Characterization of Squeeze Film Damping in Force Rebalance Accelerometers

Force rebalance-type accelerometers are mainly used in inertial navigation systems of aircraft, and the characterization of the resulting squeeze film damping (SFD) is essential for estimating dynamic response characteristics of these accelerometers. In this study, a methodology for modeling SFD and experimentally verifying this model for force rebalance-type accelerometers is presented. Modeling of the SFD effect involves determining an effective damping coefficient as a function of pendulum displacement. Damping force and pressure distribution due to SFD are obtained for a range of pendulum displacements via finite element analysis (FEA). The accelerometer is modeled as both an open- and closed-loop system, where an identified damping model for SFD is also used. The open-loop model is verified by comparing the step response of the system, and the closed-loop model is verified by comparing the frequency and shock responses of the system via simulations and experiments. Simulation and test results of both open- and closed-loop systems show close agreement. The presented results indicate that in systems with similar dimensions and material properties, damping due to SFD in a force rebalance accelerometer can be accurately modeled as a function of pendulum displacement using the method described in this research study.