Automated tuning of the nonlinear complementary filter for an Attitude Heading Reference observer

In this paper we detail a numerical optimization method for automated tuning of a nonlinear filter used in Attitude Heading Reference Systems (AHRS). First, the Levenberg Marquardt method is used for nonlinear parameter estimation of the observer model. Two approaches are described; Extended Kalman Filter (EKF) based supervised implementation and unsupervised error minimization based implementation. The quaternion formulation is used in the development in order to have a global minimum parametrization in the rotation group. These two methods are then compared using both simulated and experimental data taken from a commercial Inertial Measurement Unit (IMU) used in an autopilot system of an unmanned aerial vehicle. The results reveal that the proposed EKF based supervised implementation is faster and also has a better robustness against different initial conditions.