PD Integrated Sliding Mode Controller design for Attitude Tracking Control of Rigid Body Spacecraft

Tracking performance is critical for spacecraft attitude tracking control. In this paper, we develop control law to obtain efficient tracking performance for attitude maneuver of rigid body spacecraft in the presence of external disturbance and system parameter uncertainties. The control law capitalize robustness of the sliding mode control (SMC) to model parameter uncertainties and fluctuations, while taking advantage of easy and simple design of proportional derivative (PD) control. Initially, SMC law is developed for the nonlinear spacecraft attitude control system then PD control is introduced in the input control scheme to alleviate chattering. It is assumed that external disturbance and spacecraft inertia bounds are unknown. Adaptive update law is developed to obtain the bounds. Stability of closed loop system is analyzed using Lyapunove’s theory. The proposed control scheme gives smooth and efficient tracking performance. Robustness and effectiveness of the control law is proven through simulation results.