AHRS MEMS accelerometers
Attitude and Heading Reference Systems (AHRS) are multi-axis sensors which use inertial navigation in order to calculate the position and velocity of an aircraft, namely heading, altitude and yaw. These sensors replace mechanical gyroscopic flight instruments, providing superior reliability and accuracy, featuring solid-state or MEMS gyrometer, accelerometers and magnetometers on all three axes. AHRS sensors are often faulty in terms of gyro bias drifts, requiring a filter structure and independent measurements from accelerometers in order to keep an aircraft on its true trajectory. As such, the role of an accelerometer in an AHRS application is to provide the initial altitude reference and on-flight corrections required to correct gyro drifts.
Accelerometers for AHRS applications
High-accuracy AHRS accelerometers are used in order to prevent the large wings of the aircraft from colliding with the ground during take-off and landing. This type of application calls for accelerometers with a bias stability higher than 2 mg in temperature range, linearity, second order effects and axis misalignment.
Lower classes of AHRS are used to provide assistance to pilots or as backup systems. They are often encountered in small civilian airplanes and UAVs. In these cases, MEMS accelerometers provide an ideal solution.
The MEMS Revolution
MEMS accelerometers provide exceptional levels of performance in terms of long-term stability, temperature stability and accuracy and are able to function successfully under harsh conditions. However, it’s important to note that different applications call for MEMS accelerometers with different ranges. As such, high-end and medium AHRS performance usually requires accelerometers with a range of 10g to 30g, while lower-end solutions can make do with 5g sensors.
Safran Colibrys accelerometers for AHRS applications
Safran Colibrys manufactures the following products for AHRS applications. It’s important to note that they come with acceleration ranges of 2g, 5g, 10g and 30g.
- MS1000 family – MEMS accelerometers offering a the best compromise for Bias stability overall performances and cost effective. Product has been certified FAA/EASA DAL A by customers.