Mobility and kinematic analysis of a parallel mechanism with both PPR and planar operation modes

This paper proposes a 1-R (P) under barU-2-U (P) under barU parallel manipulator with both PPR and planar operation modes. The mobility of the moving platform of the parallel manipulator in the two operational modes is analyzed via screw theory. The parallel manipulator has 3 degrees-of-freedom and allows the moving platform to move along a plane in the planar operation mode and to rotate about an axis that translates along a plane in the PPR operation mode. The transition between the two operational modes through transitional configurations is also discussed. The inverse and forward kinematic analysis and singularity analysis of the parallel manipulator are then dealt with by a vector approach. Finally, the constant orientation workspace and the reachable workspace are presented for the parallel manipulator in both operation modes.