Time-Energy Efficient Finite Time Attitude Tracking Control of Spacecraft Using Disturbance Observer

Abstract

In this paper, the attitude controller of spacecraft tracks the time-energy near-optimal angular velocity generated by the Legendre Pseudospectral method (LPSM). The near-optimal reference trajectory is obtained offline by applying the LPSM on the nominal spacecraft dynamics, which is without noises and disturbances. The proposed tracking control scheme works online, and along with the tracking of the near-optimal path, it also rejects the external disturbances and noises. The composite control law is developed by combining the sliding mode control (SMC) and the output of a finite-time disturbance observer. The SMC ensures the finite tie results whereas the disturbance observer helps in avoiding the chattering in control. The stability analysis of relative dynamics under the proposed scheme guarantees the convergence of sliding surface and relative states in finite-time. The simulation analysis further illustrates the effective performance of the proposed strategy.