Synthesis of planar parallel mechanisms while considering workspace, dexterity, stiffness and singularity avoidance

It is a generally well-known fact that the design of parallel mechanisms while optimizing performance is quite difficult. In this paper, a reliable synthesis method capable of optimally selecting the geometrical parameters of planar parallel mechanisms is presented. Three different architectures are considered and a genetic algorithm is used to perform the optimization. The performance of each mechanism is evaluated according to four different criteria: workspace, singular configurations, dexterity, and stiffness. In order to make the synthesis method as realistic as possible, mechanical constraints affecting the angular rotation of the 2-R (P) under barR and 3-R (P) under barR mechanisms' passive revolute joints are considered. Moreover since the conventional methods for computing the dexterity and the stiffness index are not valid for the 3-R (P) under barR and 3-(R) under bar RR mechanisms, an alternative computation method is used.