Quantitative precision attitude tracking control of flexible satellite under unknown disturbance

Artificial satellites usually need to carry some flexible appendages to meet the communication and energy requirements. The coupling effect between these appendages and the central rigid body will seriously affect the response speed and control precision of attitude control. Aiming at the fast and high-precision attitude control problem of flexible satellite, a continuous nonsingular quantitative precision attitude tracking control scheme is proposed. Firstly, a nonsingular terminal sliding mode is designed. If the value of the terminal sliding mode is retained within a specified neighborhood near zero, the attitude tracking error will converge to the demanded precision within the required time and maintain it over a long term. Then, a continuous nonsingular attitude tracking controller is constructed by combining the performance function method with the designed terminal sliding mode. Under the proposed controller, the terminal sliding mode will keep within the above specified neighborhood near zero after the specified moment, thus achieving the quantitative precision attitude tracking of flexible satellite. In reality, the satellite is affected by various disturbances, and the vibration of the flexible appendages is difficult to measure in real time by the sensors. Motivated by them, two adaptive laws are designed to reject the external disturbance torque with unknown upper bound and the rigid-flexible coupling effect resulting from flexible vibration, respectively. Finally, the effectiveness of the proposed attitude control scheme is verified by numerical simulations.