Snap-action bistable micromechanism actuated by non-linear resonance

• Autores: Jasmina Casals-Terré
• Directores de la Tesis: R. Capdevilla Pages (dir. tes.), Andrei Shkel (codir. tes.)
• Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2007
• Idioma: inglés
• Tribunal Calificador de la Tesis: Salvador Cardona i Foix (presid.), Lluís Jofre i Roca (secret.), Jordi Romeu Garbi (voc.), José Antonio Plaza Plaza (voc.), H. Rangel Roger (voc.)
• Materias:
  • Física
    • Mecánica
  • Ciencias tecnológicas
    • Tecnología electrónica
      • Dispositivos semiconductores
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• Resumen

  • In the thesis a novel electromechanical micro-switch is proposed, analyzed, designed and experimentally demonstrated. The device utilizes "resonance-like" phenomena for switching between statically stable states of a bistable structure. The design concept is implemented using Micro Electro Mechanical Systems (MEMS) technology.

    The design utilizes a bistable structure which is electrostatically actuated to drive the microstructure into oscillation. This oscillation is amplified at the nonlinear resonance frequency of the structure achieving a large deviation from its static equilibrium, sufficient to switch between two stable states of the bistable structure.

    Utilization of this switching strategy requires less power consumption than in the case of the conventional switches. This is the first bistable mechanism design which suggests to take advantage of "resonancelike" phenomena in bistable mechanisms to switch between stable states. An analytical model of the mechanical restoring force of two diferent types of bistable mechanism has been developed. These designs are perfectly suitable to fabricate MEMS bistable devices.The complete dynamic model of a bistable mechanism has been developed to validate the advantage of driving bistable devices using the "resonance-like" phenomena in bistable mechanisms.

    The conditions that provide snapping to the second stable have been derived using energy methods. This analysis helps MEMS designers to predict in advance under which conditions (voltage applied), the system will snap. Three different strategies have been analyzed: Static Snapping, Dynamic Snapping (due to the overshoot when a step input is applied) and AC dynamic snapping. This last strategy has been demonstrated to provide important voltage savings.

    Besides the voltage savings already mention, the use of bistable systems offer more robustness due to state retention in case of power failure.