Active damping control of micromachined devices in a low atmospheric pressure environment

Some harsh environments contain high frequency, high amplitude mechanical vibrations. Unfortunately some very useful components, such as MEMS gyroscopes, can be very sensitive to these high frequency mechanical vibrations. Passive micromachined silicon lowpass filter structures (spring-mass-damper) have been demonstrated in recent years. However, the performance of these filter structures is typically limited by low damping. This is especially true if operated in low pressure environments, which is often the optimal operating environment for the attached device that requires vibration isolation. An active micromachined vibration isolation filter can be realized by combining a state sensor, and electrostatic actuator and feedback electronics with the passive filter structure. Using this approach, a prototype active micromachined vibration isolation filter is realized and used to decrease the filter Q from approximately 180 to approximately 50, when evaluated in a low pressure environment. The physical size of these active filters is suitable for use in or as packaging for sensitive electronic and MEMS devices, such as MEMS vibratory gyroscope chips.