Abstract
In this paper, a yaw attitude error estimation of the low altitude zero-momentum three-axes stabilized satellite is discussed. For the satellite, the sensors are earth sensor, gyro which detects angular velocity. The actuators are orthogonal three reaction wheels.
Gyro input axis is laid in roll-yaw plane, and its output signal is not yaw error angle but is nearly equal to a linear sum of yaw error angle and its derivative when attitude errors are small.
The proposed estimation algorithm, which estimates yaw error angle and its derivative separately, uses a reduced-order observer, which dimension is two. Measurement variables of the observer are gyro output signal, roll error angle, yaw wheel angular rate and roll wheel angular rate. Input variables of the observer are roll and yaw wheel control torques and disturbance torques. However, no information about disturbance torques is required according to the appropriate selection of the observer parameters.
By some simulation results for the digital attitude control, an efficiency of the proposed yaw error estimation algorithm is confirmed.
