Time-Optimal Nonlinear Feedback Control for the NPSAT1 Spacecraft, IEEE-ASME (2005; Monterey, California)

Abstract

NPSAT1 is a small satellite being built at the Naval Postgraduate School, and due to launch in January 2006. It uses magnetic actuators and a pitch momentum wheel for attitude control. In this paper, a novel time-optimal sampled-data feedback control algorithm is introduced for closed-loop control of NPSAT1 in the presence of disturbances. The feedback law is not analytically explicit; rather, it is obtained by a rapid re-computation of the open-loop time-optimal control at each update instant. The implementation of the proposed controller is based on a shrinking horizon approach and does not require any advance knowledge of the computation time. The ground- test simulations show that the proposed control scheme performs well in the presence of parameter uncertainties and external disturbance torques.