An optimal attitude control of small satellite with momentum wheel and magnetic torquerods

In order to improve the pointing accuracy of a small satellite, the attitude control system is controlled with pitch-axis momentum and three-axis magnetic torquerods. The satellite dynamics equation and kinematic equation are built with the method of quaternion. For each of the three body axes, well-known PD control torque equations are adopted. Three position, three rate, and a dumping control gains are optimally found by building up the optimal attitude control model. In the model, two single objectives: the minimum of the transient time and the minimum of the sum of both the square sum of the attitude angle error and the square sum of the angle rate error are integrated into the multi objectives with multiobjective optimization method. The constraints require that the attitude angle, the angle rate, the three-axis dipole moment and the pitch wheel momentum should not exceed the required value. Finally, an application to the attitude control of a small satellite is presented as an example. Results show that the optimal control algorithm is feasible, effective, and reliable, and attitude control performance is also significantly improved after optimization, compared to the traditional PD control.