A variable coefficient nonsingular fast terminal sliding mode control method based on ESO

This paper presents a variable coefficient nonsingular fast terminal sliding mode (VCNFTSM) control method with the extended state observer (ESO) for a class of second-order uncertain SISO nonlinear systems subject to external disturbance. First, a new variable coefficient double exponential reaching law is combined with NFTSM surface function to get finite time fast convergence in both reaching phase and sliding phase. Then, the system uncertainty and external distractions are estimated and compensated effectively by introducing the ESO. Furthermore, it is proved theoretically that the controller based on ESO can make the nonlinear system states converge to a small neighborhood around the equilibrium in finite time. Finally, simulation results show that the proposed control algorithm can not only shorten the system reaching time and improve the system control precision but also reduce system chattering effectively.