Adaptive Refined Disturbance Observer-Based Velocity-Tracking Control for Gimbal Servo System With Multiple Disturbances

Multiple disturbances are the main factors to degrade high-accuracy velocity tracking of gimbal servo system in control moment gyro. In this article, a noncascade structured velocity-tracking control scheme in accordance with an adaptive refined disturbance observer (ARDO) is figured out and applied to suppress multiple disturbances and promote tracking accuracy. However, because disturbances affect the current directly through the same channel under the noncascade structure, there are two issues: 1) overcurrent protection and 2) mismatched disturbance repression. For this purpose, a finite-time current-constrained controller is constructed to ensure the current constraint and handle the mismatched problem simultaneously. An ARDO consists of a disturbance observer (DO) to estimate rotor imbalance disturbance that is modeled by an exogenous system, and an adaptive sliding mode DO to handle residual disturbances with unknown change rate. Ultimately, experimental verifications are conducted to confirm the validity of proposed composite control strategy.