Attitude Recovery of a Flexible Spacecraft Based on a Novel Lyapunov Function

In this paper after modeling a spacecraft with two symmetric and flexible solar appendages in planar motion, using Lyapunov’s direct method it is proved that a simple proportional-derivative (PD) control law can globally asymptotically stabilize the system. In other words, this control law reorients the attitude and body’s angular velocity of the spacecraft to the origin while appendages’ vibration is suppressed. Then using a new nonlinear PD control law, performance of the control system is improved in some aspects. Stability analysis of nonlinear PD control law is also guaranteed using Lyapunov’s direct method. Simplicity of control law structure, no need to feedback from flexuralcoordinate and also no need to know the parameters of the system (like moment of inertia) or any bound of parameters’ variations are the most important advantages of this control law. To validate the model of the system and the control law performance, ADAMS/View software is linked to MATLAB software to replace the mathematical dynamic model of the spacecraft. A satisfactory performance of the dynamic model and the control strategy is shown by means of simulation.

Keywords:

attitude recovery , flexible spacecraft , PD control , Lyapunov function