18 May 2009 Position encoding and closed loop control of MOEMS translatory actuators
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We present a new method for detecting the accurate position of micro-electro-opto-mechanical system (MOEMS) devices, thus enabling the implementation of closed-loop controls. The ensuing control mechanism allows building robust MOEMS-based Fourier-transform infrared (FTIR) spectrometers with large mechanical amplitudes and thus good spectral resolutions. The MOEMS mirror device, a rectangular 1.65 mm² metalized plate mirror suspended on bearing springs and driven by comb-structured electrodes, is driven by a rectangular signal with a duty cycle of 50% and high voltage levels up to 140 V at a frequency near twice its mechanical resonance frequency. Out-of-plane mirror displacements of up to ±100 μm have thus been achieved. To handle the high bandwidth of the sinusoidal mirror position reference signal, which is generated by a laser reference interferometer, an analog position detection circuit is necessary. This dedicated circuit demodulates the reference signal and generates a highly accurate control signal returning the zerocrossing position of the mirror. This permits the implementation of a closed-loop control, which ensures optimally stable MOEMS mirror movement and maximal mechanical amplitude, even under varying environmental conditions. While this solution has been developed for a specific MOEMS device, the principle is widely applicable to related components.
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M. Lenzhofer, M. Lenzhofer, A. Tortschanoff, A. Tortschanoff, A. Frank, A. Frank, T. Sandner, T. Sandner, H. Schenk, H. Schenk, M. Kraft, M. Kraft, A. Kenda, A. Kenda, } "Position encoding and closed loop control of MOEMS translatory actuators", Proc. SPIE 7362, Smart Sensors, Actuators, and MEMS IV, 736212 (18 May 2009); doi: 10.1117/12.820335; https://doi.org/10.1117/12.820335

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