Designing an Adaptive Control Algorithm for Amirkabir's Laboratory Attitude Simulator of a Spacecraft

In this paper, after presenting a brief introduction about Amirkabir University of Technology’s attitude simulator, governing equations are obtained. Viscous friction model is chosen to model the existing friction in the bearings of the attitude simulator. The main purpose of this paper is to design an adaptive attitude control algorithm for the attitude simulator in order to control it in the desired path and estimate the coefficients of friction due to simulator’s bearings. In order to prevent singularity in simulations, Rodriguez parameters are used for kinematics representation. Firstly, the governing equations are transformed into a robotic form. The moments of inertia and coefficients of viscous friction model are assumed as uncertainties. Then, by introducing a Lyapunov function, the stability of the system is checked and the parameters are estimated. The adaptation law is obtained by the Lyapunov function and the stability of the system is then proved. In order to demonstrate the efficiency of this adaptive control algorithm, a nonlinear Lyapunov-based attitude control algorithm is designed and compared to the adaptive controller. The simulations are done in Matlab software package and the parameters of the moment of inertia matrix and coefficients of viscous friction model are estimated by the adaptation law of the controller. During the simulation, the rotational velocity of the reaction wheels are obtained and it is shown that this attitude control algorithm is implementable on the attitude simulator.