This study investigates a novel fractional-order nonsingular terminal sliding mode controller via a finite-time disturbance observerforaclassofmismatcheduncertainnonlinearsystems.Forthispurpose,a finite-timedisturbanceobserver–based fractional-order nonsingular terminal sliding surface is proposed, and the corresponding control law is designed using the Lyapunov stability theory to satisfy the sliding condition in finite time. The proposed fractional-order nonsingular terminal sliding mode control based on a finite-time disturbance observer exhibits better control performance; guarantees finitetime convergence, robust stability of the closed-loop system, and mismatched disturbance rejection; and alleviates the chatteringproblem.Finally,the effectivenessofthe proposedfractional-orderrobustcontrollerisillustratedviasimulation resultsofboththenumericalandapplication exampleswhicharecomparedwiththefractional-ordernonsingular terminal sliding mode controller, sliding mode controller based on a disturbance observer, and integral sliding mode controller methods.

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