Design and Assessment of a 6-DOF Micro/Nanopositioning System

A six degree-of-freedom (6-DOF) parallel positioning system with high resolution, high repeatability, and low parasitic motions was proposed. It mainly consists of three identical limbs. Each limb consists of two symmetrical six prismatic-universal-spherical branches. First, the design process for a novel 6-DOF limb with input displacement reduction was introduced. By applying bipods and linear displacement output mechanisms, these novel limbs with symmetric configurations were designed. Moreover, a numerical compliance/stiffness model of the proposed mechanism was built based on the matrix method. This numerical model was verified by ANSYS finite-element analysis (FEA) software package. Hence, the input stiffness, the output compliance, and the stroke of the mechanism can be theoretically estimated. Furthermore, a prototype made of stainless steel 431 was successfully manufactured by wire electrical discharge machining process. It is actuated and sensed by piezoactuators and capacitive displacement sensors, respectively. Finally, the working performances of this proposed mechanism were experimentally investigated. It shows that the spatial resolution can be achieved in 10 nm × 10 nm × 5 nm × 100 nrad × 100 nrad × 200 nrad in an open-loop control. The closed-loop positioning accuracy in 3σ (σ, standard error) can reach 30 nm × 30 nm × 15 nm × 150 nrad × 150 nrad × 300 nrad. The experimental results not only validate the effectiveness of the proposed positioning system but also verify the nanometer-scale spatial positioning accuracy within several tens of micrometers stroke range. The proposed micro/nanopositioning system may expand the actual application of alignment optical elements in projection lenses of 193 nm immersion lithography