A new high performance sigma-delta MEMS accelerometer for inertial navigation

MEMS accelerometers have proven high reliability, cost-effectiveness and versatility in recent years for consumer grade applications. Sagem and Colibrys have long been involved in MEMS accelerometers, with the ACSIL sensor that has been around for over 20 years on APIRS Attitude and Heading Reference Systems and more recently the MS90xx product family. MEMS sensors have been expected to reach inertial navigation grade performance for some years, however very few indeed have been up to the task. In this paper, we present the latest capacitive spring mass sigma-delta closed-loop accelerometer design by Sagem and Colibrys. We will present the key concepts for high performance, system architecture and the experimental results obtained on our prototypes. Compared to previous publications, performance has been significantly improved thanks to improvements in MEMS design, packaging and electronic control. The resulting design features compact size despite full digital electronic integration, excellent robustness to shocks and vibrations, and unmatched performance for a MEMS accelerometer. Great emphasis was placed on having an autonomous sensor, requiring only power supplies and a digital communication interface. High performance is thus achieved independently of external high precision components such as voltage references or A/D converter.