A 3-RRR Spherical Parallel Manipulator Reconfigured with Four-bar Linkages

In this paper, a reconfigurable parallel wrist manipulator, which is based on a coaxial actuated spherical mechanism with full-circle twist, is presented. The reconfiguration of the wrist is realized through a simple four-bar linkage in each independent limb to change one geometric parameter for variations of performances, which eases motion control. The workspace, dexterity and singularity of the wrist manipulator in different configurations are investigated, with consideration of the effect of an adjustable angular parameter on the manipulator performance. The relationship between the reconfigurable parameter and the manipulator performance turns out to be linear approximately. Since this parallel wrist manipulator can generate a full-circle twist movement, it can extend the applications of the wrist mechanisms. Moreover, this reconfigurable wrist manipulator can meet various task requirements due to its real-time performance enhancement.