On the Design of a 3-PRRR Spatial Parallel Compliant Mechanism

Because wear, clearance and backlash can be reduced or eliminated, one of the important advantages of compliant mechanisms is their potential to increase the mechanism precision dramatically. In this paper, a spatial compliant mechanism based on the 3-PRRR parallel mechanism driven by linear motors is presented. The design methodology is described and the kinematic and static models are developed. Using the “transmission ratio”, an effective and simple compensation method is designed. The performances of this mechanism are studied with the help of the structure simulation module in Pro-Mechanica. Using an open-loop control with compensation, measurements over a 20×20×20 mm³ workspace show that the position accuracy is smaller than 1 μm, i.e., 0.05% of the full range of motion and that the orientation error is less than 1 μradian.