Novel Logarithmic Non-Singular Terminal Sliding Mode and Its Application in Attitude Control of QTR

In this study, we mainly focus on the attitude control problem of a quad tilt rotor aircraft with respect to unknown external disturbance. We propose a class of control methods, based on a novel logarithmic fast non-singular terminal sliding surface, a new fast reaching law and extended state disturbance observer. A logarithmic non-singular terminal sliding surface is used owing to its convergence in finite time and significant robustness. A fast reaching law with two order characteristics of the sliding mode is designed. This reaching law can be used reduce the convergence time of traditional reaching law. In addition, the extended state disturbance observer is utilized for online estimation and to compensate for system disturbance. The simulation experiment results show that the control strategy proposed in this paper outperforms the traditional non-singular fast sliding mode control.