Disturbance Observer Based Terminal Sliding Mode Control for an Electromagnetic Actuated Micropositioner With Prescribed Performance

Precise and smooth control of an electromagnetic actuated micropositioner is a challenging task due to the system's nonlinear electromagnetic dynamics, as well as its unique structure and application scenarios. The main challenges include high-order nonlinearity, modeling uncertainties, input buffeting, hysteresis, and vulnerability to interference. To address these comprehensive factors, a composite control scheme is proposed in this letter. At first, a new adaptive sliding mode disturbance observer, primarily based on position feedback, is introduced to eliminate the influence of external disturbances and uncertainties. A backstepping strategy is implemented that significantly improves the practicality of disturbance observer in micropositioning systems. A terminal sliding mode controller is then proposed to obtain high robustness and fast convergence, while prescribed performance technique is utilized to guarantee transient and steady-state response characteristics. For higher accuracy, transformed errors are used to construct an integral type recursive sliding manifold in this controller. The superiority of the proposed method is demonstrated through both simulation and experimental results.