Design of an Adaptive Fuzzy Super-Twisting Sliding Mode Controller for an Uncertain 2-DOF Robotic Manipulator

Abstract

Robotic manipulators are highly coupled, multi-input multi-output (MIMO) nonlinear systems with uncertainties and extremely time-varying dynamic capabilities. These features make it very difficult to control the trajectory of a robotic manipulator. To overcome this problem, the Adaptive Fuzzy Super-Twisting Sliding Mode Controller (AF-STSMC) is presented in this paper. It allows 2-DOF robot manipulators to accurately track trajectories while controlling uncertainty parameters that have an impact on the robot manipulator's ability to track the target joint angular position. The Lagrange Equation is solved to produce the dynamic model of a two-link robot manipulator. The Lyapunov direct method was used to investigate the stability of the system. The controller was implemented using MATLAB/Simulink software and its performance was evaluated. The simulation results demonstrated that the proposed controller eliminated chattering phenomena from the control effort and reduced the integral absolute tracking error (IAE) to 0.01465 rad and 0.003862 rad for link-1 and link-2 respectively. However, the integral absolute tracking error (IAE) of link-1 increased to 14.24 rad for the Sliding Mode Controller (SMC), 0.0977 rad for Super-Twisting Sliding Mode Controller (ST-SMC), and 0.06819 rad for Adaptive Fuzzy Sliding Mode Controller (AF-SMC). while the IAE of link-2 increased to 5.723 rad for the Sliding Mode Controller (SMC), 0.306 rad for Super-Twisting Sliding Mode Controller (ST-SMC), and 0.04391 rad for Adaptive Fuzzy Sliding Mode Controller (AF SMC). The conventional controllers (SMC, ST-SMC, and AF-SMC) were designed for comparison with the proposed AF-STSMC. The simulation results verified that the designed controller (AF-STSMC) has a superior tracking performance, is robust, and is not sensitive to applied frictional uncertainties as compared to other three controllers