RECONFIGURATION ANALYSIS OF A VARIABLE DEGREES-OF-FREEDOM PARALLEL MANIPULATOR WITH BOTH 3-DOF PLANAR AND 4-DOF 3T1R OPERATION MODES

Reconfiguration analysis is essential for the design and control of multi-operation-mode parallel manipulators (PMs). This paper deals with the reconfiguration analysis of a variable-DOF (degrees-of-freedom) multi-operation-mode E/PPPR=PM, i.e. a PM with both 3-DOF planar operation mode and 4-DOF 3T1R (or Schonflies motion which has three translational DOF and 1 rotational DOF) operation mode. The axes of rotation of the moving platform in the 3-DOF planar operation mode are not parallel to the axes of rotation of the moving platform in the 4-DOF 3T1R operation mode. In the reconfiguration analysis, the orientation of the moving platform is represented using a Euler parameter quaternion (also Euler-Rodrigues quaternion). The reconfiguration analysis shows that the E/PPPR=PM has two 4-DOF 3T1R operation modes and two 3-DOF planar operation modes, including the two expected operation modes. The transition configurations between each pair of operation modes are also identified.