Research ArticleSliding mode output feedback control based on tracking error observer with disturbance estimator

- This paper realizes sliding mode output feedback tracking control by a tracking error observer.
- The original tracking error observer is created based on a novel disturbance estimator.
- Disturbance in the considered system can be vanishing or nonvanishing and without known bound.
- The model of system can be of moderate accuracy, the presented method is not very sensitive to model.
- Results based on one degree-of-freedom (DOF) system can be extended to higher DOF systems easily.

For a class of systems who suffers from disturbances, an original output feedback sliding mode control method is presented based on a novel tracking error observer with disturbance estimator. The mathematical models of the systems are not required to be with high accuracy, and the disturbances can be vanishing or nonvanishing, while the bounds of disturbances are unknown. By constructing a differential sliding surface and employing reaching law approach, a sliding mode controller is obtained. On the basis of an extended disturbance estimator, a creative tracking error observer is produced. By using the observation of tracking error and the estimation of disturbance, the sliding mode controller is implementable. It is proved that the disturbance estimation error and tracking observation error are bounded, the sliding surface is reachable and the closed-loop system is robustly stable. The simulations on a servomotor positioning system and a five-degree-of-freedom active magnetic bearings system verify the effect of the proposed method.