Superflex: a Synergistic Combination of Vibrating Beam and Quartz Flexure Accelerometer Technology

Brian L. Norling

Abstract:	Vibrating beam technology offers a significant advancement in the field of accelerometers for inertial navigation. The inherently digital output of the vibrating beam accelerometer eliminates the cost, size, weight, power consumption, and performance errors associated with digitizers. The crystalline quartz vibrating beam sensing elements are extremely stable and are compatible with low-cost, high-volume production techniques developed in the watch crystal industry. Low power consumption is common to this type of device. The Sundstrand vibrating beam, force-to-frequency converter utilizes two slender beams in a geometry analogous to a double-ended tuning fork. This configuration provides perfect dynamic balance of the resonator, which eliminates coupling and energy loss to the connecting structure. This eliminates the need for relatively large and complex dynamic isolators. The slender beams of the crystal change frequency as a function of force in a manner similar to a musical stringed instrument. The Superflex mechanism design is an innovative approach which combines the unparalleled bias stability of an amorphous quartz flexure suspension with the scale factor stability of the crystalline quartz vibrating beam force sensor. This unique mechanization concept provides a synergistic marriage of these two attributes. It uses a form of symmetry in the flexures and sensing crystals which decouples static error stresses such as differential thermal expansion and permits all axis caging of shock overloads. It also substantially eliminates cross-coupling errors. whlch have been a major shortcoming of open-loop accelerometers. Errors due to nonlinearities inherent in all vibrating beam force sensors are substantially eliminated by combining dual sensors in a push-pull mode with a single, nonpendulous proof mass. Software compensation for bias, scale factor, and axis alignment temperature coefficients allows design for maximum stability instead of minimum T.C.
Published in:	Proceedings of the 43rd Annual Meeting of The Institute of Navigation (1987) June 23 - 25, 1987 Dayton, Ohio
Pages:	26 - 33
Cite this article:	Norling, Brian L., "Superflex: a Synergistic Combination of Vibrating Beam and Quartz Flexure Accelerometer Technology," Proceedings of the 43rd Annual Meeting of The Institute of Navigation (1987), Dayton, Ohio, June 1987, pp. 26-33.
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