Retrospective Cost Adaptive Control of Spacecraft Attitude

We apply retrospective cost adaptive control (RCAC) to spacecraft attitude control. First, we develop results for angular rate control. These results are then extended to attitude control. We examine two problems for each of the controllers. For both problems, the spacecraft has an arbitrary initial angular rate, and in the case of attitude control, an arbitrary initial attitude. The objective for the first problem is to bring the body to rest and to a specified attitude in the attitude control case. The second problem seeks to bring the spacecraft to spin about a specified body axis, which, in the case of attitude control, is inertially pointed. We first test the algorithm using an estimate of the spacecraft’s Markov parameters obtained from discretization of the linearized Euler’s and Poisson’s equations. Then, we limit the dependence on knowledge of the mass properties by removing inertia information from the Markov parameter. Finally, we test for robustness by scaling the Markov parameter and rotating the actuator matrix.