Variable structure control for spacecraft attitude tracking based on characteristic model

For spacecraft attitude tracking control problem, the second order time-varying characteristic model of spacecraft is established according to the attitude dynamics equations. The identified characteristic model is regarded as a discrete-time system with slow time-varying uncertainties based on the feature that model coefficient is slow time-varying and bounded. Introducing attenuation sliding surface and power reaching law, two kinds of new control methods are proposed by combining characteristic model and sliding mode variable structure control methods. The theory analysis demonstrates that the proposed methods can make the system globally uniformly ultimately bounded. Simulation results show that the sliding mode control method with power reaching law effectively improves the dynamic characteristics of the system with strong robustness.