Nonlinear pitch oscillation and control of a gravitational stabilized sailcraft perturbed by solar pressure torque

The sailcraft based space missions is deeply influenced by its attitude dynamics since the solar radiation pressure force for propellantless orbital maneuver is dependent on its orientation with respect to the sun line. Therefore, it is essential to explore the attitude motion evolution of a sailcraft and understand its attitude dynamic characteristics. To address this, nonlinear pitch dynamics of a sailcraft in an Earth orbit with a sliding mass as an attitude control actuator is focused on. Firstly, the Lagrange equation method is adopted to establish the pitch dynamics of a sailcraft subjected to the gravitational gradient torque, solar radiation pressure torque considering the Earth's occlusion of sunlight, damping torque, and the attitude control torque (this torque is generated by positioning the sliding mass at proper location). Secondly, the possible occurrence of chaotic pitch motion free of control torque is analytically predicted for the sailcraft in the circular and elliptical orbits using the Melnikov method respectively. The effectiveness of the Melnikov method is verified using various numerical methods such as phase plane, Poincaré sections, and power spectrum density. Furthermore, the influence of various parameters on the chaotic evolution is analyzed in detail. Lastly, to control the chaotic pitch motion onto the selected unstable periodic orbit obtained using the close return pairs, a sliding mode controller based on control input anti-saturation considering the position restriction of the sliding mass is developed. The effectiveness of the developed pitch chaos stabilization controller is verified by two numerical simulation cases.