A laterally sensitive quartz vibrating beam accelerometer for inertial navigation application

To improve the sensitivity and stability of a quartz vibrating beam accelerometer (QVBA), a laterally sensitive structure was developed that utilizes the force-frequency characteristics of a quartz double-ended tuning fork (DETF) to realize quasi-digital measurement of acceleration. Two DETFs were purposely designed for the sidewalls of the proof mass, and the hinge of the spring-mass structure was along the proof-mass thickness, which improved the sensitivity. Laterally sensitive structures can also solve the fabrication problems of hinges, including accuracy, deformation, and residual stress. A femtosecond laser was used to release the anchor between the out-of-frame and the proof mass to protect the hinge. The isolation structure was designed to float both the DETFs and hinge to reduce the interference of external stress. Electrodes were deposited on the four surfaces of the vibrating beam in a three-segment configuration to excite the DETF into the antiphase in-plane vibration model. As a result, an accelerometer prototype is fabricated, and the performance characterization results exhibit the sensitivity and stability of 188.61 Hz/g and 7.81 ppm, respectively, and the bias instability (Allan deviation) of 1.26 μg, which proves the design rationality of laterally sensitive QVBA.