Translational parallel manipulator with Pa2 kinematic joints

Abstract

The kinematic pair Pa2 is composed of two interlinked parallelograms. It has two degrees of freedom that generate a translational plane variable with position. It has a structure different from the PaPa pair, which is composed also by two parallelograms but generates a constant translational plane. Currently, the Pa2 pair is used at conceptual level but it is not used in al-most any practical application. There are advantages and drawbacks in using it. The main drawback is the high number of redundant constraints that this pair possesses. However, sub-stituting carefully the revolute joints by spherical joints can eliminate these redundant con-straints. Also, this pair constitutes a more rigid structure that replaces adequately the problem-atic passive prismatic joints. In this paper, will be presented a preliminary study of a translational parallel manipulator (PM) based on the use of the Pa2 pair: the 3-PPa2 that contains redundant constraints in its global structure. To study the potentiality of the PM presented in this paper, the following analyses will be done: position and velocity (direct and inverse kinematics), workspace and singularity analysis. Also the potentiality to be optimised will be studied.