What Is an IMU?
An IMU (Inertial Measurement Unit) is a motion sensor that combines an accelerometer and a gyroscope (sometimes also a magnetometer) in a single package. It fully tracks an object's motion and orientation.
What Does It Contain?
| Type | Contents |
|---|---|
| 6-axis | Accelerometer (3) + Gyroscope (3) |
| 9-axis | + Magnetometer (3, compass) |
Sensor Fusion
A single sensor (e.g. a gyroscope drifts, an accelerometer is jittery) can't give a reliable orientation on its own. Sensor fusion algorithms (e.g. the Kalman filter) combine these sensors to produce a stable angle/orientation.
Where Is It Used?
Drone flight control, robot balance, VR/AR headsets, motion capture and vehicle navigation (when GPS is lost).
Compass and Absolute Heading (9-Axis)
The magnetometer in a 9-axis IMU reads the Earth's magnetic field to give the absolute heading (compass). While the accelerometer and gyroscope measure relative motion, the magnetometer answers "which way is north" and prevents long-term heading drift.
Common Mistakes
- Trusting raw data: without fusion the angle is unstable.
- Placing the magnetometer near metal: magnetic interference corrupts the compass.
- Skipping calibration: every IMU needs calibration at startup.
Frequently Asked Questions
6-axis or 9-axis?+
What is the MPU6050?+
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