Inertial measurement unit

Inertial sensors are used to measure acceleration and angular rates. By combining several inertial sensors in an inertial measurement unit (English inertial measurement unit, IMU ), the accelerations of the six freedoms are measured. IMU is a main component of an inertial navigation system. IMUs are used inter alia in air navigation, robotics, and image stabilization for motion detection.

Development

Starting point for the development of inertial sensors were findings from the vibration mechanics, electrical engineering and other fields of physics. Originally inertial sensors were manufactured precision engineering, today's state of the art is the micromechanical Customize. Between 1990 and 1998, the performance of micro-mechanical gyroscopes could be increased tenfold every two years. Further improvements are achieved by the use of adaptive filtering techniques. For example, can be to determine the angle of inclination of an aircraft, even if the unit of measurement is disturbed by lateral acceleration forces when moving off.

Technical significance

In an interplay of several inertial sensors often come the strengths of this technology out in the application. The combination of different inertial sensors is referred to in microsystems technology as inertial measurement units (English: Inertial Measurement Unit (IMU ) ). They enable collection for part of complex and multi-axis motion processes with up to six degrees of freedom. Inertial measurement units are used for the precise detection of rotational movements, accelerations and inclinations of the room. Due to the small size of the signals occurring in the sensor are very small and usually require a data preparation following as an interface for further processing. Data processing systems are also called Attitude Heading Reference system ( AHRS ).

Sensors

Inertial measurement units usually include the following sensor types:

• Three orthogonally arranged acceleration sensors ( also referred to as translational sensors) to detect linear acceleration in the x or y or z-axis. It can be calculated by integrating twice the translational movement.
• Three orthogonally mounted gyroscopes ( also referred to as gyroscopic sensors) measuring the angular velocity around the x -and y- and z -axis. It can be calculated by a simple integration of the rotational movement.

For determining the integration constant to improve the accuracy and to the drift of the sensors mentioned above to be corrected, for example, magnetic field sensors (compass sensors) and GNSS sensors additionally be used.

Military importance

Inertial sensors and navigation systems are important components of long-range missiles or cruise missiles, especially those with small design. The sensors therefore often subject to import or export restrictions.