms (PGCM) are flexible structures which generate some desired path and/or transmit force by undergoing elastic deformation (under some applied load) instead of through rigid linkages/joints as in rigid body mechanism. In the present work, multi-objective problem is posed for evolving of PGCM using local-search based genetic algorithm. Minimization of weight of structure and minimization of input energy to the structure have been considered as two conflicting objective functions subjected to maximum of 10% of deviation between five precision points of prescribed path and corresponding five points obtained on the actual path of a specified point on structure after FEM analysis and a constraint on stress. Geometrical non-linear finite element model is used for the synthesis of PGCM. On the basis of the calculated function and constraint values, an evolutionary algorithm (NSGA-II) is used to find the optimal solution. A local search based multi-objective GA is used to reduce the computational time and improve the quality of GA solutions. The Pareto-optimal front obtained shows different trade-off solutions from minimum weight to the maximum weight of structure. The minimum weight solution is corresponding to the maximum input energy to the structure and vice-versa.