S.M.K Akhlaghi - Mechanical Engineering Department, Babol University of Technology, Mazandaran
Mojtaba Monjezi - Mechanical Engineering Department, Islamic Azad University, Susangerd Branch, Susangerd
Mehdi Monjezi - Mechanical Engineering Department, Islamic Azad University, Susangerd Branch, Susangerd

In this paper, the optimal designs of three planar 3-DOF parallel manipulators with 4-RPR, 3-RPR and 2-RPR structures are compared. The optimization of the manipulators are performed based on dexterityindex, subject to constant orientation workspace. Therefore, it is expected that by introducing thesedexterity indices as the quality measures throughout the workspaces, the parallel manipulators can beimproved at the cost of a minor reduction in their workspaces. The optimizations are performed usingparticle swarm optimizer with Semi-active congregation which improves the performance of PSO withpassive congregation. Finally, it is shown that the 4-RPR parallel manipulator has a better performancethan 2-RPR and 3-RPR manipulators according to the dexterity index.

Parallel manipulator, dexterity, optimization, semi-active congregation