Dynamics analysis and control of a spacecraft mechanism with joint clearance and thermal effect

In this chapter, a nonlinear dynamics modeling method for a rigid-flexible coupling satellite antenna system is proposed using Lagrange’s equations. The satellite antenna system comprises a laminated shell reflector undergoing a large overall motion. First, the complete expressions of nonlinear terms of elastic deformation and coupling terms between rigid motion and large deflection are considered in the dynamics equations. Second, disturbance effects of satellite antenna are analyzed by considering dynamics error in flexible joints. Third, heat conduction equations are derived using the thermo-elastic dynamics theory, the coupling dynamics equations are established by including a coupling stiffness matrix and thermal load undergoing a large overall motion. Finally, a nonlinear control algorithm for improving the pointing accuracy of the satellite antenna is proposed for trajectory tracking and system vibration elimination. Then, the asymptotic stability is established using Lyapunov stability theory. The results of dynamics characteristic analysis show that the dynamics, thermally coupled with a structure deformation, induces both unstable vibration and coupled flutter. Further, the coupling effect seriously degrades the antenna pointing accuracy and leads to disturbances on satellites. Simulation results show that the adaptive controller can ensure that antenna pointing progressively approaches the expected trajectory, and it demonstrates that the proposed control scheme is feasible and effective.