Abstract
A one degree-of-freedom precision position control system using an electrostatically actuated and capacitively sensed beam is reported. The beam is allowed to rock on a 10 µm high fulcrum which is fabricated from SU-8 deposited onto a glass substrate. The fulcrum establishes the nominal working gap between the beam and two electrodes located on the substrate. The differential capacitance formed by the beam and electrodes is sensed, however, the electrodes are also simultaneously used for applying controlled electrostatic forces to the beam. The system is unstable so feedback control is necessary to establish a desired stable gap but only after an appropriate feedforward filter that compensates for the forcer-to-pick-off coupling is implemented. The RMS displacement noise from DC to 100 Hz is 7 nm, and the gap can be regulated from DC to 600 Hz.
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