Makoto Mita

An electrostatic micro actuator with an electrical contact between the electrodes is known to show a limit-cycle behavior due to the combination of electrostatic pull-in and release. We newly used an electrical circuit simulator to make an equivalent circuit model to reproduce the limit-cycle by multi-physics simulation. This simulation results were found to explain the experimenntally observed behavior of the developedMEMS voltage to frequency convertor (VFC).

We have developed an inertia-driven micro actuator for harsh environment of space. Different from the conventional PZT-driven or other actuators, the newly developed electrostatic mechanism is free from the material property change due to temperature. A mass suspended in the actuation system is designed to collide with the internal wall to give thrust by the impact-type inchworm mechanism.

An equivalent circuit model for the semi-parallel plate electrostatic torsion mirror has been developed based on the electrical circuit simulator. An analytical model for the electrostatic torque has been translated into a nonlinear dependent current source as a function of input voltages that interpret the drive voltages and the mirror angle. A use of the suspension width as a fitting parameter explained well the experimental results of frequency response and the mirror's static deflection.

A newly developed multi-physics simulation tool for MEMS (microelectromechanical systems) has been applied to a branched suspension structure to study the versatility of analysis. More than two suspension modules or actuator modules can be connected to a mass module that solves the equation of motion without modifying the internal equivalent circuit module, thanks to the carefully designed signal handling method, where displacement and velocity are interpreted as voltage while mechanical force as electrical current. A 4-bit microelectromechanical digital-to-analog converter of displacement has been modeled as a verification to reproduce the micromechanical behavior.