Robust sliding model control-based adaptive tracker for a class of nonlinear systems with input nonlinearities and uncertainties

Abstract

A robust adaptive tracker is newly proposed for a class of nonlinear systems with input nonlinearities and uncertainties. Because the upper bounds of input nonlinearities and uncertainties are difficult to be acquired, the adaptive control integrated with sliding mode control (SMC) and radial basis function neural network (RBFNN) are utilized to cope with these undesired problems and effectively complete the robust tracker design. The main contributions are concluded as follows: (1) new sufficient conditions are obtained such that the proposed adaptive control laws can avoid overestimation; (2) A smooth [Formula: see text] function is introduced to eliminate the undesired chattering phenomenon in the traditional SMC systems; (3) A robust tracker is proposed such that the controlled system outputs can robustly track the pre-specified trajectories directly, even when subjected to unknown input nonlinearities and uncertainties. Finally, the numerical simulation results are illustrated to verify the proposed approach.

Adaptive sliding tracking control for nonlinear uncertain robotic systems with unknown actuator nonlinearities

“…11, it can be observed that ASTC has better tracking effect when compared with the proposed tracking controller in ref. [36]. Furthermore, ASTC is able to eliminate the undesired chattering effectively with less control inputs in Fig.…”

“…• Case 2: Single-link robot system In this case, a single-link robotic arm in ref. [36] is utilized to verify the effectiveness and validity of ASTC. For ease of comparison studies, both the desired joint trajectory and the complex actuator nonlinearity existing in the robot in ref.…”

“…For ease of comparison studies, both the desired joint trajectory and the complex actuator nonlinearity existing in the robot in ref. [36] are utilized for simulation, which are described as Fig. 11, it can be observed that ASTC has better tracking effect when compared with the proposed tracking controller in ref.…”

“…The trajectories of the pre-specified reference r 1 (t) and displacement y 1 (t) by using the proposed tracking controller [36].…”

“…The control input responses of the proposed continuous tracking controller [36]. (b) The control input responses of adaptive sliding tracking control.…”