Nonsingular fast terminal sliding mode control based on neural network with adaptive robust term for robotic manipulators with actuators

Abstract

For accurate trajectory tracking of robotic manipulators with actuators, a novel nonsingular fast terminal sliding mode control (NFTSMC) strategy based on radial basis function neural network (RBFNN) is put forward and investigated in this paper. Because of the existence of nonsingular fast terminal sliding mode (NFTSM) manifold, the controller possesses high precision and fast convergence. Considering that it is difficult to obtain accurate model parameters owing to modeling errors or external disturbances, RBFNN is used to approximate the nonlinear uncertainties due to its simple structure and great generalization ability. A new adaptive law is designed to adjust RBFNN. In order to compensate the estimation errors and suppress other unstable factors, a robust term is introduced. A new adaptive law is developed to flexibly adjust the robust term. Then, Lyapunov theory is applied to prove the system stability and finite-time convergence. Finally, a small-sized industrial robotic manipulator Epson LS3-401S with its first two joints is taken as the simulation plant, and several simulations between the proposed controller and the other two controllers are performed. External disturbances and other two conditions are considered to simulate the real environment, and the corresponding results verify the effectiveness and superiority of the proposed controller.

Fixed-time nonsingular terminal sliding mode control for trajectory tracking of uncertain robot manipulators

“…Unfortunately, although TSMC and FTSMC can guarantee that the tracking errors converge in a finite-time, there will be singularity problem. The emergence of nonsingular TSMC (Feng et al, 2002(Feng et al, , 2013 and fast nonsingular TSMC (Boukattaya et al, 2018;Lu et al, 2022;Yi and Zhai, 2019) address this problem. In practice, robot manipulators need strict time response restrictions to improve production efficiency and safety.…”

Extended state observer–based improved non-singular fast terminal sliding mode for mobile manipulators

“…As compared to the developed SM surfaces, the NFTSM avoids singularities and has a fast finite-time reaching even when the state is far from the equilibrium point (Boukattaya et al, 2018). In view of these promising features, the NFTSM controller has gained popularity for high-accurate tracking control problems in robotic systems such as in RM (Boukattaya et al, 2018; Geng et al, 2014; Lu et al, 2022), robotic knee prosthesis (Huang et al, 2022), underactuated quadrotor UAV (Labbadi and Cherkaoui, 2020), and mobile lower limb exoskeleton (Hernandez et al, 2020). Furthermore, non-singular fast terminal sliding mode control (NFTSMC) techniques have been a few works published recently to solve the problem of tracking trajectory of MM.…”