Mahboobeh Hossein Nejad - Mechanical Engineering Department, Amirkabir University of Technology, ۴۲۴Havez Ave
Mansour Kabganian
Reza Nadafi - Institute of Space Science and Technology, Amirkabir University of Technology, ۴۲۴Havez

An adaptive-sliding mode control law is derived to control the attitude of a flexible spacecraft and suppress the unwanted vibration of its flexible appendages. The difficulty of the problem lies in the highly nonlinear dynamic coupling between elastic and rigid parts of the spacecraft. The space-craft dynamics is derived using Lagrange equations and the deflection of appendages is modeled using Euler-Bernoulli beam theory. The sliding surfaces are introduced based on the sliding mode control technique. The asymptotic stability of the flexible spacecraft on the sliding surfaces is as-sured via Lyapunov method. The control law is designed such that the sliding condition is satisfied and the system reaches the sliding surfaces in finite time. The controller only needs the knowledge of the spacecraft states. The absence of measurements of the parameters is compensated by appropriate dynamics of the controller, which supplies their estimates. An adaptation law estimates the unknown parameters. Simulation results show not only precise attitude control of the flexible spacecraft is accomplished but also the elastic vibration during slew maneuver is suppressed effectively.

flexible spacecraft; attitude control; adaptive sliding mode control