Novel Nonsingular Fast Terminal Sliding Mode Control for a Class of Second-Order Uncertain Nonlinear Systems

Abstract

This paper presents a novel nonsingular fast terminal sliding mode control scheme for a class of second-order uncertain nonlinear systems. First, a novel nonsingular fast terminal sliding mode manifold (NNFTSM) with adaptive coefficients is put forward, and a novel double power reaching law (NDP) with dynamic exponential power terms is presented. Afterwards, a novel nonsingular fast terminal sliding mode (NNFTSMNDP) controller is designed by employing NNFTSM and NDP, which can improve the convergence rate and the robustness of the system. Due to the existence of external disturbances and parameter uncertainties, the system states under controller NNFTSMNDP cannot converge to the equilibrium but only to the neighborhood of the equilibrium in finite time. Considering the unsatisfying performance of controller NNFTSMNDP, an adaptive disturbance observer (ADO) is employed to estimate the lumped disturbance that is compensated in the controller in real-time. A novel composite controller is presented by combining the NNFTSMNDP method with the ADO technique. The finite-time stability of the closed-loop system under the proposed control method is proven by virtue of the Lyapunov stability theory. Both simulation results and theoretical analysis illustrate that the proposed method shows excellent control performance in the existence of disturbances and uncertainties.

Survey of Advanced Nonlinear Control Strategies for UAVs: Integration of Sensors and Hybrid Techniques

“…• Optical Flow Sensors: When combined with cameras, these sensors allow UAVs to detect and avoid obstacles by analyzing visual data and adapting their flight path accordingly [152]. • Stereo Vision: By using two cameras to simulate 3D vision, UAVs can gauge the distance and size of obstacles, then adjust their flight to avoid collisions [153].…”

“…While AFTSMC is designed to be adaptive to such uncertainties, in practice there may be situations where the uncertainties are too large or the adaptation process is too slow to compensate adequately. Several researchers have proposed modifications to AFTSMC to improve its robustness, such as using disturbance observers or incorporating online learning algorithms [ 151 , 152 ].…”

Novel robust approach–based dynamic global terminal synergetic tracking control for uncertain second-order systems: Wind turbine system and power converter applications

“…Based on the output of HTNDO presented in equation (25), the composite anti-disturbance control (DGTSC-HTNDO) is designed as…”

“…In order to guarantee the error dynamics can quickly converge to the origin regardless of the initial conditions, the dynamic coefficients α ( e ) , β ( e ) , and c ( e ) should be selected properly. Pan et al 20 and Pan and Zhang 25 used dynamic coefficients α ( e ) and β ( e ) . These functions are good enough for improving the speed convergence.…”

“…In Guo et al, 24 the singularity issue has been successfully avoided via nonsingular terminal SMC in hydraulic servo systems. Pan and Zhang 25 designed a nonsingular fast terminal SMC (FTSMC) for controlling two link rigid robot manipulator. Moreover, Barambones et al 26 proposed a high-order SMC based on super-twisting algorithm for controlling the wind turbine speed and improving the maximum power extraction.…”