Inertialsystems

Inertial systems, commonly referred to as inertial navigation systems (INS), are self-contained devices or sets of devices that measure the forces and rotations acting on a vehicle to estimate its position, orientation, and velocity. They rely on an inertial measurement unit (IMU) that contains accelerometers to sense linear acceleration and gyroscopes to sense angular velocity. By integrating acceleration over time and applying rotational rates, the system computes the trajectory and attitude from a known initial state.

Two main configurations exist: strapdown and gimbaled (or stabilized) platforms. Strapdown systems mount sensors directly to the vehicle frame and rely on computational orientation to interpret measurements; gimbaled systems stabilize the sensors on a motor-driven platform to separate motion from vehicle motion. Modern INS typically use strapdown architectures with MEMS, FOG, or ring-laser gyroscopes.

Because the measurements contain biases, noise, and scale errors, inertial navigation is subject to drift: small biases in gyroscopes accumulate into orientation errors, and accelerometer biases lead to velocity and position drift. Kalman filters or complementary filters are used to fuse inertial data with external aiding sources such as GPS, Doppler radar, or magnetometers to bound errors.

Applications include aerospace (aircraft flight control, missile guidance), maritime and underwater navigation, space vehicles, and increasingly autonomous ground vehicles and drones. In GNSS-denied environments, INS can provide continued navigation, though accuracy degrades without aiding data.

History: early inertial navigation emerged in the mid-20th century with gyroscope-based devices; advances in MEMS, fiber-optic gyros, and ring-laser gyros have improved accuracy, size, and cost. Modern systems range from high-precision aircraft-grade units to compact MEMS-based modules used in consumer electronics and robotics.