Predefined-Time Attitude Tracking Robust Control of Flexible Spacecraft Under Multiple Disturbances

To overcome external environmental disturbances, inertial parameter uncertainties, actuator failures and input saturation, and the structural vibration of flexible appendages, predefined-time attitude tracking based on sliding-mode control for flexible spacecraft is proposed. First, a rotation matrix is adopted for spacecraft attitude description to avoid an unwinding phenomenon. Next, to enhance the robustness of attitude control, a radial basis function neural network is applied to estimate and compensate the lumped disturbances in attitude tracking. Then, based on the predefined-time stability, an adaptive sliding-mode controller is designed to ensure that the maximum convergence time of the system can be arbitrarily configured by setting simple parameters and independent of initial states. The system stability is further proved by the Lyapunov theory. Finally, numerical simulations indicate that the proposed controller can achieve high-precision convergence more rapidly compared to the existing finite-time attitude tracking controller. This work provides new references for high-precision attitude tracking of flexible spacecraft by predefined control with multidisturbance suppression.