Abstract: A synthesis method of branched link with actuation redundancy for 3-translational parallel mechanisms (3T parallel mechanisms) is presented. All the possible inner singular situations are analyzed based on the screw theory. Then based on the linear relevance of screw system and the theory of singularity elimination by actuation redundancy, branched chains with actuation redundancy are synthesized systematically, which can eliminate the inner singularity for 3T parallel mechanisms. And according to the constraint screw system and degrees of freedom of the different added branched chains, the position and number of them is determined. Finally, branched chains with actuation redundancy are synthesized systematically which can eliminate inside singularity for 3-RRUR. by this method. The results show that this method is simple, effective, and can eliminate the singularity of the 3T parallel mechanisms.

Key words: branched chain with actuation redundancy, hybrid screw group, inner singularity, parallel mechanism