Extended and unscented Kalman filtering for attitude estimation application to the active control system for microsatellite -A comparative study

Unscented Kalman filter (UKF) has been proven to be a superior alternative to the extended Kalman filter (EKF) when solving the nonlinear system in previous literatures. In order to explore the application of the UKF in the attitude estimation and control system (ADCS) on board low earth orbit (LEO) microsatellite, a comparison study is performed of the UKF over the classical EKF. The full-state knowledge, required for the control loop is provided through EKF and UKF for satellite three-axis attitude and rate estimation using magnetometer and sun sensor measurements, while the control torque is generated via wheels and magnetorquers. This paper presents the various steps of the design of the UKF and a comparative study with the EKF for ADCS applied on (LEO) microsatellites. The resulted ADCS clearly indicate that the EKF and the UKF have almost similar attitude estimation accuracy. However, the computational demand of the UKF lead to the conclusion that the EKF is a more logical choice for estimating the attitude of the LEO microsatellite.