Finite-Time Control of Satellites in Elliptic Orbits Despite Uncertainties Using Solar Radiation Pressure

The development of a new robust finite-time control system, for the control of satellites in elliptic orbits with uncertain dynamics using solar radiation pressure (SRP), is the subject of this paper. The nonaffine-in-control spacecraft model includes the gravity gradient torque, the control torque produced by two solar flaps, and external time-varying disturbance torque. The interest in this paper is to control the pitch angle trajectory of the spacecraft using the solar torque. A robust control system is designed for the trajectory tracking of reference pitch angle trajectory in finite time. The control system includes a nominal nonlinear finite-time continuous tracking control law and a higher order sliding mode (discontinuous) control law for the compensation of uncertainties in the spacecraft model. The nominal controller is designed based on the notion of geometric homogeneity of vector fields. It is shown that in the closed-loop system including the nominal and sliding mode control law, finite-time control of the complete state vector associated with the pitch error dynamics to the origin is accomplished. Numerical results confirm that the controller achieves precise attitude control, despite large uncertainties and external disturbance moment