Observer-based attitude control of spacecraft under actuator dead zone and misalignment faults

The paper discusses the effect of non-smooth dead-zone (NDZ), and input actuator misalignment (AMA) during spacecraft attitude tracking maneuver in presence of parametric uncertainties and external perturbations. Initially, the input AMA and NDZ models are formulated to transform spacecraft attitude model dynamics. Subsequently, a new second order disturbance observer (SODO) is devised to get the total disturbance. The observer is developed considering system perturbations as extended states, with an additional term Introduced to improve the observer performance. Finally, a distinctive integral sliding mode control (ISMC) law is developed and integrated with the proposed SODO to perform spacecraft attitude control operations. Comparative simulations are conducted on the spacecraft attitude control model with input AMA, NDZ, system parametric uncertainties and external disturbances to show the effectiveness of the proposed control structure.