Non-Linear Adaptive Attitude Control of Rigid Body in Space

This paper looks at the attitude control of space vehicles. In this research, a new self-tuning adaptive attitude control law has been developed for spatial tracking control of a general rigid satellite. The goal of this research is to demonstrate an adaptive control system that can accurately compensate for modeling and parameters uncertainties. This method can be adapted to unknown parameter variation, for typical flight regimes. Our approach is based on obtaining general rigid body kinematics and dynamics equations. Among different approaches used for defining attitude of a rigid body quaternions or Euler parameters are used in this study. The control law is based on the theory of non-linear feedback linearization. It is shown that the control law is stable according to Lyapunov stability criteria. The design variables of system are inertia properties of rigid body. It is assumed that inertia tensor of the body is unknown. The inertia tensor is estimated using standard least square with bounded gain forgetting method.

The total controller and plant model is simulated using MATLAB. Simulation results are provided to illustrate the salient features of the approach. This results show the stability of system, i.e. the adaptive controller is stable and all tracking errors and state variables errors converge to zero. Also according to simulation results, it was confirmed that by using bounded gain forgetting method with standard least square, the estimator would be faster and the estimation errors would be smaller in comparison with using standard least square estimator alone.