Finite‐time disturbance observer‐based modified super‐twisting algorithm for systems with mismatched disturbances: Application to fixed‐wing UAVs under wind disturbances

Abstract

This article proposes a finite-time disturbance observer-based modified super-twisting algorithm (FDO-STA) for disturbed high-order integrator-chain systems under matched and mismatched disturbances. We first design a finite-time observer for disturbance estimation, in which we show the finite-time convergence of disturbance estimation errors to zero. Second, by employing the estimates of disturbances and their derivatives, a new dynamic sliding surface is derived, which ensures the finite-time convergence of the controlled output to zero in the sliding phase. Then, based on the estimates of disturbances and their derivatives, the designed sliding surface, and a modified super-twisting algorithm, we develop the FDO-STA, which guarantees the finite-time convergence of the sliding variable to zero in the reaching phase.Rigorous analysis is provided to show the finite-time stability of the overall closed-loop system under the proposed control scheme. We finally apply the proposed FDO-STA framework to the path following control for fixed-wing UAVs under wind disturbances. Various simulation results are provided to show the effectiveness of the proposed controller, compared with the existing control approaches. K E Y W O R D Sfinite-time disturbance observer, fixed-wing UAVs, matched and mismatched disturbances, modified super-twisting algorithm, path following control INTRODUCTIONVarious industrial engineering systems, such as aerospace systems, mechatronics systems, and chemical systems, have reported the existence of mismatched disturbances entering the control systems through different channels from the control inputs. 1 In general, the control performance is adversely affected by mismatched disturbances, which may even

Adaptive dynamic programming‐based adaptive‐gain sliding mode tracking control for fixed‐wing unmanned aerial vehicle with disturbances

“…Consider system ( 6) with Assumptions 1-3. Let the ISM S, sliding mode control law M s and gain-adaptation law be designed as (10), (12), and ( 13)- (15), respectively. Then, the trajectory of system ( 6) can reach the ISM in finite time.…”

“…, 𝜍 l will be positive and then the inequality VL ≤ −𝜈 l V The proof of Theorem 1 is completed. ▪ Following Theorem 1, the state trajectory of system (6) reaches the sliding manifold S under the control law (12). According to (11) and Ṡ = 0, the equivalent control law is…”

“…In addition, sliding mode control (SMC) plays an important role on designing control scheme for many complex uncertain flight systems, such as multiple UAVs, 8,9 hypersonic vehicles, 10,11 and fixed-wing UAV. 12 This algorithm ensures finite-time convergence of the sliding mode output by utilizing a discontinuous control and owns inherent insensitivity and robustness to plant uncertainties and external disturbances. In addition, the SMC algorithms are combined with fuzzy logic, 13 backstepping, 14 and adaptive control, 15,16 to improve control performance.…”

“…Recently, various control algorithms, for examples, model prediction control, 4 dynamic surface control, 5 deep reinforcement learning method, 6 and linear quadratic regulator, 7 have been employed in flight control field and promoted further study in this field. In addition, sliding mode control (SMC) plays an important role on designing control scheme for many complex uncertain flight systems, such as multiple UAVs, 8,9 hypersonic vehicles, 10,11 and fixed‐wing UAV 12 . This algorithm ensures finite‐time convergence of the sliding mode output by utilizing a discontinuous control and owns inherent insensitivity and robustness to plant uncertainties and external disturbances.…”

A composite controller design using an adaptive internal type-2 fuzzy logic system and the fixed-time disturbance observer for an air-breathing hypersonic vehicle with a variable geometry inlet

“…37 Although the traditional observer can ensure the finite-time convergence of the observation error, the convergence time depends on the initial conditions. 38,39 If the initial deviation is far from the equilibrium position, the system will be hard to stabilize. Therefore, a fixed-time disturbance observer is designed to estimate the lumped uncertainty accurately and quickly.…”