A compact, two-stage, vertical actuator with built-in sensors has been developed for the Molecular Measuring Machine (M3) and other potential precision instrumentation applications, such as scanning probe microscopy (SPM). In this article, we describe the design, performance and calibration process for the Z-motor assembly. The coarse-motion actuator is an inchworm-like motor driven by three multi-stacked piezoelectric ceramics groups. It is capable of translating the probe tip over a 3 mm range at speeds up to 35 um's with overshoot-free steps ranging from 1 um to 2 um. Its potentiometer-type coarse-motion position sensor has a sensitivity of about 0.18 V/V/mm and a noise floor of 2 um. The fine-motion stage generates guided high-speed motion for servo tracking of the samples. It is comprised of three parallel piezoceramic actuators, a flexure-hinge motion amplifier, a cross-motion decoupling mechanism, and an output motion shaft that is guided by diaphragm flexures. The stroke of the fine-motion actuator is more than 6 um. A differential capacitance gage is used as the fine-motion position sensor. It is designed with three equal sections and has the capability to measure displacement and tilt of the fine-axis motion. The total measuring range of the differential capacitive sensor is 30 µm, and the noise floor is less than 0.5 nm (1 um).
Conference Dates: October 19-24, 2008
Conference Location: Portland, OR
Conference Title: American Society for Precision Engineering, Annual Meeting | 23rd | Proceedings of ASPE 23rd Annual Meeting | American Society for Precision Engineering
Pub Type: Conferences
Molecular Measuring Machine, scanning probe microscope, compact piezoceramic actuator, flexure design, differential capacitive sensor, precision motion, nanometrology