Design of a Rapid Tangent Sigmoid Function Tracking Differentiator

Robust Super-Twisting Sliding Mode Backstepping Control Blended with Tracking Differentiator and Nonlinear Disturbance Observer for an Unknown UAV System

“…In this section, simulations for three cases, including the nominal system, perturbed system without the observer, and perturbed system with the observer are conducted to evaluate the performance of the proposed controller and disturbance observer for the hexacopter UAV system. Four control systems were designed to compare the proposed scheme with the conventional methods: namely, the standard BSC system (BSC); Levant's tracking differentiator [31,32] based BSC system (YTBSC) studied by Yu et al [50]; Zong's tracking differentiator [28,29] based BSC system (ZTBSC), where the adopted controller is designed according to those in [50]; and proposed tracking differentiator and supertwisting algorithm based BSC system (PTSBSC). The system parameters of the hexacopter UAV are listed in Table 1 of [10].…”

“…The second one, which was proposed by Zong et al [28,29], is the tangent sigmoid function tracking differentiator given by .…”

“…To compare of the proposed observer with the conventional observers, two disturbance observers were provided. The first observer is designed using the structure of the tracking differentiator proposed by Zong et al [28,29] expressed in (20) as follows:…”

“…Hence, this leads to an increase in complexity. The tracking differentiator methods [24][25][26][27][28][29][30] were recently investigated as a potential solution. Furthermore, the second-order finite-time command filter [31][32][33] was considered to obtain improved properties to guarantee finite-time convergence and avoid increases in complexity, given that the traditional BSC schemes were designed in the point of infinite-time convergence.…”

“…Furthermore, the second-order finite-time command filter [31][32][33] was considered to obtain improved properties to guarantee finite-time convergence and avoid increases in complexity, given that the traditional BSC schemes were designed in the point of infinite-time convergence. However, the traditional tracking differentiators exhibit the disadvantage of slow convergence time, though the recently developed tracking differentiators in [27][28][29] show more improved performance than those of the previous ones.…”