  This paper deals with the comparison of planar parallel manipulator
architectures based on a multi-objective design optimization approach. The
manipulator architectures are compared with regard to their mass in motion and
their regular workspace size, i.e., the objective functions. The optimization
problem is subject to constraints on the manipulator dexterity and stiffness.
For a given external wrench, the displacements of the moving platform have to
be smaller than given values throughout the obtained maximum regular dexterous
workspace. The contributions of the paper are highlighted with the study of
3-RPR, 3-RPR and 3-RPR planar parallel manipulator architectures, which are
compared by means of their Pareto frontiers obtained with a genetic algorithm.
