Attitude control of an underactuated spacecraft using tube-based MPC approach

Feasibility of achieving 3-axis stabilization of an asymmetric spacecraft for cases where there is no control available in one axis (underactuated spacecraft) is explored in this paper. A novel control design methodology is presented which can steer an underactuated spacecraft to the close neighborhood of the origin. A passive fault tolerant control (FTC) is defined which controls and maintains the attitude of spacecraft near the desired point in presence of uncertainty, disturbances, control constraints and actuator faults. According to the general conditions of an underactuated spacecraft, a tube-based model predictive control (MPC) scheme is developed based on the nonlinear kinematic and dynamic equations of a spacecraft motion. The controller solves two optimal control problems, one which solves a standard problem for the nominal system to define a central guide path, and an ancillary problem to steer the states towards the central path despite the uncertainties and disturbances. Numerical simulation results for a detumbling of a desired orientation maneuver are presented to illustrate the capability of the proposed attitude control method.