Simultaneous actuation and displacement sensing for electrostatic drives

Abstract

This paper presents a method for driving a MEMS electrostatic actuator, while simultaneously sensing the resulting displacement/capacitance without the use of an additional physical sensing structure. The approach superposes the sensing and actuation signals into a single input into the system and obtains its mechanical (displacement) response from the modulation (amplitude or phase) it produces on the sensing input. The approach is analyzed and experimentally shown to produce an amplitude modulation of 0.1857 mV µm −1 of displacement on electrostatic drive that produces a displacement of 14 µm at 100 V and a 0.55 pF capacitance change from a nominal capacitance of 0.35 Pico farads. The approach enables a very cost-effective and convenient approach to detect the displacement of MEMS devices for a variety of applications in the laboratory environment, and provide a potential feedback signal for closed-loop control of electrostatically driven MEMS devices.

Tilted Beam Piezoresistive Displacement Sensor: Design, Modeling, and Characterization

“…Substituting the unknown coefficients (A, B, C, D) in (8), M 0 is calculated as a function of F and λ in (12).…”

“…Implementation of this technique is often compatible with standard microfabrication processes. However, capacitive sensors occupy a large fraction of the chip and may need complicated readout circuits to detect small capacitance variations [11], [12].…”

MEMS Nanopositioner for On-Chip Atomic Force Microscopy: A Serial Kinematic Design

“…By implementing the capacitive sensing concept, it is also possible to maintain the displacement range of the stage in the X axis by using the comb drive structures simultaneously for both sensing and actuation. This is normally performed by using a high-frequency sensing signal superimposed on the actuation signal for both combs and then retrieving the displacement data using demodulation techniques [25], [26].…”

Control Methods in Data-Storage Systems

“…They have also been used in [232] where these electrostatic actuators are exploited for simultaneous sensing. An alternative approach to simultaneous sensing and actuation in electrostatic MEMS drives was first introduced in [240]. Similar methods had already been implemented in HDDs [241], [242], and in piezoelectrically actuated nanopositioners [243].…”