IMU aiding using two AHRS units

This paper describes usage of two modified attitude heading and reference systems whose two pressure sensors are used to provide a new source of altimetry information that allows determination of position angles and inertial measurement unit sensor error models. The system is called Pressure Reference System. The two collaborating units use MEMS based triads of gyroscopes, accelerometers, magnetometers and multiple pressure sensors each. The two modules with their pressure sensors allow us to perform altitude measurements at two places from which a position angle can be determined. The altimetry data are recalculated to the position angle that is stable in time and does not suffer by drift errors amplified by the numerical integration algorithm used in inertial measurement units. This new information is fed back to the module as a correction signal for MEMS sensors and it is used to remove their drift errors. The method used for data fusion is described in this paper together with error model identification method, a testing system, laboratory test procedure and its results.