High performance inertial navigation grade sigma-delta MEMS accelerometer

Abstract

Traditional inertial grade accelerometers, based on vibrating quartz structures, which have excellent dynamic range, are vital components in avionics. However, such kinds of accelerometers suffer from high cost and exhibit post-shock stability degradation in particular high-shock, high-vibration environments. MEMS fabrication process is an inherently rugged technology and has great potential to bring forth novel solutions on the harsh environment and safety critical applications. This paper reports on a very high performance closed-loop MEMS accelerometer targeted at inertial navigation applications. The chasing primary goal is not for the lower costs and small size, but the performance; the MEMS accelerometer's specifications compete with very high performance accelerometers. The demonstrated MEMS accelerometer is a bulk manufactured capacitive sensor with 11g input full scale over a 300 Hz bandwidth, which is controlled by highly optimized closed-loop electronics. The one-bit sigma-delta 5th-order regulation loop leads to dramatic linearity improvement and consequently vibration rectification factor (VRE). The major improvement in bias stability comes from MEMS design and process flow. Measurements show a long-term bias stability of ±0.1mg, a VRE of better than 10µg/g2, an in-band noise floor of 1µg/vHz and a 120dB dynamic range in a 100 Hz bandwidth. Additional attraction is the low power consumption of the MEMS accelerometers, which makes the power consumption critical applications feasible in the future unmanned air vehicles (UAV).