/aɪ ɛm ˈjuː/
noun — "a sensor system that measures motion, orientation, and acceleration."
IMU (Inertial Measurement Unit) is an electronic device that combines accelerometers, gyroscopes, and sometimes magnetometers to measure linear acceleration, angular velocity, and orientation of a moving object. IMUs are critical in navigation and control systems where GPS or other external references may be unavailable or unreliable, such as drones, autonomous vehicles, spacecraft, robotics, and IoT devices. They allow systems to track motion and estimate position through dead reckoning.
Technically, an IMU integrates multiple sensors into a single module. Accelerometers measure acceleration along three orthogonal axes, gyroscopes detect rotational motion around those axes, and magnetometers provide heading relative to the Earth’s magnetic field. Sensor outputs are fused using algorithms such as Kalman filters to estimate orientation, velocity, and position. High-performance IMUs may include gyroscopes with low bias drift and accelerometers with low noise floors for precise navigation.
Key characteristics of IMUs include:
- Multi-axis sensing: captures motion in three dimensions for comprehensive navigation.
- Sensor fusion: combines accelerometer, gyroscope, and magnetometer data for accurate orientation and motion estimation.
- Drift and bias management: requires calibration and filtering to reduce cumulative errors over time.
- High sampling rates: supports fast and dynamic movement tracking.
- Compact and robust: designed for embedded applications in drones, vehicles, and mobile devices.
In practical workflows, IMUs are used in autonomous drones to maintain stable flight when GPS signals are weak or blocked. For example, a drone may use the IMU to detect pitch, roll, and yaw changes, feeding this data into the flight controller to adjust motor outputs in real time. In robotics, IMUs help track movement through indoor environments, supplementing visual or lidar-based navigation. In IoT devices, they can monitor vibration, motion, or orientation for analytics and control.
Conceptually, an IMU is like the inner ear of a machine: it senses every tilt, turn, and acceleration, providing the system with a sense of balance and spatial awareness even when external cues are absent.
Intuition anchor: IMUs act as the proprioception of devices, enabling accurate navigation, motion tracking, and orientation in environments where external references are limited or unavailable.