Experimental analysis and characterization of electrostatic-drive tri-axis micro-gyroscope

A planar micro-machined tri-axis gyroscope in decoupled-mode mechanical structure is presented, verified for superior detection capability and analyzed by experiments in this paper. Initially, the natural frequencies of sense modes are successfully tuned to match the natural frequency of drive mode by polarization voltages onto the associated sensing electrodes so that the inherent bias frequency at each sense mode can be removed. Secondly, the undesired cross-axis coupling effects between drive mode and sense modes are substantially suppressed by the cooperation of mechanical design and an integrated Automatic Gain Control (AGC) loop for drive mode. For highly reliable tuning to ensure resonance, the AGC and PLL (Phase Lock Loop) are integrated with a PID (Proportional, Integral and Differential) feedback controller to eliminate steady-state errors and overshoots. The performance of the micro-gyroscope is analyzed and evaluated by experiments. The achieved scale factors (the reflected voltage to the detected angular rate) of the proposed tri-axis micro-gyroscope are 50.4 μV/°/s, 60.3 μV/°/s, and 71.2 μV/°/s for X-, Y- and Z-axes (principal axis: Z  -axis) respectively. The resulted resolutions are about 0.72°/s/Hz, 143°/s/Hz and 0.42°/s/Hz for X-, Y- and Z-axes respectively. The Cross-axis sensitivities are reduced down to 22%, 9% and 1.84% for X-, Y- and Z-axes respectively. S/N ratios reach 59.3, 13.8, and 140.1 for X-, Y- and Z-axes respectively. The experimental results illustrate that the gyroscope exhibits superior to detect exerted angular rate, in addition to successful suppression upon the cross-axis perturbation between drive mode and sense mode. Principle-axis sensitivity, resolution and floor noise are all numerically evaluated. Further more, cross-axis sensitivity, Signal-to-Noise Ratio (SNR) and measurement error are investigated. Finally, a few comparisons with the other typical types of gyroscopes are reported.