Fabrication error sensitivity analysis of three-degree-of-freedom parallel submicron positioning stage

A new type of six-degree-of-freedom (DOF) precision positioning stage is designed and investigated in this study. This stage may be applied to couple and align an array waveguide grating (AWG) with a fibre array. It has an X-Y horizontal motion stage which consists of an X-Y horizontal motion mechanism and wedge-shaped mechanism for reducing positioning error. In addition, a rotational servo stage which provides the vertical gamma-axis rotational DOF is arranged on the horizontal X-Y motion stage. The precision positioning stage is complete with three degrees of freedom parallel kinematic mechanism (alpha, beta, and Z axes) on the rotational servo stage. To control this positioning stage precisely, an error model is obviously necessary and it is established in this paper. Because the assembly technology of three-DOF serial positioning stage is well developed, only the fabricating error parameters of the three-DOF parallel kinematic positioning stage are considered and investigated. The inverse and forward kinematics of the stage including error correction will be developed. The error sensitivity is analysed and the results will be used to improve the performance of the developed system. According to the analysis results, the positioning accuracy of Y-0-axis is affected insignificantly by fabricating errors. Therefore, the optical axis of AWG or fibre array on the loading flat-top should be parallel to the X-0-axis if this positioning stage is applied to couple an AWG with a fibre array.