Lead-time composite control of the single-gimbal control moment gyro under multi-source disturbances

Servo systems for spacecraft attitude control face two core challenges: 1) Traditional prescribed-time control tends to cause controller gain explosion in pursuit of fast convergence; 2) Coupled high-frequency disturbances, flexible vibrations, parameter uncertainties, and multi-source disturbances severely restrict control accuracy and dynamic performance. To address these issues, this paper proposes a lead-time composite control framework, which integrates an inner-loop lead-time high-frequency disturbance observer (LTHFDO), an outer-loop lead-time super-twisting extended state observer (LTSTESO), and a lead-time second-order integral sliding mode controller (LTSISMC). The dual observers achieve refined separation and accurate estimation of multi-source disturbances. The controller guarantees lead-time stability without gain explosion, suppresses chattering, and eliminates steady-state errors. Comparative simulations verify that the proposed scheme can accurately estimate and compensate for disturbances, shorten the convergence time by 15% and reduce the steady-state error amplitude by more than 80% compared with typical existing methods, demonstrating its superiority and effectiveness.