High Accuracy Control for Gimbal Servo System Based on NTSMC and FTESO

This study aims to enhance the accuracy of gimbal servo system due to the multiple disturbances and the conditions of time-varying speeds in Control Moment Gyros (CMG). The accuracy can be decreased by the unbalanced torque, coupling torque, friction torque and high frequency noises. Besides, error states can not be ensured to converge to zero at an ideal speed within finite time. A novel robust method that consists of the nonsingular terminal sliding mode control (NTSMC) combined with finite time extended state observer (FTESO) and a novel reaching law of improved double power reaching law (IDPRL) is proposed. All the uncertain disturbances can be observed and compensated feedforward to the speed controller on the basis of FTESO. The convergent speed and accuracy of time-varying speed system can be improved by the nonlinear terms of IDPRL. The validity and feasibility of the proposed method is effectively demonstrated by many simulations.