Design of non-serial, non-parallel flexural transmissions as applied to a micro-machined MEMS tuning fork gyroscope

Abstract

The purpose of this work is to develop and implement design rules for flexures that emphasize directionality. This work is important for flexure designs that cannot be broken down into equivalent series or parallel components. The impact of this work is illustrated in the implementation of a high-performance micro-electromechanical system (MEMS) tuning fork gyroscope (TFG) that may be used for inertial navigation, automobile rollover detection, video games, and smartphones. These design rules build upon Freedom Actuation and Constraint Topologies (FACT), pseudo-rigid body modeling (PRBM), and constraint based-design (CBD) to include directionality. Flexural transmissions may be used to couple the motion of a plurality of stages to have different types (translations, rotations, and screws), different transmission ratios, and different directions on different axes. These design rules are implemented to create a MEMS TFG that exhibits coupled mass motions and decoupled mode shapes. A MEMS gyroscope was designed and modeled and a meso-scale prototype was made to verify the models and test sensitivity to fabrication errors. The design has 49% separation between desired and undesired modes. The meso-scale prototype and finite element analysis (FEA) suggest that the TFG design developed from these rules exhibits a 4x reduction in sensitivity to quadrature error.