Bounded control of PMLSM servo system based on fractional order barrier function adaptive super-twisting approach

The performance of permanent magnet linear synchronous motor in tracking is influenced by payload uncertainty and unknown disturbances. Traditional constant-gain super-twisting control typically use a high control gain exceeding the total disturbances to maintain the stability of the system. However, these controllers may lead to control input oversaturation when disturbances decrease and the control gain is not appropriately chosen. To address this issue, this paper proposes a new Fractional Order Barrier Function Adaptive Super-Twisting (FOBFAST) control strategy. The advantages of FOBFAST include: (1) mitigation of system chattering through the design of the super-twisting algorithm and the fractional-order integral terminal sliding mode manifold; (2) achieving convergence of system error to a predetermined zero-neighborhood without requiring information about the disturbance upper bound; (3) dynamic adjustment of control gain to a smaller value as tracking error converges to the origin. Furthermore, an improved barrier function is proposed to address the issue of large control amplitudes, limiting the maximum allowable control gain and ensuring system stability. Experimental results demonstrate that the proposed control strategy not only enhances position tracking performance but also exhibits superior robustness.