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Real-time closed-loop control for micro mirrors with quasistatic comb drives

: Schroedter, Richard; Sandner, Thilo; Janschek, Klaus; Roth, Matthias; Hruschka, Clemens


Piyawattanametha, Wibool (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
MOEMS and Miniaturized Systems XV : 15-17 February 2016, San Francisco, California, USA
Bellingham, WA: SPIE, 2016 (Proceedings of SPIE 9760)
ISBN: 9781628419955
Paper 976009, 13 S.
Conference "MOEMS and Miniaturized Systems" <15, 2016, San Francisco/Calif.>
Fraunhofer IPMS ()

This paper presents the application of a real-time closed-loop control for the quasistatic axis of electrostatic micro scanning mirrors. In comparison to resonantly driven mirrors, the quasistatic comb drive allows arbitrary motion profiles with frequencies up to its eigenfrequency. A current mirror setup at Fraunhofer IPMS is manufactured with a staggered vertical comb (SVC) drive and equipped with an integrated piezo-resistive deflection sensor, which can potentially be used as position feedback sensor. The control design is accomplished based on a nonlinear mechatronic system model and the preliminary parameter characterization. In previous papers [1, 2] we have shown that jerk-limited trajectories, calculated offline, provide a suitable method for parametric trajectory design, taking into account physical limitations given by the electrostatic comb and thus decreasing the dynamic requirements. The open-loop control shows in general unfavorable residual eigenfrequency oscillations leading to considerable tracking errors for desired triangle trajectories [3]. With real-time closed-loop control, implemented on a dSPACE system using an optical feedback, we can significantly reduce these errors and stabilize the mirror motion against external disturbances. In this paper we compare linear and different nonlinear closed-loop control strategies as well as two observer variants for state estimation. Finally, we evaluate the simulation and experimental results in terms of steady state accuracy and the concept feasibility for a low-cost realization.