mems gyroscope accelerometer inertial

**MEMS Inertial Sensors** are **miniaturized mechanical structures coupled to capacitive transducers detecting proof-mass displacement from acceleration, rotation, or vibration via coriolis effects and resonant frequencies**. **Sensing Principles:** - Capacitive transduction: displacement of proof mass changes gap/area → capacitance change → detected as charge - Proof mass: suspended spring-damper mechanical resonator - Coriolis effect in gyroscope: vibratory MEMS; rotation perpendicular to drive axis induces sense-axis displacement - Accelerometer: proof-mass displacement directly proportional to applied acceleration **Resonator Design:** - Spring constant and mass set natural resonance frequency (typically 10-100 kHz MEMS range) - High-Q resonator achieved via vacuum-sealed cavity (quality factor 10,000+) - Damping: controlled via air gap pressure - Thermal noise floor (Brownian motion): fundamental limit from kT energy **Key Performance Metrics:** - Bias instability: zero-drift over time (stability < 10°/hour for navigation grade) - Angle random walk (ARW): white noise spectral density of angular rate - Cross-axis sensitivity: isolation of x/y/z axes - Bandwidth: ~1 kHz typical for tactical MEMS **Package and Integration:** - MEMS die bonded to ASIC readout electronics in same package - Tri-axis accelerometer: three orthogonal proof masses - Integrated gyroscope+accelerometer: 6-axis IMU for inertial navigation - Sensor grades: automotive (1-10°/hour drift), tactical (0.1-1°/hour), strategic navigation **Applications and Market:** Consumer/automotive/aerospace use MEMS IMU for dead-reckoning, gesture recognition, and stabilization—cost-effective alternative to large ring-laser gyros or fiber-optic gyros for non-navigation applications.