Generalized Disturbance Estimation Based Continuous Integral Terminal Sliding Mode Control for Magnetic Levitation Systems

For the purpose of better inhibiting the chattering phenomenon and elevating the control performance of the magnetic levitation system under multiple disturbances, a continuous integral terminal sliding mode controller (CITSMC) based on generalized disturbance estimation (GDE) is put forward in this paper. Firstly, stemming from the mechanism modeling approach, an approximate nonlinear model of the magnetic levitation ball system is established, and then the integral terminal sliding mode controller (ITSMC) is designed to guarantee finite-time convergence. Due to the system's vulnerability to multiple external disturbances, the switching gain needs to be selected at a larger value, which will lead to serious chattering problem. As a result of these concerns, a generalized disturbance estimator is proposed, which can effectively estimate and compensate for the multiple disturbances and reduce chattering by selecting a smaller switching gain value. To further eliminate the negative influence of chattering, the super-twisting reaching law is introduced in the design process of ITSMC. The proposed composite controller has the advantages of being chattering-free and having robust anti-interference capabilities. Computer simulations and experiments are employed to double-check the effectiveness and ascendancy of the proposed strategy. Note to Practitioners-Magnetic levitation systems are subject to complicated external multiple disturbances and internal uncertainties as typical open-loop unstable systems with nonlinearity. As a consequence, developing a powerful controller for magnetic levitation systems is a challenging proposition. Firstly, aiming at the asymptotic convergence problem of traditional sliding mode, an integral terminal sliding mode controller is devised to realize finite-time convergence and avoid singularity. Secondly, a generalized disturbance estimator has been proposed for estimating and compensating for multiple disturbances. Finally, for the chattering problem, a continuous integral terminal sliding mode controller combined with super-twisting is designed to effectively eliminate the adverse effects of chattering. Simulation and experimental results verify the effectiveness and superiority of the proposed method.