Fuzzy Sliding Mode Control of Nonparallel-ground-track Imaging Satellite with High Precision

In this paper, a high-precision attitude tracking controller is proposed for the next-generation intelligent optical satellite with nonparallel-ground-track imaging (NPGTI) mode, where imaging targets and sub-satellite track are not parallel. First, the specific method of attitude steering for NPGTI mode is investigated to obtain the desired attitude and angular velocity. Then a nonsingular fast terminal sliding mode controller (NFTSMC) is designed based on the tracking error dynamics and kinematics described by unit error-quaternion to guarantee the tracking of the desired attitude. Accounting for the disadvantage of the chattering, a Chebyshev neural network (CNN), whose basis functions are implemented using only desired signals is then introduced to enhance the control precision by estimating the total perturbation of the system. Finally, numerical simulations are performed to testify the effectiveness of the control scheme in the presence of environmental disturbances and parameter uncertainties, and the results show that the proposed control scheme can meet the stringent requirements of control precision for the intelligent optical satellite with fast convergence speed, good robustness, and easy engineering implementation.