Inertial sensors

INS = Inertial Navigation System
IMU = Inertial Measurement Unit
Gyros and acceleration sensors
Based on conservation of momentum/inertia or changes of the path length (optical gyros)
no external support needed, work everywhere under the known physical laws

Gyro performance

Classification according to bias drift
Rate grade 10 –10000 deg/h
Tactical grade 0,01 –10 deg/h
Navigation grade <0,01 deg/h
Mechanical, optical (fog, laser ring), MEMS (tuning fork, vibrating ring)
Dynamic area: few Hz –500Hz

Active Ring-laser Gyro

Active optical resonator
Resonator is a laser itself (active)
If gyro is rotated counter-clock wise direction, the counter-clock wise beam is travelling slightly longer than the opposite beam
The change in the path length is proportional to the rotation rate
In very small rotation rates there is a dead-band because of frequency lock-in