Workspace analysis of a six-degrees of freedom, three-prismatic-prismatic-spheric-revolute parallel manipulator

This paper studies the workspace of a six-degrees-of-freedom parallel manipulator of the general three-PPSR (prismatic-prismatic-spheric-revolute) type. It is known that a drawback of parallel manipulators is their limited workspace. To develop parallel mechanisms with a larger workspace is of use to potential applications. The mechanism of a three-PPSR manipulator and its variations are briefly analysed. The workspace is then investigated and the effects of joint limit and limb interference on the,workspace shape and size are numerically studied. The constituent regions of the workspace corresponding to different classes of manipulator poses are discussed. It is shown that the workspace of this parallel manipulator is larger than that of a comparable Stewart platform, especially in the vertical direction.