The limited thickness of structural layers attained in current surface-micromachining processes results in very small sensing capacitances and higher actuation voltages, restricting the performance of the surface-micromachined gyroscopes.
University researchers have developed a novel gimbal-type torsional z-axis micromachined gyroscope with a non-resonant actuation scheme,that measures angular rate of an object with respect to the axis normal to the substrate plane (the z-axis). The design concept is based on employing a 2 degrees-of-freedom (2-DOF) drive-mode oscillator comprised of a sensing plate suspended inside two gimbals. By utilizing dynamic amplification of torsional oscillations in the drive-mode instead of resonance, large oscillation amplitudes of the sensing element is achieved with small actuation amplitudes, providing improved linearity and stability despite parallel-plate actuation. The device operates at resonance in the sense direction for improved sensitivity, while the drive direction amplitude is inherently constant within the same frequency band. Thus, the necessity to match drive and sense resonance modes is eliminated, leading to improved robustness against structural and thermal parameter fluctuations.
Micromachined gyroscopes have a wide application range, including high performance navigation and guidance systems, automotive safety systems like yaw and tilt control, roll-over protection and next generation airbag and antilock brake systems, and also consumer electronics applications like image stabilization in video cameras, virtual reality products, and pointing devices. Also, orders of magnitude reduction in production cost is achieved by surface micromachining.
|United States Of America||Issued Patent||7,421,898||09/09/2008||2004-508|