Part 2 of this two-part paper presents the experimental assessment of a micromachined capacitive incremental position sensor for nanopositioning of microactuator systems with a displacement range of 100 μm or more. Incremental sensing in combination with quadrature detection reduces the requirements for dynamic range for the sensor. Two related concepts for the position sensor are presented. In the incremental capacitance measurement mode (ICCM), the periodic change in capacitance between two periodic geometries S1 and S2 is measured to determine the relative displacement between S1 and S2 with a gap distance of ∼1 μm. In the constant capacitance measurement mode (CCMM), the distance between S1 and S2 is controlled to keep the mutual capacitance constant. Integration of the concepts with conventional comb-drive microactuators in a two-mask surface-micromachining process has been demonstrated. The changes in capacitance are measured using a synchronous detection technique with custom-made electronics. For quasi-static displacements over a range of 32 μm, an estimate for the displacement reproducibility is ∼25 nm for ICMM and ∼10 nm for CCMM, which includes hysteresis, drift and noise and errors in the actuation voltages. CCMM also shows a better performance in terms of nonlinearity and this confirms the conclusions based on the analysis and simulation results presented in part 1. The measurement method and implementation are demonstrated in quasi-static and dynamic experiments and can serve as an important tool to characterize the performance of the capacitive sensor, microsystem and setup. The feasibility of nanometer precision over a long displacement range is demonstrated and this proves the high potential of the two capacitive incremental position sensing concepts.
Kuijpers, A. A., Krijnen, G. J. M., Wiegerink, R. J., Lammerink, T. S. J., & Elwenspoek, M. C. (2006). A micromachined capacitive incremental position sensor: part 2. experimental assessment. Journal of micromechanics and microengineering, 16(IEEE Produ/6), S125-S134. https://doi.org/10.1088/0960-1317/16/6/S19