The model of multi-level lever-arm in position and orientation system

The Position and Orientation System (POS) is an integrated motion measurement system of Inertial Navigation System (INS)/Global Positioning System (GPS) for airborne remote sensing motion compensation. Multi-level lever-arm exists among each subsystem and each has its individual characteristics. The error model of individual lever arm was built up. In the INS subsystem, the accelerometer's output error caused by the size-effect error namely the displacement of the sensing center of accelerometer (CA) from the center of inertial sensing assembly (CISA) is of 100 μg level, which relates to the fixing orientation error of inertial measurement unit (IMU). The accelerometer's output error caused by the outer lever arm namely the displacement of CISA from mass center of vehicle (MCV) is of mg level, which is not determined for that the MCV is changing in the mission of flying. Between IMU and GPS, The position and velocity error which was caused by first level lever arm namely the displacement of ISA from the center of GPS was taken as the measurement for extended Kalman filter (EKF). Besides, between sensing load and IMU, the second level lever arm namely the displacement of ISA from the center of remote sensing load is determined, the motion error can be eliminated provide the measurement of POS is accurate. The simulation and flying experiment shows that the inner and outer level arm will introduce the ill acceleration which will produce the position error of 10 ^-3 and 10 ^-4 level in meters provide the GPS signal is normal, the first level and second level lever arm can produce position error in meter's level, the position error and velocity error can be taken as the measurement in EKF to realize integration of SINS/GPS.