Spacecraft Attitude Control without Prior Modeling Using Predictive Cost Adaptive Control

This paper considers attitude control of a rigid spacecraft using predictive cost adaptive control (PCAC). The inertia matrix of the spacecraft is assumed to be unknown, and the axes of the torque actuators and angular-rate sensors are assumed to be mutually orthogonal but otherwise unknown. PCAC is applied to Euler’s and Poisson’s equations as a sampled-data controller. The goal of this numerical investigation is to assess the effectiveness of PCAC for attitude control under high levels of modeling uncertainty. The present paper includes two studies. First, PCAC attitude control is simulated using various attitude representations, namely, 3-2-1 Euler angles with and without wrapping, 3-1-3 Euler angles, direction cosine matrices, quaternions, modified Rodrigues parameters, and sines and cosines of the Euler angles. The advantages and performance of each method are compared through simulation. Finally, nadir pointing along an elliptical orbit is considered with and without solar radiation pressure disturbances.