Majid Abnili - MSc student, Mech. Eng. Dep., University of Isfahan, Isfahan, Iran
Maryam Malekzadeh - Assistant professor, Mech. Eng. Dep., University of Isfahan, Isfahan, Iran

In this paper, the problem of attitude control of a 3D spacecraft is investigated. A controller and a reducer- order observer are presented. The controller is based on optimal control, while the observer approach is Luenberger. By using Gyros, the angular velocities can be feedback and angular positions are estimated. It is assumed that only three torques in three directions on the hub are used. Actuator saturation is also considered in the design of controllers. To evaluate the performance of the proposed controllers, an extensive number of simulations on a nonlinear model of the spacecraft are performed. Simulation results confirm the ability of the proposed controller and observer in tracking the attitude trajectory.

spacecraft attitude control, reduced-order observer, LQR, actuator saturation