High-G Survivable MEMS Three-Axis Accelerometer

Abstract This paper investigates the design and analysis of a polysilicon MicroElectroMechanical Systems (MEMS) inertial sensor. The planar MEMS accelerometer design measures acceleration in all three axes using a single chip. The 400-micron square polysilicon planar chip is comprised of a circular proof mass (x-y axis) with four inter-digitated arms attached to an outer frame via four crab-like legs to measure in-plane accelerations. A cantilever beam is integrated within the circular proof mass to allow for out-ofplane (z-axis) measurements. The MEMS accelerometer can be fabricated using standard integrated circuit microfabrication techniques. The accelerometer’s response to a 12,500 g (axial) and 1,000 g (radial) dynamic gun-launch input load is analyzed using Simulink and the stresses are determined using the finite element analysis (FEA) software, Abaqus. Stress magnitudes on the proof mass at critical attachment locations from both the axial and radial load conditions are well below the yield strength of polysilicon, confirming survivability at tactical 155mm gun-launch. System dynamic modeling in Simulink shows the response of the in-plane (circular, x-y axis) and out-of-plane (cantilever beam, z-axis) proof masses due to the g-loads are within design limits, avoiding sensor breakage and the need for shock stops. Additional Simulink modeling with a voltage input provides insight into electromechanical response. The planar chip three-axis accelerometer design and analysis in this paper meets the requirements for use in military applications, where small size, weight, and power are critical parameters for volume constrained precision guided munitions.