Experimental characterization of linearly and nonlinearly modulated digital microactuators for high-precision nano-positioning

Abstract

This thesis investigates a nonlinearly modulated digital microactuator for applications to high-precision nano-positioning. The present digital microactuator uses a new class of nonlinear micromechanical modulator in order to produce a precision displacement output, immune to electrical noise and microfabrication uncertainty. We consider two types of the micromechanical modulators: a conventional linear micromechanical modulator and a proposed nonlinear micromechanical modulator. We design, analyze and fabricate two sets of prototypes. In the first prototype set, we connect the linear and nonlinear modulators to the analog microactuators in order to characterize the displacement modulation curves of the linear and nonlinear modulators. The second prototype set includes the linear and nonlinear modulators, connected to the digital microactuators, which are designed to compare the repeatability of the linearly and nonlinearly modulated digital microactuators. The linear and nonlinear modulators are designed such that they produce the same displacement output of 5.46±0.10㎛ for the fixed digital input of 15.2㎛. From the experimental study on the first prototype set, the measured linear and nonlinear modulation curves coincide well with the theoretically estimated linear and nonlinear curves. From the experimental study on the second prototype set, the modulated output of the linearly and nonlinearly modulated digital microactuators shows the repeatability of 27.8nm and 12.3nm, respectively, under an identical measurement uncertainty of ±7.6nm. We experimentally prove that, compared to the conventional linear micromechanical modulator, the proposed nonlinear micromechanical modulator improves the repeatability of the digital displacement output, showing potential for high-precision nano-positioning applications.