Silicon-based micro-electromechanical systems (MEMS) can be fabricated usingbulk and surface micromachining technology. A micro mirror designed as anoscillatory MEMS constitutes a prominent example. Typically, in order tominimize energy consumption, the micro mirror is designed to have high qualityfactors. In addition, a phase-locked loop guarantees resonant actuation despitethe occurrence of frequency shifts. In these cases, the oscillation amplitudeof the micro mirror is expected to scale linearly with the actuation inputpower. Here, however, we report on an experimental observation which clearlyshows an amplitude depletion that is not in accordance with any linearbehaviour. As a consequence, the actuation forces needed to reach the desiredoscillation amplitude are by multiples higher than expected. We are able toexplain the experimental observations accurately by introducing a singledegree-of-freedom model including an amplitude-dependent nonlinear dampingterm. Remarkably, we find that the nonlinear damping shows a clear gas pressuredependency. We investigate the concepts and compare our findings on twodifferent micro mirror design layouts.
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