Attitude and Heading Reference Systems
Encyclopedia
An attitude heading reference system consists of sensors on three axes that provide heading, attitude and yaw information for aircraft. They are designed to replace traditional mechanical gyroscopic flight instruments
and provide superior reliability and accuracy.
AHRS consist of either solid-state or MEMS
gyroscopes, accelerometers and magnetometers on all three axes. The key difference between an IMU
and an AHRS is the addition of an on-board processing system in an AHRS which provides solved attitude and heading solutions versus an IMU
which just delivers sensor data to an additional device that solves the attitude solution. A form of non-linear estimation such as a Kalman filter
is typically used to compute the solution from these multiple sources. AHRS differ from traditional inertial navigation systems by attempting to estimate only attitude (i.e. roll, pitch, yaw a.k.a heading) states, rather than attitude, position and velocity as is the case with an INS.
AHRS have proven themselves to be highly reliable and are in common use in commercial and business aircraft. AHRS are typically integrated with Electronic Flight Information Systems (EFIS) (which are the central part of so-called glass cockpit
s) to form the Primary Flight Display. AHRS can be combined with air data computers to form an "air data, attitude and heading reference systems" (ADAHRS), which provide additional information such as airspeed, altitude and outside air temperature.
The OpenPilot
project offers a MEMS based AHRS unit with code licensed under the GPL.
Flight instruments
Flight instruments are the instruments in the cockpit of an aircraft that provide the pilot with information about the flight situation of that aircraft, such as height, speed and altitude...
and provide superior reliability and accuracy.
AHRS consist of either solid-state or MEMS
Microelectromechanical systems
Microelectromechanical systems is the technology of very small mechanical devices driven by electricity; it merges at the nano-scale into nanoelectromechanical systems and nanotechnology...
gyroscopes, accelerometers and magnetometers on all three axes. The key difference between an IMU
Inertial measurement unit
An inertial measurement unit, or IMU, is an electronic device that measures and reports on a craft's velocity, orientation, and gravitational forces, using a combination of accelerometers and gyroscopes. IMUs are typically used to maneuver aircraft, including UAVs, among many others, and...
and an AHRS is the addition of an on-board processing system in an AHRS which provides solved attitude and heading solutions versus an IMU
Inertial measurement unit
An inertial measurement unit, or IMU, is an electronic device that measures and reports on a craft's velocity, orientation, and gravitational forces, using a combination of accelerometers and gyroscopes. IMUs are typically used to maneuver aircraft, including UAVs, among many others, and...
which just delivers sensor data to an additional device that solves the attitude solution. A form of non-linear estimation such as a Kalman filter
Kalman filter
In statistics, the Kalman filter is a mathematical method named after Rudolf E. Kálmán. Its purpose is to use measurements observed over time, containing noise and other inaccuracies, and produce values that tend to be closer to the true values of the measurements and their associated calculated...
is typically used to compute the solution from these multiple sources. AHRS differ from traditional inertial navigation systems by attempting to estimate only attitude (i.e. roll, pitch, yaw a.k.a heading) states, rather than attitude, position and velocity as is the case with an INS.
AHRS have proven themselves to be highly reliable and are in common use in commercial and business aircraft. AHRS are typically integrated with Electronic Flight Information Systems (EFIS) (which are the central part of so-called glass cockpit
Glass cockpit
A glass cockpit is an aircraft cockpit that features electronic instrument displays, typically large LCD screens, as opposed to the traditional style of analog dials and gauges...
s) to form the Primary Flight Display. AHRS can be combined with air data computers to form an "air data, attitude and heading reference systems" (ADAHRS), which provide additional information such as airspeed, altitude and outside air temperature.
The OpenPilot
OpenPilot
OpenPilot is a Free software unmanned aerial vehicle project for model aircraft aimed at supporting both multi-rotor craft as well as fixed wing aircraft...
project offers a MEMS based AHRS unit with code licensed under the GPL.
See also
- Acronyms and abbreviations in avionicsAcronyms and abbreviations in avionics-A:*ACARS: Aircraft Communications Addressing and Reporting System.*ACAS: Airborne Collision Avoidance System.*ACP: Audio Control Panel.*ACS: Audio Control System.*ADAHRS: Air Data and Attitude Heading Reference System.*ADC: Air Data Computer....