Robust Sliding Mode Control-Based a Novel Super-Twisting Disturbance Observer and Fixed-Time State Observer for Slotless-Self Bearing Motor System

The disturbance and uncertainty of the motor drive systems are very complicated terms. There is no exception for the slotless-self bearing motor (SSBM), where the perturbations of the bearing motor are mainly came from the outside as the wind affect, from inside as the thermal changing of the coils, and incorrect modeling of the winding processes. First, to delete these inversed terms, this paper proposes a new super-twisting disturbance observer (STDOB) to obtain the desired goal of the robust control design. The proposed disturbance observer was based on the information of measured and estimated states with the aim of softening the cost of the measurement. Second, to estimate the velocities and accelerations of the movements on x- and y- axes, the stability concept of homogeneous function-based was used to design the fixed-time state observers (FTSOBs) for these axes. The state of the rotational operation on \omega - axis was estimated with a fixed-time state observer. Third, to control the positions and rotational speed, a variable boundary layer thickness (VBLT) fixed-time sliding mode control (FTSMC) was designed to force these positions and speed states converge to the desired goals. Finally, the stability of the proposed control algorithm was theoretically verified by using Lyapunov condition and simulation of MATLAB software. The obtained states were acceptably stable with small overshoots, small settling-times, and stable steady-states.