摘要：An attitude and heading reference system (AHRS) is a nonlinear state estimator unit for computing orientation in 3D space. This paper designs an AH RS using three approaches: an in variant observer, an invaria nt exte nded Kalman filter (IEKF), and a conventional extended Kalman filter (EKF). The three designs are validated in experiment versus a ground truth, dem on strati ng the practical interest of the invariant observer methodology and the advantage of the IEKF over the EKF under model uncertainty.