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As the carrier rocket fuel is usually highly toxic, inflammable and explosive, the technology of automatic fuel filling has attracted wide attention. The key to the automatic fuel filling technology is to realize the high-precision tracking of the swaying rocket body under wind load by controlling the ground docking platform. This paper proposes a nonlinear robust control strategy for a 3-DOF motor-driven automatic docking servo system which is applied to track rocket body. To avoid complex modeling and facilitate the control design, the speed-loop of each degree is approximated as a proportional element and then each system is described as a simple first-order model with lumped disturbance. In the proposed controller design, an extended state observer (ESO) is constructed to estimate and compensate the lumped disturbance, and a robust integral of the sign of the error (RISE) feedback is synthesized to suppress the remaining estimation error to further improve the tracking accuracy. The proposed control method requires almost no model information and can achieve excellent asymptotic tracking accuracy. Comparative simulation results show the superiority and effectiveness of the proposed strategy.
Inspec keywords: fuel systems; rockets; observers; tracking; robust control; nonlinear control systems; feedback; servomechanisms; control system synthesis; electric motors; aerospace control
Subjects: Stability in control theory; Aerospace control; Nonlinear control systems; Control system analysis and synthesis methods; Electric actuators and final control equipment