Unknow Input Observer-Based Attitude Control

Considering modeling error or disturbance as an unknown input, employing the unknown input observer (UIO) [1] to estimate modeling error or disturbance is another solution to design an attitude controller with high pointing accuracy. The development of a UIO-based attitude controller for satellite was discussed in [2]. Motivated by the advantages of UIO-based control, this chapter first presents a UIO-based robust control approach for flexible satellite’s attitude stabilization maneuvers with fixed convergence time.