Hysteresis-Based Mechanical State Programming of MEMS Mirrors

The programming of different mechanical states of a MEMS mirror is presented here. The mirror is based on a smart material called vanadium dioxide (VO 2 ) and actuated through Joule heating. The system exhibits dynamical and hysteresis nonlinearity. While hysteresis is largely deemed undesirable, in this paper, the hysteretic behavior of the VO 2 is exploited to program tilt angles of the device. The programming is realized by applying a constant current of 7.02 mA (with an electrical power of 5.1 mW) to pre-heat the VO 2 film and adding electrical pulses to move between states. Furthermore, the capability of programming any particular mechanical state across the phase transition of the VO 2 is demonstrated. A Preisach model is adopted to characterize the hysteretic relationship between the input current and the pitch angle at the steady state, and to compute the input pulse for generating the desired pitch output via an iterative algorithm. Experiments are conducted to demonstrate the effectiveness of the proposed approach, where two sequences of pitch angle values, with a triangular profile and a random profile, respectively, are successfully programmed with an average error of 0.03°. [2017-0284]