Wednesday 10.04.2024 at 14:00
Wolfson Building of Mechanical Engineering, Room 206
COMPLIANT PARALLEL MOTION LINKAGE AMPLIFICATION MECHANISM FOR RESONANT FORCE/ACCELRATION SENSING
Shay Goldstein
M.Sc. Student, under the supervision of Prof. Slava Krylov
School of Mechanical Engineering, Tel Aviv University, Tel Aviv, Israel
Inertial sensors such as angular rate sensors (gyroscopes) and accelerometers are among the most successful examples of applications relying on the microelectromechanical systems (MEMS) technology. These low-cost, small size, energetically efficient low power consumption devices are widely implemented in consumer electronics, automotive, and airspace industries and serve as key components of autonomous robots and advanced high-end navigation, guidance, and control systems. Within the inertial MEMS area, resonant accelerometers attract the steadily increasing attention of researchers and MEMS developers. The operational principle of these devices is based on the monitoring of the acceleration-dependent resonant frequency of a vibrating sensing beam attached to a proof mass and stretched (or compressed) by an inertial force. Resonant accelerometers are distinguished by a wider measurement range combined with uncompromised sensitivity, lower noise, and improved robustness when compared to the statically operated acceleration sensors. Among the challenges of resonant accelerometers’ mechanical design is the development of a force amplification mechanism usually unavoidable to reach the required sensitivity, along with mitigation of undesirable output nonlinearities and cross-axis couplings.
The present work is focused on the theoretical investigation of the vibrating beam accelerometer (VBA) implementing a recently suggested compliant parallel motion linkage amplification mechanism. The device incorporates two vibrating sensing beams attached at their ends to four proof masses. The unique compliant force amplifier architecture allows to reach high sensitivity and purely extensional, without any bending, deformation of the sensing beams, but may result in undesired nonlinearities and structural cross-couplings. The primary objective of the work was to explore the possibility of sensor performance enhancement by addressing the challenges related to the output nonlinearity and cross-axis effects mitigation. The reduced order (RO) model of the device was built using the stationary potential energy principle. The hierarchy of models included fully and weakly nonlinear and linearized models. The nonlinear equilibrium equations were solved numerically and the sensing beams’ frequency shifts due to the acceleration were calculated. The RO model predictions were compared to the results of the three-dimensional numerical finite elements analysis. Our results show that careful mechanical design is instrumental in the achievement of the highest force amplification and therefore, the highest sensitivity, low scale factor nonlinearity, and low cross-axis sensitivity. Our results provide useful insights extending the arsenal of tools that can be used by the designers of a large variety of dynamically operated inertial, pressure, magnetic, and electric field microsensors based on resonant frequency monitoring.
