Adaptive Global Terminal Sliding Mode Control Scheme with Improved Dynamic Surface for Uncertain Nonlinear Systems

This paper proposes an adaptive global terminal sliding mode control scheme for tracking control of uncertain nonlinear systems. Using the proposed global sliding surface, the reaching period is omitted and the robust performance of the whole system is improved. The discontinuous sign function is involved in the controller derivative and then, the control signal achieved after integration is continuous and attenuates the chattering problem. Two adaptation laws are employed to cope with the uncertainties and disturbances whose upper bounds are not required to be known, where the proposed technique is more flexible in the real implementations. This method guarantees robustness against uncertainties, disturbances and nonlinearities of the system. Moreover, the proposed scheme removes the chattering phenomenon using the adaptive-tuning parameters and hyperbolic tangent function in the reaching control law. Numerical simulations display the success and applicability of the proposed scheme in comparison with the results of the other method.