Analysis of the Total Orientation Workspace of a Type of n-PPPS Parallel Manipulator*

The total orientation workspace (TOW) is fundamental to the design and application of a parallel manipulator. Among various PM structures, a type of n-PPPS PMs, whose limbs consisted of three active prismatic joints and one passive spherical joint, is widely used in assembly tasks of jointing cabin sections. In this paper, the shape of the TOW of the type of n-PPPS PM is proved to be a cuboid. And this property is utilized to transfer the TOW determination problem to solving six minima and maxima with the help of nonlinear optimization algorithm, which reduces the computation cost greatly comparing to general workspace determination algorithms. Then, a 4-PPPS PM is taken as an example to carry out comparisons on computation speed and accuracy with a general TOW solving method based on workspace search, and the experiment results show the superiority of the proposed method. In the end, the influence of limb distances and angle ranges of the TOW on the volume rate of the TOW is analyzed as a concrete example of the application of the proposed method to guide manipulator design and application.